Page 198 - Peri-implant health: the effect of implant design and surgical procedure on bone and soft tissue stability

CHAPTER 8
Compared to the three-years follow-up of Study III no further changes occurred regarding peri-implant bone stability and peri-implant health.
A recent systematic review and meta-analysis of 16 studies concluded in a quantitative analysis that subcrestal and equicrestal implant placement yielded comparable peri-implant bone loss.41 However, in the presence of a thin tissue, a subcrestal placement of the implant is preferred, because it may reduce the risk for implant exposure in the future, thus avoiding peri-implant pathologies. More studies suggested a certain minimum width of peri-implant mucosa as a prerequisite, allowing a stable soft tissue attachment.42-46 The results of Study III and IV are in line with the aforementioned papers. Hence, one should anticipate the preferred biologic width establishment to prevent early implant surface exposure caused by initial bone remodeling by adopting implant depth positioning in relation to soft tissue thickness.
Radiographic analysis of the subcrestally and equicrestally placed implants showed a minimal bone loss over time after the initial bone remodeling, although it was not clinically relevant. The findings of Study III and IV are in accordance with earlier published papers, showing comparable results for peri-implant bone stability in patients treated with a two-implant overdenture in the mandible.47-49
Part of Study III and Study IV showed that equicrestally placed implants yielded significant more bone loss during initial remodeling. The boxplot representation in Study IV showed that 75% percent of the equicrestelly placed implants had a bone level between 0 and almost 1 mm at 6 months. Moreover, 25% of this treatment group showed a bone level between 1 and 2.45 mm, resulting in a median bone level of 0.59 mm compared to a median bone level of 0.00 mm for the subcrestally placed implants. One could conclude a higher risk for implant surface exposure to the soft tissues in the equicrestally placed implant group.
There was no statistically significant difference in bone level change between 6 and 60 months, despite direct exposure of the implant threads. One should keep in mind that all patients in the present study were fully edentulous and compliant with oral hygiene. Whether this outcome is also valid in non-compliant patients is questionable, as suggested by scarce evidence. It is improbable, that scientifically sound, randomized controlled trials in humans could be initiated in non-compliant
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