The present investigation compared the occurrence of dental caries among children and teens with and without SCD. There was a low occurrence of dental caries in children with SCD in comparison to their controls. Among teens, we found no statistical differences when compared to controls in their caries experience, measured by the DMFT index, or the prevalence of untreated caries observed by the decayed component. Our result is similar to that observed in a study of 54 American teenagers with a mean age of 14 years, with sickle cell disease genotypes HbSS and HbSC . The mean DMFT found in the afore mentioned study was 1.94 (2.7) in the SCD group and 2.96 (4.10) in the control group. However, considering the 2 genotypes separately, a significant difference was seen only in teenagers with SCD HbSC (p < 0.2). The lack of a significant difference in caries experience between American SCD teenagers HbSS and healthy controls was explained, in part, as a large exposure to fluoride through the drinking water, since children with SCD need to pay attention to hydration when preventing pain crisis .
In our results, the minor occurrence of dental caries in the children group was attributed to their receipts of major health care surveillance provided via access to free dental treatment at Hemominas - MG, Brazil. The literature shows a great resilience capacity of children`s families with chronic diseases including sickle cell disease [20, 21]. Mothers of children with SCD often leave their jobs to devote themselves to the child's health needs [20, 21]. Many parents incorporate the role of caregiver or manager for the child´s disease in its own sense of life [20, 21]. In this manner, it is suggested that the SCD children`s health care from their parents had influenced the lower caries experience of their children.
We attribute the lack of significant differences in caries experience between SCD teenagers and the control group to the age of adolescents. The behavior of older children may differ from that of younger children. Teenagers can see the supervision of their parents as a threat to their growing desire of independence, resulting in a resistance to the appropriate behaviors to health [21, 22]. This independence of adolescents with SCD would result in less attention to preventative measures such oral hygiene and a healthy diet, making adolescents with SCD as susceptible to dental caries as their control group.
The experience of dental caries among children with SCD and their peers (without SDC) was similar to the experience observed among 160 children with SCD aged 3 to 12 years in Recife, Brazil . Among children in Recife, there was an average DMFT score of 1.5 . This result is close to what we found. However, comparing our results with data from a national survey carried out in Brazil (dmft = 2.43 and DMFT = 2.07) , our results reflected better oral health. Comparing the results of this study with those observed in research conducted with Indian SCD children, there was a higher dental caries experience between Indian SCD children aged 3 to 15 years (Hb SS and Beta thalassemia) in comparison with controls . We believe that one reason for the discrepancy in their findings and our results may be due to differences in the oral health care systems between India and Brazil. In the Brazilian context, oral health care for pediatric SCD patients is provided free of charge by the government. In contrast, In India, the development of appropriate models of health for the diagnosis and follow-up of patients presents a challenge that should not be underestimated . In this case, the characteristics of the Brazilian health system could break the link between socioeconomic conditions and health. Another possible explanation is that our controls were selected from the school friends of SCD patients. There is homophily in social networks [26–28]. This could have resulted in greater similarity of dmft/DMFT scores between patients and their controls (compared to a truly random control population).
Dental caries is a multi-factor disease and controlling factors can be challenging. In our regression analyses, low family income was shown to be a significant associated factor in younger children. Socioeconomic factors have been previously shown to be a robust predictor of caries risk. Lower income may be associated with lower health literacy (concerning oral hygiene practices) as well as lower access to preventive health care information [29, 30]. Our results agree with previous studies showing that income can be considered a co-factor in the relationship between SCD and oral health [10, 12].
Our study revealed a higher frequency of gingival bleeding in adolescents with SCD when compared to the control group. This result differs from that observed in a study of Brazilians between 16 and 68 years of age . According to that study, SCD does not predispose an individual to periodontal disease . The comparison of these studies requires caution since there is no difference in the age of the participants. In the present study, we believe that the association between SCD and bleeding gums can be attributed to the resistance of the appropriate behaviors to health , resulting in inadequate oral hygiene, which is a common risk factor for dental caries and periodontal disease.
There was no difference in OHRQoL among participants with SCD and controls. A similar result was found in SCD teenagers and controls in Ohio (USA) . As described by these authors, the lack of association may be explained by the patient selection bias. The present study only included participants who were not suffering from a painful crisis at the time of the survey, the medical conditions other than SCD, and in emergency dental appointments in the past three months. These facts may have led to the evaluation of only patients in good health, masking the OHRQoL during the acute pain that is a characteristic of SCD.
We would have expected parental education to be a strong predictor of caries. Less educated parents have less health literacy. However, considering the schooling level of the fathers and mothers of all the children in our study, we observed that 76 % of parents had completed up to eight years of study. It is a very homogeneous sample for the low level of education. This could be a reason for not having found a relationship between the prevalence of caries in children and the level of parental education, either in univariate or multivariate analysis. This result agrees with the study of 160 Brazilian children with SCD aged 3–12 years in Recife, Brazil . There was no significant relationship between parental education level and dmft/DMFT index, or any of the variables examined: decayed, missing and filled teeth . Over half of the parents (56.3 %) had not completed their elementary education, 18.1 % had completed elementary school, and 18.1 % had completed high school .
In the present study, the disease's clinical severity was associated with dental caries in children suffering from SCD. Disease's clinical severity is associated with vaso-occlusion within the vasculature of the pulpal tissue that may account for the pain experienced by SCD sufferers, and that the same infarction process that afflicts other organs in the body may also affect the dental tissue . Other studies examined histological changes in the dental tissue with regard to SCD and disease's clinical severity. Sickle-shaped cells were observed in the vessels of the pulp of teeth from patients 24 to 96 h after an acute sickle cell crisis attack . The authors concluded that significant pathological changes were observed in the dentin and pulp and suggested that they were most likely due to stasis of the sickle cells in the capillaries, which created a hypoxic situation, causing tissue infarction. The authors stated that the changes observed were not pathognomonic, but that findings suggest that the sickle cell disease's clinical severity has a higher susceptibility to poor oral health [32, 33]. The knowledge of the association between dental caries and the severity of SCD allows dentists to gain a greater understanding of the problem and the role of pediatric dentists in the overall health of children.
The main limitation of this study was that we examined a specific population from one city in southern Brazil. Accordingly, our findings should be interpreted in the light of external generalization. Prospective studies which have larger and more diverse samples involving hospitalized patients, should complement our data and would provide a better understanding of the relationship between the severity of SCD and oral health. Dental radiographs were not obtained; thus, carious lesions that can only be detected radiographically were missed. Moreover consumption of sugar was not assessed. In terms of the strengths of our study, we conducted oral examinations on every subject, and components of the caries burden index (dmft/DMFT) were separated, making it possible to differentiate active disease from treated disease. We included a matched control group consisting of healthy peers. Lastly, the high degree of reproducibility of the diagnoses, as measured by the kappa statistics, contributed to the internal validity of the study.