Ⅰ. INTRODUCTION
Osteoporosis is characterized by a decrease in bone quantity and quality, resulting in weakness of bone strength. It is a disease that increases the risk of fracture1). Bones that are broken commonly are the spine, the bones of the forearm and the hip2). Bones can weaken to the point where a fracture occurs even in daily activities. After a fracture, along with chronic pain, it becomes difficult to perform normal activities1).
Aging, female, and low estrogen level are widely known risk factors for osteoporosis. These risk factors involve excessive alcohol drink, smoking, inadequate physical activity, and inadequate calcium and vitamin D intakes. Caucasian or Asian race, low body weight, and tall stature are also risk factors. Several diseases such as hypogonadal conditions, rheumatoid arthritis, hyperparathyroidism can also cause osteoporosis. Medications including glucocorticoids, some antipsychotic drugs, chemotherapy drugs, proton pump inhibitors, and selective serotonin reuptake inhibitors can cause low bone density2).
Osteoporosis is correlated with an increased risk of death3). Several studies have reported the increased risk of death is correlated with fractures of the hip and spine4). Therefore, if the diagnosis of osteoporosis is processed through panoramic radiographs that are usually taken in dentistry, the patient's osteoporosis-awareness rate will be increased. Also, an early diagnosis and treatment of osteoporosis in a specialized medical institution will be possible, which will prevent fractures and reduce the risk of death.
Several Bone Mineral Density(BMD) measurement techniques, such as dual energy X-ray absorptiometry(DXA), have been developed and applied. When T-score, the standard deviation above and below the mean bone density, is estimated, diagnosis of osteoporosis is performed when the T-score is -2.5 or less in the lumbar spine or femoral neck5). In addition to this, according to technology development, quantitative computerized tomography(QCT), quantitative ultrasound(QUS) and Micro-computed tomography are used to characterize bone structure. Although DXA is a popular bone density measuring method, it can be limitedly used due to its high cost. Meanwhile, panoramic radiographs are taken generally in dental clinics for initial diagnosis and treatment planning. Several indices on panoramic radiographs have been reported to be useful to detect osteoporosis 6-10). Osteoporosis determination using mandibular cortical shape on panoramic radiographs is significantly associated with that using BMD on DXA6-16).
In situations where only a panoramic radiograph is used without DXA, it seems more appropriate to diagnose suspected low bone density(SLBD) rather than osteoporosis. Therefore, the purpose of this study was to study the prevalence and awareness of SLBD by reading panoramic radiographs of Korean female in her 50s to 90s.
Ⅱ. MATERIALS and METHODS
Study subjects
This study was conducted on patients who had taken panoramic radiography at Chonnam National University Dental Hospital from July 1, 2015 to June 30, 2017. Only female from their 50's to 90's were classified according to age. And 100 people of each age group were randomly selected for the study. However, in the case of female in their 90s, the number of the patients was 15(Table 1).
Interpretation of SLBD using panoramic radiographs
SLBD were diagnosed by examining the shape of cortical bone in the patient's panoramic radiographs. Panoramic radiographs were obtained as a digital image using Kodak8000c (Carestream Health Inc, Rochester, NY, USA) and were interpreted using the image reading system PiView Star (Infinite, Seoul, Korea).
To identify postmenopausal female with SLBD, the first defined cortical shape classification on the panoramic radiograph is shown as follows 12).
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C1 : The endosteal border of the cortex is even and sharp on both sides.
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C2 : The endosteal border has semilunar defects (lacunar resorption) or appears to form endosteal cortical remnants.
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C3 : The cortical layer forms a severe endoteal cortical remnant and is clearly porous.
Panoramic radiographs of 415 middle-aged female were reviewed and classified into C1-C3. C1 was normal, and C2 and C3 were diagnosed as SLBD (Fig. 1-2).
Awareness and treatment rates of patients diagnosed with osteoporosis
The electronic record charts of patients diagnosed with SLBD on panoramic radiographs were reviewed. In the electronic record chart, the number of patients diagnosed as osteoporosis at the past medical history and the number of patients who had the a history of osteoporosis treatment were counted.
