Journal of Prosthodontic Research
Online ISSN : 1883-9207
Print ISSN : 1883-1958
ISSN-L : 1883-1958
Volume 67, Issue 1
Displaying 1-23 of 23 articles from this issue
Editorial
Guest Editorial
Letter to the Editor
Review articles
  • Adam Bzeu, Sarah-Jayne Campbell, Richard M Foxton, Sophie Watkins
    2023 Volume 67 Issue 1 Pages 4-11
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: February 21, 2022
    JOURNAL OPEN ACCESS

    Purpose This literature review aimed to investigate predictability of re-establishment of the occlusion following placement of restorations at an increased OVD, duration and to assess the quality of the available evidence.

    Methods An electronic search of articles using MEDLINE (1946-01/2019), EMBASE (1974-01/2019) and the Cochrane databases was undertaken. Search terms included dental restoration, vertical dimension and time. Studies involving placement of restorations at an increased OVD and recorded the time taken for the occlusion to re-establish were included. Eligibility assessments were carried out independently by two reviewers who also undertook independent extraction of predefined data fields, including study quality indicators.

    Results The search provided 61 results with 11 being relevant. A further 5 papers were identified for full text analysis. 4 papers used similar data from previous studies and 3 were excluded after full text assessment.. A final total of 9 papers were included in the review. It was indicated that the technique of placing restorations at an increased OVD appears to be clinically predictable in terms of re-establishment of occlusion and appears to occur most rapidly in younger patients.

    Conclusions The time taken for the occlusion to re-establish was between 15 days to 24 months. However, there is a need for prospective studies to evaluate the process in terms of success, predictive variables and specifically how long the process takes and this information would be helpful for both clinicians and patients, so that they know what to expect before embarking on a treatment.

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  • Takeru Kondo, Keiichi Kanayama, Hiroshi Egusa, Ichiro Nishimura
    2023 Volume 67 Issue 1 Pages 12-22
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: February 21, 2022
    JOURNAL OPEN ACCESS

    Purpose: Tooth extraction is a last resort treatment for resolving pathological complications of dentition induced by infection and injury. Although the extraction wound generally heals uneventfully, resulting in the formation of an edentulous residual ridge, some patients experience long-term and severe residual ridge reduction. The objective of this review was to provide a contemporary understanding of the molecular and cellular mechanisms that may potentially cause edentulous jawbone resorption.

    Study selection: Clinical, in vivo, and in vitro studies related to the characterization of and cellular and molecular mechanisms leading to residual ridge resorption.

    Results: The alveolar processes of the maxillary and mandibular bones uniquely juxtapose the gingival tissue. The gingival oral mucosa is an active barrier tissue that maintains homeostasis of the internal organs through its unique barrier immunity. Tooth extraction not only generates a bony socket but also injures oral barrier tissue. In response to wounding, the alveolar bone socket initiates regeneration and remodeling through coupled bone formation and osteoclastic resorption. Osteoclasts are also found on the external surface of the alveolar bone, interfacing the oral barrier tissue. Osteoclasts in the oral barrier region are not coupled with osteoblastic bone formation and often remain active long after the completion of wound healing, leading to a net decrease in the alveolar bone structure.

    Conclusions: The novel concept of oral barrier osteoclasts may provide important clues for future clinical strategies to maintain residual ridges for successful prosthodontic and restorative therapies.

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  • Donato Antonacci, Massimo Del fabbro, Patrizio Bollero, Michele Stocch ...
    2023 Volume 67 Issue 1 Pages 23-34
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: March 24, 2022
    JOURNAL OPEN ACCESS

    Purpose: There is no clinical consensus to determine the right balance between underpreparation and marginal bone level changes. The purpose of this systematic review and meta-regression was to investigate the influence of the type of drilling preparation of the implant site in relation to the bone mineral density on the clinical success, expressed in terms of the MBL and implant failure rate.

