Purpose : This study aimed to clarify the influence of the thickness of the implant collar part on the maximum bending load, amount of deformation, and strain.

Materials and Methods : The collar-part thickness was changed to 0.7 (T07), 0.8 (T08), and 0.9 (T09) mm, and the titanium abutment was processed to the same size among the three groups. The maximum bending load, amount of deformation, and strain (loading from 100 to 800 N) were measured and the inner region was observed using CT. In each measurement, superstructures with an inclination angle of 20° and 30° and superstructure length of 10 mm were set.

Results and Discussion : The maximum bending load at an inclination of 20° increased with an increase in thickness. On the other hand, the maximum bending load at an inclination of 30° was the smallest in T07 and no difference was noted between T08 and T09. The amount of deformation was the largest in T07 at both inclination angles, whereas no difference was noted between T08 and T09. At an inclination of 20°, 0.1% or greater strain was caused by loading 500 N in the T07 preparation and by loading 600 N in T08 and T09. At an inclination of 30°, 0.1% or greater strain was caused by loading 400 N in T07 and T08 and by loading 500 N in T09. Strain by loading 800 N at an inclination of 20° was 0.3% or smaller in all three types of preparation and that at an inclination of 30° was 0.3% or greater in the preparations other than T09. No difference in strain of T09 was noted between the two inclination angles from loading 300 N. On internal observation, a gap was present at the tips of the abutment and collar part, and the upper part of the screw showed plastic deformation and entered the grinding swarf discharge hole.

Conclusion : For T07, technical complications should be considered because the maximum bending load is small and the deformation is large. As for T07 and T08, it is necessary to consider biologic complications because there is a large strain at an inclination of 30°.