Background: Ameloblastomas, the second-most common odontogenic tumors, are locally aggressive benign lesions that derive from cellular components of the enamel organ. Objective: The objective of the study is to assess the possible influence of cell proliferation markers Ki-67 and proliferating cell nuclear antigen (PCNA) on the biological behavior of ameloblastomas. Materials and Methods: A PubMed database search through February 2018, using the following medical subject headings (MeSH) terms were performed: “ameloblastoma” and (“Ki 67 antigen” or “proliferating cell nuclear antigen”). Selection Criteria: Studies with findings on cell proliferation markers in ameloblastoma. There were no restrictions regarding language or date of publication. Data Analysis: The data were analyzed using statistical software RevMan 5.3 (The Cochrane Collaboration, Oxford, UK). For continuous outcomes, the estimates of effects of an intervention were expressed as mean differences using the inverse variance method together with 95% confidence intervals. Results: Fourteen studies on cell proliferation markers in ameloblastoma were included in this meta-analysis. A greater significant Ki-67 expression in recurrent ameloblastomas (P < 0.01), in follicular type of solid/multicystic ameloblastomas (P < 0.05) and maxilla located ameloblastomas (P < 0.05) was found. In contrast, no significant influence of Ki-67 expression was observed in the following parameters: clinical type of ameloblastoma, histological type of unicystic ameloblastoma, age, gender, or size of the lesion. Finally, PCNA expression had no significant influence in any case. Conclusions: Ki-67 but not PCNA antigens seem to have an influence on the biological behavior of ameloblastomas.

Objective: The objective is to study oral cancer among Yemenis, determine the common types, common sites, and the pattern of the disease in relation to age and gender, and define the possible risk factors associated with its development. Materials and Methods: The present study is a prospective descriptive hospital-based study carried out at Al-Gomhori Teaching Hospital in Sana'a in the period 2009–2012. Data were collected from history (using a questionnaire form), clinical examination of patients, and from the histopathology results of the biopsies. Results: During the study period, 319 cases of oral cancers were seen. The majority of patients (92%) were over the age of 40 years, and the peak incidence is the seventh decade of life. Squamous cell carcinoma was the most common type of oral cancers accounting for 90.3%, followed by salivary gland tumors. The gingiva was the most frequent site accounting for 27.9%, followed by the tongue accounting 27.3%. Shammah (traditional name of smokeless tobacco in Yemen and Saudi Arabia) was the main risk factor and associated with development 65.2% of oral cancers. Conclusion: Oral cancer in Yemen as in all countries still remains the disease of the elderly and deprived patient. The majority of patient were over the age of 40 years. Males were affected more than females, male to female ratio was 1.2-1. Squamous cell carcinoma was the most common type of oral cancers. Gingiva was the most affected sites, followed by the tongue. Shammah (traditional-name of smokeless tobacco in Yemen and Saudia Arabia) was the main risk factor and play an important role to development of oral cancers.

Objective: the aim is to study the facial skin cancer among Yemenis, determine the common types, common sites, the pattern of the disease, and the possible risk factors associated with it. Materials and Methods: The study is a prospective descriptive hospital-based study carried out at Al-Gomhori Teaching Hospital in Sana'a. The material consisted of Yemen patients attending the Department of Oral and Maxillofacial Surgery and who were diagnosed clinically and histopathologically with having facial skin cancer. Patients who had previous treatment (surgical, radiation, or chemotherapy) or who have recurrent cancer, or who refused to participate in the study were excluded from the study. Results: During the study period, 100 cases of facial skin cancers were seen, 66 cases (66%) were male and 34 cases (34%) were female. The male-to-female ratio was 1.9–1. The majority of patients (94%) were over the age of 40 years, and the peak incidence was the 7^th decade of life. Basal cell carcinoma was the most common type accounting for 72% followed by squamous cell carcinoma 27% and malignant melanoma 1%. The infra-orbital region was the most affected site accounting (21%), followed by the naso-labial region and the nose (18%) for each, the temporal region (14%) and the check (12%). Outdoor work was the main risk factor and associated with the development of 70% of facial skin cancer. Conclusion: Facial skin cancers in Yemen still remains the disease of the elderly and deprived patients. The majority of patients (94%) were over the age of 40 years. Males were affected more than females. The male to female ratio was 1.9-1. Basal cell carcinoma was the most common type. Infera-orbital region was the most affected site, followed by the Naso-labial region. Prolonged exposure to sunlight (outdoor work) was the main risk factor that play an important role to development of facial skin cancer among Yemenis.

Introduction: Work-related musculoskeletal disorders are one of the main occupational health hazards affecting dental practitioners. Prolonged sitting and awkward posture can lead to work-related musculoskeletal disorders. This can result in early retirements. Therefore, ergonomic principles should be followed to establish a safe, healthy, and comfortable working environment for dental practitioners, as this also affects the quality of work. Aim: The aim of this study was to evaluate the implementation of ergonomic principles in routine dentistry. Materials and Methods: A single photograph of each practitioner while working on their patient was clicked, and a grid was then developed over these photographs. An assessment form was formulated which was used to evaluate various parameters. The parameters included eye, neck, elbow, upper back, lower back, thigh, and distance of headlight from the oral cavity. Measurements were done manually using ruler and protractor. After assessing all the parameters and determining the values, the evaluation of the results was done using Chi-square test. Results: The photographic analysis was completed by a total of 75 individuals, where 56 (74.6%) were female and 19 (25.3%) of them were male dental practitioners. None of the operators had a correct position of the neck, thus the neck being the most neglected parameter. Only three individuals were observed to follow the correct position of the elbow (P = 0.530). The majority of the individuals failed to position their back (P = 0.098) in the correct manner while performing clinical work. Moreover, it was found that only 15 individuals were following the correct thigh position while operating. Conclusion: Proper implementation of ergonomic principles and maintenance of balanced posture can prevent the occurrence of musculoskeletal disorders and thus increases the work productivity.

Background: The purpose of this study was to effect of ambient pH and different two chewing cycles of wear on restorative nanohybrid- and microhybrid-filled composite material in intraoral tribology. Methods: All specimens were stored in the artificial saliva for 7 days before the chewing tests. Then, composite specimens were subjected to chewing simulation using a computer-controlled chewing simulator (F = 50N [vertical movement 2 mm and horizontal movement 0.7 mm] 120.000 and 240.000 chewing cycles, 1.2 Hz frequency, and 37°C ambient temperature), immersed artificial saliva (about pH = 5.7), and citric acid solution (about pH = 3.2). Steatite balls were used as antagonists for every experiment chewing test cycle (d = 6 mm). Specimen's microhardness values determined with Vickers hardness method before chewing tests. Mean volume loss values were determined using noncontact three-dimensional (3D) laser scanning device. Furthermore, two-dimensional and 3D analysis of the mean volume loss wear surface of the composite material was performed both immersed artificial saliva and citric acid. Mean values and standard deviations were calculated and statistical analysis was performed using one-way analysis of variance. In addition, scanning electron microscopy analysis was performed to examine surface wear tracks. Results: The surface morphology of both composite materials was severely damaged in immersed citric acid solution. This can be explained by the more damage to the organic matrix structure of the composite material in citric acid solution than immersed artificial saliva. Conclusion: The results obtained in this study will help to understand the effect of the pH value of the third abrasive surface on the composite material in the three-body wear mechanism.