Faculty of Dental Medicine, University of Porto, Portugal.
Department of Prevention, Pediatric Dentistry and Orthodontics, Programme for Integral Dental Treatment of Pediatric Patients, Complutense University of Madrid, Spain.
Eur J Paediatr Dent. 2014 Sep;15(3):258-64.
This study was conducted to determine frequency, distribution and magnitude of infraocclusion in primary mandibular molars; to evaluate root resorption, the frequency of premolars agenesis and the association between primary molar infraocclusion and premolar agenesis.
The sample consisted of 472 children who were subdivided in 3 age groups. The magnitude of infraocclusion was determined following the Bjerklin and Bennett method modified by the authors. Radicular resorption was determined using the rating scale proposed by Bjerklin and Bennett evaluating mesial and distal roots separately. The development degree of corresponding premolars was determined using the Demirjian method.
One hundred and three (21.8%) children presented infraocclusion. The first primary molar presented infraocclusion in a significantly higher frequency. Considering the 3 scores of infraocclusion, 61.1% of the affected molars were classified as mild infraocclusion. No differences were found considering the root resorption pattern for primary molars, infraoccluded or not. Significant differences were found in the presence of agenesis in the group of infraoccluded molars.
The present study identified a high percentage of infraocclusion, demonstrating that the type of molar is an influent variable, that the first primary molar is the most affected one, especially mandibular molars, and that the majority was mainly of a mild degree. There were no significant differences between the exfoliation of infraoccluded and non infraoccluded primary molars. However, radicular resorption of infraoccluded molars presented a clear delay or was totally absent in infraoccluded molars associated with premolar agenesis. Significant differences in the presence of agenesis beneath infraoccluded molars were observed.
本研究旨在确定下颌第一乳磨牙内倾的频率、分布和程度；评估根吸收、前磨牙缺失的频率以及下颌第一乳磨牙内倾与前磨牙缺失之间的关系。
样本由 472 名儿童组成，分为 3 个年龄组。内倾程度采用作者改良的 Bjerklin 和 Bennett 方法确定。根吸收采用 Bjerklin 和 Bennett 提出的评分标准评估，分别评估近中根和远中根。相应前磨牙的发育程度采用 Demirjian 方法确定。
103 名（21.8%）儿童存在内倾。第一乳磨牙内倾的发生率明显较高。考虑到 3 个内倾评分，61.1%受影响的磨牙被归类为轻度内倾。无论内倾或非内倾磨牙的根吸收模式如何，均未发现差异。在存在缺失的情况下，内倾磨牙组存在显著差异。
本研究发现了较高百分比的内倾，表明磨牙类型是一个影响因素，第一乳磨牙是最易受影响的，特别是下颌磨牙，而且大多数主要是轻度的。内倾和非内倾乳磨牙的脱落没有显著差异。然而，与前磨牙缺失相关的内倾磨牙的根吸收明显延迟或完全缺失。在存在缺失的情况下，观察到内倾磨牙下方的显著差异。
