The results of this cluster randomized clinical trial show a clear effect of extraction of severely decayed primary teeth on weight gain in underweight Filipino children, although there was no increase in height gain. The findings were consistent with previous non-controlled studies [8
]. However, our results differ from those of [Gemert-Schriks et al. 11
] and [Alkarimi 12
] who reported insignificant changes in mean anthropometric outcomes of dentally treated children compared to untreated controls, although the changes they reported in weight showed the same trend as those reported here. The difference in findings could be attributed to the fact that not all the children in their studies were underweight and children had less severe dental decay than in the present study. That could result in treatment having effect on weight gain, as there was less dental sepsis and dental impacts to eliminate. Another factor that affected the outcomes of Gemert-Schriks’ study is that dental infection was not eradicated; children developed new severe caries lesions during the course of their study.
There are several plausible mechanisms for the effect of dental extractions of teeth with severe caries on increased velocity of weight gain [22
]. Untreated severe dental decay and the resulting pain may contribute to disturbed sleeping habits and inadequate caloric intake of children. Inadequate sleep may also affect secretion of growth hormones [23
] or may cause excessive energy expenditure, while impacts on eating may affect quality and quantity of nutritious food consumed. These theories are partially supported by findings from [Anderson et al. 24
] and [Acs et al. 25
] that showed that after dental treatment significant improvement was noted in the children’s pain and discomfort experience, sleep patterns and in their appetite and quantity of foods eaten. Another explanation is that dental inflammation from pulpitis and dental abscesses suppresses growth through a metabolic pathway by reducing hemoglobin as a result of depressed erythrocyte production in the bone marrow [26
]. However, based on currently available research, no theory can be confirmed or excluded.
In the present study some children’s WAZ has deteriorated. This suggests that other medical, social, or environmental factors may have interacted in the association between severe dental decay and growth. Most of the children participating in this study were from very deprived municipalities, where access to food has the highest priority for a large segment of the population and could contribute to parental stress [27
]. Several studies emphasized the importance of parental stress on the child’s failure to thrive [28
]. Other factors, such as poor environments, parasitic infections and dietary factors are more likely to have a stronger influence on weight gain than dental treatment. For example, the prevalence of soil-transmitted helminths infestation in under-5-year-olds in the Philippines ranged from 49% to 93% [29
]. Worm infestation has harmful impacts on nutrition as parasites retard growth through decreased nutrient intake and disturbed metabolism. Other medical factors such as anemia, infectious diseases, respiratory tract infections and diarrhea can play an important role in weight gain [28
]. These factors were not assessed in this study, and may result in an underestimation of the association between severe dental decay and growth. However, it is unlikely that those factors alone may explain the observed differences between Group A and B, since these factors were evenly distributed between the two groups.
Another factor that should be noted is that a small number of children in the study had a higher pufa-score than the number of teeth extracted during the intervention, because they required more extractions than was considered acceptable for such young underweight children. The remaining teeth with pulp involvement that were not extracted may explain why there was deterioration in the weight-for-age of some children even after (partial) dental treatment.
A notable finding in this study was that both Group A and Group B children significantly decreased in HAZ after they were dentally treated, while Group B children significantly improved in HAZ in the months before they received treatment. Height, however, takes more time to change than weight. Given the short time span of four months between dental treatment and follow-up, the significant HAZ changes could potentially be explained as saltation and stasis, whereby infant growth follows a series of rapid growth spurs (saltation), separated by periods of stasis [30
]. This indicates that children first accrue the necessary mass by putting on weight to subsequently grow in height. This may be an explanation for some of the significant fluctuations in HAZ observed in this study.
One of the main strengths of this study was that the data were derived from a cluster randomized clinical trial, with data collected before and after the intervention. The findings show the benefit of the dental treatment on weight gain. A novel approach of this study is that growth indicators were analyzed as raw values, z-scores (standardized for age and sex from a reference population) and as conditional growth velocity (controlling for initial anthropometric measurements). Some potential limitations of this study should be taken into account. They include the relatively small sample size and the considerable number of children lost to follow-up. However, the 81.2% follow-up rate is satisfactory, especially considering the difficult conditions prevailing at study sites.
Further research is needed to investigate the effects of severe dental decay in children on body constitution and growth and the causal mechanisms for their relationship. Future studies need to investigate the metabolic pathways and incorporate parameters related to general health, infectious diseases, psychosocial relationships and environmental factors. Ideally, the measurements of these variables should precede the measurements of the outcomes, namely, ‘weight and height gain’, to assess temporality. The time span between dental treatment and the assessment of anthropometric measures should be prolonged and anthropometric indicators should be regularly monitored in order to investigate the effect of dental treatment on height.