Factors influencing transfer accuracy of cone beam CT-derived template-based implant placement

Objectives: The aim of the present investigation was the analysis of the factors presumptively affecting the accuracy outcome of cone-beam computed tomography (CBCT)-derived laboratory-based surgical guides for implant placement in partially edentulous patients. Materials and methods: In 52 partially edentulous patients a total of 132 implants were placed following CBCT diagnostics with the aid of laboratory-fabricated, tooth-borne templates. Based on the image fusion technique measurements were done to calculate linear and angular deviations between virtually planned and placed implants. The implant sites were stratified according to four factors that presumably may influence the transfer accuracy: (i) type of arch (maxilla/mandible), (ii) kind of template (single-tooth gap/interrupted dental arch/shortened dental arch/reduced residual dentition), (iii) surgical technique (flapless/open flap), (iv) number of sleeve-guided site preparation steps (fully guided placement/freehand placement/freehand final drilling). The data were analyzed using analysis of variance and the Bonferroni test. Results: The transfer accuracy of shoulder level, apex level, and angulation was similar for maxilla and mandible as well as for flapless and open flap approach. The differences were small in magnitude and reached no or only a borderline statistical significance. At implant sites in the reduced residual dentition group, the discrepancies were more pronounced than in the singletooth gap group, whereas no significant differences could be determined between free ending templates in the shortened dental arch and bilateral anchored templates in the interrupted dental arch. Implant placement through the guide allowed a more accurate implementation of the virtual plan to the surgical site than freehand insertion or freehand final drilling. Conclusion: CBCT-derived laboratory-based surgical templates enabled an implant placement in the cancellous maxilla as well as flapless procedures without compromising the transfer accuracy. The number and distribution of the remaining teeth as well as the number of sleeve-guided implant site preparation steps influenced the extent of deviation that can be achieved in partial edentulism.