Many scientific studies have investigated smile aesthetics, often using digitally altered images and photographs for evaluation [3, 14, 16, 20,21,22,23]. The present study evaluated the perception of facial, dental, and smile aesthetic variations among dentistry students and examined whether these perceptions differed based on education level, gender, and the presence of a dentist in the family. In the present study, variations in the perception of aesthetic criteria among students were observed, indicating that not all criteria were evaluated similarly. Therefore, the first null hypothesis (H1) was rejected. Regarding the second null hypothesis (H2), gender influenced the perception of lower facial height, and significant differences were found between preclinical and clinical students in their evaluation of midline diastema, occlusal plane inclination, clinical crown length, and various dental modifications. However, the presence of a dentist in the family had no significant effect. Accordingly, the second hypothesis was partially rejected.
The attractiveness of the face directly influences the appeal of a smile. Aesthetic evaluations depend not only on dental features but also on facial aesthetics. However, the use of a full-face smile as a gold standard for dentofacial aesthetic analyses remains debated. It is important to consider that factors such as soft tissue, buccal corridors, and gingival display, along with intraoral features, also contribute to aesthetic appeal [24]. Intraoral images allow observers to focus more on dental elements (e.g., smile, gingiva, color, and dental components) by reducing distractions from other aspects [21]. Therefore, this study employed both full-face and intraoral photographs to assess facial and smile aesthetics.
Kovačić et al. evaluated how education level and gender influenced dental students’ perceptions of various aesthetic criteria, including tooth shade. They found that clinical students were more critical and rated modifications, particularly lighter tooth shades, with lower scores compared to preclinical students [16]. In present study, however, no manipulations were made to tooth color to ensure the standardization of the photographs and to allow for the evaluation of only the specified criteria. Aesthetic assessments were conducted using standardized reference photographs of a single model, with variables such as tooth color kept constant. This approach ensured that the potential impact of color changes on aesthetic perception was eliminated, providing a controlled basis for evaluating other aesthetic parameters.
In the literature, the impact of gender on dentofacial aesthetic perception has been reported to be largely culture-dependent. Abu Alhaija et al. also found that gender influences aesthetic perception, with women being more sensitive to gingival display and midline diastema than men [25]. However, Moore et al. and Ioi et al. reported that men and women assess smile attractiveness similar manner [26, 27]. In a literature review evaluating dental students’ perceptions of dental aesthetics, it was reported that female students tend to have a more critical self-perception regarding the characteristics of an ideal smile. Furthermore, it is important to consider that dental students’ aesthetic perceptions are also influenced by their level of education and cultural factors [9].
In this study, a statistically significant gender difference was observed only in the lower facial height criterion, with female students demonstrating a higher aesthetic perception compared to their male counterparts (p = 0.014). The majority of participating dentistry students evaluated the reference photo as the most aesthetically pleasing and acceptable face. Among the evaluated photos, those with increased lower facial height received the lowest aesthetic scores. Additionally, lower facial height was one of the criteria where students exhibited the highest aesthetic perception. There are very few studies in the literature that examine how dentistry students evaluate lower facial height. In the study by Alhammadi et al., the majority of students considered slightly reduced, slightly increased, or average vertical facial proportions as the most aesthetically pleasing, which differs from the findings of the present study [3]. Unlike Alhammadi et al., both extreme variations—particularly increased lower facial height—were perceived less favorably, while the unaltered reference image was most preferred. These differences may be attributed to cultural, demographic, or methodological variations between the two studies.
In this study, the overall aesthetic perception among dental students was found to be high (82.63 ± 8.5). This value was higher than those reported by Omar and Tai [14] and similar to the findings of Alhammadi et al. [3]. The lowest perception score was observed for the buccal corridor, followed by facial symmetry. Less than 25% of dental students (12.3% of preclinical and 15% of clinical students, score 5, Table 7) correctly identified the standards for the buccal corridor. Detailed analysis of the results revealed that a reduced and narrow buccal corridor was perceived as more aesthetic in this study. Despite the challenges faced by the students, the reference photograph for this criterion was rated as the least aesthetic by only 0.8% of preclinical students and 2.1% of clinical students (score 1, Table 7). Similarly, a previous survey-based study also identified the buccal corridor as the lowest-rated aesthetic evaluation criterion [3]. Another study conducted in Japan reported that dental students and orthodontists showed similar perceptions of the buccal corridor [27]. Although our study did not include orthodontists, this literature finding highlights how the perception of this feature may vary across different educational or cultural contexts. The fact that Japanese dental students evaluated the buccal corridor similarly to orthodontists may be attributed to the superior quality of undergraduate dental education in Japan. The buccal corridor has been reported as a challenging criterion to assess, even for dental specialists [28], and it plays a significant role in overall smile aesthetics [29]. Furthermore, the lack of a significant difference between clinical and preclinical students in evaluating the buccal corridor highlights the need for improved education and training on this complex aesthetic parameter.
