The relationship of tooth shade and skin tone and its influence on smile attractiveness in native South Indians: A web-based cross sectional survey

Abstract

Objectives

This study aimed to investigate the influence of tooth shade and skin tone on smile attractiveness among native South Indians. The primary research question was whether there is a significant relationship between these variables and perceived smile attractiveness.

Materials and methods

A web-based cross-sectional survey was conducted with approval from the Institutional Review Board of (Thai Moogambigai Dental College and Hospital, Chennai). Standardized smile photographs of two South Indian models (one male and one female) were digitally modified to display four different tooth shades and four different skin tones, resulting in 32 images. These images were incorporated into a Google Form along with a questionnaire and a Visual Analog Scale (VAS) for attractiveness rating. The survey was distributed to 1200 participants, including both dental professionals and the general population, with 1000 valid responses recorded. Statistical analysis was performed using IBM SPSS Statistics, employing parametric tests to evaluate the data.

Results

The study found that lighter tooth shades were consistently rated higher in attractiveness for both genders. Lighter tooth shades such as FS1T1 and FS2T1 scored means of 6.88 and 7.27 respectively for females, while darker shades like FS1T4 scored lower with a mean of 4.95. Similarly, males showed a preference for lighter tooth shades with MS1T1 and MS2T1 scoring means of 5.57 and 5.78 respectively compared to darker shades like MS1T4 with a mean of 3.63. Significant differences were noted across age groups and genders, with younger participants and females showing a stronger preference for lighter tooth shades.

Conclusions

The study concludes that both tooth shade and skin tone significantly influence smile attractiveness, with a clear preference for lighter tooth shades among the surveyed population. These findings suggest the importance of considering these factors in aesthetic dental treatments to enhance patient satisfaction and achieve optimal results.

Clinical relevance

The results underscore the necessity for dental practitioners to take into account both tooth shade and skin tone when planning aesthetic dental treatments. This approach will help in achieving a more harmonious and natural appearance, ultimately improving patient satisfaction with the treatment outcomes. Future research should continue to explore the cultural and individual factors that contribute to these preferences in dental aesthetics.

1. Introduction

Teeth and skin attractiveness play significant roles in the perception of facial aesthetics, influencing social interactions and self-esteem.¹ The aesthetic appeal of teeth is primarily associated with their color, shape, and alignment. Tooth color is a crucial aspect, and it is influenced by various factors such as age, dietary habits, and genetic predispositions.² The selection of an appropriate tooth shade is critical in dental treatments and is often guided by shade guides, which help ensure a harmonious match with the patient's natural dentition.³

Skin color also plays a significant role in the perceived attractiveness of teeth. Studies have shown that there is a relationship between tooth shade and skin color, with lighter skin tones often associated with lighter tooth shades.2, 3, 4 This correlation is essential for dental professionals when selecting artificial teeth for prosthetic rehabilitation or aesthetic restorative materials for cosmetic dental treatments, as it helps achieve a more natural appearance that complements the patient's overall facial complexion.^5,6 The perception of tooth color can also vary based on the surrounding facial features, making it a subjective experience influenced by individual preferences and cultural factors.⁴

Furthermore, the aging process has a notable impact on both teeth and skin. As people age, their teeth tend to darken and become less translucent, which can affect their overall appearance and attractiveness. This change is primarily due to the accumulation of extrinsic stains and the natural wear of the enamel, revealing the darker dentin beneath.² Similarly, skin undergoes changes with age, including variations in texture, pigmentation, and elasticity, which can also influence the overall aesthetic appeal of a smile.⁶ Hence, the attractiveness of teeth and skin is interdependent and plays a critical role in facial aesthetics.

Existing studies on assessing smile attractiveness have focused on Italian, South American, and European populations.^1,4,10,11 Research on the relationship between South Indian skin tones and tooth shade has been previously explored.^3,9 However, the role of skin tones and tooth shade in the smile attractiveness of native South Indians has not been investigated. Therefore, in this study, we assessed the smile attractiveness of two South Indian individuals (one male and one female) through photographs. The null hypothesis evaluated was that tooth shade and skin tone do not have a significant influence on smile attractiveness among native South Indians.

