Evaluation of the relationship between caries indices and salivary secretory IgA, salivary pH, buffering capacity and flow rate in children with Down's syndrome.

The aim of this study was to compare the caries prevalence and salivary secretory IgA (sIgA), salivary pH, buffering capacity and flow rate between Down's syndrome (DS) and control subjects. Seventy-three institutionalised children with DS and 70 normal children aged 7-12 years old were included in this study. Tooth-brushing habits and daily dietary sugar exposures of the children, family income and education levels of the parents were recorded. DMFS and dfs scores were assessed according to the World Health Organisation's criteria and stimulated whole saliva samples were collected. Salivary sIgA levels were determined by radial immunodiffusion technique, the average salivary flow rate was measured from the total volume, and salivary pH and buffering capacity were determined using a pH micro-electrode. All data were analysed using SPSS version 11.0. The DMFS and dfs scores were significantly lower in the DS group than the control group (P < 0.05). Otherwise, the difference in plaque scores between the DS and control groups was not statistically significant (P > 0.05). There were no significant differences in tooth-brushing habits and daily dietary sugar exposures of the children, family income and education levels of the parents between the two groups (P > 0.05). Salivary sIgA levels were significantly higher in the DS group (P < 0.05). Salivary pH, buffering capacity and flow rate were quite similar in both the DS and control groups (P > 0.05). In conclusion, the patients with DS had a significantly lower prevalence of caries and significantly higher levels of salivary sIgA in this study. This finding tends to support the hypothesis that higher levels of salivary sIgA may protect against dental caries.