The second lowest aesthetic perception criterion, facial symmetry, was correctly identified by less than half of the students. Facial symmetry, defined as the balanced alignment of facial features relative to the mid-sagittal plane, is a fundamental aspect of facial beauty and attractiveness [30]. Recognizing facial symmetry is crucial for clinicians in diagnosis and treatment planning, as well as for patients in achieving desired aesthetic outcomes. In our study, 22.5% of preclinical students and 25.8% of clinical students (Table 7) perceived the reference photograph as aesthetic, with no significant difference between the two groups. Additionally, this criterion was not influenced by gender. Notably, facial symmetry was the criterion with the highest rate of reference image being rated as the least esthetic among clinical students, at 7.10% (Table 11), indicating that some participants may have misinterpreted the ideal image in this category. Although one study reported that the vast majority of dental students could detect facial asymmetries up to 2 mm [3], another study suggested that deviations of up to 5 mm may still be perceived as within the normal range [31]. In the present study, facial asymmetry of up to 4 mm was also perceived as aesthetic. Discrepancies between studies may stem from methodological variations and differences in evaluator populations.
The facial profile, often used by orthodontists to clinically assess facial harmony, is a significant factor in determining facial attractiveness [3]. In this study, students found straight, slightly convex, and then concave profiles to be the most aesthetic, in that order. Among the participants, 38.3% of preclinical students and 41.7% of clinical students (Table 7) rated the reference photograph as aesthetic, with no significant difference between the groups. Similar findings have been reported in previous studies, where straight and slightly convex profiles were generally perceived as more attractive [32]. In the study by Torul et al., no significant difference was found between preclinical and clinical students; however, unlike our findings, they identified a difference between male and female students [33].
The harmony between clinical crown length and gingival display during a smile plays a critical role in aesthetics and holds significant clinical importance in smile design planning. Excessive gingival display, commonly referred to as a gummy smile (> 3 mm), is often considered unaesthetic [34]. In this study, the gingival display criterion was among the parameters where dental students demonstrated a high level of aesthetic perception. Notably, more than 75% of students accurately perceived the reference photograph as aesthetic, with no significant differences between preclinical and clinical students or between male and female participants.
Consistent with these findings, it was reported that the majority of dental students, regardless of gender, were able to recognize normal gingival display or an increase of up to 1 mm [3]. Ayyildiz et al. reported significant differences between preclinical and clinical students in their evaluation of gingival smiles as part of facial aesthetics [34]. Similarly, Čalušić Šarac et al. found that expert dentists, doctors, and clinical dental students assessed gingival asymmetries more critically, noticing even minor variations, whereas preclinical students and laypeople could only detect gingival asymmetries of 2 mm or more [35]. The consistent and high level of perception observed for this criterion may suggest that the dental curriculum effectively promotes awareness of gingival aesthetics.
In the present study, a midline deviation of up to 1 mm was perceived by more than 75% of dental students. While 27.7% of preclinical students and 44.2% of clinical students rated the reference photograph as the most aesthetic, this difference was not statistically significant (Table 7). Consistent with the findings of this study, a previous study also reported that more than 75% of students perceived midline deviations of up to 1 mm as acceptable [3]. However, in that study, it was noted that this criterion was more accurately identified by male students, differing from the present findings [3]. In another study, it was reported that midline deviations of 2 mm or less were considered acceptable by females, whereas deviations of 3 mm or more were deemed acceptable by males [36]. Vertically, the facial midline is determined by two anatomical reference points: the nasion and the philtrum. Aesthetically, the dental midline is expected to align with the facial midline. According to the literature, the average acceptable deviation is generally reported to be 2.38 mm [37]. However, Rodrigues et al. found no difference in the perception of an ideal smile and a midline deviation of up to 3 mm [7]. Tahir et al. reported that dental professionals were able to detect midline deviations exceeding 2mm, whereas laypersons did not notice deviations up to 4 mm [22]. In this study, detailed analysis of the data revealed that more than half of the students identified a 4 mm deviation as the least aesthetically acceptable.
In this study, clinical students exhibited significantly higher aesthetic perception than preclinical students in detecting changes in Q7 midline diastema, Q8 occlusal plane inclination, Q9 clinical crown length, and Q10 different dental modifications, with statistically significant differences. Similar to the present study, previous research has reported that clinical students are more successful than preclinical students in detecting minimal changes and that aesthetic awareness increases with higher levels of education [3, 38]. A previous study conducted among dentists, dental students, and laypersons demonstrated the impact of education on aesthetic perception. While a direct comparison between preclinical and clinical students was not made, the findings highlighted the influence of educational level on aesthetic awareness [39]. A review study indicated that the examined studies consistently reported an improvement in students’ ability to analyze aesthetics as they gain more knowledge and clinical experience [9]. This may be due to the fact that students in their early years primarily focus on general medical courses, and dental courses are limited during the early years of their curriculum. In contrast, clinical dental students in higher years are exposed to more dental courses and clinical practice; therefore, they may have become more critical of small deviations from an ideal smile.
