2019, Number 3
Esthetic evaluation of upper incisor inclination
Full text
Language: English/Spanish [Versión en español]
References: 9
Page: 146-151
PDF size: 144.08 Kb.
ABSTRACT
Introduction: Smile esthetics is important for the self-perception of most people but evaluating esthetics can be a subjective matter. Dentistry has established some parameters for a more objective evaluation, based on proportion and symmetry. One of these parameters is upper incisor inclination. Objective: To determine whether upper incisor inclination from a profile view of a smile influences the esthetic perception of 3 groups of raters in the areas of orthodontics, prosthetics, and laypersons. Material and methods: A 30-year-old post-graduate female student was selected. She presented a straight profile, aligned midlines, Class I canine and molar relationship, and normal upper incisor inclination. Her profile smile was modified with seven different incisor angulations. Ninety surveys were done in Mexico City, the order of the pictures was aleatory to avoid bias. The statistical analysis was performed using ANOVA and Fisher's and Tukey's tests. Results: There was a significant statistical difference between the three surveyed groups about the perception of the smile as modified by the inclination of the upper incisors. There was not enough scientific evidence to select one inclination as the best. Conclusions: The surveyed profession determines the esthetic perception of the profile smile according to upper incisor inclination.INTRODUCTION
Physical appearance has a significant impact on the mutual perception between human beings. Smile is known to be one of the main factors for facial esthetics. For many people it is even considered as the most important facial characteristic in a person. According to Van der Geld, P. et al., an attractive smile can have a significant impact on an individual's psychological health, directly affecting her/his self-perception and self-esteem.1
Over the years, esthetic medicine, and particularly esthetic dentistry and orthodontics, have established certain evaluation parameters to rate the smile objectively. There is a difference between properly aligned teeth and beautiful teeth,2 so certain reference factors such as symmetry, golden proportions, smile arch, and upper incisor inclination have been proposed, the latter being the most novel.
On the basis of this parameter, it can be said that for years the orthodontists have maintained that the ideal incisor angle is within the norm, even with a slight buccal inclination.3 Lately, however, new theories hold that a slight lingual inclination might be more favorable in the esthetic perception of a smile.
In the daily consultation of an orthodontist one of the main challenges is not to neglect the esthetic expectations of a patient that is starting a treatment. It is believed that the esthetic criteria of a professional may not agree with those of the laypersons. According to authors such as Kokich et al. and Thomas et al.,4,5 most of the time the patient presents to the dental office looking more for esthetics than for function.
MATERIAL AND METHODS
We selected a 30-year-old female student of the third year of Orthodontics at the National Autonomous University of Mexico (UNAM). She had a straight profile, aligned midlines, and Class I canine and molar relationship. Next, we took radiographs to verify whether she met the necessary skeletal characteristics.
The radiograph examination showed that the student presented a class I skeletal pattern and normal upper incisor inclination according to Ricketts and Jarabak cephalometric analysis. She was offered to participate in the study and signed an informed consent.
Subsequently, several smiling profile photographs were taken with a Nikon camera at a distance of one meter, and the clearest and with the best angle was selected. Then, with the help of an editing program (Adobe Photoshop) seven alterations were made to the photograph in the angulation of the upper incisors (0o, 5o, 10o, 15o, -5o, -10o, -15o) and seven separated images were created, respectively, and printed.
Once the photographs were ready, 90 binders for the survey were assembled, including an instructions sheet, a second sheet where the respondent provided personal data (name, age, and profession), the survey with seven rules representing a 100-mm VAS scale (Visual Analog Scale), with 5 numerical points to score each photograph, and lastly, the photographs. The images were randomly ordered for each respondent so that biases were avoided.
The surveys were conducted in Mexico City for two months. The data obtained were entered into an Excel sheet that allowed us to sort the scores for each photograph and perform the statistical tests.
A one-factor ANOVA statistical test was performed to determine statistically significant differences in the mean of esthetic perception scores within each surveyed group (intra-group). A two-factor ANOVA was performed for the analysis of the interaction between the "profession" and "incisor inclination" variables between groups. Lastly, Fisher's and Tukey's multiple comparison analyses were done to determine the statistically significant differences between respondents' scores in each group in order to know whether there were preferences for a specific incisor inclination. All tests were carried out using Minitab statistical analysis software.
