Kee-Joon Lee

Yonsei University, Korea

Transverse discrepancy is not easily recognized by the patient and the orthodontic envelope of discrepancy is reportedly narrow in the transverse direction, which is why surgically assisted palatal expansion is recommended for the correction of maxillary transverse deficiencies in grown-up patients. However, active correction of transverse deficiencies may provide clues to many clinical cases as long as the modality is appropriate. Hence the validity of either surgical or nonsurgical treatment possibilities need to be discussed based on the following aspects.
1. Feasibility: Previous studies suggested that unlike the cranial sutures, true bony union in the facial sutures is rare even during adulthood, which supports the feasibility of nonsurgical maxillary expansion. In contrast, segmental expansion osteotomies caused significant relapse afterwards. Surgically assisted RPE would needs subsequent surgical relocation of jawbone following surgical expansion, which may not be justified in terms of morbidity and convenience. Clinical cases will be shown to demonstrate the diagnosis and treatment of various transverse discrepancies.
2. Tissue response: Our previous study revealed that the tensile stress applied to the suture mesenchyme in the aged group induced active bone formation associated with elevation and relocation of Erk positive cells, similar to the young group. Subsequent proliferation and differentiation of the bone cells were obvious but certain differences in bone turnover and expression patterns between groups were also observed. In spite of the slight delay in response, mesenchymal cells in the facial suture appear to retain remarkable potential for further proliferation and differentiation, implying significant bone formation activity.
Hence it was presumed that non-invasive expansion protocol to maximize bone formation activity along the suture needs to be encouraged. In this presentation, several cases showing maxillary transverse deficiency will be shown, with special emphasis on the role of the suture cells in the feasibility and the stability of maxillary expansion. According to the theoretical background and clinical examples, it appears that deficiency in the maxillary posterior region, not necessarily the anterior region necessitates true orthopedic expansion which secures reliable non-extraction in severe crowding, non-surgical treatment for Class III/asymmetry, as well as the facilitation of surgery-first protocols.