Evaluation of hyposalivation
Based on the principle that "status is determined by clinical examination but explained by the case history," the following points should be considered for proper diagnosis of hyposalivation:
1. Stimulated salivary secretion rate
2. Resting SSR
3. Anamnestic data: possible side effects of medication; systemic diseases known to cause salivary gland hypofunction; difficulty in swallowing dry food; difficulty in speaking; soreness of the oral mucosa; frequent episodes of sore throat; difficulty in tolerating removable dentures
4. Tenderness of salivary glands to palpation or swelling of the glands
5. Inflammatory changes in the oral mucosa or tongue
6. Indicative test: Does the examination mirror stick to the cheek mucosa?
7. Atypical pattern of caries (lesions on smooth surfaces or on the tips of incisors or cusps)
If most of these above features are present and the resting SSR is low, the diagnosis almost certainly includes hyposalivation, and the patient should be considered at high risk of developing caries. Apart from measurement of SSR, the other anamnestic and clinical variables have already been discussed in detail. The importance of repeated measurements of SSR in the individual patient, and particularly in caries-susceptible individuals, cannot be overemphasized. There are noninvasive, painless techniques for sampling not only whole saliva but also saliva from the individual major and minor salivary glands. Whole saliva is easily obtained and in most cases a good indicator of whole-mouth dryness. Disease in a major salivary gland can often be diagnosed from secretion collected directly from the gland.
The purpose and method of the collection procedures should be explained to the patient beforehand. Saliva should be collected about 1 1/2 to 2 hours after eating or after an overnight fast. Patients should be instructed to do nothing that might stimulate the SSR prior to the collection, including mastication of food, chewing gum, or candy; smoking; toothbrushing; mouthwashing; or drinking. The test should be conducted in quiet surroundings. Detailed instructions for standardized measurements of SSR are shown in Box 11.
To obtain a mean SSR, sampling should be repeated at least once, at about the same time of day. If the patient's baseline has been established earlier, the values obtained can be used as a comparative indicator of the patient's present salivary status. If the baseline is not known, as is usually the case, the SSR is compared with the relevant standards for the population (see Table 13). As with any test, the results should be interpreted in light of the patient's history, the presence of any signs of disease, and the results of other tests.
Whole saliva may be collected and measured by a variety of volumetric and
gravimetric techniques: draining (drooling), spitting, suction, and swab. The
volumetric methods to be described, especially a combination of the drooling and
spitting techniques, are easily carried out in the dental or medical office.
Either of two measuring devices may be used: a Sialometer or any finely calibrated
measuring cylinder. The Sialometer is a specially constructed, reusable device that
allows collection of both resting and stimulated saliva in a single vessel.
Alternatively, the following equipment can be obtained from chemical supply houses:
two funnels and two measuring cylinders, each with a volume of about 12 mL,
calibrated to no less than 0.1 mL.
Measurement of stimulated whole SSR. In the clinic, the usual procedure is to measure
SSR during masticatory stimulation (ie, while the patient chews a piece of paraffin).
To achieve reliable, standardized results, the patient should be given detailed
instructions (see Box 11). The patient is instructed to chew the 1-g piece of paraffin
for 1 minute to soften it and then to swallow or spit out all saliva. The patient then
chews the softened bolus of paraffin for a fixed time (5 minutes), spitting the saliva
into the graduated cylinder. Foam can be avoided or reduced by using an ice-chilled
beaker or by the addition of a drop of octanol. The secretion rate is calculated in
milliliters per minute.
As an alternative to mechanical stimulation by chewing, saliva may be stimulated
chemically by a 2% solution of citric acid (made up at a local pharmacy), applied to
the laterodorsal surface of the tongue at 30-second intervals, for 2 minutes. The
patient then spits the saliva into the receiving vessel. The procedure is repeated twice
more, for a total collection time of 6 minutes. As before, the SSR is expressed as
milliliters per minute.
Measurement of unstimulated (resting) SSR. It is impossible to sample true "resting"
saliva, because the SSR is always influenced by some kind of stimulus during
consciousness. Nevertheless, a sample collected by passive drooling, without any
deliberate physical or chemical stimulation, is more reliable than stimulated saliva as
an indicator of reduced SSR and hyposalivation.
When resting secretion is collected, the patient is instructed to sit in a relaxed
position, with the elbows resting on the knees and the head lowered between the arms,
the so-called coachman's position. This position is also good for the collection of
stimulated saliva. Even slight movements of the tongue, cheeks, jaws, or lips should
be avoided. The lips are only slightly apart, and the patient allows the saliva to drool
passively over the lower lip into the measuring cylinder, avoiding actively spitting.
For healthy adults, the resting SSR should exceed 0.1 mL/min. In patients suspected
to have hyposalivation, the sampling period should be 15 minutes, to avoid bias
caused by fluctuations in the SSR. For clarity, the results should be expressed in
milliliters per minute and in milliliters per 15 minutes.
Measurement of SSR from the major salivary glands. Parotid saliva is usually
obtained in a modified, two-chambered Carlson-Crittenden collector). The inner
chamber is placed over the orifice of Stensen's duct; the outer chamber is attached, via
thin tubing, to a rubber bulb that, when compressed, creates a slight negative pressure
and permits the device to adhere to the surrounding mucosa. This device makes it
possible to collect pure parotid saliva in a noninvasive manner.
A simple method that makes it easy for the dentist to collect submandibular and
sublingual saliva has also been reported. The region of Wharton's ducts is isolated
with gauze, and the orifices of Stensen's ducts are covered. The saliva, resting or
stimulated, that has collected during a known time is aspirated with a plastic
micropipette. The flow rate is expressed as milliliters per minute per pair of
submandibular or sublingual glands.
Measurement of SSR from minor salivary glands. Saliva may be obtained from the
minor salivary glands of the lower lip or the palate. The minor glands are dried and
isolated with gauze or cotton rolls. For resting saliva, the fluid that is present at the
orifice of one or more of these glands after 2 minutes is adsorbed onto filter strips
(Perio-Paper). The volume of fluid on each strip is read electronically in a special
device (Periotron). For stimulated minor gland saliva, the tongue is swabbed with 2%
citric acid solution, as described earlier. The results are expressed as microliters per
minute. Because the number of glands and the area sampled vary, the SSR is
semiquantitative.
