Are Mini Dental Implants Suitable for Support of Crowns or Small Bridges in the Mandibular Incisor Region? A 5-year Longitudinal Study

Abstract

It has not been previously studied whether 1-piece category 1 narrow dental implants (≤2.5mm wide) can successfully support crowns or small bridges. The purpose of this study was to evaluate the long-term benefits of the fixed-type mini dental implants (MDIs) for replacement of mandibular incisors. In a prospective cohort study, fixed-type 1-piece MDIs, replacing single or multiple mandibular incisors, supporting metal-ceramic single crowns (unsplinted group), or splinted crowns/small bridges (splinted group) were observed over the period of 5years. The primary predictor was the splinting status. The primary outcome variables were peri-implant marginal bone level (MBL) change, success, and survival rates (assessed as per Pisa Consensus Conference). The secondary outcomes were dental patient-reported outcome measures (dPROMs) and oral hygiene assessment. Descriptive statistics, Chi-squared test, t-test, Mann-Whitney and Wilcoxon tests, Kaplan-Meier survival analysis, log-rank (Mantel-Cox) comparison, Cox proportional hazard analyses adjusting for number of implants, Spearman correlation, and repeated measures were used for data analysis. From 44 participants (mean age 56.02±5.72years), 40 completed the 5-year study: 23 in the splinted and 17 in unsplinted group. Three subjects did not respond, while 1 MDI failed (third year) in the unsplinted group. Mean marginal bone level (MBL) change in both groups was small; however, it increased over time (-0.22±0.38mm after 1 year; -0.54±0.56mm after 5years; P<.05). After 5years mean MBL change was -0.59±0.71mm in the unsplinted and -0.50±0.41mm in the splinted group (P>.05). Survival analysis revealed no significant difference between the unsplinted (85.7% success, 4.8% failures, and 9.5% satisfactory survivals) and splinted group (93.4% success and 6.6% satisfactory survivals) (P>.05). The group affiliation (unsplinted vs splinted) and number of implants were not significant predictors of MDI failure or survival rates (P>.05). Significant improvement in dPROMs after rehabilitation remained unchanged over 5years (P>.05). Modified plaque index significantly increased over time, correlating with the MBL loss. MDIs supporting crowns and/or small bridges in the mandibular incisor region showed small rates of marginal bone loss, acceptable success, and survival rates and improved dPROMs over a 5-year observation period.