Journal of Prosthodontic Research
Online ISSN : 1883-9207
Print ISSN : 1883-1958
ISSN-L : 1883-1958
Advance online publication
Showing 1-46 articles out of 46 articles from Advance online publication
  • Mª Fernanda Solá-Ruiz, Mar Baixauli-López, Ana Roig-Vanaclocha, Jose A ...
    Type: Original Article
    Article ID: JPR_D_20_00034
    Published: 2021
    [Advance publication] Released: October 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the clinical behavior and survival of full coverage monolithic zirconia crowns on posterior teeth over a 5-year follow-up.
    Methods: Fifty patients were recruited and underwent restoration with a Lava Plus monolithic zirconia crown (Lava™ Frame Zirconia, 3M Espe, Germany) on premolars or molars. Patients were monitored over a 5-year follow-up (2014-19), recording any biological and/or mechanical complications; these data were used to estimate the crowns’ success rate. Periodontal clinical parameters were recorded (pocket probing depth (PPD), plaque index (PLI), bleeding on probing (BOP), and gingival recession (GR)). Wear to the zirconia crowns and antagonist teeth were also evaluated with Geomagic software (3D Systems, U.S.A.). Patients’ satisfaction with treatment was evaluated in a questionnaire.
    Results: For the 50 monolithic zirconia crowns analyzed, the survival rate was 98% after 5 years. Only 6% of the crowns presented some type of complication (two debonding and one root fracture). No fracture or fissures were detected. GR and BOP were the only clinical parameters found to be significantly greater around teeth restored with crowns. The monolithic zirconia crowns suffered less wear than the enamel of antagonist teeth. Patient’s general satisfaction with treatment was high.
    Conclusions: Monolithic zirconia crowns on posterior teeth are a highly predictable treatment option, with a high survival rate. The single treatment failure was due to a biological complication arising from root fracture. This treatment may be recommended as a treatment that conserves dental structure, and requires minimal dental preparation.
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  • Adriano F. Lima
    Type: Original Article
    Article ID: JPOR_2019_405
    Published: 2021
    [Advance publication] Released: October 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the effect of glass-reinforced ceramics (leucite and lithium disilicate) with different thicknesses (1, 2, and 3 mm) on the wavelength and irradiance spectrum of blue and violet lights. In addition, the effect of the ceramics on four current light-curing units (LCUs) was evaluated: a halogen lamp, a single peak LED, and two multi-peak LEDs.
    Methods: Ceramic discs of different thicknesses (1, 2, and 3 mm) were obtained from computer-aided design and computer-aided manufacturing (CAD-CAM) blocks. The irradiance, radiant exposure, and emission spectrum of the four LCUs were analyzed using a spectrometer-based instrument. To evaluate the violet and blue lights, a specific device that provides a narrow emission spectrum was used.
    Results: The ceramics reduced the irradiance of all the tested LCUs. However, the wavelength of the transmitted light was only altered slightly. The effect of leucite and lithium disilicate varied according to the type of LCU and thickness of the ceramic disc evaluated.
    Conclusions: From the results, it could be concluded that the thickness of the leucite and lithium disilicate ceramic significantly reduced the irradiance of the light emitted by the LCUs, with minimal changes on the wavelength spectrum of the lights. The effects of the ceramic on irradiance and transmitted wavelengths of the blue and violet lights was slightly different.
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  • Yolanda Freire, Esther Gonzalo, Carlos Lopez-Suarez, Jesus Pelaez, Mar ...
    Type: Original Article
    Article ID: JPR_D_20_00003
    Published: 2021
    [Advance publication] Released: October 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the influence of intraoral and extraoral digitization systems on marginal discrepancy of monolithic lithium disilicate and monolithic zirconia computer-aided design-computer-aided manufacturing (CAD-CAM) crowns.
    Methods: Forty standardized machined stainless steel specimens with the characteristics of a first molar were manufactured and randomly assigned to two groups (n=20 each), depending on their material: monolithic lithium disilicate ceramic (LM), and monolithic zirconia (ZM). Then, each group was subdivided into two depending on the scanning system used: intraoral scanner (IOS), and extraoral scanner (EOS). The digitization process was standardized with two methacrylate devices, one for each scanner. After scanning and manufacturing of the crowns, the marginal discrepancy was measured under a scanning electron microscope (SEM). Data analysis was made using two-way analysis of variance (ANOVA) and the effect size with Cohen's d.
    Results: All the measurements were within the limits considered acceptable. Regardless the restorative material significant differences between scanners were observed, being the effect from low to moderate. However, no differences were observed between the scanners in either the lithium disilicate or zirconia group.
    Conclusions: The intraoral scan showed lower marginal discrepancy than the extraoral scan in CAD-CAM monolithic crowns, but these differences were not observed in each of the ceramic systems.
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  • Noriyuki Narita, Hiroshi Endo, Tomohiro Ishii, Taira Kobayashi, Takesh ...
    Type: Original Article
    Article ID: JPR_D_20_00004
    Published: 2021
    [Advance publication] Released: October 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This study was performed to examine how denture wearing improves jaw and neck muscle coordination during chewing in partially edentulous elderly patients.
    Methods: Sixteen patients classified as Eichner’s index B2 or B3 and 16 young dentate subjects were enrolled. Jaw and neck muscle activities during chewing were recorded using electromyography with and without denture wearing, then analyzed using intermuscular Electromyography (EMG)-EMG transfer and EMG-EMG coherence function analyses to clarify quantitative, temporal, and functional coordination of jaw and neck muscle activities while chewing. Occlusal force and masticatory scores were also determined.
    Results: Denture wearing increased the power values for jaw closing muscle activities, and improved occlusal area and force, and masticatory score. Gain values for jaw closing and opening muscle activities were decreased in those wearing dentures compared to those not wearing dentures. Denture wearing resulted in equivalent gain values for jaw closing and opening muscle activities as compared to the young subjects. Coherence values for chewing and non-chewing side neck muscle activities were increased as compared to not denture wearing.
    Conclusions: The suitability of denture wearing can be evaluated from the viewpoint of gain as a quantitative parameter showing coordination between jaw closing and opening muscle activities. Such evaluation can be performed from the viewpoint of coherence as a parameter of functional coordination between jaw and neck muscle activities during chewing in partially edentulous elderly patients. The gain parameter in regard to jaw muscle activities may be compensated to a state equivalent to that seen in young subjects by wearing an appropriate denture.
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  • Beshr Hajhamid, Grace M. De Souza
    Type: Original Article
    Article ID: JPR_D_20_00018
    Published: 2021
    [Advance publication] Released: October 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: Ionizing radiation therapy (RT) is the main option for head and neck cancer treatment, but it is associated with multiple side effects. This study aimed to evaluate the effect of RT associated with chewing simulation on the surface of human enamel and Yttria-partially stabilized zirconia (Y-TZP).
    Methods: Maxillary premolar cusps and Y-TZP slabs were divided in 7 experimental groups: CO: no RT (control); EZ groups had irradiation applied to both, enamel and zirconia samples (simulating restoration prior to RT); E groups had irradiation applied to enamel only (simulating restoration after RT). RT doses were either 30, 50 or 70 Gray (Gy). Enamel cusps were abraded against zirconia slabs in a chewing simulator (CS - one million cycles/ 80 N/ 60 mm/min, 2 mm horizontal path, artificial saliva, 37˚ C). Zirconia hardness was evaluated before CS; zirconia roughness and enamel volume (wear) were evaluated before and after CS. Hardness and wear data were analyzed by one-way Analysis of Variance and Tukey post hoc test. Roughness was analyzed by Repeated Measures test and Bonferroni test (p=0.05).
    Results: There was no significant effect of enamel or zirconia irradiation on enamel cusp wear (p=0.226), regardless of the irradiation dose used - up to 70 Gy. Irradiation also did not affect Y-TZP surface roughness (p=0.127) and hardness (p=0.964).
    Conclusions: RT does not promote significant changes to the surface characteristics of zirconia. Irradiated enamel abraded against zirconia does not show higher wear volume when compared to non-irradiated enamel.
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  • Yukiko Narahara-Eno, Tatsuya Fukuda, Hitoshi Taga, Hideaki Nakayama, Y ...
    Type: Original Article
    Article ID: JPR_D_20_00118
    Published: 2021
    [Advance publication] Released: October 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: In the treatment of obstructive sleep apnea (OSA), there is not yet a convenient tool for deciding whether a mandibular advancement oral appliance (OA) is adequately adjusted or when to perform post-treatment sleep-testing. We hypothesized that a gradual reduction in the STOP (snoring, tiredness during daytime, observed apnea, high blood pressure) score, i.e., fewer Yes responses in the STOP questionnaire, in patients undergoing OA treatment could be an indicator of better OA adjustment and, thus, the best timing for follow-up polysomnography.
    Methods: The STOP score was recorded at every patient visit when the OA was adjusted ventrally as necessary (i.e., STOP group). We considered that the appropriate timing for follow-up polysomnography was when the STOP score stopped decreasing. A historical control group was established from consecutive patients without a STOP score.
    Results: In the STOP group (n=57), the median (interquartile range) of STOP scores gradually decreased with OA treatment, from 3 (2-3) to 0 (0-1) (p<0.05). While the apnea hypopnea index (AHI) was improved in both the STOP group (19±10 to 5±4 /hr, p<0.01) and the control group (n=61; 19±7 to 8±7 /hr, p<0.01), there was a significant difference in follow-up AHI between the two groups (p<0.05) after controlling for gender (male), age, body mass index, and baseline AHI: a superior treatment outcome in the STOP group.
