1. Dental Implant Research Center, Department of Oral and Maxillofacial Radiology, Dental School, Hamadan University of Medical Science, Hamadan, Iran.
2. Department of Biostatistics and Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.
3. Department of Oral and Maxillofacial Radiology, Dental School, Zanjan University of Medical Science, Zanjan, Iran.