Bone Metabolism in the Mandibular Edentulous Region of the Beagle Dogs

本研究旨在研究无牙颌比格犬的骨代谢。分别于术后3个月（n=3）、4个月（n=1）、5个月（n =3）、6个月（n=2）和9个月（n=4）处死13只雌性比格犬。在处死前14天和7天，分别用四环素和钙黄绿素对犬进行双标记。解剖下颌骨，用双能X线骨密度仪进行分析。测量无牙区的骨密度（BMD）。随后，位于第二前磨牙的缺牙骨进行不脱钙骨组织形态计量学处理。在距骨内膜表面250 μ m的松质骨区域测量参数。测量以下参数：骨小梁体积（BV/TV）、骨结构的Feret X/Y和骨髓面积、骨形成的矿化表面（MS）和骨吸收的破骨细胞表面（OS/BS）。采用斯皮尔曼等级相关分析拔牙后3 ~ 9个月测量值的时序变化。此外，通过Mann-Whitney U检验评估3个月、5个月和9个月组之间的差异。BMD测量结果显示，在实验期间连续下降。组织形态计量学测量值显示BV/TV、Feret X/X和Marrow Area增加，MS和OS/BS减少，提示骨小梁结构的快速变化与牙齿缺失引起的力学状态改变相对应。

This study was conducted to investigate the edentulous bone metabolism of beagle dogs. Thirteen female beagle dogs had all premolars extracted and were sacrificed after 3 months (n=3), 4 months (n=1), 5 months (n=3), 6 months (n=2) and 9 months (n=4). Dogs were double-labeled with tetracycline and calcein, 14 days and 7 days prior to sacrifice, respectively. Mandibles were dissected and analyzed with dual energy X-ray absorptiometry. Bone mineral density (BMD) was measured in the edentulous region. Subsequently, the edentulous bone located at the second premolar was processed undecalcified for bone histomorphometry. The parameters were measured in the cancellous bone area 250 mum from the endosteal surface. The following parameters were measured ; trabecular Bone Volume (BV/TV), Feret X/Y and Marrow Area for bone structure, Mineralizing Surface (MS) for bone formation and Osteoclast Surface (OS/BS) for bone resorption. The sequential changes of measured values from 3 months to 9 months after extraction were analyzed by the Spearman rank correlation. Additionally, the differences between two groups of 3 months, 5 month and 9 month group were evaluated by the Mann-Whitney U test. The results of the BMD measurements showed a successive decrease during the experimental period. The values of histomorphometric measurement exhibited an increase of BV/TV,Feret X/X and Marrow Area, and a decrease of MS and OS/BS.It may be suggested that structure of trabecular bone which changed repidly corresponded to the alteration of mechanical status caused by tooth loss.