Evaluation of Marginal Gap and Fracture Resistance of Different CAD/CAM Blocks for Indirect Restorations of Mutilated Molar Teeth

Aim: To evaluate fracture resistance and vertical marginal gap in permanent molars restored with nano-ceramic hybrid CAD/CAM material (Grandio blocs) and reinforced composite CAD/CAM material (BRILLIANT Crios Block) compared to the IPS e.max ceramic Onlay restoration.Methods: Total of 36 cracks and caries-free human mandibular first molars, extracted for periodontal reasons, selected and randomly assigned into three groups (n= 12). Group (A1) received onlay restorations: Grandio blocks, Group (A2) onlay restorations: BRILLIANT Crios blocks and Group (A3) onlay restorations: IPS e.max ceramic. Teeth were mounted on Teflon molds; standardized cavities were prepared by CNC milling machine. Restorations were fabricated by Cerec in-Lab CAD/CAM and cemented after surface treatment using Theracem self-adhesive resin cement. Specimens were subjected to thermocycling (5000 cycles). Marginal gap was captured using CCD digital camera mounted on stereo microscope, fracture resistance was recorded using computer-controlled materials testing machine with a load of 5 kN. Results were analyzed statistically using student's "t" test. Level of significance was taken at P < 0.05.Results: Regarding vertical marginal gap, IPS e.max group recorded less marginal gap in all surfaces at different points showing statistically significant difference compared to hybrid composite groups (P<0.016). Regarding fracture resistance, IPS e.max group recorded slightly lower mean value when compared with hybrid composite groups, showing no statistically significant difference (P>0.05) between groups. Conclusion: The use of IPS e.max press or hybrid composite blocks in combination with adhesive technologies can lead to more conservative, economic, and esthetic approach in restoration of heavily compromised teeth.