Bruxism is repetitive masticatory muscle activity characterized by clenching and grinding of the teeth and/or bracing or thrusting of the mandible. It can occur during sleep or wakefulness, representing a separate etiology of these phenomena. Disorders in the serotonin and dopamine systems are associated with the development of bruxism, which emphasizes their potential role in its occurrence. The association of this phenomenon with chronic inflammation, oxidative stress, and cardiovascular changes has been reported. Co-occurrence of bruxism with obstructive sleep apnea has been demonstrated. Bruxism may be the result of certain diseases, medications, stimulants or stress, both psycho-emotional and stress resulting from the action of factors harmful to the body, stimulating the activity of the sympathetic nervous system. Based on the available literature, the etiology and pathophysiology of this phenomenon cannot be scientifically determined in an unambiguous way due to the lack of randomized studies, standardized parameters for assessing bruxism, or criteria for the size and assessment of the studied populations. Introducing diagnostic criteria and gradation in the diagnosis of bruxism, work on the pathophysiology of this phenomenon, assessment of co-occurring diseases and conditions will certainly contribute to the creation of valuable studies, the results of which will be used in everyday clinical work.