Material and methods

Twenty-four consecutive patients, all scheduled for fixed orthodontic treatment at a private dental clinic, were selected for this study. The sample consisted of 10 boys and 14 girls with a mean age of 14 years 1 month. The inclusion criteria were as follows: complete permanent dentition up to the first molars, no vestibular caries or fillings, no hypocalcified teeth, no dental fluorosis, and no endocrine disorders (eg, diabetes).

A split-mouth study was conducted, applying the varnish to quadrants 1 and 3, with quadrants 2 and 4 as the untreated controls. Opposing quadrants were chosen to eliminate any bias resulting from handedness, which can affect the uniformity of brushing accuracy. The 6 varnished and the 6 control teeth were the central incisors, the canines, and the second premolars: ie, teeth from each of the maxillary and mandibular anterior, medial, and posterior sectors.

The patients were randomly assigned to 2 subgroups according to the frequency of Duraphat application: group 1, comprising 13 patients (5 boys, 8 girls), in whom Duraphat was applied every 3 months; and group 2, comprising 11 patients (5 boys, 6 girls), in whom Duraphat was applied every 6 months. Four to 7 days before bonding, both groups were given a professional scale and polish and attended a hygiene motivation session. All patients received a hygiene kit that contained a medium-bristle toothbrush (G-U-M; Sunstar Americas, Chicago, Ill).

Before the trial all patients had a dental examination with caries control, periodontal evaluation, and plaque index. An oral hygiene session with motivation by the dental hygienist was conducted 7 days before the appliances were placed.

Before bonding, the 24 subjects’ teeth were cleaned with a pumice stone and a brush mounted on a low-velocity contra-angle handpiece, and the enamel mineralization of all sample and control teeth was measured with a DIAGNOdent Pen 2190 (KaVo, Biberach an der Riss, Germany).

The DIAGNOdent Pen 2190 contains a diode laser with a wavelength of 655 nm and power less than 1 mW. It can detect small alterations in the tooth substance, invisible to the naked eye, up to a depth of 2 mm. According to the literature, the DIAGNOdent has great specificity and accuracy, similar to visual-tactile examinations and radiography (identifying 70%-80% of lesions), compared with histology testing, if it is used on clean teeth (without tartar buildup) and without fluoridated substances. The DIAGNOdent Pen 2190 measures the fluorescence emitted by the tooth in response to irradiation of a certain wavelength; a reading between 0 and 13 indicates healthy enamel, between 14 and 20 suggests initial demineralization, between 21 and 29 means considerable demineralization, and greater than 30 indicates dental caries.

The laser was calibrated for each patient according to the manufacturer’s guidelines, and readings were taken at 4 labial sites on the enamel (gingival, occlusal, mesial, and distal) as suggested by Banks and Richmond ( Fig ). Initial values (T0) were recorded in the patients’ dental records.

Dividing the tooth surface to evaluate enamel demineralization, as proposed by Banks and Richmond. The blue circle is the mark on the distal gingival portion of the Damon bracket. G , Gingival; M , mesial; O , occlusal; D , distal.

After the initial readings, medical-grade steel brackets, self-ligating Damon Q (Ormco, Orange, Calif), were bonded to the teeth with a light-cured composite. The dental arcades were then isolated, and the vestibular surfaces were dried and treated. Duraphat (5% sodium fluoride) was applied to the vestibular enamel around the brackets of the maxillary right central incisor, canine, and second premolar and the mandibular left central incisor, canine, and second premolar using a microbrush. After about 5 minutes of hardening time, the patient was instructed on how to perform oral hygiene procedures and asked to refrain from eating or drinking for 4 hours, as the manufacturer recommends. All patients received a hygiene kit containing a manual orthodontic toothbrush, which was replaced every 3 months.

In follow-up visits, mineralization of the enamel was measured as follows: the vestibular surfaces of all teeth were cleaned using a brush mounted on a low-velocity contra-angle handpiece, and the residual varnish was removed with an air polishing system (TPC Advanced Technology, City of Industry, Calif) to prevent its being read as a false positive. The fluorescence emitted at the 4 sites, each 1 mm from the bracket, was measured on all sample and control teeth using the DIAGNOdent Pen 2190, and then the Duraphat varnish was reapplied, as per the manufacturer’s instructions, on the teeth in the first and third quadrants. Measurements were taken, and fluoride varnish was reapplied at 3, 6, 9, and 12 months after appliance fitting (T1, T2, T3, and T4, respectively) in group 1, and at 6 and 12 months after bonding (T2 and T4, respectively) in group 2. All patients were given a new hygiene kit (including a toothbrush) every 3 months, and a professional scale and polish every 6 months.

All measurements from the DIAGNOdent were recorded on an Excel spreadsheet (Microsoft, Redmond, Wash), and the significance of any differences was evaluated by the chi-square test at a significance level of P <0.01. A general linear model was used because the measurements had a non-Gaussian distribution. Coefficient plots were also generated to illustrate the significance of each value with respect to the reference (intercept).

During the study, every 6 months, all patients attended ab oral hygiene session and evaluation with the plaque index.

Results

The total number of measurements taken was 4704: 3120 in group 1 (Duraphat applications every 3 months) and 1584 in group 2 (Duraphat applications every 6 months). Table I shows the numbers of measurements and the mean values for the degrees of mineralization from T1 through T4 in treated and untreated teeth; Table II shows the mean readings from the 3 sectors (anterior, medial, and posterior) in treated and untreated teeth; and Table III shows the average readings in sites treated or not every 3 months and every 6 months.

Table IV shows a greater tendency toward demineralization in the untreated vs the treated teeth, although both linear and coefficient analyses showed that the difference was not significant at any of the 4 measurement times (3, 6, 9, and 12 months).

Table IV

Correspondence between degree of demineralization, length of treatment, and treatment

	Chi-square	df	P (+χ 2 )
Reference value	138.63	1	0.0000
Length of treatment	90.51	4	0.0000
Treated teeth	0.18	1	0.6710
Treated teeth/length of treatment	3.49	4	0.4792

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