Prediction of maxillary canine impaction using sectors and angular measurement.

Maxillary canine impaction has an incidence of 1 in 100 in the general population and has been reported as much higher in an individual orthodontic practice. Because patients with canine impactions generally have longer treatment times, depending on the location of the impacted tooth, early identification of impaction is of critical interest to the orthodontist. Sector location and angulation of the unerupted tooth have been analyzed previously as predictors of canine eruption after deciduous extraction. Additionally, sector location has been studied as an indicator of eventual impaction, resulting in good predictive success. In this study, angulation of the unerupted tooth was measured from panoramic radiographs and added to sector location to see whether the combination of these factors could predict impaction more accurately than sector alone. Results verified earlier findings for sector: canines that become impacted will overlap the adjacent lateral incisor in 82% of cases. Logistic regression analysis also determined that once the canine overlaps the midline of the lateral incisor, there is a greater than 0.87 chance of impaction. Sector was found to be the better predictor of impaction, with angulation adding little supplementary predictive value.

Bonding of stainless steel brackets to enamel with a new self-etching primer.

The purpose of this study was to measure the shear bond strength of stainless steel brackets bonded to enamel in vitro with a recently developed self-etching primer (Transbond Plus Self Etching Primer, 3M Unitek, Monrovia, Calif). Forty-eight extracted human teeth were obtained and randomly divided into 4 groups of 12: (1) control group with a conventional etchant and separate primer, (2) experimental group with the self-etching primer, left for 15 seconds before bonding, (3) same as group 2, but with the primer left for 2 minutes before bonding, (4) same as group 2, but with the primer left for 10 minutes before bonding. For each group, stainless steel brackets were mounted onto the prepared enamel, stored for 24 hours at 37 degrees C, and tested in a testing machine with a crosshead speed of 1 mm/min. There was no significant difference in the bond strength between the 4 groups as determined by analysis of variance (ANOVA) (P <.05). Under the conditions of these experiments, a 10-minute delay in bonding after application of the self-etching primer might not be deleterious to adhesion.