Ⅲ. RESULTS
Four-hundred-and-fifteen female patients(mean age 70.4 yrs ± 11.4 yrs) between the age 50s to 90s were randomly selected for this study. The panoramic radiographs taken from the patients were reviewed for interpreting SLBD on the basis of mandibular cortex index. SLBD was diagnosed in 10 females(10%) in their 50s, 26(26%) in their 60s, 52(52%) in their 70s, 72(72%) in their 80s, and 15 (100%) in their 90s at the review. Among 415 patients, 175 females( 42.17%) were diagnosed with SLBD. Among 175 patients, the patients recorded as SLBD in the medical history were analyzed. As results, 1 female(10%) in their 50s, 5(19.2%) in their 60s, 10(19.2%) in their 70s, 19(26.3%) in their 80s, and 4(26.7%) in their 90s were recorded as SLBD. In total, 39 females(22.3%) out of 175 patients were aware of osteoporosis. In addition, 0 female(0%) in their 50s, 3(60%) in their 60s, 10(100%) in their 70s, 17(89%) in their 80s, and 4(100%) in their 90s have received or were receiving treatment for osteoporosis. In total, 34 females(87%) out of 39 patients received or were receiving treatment for osteoporosis( Table 2-4).
Ⅳ. DISCUSSION
The purpose of this study was to study the prevalence and awareness of low bone density by reading panoramic radiographs of Korean female in her 50s to 90s. The prevalence of SLBD was investigated using only the shape of the mandible inferior cortex on panoramic radiographs without DXA, and awareness and treatment rates of osteoporosis were investigated based on electronic records using the past medical history. In this study, 175(42.17%) out of 415 females that had taken panoramic radiographs in their 50s to 90s were diagnosed with SLBD. When examining the medical history of patients diagnosed with osteoporosis, the ratio of patients who knew they had osteoporosis were 39(22.3%) out of 175. The osteoporosis-awareness rate was low and this was because patients were left unaware that they had osteoporosis. This can be a factor that aggravates the disease or increases the risk of fracture. On the other hand, in patients who were aware of having osteoporosis, the treatment rate were very high with 34(87%) patients out of 39, which might demonstrate that the treatment rate is likely to increase if the patient is aware of osteoporosis.
Haversian canal dilatation in the mandibular cortex increases in patients with osteoporosis23), which can be seen as black lines parallel with the mandibular cortex on panoramic radiographs. The Haversian canal finally grows together and the mandibular cortex disappear in patients with severe osteoporosis. Diagnosis of SLBD is possible on dental panoramic radiographs. This is because changes in the mandible inferior cortex are related to changes in bone density in the femur neck. The method for examining SLBD on panoramic radiographs is to measure the cortical bone thickness in the lower mental foramen, or to evaluate the erosive change of the endosteal layer of cortical bone and the degree of bone residue, and the state of SLBD in cortical bone6-16).
Taguchi et al.13-14) studied osteoporosis diagnosis on panoramic radiographs using mandibular cortical shape in postmenopausal female and reported that panoramic radiographs had diagnostic sensitivity of 80-87% and specificity of 64~66% compared to DXA. Kim et al.15) performed multiple linear regression analysis for the association between mandible cortical shape on panoramic radiograph and bone mineral density on DXA and reported that association of MCI with BMD was detected at the lumbar spine, femoral neck and total hip (p < 0.05). Those studies showed that mandibular cortical shape is useful index for the diagnosis of osteoporosis.
Taguchi16) suggested caution should be taken to whether the trabecular bone tail is connected to the mandible inferior cortex. In this case, even young people may be misdiagnosed as osteoporosis. Since very thin cortical bone can be included in C1 and judged as normal, very thin cortical bone should be diagnosed as osteoporosis. This study interpreted panoramic radiographs taking these points into consideration. Furthermore, in situations where only a panoramic radiograph is used without DXA, it seems more appropriate to diagnose suspected low bone density(SLBD) rather than osteoporosis.
