The Radiological Assessment of Root Features and Periodontal Structures in Endodontically Treated Teeth Subjected to Forces Generated by Fixed Orthodontic Appliances. A Prospective, Clinical Cohort Study

The various side effects of orthodontic treatment with fixed orthodontic appliances (FOAs) and their impact on apical and periodontal structures have been widely reported. However, the existing data is not yet conclusive. Aims and objectives: To investigate the status of roots and periodontium in endodontically treated teeth that have undergone orthodontic treatment with the use of FOAs and to evaluate their impact on apical/periodontal structures. Material and methods: The prospective clinical cohort study initially involved 69 participants aged 16–40, without underlying systemic conditions, who received orthodontic treatment with ligatureless FOA systems due to different types of mild and moderate malocclusions. To meet the required criteria, 88 teeth in 34 patients were assessed clinically and radiologically. Participants had at least one tooth treated endodontically while the corresponding tooth from the same anatomical group on the opposite side was vital and intact (a ‘split-mouth’ approach). Four cohorts were allocated: Group IA consisted of 15 teeth, treated utilising the principles of modern endodontics, that were subjected to orthodontic forces no less than six months after completing the root canal obturation. Group I consisted of 13 similarly endodontically treated teeth, which commenced orthodontic treatment at least six months after the completed endodontic therapy. Group II contained 16 teeth treated by conventional endodontic methods and the control group, Group III, contained 44 clinically and radiologically intact teeth (incisors and premolars) with vital and sound dental pulp. The response of apical and periodontal structures to FOAs was determined by data collected from intraoral periapical radiographs taken within the course of five consecutive appointments during the orthodontic treatment. Results: No statistically significant differences were observed in susceptibility to FOA-induced external apical root resorption (EARR) between combined Groups IA + IB and II. An association was, however, demonstrated, between the occurrence of EARR and the degree of expansion of the periodontal ligament (PDL) space, regardless the method of root canal treatment. Cumulative data revealed a positive correlation between the width of the PDL space and the stage of FOA treatment (the third and the fourth appointment). The subtle changes in radiological length of roots have been observed (min 0 mm/max 0.38 mm), particularly between the second and third appointment in Group II (p < 0.05). Conclusions: The standard orthodontic therapy with FOAs is a safe option with predictable outcome for persons who have recently received endodontic therapy. The anterior teeth, predominantly incisors, were more susceptible to minimal EARR than premolars, which suggests that the rate of EARR occurrence may depend upon the original morphology of the apical portion of the root. The use of additional orthodontic forces increases the risk of EARR and is associated with a higher incidence of radiologically detected PDL space widening.