    Conclusions: The appropriate timing for follow-up sleep-testing in OSA patients undergoing OA therapy is when the STOP score stopped decreasing. This evaluation using the STOP score partly resolves the current “trial-and-error nature” of OA adjustment and facilitates proper post-treatment sleep-testing.
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  • Pablo Soares Machado, Gabriel Kalil Rocha Pereira, Camila da Silva Rod ...
    Type: Original Article
    Article ID: JPOR_2019_336
    Published: 2021
    [Advance publication] Released: October 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the influence of quantity and positioning of veneered zirconia specimens during firing of porcelain on their fatigue performance and colorimetric differences.
    Methods: Bilayer discs (Ø=15 mm) were made, following ISO 6872 guidelines, using a Y-TZP core (yttria-stabilized tetragonal zirconia polycrystal ceramic; VITA In-Ceram YZ) and a feldspathic veneering material (VITA VM9), being both layers with 0.7 mm thickness. Y-TZP discs were sintered, the veneering material was applied over it, and the bilayer specimens were fired according to two factors (n=20): ‘quantity’ (1 or 5 samples per firing cycle; G1 and G5 groups respectively) and ‘positioning’ of the specimens inside the furnace (center or periphery of the refractory tray; G5C and G5P groups, respectively). The CIEL*a*b* parameters were recorded with a spectrophotometer and the color difference (ΔE 00 ) and translucency (TP 00 ) were calculated using CIEDE2000 equations. The step-stress fatigue test was performed with the veneer facing down (region of tensile stress concentration), 10 Hz frequency, initial tension of 20 MPa for 5,000 cycles, followed by steps of 10,000 cycles using a step size of 10 MPa, up to 100 MPa; data from strength and number of cycles for failure were recorded for statistical analysis.
    Results: Unacceptable color differences (ΔE 00 >1.8) were observed comparing G5C vs. G1 (quantity) and G5C vs. G5P (positioning), meanwhile translucency parameters were not affected. Besides, only the ‘quantity’ factor influenced the fatigue performance (G1>G5C). None of the tested specimens survived beyond 90N and/or 75000 cycles.
    Conclusions: The quantity and position of the specimens during firing influence the final color of porcelain-veneered zirconia, and firing one specimen per cycle improved the fatigue performance of the bilayer system.
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  • Pablo Soares Machado, Gabriel Kalil Rocha Pereira, Camila Pauleski Zuc ...
    Type: Original Article
    Article ID: JPOR_2019_553
    Published: 2021
    [Advance publication] Released: October 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This study evaluated the influence of different surface treatments of zirconia used to enhance bonding with veneering porcelain, and thermocycling on the resistance to porcelain cracking and delamination during fatigue test.
    Methods: Bilayer ceramic discs were made from zirconia blocks (IPS e.max Zircad MO, Ivoclar Vivadent – 0.7 mm thickness) and randomized into 8 groups (n= 15) according to two factors: ‘zirconia surface treatment’ (Control; Grinding – diamond bur; Air-abrasion – aluminum oxide particles; and Liner – application of a ceramic liner [IPS e.max Zirliner, Ivoclar Vivadent]); and ‘thermocycling’ (presence – 12,000 thermal cycles; 5-55ºC; or absence). The discs were veneered with porcelain (IPS e.max Ceram, Ivoclar Vivadent – 0.7 mm; totaling 1.4 mm thickness) according to ISO 6872:2015 for biaxial flexure strength testing. Fatigue tests (step-stress approach; 20 to 100 MPa; step of 10 MPa; 10,000 cycles per step; 10 Hz frequency) were run, followed by the data analysis (Kaplan-Meier and Mantel-Cox post-hoc tests). Analysis of roughness, topography, crystallographic phase arranges and fractography were also executed.
    Results: The surface treatment and thermocycling did not influence the porcelain crack nor delamination resistance. When only comparing the surface treatments for crack resistance outcome, the liner application depicted the worst fatigue performance in comparison to grinding and air-abrasion, while all groups were similar for delamination.
    Conclusions: Neither the surface treatment of the zirconia nor the thermocycling influences the porcelain crack resistance or the resistance to delamination of the bilayer porcelain-veneered zirconia specimens.
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  • Hao Ding, James Kit-Hon Tsoi, Chi-wai Kan, Jukka P. Matinlinna
    Type: Original article
    Article ID: JPR_D_20_00002
    Published: 2021
    [Advance publication] Released: October 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To seek a simple solution that can recycle and regenerate dental CAD/CAM zirconia green blanks from its waste residuals.
    Methods: Waste residuals (3M® Lava™ Plus HT) were pulverized after dry milling and cutting, and subsequently sieved before pickling in a 0.5 M nitric acid. These powders were then dry-pressed and pre-sintered into blocks at seven different temperatures in the range 800−1100 °C. New zirconia blocks flagged with the same batch numbers were used as control. These blocks were cut into bars before subjected them to manufacturer-recommended sintering at 1450 °C. Crystalline phases (by XRD), elemental compositions (by EDX), surface morphologies (by SEM), machinability, linear shrinkage rate, relative density, and Knoop microhardness were evaluated before and after sintering, and four-point flexural strengths were also evaluated for the sintered zirconia bars.
    Results: Only tetragonal phases were found in both pre- and fully-sintered recycled zirconia blocks. SEM results showed that pre-sintered samples at 950 °C had smooth and flat surfaces with evenly distributed particles. Recycled and control zirconia blocks had similar elemental compositions. Results from machined surface, linear shrinkage rate, relative density, and Knoop microhardness established that 950 °C and 1000 °C were suitable pre-sintering temperatures for recycling zirconia. Pre-sintered recycled zirconia had no significant differences in flexural strengths, however, samples pre-sintered at 1000 °C exhibited the closest value (897 MPa) compared to that of the control (904 MPa).
    Conclusions: Dental CAD/CAM zirconia can be recycled and reused from its waste residuals by adopting a simple method that requires a pre-sintering at 950 or 1000 °C.
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  • Nicola U. Zitzmann, Anja von Büren, Fabienne Glenz, Nadja Rohr, Tim Jo ...
    Type: Original Article
    Article ID: JPR_D_20_00014
    Published: 2021
    [Advance publication] Released: October 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The aim of this retrospective cohort study was to investigate the long-term outcome of metal- and all-ceramic resin-bonded fixed dental prosthesis (RBFDP) up to 17 years, and to evaluate potential factors influencing the risk for complications.
    Methods: Patients who were treated with RBFDP to replace teeth in the anterior or first premolar region in an university setting were identified from electronic records. Data collection comprised dental and periodontal parameters, periapical radiographs, and assessment of the RBFDP. Patient-reported satisfaction was evaluated on visual analog scales (VAS), and 5-year cumulative survival and success rates were calculated. Cox regression models were used to compare metal- versus all-ceramic RBFDPs.
    Results: Seventy-one patients with RBFDP replacing 65 anterior teeth and 6 premolars were included with a mean observation period of 56.1 (±42.7) months. RBFDP cumulative survival rate was 86.7% and cumulative success rate 71.7% after 5 years, with no significant difference between metal-and all-ceramic RBFDPs. The risk for RBFDP failure was significantly higher with more than one pontic (OR 6.1; p=0.033), or negative pulp vitality testing of abutments (OR 7.3; p=0.042), while complications tended to be increased with two-wings compared to one-wing RBFDP (OR 5.4; p=0.054).
    Conclusions: Metal- and all-ceramic RBFDPs facilitated good long-term results, particularly with one-wing, one-cantilever, and vital abutment teeth.
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  • Fumi Yoshioka, Shogo Ozawa, Ayumi Matsuoka, Jun Takebe
    Type: Original article
    Article ID: JPR_D_20_00015
    Published: 2021
    [Advance publication] Released: October 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: Patients with facial prostheses face challenges such as maintenance of the prosthesis in place, especially around the margins, because of movement of surrounding facial skin. Conventional facial prostheses are fabricated on stationary models based on two points: neutral expression and smiling expression. We developed four-dimensional (4D) facial expression models which shape facial expressions that change over several points in time using a morphing technique. We fabricated facial prostheses using 4D models and evaluated their accuracy and fit compared with prostheses generated with the two-expression technique.
    Methods: Seven patients with nasal defects or nasal deformities participated in this study. Facial expression morphing prostheses were fabricated based on the 4D scanned data of each patient, using five points between neutral expression (0%) and smiling (100%). Five nasal prostheses, one for each point, were evaluated in each patient objectively and subjectively for accuracy and fit.
    Results: On subjective evaluation, the nasal prostheses fabricated using the 4D facial expression models had better marginal sealing over the range from the neutral expression to smiling, and showed better attachment during facial movement on objective evaluation.
    Conclusions: Facial prostheses fabricated using 4D facial expression models provided better marginal sealing than those fabricated using conventional two-point modeling.
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  • Simonne Salazar, Yoko Hasegawa, Satsuki Kikuchi, Koh Kaneda, Hiroyuki ...
    Type: Original article
    Article ID: JPR_D_20_00045
    Published: 2021
    [Advance publication] Released: October 06, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This study investigated the impact of the renewal of a removable prosthesis on the masticatory function by subjective and objective measures and its variation among the types of occlusal support.
