ABSTRACT
Context: Bracket debonding is a common problem during orthodontic treatment. This type of failure is associated to masticatory forces, poor adhesion, and the need for repositioning the piece. Aims: The objective of this work was to compare the shear bond strength of debonded brackets that were reconditioned using different protocols (alumina blasting versus hydrofluoric etching). Settings and Design: This was an in vitro experimental study with 45 stainless steel orthodontic brackets. Subjects and Methods: They were randomly divided into three groups: (1) New brackets (n = 15), (2) brackets reconditioned using 10% hydrofluoric acid for 60 s (n = 15), and (3) brackets reconditioned by aluminum oxide blasting until complete removal of the remaining resin (n = 15). In Groups 2 and 3, the insertion of composite resin proceeded in two stages to simulate a type of bracket failure in which the bonding resin was left at the bracket base. For the shear test, the assembly composed by the metallic support, and specimen was taken to the Instron universal testing machine in which the specimens were loaded using a semicircle‑shaped active tip in the region of the bonding interface parallel to the surface of the bracket at a speed of 0.5 mm/min. Statistical Analysis Used: The data were subjected to D’Agostino’s normality test to have their distribution checked. Analysis of variance and Tukey’s test (P < 0.01) were used to compare the findings between groups. Results: The results indicated that Group 1 (new brackets) showed higher bond strength than that obtained for the group treated with hydrofluoric acid (Group 2, P < 0.01). The bond strength value obtained for the group treated with alumina blasting (Group 3) was statistically similar to those obtained for Groups 1 and 2. Conclusions: The aluminum oxide blasting technique was effective for the reconditioning of orthodontic brackets. Nevertheless, the reconditioning technique using 10% fluoridric acid for 60 s was not efficient for clinical use.
ABSTRACT
Purpose: The aim of this study was to test the null hypothesis that there is no change in the lower anterior teeth's crown size when measured just after the treatment with Frankel-2's orthopedic appliance and in a long-term posttreatment follow-up. Materials and Methods: The sample was composed of 34 plaster models belonging to 9 male and 8 female individuals, treated at the College of Health, Methodist University of São Paulo, São Bernardo do Campo, São Paulo, Brazil, with mean age of 12 years and 6 months (standard deviation [SD] =7 months) at T1 (end of the treatment with Frankel-2's function regulator), and 19 years and 8 months (SD = 7 months) at T2 (7.11 years after the end of the treatment). Results: The distance from the incisal edge to the most concave portion of the gingival margin of the lower incisors and canines was measured using a digital caliper. Data analysis was carried out by means of Student's t-test and paired-t test. Among the lower anterior teeth, the teeth 31, 33, 42 and 43 showed a statistically significant increase in their crown length, whereas the teeth 32 and 41 showed no changes. Conclusion: It can be concluded that there is a tendency to increase the clinical crown of lower anterior teeth throughout the years after the mandibular advancement treatment by using functional devices, rejecting the null hypotheisis.