Evidence for Prosthodontic Intervention to the Shortened Dental Arch (SDA)

目的：在过去的二十年里，缩短牙弓（SDA）的概念被引入作为后牙无牙患者的治疗策略！即不需要修复缺失的磨牙区域。另一方面，临床经验提示各种可能的功能障碍开始不稳定的咬合。本研究的目的是阐明SDA的概念是否适用于所有的后牙无牙患者。研究选择：本研究纳入10例单侧后牙缺失患者，对其进行SDA状况的多重评价。该评估包括客观评估（TMJ的x线评估和最大自觉握紧时髁突位移的测量）和主观评估（问卷调查）。结果：50%的患者影像学表现异常。咬合时，无牙侧髁移位值明显高于无牙侧髁移位值。40%的受试者对SDA条件表现出高水平的抱怨。结论：这些结果提示了口腔功能的潜在风险。对于没有任何积极治疗的SDA患者是“观望”还是立即开始义肢干预，我们希望提出临床指导方针。

Purpose : In the last two decades, the Shortened Dental Arch (SDA) concept has been introduced as a treatment strategy for posterior edentulous patients! i.e. there is no need to restore the missing of molar region. On the other hand, clinical experience suggests various possibilities for functional disturbance starting from instability of occlusion. The purpose of this study is to clarify whether SDA concept fits for all posterior edentulous patients.Study selection : Ten patients with unilaterally posterior tooth missing were enrolled in this study, and a multiple evaluation for SDA condition was applied to them. This evaluation consists of the objective evaluation (radiographic evaluation for TMJ and measurement of condylar displacements during maximum voluntary clenching) and the subjective evaluation (questionnaire).Result : Abnormal radiographic appearances were observed in 50% of subjects. Condylar displacements during clenching were significantly high value in the edentulous-side condyle compared to that in the dentulous-side condyle. 40% of subjects showed high level of complains for SDA conditions.Conclusions : These results indicated the potential risks for the oral functions. We wish to propose the clinical guidelines for making a decision whether to "wait and see" the SDA patients without any positive treatment or to start prosthetic intervention immediately.