Data from the National Health and Nutrition Examination Survey, conducted between 2008 and 2011 in Korea, showed that the prevalence rate of osteoporosis were 40.1% and was proportionate with the age increase in females over the age of 5017). These results were very similar to those of this study using panoramic radiographs. The prevalence rate of females in their 50s or older in Korea were average 4 times higher than of American females18). It can be seen that females in their 50s or older in Korea are in a state of being vulnerable to osteoporosis. The elders in Korea has a higher prevalence of osteoporosis than other countries. Therefore, more attention should be paid to prevent, and early diagnosis and treatment should be made19).
According to the National Health and Nutrition Examination Survey, conducted between 2008 and 2011 in Korean females, among patients with osteoporosis, the proportion of patients who were aware that they had osteoporosis were 37.8%19). In this study, when examining the medical history of a patient diagnosed with osteoporosis, the proportion of patients who knew they had osteoporosis were 39 (22.3%) patients out of 175. These results mean that there is a problem in the secondary prevention of early detection and treatment of osteoporosis among osteoporosis patients in Korea. The symptoms of osteoporosis are difficult to feel on their own before a fracture occurs. Instead of relying on sudden discovery, preventive and early treatment should be carried out by conducting regular health examinations.
Osteoporotic fractures can be a direct cause of death and cause long-term morbidity and socioeconomic consequences from a cost standpoint. In particular, although hip fractures are less common than other osteoporotic fractures, many studies are in progress because of severe activity decline and high mortality after hip fracture19). Abrahamsen et al.20) reviewed an extensive literature on mortality after hip fracture and reported results varying from 5% to 50% for 1-year mortality. The reason for the variable difference in mortality rate is complex, but the age of the targeted patient acts as an important factor. 1-year mortality rate after hip fracture in patients aged 50 years and older cases showed generally similar patterns. Tsuboi et al.21) reported mortality rates from hip fractures after the long-term follow-up for 10 years. They reported that 1-year mortality rate were 19%, 2-year mortality were 23%, 5-year mortality were 51% and 10-year mortality were 74%. There is no study on mortality by long-term follow-up in Korea yet.
Fractures accompanied with osteoporosis lead to an increase in mortality, along with various difficulties in daily activities. After wrist fractures accompanied with osteoporosis, most females experience long-term sequelae, including symptoms, behavioral problems, deformities, and impairment of the ability to perform activities of daily life. In the case of a vertebral fracture accompanied with osteoporosis, not only deformities but also pain, decreased lung function, balance and gait disorders, digestive disorders and loss of self-confidence are experienced, and depression is also common. As a result, it causes problems such as persistent disability and reduced quality of life. Especially, the decline in activity and quality of life of patients who have experienced hip fractures are the most serious19). It also increases economic burden. Direct and indirect costs for medical expenses of females aged 50 years or older with osteoporotic spinal fractures were estimated and reported to be 131,472 people from 2002 to 200422). Overall medical cost was 66.18 billion won in 2003 alone. It was equivalent to 0.27% of 24.7 trillion wons of total health insurance medical expenses and was equivalent to 1.0% of about 6.6 trillion wons of medical expenses for the population aged 50 and over. However, considering various indirect costs such as rehabilitation of patients with osteoporosis, disability in daily life, and long-term nursing care, medical cost would be much more19).
Recently, researches about testing artificial intelligence in interpreting osteoporosis on panoramic radiographs have been reported. Artificial intelligences have showed high accuracy in reading osteoporosis on panoramic radiographs24-27).
In conclusion, this study showed that the prevalence rate of SLBD was 42.17%(175 in 415), the osteoporosis-awareness rate 22.3%(39 in 175), and the treatment rate 87%(34 in 39). While the osteoporosis-awareness rate was low, the treatment rate was relatively high. Therefore, it can be suggested that osteoporosis-awareness rate by diagnosing SLBD with dental panoramic radiographs be increased to help patients to receive proper treatment.
