Accuracy of virtually planned and CAD/CAM-guided dental implant surgery

Abstract

The treatment with dental implants was introduced in the 1960s as an aid for patients who were missing teeth. Recently CAD/CAM guided surgical concepts have been launched on the market as a solution for treating single, partial or completely edentulous patients with dental implants. The mucosa based surgical templates is one of the fairly new dental implant systems on the market for treating patients. With this new technique it is crucial to thoroughly evaluate the accuracy, in order to avoid damaging sensitive anatomical structures of patients. Another factor of importance to consider, is the possibility to connect the bridge immediately onto the CAD/CAM guided placed implants. Companies could also benefit from more knowledge about accuracy in order to, i.e., further improve the instructions and the hardware to further enhance the security and usability of the systems.

The general aim of this project was to evaluate the accuracy between virtually planned and actually placed dental implants using a surgical guide. Study I and III aimed to compare the deviation between the position of virtually planned implants and the position of implants placed with a CAD/CAM-guided surgical template in the mandible and maxilla. The aim of Study II was to perform virtual variation simulations on virtually planned implant placements and to compare them with corresponding results from actual surgeries, performed on human cadavers in Study I. In Study IV the aim was to evaluate the deviation between the results obtained from five different surgeons, from CAD/CAM guided implant surgery on plastic jaw models. Completely edentulous human cadavers, patients and plastic maxilla jaw models were included in Study I, III and IV. Study II utilized 3D STL files obtained from Study I.

Study I and III, demonstrated a statistical significant difference between the virtually planned implant positions and the clinically placed implant positions after surgery. Study I demonstrated a statistically significant difference between mandibles and maxillae for the outcome variables, hex, apex and depth measurements, with smaller deviations for the maxilla. In Study III it was found that the patients moved during the preoperative and postoperative CBCT scans. When combining the movement factor between the virtually planned implants and actually placed implants positions, a statistical significant difference was observed for the hex and apex. If the movement factor was included, a statistical significant difference was found between the maxilla and mandible for the outcome variable angle.

In Study II, the implant distributions were neither static nor normally distributed. Thus, within the limitations of this study, the definitive geometrical variations of the implants were not static, as they depend on the individual anatomy of the jaws and the ability to place the CAD/CAM-guided surgical template in the proper position. The Mann-Whitney U test showed that the definitive implant distributions in this study could not be assumed to be normally distributed.

In Study IV a statistically significant difference was observed between all five surgeons for the outcome variables, apex, depth and angle. A statistically significant difference was also found between the virtually planned implant positions and the actually placed implant positions for the outcome variables, apex, hex and depth. The mean value was smallest for the plastic jaw model study and largest for the human cadaver study, for the outcome variables, apex, hex and angle. For the depth, the smallest mean value was present in the patient study and largest in the plastic model study. However, the human cadaver study and patient study presented a larger range in deviation.

Further studies have to be performed to evaluate the contributing factors of all steps involved in CAD/CAM guided surgery. In order to further improve knowledge about guided surgery accuracy, it is important to perform accuracy studies on conventional surgery in order to compare the results and, thus, provide a more secure treatment to the patients. In other words, the most important goal is to provide the most secure treatment available for the patients.