Esthetic perception and economic value of orthodontic appliances by lay Brazilian adults

Methods: Eight diferent combinations of orthodontic appliances and clear tray aligners were placed in a consenting adult with pleasing smile. Standardized frontal photographs were captured and incorporated into a research album. A sample of adults (n = 252, median = 26 years old) were asked to rate each image for (1) its attractiveness on a visual analog scale and (2) the willingness to pay (WTP) for a cosmetic appliance when compared to a standard metalic appliance and a clear tray aligner. Comparisons between the appliances’ attractiveness were performed using the Friedman’s test and Dann’s post-hoc test. Correlation between appliances’ attributed value, socioeconomic status, age, gender, and esthetic perception was assessed using Spearman’s correlation analysis.


InTRODuCTIOn
During the past years, orthodontics has greatly evolved regarding esthetic materials.Nowadays, orthodontic brackets are becoming smaller and more discrete; in addition, the esthetic appliances represent an alternative for patients that are reluctant to use metallic appliances.Orthodontic appliances have evolved according to public demand and available technology, especially with the underlying goal of reducing the appliances' visibility. 1,2The esthetic paradigm shift in dentistry, especially in orthodontics, has shown the urgency to incorporate esthetics to the functional goals and requirements of the orthodontic treatment, 2 , leading to an increase in the demand for orthodontic appliances even more inconspicuous.Therefore, this demand has been primarily driven by the consumers' desire for esthetic alternatives and the competitiveness of the orthodontic industry and specialty. 3nnovations in the aesthetics of orthodontic appliances may also be a major factor in the increase in adult patients' acceptability to orthodontic treatment.Patients considering to undergo orthodontic treatment now have can choose from diferent appliances currently available, including conventional stainlesssteel, ceramic, lingual and clear plastic aligners. 1Even though orthodontists can use these resources to increase patients' acceptability to orthodontic treatment, few studies have evaluated the attributed value of orthodontic appliances. 4 previous study assessing perceived orthodontic appliance attractiveness indicated that adult patients prefer less metal showing in their orthodontic appliances and were less willing to accept treatment with appliances they consider to be unesthetic. 3,4In the same way, another study revealed that 67% of Sweden young adults would probably not or deinitely not wear visible appliances in spite of a functional treatment indication; and there was also a rejection rate of 33% to conventional orthodontic treatment. 5Another aspect is the social perceptions of adults wearing orthodontic appliances, since the judgments concerning their personal characteristics are inluenced by dental appearance and orthodontic appliance design. 6ust as a variety of social, cultural, psychological and personal factors influence the self-perception of dental appearance and the decision to undergo orthodontic treatment, 7,8,9 these factors may also exert an important influence in the perception and acceptability of different orthodontic appliances, indicating that, different populations should be investigated.Understanding the factors involved in the perception of different orthodontic appliances in a particular population enables a better planning of resources and strategies in the private practice, since the appearance of orthodontic appliances plays a significant role in patients' decisions to undergo orthodontic therapy. 4he preferences for appliances can also be evaluated in terms of their attributed value to patients. 10,11he employment of the willingness-to-pay (WTP) assessment technique has been increasing in diferent areas , allowing to estimate the attributed value of the health care technologies. 11It is a way of measuring value in monetary terms by a cost-beneit analysis once it assigns monetary values to both costs and outcomes of health care and calculates the net beneit.WTP allows a monetary rating to be attributed to novel health care interventions or outcomes by asking people how much they would pay to obtain the beneits of a speciic treatment.This value is set as raters are asked to respond to a hypothetical, conditional question -e.g., ''what is the maximum amount you would be willing to pay to access a new intervention, existing the need to undergo treatment?''Such a question is intended to elicit a monetary valuation of the merit, worth or beneit which each subject associates with the speciic intervention under consideration.Although the same general question is asked any WTP study, the question can be asked in various formats to adapt to the study. 12When applied to orthodontics, this method may provide a way to determine the value of diferent appliances for patients of diferent ages and sociocultural realities. 3he purpose of this study was to evaluate the esthetic perception of lay Brazilian adults on diferent orthodontic appliances designs and its inluence in the attributed value of orthodontic treatment, considering raters' socioeconomic status, age and gender.

