Year : 2010 | Volume
: 21 | Issue : 2 | Page : 231--237
Salivary cortisol response to psychological stress in children with early childhood caries
Halaswamy V Kambalimath, Uma B Dixit, Parimala S Thyagi
Department of Pediatric Dentistry, P.M.N.M. Dental College and Hospital, Bagalkot, Karnataka, India
Halaswamy V Kambalimath
Department of Pediatric Dentistry, P.M.N.M. Dental College and Hospital, Bagalkot, Karnataka
Aims and Objectives: Early Childhood Caries (ECC) is a multi-factorial disease and has numerous biological, psychological, and behavioral risk factors. In this study, we have attempted to study psychological stress as a risk factor for early childhood caries by investigating and comparing the response of event-related stress on salivary cortisol level in children with ECC and those without ECC and also compared the adaptability to various dental procedures in children with early childhood caries and without early childhood caries.
Materials and Methods: One hundred children aged between four and five years were examined in the school and 16 pairs of children with caries and without caries were selected after cross-matching them on various risk factors for Early Childhood Caries. Oral prophylaxis and topical fluoride treatment procedures were used as stressors and salivary samples were collected at the time of arrival for the treatment, after Oral Prophylaxis and Fluoride treatment. The salivary samples were analyzed by radioimmunoassay for an unbound plasma cortisol level.
Results: Statistical analysis was performed using a paired t-test, on the collected data, to compare the mean values of the salivary cortisol across the group and within the groups to evaluate the cortisol response to stress. No significant differences were found between the salivary cortisol levels prior to treatment, post oral prophylaxis, or post fluoride treatment at the first and second appointments of both groups. At the first appointment, the fluoride treatment caused a significant increase in the salivary cortisol level over the pretreatment level, in both the groups, but it was not evident in either of the two groups studied at the second appointment.
Conclusion: We have concluded that the stress produced by different dental procedures was similar in children from the two groups studied, and the coping ability of the children was also similar in both the groups. Small sample size may be one of the reasons why no significant differences were found between the groups. Similar study needs to be repeated with a larger sample size.
|How to cite this article:|
Kambalimath HV, Dixit UB, Thyagi PS. Salivary cortisol response to psychological stress in children with early childhood caries.Indian J Dent Res 2010;21:231-237
|How to cite this URL:|
Kambalimath HV, Dixit UB, Thyagi PS. Salivary cortisol response to psychological stress in children with early childhood caries. Indian J Dent Res [serial online] 2010 [cited 2021 May 16 ];21:231-237
Available from: https://www.ijdr.in/text.asp?2010/21/2/231/66642
Early childhood caries (ECC) has been defined as the presence of one or more decayed (non-cavitated or cavitated), missing (due to caries), or filled tooth surfaces in any primary tooth in a child 71 months of age or younger.  Early Childhood Caries is a multifactorial disease and has numerous biological,  psychological, and behavioral risk factors.  Various risk factors such as the infant feeding pattern,  early transmission of streptococcus,  frequency of carbohydrate consumption,  poor oral hygiene,  prenatal and postnatal insults, , malnutrition,  parent's educational level,  and mother's working status  have been studied in relation to early childhood caries.
An association between stress and dental caries in adults was observed by Sutton,  in 1962, who reported presence of acute dental caries in adults with periods of increased personal stress in the preceding months. Similar reports were also published later by Krasner.  Various animal studies have been carried out to study this relationship. Incidence of dental caries has been shown to increase upon subjecting the animals to different stressors. , Manhold and Manhold conducted an epidemological study on humans and found a significant correlation between decayed missing filled ratings and their personality scores in a sample of 50 adults.  Some studies on individuals among special population groups, with drastic changes in their living environment, for example, immigrants, , political refugees  or prison inmates,  have shown much greater caries experience than among their counterparts living in normal situations.