2. Materials and Methods

This study was designed as a web-based, cross-sectional survey, and approval from the Institutional Review Board of (Thai Moogambigai Dental College and Hospital), was obtained (237/2024/IEC/TMDCH).

Two models were selected for the study: a 23-year-old South Indian female and a 22-year-old South Indian male as shown in Fig. 1, Fig. 2 respectively. A standardized frontal view smile photograph, capturing the teeth, lips, and surrounding skin under ambient lighting conditions, was taken using a digital camera (D7000; Nikon Corporation). To minimize confounding variables, the images were cropped to exclude the nose and chin, focusing solely on the key aesthetic components of the smile.

Fig. 1.

Female smile photograph.

Fig. 2.

Male smile photograph.

The images were then digitally modified similarly to a previous study.¹⁰ The selected smile image was processed using Adobe Photoshop (version 23.4, June 2022), allowing for the separation of the teeth, gums, lips, and skin into four distinct layers. This segmentation enabled precise adjustments to hue, vividness, saturation, and lighting, ensuring that the images matched the reference shade scales. This approach facilitated the creation of a complete set of modified photographs with all the desired variations. Four different tooth shades (1M1 as T1, 2M1 as T2, 3M1 as T3, 4M1 as T4) were represented using the Vita 3D Master guide, and four different skin tones (S1: darker white skin, S2: light brown skin, S3: brown skin, S4: dark brown skin) were based on the Fitzpatrick skin guide. As a result, 32 modified smile images (16 for males and 16 for females) were obtained, as shown in Fig. 3, Fig. 4. Each smile image was coded according to a systematic scheme that considered the participant's gender, skin shade, and tooth shade. For example: the FS1T1 code is for a Female (F) with darker white skin (S1) and 1M1 tooth shade (T1). Similarly, for a male (M) it was coded as MS1T1.

Fig. 3.

Digitally modified Female (F) smile photographs (T represents different tooth shades whereas S represents different skin tones).

Fig. 4.

Digitally modified Male (M) smile photographs (T represents different tooth shades whereas S represents different skin tones).

The 32 images were incorporated into a Google Form (https://forms.gle/4RcqGCsX6Dw93piD7), which also included a questionnaire and a Visual Analog Scale (VAS) ranging from 1 to 10 for participants to rate the attractiveness of each smile. Additionally, the form contained the Ishihara test to screen for color vision deficiency. The form was validated by five experts before being distributed. The survey distribution started on 7th January 2023 and was closed on 19th January 2023.

Participants were instructed to view the images in a dark room with their display (mobile phone or laptop) brightness adjusted for comfortable viewing, and a gap of 5s was recommended between each image.¹⁰

3. Statistical analysis

A pilot study involving 60 participants, including both dentists (n = 30) and non-dentists (n = 30), was conducted to determine the sample size required for the main study. Based on the results, an alpha error probability of 0.05 and a power of 85 % were established. This calculation resulted in a required sample size of 904 participants, which was rounded up to 1000 to ensure a sufficient response rate and robust data collection. Participants were reached through professional networks, online platforms, social media, and visitors or patients at the dental college OPD. The inclusion criteria required participants to be South Indian, have access to the internet, and provide informed consent to participate in the survey. Out of the 1200 distributed forms, 1000 responses were recorded.

Statistical analysis of the data was done using IBM SPSS Statistics (Windows, Version 26.0; Armonk, NY: IBM Corp.). Descriptive statistics, including the mean, standard deviation, and standard error, were calculated for the VAS score of all the images. The normality of the data assessed using the Kolmogorov-Smirnov test revealed that the data followed a normal distribution. Therefore, further analysis was done using parametric tests. The comparison of mean VAS values between the age groups was done using a one-way ANOVA followed by Tukey's HSD and Bonferroni adjustment for multiple comparisons. Multivariate test statistics (Pillai's Trace and Wilks' Lambda) were performed to determine the significance of differences in ratings across groups. A comparison between gender and the dentist group was done using an independent sample t-test. The level of significance in the present study was kept at p < 0.05.

