Effect of Reinforcement on the Flexural Properties of Injection-Molded Thermoplastic Denture Base Resins.

PURPOSE: To evaluate the effect of reinforcement on the flexural properties of injection-molded thermoplastic denture base resins. MATERIALS AND METHODS: Three injection-molded thermoplastic denture base resins (polyamide, polyester, polycarbonate) were selected for this study, and a conventional heat-polymerized denture base resin (PMMA) was used as a control. Continuous unidirectional glass fiber-reinforced composite (FRC) and metal wire were used for reinforcement. Reinforced bar-shaped specimens (65 mm long, 10 mm wide, 3.3 mm high) were fabricated (n = 10). The flexural strength at the proportional limit (FS-PL) and the elastic modulus were measured using a three-point bending test. RESULTS: All the denture base material specimens reinforced with FRC possessed a significantly higher FS-PL compared to those without reinforcement. The FS-PL of the polycarbonate specimens reinforced with metal wire was significantly higher than that without reinforcement, and there was no significant difference in the FS-PL between the polycarbonate specimens reinforced with FRC and those with metal wire. The order of the elastic modulus according to the denture base material, arranged in terms of statistical significance, was as follows: PMMA (3.46 ± 0.53 GPa) > polycarbonate (2.69 ± 0.48 GPa) > polyester (2.00 ± 0.39 GPa) > polyamide (1.14 ± 0.35 GPa). The order of the elastic modulus according to the reinforcement, arranged in terms of statistical significance, was as follows: metal wire (2.74 ± 0.96 GPa) > FRC (2.40 ± 0.89 GPa) > no reinforcement (1.82 ± 0.83 GPa). CONCLUSION: Continuous unidirectional glass fiber-reinforced composite (FRC) reinforcement had a satisfactory reinforcing effect for the injection-molded thermoplastic denture base resins.

Leadership of school principals for school health implementation among primary schools in Mataram, Indonesia: a qualitative study.

BACKGROUND: Health-promoting schools (HPS) are acknowledged as a comprehensive approach to improving children's health and educational outcomes through learning and school life. Principals are key players in HPS implementation. However, concrete leadership practices in HPS in low- to middle-income countries have not been clarified. Therefore, this study aimed to explore and generate themes surrounding the leadership practices of principals in implementation of school health in Indonesia, a predominantly Muslim country consisting of diverse religions that have expanded HPS at the national level. METHODS: In-depth interviews and focus group discussions (FGDs) were conducted with the principals, teachers, parent representatives, and school board committee members in 10 target schools. FGDs were conducted with school health supervisory board members in Mataram City. All interviews were recorded and transcribed. Thematic analysis was undertaken to generate themes. RESULTS: The principals demonstrated leadership practices based on their religious beliefs, values, and morals. This may suggest that beliefs and morals support an understanding of their responsibility to ensure the well-being of all school community members, regardless of religion, in a diverse environment that is predominantly Muslim but also multicultural and multi-religious. Further, these beliefs and morals might reinforce implementation of school health. Importantly, the principals' coordination skills in cooperating with multiple sectors might contribute to successful implementation of school health. Also, principals emphasized they were tasked to develop capacity for implementation of school health. Thus, principals should understand leadership in the implementation of school health as their duty from the training stage to encourage health at the school level. CONCLUSION: In this study, "have professional educators' beliefs and religious beliefs and Indonesia's morals" was generated as a new theme, whereas several common themes were found as in previous studies. The results of this study suggested the importance of leadership by principals in the implementation of school health. Strengthening the capacity of school principals by integrating the contents of school health leadership practice into pre- and in-service training through the development of a policy on principals' duties in school health might contribute to the successful implementation of school health.

Teachers' conflicts in implementing comprehensive sexuality education: a qualitative systematic review and meta-synthesis.

INTRODUCTION: Comprehensive sexuality education (CSE) enables children and young people to learn about the cognitive, emotional, physical, and social characteristics of sexuality. Teachers experience conflicts in teaching CSE due to different cultural and religious backgrounds. This qualitative systematic review aimed to describe the conflicts experienced by teachers in the implementation of CSE in schools. Furthermore, this study aimed to identify the causes of conflict among teachers in implementing CSE. METHODS: This article focused on teachers' conflicts in implementing CSE from 2010 to 2022. Online bibliographic databases, such as PubMed, Web of Science, and ERIC, were used to search for relevant articles. The following search term was used: Teacher, Comprehensive Sexuality Education, and Conflict. RESULTS: A total of 11 studies were included in the review. All 11 studies were conducted in countries with a predominantly Christian population. The majority of the studies were conducted in Africa. The study respondents included teachers, school principals, and school coordinators. The studies identified that CSE implementation is related to multiple conflicts, depending on the context of the country. Five themes on the causes of conflict emerged from the thematic meta-synthesis: (1) Hesitancy in talking about sex education among teachers due to the cultural and religious context; (2) non-integration of traditional sex education into comprehensive sexuality education, (3) fostering effective facilitation of CSE among teachers, (4) determining the appropriate age to start sex education, and (5) roles of stakeholders outside the school. CONCLUSIONS: This qualitative systematic review and thematic meta-synthesis highlighted several conflicts among teachers in CSE implementation. Despite the teachers having a perception that sex education should be provided, traditional sex education has not yet transformed to CSE. The study findings also emphasize the need to identify the teacher's role in CSE implementation. The thematic meta-synthesis also strongly reflected the context of Christianity in Europe and Africa; thus, further research on the religious context in other regions is needed.

