Under the ultraviolet lights at a party, club or bowling alley, natural teeth often glow a bluish-white, while a filling, crown or veneer next to them may look darker or a slightly different colour. That glow is fluorescence, and most of it comes from the dentine under the enamel. Laboratory studies suggest whitening can reduce it, and one laboratory study found that in sunlight, fluorescence made very little difference to measured tooth colour.
The glow comes mostly from the dentine
Fluorescence happens when a material absorbs light at one wavelength and gives it off again at a longer one. Teeth do this naturally: they absorb ultraviolet light, which we cannot see, and give off visible light. A 2026 review by Corfield and Higgins from Adelaide University (Dentistry Journal) reports that natural teeth usually give off light with peaks between 410 and 500 nanometres, in the blue range, and that dentine fluoresces more strongly than enamel. The authors attribute the effect mainly to organic components within the dentine.
Enamel, the outer layer, fluoresces less than the dentine beneath it, so much of the glow you see comes from the dentine. Our article on why some teeth look see-through at the edges explains how enamel and dentine work together in everyday tooth colour. A 2015 review by Lee in the Journal of Biomedical Optics describes the peak emission of teeth at about 440 nanometres and notes that, under light with an ultraviolet component, fluorescence gives teeth a quality of vitality.
In daylight the effect is small
Various studies have claimed that fluorescence makes teeth look whiter and brighter in daylight. Hein and ten Bosch tested this in Dental Materials in 2018. They measured 35 extracted, hydrated teeth lit by sunlight, once with its ultraviolet part filtered out and once without the filter. The average colour difference between the two conditions was about 0.5 in CIELAB colour units (ΔE*), and the authors concluded that ultraviolet-induced fluorescence from sunlight does not make teeth whiter and brighter.
It was a laboratory study on extracted teeth, so it does not capture everything about a living smile. It does suggest that the glow you see under a black light, where visible light is dim and ultraviolet is strong, is not a guide to how white your teeth look in daylight. For more on how everyday lighting affects the way teeth look, see our article on ring lights and tooth shade.
Why fillings, crowns and veneers can stand out under a black light
Tooth-coloured materials are designed to look like natural teeth, and resin composites increasingly include fluorescent agents to copy the way teeth glow under ultraviolet. The Corfield and Higgins review found that resin composites commonly use rare-earth oxide fluorophores and often emit light at similar wavelengths to teeth, but the strength of the glow varies considerably between brands and shades and can change as the material ages. The authors concluded that, despite progress, the differences still usually allow a restoration to be told apart from natural tooth, which is why fluorescence remains useful for identifying dental work, including in forensic dentistry.
Australian researchers found the same variety. Kiran and colleagues (Forensic Science International, 2017) photographed many tooth-coloured materials, including composites, ceramics and resin-reinforced glass-ionomer cements, under a range of light sources. Violet (ultraviolet-A) light showed the greatest differences between the materials and tooth structure, emission patterns varied between materials, and the glass-ionomer cements glowed a bluish-pink. For dental ceramics, Atri and colleagues (Journal of Esthetic and Restorative Dentistry, 2021) compared five dentine ceramic systems with natural dentine and found that three were less fluorescent than natural dentine, while two showed no significant difference.
So a composite bonding repair or a veneer that blends in well at the dinner table may look darker, brighter or a little tinted under a black light. These differences come from the fluorescence of the material itself, which varies between products and can change as the material ages.