    Methods: Seventy-eight patients who received newly fabricated removable denture patients participated in this study. For the objective assessment, masticatory performance was measured using test gummy jelly. For the subjective assessment, standardized questionnaires about food acceptability and the oral health-related quality of life (OHRQoL) were used. Pre- and post-insertion assessments were performed for each subject. Subjects were divided into three groups according to their posterior occlusion: with posterior occlusion (w/PO), without posterior occlusion (w/o PO) and edentulous. Wilcoxon’s signed rank test was used to compare the pre- and post-treatment measurements of each assessment. The analysis of covariance and a multiple comparison were used to assess the effect of new dentures and differences due to occlusal support.
    Results: The masticatory performance, OHRQoL and food acceptability following prosthodontic treatment were significantly improved by new denture insertion. The masticatory performance among groups varied to a relative degree. The rate of masticatory performance improvement for edentulous subjects was twice that in w/PO subjects. The OHRQoL was significantly lower in the w/o PO and edentulous groups with old denture than patients w/PO. The food acceptability improved most markedly in the edentulous group.
    Conclusions: The improvement in the masticatory performance by new denture insertion varied among types of occlusal support. Re-establishing the occlusal support of edentulous patients may help restore their OHRQoL and improve food acceptability.
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  • Masanao Inokoshi, Kosuke Nozaki, Tomohiro Takagaki, Yohei Okazaki, Kum ...
    Type: Original Article
    Article ID: JPOR_2019_330
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To assess the degree of conversion (DC) of dual-curing composite cements when cured through ceramic-veneered zirconia disks.
    Methods: Portions of mixed cement, either G-CEM LinkForce (GC), Panavia V5 (Kuraray Noritake) or ResiCEM (Shofu), were placed on the ATR crystal of a Fourier Transform Infrared Spectroscope (FTIR; iS50, Thermo Scientific) and squeezed to a 100-µm film thickness using a microscopy cover glass. DC (%) of the composite cements applied in self-curing mode was measured in the dark at 37°C. Following the dual-curing mode, the cements were light-cured directly (positive control) or through a ceramic-veneered zirconia disk (0.5-mm thick zirconia with a 1.0-mm thick veneering ceramic) for 40 sec using two light-curing units (G-Light Prima 2, GC; PenCure, Morita). Per experimental group, 5 tests were conducted to measure DC in self-cure and dual-cure mode (n=5). FTIR spectra of the composite cement films were acquired to determine DC every min up to 30 min. DC of the composite cements was statistically compared using two-way repeated-measures ANOVA (α=0.05).
    Results:For all cements investigated, the self-curing mode resulted in significantly lower DC at 10, 20 and 30 min than the light-curing mode. When the composite cements were light-cured through the zirconia disk, DC at 30 min dropped significantly for ResiCem (Shofu), while not for Panavia V5 (Kuraray Noritake) and G-CEM LinkForce (GC).
    Conclusions: Self-curing slows down polymerization but does not reach for all composite cements the highest (light-cured) DC. Ceramic-veneered zirconia-based restorations may affect DC of some composite cements.
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  • Maximiliane Amelie Schlenz, Marianne Skroch, Alexander Schmidt, Peter ...
    Type: Original Article
    Article ID: JPOR_2019_466
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To investigate fatigue damage over time, monolithic posterior computer-aided-designed/computer-aided-manufactured (CAD/CAM) crowns were artificially aged in a mouth-motion-simulator, and damage was monitored with optical coherence tomography (OCT).
    Methods: Forty-eight crowns were milled of six different CAD/CAM-materials (n=8), including 3Y-TZP (Lava Plus,‘3Y’), 4Y-PSZ (Pritidentamultidisc,‘4Y’), 5Y-PSZ (Prettauanterior,‘5Y’), zirconia-reinforced lithium silicate (CeltraDuo,‘ZLS’), hybrid ceramic (Vita Enamic,‘VE’),and resin composite (BrilliantCrios,‘COM’), and were adhesively luted on CAD/CAM-milled human molars. Specimens were artificially aged in a mouth-motion-simulator (50-500N, 2Hz, 37°C) for a period of 1 million cycles. Before loading and every 250,000 cycles, the specimens were investigated with spectral domain (SD)-OCT (RS-3000). The maximum vertical and horizontal damage were measured with imaging-processing-software (ImageJ). After testing, the specimens were sliced and analysed via light microscope (Zeiss) to compare the new OCT method with the established light microscope method. Data were subjected to ANCOVA and 2x4-ANOVA.
    Results: No failure occurred during mouth-motion-simulation. However, all specimens (except for 3Y and 4Y) showed fatigue damage. There was a significant difference in the maximum damage between the CAD/CAM-materials (p<.05). ZLS exhibited the highest damage, followed by VE, COM and 5Y. While damage associated with 5Y was initially noticed after 750,000 cycles, all other materials already showed crack formation after 250,000 cycles. Furthermore, a linear increase in damage over time was noticed in all materials. Due to the shallow light penetration of OCT, damage in the outer area could only be visualized with light microscope.
    Conclusions: OCT is feasible for monitoring fatigue damage over time within different CAD/CAM-materials, particularly for subsurface damages.
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  • Milica Jovanović, Miloš Živić, Marko Milosavljević
    Type: Review Article
    Article ID: JPOR_2019_404
    Published: 2021
    [Advance publication] Released: September 26, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: A bioactive high performance polymer (BioHPP) and computer-aided design/computer-aided manufacturing (CAD/CAM) composite resin materials are a relatively new class of dental biomaterials, that are biocompatible and have good aesthetic features. In this review paper, we will summarize literature and publication data on the characteristics of the mentioned materials, as well as their potential application in the dental prosthetics.
    Study selection: Available studies and literature reviews from PubMed, SCIndex, Scopus and Google Scholar corresponding to polyetheretherketone (PEEK), high-performance polymers, reinforced composite materials, composite materials, resins, glass-fiber reinforced materials, CAD/CAM materials, dental implants, removable and fixed dental were reviewed.
    Results: To avoid many disadvantages of metals and their alloys in dental practice, such as inadequate color, high density, thermal conductivity and possible allergic reactions, materials based on polymers (such as BioHPP), and CAD/CAM composite resins are being developed. These materials have significantly better aesthetics and physical-mechanical properties. They are biocompatible materials that are lightweight, resistant, durable, exhibit high bending and compression resistance.
    Conclusions: The use of CAD/CAM composite resin materials and BioHPP in dentistry has begun recently, so the data about their potential clinical use are limited. Most of their features have been demonstrated through laboratory testing, while clinical studies are relatively scarce, so the need for further clinical trials is emphasized.
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  • Luciana Goguta, Diana Lungeanu, Radu Negru, Mihaela Birdeanu, Anca Jiv ...
    Type: Original article
    Article ID: JPOR_2019_556
    Published: 2021
    [Advance publication] Released: September 26, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This in vitro study aimed at ascertaining the retention forces for telescopic crowns fabricated with Selective Laser Manufacturing (SLM) and Selective Laser Sintering (SLS) additive technologies, and Computer Aided Design – Computer Aided Manufacturing (CAD–CAM) subtractive technology, by using suitable materials for each.
    Materials and Methods: Full-factorial design was employed for experimental testing, considering the following three factors: (a) inner crown material ‒ technology (zirconia ‒ CAD-CAM; metal-alloy ‒ SLS; metal-alloy ‒ SLM); (b) tooth type (canine or molar); (c) wet vs. dry conditions (i.e. either with or without artificial saliva). The roughness of the inner crowns was analyzed through atomic force microscopy. Three-way analysis of variance (ANOVA) was applied for statistical analysis, followed by Tukey's post-hoc comparisons between the crown types.
    Results: The retention force mean values were between 3.8 N (dry, SLM) and 14.8 N (artificial saliva, SLS), with statistically significant (p<0.001) differences between the three types of inner crowns and interaction with the tooth type. No significant interaction was found between crown or tooth types and the wet vs. dry testing conditions. The zirconia crowns' retention force was significantly (p<0.001) higher compared to similar SLM crowns, with 95% CI (3.62; 5.55) N for the differences. Zirconia was sig nificantly (p<0.001) less retentive compared to similar SLS crow ns, with 95% CI (-5.99; -4.06) N for the differences. The roughness decrease and subsequent loss of retention force was the largest in zirconia.
    Conclusions: The SLS inner crowns showed the best retention, followed by zirconia and SLM inner crows.
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  • Hatem M. El-Damanhoury, Nesrine A. Elsahn, Soumya Sheela, Maria D. Gai ...
    Type: Original article
    Article ID: JPOR_2020_50
    Published: 2021
    [Advance publication] Released: September 26, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the effect of Er:YAG laser on the roughness, surface topography, and bond strength to resin luting cement based on chemical and micro-abrasion pretreatments of different computer-aided design/computer-aided manufacturing materials.
    Methods: A polymer-infiltrated-ceramic-network (PICN) material (Vita Enamic, VE), three indirect resin composite (Cerasmart, CS; Shofu HC, SH; Lava Ultimate, LU), and one lithium disilicate ceramic (IPS e.max CAD, EM) blocks were subjected to one of the following pretreatments: no treatment (NC ), Er:YAG etching with one of two powers (either 3 or 6 W), hydrofluoric acid (HF) etching, self-etching ceramic primer (ME), or micro-abrasion (MA). The shear bond strength (SBS) of resin luting cement to pretreated materials was tested. Surface roughness was measured via atomic force microscopy, and surface topography was analyzed via scanning electron microscopy. Two-way analysis of variance, Tukey post-hoc test, and Pearson correlation were applied.
