Study design

This was a prospective cross-sectional study. Ethical approval was obtained from the institution ethical review board (Ref no: JEP-2025–207).

Reflective devices (mirror types and digital reflections)

Six types of mirrors were utilised in this study. These included: (1) a full-length mirror (94 × 34 cm); (2) a medium-sized mirror (48 × 38 cm); (3) a small mirror (24.5 × 19.5 cm); (4) a dual-sided square pocket-size mirror (6.8 × 6.8 cm), featuring a standard reflective surface on one side and a magnified mirror on the reverse; and (5) a handheld tooth-shaped mirror, approximately 5.5 × 3.5 cm in size.

All mirrors were constructed with clear glass and enclosed in lightweight black plastic frames, except for the tooth-shaped mirror, which was made of white plastic.

For the digital reflection condition, the smartphone front-facing camera of an iPhone 12 Pro (Apple Inc., California, USA) was used. This device features a 12-megapixel TrueDepth camera with an ƒ/2.2 aperture and a wide-angle field of view equivalent to approximately 23 mm. The camera includes software-based image stabilisation. During the study, the camera was operated in selfie video mode, with no filters applied and the screen brightness standardised at 50%.

Sample size

The sample size was calculated using G*Power version 3.1 (Heinrich Heine Universität Düsseldorf, Germany), based on an effect size of 0.15, a power of 0.95, and an alpha level of 0.05. The calculation assumed one group with seven repeated measurements. The minimum required sample size was 68 participants. To account for potential dropouts or incomplete questionnaires, the final sample size was increased to 83 participants.

Participant recruitment

Participants were recruited from the members of the Faculty of Dentistry, Universiti Kebangsaan Malaysia. Inclusion criteria included a person aged 18 years or older. Exclusion criteria were the presence of any visual impairment that could affect visual perception or subject undergoing any active dental treatment that might influence the appearance of their teeth or alter their perception of dental aesthetics. Convenience sampling was employed, whereby all eligible students and support staff were approached, informed about the purpose of the study, and invited to participate. Written informed consent was obtained from all participants prior to their involvement.

Randomisation

Device presentation order was determined using simple randomisation. Each mirror type and the smartphone-based digital reflection were assigned a unique numerical identifier. An online random sequence generator (Random.org; Randomness and Integrity Services Ltd., Ireland) was used to generate a unique presentation order for each participant immediately prior to data collection.

Data collection

The assessment environment was standardised for all participants. All assessments were conducted in a clinical setting under consistent neutral white ceiling lighting, with no additional or directional light sources introduced. All mirrors were disinfected with alcohol-based wipes between participants, and any visible debris or marks were removed using a microfibre cloth prior to each assessment.

The full-length and medium-size mirrors were positioned vertically, with a standardised viewing distance of approximately 2 feet. The remaining mirrors were placed on a tabletop surface, and participants approached each device sequentially according to the randomised order assigned prior to assessment.

For the tabletop mirrors and the smartphone front-facing camera, participants were permitted to hold the device at a comfortable self-selected distance. They were allowed to observe their dental appearance for as long as they wished before proceeding to the next device. Following each viewing, participants completed a questionnaire assessing perceived dental attractiveness.

The use of a self-selected viewing distance for handheld mirrors and the smartphone front-facing camera was informed by pilot testing. When a fixed viewing distance was applied, participants reported difficulty assessing their dental appearance due to the limited field of view of smaller reflective surfaces and differences in visual acuity. Allowing a self-selected distance improved visual clarity and more closely reflected typical clinical and everyday usage. In contrast, a standardised viewing distance was maintained for the full-length and medium-size mirrors, which are commonly wall-mounted in clinical and domestic settings.

Questionnaire

The questionnaire was adapted from the instrument developed by Yuen et al. (2023) and was administered in Malay [21]. The original questionnaire had previously undergone forward and backward translation, as well as validation in the Malay language. Prior to the present study, the adapted version was reviewed by two orthodontists to assess its clinical relevance, clarity, and suitability for the study population. Feedback was also sought from the adapted questionnaire developer, and minor refinements were made accordingly. The questionnaire was subsequently pilot-tested among five participants who were not included in the main study to evaluate clarity and comprehensibility. No further modifications were required.

Basic demographic information, including name, age, and ethnicity, was also collected. For each condition, participants rated their dental appearance using a visual analogue scale ranging from 0 (least attractive) to 10 (most attractive) [22]. Once a session with a particular mirror or the smartphone was completed, participants were not permitted to return to any previous viewing device.