    Study Selection: A thorough search was performed using the digital databases MEDLINE PubMed, EMBASE, and Cochrane Central Register of Controlled Trials by entering research lines or various combinations of free words. The main keywords used were “dental implants”, “bone density”, and “torque”.

    Results: The mean bone resorption in the conventional preparation group was -0.43 (± 0.28) mm, whereas it was -0.80 (± 0.37) mm in the underprepared group. For the D1/D2/D3 bone group, the slope was significantly different from zero and linearity; the D4 bone group slope was not significantly different from zero and was almost parallel, although it was significantly different from linearity. The box and whiskers plot shows that the MBL in underprepared sites tended to be significantly higher with a higher variation than that in conventionally prepared sites.

    Conclusions: Within its limits, our meta-regression analysis showed that MBL is influenced by the type of drilling preparation and bone mineral density. In particular, a lower MBL was observed in the D1 bone with conventional preparation than with underpreparation. Moreover, a greater implant-to-osteotomy site mismatch was positively associated with greater MBLs in the bone densities of D1/D2/D3.

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  • Kevin Sheng-Kai Ma, Li-Tzu Wang, Markus B. Blatz
    2023 Volume 67 Issue 1 Pages 35-44
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: June 10, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    Purpose: The efficacy of etch-and-rinse, selective enamel-etching, and self-etching protocols for universal adhesives in follow-ups of over 12 months was compared in a network meta-analysis.

    Study selection: Randomized controlled trials (RCTs) published from 1998 to 2022 that compared marginal staining, marginal adaptation, retention and fractures, post-operative sensitivity, or recurrence of caries that took place over 12-months post-restoration were selected. A network meta-analysis determined the performance of each adhesive protocol.

    Results: After screening 981 articles, 16 RCTs were subjected to data extraction. Of which, 674 patients with 2816 restorations, were included in the network meta-analysis. The pooled risk of marginal discoloration following self-etching was significantly higher than that following etch-and-rinse at over 12, 24, and 36 months, which was time-dependent. The pooled risks of unfavorable marginal adaptation and unfavorable retention and fractures following self-etching were also significantly higher than that following etch-and-rinse, with the rates of unfavorable retention and fractures in non-carious cervical lesions increasing in a time-dependent manner. The pooled risks of marginal discoloration, unfavorable marginal adaptation, retention and fractures were similar between etch-and-rinse and selective enamel-etching protocols. Post-operative hypersensitivity and recurrence of caries were not significantly different among etch-and-rinse, selective enamel-etching, and self-etching protocols.

    Conclusions: In follow-ups over 12 months, esthetic and functional outcomes of restorations completed with an etch-and-rinse adhesive protocol were superior to the ones achieved with a self-etching strategy without selective enamel-etching. Selective enamel etching is recommended for self-etching systems. Biological responses were similar for all three adhesive strategies.

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  • Mohamed Alghauli, Ahmed Yaseen Alqutaibi, Sebastian Wille, Matthias Ke ...
    2023 Volume 67 Issue 1 Pages 45-54
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: May 12, 2022
    JOURNAL OPEN ACCESS

    Purpose: Various oral rehabilitation approaches are available for severely worn dentition. However, evidence-based guidelines for permanent treatment are limited. This review aims to investigate clinical observational findings and compare in-vitro outcomes of thin and ultrathin occlusal veneers using different materials and approaches.

    Methods: An electronic search of online databases, such as PubMed (MEDLINE), BioMed Central (BMC), Cochrane, and Scopus, was performed for the 2009 - Jun 2021 period, following the PRISMA 2020 criteria. The reports sought for retrieval were all the articles evaluating the clinical outcomes of permanent full-mouth rehabilitation, and all in-vitro records that investigated and compared fracture strength, survival rate, and modes of failure of ultrathin (0.3 - 0.6 mm), thin (0.5 - 0.8 mm), and thick (0.8-1.5 mm) occlusal veneer restorations, with regard to the available indirect restorative materials. The Newcastle Ottawa risk of bias criteria was used to judge the clinical studies and a modified consort statement was used for the evaluation of in-vitro studies. The data of the included studies were extracted and grouped based on the similarity of the outcomes and study protocols. Data heterogeneity determined the qualitative and quantitative grouping of the results.