    Results: Etching EM and VE with HF or the ME resulted in the highest SBS values in their groups (P < 0.05). LU, SH, VE, and CS indicated similar SBS values when treated with 3 W, 6 W, and MA. The highest surface roughness (Sa ) values were obtained for the LU, CS, and VE groups when treated with 6 W, whereas the lowest Sa values were obtained for CS when treated with the ME and EM when treated with the ME or 3 W. Only SH and CS indicated a significant correlation between surface rough ness and bond strength.
    Conclusions: Er:YAG laser etching is comparable to micro-abrasion when treating resin composite blocks and may induce fewer surface cracks. HF etching remains the gold standard for the treatment of glass-based ceramics and PICNs.
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  • Kodai Hatta, Kazunori Ikebe
    Type: Review article
    Article ID: JPOR_2019_567
    Published: 2021
    [Advance publication] Released: September 15, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: Sarcopenia has recently been attracting attention as an early sign of the need for nursing care in older adults. Some studies have reported that oral health is related to sarcopenia and its diagnostic factors (hand grip strength, walking speed, and skeletal muscle mass). However, the relationship between oral health and sarcopenia remains poorly investigated and no review to date has compiled the available research on this relationship. The aim of this review was to summarize the current evidence describing the association between oral health and sarcopenia.
    Study selection: The internet database PubMed was searched using various combinations of related and synonymous keywords for “oral” or “dental” or “oral health” or “oral function” and “sarcopenia” or “walking speed” or “hand grip strength” or “skeletal muscle mass.” A total of 27 studies found to be eligible were critically evaluated and their key findings were summarized.
    Results: Most of the studies were cross-sectional and conducted in Japan. A wide range of oral factors, including number of teeth, occlusal support, periodontal state, occlusal force, mastication, tongue pressure, and swallowing, were covered. The overall findings were that oral health indices could be significantly associated with sarcopenia and its diagnostic factors.
    Conclusions: Relationships may exist between aspects of oral health and sarcopenia or its diagnostic factors. However, reports showing associations between oral health and sarcopenia are scarce, and definitive conclusions could not be drawn. Further longitudinal studies are necessary to confirm these relationships.
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  • Kairi Hayashi, Hiroshi Churei, Abhishekhi Shrestha, Tatsu Suzuki, Hisa ...
    Type: Case report
    Article ID: JPOR_2019_573
    Published: 2021
    [Advance publication] Released: September 15, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: Wearing a sports mouthguard is not only recommended in collision sports, such as American football, boxing, and rugby football, but also in low-contact sports, such as basketball, handball, and soccer. It is recommended to remove oral prosthetic devices while playing sports to avoid the risk of fracturing the device. However, players with maxillectomy must wear obturator-type prosthetic devices for speech, breathing, and deglutition even while playing sports. Therefore, there is a need for an oral appliance to prevent dental injury while playing sports without the risk of fracturing the device for players who have undergone maxillectomy.In this case, we fabricated and proposed overlay-type and obturator-type customized sports mouthguards for a patient who had undergone maxillectomy and assessments of satisfaction, speech intelligibility, nasopharyngeal closure function, and swallowing function while playing soccer.
    Results: The patient was only satisfied with the obturator-type mouthguard, and the results of the speech intelligibility, nasopharyngeal closure function, and swallowing tests using the obturator-type mouthguard showed no differences compared to those associated with the previously used prosthetic device.
    Conclusions: This case may help highlight the importance of providing obturator-type mouthguards for players who have undergone maxillectomy to prevent dental injury and physical and mental discomfort.
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  • Tomohito Nakagawa, Shintaro Tsuka, Fumiko Aonuma, Tomotaka Nodai, Taka ...
    Type: Original article
    Article ID: JPOR_2019_629
    Published: 2021
    [Advance publication] Released: September 15, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: In this study, we aimed to investigate the effect of glucose metabolism on bone healing after tooth extraction in an osteoporosis rat model administered zoledronic acid (ZA) and dexamethasone (DX).
    Methods: In total, 24 male Wistar rats (4 weeks old) were randomly assigned to four groups: Control (subcutaneous physiological saline), ZD (subcutaneous ZA and DX twice a week), Ins+ZD (subcutaneous insulin followed by ZD treatment), and Met+ZD (oral metformin followed by ZD treatment). Blood was collected every two weeks . Two weeks after treatment initiation, the first molar tooth on the right maxilla was extracted from all rats. Four weeks later, the rats were sacrificed, and bone healing was assessed. Maxillae samples were fixed and scanned using micro-computed tomography for quantifying areas of bone defects. Hematoxylin-eosin and tartrate-resistant acid phosphatase (TRAP) staining were performed to evaluate bone apoptosis and osteoclast number.
    Results: In all experimental groups, body weight was statistically lower than that in the Control group, with no changes observed in uncarboxylated osteocalcin concentrations. The radiological analysis revealed that insulin or metformin administration improved healing in the tooth extraction socket (p < 0.01). Histological examination revealed that the osteonecrosis area was reduced in the Ins+ZD and Met+ZD groups (p < 0.01). TRAP staining presented increased osteoclast numbers in the ZD group when compared with that observed in the Control.
    Conclusions: Tooth extraction with long-term ZA and DX administration inhibited bone remodeling and induced bisphosphonate-related osteonecrosis of the jaw-like lesions. Metformin exerted protective effects ag ainst osteonecrosis of the jaw.
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  • Akinori Tasaka, Haruna Okano, Takahiro Shimizu, Yoshimitsu Kato, Shizu ...
    Type: Original article
    Article ID: JPOR_2020_10
    Published: 2021
    [Advance publication] Released: September 15, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The purpose of this study was to investigate the accuracy of removable partial denture frameworks fabricated by 3D-printed pattern casting (AM-Cast) and selective laser sintering (SLS) under different co nditions with a reinforcement bar.
    Methods: A partially edentulous model was scanned with a dental laboratory scanner, and CAD software was used to design the framework. Reinforcement bars (n=0-2) were set on the lingual side of the framework. 3D scanning of the fabricated frameworks by AM-Cast and SLS was performed, and the obtained data were overlapped with the design data. The differences in shape among setting conditions of the bar were statistically compared using the Bonferroni method after the Kruskal–Wallis test.
    Results: The ranges in differences of the AM-Cast-0, AM-Cast-1, and AM-Cast-2 were -0.167 to 0.128 mm, -0.101 to 0.105 mm, and -0.185 to 0.015 mm, respectively. The ranges of SLS-0, SLS-1, and SLS-2 were -0.166 to 0.035 mm, -0.182 to 0.049 mm, and -0.138 to 0.038 mm, respectively. Large discrepancies were observed at the joining area of the lingual bar on the right side of the AM-Cast. A significant difference was found between the AM-Cast-0 and AM-Cast-1, and between the AM-Cast-0 and AM-Cast-2.
    Conclusions: The setting conditions of the reinforcement bar affected the accuracy of the lingual bar in the AM-Cast; however, no effect was observed on the displacement of the central area of the lingual bar in SLS. Setting a single reinforcing bar on the retentive latticework contributed to improving the accuracy of the lingual bar in the AM-Cast but not the displacement of the central area of the lingual bar in SLS.
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  • Shataer Awuti, Yuka I. Sumita, Mahmoud Elbashti, Shajidan Kelimu, Amel ...
    Type: Original article
    Article ID: JPOR_2019_326
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This study sought to geometrically evaluate the effect of a mandibular prosthesis on facial asymmetry in patients with one of two different types of mandibulectomy defect.
    Methods: Facial data from 20 participants (9 men and 11 women; mean age 68 years) with either a reconstructed segmental defect (segmental group,n = 10) or a marginal mandibulectomy defect (marginal group, n =10) were acquired with a non-contact three-dimensional (3D) digitizer. Facial asymmetry was evaluated by superimposing a facial scan onto its mirror scan using 3D evaluation software. Facial scans with and without the mandibular prosthesis in place were also superimposed to evaluate the effect of the mandibular prosthesis.
    Results: Facial asymmetry differed significantly between subjects with and without the prosthesis in the segmental group (P = 0.005) but not in the marginal group (P = 0.16). There was no significant difference in the effect of the prosthesis on facial appearance between the two groups (P = 0.052). The ratio of 3D deviation of facial asymmetry without the prosthesis and in the mirror scan with the prosthesis differed significantly between the two groups (P = 0.01).
    Conclusions: Placement of a mandibular prosthesis has a notable effect on facial asymmetry in patients with segmental mandibulectomy defects.
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  • Marcos Cezar Pomini, Adriana Postiglione Buhrer Samra, Amanda Regina F ...
    Type: Review article 
    Article ID: JPOR_2019_338
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To critically review the literature using mini-implants for prosthetic rehabilitation of growing patients and to analyze the survival rates and clinical behavior of mini-implants.
