Efficacy of soft tissue augmentation procedures on tissue thickening around dental implants: A systematic review and meta-analysis

Objectives The first focused question (FQ1) was: What is the efficacy of connective tissue graft (CTG), as compared to the absence of soft tissue grafting procedure, in terms of gain in peri-implant soft tissue thickness (STT) reported by randomized controlled clinical trials (RCTs) or controlled clinical trials (CCTs)? The second focused question (FQ2) was: What is the efficacy of CTG, as compared to soft tissue substitutes, in terms of gain in peri-implant STT reported by RCTs or CCTs? Materials and methods A manual and electronic search was performed for each question to identify RCTs and CCTs published up to July 2020. The primary outcome variable was changes in peri-implant STT and secondary outcomes were marginal bone level (MBL), clinical parameters for the diagnosis of peri-implant health, changes in the position of peri-implant soft tissues, esthetic outcomes, and patient-related outcome measures (PROMs). For primary and secondary outcomes, data reporting mean values and standard deviations for each study were extracted. Weighted mean differences (WMDs) or standardized mean differences as well as 95% confidence intervals (CIs) and prediction intervals (PIs) were calculated. Results Eight trials were included to answer the first focused question and eight to answer the second one, providing data for 254 and 192 patients, respectively. For the first focused question, a statistically significant difference of 0.64 mm in STT was found in favor of the grafted group (n = 8; 95% CI [0.16; 1.13]; 95% PI [-1.06; 2.35]; p = .01). Moreover, sites treated with CTG exhibited statistically significant less recession than implants without a graft (n = 4; WMD = 0.50 mm; 95% CI [0.19; 0.80]; 95% PI [-0.70; 1.69]; p < .001). For the second focused question, the meta-analysis showed a statistically significant gain of STT in the CTG group when compared to soft tissue substitutes (n = 8; WMD = 0.51 mm; 95% CI [0.28; 0.75]; 95% PI [-0.09; 1.12]; p < .001). Furthermore, the use of CTG resulted in significantly higher pink esthetic score values (n = 3; WMD = 1.02; 95% CI [0.29; 1.74]; 95% PI [-3.67; 5.70]; p = .01) and less recession (n = 2; WMD = 0.50 mm; 95% CI [0.10; 0.89]; 95% PI [not estimable]; p = .014) when compared to soft tissue substitutes. No statistically significant differences between groups were observed for any of the following secondary variables: MBL, clinical parameters for the diagnosis of peri-implant health, position of the interproximal tissues, keratinized mucosa or PROMS (p > 0.05), except for medication intake, which was significantly higher when using CTG as compared to soft tissue substitutes (n = 2; WMD = 1.68; 95% CI [1.30; 2.07]; 95% PI [not estimable]; p < .001). Conclusions Soft tissue augmentation procedures are efficacious on soft tissue thickening and, in particular, CTG demonstrated a significant STT gain when compared to no graft or soft tissue substitutes.