Is Baseline Vertical Implant Positioning Relative to Adjacent Teeth Associated with Peri-Implant Outcomes? A Systematic Review and Meta-Analysis

Background: Vertical implant positioning may influence peri-implant health outcomes and long-term stability; however, the impact of baseline vertical implant positioning relative to adjacent teeth remains unclear. The aim of this systematic review and meta-analysis was to assess the association between baseline vertical implant positioning and peri-implant clinical and radiographic outcomes. Methods: The Cochrane Central Register, PubMed, SCOPUS, and Web of Science were searched. Vertical implant positioning relative to adjacent teeth was assessed using two radiographic reference distances: implant platform to cemento-enamel junction (IP–CEJ) and implant platform to adjacent interproximal alveolar bone level (IP–ABL). The primary outcome was peri-implant marginal bone loss (MBL). Secondary outcomes included implant survival and success rates, peri-implant mucositis and peri-implantitis prevalence. Risk of bias was assessed using the Moga checklist, and certainty of evidence was evaluated according to GRADE. Results: Four studies including 267 implants fulfilled the inclusion criteria. The pooled mean baseline IP–CEJ and IP–ABL distances were 4.69 mm (95% CI 2.05 to 7.32) and 2.13 mm (95% CI 1.29 to 2.98), respectively. The pooled mean marginal bone loss after at least 12 months, based on three studies, was 0.21 mm (95% CI −0.28 to 0.70). Conclusions: The available evidence is insufficient to determine whether baseline IP–CEJ or IP–ABL distances are associated with peri-implant outcomes or to identify an optimal range of vertical implant positioning. The findings should be interpreted cautiously because the certainty of evidence is very low, highlighting the need for prospective studies with long-term follow-up.