MATERIAL AnD METHODS
This research was approved by the ethics research committee of Rio de Janeiro State University where this study was performed.

Esthetic perception and economic value of orthodontic appliances by lay Brazilian adults original article
An adult volunteer was selected for receiving the appliances and pictures capturing.Selection criteria were: Well aligned teeth, proper gingival and incisor display and the absence of strong gender markers in the circum-oral region.The volunteer was also asked to sign de informed consent.Digital image capture was made in frontal view with an SLR camera (EOS Rebel T1, Canon, Oita, Japan) equipped with a 100 mm macro lens (Macro Lens EF 100 mm, Canon, Oita, Japan) and a ring flash (Macro Ring Light MR-14ex, Canon, Oita, Japan).Traditional metal brackets (Masel, California, USA), self-ligated metal brackets (Tellus, Eurodonto, Brazil), golden metal brackets (GAC International, New York, USA) and sapphire esthetic orthodontic brackets (Radiance, American Orthodontics, Wisconsin, USA) were temporarily bonded to the dental surfaces of the maxillary arch without acid etching.For the simulated bonding of the appliances, Transbond XT (3M Unitek, California, USA) adhesive was used.A 0.020-in stainless steel archwire (GAC International, New York, USA) was used as reference for brackets positioning, allowing reproducibility for placement of various bracket systems.Brackets were bonded from upper right second molar to upper left second molar.A clear tray was fabricated and imaged to simulate clear tray alignment systems such as Invisalign (Invisalign, Align Technology, California, USA).Two trays were produced: One simulating attachments in front teeth (12 and 22 in vestibular side) and one with no attachments.Attachments were transparent, rounded, and had approximately a three millimeters radius.
Camera settings were manually set, and all incamera image enhancement features were turned of to ensure images' reproducibility.Lighting conditions were constant for all images acquired.
All photographs of the volunteer's smile were performed in the natural head position, with the aid of the cephalostat of the UERJ Dental Radiology Clinics, thus ensuring the correct positioning of the head.The ear positioners restricted excessive lateral movement while the nasion positioner limited vertical movements.(Fig 1).The camera was attached to a tripod and positioned at a fixed distance of 110 cm in a straight line between the patient's face and the camera lens.
The photo album was composed of three sheets of photo-quality color prints.Each sheet had 29.7 cm x 21 cm.The irst sheet comprised eight images, with all compositions of orthodontic appliances described Feu D, Catharino F, Duplat CB, Capelli Junior J above randomly grouped in a grid and labeled with letters A to H (Fig 2).Each photograph had a 10 cm x 5 cm size.The second and third sheets was composed of two pictures each and had the purpose of evaluating the monetary value of the apparatus.The second sheet (Fig 3) had a picture of the traditional ixed metallic appliance labeled ''Picture A'' and one of a ixed esthetic appliance labeled ''Picture B''.The third sheet had a picture of a ixed esthetic appliance labeled ''Picture A'' and one of the clear tray aligner labeled ''Picture B'' (Fig 4).These sheets also had 29.7 cm x 21 cm, and each picture had 10 cm x 5 cm.
Eligibility to participate in the survey included any willing adult from 17 to 63 years old who had never undergone orthodontic treatment with brackets or aligners, was not a dentist or a dental student, was at the University campus in the four days of data collection and signed the informed consent form.
Two trained and blinded dental students collected the data.All surveys included a demographic and socioeconomic status information forms, instructions, the image-rating scales and the album.Socioeconomic status was measured with the "Brazil Economic Classification Criteria", 13 which classifies people into eight socioeconomic categories according to the educational level of the head of the household and the ownership and consumption of common goods and services (e.g., VCRs, DVDs, color TVs, housekeeper).
Each rater (n = 252) received the album containing the smiles' photographs and a rating sheet with a 100 mm visual analog scale (VAS).The straight lines on the left side indicated "very unattractive" and, on the right side, "very attractive."The subjects were presented the images that should be rated (Fig 2) and instructed to use the VAS.They were also told not to compare the album smiles.After the attractiveness evaluation, questions were asked to determine the perceived value of cosmetic orthodontic appliances by using the WTP method.
The questions were directed to the evaluation of sheets 2 and 3.The rater received these instructions: ''Assume the appliances in picture B are more expensive than those in Picture A. How much more would you be willing to pay for them to be placed on your teeth?''After that question, a second question asked how much more money the rater would be willing to pay to have Picture B appliances placed on ''your child's teeth''.The rater could check a box to represent the amount he or she would pay for Picture B appliances, ranging from US$50 to US$3500 (Table 1).Alternatively, if the rater would not pay additional money for the appliances in Picture B, the option: ''None, I would prefer Picture A appliance'' could be chosen.The procedure was repeated for sheets 2 ( The scores were measured by a calibrated dentist using a digital caliper (MGF 505646, Mitutoyo, Tokyo, Japan) that was positioned on the left-most point of each line of the visual analog scale and opened to the mark made by the rater.Values in millimeters were registered as scores.

