Case48

An open bite with a Class I molar relationship and significant overjet. A case in which Phase I treatment was performed during the mixed dentition and Phase II treatment was performed during the permanent dentition. Because the maxillary anterior teeth are significantly protruding, the lower lip pushes the maxillary anterior teeth upward and forward when the lips are closed. Although the patient was in the mixed dentition, we determined that the condition was affecting growth and therefore proceeded with the first phase treatment. During the permanent dentition, the patient developed Class I protruding dual dentition accompanied by a slight open bite in the anterior region. This case was treated as an extraction case to reposition the front teeth backward and achieve harmony in the soft tissues surrounding the oral cavity.

Changes in the anteroposterior position of the front teeth alter the muscle tension in the soft tissues surrounding the oral cavity (7–11). The function of the structures surrounding the oral cavity as masticatory organs depends not only on a tight occlusion and the masticatory muscle groups involved in chewing, but also on the functions of the tongue and lips.