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Profile in Oral Health: Salivary Testing in the Office by Timothy Ives, RDH, BSc (Hons), FHEA and Dave Bridges, RDH, BS

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by Timothy Ives, RDH, BSc (Hons), FHEA and Dave Bridges, RDH, BS

Building on the CE course published in the March 2013 issue of Dentaltown Magazine on xerostomia, it's now time to apply that information to clinical practice. Testing saliva chariside can be just a few observations during a regular dental hygiene visit or several steps that require a separate appointment. Patients found to be at risk of caries are good candidates for a saliva testing visit. Gathering data about the pH, flow rates and buffering capacity of saliva will provide valuable baseline information and the evidence to support your recommended interventions to prevent further caries.

Reduced salivary flow or hyposalivation can be measured clinically. The subjective feeling of a dry mouth is referred to as xerostomia. Reduced saliva flow can cause a problem in a number of ways. Firstly, patients will not produce enough saliva during eating to be able to easily chew their food, form a bolus and swallow. From a caries perspective, they don't produce enough saliva to dilute and wash away dietary acid or acid formed as a result of bacterial metabolism of sugars. They also have, in effect, a buffering problem. There are insufficient minerals being excreted to neutralize acid. This means that any acid in the mouth is present for much longer than would otherwise be the case, increasing the risk of net mineral loss from the teeth. If the mouth is maintained at a lower pH, acidogenic bacteria implicated in caries will thrive in these low pH conditions. The biofilm selects for the environment in which it develops. The lower the pH, the more acid-producing bacteria will be found in the biofilm. The higher the pH, the fewer acid-producing bacteria will be found.

Side effects of medication and dehydration both impact saliva levels. Saliva production drops when a person is dehydrated. The average person should consume approximately two liters of water a day. This amount needs to be increased for people with physical occupations, those participating in sports activities and active children. Dehydration has a domino effect on the dilution and buffering effects of saliva, major contributors to the homeostasis of the oral environment.

Chairside Testing

Xerostomia

Salivary testing in the office begins with a visual assessment of xerostomia. The Challacombe Scale was developed based on research conducted at King's College London Dental Institute, under the supervision of Professor Stephen Challacombe. Its purpose is to visually identify and quantify xerostomia. The Challacombe Scale works as an additive score of one to 10, with 1 being the least severe xerostomia and 10 being the most severe xerostomia. Each of the 10 aspects observed scores one point, providing a total score. Symptoms of xerostomia will not necessarily progress in the order listed, but summated scores indicate likely patient needs. Any cumulative score higher than three is likely to be a high-risk patient.
  1. Mirror sticks to buccal mucosa
  2. Mirror sticks to tongu
  3. Saliva frothy
  4. No saliva pooling in the floor of the mouth
  5. Tongue shows generalised shortened papillae
  6. Altered gingival architecture (i.e.: smooth)
  7. Glassy appearance of oral mucosa especially palate
  8. Tongue lobulated/fissured
  9. Cervical cavitations on more than two teeth
  10. Debris on palate or sticking to teeth
If the Challacombe score indicates xerostomia, it's time to begin chairside saliva testing. Easy tests can be done for viscosity, pH, resting and stimulated flow rates and buffering capacity.

Viscosity

The viscosity of saliva is related to the proportion of proteins, such as mucin, to water and can be assessed by simply looking underneath the tongue. Saliva is 99 percent water and should be clear, like water, not thick, stringy, frothy or bubbly. It is thought that thicker saliva results in poor pellicle coverage leaving the enamel naked to the various acidic challenges in the mouth. The quality of the saliva usually relates to the resting flow rate and it can be altered by systemic diseases, medications and radiation therapy, which affect the flow and/or salivary protein compositions. The viscosity of saliva may also be related to overall hydration levels however, for others, it may just be a physiological feature to note.

The viscosity can be viewed simply by looking under the tongue. If the clinician is unsure, then massage the salivary duct underneath the tongue, which will activate this area and ensure that a good picture can be obtained. Assign the standing saliva to one of three categories: thick/stringy, frothy/bubbly or thin/watery.

Resting Flow Rate

The majority of the resting saliva comes from the submandibular glands. This saliva is much lower than stimulated saliva (which comes mostly from the parotid glands) in minerals, proteins and enzymes and is naturally more acidic. The pH of this saliva can also be affected by physiological changes such as hormonal issues, medications and diseases. A low pH for resting saliva will have a negative effect on the acid value of the biofilm pH, as this will be encouraging the right conditions for the development of acidogenic bacterial strains. This should also affect the remineralization protocol recommended by
the clinician.

The lower lip is dried using a piece of gauze or tissue paper and a timed observation is carried out until small beads of saliva start to appear. If saliva appears in small beads in less than 30 seconds, this indicates the patient is sufficiently hydrated and has a healthy resting flow rate.

