Updated on August 30, 2026: This guide has been refreshed with current dental guidance, clearer information about craze lines versus cracked teeth, updated treatment considerations, and additional original visuals.
What are craze lines in teeth?
Craze lines are fine cracks in tooth enamel that occur without loss of tooth structure. The American Association of Endodontists classifies them as the most superficial type of tooth crack and describes them as extremely common in adult teeth.
Because they remain within the enamel, true craze lines are generally considered an appearance issue rather than a dental disease. They are especially noticeable on front teeth because light passes through enamel and can make fine vertical lines easier to see.
Think of them less like a tooth that has “broken” and more like a fine line that has developed within the outer enamel after years of normal use and repeated mechanical stress.
What do craze lines look like?
A craze line may look like a faint vertical hairline running through part of a tooth. Some are nearly invisible unless the tooth is viewed under bright light. Others become more obvious because pigment collects along the line and creates contrast with the surrounding enamel.
You might notice one line on a single tooth or several lines across multiple teeth. They can be easier to spot on incisors—the front teeth you see when you smile.
Craze line vs. cracked tooth: What's the difference?
This is the distinction that matters most.
A craze line is limited to enamel. A cracked tooth extends deeper into the tooth structure. The American Association of Endodontists distinguishes craze lines from fractured cusps, cracked teeth, split teeth and vertical root fractures because the depth and location of a crack can dramatically change its significance and treatment.
| Feature | Craze line | Cracked tooth |
|---|---|---|
| Depth | Limited to the outer enamel | Extends beyond the enamel into deeper tooth structure |
| Pain | Typically painless | May cause pain, although symptoms can vary |
| Temperature sensitivity | Not typical of a true enamel-only craze line | Hot or cold sensitivity can occur |
| Pain when biting | Not expected | Can occur, sometimes when biting down or releasing the bite |
| Effect on the tooth | Usually cosmetic | May threaten the structure or health of the tooth depending on depth and location |
| Treatment | Usually none unless appearance is a concern | Depends on the type, depth and location of the crack |
What causes craze lines?
There is not always one identifiable cause. Teeth are exposed to millions of chewing contacts over a lifetime, and enamel can gradually develop fine cracks as part of cumulative wear.
This helps explain why craze lines are so common in adults and why they may become more noticeable with age. If you are interested in the bigger picture, our guide to how natural teeth change with age explains how tooth shape, enamel and wear can evolve over time.
Factors that may increase mechanical stress on teeth include:
- Years of normal biting and chewing forces
- Teeth grinding or sustained clenching
- Chewing ice or other very hard objects
- Using your teeth to open packaging or hold hard objects
- Dental trauma or a direct impact to a tooth
- Repeated stress concentrated on certain teeth because of individual bite mechanics
The presence of craze lines does not necessarily mean that you have a harmful habit or dental problem. In many people, they simply represent superficial changes that have accumulated over time.
Can teeth grinding cause craze lines?
Grinding and clenching—collectively known as bruxism—can place substantial repeated forces on teeth. The National Institute of Dental and Craniofacial Research notes that bruxism can contribute to enamel cracks and other tooth damage.
That makes bruxism a reasonable factor to consider when a person has signs of tooth wear or cracking. It does not, however, mean that every craze line was caused by grinding or that a person with craze lines necessarily has bruxism.
What about clenching during the day?
Bruxism does not happen only while we sleep. Some people repeatedly clench, brace or hold their teeth together while working, concentrating, driving or dealing with stress. This is called awake or daytime bruxism.
If you frequently notice your teeth touching while you are awake, jaw tension or tooth soreness, mention it to your dentist. Managing the behavior itself is important; an oral appliance does not automatically stop the underlying clenching habit.
Are craze lines dangerous?
True craze lines are generally harmless. They are confined to enamel and, according to the American Association of Endodontists, are ordinarily of no concern beyond appearance.
That is an important distinction because people often discover a fine line in a tooth and immediately worry that the tooth is about to break. A visible line by itself does not tell you that.
Symptoms change the conversation. A superficial craze line should not typically cause significant pain.
If temperature sensitivity is your main concern, our guide to why teeth become sensitive to hot and cold explains several other common causes, including exposed dentin, gum recession, cavities and deeper cracks.
Can you prevent craze lines?
Probably not completely. Craze lines can develop as teeth accumulate years of normal mechanical stress, so having a few of them does not mean you have done something wrong.
You can, however, reduce unnecessary stress and protect the tooth structure you have.
- Do not chew ice, pens or other very hard non-food objects.
- Avoid using your teeth as tools to tear, twist or open things.
- Keep regular dental appointments so changes in teeth and restorations can be monitored.
- If you grind or clench, discuss management options with your dentist.
- If you clench while awake, work on keeping your jaw relaxed and your teeth apart when you are not chewing or swallowing.
- Wear appropriate protection during sports or activities where dental trauma is possible.
