This study used randomized, controlled split-mouth experimental design to compare the effects of pre-operative APD application (test side) and rubber-cup prophylaxis with paste (control side) on teeth bleaching. The flow chart of study design was given in Figure 1.
Among the patients who applied to the Cukurova University, Dental Faculty, Department of Oral Diagnosis for whitening treatment and volunteered to participate in the study and redirected to Department of Restorative Dentistry.
The inclusion criteria were:
- being at least 18 years of age
- having minimum of 20 natural teeth (including incisors, canines, and premolars in both arches)
- having good oral hygiene (Plaque index <1, Gingival index <1)
The exclusion criteria were:
- having restorations or active caries on the anterior teeth of either arch
- presence of tetracycline staining or fluorosis
- general hypersensitivity
- gingival recession or periodontal disease
- smokers
- pregnant or lactating women
- history of prior bleaching treatment
Sample size calculation
The sample size analysis for paired-sample t-test was done by G-Power package program. The sample size calculation was based on a previous study [9]. The expected mean difference of for the color change parameter between groups was 2,2 units with a standard deviation of 3,3 - 3,7 (the specified power of 80% and the Type I error rate of 5%). The calculated sample size was 21 patients while 23 patients (10% more) were included in the study to compensate possible dropouts.
Study protocol
Clinical parameters
Tooth color was measured using spectrophotometer VITA Easyshade V (Vita Zahnfabrik, Germany). The spectrophotometer was calibrated before use in each participant and the device tip was placed on middle thirds of the labial surface of teeth as suggested by the manufacturer’s manual.
The tooth color was measured before initial prophylaxis (baseline), immediately after bleaching and after one week. The digital spectrophotometer used in the current study measures the shade of teeth based on the CIE L*a*b* color space system [10]. This system expresses color as three values: L* for the lightness from black (0) to white (100), a* from green (−) to red (+), and b* from blue (−) to yellow (+). The following values were recorded in the units of CIE L*a*b* color space.
-Data of lightness (L*) and a* and b*axis
-DE: calculated as: DE = [(DL *)2+ (Da *)2 + (Db *)2]1/2
While making Shade guide units (SGU) measurements, the bleached index is set according to the VITA Bleached guide 3D-MASTER at spectrophotometer for the measured shade. The measured bleached index after treatment was subtracted from the baseline value. The difference corresponded to the change of the SGU (D SGU) achieved immediately and 1 week after the bleaching treatment.
Randomization
The patients had bleaching treatment on the maxillary anterior area including right and left canines. The registration of the patients has been done by Department of Oral Diagnosis and randomly allocated by ZGBK. The right and left sides of the patients were randomized by toss of a coin to receive polishing with rubber cup prophylaxis or air powder polishing system before bleaching.
Clinical procedures
The rubber cup prophylaxis was applied with low-speed handpieces. A rubber cup was attached to the prophy-angle. The handpiece used at a steady slow pace of 2500–3000 rpm. The rubber cup contacted (Pro-Cup, Light Blue, Soft, KerrHawe S.A., Bioggio, Switzerland) each tooth surface for an average of 5 seconds together with polishing paste consisting of flour of pumice, glycerin and fluoride (Cleanic, KerrHawe S.A., Bioggio, Switzerland).
The air polishing treatment was performed by AIRFLOW® Master device (EMS, Nyon, Switzerland) with a six LED power setting (2.2 bars dynamic pressure inside powder chamber) and an 11 LED (35 mL/min) water setting for 30 seconds (powder consumption was 1.1 g). Sodium bicarbonate air-powder polishing powder (AIR-FLOW® Plus, EMS Electro Medical Systems, Nyon, Switzerland) was used. The nozzle was held 3–4 mm from the tooth surface and the tip was angulated diagonally. The spray was delivered for an average of 5 seconds using a constant circular motion for each tooth. The spray was directed towards the middle one-thirds of the exposed tooth [11].
The bleaching agent (Opalescence Xtra Boost/ Ultradent, South Jordan, UT, USA) was prepared and used following the manufacturer’s instructions. Opal Dam (Ultradent, South Jordan, UT, USA) was used for protection of the gingiva. The bleaching gel was then applied to form 1–2 mm thickness on the buccal surfaces of the teeth of both arches. The gel remained on teeth for 15 minutes and was then suctioned from teeth using a surgical suction tip. This application was repeated a second time in the same session.
Statistical Analysis
The assumption of normal distribution of difference scores were examined prior to conducting the analysis. The assumption was considered satisfied for many differences of color scores, some of them not satisfied which were indicated with asterisk (*) in Table 1.
The proper reporting for non-normal distributed (skewed) data were summarized by using median (minimum and maximum) value instead of mean and standard deviation. Because of a consistent illustration in the Table 1 for parametric and non-parametric tests the both descriptive statistics mean ± SD, and Median (min, max) noted across all treatment levels.
The differences of color scores of the teeth were assessed for normality assumption by Shapiro-Wilks test (p>0.05) and homogeneity of variances were assessed by Levene’s Test for Equality of variances (p>0.05).
The paired t-test were used if the normality assumptions were valid, otherwise the Wilcoxon-signed rank test were used to compare the rubber-cup and air-powder polishing treatments, and for the differences of 1 week and immediate values.