Comparative Fracture Resistance of Composite Veneered Polyether Ether Ketone Crowns with Ceramic and Composite Veneered Zirconia Crowns

Objectives: The objective of this study was to evaluate and compare the fracture resistance of Polyether ether ketone veneered composite crowns with composite and ceramic veneered zirconia crowns.
Material and Method: Thirty readly prepared ivory teeth of mandibular right first molar with standardized reduction of (1.5mm for occlusal reduction and 1.2mm for axial reduction with 6 degree convergence angle) with a circumferiential shoulder finish line with rounded angles were fitted in acrylic resin blocks. Full contoured crown wax pattern was made on the readly prepared ivory teeth using inlay wax, then a silicon index for the crown was made to standardize the crown and the veneering layer thickness for all groups. The prepared ivory teeth were scanned and crowns substructures were fabricated using the CADCAM milling process for different groups as follow, (G1): Zirconia substructure veneered with composite (n=10). )G2): Zirconia substructure veneered with ceramic (control group n=10). )G3): BIOHPP/PEEK substructure veneered with composite (n=10). Crowns of the three groups were stored in distilled water for 24 hours at 37℃, then subjected to thermocycling for 10,000 cycles (5-55ºC) with a 30-s dwell time, 20 seconds transfer time, then subjected to mechanical stressing in chewing simulator with maximum vertical load of 10 kg with cyclic frequency of 1.7 Hz for 240,000 cycles, load was applied occlusally with a custom-made load applicator [steel rod with flat tip (20x25mm) attached to the upper movable compartment of the machine. Crowns fracture resistance were tested using the universal testing machine by applying a load with a 4.2 mm diameter steel ball at a crosshead speed of 1 mm/min occlusally in the middle of the crown central fossa and the maximum load causing crown fracture was recorded in newton.
Results: One-way ANOVA test showed a high statistically significant difference (F=, 17.404, P <0.001) between different studied group as regard fracture resistance with the highest mean value was recorded for crowns fabricated with PEEK frame work veneered with composite crowns.
Conclusion: Crowns constructed from PEEK substructure and veneered using composite gave highly significant results than the other two groups. All groups gave comparable results withstanding the fracture forces beyond the maximum masticatory biting force.