The effect of implant-abutment junction position on crestal bone loss: A systematic review and meta-analysis

To investigate the effect of the apico-coronal implant position on early and late crestal bone loss (CBL), in bone and tissue level implants.

Electronic and manual literature searches were conducted for controlled clinical trials reporting on CBL before and after functional loading of implants. Random effects meta-analyses were applied to analyze the weighted mean difference (WMD) and meta-regression was conducted to investigate any potential influences of select confounding factors.

Fourteen articles were included in the systematic review and 12 were included in the quantitative synthesis. For bone level implants, WMD comparing early CBL in equi and subcrestal placement was 0.15 mm (P = .18). For analyses of late CBL in bone level implants, equi and subcrestal placement revealed a 0.03 mm WMD (P = .88). Where in supra and subcrestal placement, WMD was 0.04 mm (P = .86). The comparison presented considerable heterogeneity between these two arms, where the P value for chi-square test presented as .006. Finally, for CBL between supra and equicrestal placement, WMD was -0.64 mm (P < .0001), favoring the supracrestal group. For tissue level implants, WM of early and late CBL in implants placed equi-crestally was 0.68 ± 0.12 mm and 0.69 ± 0.54 mm, respectively, where for implants placed sub-crestally, the WM of CBL was 1.72 ± 0.15 mm and 2.26 ± 0.63 mm, respectively.

Within the limitations of this study, it is recommended to place tissue level implants equicrestally, and bone level implants subcrestally.