Impact of Preformed Anatomic Caps on Peri-implant Soft Tissues Width-to-Thickness Ratio: A Retrospective Three-Dimensional Analysis.

OBJECTIVES: The study aimed to assess the biologic quotient, defined as the width-to-thickness ratio between Gingival Width (GW) and Mucosal Thickness (MT), in implant-supported restorations using Preformed Anatomic Caps (PAC, test group) versus conventional healing abutments (control group). MATERIALS AND METHODS: Following dental implant placement in the edentulous ridge with partial-thickness flap elevation, each patient underwent a split-mouth treatment from January 2018 to December 2022, consisting of a conventional healing abutment on one side and a preformed anatomic cap on the contralateral side. Optical scans were used to evaluate the stability of the biologic width-to-thickness ratio over time. The three-dimensional data were voxelized and superimposed to measure the GW and MT digitally, and their biologic width-to-thickness ratio (GW/MT) at different time points was calculated. Superimpositions were performed using MatLab (version 7.0.1, The MathWorks, Natick, MA, USA) and measurements were performed with Dentascan software (JD-igital Guide powered by RealGUIDE™ 5.3, Cantù, Italy). Changes from 2 months to 2 years post-surgery were analyzed. The Wilcoxon signed-rank test, with a significance level set at p < 0.01, was used to compare the paired data. Multivariate regression analysis was performed to assess the potential influence of age, sex, implant arch, and implant position on the observed variables. RESULTS: Data from 30 patients (mean age 52.9±7.8 years; 28 premolars and 32 molars) were analyzed. Gingival widths increased significantly in the test group (+0.3±0.3mm, p<0.0001) and decreased in the control group (-1.4±0.3mm, p<0.0001) over 2 years. Mucosal thickness showed small, non-significant increases in both groups. The biologic width-to-thickness ratios remained stable in the test group (1:1.54 to 1:1.48) but changed significantly in controls (1:1.48 to 1:3.06, p<0.0001). Multivariate regression showed that age, sex, implant arch, and implant position did not independently influence changes in GW, MT, or GW/MT ratio. Subgroup and sensitivity analyses confirmed these findings. CONCLUSIONS: From 2 months to 2 years after surgery, the biologic width-to-thickness ratio remained stable in patients rehabilitated with preformed anatomic caps. The biologic width-to-thickness ratio could serve as a reference parameter for clinicians to assess the maintenance, stability, or loss of the natural appearance of the peri-implant mucosa over time.