EFFECTS OF CALCIUM INTAKE ON ALVEOLAR BONE

充足的钙摄入对预防骨质疏松性骨折的好处是公认的。由于牙槽骨受影响的方式与其他骨骼相同，因此假定饮食中的钙水平也会影响其密度。有研究表明，牙周炎时牙槽骨密度增加可能会增加骨质流失。本研究的主要目的是在大鼠模型中评估钙摄入对牙槽骨的影响，及其减少老年牙周炎引起的骨质流失的能力。选择大鼠是因为它们以前在骨骼和牙周炎研究中广泛使用，而且它们的寿命相对较短，可以在老年时评估钙摄入的影响，当它的益处最有价值时。将使用两种钙摄入水平：低和高。将讨论以下目标：测定两组老年（20个月）牙槽骨骨密度的差异。2. 比较两组老年牙周炎所致牙槽骨丢失的差异。3. 描述两个动物组在研究期间颅骨和颅骨后变化的骨密度测量。动物将在1月龄时被随机分配到两个钙摄入组中的一个，并一直持续到20月龄。到那时，一些动物将被安乐死，以进行Aim 1的侵入性骨骼测量。其余的动物将被诱导牙周炎，这些动物将被跟踪到23个月大。在1、3、8、13、20和23个月大时收集的非侵入性纵向数据将包括使用双x线x线摄影（颅骨和非颅骨）测量骨密度，以及臼齿（牙槽骨）的口腔内x线摄影。Aim 1的主要结局变量是牙槽骨密度，Aim 2的主要结局变量是牙槽骨丢失。将使用双x线吸收仪和口腔x线片像素强度测量去牙槽骨密度。牙槽骨丢失将在磨牙颊部使用形态测量法测量，并在口内x线片上进行x线摄影。此外，将使用组织形态学测量骨代谢的静态和动态参数。功率计算表明，每组需要21只动物才能检测到至少5%的牙槽骨密度（目的1）。总共需要24只动物来检测两个钙摄入组中任何一个组的牙槽骨丢失至少有10%的差异（目标2），在0.05的显著性水平上幂为80%。为了在雄性和雌性大鼠中同样精确地测试钙摄入量的影响，两性都需要相同的样本量。这些计算包括在这些老年大鼠中估计20%的死亡率。这项研究可能表明膳食钙摄入对牙齿/口腔面部健康的益处。这个额外的好处可能有助于促进这种预防性治疗。

The benefits of sufficient levels of calcium intake in the prevention of osteoporotic fractures are well recognized. Since alveolar bone is influenced in the same manner as other bones, dietary calcium levels are assumed to also affect its density. It has been suggested that increased alveolar bone density may increased bone loss during periodontitis. The primary goal of this study is to evaluate the effects of calcium intake on alveolar bone, and its capacity to decrease periodontitis-induced bone loss at old age, in a rat model. Rats were chosen due to their previous extensive use in bone and periodontitis studies, and their relative short life span which allows evaluation of the effects of calcium intake at old age, when its benefits are of most value. Two calcium intake levels will be used: low, and high. The following aims will be addressed: 1. Test the difference in alveolar bone density at old age (20 months) between the two calcium intake groups. 2. Test the difference in periodontitis-induced alveolar bone loss at old age between the two groups. 3. Describe how bone density measures of cranial and post-cranial change during the study period in the two animal groups. Animals will be randomly assigned to one of the two calcium intake groups at age 1 month, and followed until the age of 20 months. At that time, some of the animals will be euthanized for invasive bone measurements for Aim 1. Periodontitis will be i induced in the remainder of the animals who will be followed until the age of 23 months. Non-invasive longitudinal data collected at the age of 1,3,8,13,20 and 23 months will include bone density measurements using dual x-ray radiography (cranial and non-cranial bones), as well as intra-oral radiographs of the molars (alveolar bone). The primary outcome variable for Aim 1 will be alveolar bone density, and for Aim 2 alveolar bone loss. Alveolar bone density will be measured on defleshed jaws using dual x-ray absorptiometry and pixel intensity on oral radiographs. Alveolar bone loss will be measured on the buccal of the molars using morphometry on defleshed jaws, and radiographically on intraoral radiographs. In addition, static and dynamic parameters of bone metabolism will be measured using histomorphometry. Power calculations indicate that 21 animals per group will be needed to detect a minimum of 5% in alveolar bone density (Aim 1). A total of 24 animals will be needed to detect a minimum of 10% difference in alveolar bone loss (Aim 2) between any of the two calcium intake groups with a power of 80% at a 0.05 significance level. To test the effect of calcium intake with equal precision in male and female rats, a equal sample size will be required for both genders. These calculations include an estimated 20% mortality rte in these elderly rats. This study may indicate the benefits of dietary calcium intake on dental/orofacial health. This additional benefit may help to promoter this preventive therapy.