Mrs. Smith is in today for a second opinion.  Last week, Dr. Molar told her she has 5 cavities!  She hasn’t had a cavity in years, and she’s skeptical.  Today, Dr. Prince diagnoses only one cavity.  Why the differing opinions?  Is Dr. Molar unethical in his diagnosis and looking to make his next boat payment?  No, not necessarily.  Lets look at one way cavities are diagnosed:

Basic x-ray anatomy of a tooth:

  • Enamel Layer – Red
  • Dentin Layer – White
  • Junction – Blue

Check up x-rays are best for diagnosing cavities between your teeth.  Generally, they develop at the contact, where adjacent teeth touch.  Check up x-rays are not as useful for diagnosing cavities that develop on the chewing surfaces of teeth unless the cavity is advanced.

What does a cavity look like on an x-ray?  Dark triangles in the enamel perimeter PLUS a dark halo in underlying dentin.  You want to see the triangle in enamel extend all the way to the junction between enamel and dentin. If the dark triangle stops short of this junction, it’s very possible this process of tooth breakdown is reversible with a combination of good oral hygiene, improved diet and fluoride.

On the x-ray above, you can see the upper tooth has both the black triangle in enamel that extends to the junction plus the dark halo in dentin.  This tooth has a cavity.  The bottom teeth have small black triangles in enamel only.  I may be comfortable watching these areas with the patient’s understanding and approval.  Dr. Molar may be more aggressive treating these smaller lesions right away, realizing they may progress past the junction into dentin within 6-12 months.  Of course there are other factors that come into play, but appearance on an x-ray is a very useful tool.

Visual examination is more useful for diagnosing chewing surface cavities in pits and fissures of a tooth. Stain and decay can look very similar, but that’s a topic for a future blog post.

Be an active participant in your oral health care.  Ask your dentist to show you your x-rays and intra-oral photographs of your teeth.  Education is key and will lead to improved care.

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