EFFECTS OF CALCIUM INTAKE ON ALVEOLAR BONE

充足的钙摄入量在预防骨质疏松性骨折方面的益处是公认的。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。已有研究表明，牙槽骨密度增加可能会增加牙周炎期间的骨丢失。本研究的主要目的是在一种大鼠模型上评价钙摄入对牙槽骨的影响，以及其减少老年牙周炎引起的骨丢失的能力。之所以选择大鼠，是因为它们以前在骨骼和牙周炎研究中被广泛使用，而且它们的寿命相对较短，可以在老年时评估钙摄取的影响，而此时钙的好处是最有价值的。将使用两种钙摄入量：低钙和高钙。主要研究内容如下：1.检测老年(20个月)两个钙摄入量组大鼠牙槽骨密度的差异。2.检测两组老年牙周炎所致牙槽骨丢失的差异。3.描述两组动物在研究期间如何测量颅骨和颅后骨密度的变化。动物将在1个月大的时候被随机分配到两个钙摄入量组中的一个，并一直跟踪到20个月大。届时，一些动物将被安乐死，进行侵入性骨骼测量，以达到目标1。其余的动物将被诱导牙周炎，并将被跟踪到23个月大。在1、3、8、13、20和23个月时收集的非侵入性纵向数据将包括使用双重x射线照相(颅骨和非颅骨)以及磨牙(牙槽骨)的口腔内X光照片测量骨密度。目标1的主要结果变量是牙槽骨密度，目标2的主要结果变量是牙槽骨丢失。牙槽骨密度将使用双重x射线吸收测量仪和口腔X线片上的像素强度来测量。磨牙的牙槽骨丢失将在磨牙颊面上使用偏颌的形态测量法测量，并在口腔内X线片上测量。此外，还将使用组织形态计量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(目标1)。总共需要24只动物来检测两个钙摄入量组中任何一个组之间的牙槽骨丢失(目标2)至少10%的差异，功率为80%的钙摄入量组在0.05显著水平上。为了在雄性和雌性大鼠身上同样精确地测试钙摄入量的影响，男女大鼠都需要相同的样本量。这些计算包括这些老年大鼠估计20%的死亡率RTE。这项研究可能表明膳食钙摄入量对牙齿/口腔健康的好处。这一额外的好处可能有助于促进这一预防性治疗。

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.