Purpose: Several studies reported better outcomes when restoring edentulous mandible with unsplinted IODs compared to CCDs; however, it is not clear if these outcomes remain when the full literature is considered. The aim of this systematic review is to compare conventional complete dentures (CCDs) to unsplinted implant-retained overdentures (IODs) with regard to efficacy, satisfaction and quality of life.

Study selection: The main question addressed was: How do CCDs compare to unsplinted IODs with regard to efficacy, satisfaction and quality of life? Three databases were electronically searched to identify articles comparing CCD to unsplinted IOD. Twenty-six articles were selected and reviewed in full. Of these selected articles, twenty-five compared CCDs restoring function in both arches to a maxillary CCD opposing a mandibular IOD retained by two unsplinted implants. Only one articles compared a maxillary CCDs to a maxillary IOD.

Results: Outcome measures varied among the studies, including the Oral Health Impact Profile (OHIP), visual analogue scales (VAS), and masticatory performance tests. Overall, IODs were associated with significantly better patient's masticatory performance and quality of life as indicated by Oral Health as Related to Quality of Life (OHRQoL). Mandibular unsplinted IODs were more likely than CCDs to be associated with improved OHRQoL for edentulous patients and were associated with significantly higher ratings of overall satisfaction, comfort, stability, ability to speak and ability to chew.

Conclusions: Results of this systematic review indicate the superiority of IODs retained by two unsplinted mandibular implants when compared to CCDs with regards to efficacy, satisfaction and quality of life.

Purpose: To evaluate the current status of all-ceramic inlay-retained fixed dental prostheses (CIR-FDPs) for the replacement of posterior teeth.

Study selection: Screening of titles and abstracts, full-text analysis for inclusion eligibility, quality assessment, data extraction and evaluation of the scientific evidence were performed independently by two reviewers. The electronic databases MEDLINE/PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and Compludoc were searched with no restriction to publication date or language. The quality of the studies was evaluated through: the original 'QDP' ('Questionnaire for selecting articles on Dental Prostheses') (for research papers); the 'Guidelines for managing overviews' of the Evidence-Based Medicine Working Group (for reviews); the Cochrane risk of bias tool; and the GRADE scale for grading scientific evidence.

Results: This review started with 4942 articles, which were narrowed down to 23 according to the selection criteria. The data was not statistically treated because of the heterogeneity of the studies. Zirconia-based CIR-FDPs may be recommended for restoring posterior single missing teeth, although the prosthesis/tooth bonded interface has yet to be improved. The addition of lateral wings to the classical inlay preparation seems promising. The weakest parts of CIR-FDPs are the connectors and retainers, while caries and endodontic problems are the most common biological complications. The fabrication of CIR-FDPs with monolithic zirconia may eliminate chipping problems.

Conclusions: A three-unit CIR-FDP is a viable treatment option for replacing a posterior missing tooth. Appropriate case selection,abutment preparation andluting procedures may be decisive for clinical success.

Purpose: The aim of this study was to evaluate fatigue resistance of dental fixtures with two different fixture-abutment connections by in vitro fatigue testing and in silico three-dimensional finite element analysis (3D FEA) using original computer-aided design (CAD) models.

Methods: Dental implant fixtures with external connection (EX) or internal connection (IN) abutments were fabricated from original CAD models using grade IV titanium and step-stress accelerated life testing was performed. Fatigue cycles and loads were assessed by Weibull analysis, and fatigue cracking was observed by micro-computed tomography and a stereomicroscope with high dynamic range software. Using the same CAD models, displacement vectors of implant components were also analyzed by 3D FEA. Angles of the fractured line occurring at fixture platforms in vitro and of displacement vectors corresponding to the fractured line in silico were compared by two-way ANOVA.

Results: Fatigue testing showed significantly greater reliability for IN than EX (p < 0.001). Fatigue crack initiation was primarily observed at implant fixture platforms. FEA demonstrated that crack lines of both implant systems in vitro were observed in the same direction as displacement vectors of the implant fixtures in silico.

Conclusions: In silico displacement vectors in the implant fixture are insightful for geometric development of dental implants to reduce complex interactions leading to fatigue failure.

Purpose: The purpose of this study was to investigate the color stability of a glass-fiber-reinforced thermoplastic (GFRTP), for use in non-metal clasp dentures (NMCDs).

