Subject. Tobacco smoking is a common bad habit in the world. The problem of smoking affects not only social, but also medical, including dental, aspects. The irritating effect of nicotine on the oral mucosa and salivary glands leads to the development of stomatitis, xerostomia and halitosis. Prevention of diseases of the oral cavity of smokers has its own characteristics in connection with changes in plaque and oral fluid. The article presents the experience of rapid diagnostics of the negative effects of smoking as a controlled process in the practice of a dentist. The aim is to evaluate the effectiveness of rapid diagnosis in chronic smokers based on a statistical analysis of the type of microcrystallization of mixed saliva (CC). Methodology. A clinical examination of the oral cavity of 120 volunteers (58 women and 62 men) aged 18 to 44 years (average age - 22.50 ± 2.59 years) was conducted. The main group of smokers included 75 people, the comparison group (non-smoking volunteers) - 45. SS sampling and statistical analysis of microcrystallization types in smokers and non-smokers were performed twice: before and 15 minutes after smoking. Results. The appearance of pathological morphotypes of microcrystallization SS indicates the negative effect of tobacco smoking on oral fluid. Data were obtained on the deterioration of the function of saliva in smokers, which creates the conditions for enhancing pathological processes in the oral cavity. Conclusions. Smoking negatively affects the morphological picture - the microcrystalline structure of the SS. Structural changes in crystallized SS can serve as diagnostic signs of diseases and can be used in the diagnosis and prevention of diseases of the oral organs during smoking.