RESUMO
This study aimed to fabricate nano-hydroxyapatite (nHA) grafted/non-grafted E-glass-fiber-based (nHA/EG) and E-glass fiber (EG) orthodontic retainers and to compare their properties with commercially available retainers. Stainless-steel (SS) retainers and everStick Ortho (EST) were used as control groups. The retainers were evaluated with Raman spectroscopy and bonded to bovine teeth. The samples were fatigued under cyclic loading (120,000 cycles) followed by static load testing. The failure behavior was evaluated under an optical microscope and scanning electron microscope. The strain growth on the orthodontic retainers was assessed (48h and 168h) by an adhesion test using Staphylococcus aureus and Candida albicans. The characteristic peaks of resin and glass fibers were observed, and the debonding force results showed a significant difference among all of the groups. SS retainers showed the highest bonding force, whereas nHA/EG retainers showed a non-significant difference from EG and EST retainers. SS retainers' failure mode occurred mainly at the retainer-composite interface, while breakage occurred in glass-fiber-based retainers. The strains' adhesion to EST and EG was reduced with time. However, it was increased with nHA/EG. Fabrication of nHA/EG retainers was successfully achieved and showed better debonding force compared to other glass-fiber-based groups, whereas non-linear behavior was observed for the strains' adhesion.
RESUMO
AIM AND OBJECTIVE: The present study assessed the influence of Azadirachta indica (AI) powder on the mechanical, surface, and optical properties of heat-polymerized polymethyl methacrylate (PMMA) denture base material. MATERIALS AND METHODS: A total of 300 heat-polymerized PMMA acrylic resin specimens were fabricated with dimensions of 65 × 10 × 3.3 ± 0.01 mm for flexural strength, 50 × 6 × 4 ± 0.01 mm for impact strength testing, and 15 × 2 ± 0.01 mm for surface roughness, hardness, and translucency testing. The specimens were distributed into six groups (n = 10) based on AI powder concentration: An unmodified control group and AI powder-modified groups with 0.5, 1, 1.5, 2, and 2.5 wt% of acrylic resin powder. Universal testing machine was used to measure flexural strength and Charpy's impact tester for impact strength. Surface roughness, hardness, and translucency were assessed using a profilometer, Vicker hardness tester, and spectrophotometer, respectively. One-way analysis of variance (ANOVA) and posthoc Scheffe's test were utilized; p ≤ 0.05 was considered a statistically significant difference. RESULTS: ANOVA showed no significant differences in terms of impact strength (p = 0.175) and surface roughness (p = 0.371), while significant differences were detected in terms of flexural strength, hardness, and translucency (p = 0.001). According to post hoc Scheffe's test, there was a significant decrease in flexural strength for AI groups (p < 0.001) except 0.5% AI group (p = 0.66), while impact strength had no significant difference between AI groups (p = 0.175). Hardness had an insignificant difference between control and modified groups (p>0.05), with exception of 2.5% AI group (p = 0.001). For translucency, a significant difference was found between control and all modified groups (p<0.05). CONCLUSION: Incorporating AI powder into heat-polymerized denture base material did not significantly alter impact strength, surface roughness, or hardness, except at 2.5% AI concentration, where hardness decreased. On the contrary, flexural strength and translucency were significantly affected. CLINICAL SIGNIFICANCE: This study contributes to establishing a new approach for denture stomatitis disease treatment and prevention with the lowest adverse effect on denture properties.
