Until very recently there has been minimal research in the area of nutritional iron status and caries. This study provided an opportunity to explore this relationship by comparing the ferritin and haemoglobin levels between children undergoing rehabilitative dental surgery for S-ECC and cavity-free children recruited from the community.
While there was no statistically significant difference observed between the two groups with respect to average iron concentrations, there was a significant difference in the number of children exhibiting low ferritin levels. In fact, our study reveals that those undergoing dental surgery were significantly more likely to be classified as having low ferritin (p=.033). This is largely congruent with findings from another Canadian team that identified 80% of their dental surgery cohort as having unacceptable ferritin levels and 28% having low haemoglobin status
. Our present study displayed a similar trend, as 70.5% of participants had unacceptable ferritin levels. In fact, the adjusted odds of children with S-ECC having low ferritin was nearly double that of cavity-free children. More recently, another group has reported a similar significant relationship between rampant caries during childhood and low ferritin status
. They reported that children with rampant caries had significantly lower levels of ferritin, haemoglobin, and iron than a group of caries-free controls
. Both studies as well as our own study suggest that there is in fact a relationship between S-ECC and overall iron levels.
Overall, we found that children with S-ECC had significantly lower haemoglobin levels than the caries free controls. This included differences in mean haemoglobin concentrations and groupings based on existing laboratory thresholds. Meanwhile, when previously published definitions of iron deficiency and iron deficiency anaemia
 were applied to the study data, we found that the S-ECC group was overrepresented in both conditions. Compared to our Canadian colleagues, we observed a higher prevalence of both iron deficiency (14.6% vs. 6%) as well as iron deficiency anaemia (18.9% vs. 11%)
. As a whole, the observations made by the present study show agreement with their findings, though the higher prevalence of iron deficiency and iron deficiency anaemia (even with the inclusion of a control group) suggests that children from these regions of Manitoba with S-ECC may be at an elevated risk.
When the WHO’s groupings for anaemia were applied, 29.5% of our entire study sample were found to be anaemic. Meanwhile, the proportion of Canadian preschool children estimated to be anaemic is only 7.6%. This statistic, however, relied on a slightly different threshold value (with only those falling below 110 g/L being considered anaemic) which, when applied to the study data, indicated that 27.6% of our entire sample was anaemic.
The two other recent reports on iron status and severe caries are novel, but have some limitations
[14, 19]. One did not include a comparison group of cavity-free children and only observed those with rampant decay undergoing rehabilitative surgery
. The other recruited their children with severe caries based upon a definition of having a microcytic anaemia due to an underlying iron deficiency
. As such, it is expected that these children would naturally display lower levels of iron. Despite this shortcoming, their work provides evidence that the relationship between iron levels and S-ECC is salient. Interestingly, this group also observed significant improvements in ferritin and haemoglobin levels after rehabilitative dental surgery
. While the specific nature of this relationship is currently unknown, there are several plausible explanations as to why the iron levels of a child are associated with the presence of S-ECC. One hypothesis is that the low haemoglobin levels often observed in S–ECC children may be attributed to the body’s inflammatory response, which may accompany rampant forms of dental caries (especially those involving pulpitis or abscesses). Inflammation associated with S–ECC may trigger a series of events which ultimately leads to the production of cytokines, which may, in turn, inhibit erythropoiesis and thus reduce the level of haemoglobin in the blood
 (and therefore the level of iron). The reduction of haemoglobin levels is a common occurrence in many chronic diseases and, if severe enough, may lead to “anaemia of chronic disease”. S-ECC may be one such chronic disease. It is also recognized that the pain experienced by children with S–ECC may lead to altered eating habits
. These eating habits may lead to nutritional deficiencies such as low iron levels. Additionally, differences in nutritional status between caries-free children and those with S-ECC may also be shaped by household economics. Limited funds may restrict a family’s ability to purchase nutritious foods. Low socioeconomic status is known to be associated with increased risk for anaemia
. We attempted to control for the influence of household finances in our logistic regression models and still found that after controlling for yearly household income and multivitamin use that children with S-ECC were at increased risk of having a nutritional deficiency.
The implications of a relationship between iron and S-ECC have the potential to be far-reaching, as a child’s iron status has been demonstrated to have a significant impact on health. For instance, learning and memory deficits, decreased fine motor skills, and increased anxiety may all be observed in children suffering from iron deficiency
. The ability to recognize early warning signs of low iron levels (such as S-ECC) may allow patients to receive the necessary interventions before the longstanding effects of iron deficiency are able to take root. Perhaps pre-operative assessments for children requiring dental surgery to treat S-ECC should include evaluation of iron and haemoglobin levels.
This study was not without its limitations. The study design was cross-sectional and does not allow for the determination of true cause and effect. While our groups were essentially matched by sex and age, we were not able to match by socioeconomics. Since S-ECC is influenced by the social determinants of health, more children in this group were from lower income households. It was also very challenging to find cavity-free peers from similar neighbourhoods and backgrounds to participate. For obvious reasons there are some differences between children with and without S-ECC that are impossible to control for as they are key determinants (e.g. household income, parental education, etc.). While we did not measure caries rates in the S-ECC group, all had multiple cavitated carious lesions requiring treatment under GA. While informative and applicable to the general population of S-ECC children, the results from this study are not necessarily transferrable to the general population of Manitoban preschoolers. Despite these challenges, the sample size provided sufficient statistical power to assess whether associations were present.