## 4 Discussion  
DH is a very annoying clinical problem. DH patients feel an intense pain when teeth come in contact with hot, cold, acidic, or sweet liquids and foods. The clinician has to identify and correct the responsible factors and establish a therapeutic plan with a desensitizing effect that leads to the cessation of pain as fast as possible and for the longest time. Nowadays, there is no verified protocol that can eliminate the pain from DH, even when combining various protocols. The treatment of DH is based on the concept of reducing the fluid movement inside the dentin tubules by narrowing or occluding the tubules' openings. In fact, according to the hydrodynamic theory, the effectiveness of dentin-desensitizing agents is directly related to their capacity of sealing the dentin canaliculi, maintaining a constant intracanalicular pressure [22; 23]. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Time** & \multicolumn{2}{c}{**SG 1 (n28)**} & \multicolumn{2}{c}{**SG 2 (n34)**} & \multicolumn{2}{c}{**SG 3 (n32)**} & \multicolumn{2}{c}{**SG 4 (n30)**} \\ \hline  & **Total** & **Mean** & **Total** & **Mean** & **Total** & **Mean** & **Total** & **Mean** \\ \hline t0 & 142 & 5.29 & 179 & 5.26 & 172 & 5.55 & 155 & 5.34 \\ t1 & 38 & 1.41 & 43 & 1.26 & 30 & 0.97 & **26** & **0.90** \\ t2 & 46 & 1.70 & **41** & **1.20** & 39 & 1.26 & 50 & 1.72 \\ t3 & 59 & 2.19 & **51** & **1.5** & 62 & 2 & 72 & 2.48 \\ t4 & 86 & 3.19 & **65** & **1.91** & 99 & 3.19 & 101 & 3.63 \\ \(p\) value & \(p\) < 0.0001 & & \(p\) < 0.0001 & & \(p\) < 0.0001 & & \(p\) < 0.0001 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Total and mean values of discomfort scores (VAS) at baseline (t0), immediately after the treatment test (t1) and, after 1 week (t2), 1 month (t3) and 6 months (t4) for each study group. The values with greater pain control are highlighted in bold. Statistical correlation between VAS value at baseline vs. all VAS values at different times using the Wilcoxon signed-rank test. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Study Groups** & **t1** & **t2** & **t3** & **t4** \\ \hline SG 1 vs. SG 2 & 0.43 & 0.99 & 0.00 \({}^{**}\) & 0.00 \({}^{**}\) \\ SG 1 vs. SG 3 & 0.01 \({}^{*}\) & 0.75 & 0.00 \({}^{**}\) & 0.96 \\ SG 1 vs. SG 4 & 0.00 \({}^{**}\) & 0.91 & 0.28 & 0.03 \({}^{*}\) \\ SG 2 vs. SG 4 & 0.04 \({}^{*}\) & 0.00 \({}^{**}\) & 0.00 \({}^{**}\) & 0.00 \({}^{**}\) \\ SG 3 vs. SG 4 & 0.63 & 0.00 \({}^{**}\) & 0.99 & 0.02 \({}^{*}\) \\ \hline \hline \end{tabular} \({}^{*}\)\(p\) < 0.05; \({}^{**}\)\(p\) < 0.01.  
\end{table} 
Table 2: Statistical correlation of VAS scores between each group immediately at end of treatment (t1), at 7 days (t2), at 1 month (t3), and at 6 (t4) months from the treatment. P: Wilcoxon signed-rank test. The present study was realized using a single-blind and randomized design evaluating the effectiveness of NaF in a gel and of a desensitizer agent, VivaSens, used either alone or in association with a DL for the treatment of DH caused by NCCLs, on the basis of the VAS score recorded by each patient after EAT stimulus immediately at end of treatment (t1), after 1 week (t2) and after 1 (t3) and 6 (t4) months from the treatment. The results demonstrated that all procedures used provided clinical improvement, with the reduction of pain. The analysis of the total VAS scores for each group after EAT showed a higher relief of pain immediately at the end of the treatment when the solution of VivaSens--that created a film like a varnish on the teeth surface with NCCLs--was used in association with laser irradiation (Group 4, with a total VAS score 26 and mean of 0.90), compared to the results obtained when VivaSens was used alone (Group 3, with a total VAS score 30 and mean of 0.97) or when NaF was applied alone (Group 1, with a total VAS score 38 and mean of 1.41) or in association with DL (Group 2, with a total VAS score 43 and mean of 1.26).