The all-ceramic, inlay supported fixed partial denture. Part 3. Experimental approach for validating the finite element analysis

Durability of cantilever inlay-retained fixed dental prosthesis fabricated from multilayered zirconia ceramics with different designs

PURPOSE

The purpose of this in-vitro study was to investigate the effect of framework design on fracture resistance and failure modes of cantilever inlay-retained fixed partial dentures (IRFDPs) fabricated from two multilayered monolithic zirconia materials.

MATERIALS AND METHODS

Seventy-two natural premolar teeth were prepared as abutments for cantilever IRFDPs using three designs: mesial-occlusal (MO) inlay with short buccal and palatal wings (D1), MO inlay with long palatal wing (D2), MO inlay with long palatal wing and occlusal extension (D3). Full-contoured IRFDPs were fabricated from two monolithic zirconia materials; IPS e.max ZirCAD Prime and Zolid Gen-X. Adhesive surfaces were air-abraded and bonded with MDP-containing resin cement. Specimens were subjected to thermocycling (5-55 °C, 5000 cycles); then, mechanical loading (1.2 × 10⁶ cycles, 49 N). Surviving specimens were loaded until failure in the universal testing machine. All specimens were examined under stereomicroscope, and two samples from each group were evaluated using Scanning Electron Microscope.

RESULTS

Mean failure loads were not significantly different between different framework designs or between two materials. However, IPS e.max ZirCAD Prime showed significantly higher failure rate than Zolid Gen-X during dynamic fatigue (p = 0.009). Samples with D1 design showed higher debonding rate, D2 failed mainly by fracture of the palatal wing and debonding, and D3 failed mainly by fracture of the abutment tooth. Debonded restorations showed mainly mixed failures.

CONCLUSION

Cantilever IRFDPs with framework designs that maximize adhesion to enamel exhibited promising results. IPS e.max ZirCAD Prime was more susceptible to fractures with the long palatal wing design.

Effect of restoration material on stress distribution on partial crowns: A 3D finite element analysis

Background/purpose

Various restoration materials have been used to restore as onlay materials to restore highly defected molar teeth. Different mechanical and physical properties of these materials may affect the success or survival of the restoration. The purpose of this study was to evaluate the restoration materials effects on stress distribution.

Materials and methods

Three dimensional finite element analysis (FEA) was used to evaluate the stress concentrations and distributions at the restoration and the tooth. Maxillar first molar tooth constructed to evaluate the stress distribution and concentration levels at the restorations and the tooth structure. Two kinds of restoration materials, bulkfill composite and conventional hybrid composite was evaluated for direct method, while full ceramic and indirect composite was used for indirect method. A load of 200 N was applied on the restorations and stress levels were calculated by von Mises stress values.

Results

Highest stress concentration was observed at the ceramic restoration (3.77 GPa). Stress levels were 2.90 GPa for bulkfill composite and 2.14 GPa for direct and indirect composite. At the tooth structure the stress levels were 3.33 GPa, 3.18 GPa and 2.48 GPa for bulkfill, direct and indirect composites respectively. The lowest stress values was observed with the porcelain restoration (1.69 GPa). Stress concentrations at the adhesive system were 2.10 MPa for bulkfill composite, 1.35 MPa for direct and indirect composites and 1.25 Mpa for porcelain restoration.

Conclusion

The restoration material affects the stress levels at the restoration and the tooth while the stress concentration areas remained nearly the same.

Considerations for ceramic inlays in posterior teeth: a review

This review of ceramic inlays in posterior teeth includes a review of the history of ceramic restorations, followed by common indications and contraindications for their use. A discussion on the potential for tooth wear is followed by a review of recommended preparation design considerations, fabrication methods, and material choices. Despite the improved materials available for fabrication of porcelain inlays, fracture remains a primary mode of inlay failure. Therefore, a brief discussion on strengthening methods for ceramics is included. The review concludes with a section on luting considerations, and offers the clinician specific recommendations for luting procedures. In conclusion, inlay success rates and longevity, as reported in the literature, are summarized.