Influence of abutment height on strain in a mandibular overdenture.

The purpose of this study was to investigate the influence of coping heights on the strain around the abutment teeth and at the middle part of mandibular overdentures, using strain gauges. A mandibular edentulous model with a silicone artificial mucosa of thickness 2 mm was made. Two artificial roots were embedded on both sides in the canine position. The coping had a dome-shaped upper surface at a height of 0, 2, 4 and 6 mm. On the lingual polished surface of the overdenture, three strain gauges were attached in the left canine position at the vertical level corresponding to the top of the 6, 4 and 2 mm copings and two strain gauges were attached in the middle section (upper and lower). A vertical loading of 49 N was applied on the occlusal surface of first premolar, first molar and second molar. When loading on the first premolar adjacent to an abutment, the largest tensile strain was observed on the overdenture surface close to the top of each coping, independent of coping heights. When loading on the first premolar on the opposite side, the tensile strains around the coping were remarkably smaller. In the middle part of the overdenture, the compressive strains became larger by reducing the coping height or loading on distal point. The largest tensile strain was observed on the overdenture surface close to the top of copings, independent of coping heights.