In vitro and comparative in vivo accuracy analysis of static computer-assisted implant surgery in fully edentulous patients

Introduction With the development of static computer-assisted implant surgery (s-CAIS), knowledge of the potential maximal implant deviation is crucial. New methods such as intraoral scanning (IOS) for studies on accuracy of s-CAIS are recommended, at the same time further research is needed to improve the precision of IOS even for whole arch scanning. In the present study, the authors evaluated the accuracy of two different implant systems in fully edentulous patients in the mandible and the maxilla as well as the different factors that could influence the accuracy of computer-assisted implant placement such as sleeve position, drilling key height, total drilling length, implant diameter and length. The aims of this study were: -to evaluate the accuracy of static computer-assisted implant surgery in edentulous patient both in vivo and in vitro with two different evaluation techniques and investigate if both can be applied in edentulous patients (part 1). -to clinically evaluate and compare the accuracy of implant placement of two different macrodesign implant systems and to individuate the factors influencing the precision of s-CAIS (part 2). Materials and methods For part 1 of the study a patient with terminal dentition was selected. Four implants were inserted using s-CAIS with a bone-supported stackable template. Segmentation used for designing a template was 3D printed. Four implants of the same characteristics were placed at the model utilizing the same protocol of s-CAIS and surgical template. The CBCT and laboratory scanning were then performed at the model. Data were uploaded to the software and accuracy values were automatically generated. In part 2 a total of 95 dental implants were placed in 20 patients utilizing s-CAIS. In group one, 42 tapered implants with fully guided adapter were placed in 10 patients. In group two, 53 self-tapping implants with fully guided mounter were placed in 10 patients. All patients received the second CBCT scan to obtain data in DICOM format for analysis in a specific software. Results Part 1: A statistical analysis was not attempted since all measurements were performed in the same patient and model. However, when comparing in a descriptive way the accuracy of the two methods of treatment evaluation in the in vitro scenario, comparable results were obtained, except for the angle. Hence, IOS was not considered a reliable and standardizable method for assessing accuracy of s-CAIS either in vitro or in vivo, since several limitations are still reported in the literature for fully edentulous patients. Part 2: After 1 year, implant survival rate in group 1 was 97.3% (n=41/42); in group 2 it was 98.1% (n=52/53). The overall mean 3D offset at the implant base was 1.674 +/- 0.952 mm, at the tip 1.893 +/- 1.147 mm, the mean angle of deviation was 4.068 +/- 3.111° for group 1. For group 2, the overall mean 3D offset at the implant base was 1.555 +/- 0.856 mm, at the tip 1.663 +/- 0.951 mm, the mean angle of deviation was 2.271 +/- 2.030°. Self-tapping implants had significantly less vestibular deviation at implant base (p=0.013) and angular deviation (p=0.006) than tapered implants. Conclusions Treatment evaluation in vitro using IOS provides comparable results to those of CBCT in edentulous patients. Accuracy evaluation of computer-assisted implant placement utilizing CBCT in edentulous patients can be recommended, as intraoral scanning procedure in edentulous is not yet validated. During computer-assisted implant planning there are several factors that influence the accuracy of s-CAIS to be considered: implant macrodesign, jaw treated, implant diameter and length, sleeve position, drilling key height, total drilling length. Self-tapping implants showed higher accuracy of computer-assisted placement if compared to tapered implants. Future studies should be orientated in standardizing evaluation methods of s-CAIS accuracy.