The ability to react to a stressor in each human being is different and depends on the individual's personality as well as his / her physical strength or health. In humans the biochemical response to stress begins with the activation of the hypothalamus-pitutary-adrenal system, or HPA. This system first activates the release of steroid hormones, glucocorticoids, including cortisol, the primary stress hormone in humans. The HPA system then releases a set of neurotransmitters known as catecholamines, which include dopamine, norepinephrine, and epinephrine or adrenaline. Catecholamines trigger an emotional response of fear and suppress activity in parts of the brain, allowing a human to react quickly to a stressful situation. As the crisis passes, the plasma cortisol levels return to normal due to the inhibitory feedback mechanism, and the body's various organ systems return to normal.
In chronic stress, however, the organ systems of the body do not get the opportunity to assume a normal function and remain over- or under-activated for a longer term. Chronic stress affects the oral cavity in many ways. It has been seen that chronic stress reduces salivary flow rates.  Corticosteroids cause atrophic changes in the major salivary glands, which may affect the total volume of saliva (quantity) and its composition (quality). 
Chronic stress is also related to the increased incidence of plaque formation.  Corticosteroids released during stress inhibit the immune response. This causes an inhibition of salivary immunoglobulins (especially IgA), as well as other antimicrobial proteins present in the saliva, such as, lactoferrin, lysozyme, and lactoperoxidase. Catecholamines may exert a direct effect on the plasma cells to decrease the synthesis of secretory immunoglobulin A. This allows the cariogenic bacteria to multiply. Changes in the quality and quantity of the saliva concomitantly, may lead to the increased adherence and generation of a cariogenic biofilm on the tooth surfaces and increase caries susceptibility. 
85% to 95% cortisol released in response to stress is bound to a corticosteroid binding globulin and only 5-15% remains unbound in the circulation.  The biochemical properties of cortisol allow it to enter other body fluids including the saliva. Transfer of cortisol from the blood to the saliva occurs by passive diffusion,  and therefore, the concentration of cortisol in the saliva does not depend on the salivary flow rate. Measurement of salivary cortisol is noninvasive and is relatively easy to perform in infants and children and offers a convenient way to monitor the systemic adrenocortical response to stress, as long as the possible sources of variances are given due consideration.  Radioimmunoassay (RIA) is stated to be a sensitive analytical method to measure salivary cortisol and is used most frequently for the determination of the steroid, in response to perceived stress. ,,,
Psychological stressors are stimuli that affect emotion and result in fear or frustration and are among the most potent activators of the HPA axis leading to secretion of cortisol. , Reliable stressors such as the Triers Social Stress Test are used to induce stress in adults to measure salivary cortisol response to psychological stress.  However, such stressors have not been used in children. It has been reported that dental treatment may cause extreme stress in children, who have never had a dental treatment experience before, as demonstrated by increased salivary cortisol levels. ,,,
Very few studies have been conducted to evaluate the relationship between stress and dental caries in children. Shimura et al, studied the relationship between anxiety and dental caries in children, and found that prevalence of proximal dental caries in the high-anxiety group was significantly higher than that in the low-anxiety group. They concluded that dental caries was not simply caused by acid produced from the acidogenic bacteria, but might also be attributed to an imbalance and aberration in the integrity of the host, which could be caused by anxiety, other psychosomatic problems, and the irregularity of life pattern.  Scarcity of literature on the relationship between dental caries and stress in children led to this study, in which we have attempted to evaluate stress as a risk factor for early childhood caries.
Aims and Objectives
To investigate and compare the response of event-related stress on the salivary cortisol level in children with early childhood caries and those without early childhood caries.To compare the adaptability to various dental procedures in children with early childhood caries and without early childhood caries.