4. Results

The analysis included responses from 1000 participants who evaluated 32 images, with 16 for males and 16 for females, based on varying tooth shades and skin tones. The descriptive statistics revealed that lighter tooth shades consistently scored higher in attractiveness for both genders. For instance, the mean attractiveness scores for females with lighter tooth shades FS1T1 and FS2T1 were 6.88 and 7.27, respectively, while darker shades like FS1T4 scored lower with a mean of 4.95 as shown in Table 1. Similarly, males showed a preference for lighter tooth shades, with MS1T1 and MS2T1 scoring means of 5.57 and 5.78, respectively, compared to the darker MS1T4 with a mean of 3.63 as shown in Table 2.

Table 1.

Descriptive statistics for female smile attractiveness.

Image	Mean	Std. Deviation
FS1T1	6.88	2.38
FS1T2	6.20	2.34
FS1T3	5.53	2.42
FS1T4	4.95	2.73
FS2T1	7.27	2.23
FS2T2	6.53	2.04
FS2T3	5.92	2.44
FS2T4	5.43	2.75

Table 2.

Descriptive statistics for male smile attractiveness.

Image	Mean	Std. Deviation
MS1T1	5.57	2.42
MS1T2	4.75	1.98
MS1T3	4.07	1.97
MS1T4	3.63	2.17
MS2T1	5.78	2.44
MS2T2	5.60	2.13
MS2T3	4.45	1.99
MS2T4	3.93	2.03

The analysis further explored the differences across age groups and genders. Participants aged 18–30 rated lighter tooth shades higher than older age groups, with a significant difference noted in the ANOVA for FS1T4 and post-hoc tests indicating higher ratings for the above-50 age group as shown in Table 3. Gender differences were also significant, with females rating FS1T4 lower than males, as shown by the independent t-test as shown in Table 4. The multivariate tests, including Pillai's Trace and Wilks' Lambda, demonstrated significant interactions between skin tone and tooth shade, with a preference for lighter skin tones and tooth shades as shown in Table 5.

Table 3.

ANOVA for FS1T4 by age group.

Age Group	N	Mean	Std. Deviation
18–30 years	597	4.64	2.38
31–50 years	308	4.46	2.32
Above 50 years	95	5.31	2.56

Table 4.

Independent samples T-Test for FS1T4 by gender.

Gender	N	Mean	Std. Deviation
Female	641	4.41	2.37
Male	359	5.08	2.37

Table 5.

Multivariate tests for interaction between skin tone and tooth shade.

Test	Value	F	Hypothesis df	Error df	Sig.
Pillai's Trace	0.486	62.023	15	985	0.000
Wilks' Lambda	0.514	62.023	15	985	0.000

An independent sample t-test showed that FS2T1 was rated higher by females as compared to males as shown in Table 6. FS1T4 was rated lower by females as compared to males as seen in Table 4. Additionally, FS2T1 was rated higher by non-dentists when compared with dentists as depicted in Table 7. ANOVA for FS2T1 across age groups indicated significant differences, with participants aged 18–30 years rating it the highest, followed by those aged 31–50 years and those above 50 years as shown in Table 8.

Table 6.

Independent samples T-Test for FS2T1 by gender.

Gender	N	Mean	Std. Deviation
Female	641	7.14	2.045
Male	359	6.81	2.135

Table 7.

Independent samples T-Test for FS2T1 by dentists and non-dentists.

Group	N	Mean	Std. Deviation
Non-Dentist	587	7.19	2.159
Dentist	413	6.78	1.946

Table 8.

ANOVA for FS2T1 by age group.

Age Group	N	Mean	Std. Deviation
18–30 years	597	7.19	2.036
31–50 years	308	6.77	2.110
Above 50 years	95	6.78	2.194

5. Discussion

A significant correlation between tooth shade and skin color was previously identified, showing that individuals with medium-to-dark skin tones often have lighter teeth, while those with lighter skin tones tend to have darker teeth.² Further studies examined the interrelationships among teeth, skin, eye, and hair colors, highlighting the necessity of considering these correlations in aesthetic dental treatments to achieve a harmonious appearance.⁷ The influence of gender and skin color on tooth shade preferences was specifically noted in a Saudi population, where lighter shades were generally preferred by individuals with lighter skin.⁸

Contradicting the above earlier findings, another study demonstrated that gender and skin color did not significantly affect tooth shade value, indicating a need for more research in this area.⁹ Additionally, the perceived attractiveness of smiles was found to be influenced not only by tooth shade but also by the surrounding skin color, with a general preference for lighter tooth shades.⁴ Finally, the use of skin color as a guide for selecting artificial tooth colors was supported, showing that fair-skinned individuals typically have lighter teeth.³

