Why Are My Teeth Yellow? The Science Behind Your Shade | DRJB Smile Clinic

By Dr John Barclay | DRJB Smile Clinic, Ruabon, North Wales

The Science Behind Your Shade

When you ask, “Why are my teeth yellow?”, the honest answer isn’t “poor brushing” or “too much coffee. ”Tooth colour is far more complex — and far more interesting — than that.

Your shade is shaped by:

• biology

• ageing

• enamel thickness

• dentine behaviour

• light physics

• surface texture

• past dentistry

• lifestyle

• genetics

Let’s walk through the real science of your shade — the DRJB way.

What is the ideal tooth shade… for YOU

The most naturally beautiful smiles follow one simple, universal rule:

Your teeth should be slightly lighter than your sclera (the whites of your eyes).— Magne, “Influence of Symmetry & Balance on Smile Perception”

Why?

• The sclera is your face’s brightness anchor.

• Teeth darker than the sclera look tired or aged.

• Teeth much lighter than the sclera look artificial, chalky, or overdone.

• Teeth that sit just above scleral brightness look healthy, youthful and balanced.

This is not a trend. It’s a cross-cultural aesthetic principle.

And it’s why Turkey Tippex white always looks wrong in real life — too opaque, too flat, too bright for the face.

Tooth colour isn’t on the surface — it’s deep inside

✔ Enamel

• translucent

• glass-like

• contains rod sheaths

• scatters light

• has natural opalescence & fluorescence

• contributes brightness and halo

✔ Dentine

• yellow–brown

• deep

• warm

• contains tubules

• determines most of your tooth’s “colour”

✔ What you see = LIGHT

1. Light enters enamel

2. Scatters through enamel rods

3. Reaches dentine

4. Scatters again

5. Travels back out

6. Your brain interprets this as “shade”

Shade is physics, not just pigment.

Natural tooth shades vary — far more than people realise

Most healthy adults naturally sit around:

• A2

• A3

• A3.5

• B2–B3

Young teeth?Usually A1–B1, sometimes brighter.

BL shades? They do not occur naturally in adults. Only whitening produces them.

Where do you sit on the shade spectrum?

Insert your real patient shade photos here:

Shade anomalies — when colour signals something deeper

⚪ Fluorosis

Chalky white flecks or brown patches.

Whitening helps the background; infiltration/bonding blends patches.

⚫ Tetracycline staining

Grey/blue/brown banding deep in dentine.

Whitening helps slowly. Veneers are often needed for full masking.

🟤 Hypoplasia

Cream-yellow opacities with weaker enamel. Grooves, pits, missing enamel.

Often needs whitening + bonding or veneers.

Enamel Thickness: Why Younger Teeth Look Brighter (and How We Can Bring That Brightness Back)

Your enamel acts like frosted glass: the thicker it is, the brighter your tooth looks.

Here’s a cross-section:

Typical enamel thickness on a maxillary central incisor:

• 0.3 mm near the edge

• 0.5 mm mid-surface

• 0.7 mm near the gumline

Even tiny differences like this change how teeth look.

Most patients blame coffee. But the biggest factors are biological.

Thicker enamel (younger teeth)

• more light scattering

• higher visual brightness (value)

• less dentine influence

• youthful glow

Thinner enamel (age, wear, erosion)

• less reflection

• more translucency

• more dentine showing through

• warmer, yellower appearance

This is biological ageing — not brushing failure.

But enamel isn’t the only layer changing…

Dentine thickens over life — making teeth look darker

As you age (or clench/grind), your tooth lays down secondary dentine.

More dentine = more yellow underlying colour.

So with age:

• enamel gets thinner

• dentine gets thicker

• more light is captured inside dentine

• less is reflected back out

• teeth look darker and warmer

This is completely normal.

TLDR — The Optical Ageing Summary

As we age:

→ Enamel gets thinner

⬇ reflection⬆ translucency⬇ brightness

→ Dentine gets thicker

⬆ yellow warmth⬆ colour influence

Result:

👉 Teeth naturally look more yellow — even with perfect brushing.

The good news:

👉 Whitening, bonding, or enamel-mimicking ceramics can restore brightness by changing how light behaves in your tooth.

