Regeneration of trigeminal nerve ending mechanoreceptor function.-As an indication of ideal orthodontic treatment intervention time.

以往的研究表明，颞下颌关节（TMJ）机械感受器在咀嚼运动的早期即已成熟，当咀嚼负荷降低时，TMJ机械感受器的功能不能维持。本研究的目的是调查是否恢复适当的颞下颌关节负荷在生长早期可能会导致颞下颌关节机械感受器功能的恢复。将99只2周龄雄性Wistar大鼠分为两组，开始喂食颗粒饲料[对照组（n=33）]或流质饲料[实验组（n=66）]。实验组又分为换料组和流食组，换料组从第5周开始用颗粒饲料代替流食。在第5、7和9周记录三叉神经节的TMJ机械感受器活动。测量各组大鼠的放电阈值和最大瞬时放电频率，并与对照组进行比较。将每个实验亚组中单个TMJ单位的放电特性与对照组中的放电特性进行比较。在饮食改变组中，颞下颌关节单位的放电特性在7周时得到恢复。因此，在生长早期给予适当的颞下颌关节负荷，可促进颞下颌关节机械感受器功能的恢复。

Previous studies have reported that the maturation of temporomandibular joint(TMJ) mechanoreceptors was promoted in the early masticatory stage and TMJ mechanoreceptors could not sustain their function when masticatory loading was decreased. The purpose of the present study was to investigate whether a resumption of proper TMJ loading during the early growth period could lead to the restoration of TMJ mechanoreceptor function. Ninety-nine 2-week-old male Wistar rats were divided into two groups and feeding was started with either pellets[ control group(n=33)] or liquid diet[ experimental group(n=66)]. The experimental group was further divided into changing-diet(n=33) and liquid-diet(n=33) groups ; the former was fed pellets instead of liquid diet from 5 weeks. TMJ mechanoreceptor activities were recorded from the trigeminal ganglion at 5, 7 and 9 weeks. The firing threshold and maximum instantaneous firing frequency were measured in each group in comparison with the control group. The firing properties of single TMJ units in each experimental subgroup were compared to those in the control group. In the changing-diet group, the firing properties of TMJ units were recovered at 7 weeks. In conclusion, proper TMJ loading during the early growth period can lead to the restoration of TMJ mechanoreceptor function.