Smile esthetics from odontology students' perspectives
ABSTRACT
Objectives:
To analyze the perception of smile esthetics and its alterations in dental degree students; to determine whether there are differences in that perception among students in different study years on those courses and between genders; and to determine if the circumstance of having received prior orthodontic treatment could influence that perception.
Material and Methods:
Students (n = 192) in different study years of the dental degree course at the University of Valencia, Spain, analyzed two photographs of a patient in which, by means of computer software, midline diastema, upper and lower midlines, crown length of the maxillary right central incisor, occlusal cant, and “gummy” smile were altered. Students assessed the photographs on a scale from 1 to 10. Statistical analyses for assessing each group's level of perception were carried out.
Results:
After checking the validity of the study, it was observed that the students' ability to detect alterations in smile esthetics did not improve over their degree courses, given that the differences do not present a linear development. There were no differences between genders and between those who had or had not undergone an orthodontic treatment.
Conclusions:
There are no statistically significant differences between the results of students in different study years or between genders. The circumstance of having undergone prior orthodontic treatment is not a determining factor in the ability to perceive such anomalies.
INTRODUCTION
Esthetics is a quality of enormous importance in our society. Sometimes we, as orthodontists, forget that facial attractiveness is a factor of interest to everyone and that the ultimate source of esthetic values must be the general public and not what orthodontists may believe.1 It is easy to understand how severe malocclusions negatively affect self-esteem; however, the effect of lesser esthetic problems varies depending on the person and on social and cultural factors.2 It is, therefore, essential to control the ways orthodontic treatments affect dentofacial esthetics, which is possible if we understand the principles that govern the balance between teeth and oral soft tissues when we smile and what constitutes a symmetrical smile with appropriate proportions between teeth, gums, and lips.1,3–10
Studies in the literature have analyzed the perception of smile esthetics in non–dental professionals.1,4,7,8,10–17 As for the perception of smile esthetics in dentistry students and future dental professionals, we only found one recent study in the literature9 that compared dentistry students with a group of orthodontists. Moreover, we did not find any study on Spanish students. These were the reasons why we decided to undertake a study on dentistry degree students at the University of Valencia, Spain.
The aims of the study were to (1) analyze the perception of smile esthetics and alterations in dentistry degree students, (2) determine whether there are differences in that perception among students in different study years, (3) identify whether there are differences in that perception between students of different genders, and (4) determine whether the circumstance of having undergone prior orthodontic treatment influenced the perception of smile and its alterations.
MATERIAL AND METHODS
A cross-sectional descriptive study was carried out and approved by the Ethics Committee of research into Humans of the Experimental Research Ethics Committee of the University of Valencia. Two hundred ten dentistry degree students at the University of Valencia, Spain, were randomly selected. The inclusion criteria were that they were present when the sample was gathered and that they correctly filled in the questionnaires given to them. Of the 210 students, 192 met the inclusion criteria and formed the sample: 112 women and 80 men. Of these, 121 had previously undergone orthodontic treatment. The mean age was 22.2 years (range = 18–36 years old). The population to be studied was selected by means of nonconsecutive population sampling (chance does not arise in this selection: volunteers who fulfilled the inclusion criteria were chosen and recruited until we reached the number required). The distribution per study year was 39 first-year, 46 second-year, 30 third-year, 39 fourth-year, and 38 fifth-year students.
Each student filled in a questionnaire with first name and surname, age, study year, and whether or not they had undergone orthodontic treatment. In addition, each student signed a document stating that he or she understood that the study officially complied with the law on data protection.
Method
Two photographs were used: the first a frontal, intraoral view, allowed subjects to see the teeth and soft tissues; the second a frontal extraoral smile view, in which we included the nose and chin of a female patient (to eliminate possible confusion variables) treated in the master of the orthodontics teaching unit of the University of Valencia. The first intraoral photograph had a clinically acceptable occlusion so that the digital alterations could be made from a reference considered normal.
Both photographs were modified using the image manipulation computer program Gimp (GNU Image Manipulation Program) version 2.8.2 for Windows (this software is free from the University of Berkeley). We thus obtained six groups of photographs in which the following were gradually modified:
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Group 1. Modification of midline diastema (Figure 1A through D)
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Group 2. Modification of upper and lower midline (Figure 2A through H)
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Group 3. Modification of crown length of the maxillary right central incisor (Figure 3A through D)
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Group 4. Modification of occlusal cant (Figure 4A through D)
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Group 5. Modification of “gummy” smile (Figure 5A through D)
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Group 6. Repeated photographs (Figure 2B and F, 3B, 5B)
Citation: The Angle Orthodontist 84, 2; 10.2319/032013-226.1
Citation: The Angle Orthodontist 84, 2; 10.2319/032013-226.1
Citation: The Angle Orthodontist 84, 2; 10.2319/032013-226.1
Citation: The Angle Orthodontist 84, 2; 10.2319/032013-226.1
Citation: The Angle Orthodontist 84, 2; 10.2319/032013-226.1
Group 6 was made up of four photographs, called standardized photographs, that had already appeared in the previous groups; these photographs allowed us to check the validity of the study.
