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Mark Bornfeld, DDS
Mark Bornfeld, DDS, Dentist
Category: Dental
Satisfied Customers: 6013
Experience:  Clinical instructor, NYU College of Dentistry; 37 years private practice experience in general dentistry, member Academy of General Dentistry, ADA
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how can i tell if a tooth is cracked below the gum line about

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how can i tell if a tooth is cracked below the gum line? about a month ago i was eating popcorn and bit into something that was hard. i froze up thinking the tooth would just crumble and fall apart. Nothing happened. I went in to the dentist to have a tooth on the oppisite side filled and that evening started to chew only on the side of the mouth where the hard thing hit. i felt mild pain, (also this tooth has gum recession on the front and back), and then sharp pain. so i stopped chewing so hard. it took a week for the the tooth to feel "normal" again. i can push on it with my finger and get a mild discomfort similar to hot and cold sensitivity discomfort. my dentist used a desentizer on this tooth, but only on the front of it. this is a molar on the lower jaw. i dont normally eat on that side of my mouth, but was wondering how can my dentist tell if its cracked below the gum line? an xray? i heard you cant always see that. and could it just be sensitivety to pressure?
Dear ,

In truth, a crack in a tooth is not always easy to diagnose. You are correct that tooth cracks are almost never visible on x-ray, because the orientation of most tooth cracks causes them to run parallel to the x-ray film, rather than perpendicular. If a crack is of longstanding duration, the presence of a crack can sometimes be inferred by visible destruction of bone adjacent to the root. However, this diagnostic strategy is impractical, because most patients with cracked teeth cannot wait long enough for bone damage to become conspicuous.

Because cracks in teeth almost always originate at a level above the gum line, it is often possible to detect them with a combination of diagnostic tools:
  • if sequential tapping on each of the cusp tips of the tooth identifies one particular cusp that is more sensitive than the others, this implies the presence of a crack. A simple tool for the diagnosis of tooth cracks is the Tooth Slooth.
  • removal of all fillings or other restorations in the tooth will permit the examination of the interior of the tooth under high magnification-- either with magnifying loupes or an operating microscope; close visual inspection can sometimes permit direct visualization of a crack.
  • transillumination of the tooth (using high-power oblique illumination with high magnification) can sometimes detect cracks due to a disconinuity of light conduction across the fracture line.
These diagnostic tools are available to most dentists.

I should say that a traumatic blow to a tooth followed by sensitivity does not necessarily mean that the tooth has been cracked. A high-magnitude force directed at a tooth can be directed through the root to the periodontal tissues, which can sustain a bruise-- much like hitting one's thumb with a hammer can produce significant soft tissue injury that is short of a fractured thumb. The gradual improvement in symptoms is a favorable sign, but insufficient in itself to rule out either root fracture or pulpal injury. The tooth should be followed by your dentist for the emergence of other signs of infection, such as an upturn in symptoms, the emergence of an abscess or "gum boil", or more subtle indicators of infection as evidenced on future x-rays.

Good luck!

Edited by Mark Bornfeld DDS on 11/24/2009 at 4:31 PM EST
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