Guided access cavity preparation using cone-beam computed tomography and optical surface scans - an ex vivo study

AimTo evaluate exvivo, the accuracy of a preparation procedure planned for teeth with pulp canal obliteration (PCO) using a guide rail concept based on a cone-beam computed tomography (CBCT) scan merged with an optical surface scan. MethodologyA total of 48 teeth were mounted in acrylic blocks. An apical canal preparation was created to simulate remnants of an apical root canal that acted as the target for a drill path. The test blocks were surface scanned, and merged with a CBCT scan, and a guide rail was made. A pathway for the bur was created through a metal sleeve within the guide rail into dentine. The distance was measured between the centres of the performed drill path and the apical target by two examiners. A maximum distance of 0.7mm was defined based on the radius of the bur (0.6mm) and the radius of a root canal just visible on a radiograph (0.1mm). The t-test was used for evaluation, and intra- and inter-examiner reproducibility was expressed by intraclass correlation coefficients. ResultsThe mean distance between the drill path and the target was significantly lower than 0.7mm, and null hypothesis H-0: =0.7 was rejected (CI 95%: 0.31;0.49, P<0.001). Intra- and inter-examiner agreements reached excellent levels. ConclusionsThe combined use of CBCT and optical scans for the precise construction of a guide rail led to a drill path with a precision below a risk threshold. The present technique may be a valuable tool for the negotiation of partial or complete pulp canal obliteration.