Narrow-Diameter Implants in the Anterior Region: A Meta-analysis

Purpose: Implants in the anterior region are challenging, and literature reporting outcomes of narrow-diameter implants (NDIs) in anterior sites is scarce. This systematic review summarized evidence of functional and esthetic performance of anterior single crowns supported by NDIs. Materials and Methods: Ten databases were searched to find studies evaluating anterior single crowns supported by NDIs. Risk of bias was assessed, and random-effects meta-analyses were applied to analyze mean differences in survival, success, and marginal bone level (MBL). The review was registered in the PROSPERO database (CRD42018089886). Results: Twenty-one studies meeting the screening criteria were included for qualitative analysis, and three for meta-analysis. A total of 892 NDIs, placed in 736 patients, were analyzed. Follow-up duration varied from 12 months to 14 years (mean: 40 months), and 16 failures (implant loss) were recorded. Fixed-effect meta-analysis (I-2 = 0%) of survival rate revealed a risk difference of 0.02 (95% CI: -0.03 to 0.08) between NDIs and controls (regular-diameter implants), without differences between groups (P = .39). Success rates ranged from 84.2% to 100% (mean: 95.2%). Random-effects meta-analysis (I-2 = 56%) of MBL indicated a mean difference of 0.02 mm (95% CI: -0.21 to 0.25), without differences between groups (P = .87). Conclusion: Single crowns supported by NDIs are a predictable treatment, since their survival rate and MBL are comparable to those supported by regular-diameter implants. Due to data shortage reporting esthetic outcomes, more studies are needed to evaluate the long-term performance of the single crowns supported by NDIs in the anterior region.