Association between dental caries experience and salivary profile among autoimmune thyroid disease subjects - a cross-sectional comparative study

Introduction

The immune system is dysregulated in autoimmune thyroid disease (AITD), which leads to an attack on the thyroid gland. Its two primary clinical symptoms are Graves disease (GD) and Hashimoto’s thyroiditis (HT). An estimated 5% of the general population is thought to be affected by HT and GD. AITD develops when genetically susceptible people lose their tolerance to thyroid antigens in conjunction with environmental factors such altered microbiota. Both symptoms are marked by aberrant thyroid functioning and T and B cell infiltration into the thyroid that is responsive to thyroid antigens.¹

AITD is unique to thyroid gland and women are affected 4–10 times more frequently than males.² The most prevalent forms, Hashimoto’s thyroiditis (HT) and Graves’ disease (GD), have many immune characteristics in common. The primary characteristic of AITD is the emergence of antibodies against thyroid peroxidase (TPO), thyroglobulin (TG), and thyroid stimulating hormone receptor (TSH-R).³

A combination of main and minor salivary gland secretions, gingival crevicular fluid, cellular debris, and bacteria are all present in saliva. Saliva serves a wide range of purposes, including the defence of the mouth cavity, digesting owing to salivary amylase, immunity to microbes, and, most critically, for use in diagnostic activities. The use of saliva in diagnostic procedures is expanding since it is simple, non-invasive, and affordable. Enzymes, hormones, antibodies, antibacterial components, growth factors, and other substances that enter from the blood through the gaps between cells can all be found in saliva. Some of the conditions for which saliva has significant diagnostic potential are oncological, endocrine, cardiovascular, rheumatic, autoimmune, neurological, or viral illnesses.¹

Dental caries is seen as a complex microbiological illness. It is a multifactorial disease of the teeth that results in a localised loss of tooth structure. It is caused by the interaction of dietary carbohydrates, tooth substrate, and cariogenic bacteria in the dental biofilm, which produces acid after carbohydrate fermentation and causes changes in the pH of the biofilm, which leads to mineral loss (demineralization) as a result of disturbances in the physiologic equilibrium between the biofilm and tooth. Previous studies have discovered an increase in the prevalence of dental caries in people with thyroid dysfunction, either as a result of the disease process itself, as a result of the surgical treatment (thyroidectomy), or as a result of medication taken that worsens oral and dental conditions.⁴

The amount and quality of saliva generated are both impacted by AITD, which either directly or tangentially affects salivary gland secretory function. The primary determinants of salivary defence are its composition, buffering ability, pH and flow rate. Saliva production, when reduced, has an impact on mouth health and can cause complications like oral candidiasis, gum disease, tooth cavities, and other pharyngeal and oral disorders.³

Previous studies have examined the major involvement of the salivary glands in instances with AITD, which suggests that the development of thyroid and salivary gland immunological diseases may have a same mechanism.⁴ According to animal research, thyroid malfunction alters basal metabolic rate, which may therefore have an impact on the salivary gland’s secretary unit.⁵

There are very few studies demonstrating how AITD affects the salivary ducts. Because of this, the following research topic guided the execution of this study: Do AITD participants’ experiences with tooth caries and their salivary characteristics correlate? The link between dental caries history and salivary profile among AITD patients was postulated to exist. The objectives were to evaluate the relationship between tooth caries and salivary profile in AITD individuals and to contrast it with controls who were of a similar age and gender.

Methods

Results

This study included 100 AITD subjects and 100 healthy subjects (controls). The mean age for AITD group and control group were 32.20 ± 4.21years and 33.93 ± 5.55 years respectively. There was a higher proportion of female participants than males. The majority of the study subjects belonged to lower middle class (85.8%). Between the research groups, there was no statistically significant variation in terms of age (p = 0.06), gender (p = 0.30), or socioeconomic position (p = 0.29) (Table 1).

The majority of research subjects (AITD: 75%, control: 68%) had never been to the dentist. The majority of those who had attended a dentist had done so within the previous year (AITD: 72%, control: 53.1%). Tooth extraction (AITD: 40%, control: 46.9%) was the most frequently reported dental procedure, and pain was the primary factor driving dental visits (AITD: 60%, control: 62.5%). Between the research groups, there was no statistically significant variation in the duration since last dental visit (p = 0.05), the causes for the dental appointment (p = 0.82), or the type of treatment received (p = 0.76).