Statistical analysis
Sample size calculation showed that a total of 252 individuals would provide a 80% probability to the study of detecting a treatment diference at a one-sided 0.05 signiicance level, if the true diference between treatments is 0.30 times the standard deviation. 3The VAS scores were evaluated by intraclass correlation coeicient (ICC) with 95% upper and lower conidence bounds.For the WTP responses, the weighted kappa statistic was applied.Twenty subjects from the same University Campus, which were not included in the study group, were used to test the intrarater reliability.The interviews were repeated seven to ten days latter.
Descriptive statistics for perceived attractiveness VAS ratings were calculated.The Kolmogorov-Smirnov test showed lack of normality of distribution and heteroscedasticity for all groups except for sapphire esthetic brackets with metal wire.Comparisons of groups' attractiveness were carried out using nonparametric statistics with the Friedman test (analysis of variance [ANOVA] on ranks for repeated measures) followed by Dann's multiple comparison post-hoc test (GraphPad Prism 5 software).The correlation between the economic value (WTP), socioeconomic status, age, gender and esthetic perception was calculated by using the Spearman correlation analysis and represented with the r value.Raters' ages were divided at the median (26 years) to assess whether it could inluence the results.

RESuLTS
Intraexaminer reliability was high for attractiveness assessment: Mean ICC = 0.83 (95% CI, 0.78-0.99)and for attributed value assessments: Kappa, 0.89 [95% CI, 0.81-0.98],indicating substantial consistency. 14he median for raters' age was 26 years old (IR= 22-40) and the socioeconomic status is described in Table 2. Descriptive statistics for the perceived attractiveness VAS ratings of sheet 1 are reported in Table 3 and Figure   The clear aligner without attachments had the best evaluation scores, followed by the sapphire brackets with esthetic wire and then by the clear aligner with attachments.The golden metal brackets received the worse scores.The data show a general score hierarchy, with decreasing attractiveness as the amount of displayed metal increases, and worsening with the golden version.
Appliances perceived attractiveness for males and females was compared, showing signiicant difference between them, and it is described in Figure 6 and Table 4. Men showed a general tendency to assign lower scores than women.Similarly, there was a signiicant diference in the perception of groups of 17-26 years and 27-63 years of age, which is shown in Figure 7 and Table 5.
The correlation assessment between the attributed value (WTP) and the esthetic perception of the metal brackets with gray elastomeric ligatures (option A) in comparison with sapphire brackets with metal archwire (Option B) in sheet 2 revealed a weak 14 but signiicant correlation regarding the raters themselves, and an even weaker and non signiicant result for their child.For the sapphire brackets with metal archwire (Option A) in comparison with the clear aligner with attachments (Option B) in sheet 3; there was also a weak 14 but signiicant correlation for the raters themselves, with similar results for their child (Table 6).Comparison between genders regarding WTP (Table 7) showed similar results to the total sample, with more signiicant results for sheet 3, with a slight tendency for women to pay less for appliances they considered more esthetic.
In sheet 2, the correlation between WTP and age showed a weak and non-signiicant correlation for the two age groups (Table 8).However, younger subjects (17-26 years) showed a tendency to pay more for the aligner in sheet 3. Correlation was signiicant and moderate. 14Socioeconomic status had a signiicant correlation, showing that as better is the socioeconomic status, as higher is the WTP for an esthetic appliance (Table 9).Correlation was similar and statistically signiicant for sheets 2 and 3.

