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.
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