Artun Jon, Thalib Lukman, Little Robert M
Department of Developmental and Preventive Sciences, Faculty of Medicine, Kuwait University, Kuwait.
Eur J Orthod. 2005 Dec;27(6):590-6. doi: 10.1093/ejo/cji049. Epub 2005 Jul 11.
The purpose of this study was to analyse the effect of premolar extraction therapy on third molar angulation during active treatment, and to test the significance of such changes on subsequent impaction of the third molars. Lateral cephalograms made before (T1) and after (T2) treatment and at long-term follow-up (T3) of 157 patients treated non-extraction (non-ex) or with extraction of four premolars (ex), all accurately diagnosed for impaction versus eruption of at least one third molar at T3, were evaluated. Linear regression models demonstrated that the maxillary third molars uprighted more from T1 to T2 (P < 0.05) and were less distally angulated at T2 (P < 0.01) in the ex than in the non-ex patients. No such differences were detected in the mandible (P > 0.05). The regression models also showed similar uprighting of the maxillary and mandibular third molars from T1 to T2 and similar angulation of the maxillary third molars at T2 in those patients with subsequent eruption and impaction (P > 0.05), but more mesially angulated mandibular third molars at T2 in the impaction patients (P < 0.01). Chi square testing demonstrated a higher frequency of distal tipping of the maxillary third molars from T1 to T2 in the impaction patients (P < 0.01), while mesial tipping from T1 to T2 of the mandibular third molars occurred with similar frequency in the two patient groups (P > 0.05). Chi square analysis also showed a higher frequency of greater than 30 degree distal angulation as well as an amount mesial angulation of the maxillary third molars at T2 (P < 0.01), and a higher frequency of greater than 40 degree mesial angulation of the mandibular third molars at T2 (P < 0.01) in patients with impaction than in those with eruption.
本研究的目的是分析拔除前磨牙治疗对积极治疗期间第三磨牙倾斜度的影响，并检验这种变化对后续第三磨牙阻生的意义。对157例接受非拔牙（非拔组）或拔除四颗前磨牙（拔牙组）治疗的患者在治疗前（T1）、治疗后（T2）以及长期随访（T3）时拍摄的头颅侧位片进行了评估，所有患者在T3时均被准确诊断为至少有一颗第三磨牙阻生或萌出。线性回归模型显示，与非拔组患者相比，拔牙组患者上颌第三磨牙从T1到T2时直立更明显（P<0.05），且在T2时远中倾斜度更小（P<0.01）。在下颌未检测到此类差异（P>0.05）。回归模型还显示，在后续有萌出和阻生的患者中，上颌和下颌第三磨牙从T1到T2时的直立情况相似，上颌第三磨牙在T2时的倾斜度也相似（P>0.05），但阻生患者下颌第三磨牙在T2时近中倾斜度更大（P<0.01）。卡方检验显示，阻生患者上颌第三磨牙从T1到T2时远中倾斜的频率更高（P<0.01），而两组患者下颌第三磨牙从T1到T2时近中倾斜的频率相似（P>0.05）。卡方分析还显示，阻生患者中上颌第三磨牙在T2时远中倾斜大于30度以及近中倾斜的频率更高（P<0.01），下颌第三磨牙在T2时近中倾斜大于40度的频率也更高（P<0.01）。
