Dental MythBuster #9 – You can’t get a cavity under a crown

This is one dental myth that I wish I did not have to see.  The myth typically plays out like this:

“Mrs. Jones, I can see both on the x-ray and upon clinical exam that there is decay on this particular tooth.”

She will typically respond by saying:

“How can I have a cavity on that tooth? It has a crown!”

After years of practicing dentistry, I can say that this happens about 98% of the time when there is decay on a tooth which already has a crown. So this dental myth definitely needs to be busted!

Photograph of a cavity under a crown

Seeing is believing, so let’s take a look at a photo I took of a patient in my dental office in Orange, CT.

Photo showing a cavity, also known as dental decay, under a dental crown

A cavity, known more formally as dental decay, evident underneath a crown on a lower molar on a patient of mine in Orange, CT.

The decay is visible in the above photo at the gum line. Treatment will most likely involve a new crown. Without treatment, this patient will lose his tooth eventually.

By looking at the photo, you can see that it is possible to get decay under a crown. So the myth is busted! But let’s look at how it happens.

What are dental cavities?

Dental decay photo showing a cavity on an upper canine tooth

Decay on an upper canine near the gum line.

Dental decay (known less formally as dental cavities) occurs when bacteria inside the mouth ingest certain foods and then attack the teeth. This leads to a weakening of the tooth and can ultimately lead to an actual hole (a.k.a cavity) in the tooth.

Decay can occur on any part of any tooth in the mouth. It can occur on teeth that have never had a filling before. Or the decay can start on teeth that have had fillings, crowns, or root canals.  It can start at age 2 or age 100! For a more detailed explanation, you can refer to a page I authored on my main practice website.

How teeth with dental crowns can develop decay

As stated earlier, decay can develop on any tooth. But cavities are more likely to occur in certain areas.

Dental x-ray radiograph showing decay or cavities under or below a dental crown

The red circles indicate the decay at the margin of two different crowns.

When it comes to teeth with crowns, the area most susceptible to developing decay is the margin. The margin, as you would guess, is where the crown meets the tooth. It is the weak spot. It is the Achilles Heel.

Food and other debris can collect right at the margin. A crown that was poorly made will collect even more food. If you combine this with a diet rich in sugar or acid, along with home hygiene that is not ideal, you have a perfect storm. That perfect storm affected the two crown to the upper right on the x-ray, resulting in decay.

Another Dental Myth Busted

The above photos, descriptions, and x-ray show that even with a crown, a tooth can still develop a cavity. So it bears repeating:

Crowns will protect an already weakened tooth but you still need to brush and floss sensibly. If you don’t, you can develop decay just like you would on any other tooth.



  1. Crowns are a good fix for a lot of dental problems but you have to treat them like real teeth! They won’t stop gum disease and decay if you don’t brush and floss and have regular checkups.

  2. Can the cavity at the bottom of the crown’s gum line be corrected.

  3. Hello. I have a great Dentist. No complaints. Yesterday I went in for pain at I think #15 or 17#? Upper left? Back. I was given quite a nerve block and I expected this because the pictures he took, and showed me (so cool). We were on an “exploratory mission”. The crown had worn and the metal filling cracked. he explained no abcess showed in xray. Everything went OK he cleaned out decay did a build up and temp crown in place and due to copious bleeding from bad flossing and nsaid use I was given a microbial mouth rinse. Something weird happened one on the shots went up my nose to eye. I could feel every nerve. Now my left nare just runs and I have been sneezing nonstop. Taking claritin helps. I will say that prior to appt I was experiencing left side headache pain. Any thoughts?

    • Becky,
      There’s a lot going on in your story. An injection in the upper left can give your left nostril the feeling that it is running when it really is not. And those injections can produce numbness close to your eye. But I would explain this to your dentist and she what he has to say.

      • Dear Dr. Calcaterra-
        I was in to see my dentist yesterday to have her look at a ten yr old dental bridge that has some hot cold sensitivity lately. She told me after taking an xray of one of the bridges supporting teeth that I have a pretty big cavity inside of this crown. I was surprised and disappointed to hear this as bridges are very expensive. Plus I am wondering how a cavity can form on a crowned tooth-not on the margin but deeper inside the crown. How can this be? I am so hummed to hear this news. Especially since I have had a lot of dental issues in my life thus far. A few years back I had 2 teeth pulled and implants put in their place. Well after the implants they never moved back up. In fact they are still receeded around those 2 implanted teeth. And the dentist who did the implants can’t/won’t tell me why this has happened. Its so bad that the implant screws are visable! And the worst part is i payed $6000.00 for this procedure. Anyway if theres any advice/feedback you ca. Offer me i would greatly appreciate your help. Thank you for your time and consideration. -Amy B.t tell me why this has happened. Its so bad that the implanty screws are visable! Its horrible! And worst plart is that I payed $6000.00 for these implants. Anyway if there’s any I co/feedback

      • Luccas santos says

        Hi, I am getting a crown(maybe, I don’t really know) and I am really nervous. I see people who have a decay when they have a crown. I was wondering, can u get a decay even with a crown.? I am just really nervous…. This is my first one. Also, wats better a filling or a crown.

  4. Went into a new dentist for a cleaning and a loose crown. When the dentist went in to recement the crown he stated that I had some decay underneath. He cleaned the area and showed me the hole. He stated it was small and since the backside of my tooth was still stable he could reuse my crown. That was great but then I thought he would clean the decay more than just wiping out and having me rinse with an antibacterial mouth wash. I did ask if I should get a new crown and it was stated that they would watch it and let me know when it is needed. My concern is was it properly treated or should the decay hole have been filled then recemented?? I just don’t want to find that it wasn’t treated right and then I wind up with a root canal. Any thoughts?

