## 4 Discussion  
In Kenya, dental health services are private, and turning to a dental practice is too expensive for much of the population. In most cases, children with caries do not have the opportunity to cure the disease by receiving fillings; therefore, the lesion affects the entire element, which then remains in the oral cavity, infecting the surrounding elements, the mucous membranes, and the entire oral cavity. There may be a relationship with the ascertained lack of vitamins and calcium with which these subjects live, but even more interesting is the potential relationship with fluoride. The caries-preventive benefits of fluoride, due to its incorporation in the structure of dental enamel, reduce the solubility of enamel and inhibit demineralization by promoting remineralization of the teeth. On the other hand, at high concentrations, if the consumption of fluoride is greater than optimal, it can lead to increased enamel porosity, with the consequent manifestation of dental fluorosis. Fluorosis only affects developing teeth, and certain stages of development are more susceptible than others. As found in the present study, and according to the literature [16,17], there is a relationship between delayed dental exchange and excessive intake of fluorine (and in children taking sodium fluoride), with a delay in the eruption of the teeth recorded up to a maximum of 0.7-2 years. Dental fluorosis is also more prevalent in late-erupting permanent teeth, but other studies are necessary to better understand the real relationship between fluoride intake levels and dental fluorosis of late-eruptive teeth. The high incidence of fluorosis in our sample (almost 80%) is due to the fact that, in Nairobi's suburbs, the population lives without adequate aqueducts and pipes for drinking \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & **OR** & \multicolumn{2}{c}{**95\% CI**} & \multicolumn{2}{c}{_p-Value_} \\ \hline
**Age** & 0.9 & 0.45 & 2.08 & 0.86 \\ Gender & 1.1 & 0.52 & 1.95 & 0.74 \\ Mother’s work & 1 & 0.54 & 2.24 & 0.48 \\ Father’s work & 1.2 & 0.62 & 2.19 & 0.34 \\ Mother’s educational level & 1.1 & 0.81 & 1.35 & 0.66 \\ Father’s educational level & 1.3 & 0.76 & 3.11 & 0.28 \\ No. of subjects in household & 0.9 & 0.63 & 1.88 & 0.82 \\ Eating times & 1.1 & 0.44 & 4.97 & 0.59 \\ Sweets during meals & 3.9 & 1.54 & 4.27 & \textless{}0.01 * \\ Sweets between meals & 3.6 & 2.12 & 5.84 & \textless{}0.01 * \\ Soft drinks during meals & 2.8 & 1.43 & 4.48 & \textless{}0.01 * \\ Soft drinks between meals & 4.3 & 1.93 & 8.28 & \textless{}0.01 * \\ Tooth-brushing frequency & 2.8 & 1.43 & 4.48 & \textless{}0.01 * \\ Use of toothpaste & 3.8 & 2.02 & 8.36 & \textless{}0.01 * \\ Parents’ toothbrush and toothpaste & 0.7 & 0.43 & 1.26 & 0.76 \\ Toothpaste use & 1.2 & 0.57 & 3.92 & 0.52 \\ Parents’ dentist & 10.2 & 3.22 & 21.57 & \textless{}0.01 * \\ Bleeding & 12.1 & 5.46 & 26.33 & \textless{}0.01 * \\ Calculus & 12.1 & 5.46 & 26.33 & \textless{}0.01 * \\ \hline \hline \end{tabular} \({}^{*}\)Statistically significant difference. OR = odds ratio; 95% CI = 95% confidence interval.  
\end{table} 
Table 2: Multivariate model of the associations between caries and the explanatory variables. water and digs wells that reach as deep as 30 meters to be able to supply themselves with water. These waters are not controlled and are rich in bacteria and elements that are harmful to humans, which in the long run can have serious consequences for the body. One of these elements is fluorine--a substance that, in developed countries, is controlled and filtered by aqueducts in order to allow the supply of drinking water to our homes. The concentration of fluorine in the waters of the rural area around Nairobi ranges from 0.50 to 72 mg/L [10], and it is often greater than the concentration of 1.5 mg/L recommended by the WHO [11].