What whitening does to fluorescence in laboratory studies
Whitening gels release peroxide that moves through the enamel and breaks down coloured molecules, particularly in the dentine; our article on how peroxide whitening works covers the chemistry. Because the dentine is also the main source of fluorescence, researchers have asked whether whitening changes the glow.
| Study | What was tested | What changed |
|---|---|---|
| Caneppele and colleagues, Brazilian Dental Journal, 2015 | Discs of bovine (cow) enamel and dentine, soaked in 35% hydrogen peroxide for one hour, repeated after seven days | Dentine fluorescence fell significantly; enamel fluorescence did not. Both lightened, dentine more so. |
| Liang and colleagues, Photobiomodulation, Photomedicine, and Laser Surgery, 2020 | Slabs of human enamel treated with 30% hydrogen peroxide at three different pH levels | Fluorescence intensity fell as whitening progressed, and the change was linked to changes in colour and translucency. |
Both studies used small pieces of tooth in a laboratory, with higher peroxide concentrations than take-home gels, so they cannot say exactly how much a whitened smile will change under a black light. In the Liang study, the fall in fluorescence was not explained by mineral loss from the enamel surface, and the authors suggested fluorescence could one day be used to measure how well bleaching has worked. Taken together, the studies suggest that a fall in fluorescence after whitening goes along with the changes that make the tooth look lighter.
If you have tooth-coloured fillings or veneers on your front teeth, it is worth talking with your dentist before whitening, because whitening can affect the colour match between natural teeth and dental work. Our article on whitening with veneers or crowns explains the planning.
Dentists also use fluorescence to look for problems
Fluorescence is not only cosmetic. The Lee review describes methods that use the fluorescence produced by specific wavelengths of light to help detect dental decay and calculus (tartar). If one tooth looks very different from its neighbours under ultraviolet and you are not sure why, it may be a filling or other dental work, and a dentist or OHT can check it at your next visit.
Questions about teeth under ultraviolet light
Does glowing less after whitening mean my teeth are damaged?
These laboratory studies do not show that a lower glow is a sign of damage. Caneppele and colleagues found the drop in fluorescence was in the dentine, which also lightened the most, and Liang and colleagues found the change was not explained by surface mineral loss. Whitening can cause tooth sensitivity, which studies of take-home whitening report is usually mild, so follow the instructions from your dentist or OHT.
Will my veneers glow like my natural teeth?
It depends on the material. Atri and colleagues found some ceramics fluoresced similarly to natural dentine and others less, so veneers may look different from natural teeth under a black light.
Can whitening make teeth glow more?
The laboratory studies above do not suggest so: they recorded fluorescence staying the same or falling.
Planning whitening around how your teeth look
At Lumi Dental in Melrose Park, our whitening options, Lumi Home, Lumi Refresh and Lumi Radiance, all include Boutique take-home whitening, and results vary from person to person, so we do not promise a particular shade. See our teeth whitening page for how each option works, or book a free cosmetic consult to talk it through.
Sources
- Corfield T, Higgins D. Fluorescence in direct dental resin-based composites and natural teeth: a narrative review. Dent J (Basel). 2026;14(9):535. PubMed 42782922
- Lee YK. Fluorescence properties of human teeth and dental calculus for clinical applications. J Biomed Opt. 2015;20(4):040901. PubMed 25875625
- Hein S, ten Bosch JJ. The effect of ultraviolet induced fluorescence on visually perceived tooth color under normal light conditions. Dent Mater. 2018;34(5):819-823. PubMed 29525359
- Kiran R, Walsh LJ, Forrest A, Tennant M, Chapman J. Forensic applications: fluorescence properties of tooth-coloured restorative materials using a fluorescence DSLR camera. Forensic Sci Int. 2017;273:20-28. PubMed 28213184
- Atri F, Safi M, Salehzadeh S, et al. Analysis of color and fluorescence of different dentin ceramics and natural human dentin's to enhance shade matching. J Esthet Restor Dent. 2021;33(7):1029-1037. PubMed 34101330
- Caneppele TM, Rocha Gomes Torres C, Bresciani E. Analysis of the color and fluorescence alterations of enamel and dentin treated with hydrogen peroxide. Braz Dent J. 2015;26(5):514-8. PubMed 26647938
- Liang S, Wang M, Wang Y, Jiang T. A pilot study about the effect of laser-induced fluorescence on color and translucency of human enamel during tooth bleaching. Photobiomodul Photomed Laser Surg. 2020;38(3):151-159. PubMed 31934811
This article is general information only and is not a substitute for advice about your own situation from a dentist.
