Journal of Dental Medicine

Background and Aim: Recycling of brackets can significantly reduce the price of fixed orthodontic appliances but if the bond is more prone to failure during treatment, this potential benefit will disappear. The aim of this study was to investigate the effect of chemical recycling on bond strength of metal orthodontic brackets and failure pattern of recycled brackets.

Material and Methods: In this experimental study Instron machine was used to measure shear bond strength (SBS) of brackets in two stages on 60 human maxillary first premolars using No-Mix composite. Shear bond strength and pattern of failure were compared between recycled and new brackets in two stages. Data were analyzed by ANOVA and Duncan tests. Adhesive Remnant Index was evaluated in different groups by Pearson Chi-square test. P<0.05 was considered as the limit of significance.

Results: Statistical analysis showed that the mean values of SBS for new bracket group was 12.00 MPa and for recycled group and double recycled group, 9.94Mpa and 10.00 MPa respectively. A significant reduction (about 18%) in bond strengths of brackets was observed at the first time of recycling. Recycling at the second time had no significant influence on the bond strength. Pattern of bond failure of these brackets showed that a great amount of residual adhesive material was remained on the teeth surfaces after debonding of recycled brackets which indicates that cleaning the teeth surfaces after debonding of recycled brackets is more time consuming.

Conclusion: Based on the results of this study, before using recycled brackets, several advantages and disadvantages must be considered.

Background and Aims: Approximately 5% of cancers involve structures of oral cavity. Partial resection of maxilla (maxillectomy) may be performed in these cases. Maxillectomy often results in significant functional disabilities such as inability in mastication, deglutition and speech with adverse impact on psychological status and social life of patients. Obturator prosthesis is a prosthodontic treatment to separate nasal and oral cavities and restore the critical above mentioned functions. The assessment of speech is considered to examine speech function restored by the treatment. The purpose of this study was to evaluate the speech in patients with resected maxilla who have been treated by obturator prosthesis from a pool of related patients in the Prosthodotnics department of dental faculty, Tehran University of Medical Sciences. The evaluation was performed with computer software using sentence intelligibility (SI) test.

Materials and Methods: This cross sectional study was conducted on 10 subjects (23-66 years) referred to the Prosthodontics department of the faculty and received an obturator. After primary examination of the prosthesis, the patients completed SI test in an acoustic room under guidance of a speech therapist. The performed tests were analyzed by the speech therapist. In addition, the SI with and without the prosthesis was evaluate by lay audience. The statistical analyses were performed using Wilcoxon-signed rank test and Weighted Kappa.

Results: Significant differences were found between SI tests with and without the obturators (P<0.001). Two of 10 patients showed problems in speech function using obturator.

Conclusion: Within the limitations of the present study, obturators had significant effect on improvement of the speech outcomes of examined patients. Improvement of the quality of life could be predicted.