External apical root resorption of posterior teeth in asthmatics after orthodontic treatment

External apical root resorption is an undesirable sequela of orthodontic treatment, resulting in loss of tooth structure from the root apex, It has been proposed that systemic factors, such as the inflammatory mediators produced in asthma, may enter the periodontal ligament and act synergistically to enhance root resorption. The aim of this study was to determine if asthmatic patients exhibited a higher incidence or severity of external apical root resorption compared with healthy (no medical conditions) patients after fixed orthodontic treatment. Records were obtained from patients treated with fixed appliances; 99 were healthy and 44 had asthma. Using OPGs (panoral films), posterior external apical root resorption was measured on all first and second premolars, mesiobuccal and distobuccal roots of the upper first molars, and mesial and distal roots of the lower first molars, giving 4 measurements per quadrant. A 4-grade ordinal scale was used to determine the degree of external apical root resorption. Combined tooth analysis (adjusted for treatment time, appliance, and extractions) showed that asthmatics had significantly more external apical root resorption of posterior teeth after treatment compared with the healthy group (P = .0194). Tooth-by-tooth analysis (adjusted for treatment time, appliance, extractions, headgear, overbite, overjet, sex, and age at start of treatment) found the upper first molars were most susceptible to external apical root resorption. Although the incidence of external apical root resorption was elevated in the asthma group, both asthmatics and healthy patients exhibited similar amounts of grade 2 (moderate) and grade 3 (severe) resorption.