# Oral Impacts of Aligners versus Fixed Self-Ligating Lingual Orthodontic Appliances
## 2 Materials and Methods  
The study was performed according to the Declaration of Helsinki guidelines on experimentation involving human subjects. Informed consent was obtained from all participants. All patients treated with the Invisalign(r) compliance were supervised by an experienced Invisalign instructor, whereas all patients with lingual appliances were supervised by an experienced lingual appliance instructor. Patients were presented with the pros and cons of both appliances, and the patient's decision regarding the desired type of appliance was respected. A total of 47 consecutively treated adult patients with either Invisalign(r) or lingual fixed orthodontic appliances, over the first 3 months of the treatment, were enrolled in this prospective longitudinal clinical study. Two groups of adult patients were evaluated, including 21 treated with Invisalign(r) (13 females, 8 males, aged 32.9 \(\pm\) 2.38 years (mean \(\pm\) SE)) and 26 with In-Ovation L(r) active self-ligating 0.018-inch lingual brackets (18 females, 8 males, aged 38.5 \(\pm\) 2.12 years (mean \(\pm\) SE)). Calculation of the required sample size was based on an assumed minimum clinically significant difference of 10 units in the 0-100 HRQoL scale between the two groups at Day 1. Standard deviations were assumed to be common in the two groups and equal to 11 units, according to initial results from the first 10 patients. Setting the desired level of power to 0.80 at an alpha level of 0.05, the resulting sample size was 21 patients per group. Patients who met the following inclusion criteria were eligible to participate in the study:  
(a) Caucasian origin; (b) treatment need for both dental arches with required lateral cephalometric radiograph; (c) no inherited or acquired craniofacial deformities; (d) no neurologic disorders or tongue thrust habits; (e) no hearing deficits or history of speech/hearing therapy; and (f) no previous orthodontic treatment. The cephalometric radiographs were obtained with the aid of a cephalostat that ensures reproducible and stable patient positioning. The initial wire inserted in the lingual fixed orthodontic appliances was 0.012-inch NiTi wire and was maintained for the first three months. In the Invisalign group (SmartTrack: multi-layer aromatic thermoplastic polyurethane 0.75 mm), bite ramps that may influence speech were not used and the aligners were changed every 7 days. Patients were instructed to wear the aligners for 22 h per day, excluding eating and brushing. Patients with aligners were instructed to only drink water and to abstain from coffee, tea or red wine. Patients were asked to track their cooperation with this timetable daily, and their adherence was reinforced at each appointment. If the edge of the aligner was rubbing against the lips, tongue or gums, it was smoothed off or trimmed without compromising the way it fitted. Assessments of the treatment need with the IOTN and the cephalometric evaluation were performed for each patient by two examiners, who were not involved in the treatment of the patients and were blinded to the treatment group assignment [26]. Cephalometric evaluation included skeletal classification (ANB), vertical position of the mandible (GoGn-SN), upper and lower incisor inclination (U1/PP and L1/MP), and facial divergency (Z-angle). Questionnaires and speech samples were gathered at the following intervals: T0, immediately prior to appliance insertion; T1, immediately following appliance insertion for the speech samples and the first day following appliance insertion for the questionnaires; T3, 3 months post-insertion. Ratings of oral impacts and satisfaction were performed using the HRQoL instrument, filled out by the patients (Appendix A). This questionnaire has been used and validated in previous studies [9; 10; 11; 12; 13; 14; 15; 16]. Speech samples were collected for evaluation by professionals. These samples were obtained in a video imaging room with a reduced-noise environment.