title: Guided access cavity preparation using cone-beam computed tomography and optical surface scans - an ex vivo study.
abstract: OBJECTIVE
  To evaluate ex vivo, 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.
  
  
  METHODS
  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 0.7 mm was defined based on the radius of the bur (0.6 mm) and the radius of a root canal just visible on a radiograph (0.1 mm). The t-test was used for evaluation, and intra- and inter-examiner reproducibility was expressed by intraclass correlation coefficients.
  
  
  RESULTS
  The mean distance between the drill path and the target was significantly lower than 0.7 mm, 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Private practice, Allerød, Denmark.
authors.forename: J
authors.identifier: http://orcid.org/0000-0003-1820-2754
authors.initials: J
authors.lastname: Buchgreitz
authors.affiliation: Private practice, Allerød, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Buchgreitz
authors.affiliation: Section of Cariology & Endodontics, Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: D
authors.initials: D
authors.lastname: Mortensen
authors.affiliation: Section of Cariology & Endodontics, Department of Odontology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: L
authors.initials: L
authors.lastname: Bjørndal
mesh_terms: D054893:Cone-Beam Computed Tomography; D003737:Dental Cavity Preparation / Q000379:methods*; D003782:Dental Pulp; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D004708:Endodontics; D006801:Humans; D055096:Optical Devices; D014070:Tooth / Q000033:anatomy & histology
keywords: CBCT; access cavity; endodontics; pulp canal obliteration; trauma