Cracked Tooth Diagnosis
When You Can Feel It But No One Can Find It
Cracked teeth are the masters of disguise. The pain is real but the X-ray looks normal. Diagnosing a cracked tooth requires specialized tools and experience that an endodontist brings — microscope, transillumination, bite tests, and sometimes CBCT 3D imaging.
Patient Education
What a cracked tooth feels like — and what to do
A short video from the American Association of Endodontists explaining cracked-tooth symptoms, why early treatment matters, and how endodontists often save the tooth.
Symptoms of a Cracked Tooth
If any of these sound familiar, schedule an evaluation. Cracks rarely improve on their own and almost always get worse over time.
Sharp pain when biting down
Especially when biting on something hard or fibrous like nuts, raw vegetables, or seeds. The pain often comes from biting at one specific angle.
Pain when releasing the bite
A classic cracked-tooth sign. Pain when biting down is common, but pain on release is highly suggestive of a fracture.
Lingering cold sensitivity
Brief cold sensitivity is normal — but if cold sensitivity lingers for 30+ seconds after the cold is removed, that's a sign the pulp is involved.
Pain that's hard to pinpoint
You may feel the pain but can't tell exactly which tooth it's coming from. Cracks often refer pain to neighboring teeth.
Intermittent pain
The pain may come and go for weeks or months, making it tempting to ignore. Cracks rarely heal on their own and often worsen.
No visible damage
Cracks are often invisible to the naked eye and don't show up on standard X-rays. Diagnosis requires specialized tools.
Types of Tooth Cracks
Not all cracks are equal. The type and depth determines whether the tooth can be saved — and how urgent treatment is.
Craze Lines
Cosmetic only
Tiny surface cracks in the enamel. Very common, harmless, and require no treatment.
Fractured Cusp
Treatable
A piece of the chewing surface breaks off. Usually doesn't reach the pulp. Often restored with a crown.
Cracked Tooth
Endodontic urgency
A crack runs from the chewing surface vertically toward the root. If caught early, can often be saved with a root canal and crown. Treatment delay is risky — the crack can extend.
Split Tooth
Often unsavable
A crack has progressed and the tooth is now in two distinct segments. Usually too late for endodontic treatment — extraction often required.
Vertical Root Fracture
Usually unsavable
The crack starts at the root and progresses upward. Almost always requires extraction. CBCT is critical for diagnosis.
How We Diagnose a Cracked Tooth
Cracks rarely show on X-rays — that's why patients sometimes go months without a clear answer. Our diagnostic process combines several techniques because no single test is conclusive on its own.
Bite Test (Tooth Slooth)
We have you bite on a small plastic instrument placed on each cusp individually. Sharp, brief pain when biting on a specific cusp — and especially on release — strongly suggests a crack at that location.
Cold Test
We apply a brief cold stimulus to the tooth. A normal response is a quick sensation that resolves immediately. Lingering pain (over 30 seconds) suggests pulp inflammation, often associated with a deeper crack.
Transillumination
We shine a bright fiber-optic light through the tooth. A solid tooth lights up uniformly. A crack blocks the light, leaving a dark line that reveals its location.
Microscope Examination
Under the Zeiss OPMI microscope at up to 25× magnification, cracks invisible to the naked eye become clearly visible. We sometimes apply a drop of methylene blue dye to make hairline cracks even more obvious.
CBCT 3D Imaging (When Needed)
For suspected deeper or root-level fractures, we take a CBCT scan. Unlike standard X-rays, CBCT shows the tooth from every angle and can detect bone changes around a fractured root.
Don't Wait — Here's Why
Cracks extend over time. A tooth that could be saved with a root canal and crown today may need to be extracted in three months. Every time you bite down on the tooth, the crack can extend a little further toward the root.
If you suspect a cracked tooth, avoid chewing on that side and schedule an evaluation as soon as possible.
Treatment Options
Root Canal + Crown (Most Common)
When the crack reaches the pulp but hasn't extended into the root, a root canal removes the inflamed pulp and a crown placed by your dentist holds the tooth together. Success rates are high when treatment is timely.
Crown Only (No Root Canal Yet)
If the crack is shallow and the pulp is healthy, your dentist may place a crown to prevent further fracture without needing a root canal. We monitor with follow-up visits — sometimes a root canal becomes necessary later.
Extraction (When Unavoidable)
If the crack has split the tooth or extended below the gum line into the root, extraction is usually the only honest option. We'll explain why and discuss replacement options with your dentist (typically an implant).
What the evidence shows
Our crack-management approach follows the published outcome literature and the AAE's prognosis framework — not a preference for any restorative product or implant:
- In a 2026 Journal of Endodontics analysis of 263 root-canal-treated posterior cracked teeth, overall success was 82.9% and survival 89.7% at a mean 40 months — but prognosis ranged from about 98% for cracks confined to the crown down to roughly 33% once a deep crack was joined by a periodontal pocket.[1]
- A vertical root fracture extending below the bone carries a poor prognosis and usually means extraction; modern surgical-diagnosis data confirm VRF risk rises with deep probing depths and specific radiographic signs.[2]
- Treatment is matched to crack depth using the AAE's favorable / questionable / unfavorable framework — craze lines monitored, crown-confined cracks restored, pulp-involved cracks treated with root canal plus a crown, and sub-osseous cracks extracted.[3]
Frequently Asked Questions
Can a cracked tooth heal on its own?
No. Unlike a broken bone, dental enamel cannot repair itself. Cracks tend to extend deeper over time as you continue to chew on the tooth.
Why didn't my dentist see it on the X-ray?
Standard X-rays look at the tooth from one angle and only show density changes. Most cracks run along the plane the X-ray travels through, making them effectively invisible. Diagnosis requires specialized tools an endodontist uses every day.
Will I need a crown afterward?
Almost always, yes. A cracked tooth needs to be protected by a full-coverage crown from your general dentist. This is typically placed a few weeks after the root canal.
Can a cracked tooth always be saved?
Not always. The earlier you seek evaluation, the better the prognosis. If the crack stays limited to the crown of the tooth, a root canal and crown can save it. If the crack has extended into the root, extraction is often the only option.
How long does treatment take?
The diagnostic visit takes 30–60 minutes. If a root canal is needed, that's usually a separate 60–90 minute appointment, often the same day if you'd prefer.
Based on the research
Microfractures invisible at low magnification become obvious at 16–25×.
Kim & Kratchman, Journal of Endodontics 2006 — foundational review of modern endodontic microsurgery.
The microscope is the diagnostic tool that finally lets us see what's actually happening inside a cracked tooth. A diagnosis made under high magnification is a different kind of diagnosis than one made by eye — and it's the difference between treating the right problem and treating the wrong one.
See the researchCracked tooth diagnosis and treatment — serving 30+ Bay Area cities
Dr. Jason Kung provides cracked tooth diagnosis and treatment to patients across Silicon Valley from our Sunnyvale office. Evening and weekend hours, same-day emergencies, free on-site parking.
Get a Definitive Answer
If you've been told "we can't find anything wrong" but you can feel something is, you deserve a proper diagnosis. Dr. Kung specializes in finding what others miss.
Same-day evaluation available · Mon–Sun
See also: root resection & hemisection — when a vertical root fracture is isolated to one root of a multi-rooted molar, removing just that root can save the rest of the tooth.