Ct Of Quartz-Tungsten-Halogen And Light-Emitting Diode-Curing Units On The Depth Of Cure And Flexural Strength Of A Nanohybrid Composite Resin: An In Vitro Study

Introduction: Over the years, the demand for esthetic dentistry has grown dramatically and there has been a rapid developmentof new adhesive restorative materials with nanotechnology that can restore the color and characteristics of natural tooth. Topolymerize these materials, light-curing dental materials extensively used are quartz-tungsten-halogen (QTH) and light-emittingdiode (LED)-curing units. Literature search revealed that depth of cure and flexural strength are the most important propertiesof composite resin materials, relevant to the clinical technique of incremental packing and curing.Purpose: The objectives of the present study were to evaluate and compare the depth of cure and flexural strength of ananohybrid composite resin.Materials and Methods: Two light-curing units were selected for this study: QTH (Bonart, Unicorn) and LED (Ivoclar Vivadent,Bluephase® N). The depth of cure was evaluated with scraping technique using digital caliper and flexural strength was evaluatedusing universal testing machine with a crosshead speed of 1 mm/min.Results: Descriptive statistics was employed to measure the mean and standard deviation of the depth of cure and flexuralstrength. Unpaired “t”-test was used to compare the study variables. Statistical significance was fixed at ≤0.05 and LED-curingunit showed significantly greater depth of cure and flexural strength when compared to QTH curing unit.Conclusion: Curing effectiveness of resin composite is dependent on the light-curing unit.

Effect Of Preheating On Surface Roughness And Microhardness Of A Nanohybrid Composite Resin - An In Vitro Study

Introduction: The success of dental composites in restorative dentistry stems from their good aesthetic properties andadequate durability. The clinical performance of composite resins is directly related to the degree of monomer conversion afterphoto polymerization. Placing composites at an elevated temperature reduce their viscosity and increase the efficiency ofpolymerization. Heating the composite prior to placement in the cavity increases monomer conversion rate and therefore theduration of the irradiation period may be reduced.Purpose of Study: Evaluate and compare effect of pre-heating on surface roughness and microhardness of nanohybrid compositeresin subjected to two different temperatures and two different durations using light emitting diode curing unit (LED LCU).Methods: Nanohybrid composite resin was tested at two temperatures (37°C and 55°C) and pre-heating of composite wasdone using incubator at two durations (10 and 20 minutes) respectively. Samples were injected into cylindrical Teflon molds andthe top surface of the specimens were polymerized using LED LCU for 40 s. After preservation for 24 h, specimens checkedfor surface roughness and Vickers hardness measurements. Statistical analysis were performed using one-way analysis ofvariance and Tukey post hoc test at a level of significance of P < 0.05 for both surface roughness and microhardness.Results: Pre-heating of composite affect on microhardness and did not influence on surface roughness.Conclusion: Pre-heating of resin composite increases microhardness and no significant effect on roughness.

Effect of protective coating on marginal integrity of nanohybrid composite during bleaching with carbamide peroxide: A microleakage study.

Aim: The aim of the study was to evaluate the microleakage on the marginal integrity of nanohybrid composite during bleaching with carbamide peroxide after applying a protective coating of G‑Coat plus (GC, Japan). Materials and Methods: Class V cavities were prepared and restored with nanohybrid composite restoration in 60 freshly extracted noncarious premolars extracted for orthodontic reasons. Then they were divided into 3 groups. Group 1 ‑ bleaching with carbamide peroxide without G coat plus (n = 20), Group 2 ‑ bleaching with carbamide peroxide with G‑Coat plus (n = 20), Group 3 ‑ without bleaching procedure (n = 20) (control group). In Group 2, G coat plus was applied over the restorative surface and margins. Then all teeth in Groups 1 and 2 were taken and mounted in dental stone. Bleaching trays were custom fabricated over the cast with the help of a heated vacuum‑forming machine. 10% carbamide peroxide (opalescence PF) was applied over the tooth, and the bleaching process was done for about 2 weeks. Then all samples underwent thermocycling and were then immersed in the 2% methylene blue solution for 24 h and observed under a stereomicroscope to evaluate the amount of dye penetration. Data were compared using Kruskal–Wallis test and Mann–Whitney test using SPSS Inc.; Chicago, IL, USA, Version 17.0. Results: Mann–Whitney test shows that the difference in microleakage between Group 1–Group 2 and Group 2–Group 3 is statistically significant (P < 0.05). Conclusion: Significant reduction in microleakage was seen in Group 2 when compared to other groups.

Comparative study of surface roughness between several finishing and polishing procedures on ormocer-based composite resin and nanohybrid composite resin / 대한치과보철학회지

STATEMENT OF PROBLEM: Proper finishing and polishing enhance both the esthetics and the longevity of restored teeth. Blade finishing technique would be suited for smoothing and finishing. Evaluation of this technique are necessary. PURPOSE: The purpose of this study was to evaluate the blade finishing and polishing procedures on the surface profile and roughness of ormocer-based composite resin and nanohybrid composite resin. MATERIAL AND METHODS: The material included a ormocer-based composite resin (Admira(R) & Admira(R) Flow); a nanohybrid composite resin (Grandio(R) & Grandio(R) Flow). One hundred forty specimens of each group were prepared using a mylar strip and randomly divied into blade finishing and rubber polishing groups (n=10). The average surface roughness (Ra) in micrometers was measured and the surface profile was examined by scanning electron microscopy (SEM) (Magnification X 200). The data were analyzed by Mann-Whitney Test at 0.05 significance level. CONCLUSION: The results of this study indicated that the mylar strip produced the smoothest surface on all materials and among the finishing-polishing methods was not significanct difference (P>0.05). Ormocer-based flowable composite resin performedthe lowest variability in initial surface roughness among the tested materials.