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An In Vitro Trial on the Effect of Arch Form on Connector Size Requirements

Now online in the Journal of Prosthodontics, a new in vitro study co-authored by ACP members, Ryan J. Coello DMD, MS, FACP, Cynthia Aita-Holmes DMD, FACP, and Walter G. Dimalanta DDS, FACP.

The purpose of this study was to test the fracture resistance of maxillary canine to canine fixed partial denture with four missing incisors, with increasing anterior-cantilevers of the pontics and varying connector sizes.

Two 3D-printed titanium alloy models simulating a maxillary canine to canine fixed partial denture (FPD) with four pontics replacing the incisors were used as master models. Zirconia FPDs were digitally designed and milled with two different connector sizes (9 and 12 mm2) each, with three different anterior cantilevers (7, 10, and 13 mm) accounting for 6 test groups.

A sinusoidal cyclic wave form load from 50N to 280N was applied using a universal testing machine. In total, 9 out of the 42 samples fractured before the 5,000,000 cycle mark. The difference in the proportion of fractured samples was not statistically significant when comparing the 9 and 12 mm2 connector size; on the other hand, it proved to be statistically significant when comparing the 7 mm cantilever with the 10 and 13 mm cantilevers combined, indicating that an anterior cantilever of 7 mm had a significantly greater proportion of FPDs that fractured.

The authors conclude that retainer crown thickness may be a more important parameter than connector size thickness. Based on the results, a smaller connector size (9 mm2) may be used to improve the esthetics of pontics in long span anterior FPDs

Coello RJ, Aita-Holmes C, Dimalanta WG, Wenger K. An in vitro trial on the effect of arch form on connector size requirements in long span anterior zirconia fixed dental prostheses. J Prosthodont. 2022; 00: 00– 00. https://doi.org/10.1111/jopr.13601

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