2020 Volume 33 Issue 1 Pages 36-44
This study was conducted to clarify the relation between the maximum bending load, deflection and strain applied to an implant collar and the ratio of superstructure length to implant body length. The length I of the implant body was maintained at 12.4 mm, whereas the superstructure length was varied (9, 10, 12, or 15 mm). For each superstructure length, the distance (1.5 mm) between the superstructure margin and bone level was added and this length (i.e., superstructure length + 1.5 mm) was denoted as C. Thus, the C/I ratios were 0.85, 0.93, 1.09, and 1.33, respectively, for the four superstructure lengths. The implant with its mounted superstructure was fixed at an inclination angle of 30°. The maximum bending load tended to decrease as the superstructure length increased and was the lowest when the C/I ratio was 1.33, where its value was 57.6% of the maximum bending load that was observed for a C/I ratio of 0.85. The deformation increased up to the maximum bending load as the superstructure length increased. For C/I ratios of 0.85 and 0.93, the strain on the implant collar was ＜0.1% when the load was 150-250 N ; for C/I ratios of 1.09 and 1.33, the strain was ＞0.1% when the load was 150 N. When the load was 300 N, the strain was ＞0.1% for all the C/I ratios. Further, the maximum and minimum strains were 0.36% and 0.11% for C/I ratios of 1.33 and 0.85, respectively. When the load was 500 N or more, for the C/I ratio of 1.33, the strain was the limit value (2.1%) of the strain gauge. We observed that the strain applied to the implant collar increased as the superstructure length increased. This indicated that the superstructure length should be considered to be relative to the length of the implant in implant treatments.
