Evaluation Of Micro-implant Anchorage Placement Sites In The Maxillary Posterior Region In Skeletal Class Ⅱ Adults With Different Vertical Facial Patterns: A Cone-beam Computed Tomography Study

Objective: To provide reference for the selection of micro-implant anchorage placement sites by evaluating the thickness of buccal cortical bone and buccolingual bone as well as the interradicular distance of maxillary posterior area in patients with different vertical facial types.Methods: 34 cases of skeletal class Ⅱ adult patients were divided into three groups according to mandibular plane angle: hyperdivergent,normodivergent and hypodivergent.CBCT was used to measure the interradicular distance of the maxillary second premolar and the first molar at the height of 3 mm,5 mm and 7 mm from the alveolar crest,the thickness of buccal cortical bone and buccolingual bone at the angles of 0 °,45 ° and 60 °,respectively.Results:1.Comparison between the right and left sides of the measured data: there were no statistically significant differences in buccal cortical bone thickness,buccolingual bone thickness,and interradicular distance between the right and left sides of the hyperdivergent,normodivergent and the hypodivergent(P>0.05).2.Intergroup comparison: Except for the mean value of buccolingual bone thickness in the hyperdivergent group at 0° implantation at a height of 5 mm from the top of the alveolar ridge,which was less than that in the hypodivergent group,and the difference was statistically significant(P=0.012),there were no statistically significant differences in buccal cortical bone thickness,buccolingual bone thickness at the same height and angle,and interradicular distance at the same height among the three groups(P>0.05).3.Intra-group cross-sectional comparison: the buccal cortical bone thickness at 3 mm,5mm and 7 mm height from the top of the alveolar crest at 0°,45° and 60° implantation,respectively,were statistically different in the hyperdivergent group(P<0.05),where the buccal cortical bone thickness: 60°>45°>0°.In the normodivergent group,the buccal cortical bone thickness was statistically greater at a height of 3 mm from the top of the alveolar ridge at 60° than at the same height at 0° and 45°,with a statistically significant difference(P<0.05);the buccal cortical bone thickness was statistically different at a height of 5 mm and 7 mm from the top of the alveolar ridge at 0°,45° and 60°,respectively(P<0.05),with the buccal cortical bone thickness: 60°>45°>0°.In the hypodivergent group,the buccal cortical bone thickness at 0° implantation at 3 mm and5 mm from the top of the alveolar ridge was less than that at 45° and 60° implantation,and the difference was statistically significant(P<0.05);the buccal cortical bone thickness at 0°,45° and 60° implantation at 7 mm height was statistically different(P<0.05),in which the buccal cortical bone thickness was 60° > 45° > 0°.The buccolingual bone in the hyperdivergent and normodivergent groups was greater at 7 mm height from the top of the alveolar ridge at 0° implantation than at the same height at 60°implantation,and the difference was statistically significant(P<0.05).The buccolingual bone in the hypodivergent group was greater at 0° implantation at 5 mm and 7 mm height than at 60° implantation at the same height,and the difference was statistically significant(P<0.05).4.Intra-group longitudinal comparison: the buccal cortical bone thickness in the hyperdivergent and hypodivergent groups was greater at 7 mm height from the top of the alveolar ridge at 0° implantation than at 3 mm height from the top of the alveolar ridge at the same angle implantation,with a statistically significant difference(P<0.05).In the normodivergent group,the buccal cortical bone thickness was greater at 7 mm height from the top of the alveolar ridge at 0° than at 3 mm and 5 mm height at the same angle,with a statistically significant difference(P<0.05);the buccal cortical bone thickness was greater at 7 mm height at 45° than at 3 mm height at the same angle,with a statistically significant difference(P=0.015).The buccolingual bone thickness in the three groups was greater at 3 mm height from the top of the alveolar ridge at 45° and60° implantation than at 7 mm height from the top of the alveolar ridge at the same angle,with a statistically significant difference(P < 0.05).The interradicular distances in the hyperdivergent and normodivergent groups were greater at 7 mm height from the top of the alveolar crest than at 3 mm height,with statistically significant differences(P< 0.05).Conclusions:1.Skeletal Class Ⅱ adults do not need to be overly concerned about the vertical skeletal patterns when clinically implanting micro-implant anchorage between the second premolar and the first molar in maxillary.2.It’s greater at 5mm height from the alveolar crest and at 60°implantation when the micro-implant anchorage is placed between the maxillary second premolar and first molar in skeletal Class Ⅱ adults.