| Objective:In this study, with the aid of the reconstruction of CT data,3D registration, CAD technology, Rapid prototyping, the template for placement of miniscrew and imlant were designed and manufactured. After registration of pre and post-operative CT data, the deviation between the actual miniscrews/implants and virtual ones was measured and the accuracy of two kinds template were evaluated respectively. And the deviation was 3D measured for analyses of the source of the deviation to improve the design of template. At the same time, the place for miniscrews placement (the interradicular position of second premolar and the first molar) was measured and evaluated. Develop 3D registration method for assessment of outcome of orthodontic treatment.Materials and Methods:1.11 patients who had bimaxillary protrusion, and agreed to extract the 4 first premolars,34 miniscrews were planned to provide absolute anchorage. After preparing mounted diagnostic casts with fully extended vestibular borders of the jaws, the radiographic templates were fabricated by use of the vacuum former technique and the patients and the radiographic template were scanned before the procedure with double-scan technique. And the 3D virtual model of teeth and maxillary/mandible were reconstructed basing on the CT data in the Mimics software respectively and superimposing the 2 sets of scans(with the radiographic markers as reference points. The virtual miniscrews were placed in a safe and optimal position when the roots of teeth were visualized, and the insertion site and angle were decided. The drill template was designed with the radiographic guide and the 3D information of the planned drill paths and fabricated the stereolithography template via a CAD/CAM procedure. When the position for the miniscrews was decided, a plane was created along the cylinder, and the distance between the two roots for miniscrew was measured at this plane. After registration of the pre and post-operative CT data, the deviation between the actual miniscrews and virtual miniscrews was 3D measured. Compare the actual and allowed deviation,the accuracy and security was evaluated.2. The CAD/CAM templates for 4 completely edentulous jaws were designed and fabricated basing on the preoperative CT data and the stone models of the jaws sample. And 14 implants (OSSTEM) were placed in the posterior region of the jaws aided by the CAD/CAM template. The pre and postoperative CT was registered by the point to point method, and the deviation between actual and virtual implants was measured to assess the accuracy of the template.Results:The interradicular safe zone for miniscrew of the 11 patients ranged from 3.7～4.5 mm and 4.12±0.247 mm(mean±SD) in average, and the allowed deviation ranged from 0.65-1.05mm and 0.86±0.125mm(mean±SD) in average. The templates were adapted on the patients in a satisfactory and stable manner. All the placement of the miniscrews was performed smoothly without any problem. The deviations of the position at the disto-mesial, vertical, bucco-palatal direction were 0.42±0.13mm, 0.47±0.12mm,0.59±0.26mm at the tip respectively and 0.10±0.012mm at the insertion sites. The miniscrew deviation of angle from the planned position at the disto-mesial, vertical, bucco-palatal direction was 1.2±0.43degrees,1.3±0.41 degrees, 1.6±0.79degrees respectively. No statistically significant differences were observed between the deviations at disto-mesial and vertical directions, and the bucco-palatal deviation was greater than other two directions, showed a significant difference. The deviation of template guide group was significantly smaller than allowed deviation, the difference was statistically significant (P<0.05).2. With the aid of CAD/CAM template, the deviations of the position at the tail of the implant, at the tip of the implant and the projected deviation of angle were 0.19±0.07 mm,0.47±0.12 mm, and 1.79±0.68 degrees respectively. The deviations of the position at the disto-mesial, vertical, bucco-palatal direction were 0.22±0.08mm, 0.25±0.06 mm,0.30±0.11mm at the tip respectively and 0.10±0.03mm,0.08±0.02mm, 0.13±0.04 mm at the head. The miniscrew deviation of angle from the planned position at the disto-mesial, bucco-palatal direction was 1.2±0.38 degree,1.24±0.3 degree respectively, showed no significant difference.Conclusion:In light of the results obtained, the new template for miniscrew and implant has high accuracy, and is especially applicable for severe clinical cases that require precise miniscrews placement.
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