    Study Selection: Controlled clinical trials and case reports published in English, from January 2006 to October 2018, in a peer-reviewed journal in PubMed, Scopus, LILACS, and Cochrane Library databases. Studies using mini-implants for prosthetic rehabilitation in growing patients were included. Articles reporting mini-implants with a diameter greater than 3 mm, recruitment of adult participants, use of implants with other purposes than prosthodontic rehabilitation, and with a follow-up period shorter than 1 year, were excluded from the analysis. The selection was performed independently by two reviewers.
    Results: The selection resulted in the inclusion of eight articles. Although the studies presented heterogeneous protocols and follow-ups (varying from 1 to 8 years), only one case of failure was reported, which corresponded to crown displacement. All rehabilitation procedures were performed in the anterior region using mini-implants with different diameters (1.3-2.9 mm) and lengths (9-14 mm). The prosthetic rehabilitation included individual crowns and/or overdentures.
    Conclusions: Mini-implant prosthetic rehabilitation seems to be a viable and promising option for provisional rehabilitation of growing patients, since it seems to preserve the bone structure while restoring function and esthetics until growth ceases, when then mini-implants can be replaced by standard implants.
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  • Chauvel-Picard Julie, Korn Paula, Corbin Sara, Brosset Sophie, Bera Je ...
    Type: Original Article
    Article ID: JPOR_2019_345
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: Many studies have shown the ability of low intensity pulsed ultrasound (LIPUS) to stimulate the bone, cartilage and tendon regeneration but only a few studied LIPUS interest in the regeneration of the oral mucosa. The purpose of this study is to assess the ability of LIPUS to stimulate the regeneration of the palatal mucosa in a porcine model.
    Methods: Ten adults mini-pigs were used. Two mucosal wounds were realised on the left and right side of the palate of each pig. The right side was treated with LIPUS at 1 MHz of frequency and 300 mW/cm2 of acoustic intensity. The left side was not treated. The morphology of the wound was evaluated using a polymer silicone molding.
    Results: The difference between two sides was significant from day 7 with a p value < 0.0001. At day 21, the wound is completely healed on all pigs with LIPUS. The control soft tissue defect exposed a healing of 80%.
    Conclusions: The present study showed that the use of LIPUS on the oral mucosa accelerates the healing of the masticatory mucosa.
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  • Toshihito Takahashi, Kazunori Nozaki, Tomoya Gonda, Kazunori Ikebe
    Type: Original Article
    Article ID: JPOR_2019_354
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The purpose of this study was to develop a method for classifying dental arches using a convolutional neural network (CNN) as the first step in a system for designing removable partial dentures.
    Methods: Using 1184 images of dental arches (maxilla: 748 images; mandible: 436 images), arches were classified into four arch types: edentulous, intact dentition, arches with posterior tooth loss, and arches with bounded edentulous space. A CNN method to classify images was developed using Tensorflow and Keras deep learning libraries. After completion of the learning procedure, the diagnostic accuracy, precision, recall, F-measure and area under the curve (AUC) for each jaw were calculated for diagnostic performance of learning. The classification was also predicted using other images, and percentages of correct predictions (PCPs) were calculated. The PCPs were compared with the Kruskal-Wallis test (p = 0.05).
    Results: The diagnostic accuracy was 99.5% for the maxilla and 99.7% for the mandible. The precision, recall, and F-measure for both jaws were 0.25, 1.0 and 0.4, respectively. The AUC was 0.99 for the maxilla and 0.98 for the mandible. The PCPs of the classifications were more than 95% for all types of dental arch. There were no significant differences among the four types of dental arches in the mandible.
    Conclusions: The results of this study suggest that dental arches can be classified and predicted using a CNN. Future development of systems for designing removable partial dentures will be made possible using this and other AI technologies.
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  • Zheng Zheng, Xiaogang Ao, Peng Xie, Fan Jiang, Wenchuan Chen
    Type: Review Article
    Article ID: JPOR_2019_356
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The concept of biological width has been proposed and widely used in oral implantation. This review aimed to summarize the biological width around implant in detail.
    Study selection: An electronic search of the literature prior to March 2019 was performed to identify all articles related to biological width in periimplant soft tissue. The search was conducted in the MEDLINE (National Library of Medicine) database accessed through PubMed with no date restriction. The following main keywords were used: “implant”, “biological width”, “soft tissue”, “junctional epithelium”, “peri-implant epithelium”, “connective tissue”, “gingiva”, “mucosa” (connecting multiple keywords with AND, OR).
    Results: The identified researches focused on several aspects related to biological width in oral implantation, namely the concept, formation, remodeling, dimension, structure and function.
    Conclusions: Based on of the reviewed literature, the concept, formation, remodeling, structure, dimension, and functional significances of periimplant biological width are explored in this narrative review. The formation of biological width around implant is a complex process after several weeks of healing. The biological width around implant is a 3-4mm distance from the top of the peri-implant mucosa to the first bone-to-implant contact or the stabilized top of the adjacent bone, consisting of sulcular epithelium, junctional epithelium and fibrous connective tissue between the epithelium and the first bone-to-implant contact or the stabilized top of the adjacent bone. The biological width forms a biological barrier against the bacteria, influences the remodeling of soft and hard tissue around implant and has implications for clinical aspects of dental implantation.
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  • Manami Abe, Masahiro Wada, Yoshinobu Maeda, Kazunori Ikebe
    Type: Original Article
    Article ID: JPOR_2019_376
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The purpose of this study was to evaluate the occlusal force adjusting ability of implant-supported overdenture (IOD) wearers, as compared with natural teeth and complete dentures.
    Methods: Subjects were those with natural dentition (ND group; 19 subjects), those with implant-supported overdentures (IOD group; 7 subjects), and those with complete dentures (CD group; 14 subjects). Subjects were asked to hold test foods (peanuts and biscuits mounted on a custom-made apparatus with a force transducer) between their anterior incisors (hold phase) and split test foods (split phase). The mean value of the occlusal force during the hold phase (hold force), the peak force rate during the split phase (peak force rate), the time required to split test foods (duration), and the maximum occlusal force in the split phase (split force) were selected as outcomes. Data were analyzed with Wilcoxon’s signed rank test, the Kruskal-Wallis test, and multiple regression analysis (Statistical significance levels: 5%).
    Results: For peanuts, the peak force rate for the ND group was significantly higher than the IOD and CD groups. The duration of the CD group was significantly longer than the ND and IOD groups. Multiple regression analysis indicated that even with adjustment for age and sex, there were significant differences in the peak force rate between the ND and the IOD, CD groups, and in the duration between the ND and CD group.
    Conclusions: Subjects with IODs showed superior ability to adjust occlusal force, as compared with complete dentures, although it didn’t match the natural dentition.
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  • Alessandro Pozzi, Lorenzo Arcuri, Michael S. Block, Peter K. Moy
    Type: Technical procedure
    Article ID: JPOR_2019_386
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To introduce a digitally assisted technique to achieve the ideal soft and bone tissue interface for anatomic-driven pink free implant supported fixed prosthesis, and prefabricate an interim prosthesis to be used the day of the surgery as a prosthetic scaffold to condition the healing.
    Methods: The digital assisted soft tissue sculpturing (DASS) technique allows the previsualization of the ideal soft and bone tissue interface and fabricate a computer aided design computer aided manufacturing (CAD-CAM) anatomic-driven pink free complete arch interim prosthesis for the immediate loading. Bone and soft tissue interface as well as the interim prosthesis design are performed in a segmented multiple standard tessellation language (STL) file embedding the bone anatomy, the intraoral surface anatomy (dental and soft tissue), the digital wax-up and the implant positioning. The interim prosthesis is used as a prosthetic scaffold to guide the soft and bone tissue surgical sculpturing and regeneration.
    Conclusions: The DASS technique is a predictable integrated digital workflow that simplifies the achievement of a scalloped tissue interface for pink free fixed implant prosthesis, reestablishing the mucosal dimension required for the protection of underlying bone while maintaining tissue health. The surgical sculpturing and maturation of the soft and bone tissue is driven and enhanced by the xenogeneic collagen matrix grafting and prosthetic scaffold effect of the digitally prefabricated interim prosthesis delivered the day of the surgery.
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  • Takuya Shimomoto, Tamaki Nakano, Ayumi Shintani, Shinji Ono, Masaki In ...
    Type: Original Article
    Article ID: JPOR_2019_391
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This study investigated the relationship between peri-implant tissue health and the presence of keratinized mucosa (≥ 2 mm) using multivariate analysis.
    Methods: A total of 334 dental implants placed in 111 partially edentulous patients (34 males, 77 females) and restored with fixed prostheses were included in this study. The patients were recalled 12–146 months after completion of the prosthodontic treatment. Clinical parameters included modified plaque index (mPI), modified bleeding index (mBI), probing pocket depth (PPD), and radiographic bone loss (BL). The effects of the following potential explanatory variables on these parameters were analyzed: the presence of keratinized mucosa, age, sex, oral hygiene status, history of periodontitis, cigarette smoking, implant site, and time elapsed since prosthesis delivery. Statistical analysis included multivariate ordinal logistic regression and generalized estimating equations. Significance wa s established when two-sided p-values were less than 0.05.
    Results: The mPI, mBI, and PPD in the presence or absence of keratinized mucosa did not show statistically significant differences. However, the presence of keratinized mucosa was significantly related to BL (odds ratio 4.33, p < 0.01).
