Spyropoulos M N, Tsolakis A I
Department of Orthodontics, University of Athens, Greece.
Eur J Orthod. 1997 Apr;19(2):211-8. doi: 10.1093/ejo/19.2.211.
Unilateral condylar injury is known to be a frequent cause of mandibular asymmetry. Whether this is due to the trauma itself or to the disturbed function that follows the injury is a very important question with ramifications for clinical complications related to facial asymmetries. The aim of this study was to test the hypothesis that mandibular function in a protruded position can compensate for the absence of one condyle and prevent potential growth asymmetries. Forty-eight 4-week-old rats were divided into two experimental and two control groups consisting of 12 animals each, as follows: (A) unilateral condylectomy was performed on the right side and the mandible was left to function normally; (B) after unilateral condylectomy on the right side, the mandible was forced to function in a protruded position; (C) a sham operation was performed in the condylar area of the right side but no appliance was used; and (D) 12 animals were used as controls without any operation or appliance. Mandibular protraction was achieved by means of a specific appliance, acting via rubber bands, pulling the mandible in a straight, forward direction with a force of 25 g for 12 hours per day. The experimental period was 30 days. Dorsoventral radiographs were taken and vital dyes were administered at three time intervals, i.e. on days 1, 15 and 30, for all animals. Cephalometric analysis included 14 measurements. Findings resulting from statistical analysis and comparisons of measurements obtained in the four groups can be summarized as follows: (i) when comparing group A with groups C and D, less growth was found in the right mandibular sides in group A; (ii) when comparing group B and groups C and D, less growth was found in the right mandibular sides in group B; (iii) when comparing groups A and B, more growth was found in the right mandibular sides in group B; (iv) when comparing the right and left mandibular sides in group A, less growth was found in the right side; and (v) when comparing the right and left mandibular sides in group B, no significant growth differences were found. These findings support the hypothesis that altered mandibular function in a protruded position can compensate for the effects of unilateral condylectomy and prevent the appearance of skeletal mandibular asymmetries in growing rats.
单侧髁突损伤是下颌骨不对称的常见原因。这是由于创伤本身还是损伤后功能紊乱所致，这是一个非常重要的问题，对与面部不对称相关的临床并发症有影响。本研究的目的是检验以下假设：下颌骨处于前伸位置时的功能可以弥补一侧髁突缺失，并防止潜在的生长不对称。48只4周龄大鼠分为两个实验组和两个对照组，每组12只动物，具体如下：(A) 右侧进行单侧髁突切除术，下颌骨正常功能；(B) 右侧单侧髁突切除术后，下颌骨被迫在前伸位置发挥功能；(C) 在右侧髁突区域进行假手术，但不使用矫治器；(D) 12只动物作为对照组，不进行任何手术或使用矫治器。通过一种特殊的矫治器实现下颌前伸，该矫治器通过橡皮筋起作用，以25克的力每天向前直拉下颌骨12小时。实验期为30天。对所有动物在第1天、第15天和第30天这三个时间点拍摄背腹位X线片并注射活性染料。头影测量分析包括14项测量。四组测量结果的统计分析和比较结果总结如下：(i) 将A组与C组和D组比较时，A组右侧下颌骨生长较少；(ii) 将B组与C组和D组比较时，B组右侧下颌骨生长较少；(iii) 将A组和B组比较时，B组右侧下颌骨生长较多；(iv) 在A组中比较右侧和左侧下颌骨时，右侧生长较少；(v) 在B组中比较右侧和左侧下颌骨时，未发现显著的生长差异。这些结果支持以下假设：下颌骨在前伸位置的功能改变可以弥补单侧髁突切除术的影响，并防止生长中大鼠出现下颌骨骨骼不对称。
