Research Article Rheumatology and Orthopedic Medicine Rheumatol Orthop Med, 2017 doi: 10.15761/ROM.1000111 Volume 2(1): 1-4 Hormone replacement therapy afects mandibular bone architecture in postmenopausal women: a fractal dimension assessment Afonso Celso Souza de Assis 1 , Thiago de Oliveira Gamba 2 , Mari Eli Leonelli de Moraes 1 , Luiz César de Moraes 1 , Isadora Luana Flores 3 * and Sérgio Lúcio Pereira de Castro Lopes 1 1 Department of Diagnosis and Surgery, São José dos Campos Dental School, UNESP, São José dos Campos, São Paulo, Brazil 2 Department of Oral Diagnosis, Piracicaba Dental School, UNICAMP, Piracicaba, São Paulo, Brazil 3 Department of Dentistry, UFJF, Campus Governador Valadares, Governador Valadares, Minas Gerais, Brazil Abstract Osteoporosis is an age-related health problem involving estrogen defciency and the hormone replacement therapy (HRT) is still widely used as an antiresorptive agent. However, the efect on bone microarchitecture needs to be further investigated. To evaluate the efect of HRT on mandibular bone architecture in postmenopausal women using fractal analysis on digital panoramic radiographs. Seventy-fve digital panoramic images including 25 images of women aged 20-39 years (negative control, G1), 25 images of women aged 40-59 years who were not taking HRT (positive control, G2) and 25 images of women aged 40-59 years who were taking HRT (G3) were submitted to fractal analysis using ImageJ software to compare the bone density between the groups. Statistical diferences were observed between the fractal indexes in the 3 groups on both sides and the fractal dimension (FD) of group G3 was statistically greater than that of G1 and G2 on both sides. A signifcant moderate positive correlation (0.3<ϕ<0.49) was found between age and FD on the left mandible in G3. Postmenopausal women under HRT present higher values for FD and these agents can afect the architecture of mandibular bone. Correspondence to: Dr. Isadora Luana Flores, Área de Estomatologia e Patologia Oral Departamento de Odontologia, Universidade Federal de Juiz de Fora Campus Governador Valadares – UFJF/GV Rua Israel Pinheiro, 2000 Bloco D9 CEP 35020-220 Governador Valadares – MG – Brazil, Tel: +55 33 33011000 Ramal 6539, E-mail: isadoraluanafores@gmail.com Key words: fractal, hormone replacement therapy, mandible, osteoporosis, panoramic radiography Received: January 09, 2017; Accepted: February 10, 2017; Published: February 13, 2017 Introduction Osteoporosis is a disease of the skeletal system characterized by loss of bone mass and clear deterioration of bone microarchitecture resulting in areas highly susceptible to spontaneous fractures [1,2]. In postmenopausal women, the combined efects of estrogen deprivation, increased production of follicle-stimulating hormone (FSH) and a decrease in calcium absorption increases the risk of postmenopausal osteoporosis [2,3]. Among the major pharmacological interventions, hormone replacement therapy (HRT) is still widely available for the prevention and treatment of postmenopausal osteoporosis to reduce the rate of bone loss [2,4]. In the jaw bones, an apparent enhancement of the oblique line is relatively common in intraoral and panoramic radiographs, especially in patients aged more than 50 years, because there is an evident loss of trabecular bone mass of the mandible body and low cortical bone loss [1,2] . Moreover, resorption of the inferior mandibular cortex can be detected by panoramic radiograph [5]. Tus, as panoramic radiographs are ofen requested in the dental clinic, this imaging modality can be used as a screening tool to assess the level of bone mineral density and predict the presence of osteoporosis, so that patients can be referred for more complex tests such as bone densitometry [2,6]. Fractal analysis is an efective and useful quantitative method to analyze the trabecular bone pattern through complex measurements of geometric structures throughout the image [7]. Dental radiographs, such as periapical radiographs, provide an efcient method for determining the fractal dimension (FD) by evaluating the changes in bone porosity [2,6]. Nevertheless, only seven studies used panoramic radiographs for FD analysis in osteoporotic patients [1,7-12] and no previous articles observed the bone architecture in patients under HRT. We hypothesize that HRT alters the jaw bone pattern and; therefore, the purpose of the present study was to evaluate the efect of HRT on the architecture of mandibular bone in postmenopausal women using fractal analysis on digital panoramic radiographs. Materials and methods Patients Tis study followed the guidelines of the Declaration of Helsinki and Tokyo for research in humans and was approved by the local ethics committee of São José dos Campos Dental School – UNESP (protocol number: 027/2011-PH/CEP). All patients received verbal information and informed consent was obtained from all participants included in the study. Digital panoramic radiographs of 75 women were distributed into 3 groups as follows: G1, 25 images of women aged 20-39 years (negative control); G2, 25 images of women aged 40-59 years who were