Evaluation of color stability of orthodontic aligners: <i>in vitro</i> study

SHIMIZU, Roberto Hideo; DIAVÃO, Maria Fernanda Castoldi; DALLEDONE, Mariana; GASPARELLO, Gil Guilherme; SHIMIZU, Beatriz Almeida; SOUZA, Evelise Machado de; TOYOFUKU, Ana Cláudia Moreira Melo

doi:10.1590/1807-2577.20250010

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Original Article • Rev. Odontol. UNESP 54 • 2025 • https://doi.org/10.1590/1807-2577.20250010 linkcopy

Evaluation of color stability of orthodontic aligners: in vitro study

Avaliação da estabilidade da cor de alinhadores transparentes: estudo in vitro

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Introduction The esthetics of orthodontic aligners is directly related to the optical stability of the thermoplastic materials used in their fabrication.

Objective This study aimed to evaluate the transparency stability of thermoplastic materials used in the fabrication of orthodontic aligners after exposure to staining solutions.

Material and method A total of 160 specimens were prepared and divided into two groups based on the material: ClearQuartz (QTZ) and SmartTrack (INV), with 80 specimens each. Each group was further subdivided into five subgroups (n = 16) according to the immersion solution: coffee, tea, Coca-Cola, red wine, and artificial saliva (control). Transparency measurements were performed using a VITA EasyShade Compact spectrophotometer, focusing on the buccal surface of the lower first and second molars. The specimens were immersed in the solutions for 14 days, with daily replacement of the liquids. Assessments were conducted at four times: baseline (T0), 24 hours (T1), 7 days (T2), and 14 days (T3), under controlled environmental conditions.

Result Tea, red wine, and coffee solutions produced statistically significant differences in transparency between QTZ and INV at all evaluation time points. In the Coca-Cola group, no significant difference was observed between the materials at T1–T0, but differences emerged at later intervals. For the artificial saliva control, a significant difference was found only at T3–T0, with no significant variation at earlier time points.

Conclusion SmartTrack specimens demonstrated lower transparency stability compared to ClearQuartz, particularly after exposure to staining agents such as tea, coffee, Coca-Cola, and red wine, across most time intervals evaluated.

Descriptors:
Aesthetic aligners; pigmentation; orthodontics; colorimetry; clear aligners

Variable	E	Group								p-value
		CC				INV
		M	MD	DP	IIQ	M	MD	DP	IIQ
Tea	T1 - T0	1.64	1.65	0.20	0.20	4.39	4.10	0.81	1.12	<0.001*
	T2 - T0	1.72	1.63	0.36	0.53	10.65	10.65	1.73	2.48	<0.001*
	T3 - T0	3.15	3.09	0.51	0.58	12.03	11.54	1.45	1.90	<0.001*
Red wine	T1 - T0	1.28	1.22	0.18	0.17	6.66	6.56	0.64	0.41	<0.001*
	T2 - T0	0.79	0.77	0.22	0.36	22.90	22.41	1.79	2.10	<0.001*
	T3 - T0	1.38	1.39	0.18	0.24	28.88	28.26	2.16	3.57	<0.001*
Coca-Cola	T1 - T0	2.13	2.05	0.29	0.33	2.21	2.14	0.27	0.41	0.423**
	T2 - T0	1.14	1.10	0.30	0.30	2.39	2.30	0.33	0.42	<0.001*
	T3 - T0	0.96	0.92	0.32	0.23	2.17	2.15	0.19	0.25	<0.001*
Coffee	T1 - T0	2.44	2.37	0.28	0.39	15.91	15.67	1.25	2.09	<0.001*
	T2 - T0	4.28	4.17	0.84	0.98	45.42	45.79	3.68	3.94	<0.001*
	T3 - T0	9.00	8.99	1.13	1.87	55.24	55.91	2.70	4.58	<0.001*
Saliva (CG)	T1 - T0	0.80	0.79	0.22	0.23	0.64	0.63	0.42	0.55	0.202**
	T2 - T0	0.26	0.26	0.088	0.12	0.24	0.19	0.20	0.15	0.243*
	T3 - T0	0.28	0.26	0.13	0.14	0.48	0.48	0.26	0.42	0.012*

