The present study tried to find if ECC is related with sAA enzyme activity, BMI, nutritional and oral hygiene related variables. The sAA activity was found to be significantly higher in caries-free children, indicating an inverse relationship between the ECC and sAA; which was consistent with Borghi et al.'s findings . Similarly, Scannapieco et al. noted that sAA could attach to cariogenic bacteria and facilitate their elimination from the oral cavity, and consequently reduce the incidence of ECC. In contrast, another study reported the mean amylase activity, total protein concentrations, and total IgM to be similar in caries-free and ECC groups. However, this could be due to their limited sample size (20 in each group), which precluded any significant difference . Sitaru et al. also detected that caries-active children had higher levels of salivary enzyme activity compared with caries-free groups, and pronounced sAA as a predictive biomarker in preventive dentistry.
Controversies also exist about the concentration of this protein in saliva. Compared with caries-free controls, higher concentrations of sAA were detected not only in children with ECC [19, 24, 31], but also in caries-susceptible young adults, particularly overweight adolescent girls [10, 25, 32]. Seemingly, excessive amounts of sAA contribute to hydrolysis of starch and acid release by cariogenic bacteria, and thereby raise the risks of dental caries. In contrast, Mojarad et al. concluded that ECC might also be developed in case of decreased sAA concentration. Such a controversy can be justified by the multicomponent nature of human saliva (water, several electrolytes, mucus, glycoproteins, enzymes, and antibacterial compounds), which incorporates a confounding effect that does not allow assessing the effect of a single component in such a media .
Carbohydrates and sugar are extensively approved as the chief dietary elements that account for the incidence of dental caries [33–36]. Similarly, the current findings confirmed that dental caries are significantly associated with brushing and all dietary habits, particularly the amount and frequency of sugar consumption. The frequency of sugar intake (restricted to main meals or between meals) is reported to play an important role in both dental caries and childhood malnutrition . Moreover, improper feeding practices, lack of parental education, and poor oral hygiene are known to raise the risk of ECC. Oral health is imperative for children to maintain the oral functions such as eating and speech, as well as developing a positive self-image .
Pediatric growth disorders have always been a multidisciplinary clinical concern for the specialists, dentists included. Recently, more investigations have been focused on the metabolic effects of obesity on oral health like higher risks of caries and periodontal diseases . Although the relationship between ECC and BMI has been formerly evaluated, the mean BMI, BMI percentiles, or mean weight have been assessed in populations of different ages and mixed sexes . However, in the present study, adjusting the z-scores for both age and sex by Health Watch Pro software yielded more logical report of means.
In line with some previous studies, the current findings revealed the dental caries to be more prevalent among underweight children; however, this was not statistically significant. Kumar et al.  noted that the socio-economic level affected the association between BMI and dental caries. Accordingly, overweight children of high socio-economic families had less dental caries than the normal-weight children.
Conflicting results have been obtained regarding the relationship between dental caries and BMI in children . While some studies rejected any association between dental caries and obesity [7, 35, 37, 38], Hooley et al.'s recent systematic review provided document that proved dental caries is relatable to both low and high BMI . Unlike the present study, some studies noted the dental caries to be more frequent in obese children (BMI > 30) than those with normal body weight (BMI < 25) [12, 17, 40, 41]. Pannunzio et al.  attributed the higher prevalence of caries in obese children to the decreased activity of salivary peroxidase enzyme, which accounts for the antibacterial and antioxidant features of saliva.
It is recommended to emphasize the importance of oral hygiene provide nutritional counselling, and take appropriate preventive measures for the children with growth disorders. Both malnutrition and dental caries can have lifelong negative repercussions for children. An interdisciplinary approach between the pedodontists and primary health care providers or pediatricians can offer a good opportunity to prevent chronic oral diseases and treat these childhood diseases .
In the present study, the regression analysis identified the ECC risk factors that were associated with the interaction of sAA activity, snacking time and stickiness. It implies that in caries-active children with genetically lower levels of sAA activity, incorrect dietary habits can exacerbate the susceptibility to dental caries formation .
Due to the small sample size and difficulty of sample collection especially in caries-free group, it was impossible in this study to match the variables such as oral hygiene and nutritional habits between the case and control groups. However, they were almost similar regarding the general characteristics such as sex, age and parents’ education level. Further studies are suggested to match the confounding variables such as oral hygiene, nutritional habits, salivary immunoglobulins, and stress level to assess the correlation between sAA and ECC more precisely. Larger sample size and evaluating more clinical and biochemical parameters are recommended to predict the potential factors that affect the initiation and development of dental caries.