The above studies collectively emphasize the importance of considering skin tone in dental aesthetic treatments to achieve a natural and aesthetically pleasing appearance, while also reflecting the complex interplay of cultural and individual preferences in dental aesthetics.^1,2 With a large sample size of participants, our study uniquely considers the perspectives of both Indian dentists and non-dentists across various age groups, who rated 16 different digitally modified smile photos of a male and a female with varying skin and teeth shades. This approach not only broadens the demographic scope of research but also provides a culturally specific insight into aesthetic preferences, further enriching the field's understanding of how these factors influence perceived dental aesthetics. Our findings consistently showed that lighter tooth shades were preferred over darker shades, irrespective of the participant's age or gender. This aligns with previous research indicating a general preference for lighter teeth among various populations.2, 3, 4^,8,10

Several studies have demonstrated the correlation between tooth shade and skin color. For instance, a study in the US suggested that individuals with lighter skin tones tend to have darker teeth, whereas those with darker skin tones often have lighter teeth.² On the contrary, another study in India emphasized that lighter skin tones are associated with lighter tooth shades.³ These findings underscore the importance of considering skin tone when selecting tooth shades for aesthetic dental treatments to achieve a natural and harmonious appearance.

Our study's results, showing higher attractiveness ratings for lighter tooth shades, are consistent with the findings of Sabherwal et al.⁴ and Labban et al.,⁸ who also noted a preference for lighter tooth shades regardless of the participant's gender or skin tone. This preference for lighter shades highlights the influence of cultural and individual aesthetic standards on perceived dental attractiveness.

Our findings indicated significant gender differences in the perception of smile attractiveness. Female participants rated lighter tooth shades higher and darker shades lower compared to male participants. This gender difference aligns with the study by Sabherwal et al.,⁴ which reported that women tend to prefer lighter tooth shades.

Furthermore, our study revealed significant differences in attractiveness ratings across different age groups. Participants aged 18–30 rated lighter tooth shades higher compared to older age groups, suggesting that younger individuals may have a stronger preference for brighter and whiter teeth. This is consistent with the findings of Veeraganta et al.,⁹ who noted age-related differences in tooth shade preferences.

Our study demonstrated significant interactions between skin tone and tooth shade, with a clear preference for lighter skin tones and tooth shades. Hence, the null hypothesis was refuted. This is supported by previous research indicating that skin color can serve as a useful guide for selecting tooth shades in prosthetic and cosmetic dental treatments, as it helps achieve a more aesthetically pleasing and natural appearance.²

The primary limitations of the study include the homogeneity of the enrolled sample, which consisted exclusively of South Indian participants, and the lack of a well-defined reference scale for categorizing skin tone. This study employed digitally altered photographs to simulate various tooth shades and skin tones. While this allowed for control and consistency, these digitally modified images may not perfectly reflect real-life variations in tooth color or skin tone, potentially limiting the ecological validity of the results. Another shortcoming in this study was the possibility of biases related to participant self-selection, technological variability (e.g., different screen brightness and resolutions), and environmental factors that may have influenced how participants viewed the images. While efforts were made to standardize the viewing conditions, such biases remain a limitation in online surveys.

Future studies should explore the use of skin shade templates like the Fitzpatrick skin guide as an additional tool to tooth shade guides to enhance smile attractiveness.⁸

6. Conclusion

The present study confirms that tooth shade and skin tone significantly influence smile attractiveness, with lighter tooth shades being universally preferred. These findings have practical implications for dental practitioners, emphasizing the need to consider both tooth shade and skin tone in aesthetic dental treatments to enhance patient satisfaction and achieve optimal aesthetic results. Future research could further explore the underlying reasons for these preferences and investigate how cultural and individual factors contribute to the perception of dental aesthetics.

Informed consent

The informed consent was obtained from the survey participants verbally.

Conflict of interests

All authors declare no financial and non-financial conflict of interests.

Ethical approval

For this study design, ethical approval was obtained from ‘INSTITUTIONAL ETHICS COMMITTEE’ of (xxxxxxx).

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.