Material	$∆ a^{*}$	Group								p-valor
		CC				INV
		M	MD	DP	IIQ	M	MD	DP	IIQ
Tea	T1 - T0	0.35	0.33	0.08	0.09	-0.13	-0.10	0.13	0.20	<0.001*
	T2 - T0	0.44	0.43	0.18	0.27	-0.46	-0.43	0.13	0.16	<0.001*
	T3 - T0	0.78	0.77	0.16	0.20	-0.28	-0.27	0.15	0.09	<0.001*
Red wine	T1 - T0	0.81	0.82	0.12	0.14	-0.29	-0.27	0.23	0.28	<0.001*
	T2 - T0	0.70	0.68	0.21	0.36	-1.62	-1.52	0.35	0.40	<0.001*
	T3 - T0	1.26	1.27	0.17	0.26	-0.58	-0.50	0.47	0.62	<0.001*
Coca-Cola	T1 - T0	0.25	0.27	0.07	0.11	0.12	0.12	0.08	0.09	<0.001**
	T2 - T0	-0.06	-0.05	0.09	0.12	-0.34	-0.33	0.09	0.08	<0.001*
	T3 - T0	0.25	0.20	0.13	0.06	0.04	0.00	0.11	0.13	<0.001**
Coffee	T1 - T0	0.27	0.28	0.06	0.08	-2.60	-2.20	1.68	0.41	<0.001*
	T2 - T0	0.15	0.18	0.16	0.18	-3.35	-3.33	0.34	0.41	<0.001*
	T3 - T0	0.53	0.57	0.20	0.27	0.34	0.37	0.67	0.84	0.396*
Saliva	T1 - T0	0.09	0.10	0.08	0.06	-0.004	-0.03	0.13	0.14	0.022**
	T2 - T0	0.15	0.13	0.08	0.10	0.03	0.03	0.09	0.08	0.001**
	T3 - T0	0.16	0.17	0.08	0.10	0.35	0.30	0.23	0.25	0.008*
Material	$∆ b^{*}$	M	MD	SD	IIQ	M	MD	SD	IIQ	p-value
Tea	T1 - T0	1.61	1.60	0.19	0.19	4.38	4.10	0.82	1.14	<0.001**
	T2 - T0	1.65	1.60	0.36	0.57	10.64	10.63	1.73	2.49	<0.001*
	T3 - T0	3.05	3.02	0.51	0.55	12.03	11.53	1.45	1.91	<0.001*
Red wine	T1 - T0	0.97	0.92	0.20	0.18	6.65	6.55	0.63	0.40	<0.001*
	T2 - T0	0.33	0.33	0.20	0.11	22.84	22.37	1.79	2.05	<0.001*
	T3 - T0	0.51	0.48	0.22	0.14	28.87	28.25	2.16	3.54	<0.001*
Coca-Cola	T1 - T0	2.11	2.03	0.29	0.33	2.21	2.13	0.27	0.40	0.360**
	T2 - T0	1.13	1.10	0.31	0.31	2.36	2.27	0.33	0.42	<0.001*
	T3 - T0	0.92	0.83	0.33	0.23	2.17	2.15	0.19	0.26	<0.001*
Coffee	T1 - T0	2.42	2.35	0.28	0.38	15.62	15.43	1.16	1.35	<0.001*
	T2 - T0	4.28	4.17	0.84	0.97	45.30	45.68	3.70	4.00	<0.001*
	T3 - T0	8.98	8.97	1.13	1.86	54.99	55.88	2.60	4.68	<0.001*
Saliva	T1 - T0	0.79	0.78	0.22	0.23	0.56	0.62	0.52	0.64	0.115**
	T2 - T0	-0.06	-0.08	0.21	0.37	-0.14	-0.13	0.27	0.17	0.402**
	T3 - T0	0.021	0.00	0.26	0.40	0.17	0.083	0.31	0.37	0.149**

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[TFN1] ^*
U Mann-Whitney Test; **t Student test; M = mean; MD = median; DP = standard deviation; IIQ = interquartile range.