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

Abstract

To 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. A 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. The mean distance between the drill path and the target was significantly lower than 0.7mm, and null hypothesis H0 : μ=0.7 was rejected (CI 95%: 0.31;0.49, P<0.001). Intra- and inter-examiner agreements reached excellent levels. The 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.