Long-term 3-dimensional stability of mandibular advancement surgery.

PURPOSE: To evaluate 3-dimensional changes in the position of the condyles, rami, and chin from 1 to 3 years after mandibular advancement surgery. MATERIALS AND METHODS: This prospective observational study used pre- and postoperative cone-beam computed tomograms of 27 subjects with skeletal Class II jaw relation and normal or deep overbite. An automatic technique of cranial base superimposition was used to assess positional and bone remodeling changes that were visually displayed and quantified using 3-dimensional color maps. Analysis of covariance with presence of genioplasty, age at time of surgery, and gender as explanatory variables was used to estimate and test adjusted mean changes for each region of interest. RESULTS: The chin rotated downward and backward 1 to 3 years after surgery. Changes of at least 2 mm were observed in 17% of cases. Mandibular condyles presented with displacements or bone remodeling of at least 2 mm on the anterior surface (21% of cases on the left side and 13% on the right), superior surface (8% on right and left sides), and lateral poles (17% on left side and 4% on right). Posterior borders of the rami exhibited symmetric lateral or rotational displacements in 4% of cases. CONCLUSION: In the hierarchy of surgical stability, mandibular advancement surgery is considered one of the most stable surgical procedures. However, 1 to 3 years after surgery, approximately 20% of patients had 2- to 4-mm changes in horizontal and vertical chin positions or changes in condylar position and adaptive bone remodeling.

Primer on the base of polycarbonate brackets: should we apply it or not?

OBJECTIVE: The purpose of this study was to evaluate shear bond strength of polycarbonate brackets bonded with or without the previous application of primer on their bases. MATERIALS AND METHODS: Forty-six extracted bovine permanent mandibular incisors were obtained and randomly divided into two groups of 23 each: group 1 (control), 37% phosphoric acid and direct bonding with Orthoprimer (Morelli Orthodontic Products, São Paulo, Brazil) and Orthobond (Morelli Orthodontic Products); and group 2, Orthoprimer application on bracket base prior to conventional bonding. Polycarbonate maxillary central incisor brackets (Composite, Morelli Orthodontic Products) were used in this study. All products were used according to the manufacturer's instructions. An Universal Testing Machine was used to apply an occlusal shear force directly onto the enamel-bracket interface at a speed of 0.5mm/min. The groups were compared using Student's t-test. RESULTS: Mean results and standard deviation (in MPa) for the groups were: group 1 - 5,81 (1,90); and group 2 - 6,09 (1,28). Significant difference was not observed in the bond strengths of the two groups evaluated (p=0.5601). The adhesive remnant index (ARI) did not indicate significant difference (p=0.617) between the two groups. CONCLUSIONS: These results indicated that primer application on polycarbonate bracket base did not result in increased bond strength.