Reliability

After two weeks, 10% of the participants were asked to repeat the same assessment to evaluate intra-rater reliability.

Statistical analysis

Data were analysed using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were calculated for each mirror type and the digital reflection. A repeated measures ANOVA was performed to assess differences in perceived dental appearance. Post hoc pairwise comparisons were conducted using the Bonferroni correction. A p-value of less than 0.05 was considered statistically significant. Intra-rater reliability was assessed using the Intraclass Correlation Coefficient (ICC) [14].

Results

Participant demographics

A total of 83 participants completed the study. The median age was 24.0 years (IQR = 18.0). The sample consisted of 69 females (83.1%) and 14 males (16.9%). In terms of ethnicity, 56.6% identified as Malay, 31.3% as Chinese, 9.6% as Indian, and 2.4% as other ethnic backgrounds (Table 1).

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Table 1. Participant Demographics.

https://doi.org/10.1371/journal.pone.0345596.t001

Descriptive ratings of dental attractiveness

The medium-size mirror had the highest mean attractiveness score (mean = 7.675, 95% CI: 7.327 to 8.023), followed by the full-length mirror (mean = 7.241, 95% CI: 6.781 to 7.701), and the small-size mirror (mean = 7.072, 95% CI: 6.620 to 7.524). Lower scores were observed for the pocket-size mirror with magnification (mean = 5.494, 95% CI: 4.979 to 6.009) and the handheld tooth-shaped mirror (mean = 5.747, 95% CI: 5.249 to 6.244) (Table 2).

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Table 2. Descriptive Statistics and Repeated Measures ANOVA Results for Dental Attractiveness Scores by Mirror Type and Digital Reflection.

https://doi.org/10.1371/journal.pone.0345596.t002

Comparison of mirror types and digital reflections

The repeated measures ANOVA revealed a statistically significant difference in perceived dental attractiveness scores across the different mirror types and digital reflection methods (Table 3), F(4.620, 378.833) = 15.570, p < 0.001.

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Table 3. Post Hoc Pairwise Comparisons of Mirror Types and Digital Reflection on Dental Attractiveness Scores (Bonferroni Adjusted).

https://doi.org/10.1371/journal.pone.0345596.t003

Post hoc Bonferroni-adjusted pairwise comparisons showed that the Medium-size Mirror received significantly higher attractiveness ratings than the Pocket-size Mirror (Standard) (mean difference = 0.831, 95% CI: 0.154 to 1.509, p = 0.005). The Pocket-size Mirror (Standard) was also rated significantly higher than the Pocket-size Mirror (Magnification) (mean difference = 1.349, 95% CI: 0.459 to 2.240, p < 0.001). In addition, the Pocket-size Mirror (Magnification) and the Handheld Tooth-shaped Mirror were consistently rated significantly lower than the Full-length Mirror, Medium-size Mirror, Small-size Mirror, and Smartphone Front-facing Camera (all p < 0.05). The Smartphone Front-facing Camera received significantly higher ratings than both the Pocket-size Mirror (Magnification) (mean difference = 1.325, 95% CI: 0.283 to 2.368, p = 0.003) and the Handheld Tooth-shaped Mirror (mean difference = 1.072, 95% CI: 0.102 to 2.042, p = 0.018).

In contrast, no statistically significant differences were observed between the Full-length Mirror, Small-size Mirror, and Pocket-size Mirror (Standard) (all p > 0.95). Similarly, the Smartphone Front-facing Camera did not differ significantly from the Full-length Mirror, Medium-size Mirror, Small-size Mirror, or Pocket-size Mirror (Standard) (all p > 0.05). No significant differences were identified between the Small-size Mirror and the Medium-size Mirror (p = 0.340), or between several other mirror combinations where confidence intervals crossed zero, indicating comparable perceptions of dental attractiveness across these devices.

Intra-rater reliability

Overall, poor intra-rater reliability was observed for most reflective devices (Table 4). However, the handheld tooth-shaped mirror and the medium-size mirror demonstrated moderate agreement, with intraclass correlation coefficients of 0.633 and 0.590, respectively.

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Table 4. Intra-Rater Reliability of Dental Attractiveness Scores by Mirror Type and Digital Reflection.

https://doi.org/10.1371/journal.pone.0345596.t004

Summary of the results

This study demonstrated that perceived dental attractiveness varied according to the type of reflective device used, with a significant overall effect of viewing modality observed in the repeated measures ANOVA. When mirror size was considered, no significant differences were found among the Full-length, Medium-size, Small-size, and Pocket-size Mirrors (Standard), indicating that mirror size alone did not substantially influence perceived dental attractiveness. Although the Medium-size Mirror achieved the highest mean attractiveness score, this difference was not statistically significant compared with the other non-magnified mirrors.

