The resin nanoceramic Lava Ultimate can be used as a durable substitute for glass-ceramic chairside CAD/CAM material.

Objectives. To evaluate crosslink densities of two bulk fill composite resins and determine if the used Food Simulating Organic Solvent (FSOS) affected them. Methods. Forty specimens were prepared from SureFill and SonicFill bulk fill composite resins, 20 each. All specimens were stored dry for 24 h. Each group was divided into 2 subgroups: stored in ethanol (E) 75% or in methyl ethyl ketone (MEK) 100% for 24 h. Crosslink density was evaluated by calculating the difference between the Vickers hardness numbers of the specimens stored dry and after their storage in FSOS. The data were statistically analyzed using t-test. Results. The means of crosslink density in E and MEK were 6.99% and 9.44% for SureFill and 10.54% and 11.92% for SonicFill, respectively. t-test displayed significant differences between crosslink densities of SureFill and SonicFill: (P < 0.0001) in E and (P = 0.02) in MEK and between crosslink densities of SureFill in E and MEK (P = 0.02). Conclusions. Crosslink density of bulk fill composite resin can be evaluated using E or MEK. SureFill has higher crosslink density than SonicFill in both E and MEK.

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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.

Occlusal rest provides support for removable partial dentures (RPD). Rest seats are ideally prepared in enamel, but the abutment teeth might be restored or need restorations. This study compared the fracture strength of abutments restored with composite to amalgam restorations after rest seat preparation. Disto-occlusal cavities were prepared in 30 extracted human maxillary premolars. The specimens were allocated in three groups (n = 10) based on the type of restoration. All the specimens were exposed to thermomechanical aging followed by cycling loading. Fracture strength was tested using a universal testing machine, and then, the fracture mode was recorded. The data were analyzed using Kruskal–Wallis test with a significance level set at 0.05. The fracture mode was recorded as catastrophic or non-catastrophic. The fracture strength between all tested groups showed no significant difference. The highest and lowest fracture strength were recorded on amalgam and Tetric N-Ceram groups, respectively. Composite Tetric N-Ceram showed equal distribution of fracture sites on the restorative materials and teeth, it also displayed the highest number of non-catastrophic fractures unlike other groups where the fracture occurred more within the restorations. The fracture strength of composite was comparable to that of amalgam restorations with prepared rest seats.