Page 178 - Peri-implant health: the effect of implant design and surgical procedure on bone and soft tissue stability

CHAPTER 7
Bone level in the present study is comparable with a recent published RCT by Slot and colleagues with a 5-year follow-up of 29 patients treated with four of six implants in the maxillary posterior region to support a bar retained overdenture.15 The mean bone loss between the placement of the overdenture and 5-year evaluation was 0.58 mm (SD 0.51) for the four-implant group. The present study showed a mean probing pocket depth of 4.5 mm and 45% (33 out of the 74 implants) showed bleeding on probing. The study by Slot and colleagues showed comparable findings, with a mean probing of 4.3 mm and 48% of the implants scored positive on the bleeding index. Mean loss of peri-implant bone between baseline and the 5-year evaluation was 0.58 ± 0.51 mm in the four-implant group.15
Regarding the implant–abutment connection, the results of the present study are not in accordance with a systematic review and meta-analysis with 11 included studies, which compares the effect of an internal or external implant–abutment connection on bone loss.24 The systematic review concluded that internal connections had lower marginal bone loss when compared to external connections. However, several included studies used a study design where confounding factors such as design factors like implant brand, implant surface, thread design, and platform-shift were not controlled. Due to the presence of more than one different design factor between the study implants, the interpretation of 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 the platform switching, which is more frequently found in implants with internal connections.25,26
A systematic review with meta-analysis concluded that a microthreaded neck design reduces the amount of marginal bone loss.27 The three RCTs in the meta- analysis represent in total 57 implants in each treatment group in only partially edentulous patients. Only two out of the three studies found a statistically significant difference in marginal bone loss between the two study implants. The overall mean difference in the meta-analysis was significant and in favor of the implants with micothreaded neck design. However, the difference was only -0.09 mm with a 95%CI of -0.18, -0.01 and 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
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