牙囊在牙根发育中作用的实验研究

Experimental Study of the Dental Follicle′s Function in Tooth Root Development

目的研究牙囊在牙根发育中的作用。方法8只出生5d的Balb/c小鼠随机分为含牙囊组和去除牙囊组,取其双侧下颌第一磨牙牙胚分别异位移植到Balb/c成年裸鼠背部肌层中,移植后第7天和第14天分别取出植入的牙胚,常规制片,苏木精-伊红染色,观察牙胚发育情况。另取1只出生5d的Balb/c小鼠的下颌第一磨牙牙胚作为对照。结果肉眼观察发现移植后牙胚生长于肌肉浅层,组织相容性好,表面有丰富的毛细血管。组织学观察表明:移植后的两组牙胚牙冠均可部分继续发育并矿化,但含牙囊组牙胚比去除牙囊组发育更快,体积较大,钙化程度较高。虽然两组牙胚上皮根鞘根向延伸均不明显,但含牙囊组牙根有一定程度的发育,牙齿有根向生长的趋势,而去除牙囊组牙齿未见根向生长的趋势。移植后第7天两组牙胚均出现炎症反应,到移植后第14天则均未见明显的炎症。结论牙囊在牙齿发育特别是牙根的形成中起重要作用,能够引导牙根向正常方向生长并形成牙根。

Objective To study role of dental follicle in tooth root development. Methods Sixteen mandibular first molar dental germs from eight five-day postnatal Balb/c mice were divided into two groups randomly. Dental follicle of germs in one group was undetached and that of another group was removed. Subsequently, each of the germs was separately transplanted to back-muscles of adult nude mice. At seventh and fourteenth day after transplanting, the germs were collected, fixed, demineralized, dehydrated, and embedded in wax in sequence. Serial sections of 5 μm thick were made following the routine methods, stained with haematoxylin-eosin dying solution, and observed under a light microscope. Results All implantations were located in the back-muscles with abundant capillary vasculature. Under microscope, although all tooth germs could further develop after grafting, tooth germs without dental follicle developed slowly with small size and low calcification compared to those with dental follicle. Although position of Hertwig＇s epithelial root sheath of all germs seemed no changing, roots of the group with dental follicle could further develop and the roots develop toward the apical direction; this tendency couldn＇t be seen in the germs of another group. Inflammatory cells could be seen in and out of the pulp cavity of the two groups at 7^th day after grafting, while no obvious inflammatory cell was observed at 14^th day after grafting. Conclusion Dental follicle play an important role in tooth root development. It probably can lead tooth root to develop in normal direction.