Biomechanics of splinted/non-splinted crowns supported by various implant designs

Objective: This study compared biomechanics among standard implant (D 3.75mm), wide implant (D 5.0mm) and double implants (D 3.75mm) with and without splinted crowns for posterior, fixed, partial denture restorations. Methods: Six 3D finite element (FE) models were constructed using computed tomographic images and the computer-aid design (CAD) system, based on a cadaver mandibular block containing the 2nd premolar and the 1st molar. In each FE model, the premolar implant used the standard diameter only, while the molar implant used one of the following designs: standard, wide, and double implants. For each model, one splint and one non-split case were simulated. A 100N force was applied to buccal cusp of the model with 45 degree of lingual inclination. The bottom surface of the mandible was constrained in all directions. The models were validated via an in-vitro experiment. Results: The experimental data agreed with FE predictions (correlation coefficient = 0.97), which verifies our models. Regardless of splinted or non-splinted designs, both the wide and double implants decreased stresses on crestal bone of molar regions by 35-50% compared to the standard implant. The reduction was slightly greater in the non-splinted cases. Splinting standard implants did not reduce stresses. However, splinting did decrease stresses at premolar region by 21% and 19.5% for the wide and double implants design, respectively. Conclusion: The biomechanical advantages of using the wide implant and the double-implant are almost identical. The benefit of load sharing by the splinting prosthesis is notable only when the two supporting implants have difference in sustaining ability; that is a concept of using the standard implant on premolar region and the wide or double-implant on the molar region with splinted crowns. (Acknowledgement: Supported in part by NSC 922320B006058 form National Science Council,Taiwan.)