    Conclusions: The results of our study suggest that the presence of keratinized mucosa is useful for reducing bone resorption and can help to maintain peri-implant tissue health
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  • Julian Zacher, Robert Bauer, Step hanie Krifka, Martin Rosentritt
    Type: Original Article
    Article ID: JPOR_2019_403
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This study investigated the in-vitro performance of anterior implant-supported fixed dental prostheses (FDP). The effect of ceramics, fabrication, finalization and the presence of a screw-channel wa s investigated.
    Methods: Identical anterior ceramic FDPs (tooth 11-13; n=80) were milled (Lithiumdisilicate (LiSiCAD, emaxCAD, Ivoclar-Vivadent), Lithiumaluminiumsilicate (LiAlSi, experimental material) or pressed (Lithiumdisilicate (LiSiPress, emaxPress, Ivoclar-Vivadent), Lithiumsilicate (ZLS, CeltraPress, Dentsply Sirona). FDP-groups (n=8 per material and group) simulated a cemented or screw-retained approach. After cementation or screwing on titanium abutments, thermal cycling and mechanical loading (TCML) was performed on all restorations to mimic 5-year clinical performance. Performance and fracture force were determined and failures were analyzed. Statistics: (Kolmogorov-Smirnov-test, one-way-ANOVA; post-hoc-Bonferroni, multivariate-regression, α=0.05).
    Results: All FDPs survived TCML without aging, cracks, fractures or chipping. For FDPs without screw channel fracture values varied between with 839.8±112.3N (LiAlSi glazed) and 1485.9±232.6N (LiSiCAD). With screw channel, fracture results varied between 701.4±220.1N (LiALSi glazed) and 1516.3±253.7N (LiSipress). The type of material had a significant influence on the fracture results (LiSi>ZLS>LiAlSi; p≤0.012). Fabrication and finalization had no influence on the results. A screw channel did not significantly (p≥0.135) reduce the fracture force of the FDPs. Type of failure was mostly characterized by a fracture of the connector (LiSi, LiAlSi) or the abutment (ZLS, LiAlSi).
    Conclusions: FDPs survived TCML without failures indicating that the in vitro performance was not influenced by the tested parameters. Composition of ceramic material has significant influence on the fracture resistance of implant supported LiSi based FDPs. Screw channel, fabrication or finalization did not weaken the FDPs.
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  • Kenji Fueki, Yuka Inamochi, Eiko Yoshida-Kohno, Noriyuki Wakabayashi
    Type: Original Article
    Article ID: JPOR_2019_418
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The aim of this study was to compare the cost-effectiveness of thermoplastic resin removable partial dentures (TR-RPDs) with metal clasp-retained removable partial dentures (MC-RPDs), from the patients’ perspective.
    Methods: Patient-reported outcome measures (Oral health-related quality of life [OHRQoL], patient satisfaction, oral appearance) were assessed among 24 partially dentate subjects who completed a randomized crossover trial comparing TR-RPDs and MC-RPDs. The prosthetic treatment fee for patients was used as the direct cost. The cost of achieving a clinically minimum important difference (MID) in Oral Health Impact Profile (OHIP) summary score, and the incremental cost-effectiveness ratio (ICE R) for each outcome measure were determined.
    Results: OHRQoL, patient satisfaction, and oral appearance was rated higher with TR-RPDs compared to MC-RPDs. The median cost of achieving a MID in OHRQoL with TR-RPDs ($698) was 6.5 times higher than that with MC-RPDs ($107). The ICER was $67 for the OHIP summary score, $195 for the satisfaction score, and $1,169 for the oral appearance rating.
    Conclusions: Although TR-RPDs provide better OHRQoL, patient satisfaction, and oral appearance than MC-RPDs, the cost-effectiveness of TR-RPDs was inferior to MC-RPDs from the patients’ perspective.
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  • Elisa Zancanaro de Figueiredo, Gabriela de Souza Balbinot, Vicente Cas ...
    Type: Original Article
    Article ID: JPOR_2019_420
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To synthesize niobium silicate particles (SiNb) and incorporate into resin-based luting agents.
    Methods: SiNb particles were synthesized and characterized by x-ray diffraction, FTIR spectroscopy, particle size, and specific surface area. Luting agents were formulated with 50 wt% BisGMA, 30 wt% TEGDMA and 20 wt% UDMA. BAPO was used as a photoinitiator in 1mol%. The SiNb particles were incorporated into the agents at concentrations of 50 wt% (SiNb50%) or 65% wt% (SiNb65%). Barium glass particles at the same concentrations were used as controls (SiBa50% and SiBa65%). Refractive index, degree of conversion (DC), polymerization kinetics, softening in solvent, radiopacity, film thickness, color stability, flexural strength (FS) and micro shear bond strength (µSBS) were evaluated.
    Results: SiNb particles were successfully synthesized with an adequate structure to be applied as inorganic fillers. SiNb groups had higher DC, lower %ΔKHN, greater film thickness and greater radiopacity than the SiBa groups. Color stability was greater for SiNb50% and SiNb65% after six months of storage, as demonstrated by ΔE00. ΔWID values were lower for the SiBa groups. FS results decreased over time, and lower values were found for SiNb. In µSBS, the values of SiNb65% were higher at 24 h (45.22 MPa) and at six months (36.83 MPa), with statistically differences from values for the SiBa groups.
    Conclusions: SiNb particles were successfully synthesized using the sol-gel method, and their incorporation into luting agents at a concentration of up to 65% improved the physicomechanical characteristics and color stability of these agents.
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  • Hiroaki Shimizu, Hikaru Arakawa, Takuya Mino, Yoko Kurosaki, Kana Toku ...
    Type: Case report
    Article ID: JPOR_2019_429
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Patients: The patient was a 55-year-old woman with left upper molar free-end edentulism and 9 full cast metal crowns in her mouth. Three three-dimensional (3D) images were superimposed: a computed tomography (CT) image with the patient wearing the CT-matching template (CTMT) with six glass ceramic markers, which hardly generate any artifacts, on the template surface, and oral plaster model surfaces with and without CTMTs. Metal artifacts were automatically removed by a Boolean operation identifying unrealistic images outside the oral plaster model surface. After the preoperative simulation, fully guided oral implant surgery was performed. Two implant bodies were placed in the left upper edentulism. The placement errors calculated by comparing the preoperative simulation and actual implant placement were then assessed by a software program using the 3D-CT bone morphology as a reference. The 3D deviations between the preoperative simulation and actual placement at the entry of the implant body were a maximum 0.48 mm and minimum 0.26 mm. Those at the tip of the implant body were a maximum 0.56 mm and a minimum 0.25 mm.
    Discussion: In this case, the maximum 3D deviations at the entry and tip section were less than in previous studies using double CT.
    Conclusions: Accurate image fusion utilizing CTMT with new reference markers was possible for a patient with many metal restorations. Using a surgical guide manufactured by the new matching methodology (modified single CT scan method), implant placement deviation can be minimized in patients with many metal restorations.
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  • Yoshiaki Arai, Mutsumi Inanobe-Takatsuka, Makiko Takashima, Shin Ogawa ...
    Type: Original article
    Article ID: JPOR_2019_431
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The purpose of this study was to determine whether removing the superstructure of the implant bridge in cases of full-arch implant restorations for edentulous atrophic arches at the abutment level during professional mechanical plaque removal (PMPR) affects bacterial counts.
    Methods: This crossover clinical trial included 20 patients who received screw-retained prostheses at the abutment level. Patients were randomly assigned to two groups and received PMPR with or without removal of the superstructure. After a three-month washout period, the type of treatment was reversed between the groups. Bacterial counts around the cylinder and abutment were measured and compared before and after PMPR.
    Results: Bacterial numbers around the cylinder and abutment were significantly reduced after PMPR as compared with before PMPR regardless of whether the superstructure was removed (p <0.05). However the ratio of subjects with bacteria at 1.0 × 105 colony forming unit/ml (cfu/ml) or more after PMPR was significantly higher when the superstructure was not removed (p < 0.05). Among patients with bacterial counts of less than 10 × 105 cfu/ml, bacterial loads were reduced to less than 1.0 × 105 cfu/ml even when superstructures were not removed. Among patients with bacterial load of >10 × 105 cfu/ml, bacterial numbers were not reduced to <1.0 × 105 cfu/ml when PMPR was performed without removing the superstructure.
    Conclusions: Removal of the superstructure in cases of full-arch implant restorations for edentulous atrophic arches during PMPR reduces bacterial numbers around the implant bridge at the abutment level.
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  • Mengqi Liu, Lulu He, Hang Wang
    Type: Original Article
    Article ID: JPOR_2019_436
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The aim of this system review was to evaluate clinical and radiographic performance of one-piece implant (OPI) and two-piece implant (TPI).
    Methods: Electronic database searches were performed in MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and OpenGrey databases up to May 2019. Two authors individually screened the related literatures according to the inclusion and exclusion criteria. Main clinical outcomes included failure and complication rates. Radiographic outcomes were peri-implant bone loss between baseline and last available follow-up.
    Results: Finally, 11 articles reporting 10 different studies were included in this review. No statistically significant difference (P = 0.22) in risk of failure was found between the two types of implants (RR: 0.49, 95% CI: 0.16-1.53). Peri-implantitis accounted for most failures and complications and there was no statistically significant difference in risk of peri-implantitis no matter after 1 year follow-up (RR: 1.15, 95% CI: 0.37-3.53, P = 0.81) or at 2-3 years (RR: 1.95, 95% CI: 0.23-16.63, P = 0.54). With regard to the marginal bone loss (MBL) around implants, subgroup meta-analysis by platform switching versus platform matching showed a significant MBL-reducing effect for TPI when compared to OPI (WMD: 0.21mm, 95% CI: 0.07-0.36mm, P = 0.004) in the platform-switching subgroup, while no significant difference in MBL was observed between the two groups in the platform-matching subgroup (P = 0.67).
