Background: Permanent tooth impaction is a relatively common abnormality in which early treatment can prevent from other developmental disorders. Maxillary central impaction can occur because of mesiodens, dilacerations, trauma to deciduous tooth and space deficiency. Prevalence of maxillary central impaction is 0.06%-2.0%. Methods: In this retrospective, case-control study, 28 people with impacted maxillary central incisor and 56 as the control group were studied. All participants were 8-12 years old. The data were collected from private offices of orthodontists and special pediatric dentists and Hamadan dental school. The data required were diagnostic models, initial panoramic radiography and initial lateral cephalometry radiography. Data analysis was done by SPSS software using t test and chi-square test. Results: The most common causes of maxillary central impaction were: mesiodens (74.4%), dilacerations (14.3%), space deficiency (10.7%) and cyst (3.6%). 89.3% of cases had unilateral maxillary central impaction and 10.7% had bilateral maxillary central impaction. There was a significant relation between skeletal class II and maxillary central impaction. ANB angle was significantly higher in impaction group than in control group (P < 0.05). In most of the patients with maxillary central impaction, ipsilateral canines had upper position compared with the contralateral side (60%). Conclusions: Presence of mesiodens was the most important reason for maxillary central incisor impaction, and class II jaw relation is more common in patients with maxillary central incisor impaction, which higher incidence of vertical disorders can be a bigger challenge in these patients.

Background and Aim: Life-threatening medical emergencies might happen at any time to a patient in a dental office. These emergencies should be treated immediately and cannot be avoided or referred. The purpose of this study was to assess the knowledge and attitude of dentistry professors, residents, and interns towards medical emergencies at the dental faculty of Hamadan University of Medical Sciences. Materials and Methods: A cross-sectional study was conducted among 174 dental practitioners practicing as dentistry professors, residents or interns at the dental faculty of Hamadan University of Medical Sciences. A questionnaire comprised of three parts, including demographics, knowledge, and attitude, was distributed among the participants. The collected were tabulated and analyzed using SPSS 24. The results were reported in terms of the frequency. Comparisons were made using one-way analysis of variance (ANOVA) with a 95% confidence interval (CI). P<0.05 was considered statistically significant. Results: The residents' knowledge score was significantly higher than that of the faculty members (P=0.02). The faculty members' score was higher than that of the interns but the difference was not significant. Less than half of the participants stated that the quality of the provided theoretical educations was satisfactory. Conclusion: The results indicate the lack of proper medical emergency preparedness among the studied dentists. It seems that periodic theoretical and practical medical emergency training courses are necessary for dentists during education and, more importantly, after graduation.