Materials and Methods
A total of 30 children between the ages of four and five years were selected for this study in the following manner: One hundred children in the age group of four to five years, who did not give a history of prior dental experience were selected for an initial screening conducted in a school. All children were subjected to oral examination in natural daylight using a mouth mirror and explorer. Children with at least one carious lesion were categorized as having early childhood caries. Height and weight were measured for each child and these measurements along with the age were used to calculate the weight percent for age and weight percent for height using standard charts by the NCHS (National Center for Health Sciences). The nutritional status of each child was then evaluated using the Waterlow classification  [Table 1].
From 100 children who were initially screened, 20 children were excluded from the study as they exhibited poor nutritional status according to the Waterlow classification. Parents of the remaining 80 children were asked to fill a specially designed questionnaire, to obtain relevant information regarding age, sex, and various risk factors for caries, namely, education of parents, feeding habits, dietary habits, salivary contact between parents and the child, birth events, and medical condition. After explaining the methodology and aim of this study to the parents, informed consents and filled questionnaires were obtained from the parents of 62 children.
Among these 62 children, 35 children showed at least one carious lesion, whereas, 27 children were without any caries. From these children, 15 children with caries (assigned to the Caries Group) and 15 children without caries (assigned to the Control Group) were selected as follows. In order to quantitatively measure the risk factors in each child, they were scored depending on the information received from the questionnaire. The scores for each risk factor were added and the mean value was calculated for children with caries and children without caries. The children in whom at least one risk factor score was one standard deviation away from the mean score were excluded from the study. [Table 2] gives details of the children excluded from the study. The parents of two children showed hesitance at a later stage, and hence, were excluded from the study.
Dental procedures of oral prophylaxis and application of fluoride gel were selected as stressors in this study as both the procedures were painless.
Children were called for the treatment between 1 pm and 4 pm to avoid diurnal changes in cortisol level.  On arrival, the children were asked to rinse their mouth with water and then the pre-treatment salivary sample was collected. A preformed dental cotton roll was kept under the tongue for four to five minutes. The dampened cotton role was then placed into the barrel of a clear 2 ml disposable syringe, and the plunger was used to express the saliva into the labeled bottles. Children then received oral prophylaxis of maxillary teeth. The second salivary sample (post-oral prophylaxis) was collected in a manner similar to the one mentioned earlier. Topical fluoride treatment was then rendered with the help of 1.23% APF gel and polyvinyl trays for maxillary teeth. After completion, the third salivary sample (post-fluoride treatment) was collected. The second treatment appointment was given after one week. At this second visit oral prophylaxis and topical fluoride treatment were performed for the mandibular teeth. Pretreatment, post-oral prophylaxis and post-fluoride treatment salivary samples were collected.
All salivary samples were stored at -10oC. The salivary samples were analyzed for unbound salivary cortisol with the help of commercially available Coat-a-Count kit (Diagnostic Product Corporation, Los Angeles, CA, USA). The salivary cortisol levels were calculated by plotting percentage binding of salivary samples on the standard curve obtained earlier with the help of calibrators.
The collected data were analyzed statistically using the paired t-test to evaluate differences in salivary cortisol levels, before and after subjection of a stressor, between the caries and the control groups. The adaptability of the children to the stressor in both the groups was evaluated by comparing the post-treatment salivary cortisol levels on the first and second visit.
Distribution of children in the Caries Group and the Control Group by age and other risk factors is presented in [Table 3]. The differences in the mean values of the factors evaluated between the groups were not statistically significant.
The salivary cortisol levels of the children from both the groups were obtained as a measure of psychological stress to stressors selected for the study.
Comparison of salivary cortisol levels between the groups
[Table 4] presents the comparison of the mean values of salivary cortisol levels between the two groups, prior to treatment and following oral prophylaxis and fluoride treatment at the two appointments.
Prior to treatment, the mean salivary cortisol values were found to be 0.40 mg/dl for the Caries Group and 0.37 mg/dl for the Control Group. No significant difference was found between the two groups. After subjecting the children to oral prophylaxis, the mean salivary cortisol level for the Caries Group was found to be 0.34 mg/dl and for the Control Group it was 0.44 mg/dl; the difference being statistically not significant. Similarly, no significant differences were found in the mean post-fluoride treatment salivary cortisol levels between the two groups (Caries Group: 0.63 mg/dl and Control Group: 0.60 mg/dl).