Can a night guard prevent craze lines?
A night guard should not be marketed as a guaranteed way to prevent craze lines.
Its more established role is to protect teeth from damage associated with grinding and clenching. A properly fitted appliance separates the upper and lower teeth and reduces direct tooth-to-tooth wear. It does not erase existing craze lines, and it does not necessarily stop the neurological or behavioral activity behind bruxism.
If grinding or clenching is part of your situation, you can learn more about how protective appliances work in our complete guide to custom night guards.
Why do craze lines become darker or more noticeable?
Some craze lines become easier to see over time because pigment creates contrast within or around the fine enamel line. Coffee, tea, red wine, tobacco and other sources of dental staining can make superficial lines appear more noticeable.
Good brushing, daily interdental cleaning and regular professional dental cleanings can help control general surface staining. They will not physically remove an existing crack in enamel.
If one line suddenly looks very different, becomes associated with pain or seems to have changed after trauma, have a dentist look at it rather than assuming the change is only staining.
Can you get rid of craze lines?
Craze lines usually do not need to be medically “fixed.” If they are healthy, stable and painless, leaving them alone is often completely reasonable.
When their appearance bothers you, a dentist can determine whether cosmetic treatment makes sense. Options may include:
Dental bonding
Tooth-colored composite resin can sometimes be used to camouflage visible lines and other small cosmetic imperfections. Bonding is generally more conservative than placing a veneer because less tooth preparation may be required.
Porcelain or composite veneers
Veneers cover the visible front surface of a tooth and can conceal craze lines along with changes in color, shape or symmetry. Because veneer treatment involves a larger long-term commitment than simply monitoring a harmless craze line, the cosmetic benefit should be weighed against the amount of tooth preparation involved.
Professional teeth whitening
Whitening does not repair or remove a craze line. In some cases, however, lightening the overall tooth color can reduce the contrast between the line and the surrounding enamel and make it less noticeable.
Results vary, particularly when a line has picked up darker pigment. A dentist can help determine whether whitening, bonding, veneers or no treatment at all makes the most sense for the appearance you are trying to change.
How common are craze lines?
Very common. The American Association of Endodontists describes craze lines as extremely common in adult teeth.
That is worth remembering if you first notice one while examining your teeth under bright bathroom lighting. Finding a fine enamel line does not automatically mean something is wrong.
Craze lines may also appear more prominent as teeth age because years of function, enamel wear and staining make subtle surface changes easier to see.
Frequently asked questions about craze lines
Do craze lines mean my tooth is going to crack?
Not necessarily. Craze lines are already classified as very shallow enamel cracks, but they are distinct from a deeper cracked tooth and are extremely common in adults. A painless craze line does not automatically mean the tooth is structurally failing. New pain, biting sensitivity or other changes should still be evaluated by a dentist.
Can craze lines heal on their own?
Enamel does not regenerate the way skin or bone can, so an established craze line does not simply knit itself back together. Fortunately, most craze lines do not need to heal because they are superficial and usually harmless.
Are vertical lines on teeth always craze lines?
No. Fine vertical enamel lines are often craze lines, but photographs and visual inspection at home cannot reliably determine the depth of every crack. A dentist can assess a suspicious tooth, particularly when symptoms are present.
Can craze lines cause tooth sensitivity?
A true craze line is limited to enamel and is typically painless. If a tooth with a visible line is sensitive to temperature, sweets, pressure or biting, do not automatically blame the craze line. Other causes—including exposed dentin, decay, gum recession or a deeper crack—may need to be ruled out.
Can teeth whitening remove craze lines?
No. Whitening changes tooth color; it does not repair the enamel line itself. It may make some craze lines less noticeable by reducing color contrast, although results vary.
Should I wear a night guard because I have craze lines?
Craze lines alone are not a reason for everyone to wear a night guard. If you also grind or clench your teeth, your dentist may recommend an oral appliance to protect your teeth from those forces. The goal is protection from bruxism-related damage rather than treatment of the craze lines themselves.
Can a dentist tell whether a line is only in the enamel?
Dentists use your symptoms together with a clinical examination and, when appropriate, techniques such as magnification, transillumination, biting tests and periodontal probing to investigate suspected cracks. No single photo or at-home test can reliably classify every dental crack.
The bottom line
Craze lines can look alarming when you first notice them, but most are simply superficial cracks within the outer enamel. They are common in adult teeth, typically painless and usually do not require treatment.
The important question is not simply whether you can see a line—it is whether the tooth has symptoms suggesting something deeper may be happening.
If the tooth feels normal and your dentist confirms that the line is superficial, treatment may be unnecessary. If you have pain with chewing, temperature sensitivity, trauma or another change in the tooth, have it professionally evaluated.
And if grinding or clenching is contributing to broader tooth wear, addressing that habit and protecting your teeth can help preserve healthy tooth structure over the long term.