Abstract
Background: The oral-gut axis is a critically important bidirectional communication pathway between the oral cavity and the gastrointestinal (GI) tract. While dentistry and gastroenterology have traditionally performed independently, new physiological findings have highlighted complex interrelationships involving autonomic nervous system reflexes, oral biomechanics, and neuroendocrine signaling.
Pathological Interactions: A strong pathological association has been observed between gastroesophageal reflux disease (GERD) and sleep bruxism, particularly rhythmic masticatory muscle activity (RMMA). Acid exposure in the esophagus activates sympathetic-driven visceral autonomic reflexes, triggering masticatory muscle activity and the swallowing of saliva. Since bicarbonate and growth factors in saliva neutralize refluxed acid, nocturnal bruxism is considered a protective response to reflux. Clinically, PPI therapy significantly reduces the frequency of RMMA and episodes of acid reflux.
Biomechanical and Motor Function Regulation: Oral biomechanics directly influence GI transit. Malocclusion and impaired masticatory comminution increase functional load on the GI tract, resulting in delayed gastric emptying and an increased frequency of transient lower esophageal sphincter relaxation, which exacerbates GERD. Conversely, the act of mastication transiently suppresses parasympathetic tone, temporarily delaying initial gastric emptying, it promotes late-phase transit through central autonomic nervous system regulation.
Endocrine and Sensory Signals: Mechanical and sensory input from the oral cavity regulates metabolic homeostasis. Mastication promotes the postprandial secretion of incretins, such as glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, which stimulate insulin release and suppress postprandial blood glucose spikes. Furthermore, targeted oral care and mechanical stimulation increase plasma ghrelin concentrations, enhancing appetite and GI motility in vulnerable populations, such as elderly individuals requiring long-term care.
Conclusion: The oral-gut axis integrates pathological, biomechanical, and endocrinological mechanisms. Interdisciplinary approaches-such as orthodontic correction, targeted mastication, and daily oral care-offer strategies as viable nonpharmacological therapies for managing GERD, optimizing GI motility, and regulating metabolic hormone pathways. Future prospective studies focusing on these specific pathways will further clarify the therapeutic potential of targeting the oral-gut axis.