A comprehensive search was conducted in 4 databases (Pubmed, Web of Science, Embase and Cochrane) followed by manual search up to June 2022. Inclusion criteria were clinical studies in English involving healthy adults (≥18 years old) with a single titanium implant placed in the incisor, cuspid, or premolar position. The focus was on randomized controlled trials (RCTs) comparing immediate implant placement (IIP) with flap surgery to IIP with flapless surgery, with data available on at least one outcome variable of interest. Reference lists were screened for additional studies, and the U.S. National Library of Medicine database was searched for grey literature. Two reviewers independently evaluated studies for eligibility at the title and abstract levels, the selected full text, the risk of bias and extracted the data. Disagreements were resolved with a third reviewer. Inter-rater reliability was assessed using kappa coefficient. The authors of the included studies were contacted to obtain missing or incomplete data. RCTs were assessed for bias using the Cochrane risk-of-bias tool (RoB 2), considering randomization, intervention deviations, missing data, outcome measurement, and result selection.

The key study factor is the impact of mucoperiosteal flap elevation and flapless surgery on buccal hard and soft tissue changes, as well as clinical, aesthetic, and patient-reported outcomes (PROs) in single IIP sites. The exclusion criteria included acute infection at the extraction site, zirconia implants, alveolar socket shield technique, vertical ridge augmentation, patients taking medications/therapies affecting bone metabolism, patients with bone metabolism pathologies, implants placed in tumor-affected sites, missing information on augmentation procedures, additional therapies affecting healing outcomes, and insufficient surgical protocol information.

This study aimed to compare the effects of flapless surgery and full thickness flap surgery on various parameters, including horizontal buccal bone change (primary outcome), implant survival, vertical buccal bone change, pain, probing depth, bleeding on probing, marginal bone level change, vertical papillary change, and vertical midfacial soft tissue change (secondary outcomes), in IIP based on RCTs.

Five RCTs were included, involving 140 patients who received 140 single immediate implants, with 68 implants placed using a flapless approach and 72 implants placed with flap surgery. The patients' mean age ranged from 30 to 67 years, and the follow-up period ranged from 6 to 12 months. Four RCTs focused on intact or nearly intact alveoli, while one RCT included cases with missing buccal bone walls. The meta-analysis showed a significant difference in horizontal buccal bone change between flapless and open-flap surgery, favoring the flapless approach (mean difference = 0.48 mm (95% confidence interval [CI] [0.13, 0.84], p = .007)). Implant survival rates did not differ significantly between the groups (RR 1.00, 95% CI [0.93, 1.07], p = .920). Limited data were available for other secondary outcomes, but the available studies consistently favored flapless surgery for vertical buccal bone change and pain sensation after surgery. Only one study provided clinical and aesthetic outcomes. Three RCTs were found to have a high RoB due to inappropriate outcome measurement methods and potential awareness of the intervention. However, based on GRADE guidelines, flapless surgery is strongly recommended, primarily due to the inclusion of two RCTs with a low RoB in the quantitative analysis.

Flapless surgery for immediate implant placement resulted in less horizontal buccal bone change than flap surgery based on CBCT data, but the clinical and aesthetic relevance remains unclear due to underreported outcomes. Further research is required to explore flapless surgery's long-term effects, its applicability in diverse clinical scenarios, comprehensive reporting of PROs, and collaborative multi-center approaches.