* Department of oral diagnosis, college of dentistry, Hawler medical university, Erbil, Iraq.

Introduction: The purpose of this study was to find out the prevalence of C-shaped canals configurations in mandibular 2nd molar and to investigate the gender prevalence. Materials and Methods: A sample of 1200 patients’ cone beam computed tomography (CBCT) scans were screened and evaluated by a maxillofacial radiologist assessed the axial, sagittal, and coronal sections. Inclusion criteria applied to 801 patients (452 females and 349 male) aged 14–75 years were included in this study with total of 1567 mandibular 2nd molar was evaluated. Inclusion criteria: Available CBCT images of mandibular posterior teeth with at least one mandibular 2nd molar in the scan, absence of root canal treatment, absence of coronal or post coronal restorations, absence of root resorption or periapical lesions, and high-quality images. Canal configuration was classified by criteria’s which described by Fan et al. (2004): (i) Fused roots, (ii) a longitudinal groove on the buccal or lingual surface of the root, and (iii) at least one cross-section of the canal belongs to the C1, C2, or C3 configuration. Results: Considering 801 patients, 97 (12.1%) patients females 57 (7.1%) and 40 (5%) males had a C-shaped canal with no statistical difference between females and males (P > 0.05). Conclusion: The occurrence of C- shaped canal mandibular 2nd molar is approximately 12.1% and no significant difference was found by gender.

Overhanging tooth restorations due to environmental change of the balance between beneficial bacteria and periodontopathogens lead to periodontal breakdown. This study aim was to evaluate the periodontal status after using different techniques for amalgam overhang removal. The proximal restorations were examined clinically and then radiographically by taking bitewing radiograph. From a total of 1200 patients examined in College of Dentistry, Hawler Medical University and (Khanzad) Specialized Centre for Dentistry for presence of proximal amalgam restoration, for this interventional and prospective study, 45 patients with amalgam overhang were divided into three groups each 15 patients according to size and position of amalgam overhang each had one type of the following treatment (Refilling, Diamond Bur, EVA system) and 15 patients without amalgam overhang (control group) selected completed the trial. Clinical periodontal parameters were measured in teeth with amalgam overhang at baseline, 2 week, 1 and 3 months after removal of amalgam overhang. The results showed that the periodontal parameters showed a gradual decrease in all groups throughout the follow-up visits (except calculus index) and became a statistically significant in the 3 months follow-up following treatment (P < 0.001), with more reduction found in refilling group followed by EVA system then diamond bur group. In conclusion that it is better to replace the restoration rather than to use the other methods of treatment according to periodontal health which recorded by periodontal parameters.