Step 1: Review the Patient’s Medical History

A comprehensive medical history helps identify systemic diseases, medications, and treatments that may reduce salivary flow- an essential protective factor in oral health. Saliva plays a critical role in buffering acids, promoting remineralization, and supporting antimicrobial defenses. When salivary function is compromised (xerostomia), these protective mechanisms are weakened, significantly increasing the risk of dental caries, especially among high-risk populations such as older adults and those with chronic health conditions.^1,7

Several systemic diseases and conditions can lead to xerostomia (dry mouth), which increases the risk of dental caries by reducing the protective functions of saliva. These include autoimmune diseases such as Sjögren’s syndrome, which primarily affects middle-aged women and involves immune-mediated destruction of salivary and lacrimal glands, and lupus erythematosus and rheumatoid arthritis. Metabolic and endocrine disorders such as diabetes mellitus, thyroid dysfunction, and pancreatic or liver diseases also contribute. Neurological conditions like Parkinson’s disease and Alzheimer’s disease, respiratory conditions such as asthma (especially with inhaler use), and genetic disorders like cystic fibrosis are also associated with reduced salivary flow. Hormonal changes during pregnancy, perimenopause, and menopause, along with anorexia nervosa and other psychiatric illnesses, further impact salivary function. Additionally, lifestyle factors including tobacco use, alcohol consumption, and drug abuse, especially with opioids and methadone, have been shown to significantly impair salivary gland activity.^7-9

More than 500 medications are associated with salivary gland hypofunction, and it is estimated that over 90% of the most frequently prescribed medications in the U.S. can cause dry mouth as a side effect. Medications in the following classes are most commonly implicated: antidepressants, antipsychotics, hypnotics, antihistamines, anticholinergics, antihypertensives, diuretics, appetite suppressants, muscle relaxants, and expectorants. Many of these drugs affect the autonomic nervous system, which regulates salivary secretion, leading to decreased salivary output and elevated caries risk.^7,8,10

Cancer therapies are a well-established cause of xerostomia. Chemotherapy may reduce salivary flow due to cytotoxic effects on salivary glands, while radiotherapy to the head and neck region can irreversibly damage salivary acinar cells, leading to long-term salivary dysfunction. The extent of xerostomia depends on the radiation dose and the area treated. These therapies significantly elevate the risk of dental caries, mucosal infections, and oral discomfort.^7,11,12

Older adults are more susceptible to dry mouth (xerostomia) due to age-related physiological changes in salivary gland function and their increased use of medications, many of which have xerogenic effects. Polypharmacy, defined as the regular use of five or more medications, is common in older populations and significantly contributes to salivary gland hypofunction. Studies have shown that age itself may not reduce salivary output significantly, but the cumulative impact of multiple medications and comorbidities leads to a higher prevalence of dry mouth in this group.^7,13,14 Patients often report dry mouth due to discomfort, such as difficulty swallowing, speaking, or altered taste. Clinically, signs of xerostomia may include a dry or sticky oral mucosa, frothy or absent saliva, and a tendency for the dental mirror to stick to the buccal mucosa or tongue. These clinical observations, combined with patient-reported symptoms and medication history, help identify those at risk of caries due to salivary dysfunction.^10,15