The aim of this prospective randomized clinical trial was to determine the effect of using fluoridated paste (Dentsply, York, Pa) compared with plain pumice (Ortho Technology, Tampa, Fla) on the clinical bond failure rates of precoated brackets bonded with self-etching primer.
A split-mouth technique was used. The teeth in the maxillary right and mandibular left quadrants were prepared with a fluoridated paste only, and the teeth in the maxillary left and mandibular right quadrants were prepared with plain pumice before bonding the precoated brackets. A total of 627 brackets in 34 orthodontic patients (20 female, 14 male) were included in this study; 315 brackets were bonded after pumice treatment, and 312 were bonded after paste treatment. The patients were followed for 6 months to determine the rates of bracket failure.
The overall failure rate was 8%. The failure rates for pumice and paste were 4.8% and 11.2%, respectively. The McNemar test showed a statistically significant difference between the 2 groups. Based on tooth type, the failure rate of the maxillary canine and the mandibular central incisor brackets were significantly different for paste and pumice. There was also a difference in the survival rates of the brackets in both groups.
Preparation of the enamel surface with fluoridated paste before bonding with self-etching primer is not recommended. However, the use of plain pumice is recommended, even if it is time-consuming.
Bonding of orthodontic brackets requires enamel surface preparation by removing the organic pellicle. This removal is achieved with either pumice or fluoridated paste applied with a rubber cup or brush. Afterward, the enamel surface either is etched with 37% phosphoric acid for 15 to 30 seconds or a self-etching primer. If the enamel surface is prepared with an acid, rinsing and drying of the surface are required. Then, a primer is applied to the enamel surface before placement of the bracket precoated with adhesive. The use of a self-etching primer reduces the bonding time of each bracket from 170 seconds to 111 seconds compared with the conventional 2-stage technique.
Previous studies have investigated the effect of various factors, including fluoride liquid, paste, varnish, and blood contamination on the bond strength of brackets. However, the effect of enamel preparation with fluoridated paste on precoated brackets bonded with self-etching primer needs to be shown in vivo.
The purpose of this prospective randomized split-mouth clinical trial was to determine the effect of fluoridated paste on the clinical bond failure rates of precoated brackets bonded with a self-etching primer compared with pretreatment with plain pumice.
Material and methods
Thirty-four consecutive patients (20 female, 14 males) were enrolled in this study based on the following inclusion criteria: the need for orthodontic treatment with fixed maxillary and mandibular orthodontic appliances, no history of previous orthodontic treatment, no dietary habits, and no tooth decalcification or fluorosis. The patients were asked to enroll voluntarily in the study after explanation of the procedure, and written approval was signed by the patient or one of the patient’s parents. The teeth in the maxillary right and the mandibular left quadrants were prepared with a fluoridated paste (Dentsply, York, Pa) only. The teeth in the maxillary left and the mandibular right quadrants were prepared with plain pumice (Ortho Technology, Tampa, Fla) before the bonding of precoated brackets (3M Unitek, Monrovia, Calif) loaded with Transbond XT adhesive composite (3M Unitek). At the bonding appointment, the teeth were isolated with a cheek retractor and a salivary ejector. For both the fluoridated paste and the pumice sides, the paste and the pumice were loaded onto a rubber cup in a slow contra-angle hand piece. After preparation, all teeth were rinsed and air dried for 5 seconds. The precoated brackets were bonded by using a self-etching primer (3M Unitek) in a 1-stage process. Bonding of brackets in every quadrant was performed separately, starting with the maxillary right side, in a standardized manner. The self-etching primer was mixed according to the manufacturer’s instructions, applied, and agitated on each tooth surface for 5 seconds, and then air dried to a thin film. The precoated brackets were then placed on the teeth and firmly seated by using a periodontal probe. Excessive adhesive material was removed from the periphery of the brackets. After proper seating of the brackets, the adhesive material was light-cured for 5 seconds with an Ortholux light-cure unit (3M Unitek) in the area between adjacent brackets. The brackets were mesh-based stainless steel orthodontic brackets. All patients were given a standard oral hygiene protocol and instructed to avoid certain hard foods during their orthodontic treatment. The oral hygiene practices of the patients were monitored during the course of treatment.
Since some patients were required to undergo tooth extractions for orthodontic purposes, the number of brackets used in each patient was recorded. Bracket failures were followed for 6 months. Any bracket that failed during treatment was rebonded with Transbond XT after conventional acid etching with 37% phosphoric acid. These brackets were excluded from the trial, and their further failures were not recorded. Data on bond failures were collected and recorded for each patient.
Descriptive statistics were used to describe the frequency of bracket failures in both the fluoridated paste and the pumice groups. The McNemar nonparametric statistical test was used to compare bracket failures in each group. In addition, a comparison of bracket failure rates according to tooth type was also performed. The survival rates of the brackets in both groups was compared byusing the Kaplan Meier test.
The total number of brackets included in this study was 627 for both the pumice and the fluoridated paste groups. There were 315 brackets on the pumice side and 312 brackets on the paste side. Bracket failures were followed over 6 months. The overall failure rate was 8%. The failure rates of the brackets were 4.8% on pumice-treated teeth and 11.2% on paste-treated teeth ( Table I ). The nonparametric statistical McNemar test showed that the failure rate after fluoridated-paste treatment was significantly higher than that after pumice treatment ( P <0.001) ( Table I ).
|Group||Brackets (n)||Failed brackets (n)||Failures (%)|
The McNemar statistical test was then used to compare the failure rates between the groups according to tooth types in the maxillary and mandibular arches. Four maxillary canine brackets bonded to paste-treated teeth failed, whereas no brackets bonded to pumice-treated teeth failed. Similarly, 3 mandibular central incisor brackets on paste-treated teeth failed compared with none on pumice-treated teeth. Thus, the failure rates of maxillary canine and mandibular central incisor brackets were significantly higher after paste treatment ( P <0.001) ( Table II ).
|Location and tooth type||n||Fluoridated paste failures (n)||n||Pumice failures (n)||Significance (2-tailed)|
|Central incisor||34||3||34||0||0.000 ∗|