Background: Various treatment options are indicated for the restoration of teeth with mesio-occlusal-distal cavities. To minimize the formation of interfacial stresses, several clinical techniques have been suggested such as placement of stress absorbing intermediary layers and by changes in filler technology & monomer chemistry. Methods: Freshly extracted forty intact maxillary premolars (for orthodontic purpose) without caries were selected. Forty teeth were randomly divided into 4 groups of 10 teeth in each group. Group I (n=10) - CERAM X SPHERE TEC With SDR liner, Group II (n=10) - FILTEK Z 250 With SDR LINER, Group III (n=10) - CERAM X SPHERE TEC (2mm increments), Group IV (n=10)- FILTEK Z 250 (2mm increments).Standard MOD cavities were prepared and restored. These specimens were stored in distilled water at 25°C for 1 week. Specimens tested in a universal testing machine. Mean was calculated for each group. A One Way Analysis Of Variance (ANOVA) was used to compare the forces at which fracture occur between the study groups. Pair wise comparison of between the study groups was done using Tukey Post hoc test at a 95% significance level. Results: There was no statistically significant difference (p< 0.05) among all the groups. However the groups with SDR liner group-I (1.29), group-II (1.30) showed better performance when compared to groups without liner group-III (1.18), group-IV (1.185). Conclusion: Within the limitation of this in vitro study, it can be concluded that nanocomposite restoration with liner displayed fracture resistance values similar to incrementally placed nanocomposite without liner.
Key words: Nano hybrid composite, SDR, Fracture Resistance, Universal testing machine