Evaluation of computer-assisted virtual treatment planning and template-guided surgery in dental implant treatment

One of the newly introduced concepts in implant dentistry is computer-guided surgery. The development of 3D implant planning software and imaging technology provide clinicians with 3D information of patients’ bony structures. Furthermore, the combination of such image technologies and the CAD/CAM technology allows fabrication of surgical templates and implant supported prostheses preoperatively based on the virtual treatment planning. However, whether the new method can offer patients as successful and reliable treatment as the conventional methods has not yet been shown scientifically. The general aim of this thesis was to evaluate computer-assisted virtual treatment planning and template-guided implant surgery. Study I and Study II aimed to evaluate the clinical performance, including survival rates, complications, soft tissue conditions, and marginal bone changes following the template-guided surgery in combination with immediate loading of a prefabricated prosthesis. In Study III and Study IV, the aim was to verify the accuracy of virtually planned and template-guided implant surgery. Patients with edentulous maxilla, mandible or both, consecutively treated using the NobelGuideTM and Teeth-in-an-HourTM were included in this project. In Study I, survival rates and complications during the follow-up period were investigated. The results showed that survival rates of implants and prostheses were lower compared to those following conventional treatment protocols. Furthermore, complications occurred in as many as 42 % of the treated cases. Most observed complications were related to this specific technique or hardware. Study II assessed soft tissue conditions and marginal bone changes at ≥ 1 year follow-up. A pressure-like-ulcer was one of the most frequently observed complications during the follow-up period. Although the mean marginal bone loss after functional loading in Study II was within the range of other reports presenting mean bone loss data after immediate loading, our patients showed a wide range of bone loss at several sites, where the bone loss was greater than commonly used successful level (< 1.5 mm after 1 year of prosthesis connection). Study III and IV showed that there were significant differences between virtually planned implant positions and the clinically placed implant positions. In Study III, the accuracy was assessed by matching the implant planning data based on the pre-operative CT scan and the post-operative CT scan from ≥ 1 year follow-up. In this matching method, patient movement during CT scan was one of the main factors that contributed to the deviations. In Study IV, we developed a novel method. In this method, two plaster models were compared, one created from the surgical template and the other made from impressions on copings attached to the implants in patients at ≥ 1-year follow-up. The matching procedure, best-fit alignment, might have led to the smaller deviations compared to the results of CT matching method. In the guided-surgery technique used in these studies, the surgery including prosthesis connection was completed within 30-45 minutes, with minimal surgical trauma in the majority of individuals. In addition, the patients’ post-operative discomfort such as pain and swelling was almost negligible in successfully treated cases. However, the results in the present studies imply that the method of computer-assisted treatment and template-guided surgery must still be regarded as being in an exploratory phase. Further investigations regarding the clinical performance and products as well assessments from the patient’s viewpoint will lead to more optimal results and improvement of the system.