The present invention provides a composition comprising olive oil, trimethylglycine and xylitol for treating xerostomia and disorders associated thereto, with very good results in increasing the unstimulated salivary flow, in alleviating the symptoms of xerostomia, including the pain associated to xerostomia, as well as improving the quality of life of affected persons. The composition of the invention has also been proved to protect dentin against demineralization in acid conditions.