Methods: GFRTPs composed of E-glass fibers and polypropylene with 2 mass% of pigments were fabricated using injection molding. According to our previous study on the optimum fiber content for GFRTPs, we prepared GFRTPs with fiber contents of 0, 10, and 20 mass% (GF0, GF10, and GF20). Commercially available NMCD and PMMA materials were used as controls. The color changes of GFRTPs at 24 h, and at 1, 2, and 4 weeks of coffee immersion at 37 °C were measured by colorimetry, using the Commission Internationale de l'Eclairage (CIE) Lab system. The color stabilities of the GFRTPs were evaluated in two units: the color difference (ΔE*) and National Bureau of Standards (NBS) units.

Results: After immersion, none of the GFRTPs showed visible color change. From the colorimetry measurement using the CIE Lab system, the ΔE* values of the GFRTPs were 0.65–2.45. The NBS values of the GFRTPs were 0.60–2.25, all lower than the threshold level of 3.0, demonstrating clinically acceptable color changes. On the other hand, an available polyamide-based NMCD material exhibited "appreciable" color change, as measured in NBS units.

Conclusions: The results indicate that the GFRTPs showed clinically acceptable color stability and might be satisfactory for clinical use. Therefore, GFRTPs are expected to become attractive materials for esthetic dentures.

Purpose: To investigate the strains around mini-dental implants (MDIs) and retromolar edentulous areas when using different numbers of MDIs in order to retain mandibular overdentures.

Materials and methods: Four different prosthetic situations were fabricated on an edentulous mandibular model including a complete denture (CD), and three overdentures, retained by four, three or two MDIs in the interforaminal region with retentive attachments. A static load of 200 N was applied on the posterior teeth of the dentures under bilateral or unilateral loading conditions. The strains at the mesial and distal of the MDIs and the retromolar edentulous ridges were measured using twelve strain gauges. Comparisons of the mean microstrains among all strain gauges in all situations were analyzed.

Results: The strain distribution determined during bilateral loading experienced a symmetrical distribution; while during unilateral loading, the recorded strains tended to change from compressive strains on the loaded side to tensile strains. Overall, the number of MDIs was found to be passively correlated to the generated compressive strain. The highest strains were recorded in the four MDIs followed by three, two MDIs retained overdenture and CD situations, respectively. The highest strain was found around the terminal MDI.

Conclusions: The use of a low number of MDIs tends to produce low strain values in the retromolar denture-bearing area and around the terminal MDIs during posterior loadings. However, when using a high number of MDIs, the overdenture tends to have more stability during function.

Purpose: The purposes of the present study were to examine the pressure transmission area and maximum pressure transmission of thermoplastic resin denture base materials under an impact load, and to evaluate the modulus of elasticity and nanohardness of thermoplastic resin denture base.

Methods: Three injection-molded thermoplastic resin denture base materials [polycarbonate (Basis PC), ethylene propylene (Duraflex), and polyamide (Valplast) ] and one conventional heat-polymerized acrylic resin (PMMA, SR Triplex Hot) denture base, all with a mandibular first molar acrylic resin denture tooth set in were evaluated (n = 6). Pressure transmission area and maximum pressure transmission of the specimens under an impact load were observed by using pressure-sensitive sheets. The modulus of elasticity and nanohardness of each denture base (n = 10) were measured on 15×15×15×3 mm³ specimen by using an ultramicroindentation system. The pressure transmission area, modulus of elasticity, and nanohardness data were statistically analyzed with 1-way ANOVA, followed by Tamhane or Tukey HSD post hoc test (a =.05). The maximum pressure transmission data were statistically analyzed with Kruskal–Wallis H test, followed by Mann–Whitney U test (a =.05).

Results: Polymethyl methacrylate showed significantly larger pressure transmission area and higher maximum pressure transmission than the other groups (P <.001). Significant differences were found in modulus of elasticity and nanohardness among the four types of denture bases (P <.001).

Conclusions: Pressure transmission area and maximum pressure transmission varied among the thermoplastic resin denture base materials. Differences in the modulus of elasticity and nanohardness of each type of denture base were demonstrated.

Purpose: The objective of the present study was to investigate the relationship between masticatory function-related factors (masticatory performance, occlusal contact area, maximum bite force, number of chewing strokes, and muscle activity) and the stress-relieving effects of chewing.