    Results: Two clinical and 17 in-vitro studies were included. Data exhibited heterogeneity within the materials, variables, testing protocols and observation periods. Therefore, only qualitative synthesis of the results was feasible. Clinically used 1 mm lithium disilicate overlays and ultrathin one-step no-prep polymer infiltrated ceramic network (PICN) occlusal veneers exhibited very high success and survival rates. The analysis of in-vitro studies exhibited variable survival rates and fracture load values, based on materials, thickness, and restorative approaches used.

    Conclusions: Within the limitations of this systematic review, it can be concluded that the clinical outcomes of thin and ultrathin occlusal veneers/overlays are auspicious. In-vitro experimental results support the usage of the thin and ultrathin occlusal veneers.

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Original articles
  • Chunwoo Lee, Satoshi Yamaguchi, Satoshi Imazato
    2023 Volume 67 Issue 1 Pages 55-61
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: December 29, 2021
    JOURNAL OPEN ACCESS

    Purpose: Degradation of silane coupling layers by water ingress in computer-aided design/computer-aided manufacturing (CAD/CAM) of resin composites has been reported qualitatively. In this study, we quantitatively evaluated how water absorption of CAD/CAM resin composites affects the silane coupling layer by in vitro and in silico methods.

    Methods: A Katana Avencia block (KAB) and an experimental matrix block composed of only a matrix resin were used to evaluate the effect of water immersion for seven days on the elastic modulus. X-ray photoelectron spectroscopy (XPS) with fluorine-labeling of the KAB was performed to evaluate the atomic percentage of F1s, which represents the hydrolysis amount by water immersion. In silico analysis of the three-dimensional model of the KAB was performed to determine the coupling ratios before and after water immersion.

    Results: The elastic modulus of the KAB was 8.2 GPa before and 6.9 GPa after immersion in water. The atomic percentages of F1s in the after- and before-immersion groups were 14.31% and 11.52%, respectively, suggesting that hydrolysis of the silane coupling layer occurred during water immersion. From in silico analysis of the three-dimensional model of the KAB, the coupling ratio was predicted to be 78.2% before water immersion. After water immersion, the coupling ratio was predicted to be 68.4%.

    Conclusions: The in vitro and in silico approaches established in this study were able to predict the silane coupling ratios of CAD/CAM resin composites, and they showed that the silane coupling ratio decreased by water absorption.

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  • Masanori Iwasaki, Yuki Ohara, Keiko Motokawa, Misato Hayakawa, Maki Sh ...
    2023 Volume 67 Issue 1 Pages 62-69
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: January 27, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    Purpose: To establish age- and sex-specific population reference values for tongue pressure (TP) in community-dwelling Japanese older adults.

    Methods: For this analysis, we pooled four population-based studies on community-dwelling adults aged ≥65 years that measured TP using a JMS tongue pressure measuring device. We calculated the means and deciles of TP per 5-year age group for each sex. We also estimated age trends in TP for men and women.

    Results: In total, 5,083 individuals (2,150 men and 2,933 women, with a mean [standard deviation] age of 75.2 [6.5] years) were included in the present analysis. In male participants, the mean (standard deviation) TPs for ages 65–69, 70–74, 75–79, 80–84, and ≥85 years were 34.0 (8.4), 32.2 (8.1), 30.8 (8.3), 28.4 (8.9), and 24.4 (8.2) kPa, respectively. In female participants, the corresponding values were 31.5 (7.1), 30.5 (7.5), 29.6 (7.3), 28.4 (8.0), and 26.4 (7.6) kPa, respectively. For both sexes, there were significant declining trends in TP with advanced age. In addition, the interaction between age and sex had a significant effect on TP (regression coefficient [95% confidence interval] = -0.18 [-0.25 to -0.11] when age was modeled as a continuous variable and sex was modeled as a categorical variable [coded as 0=women, 1=men]).

