Abstract

Introduction

Dental caries is a widespread chronic infection caused by cariogenic bacteria that adhere to teeth, primarily comprising Streptococcus mutans. These microorganisms break down sugars into acid over time, demineralizing the tooth’s structure, thus causing dental caries. As one of the most prevalent diseases in the world, it presents a significant healthcare challenge. This crippling dental condition affects almost the entire population.¹ By implementing proper preventative measures tailored to each individual’s needs, this condition can be successfully prevented. To achieve this, it is first necessary to identify the interindividual differences that predispose some individuals to a higher incidence of caries.

Numerous studies have demonstrated that our dietary habits are genetically predetermined and consequently influence how someone experiences caries. The TAS2R38 gene mediates the genetic influence on how bitter tastes are perceived. This gene controls the insensitivity to bitter tastes, such as 6-n-propylthiouracil (PROP) and phenylthiourea [phenylthiocarbamide (PTC)]. Some people find these substances to be very bitter, while others find them tasteless. These individuals can be classified as tasters and nontasters, respectively. Individuals who are categorized as tasters have a reduced tolerance for extremely potent flavors and prefer more delicate flavors. Most nontasters enjoy sweet and strong flavors in their cuisine. This preference increases the risk of dental caries in nontasters. Hence, the provision of this particular test proves to be an essential aid in identifying children at risk and giving them the necessary preventive treatments.²

A sexually dimorphic feature that is lower in males than in females is the ratio of second to fourth digit lengths (2D:4D ratio). Typically, the second (index) finger is shorter than the fourth (ring) finger. It is believed that prenatal sex hormone regimens have an impact on sexual dimorphism with regard to the 2D:4D digit ratio. A low (masculine) digit ratio may result from high prenatal androgen levels. According to the literature, prenatal androgens are exposed to the fetus while it is within the womb, and the concentration of this exposure determines how they perceive flavor, which in turn affects their oral health.³

The application of indicators like genetic taste perception and hormonal fingerprint helps to understand an individual’s caries risk and apply appropriate preventive strategies.

Materials and Methods

Study Design

Children coming to the dental OPD, meeting the inclusion criteria and with consenting parents, were divided into groups based on their biological gender, that is, male or female. The first test performed was the determination of their genetic taste perception using PTC strips (Trade Name: PL Precision Laboratories–PTC Test Paper). The child was asked to hold out their tongue, and the strip was placed on the anterior part and tip of the tongue due to the high concentration of filiform papillae in this region. Any sensation of bitter taste was considered a positive response, and the subject was classified as a taster. Nontasters gave a null response to the taste test and only perceived a paper-like taste sensation (Fig. 1).

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Fig. 1:

Testing for genetic taste perception using commercially available PTC strips

The hormonal fingerprint was recorded using a vernier caliper, measuring from the midpoint of the ventral proximal crease of the digit to the tip of the digit of the right hand. In cases where multiple creases were present, the lowermost crease was used for measurement. The 2D:4D ratio was calculated, followed by the distribution of subjects according to a low digit ratio if <1 and a high digit ratio if ≥1 (Fig. 2).

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Fig. 2:

Measurement of hormonal fingerprint

Following this, a brief diet history was recorded to determine the individuals’ preference for sweeter foods and stronger flavors, along with a clinical examination. The caries experience [decayed, missing, and filled teeth index (DMFT)/deft index] was recorded, and subjects with a total DMFT/deft score of >5 were considered to have a high caries rate. Both of these parameters were recorded last to eliminate the risk of operator bias.

Data was analyzed using Statistical Package for the Social Sciences version 23 software, keeping the level of significance at 5%.

Results

The majority of the population belonged to the taster group (54%). Females showed a higher percentage of tasters (64.6%) compared to males (43%), although the difference was statistically insignificant (Table 1).

Around 97.7% of nontaster subjects showed a significant preference for the consumption of sweeter and stronger flavors, compared to 32% of tasters with these dietary preferences (Table 2).

The association of caries status with taste perception showed that 22 nontaster subjects (50%) had severe caries status, whereas 21 taster subjects (40.4%) had low caries status. Twenty nontaster subjects (45.5%) had moderate caries status, whereas 19 taster subjects (36.5%) had moderate caries status. This difference in caries status between taster and nontaster subjects was significant (Table 3).

The digit ratio comparison between males and females showed a nonsignificant difference. The association of caries status with digit ratio revealed that the majority of subjects with a high digit ratio had either low caries (33.3%) or moderate caries (42.4%); whereas, the majority of subjects with a low digit ratio had either moderate caries (39.7%) or severe caries (41.3%) status. However, this difference in caries status between subjects with high and low digit ratios was nonsignificant (Tables 4 and ​and55).

The comparison of digit ratio with the taste test showed that the majority of taster subjects had a high digit ratio (66.7%), whereas the majority of nontaster subjects had a low digit ratio (52.4%) or severe caries (41.3%) status. However, this difference in the taste test between subjects with high and low digit ratios was nonsignificant.

