Space Changes after Premature Loss of a Mandibular Primary Second Molar

Background: Although there are many studies on the space changes after premature loss of the primary second molars, there is still lack of research with high methodological quality. In this study, the research method used established protocol to observe the longitudinal space changes after premature loss of the primary second molars. Methods: Thirteen children (mean SD aged 6.74 1.15 years) who experienced unilateral premature loss of mandible primary second molar were included. Study casts were obtained from participants 2 or 3 days after the tooth was removed, as well as at a follow-up appointment 19 months later. Seven reference lines were measured and compared on the study cast including D+E space, arch width, arch length, interprimary first molar width, intercanine width, intercanine length and arch perimeter. Results: At 19-month follow-up, the D+E space on the extraction side was significantly shorter than the control side and the initial D+E space on the extraction side (P ＜ 0.05). There were no significant differences in the longitudinal comparisons of arch width, arch length, and arch perimeter changes in the 19-month follow period. However, the intercanine width, intercanine length and inter-primary first molar width showed significantly longer than the initial measurements (P ＜ 0.05). Conclusions: The 19-month space changes after the premature loss of mandibular primary second molar consist mainly of distal movement of the primary first molar. Slight mesial movement or tilting of first permanent molar was compensated by increasing intercanine width, intercanine length and inter-primary first molar width. Comprehensive space analysis for each individual is necessary to decide the need of a space maintainer.

關鍵字

Mandibular primary second molar ； Premature loss ； Space changes

並列摘要

背景：儘管有許多第二乳臼齒過早脫落後齒列空間變化的研究，但仍缺乏精細的研究方法。本研究利用先前研究所建立之模式，與其個別的控制組作比較，觀察下顎第二乳臼齒過早脫落之齒列空間變化。實驗方法：針對13位，平均年齡6.74 1.15歲，單側下顎第二乳臼齒提早脫落的孩童，於剛拔牙後及追蹤19個月後印模，使用數位型電子測規量測齒列牙弓發育之七個測量值，分別為D + E space、牙弓寬度（arch width）、牙弓長度（arch length）、第一乳臼齒間寬度（inter-primary first molar width）、牙弓周長（arch perimeter）、犬齒間長度（intercanine length）及犬齒間寬度（intercanine width）。結果：19個月後拔牙側的D + E space比起對照組和剛拔牙時顯著較短。其他數值比起一開始，19個月後的犬齒間長度、犬齒間寬度及第一乳臼齒間寬度顯著變長，而牙弓寬度、牙弓長度、牙弓周長則無顯著差異。結論：在19個月的追蹤下，第二乳臼齒過早脫落後之空間變化主要為第一乳臼齒遠心移動。些微恆牙第一大臼齒近心移動被增加的犬齒間長度、犬齒間寬度以及第一乳臼齒間寬度所補償。在做空間維持器之前需要詳細做個人的空間分析。

並列關鍵字

下顎第二乳臼齒；過早脫落；齒列空間變化

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