More than 30 seconds for beads of saliva to appear indicates moderate flow rate. If it takes more than 60 seconds for the saliva to appear, the flow rate is significantly reduced. Greater than 30 seconds indicates dehydration and/or a xerostomia issue, higher than a minute demonstrates a very low flow rate. A discussion with the patient regarding fluid consumption is recommended, which is considered in conjunction with the medical history. If the patient isn't drinking enough fluid this needs to be managed and the appropriate advice given to increase fluid intake.

Resting pH

To gather resting saliva, the patient is asked to refrain from swallowing for 30 seconds and then instructed to expectorate all saliva into a cup. The sample is tested with universal indicator paper, allowed to dry for one minute and the pH assessed against a universal indicator color scale.

This example demonstrates an acidic resting pH. Patients with a low resting pH need as much help as possible. A good education in the implications of this to the patient is very important and neutralization of the acidity as regularly as possible is key. This can be achieved through alkaline foods such as cheese and nut snacks, baking soda toothpastes and rinses. The introduction of neutralizing gum and mints especially those containing xylitol are effective. A fluoride rinse as an adjunct at mid-day would be recommended proceeded by a neutralizing product.

Stimulated Flow Rate

Low stimulated flow rate may be due to a number of factors, from dehydration to medication side effects and radiation treatment of the head and neck. Other causes include physiological problems with the saliva glands' excretory systems or the ducts that carry saliva into the mouth. Sixty-eight percent of xerostomia is caused by medication side effects.

In order for patients to notice that they have a dry mouth, the flow rate has usually dropped by 50 percent. Patients may typically report taking a drink to bed with them at night, waking up with a dry mouth or reporting difficulty in chewing, swallowing and speaking.

The stimulated saliva test serves a dual purpose. It enables the production of saliva stimulated by the act of chewing to be measured. It also provides a sample of saliva that can have its buffering efficacy tested. In this test, the patient is given a piece of unflavored paraffin wax to chew. This is of a similar nature to chewing gum.

The patient chews normally and expectorates any saliva produced into a measuring cup for five minutes. The amount produced in that time is measured. A normal production rate is around 1ml per minute. Some patients have a higher flow rate than this!

Buffering

Buffering is the ability to resist a change in pH. However stimulated saliva from the parotid glands does not buffer in the true sense - acid is neutralized by bicarbonate in saliva - though the term is commonly used. It also provides calcium and phosphate, which are essential for the remineralization of the tooth. The buffering test measures for all these minerals.

The patient's buffering capacity is a physiological factor that cannot be changed by clinical intervention, although there is good evidence to support this might change throughout life and can be affected by such factors as medication, disease and physiological changes such as pregnancy, where there is a reduced calcium level in saliva. The buffering capacity of stimulated saliva is related to mineral content. Stimulated saliva normally contains higher levels of bicarbonate. This may be lacking in patients who have low buffering. Low saliva flow also affects overall mineral availability.

The buffering capacity is measured by taking some of the stimulated saliva from the previous test into a pipette. A drop of saliva is placed on each of the three pads on the test strip taking care to cover the whole pad. One drop of stimulated saliva is placed on each square using the pipette.

The strip is then tipped on its side and gently tapped to shake off the excess saliva. The strip is then left for two minutes. After this time, the pads are assessed for color change and scored according to the guide. All three scores are added together to give a buffering index.



Conclusion

Saliva testing provides you with objective measurements to confirm what you often observe clinically in patients with xerostomia. You can incorporate some of these objective tests into your current dental hygiene visit or provide all of them in a separate appointment for patients at risk of dental caries. The more information you have, the better your plan will be to cure caries for your patients.

Author Bios
Tim Ives, BSc (Hons) RDH, FHEA, spent 22 years in the Royal Air Force, much of that time providing dental hygiene services. His tours of duty included Hong Kong, Cyprus, Germany, New Zealand, Holland and the UK. Tim is a founding member of O'Hehir University, an online institution providing a degree completion program for dental hygienists. He has a passion for minimally invasive dentistry (MID) and co-runs an MID based web site with his friend, colleague and co-author, Dave Bridges: - www.dentalvillage.co.uk.

Dave Bridges, RDH, BSc, served for nine years in the Royal Air Force, originally working as an Aircraft Engineer. After five years, an injury forced retraining in dental assisting and hygiene skills. In 1987 he qualified as a dental hygienist as has worked as a clinician since then. Dave considers himself a hopeless gadget fan and technophile which explains his role in the MID Web site - www.dentalvillage.co.uk - developed with his friend, colleague and co-author Tim Ives.

The authors of this article are also the co-authors of the upcomoing book Curing Caries.
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