In contrast, magnification had a clear effect on perception. The Pocket-size Mirror with magnification was consistently rated significantly lower than the Pocket-size Mirror (Standard) and all other non-magnified devices, suggesting that magnification negatively influenced perceived dental attractiveness.

Mirror shape also appeared to influence perception. The Handheld Tooth-shaped Mirror, which differs from the rectangular or square mirrors used in the other devices, received significantly lower ratings compared with most other reflective devices. This finding indicates that unconventional mirror geometry may adversely affect self-perception of dental attractiveness.

When comparing digital and non-digital reflections, the Smartphone Front-facing Camera showed no significant differences in perceived dental attractiveness compared with non-magnified physical mirrors, suggesting that digital reflection provides a broadly comparable perception of dental attractiveness.

Intra-rater reliability was generally poor across most devices, with only the Medium-size Mirror and the Handheld Tooth-shaped Mirror demonstrating moderate agreement. The remaining devices showed poor reliability, indicating substantial variability in repeated self-assessments regardless of mirror size or modality.

Interpretation

The absence of significant differences among the full-length, medium-size, small-size, and standard pocket mirrors suggests that mirror size alone does not substantially influence perceived dental attractiveness. One possible explanation is that the visual geometry and proportions of the dentition remain consistent across different mirror sizes [3]. Although the extent of surrounding facial context varies, this does not appear to meaningfully affect dental-focused self-assessment. It is likely that participants directed their visual attention primarily towards their teeth rather than the broader facial appearance, resulting in comparable ratings across these mirror sizes.

In contrast, magnification emerged as an influential factor. Despite having a similar physical size to the standard pocket mirror, the magnified mirror consistently received lower ratings. This suggests that increased visual detail, rather than mirror size per se, may amplify perceived imperfections and negatively affect self-perception.

Mirror shape also appeared to influence perception. The handheld tooth-shaped mirror, which differs in geometry from conventional rectangular or square mirrors, was rated significantly lower than most other devices. While the precise mechanism was not measured, the unusual and asymmetric shape may provide a less intuitive visual reference, potentially interfering with proportional interpretation of the dentition. This interpretation remains hypothetical and should be explored further in future work.

Digital reflection using the smartphone front-facing camera did not differ significantly from non-magnified physical mirrors, despite differences in image processing, colour rendering, and screen-based display. This suggests that, at a group level, digital reflections may convey a perception of dental attractiveness comparable to that of conventional mirrors, even when the image is not mirror-reversed as in photographs. Software enhancement or colour tone variation alone does not appear sufficient to systematically alter self-perception in this context.

A key finding of this study was the generally poor intra-rater reliability observed across most reflective devices, including mirrors of varying sizes, magnified mirrors, and the digital reflection. This indicates that reflective-based self-assessment of dental attractiveness is inherently unstable over time, even when dental features remain unchanged. Although the Medium-size Mirror and the Handheld Tooth-shaped Mirror demonstrated moderate agreement, overall reliability remained limited. These findings suggest that reflective devices—whether optical or digital—may not be ideal tools for repeated or longitudinal assessment of dental attractiveness.

Comparison to other studies

To date, no published studies have directly examined the effect of different mirror types or digital reflection devices on self-perceived dental attractiveness. However, relevant insights can be drawn from studies in related fields, where the influence of image familiarity and reflection format on self-evaluation has been explored.

Al-Bitar et al. (2023) [19] demonstrated that individuals tend to prefer their mirror-reversed facial images over true, non-reversed photographs, a phenomenon attributed to perceptual familiarity. In contrast, observers evaluating others tended to prefer the true image. The authors highlighted how even minor facial asymmetries may appear exaggerated when image orientation is altered, leading to increased dissatisfaction when individuals are exposed to unfamiliar representations of themselves. These findings are relevant to the present study, as certain reflective devices—such as magnified pocket mirrors or tooth-shaped mirrors—may present dental features in a manner that participants are unaccustomed to, potentially contributing to lower attractiveness ratings.

