Aim To evaluate two- and three-dimensionally the effect of resorbable collagen-based bone-filling material on periapical healing of endodontic lesions with four-wall defects following endodontic microsurgery (EMS).

Methodology This parallel, randomized controlled superiority clinical trial involved 86 lesions with the strictly endodontic origin and four-wall defect morphology. EMS procedures were performed by calibrated postgraduate residents. Before flap closure, osteotomies were randomized to the control or treatment group. In the control group, the flap was repositioned with no material added. In the treatment group, a collagen-based bone-filling augmentation material was placed into the osteotomy. Clinical and radiographic examinations were completed after 12 months. Periapical healing was evaluated by blinded evaluators using periapical (PA) radiographs according to Molven's criteria and cone beam computed tomography (CBCT) scans according to PENN's 3D criteria. Cortical plate healing was scored according to the RAC/B index. The data were analysed using Fisher's exact test, Logistic regression models and Chi-squared test. The significance level was predetermined at p < .05.

Results Sixty-six cases were evaluated at the 12-month follow-up, with 30 and 36 cases in the control and treatment groups, respectively. Only the asymptomatic cases (control = 26, treatment = 32) were included in the radiographic evaluation. Twenty-three cases (88.5%) in the control and 28 (87.5%) cases in the treatment group demonstrated complete healing on PA radiographs (p = 1.000). On CBCT, 10 (38.4%) and 21 (65.6%) cases had completely healed in the control and treatment groups, respectively (p = .095). The re-establishment of the buccal cortical plate was detected in 12 (46.2%) and 22 (68.8%) cases in the control and treatment groups, respectively (p = .243).

Conclusion Within the limitations of the present study, the use of collagen-based bone-filling material had no statistically significant effect on the periapical healing of endodontic lesions with four-wall defect following EMS at the 12-month follow-up when evaluated by PA radiographs or CBCT scans. However, the observed higher percentage of a re-established cortical plate in the treatment group could suggest a clinical benefit that is of interest after surgical endodontic treatment.