Loescher A R, Holland G R
Department of Oral and Maxillofacial Surgery, University of Sheffield School of Clinical Dentistry, Charles Clifford Dental Hospital, England.
Anat Rec. 1991 May;230(1):57-72. doi: 10.1002/ar.1092300107.
The distribution and morphological characteristics of myelinated and non-myelinated axons innervating the lower canine periodontal ligament (PDL) in adult cats have been analysed. After perfusion fixation and decalcification, the teeth were slit transversely, divided into segments, and embedded in plastic. Ultrathin sections of each segment were examined in the electron microscope and used to reconstruct the whole PDL at 1, 4, 7, and 9 mm from the tooth apex. One millimeter from the tooth apex there were a mean of 920 myelinated axons and 1,415 non-myelinated axons. The numbers of axons declined toward the tooth crown. Bundles of myelinated and small non-myelinated axons lay adjacent to the blood vessels midway between the bone and cementum. Isolated myelinated axons appeared to have split away from these main nerve bundles and entered the avascular zone of the ligament, where they lost their myelin sheaths to become large non-myelinated axons rich in mitochondria. These non-myelinated axons sometimes appeared to be linked to collagen fibres and were thought to be the mechanoreceptor terminals. Twelve weeks after sectioning and inferior alveolar nerve, the total number of axons innervating the periodontal ligament was 50% of that found in the contralateral controls. The large non-myelinated axons had smaller mean diameters and contained fewer mitochondria, a change which may be consistent with a reduction in mechanoreceptor excitability.
对成年猫支配下犬齿牙周韧带（PDL）的有髓和无髓轴突的分布及形态特征进行了分析。经灌注固定和脱钙后，将牙齿横向切开，分成节段，然后包埋于塑料中。对每个节段的超薄切片进行电子显微镜检查，并用于重建距根尖1、4、7和9毫米处的整个牙周韧带。距根尖1毫米处，平均有920条有髓轴突和1415条无髓轴突。轴突数量向牙冠方向递减。有髓轴突束和细小无髓轴突束位于骨与牙骨质之间中途的血管旁。孤立的有髓轴突似乎从这些主要神经束分离出来，进入韧带的无血管区，在那里它们失去髓鞘，变成富含线粒体的大型无髓轴突。这些无髓轴突有时似乎与胶原纤维相连，被认为是机械感受器终末。切断下牙槽神经12周后，支配牙周韧带的轴突总数为对侧对照的50%。大型无髓轴突的平均直径较小，线粒体较少，这种变化可能与机械感受器兴奋性降低一致。
