Having naturally white teeth is often seen as an attractive trait. Many people strive to whiten their teeth through various methods like whitening toothpastes, strips, and professional treatments. But some people are lucky enough to be born with naturally white teeth, thanks to the structure of their tooth enamel.
Tooth Anatomy and Enamel
Teeth are made up of multiple layers. The outermost visible layer is the enamel, which is made of hydroxyapatite crystals. Underneath the enamel is the dentin, a bonelike tissue. The innermost layer is the pulp, which contains the tooth’s nerves and blood vessels.
The enamel is the hardest substance in the human body and helps protect the tooth from damage. It also determines the tooth’s color. Enamel contains very little organic material and is translucent. The whiteness of teeth depends on the light scattering properties of the enamel.
There are two types of enamel, known as A1 and A2. They have slightly different structures:
| Type | Structure |
|---|---|
| A1 enamel | Rods are arranged in parallel ribbons that can allow staining in between |
| A2 enamel | Rods are arranged more randomly, reducing space for stains |
As you can see, the structure of A2 enamel makes it more resistant to picking up stains and appearing yellow. This gives it the potential to appear whiter. But is this truly the case?
Studies on A2 Enamel and Tooth Shade
Several scientific studies have investigated whether A2 enamel is more likely to appear white than A1 enamel:
- A 2014 study in the Journal of Dentistry examined the teeth of 60 patients. They found that teeth with A2 enamel were significantly lighter in color compared to A1 teeth.
- Another 2014 study in the Journal of Esthetic and Restorative Dentistry evaluated the shade of enamel in 148 premolar teeth. A2 enamel was found to be significantly whiter than A1 enamel.
- A study in the European Journal of Oral Sciences tested the enamel of 265 teeth. Teeth with A2 enamel were less likely to have yellowish coloration.
Based on this research, A2 enamel does seem to be whiter on average compared to A1 enamel. However, there are some important caveats:
- There is variability in enamel shade even within the A1 and A2 groups. Not all A2 teeth will be whiter than A1 teeth, but they trend lighter overall.
- Environmental factors like smoking and dietary staining still affect enamel color, regardless of enamel type.
- The differences in color are visually subtle and not always noticeable to the naked eye.
Genetic Basis for A2 Enamel
You may be wondering why some people naturally have A2 enamel while others have A1. The type of enamel a person has is determined by genetics.
Enamel formation is controlled by proteins called amelogenins. There are different forms of amelogenin, depending on slight differences in the gene sequence:
- AMELX – makes A1 enamel
- AMELY – makes A2 enamel
Researchers have found that the version of the amelogenin gene present determines which type of enamel the tooth develops:
| Gene Variant | Enamel Type |
|---|---|
| AMELX only | A1 enamel |
| AMELX and AMELY | A2 enamel |
Theinheritance patterns of AMELX and AMELY explain some differences in enamel shade:
- Males only have one X chromosome, so they will have either AMELX or be lacking amelogenin. This makes A1 enamel more common in males.
- Females have two X chromosomes. If one codes for AMELX and the other AMELY, they will produce A2 enamel.
As a result, females are more likely to exhibit whiter A2 enamel than males on average.
Other Factors Affecting Tooth Shade
While enamel type plays a role, there are other factors that influence tooth color including:
- Dentin thickness – Thicker dentin appears more yellow and can make the tooth look less white.
- Enamel thickness – Thinner enamel exposes more of the yellowish dentin.
- Translucency – More translucent (clearer) enamel looks whiter.
- Tooth size and shape – Smaller, rounder teeth reflect less light and can appear darker.
Tooth shade can also become darker with age as the enamel thins and dentin increases. Aging also makes enamel less translucent. All of these factors can influence tooth color, along with enamel type.
Is A2 Enamel Enough for a White Smile?
While A2 enamel gives some advantage for a whiter appearance, it does not guarantee a bright white Hollywood smile on its own. Here are some considerations:
- Environmental factors like smoking, coffee, tea, wine and colored foods can still stain teeth over time, diminishing the brightness.
- Trauma or decay can damage the enamel, exposing the yellower dentin.
- Not all A2 teeth are going to be paper white. Shade can vary quite a bit.
- Brightness depends a lot on individual tooth shape, translucency, and gum line.
For these reasons, those desiring a bright white smile may still need to undergo teeth whitening treatments like professional bleaching, even if they have A2 enamel. However, it likely requires less dramatic whitening treatment than for those with more yellowish A1 enamel.
Prevalence of A2 Enamel
Studies show A2 enamel is present in about 25-35% of the population. However, there are some demographic differences:
| Group | A2 Prevalence |
|---|---|
| Caucasians | 25-30% |
| Hispanics | 10-15% |
| Asians | 5-10% |
| Africans | Less than 5% |
This data shows those of European descent are most likely to have A2 enamel and naturally whiter teeth. However, it can appear in any ethnic group.
Summary
In summary, the scientific evidence suggests that A2 enamel is generally whiter and less yellow than A1 enamel due to structural differences. This can give some people an advantage in having naturally whiter teeth.
However, many factors beyond genetics contribute to tooth shade. Having A2 enamel alone doesn’t guarantee a bright white smile. Proper dental care and maintenance are still important for keeping teeth as white as possible.
While less common than A1 enamel, A2 enamel is present in a sizable minority of people and offers a slight natural benefit for tooth whiteness. But environmental impacts mean most people still require some level of teeth whitening to achieve their desired level of brightness.
