This study was single center, one-blinded, 2-arm parallel, randomized clinical trial with a 1:1 allocation ratio. No changes were made to the protocol after trial commencement. Initially, 60 patients who had been referred to a tertiary clinic in Kayseri, Turkey for orthodontic treatment between October 2011 and June 2013 were assessed for eligibility by the clinicians (A.Y.). The inclusion criteria for the experiment groups in this study were mild to moderate crowding in the maxillary and mandibular dental arch, good oral hygiene, absence of craniofacial anomalies, no previous orthodontic treatment and no deciduous, congenitally missing or extracted teeth. 60 patients were examined in the trial. Thirty-six patients were divided into groups with equal numbers of patients in each group. The study was completed with 31 patients. An analysis was performed on the 15 patients in the indirect bonding group and the 16 patients in the direct bonding group. Approval for the study was obtained from the Local Ethics Committee of the Faculty of Medicine at Erciyes University in Kayseri, Turkey (11-3585). Informed consent was obtained from all the patients included in the study. The consent was obtained from those over 18 years of age directly, and from the parents of those under 18 years of age. Standard treatment records, which are photographs, dental models and radiographs, were taken in the beginning of treatment and at the end of treatment from all patients included in the study. The patients were randomly allocated to 1 of 2 treatment groups: indirect bonding and direct bonding. In the direct bonding group, after the plaque structure on the teeth was cleaned with pumice and white elastic bur were etched with 37% phosphoric acid gel (3M-Dental Products, St Paul, Minnesota, USA) for 30 seconds, the teeth were rinsed and dried with oil-free compressed air for 15 seconds. After drying the enamel surface, the liquid primer Transbond XT (3M-Unitek, Monrovia, California, USA) was applied with a small brush and spread with oil-free compressed air. Pre-adjusted metal brackets which had values for the Roth prescription were then bonded using the conventional adhesive with a standard protocol and polymerized for 3 seconds per bracket with a multiwave light-emitting diode curing light.

In the indirect bonding group, alginate was utilized to take impressions of the maxillary and mandibular arches, and hard dental stone was used to cast the dental models. Following the trimming and drying of the dental models dried, guidelines were drawn for vertical and horizontal bracket-positioning using a black pencil. The separating agent Al Cote (Dentsply Trubyte, York, Pennsylvania, USA) was administered onto the surfaces of the teeth surfaces using a brush, and the casts were left to dry. The same brackets used in the direct bonding technique were used. The composite adhesive was administered onto the base of the bracket, and the bracket was then placed onto the marked area on the tooth surface. The excess resin was carefully removed with a hand instrument. After positioning the bracket, the composite adhesive was polymerized with a multiwave light-emitting diode curing light. After positioning of the bracket on the transfer models, the composite adhesive was polymerized for 3 seconds, and a 2-layer transfer tray was prepared using translucent soft silicone and thermoformed rigid Essix Plus plastic. The base of the brackets in the transfer tray was sandblasted to remove the separating agent. A flowable composite adhesive was applied to the bracket bases, and the transfer tray was then seated on the arch segment. The composite adhesive was polymerized for 3 seconds before and after removing the transfer tray. Excessive composite adhesive remnants were then removed using a tungsten carbide bur in an air rotor instrument. For all of the patients included in the study, orthodontic treatment and recommendations for how to use toothpaste containing fluoride, how to brush their teeth and diet habits were also added to reduce the number of white spot lesions and provide better treatment. The QLF images of all patients who underwent direct and indirect bonding were taken by the same observer in the beginning of fixed orthodontic treatment (T0) and immediately after removal of the appliances (T1) at the end of the treatment period using a QLF-D Biluminator 2-camera system (Inspektor Research Systems, Amsterdam, The Netherlands).