This study had an analytical, comparative, and descriptive design. It comprised a population of specialists in orthodontics, oral rehabilitation, and laypersons. The sample was made up on the one hand of a model chosen for convenience and on the other of a group of non-randomly chosen respondents. The study had two independent variables, namely respondent's profession and incisor inclination, and a dependent variable given by the esthetic perception score.
RESULTS
Two- factor ANOVA (Table 1):
The analysis showed that the inclination of the central incisor had a statistically significant effect on the score or esthetic perception of the smile (p = 0.00). Likewise, the effect of the profession on the score or esthetic perception of the smile was significant (p = 0.00).
The analysis also revealed that the interaction of the two factors was significant for a 5% significance level (p-value = 0.047). The interaction profile showed that the inclination of the central incisor can be perceived differently according to the respondent's profession. For example, non-odontologists (Non-ODs) evaluated both retroclination and severe proclination (15 and 10 degrees) higher than oral rehabilitators. However, they evaluated minor inclinations (-5 to 5 degrees) lower than the rehabilitators. On the other hand, orthodontists evaluated with lower scores all inclinations compared with non-odontologists, with the exception of a 5-degree proinclination. In that case, they evaluated it higher than the non-odontologists (Figures 1 y 2).
One-factor ANOVA (Table 2):
Orthodontists:
In the orthodontists' group there was a statistically significant difference in esthetic perception according to the degree of inclination of the central incisor.
According to Fisher's and Tukey's multiple comparisons, for orthodontists the inclination between -5 and 5 degrees was perceived as more esthetic compared with inclinations of -15, -10, 10, and 15; nevertheless, there was no scientific evidence to ensure a significant preference for a specific inclination within the range of -5 to 5 degrees.
Despite this, the highest score was for 5 degrees, suggesting some preference on the part of orthodontists for mild proclination.
Non-Odontologists (Table 3):
In this group there was also a statistically significant difference in esthetic perception according to the degree of inclination of the central incisor.
However, according to Fisher's and Tukey's multiple comparisons there was no greater difference in the esthetic perception of the smile in a range higher than -10 to 10 degrees, but the highest score was for 0.
Specialists in oral rehabilitation (Table 4):
As in the case of the other two groups, in the group of specialists in rehabilitation a statistically significant difference was also found in the esthetic perception according to the degree of inclination of the central incisor.
Fisher's and Tukey's Multiple comparisons showed that for oral rehabilitators the inclination between -5 and 5 degrees was perceived as more esthetic compared with inclinations of -15, -10, 10 and 15 degrees. Like with orthodontists and non-odontologists, there was no evidence of a preference within the range of -5 to 5 degrees; however, the highest score was for 0.
DISCUSSION
We considered it important to use a method already mentioned in the literature as valid and successful by authors such as Wagner et al.,6 where an altered image is used for the performance of several evaluations.
We agree with Sarver and Ackerman7 in that the harmony of a smile must be assessed from various perspectives. This study chose the profile view as there is less research from this standpoint.
As we could see throughout this study, although the esthetics of a smile are subjective there are certain parameters that can help to carry out an evaluation in a more objective way. Among these is the inclination of the upper incisors. On this subject we agree with the study by Nathalie Ghaleb et al.,3 who argue that the patient's opinion should be considered and where it can be observed that ordinary people have preference for smaller incisor angles. On the other hand, we disagree with Schabel et al.,8 who have contended over the years that a slight proclination is better for dental and facial esthetics.
Finally, like Kokich et al.,9 we deem it necessary to take into account the differences in the perception of experts and laypersons. Even though the experts look more at details, their opinion is far from that of ordinary people.
CONCLUSIONS
- • The profession of the respondent does determine the assessment of a smile.
- • The inclination of the upper incisors influences the esthetic perception of a profile smile.
- • There is a significant interaction between profession and incisor inclination.
- • The highest score for specialists in oral rehabilitation and laypersons was for 0 degrees.
- • The highest score for orthodontists was for 5 degrees.
- • Orthodontists should pay more attention to the patients' preferences.
- • In future studies, the sample should be increased to find more significant results and/or take into account other factors.
REFERENCES
AFFILIATIONS
1 Pos-graduate Studies and Research Division (DEPeI). National Autonomous University of Mexico (UNAM).
CORRESPONDENCE
Fabiola Hernández Girón. E-mail: fabiolahgiron@gmail.comReceived: Septiembre 2018. Accepted: Febrero 2019.