Influence of Pontic Length on the Structural Integrity of Zirconia Fixed Partial Dentures (FPDs).

Objective: This study aims to evaluate the influence of pontic length and design on the fracture resistance of zirconia fixed dental prostheses (FDPs). By assessing different span lengths under controlled mechanical loading conditions, the research seeks to provide insights into optimizing the structural integrity of zirconia dental bridges.

Materials and methods: A total of 20 zirconia bridges were fabricated and tested in vitro. Ten bridges were designed to replace a single missing molar (tooth 46), with a pontic span of 11 mm, while the remaining ten were crafted for two missing teeth (35 and 36), featuring a longer pontic span of 17 mm. The zirconia frameworks were milled using the Wieland Zenotec^® Select Hybrid system and cemented onto metal abutments with Voco Meron Plus QM resin-reinforced glass ionomer cement. The specimens were subjected to occlusal loading using a ZwickRoell ProLine Z005 testing machine at a crosshead speed of 1 mm/min until fracture occurred.

Results: The mechanical testing revealed a significant correlation between pontic length and fracture resistance. The mean fracture resistance for three-unit bridges (single pontic) was 3703 N, whereas four-unit bridges (double pontic) exhibited a significantly lower resistance of 1713 N. These findings indicate that increased span length reduces the fracture resistance of zirconia restorations due to higher stress accumulation and reduced rigidity.

Conclusions: This study underscores the importance of pontic length and design in determining the fracture resistance of zirconia restorations. Shorter spans exhibit greater structural stability, reinforcing the need for careful treatment planning when designing multi-unit zirconia bridges. By optimizing bridge parameters, clinicians can improve clinical outcomes and extend the longevity of zirconia prostheses in restorative dentistry.