Correction of Skeletal Crossbite by Extraction of Two Lower Premolars

Objectives: To evaluate the clinical effects of the orthodontic treatment with extracting two lower premolars in adult skeletal crossbite cases. Methods: Twelve adult skeletal crossbite cases, diagnosed to be in the borderline surgical-orthodontic range but refused the surgical treatment, were selected in the study. The ages range from 18 to 30 years old and the average age was 23.4±4.6 years. In these cases, two first or second premolars in the mandible were extracted and the Standard Edgewise technique was adopted. Lateral cephalometric radiographs were taken before and after treatment for analysis. The arithmetic mean and standard deviation were calculated for each variable and paired t-test was performed. Results: At the end of the treatment, normal overjet and overbite were established with Class ¢ó molar and Class ¢ñ canine relationships. There appeared to be no significant skeletal changes after treatment (P°Ý0.05). L1-MP angle decreased by 8.1°; U1-L1 angle increased by 7.7°; L1-NB angle decreased by 7.3°and L1-NB distance decreased by 4.8 mm. Statistically significant differences were found in these changes (P£¼0.01). The soft-tissue profile was improved significantly. Li-E°¢Li-H and Li-RL2 distances decreased by 3.2 mm°¢3.4 mm and 4.1 mm respectively (P£¼0.01). Conclusions: Success in the treatment of the adult skeletal crossbite can be achieved with extraction of two lower premolars. All the patients finished with stable occlusion and a tendency to straight profile. It is suggested that this treatment method could be an alternative to orthognathic surgery in borderline skeletal crossbite cases.