DISCuSSIOn
Adult patients display pronounced diferent attitudes to the type of appliance they wear. 15They have indicated embarrassment and bashfulness, 16 arising from the presence of a perceptible appliance, and negative peer reaction, 15 especially from their partners, as discouraging aspects of treatment.The perception of young adults undergoing orthodontics by others is particularly important for major life events such as employment and inding a partner.Therefore, an orthodontic appliance with the most positive social assessment would favor patient acceptance.For this reason, this study's findings have direct clinical implications for the orthodontics practice.Orthodontists must choose between available appliances to provide options that are acceptable to patients and work in harmony with their biomechanical philosophy.This study showed that there were four general preference levels regarding types of appliances based on their appearance: 1) Clear aligners are preferred over sapphire appliances, except when attachments are present on anterior teeth; 2) In these cases, sapphire appliances with esthetic wires are preferred over the clear trays, but this was not statistically significant; 3) Sapphire brackets with both archwires are also preferred over stainless steel, but among those, traditional metal brackets with gray ties were preferred over self-ligated brackets and over metal brackets with green ties; 4) Golden metal brackets had the worse esthetic perception in this sample.
In the present study, all raters were University students or employees.This could have introduced bias into the results; especially with regard to their cultural and social background. 26This was the main reason to apply a socioeconomic survey that allowed investigating whether it would inluence the results.The survey showed that this sample was homogeneously distributed between the status A2, B1, B2 and C1 and socioeconomic status did not inluence the esthetic perception of the appliances.However, it did inluence the WTP for a more esthetic appliance.
Another issue worth discussing was the brackets positioning, which in spite of the 0.020-in archwire used as reference, showed minor variations.However, it is most likely that these minor variations did not significantly impact our findings, especially because all appliances were installed on a model with well-aligned teeth.Although this situation might not represent the clinical appearance of these appliances during the early stages of treatment, well-aligned teeth were chosen to reduce variables that could distract from the evaluation of appliance esthetics and allow a more accurate comparison with the results of previous studies.
A similar study was recently carried out, 6 interestingly, however, no signiicant diferences were found between metallic, golden, and ceramic brackets for any of the assessed sample.Golden appliances are not widely used, leading the authors to believe that this may have inluenced the results, since raters would not be able of identifying it properly Nevertheless, the present study showed that this brackets had the worse esthetic perception in the studied population.According to Jeremiah et al, 6 the clear aligner also had the higher attractiveness ratings.These indings indicate that a reduced appliance visibility appears to be the standard for social acceptance, corroborating our indings.In the present study, when the clear aligner was noticed, due to the presence of anterior attachments, it became less attractive than ceramic brackets.However no other study has previously evaluated the perception of anterior attachments, therefore, these results cannot be compared with other population.
Roswall et al 3 and Ziuchkovski et al 4 also evaluated appliances' esthetic perception and obtained similar results when compared with the present study.
The authors found that the overall trend in appliance attractiveness seems to relate to the amount of visible metal.Clear tray appliances with no visible metal received the highest ratings in attractiveness.Authors believe that this could explain why alternative orthodontic appliance systems such as clear tray aligners have grown in popularity. 18In fact, the present study and other three 3,4,6 researches have shown similar results about clear tray aligners.Besides the positive esthetic perception and the increasing consumer and professional demand for such appliances, questions regarding this system's efficacy requires further research, since there is still much to learn about its biomechanics. 19,20 possible reason for the marked diferences in the results shown by Jeremiah et al 6 and Ziuchkovski et al, 4 Roswall et al, 3 and the present study, regarding the perception of esthetic and metal brackets is that Jeremiah et al 6 used standardized full-face photographs of a young adult female, whereas the other studies used smiles with no strong gender markers in the circum-oral region.The indings from Berto et al, 21 who also used standardized lateral full-face close-ups photographs (modiied by adding appliances) of a young female adult, difer from all studies discussed above.In their study, Brazilian laypeople perceived a smile with an esthetic appliance as signiicantly less attractive than a smile with a metal appliance or with no appliance.This could have been caused due to a diferent perception of the sapphire appliance, used in the present study, and the ceramic appliance, used in Berto et al 21 and Jeremiah et al 6 studies.On the other hand, this possibility is questionable once Roswall et al 3 and Ziuchkovski et al 4 also used ceramic brackets and found results that corroborates the present study.
