Cosmetic Dentistry Blog Cosmetic and General Dentistry Questions Answered

August 29, 2013

There are a lot of things that can look like decay on the x-ray under a filling. Be careful here.

I have had a filling in the back of my lateral incisor (#7) since childhood that has been replaced several times over the past 10 years due to leaky margins, etc. The last time it was filled was in January of this year when my then dentist placed a pulp cap to avoid a root canal. There was minimal bleeding and he used a caries detector with dye to remove any caries by hand to avoid drilling too close to the pulp and then filled it.

I did not have any discomfort to hot or cold or any pain afterward. I still do not have any pain in this tooth on tapping or when eating and it feels fine but it was discovered at my new dentist that there is what looks like some decay under the filling on x-rays during my last exam in June with my current dentist and she says I have to have a root canal and a crown placed.

My question would be; if there is no sensitivity/discomfort in this tooth, would it be possible to remove the filling, clean out the decay and then place another filling or do I have to accept the root canal/crown diagnosis? I have already researched and contacted Dr. Hurley in Bedminster for the crown after finding her on your provider list for New Jersey, but would of course like to postpone the “bigger” treatment if possible. Thank you so much in advance for your attention and advice and I love your very informative website.
– Kathryn from New Jersey

I’ll go a step further even beyond your suggestion of waiting to have this root canal done. And I’ll be direct. No, I would not have this new dentist do a root canal and crown on this tooth. It sounds to me like they are a little too eager to do something quite aggressive here. Have another dentist look at this.

It’s interesting how you put the diagnosis – “It was discovered that there is what looks like some decay under the filling on x-rays during my last exam.” There are a lot of things that can “look like decay” on an x-ray. An empty space, a radiolucent glass ionomer base, or any of a number of radiolucent filling materials can “look like decay.” If the filling looks intact and isn’t leaking, after a close visual exam, I would leave it alone. If the tooth is infected, it would show up on an x-ray of the ROOT of the tooth.

A tooth that becomes infected will almost always hurt at some point, though there are exceptions. It will start by being sensitive to cold and ordinarily that will blossom into a full-fledged spontaneous toothache. The toothache, if untreated, will go away, and the tooth will die, after which it will usually become sensitive to biting on it. But that may not happen. It is uncommon for a tooth to die quietly, with no symptoms, but it does happen. The way to diagnose that is not by seeing something that “looks like decay under the filling,” but by seeing signs of infection around the end of the root of the tooth on the x-ray.

Finally, this idea of doing a crown on a lateral incisor after a root canal – I would not let them do that, even if it DOES need a root canal. A lateral incisor is a very thin and delicate tooth. To prepare a lateral incisor for a crown, most of the tooth structure has to be removed, leaving it very weak and vulnerable to breaking off. The average lateral incisor is going to have a diameter at the neck of the tooth of about 5 millimeters. To do a crown, at least a millimeter has to be ground off all the way around, leaving it with a diameter now of about 3 millimeters – which represents a decrease in resistance to lateral fracture of more than 60%. So, even though a back tooth with a root canal treatment needs a crown to keep it from fracturing, a front tooth is a completely different situation.

Now, if you don’t do a crown on a front tooth after a root canal, it will be susceptible to discoloration. But that susceptibility can be decreased and postponed by several years by careful handling of the tooth after the root canal. If all the root canal filling material is cleaned out of the part of the tooth that shows – carefully cleaned out inside down to the root of the tooth. Then, a translucent post can be placed in the root canal space to reinforce the strength of the tooth. If that is done, it could be five or ten years before the tooth shows any signs of discoloration, and you could do a crown then.

And furthermore, if you are going to have a single porcelain crown done on a front tooth, you definitely want a dentist with good artistic ability, such as Dr. Hurley, to do it.

– Dr. Hall
follow up: The next day, Kathryn sends an x-ray of the tooth, and I offer my opinion. It appears that this tooth does not need a root canal treatment. There is a dark area next to the tooth, but it doesn’t extend near the pulp, and there are definite signs that the root is healthy.

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About David A. Hall

Dr. David Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does complete Internet marketing for dentists.

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