A Guide For Microscrew Implant Positioning In The Safe Zone Of Alveolar Bone

Objective:To rebuild the three-dimensional image of crane-facial after 16 helical CT and establish CT measurement criteria of different depth from alveolar crest and provide an anatomical map to assist the clinician in miniscrew/microsrew placement in a safe location between dental roots. Materials and Methods:Helical CT images of 25 maxillae and 25 mandibles were examined, and then three-dimensional models were rebuilt. For each interradicular space , the mesiodistal and the buccolingual distances were measured at 2.5, 5, 7.5, and 10 mm from the alveolar crest. Measurements distal to the canines are presented,including the tuber maxillae. Both the buccal and palatal were measured in the mesiodistal distances between the second premolar and the first molar, between the first molar and the second molar.SPSS13.0 software was used to calculating mean value and standard deviation. Results:1. In the maxilla, the greatest amount of mesiodistal bone was on the palatal side between the second premolar and the first molar (4.7 mm SD 1.0, at 7.5mm depth); the least amount of bone was at the tuberosity (0.3 mm SD 4.1, at 10mm depth). In the buccopalatal dimension, the greatest amount of space was between the first and second molars (15.6 mm SD 1.1, at 7.5 mm from the alveolar crest);the least amount of bone was at the tuberosity(0.6 mm SD 5.7, at 10mm from the alveolar crest). In the maxilla at 10mm depth, both the buccopalatal and the mesiodistal values are low because of the frequent presence of the maxillary sinus.2. In the mandible, the greatest amount of bone in the mesiodistal dimension was between first and second molars (4.4 mm SD 1.7, at 7.5mm depth); the least amount of bone was between the first premolar and the canine (2.5 mm SD 0.4, at 2.5mm depth). In the buccolingual dimension, the greatest amount of bone was between the first and second molars (14.7 mm SD 1.6, at 7.5mm depth); the least between the first premolar and canine (8.9 mm SD 0.5, at 2.5mm depth) and between the first and second premolars (8.9 mm SD 0.8,at 2.5mm depth). Conclusions:1. In the maxilla, the greatest amount of mesiodistal bone was on the palatal side between the second premolar and the first molar. The least amount of bone was in the tuberosity. The greatest thickness of bone in the buccopalatal dimension was between the first and second molars, whereas the least was found in the tuberosity.2. In the mandible, the greatest amount of mesiodistal dimension was between first and second premolar. The least amount of bone was between the first premolar and the canine. In the buccolingual dimension, the greatest thickness was between first and second molars. The least amount of bone was between first premolar and the canine and between the first and second premolars.