Effect of long-term water immersion or thermal shock on mechanical properties of high-impact acrylic denture base resins.

The purpose of this study was to investigate the effect of long-term water immersion or thermal shock on the mechanical properties of high-impact acrylic denture base resins. Two high-impact acrylic denture base resins were selected for the study. Specimens of each denture base material tested were fabricated according to the manufacturers' instructions (n=10). The flexural strength at the proportional limit, the elastic modulus and the impact strength of the specimens were evaluated. The flexural strength at the proportional limit of the high-impact acrylic denture base resins did not change after six months' water immersion or thermocycling 50,000 times. The elastic moduli of the high-impact acrylic denture base resins significantly increased after six months' water immersion or thermocycling 50,000 times. The impact strengths of the high-impact acrylic denture base resins significantly decreased after water immersion or thermocycling as described above.

Flexural strengths of reinforced denture base resins subjected to long-term water immersion.

Objective This study evaluated the flexural strengths of reinforced denture base resins subjected to long-term water immersion. Materials and methods Acrylic denture base resin reinforced with metal wire or glass fiber-reinforced composite (FRC), and without reinforcement were tested. Bar-shaped specimens were fabricated. Half of the specimens were stored in 37 °C distilled water for 50 hours (h), the other half were stored in 37 °C distilled water for 180 days (d) before testing. Ten specimens were fabricated per group for each reinforcement/water immersion period combination. The ultimate flexural strength and flexural strength at the proportional limit of reinforced denture base resin were tested. Results The 180 d bulk specimen possessed significantly lower ultimate flexural strength compared with the 50 h bulk specimen (p < 0.05). The ultimate flexural strength of the 50 h metal, 50 h FRC, 180 d metal and the 180 d FRC reinforcement specimens were not significantly different from each other (p > 0.05). The 180 d bulk specimen had a significantly lower flexural strength at the proportional limit compared to the 50 h bulk specimen. The 180 d reinforced specimens of metal and FRC were not significantly different from each of the 50 h specimens. Conclusion The flexural strengths of a reinforced denture base resin did not change after long-term water immersion.

Reinforcing effect of glass fiber-reinforced composite reinforcement on flexural strength at proportional limit of a repaired denture base resin.

Objective: This study evaluated the reinforcing effect of glass fiber-reinforced composite (FRC) reinforcement on flexural strength at the proportional limit (FS-PL) of a repaired denture base resin. Materials and methods: Repaired denture base resins reinforced with metal and with FRC reinforcement, and that without reinforcement were tested. The ultimate flexural strength, the FS-PL and the elastic modulus of repaired denture base resins were tested. The joint efficiency (times) of the repaired denture base resins on the intact denture base resin was evaluated. Results: The repaired denture base resins reinforced with metal reinforcement and with FRC reinforcement had significantly higher ultimate flexural strength than the repaired denture base resin without reinforcement (p < 0.05) and were not significantly different from each other (p > 0.05). The FS-PL of a repaired denture base resin reinforced with the FRC reinforcement was similar to that with the metal reinforcement (p > 0.05), and these were significantly higher than the FS-PL of a repaired denture base resin without reinforcement (p < 0.05). The elastic modulus of the repaired denture base resin reinforced with the FRC reinforcement was significantly lower than that with metal reinforcement (p < 0.05) and was significantly higher than that without reinforcement (p < 0.05). The joint efficiency of the FRC reinforced specimen was 0.98. Conclusion: The FRC reinforcement had a reinforcing effect on the FS-PL of a repaired denture base resin.

Effect of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin.

OBJECTIVES: The aim of this research was to investigate the effects of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin. METHODS: PMMA powder was applied after heat treatment at 100°C for 2h (code: HT100) or 130°C for 2h (code: HT130). The test specimens were fabricated from autopolymerizing resin to investigate the flexural properties of denture base resin cross-linked with methacrylated dendrimer, the surface microhardness of PMMA beads, and the thickness of the swollen layer of PMMA beads. The specimens were autopolymerized, and all specimens were stored in 37°C water for 24h. Half of the specimens were immersed in 37°C water for an additional 6 months (water storage period: 24h and 6 months). The flexural strength and flexural modulus (n=10/group) were measured with a three point bending test. Statistical analysis was performed using ANOVA and the Newman-Keuls test at a significance level of 0.05. RESULTS: Heat treatment and the water storage period had a significant effect on flexural strength. The flexural strength of HT130 showed significantly higher values than in other groups. The surface microhardness of PMMA beads of HT130 showed a significantly greater microhardness than other groups. The thickness of a swollen layer of PMMA beads of HT100 and HT130 was significantly decreased. CONCLUSIONS: The flexural strength and the surface microhardness were increased after heat treatment at 130°C. The thickness of a swollen layer of PMMA beads was decreased after heat treatment.