At the second appointment, the pre-treatment mean salivary cortisol levels were found to be 0.38 mg/dl for the Caries Group and 0.50 mg/dl for the Control Group. No significant difference was found between the two groups. Post-oral prophylaxis mean salivary cortisol level for the Caries Group was found to be 0.35 mg/dl and that for the Control Group was found to be 0.50 mg/dl. Although the Control Group had a higher value, the difference was not statistically significant. Similarly, the post-fluoride treatment mean salivary cortisol level for the Caries Group was found to be lower (0.42 mg/dl) than that of the Control Group (0.52 mg/dl), however, the difference was not statistically significant.
Effect of stressors on salivary cortisol levels
[Table 5] presents the comparison of mean salivary cortisol levels obtained prior to treatment, post oral prophylaxis, and post fluoride treatment at the first and second appointments, for children in both the groups.
In the Control Group, post-oral prophylaxis salivary cortisol level (0.44 ± 0.21 mg/dl) showed an increase over the pretreatment level (0.37 ± 0.18 mg/dl), however, the difference was not statistically significant. The post-fluoride treatment salivary cortisol level also showed an increase (0.60 ± 0.35 mg/dl) over the pretreatment level and this difference was found to be statistically significant.
Children in the Caries Group also showed an increase in post-oral prophylaxis salivary cortisol level as compared to the pretreatment value, although the difference was statistically not significant. Increase in post-fluoride treatment salivary cortisol level (0.63 ± 0.73 mg/dl) over the pre-treatment level was found to be statistically significant.
In the Control Group, no statistical differences were found between the post-oral prophylaxis (0.50 ± 0.38 mg/dl) and post-fluoride treatment (0.52 ± 0.40 mg/dl) salivary cortisol levels and the pre-treatment level (0.50 ± 0.37 mg/dl). Children in the Caries Group showed slight decrease in the post-oral prophylaxis salivary cortisol level (0.35 ± 0.32 mg/dl) compared to the pre-treatment value (0.38 ± 0.26 mg/dl), however, the difference was not statistically significant. The post-fluoride treatment salivary cortisol level (0.42 ± 0.41 g/dl) showed a slight increase over the pretreatment level, however, this difference, too, was not found to be statistically significant.
Ability of children with and without caries to adapt to stressors
[Table 5] presents the statistical comparison of the mean salivary cortisol levels of children in both the groups between the first and second appointments. Although the mean post-fluoride treatment salivary cortisol level was found to be increased over the pretreatment level in both the groups, the differences were not statistically significant.
Early childhood caries is a multifactorial disease and various risk factors have been studied and identified. In this study, we attempted to control some of the environmental risk factors other than stress. Children were selected and assigned to the study groups after cross-matching them for feeding habits, dietary habits, oral hygiene practices, salivary contact between the parents and the child, prenatal and postnatal insults, and education of parents. This was possible because of the evaluation of these factors on a quantitative basis, and by giving those scores. Selection of the school controlled the risk factor of the socioeconomic status, as all the children attending school were from a higher middle class economic background. The nutritional status was controlled by excluding children exhibiting current malnutrition according to the Waterlow classification. Controlling some of the significant environmental risk factors made it possible for us to study the association between stress and early childhood caries in children.
Selection of sample size in this study was based on power calculations. The expected power of the salivary cortisol levels between the two groups was 0.5 to 1 and the level of significance was set at 5%. The estimated power was assumed to be 80%. With this information, a minimum sample size was found to be 15, with power at 0.75 or 75%.
