Typodont model study on double keyhole loop in mandibular extraction space closure / 口腔疾病防治

Objective@#To analyze the impact of the activation mode on the results of space closure in the mandibular arch using a double keyhole loop (DKHL) with a typodont model and reverse engineering technique to provide guidance for clinical treatment. @*Methods@#Nine normal mandibular typodont models after leveling were randomly divided into 3 groups, which then underwent three types of DKHL activation for space closure. Each model was assessed at the initial stage and after the warm water bath, and the images were superimposed to measure the displacement of special crown and root mark points. All statistical analysis of the data was performed using SPSS 19.0@*Results@# After equal activation times, the root retraction of anterior teeth and the crown forward position of posterior teeth in groups activated at the distal loop (conditions 2 and 3) were much greater than those in the group activated horizontally (condition 1). Activation between mesial and distal loops (condition 3) induced significant anterior tooth intrusion, together with elongation and buccal inclination of posterior teeth. The displacement of mark points among the three conditions showed a statistically significant difference. @* Conclusion @# The movement of mandibular anterior and posterior teeth could be flexibly controlled through different DKHL activation modes, which should be chosen carefully according to individual conditions.

Bilateral macrodontia of mandibular second premolars: a case report

Macrodontia is a rare dental anomaly characterized by an excessive enlargement of all tooth structures that generally could be related with some syndromes. Until today, there is a low prevalence of bilateral macrodontia. The present report shows a patient with bilateral macrodontia in mandibular second premolars and with a clear medical history of him and his parents without any syndromes or other dental anomalies. It is important to know macrodontia because the crown shape of teeth is more predisposed to caries and may cause some problems in the occlusion of the patient. By the above, is important to acquire a deeper knowledge about this anatomical variation, as well as must be prepared to perform a carefully treatment of the compromised teeth. The aim of this study was to describe this case with a bilateral rare condition of interest to dentists.

Influence of crown shape on root coverage therapy

OBJECTIVES: The aim of this study was to evaluate the influence of the crown shape on the outcomes of root coverage procedures. MATERIAL AND METHODS: Eighty patients with Miller class I gingival recessions in maxillary canines or premolars were selected. The recession areas were treated using the subepithelial connective tissue grafting. The following clinical parameters were analyzed: crown length (CL) and width (CW), recession height and width, probing depth, clinical attachment level, width and thickness of the keratinized tissue and percentage of root coverage achieved. These measurements were recorded at baseline and 6 months after the surgical procedure. The CW/CL ratio was calculated for each tooth and the median obtained (0.83). Patients were then ranked into two groups, according to the shape of the tooth with gingival recession: Group A - square crown shape (CW/CL values above 0.83) and Group B - long and narrow crown shape (CW/CL values below 0.83). RESULTS: No statistically significant differences (p>0.05) were found between groups in any of the clinical parameters at baseline. After 6 months, both groups presented improved clinical outcomes for all parameters analyzed compared to baseline (p>0.05). The mean percentages and standard deviations of root coverage achieved in Group A and Group B was 91.37 (16.75) and 85.49 (23.55), respectively (p>0.05). CONCLUSIONS: Crown shape did not influence the root coverage obtained with the subepithelial connective tissue graft technique.