The influence of thin as compared to thick peri-implant soft tissues on aesthetic outcomes: A systematic review and meta-analysis

Abstract

Objectives: In systematically healthy patients with an implant-supported fixed restoration (P), what is the influence of thin (E) as compared to thick (C) peri-implant soft tissues on aesthetic outcomes (O)?. Methods: Following an a priori protocol, a literature search of six databases was conducted up to August 2020 to identify prospective/retrospective clinical studies on healthy patients with an implant-supported fixed reconstruction. Measurement of the buccal soft tissue thickness and an aesthetic outcome was a prerequisite, and sites presenting with a buccal soft tissue thickness of <2 mm or shimmering of a periodontal probe were categorized as a thin phenotype. After study selection, data extraction, and risk of bias assessment, random-effects meta-analysis of Mean Differences (MD) or Odds Ratios (OR) with their corresponding 95% Confidence Intervals (CI) were conducted, followed by sensitivity analyses and assessment of the quality of evidence. Results: Thirty-four unique studies reporting on 1508 patients with 1606 sites were included (9 randomized controlled trials, one controlled trial, 10 prospective cohort studies, 8 cross-sectional studies, and 6 retrospective cohort studies). The mean difference of the pink aesthetic score (PES) after the follow-up was not significantly different between thin (<2.0 mm) or thick soft tissues (≥2.0 mm) or phenotypes (12 studies; MD = 0.15; [95% CI = −0.24, 0.53]; p =.46). PES changes during the follow-up, however, were significantly in favour of thick soft tissues (≥2.0 mm) or phenotypes (p =.05). An increased mean mucosal thickness was associated with an increased papilla index (5 studies; MD = 0.5; [95% CI = 0.1, 0.3]; p =.002) and an increase in papilla presence (5 studies; OR = 1.6; [95% CI = 1.0, 2.3]; p =.03). Thin soft tissues were associated with more recession, −0.62 mm (4 studies; [95% CI = −1.06, −0.18]; p =.006). Patient-reported outcome measures (patient satisfaction) were in favour of thick soft tissues −2.33 (6 studies; [95% CI = −4.70, 0.04]; p =.05). However, the quality of evidence was very low in all instances due to the inclusion of non-randomized studies, high risk of bias and residual confounding. Conclusion: Within the limitations of the present study (weak study designs and various soft tissue measurements or time-points), it can be concluded that increased soft tissue thickness at implant sites was associated with more favourable aesthetic outcomes.