Changes of radiopacity around implants of different lengths: Five-year follow-up data of a randomized clinical trial

Objective To follow-up the radiographic changes in peri-implant bone of short (6 mm, test group) and long (10 mm, control group) single-unit implants five years after loading. Materials and methods Forty-three implants of the test and 44 implants of the control group could be reassessed from 96 originally included implants. Standardized areas of interest (AOI) were defined in the peri-implant bone at pre-defined locations at mid-length on both sides of the implants, and at the apex. An arbitrary mean grey scale value (GSV) was calculated for the AOI after brightness calibration of the radiographs. Changes for GSV were calculated and tested for possible inter- and intra-group differences using the Mann-Whitney and Wilcoxon tests. Results The calculated intra-group differences between baseline and 5 years in the test group accounted for 2.4 +/- 19.6 (i.e. slight brightening) and -6.2 +/- 20.2 for the control group (i.e. slight shading), which resulted in a statistically significant difference in GSV change (p < .05). Crown-to-implant ratio was the only parameter showing an effect on GSV change (p = .001). Conclusions Assessing conventional radiographs, longer implants showed a slightly stronger change of radiopacity of the peri-implant bone (slight loss of density) than short ones (slightly enhanced density) after five years of loading.