抄録
To diminish the amount of irreversible tooth reduction during preparation for a fixed restoration of missing teeth, supplementary preparation of small pins in addition to conventional tooth reduction techniques has been advocated. Among them, the most epoch-making one might be UDA system reported by S. Sandhaus in 1985, making it possible to support the conventional pontic structure with minimal tooth reduction (pin holes) prepared on the proximal tooth surfaces of the abutment teeth. However, the diameter and length of the pins and the head size of the preparation instrument was eventually too big for Japanese adults who have less thick teeth. On the basis of the concept, we redesigned the whole system (pin size, preparation instrument head) for Japanese adults. Furthermore, to reinforce the reduced mechanical retention ascribed to the reduced adherent area of the newly-designed smaller pin to the smaller pin hole, titanium-nickel shape memory alloy was utilized. In this paper, the detail of the pinhole preparation instrument was described and its redone precision of the holes prepared by the instrument was assessed. The standard deviation range of the diameter of the prepared pin-holes was from 1/100 to 5/100 mm. Based on the X-ray estimation of the enamel and dentin thickness in the proximal tooth surface of an extracted tooth sample, the most suitable pin hole position for each tooth was advocated.
