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The purpose of this study was to compare the bond strength of orthodontic brackets using laser versus acid etching.Debonding of brackets is a common problem in orthodontic treatments.Eighty extracted premolar teeth were divided into two groups. The enamel of the teeth in group A and B were etched using CO2 laser and phosphoric acid, respectively. The brackets were bonded to the teeth using Transbond XT and then debonded from the teeth by Instron machine. The remaining composite on the tooth surface was removed by a tungsten carbide polishing bur. Both groups were divided into two subgroups (A1, A2 and B1, B2). The teeth were prepared again with laser in A1, B1 subgroups and with acid in A2, B2 subgroups. At each stage, the shear bond strength and residual adhesive index were measured. One way ANOVA and χ(2) tests were used to analyze data.The mean shear bond strength was significantly lower in group A and higher in group B compared with all other groups (p0.05). Most of the bond failures were degree 0 and 1 in groups A, A1, and B1, and degree 2 and 3 in groups B, A2, and B2.Primary preparation with acid has a higher bond strength value than does CO2 laser. Less adhesive residue remained on enamel after tooth preparation with laser following debonding. Secondary preparation of the enamel using laser has higher bond strength value than does primary preparation with laser, which can rationalize use of laser in rebonding of brackets.

Pyknodysostosis is a rare bone disease that has autosomal dominant trait. It is character-ized by short stature, diffuse osteosclerosis, acro-osteolysis, finger, and nail abnormalities. Other features include open fontanelles and sutures, relative proptosis and obtuse man-dibular gonial angle with relative mandibular prognathism. Intraoral features such as den-tal abnormalities also have been reported.In this report, a case of pyknodysostosis in a 9-year-old boy is presented. Most of the ob-served features were comparable to the other case reports but some findings such as re-peated chest infection, sleep apnea, kyphosis, scoliosis, root shortness, pulp narrowing, supernumerary and hypodontia could not be observed in this case.Instead, in this patient features such as anterior open bite and decreased anterior tooth dis-play, not reported in other cases, was evident.

Bond failure after rebonding for newly placed brackets can be reduced by appropriate enamel surface treatment. This in vitro study investigated the effect of two enamel surface treatments on the bond strength of metallic brackets in the rebonding process. After debonding the brackets and removing the residual adhesive on the enamel surface of 50 upper premolar teeth, the teeth were divided into two equal groups. In the first group, the enamel surface was etched with phosphoric acid 37 per cent, and in the second group, the teeth were sandblasted prior to acid etching. After bonding of the new brackets, the shear bond strength (SBS), probability of bond failures, and adhesive remnant index (ARI) were determined and compared with the t-test, Weibull analysis, and chi-square test. Mean SBS in both groups did not differ significantly (P = 0.081). Most bond failures occurred with ARI scores of 2 and 3, and the difference between the two groups was statistically significant (P < 0.001). Weibull analysis showed that for a given stress, the probability of failure differed between groups. Enamel surface preparation with sandblasting prior to acid etching did not significantly improve SBS in bracket rebonding and left more residual adhesive remnants on the enamel surface.