Relationship Between Plaque-pH and Dental Caries in Adolescents

Objectives: To study the relationship between plaque-pH and different caries-related variables in a group of young people with varying caries prevalence. Methods: 100 individuals in the age of 14-15 years participated. They were all patients at two Public Dental Health Clinics in the Göteborg area. For each participant, the following data were collected: i) caries score (DFT, DFS, DiFS), ii) changes in plaque-pH following a mouth rinse with 10% sucrose, iii) secretion rate and buffer capacity of stimultated whole saliva, iv) oral microflora of saliva and plaque, and v) plaque amount. Questions related to dietary habits and fluoride intake were answered. Registration of plaque-pH, at normal oral hygiene, was carried out at four sites in the upper premolar and front regions using the microtouch technique. This was carried out before (0 min) and at different time points up to 20 min after the rinse. Various plaque-pH variables, including the area under the curve (AUC_5.7 and AUC_6.2), were calculated. Results: A correlation between caries score and minimum pH, maximal pH-decrease and AUC_6.2 was found (r=0.35-0.43); the highest r-value for the individuals with the largest number of initial caries lesions. Based on the questionnaire, correlations between caries score and both oral hygiene and consumption of sweets were found (r=0.27-0.33). There were also correlations between pH-variables and the number of meals/day as well as the plaque amount (r=0.23-0.89). When adjusting for gender, salivary secretion rate, buffer capacity and the number of mutans streptococci, the correlation between AUC_6.2 and initial caries rose to about 0.5. Conclusion: The results show a relationship between plaque acidogenicity and caries prevalence. This was strongest between the different pH-variables and the number of initial caries lesions.