STOMATOLOGY EDU JOURNAL 2017, Volume 4, Issue 2 2 | Page 28

2.3. Application method The targeted area was first cleaned with a cotton pellet. Then, the dentist mixed the powder with the liquid for 15 s to obtain a paste that was immediately applied on the treated areas with a microbrush by gently brushing for 2 min (Fig. 1 to 4). In the same visit, both test and placebo treatments were applied to each patient according to a randomization list. Patients were then asked to rinse their mouth, and within 15 min after the treatment the blinded dentist applied the same air blast stimuli under the same conditions to assess pain scores after treatments (POST). Patients were recalled for hypersensitivity assessment of the treated areas after 1 week. At that time point, after data collection, both dentist and patients were un- blinded regarding the test or placebo treatment, and the test treatment was applied to the area that previously received the placebo compound. Patients were then recalled after 1, 3 and 6 months and at each recall the dentist assessed only tooth areas that were treated with test compound since the beginning of the trial. Figure 2. Application of the tested DD on right maxillary teeth (test site), same area depicted in Fig 1. 2.3. Statistical analysis All statistical analyses were performed using statistical software (JMP 10.0, SAS Institute Inc, Cary, NC, USA). A preliminary check of the normality of distribution and homogeneity of variances was performed using Shapiro-Wilk’s and Levène’s tests (p<0.0001 and p=0.0014, respectively). Since data did not belong to continuous variable (0-10 ordinal VAS scores), were not normally distributed and homoscedasticity was not respected, non- parametrical ANOVA and non-parametric comparisons for each pair using Wilcoxon method (p<0.05) were used to highlight significant differences between groups. 104 Figure 3. Dental occlusal erosions bilaterally on palatal side of maxillary frontal and lateral teeth. Air blast test scored 8. Patient was referred to a gastroenterologist physician. He was later diagnosed with gastroesophageal reflux disease (GERD) and given treatment. Patient refused restorative therapies, requesting treatment of pain symptoms only. Figure 5. Box plot depicting the main findings of the study. The minimum and maximum values and the 25th, 50th, and 75th  percentiles  are shown in red. Different superscript letters indicate significant differences between groups (p<0.05) as assessed by Wilcoxon method. The test DD was compared with a placebo for up to 1 week, then its effect on reducing pain perception was monitored for 6 months. Figure 4. Application of the test DD on the same area as in Fig 3. Figure 1. Patient requesting desensitization treatment for vestibular areas of maxillary teeth. No presence of cervical lesions or abrasions could be identified as well as other lesions, yet upper right and upper left canines and premolars scored 7 on VAS after air blast test. CALCIUM PHOSPHATE NANOPARTICLES REDUCE DENTIN HYPERSENSITIVITY: A RANDOMIZED, PLACEBO-CONTROLLED STUDY 3. Results All 25 subjects completed the trial without requesting alternative desensitization treatments or dropping out from the trial. No adverse reactions were reported. The results of the study are displayed in Fig. 5. Both DD and placebo significantly decreased VAS scores comparing POST and PRE (p<0.0001) measurements, thus showing similar efficacy (35% and 28%, respectively). DD application further decreased scores after 1 week (63% in comparison with PRE), while placebo application did not show significant differences when compared to POST (p=0.09). The scores from the areas treated with the DD maintained, throughout the observational period, the levels obtained after 1 week (maximum decrease in scores = 69% after 3 months). At 6 months, a small, non-significant increase in VAS scores was also observed. 4. Discussion Dentin hypersensitivity is an increasing occurrence, and dental materials or procedures able to reduce the patient’s sensitivity are increasingly needed. A variety of therapies are currently available, 2,4,6 but the most modern and biocompatible approach seems to be the one aiming at reconstituting a barrier and closing the open orifices of the tubules by using biomimetic materials and techniques. 