In dentistry, Babeer et al. (2021) [23] showed that small, controlled alterations in the vertical position of anterior teeth had a marked effect on perceived smile attractiveness. Their findings illustrate that subtle visual changes can significantly influence aesthetic judgements. While that study focused on anatomical modifications rather than reflective devices, it supports the broader notion that increased visibility of detail—such as that introduced by magnification—may heighten sensitivity to minor features and negatively affect aesthetic perception.

Generalisability

The findings of this study are applicable to the specific mirror types and smartphone model evaluated. The mirrors selected were based on those most commonly used in the authors’ faculty dental clinic, and results may differ with mirrors of other sizes, shapes, or reflective properties that were not tested.

Similarly, mirror shape may affect perception. This study examined predominantly rectangular and square mirrors, along with a tooth-shaped handheld mirror. Other commonly available shapes, such as circular or oval mirrors, were not assessed and may produce different perceptual effects due to variations in visual framing and symmetry.

The generalisability of findings related to digital reflection is also limited by the smartphone model used [15]. The front-facing camera employed a wide-angle lens equivalent to 23 mm, which is known to introduce geometric distortion and may alter perceived dental proportions and facial features [16,17]. Different smartphones use lenses with varying focal lengths and optical characteristics, which may lead to different self-assessment outcomes. In addition, smartphone images undergo digital processing, including adjustments to contrast, sharpness, brightness, and, in some cases, facial enhancement. These processing algorithms vary across manufacturers and software versions.

The sampling strategy further limits generalisability. Although both students and staff were included, the majority of participants were undergraduate dental students from a dental faculty, a group likely to have heightened awareness of dental aesthetics and increased sensitivity to subtle visual differences. This professional exposure may have amplified perceptual variations between reflective devices. Moreover, the sample was predominantly female, which may have introduced additional bias, as females have been reported to be more attentive to facial and dental appearance than males [24].

Limitations

Several methodological limitations should be considered when interpreting the findings of this study. First, a self-selected viewing distance was permitted for certain reflective devices, particularly handheld mirrors and the smartphone front-facing camera. While this approach improved visual clarity and more closely reflected real-world usage, it reduced experimental standardisation and may have introduced inter-participant variability. Differences in viewing distance and the amount of time spent assessing each device may have influenced perceived dental attractiveness.

Second, the assessment relied on a single quantitative outcome—participants’ ratings of dental attractiveness—without incorporating qualitative feedback. As a result, the study was unable to capture participants’ subjective reasons for rating differences between reflective devices, such as perceived distortion, clarity, comfort, or familiarity. Incorporating qualitative components in future research could provide deeper insight into how and why different reflective devices influence self-perception.

A further major limitation was the predominantly poor intra-rater reliability observed across most devices. Intra-rater reliability was assessed in a relatively small subsample, which may have limited the precision of the ICC estimates and reduced the ability to detect stable agreement. In addition, the use of a 10-point visual analogue scale may have contributed to variability, as such scales depend heavily on subjective judgement and may be interpreted inconsistently across repeated assessments. Fluctuations in attention, mood, or visual focus may also have influenced repeated self-ratings of dental attractiveness.

Given the observed poor reliability, the findings should be interpreted primarily in terms of relative differences between reflective devices at a group level rather than absolute numerical scores. The results highlight the need for further investigation of the reliability of reflection-based self-assessment using larger sample sizes, repeated assessments, and more anchored or categorical rating systems.

Clinical implication

The findings highlight several practical considerations for clinicians assessing patient-perceived dental attractiveness. For routine evaluations of overall dental attractiveness, mirrors of standard sizes—full-length, medium, or small—can be used interchangeably, as no significant differences in perceived attractiveness were observed between these devices. Among these, the medium-size mirror tended to receive the highest mean ratings, suggesting it may provide a slightly more favourable view, although all standard mirrors remain acceptable for clinical use.

Mirrors with magnification are better suited for assessing fine procedural details, such as tooth surface characteristics or alignment corrections, but may lead to lower perceived dental attractiveness compared with standard mirrors, as magnification can exaggerate minor imperfections. Tooth-shaped mirrors should generally be avoided for aesthetic self-assessment, given their restricted and asymmetric field of view, which may negatively influence patient perception.

Digital reflections via smartphone front-facing cameras can be used as a supplementary tool, reflecting how patients commonly view themselves. However, due to potential image distortion, software enhancements, and colour differences, clinicians should interpret digital assessments cautiously. Furthermore, repeated self-assessment using reflective devices—whether mirrors or digital screens—may be unreliable due to low intra-rater consistency, and should not be relied upon to track changes in dental attractiveness over time.