Azizi Fateme, Shahidi-Zandi Vahid
Orthodontic Department, Dental school, Kermanshah University of Medical Sciences, Kermanshah, Iran.
Orthodontic Department, Dental school, Hamadan University of Medical Sciences, Shahid-Fahmideh Street, Hamadan, Iran.
Int Orthod. 2018 Mar;16(1):82-90. doi: 10.1016/j.ortho.2018.01.023. Epub 2018 Feb 17.
The aim of this study was to determine the effect of first premolar extraction with different anchorages as well as non-extraction on mandibular third molar angulation.
The pretreatment (T1) and posttreatment (T2) panoramic radiographs of one hundred patients from Hamadan (Iran), who underwent fixed orthodontic treatment were investigated and the angle between long axis of right mandibular third molars and a constructed horizontal plan (HRP) was measured. The sample was equally divided into four groups including first premolar extraction with maximum anchorage, that with moderate anchorage, that with minimum anchorage and non-extraction group.
In the first premolar extraction groups with moderate and minimum anchorages, third molar angulation increased (8.12 and 7.48°, respectively) significantly from T1 to T2 (P=0.001 and 0.003, respectively), but in the first premolar extraction group with maximum anchorage and non-extraction group, increase in third molar angulation (2.84 and 0.8°, respectively) was not statistically significant (P=0.082 and 0.943, respectively). Third molar uprighting was significantly different among four groups using one-way ANOVA (P=0.004). Tukey (HSD: honestly significant difference) post hoc test indicated that difference in third molar angulation was statistically significant between first premolar extraction group with moderate anchorage and non-extraction group (P=0.007) and also between the first premolar extraction group with minimum anchorage and non-extraction group (P=0.024).
The first premolar extraction groups with moderate and minimum anchorage may lead to more chance of third molar eruption and this can be helpful in borderline cases to consider third molar angulation as one of determining indicators to decide whether to extract or not to extract first premolars.
本研究旨在确定不同支抗下第一前磨牙拔除以及不拔牙对下颌第三磨牙角度的影响。
对来自伊朗哈马丹的100例接受固定正畸治疗患者的治疗前（T1）和治疗后（T2）全景X线片进行研究，测量右侧下颌第三磨牙长轴与构建的水平平面（HRP）之间的角度。样本被平均分为四组，包括最大支抗下第一前磨牙拔除组、中度支抗下第一前磨牙拔除组、最小支抗下第一前磨牙拔除组和不拔牙组。
在中度支抗和最小支抗的第一前磨牙拔除组中，从T1到T2第三磨牙角度显著增加（分别为8.12°和7.48°）（P分别为0.001和0.003），但在最大支抗下第一前磨牙拔除组和不拔牙组中，第三磨牙角度增加（分别为2.84°和0.8°）无统计学意义（P分别为0.082和0.943）。使用单因素方差分析，四组之间第三磨牙直立情况有显著差异（P = 0.004）。Tukey事后检验表明，中度支抗下第一前磨牙拔除组与不拔牙组之间第三磨牙角度差异有统计学意义（P = 0.007），最小支抗下第一前磨牙拔除组与不拔牙组之间第三磨牙角度差异也有统计学意义（P = 0.024）。
中度支抗和最小支抗的第一前磨牙拔除组可能导致第三磨牙萌出的机会增加，这在临界病例中有助于将第三磨牙角度作为决定是否拔除第一前磨牙的决定指标之一。
