The aim of this study was to evaluate flexural strength, elastic modulus and dynamic mechanical analysis (DMA) of heat-polymerized polymethyl methacrylate resin, polyamide resin and glass fiber-reinforced polyamide resin. Materials and MethodsThree groups were determined according to denture base materials as polymethyl methacrylate resin (H), polyamide resin (P) and glass fiber reinforced polyamide resin (R). Sixteen specimens for each denture base material were prepared with dimensions of 64x10x3.3 mm for three-point bending test. Two specimens for each denture base material were prepared with dimensions of 30x10x3 mm for DMA. Polymethyl methacrylate and polyamide specimens were prepared according to the manufacturer's recommendations. The silane was applied to glass fibers (4.5 mm length) 2% by weight of the polyamide resin, they were placed in polyamide resin cartilages and injected to the mold. The thermal aging procedure was applied to half of specimens of each material (n=8). Flexural strength and elastic modulus of the specimens were determined by three-point bending test at a speed of 5 mm/ min. DMA was performed to 1 specimen from each group to evaluate viscoelastic properties. Data were analyzed with one-way ANOVA, Tukey and Paired t tests. ResultsA statistically significant difference was found in flexural strength and elastic modulus values of denture base materials (p=0.00). The highest flexural strength and elastic modulus values were observed in polymethyl methacrylate group. There was no significant difference between polyamide and glass-fiber reinforced polyamide groups (p=0.497). No significant difference was determined in all threedenture base materials before and after aging procedure. ConclusionThe reinforcement with glass-fibers did not affect the flexural strength and elastic modulus of polyamide resin.
Objective: The aim of this study was to evaluate and compare the microtensile bond strengths of four current adhesive materials that contain different monomers at deep and superficial dentin. Material and Methods: Forty non-carious human third molars (n = 5) were used in the study. Specimens were divided into two main groups according to dentin thickness as superficial and deep dentin. Groups were further divided into four subgroups in terms of the adhesive systems used: Nova Compo B Plus (NCBP), Nova Compo B (NCB), Futurabond M (FB) and Clearfil S3 Bond Plus (CS3). All specimens were bonded to resin composite and stored in 37 °C water for 9-months. Teeth were sectioned into 3 x 3 mm x 1mm thick beams. Microtensile bond strength test was carried out by using a universal testing device (1 mm/min). After fracture, failure types were observed using an optical microscope and the fractured dentin surfaces were observed by a scanning electron microscopy (SEM). One-way ANOVA and Tukey tests were used to compare the adhesive system in each dentin group. An unpaired T-test was used to compare the dentin thickness in each adhesive material. Results: As compared to deep dentin, superficial dentin showed higher µTBS values in groups NCBP, FB and CS, as opposed to group NCB. Only NCB revealed higher bond strength at deep dentin layers when compared to superficial dentin. In the superficial dentin group, NCBP showed the highest bond strength value, while NCB showed the lowest bond strength. In the deep dentin group, while NCB showed the highest bond strength value, NCBP revealed the lowest bond strength value after 9-months storage. While 4-META and 10-MDP monomer combination (NCBP) resulted in the highest bond strength value among the adhesive systems in the superficial dentin group, the monomer combination (NCB) resulted in the highest bond strength in deep dentin group. Conclusions: Microtensile bond strength performance are affected by both the type of monomer in the adhesive combination and the depth of the dentin. KEYWORDS Adhesive system; dentin thickness; hydrophobic monomer; microtensile bond strength; scanning electron microscopy.
Bu çalışmanın amacı, dört farklı yüzey bitirme metodunun ve yaşlandırma işleminin dental hibrit seramik materyalde yüzey pürüzlülüğü ve renk stabilitesi üzerine etkisinin değerlendirilmesidir. Gereç ve Yöntem: Hibrit seramik bloklar 12x14x1 mm boyutlarında hazırlandı ve örnekler yüzey bitirme metotlarına göre; teknisyen kitiyle polisaj (ET), klinik kitiyle polisaj (EC), kumlanan yüzeye sealant ajanı uygulama (ES) ve asitlenen yüzeye sealant ajanı uygulama (EA) olmak üzere 4 alt gruba ayrıldı (n=10). Renk parametreleri ve yüzey pürüzlülük değerleri ölçüldü. Tüm örneklere yaşlandırma işlemi uygulandı. Renk ve yüzey pürüzlülük değerleri tekrar ölçüldü. Renk değişim (ΔE) değerleri hesaplandı ve verilerin analizi Kruskal Wallis, Bonferroni Dunn ve Wilcoxon signed ranks testleri kullanılarak yapıldı. Her gruptan 2 örnekte Taramalı Elektron Mikroskobuyla (SEM) yüzey analizi yapıldı. Bulgular: Farklı yüzey bitirme işlemi uygulanan grupların ΔE değerleri arasında istatistiksel olarak anlamlı fark gözlenmedi. Yaşlandırma işlemi öncesi ve sonrasında, EA grubu en düşük yüzey pürüzlülük değerlerini gösterdi. Yaşlandırma işlemi sonrasında ES grubunun yüzey pürüzlülük değerleri yükseldi. Sonuç: Hibrit seramik materyalin renk stabilitesi yüzey bitirme metodundan etkilenmedi ve en düşük yüzey pürüzlülük değerleri asitlenmiş yüzeye sealant ajanı uygulanan grupta görüldü.
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