Introduction: The existing bone is regarded as an important criteria in dental implants. In this regard, the radiographic modality is of great significance in quantifying the remaining bone, and CBCT accurately represents height and width of the existing bone. Therefore, this study aimed to evaluate the frequency distribution of the edentulous posterior mandibular ridge types using cone beam computed tomography in an Iranian population.Methods: In this cross-sectional descriptive study, CBCT scans of 127 patients with full edentulous mandible with an average age of 61.15 were evaluated who referred to a radiology clinic in Tehran. The images were analyzed applying OnDemand3D application and bone height and width of each area were determined. To analyze the collected data, SPSS software (ver, 17) was employed applying Fisher's exact test.Results: The ridges were classified in 4 different groups (A, B+,B-w, C-w). The frequency of ridge types A and B+in male and ridge types B-w and C-w in females were demonstrated to be higher. An increase in age led to a reduction in the frequency of type A and a rise in the frequency of type C-w. The mean bone height was higher in males in all areas. In addition, the mean bone width was higher in males in all areas except for the first molar area.Conclusions: The study results indicated that as the age increases, the height of edentulous mandible reduces, while no significant relationship was detected between the bone width and aging. As a result, with aging the evolution of bone was held to be from type A to type C-W.

Background & aim: Educational and educational programs have a certain role in the progress of each society. The aim of this study was to compare the midwifery students' satisfaction with the teaching of gynecology and infertility by lecture and peer instruction. Methods: In the present Quasi-experimental study, continuous midwifery students in 2017 were selected as the research community. Five semester midwifery students (22 students) were selected as research sample and 3 units of women's diseases and infertility as educational materials. Half of the teaching materials were taught by the professor in the first eight sessions of lectures and eight second sessions were taught by counterparts. At the end of both educational methods, students were asked to complete a questionnaire on satisfaction with the method of instruction. All students received informed consent for participation in the research. Data were analyzed by paired t-test. Results: The mean score of satisfaction with the lecture teaching method and peer teaching method was 83. 77± 9. 74, and 81. 36± 10. 58 respectively (p=0. 49). The average satisfaction score of the lecture method in the area of creating interest and encouragement to participate in learning less than the peer education method (p=0. 008), while respecting the principles and regulations related to teaching (p=0. 005), in the field of testing and The evaluation of the content of the curriculum was also higher (p=0. 07) and in the field of the appropriateness of the teaching method and its continuity with peer education was equal. Conclusion: It seemed that the use of active teaching methods had a significant effect on increasing interest in learning and motivation in students, however, students consider the lecture method a better method to understand the content and to follow the principles of teaching more effectively. Using the peer education method is suggested as a complementary method of instruction and teaching.