    Conclusions: This study determined age- and sex-specific reference values for TP, presented as means and deciles, in community-dwelling Japanese older adults aged ≥65 years. This study also demonstrated sex differences in age-related declines in TP.

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  • Shinya Oishi, Wataru Komada, Ruri Tsukahara, Shu Yoshimatsu, Daiki Kon ...
    2023 Volume 67 Issue 1 Pages 70-76
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: March 04, 2022
    JOURNAL OPEN ACCESS

    Purpose: This study aimed to evaluate the surface strain at the cervical area of endodontically treated molars with a large pulp chamber restored using a composite resin core with three different types of core build-up systems.

    Methods: Reproduction models of human mandibular molars with prepared post spaces were used in this study. Roots duplicated with a composite resin were used as the experimental teeth. Three types of core build-up systems were used: composite resin core(RC), composite resin core with fiber posts (FC), and composite resin core with a prefabricated zirconia tube (ZC). Each group comprised eight specimens. Crowns made of yttria partially stabilized zirconia were cemented with dual-cure resin cement. Four strain gauges were attached to the surfaces of each specimen: the cervical area of the root and crown, on the buccal and lingual sides. The surface strain at each cervical area was measured using a static loading test and statistically analyzed.

    Results: In the case of static loading to the buccal cusp inner slope, ZC showed a significantly lower strain than RC in the crown on the buccal side and in the root and FC in the root. In the central fossa, ZC showed a significantly lower strain than FC in the root on the lingual side.

    Conclusions: The prefabricated zirconia tube reduced the surface strain at the cervical area of the buccal/lingual root in molars; however, the effect was small in the cervical area of the crown.

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  • Yoshihiro Akashi, Atsuhiro Nagasaki, Hiroko Okawa, Takuya Matsumoto, T ...
    2023 Volume 67 Issue 1 Pages 77-86
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: February 21, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    Purpose The involvement of oral mucosa cells in mechanical stress-induced bone resorption is unclear. The aim of this study was to investigate the effects of cyclic pressure-induced cytokines from oral mucosal cells (human gingival fibroblasts: hGFs) on osteoclast activity in vitro.

    Methods Cyclic pressure at 50 kPa, which represents high physiologic occlusal force of dentures on the molar area, was applied to hGFs. NFAT-reporter stable RAW264.7 preosteoclasts (NFAT/Luc-RAW cells) were cultured in conditioned medium collected from hGF cultures under cyclic pressure or static conditions. NFAT activity and osteoclast formation were determined by luciferase reporter assay and TRAP staining, respectively. Cyclic pressure-induced cytokines in hGF culture were detected by ELISA, real-time RT-PCR, and cytokine array analyses.

    Results Conditioned media from hGFs treated with 48 hours of cyclic pressure significantly induced NFAT activity and increased multinucleated osteoclast formation. Furthermore, the cyclic pressure significantly increased the bone resorption activity of RAW264.7 cells. Cyclic pressure significantly increased the expression of major inflammatory cytokines including IL-1β/IL-1β, IL-6/IL-6, IL-8/IL-8 and MCP-1/CCL2 in hGFs compared to hGFs cultured under static conditions, and it suppressed osteoprotegerin (OPG/OPG) expression. A cytokine array detected 12 cyclic pressure-induced candidates. Among them, IL-8, decorin, MCP-1 and ferritin increased, whereas IL-28A and PDGF-BB decreased, NFAT activation of NFAT/Luc-RAW cells.

    Conclusions These results suggest that cyclic pressure-induced cytokines from hGFs promote osteoclastogenesis, possibly including up-regulation of IL-1β, IL-6, IL-8 and MCP-1, and down-regulation of OPG. These findings introduce the possible involvement of GFs in mechanical stress-induced alveolar ridge resorption, such as in denture wearers.

