Page 196 - Peri-implant health: the effect of implant design and surgical procedure on bone and soft tissue stability

CHAPTER 8
well compliant with maintenance. Statistical analysis was performed during three visits, namely directly after implant placement (t0, baseline), at 6 months (t1, initial remodeling), and at 36 months (t2). However, most visits planned according to protocol at 36 months (t2) were postponed due to the COVID-19 pandemic. This explains the mean follow-up time of 45.5 months (SD 4.82, range 35 – 58).
After initial bone remodeling due to biologic width establishment, the linear mixed-model analysis applied in this study showed no clinically relevant effect of the implant type on the bone level at t1 and t2. Although the implant position (posterior versus anterior) showed a significant effect on the bone level at t1 in favour of a posteriorly placed implant, the confidence limits (-0.365, -0.060) are suggestive of a clinically irrelevant difference. Moreover, we found no effect of implant position at t2. Between t1 and t2, all implant types showed no further relevant bone level change, indicative of a stable bone level once initial bone remodeling took place. Some implants with high bone loss at t1 showed bone gain at t2. This latter could be explained by the effect of splinting the implants with a titanium bar after t1. A similar positive effect of splinting the implants was described earlier by De Bruyn and co-workers.35
Regarding the implant-abutment connection the results of the present study are not in accordance with a systematic review and meta-analysis.36 Based on 11 studies, the authors concluded that internal connections had lower marginal bone loss when compared to external connections. However, several of the included studies used a study design that did not control for confounding factors, such as design factors like implant brand, implant surface, thread design, and platform- shift. Due to the presence of more than one different design factor between the study implants, these results should be interpreted with caution.
Two other systematic reviews also concluded that internal connections exhibit lower marginal bone loss than implants with external connections. However, they discussed that these findings are probably related to platform switching, which is more frequently found in implants with internal connections.37,38
A systematic review with meta-analysis concluded that a microthreaded neck reduces the amount of marginal bone loss.39 The three RCTs in the meta-analysis represent in total 57 implants in each treatment group in only partially edentulous
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