Post menopause and Osteoporosis-Unfolding the link

Background: Osteoporosis is one of the most systemic diseases prevalent among the postmenopausal women attributing to the increased risk of occurrence of fractures. Hence, early detection of this disease is of utmost importance which can be determined by concentration of calcium in saliva and radiographically by quantitative radiomorphometric indices like panoramic mandibular Index (PMI). Objectives: The purpose of this study is to evaluate and compare the salivary calcium levels and PMI in order to identify the risk group of osteoporosis in postmenopausal women. Methods: A case-control study was carried out among 60 female subjects who were equally categorized into two groups. Salivary calcium levels were calorimetrically assessed by spectrophotometry and PMI index was calculated using Digora software from the Digital Panoramic image obtained for individual patient. Results: The results had shown that salivary calcium among the case group was significantly higher than the control group (p value = 0.001) and PMI values among the case group were significantly lower than the control group (p value = 0.001).With the advancing duration of menopause, the salivary calcium levels were increasing and PMI values were found to be decreasing and both were statistically significant. Conclusion: The results of this study suggest that both salivary calcium and PMI can certainly be used as screening tools to identify the risk of osteoporosis among postmenopausal women.


Introduction
Osteoporosis, a silent disease, is perhaps the most common regressive disease of the bone, frequently witnessed among the postmenopausal women. Osteoporosis is a chronic systemic skeletal disease characterized by a decreased bone mass and disrupted bone tissue microstructures, resulting in increased bone fragility and increased risk of fracture (Poornima et al. 2014). The major obstacle of this disease is that it is usually not discovered until weakened bones cause pain and debilitating fractures (Haster et al. 2011). Menopause being a natural physiological process occurs during fourth to fifth decade in a life of a woman and tends to increase a woman's susceptibility to osteoporosis (Duncea et al.2013). There has often been a greater intricacy in identifying this combating disease before the clinical consequences have occurred. Though there are different strategies for screening of osteoporosis, Central dual-energy X-ray (DXA) is known to be the gold standard (Haster et al. 2011). For the past few decades, there is a vast growing importance in identifying the risk of osteoporosis by noninvasive and less expensive investigations so as to reach the hands of a common man. Saliva being the mirror of systemic diseases, its role has advanced elegantly and has steadily gained importance in various diagnostic and research arenas (Siva Reddy et al. 2008). Calcium is a key nutrient and an essential building block imparting a lifelong bone health. It is an abundant mineral in almost every cell of the human body. Calcium accounts as the main mineral component of the human skeletal system. Resorption of bone thus can result in diffusion of calcium into blood and further into the saliva (Kavitha et al. 2012). Increased levels of calcium in saliva can thus be used as a potential screening tool for assessing an individual risk for osteoporosis. According to Maryam Rabiei.et al the cut-off point for salivary calcium is 6.1 mg/dl and above which (i.e. >6.1mg/dl) can used as a screening tool to identify risk group of osteoporosis in postmenopausal women. (Maryam Rabiei et al. 2012). Radiographic imaging is an important diagnostic adjunct and has heralded a major progress in providing a comprehensive image of jaws and maxillofacial structures. Dental Panoramic radiographs are being used as auxiliary tools for assessing the mandibular cortical width among osteoporosis patients (Kavitha et al. 2012).Determination of alveolar bone loss and residual alveolar ridge resorption are often made by using panoramic radiographs. One of the best established methods to assess the mandibular cortical width is panoramic mandibular index, which was first introduced by Benson in 1991. (Duncea et al.2013). In this regard, the present study has aimed to evaluate and compare salivary calcium and panoramic mandibular index, so as to identify the risk group of osteoporosis in postmenopausal women.

Methodology
A case control study was performed in the Department of Oral Medicine, Oral Diagnosis and Radiology, Vishnu Dental College and Hospital, Bhimavaram, Andhra Pradesh, India. A total of 60 females were included in the study. The procedure was explained to the patient and informed consent was obtained from individual patient. The study was approved by the institutional Ethical committee. Patients with certain systemic diseases (Diabetes, hypertension. thyroid disorders, any developmental disorders of mandible, fractures or surgery of the mandible) were excluded from the study. The total sample of 60 females was categorized into two groups. Control group: Comprised of 30 healthy women (age range 25-40 years) having regular menstrual cycle. Case group: Comprised of 30 healthy postmenopausal women (age range 41-60years) with natural occurrence of menopause of at least 12 months to 15 years of span.

