The work aimed to establish the patterns of changes of bone tissue metabolism markers in the oral fluid of children and adult patients. There were examined 136 practically healthy individuals aged 6 to 89 years and the following groups have been formed: primary school age patients (group 1, 6-10 years, n = 16), adolescents (group 2, 11-17 years, n = 17), juvenile age patients (group 3, 18-24 years, n = 25), young adults (group 4, 25-44 years old, n = 21), middle-aged adults (group 5, 45-59 years old, n = 22), elderly adults (group 6, 60-74 years old, n = 19) and senile patients (group 7, 75-89 years old, n = 16). Oral fluid was obtained using a non-stimulatory method, and biochemical indices were determined in accordance with standardised laboratory techniques, following the ethical principles of conducting scientific medical research involving human participants. It has been established that periods of particular risk are primary school and middle age. In primary school-age children and adolescents, the physiological processes of bone growth and remodelling prevail. Between the ages of 6 and 10, these processes are accompanied by a 33% increase in ionised calcium content and a 41% increase in acid phosphatase activity, reflecting controlled bone resorption during teething. In middle-aged patients, a significant imbalance of bone metabolism transformation indexes (activation of acid and alkaline phosphatases by 31 and 32%, respectively) is a trigger for rapid progression of inflammatory and destructive periodontal processes in the subsequent age periods, and the lack of proper dispensary observation by a dentist can lead to tooth loss. It is important that at the age of 45-59, calcium homeostasis is significantly influenced by the pH of oral fluid. A strong inverse correlation has been established between the content of ionised calcium and the pH of oral fluid in middle-aged patients (r = -0.79), while in other age groups this correlation was moderate (r = -0.49 – -0.65). The obtained data justify the need to monitor the indexes of calcium and phosphate metabolism of oral fluid at different age periods and the advantages of an age-oriented approach to the prevention and personalised planning of dental treatment.