A single observer showed the photographs to different students for 3 seconds each. The students were not allowed to have a second look or to compare one photograph with the other. They had to give a score for each photograph ranging from 1 to 10 (1 = little esthetic value and 10 = high esthetic value). The photographs were ordered consecutively—not randomly—from the original to the most altered.
Data Analysis
The statistical study was carried out using the computer software program SPSS version 20.0.0 for Windows (SPSS, Chicago, Ill). To compare the reliability or validity of the study, two tests were undertaken. First, the measurement of reliability or weighted Kappa for the four photographs of the repeated series was calculated (with a confidence interval of 95%) so we could interpret the similarity of the two results from one same photograph for a single person. Second, the tests on related samples, the results of which indicated that the reliability of the study depended only on some study courses, were undertaken. After checking that the study was valid, we undertook the normality and homogeneity of variances tests and chose analysis of variance (ANOVA) to analyze the results from each of the groups.
RESULTS
Table 1 shows means and standard deviations (SDs) for all the photographs depending on dentistry year (first through fifth). Table 2, shows means and SDs for prior orthodontic treatment.
Differences in Perception of Smile and Its Alteration Depending on Study Year (Age)
Before evaluating the differences per study year, we analyzed whether differences existed by age, as total homogeneity of age did not exist within each study year. We used a regression line to determine that this has no influence. Afterward, we analyzed the study-year effect as the only factor in the evaluation of the photographs, using ANOVA analysis for all the groups of photographs, except group 3, where we used Welch analysis, as there was no homogeneity of variances. We observed that statistically significant differences existed in some series of photographs. By analyzing the standardized group of photographs, we saw that differences existed per study year among the photographs 6B and 6C (Table 3). It should be remembered that if differences exist in the standardized photographs, the conclusion could be applied to the nonstandardized photographs.
So as to see the differences between each study year, we used Tukey analysis, condensed into two homogeneous groups. The study-year factor was statistically significant but the Tukey analysis showed that the difference was nor linear; there only appeared to be differences between some study years, and the order of the same varied depending on the photograph studied.
Differences in Perception of Smile and Its Alterations Depending on Gender
With regard to differences per gender, we found no statistically significant differences by ANOVA or by including the interaction per study year and gender.
Differences in Perception of Smile and Its Alterations Depending on Prior Orthodontic Treatment
The statistical tests to assess the effect of prior orthodontic treatment showed some significant results, at least when studied as a whole. To analyze this in more depth, we carried out several tests of the interobserver effects in those photographs for which we had obtained statistically significant results on applying the ANOVA test with the study year as factor; this time we introduced the prior orthodontic treatment effect as an interaction. Only in one case did we obtain statistically significant differences (Table 4). Students in their second and third study year who had not undergone prior orthodontic treatment were able to determine slight alterations in smile esthetics. There were no differences in any other photography.
DISCUSSION
First, and before analyzing the results, we should take into consideration that in our study, as in most of those we reviewed, the alterations of teeth and soft tissues were undertaken using an image-manipulation computer program and did not truly represent changes in the mouth of a real patient. However, similar to Kokich et al.,1 we agree that if we undertake modifications using the same image and alter a single variable in each one, this is a reliable method for evaluating the esthetic perception of smile. Reliability measurement or weighted Kappa was performed for the four photographs of the repeated series so we could interpret the similarity of the two results from a single photograph for the same individual. In this instance, students in lower study years provided different scores for the same photograph.
Differences in Perception of Smile and Its Alterations Depending on Study Year (Age)
Taking the study year factor as independent variable, we analyzed all the characteristics of the smile separately. The results showed statistically significant differences, although the correlation was not linear between the different study years. This clearly showed that the ability to determine alterations in the smile does not improve as a student moves on to higher study years.
Group 1: Modification of Midline Diastema
In the case of midline diastema, all students negatively evaluated its presence. Our results contrast with those of Kokich et al.,1 where no group negatively evaluated the presence of the midline diastema when it was small.