13,14,15,16 Stoma Edu J. 2017;4(2): 102-107 http://www.stomaeduj.com In this study, we assessed the clinical efficacy, expressed as pain reduction from hypersensitive tooth areas, of a biomimetic, hydroxyapatite- forming dentin desensitizer (DD) based on calcium phosphate nanoparticles. The first null hypothesis could not be fully rejected, since immediately after application there was no significant difference between DD under investigation and placebo, meaning that the reaction to the test DD immediately after application could not be due to its activity, but simply to a placebo effect. After one week, however, there was a highly significant difference between placebo and test DD. In fact, the test DD required 1 week to reach the significantly lowest scores of pain perception, and this level was maintained for up to 6 months. The second null hypothesis could, therefore, be rejected. The tested DD is a biomimetic desensitizing compound based on the reaction between tetracalcium phosphate and dicalcium phosphate anhydrous in the presence of fluoride ions. Once water is added, the reaction produces hydroxyapatite and small parts of fluorapatite nanoparticles that precipitate as an amorphous layer on the tooth structures. Since nanocrystal deposition on enamel and dentin structures is driven by collagen backbone structures, one may speculate that the presence of these structures inside dentine tubules may help organize deposition of hydroxyapatite and fluorapatite. Thanatvarakorn et al. in 2013 17 provided some data in support of this hypothesis. They showed that the tested DD developed an immediate reduction in dentin permeability and an effective integration of the calcium phosphate rich layer with dentin surfaces, enhancing mineralization under oral Stomatology Edu Journal conditions. 17 The data obtained in this study could convey some indirect hints regarding the activity of the compound. It seems clear that the deposition of an amorphous layer of nanocrystals on the hypersensitive tooth surfaces does not lead to a reduction in pain perception greater than placebo effect. It is very likely, however, that hydroxyapatite and fluorapatite deposition inside dentinal tubules takes place at least over a one-week time period after application and is responsible for the significant reduction in pain perception when confronted to the placebo at 1 week or to the initial values. Our results confirm the assumptions of Zhou et al. 10 thus providing a clinical confirmation of their in vitro results. In their study, the effectiveness of the same DD was evaluated in reducing dentin permeability and tubule orifice occlusion. It was found that the two parameters improved depending on the time until maximum values in permeability reduction and tubules occlusion were found after one week [10]. These results are in good correlation with those of the present study, meaning that dentine permeability and occlusion of tubuli orifices (>50%) can be good indicators of reduction in pain perception. In our study, it was found that the reduction in pain perception due to the test DD did not remain significantly different between the different time points starting from 1 week for up to 6 months. This means that the effects obtained by the tested DD (remineralization, reduction in dentin permeability and tubule occlusion 10,17 ) are long-lasting, however additional studies are needed to ascertain if the test DD may express its activity over extended observation times up to one or several years. The study was performed under conditions as close as possible with those of similar studies 14,15 in order to evaluate possible differences yielded from geographical areas or pain perception. The tested DD compound was the same as the one used by Mehta et al. in 2014 14 and similar to the one tested by the same research group one year after. 15 The study design was the same as in Mehta et al., 2015, 15 except for the placebo follow-up that was stopped after 1 week in the present study. The statistical analysis was different in methodology, since in the present study no parametric analysis of data could be applied. One would speculate that, given that the material, the study design and the patient recruitment were very similar among these studies, similar results would be obtained. A first observation can be made comparing the initial pain scores to those after treatment and 1-week follow- up. The initial scores in the present study were higher than those from Mehta et al., 14,15 and reduction in pain perception after at least one week of treatment was higher than the results of Mehta et al., 15 but similar to the results the same Authors obtained one year earlier. 14 Many different explanations for these results may be provided, including the fact that pain remains an extremely subjective perception being influenced CALCIUM PHOSPHATE NANOPARTICLES REDUCE DENTIN HYPERSENSITIVITY: A RANDOMIZED, PLACEBO-CONTROLLED STUDY 105