[Mapping mini-implant anatomic sites in the area of the maxillary first molar with the aid of the NewTom 3G® system].

INTRODUCTION The goal of our study was to construct a map of the implant sites in the region of the attached gingiva around the maxillary first molars that would be appropriate locations for placement of miniscrews to serve as orthodontic anchorage. METHOD We conducted 58 radiographic examinations with the NewTom 3G(®) cone beam technique. For each interdental space, between upper second bicuspids and first molars (5/6) and between upper first and second molars (6/7), we studied the mesio-distal width and depth of bucco-lingual bone at two different levels, L1 and L2, that corresponded to the lower and upper limits of the attached gingiva in the general population. RESULTS The widths of the interdental spaces varied very little between L1 and L2 and their variances were comparable. At the level of the 5/6 space, the interdental widths displayed a Gaussian distribution, which made it possible for us to determine the confidence intervals at the two borders of attached gingiva as a function of age: IC(99%) of L1 = [2.045 ; 3.462] from 12 to 17 years or [1.594 ; 2.519] from 18 to 24 or [1.613 ; 2.5] from 25 to 48 years and IC(99%) of L2 = [2.37 ; 3.69] from 12 to 17 years or [1.5 ; 2.613] from 18 to 24 or [1.546 ; 2.619] from 25 to 48 ans. The interdental depths increased in an apical direction and their variance diminished. Even if the adequacy of the Gaussian law is less reliable in the sagittal plane, we find a greater consistency in depths in the spaces around 5/6 that allows us to establish very precise confidence levels: IC(99%) of L1 = [9.213; 10.575] and IC(99%) of L2 = [10.295; 11.593]. CONCLUSION The mesial areas of the first molars constitute safe zones for implantation of miniscrews with a maximum of 2-2.3 mm for 12 to 17 years old or 1.5-1.6 mm for 18 to 48 year olds and of a maximum of 9-10 mm in length whether the attached gingival level is strong or feeble. The distal areas of the first molars, because of their great variability, require an individualized radiographic study before any mini/screw can be placed.