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

Purpose: Implants in the anterior region are challenging, and literature reporting outcomes of narrowdiameter 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 (I2 = 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 (I2 = 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. Keywords: alveolar bone loss, esthetics, narrow-diameter implants, review (systematic), single implant, survival analysis