Purpose: Evaluation of a new ceramic-based composite resin (nanohybridOrmocer)regarding;degree of conversion, polymerization shrinkage and diametral tensile strength.
Materials& methods:One microhybrid composite resin and two types of Ormocerswere used in the study; conventional Ormocer and nanohybridOrmocer. Following the manufacturers' instructions,thirty specimens were fabricated for each material.Ten specimens for each type were used in each test. For the degree of conversion test (DC),Fourier transform infrared spectroscopy (FTIR) was employed to measure DC. For the measurement ofpolymerization shrinkage, composite resins were adapted into a metallic mould and then photopolymerized. Scanning electron microscopy(1000×) was used to observe the gap formed between the resin and the mould.For the diametral tensile strength test, cylindrical samples were placed in a universal testing machine in which the compressive load is applied perpendicular to their long axes with a crosshead speed of1.0 mm/min. ANOVA test was used to compare between the 3 groups while, LSD test was used for in-between groups comparison at significant level (p ≤ 0.05).
Results:significant differences were found in both means DC (%) and diametral tensile strength (MPa) between microhybrid composite, Ormocer and nanohybridOrmocer. A significant difference was found between the means polymerization shrinkage (µm) of microhybrid composite and nanohybridOrmocer.
Conclusion: NanohybridOrmocer (Ceramic – based polymer) demonstrated significantly lower degree of conversion, polymerization shrinkage and diametral tensile strength in comparison to microhybrid composite.However, the decrease in polymerization shrinkage in comparison to Ormocer was non-significant.
Keywords: Microhybrid composite; Ormocer; NanohybridOrmocer; Degree of conversion; Polymerization shrinkage; Diametral tensile strength.