# Clinical Applications of Nano-Hydroxapatite in Dentistry
## 3 Results
### Study Characteristics
#### 3.2.2 Dentin Hypersensitivity  
[PERSON] et al. [18] compared the effect of a nano-HAp paste versus placebo in reducing sensitivity following dental bleaching. Placebo group reported sensitivity in 51% of cases, with a mean duration of symptoms of 76 days, and the nano-HAp group showed sensitivity in 29% of cases for a mean of 36 days. The authors concluded that the use of a nano-HAp paste following bleaching significantly reduced the incidence and duration of tooth sensitivity. [PERSON] et al. [19] evaluated the effectiveness of a bleaching technique with 6% hydrogen peroxide with or without 2% nano-HAp. The adjunct of nano-HAp produced significantly lower sensitivity at 24 h post treatment. No difference was found between treatment groups at 7 and 14 days post-bleaching. The authors concluded that the two techniques had similar outcomes in terms of bleaching, and that the adjunct of nano-HAp reduced tooth sensitivity at 24 h post-treatment. [PERSON] et al. [20] compared four different desensitizing agents: (i) nano-HAp professional paste (100-nm size 20% HAp, potassium nitrate, NaF, and 9000 ppm F); (ii) nano-HAp professional paste plus a paste containing 100-nm size 10% HAp, potassium nitrate, NaF, and 900 ppm F; (iii) 8% arginine and calcium carbonate paste plus 8% arginine, calcium carbonate, sodium monofluorophosphate, and 1450 ppm F toothpaste; and (iv) NaF professional varnish with 22,600 ppm F. At the first month, no significant differences were found between treatments, which all reduced hypersensitivity. At three months, no significant difference was found among the treatments, although NaF varnish had the lowest effect in reducing hypersensitivity. Treatment with 8% arginine and calcium carbonate paste plus 8% arginine, calcium carbonate, sodium monofluorophosphate, and 1450 ppm F toothpaste increased its effect over time. Nano-HAp was as effective as the other treatments in reducing hypersensitivity. \begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Author** & **Setting, Funding** & **Study Design** & \multicolumn{3}{c}{**Sample Size Number**} & \multicolumn{1}{p{113.8 pt}}{**Follow-Up (Months)**} & \multicolumn{1}{p{113.8 pt}}{**Interventions**} & \multicolumn{1}{p{113.8 pt}}{**Study Conclusions**} \\ \hline \multirow{4}{*}{[PERSON] et al. [15]} & Dental Hospital, Industry & RCT & 30 patients, (60\% F), mean age 37.8 years, 9  
\begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Author** & **Setting. Funding** & **Study Design** & \multicolumn{3}{c}{**Sample Size Number (\% of Females), Mean Age, Number of Sites**} & \multicolumn{1}{c}{**Follow-Up (Months)**} & \multicolumn{1}{c}{**Interventions**} & \multicolumn{1}{c}{**Study Conclusions**} \\ \hline  & & & & & 1. Nano-HAp professional paste (100-min size 275-HAp, potassium nitrate, NaI, and 900 ppm P) & 1. Nano-HAp professional paste & & \\  & & & & & 2. Nano-HAp professional paste & & \\  & & & & & & size 100-\(\times\)HAp, potassium nitrate, NaI, and 900 ppm P) & 1. Nano-HAp professional paste & \\  & & & & & & size 100-\(\times\)HAp, potassium nitrate, NaI, and 900 ppm P) & 1. Nano-HAp (with or without issue 100-\(\times\)HAp, potassium nitrate, NaI, and 900 ppm P) & 1. Nano-HAp (with or without issue 100-\(\times\)HAp, potassium nitrate, NaI, and 900 ppm P) & 1. Nano-HAp distributed size 100-\(\times\)HAp, potassium nitrate, NaI, and 900 ppm P) & 1. [PERSON] et al. [21] evaluated the desensitizing effects of Nano-HAp toothpaste versus 5% calcium sodium phosphosilicate. Both treatments provided a significant reduction in sensitivity, as measured through Visual Analogue Scale (VAS), tactile test, air blast, and cold water, over the 4 weeks observation period.