Case78

A case of Protruding lower bite and Diverted bite during the mixed dentition, successfully treated without tooth extraction through consecutive Phase I and Phase II treatment.
Given the child’s chronological age, the permanent teeth erupted early, suggesting that the baby teeth were lost prematurely. Based on an assessment of various records, we performed Phase I treatment to secure space for the eruption of permanent teeth and combined this with a treatment plan that avoided tooth extraction. Treatment proceeded by creating space and placing brackets in accordance with the eruption of the permanent teeth, continuing on to treatment for the permanent dentition.

While there is sufficient space for permanent teeth to erupt in the lower jaw, there is insufficient space in the upper jaw, and this is particularly noticeable on the right side. On the cephalometric X-ray, there is no anteroposterior discrepancy between the upper and lower jaws as pronounced as that observed on the model; apart from what appears to be slight underdevelopment of the upper jaw, the morphology is largely harmonious. In addition, a panoramic X-ray revealed a pronounced mesial inclination of the right maxillary first molar, leading to the conclusion that the tooth was significantly displaced from its normal position. The treatment plan was to reposition the molars to their original positions and perform a slight expansion of the upper jaw.

Brackets were placed in a limited area, and treatment for the anterior crossbite was initiated while moving the right maxillary first molar distally (6). About 10 months after the start of treatment, we had created sufficient space and corrected most of the anterior crossbite; however, it took an additional 12 months to correct the overjet in the anterior region and achieve proper midline alignment (7). Two years after treatment began, the patient started treatment with full braces (8). As can be seen in the occlusal view of the model, the first molar has been repositioned to its proper location, and the maxillary arch has been adjusted to a size that matches the mandibular arch, including a slight expansion toward the front (9–11).