Group 2: Modification of Upper Midline
The deviation from the upper midline was detected by the students from 1 mm on, and although it was not completely linear, it was observed that the students most likely to detect it were in the higher study years.
Group 3: Modification of Lower Midline
On the other hand, deviation from the lower midline was detected by the students from 0.5 mm on, results that are in line with the study undertaken by Johnston et al.,14 but differ from the results of Pinho et al.,4 who showed that laypeople were not able to detect alterations in the deviation from the midline.
Group 4: Modification of Crown Length
The results obtained with regard to evaluating the modification of the gingival margin were detected from 2 mm on by students in all study years, results similar to those found by Kokich et al.1 and Pinho et al.4
Group 5: Modification of Occlusal Cant
As for alterations of the occlusal plane, the students in higher study years (from third year on) detected this more easily. Our results concur with those of Geron and Atalia7 but differ with those of McLeod et al.10
Group 6: Modification of Gummy Smile
In terms of gingival smile analysis, all students evaluated this as not being esthetically pleasing when gingival smile exposure was 3 mm or more. Some students define it as not very pleasant from 2 mm on, results that coincide with those of Kokich et al., Hunt et al.,8 and Ioi et al.,9 suggesting that an acceptable gingival smile would correspond to a gum exposure of up to 2 mm.
Differences in Perception of Smile and Its Alterations Depending on Gender
With regard to the gender variable, our analysis showed no significant differences in the ability to perceive anomalies of smile esthetics between genders. This was in line with some studies9,15 in contrast to other studies, such as those of Kokich et al.1 and Flores-Mir et al.12
Differences in Perception of Smile and Its Alterations Depending on Prior Orthodontic Treatment
On analyzing prior orthodontic treatment as the related factor, we saw that those who had undergone prior treatment had no greater skill in analyzing smile esthetics, results that are in line with those of previous studies.8,9
Overall Findings
Finally, we should take into account that there is a subjective component to esthetics, in that interpersonal variations make it impossible to interpret the results obtained in a general way. On the other hand, this study clearly shows that students on a dentistry degree course have not acquired the ability to determine small alterations in smile esthetics during their degree studies and that it is possibly in postgraduate dentistry studies where they acquire this skill.
Studies in the literature have been conducted solely among laypeople, dentists, orthodontists, or surgeons but not among dental students. The only study we found that analyzes the perception of dental students is the study by Ioi et al.,9 which compared a group of students in the last year of dentistry studies with orthodontists, but not among students throughout their college career. Our study demonstrates how a dental student does not acquire sufficient skill in discriminating differences in dental esthetics during dentistry studies, and it is not until studies are over that this visual esthetics skill is gained. This esthetic skill is mostly acquired during the years when a master's in orthodontics is being undertaken. We, therefore, believe our study would confirm the results of other studies demonstrating differences between general dentists and orthodontists.
CONCLUSIONS
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The ability of students in the dental degree course of the University of Valencia to detect alterations in smile esthetics does not improve throughout their degree studies; however, despite finding statistically significant differences between different study years, these did not present a linear development.
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The gender of students in a dental degree course is not a determining factor in the ability to perceive esthetic anomalies in a smile.
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Whether a dentistry student has undergone prior orthodontic treatment is not a determining factor in the ability to perceive such esthetic anomalies in a smile.
Midline diastema was created incrementally between maxillary central incisors. It was widened progressively in 0.5-mm increments. (A) Control. (B) 0.5 mm. (C) 1 mm. (D) 1.5 mm.
Upper and lower midline were modified progressively in 0.5-mm right increments. (A) Control. (B) Upper midline 0.5 mm. (C) Upper midline 1 mm. (D) Upper midline 1.5 mm. (E) Control. (F) Lower midline 0.5 mm. (G) Lower midline 1 mm. (H) Lower midline 1.5 mm. Reference points for measurements were nose and chin midlines.
Crown was shortened in 0.5-mm or 1-mm increments by adjusting the level of gingival margin of the maxillary right central incisor. (A) Control. (B) 0.5 mm. (C) 1.5 mm. (D) 2 mm. Reference points for measurements were the most superior points on the labial gingival margin of the patient's adjacent central incisor.
Occlusal cant was tilted in increments of 1° right. (A) Control. (B) 1°. (C) 2°. (D) 3°.
Gingiva-to-lip relationship was increased incrementally to produce a gummy smile. (A) Control. (B) 1 mm. (C) 2 mm. (D) 3 mm. Smile was altered by progressively moving the upper lip superiorly to alter the distance from lip to gingival margin.
Contributor Notes