This study was planned as a single-center clinical trial. The study procedures were approved by the Clinic Research Ethics Local Commission of Ordu University (2018/24). The patients and their parents signed an informed consent form describing the procedures in detail. The inclusion criteria were as follows: (1) requiring fixed non-extraction orthodontic treatment, (2) full permanent dentition except third molar, (3) good oral hygiene, (4) no smoking, (5) no radiographic alveolar bone loss, (6) Class I malocclusion with moderate or severe crowding in both arches, (7) no systemic disease, and (8) no previous orthodontic and orthognathic surgery treatment.
Thirty-five female individuals were selected at the Department of Orthodontics, Faculty of Dentistry, Ordu University, Turkey. The participants were classified into three following groups: (1) patients who will receive conventional fixed orthodontic treatment (OT; n = 14; aged 13 to 19 years), (2) patients who will receive piezocision in addition to fixed orthodontic treatment (PG; n = 9; aged 13 to 18 years), and (3) patients who will receive discision in addition to fixed orthodontic treatment (DG; n = 12; aged 13 to 18 years). Before the orthodontic treatment, panoramic radiographs, lateral cephalometric radiographs, intra- and extra-oral photographs, and maxillary and mandibular dental casts were taken. Periodontal parameters were measured initially, after the 1-month orthodontic treatment. Probing pocket depth, bleeding on probing, plaque index, and gingival index were recorded. The study sample size was calculated by using G*Power Software version 3.1.9.2 (Universität Düsseldorf, Germany) for a reduction of the total orthodontic treatment duration with a power of 85% at the 5% significance level [13].
All individuals were treated with 0.022-in. slot Roth prescription self-ligated brackets. The order of orthodontic arch wires was as follows: 0.014-in., 0.016-in., 0.018-in., 0.016 × 0.022-in., 0.017 × 0.025-in. nickel-titanium arch wires were utilised for tooth alignment, and 0.019 × 0.025-in. stainless-steel arch wires were utilised for finishing stage in groups. The patients were seen at 2–3 week-intervals. The intraoral elastics were used if necessary. The orthodontic treatment was completed when adequate criteria were provided. Fixed and removable retainers were placed at the end of the orthodontic treatment. The total orthodontic treatment duration was noted. Initial Little’s irregularity index scores were performed with a digital calliper (Mitutoyo, Tokyo, Japan) on dental stone models. In PG and DG groups, piezocision and discision procedures were performed on both dental arches 1 week after placement of bonding brackets.
Visual analog scale (VAS) was performed over the first month at different times following the bracket bonding. Lateral cephalometric skeletal and dental measurements were measured on digital radiographs. Root resorptions were identified and classified on finishing radiographs.
Piezocision procedure
Following local anaesthesia, vertical micro-incisions were performed to correspond to the centre of each interdental papilla and starting from 1 mm below the free gingival groove and passing the mucogingival line. All piezocision procedures were performed starting from teeth number 6 in both sides of the mandibular and maxillary arch. Vertical corticotomies were performed with a piezoelectric knife (Mectron Piezosurgery Device, Mectron, Genova, Italy) approximately 7 mm in length and 3 mm in depth. There was no need for suturing the incision lines; all piezocision procedures were done flapless. Irrigation was used in piezocision procedure. No hard or soft tissue grafts were applied to the vestibular region of the teeth. The patients were advised to take analgesics such as paracetamol if necessary.
Discision procedure
The disc incision protocol was performed as defined [17]. Following local anaesthesia, vertical micro-incisions were performed to correspond to the centre of each interdental papilla and starting at 1 mm below the free gingival groove and crossing the mucogingival line. Vertical corticotomies were then performed with a disc saw (Osstem Implant, Esset KIT-Saw, Seoul, Korea) approximately 7 mm in length and 3 mm in depth. There was no need for flap elevation or suturing (Fig. 1). Also, irrigation was used in discision procedure. The patients were advised to take analgesics such as paracetamol if necessary.
Statistical analyses
All data parameters were statistically analysed by using the SPSS (SPSS for Windows version 20.0; SPSS Inc., Chicago, IL) program. After performing the normal distribution test, parametric tests were performed to the parameters having a normal distribution, while non-parametric tests were performed to the parameters with non-normal distributions. The Shapiro-Wilk test was performed to test the data for normal distribution. The data were analysed by using one-way analysis of variance, Kruskal-Wallis, Mann-Whitney U test, and independent t tests. Post hoc LSD test was used for parametric variables, and the Mann-Whitney U test was used for non-parametric variables.