Jyoti G Chawda, Nandini Chaduvula, Hemali R Patel, Shikha S Jain and Arti K Lala

Dental caries is a multifactorial disease and one of the major contributing factors is saliva [1]. Secretory immunoglobulin A (SIgA) is the prominent immunoglobulin in whole saliva and is considered to be the main specific defense mechanism in the oral cavity. SIgA helps in prevention of dental caries by inhibition of bacterial adherence, reduction of hydrophobicity, agglutination of bacteria and inactivation of bacterial enzymes and toxins [2-4]. Several studies on the role of SIgA in prevention of dental caries showed contradictory results [5-7]. We compared the SIgA levels in the unstimulated whole saliva of caries free and caries active children to determine the role of SIgA in protection from dental caries.

Thirty children of both sexes, aged 4-8 years were selected randomly, from those who were enrolled. Their DMFT (decayed missing filled teeth for permanent teeth) and/or df-t (decayed, filled teeth for deciduous teeth) scores were determined and were then divided into three groups. Group I: 10 children with DMFT and/or df-t=1-5 (Low caries activity), Group II: 10 children with DMFT and/or df-t=6-10 (high caries activity), and Group III: 10 caries free children. For the children with mixed dentition, the sum total of DMFT and df-t was considered [8]. The inclusion criteria for subject recruitment were: co-operative behavior, normal growth and development, and good oral hygiene. The exclusion criteria were: congenital or systemic disease, protein energy malnutrition, obesity, dental abscesses, use of antibiotics in the past 7 days, and oral exposure to food in past two hours of sample collection.

The estimation of SIgA concentration was done using immunoturbidometry (SpinReact, SA, Gerona, Spain). The principle of the procedure is that, SIgA antibodies when mixed with salivary samples, it forms insoluble complexes which cause a change in the optical density, and is recorded on a semi automatic analyzer (based on the principle of spectrophotometer). Statistical analysis was performed by using ANOVA test where P-values less than 0.05 were considered as statistically significant.

Mean values, standard deviations and range and statistical significance of the salivary SIgA concentrations for the studied groups are shown in Table 1. The total salivary concentration of SIgA was statistically significantly higher in the Group III than that of both the Group I and II.

TABLE I Salvary Secretory Immunoglobulin A (SIgA) Levels in Caries Active and Caries Free Children (n=30)

The infectious nature of dental caries assumes the hypothesis that some form of host immunity can regulate caries activity. If immunity can regulate caries activity then SIgA might give a clear correlation [2]. It has been suggested that salivary SIgA antibodies generated by the mucosal immune system play an important role in the immune response against dental caries [6]. Bagherian, et al. [9] found higher levels of SIgA in the saliva of children who were colonized for less than 6 months with S. mutans (cariogenic organisms), and had a low DMFT score than those who had harbored S. mutans for a longer period of time (24 months) and had a high DMFT score. Hence the participants in our study were categorized into two groups based on the DMFT and/or df-t score. The levels of SIgA in subjects without any systemic or immunological disease ranges from 4-30 mg/dL [4]. Systemic conditions like protein energy malnutrition, obesity, infections, psychological stress, cigarette smoking affect SIgA levels [10]. As the children in our study group were free of such conditions, levels of SIgA detected in our study were 11-32 mg/dL which lies within this range. But, when a comparison was made for the salivary SIgA levels between all the three groups, the results obtained were on the relatively low end of the normal range of SIgA for caries active (Group I and II) subjects while they were at the relatively high end of the normal range for caries free (Group III) subjects, and the difference of SIgA levels of Group I and II with Group III were statistically significant. In the present study, a significant inverse correlation was found between SIgA and the caries activity, which is in agreement with previous reports [5,6]. Thus, it can be suggested that the secretory immune system provides local immune protection against cariogenic organisms in the oral environment and ultimately prevents dental caries.

In contrast to our study, Thaweboon, et al. [2] and deFarias, et al. [7] found that the presence of dental caries was associated with an increase of total salivary SIgA. However, Shifa, et al. [3] and Koga, et al. [11] found no correlation between dental caries and SIgA levels. The contradictory results seen in the literature may be due to different sampling methods, different criteria for patient selection, and different laboratory tests used between the studies [8]. Moreover, the concentration of salivary immunoglobulin may change depending upon the salivary flow rate, hormonal factors, emotional states, and physical activity [12].

The obtained results of this study show that the SIgA levels of the whole unstimulated saliva has some role in protection against dental caries, but regarding the severity of the disease, it does not show any significant results.

Acknowledgments: Dr Jigar Suthar (MD Path) and Mr Pinkesh Shah (Laboratory technician) for providing necessary support regarding laboratory procedures.

Contributors: JGC conceived and designed the study and revised the manuscript for important intellectual content. NC, HP, SJ, and AKL collected data and drafted the paper. NC conducted the laboratory tests, interpreted and analyzed them. The final manuscript was approved by all authors.

Funding: None.

Competing interests: None stated.

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