印象用コーピングの取り扱いが印象精度に及ぼす影響：手締め法とトルクコントロール法の差異

抄録

Purpose: It has been reported that the displacement of implants by applied force is markedly small in vivo. This suggests that in contrast to fixed prostheses of natural teeth, fixed implant prostheses need greater accuracy to avoid failure due to the inadequate force on components such as fixtures. In this study, we focused on impression manipulation that affects the fitting accuracy of superstructures. The influence of differences in the handling of impression copings on the positional relationship of implants on casts was evaluated.
Methods: For a case of right mandibular free-end edentulism from the 2nd premolar, 3 Brånemark-system implant fixtures were inserted at intervals of approximately 10 mm on an acrylic model, and abutments were connected to the fixtures. From this intra-oral assumption model, casts in which abutment replicas were jointed, were produced using custom trays and silicone rubber impression materials. Impressions were taken by the open tray method. Regarding the handling of impression coping screws, two methods were performed by 10 clinicians respectively, which were the hand-fastening method according to the manufacturerʼs instruction and the torque-control method in which screws were fastened at 15 N using a torque wrench. Regarding impression accuracy, dimensional changes were evaluated by measuring the distance between the center of fixtures on the intra-oral assumption model and that on the final casts.
Results: No significant differences in dimensional changes were found between the model and final casts produced by the two methods.
Conclusions: There are no differences of impression accuracy between the hand-fastening and torque-control methods.