Abstract
The aim of the present study was to investigate
the extent to which oral streptococci or lactic acid
producing bacteria are able to regulate pH value,
especially at low pH values associated with dentinal
carious activity using a PCR method. One millimeter-
thick sections were sliced from 24 extracted
carious human molars. The pH values on the
tooth sections were evaluated using a pH-imaging
microscope. A dentin sample (1×1×1mm) was
prepared from the areas with the lowest or highest
pH and homogenized to extract bacterial genomic
DNA. Specific primers were used for nested PCR to
mutans streptococci (MS: Streptococcus mutans
and Streptococcus sobrinus). Conserved primers
were also used for PCR to lactobacilli and gram
positive bacteria. The PCR products were separated
by electrophoresis, and then oral bacteria were
identified. There was no significant difference
between carious and intact dentin in MS identification.
However, the frequency of the product amplified
by the conserved primers in carious dentin
(16/24, 66.7%) was significantly higher than that in
intact dentin (2/24, 8.3%), and PCR products
demonstrated, by sequence analysis, various bacteria,
including oral streptococci. It was concluded
that oral streptococci may be associated with the
development of “low pH-carious dentin”.
