Salivary Glucose: A Metabolic Disease Marker
and a Risk Factor for Oral Disease Development
J Max Goodson*
The Forsyth Institute, USA
Submission: March 23, 2017; Published: April 13, 2017
*Corresponding author: J Max Goodson, The Forsyth Institute, 245 First Street, Cambridge, MA 02140, USA, Tel: 617-892-8266; Fax: 617-262-4021; Email: email@example.com
How to cite this article: J Max G. Salivary Glucose: A Metabolic Disease Marker and a Risk Factor for Oral Disease Development. Adv Dent & Oral Health. 2017; 4(3): 555640. DOI: 10.19080/ADOH.2017.04.555640
The existence of glucose in saliva as a step in development of metabolic disease including diabetes has not received adequate recognition as an oral disease risk factor. Hyperglycemia, the driving function for appearance of salivary glucose is rare in children and appears mainly in adulthood. The presence of salivary glucose modifies salivary microbial composition and affects both dental caries and gingivitis. Data on salivary pH as a surrogate measure is reviewed to suggest that pH indicator paper could serve as a surrogate chairside diagnostic of hyperglycemia.
Hyperglycemia is a defining characteristic of diabetes and also occurs in pre-diabetic states. Normal blood glucose levels are between 70 and 100mg/dL. Blood levels of greater than 100mg/dL glucose are recognized as being hyperglycemic. Glucose levels of greater than 125mg/dLare recognized as being diabetic. Impaired glucosetolerance (fasting glucose > 110mg/dL) was investigated in a large cohort of individuals (112,960 Japanese) including a wide age span (14-94) over 15 years. From these data (Figure 1) we see that impaired glucose tolerance occurred in males before females
but levels do not become an important factor in the population until around the age of 30. Even though this characteristic would likely differ considerably among world populations, the point here is that hyperglycemia occurs as individuals become adult and is rare in children. Most hyperglycemic children would be those with Type 1 diabetes. In a study of 10-year old Kuwaiti children Goodson et al. , only 2% of the children had salivary glucose values that would suggest hyperglycemia.
Glucose appears in the saliva of individuals (Figure 2) with
hyperglycemia Hartman et al. . This model predicts that normal
blood glucose does not result in salivary glucose. When blood
levels exceed 84.8mg/dL, measureable glucose appeared in saliva.
When blood values exceed 100mg/dL, saliva concentrations
exceed 1.13mg/dL. It is generally recognized that diabetics
have higher salivary concentrations of glucose than in normal
subjects Mascarenhas et al. . These values would likely differ
considerably among different populations.
When dentists speak, of salivary glucose, it is usually
associated with consumption of sweets. Sucrose is cleared from
the oral cavity with a halftime of 2.2 minutes Dawes . So, within
5 halftimes (11 minutes) there is essentially no sucrose remaining
in the mouth. In contrast, when glucose is excreted into saliva due
to metabolic disease, it is present for the entire waking period.
Even though salivary glucose concentration in diabetics is low
(around 1-3mg/dL) it is present all day. Hence, oral diseases based
on bacteria that metabolize glucose would likely be augmented.
One of the effects of high glucose is a modification of the salivary
microbiota (Figure 3). Most salivary bacteria are reduced by high
salivary glucose Goodson et al. , some to a greater degree than
others. A. actinomycetemcomitans is among the most sensitive
to salivary glucose. S. mutans and P micra by comparison are
relatively resistant to change by salivary glucose. Hence, one effect
of salivary glucose is to change the oral microbial composition. It
is proposed that this reduction in bacterial numbers is the result
of salivary acidification by the conversion of salivary glucose to
short-chain fatty acids.
The measurement of bacterial numbers is a crude measure of
bacterial effect. It is likely that he continuous presence of glucose
in saliva would also modify the metabolic nature of many oral
bacteria. For example, glutamate oxaloacetate transaminase (GOT)
and glutamate pyruvate transaminase (GPT) levels in saliva were
different in diabetics compared to non-diabetics Verma et al. .
The effects of high salivary glucose on oral disease are a
significant increase in both dental caries and gingivitis (Figure 4).
The number of carious lesions per tooth increased from 5.43%
decayed to 8.35% decayed. The gingival redness increased from
72.55% of sites to 78.58%. Measurement of salivary glucose is
technically difficult because of its low concentration (often less
than 1mg/dL and seldom more than 3mg/dL). In our studies
of Kuwaiti children, we used a glucose oxidase method with a
fluorescent label implemented on a robotic chemical platform. In
addition, we boiled samples to denature enzymes such as catalyse
that interfered with our assay and to kill bacteria that might
consume glucose in the saliva sample. A chairside equivalent of this
assay has not been devised. There may be, however, a reasonable
chairside surrogate measure for salivary glucose, namely salivary
pH (Table 1).
Casual inspection of the data of Table 1 would suggest that a
salivary pH lower than 7 could be diabetic. It has been suggested
that salivary pH could be used as a simple screening measure
for detection of metabolic syndrome or diabetes Aitken-Saavedra
et al. . Reported differences are of sufficient magnitude
to be measured by pH paper Koc Ozturk et al. ; Rai et al. 
where it served as a simple chairside diagnostic. There are other
conditions associated with lowered saliva pH. These include oral
cancer Ramya et al.  and ionizing radiation exposure Vuotila et
al. , mouth breathing Choi et al. , bulimia Paszynska et al.
, gastroesophageal reflux disease Preetha et al.  and consumption
of juices and cola-based beverages Tenuta et al. .
The added intraoral disease risk associated with
hyperglycemia found in both diabetic and prediabetic states should
be a recognized oral disease risk factor that may be evaluated by
measurement of saliva pH.