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  • Manjin Zhang, Mariko Hattori, Masako Akiyama, Mahmoud E. Elbashti, Ron ...
    2023 Volume 67 Issue 1 Pages 87-92
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: April 05, 2022
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    Purpose: This study aimed to evaluate the stability of the surface of the maxillary teeth and mucosa in cleft lip and palate (CLP) patients with a maxilla defect or tissue deficiency according to the duration of observation and cleft type.

    Methods: Pairs of maxillary casts taken from 18 patients at different time points after prosthodontic treatment were investigated in this study. All 36 casts were scanned with an intraoral scanner, and the acquired images were saved in standard tesselation language (STL) files. The two STL files for each patient were then superimposed using three-dimensional (3D) evaluation software, with 3D deviations shown as a color map. Areas with a 3D deviation within ±0.100 mm were defined as stable. The influence of cleft type and duration of observation on the ratio of stable areas to the entire maxillary surface comprising the teeth and mucosa was investigated using multiple regression analysis. Statistical significance was set at p <0.05.

    Results: Multiple regression analysis showed that the duration of observation was significantly associated with the stable area ratio (B = -23.463, P<.001), whereas cleft type was not (β = 0.13, P = 0.301).

    Conclusions: The maxillary teeth and mucosa of CLP patients changed over time, with stable areas showing a negative correlation with the observation period. However, the stability of the dental arch was not significantly affected by the cleft type. 3D analysis of the casts of CLP patients allowed for measurements and to accurately assess relapse of the maxillary arch after prosthetic treatment.

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  • Raphael De souza, Carolina Chaves, Kimia Rohani, Sabrina Bouferguene, ...
    2022 Volume 67 Issue 1 Pages 93-102
    Published: 2022
    Released on J-STAGE: January 06, 2023
    Advance online publication: March 08, 2022
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    Supplementary material

    Purpose: To determine the effectiveness of palatal brushing in the treatment of denture-related erythematous stomatitis (DES) in complete denture wearers.

    Methods: This two-parallel-arm RCT was conducted in three university clinics in Brazil, Canada, and Chile. Participants (n=77) were randomly allocated to receive (i) instructions for palatal brushing and standard oral/denture hygiene (“intervention”); or (ii) standard oral/denture hygiene instructions only (“control”). Data collection was carried out at the baseline and at 3 and 6 months after intervention. Outcomes included the magnitude of oral Candida carriage and the degree of inflammation of denture-bearing tissues. Groups were compared using generalized estimating equations and chi-square test (α=0.05).

    Results: Palatal inflammation levels were reduced significantly in the “intervention” compared to “control” group at 6 months (intervention: 70%, control: 40%; chi-square, p=0.04). There was no between-group significant difference in the Candida count from denture and palatal biofilms; however, a subgroup analysis restricted to baseline Candida carriers showed further reduction with the intervention at 6 months. No adversity was observed by trialist or reported by participants.

    Conclusions: Including palatal brushing in oral instructions for denture wearers has positive impact on DES-related mucosal inflammation. Thus, our findings endorse the inclusion of palatal brushing in standard oral hygiene instructions to treat DES.

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  • Isis Almela Endo Hoshino, Paulo Henrique Dos santos, Andre Luiz Fraga ...
    2023 Volume 67 Issue 1 Pages 103-111
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: March 09, 2022
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    Purpose: The structural integrity of the resin cement layer, the bond strength, and the biomechanical behavior of different fiberglass post cementation techniques were evaluated.

    Methods: Thirty-three bovine incisors were divided into three groups (n = 11): conventional fiberglass post (CFP), conventional fiberglass post in flared root canals (CFL), and relined fiberglass post (RFP). Six specimens from each group were submitted for high-resolution microcomputed tomography (μCT) to evaluate the integrity and presence/volume of voids at the resin cement layer. Finite element analysis (FEA) of two three-dimensional (3D) models of each group were conducted, one considered ideal (without interface defects) and another containing the conditions identified in the μCT analysis. Push-out bond strength tests were conducted for all specimens.