Discussion

Dental caries is a posteruptive bacterial infectious illness that negatively impacts the mineralized dental tissues through a gradual demineralization process. It is said to be one of the most prevalent oral ailments in the world and the primary cause of tooth loss. Dental caries is caused by a combination of physical, biological, environmental, and behavioral factors related to a person’s lifestyle, such as the quantity and strains of cariogenic bacteria, low salivary flow, and an individual’s exposure to insufficient fluoride, poor oral hygiene, and food preferences. Each of these elements impacts individuals distinctively.⁵ Saliva has been proposed as a potential biomarker after a recent study by Hegde et al. revealed a link between organic-inorganic components of saliva and dental caries. It is essential to find a biomarker useful for caries risk assessment that is consistent and stable throughout life.⁶

The aim of this study was to find associations of certain biomarkers that may play a role in increasing an individual’s susceptibility to dental caries. The biomarkers chosen for the study were hormonal fingerprint (2D:4D ratio) and genetic taste perception.

Globalization-related advances have led to an extraordinarily high incidence of poor eating habits worldwide, particularly in low- and middle-income countries. This has, in turn, elevated morbidity and mortality due to oral health-related problems, primarily dental caries and its sequelae. Prevention of these issues involves designing and implementing public health preventive programs aimed at modifying consumption behaviors and understanding the factors that influence dietary preferences and meal selection.⁷ Individual food preferences are important predictors of food intake^8,9 and are highly influenced by taste perception and taste preference. The frequency of carbohydrate consumption may be significantly influenced by inherited behavior and taste thresholds. The tendency of kids to reject certain foods may be influenced by genetic sensitivity to taste.¹⁰ Studies have identified a number of risk factors for dental caries, including a cariogenic diet, a high concentration of cariogenic bacteria, low socioeconomic position, and the influence of taste perception, which may affect food preference or rejection. Thus, being aware of a person’s preferences may make it easier to recognize children who are at a greater risk for developing dental caries.² Genetic taste perception can be determined by testing for the TAS2R38 gene, which is responsible for bitter taste perception. Fox, in 1931, noticed that some people find the taste of the chemical molecule PTC to be extremely bitter, while others find it to be tasteless.¹¹ Two compounds used for this test are PROP and PTC. Bufe et al. found that the association with TAS2R38 haplotypes was stronger for PTC than for PROP.¹²

There are various methods to test for PTC sensitivity. Early experiments used PTC crystals directly on the tongue in some cases, PTC solutions in others, or PTC-soaked paper that was subsequently dried.^13,14 In the present study, the participants comprised children aged 6–14, who lack the ability to differentiate between two taste sensations that are very close to each other in terms of bitterness. Thus, the PTC-soaked paper method was used instead of the threshold method.

In this study, the gender-based distribution of genetic taste perception showed a higher percentage of female tasters than males in line with the findings by Karmakar et al.,¹⁵ Duffy et al.,⁹ Drewnowski et al.,¹⁶ and Dusseja et al.¹⁷ This may be attributed to the presence of more fungiform papillae among females than in males, although the difference was statistically insignificant. As for consumption behaviors, 97.7% of nontasters had a preference for sweeter and stronger-flavored foods, in contrast with only 32% of sweet-liking individuals in the taster group. The nontaster subjects also showed a significantly higher level of dental caries compared to the taster subjects, which can be attributed to the preference for sweeter foods by nontasters, in conjunction with studies done by Shetty et al.,¹⁸ Lakshmi et al.,⁴ Karmakar et al.,¹⁵ and Dusseja et al.¹⁷ These findings suggest a strong positive correlation between genetic taste perception and dental caries, which can be attributed to the preference for sweeter foods by non-taster group participants.

An additional biomarker chosen for the study was the hormonal fingerprint, that is, 2D:4D ratio, a prospective marker for prenatal hormone exposure as well as the expression of the homeobox (HOX) and androgen receptor genes. According to the data, the 2D:4D ratio can be an essential determinant of how prenatal sex hormones act on the body, brain, and behavior, in addition to taste perception. The results of the present study reveal a nonsignificant difference in digit ratio in males and females in contrast to studies by Manning et al.,¹⁹ Fink et al.,²⁰ Lakshmi et al.,⁴ Verma and Hegde,²¹ and Dusseja et al.¹⁷ Most of the participants with low to moderate caries status belonged to the high digit ratio group, whereas the majority of those with low digit ratios showed either severe or moderate caries. However, these differences were statistically nonsignificant, as also found by Pallepati and Yavagal²² in his cross-sectional survey. Upon comparing the digit ratios and genetic taste perception, the majority of tasters had a high digit ratio, whereas the majority of nontaster subjects showed a low digit ratio. However, the difference was statistically insignificant. These results are in line with the study conducted by Pallepati and Yavagal²² and in contrast to the studies conducted by Verma and Hegde,²¹ and Lakshmi et al.,⁴ who found that children with low digit ratio had more caries incidence than those with high digit ratio.

Conclusion

The present study positively demonstrates an association between genetic taste perception and dental caries due to an increased preference for sweeter foods among nontasters. However, no correlation was found between genetic taste perception, the hormonal fingerprint, and the dental caries status of an individual.

Orcid

Anika Kulshrestha https://orcid.org/0000-0001-7224-1266

Footnotes

References