Acceptability comparison between Hawley retainers and vacuum-formed retainers in orthodontic adult patients: a single-centre, randomized controlled trial

Hawley retainers (HRs) and vacuum formed retainers (VFRs) are the most commonly used removable retainers in the orthodontic practice. Patients' cooperation in wearing these appliances is affected by the levels of discomfort and oral impairment. The evidence regarding their acceptably among orthodontic patients is limited. To compare the acceptability of HRs and VFRs over a 6-month period in a group of fixed orthodontic patients. Two-arm parallel-group randomized controlled trial. Patients being treated at the Orthodontic Department of Saudi Swiss Consultant Dental Centre, Al-Khobar, Saudi Arabia, who met the inclusion criteria were invited to participate. Inclusion criteria were treatment only with fixed appliances, no lateral expansion treatment, no hypodontia, no cleft lip and palate, no surgical corrections, no extraction-based plans, 18 years old or greater, and willingness to wear maxillary and mandibular removable retainers. Participants were distributed randomly using concealed envelopes into two groups: HR group and VFR group. A pilot-tested questionnaire was filled at three times: 1 week after fitting of the retainer (T1), 3 months and 6 months following appliance fitting (T2 and T3, respectively). Ten questions were given on biting, fitting of the appliance, speech, appearance, oral hygiene, durability, gingival irritation, swallowing, self-confidence, and comfort. Responses were given on a visual analogue scale. Blinding was employed during data analysis. Ninety-four patients were included primarily. Six patients in the Hawley group and two patients in the VFR group failed to complete the study. Therefore, 86 patients were included the analysis (HR group: 41; VFR group: 45). No significant differences were found between the two groups in biting, fitting of the appliance, and hygiene perception, whereas significant differences were detected in speech (P < 0.05), appearance (P < 0.001), gingival irritation (P < 0.001), durability (P < 0.001), swallowing (P < 0.001), self-confidence, and comfort (P < 0.001). No harm to any patient was noticed during the trial. Over a 6-month period of retention, VFR was significantly more acceptable than HR in speech, appearance, gingival irritation, swallowing, self-confidence, and comfort. Subjects in the HR group believed that their retainers were significantly more durable than those in the VFR group at the final assessment. Both retainers were equal regarding fitting of the appliance, biting, and hygiene perce