Whitening works by changing light behaviour — not damaging enamel

Whitening gels:

• travel through enamel rod sheaths

• reach dentine

• break chromogens into colourless compounds

• reduce light absorption

• increase reflection

• boost brightness (value)

Whitening does not thin enamel. Whitening does not erode teeth. Whitening does not damage structure.

It simply changes optics.

Why I record your shade at every exam

Shade tells me:

• how your enamel is wearing

• how dentine is behaving

• how hydration is changing

• how old composites are ageing

• whether whitening will work quickly or slowly

• how bonding or veneers should be planned

• how your smile is ageing

Shade is a diagnostic tool — not a judgement.

Your personalised shade plan (DRJB method)

✔ Hygiene

Removes surface chromogens.

✔ Boutique Whitening

Lightens enamel + dentine for natural brightness.

✔ Composite Bonding

Restores lost enamel optics, masks anomalies, improves harmony.

✔ Porcelain Veneers

For deeper colour issues: tetracycline, severe fluorosis, thin enamel, large defects.

Everything is customised. Evidence-based. Natural-looking. Never overdone.

Final thoughts: What shade should you be?

Not Hollywood white. Not BL1 on every face. And definitely not Turkey Tippex white — the flat, opaque look that erases individuality.

The perfect shade is simple:

Just slightly lighter than your sclera, and in harmony with your face.

Your teeth should look like you — only brighter, healthier and more confident.

Shade is anatomy + optics + biology + balance. Together, we’ll find the shade that belongs to you.

Start Your Whitening Journey Today

📞 01978 823490📧 wrexham2-tco@mydentist.co.uk

We’re here to help you achieve brighter, healthier, science-driven results.

Book your FREE whitening consultation

📸 Book a free 3D Smile Scan Start Your Smile Journey with our TCO team — Faz, Hannah, or Angie.

📍 DR JB Smile Clinic – Ruabon, North Wales

FAQ — The 4 Most Common Patients Questions

1. Why are my teeth yellow even though I brush every day?

Tooth colour comes mostly from the inner layers, not the surface. As enamel naturally becomes thinner and dentine becomes thicker with age, more warm colour shows through — even with excellent brushing. This is normal biology, not poor hygiene.

2. Why do teeth get yellower as we get age?

Two things happen over time: enamel thins (making teeth look more translucent) and dentine thickens (making teeth look warmer and more yellow). Together, this shifts teeth naturally toward darker, deeper shades. It’s a predictable part of ageing, just like changes in skin and hair.

3. Can whitening fix naturally yellow teeth?

Yes. Professional whitening brightens both enamel and dentine, which is why it works even for naturally yellow or age-related yellowing. Older dentine may take longer to whiten, but dentist-supervised systems give predictable, safe results without damaging enamel.

4. What shade should my teeth be naturally?

Most adults naturally sit between A2–A3 or B2–B3, and this is completely normal. The most reliable aesthetic rule is simple: your teeth should be slightly lighter than the whites of your eyes, creating a natural, balanced brightness that suits your face.

References

1. Magne P. Influence of symmetry and balance on visual perception of a smile. Journal of Cosmetic Dentistry.

2. Fondriest J. The optical characteristics of natural teeth. Inside Dentistry.

3. Paravina RD, Ontiveros JC, Cevik P, Johnston WM. Translucency of enamel and dentin: A biomimetic target for esthetic dental materials. Journal of Esthetic and Restorative Dentistry.

4. Lee Y-K. Opalescence of human teeth and dental esthetic restorative materials. Dental Materials.

5. Guo et al., 2024. Review of peroxide diffusion, enamel rod pathways, and the molecular action of whitening gels. Royal Society of Chemistry.

6. Hattab FN, Qudeimat MA. Dental discoloration: An overview. Journal of Esthetic Dentistry.

7. Goodman JR, Gilthorpe MS, Roberts IS. Tetracycline-induced discoloration of teeth. British Dental Journal.

8. J. Wilson et al. Age-related changes in tooth colour. Gerodontology.

9. Sulieman M. An overview of tooth discoloration: Extrinsic and intrinsic causes. Dental Update.

10. Sulieman M. Tooth bleaching by different concentration carbamide peroxide gels. Journal of Dentistry.

Why Are My Teeth Yellow? The Science Behind Your Shade | DRJB Smile Clinic

Why Are My Teeth Yellow? The Science Behind Your Shade | DRJB Smile Clinic