    Conclusions: The results of this review suggested that OPI and TPI showed similar short-term survival rates and incidences of complications. Nevertheless, TPI with platform switching may be a better option to reduce peri-implant bone loss.
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  • Eduardo Passos Rocha, Rodolfo Bruniera Anchieta, Regis Alexandre da Cu ...
    Type: Original Article
    Article ID: JPOR_2019_483
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the clinical outcomes of minimally invasive ceramic restorations executed by dentists with different levels of experience.
    Methods: Sixteen professionals were divided into 4 groups according to their experience levels. These included G1: up to 2 years since graduation, G2: 2-5 years, G3: 5-10 years, and G4: more than 10 years. All professionals were trained to follow the same standardized clinical protocol, but were unaware of the research objectives. A single evaluator followed the clinical treatments and recorded the complications and errors that occurred during the execution of the protocol. Ninety-one full crowns, 137 veneers, and 46 no-preparation veneers were prepared from lithium disilicate. Follow-ups were performed immediately and at 30, 180, and 360 days after the cementation and the evaluation based on the modified United States Public Health Service criteria. Ceramic chipping/fracture and debonding were considered failures. Fractures were replicated and submitted to fractographic analysis.
    Results: The highest number of failures were found in G1 followed by G3 and the lowest number of failures were found in G2. The level of success was 94% after 360 days. The fractographic analysis demonstrated the external surface of restorations as the critical area and suggested that failures might occur due to noncompliance with the clinical protocol. There was no correlation between professional experience and number of failures or patient satisfaction.
    Conclusions: Professional experience was not a decisive for patient satisfaction and success of minimally invasive ceramic restorations, and noncompliance with the clinical protocol was associated with early ceramic restoration failures.
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  • Yasmin Elashmawy, Waleed Elshahawy, Mohamed Seddik, Moustafa Abousheli ...
    Type: Original article
    Article ID: JPOR_2019_485
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This in vitro study aimed to evaluate the influence of fatigue loading on fracture resistance of endodontically treated molars restored with endocrowns using different machinable blocks.
    Methods: Endodontically treated mandibular first molars were prepared using a standardized method. Specimens were divided into 4 groups (n = 10).Anatomically shaped endocrowns groups were manufactured using VITA ENAMIC (VE) and KATANA Zirconia (KZ). Layered endocrowns groups were manufactured using IPS e.max CAD (EM) and BioHPP (BH). Half of the specimens of each group were subjected to fracture resistance test, while the other half were subjected to thermocycling and chewing simulation. After fatigue loading, specimens were loaded until failure. Specimens were examined using stereomicroscopy. Data were analyzed using ANOVA analysis of variance and Bonferroni post hoc test (α=0.05).
    Results: KZ group had the highest initial fracture resistance value (1810.20± 119.56 N) and BH had the lowest value (579.50± 76.15 N). The reduction of fracture resistance after fatigue loading was significant for KZ group (1588.30±216.25 N) and BH group (502.60±11.53 N) and non-significant to VE group (1101.70±77.05 N) and EM group (1112.10±74.12 N). Failure modes of KZ and EM groups showed high percentage of non-restorable fractures, while VE and BH groups showed high percentage of restorable fractures.
    Conclusions: Within the limitations of this study, the following can be concluded: Poly infiltrated ceramics should be considered as a proper material to be used as an endocrown material because of its ability to be restorable if failure occurred.
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  • Gerardo La Monaca, Nicola Pranno, Susanna Annibali, Cordaro Massimo, A ...
    Type: Review Article
    Article ID: JPOR_2019_494
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: This systematic review was performed to compare tooth, implant and prosthesis failures and biological and technical complications in toothimplant vs freestanding implant supported fixed partial prostheses, in order to evaluate the effectiveness and predictability in combining teeth and implants in the same fixed partial prosthesis.
    Study selection: A comprehensive and systematic literature research was conducted, according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement, to identify human trials, with a minimum sample size of 10 patients, comparing tooth-implant to freestanding implant supported fixed partial prostheses. Four groups of meta-analyses were performed based on the patients treated with toothimplant vs freestanding implant-supported fixed partial prostheses: abutment failures, biological and mechanical complications, prosthesis failures, and prosthetic (technical) complications.
    Results: The search yielded 749 records, after removal of duplicates. Based on the title assessment, the abstracts reading and the full-texts evaluation, 8 articles, published between 1999 and 2013, fulfilled the inclusion criteria and were included in the meta-analysis. The studies included were: 4 controlled clinical trials, 2 prospective and 2 retrospective cohort studies. The meta-analysis revealed no significant difference between tooth-implant and implant-implant supported fixed in the number of abutment (implant or tooth) failures, biological complications, prosthesis lost, and prosthetic complications.
    Conclusions: Within the limitations of the present systematic review, although the freestanding implant supported fixed partial prosthesis remains the first choice, joining teeth and implants to support fixed prosthesis in partially edentulous patients becomes a valid alternative with an acceptable success rate.
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  • Yuya Yoshida, Glenn Thomas Clark
    Type: Original Article
    Article ID: JPOR_2019_499
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The aim of this study was to compare and contrast the diagnostic accuracy of multiple online symptom checkers when used for the diagnosis of orofacial pain and oral medicine related disease vignettes. The comparison condition used in this study was the diagnostic accuracy achieved by advanced specialty residents on these same vignettes using a virtual patient system.
    Methods: 27 individual disease vignettes were utilized. These vignettes had a variety of orofacial pain and oral medicine diseases. Post graduate orofacial pain and oral medicine residents at our University of Southern California interacted with their randomly assigned virtual patients were analyzed [n=574]. Virtual patient accuracy was based on whether the user selected the primary diagnosis as one of their top four choices after interviewing. Eleven English-language symptom checkers accuracy was based on whether the vignettes produced the primary diagnosis as one of their top four choices. Using these data, symptom checker and virtual patient accuracy rates were calculated.
    Results: The primary diagnosis on virtual patient encounters was found within the top four choices a mean of 67.2% of the time. The primary diagnosis for the same vignettes entered into the 11 symptom checkers was found within the top four choices a mean of 5.9% of the time.
    Conclusions: The accuracy of currently available symptom checkers that patient might use for self-diagnosis of common orofacial pain and oral medicine diseases was low, this result suggest that the improved diagnostic algorithms are needed.
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  • Sebastian Franco-Tabares, Dariusz Wardecki, Keisuke Nakamura, Sina Ard ...
    Type: Original Article
    Article ID: JPOR_2019_524
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The purpose this study was to investigate the effect of Kern´s air-borne particle abrasion protocol (KAPA) and polishing on two translucent zirconias (4Y, 5Y-zirconias) compared to a traditional zirconia (3Y-zirconia).
    Methods: Two different surface treatments were analysed by X-ray diffraction (XRD) and interferometry 1) KAPA (0.1 MPa, 50 μm alumina, 10-12 mm distance, 15 sec and 30 sec and cleaning in ultrasound using isopropyl alcohol 99%) and 2) Clinical-delivery polishing paste (Zircon Brite, Dental Ventures, USA). Shear-bond strength tests (SBS’s) were performed with a highly polished and virtually flat surface in combination with a 10-MDP based cement and a surface modified by KAPA in combination with zinc phosphate cement. The SBS was expressed in terms of MPa.
    Results: The mean values for monoclinic content were 13 wt%, 7 wt% and 2 wt% for 3Y-, 4Y- and 5Y-zirconias respectively, no differences were found between 15 and 30 seconds. Polishing did not result in phase transformation to monoclinic phase in any of the zirconias. The rhombohedral phase was identified in all types of zirconias regardless of surface treatment. Shear-bond strength tests showed 5 MPa for polished/10-MDP based cement and 3 MPa for KAPA/ Zinc phosphate. Statistically significant differences were found between the two different surface treatments but not between the types of zirconias.
    Conclusions: KAPA for 15 sec seems to be equal to 30 sec regarding morphology and phase transformation. Sole micro-retention appears not to be fully responsible for the bonding phenomena of 10-MDP and zirconia that underwent KAPA.
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  • Kelynne Alcântara Brandão de Holanda, Ricardo Armini Caldas, Marina Am ...
    Type: Original article
    Article ID: JPOR_2019_527
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The present in silico study evaluated the behavior of titanium dental implants associated with abutments in zirconia and monotype zirconia implant using finite element analysis (FEA).
    Methods: A partial image of the anterior region of the maxilla was obtained by computed tomography. Three models of finite element were made using 3D modeling software (SolidWorks): Ti-Ti (control): implant morse cone (3.75 x 11mm; NobelActive) and titanium abutment (Esthetic Abutment); Ti-Zr: cone morse implant in titanium (3.75 x 11mm; NobelActive) and zirconia abutment (Procera Esthetic Abutment #9); Zr: monotype zirconia implant (4.1 x 12mm; Straumann Pure Ceramic). Computerized crowns of element 11 in lithium disilicate (IPS e.max Press, Ivoclar Vivadent) cemented in all groups were created. A load of 100N (45º) was applied simulating the excursion movement of the incisal guide. The von Mises, modified von Mises, maximum (tensile) and minimum (compression) principal stresses were obtained, compared and used for the quantitative and qualitative evaluation of the groups.
