Page 197 - Peri-implant health: the effect of implant design and surgical procedure on bone and soft tissue stability

patients. Only two out of the three studies found a statistically significant difference in marginal bone loss favouring the implants with microthreaded neck design. However, the difference was only -0.09 mm with a 95%CI of -0.18, -0.01. Thus, it is questionable if this statistically significant difference is clinically relevant. Furthermore, the authors of the meta-analysis concluded that the evidence was insufficient to draw a definite conclusion on the effect of the microthread design because too few RCTs with low risk for bias were available. Moreover, they suggested that more RCTs with adequate control for confounding factors for design are needed because many studies have compared other designs in addition to the microthread design. To our knowledge, no more recent meta-analyses or RCTs other than the present study population could be found on PubMed when the search string ‘(microthread) AND (implant)’ was used. The results from our paper confirm and strengthen the outcome described in the available meta-analysis.
It is noteworthy that the results in Study III and Study V have been established with the precondition that (1) due to the use of the specific abutment, a platform-shift between implant and abutment was created and (2) all implants were placed in relation to the soft tissue thickness. A large meta-analysis on 28 publications with 1,216 platform-shifted implants and 1,157 non-platform-shifted implants showed a significant effect on marginal bone loss favouring platform-shifted implants. However, the authors also suggested a careful interpretation of the results due to uncontrolled confounding factors.40
■ SITE-SPECIFICFACTORS
The effect of adapting the vertical position of the implant in relation to soft tissue
thickness was investigated in a part of Study III and in Study IV.
The difference in this study population in mean bone level between equicrestally and subcrestally placed implants at 6 months was 0.68 mm. The 95% confidence interval of the mean showed a 95% chance that the mean difference in the true population would be between 0.36 and 1.00 mm. Even the lower number of the mean difference of the true mean is already suggestive for clinically relevant differences in mean bone level. For all other time intervals, the same conclusion could be made.
GENERAL DISCUSSION
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