Methods: A total of 28 healthy male subjects were instructed to rest or chew for 10 min after 30 min of stress loading with arithmetic calculations. Their stress state was assessed by measuring salivary cortisol levels. Saliva was collected at three time points: before stress loading, immediately after stress loading, and 10 min after stress loading. Compared to resting, chewing produced a significantly greater reduction in the rate of change in salivary cortisol levels 10 min after stress loading.

Results: A negative correlation was observed between the rate of decrease in salivary cortisol levels and the number of chewing strokes. No significant correlation was observed between the rate of decrease in salivary cortisol levels and other measurement items.

Conclusion: In healthy dentulous people, the number of chewing strokes has been shown to be a masticatory function-related factor that affects stress relief from chewing, suggesting the possibility that more appropriate chewing would produce a greater effect psychological stress relief.

Purpose: To evaluate the marginal and internal gaps of cobalt–chromium (Co–Cr) alloy copings fabricated using subtractive and additive manufacturing.

Methods: A study model of an abutment tooth 46 was prepared by a 2-step silicone impression with dental stone. Fifteen stereolithography files for Co–Cr alloy copings were compiled using a model scanner and dental CAD software. Using the lost wax (LW), wax block (WB), soft metal block (SMB), microstereolithography (μ-SLA), and selected laser melting (SLM) techniques, 15 Co–Cr alloy copings were fabricated per group. The marginal and internal gaps of these Co–Cr alloy copings were measured using a digital microscope (160×), and the data obtained were analyzed using the non-parametric Kruskal–Wallis H-test and post-hoc Mann–Whitney U-test with Bonferroni correction.

Results: The mean values of the marginal, axial wall, and occlusal gaps were 91.8, 83.4, and 163 μm in the LW group; 94.2, 77.5, and 122 μm in the WB group; 60.0, 79.4, and 90.8 μm in the SMB group; 154, 72.4, and 258 μm in the μ-SLA group; and 239, 73.6, and 384 μm in the SLM group, respectively. The differences in the marginal and occlusal gaps between the 5 groups were statistically significant (P <.05).

Conclusions: The marginal gaps of the LW, WB, and SMB groups were within the clinically acceptable limit, but further improvements in the μ-SLA and SLM approaches may be required prior to clinical implementation.

Purpose: The purpose of this study was to determine the flexural strength and Weibull characteristics of different CAD/CAM materials after different in vitro aging conditions.

Methods: The specimens were randomly assigned to one of the six in vitro aging conditions: (1) water storage (37 °C, 3 weeks), (2) boiling water (24 h), (3) hydrochloric acid exposure (pH: 1.2, 24 h), (4) autoclave treatment (134 °C, 200 kPa, 12 h), (5) thermal cycling (5000 times, 5–55 °C), (6) cyclic loading (100N, 50,000 cycles). No treatment was applied to the specimens in control group. Three-point bending test was used for the calculation of flexural strength. The reliability of the strength was assessed by Weibull distribution. Surface roughness and topography was examined by coherence scanning interferometry. Evaluated parameters were compared using the Kruskall–Wallis or Mann–Whitney U test.

Results: Water storage, autoclave treatment and thermal cycling significantly decreased the flexural strength of all materials (p < 0.05), whereas HCl exposure or cyclic loading did not affect the properties (p > 0.05). Weibull moduli of Cerasmart™ and Lava™ Ultimate were similar with control. Vita Enamic^® exhibited similar Weibull moduli in all aging groups except the HCl treated group (p > 0.05). R_a values of Cerasmart™ and Lava™ Ultimate were in the range of 0.053–0.088 μm in the aged groups. However R_a results of Vita Enamic^® were larger than 0.2 μm.

Conclusions: Flexural strength of newly developed restorative CAD/CAM materials was significantly decreased by artificial aging. Cyclic loading or HCl exposure does not affect to the flexural strength and structural reliability of Cerasmart™ and Lava™ Ultimate.

Aim: This study assessed the effect of pretreatment of hybrid and glass ceramics using a self-etching primer on the shear bond strength (SBS) and surface topography, in comparison to pretreatment with hydrofluoric acid and silane.

Methods: 40 rectangular discs from each ceramic material (IPS e.max CAD;EM, Vita Mark II;VM, Vita Enamic;VE), were equally divided (n = 10) and assigned to one of four surface pretreatment methods; etching with 4.8% hydrofluoric acid followed by Monobond plus (HFMP), Monobond etch & prime (Ivoclar Vivadent) (MEP), No treatment (NT) as negative control and Monobond plus (Ivoclar Vivadent) with no etching (MP) as positive control. SBS of resin cement (Multilink-N, Ivoclar Vivadent) to ceramic surfaces was tested following a standard protocol. Surface roughness was evaluated using an Atomic force microscope (AFM). Surface topography and elemental analysis were analyzed using SEM/EDX. Data were analyzed with two-way analysis of variance (ANOVA) and post-hoc Bonferroni test at a significance level of α=0.05.