    Results: The CFL group had the greatest mean values of void (Thirds cervical: 73.67; middle: 95.67; apical: 47.33) and gap concentration (Thirds cervical: 14.67; middle: 15.83; apical: 8.33) compared with CFP and RFP. A significant difference in bond strength was observed between the cervical (1.33 MPa) and middle thirds (1.85 MPa) compared with the apical third (4.85 MPa) of the CFL. A significant difference was observed in the bond strength in the CFL (1.33 MPa) and RFP (3.29 MPa) in the cervical third, which were statistically similar to the bond strength of the CFP. The tensile stress distributions were similar in most structures, localized in the cervical region on the lingual surface.

    Conclusions: Structural defects in the interface layer might influence the bond strength and biomechanical behavior under the different fiberglass post cementations.

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  • Swati Singh, Sunil Kumar Mishra, Ramesh Chowdhary
    2023 Volume 67 Issue 1 Pages 112-120
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: March 23, 2022
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    Purpose: The present study was done to assess patient satisfaction and crestal bone changes with one-piece and two-piece single implant-retained mandibular overdentures (SIMOs).

    Methods: The participants included in Group 1 (n=12) received one-piece SIMOs; the participants in Group 2 (n=12) received two-piece SIMOs.Scheduled follow-ups were done at 1 month and 1 year after implant placement. Patient satisfaction and crestal bone changes were evaluated. The data obtained were analyzed statistically with independent Student t-test.

    Results: Visual analogue scale (VAS) score for patient satisfaction with one-piece and two-piece SIMOs were statistically significant at 1-year of follow-up. The patient satisfaction level on the VAS score increased (38.1 to 51.1) with group one-piece SIMOs and two-piece SIMOs (36.6 to 46.8) at baseline to 1 month (P=0.13). The patient satisfaction level increased (38.1 to 56.6) with group one-piece SIMOs and two-piece SIMOs (36.6 to 52.2) at baseline to 1 year (P=0.03). At the 1 year follow-ups, group 1 had mean crestal bone loss of 0.80 ± 0.49 mm and group 2 had 1.24 ± 0.90 mm (P=0.16). Crestal bone loss was greater in the two-piece SIMOs group at 1 month and 1 year follow-ups, but statistically it was insignificant.

    Conclusions: One-piece SIMOs seemed to be a viable treatment option with increased patient satisfaction on a VAS. Crestal bone loss was greater in the patients with two-piece SIMOs during follow-up. One-piece SIMOs was comparatively simple with less invasive procedures and needed fewer components,so considerable number of patients requiring implant retained dentures could be benefited.

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  • Na-Eun Nam, Na-Kyung Hwangbo, Gan Jin, June-Sung Shim, Jong-Eun Kim
    2023 Volume 67 Issue 1 Pages 121-131
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: May 14, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    Purpose: The purpose of this study was to test heat-treatment methods for improving the cytocompatibility of dental 3D printable photopolymer resins.

    Methods: Nextdent C&B resin and a digital light processing 3D printer were used to print all specimens, which were divided into seven groups as follows: 1-month storage at controlled room temperature, 20 to 25 °C (RT), 24-hour storage at RT, 24-hour storage in RT water, 1-min immersion in 80 °C water, 1-min immersion in 100 °C water, 5-min immersion in 100 °C water, and autoclaving. Cell viability tests, cytotoxicity tests, and confocal laser scanning microscopy were performed to analyze the cytocompatibility of the 3D-printed resin. Fourier-transform infrared spectroscopy was performed after heat-treatment to determine the degree of conversion (DC).

    Results: Immersing printed resin samples in 100 °C water for 1 or 5 min after the curing process was an effective method for increasing cytocompatibility by inducing the preleaching of toxic substances such as unpolymerized monomers, photoinitiators, and additives. Moreover, the DC can be increased by additional polymerization without affecting the mechanical properties of the material.

