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.
The aim of this study was to evaluate the effect of different surface treatments on the shear bond strength (SBS) between metal orthodontic brackets and monolithic zirconia surfaces bonded with resin composite. Fifty monolithic zirconia (4Y-TZP) disks were sintered and glazed. Specimens were divided into five groups (n = 10) for different surface treatments: control, nano second fiber laser, sandblasting, grinding and tribochemical coating (CoJet Sand 30-μm). Metal orthodontic brackets were bonded to monolithic zirconia surface by two-component orthodontic adhesive. After 500 cycles of thermocycling, shear bond strength values were measured by a universal testing machine at a cross head speed of 0.5 mm/min. The data was recorded as MPa and statistically analyzed with One-way ANOVA, Levene’s LSD tests with Bonferroni corrections. The significance level was α = 0.05. The surface topography of one specimen of each group was evaluated by scanning electron microscopy (SEM). Statistically significant difference was observed among study groups (p = 0.018). The lowest shear bond strength was observed in the control group (3.92 ± 1.9). Tribochemical coating showed the highest bond strength (7.44 ± 2.9), which was statistically different from the control and nano second laser (4.3 ± 1.4) groups but not statistically different from grinding (6.15 ± 3.1) or sandblasting (6.47 ± 3.3). SEM images showed comprehensive results of each surface treatment on monolithic zirconia. All failure modes were recorded as adhesive between the composite resin and monolithic zirconia. Based on the findings of this study, it can be concluded that grinding, sandblasting and tribochemical coating techniques showed clinically acceptable bond strength within the range of 6–8 MPa. These surface treatments can be considered suitable for achieving a durable bond between metal orthodontic brackets and monolithic 4Y-TZP ceramic surfaces.
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.
Kaybedilen dişlerin protetik rehabilitasyonu için dental implantların kullanımı, günümüz diş hekimliğinde oldıukça sık kullanılan bir tedavi seçeneğidir. Ancak, bu tedavi protokolü uygulanırken oklüzyon prensiplerine dikkat edilmediğinde komplikasyonlar ve hatta implant kayıpları görülebilmektedir. İmplant destekli protezlerin başarısızlığında rol alan ana nedenlerden biri olan aşırı oklüzal kuvvetler, krestal kemik kaybıyla birlikte implant çevresinde anaerobik sulkus derinliğini arttırarak peri-implantitise neden olabilmektedir. Mekanik prensiplere uygun bir oklüzyon elde edilmesi, kuvvetlerin ağırlıklı olarak implant gövdesinin uzun ekseni boyunca yönlendirilmesi anlamına gelmektedir. Bu derlemede, oklüzal kuvvetlerin, dental implantları ve etrafındaki kemiği nasıl etkileyebileceği açıklanacak ve oluşabilecek komplikasyonlar hakkında bilgi verilerek, implant üstü protezlerin okluzal uyumlamaları hakkında klinik önerilerde bulunulacaktır.
Objective: The aim of this study was to evaluate the anxiety levels about education, clinical practice and professional development of dental PhD and specialty program students in Turkey during pandemic process. Methods: In this study, a scale consisting of two parts was developed by researchers and an online survey portal was used to reach the participants. The first part included personal information of participants. In the second part, there were 5-point scale items with three sub-dimensions to determine the anxiety levels about COVID-19. Item pool was constructed with 23 scale items. For the construct validity, exploratory factor analysis and confirmatory factor analysis was conducted. After the exploratory factor analysis, 3 items exluded from the scale and it resulted in three-factor structure. According to the theoretical background, factors were called as “clinical practice process”, "education process" and "professional development process". When the items related to the sub-dimensions were examined, it was seen that education process includes 8 items, clinical practice process includes 9 items and professional process includes 3 items. Then, this three-factor structure with 20 items by the way one factor model based on these three subfactors were tested through confirmatory factor analysis and higher order confirmatory factor analysis. After exploratory factor analysis and confirmatory factor analysis, it was concluded that there was enough evidence for the construct validity. For the reliability study Cronbach alfa coefficients and corrected item-total correlations was calculated. It was observed that the Cronbach alpha coefficients for the education process sub-dimension, the clinical practice process sub-dimension and the professional development process sub-dimension were 0.87, 0.86 and 0.70, respectively. The stratified Cronbach alpha coefficient calculated for the overall scale was 0.90. It was referred that the scores obtained from the sub-dimensions of the scale and by the way for general score were reliable. For the corrected item-total correlations, education process sub-dimension was in the range of 0.559-0.661, clinical practice sub-dimension was in the range of 0.407-0.812, and professional development process sub-dimension was in the range of 0.487-0.534. It was concluded that all items were sufficiently distinctive and served its purpose. Moreover the data based on the scale were analyzed with t-test and Kruskal Wallis H test. With the statistically significant results of Kruskal Wallis H test, Mann-Whitney U test were conducted as post hoc. Results: A total of 208 students (156 females, 52 males) participated. There was no significant difference among anxiety levels of the groups in terms of gender and department variables (p >0.05). However, there was statistically significant difference in terms of age and education year. The students with the ages in the interval of 22-24 had significantly lower anxiety levels regarding the clinical practice process (p
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