Effect of Thermo-mechanical Cyclic Stresses on Flexural Strength of Two Aesthetic Restoratives with Modified Filler Systems

Abstract

Background: Numerous restorations have been used in dentistry to substitute the lost natural tooth structure. In attempts to improve the mechanical properties of glass ionomer, a nano-zirconia reinforced glass ionomer was introduced. The aim of the study was to compare the impact of cyclic stresses on flexural strength of two aesthetics restorative materials. Materials and methods: A nano-hybrid composite resin and a nano-zirconia reinforced glass ionomer were used in this study. A total of 80 specimens, 40 for each restorative were fabricated. In each group, 10 specimens were assigned for each aging condition as following; control, thermo-cyclic stresses, mechanical-cyclic stresses and combined thermomechanical cyclic stresses. Then the specimens were submitted to 3-point loading test using the Universal Testing Machine. Results: In all test conditions, nano-hybrid composite resin showed statistically significant higher mean flexural strength than nano-zirconia reinforced glass ionomer (61.1MPa SD ±17.3, 24.2 MPa SD ± 9.9 P-value <0.001). The control condition showed the highest statistically significant mean flexural strength (59.4 MPa SD± 26.8, P-value<0.001), while the combined condition showed the lowest statistically significant mean of flexural strength (29.7 MPa, SD±15.9, P-value <0.001). Conclusions: Nano-hybrid composite showed superior performance than zirconia reinforced glass ionomer when subjected to cyclic stresses; either thermal, mechanical or combined.

Effect of Two Different Aging Protocols on The Color and Translucency of Two Dental Resin Composite Materials

“…According to ÖZCAN M. et al, 2018, tests on the fatigue behavior of dental restorations have been conducted using cycles with very wide range of loading cycles where no specific number of cycles is agreed upon [30]. Therefore, the number of 6000 cycles for the mechanical aging protocol was chosen according to previous studies [31,32] where they are claimed to be equivalent to two weeks of intraoral service [33]. The directions of applied load were vertical and horizontal movements as it resembles the physiological chewing movements [34].…”