The majority of the AITD subjects (81%) were under anti-thyroid drugs for the past 1 year. Mean TSH values among AITD hyper and hypo groups were 0.20 ± 0.07 and 6.43 ± 1.30 respectively (Table 2). Comparing the AITD group to the control group, a substantially greater percentage of respondents reported subjective dryness (Table 3). Regarding subjective dryness, there was no statistically significant difference between the AITD hyper and hypo groups (Table 4).

When compared to the control group, the amount of stimulated and unstimulated saliva was considerably lower in the AITD group. In comparison to the control group, a considerably greater percentage of research participants in the AITD group had increased salivary viscosity. When compared to the control group, salivary pH and buffering capacity were considerably lower in the AITD group (Table 5). Regarding salivary measures, there was no statistically significant variation between the AITD hyper and hypo groups (Table 6).

Anti-thyroid medications did not significantly affect either unstimulated (p = 0.82) or stimulated salivary flow (p = 0.88), viscosity (p = 0.19), pH (p = 0.32), or buffering capacity (p = 0.36), respectively).

When compared to the control group (56%), the AITD group (72%) experienced considerably more dental cavities. Mean number of DMFT, decayed teeth (DT) and missing (MT) teeth were significantly higher in AITD group (DMFT: 3.82 ± 1.36, DT: 3.18 ± 1.06, MT: 0.45 ± 0.83) than the control group (DMFT: 1.65 ± 0.86, DT: 1.25 ± 0.53, MT: 0.19 ± 0.59) (p < 0.001). There was no significant difference between the mean numbers of filled (FT) teeth among the AITD group (0.19 ± 0.63) and the control group (0.21 ± 0.47) (p = 0.15) (Table 7). There was no statistically significant difference among the AITD hyper and hypo groups with regard to dental caries experience (Table 8).

A significant negative correlation was observed between subjective mouth dryness and “USFR” (r = -0.586, p < 0.001) and DMFT and “USFR” (r = -0.368, p < 0.001). “SFR” had a significant negative correlation with subjective mouth dryness (r = -.524, p < 0.001) and DMFT (r = -0.373, p < 0.001) respectively (Table 9).

In the linear regression model, age (β = 0.115, R² = 0.016, p = 0.45), gender (β = 0.089, R² = 0.019, p = 0.44), socioeconomic status (β = 0.021, R² = 0.001, p = 0.86), thyroid stimulating hormone (β = -0.091, R² = 0.006, p = 0.43), salivary viscosity (β = 0.125, R² = 0.02, p = 0.74), pH (β = -0.919, R² = 0.01, p = 0.12) and buffering capacity (β = 0.778, R² = 0.03, p = 0.26) were not associated with dental caries. Unstimulated saliva (β = -0.523, R² = 0.43, p = 0.006) and stimulated saliva (β = -0.476, R² = 0.32, p = 0.003) showed a significant association with dental caries (Table 10).

Discussion

Autoimmune thyroiditis is a chronic disease in which the body interprets the thyroid glands and its hormones T3, T4 and TSH as threats.¹² Sex hormones play a big role in triggering or protecting from autoimmunity. Estrogen has the ability to enhance the inflammatory process of the immune system and could contribute to AITD.^12,13 The mean age of the AITD group was 32.20 ± 4.21 years which is similar to a previous study (30.06 years).⁵ The majority of participants were female which is in line with two previous studies.^5,14

Due to the chronic nature of autoimmune illness, there will be significant financial expenses as well as a negative effect on the patient’s health and quality of life. Dental caries are more likely to occur when socioeconomic factors, lower levels of schooling, and lower revenue are combined.¹⁵ Most of the research participants were from the lower middle class. Age, gender, and socioeconomic position among the research groups did not vary numerically significantly, indicating homogeneity.

Dental visits are of utmost importance to high-risk groups like autoimmune thyroid disease subjects as they are more prone to a variety of dental problems. The majority of the research participants had never been to a dentist. Most of the trips were motivated by symptoms (pain), which shows that the respondents did not fully understand the value of a preventive dental appointment.

