ABSTRACT
@#Increasing numbers of adult patients are seeking orthodontic treatment, which increases the need for orthodontists to treat malocclusion in periodontally compromised teeth affected by periodontitis. It is essential to control active inflammation prior to initiating an orthodontic protocol to avoid further breakdown of alveolar bone caused by periodontitis. However, whether the condition of periodontal ligaments can completely recover to a normal condition after controlling inflammation and tolerate orthodontic tooth movement remains controversial. The present review elaborates, from clinical trials (macroscopic) to biological tests (microscopic), the characteristics of periodontal tissue and periodontal ligament cells with a history of periodontitis that are submitted to orthodontic force loading. The following conclusions are made: 1. Orthodontic treatment in periodontally compromised patients is unusual because of changes in periodontal condition. 2. The combination of orthodontic force loading and uncontrolled periodontal inflammation aggravates pathological bone resorption; therefore, it is crucial to perform periodontal therapy prior to orthodontic treatment. 3. The periodontal ligament can withstand proper mechanical force loading after periodontal treatment. 4. Orthodontic treatment, as an adjunctive therapy, can improve periodontally compromised tissue and pathological tooth movement.