Intraoral pH measurement of carious lesions with qPCR of cariogenic bacteria to differentiate caries activity.
OBJECTIVE
A low pH environment is created by cariogenic bacteria. This study was aimed to measure pH of carious lesions intraorally using a micro-pH sensor, and assess predominant acid-producing cariogens by qPCR to differentiate caries activities.


METHODS
103 dentine lesions classified as active or arrested caries based on the clinical and radiological examinations were collected from patients after intraoral measurement of the lesion surface pH using a micro-pH sensor. Quantitative detection of genomic DNA copies of target cariogenic bacteria (mutans streptococci and Lactobacillus spp.) in each lesion was performed using real-time PCR. Correlation between the pH ranges and the number of bacterial species was examined by Spearman test.


RESULTS
50 samples were diagnosed as active and 53 as arrested lesions. Statistically significant difference was observed on average surface pH value between active and arrested lesions (p<0.05). Prevalence of Lactobacillus spp. was higher in active lesions than in arrested lesions (76% vs. 58% of samples, respectively). When the carious lesions were categorised into four different pH ranges (up to 5.5, from 5.6 to 5.8, from 5.9 to 6.1 and 6.2 or above), increased prevalence of Lactobacillus spp. was observed with decrease of pH levels. A significant negative relationship was found between pH value and number of Lactobacillus spp. (r=-0.209, p<0.05) but no such correlation was found for mutans streptococci.


CONCLUSIONS
Intraoral pH measurement might be clinically useful to determine acidity of the local environment of carious lesions as one aspect of the caries activity assessment.


CONCLUSIONS
The population of certain bacteria may indicate activity of carious lesions. Intraoral pH measurement of the carious lesions using a micro-pH sensor may be a clinically feasible method for assessment of lesion acidity.
Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Megumi
M
Kuribayashi
Yuichi
Y
Kitasako
Khairul
K
Matin
Alireza
A
Sadr
Kanako
K
Shida
Junji
J
Tagami
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058491:Bacterial Load; D004245:DMF Index; D004269:DNA, Bacterial / Q000032:analysis; D003731:Dental Caries / Q000145:classification / Q000382:microbiology / Q000503:physiopathology*; D003732:Dental Caries Activity Tests / Q000295:instrumentation / Q000379:methods*; D003804:Dentin / Q000382:microbiology / Q000503:physiopathology; D016680:Genome, Bacterial / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000235:genetics / Q000302:isolation & purification*; D008875:Middle Aged; D009055:Mouth / Q000502:physiology*; D060888:Real-Time Polymerase Chain Reaction; D012666:Semiconductors; D013295:Streptococcus mutans / Q000235:genetics / Q000302:isolation & purification*; D016986:Streptococcus sobrinus / Q000235:genetics / Q000302:isolation & purification*; D014089:Tooth Remineralization; D055815:Young Adult
D004269:DNA, Bacterial