|
Quantifying
salivary function
Salivary function
can be quantified easily. The flow rate of saliva is measured
in volume per minute. However, since there are wide variations
in function depending on the particular gland being sampled, time
of day, and degree of secretory stimulation, standardized techniques
should be used (Malamud
and Tabak, 1993). This is critical for clinical studies where
salivary function is an outcome measure.
Unstimulated
salivary samples
Unstimulated
salivary samples require that the patient have had nothing by
mouth for at least 60 minutes. Oral activities, such as tooth
brushing or flossing and cigarette smoking, should be restricted
for this time period, as well.
The simplest sampling is unstimulated
"whole" saliva. Whole saliva represents the sum fluid contents of
the mouth. This includes the output of the major and minor salivary
glands, in addition to small quantities of other biological fluids
(gingival crevicular fluid, bronchial secretions, serum transudate),
bacteria and bacterial products, cells and debris that are present
in the oral cavity. A subject sits upright and is instructed first
to swallow the fluid in the mouth and then allow saliva to
accumulate passively without swallowing. Timing is begun and at one
minute intervals the subject is instructed to spit the contents of
the mouth into a receptacle. A collection of at least 5 minutes is
recommended. The volume collected can be determined directly if
collected in a graduated cylinder or by weight (1 gram =
1 ml).
An output of less than 0.1 ml per minute is widely accepted as abnormally low (Sreebny,
1992).
Stimulated
salivary samples
Whole saliva
can also be collected following stimulation, usually by chewing
a plain or flavored substance such as gum. Since the rate and
vigor of chewing and the amount and type of flavoring can affect
the flow rate, these must be standardized for reproducibility.
Chewing on unflavored gum base or paraffin at a rate of 60 chews
per minute is a common approach. Salivary output below 0.7 ml
per minute under these conditions is indicative of marked salivary
hypofunction (Sreebny,
1992).
Samples
from individual glands
Saliva can
be collected also from the individual salivary glands, both unstimulated
and stimulated. This is not difficult or invasive, but requires
specialized collectors and is generally reserved for a research
setting. Parotid saliva is collected with a Carlson-Crittenden
collector (Shannon,
1966) and submandibular/sublingual secretions with customized
collectors or a small vacuum device (Nederfors
and Dahlof, 1993; Wolff
et al., 1997). Minor gland secretions may be wicked on to
filter paper strips held against the mucosa. The major salivary
gland ducts can also be cannulated with fine catheters and the
secretions collected directly. The catheter may also be used to
deliver medications directly to the gland or to instill contrast
material for imaging techniques. [See figure of sialogram]
|