A descriptive tissue evaluation at maxillary interradicular sites: Implications for orthodontic mini-implant placement

Few studies have evaluated interradicular anatomy for hard and soft tissue thickness. Because interradicular sites are common regions for mini-implant placement for orthodontic anchorage, the purpose of this study was to provide a guideline to indicate the best location for mini-implants as it relates to the thickness of cortical bone and soft tissue, and to the height of the attached gingival field. CT images from 15 men and 15 women (mean age 27 years, range 23-35 years) were used to evaluate the buccal interradicular cortical bone thickness from and mesial to the central incisor to the 1st molar. To record soft tissue depth at the site of assessment for cortical bone thickness, the mucosa was pierced with a #15 endodontic K-file until the attached rubber stop rested on the mucosa. The height of attached gingiva was measured at the mid-aspect of each tooth using a caliper. There were no significant differences in cortical bone thickness within interradicular sites except for the 2nd premolar/1st molar site. There were also no significant differences in soft tissue thickness within interradicular sites except for the lateral incisor/canine and 2nd premolar/1st molar sites. The height of attached gingiva was greater in the anterior compared to the posterior region and was shortest in the premolar region. Given the limits of this study, mini-implants for orthodontic anchorage may be well placed with equivalent bone-implant contact anywhere within the zone of attached gingiva up to 6 mm apical to the alveolar crest with adequate interradicular space.