This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'A 25 year old male presents to the dental clinic for routine dental checkup. On intra-oral examination, it is revealed that deep pits and fissures are present.\nWhich of the following enzymes present in the saliva is lethal to many organisms and suppresses biofilm formation on tooth surfaces? \nSelect and explain. \nA. Lactoperoxidase, B. Amylase, C. Lipases, D. Secretory immunoglobulin A (IgA)', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Saliva is an extremely important substance for the proper digestion of foods, and it also plays a key role as a natural anticaries\xa0agent. The importance of saliva for oral health is dramatically noted after therapeutic radiation to the head and\xa0neck. After radiation, salivary glands become fibrotic and produce little or no saliva, leaving the patient experiencing an extremely dry mouth (xerostomia) (xero -\xa0dry; stoma -\xa0mouth), a condition termed hyposalivation. Such patients may experience near-total destruction of the teeth in just a\xa0few months after radiation treatment. Patients who have an autoimmune disease (e.g., Sjögren syndrome) also suffer from hyposalivation and experience severe xerostomia\xa0and can experience the same devastating effects of hyposalivation on their dentition. In addition, many common medications are capable of reducing salivary flow and increasing caries risk.\nElements of Saliva That Control Biofilm Communities', 'role': 'assistant'}]