Use of abutment-teeth vs. dental implants to support all-ceramic fixed partial dentures: an in-vitro study on fracture strength.

The aim of the present in-vitro study was to compare the fracture strength of all-ceramic Fixed Partial Dentures supported by tooth-analogues and periodontal membrane with the same supported by dental implants. As ceramics are highly brittle, they cannot withstand deformations of more than 0.1% without fracturing. Hence, when planning an all-ceramic FPD, it is essential to evaluate abutment support, as the fracture strength of all-ceramic constructions depends on the stability of the support to reduce strain in the beam of the prosthesis. The support provided by implants differs, however, from the support provided by natural teeth as the implants are anchored directly in the bone with no intermediate tissue. One question that arises is whether strain and stress in the prosthesis are lower when the prosthesis is loaded on implants compared to natural teeth and hence if all-ceramic FPDs benefit from implant support. Twenty-four three-unit all-ceramic FPDs-12 supported by two dental implants and 12 by two tooth-analogues serving as end abutments-were made. All FPDs were subjected to preloading in a preloading procedure and subsequently subjected to load until fracture occurred. Load at fracture were registered and comparisons between the two groups were made. The loads at fracture were statistically significant higher in the group supported by implants compared to the group supported by tooth-analogues (p = 0.003). Within the limitations of this in-vitro study, the following conclusions can be drawn: All-ceramic fixed partial dentures can be used in combination with dental implants. The solid support gained from implants might thus be beneficial for the outcome of such treatment due to decreased strain and stress levels in the prosthesis when loaded on implants compared to when loaded on natural teeth. Clinical studies are, however, needed to confirm these findings as there are more factors that influence the final clinical outcome.