Salivaplays a major role in oral health and modification in salivary function may have detrimental effects on both hard and soft tissues as well as a negative impact on the quality of life of the patient. Sreebny published an excellent review of the literature on this topic and the design of the saliva assessment is based on this paper. Whole saliva is a mixture of unstimulated and stimulated saliva. The production, composition and function of the two types are different so they need to be evaluated separately. The measurement of saliva flow, both unstimulated and stimulated, should be included in a regular examination so that changes can be detected and the patient advised.
Unstimulated (resting) salivary flow rates fluctuate throughout the day and will be affected by a variety of causes. While a single observation may be indicative, it will not necessarily be conclusive and repeated observation at a similar time of the day and in similar circumstances may be required before making a finite assessment. The time of day is important because of diurnal variation and also proximity to meals may have an effect. The pharmacokinetics of therapeutic medications may also be significant. This means xerostomia may be most marked in the period following absorption and distribution of a drug and then return to normal well before the next dose. Regular investigation of the following properties are recommended.
Saliva flow rates in healthy patients,
• resting flow rate for pooled saliva = 0.3-0.4 mL/minute.
• less than 0.1 mL/minute = xerostomia.
• stimulated flow rates = 1-2 mL/minute,
• less than 0.7 mL/minute = pathology.