ORIGINAL: Determination of Streptococcus Mutans and Lactobacillus Counts and their Association with Resting pH of Saliva and Dental Caries in Preschool Children in Lagos
West Afr J Med. 2023 October; 40 (10): 1041-1048 PMID: 37906512
Keywords:
Bacterial count, Lactobacillus, Preschoolers, Saliva PH, Streptococcus mutansAbstract
Background: Caries is controlled by several factors including exposure to diets rich in carbohydrates, tooth susceptibility, and the presence of some oral flora bacteria such as Streptococcus mutans (S. mutans) and Lactobacilli sp. Tooth demineralisation occurs when the pH in the oral cavity is lower than the critical pH of 5.5 which occurs because of the production of acid by the acidogenic bacteria in the oral flora when they break down sugars (substrate) for energy.
Objective: The objective of this study was to determine the salivary Streptococcus mutans and Lactobacillus counts and their association with resting pH of saliva and dental caries in pre-school children in Lagos.
Materialsand methods: Fifty preschoolers with and without caries were recruited from the dental clinic and staff primary school in Lagos University Teaching Hospital, Idi-araba respectively. Saliva was collected in Thioglycollate media. The resting pH of the saliva was measured immediately in the clinic with a pH meter (Jenway pH meter, PHS 25). In the laboratory, the samples were streaked on Mitis salivarius bacitracin agar (MSB) and Rogosa agar for S. mutans and Lactobacillus respectively and incubated anaerobically for 48 hours at 37°C. Biochemical tests and morphological characteristics of colonies were used to identify S. mutans and Lactobacillus.
Results: The children were aged between 45 to 71 months with a mean age of 56.66 7.17 months. The mean age of the caries-free group was 55.48 7.57 months and that of caries active group was 57.84 6.76 months. The caries-active subjects recorded significantly higher bacterial counts of S. mutans and Lactobacillus compared to the cariesfree subjects. Streptococcus mutans and Lactobacillus showed a negative and highly significant correlation with resting pH (r = - 0.38 and r = - 0.32 value respectively).
Conclusion: The resting pH of saliva in both groups was within normal values. Streptococcus mutans and Lactobacillus counts were significantly inversely correlated to the resting pH value of saliva. Streptococcus mutans and Lactobacillus counts were significantly higher in the caries active group.
