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COMPARISON OF THE FRACTURE RESISTANCE BETWEEN INLAY RETAINED FIXED PARTIAL DENTURES FABRICATED FROM MILLED PEEK (BIOHPP) AND MONOLITHIC ZIRCONIA (In vitro study)

Aim: To evaluate the fracture resistance of veneered PEEK Inlay Retained Fixed Partial Dentures (IRFPDs) compared to those fabricated from monolithic zirconia. Materials and methods: Mandibular typodont with removed mandibular first molar was used to receive box inlay cavity preparation on mandibular second molar and second premolar. After tooth preparation, typodont was duplicated into fourteen epoxy models using silicone mold. Epoxy models were randomly divided into two equal groups (n= 7/group). Identical IRFPDs were fabricated from two different materials. For Group I (P/C): IRFPDs were fabricated from Bre. CAM BioHPP blanks and subsequently veneered with composite (Crea.lign). For Group II (MZ): IRFPDs were manufactured using industrially prefabricated monolithic zirconia blocks (Katana HTML). All IRFPDs were bonded to their corresponding epoxy models using adhesive resin cement (Theracem), and underwent thermal cycling (10,000 cycles). Fracture resistance testing was performed on the specimens using a universal testing machine with a crosshead speed of 0.5 mm/ min. Fractured samples were examined using a digital-microscope, with 35x magnification power, to determine failure mode pattern . Results : It was found that MZ group recorded statistically significant higher fracture resistance mean value (1876.198±218.039 N) than P/C group (1282.572±160.154 N). Most failures of MZ group were cohesive in nature, where connector fracture was the predominant failure mode. In P/C group, all failures were adhesive in nature between PEEK framework and composite veneering. Conclusion: When compared to Zirconia, PEEK IRFPDs veneered with composite exhibited sufficient resistance to fracture.