Autoimmune thyroid disease has a detrimental effect on salivary glands and cause reduction in salivary secretion.^12,16 Basal metabolic rate is impacted by thyroid malfunction, and the secretary unit of the salivary duct is subsequently impacted.⁵ Salivary secretion is reduced in AITD hypothyroidism. This is believed to be connected to the hypothyroidism-related decreased metabolism. Although the cause is unclear, AITD hyperthyroidism can reduce saliva production when it is untreated or only partly managed.¹⁷

Salivary mucins have an important role in maintaining rheological properties of saliva. AITD impairs secretary unit of salivary gland and cause decreased quality of salivary mucins which in turn affects viscosity, pH and buffering capacity.¹⁸

Farsi’s criteria have been used to evaluate subjective dryness among patients with thyroid disorders. A higher proportion of AITD subjects reported subjective dryness than in the control group, suggesting the impact of AITD on salivary flow. Unstimulated and stimulated saliva were significantly reduced in the AITD group which is similar to two previous studies,^5,14 suggesting consistent association between salivary flow and AITD. A higher proportion of study subjects in the AITD group experienced increased salivary viscosity and reduced salivary pH and buffering capacity, which was also similar to a previous study.⁵ Hence, salivary parameters are significantly affected with patients with AITD.

A person with systemic hypothyroidism may have slower-healing cells and tissues, making them more vulnerable to illness. As a result, they are more likely to develop mouth and tooth conditions like dental caries, frequent mandible spasms, and bleeding lips. People who have autoimmune hyperthyroidism are more susceptible to dental caries, teeth sensitivity and pain in the jaw.¹³ Autoimmune thyroid disease increases the risk of dental caries which has been attributed to the reduced salivary flow caused by the condition.¹⁹ Dental caries experience was significantly higher in AITD group.

Indicating the efficacy of using Farsi’s criteria to assess oral dryness, a moderately significant negative association was discovered between “unstimulated salivary flow,” “stimulated salivary flow rate,” and “subjective oral dryness.” This indicates a connection between salivary flow and caries, and a marginally significant negative association was discovered between “unstimulated salivary flow,” “stimulated salivary flow rate,” and “dental caries.” Therefore, perceived dryness may be a sign of cavities development and salivary flow rate.

Dental caries was used as the result variable in a study using linear regression. In contrast to demographic factors, TSH, salivary viscosity, pH, and buffering capacity, which were not linked with dental caries, the current research discovered a highly significant correlation between salivary flow and dental caries.

The current research has some strengths and limitations. We believe that this research is the first of its kind to link salivary parameters and tooth caries in AITD. Standard kits and criteria were used to evaluate salivary parameters reflecting high internal validity.

Although it can be seen that there are risk factors, a cross-sectional research design does not allow for the evaluation of causation between study variables. Undiagnosed systemic disease could be present and could have affected the salivary metrics.

Prospective studies are recommended to understand changes in salivary parameters and the impact of drugs over a period of time among hypo and hyper AITD patients. There must be proper maintenance of oral hygiene and diet modifications.

Periodic dental management should be conducted by well trained dentists. Even if there are no comorbid conditions, dental therapy adjustments may be required for individuals who are receiving medical supervision and follow-up for an autoimmune thyroid disease.

Thyroid dysfunction can affect every system in the body, including the mouth. An overabundance or underabundance of these hormones has a negative impact on the oral cavity. The endocrinologist must be aware with the oral symptoms of thyroid dysfunctions before treating a patient with a thyroid disease. Prior to receiving dental care from a dentist, patients who have thyroid dysfunction and those who are on medication for it need to properly manage their risks. Thus, in order to preserve the patient’s thyroid and oral health, contact between the dentist and endocrinologist must be two-way.

Conclusion

The current study may indicate an underlying association between thyroid and salivary gland dysfunction. Dental caries is a multi-factorial condition where diet and oral hygiene habits play key roles. Hence, future studies should take these factors into consideration to determine whether thyroid disorder alone can cause salivary gland dysfunction resulting in oral dryness and high dental caries experience.