Positional accuracy of a prosthetic treatment plan incorporated into a cone beam computed tomography scan using surface scan registration

Statement of problem. The registration of surface scans onto cone beam computed tomography (CBCT) scans has been proposed as a method of visualizing different anatomic structures and the prosthetic treatment plan simultaneously. This method also overcomes some of the problems associated with conventional radiographic templates. However, it has not been thoroughly investigated or validated for use in implant dentistry. Purpose. The purpose of this in vitro study was to evaluate the accuracy of a prosthetic treatment plan surface scan incorporated into a CBCT scan and to compare it to conventional radiographic templates for single tooth replacement. Material and methods. Direct surface scans of a completely dentate master model with removable radiopaque teeth were made using an intraoral scanner, and indirect surface scans of a stone duplicate of the master model were made using a laboratory scanner. To simulate a clinical scenario, the mandibular left first molar was removed. A CBCT scan of the clinical scenario was made. The surface scans were registered onto the CBCT scans. Radiographic templates for the clinical scenario were fabricated, and the master model was subsequently scanned using the same CBCT scanner with each radiographic template seated. Metrology software was used to assess the accuracy of each method by measuring the 3-dimensional deviation on standard tessellation language (STL) files generated from the CBCT scans against an STL file of the completely dentate master model generated from a CBCT scan. One-way ANOVA and the Tukey HSD test were used for statistical analysis (alpha=.05). Results. The incorporation technique had a significant effect on deviation from the master model (P=.004). The overall mean 3-dimensional deviation was 0.04 mm for direct surface scan registrations, 0.03 mm for indirect surface scan registrations, and 0.33 mm for radiographic templates. Radiographic templates were significantly less accurate compared with both surface scan registration methods (P<.001), whereas no statistically significant difference in accuracy was found between the registration of a laboratory scan and that of an intraoral scan (P=.94). Conclusions. Intraoral and laboratory surface scan registration on CBCT scans were more accurate than radiographic templates for prosthetic treatment plan incorporation. The accuracy of the registration of an intraoral scan and a laboratory scan was comparable.