Reliability of Implant Surgical Guides Based on Soft-Tissue Models
The purpose of this study was to determine the accuracy of implant surgical guides fabricated on diagnostic casts. Guides were fabricated with radiopaque rods representing implant positions. Cone beam computerized tomograms were taken with guides in place. Accuracy was evaluated using software to simulate implant placement. Twenty-two sites (47%) were considered accurate (13 of 24 maxillary and 9 of 23 mandibular sites). Soft-tissue models do not always provide sufficient accuracy for fabricating implant surgical guides.
(a) Missing teeth waxed up to proper morphology and function. (b) Drill press used to create holes in the acrylic templates in a position corresponding to the center of each missing tooth. (c) Radiopaque rods (methyl methacrylate impregnated with 20% barium sulfate) placed into pilot holes made in the acrylic template.
Figure 4.. (a) Example of a simulated implant placement that was evaluated as accurate. It revealed no fenestrations, dehiscences, or violations of vital structures. (b) Example of a simulated implant placement that was evaluated as inaccurate. It is evident that if this surgical guide was to be used for implant placement, the implant would be placed far too buccal resulting in a complete buccal dehiscence. Figure 3. Distribution between accurate (shades of green) and inaccurate sites (shades of red). Although no statistical significant difference was found, a slight trend toward higher inaccuracy was noted in the mandible (30% vs 23%). Figure 4. Distribution of inaccurate sites by the reason for inaccuracy. No statistically significant difference was found between the 2 arches with regard to reason for inaccuracy. In both arches combined, the percentage of sites determined as inaccurate because of lingual plate perforations (64%, shades of purple) was greater than those that were determined as inaccurate because of buccal dehiscences or fenestrations (36%, shades of green).
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