Post-treatment stability of temporomandibular joint and occlusion after one-year retention by hawley retainer

Objective: The stability of temporomandibular joint and occlusion is still uncertain even after delivering ideal orthodontic treatment. Thus, proper posttreatment follow-up has been advised. This study investigated the stability of temporomandibular joint and dental features one year posttreatment after using Hawley retainer as retention appliances. Material and methods: Records of 21 patients who had undergone orthodontic treatment and given Hawley retainer as a retention appliance were obtained. The sample comprised 14 females and 7 males who met the inclusion criteria with an average age of 18.5 ± 3.02 years. Two sets of upper and lower teeth models were obtained at two-time points: after completion of orthodontic treatment (T1) and one year after retainer wearing (T2). Dynamic occlusions were determined by using face bow transfer, articulator mounting and measure condyle displacement (MCD). Static occlusions were assessed by using objective grading system (OGS). Vertical, anteroposterior and transverse condyle displacement were measured by analysis of the graphic registrations, produced by MCD instrument. Quantitative occlusal parameters were measured by the analysis of models using American board of orthodontics (ABO) measuring gauge. Results: The maximal recorded mean centric occlusion-centric relation discrepancies (CO-CR shift) of patients after orthodontic treatment at horizontal, vertical and transverse planes were 1.10 ± 0.46 for right condyle, 1.09 ± 0.49 for left condyle and 0.23 ± 0.16 for transverse, respectively. After one year of wearing Hawley retainer, the maximal recorded slides in centric discrepancies of patients at three planes were 1.15 ± 0.54 for horizontally left condyle, 1.05 ± 0.45 for vertically left condyle and 0.26 ± 0.18 transversely. The vertical, horizontal or transverse displacement of the condyle on either left or right side had no statistical differences after wearing Hawley retainer one year posttreatment (p > 0.05). The overjet (p = 0.031) and total OGS scores (p = 0.005) decreased significantly during one year of wearing Hawley retainer. Conclusions: Condyle positions appear to be stable one year posttreatment following Hawley retainer wearing. Although, the quantitative orthodontic treatment outcome scores of dental features decreased in patients wearing Hawley retainer one year posttreatment, still the temporomandibular joint remained stable as evidenced by similar centric occlusion-centric relation, suggesting wearing Hawley retainer does not influence its stability.