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Purpose: Registration refers to the linkage of coordinates from an image with actual patient coordinates and has been shown to be the most influential factor in the accuracy of image-guided surgery. Invasive bone markers are the gold standard but require surgical placement prior to imaging. In contrast, registration templates or external registration frames are noninvasive, but their repositioning during imaging and surgery can be a source of error. The purpose of the present study was to determine whether noninvasive registration methods can achieve an accuracy similar to that of invasive bone marker registration. Materials and Methods: Computed tomographic slices (1 mm each) of a maxillary and mandibular dental stone cast that had been prepared with target markers on the buccal and oral surfaces were registered with an optical-based navigation system simulating invasive bone markers, noninvasive registration templates, and a noninvasive external registration frame. Predicted error of the navigation system, fiducial registration error, and target registration error were evaluated. The use of five and seven registration markers was compared. Results: A total of 696 error measurements was performed. The external registration frame showed significantly worse fiducial registration error compared with the other methods, but there was no significant difference in target registration error between invasive and noninvasive registration methods. The predicted error given by the navigation system significantly underestimated target registration error. Increasing the number of registration markers from five to seven resulted in no significant differences. Conclusions: Noninvasive registration based on registration templates or external registration frames showed accuracy that was equivalent to that of invasive registration. The use of five registration markers was sufficient. The predicted error given by a navigation system should not be mistaken as 'navigation error' during clinical application. Int J Oral Maxillofac Implants 2010;25:491-498. [ABSTRACT FROM AUTHOR]

PURPOSE: The purpose of this study was to evaluate in vitro the accuracy of 2 methods for computerized tomography (CT)-guided template production via a surgical navigation system. MATERIALS AND METHODS: Oral implants were planned on CT scans of standard dental stone casts with integrated target pellets. Method 1 used the aiming device of the navigation system for direct positioning of 2-mm surgical bur tubes on the dental stone casts. In method 2, the aiming device was used to guide drillings into the dental stone casts, and the surgical bur tubes were indirectly positioned by metal rods inserted in the drill holes. In both methods the bur tubes were affixed in a resin template. The accuracy of the obtained templates was evaluated by postoperative CT scans using descriptive statistics and the Student t test (P < .05 considered significant). RESULTS: The mean accuracy (normal deviation from the defined targets) of method 1 was 0.5 +/- 0.3 mm (max 1.2 mm; n = 56). Mean accuracy for method 2 was 0.6 +/- 0.3 mm (max 1.4 mm; n = 56). No significant difference was found between the maxillary and mandibular templates. DISCUSSION: Conventional navigation systems already installed in many hospitals may be used for surgical template production. In contrast to intraoperative tool tracking, there is no need for patient tracking, and the planned implant axis can be rigidly secured as precisely as technically feasible with the help of an aiming device. CONCLUSION: Both methods of bur tube positioning may represent a precise means for CT-guided template production. [ABSTRACT FROM AUTHOR]

The objective of this article was to review the different factors and limitations influencing the accuracy of computer-aided implant surgery. In vitro and in vivo accuracy studies of articles and congress proceedings were examined. Similar results using bur tracking as well as image-guided template production techniques have been reported, and both methods allow for precise positioning of dental implants. Compared to the conventional technique, this sophisticated technology requires substantially more financial investment and effort (computerized tomographic imaging, fabrication of a registration template, intraoperative referencing for bur tracking, or image-guided manufacturing of a surgical template) but appears superior on account of its potential to eliminate possible manual placement errors and to systematize reproducible treatment success. The potential for the protection of critical anatomic structures and the esthetic and functional advantages of prosthodontic-driven implant positioning must also be considered. However, long-term clinical studies are necessary to confirm the value of this strategy and to justify the additional radiation dose, effort, and costs. [ABSTRACT FROM AUTHOR]