There are a few potential reasons why your teeth may be yellowing more at the top than the bottom. The enamel on the top teeth tends to be thinner and more translucent, allowing the yellowish dentin underneath to show through more easily. As we age, the enamel thins and the dentin thickens, making teeth appear more yellow. Additionally, the tops of teeth are more exposed to staining from foods, drinks, and habits like smoking. Understanding the causes of yellowing on the top teeth can help you take steps to whiten your smile.
Thinner Enamel on Top Teeth
Enamel is the hard, outer layer of the tooth that protects the sensitive dentin underneath. While enamel is naturally translucent, allowing some of the yellow-hued dentin to show through, it is thickest at the bottom of the tooth and thinnest near the biting surface on top. This difference in thickness means the yellowish color of the dentin underneath shows through more strongly near the tops of teeth.
Over time, as the enamel thins due to aging or acid erosion, more of the yellow dentin peeks through. This gradual process causes the tops of the teeth to appear more yellow than the bottoms covered by thicker enamel.
Enamel Thickness by Tooth Type
| Tooth Type | Enamel Thickness |
|---|---|
| Incisors | 0.1 – 0.5 mm |
| Canines | 0.7 – 1 mm |
| Premolars | 1 – 1.5 mm |
| Molars | 1.5 – 2 mm |
As seen in the table, incisors have the thinnest enamel, making them most prone to yellowing, while molars have the thickest. However, even molars have thinner enamel near the tops, leading to increased yellowing in that area over time.
Increased Dentin Deposition with Age
Underneath the enamel layer is the dentin, which naturally has a yellowish or brownish hue. With age, the enamel thins and the dentin becomes thicker due to continued deposition of dentin material over time. This increase in dentin thickness makes it more visible through the enamel, causing teeth to appear more yellow.
Dentin also contains tubules that run through it from the pulp. As we age, these tubules get wider due to deposits, allowing more dentin color to show through the enamel. The cumulative effect of thinner enamel and more visible dentin leads to gradual yellowing of teeth as we get older.
Rate of Enamel Thinning Over Time
| Age Range | Average Enamel Thinning |
|---|---|
| Under 20 | Minimal change |
| 20-40 | 5-10% decrease |
| 40-60 | 10-20% decrease |
| Over 60 | 20-30% decrease |
This table demonstrates how enamel thinning accelerates with age, allowing more yellow dentin to become visible. This effect is most pronounced on the tops of teeth where enamel is naturally thinner to begin with.
Staining on Top Surfaces
The tops of teeth are also more vulnerable to extrinsic staining from foods, drinks, and habits like smoking that can discolor enamel over time. Some common causes of surface stains on teeth include:
- Coffee, tea, red wine, and colas
- Tobacco use
- Balsamic vinegar, soy sauce, and other dark liquids
- Blueberries, blackberries, and dark-pigmented foods
- Curries and sauces with turmeric
Because we drink and eat with our front top teeth, and smokers hold cigarettes at the front of their mouths, extrinsic stains build up most on the tops of teeth. Even with good oral hygiene, it can be difficult to fully remove surface staining in these areas.
Stain Removal by Brushing
| Stain Source | Brush Removal |
|---|---|
| Coffee, tea | Moderate removal |
| Red wine, tobacco | Minimal removal |
| Curries, berries | Very minimal removal |
As shown, brushing alone is not very effective at removing some types of stubborn extrinsic stains. This allows them to accumulate on the visible top surfaces of front teeth.
Preventing Further Yellowing
While some yellowing factors like thinning enamel are inevitable with age, you can take steps to prevent additional discoloration of your teeth:
- Brush and floss thoroughly twice a day
- Use an electric toothbrush for stain removal
- Rinse with water after staining foods and drinks
- Limit staining beverages like coffee and wine
- Quit smoking and other tobacco products
- Get professional teeth cleanings every 6 months
Practicing good oral hygiene minimizes staining and protects your enamel from erosion. See your dentist regularly to remove hardened plaque buildup before it can contribute to thinning enamel.
Professional Whitening Options
If you already have yellowing mostly on the tops of your teeth, several professional whitening options can help remove stains and brighten your smile:
In-Office Whitening
This fastest method uses a concentrated peroxide gel applied to the teeth in the dental office. Then a special light or laser is used to accelerate the whitening. Results are seen after just one 30-60 minute session.
Custom-Fit Whitening Trays
Your dentist makes custom trays molded to your teeth to hold a lower-dose peroxide gel. You wear the trays for 1-2 hours per day at home. Gradual lightening occurs over 1-2 weeks.
Over-the-Counter Whitening Strips
These thin strips coated with a whitening gel can stick to your front top teeth for gentle lightening over 2 weeks of daily use. Results vary.
Always consult your dentist before trying any whitening products to choose the safest, most effective option for your situation.
When to See Your Dentist
Make an appointment with your dentist if:
- You have new yellow stains on your teeth
- Your teeth are becoming more yellow overall
- You experience tooth sensitivity or gum irritation after whitening
- You notice cracks, spots, or other enamel defects
During your exam, your dentist can identify causes of yellowing and check for any underlying conditions needing treatment. Based on the status of your enamel, gums, and overall oral health, your dentist can recommend appropriate whitening techniques and advice on preventing further discoloration.
With the right prevention and treatment, you can keep your teeth looking whiter for longer. Focus extra effort on brushing and protecting the top teeth where stains accumulate most easily. See your dentist regularly so any yellowing or enamel thinning can be caught early. With diligent oral care and professional whitening when needed, you can maintain a bright, white smile as you age.
Conclusion
In summary, teeth naturally yellow more at the top over time due to thinner enamel, increased dentin with age, and extrinsic staining. Causes include thinner enamel on the biting surfaces, the enamel thinning process accelerating as you get older, and tops of teeth being more exposed to staining foods, drinks, and habits like smoking. Prevent further discoloration by practicing good oral hygiene, limiting staining foods/drinks, quitting tobacco, and getting professional cleanings. Whitening options like in-office gel treatments, custom trays, or whitening strips can brighten your smile. See your dentist promptly if you notice new yellowing or enamel defects. With proper prevention and treatment, you can keep your teeth white even as enamel thins with age.