Fracture Resistance of 3-Unit Monolithic Zirconia Fixed Restorations Supported by three different substrates: A Comparative Study

Objectives: To evaluate the fracture resistance of monolithic zirconia fixed dental prostheses (FDPs) supported byimplants, combined tooth-implant and teeth.
Materials and methods: Thirty partially edentulous mandibular epoxy resin castswere prepared at their posterior regionsand divided in to three equal groups (n=10) as the following: (group I) casts received two implants at second premolar and molar regions, group (TI) casts received one implant at second molar region, and (group T) casts with missing lower first molar. All the restorations were constructed from monolithic zirconia. All the samples were underwent thermomechanical loading (TCML) (5,000 x5^○/55^○, 3 x10⁵ x 98 N). Then subsequently loaded until fracture using   universal testing machine. Fracture sites were evaluated macroscopically.
Results: Fracture strength for group I (1893.5±315.3N) significantly differed from group TI (1297.29±222.3N), (P 0.034) with no significantly difference from group T (1640.56±587.8N), (p = 0.488). Fracture strength of group T was higher than those of group TI with no statistically significant difference (p =0.279).
Conclusion: The type of supportive abutmentsignificantlyaffect the fracture resistance of monolithic zirconia FDPs.Connecting implants rigidly to teeth gives a comparable  fracture strength results with those of teeth connected. Monolithic zirconia FDPs have the potential to withstand the occlusal loads applied in the posterior area.