Comparison of Deformation by Stereophotogrammetry of Various Kinds of Major Connectors in Maxillary Kennedy Class I Removable Partial Dentures

Purpose: Major connectors must be rigid to perform their functions with maximum efficacy. This study investigated the deformation of four major connectors for maxillary Kennedy Class I removable partial dentures. Materials and Methods: The designs were palatal plate, U-shaped plate, palatal strap, and anteroposterior bar. The deformation properties of major connectors were comparatively analyzed by two methods. In the photogrammetric part, a stereometric camera, Avipan-100 glass films, and an analytic apparatus were used. A computerized hydraulic machine was programmed to load the eight test dentures at 4-Hz frequency under a vertical load of 100 kg and a maximum of 300,000 cycles. The fluorescence penetrant liquid inspection test was used to detect the surface microcracks. Results: The anteroposterior bar showed the least deformation. The other connectors, ranked in increasing order for the amount of deformation, were the U-shaped plate, the palatal strap, and the palatal plate. There were no microcracks in the U-shaped plate and the anteroposterior bar designs. Conclusion: Anteroposterior bar major connectors showed the least deformation among the maxillary major connector types tested. Microscopic cracks were seen in major connectors showing the highest degree of deformation and located at the depth of the hard palate.