Optical performance of monocrystalline and polycrystalline ceramic brackets: a prospective in vivo study of color stability and light transmittance
DOI:
https://doi.org/10.2340/biid.v13.46474Keywords:
Aesthetic bracket, ceramic bracket, color stability, light transmittance, radiometer, spectrophotometerAbstract
Background/Objective: Ceramic brackets are widely used in aesthetic orthodontics; however, their optical stability under intraoral conditions remains incompletely understood. While previous studies have predominantly assessed color change in vitro, prospective clinical data simultaneously evaluating both chromatic parameters and light transmittance are scarce. This study aimed to evaluate the in vivo color stability and light transmittance of monocrystalline and polycrystalline ceramic brackets after 3 months of intraoral exposure, and to determine whether crystalline structure influences the magnitude of optical degradation.
Materials and Methods: Fifty patients (13–22 years) were included in this prospective split-mouth longitudinal clinical study. Eight ceramic bracket types were evaluated: four monocrystalline (3M™ Gemini Clear, Inspire Ice™, Hubit™ Perfect Clear II, AO™ Radiance Plus™) and four polycrystalline (3M™ Clarity™ Advanced, AO™ 20/40, Dentsply Sirona Resolve™, GC™ Chic). Brackets were ligated onto archwires without bonding to enamel to prevent composite-induced discoloration. Color measurements (CIE L*a*b*) were obtained using a VITA Easyshade Compact spectrophotometer, and light transmittance was measured with an LEDex CM4000 radiometer at baseline (T0) and after 3 months (T1). Nonparametric tests (Mann–Whitney U, Kruskal–Wallis, and Wilcoxon signed-rank) were used for statistical analysis (p < 0.05).
Results: All brackets exhibited statistically significant color and transmittance changes after intraoral exposure (p < 0.001). All brands demonstrated ‘extremely marked’ color changes according to National Bureau of Standards (NBS) criteria (NBS > 6). 3M™ Clarity™ Advanced showed the highest ΔE (median: 11.22 [interquartile range, IQR: 8.48–13.31]), whereas AO™ Radiance Plus™ exhibited the greatest transmittance reduction (ΔTr: median −10.00 [IQR: −15.00 to −5.00]). A weak negative correlation was observed between ΔE and ΔTr. Crystalline structure significantly influenced baseline optical parameters (Tr0, L0, a0) but did not determine the overall magnitude of color change (ΔE) or transmittance loss (ΔTr).
Conclusions: Intraoral exposure significantly impairs the optical properties of aesthetic ceramic brackets. Crystalline structure influences baseline optical properties and the direction of chromatic shift (Δa, medium effect; Δb, small effect) but not the overall magnitude of color change (ΔE) or transmittance loss (ΔTr). Brand-specific manufacturing characteristics appear to be the primary determinants of long-term aesthetic performance.
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Copyright (c) 2026 Elif Nadide Akay Polat, Berza Yilmaz
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Biomaterial Investigations in Dentistry is a Diamond Open Access peer-reviewed journal, publishing research in oral biomaterials science. The publishing of articles is free for authors, thanks to the support of Acta Odontologica Scandinavica Society (AOSS), a not-for-profit society. 
