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Plaque control during the course of orthodontic treatment is not an easy task, and dental caries are not an unlikely complication. We examined the possibility of controlling dental caries with Nd-YAG laser irradiation in orthodontic patients. As a preliminary experiment, we used the Nd-YAG laser to irradiate an extracted tooth and then left it to soak in lactic acid. The decay of the tooth was evaluated with a scanning electron microscope (SEM); tooth decay was inhibited by the action of the laser. Twenty patients undergoing orthodontic treatment for early decalcification of the teeth (white spot lesions) were selected, and photographs were taken of their oral cavities. White spot lesions on the four incisors and two canines of the maxilla were traced on tracing paper, and their areas were calculated by computer. Ten of the patients received laser treatment and acidulated phosphate fluoride solution (APF); the other ten acted as the control group. Between 11 and 12 months later, we photographed the oral cavity as we had previously; the white spot lesions were again traced and their areas calculated. The changes in the areas of the white spots of the laser-irradiated and control groups showed the following increases: laser-irradiated group, 1.41 times; controls, 2.87 times. The difference was statistically significant. These results demonstrate that Nd-YAG laser irradiation with application of APF acts as an effective method of caries control during orthodontic treatment.

Scissor bite is defined as buccal displacement of the maxillary posterior teeth, with or without contact between the lingual surface of the maxillary lingual cusp and the buccal surface of the buccal cusp of its mandibular antagonist. Here we report treatment of bilateral scissor bite in the posterior region using rapid expansion following corticotomy. The patient was a boy aged 17 years and 11 months in whom skeletal maxillary prognathism with bilateral scissor bite was diagnosed. The distance between the tips of canines and the mesial buccal cusps of the first molars was increased by use of a bonded rapid expansion appliance following corticotomy. Appropriate occlusion and lateral profile were obtained and maintained after retention. In addition, no gingival recession, hyperesthesia, or root surface caries occurred. These results suggest that mandibular lateral expansion following corticotomy is effective in young adult patients with a narrow mandibular arch.

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