It is important to know whether the attractiveness of a smile is inluenced by the type of photographic framing used in the analysis.In addition, one must analyze methodologies that might inluence the results achieved, such as, the order and fashion of presenting the photographs and the scale used to evaluate the perception. 22Some authors believe that facial structures, such as nose and chin, may act as confounding factors, as my also happen with gender markers apparent in the smile, and therefore inluence the smile evaluation. 23he model's gender is very inluential when grading smiles attractiveness, as was found by Thomas et al. 24 The use of a Lickert scale to rank esthetic perception and a structured questionnaire about characteristics strongly associated with the model's physical appearance may also have inluenced the results of Jeremiah et al, 6 since all other studies used a VAS scale.
Similarly, the sample's characteristics can also be related to diferences in indings.In this study, raters' age and gender inluenced attractiveness perception of the appliances.Younger patients (17-26 years old) evaluated sapphire appliances and clear aligners more positively, i.e. with highest scores, and golden and metallic brackets with green ties with worse scores than patients aged 27-63 years.Regarding gender, men showed a general tendency to assign lower scores than women for all evaluated appliances.Male subjects rated sapphire appliances and clear aligners without attachments statistically equal.On the other hand, for women there was no diference between clear aligners with and without attachments, conversely to what happened to men who perceived attachments negatively.Metallic brackets with gray and green ties and also self-ligated metal appliances were similar for women, but gold metal brackets had worse evaluation.Men also perceived metal brackets diferently, considering only traditional metal appliances with gray ties more attractive than the others.Walton et al 25 also found signiicant diferences in esthetic perception of appliances between genders and diferent age groups.
WTP method was used to evaluate the attributed value of various orthodontic appliances by means of a cost-beneit analysis.The WTP was assessed using the payment scale method, described in Table 1, rather than an open-ended format due to the study design and also because no diference was found between these two methods in previous studies. 26he correlation between the attributed value (WTP) and the esthetic perception was weak, and showed that despite raters' preference for esthetic appliances, they would not be willing to pay more for clear tray and sapphire appliances according to the simulations made in sheets 2 and 3. Their socioeconomic status was significantly correlated with these results: The higher the socioeconomic status, the more raters were willing to pay for treatment with the appliances, as observed in the results for sheets 2 and 3.This may be the reason for the different result found by Roswall et al, 3 in which sample, raters with higher socioeconomic status responded with the highest WTP values for lingual appliances and a clear tray aligner.In another socioeconomic reality, different results may be found in Brazilian samples, therefore indicating that more studies are necessary to further conclusions regarding the subject.Therefore, it is important to note that this study's results cannot be indiscriminately applied to other cultural groups, with socioeconomic differences.These aspects must be analyzed and considered in this kind of analysis.When patients declared they would pay more for the esthetic appliances, adults were equally willing to pay more for appliances they deemed more desirable for their children too.
Gender had no signiicant inluence on WTP, however, male subjects had a greater trend to pay more for treatment with a clear aligner.However, age had a signiicant inluence in WTP for appliances compared in sheet 3, with younger patients being signiicantly more willing to pay more for a clear aligner.Similarly, attractiveness analysis was also inluenced by age, as previously described.Walton et al 25 evaluated children and adolescents and found that they also showed high preference for clear tray aligners.However, following the aligners, child preferred metal appliances with colored ties above all other options.This was an opposite perception when compared to adults' rates and suggests that the comparison between diferent age groups inluenced appliances' perceived esthetics and could also have an efect on the attributed value.However, more studies comparing diferent age groups are required for deinitive conclusions on the subject.