Results: Pretreatment with HFMP resulted in higher SBS and increased surface roughness in comparison to MEP and MP. Regardless the method of surface pretreatment, the mean SBS values of EM ceramic was significantly higher (p < 0.05) than those recorded for VM and VE, except when VE was treated with MEP, where the difference was statistically insignificant. Traces of fluoride ion were detected when MEP was used with VE and VM.

Conclusion: Under limited conditions, using MEP resulted in comparable SBS results to HFMP; meanwhile HFMP remains the gold standard for pretreatment of glass ceramics for resin-luting cementation.

Purpose: The objectives of this retrospective pilot study were: (1) to examine the occlusal properties (periodontal tactile sensation, occlusal force support ability, dynamic tooth mobility, occlusal force, contact area, preferred chewing side and main occluding area) of autotransplanted teeth with no clinical complications after transplantation (postoperative periods from 1 to 7 years).

Methods: Three groups were formed from 20 subjects (23 teeth in each group): autotransplanted teeth (ATP group), teeth contralateral to the recipient site (control group A), and teeth contralateral to the donor site (control group B).

Results: The tactile detection threshold of the ATP group was higher than both the control groups, and the individual occlusal force was significantly lower than control group A. The occlusal force ratio and the occlusal contact area ratio were significantly lower in the ATP group than in both control groups, while the mobility was similar in all groups. Eight out of 20 subjects chose the autotransplanted teeth side as the preferred chewing side. Especially when the recipient site was the first molar, the ATP of these subjects were included in the main occluding area. The pocket depth of the three groups was within the normal range.

Conclusions: These results demonstrate that teeth autotransplantation can achieve a mastication efficiency and periodontal condition similar to normal teeth; however, without proper healing, the periodontal sensation of autotransplanted teeth may be inferior to that of normal teeth (<250).

Purpose: The aim of this randomized placebo-controlled clinical study was to investigate the effects of a probiotic tablet containing Lactobacillus reuteri in peri-implantitis patients.

Methods: Subjects comprised 30 patients with mild to moderate peri-implantitis. A baseline clinical examination and microbiological assessment were conducted, followed by an antibiotics treatment (azithromycin, 500 mg, once a day for 3 days). Subjects were divided into probiotic and placebo groups. The clinical examination and bacterial sampling were performed 0, 4, 12 and 24 weeks after the intake of probiotics. The clinical examination included probing pocket depth (PPD), bleeding on probing (BOP), the modified plaque index (mPI), and modified bleeding index (mBI). The number of bacteria was assessed using the PCR-invader method. The Wilcoxon rank-sum test and Wilcoxon signed-rank test with Bonferroni corrections were used for data analyses.

Results: Although the number of bacteria decreased after the administration of azithromycin in both groups, they increased again thereafter. No significant difference was observed in bacterial numbers between the two groups. Although PPD in the probiotics group was significantly lower at 4 and 24 weeks than at 0 weeks (p < 0.05), a significant decrease did not occur in the placebo group. The mBI score at 24 weeks was significantly lower in the probiotics group than in the placebo group (p < 0.05). No significant difference was observed in BOP or mPI between the two groups.

Conclusion: These results suggested that probiotics prevent inflammation by affecting host responses rather than improving microbial flora in peri-implant sulci in peri-implantitis patients.

Purpose: This study evaluated the fracture strength and mode of failure of structurally compromised teeth with flared root canals restored using composite resin with four different systems.

Methods: Sixty endodontically treated bovine teeth were uniformly shaped to simulate human mandibular premolars with flared root canals. The roots were divided into four groups of 15 specimens each based on the type of restoration: composite resin core only (control), glass fiber post, cylindroid glass fiber ribbons, and glass fiber post and ribbons. All specimens were loaded until fracture occurred using a universal testing machine. Average fracture loads were compared with a one-way ANOVA and Tukey HSD test (α =.05). The modes of failure were observed and the Fisher exact test and Bonferroni correction were used for statistical analysis.

