OAC: diagnosis–morphology–location
LEAKAGE
The diagnosis for OAC was initially assessed by clinical examination using a conventional blunt probe (diameter: 1 mm) and by the patient performing the Valsalva pressure maneuver. The blunt probe was used to carefully palpate the defect in order to detect an OAC. The Valsalva pressure maneuver was additionally performed on each patient and in case of air leakage from the maxillary sinus, an OAC was also assumed. In case of a palpable defect, an apical perforation size of at least 3 mm was assessed using a 3 mm probe. In the further course, the perforation size was verified using detailed radiographic evaluation such as CBCT. The defect area, the mesial and the distal defect length were calculated. The morphology of the OAC was defined in a parallel-walled, root-shaped and inverse-root-shaped (higher apical width) design. Randomization for the treatment method was performed using a permuted block-randomization approach (block length either 2, 4, or 6) without stratification. For creating the randomization list, the R package “blockrand” (blockrand: Randomization for Block Random Clinical Trials, Greg Snow, R package version 1.5) was used.