COnCLuSIOn
Orthodontic appliance attractiveness varied significantly by the following hierarchy of appliance types: Clear tray aligners > sapphire brackets > stainless steel traditional and self-ligating brackets > golden metal appliances.Metal appliances, commonly used in orthodontic practice, were considered unattractive, while clear aligners and sapphire appliances were considered better esthetic options.Nevertheless, patients are not willing to pay more for appliances they deem more esthetic.On the other hand, socioeconomic status and age was significantly correlated with WTP.Higher socioeconomic level and age between 17 and 26 years old were significantly correlated with the willingness to pay more for an esthetic appliance.Gender was not significantly correlated with WTP.These data show that results could vary depending on the studied sample.Therefore, a socioeconomic and age analysis is mandatory in this kind of study.

ACKnOwLEDgEMEnTS
The appliances used in this study were kindly offered by Fabio Barreto from Orthoadvanced Especialidades Ortodônticas.We also would like to thank Deise Campos Caldas and Priscila Pamela Braga Jambo for the help in conducting this study.

Figure 2 -
Figure 2 -Images employed for attractiveness evaluation (first sheet): A) Sapphire esthetic brackets with metal archwire; B) clear tray with attachments ; C) golden metal brackets; D) self-ligated metallic brackets; E) traditional metallic brackets; F) sapphire esthetic brackets with esthetic archwire; G) clear aligner and H) traditional metallic brackets with green elastomeric ligatures.

Figure 3 -
Figure 3 -Images captured for the first WTP evaluation (second sheet): A) Traditional metallic brackets; B) sapphire esthetic brackets with metal archwire.

Figure 4 -
Figure 4 -Images captured for the second WTP evaluation (third sheet): A) Clear aligner with attachments; B) sapphire esthetic brackets with metal archwire.

Table 1 -
Box representing how much more raters would pay for Picture B appliances, ranging from US$50 to US$3500, in sheets 2 and 3.

Table 4 -
Statistical comparison of the VAS ratings representing attractiveness evaluation with Friedman ANOVA for repeated measures (p < 0,001) and Dunn's post-hoc test by gender.

Table 3 -
Statistical comparison of the VAS ratings representing attractiveness evaluation with Friedman ANOVA for repeated measures (p < 0.001) and Dunn's post-hoc test.
* Distinct superscripts indicate statistical significance.Figure 7 -Descriptive VAS ratings representing attractiveness evaluation for appliance type by age.

Table 5 -
Statistical comparison of the VAS ratings representing attractiveness evaluation with Friedman ANOVA for repeated measures (p < 0,001) and Dunn's post-hoc test by age.

Table 6 -
Spearman rank correlation coefficients and p values between VAS score differences and attributed value (WTP).

Table 7 -
Spearman rank correlation coefficients and p values between VAS score differences and attributed value (WTP) by gender.

Table 8 -
Spearman rank correlation coefficients and p values between VAS score differences and attributed value (WTP) by age.

Table 9 -
Spearman rank correlation coefficients and p values between socioeconomic status and attributed value (WTP).