    Conclusions: Immersing the printed photosensitive dental resins in 100 °C water for 5 min is a suitable method for increasing cytocompatibility and the DC.

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  • Yuya Komagata, Hiroshi Ikeda, Yuki Fujio, Yuki Nagamatsu, Hiroshi Shim ...
    2023 Volume 67 Issue 1 Pages 132-137
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: April 15, 2022
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    Purpose Hydrofluoric acid has been used to remove salivary contamination in dental glass-ceramics before bonding treatment. However, alternative methods are required because hydrofluoric acid is harmful. This study examined the cleaning effects of phosphoric acid and sodium hydroxide on glass-ceramics for bonding pre-treatment.

    Methods Feldspar porcelain was divided into four groups: (C) cleaned porcelain without any contamination, (S) porcelain contaminated with saliva, (SPA) porcelain cleaned with 37% phosphoric acid after saliva contamination, and (SSH) porcelain cleaned with 10% sodium hydroxide after saliva contamination. Each sample was bonded to the resin cement using a silane-containing primer. They were then subjected to a shear bond strength (SBS) test. Each surface was analyzed by scanning electron microscopy (SEM), contact angle measurements, and Fourier transform infrared spectroscopy (FT-IR).

    Results The SBS of group SSH was comparable to that of group C but significantly higher than that of groups S and SPA. SEM observations showed that saliva-like structures remained on the samples of groups S and SPA, but not on the SSH group. The contact angles of groups C and SSH were comparable and significantly smaller than those of groups S and SPA, respectively. FT-IR analysis also revealed saliva in groups S and SPA, which was absent in the SSH group.

    Conclusions The saliva remained on the porcelain even after cleaning with phosphoric acid, and SBS was not restored to the same level as before the contamination. In contrast, sodium hydroxide eliminated saliva and restored SBS to the same level as before contamination.

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  • Hang-Nga Mai, Jung-Suk Han, Hyeong-Seob Kim, Young-Seok Park, Ji-Man P ...
    2023 Volume 67 Issue 1 Pages 138-143
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: May 14, 2022
    JOURNAL OPEN ACCESS

    Purpose: This study aimed to investigate the accuracy of automatic tooth finish line registration compared to manual registration with regard to various finish line configurations and dental computer-aided design (CAD) software.

    Methods: Finish line registrations were performed on 15 digital tooth models with different finish line configurations (edge roundness radius = 0 mm, 0.2 mm, and 0.4 mm; edge angle = 30°, 60°, 90°, 120°, and 150°) using automatic and manual methods for designing virtual copings (N = 150). The discrepancies between the registered finish line extracted from the copings and the actual finish line segmented from the digitized tooth model were measured. Three-way analysis of variance (ANOVA) and post-hoc analyses with Bonferroni correction (α = 0.05) were used to analyze the results.

    Results: The finish line configurations, registration methods, and CAD software interacted with the accuracy of the registered finish line (p = 0.001). The automatic finish line registration method exhibited larger error values than the manual method, especially at high finish line edge roundness and obtuse edge angles for both EXOCAD and R2CAD software (p < 0.001). The difference in dental CAD software affected the registration accuracy in the automatic method (p < 0.001), but not in the manual method (p = 0.676).

    Conclusions: Finish line registration errors may occur when the automatic registration method is applied to the indistinct edge of tooth preparation. The accuracy of the automatic finish line registration could differ according to the CAD software program.

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  • Koudai Nagata, Koichiro Muromachi, Yusuke Kouzai, Keitaro Inaba, Erika ...
    2023 Volume 67 Issue 1 Pages 144-149
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: April 23, 2022
    JOURNAL OPEN ACCESS

    Purpose We considered the possibility of reducing industrial waste by fabricating and reusing dental models prepared using a fused deposition modeling (FDM) 3D printer and polylactic acid (PLA) filaments. The purpose of this study was to verify the accuracy of models fabricated using FDM and PLA.