Results: The fiber post and ribbon group (1035.70 N) and the fiber ribbon group (881.77 N) showed significantly higher fracture strength than the controls (567.97 N) (p <.05). The fiber post and ribbon group also showed significantly higher fracture strength than the fiber post group (769.40 N). Almost all specimens showed unrestorable root fractures (p <.008). The control group had a significantly higher ratio of core sectional fractures (p <.017).

Conclusions: Cylindroid glass fiber ribbons significantly increased the fracture strength of the composite resin post and cores in the case of the dentin within the thin root canal wall. Based on the results, this study recommends the combined use of glass fiber post and ribbons.

Purpose: This study aimed to investigate the effect of sodium fluoride (NaF) on titanium corrosion using a biofilm model, taking environmental pH into account.

Methods:Streptococcus mutans cells were used as the artificial biofilm, and pH at the bacteria–titanium interface was monitored after the addition of 1% glucose with NaF (0, 225 or 900 ppm F) at 37 °C for 90 min. In an immersion test, the titanium samples were immersed in the NaF solution (0, 225 or 900 ppm F; pH 4.2 or 6.5) for 30 or 90 min. Before and after pH monitoring or immersion test, the electrochemical properties of the titanium surface were measured using a potentiostat. The amount of titanium eluted into the biofilm or the immersion solution was measured using inductively coupled plasma mass spectrometry. The color difference (ΔE*ab) and gloss of the titanium surface were determined using a spectrophotometer.

Results: After incubation with biofilm, pH was maintained at around 6.5 in the presence of NaF. There was no significant change in titanium surface and elution, regardless of the concentration of NaF. After immersion in 900 ppm NaF solution at pH 4.2, corrosive electrochemical change was induced on the surface, titanium elution and ΔE*ab were increased, and gloss was decreased.

Conclusions: NaF induces titanium corrosion in acidic environment in vitro, while NaF does not induce titanium corrosion under the biofilm because fluoride inhibits bacterial acid production. Neutral pH fluoridated agents may still be used to protect the remaining teeth, even when titanium-based prostheses are worn.

Purpose: We describe the characteristics of a new data-logger-type ultraminiature electromyogram (EMG) system (FLA-500-SD) and methods used for recording and we show its potential in clinical applications by presenting an example of a clinical case.

Method: FLA contains electrodes, an amplifier, 12-bit analog-to-digital (A/D) converter at a sampling frequency of 1 kHz,16-bit CPU, a 3.7-V coin-shaped lithium battery, and a micro SD card. The size of FLA is 37.0×23.5×8.6 mm, and its weight is 6 g (9 g with a battery inserted). The device is wearable and patients can attach the device and operate it by themselves in daily life. Data recorded in the micro SD card are transferred to a personal computer and analyzed.

Although the device is ultraminiature and wearable, it has the capacity for recording a precise and clear masseteric surface electromyogram that is not inferior to that recorded by conventional stationary-type EMG recording systems.

Conclusions: To our knowledge, the device is the smallest and lightest device with capacity for the longest consecutive measuring time as a data-logger-type electromyograph with built-in electrodes and memory. The device is useful for analyses of masseteric activity during the whole day. In the future, it is expected that applications of the device will expanded to observation, evaluation and diagnosis of normal or abnormal gnathic functions, e.g., assessment of sleep and awake bruxism and observation of the chewing state in daily life.

Patient: A 60-year-old man presented for refabrication of his maxillary complete denture. In this case, a digital process was chosen to replace the ill-fitted complete maxillary denture. A specialized scan retractor was used to retract the mobile tissues of the lips, cheeks and vestibule while taking a digital impression. The interocclusal record obtained in the patient's mouth was scanned in order to digitally register the occlusal vertical dimension. The denture base and teeth were designed on virtual models that were mounted at the occlusal vertical dimension, and were made using CAD/CAM technology.

Discussion: Unlike conventional impression techniques, intraoral scanning is not able to be performed while the tissue is moving. This case report used a scan retractor that facilitated stretching and fixation of the vestibular area. It also helped to retract the lips and cheeks. This report also demonstrates that virtual models at OVD can be obtained without the use of conventional stone models, flasking or processing techniques. One of the main shortcomings in the existing CAD/CAM denture fabrication technology is that it is not able to produce customized denture teeth. The present article demonstrates that the digital denture fabrication workflow can provide customized denture teeth to optimize occlusion.

Conclusion: This case demonstrated how digital complete dentures can be made without requiring conventional stone models or mounting the models in an articulator.