Among the participants, 65.6% of preclinical students and 82.5% of clinical students rated the reference photograph for the midline diastema criterion as the most aesthetic. This criterion was identified as having the highest aesthetic perception in our study. Noureddine et al. evaluated both multiple diastemas of the anterior teeth and midline diastema, concluding that the midline diastema was perceived as the least aesthetic [40]. It has been suggested that its negative impact is influenced by the width of the diastema [40]. In the study by Kovacic et al., while clinical students assigned lower scores to all modified photographs compared to preclinical students, the lowest ratings in both groups were given to the lightest shades and the midline diastema [16]. In this aspect, the related studies were similar to the present study.
For the occlusal plane inclination criterion, the reference photograph was rated as the most aesthetic by 53.8% of preclinical students and 67.9% of clinical students, with a statistically significant difference between the groups. In the present study, the occlusal plane inclination was identified as the second-highest criterion in terms of aesthetic perception. Revilla-León et al. determined that occlusal plane inclinations of 0 and 1 degree showed no perceptible differences in smile evaluation among dentists, dental students, and laypersons [41]. In their study, the dentist and dental student groups gradually assigned lower scores as the inclination increased, while laypersons only gave lower scores when the occlusal plane inclination reached 3 degrees or more [41]. In the current study, almost 45% of the students rated the 4 mm inclination as the least aesthetic.
In this study, the crown length of the maxillary right central incisor was altered in increments of 0.5 mm, up to 2 mm, for each reference photograph. The reference photograph was rated as the most aesthetic by 37.5% of preclinical students and 52.5% of clinical students, with a statistically significant difference between the groups. In a study, the perceptions of dental professionals and laypersons regarding bilateral crown length alterations were evaluated, and the threshold for unattractiveness was reported as 1.0 mm for orthodontists, 1.5 mm for general dentists, and 2.0 mm for laypersons [13]. In the current study, approximately 35% of the students scored a reduction of up to 2 mm in the right central incisor as the least aesthetic appearance. Interestingly, among all the esthetic parameters evaluated, clinical crown length was the only criterion for which preclinical students most frequently identified the reference image as the least esthetic, with 4% rating it as the least attractive (Table 11). Overall, the rate at which preclinical students rated the reference image as the least esthetic was low for other criteria. This finding suggests that crown length discrepancies may be a more ambiguous or unfamiliar esthetic factor for students at earlier stages of dental education, likely due to their limited clinical experience. It also indicates that even mild, unilateral reductions in crown lengthmay not always be perceived as esthetically unfavorable by inexperienced students.
In the current study, the final question of the survey focused on various dental modifications. Modifications included the elongation of both maxillary lateral incisors to match the central incisors, slope alteration of the distal edges of maxillary lateral incisors, extension of both canines beyond the length of the central incisors, and shortening of the lateral incisors while extending the canines. The modification that students found the least aesthetic was the shortening of the lateral incisors while extending the canines, with approximately 35% of students selecting this option. Schwefer et al. also found in their study that the condition where the canines were longer than the central incisors was rated as the least aesthetic [21]. This finding is consistent with the results of our study. The reference photograph was rated as the most aesthetic by 31.6% of preclinical students and 51.7% of clinical students, with a statistically significant difference between the groups. Studies specifically assessing the perception of various dental modifications among preclinical and clinical students are limited in the existing literature. Kovacic et al. conducted a study evaluating the perception of various dental modifications [16]. Similar to our findings, they observed differences in the evaluation of these dental modifications between preclinical and clinical students. Clinical students were more proficient in evaluating dental modifications [16]. This question aimed to compare various dental modifications ranging from the most to the least esthetic, as perceived by students. These findings support the clinical relevance of assessing combined dental modifications in a single visual, as clear preference patterns still emerged.
In this study, having a dentist in the family did not have a significant impact on the aesthetic perception of dental students. The targeted academic education level, however, was more effective in acquiring the knowledge and skills necessary to notice changes in smile aesthetics criteria.
It is important to address the few limitations of this study. It was observed that the majority of students participating in this study were female. This imbalance reflects the demographic structure of the universities involved in the study, which have a higher enrollment of female students. Factors such as students’ socioeconomic status, the influence of social media, and fashion trends were not included in this study. Furthermore, the researchers focused on specific smile aesthetics criteria that they deemed significant in the perception of an aesthetically pleasing smile. Although the survey was completed online, the images were presented in a classroom setting to ensure standardization and equal visual conditions. However, this setting may have introduced response biases. Social desirability bias and the Hawthorne effect [42] could have influenced students’ answers due to the presence of peers and the structured environment. Future studies should address a broader range of variables and include analyses involving male and female subjects from diverse ethnic backgrounds. Additionally, future studies should consider including participants from different universities and regions to better reflect the influence of cultural and geographic diversity on aesthetic perception.
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