    Methods The same provisional crown was used to check the marginal fit on PLA models prepared using an intraoral scanner (IOS) and FDM, plaster models made with silicone impression material and plaster, and resin models prepared using an IOS and stereolithography apparatus (SLA) 3D printer. The marginal fit was measured using micro-computed tomography at four points on the tooth: the buccal center (B), palatal center (P), mesial center (M), and distal center (D) points.

    Results At point B, the marginal gaps were 118 ± 21.7, 62 ± 16.4, and 50 ± 26.5 μm for the PLA, resin, and plaster models, respectively, with a significant difference between the PLA model and the other two. However, the marginal gap at all other measurement points was not significantly different between the models (P > 0.05).

    Conclusions We compared the accuracy of the models fabricated using the FDM, SLA, and conventional methods. The combination of FDM and PLA filaments showed no significant differences from the other models, except at point B, indicating its usefulness. Therefore, FDM and PLA may become necessary materials for dental treatment in the future.

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  • Haruto Hiraba, Hiroyasu Koizumi, Akihisa Kodaira, Kosuke Takehana, Tak ...
    2023 Volume 67 Issue 1 Pages 150-156
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: May 14, 2022
    JOURNAL OPEN ACCESS

    Purpose: To clarify the effect of a multi-purpose primer combining several functional monomers on two prosthodontic materials (cast titanium and a gold alloy) after airborne-particle abrasion.

    Methods: Disk-shaped adherends were prepared from cast titanium (CP Titanium JIS2) and a gold alloy (Casting Gold M.C. Type IV). A silane-containing two-liquid primer (M&C primer (MC)) and two silane-free single-liquid primers (Alloy Primer (AP) and V-Primer (VP)) were used as surface-treatment agents. The shear bond strengths were determined before and after thermocycling to evaluate the adhesive durability, and the results were compared using a non-parametric statistical analysis. The effect of airborne-particle abrasion with alumina on the titanium surface was analyzed by X-ray photoelectron spectroscopy (XPS).

    Results: There was no significant difference in bond strength between the MC and AP before and after thermocycling, whereas VP showed significantly lower values. XPS revealed that the titanium acquired hydrophilic properties after the airborne-particle abrasion.

    Conclusions: The novelty of this study is that it shows that the presence/absence of the silane had no effect on the bonding of cast titanium with an acrylic resin. The study also showed that the multi-purpose primer can be used without any problems with both cast titanium and gold alloy, in combination with airborne-particle abrasion with alumina.

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Technical procedure
  • Islam E. Ali, Takafumi Otomaru, Yuka Sumita
    2023 Volume 67 Issue 1 Pages 157-160
    Published: 2023
    Released on J-STAGE: January 06, 2023
    Advance online publication: February 19, 2022
    JOURNAL OPEN ACCESS

    Purpose: We aimed to introduce a simple method for refabrication of an implant-retained obturator using the denture duplication technique while retaining the custom abutments for a patient who underwent bilateral maxillectomy and reconstruction with a free fibula osteocutaneous flap. We have proposed this technique to facilitate the impression-making procedure for this extensive maxillary defect and to avoid lengthy and complicated laboratory procedures.

    Methods: A custom tray was developed by duplicating the fitting surface of an old obturator using silicone putty. The tray was used for a bite-pressure impression wherein both definitive impression and jaw relation were obtained simultaneously, reducing the time required for the placement of a new obturator.

    Conclusions: We used the denture duplication technique to refabricate an implant-retained obturator while retaining the custom abutments. Decreased chairside time, fewer visits, the use of easily available materials, and uncomplicated laboratory procedures make this technique more economical and acceptable for patients. Using this approach, the patient was able to use the old prosthesis until the delivery of the new prosthesis. The replacement obturator that was developed using this method maintained an acceptable level of oral function.

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