Computed tomography-based evaluation of template (NobelGuide™)-guided implant positions: a prospective radiological study

Objectives: This prospective study was intended to evaluate the overall deviation in a clinical treatment setting to provide for quantification of the potential impairment of treatment safety and reliability with computer-assisted, template-guided transgingival implantation. Material and methods: The patient population enrolled (male/female = 10/8) presented with partially dentate and edentulous maxillae and mandibles. Overall, 86 implants were placed by two experienced dental surgeons strictly following the NobelGuide (TM) protocol for template-guided implantation. All patients had a postoperative computed tomography (CT) with identical settings to the preoperative examination. Using the triple scan technique, pre- and postoperative CT data were merged in the Procera planning software, a newly developed procedure - initially presented in 2007 allowing measurement of the deviations at implant shoulder and apex. Results: The deviations measured were an average of 0.43mm (bucco-lingual), 0.46mm (mesio-distal) and 0.53mm (depth) at the level of the implant shoulder and slightly higher at the implant apex with an average of 0.7mm (bucco-lingual), 0.63mm (mesio-distal) and 0.52mm (depth). The maximum deviation of 2.02mm was encountered in the corono-apical direction. Significantly lower deviations were seen for implants in the anterior region vs. the posterior tooth region (P<0.01, 0.31 vs. 0.5 mm), and deviations were also significantly lower in the mandible than in the maxilla (P = 0.04, 0.36 vs. 0.45mm) in the mesio-distal direction. Moreover, a significant correlation between deviation and mucosal thickness was seen and a learning effect was found over the time period of performance of the surgical procedures. Conclusion: Template-guided implantation will ensure reliable transfer of preoperative computer-assisted planning into surgical practice. With regard to the required verification of treatment reliability of an implantation system with flapless access, all maximum deviations measured in this clinical study were within the safety margins recommended by the planning software.