Mutans streptococci and lactobacilli on healthy and carious teeth in the same mouth of children with and without dental caries

Abstract

Interactions between mutans streptococci and lactobacilli contribute towards the microbial challenge of dental caries. A comparison was made between numbers of mutans streptococci and lactobacilli in plaque from primary teeth in healthy children and between caries-free teeth and carious lesions in the same mouth of children with caries. The study group comprised 107 nursery-school children with a clinically healthy dentition and 117 children with caries. After a dental examination with mirror only, plaque was sampled from molar tooth 84 in caries-free children. An untreated carious lesion and a healthy tooth contralateral to the lesion was sampled in children with caries. Plaque was collected using a sterile wooden toothpick, inoculated into reduced transport fluid and processed for microbiology. Results showed no relationship between mutans streptococci, lactobacilli counts and dmft in children with caries. Yet, statistically significant correlation was found in counts of mutans streptococci (r=0.46, P=0.0001) between caries-free teeth and carious lesions in the same mouth. Mutans streptococci and lactobacilli numbers were significantly higher in caries-free teeth in children with caries than in healthy children (P=0.05; P=0.01). Mutans streptococci comprised 4.3% of total viable count in caries-free children, 8.2% in caries-free teeth and 14.4% in carious lesions, while lactobacilli composed 0.02%, 0.12% and 1.2% respectively. To conclude, high mutans streptococci counts in carious lesions causes an increase of these bacteria in caries-free teeth contralateral to the lesion in the same mouth, while caries-free teeth have statistically higher numbers than healthy teeth in children without caries in which the numbers are low. Keywords: mutans streptococci, lactobacilli, carious lesions, caries-free teeth, caries-free children.