# Open-Flap Versus Minimally Invasive Flapless Techniques in Esthetic Crown Lengthening: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

## TL;DR

This study compares two surgical techniques for improving the appearance of a gummy smile and finds that one method reduces gum display more effectively.

## Contribution

A systematic review and meta-analysis comparing open-flap and flapless techniques in esthetic crown lengthening surgeries.

## Key findings

- Flapless technique significantly reduced relative gingival margin compared to open-flap.
- Flapless technique also reduced bleeding on probing compared to open-flap.
- No significant differences were found in other clinical outcomes between the two techniques.

## Abstract

Excessive gingival display (EGD) represents a high negative effect on the esthetic appearance. Esthetic crown lengthening (ECL) surgery is the cornerstone for the treatment of the gingival smile. However, whether to proceed with open-flap (OF) or minimally invasive flapless (FL) techniques remains unclear. We aimed in this systematic review and meta-analysis to compare the clinical outcomes between OF and FL in ECL surgeries. We searched PubMed, Cochrane CENTRAL, Scopus, and Web of Science (WOS) for randomized controlled trials including EGD patients undergoing ECL surgery with either OF or FL techniques. The primary outcome was the mean change of relative gingival margin (rGM), while the secondary outcomes were the mean changes in bleeding on probing (BOP), probing depth (PD), relative clinical attachment level (rCAL), and keratinized gingiva height (KGH). Continuous outcomes were assessed using standardized mean difference (SMD) with 95% confidence intervals (CIs) in a random-effects model. STATA 19MP (StataCorp LLC, College Station, TX) was used to pool all the statistical analyses. We included five RCTs with 180 patients in the analysis. Minimally invasive FL technique was associated with a significant reduction of rGM (SMD = -0.38; 95% CI -0.58 to -0.19, P < 0.001; I2 = 0%) compared to the conventional OF technique. Additionally, minimally invasive FL was associated with a significant reduction in BOP (SMD = -0.63, 95% CI -1.24 to -0.03, P = 0.04; I2= 73.31%) compared to the conventional OF technique. There were no significant differences regarding other studied outcomes. Minimally invasive FL and OF showed comparable results; however, the FL technique was associated with unfavorable clinical results of rGM for the treatment of EGD. Further large-volume RCTs are warranted to validate the findings.