Which of the following is a significant risk factor for root caries?

Root caries is strongly associated with xerostomia (dry mouth), which is caused by medications (anticholinergics, antihypertensives, antidepressants), radiation therapy, or Sjogren syndrome. Saliva normally buffers oral acids, remineralizes tooth structure, and mechanically cleanses the oral cavity. Reduced salivary flow eliminates these protective effects, allowing acidic conditions (low pH) to persist and demineralize the exposed root dentin (critical pH for dentin demineralization is 6.2, higher than enamel's 5.5). Other risk factors include gingival recession, poor oral hygiene, and frequent carbohydrate intake. A higher oral pH (alkaline) is protective, not a risk factor. The original answer suggesting pH > 7.0 as a risk factor was incorrect.