    Results: The Zr presented the lowest values of maximum, minimum, and von Mises tensions than the two pieces systems (Ti-Ti and Ti-Zr). Ti-Zr group had the highest values of tensions evaluated in this study.
    Conclusions : The type of material as well as the geometry of implant influenc ed the tension values evaluated.
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  • Merve Benli, Beril Eker Gümüş, Yusuf Kahraman, Özlem Yağcı, Duygu Erdo ...
    Type: Original Article
    Article ID: JPOR_2019_534
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: Polymers are used in dentistry on a daily basis due to their mechanical, functional and aesthetic properties. However, such biomaterials are subject to deterioration in the oral environment. Thus, this study aimed to evaluate the structural properties of five commonly used dental polymers to determine their best clinical indications.
    Methods: Four hundred-fifty samples of five dental polymers (polyethylenterephthalat - glycol modified (PG), polymethyl methacrylate (PA), ethylene vinyl acetate(E), polycarbonate (PC), polyetheretherketone (PK) were prepared to investigate their thermal, structural and chemical characteristics using energy dispersive spectroscopy (EDS), Fourier transform infrared analysis(FTIR), scanning electron microscopy (SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), X-ray diffraction(XRD), and Shore D hardness test. Data were analyzed using one-way ANOVA, Tukey’s HSD, and Levene’s tests (α=0.05).
    Results: PK (87.2) and PA (82.4) displayed the highest hardness values and smooth surfaces, as observed with SEM (p<0.001). Silica was detected in PK, PA, and E by EDS and XRD. The highest glass transition temperature was recorded for PC (145.00±2.00°C) and PK (143.00±1.87°C), while the lowest value was measured for E (50.00±2.12°C)(p<0.001).The highest mass loss was detected for PG (91.40±1.40%) by TGA.
    Conclusions: PA and PK polymers can be used for stress-containing treatments due to their mechanical properties. These two materials are also advantageous in terms of plaque accumulation as these polymers reveal smoother surfaces than other groups. Insufficient physical and thermal properties require the use of E with caution and only in limited clinical indications.
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  • Edmara T. P. Bergamo, Abbas Zahoui, Larissa Luri Amorin Ikejiri, Manoe ...
    Type: Original Article
    Article ID: JPOR_2019_537
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the influence of resin cement type, surface pretreatment and autoclave sterilization on the retention of Y-TZP crowns to Ti-base abutments.
    Methods: Y-TZP crowns were designed and milled to fit Ti-base abutments. Crowns were cemented using either a conventional resin cement (conventional) with a universal adhesive or a self-adhesive resin cement (self-adhesive), both following no surface pretreatment (No) or Ti-base abutment sandblasting (SB) (n=20/group). Half of the cemented samples were subjected to in-office autoclave sterilization. Pullout testing was performed in a universal testing machine at a speed of 1 mm/min until crown displacement. Data were statistically evaluated through a linear mixed model following post hoc comparisons by LSD test.
    Results: Pullout data as a function of cement type demonstrated higher retention for conventional relative to self-adhesive cement (p < 0.001). Ti-base sandblasting (SB) favored crown retentiveness over No pretreatment (p < 0.001). Sterilized crowns exhibited higher pullout values than non-sterile (p=0.036). All the two- and three-factor interaction analyses corroborated with the superior adhesive strength of conventional compared to self-adhesive cement (all, p < 0.011), as well as, SB relative to No pretreatment (all, p < 0.024). While autoclave sterilization maximized bond strength when self-adhesive cement (data collapsed over surface pretreatment, p < 0.050) and No pretreatment were evaluated (data collapsed over surface pretreatment, p < 0.013), no significant difference was observed for conventional resin cement (p=0.280) and SB (p=0.878) groups.
    Conclusions: Conventional resin cement and/or Ti-base sandblasting increased Y-TZP crown retentiveness, with no significant influence of autoclave sterilization. Autoclaving increased retentiveness when self-adhesive cement and/or no Ti-base pretreatment were used.
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  • Adamović Tijana, Veselinović Valentina, Trtić Nataša, Hadži-Mihailović ...
    Type: Original Article
    Article ID: JPOR_2019_581
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: Poly(methyl methacrylate) (PMMA) is the most commonly used material in the production of dental prostheses, and its application is often accompanied by the formation of biofilm. The aim of this work was the preparation of a PMMA/gold nanoparticles (AuNps) composite to improve the antimicrobial properties of heat-polymerised PMMA. The AuNPs were synthesised from gold (III) acetate by Ultrasonic Spray Pyrolysis (USP).In the present study, flexural strength and elastic modulus were investigated, as well as thermal conductivity, density and hardness of the PMMA/AuNps` nanocomposite, with different concentrations of AuNps. Flexural strength and elastic modulus were measured using a three-point bending test, and surface hardness was evaluated using the Vickers hardness test. The thermal conductivity of the samples was measured using the Transient Plane Source (TPS) technique. Density was determined by the pycnometry procedure. Statistical analysis was conducted on the data obtained from the experiments.
    Results: The flexural strength and elastic modulus of AuNps/PMMA nanocomposites decreased for all groups containing AuNps. Thermal conductivity and density increased in all groups containing AuNps compared to the control group, but it was not significant in all groups. Vickers hardness values increased significantly with an increase in AuNps` content, with the highest value 21.45 HV obtained at 0.74 wt% of AuNps. Statistical analysis was performed by means of the SPSS 19 software package.
    Conclusions: Incorporation of AuNps into heat-polymerised PMMA resin led to decrease of the flexural strength and elastic modulus. At the same time, the density, thermal conductivity and hardness increased.
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  • Beshr Hajhamid, Raheleh Mohammad Rahimi, David F. Bahr, Grace M. De So ...
    Type: Original article
    Article ID: JPOR_2019_592
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: To evaluate the effect of ionizing irradiation on human enamel and zirconia after chewing simulation.
    Methods: Twenty enamel and twenty translucent Yttria-stabilized zirconia (Y-PSZ) specimens were divided in 4 groups: Co (control) - no irradiation on enamel cusps/opposing zirconia slabs; E70 - irradiated (70 Gray) enamel cusps/opposing irradiated enamel slabs; Z70 - irradiated zirconia cusps/opposing irradiated zirconia slabs; EZ70 - irradiated enamel cusps/opposing irradiated zirconia slabs. Cusps were abraded against slabs in a chewing simulator (CS - one million cycles, 80 N, artificial saliva, 37˚C). Wear and roughness of zirconia and enamel were analyzed using a stylus profilometer. The abraded enamel was analyzed by Electron probe micro-analyzer (EPMA) and zirconia was characterized by nanoindentation and X-ray diffraction. One-way analysis of variance (ANOVA) and Tukey test were used for analysis of wear, Repeated Measures and Bonferroni test for roughness, and hardness and modulus values were compared using Wilcoxan Mann Whitney rank sum test (overall 5% significance).
    Results: Significantly higher volume loss was presented by cusps in the E70 group (p<0.001). Wear was similar between Co and EZ70 groups. There was no significant effect of irradiation on roughness of enamel or zirconia slabs (p=0.072). Irradiated Y-PSZ slabs had significantly higher hardness and modulus than non-irradiated ones and a 7% increase in m phase content was detected after irradiation.
    Conclusions: The opposing surface characteristics played a more significant role on enamel wear than did ionizing radiation. However, radiation affects Y-PSZ crystalline composition, hardness and modulus of elasticity.
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  • Shoko Miura, Shinobu Yamauchi, Shin Kasahara, Yusuke Katsuda, Masanori ...
    Type: Original Article
    Article ID: JPOR_2019_643
    Published: 2021
    [Advance publication] Released: September 09, 2020
    JOURNALS OPEN ACCESS ADVANCE PUBLICATION
    Purpose: The primary purpose of this study was to examine the clinical performance of monolithic zirconia single crowns in terms of short-term failure or complications. The secondary purpose was to detect the originating flaws of clinically failed monolithic zirconia crowns to find the causes of failure.
    Methods: A short-term prospective cohort study based on record evaluation and clinical examination of patients treated with tooth-supported monolithic zirconia crowns was performed in the Department of Fixed Prosthodontics, Tohoku University Hospital, Japan. The crowns were prepared during the follow-up period from April 2014 to July 2018. The 3.5-year cumulative success and survival rates were set as primary endpoints. Fractures of the crown or fragments were inspected under a scanning electron microscope for descriptive fractography.
    Results: During the study period, 40 monolithic zirconia crowns were placed. Four crowns experienced clinical complications, including: 1) fracture of the crown (two crowns), 2) abrasion of the crown (one crown), and 3) fracture of the antagonist tooth (one crown). The estimated Kaplan-Meier 3.5-year success and survival rates were 90.5% (95% confi dence interval [CI]: 73.1–97.1) and 92.8% (95% CI: 74.1–98.3), respectively. Fractography revealed that all fractures were initiated from the wear phase on the occlusal surface.
    Conclusions: The results of this study suggest that the molar application of monolithic zirconia crowns requires detailed attention to interocclusal clearance and the restoration of the antagonist tooth.
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