A Cone-beam CT Study On Anterior Alveolar Bone Morphology Of Adults In Skeletal Class â…  And Class â…¡ Malocclusions With Different Vertical Patterns

Objective：To evaluate the alveolar bone morphology in anterior regions of the maxilla andthe mandible, and the three dimensional position of the teeth on cone-beam computedtomographs of adults in skeletal ClassⅠ and Class Ⅱ malocclusions with differentvertical types.Methods：This study was conducted on120images of adult patients (18-36years old),who sought orthodontic treatment in Affiliated Stomatological Hospital of NanchangUniversity from September2011to December2013, including60skeletal ClassⅠmalocclusion cases(10male and10female for low angle, average angle and highangle cases, respectively) and60skeletal Class Ⅱ malocclusion cases(10male and10female for low angle, average angle and high angle cases, respectively). The DICOMdata was imported to the third-party software for secondary reconstruction to obtainsagittal sections, and the upper and lower left central incisors of each subject werechosen for measurements, including the thickness (labial, lingual, and total thicknessat the apical level), height(basal and total height), and proclination (labial and lingualalveolus proclination, labial and lingual cortical bone angle) of the upper and loweranterior alveolus, as well as the tooth proclination and the range of labial and lingualroot rotation. The multi-way classification analysis of variance (ANOVA) test andmultiple linear regression were used for variance analysis on measurements ofdifferent groups regarding gender, sagittal and vertical patterns.Results:1. Upper anterior region:(1) Lingual and total alveolar bone thickness at apical level were significantlyhigher in male than in female, in low angle groups than in the average and high anglegroups, and had negative correlation with the proclination of the central incisors. Theresults revealed no significant difference in labial alveolar bone thickness withrespect to gender, sagittal and vertical patterns. (2) The total height of alveolar bone was significantly lower in female than inmale, in low angle groups than in the average and high angle groups, and hadnegative correlation with the proclination of the central incisors. The distance fromroot apex of the central incisors to PP(palatal plane) presented difference only indifferent vertical types-the distance was fewer in low angle groups than in theaverage and high angle groups, while the latter two had no significant difference.(3) Positive correlation was determined between the proclination of labial/lingual alveolus and the proclination of the central incisors. The labial alveolusproclination and labial cortical bone angle were greater in male than in female, inClassⅠ groups than in Class Ⅱ groups, in low angle groups than in the average andhigh angle groups, while the latter two had no significant difference.(4) No significant difference was observed in the central incisors’ proclinationwith respect to gender,sagittal and vertical patterns.(5) The amount of the incisors’ root labially rotational movement wassignificantly greater in low angle groups than in the average and high angle groups,and had positive correlation with the incisors’ proclination. At the same time, theamount of the incisors’ root lingually rotational movement was significantly fewer inClass Ⅱ groups than in ClassⅠ groups, in high angle groups than in the average andlow angle groups, while the latter two had no significant difference.2. Lower anterior region:(1) Labial and total alveolar bone thickness at apical level was significantlyhigher in male than in female, in low angle groups than in the average and high anglegroups. The lingual alveolar bone thickness presented differences only in differentvertical types: low angle groups> average angle groups> high angle groups.(2) The basal and total height of alveolar bone were significantly higher in malethan in female, but no difference was found between ClassⅠ and Class Ⅱ groups, or indifferent vertical type groups.(3) There was positive correlation between the proclination of lingual alveolusand the proclination of central incisors. The labial cortical bone angle was smaller inlow angle groups than in the average and high angle groups, while the lingual corticalbone angle was smaller in high angle groups than in the average and low angle groups, while the latter two had no significant difference.(4) The central incisors’ proclination showed significant differences: ClassⅠgroups> Class Ⅱ groups, low angle groups> average angle groups> high angle groups,without difference between male and female.(5) The amount of the incisors’ root labially and lingually rotational movementwas fewer in high angle groups than the average and low angle groups, while thelatter two had no significant difference.What’s more, the labial rotation had positivecorrelation with the incisors’ proclination.Conclusion:Both upper and lower anterior alveolar bone morphology in adults werestatistically significantly correlated with gender, vertical and sagittal patterns, and theproclination of the teeth. And the morphology of the alveolar bone defined the limitof tooth movement. In clinical practice, alveolar bone morphology in differentskeletal patterns should be concerned to determine the amount and types of toothmovement to avoid iatrogenic sequelae.