A multi-centre randomized controlled trial comparing connective tissue graft with collagen matrix to increase soft tissue thickness at the buccal aspect of single implants: 1-year results.

Aim: To compare connective tissue graft (CTG) with collagen matrix (CMX) in terms of increase in buccal soft tissue profile (BSP) at 1 year when applied at single implant sites.

Materials And Methods: Patients with a single tooth gap in the anterior maxilla and horizontal mucosa defect were enrolled in a multi-centre randomized controlled trial. All sites had a bucco-palatal bone dimension of at least 6 mm, received a single implant and an immediate implant restoration using a full digital workflow. Sites were randomly allocated to the control (CTG) or test group (CMX) to increase buccal soft tissue thickness. The primary outcome was the increase in BSP at 1 year when compared with the pre-operative situation based on superimposed digital surface models. The changes in BSP over time were registered at a buccal area of interest reaching from 0.5 mm below the soft tissue margin to 4 mm more apical. Secondary outcomes included patient-reported, clinical and aesthetic outcomes.

Results: Thirty patients were included per group (control: 50% females, mean age 50.1; test: 53% females, mean age 48.2). The increase in BSP at 1 year was 0.98 mm (98.3% confidence interval [CI]: 0.75-1.20) for CTG and 0.57 mm (98.3% CI: 0.34 to 0.79) for CMX. The mean difference of 0.41 mm (98.3% CI: 0.12 to 0.69) in favour of CTG was significant (p < .001). Based on an arbitrarily chosen threshold for success of 0.75 mm increase in BSP, 89.7% of the patients in the control group and 10% of the patients in the test group were successfully treated (odds ratio = 77.90; 95% CI: 13.52 to 448.80; p < .001). Sites treated with CMX demonstrated 0.89 mm (98.3% CI: 0.49 to 1.30) more shrinkage between postop and 1 year than sites treated with CTG. In addition, CMX resulted in significantly more marginal bone loss (0.39 mm; 95% CI: 0.05 to 0.74; p = .026) than CTG. There were no significant differences between the groups in terms of patients' aesthetic satisfaction (p = .938), probing depth (p = .917), plaque (p = .354), bleeding on probing (p = .783), midfacial recession (p = .915), Pink Esthetic Score (p = .121) and Mucosal Scarring Index (p = .965).

Conclusions: CTG remains the gold standard to increase soft tissue thickness at implant sites. Clinicians need to outweigh the benefits of CMX against considerable resorption of the graft. This study was registered in ClinicalTrials.gov (NCT04210596).