A photoelastic and strain gauge comparison of two attachments for obturator prostheses

Statement of problem. The rehabilitation of patients after a maxillectomy involves the use of an obturator to seal oral-nasal-sinus communication and to facilitate mastication, swallowing, and speech. Purpose. The purpose of this in vitro study was to evaluate different attachment systems used for implant-retained obturators at dissipation loads and under shear forces. Material and methods. Photoelastic models were fabricated with 3 external hexagon implants at the incisor, canine, and first molar regions. Subsequently, overdentures were made, and metal hooks were placed at the incisor and first molar regions to displace the prostheses in the vertical, anterior, and posterior directions, with a constant speed of 50 mm/min. A photoelastic model with an O-ring or bar-clip system was placed in a circular polariscope, and tested with a universal testing machine. The images were recorded and high-intensity fringes were counted using software. For strain gauge analysis, each strain gauge was placed horizontally at the mesial and distal sides of the implants. The registered strains were submitted to 2-way ANOVA (alpha=.05). Results. The O-ring showed the lowest number of high-intensity fringes in photoelastic imaging, while the strain gauge analysis showed the lowest stress values in the bar-clip group (P=.007). Conclusions. The stress around titanium implant necks was more damaging to surrounding bone, while the bar-clip attachment system had a better biomechanical performance. The bar clip presented the lowest strain values around the dental implants and few high-intensity fringes. (AU)