Collection of saliva
The patients were comfortably seated in the Dental chair and unstimulated saliva was collected from individual patient under resting conditions. The saliva was collected for 10 minutes by spitting method in a graduated container from 9AM to 12PM to avoid diurnal variations. The collected saliva was then subjected to biochemical analysis for assessment of salivary calcium levels.

Salivary calcium analysis
The collected saliva was centrifuged at 3000RPM and supernatants were separated. To the obtained supernatants, reagents were added and concentration of calcium was calorimetrically analysed by using spectrophotometry. The findings were expressed in mg/dl.

Radiographic analysis
Orthopanoramic images were taken for each patient as an adjuvant for various diagnostic and treatment purposes. Panoramic image was obtained using PANOCEPH machine with Photostimulable phosphor plates. Linear measurements were used and specific calibrations were performed with the Digora software for windows 2.7.103.437 in order to calculate panoramic mandibular index.

Calculation of Panoramic mandibular index
A tangent was drawn across the lower margin of mandible followed by which the width of mandibular cortex at the mental area is measured as shown in figure.1. A perpendicular line was then drawn from the mental foramen upto the tangent and this distance was measured as shown in figure.1 Panoramic mandibular index was further calculated as the ratio between the width of the lower mandibular cortex in the mental area and the distance between the lower margin of the mandible and the mental foramen as proposed by BENSON (Duncea et al.2013).

Results
A total of 60 women were enrolled in the study. The mean age among the case group was obtained as 53.43years and among the control group was 32.5 years. The comparison of age among the case and control subjects is shown in Table.1. In the current study Mann-Whitney U test was performed and the mean salivary calcium levels among the case group was obtained as 6.9mg/dl and the control group was 4.8mg/dl mean which depicts that salivary calcium among the case group was significantly higher than the control group(p value = 0.001) as shown in Table.
2. The mean PMI levels among the case and control groups were 0.3 and 0.43 respectively and illustrates that mean PMI values were significantly lower than the control group(p value = 0.001) as shown in Table.3. Pertaining to the duration of the menopause, the correlation coefficient of salivary calcium and PMI were obtained as 0.86 and -0.705 and significant (2-tailed) test has ruled out that as the duration of menopause is increasing, the salivary calcium levels were increasing and PMI values were found to be decreasing and both were statistically significant (p value = 0.001) as shown in Table 4.

Discussion
Postmenopausal women are at a greater risk for osteoporosis which is attributed by low estrogen levels. Estrogen deficiency tends to cause both direct and indirect effects on the skeletal sys-tem (Wolfgang Sipos et al. 2009 )which thereby leads to condition called Osteoporosis and is often accompanied by increased resorption of bone(Siva Reddy et al. 2008). Osteoporosis is one of the most common metabolic diseases associated with ageing and goes hand in hand with increasing duration of menopause.
In the research study conducted by Singh et al., he had described that estrogen deficiency in postmenopausal women leads to decreased absorption of calcium in intestine that implies a decreased serum calcium level, as a result of which PTH hormone level increases in serum which is accompanied by increase in the serum calcium. Nevertheless, in order to maintain calcium homeostasis, there is no significant increase in serum calcium; therefore there is a possibility of elevated calcium to be excreted through saliva or kidney. ( In the current study, the mean value of the salivary calcium in postmenopausal women was obtained as 6.9mg/dl which was above the cut-off point ( 2011) has found a strong negative correlation between age and the mean PMI, which states that PMI was found to be decreasing with the advancing age as similar to this study. Saliva, as an adjuvant to the panoramic radiographs is beneficial to the patient as well as the physician since these methods are noninvasive, painless and economical. As per the previous document-ed literature and to the best for our knowledge, this is probably the first study comparing the salivary calcium levels and the PMI so as to indentify the risk of occurrence of osteoporosis among postmenopausal women.

Conclusion
Pertaining to the results of the current study, both salivary calcium and panoramic mandibular index has played an equal important role in identifying the risk group of osteoporosis at an early stage and thus these parameters can be regarded as ancillary methods in early diagnosis of osteoporosis.