It has been reported that stress potentiates anxiety in humans.  A child who is more anxious in nature will have a reduced coping ability, as compared to a child who is well adjusted and less anxious.  This child will also react with more stress to a stressor. We hypothesized that these children will have more caries than well-adjusted children. It was decided, therefore, to evaluate stress in these children in terms of salivary cortisol level, as a response to a stressor.
It has been suggested that salivary cortisol concentration may be related to the level of dental anxiety.  While selecting a stressor, dental treatment including oral prophylaxis and fluoride treatment was chosen due to its noninvasive, convenient, relatively easy, and ethical nature. As both these procedures are considered to be painless even in children with severe dental caries,  it was assumed that alteration in the salivary cortisol level in the two groups would be due to the stress and not due to the pain. Although it was reported earlier that among all restorative procedures, cavity preparation was most stressful in children,  this could not be selected as a stressor in this study, as our control sample consisted of children without dental caries.
Stress produces an activation of adrenal cortical secretion.  In this study, we selected an assessment of the salivary cortisol level as a measure of stress, as it has been proven to be a noninvasive, very accurate, and unaltered measurement of nonprotein-bound, biologically active, free cortisol plasma level. ,, In the previous studies the importance of the circadian rhythm of cortisol has been emphasized. , Considering this, the saliva samples were always collected from children in this study at the same appointment hours. All procedures were scheduled as afternoon appointments, between 12 noon and 4 p.m. Radioimmunoassay has been reported to be a sensitive analytical method by which very low concentrations of salivary cortisol can be measured. 
Our results revealed no significant differences in the mean salivary cortisol levels between the two groups before subjecting the children to dental stressors. Similar results were reported by Jones et al, who compared the salivary cortisol levels in adults with temperomandibular dysfunction (TMD), in order to evaluate stress as a risk factor for TMD. They used the modified Trier's Anxiety Test as a stressor. They found no significant differences in the salivary cortisol levels measured before participation in the test between the TMD and the Control Group. It was also reported that salivary cortisol levels might remain normal in children undergoing chronic stress. 
We observed a significant increase in the post-fluoride treatment salivary cortisol levels when compared to the pre-treatment levels at the first appointment, irrespective of the caries activity in children. These results suggest that the stressors selected by us for this study were indeed appropriate.
Such a trend of increase in the post-fluoride treatment salivary cortisol levels over pre-treatment levels at the first appointment was not evident at the second appointment in both the groups. This could be explained by the ability of children to adapt to the stressors by the second appointment. 
Children in this study did not show statistically significant differences in post-stressor salivary cortisol levels irrespective of their caries activity. Jones et al,  reported their findings regarding a sub-group of adults with temperomandibular dysfunction (TMD), who secreted less cortisol as a response to stress when compared to the remaining adults with TMD. They attributed this to hypo-secretion of cortisol due to chronic continuous pain. Altered sensitivity of hypothalamic-pituitary axis in patients with fibromyalgia has been reported in the literature. , Reduced sensitivity of hypothalamic-pituitary axis to stress as a result of chronic pain, secondary to untreated carious lesions in children from the Caries Group in this study may be the cause for their lower salivary cortisol levels.
Although we attempted to control various environmental risk factors of early childhood caries between the groups, various other inherent risk factors could not be controlled. Considering this, a similar study with a larger sample may seem to be appropriate.
Our results clearly showed that children with caries did not respond to the selected stressors differently than children without caries. Therefore, it may be inferred that stress might not be a significant risk factor in early childhood caries, from the sample that was selected for this study. The stressors chosen for this study, namely, oral prophylaxis and fluoride gel application, in particular, were found to be effective and may be used for further stress studies. Ability to adapt to the stressors at the second appointment was also found to be similar for children with or without caries. Further studies including different methods of stress analyses, utilizing a larger sample may throw more light on stress as a risk factor for early childhood caries.
We acknowledge all the staff, PG students of the Pediatric Dentistry Department of the P.M.N.M. Dental College and Hospital, Bagalkot, Karnataka, for their valuable support in conducting the study.
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