The influence of elastomeric ligatures pigmentation on smile aesthetics during orthodontic treatment

ABSTRACT Aim: To assess the influence of elastomeric ligatures, subjected to a previous in vitro pigmentation process using different substances, on smile aesthetics during orthodontic treatment, from the perception of students and professionals. Methods: Eight elastomeric ligatures of five commercial brands (3M/Unitek, American Orthodontics, Morelli, Ortho Technology, and Orthometric) (n=8) were immersed in coffee, Coca-Cola, and red wine for one minute per day, for 28 days; and another group of ligatures was immersed in artificial saliva. All samples were photographed and subsequently analyzed using the Adobe Photoshop software, by the RGB method. Afterwards, the pigmented ligatures were inserted in a patient wearing orthodontic brackets, and zoomed photographs of the smile were taken and presented to 40 evaluators, who filled in a satisfaction scale sheet to express their opinion on the smile aesthetics of each photograph. The color data were subjected to analysis of variance (ANOVA) and Tukey tests. Results: The substance with the highest pigmentation potential was coffee (p< 0.05) followed by red wine (p< 0.05). Comparison among the brands used in this study showed that American Orthodontics and Orthometric had the lowest degree of pigmentation when immersed in coffee and red wine (p< 0.05), respectively. However, the brand that showed the highest level of satisfaction among the evaluators was Ortho Technology. Conclusions: The presence of pigmented elastomeric ligatures affected smile aesthetics, when compared with the control group.


INTRODUCTION
The increasing aesthetics concern has become an important issue into fixed orthodontic appliances, and has established it as a goal for orthodontists to achieve, 1 especially during orthodontic treatment of adult patients. 2,3 To meet the aesthetic expectations of more demanding patients during orthodontic treatment, aesthetic orthodontic appliances have been designed with the aim of filling this gap in the specialty. 4 When offering these options to patients, orthodontists should use not only ceramic brackets, but accessories that also benefit this type of appliance, such as aesthetic elastic archwires and ligatures. 5 The perception of the extent to which the ligature will harm smile aesthetics has a direct effect on the commercial brand selected by the orthodontist. 6 Several studies [6][7][8][9][10][11][12] have been conducted with the purpose of indicating to orthodontists the types of ligatures that have the lowest influence on aesthetics.
However, the method used by the majority of studies analyzed was limited to laboratory tests, [6][7][8][9][10] and overlooked the most important factor when assessing aesthetics; that is subjectivity, or evaluating only aesthetic perception without standardizing and assessing the degree of elastic pigmentation, 13 making it impossible to identify the substances that most affect aesthetics. Therefore, further studies on pigmentation of elastomeric ligatures might be helpful in contributing to the improvement Miranda AGF, Godoi APT, Menezes CC, Vedovello Filho M, Venezian GC The influence of elastomeric ligatures pigmentation on smile aesthetics during orthodontic treatment 5 of these materials. 3 In addition, this is relevant for professionals, as this will allow them to prioritize the use of materials with better characteristics and enable them to offer their patients guidance with regard to their diets. In this context, the present study aimed to assess the influence of aesthetic ligatures of five commercial brands on smile aesthetics during orthodontic treatment, from the perception of students and specialists.
The ligatures were subjected to an in vitro pigmentation process with four solutions. This study tested the hypothesis that pigmentation of elastomeric ligatures would affect smile aesthetics and that there would be differences among the commercial brands and solutions tested.

MATERIAL AND METHODS
The Ethics Committee of University Center of Hermínio Ometto Foundation (FHO) approved this study (number 2.125.443).

SAMPLE SIZING
The sample calculation performed for the color stability analysis indicated that there was very low variability of samples among the elastomeric ligatures, thus providing a low coefficient of variation of 0.28% for the experiment. Therefore, the sample size of eight ligatures per group, resulting in 160 ligatures, provided a high degree of freedom in the residue analysis (DF=140), with test power higher than 0.99 for the main effects of brand and solution, and for the interaction between them.
Miranda AGF, Godoi APT, Menezes CC, Vedovello Filho M, Venezian GC The influence of elastomeric ligatures pigmentation on smile aesthetics during orthodontic treatment 6 For the aesthetic perception analysis, the sample of this study was calculated based on data from a previous study, 6  The ligatures were immersed for one minute per day in 40 ml of each solution to simulate the in vivo contact 14 (Fig 1). After one minute, the specimens were inserted in containers containing artificial saliva, with one container for each group. These containers were wrapped in PVC plastic film and stored in an incubator    were captured in the RAW format, transferred to and filed in a computer, in which they were converted to JPEG, printed at 2x magnification on 10x15 mm photographic paper, and identified with numbers from 1 to 20 (Fig 3).
A semi-structured questionnaire was prepared with 20 nominal satisfaction scales, with grades from 1 to 5, to determine the evaluator's level of satisfaction with the smile aesthetics shown in each photograph, following the method proposed by Ferraz et al. 6 Grade 1 corresponded to "very poor", 2 was "poor", 3 was "regular", 4 was "good", and 5 was "very good", and the evaluators had to select the option most representative of their satisfaction.     Table 2 shows the results of the analysis on the level of satisfaction of orthodontists and university students with smile aesthetics. Both orthodontists and students showed a higher level of satisfaction with the photographs with ligatures immersed in artificial saliva (control group) and Coca-Cola, without differences between them (p > 0.05).

DISCUSSION
The aesthetic importance of the smile has been extensively discussed in the literature. 2,[17][18][19] Orthodontics, a dental specialty that works directly with smile aesthetics, requires continuous updating of its material collection to keep up with the demands of the overall population. 4,5,[20][21][22][23][24] Therefore, testing the color change of elastomeric ligatures is required to guide orthodontists seeking to respect the decision of patients desiring an aesthetic smile even during orthodontic treatment. Therefore, several studies have been conducted 1,[6][7][8][9][10][11][12][13]15,16 with the aim of explaining which of the aesthetic elastomeric ligatures have the least effect on smile aesthetics. The limitations highlighted in the present study are the non-differentiation between pearl and clear ligatures and the absence of pre-stretching before the pigmentation process, because evidence has shown that stretching the elastomers might affect the absorption of pigmenting agents. 9 The authors suggest that further studies should be conducted, The solution with the highest pigmenting potential was coffee.
Ortho Technology was found to be the brand of ligatures most favored by both groups of evaluators (orthodontists and students).