Physical and chemical aspects of saliva as indicat... - ResearchGate

and articles or portions of articles that dealt with salivary
microbiology, fluoride treatments, food and nutrition
factors, tooth-adsorbed salivary components (that
is, acquired pellicle), pooled saliva samples, or in situ
experimental designs.
A data extraction form was developed and used
for initial calibration of the abstractors. Once a sufficient
level of agreement was attained, data from the
articles were entered directly into the evidence table.
Two persons independently abstracted data from each
article, and disagreements about articles were resolved
by discussion. Data were synthesized descriptively for
each included article according to five topic areas: 1)
general description; 2) experimental design characteristics;
3) caries status assessments; 4) saliva status assessments;
and 5) clinical evidence for the presence or
absence of a protective effect of saliva against caries.
We focused on both quantitative and qualitative aspects
of saliva, such as flow rate, buffer capacity, electrolytes,
and the various constituents of the immune and
nonimmune defense systems as well as medical conditions
known to affect salivary physiology. Data from
the studies were not further analyzed quantitatively, and
no meta-analysis was performed.
Principal Results
General Description and Quality
Assessment of the Included Studies
A total of ninety-six references are included in
Evidence Tables 1A-C, which can be viewed at the following
web site: http://www.nidcr.nih.gov/news/
consensus.asp. The studies evaluated individuals from
twenty-five different countries, primarily Sweden (24
percent), Finland (18 percent), and the United States
(14 percent), and comprised a mixture of medically
healthy and compromised subjects. The designs of included
studies had the following distribution: crosssectional
case-control (67 percent), longitudinal cohort
(3 percent), and multiple cross-sectional descriptive
samplings (30 percent). Although all studies had a minimum
of ⊕30 subjects total, half of the studies had only
ten to thirty subjects divided into one to four groups,
which conferred relatively low statistical power. Since
only two of the included studies analyzed self-reported
oral dryness, concern about any lack of correlation between
subjective symptoms and clinical measurements
was minimal. To the extent discernible, publication bias
did not appear to be an important factor in this review.
The primary outcome variable for caries was the
DMFT/S score, but considerable heterogeneity was
found due to the lack of a standard definition of caries
activity versus caries inactivity. Similarly, there was only
partial uniformity in what was defined as high or low
salivary flow rate and buffer capacity. Intra- and
intersubject variations in salivary parameters complicated
the analyses, and there was a lack of standardized
methodology to measure physiological and biochemical
parameters of saliva in relation to disease
status and progression.
Bivariate and multivariate statistical analyses
were used in 72 percent and 28 percent of the studies,
respectively. Interestingly, significant relationships
found in bivariate tests were often not demonstrated in
the multivariate models. Good evidence for protective
effects of saliva against caries was found in twenty-one
studies, weak or equivocal evidence in twenty-five studies,
and no evidence in fifty studies. It is important to
point out, however, that negative results complicate any
critical review because of uncertainty about whether
the lack of a demonstrated association results from its
true absence or from methodological factors that may
have precluded its discovery.
The majority of the studies examined the relationship
of stimulated and/or unstimulated parotid and
whole saliva to caries on the crowns of permanent teeth.
It appears that neither the salivary stimulation status
nor the method of salivary stimulation (that is, masticatory
or gustatory) is important in caries risk. There is
insufficient evidence to establish any caries risk related
to differences between whole saliva and pure secretions
from parotid, submandibular/sublingual, or minor salivary
glands. There is also insufficient evidence to establish
that the risk for caries related to various salivary
parameters is different for primary vs. permanent
teeth, crown vs. root surfaces, or different aspects of
crown surfaces.
Evidence for the Increased Risk of
Caries Associated with Salivary
Factors
Salivary flow rate. On the basis of twenty-one
studies, chronically low salivary flow rate (for example