Purpose: The aim of this study was to assess oral health status and erosive tooth wear with related risk factors among Myanmar residents in Japan.

Materials and Methods: One hundred and five Myanmar volunteers who aged 20-64-year-old participated in this study. A cross-sectional epidemiological survey including a structured questionnaire and clinical oral examination was conducted in Tokyo, Japan in 2018.

Results: The prevalence of dental caries and periodontal disease of all participants were 68.5% and 82.9%, respectively. About two-third of participants (68.6%) had higher erosive scores (score 2-3). A significant difference was observed in missing teeth (p = 0.049) and erosive score (p = 0.001) by length of stay in Japan. Maxillary anterior teeth were most commonly affected by dental erosion, while the most severe erosive status was found only in mandibular posterior teeth. The participants who took pickled foods (p = 0.048), lime (p = 0.028), vinegar drinks (p < 0.001), and citrus juices (p = 0.003) almost every day were significantly higher erosive scores. Frequent consumption of acidic drinks was significantly related with dental erosion (p = 0.004). There were significant differences in heartburn (p = 0.024) and gastroesophageal reflux (p < 0.001) by erosive score. The participants who brushed their teeth with soft texture of toothbrush showed a significant lower erosive wear (p = 0.027).

Conclusion: Erosive tooth wear is a public health issue among Myanmar residents in Japan. Expansion of awareness on erosive tooth wear and dietary counselling would be necessary to improve the condition.

Purpose: To evaluate the influence of occlusal and axial tooth reduction on the fracture load of polyetheretherketone (PEEK) molar restorations after mechanical cycling (MC).

Materials and Methods: Occlusal and axial tooth reductions were defined to two-types with each, four-types of abutment tooth were prepared. Minimal occlusal reductions were 1.0-mm and 1.5-mm, and finishing lines were chamfer and deep-chamfer (1.0/C, 1.0/DC, 1.5/C, 1.5/DC). Four groups of PEEK restorations were duplicated. The thicknesses of restorations were same as each reduction. After cementation, one-half of the specimens were subjected to mechanical cycling (group MC); the others were stored without additional stress (group MC0). All specimens were loaded vertically until fracture. The maximum fracture loads were recorded and fracture modes were observed. Fracture loads were analyzed using Dunn’s test with Bonferroni correction (α = 0.05).

Results: There were no significant differences among specimens prepared the same way in groups MC0 and MC. In group MC, the fracture load of specimens with 1.0-mm occlusal reduction were significantly higher than that of 1.5-mm. The fracture loads of PEEK restorations in all preparations were higher than maximum occlusal forces and were not decreased after mechanical cycling.

Conclusion: The fracture loads of PEEK restorations in all preparations were higher than maximum occlusal forces and were not decreased after MC. Based on these results, PEEK restorations with less preparation can withstand long-term use in the oral environment.

Purpose: In this study, the influence of bentonite addition on the handling and physical properties of tricalcium silicate is comprehensively investigated.

Materials and Methods: Bentonite and tricalcium silicate powder were used in this study and 0, 10, 20, 30 wt% of bentonite added tricalcium silicate cements were prepared. Microstructural and morphological changes in tricalcium silicate cements are evaluated with X-ray diffraction and scanning electron microscopy. To evaluate the handling properties of the cement paste, flowability and injectability, as representative handling properties, are evaluated. The compressive strength and setting time are measured using the ISO-9917 methods.

Results: Our analysis shows that as the amount of added bentonite increases, both flowability and injectability improve significantly. Further, no significant difference is observed in the compressive strength and setting time after the bentonite addition.

Conclusion: Bentonite addition improves the handling properties of the tricalcium silicate paste without causing a significant deterioration in its physical properties. These results provide important information for the development of novel tricalcium silicate-based cements with enhanced properties.