  5. Hi Dr. Calcaterra, first off I really do have a dental-phobia of sorts and have a situation that is freaking me out. I am meticulous about my teeth, I brush with a sonicare brush and floss three times per day. I don’t like sugar and stay away from it (of course alot of foods have sugar – I just don’t drink sodas or eat candy or desserts, etc.). At my last teeth cleaning everything was fine and my dentist came in for an exam and immediately told me I had decay under one of my crowns. He pointed to the x-ray and said there was “massive decay”. Well, I pointed out to him that that x-ray was a year old. He doesn’t know why he missed it, but now I’m thinking of every single bad situation there can be. Having lost confidence in him for the time being I got a second opinion from my prior dentist in the same office – and he agrees with the first guy. So in a couple weeks I need to go in and get the crown busted off to see what’s there. My second dentist was great and went over all the possibilities for what could happen. I’m hoping for the best but still freaking out about the procedure and worried about pain. My question is – is a cavity under a crown pretty much the same as any other cavity except you have to take the crown off? Or by virtue of having the crown already, is it much worse situation? I’ve dealt with decay and new crowns no problem before – this situation just scares me.

    • Jennifer,
      Getting a cavity/decay underneath an existing crown is similar to other areas. There are a couple of differences. First off, as you correctly point out, the crown usually, but not always, has to be removed to remove all the decay. The second difference is that the EXTENT of the decay is often harder to diagnose, because the crown can “hide” the decay from the x-rays. So, sometimes the decay is worse than predicted, and other times it is not as bad. Hope that helps.

      • I have a crown on a tooth with previous crack (unknown how deep) #19. Things were good for about 5 years, but now I have on again/off again pain which is increasing to the point of real discomfort. No visible decay with x-ray (non-metal CERC), but endodontist says it will need a root canal before recrowning. I wake up with the worst pain (periauricular/neck) even though I wear a nightguard and there is a decent sized margin on the buccal side. Should I just get the root canal before redoing the crown? I’m anxious! Not sure I’m doing the right thing! PS I’ve already had 3 failed root canals – two got abscessed. I brush and floss and even use the go-between brushes.

  6. Hi, from the x-Ray, it show cavity under my crown. Will the decay get any worse in one yr’s time? I like to replace it when I return to Asia in Feb 2015.

    Appreciate anyone’s reply

    • Bee,
      It is impossible to tell without seeing x-rays and evaluating it in person. However, the decay is certainly not going to diminish in size over 1 year, and will most likely get worse.

    • OMG, I’m kind of laughing at some of the responses here when people say that their x-rays show decay under a crown. Folks an x-ray cannot see through a crown, no way, no how. A dentist is going to use other methods to determine decay, and it’s still a bit of a guessing game. A lot will go by what the patient is telling the doctor as well.

      A dentist for example can take an explorer, and probe underneath the crown at the gumline and check the depth. Obviously if the tip of the tool goes pretty deep, there’s a hole or cavity there. Sensitivity to temperature or the dreaded air gun can also indicate deterioration of the enamel of the tooth under the crown. Lastly of course there’s the visual. Bacteria typically gets in because the gun recedes around the crown, and create a small area for decay to get in. You can’t really get at this stuff with a toothbrush once it starts to get too deep. Again through a visual inspection as well as probing around with some tools the dentist may be able to see the beginnings of decay at the gum line. Then again, it still can be a guessing game. If patient is complaining of obvious pain sensitivity, then this is factored into the diagnosis. The exact extent of the decay still cannot be determined until after the crown is removed. lastly, if a patient had a root canal, then you’re kind of screwed as you won’t feel anything. Suddenly one day eating whatever, “snap” and the tooth breaks off of the gum line. It’s one very big problem with root canals. I’ve lost two teeth for this very reason. Lastly, crowns do not last forever, and if you can get 10 years out of them you’re lucky. During the preparation for a crown, the dentist should fairly aggressively push back the gum, so that as it heals it will grow over the edge of the crown. Not all dentist do to the same quality of work and not all labs do good work either. I would say as a patient, when you get a new crown to inspect very carefully the junction of the crown where it meets the gum. If you notice any gap whatsoever, don’t accept the crown. A good dentist is going to reject it before you do, but not always.

  7. I just had a crown removed that was bothering me. The dentist prepared the tooth for a new crown. I asked to look at it before he put on the temporary crown. the tooth that has been bothering me was black around the edges along the gumline the small tooth infront of it also prepped for a crown looked fine. I asked the dentist what was all of the black..he said it was decay, that he cleaned out most of it and shouldn’t cause any problems. but, if he cleaned all of it out the tooth will need a root canal.. so he was just going to put on the new crown and watch the tooth? Covering a decayed tooth is not fixing it.. I would think.. he ordered porclean crowns… If the tooth is decayed around the the gumline I can’t imagine that I will not have problems with this too soon.. Am i correct.

    • As long as the decay was removed completely, you shouldn’t have any problems. That being said, it can sometimes be difficult to effectively remove all the decay in these situations. This is the best info I can give without seeing your complete case.

  8. I was told tht i have tooth decay under my teeth that has crowns. since there is a chance that it could come back with the replacement of another crown; is it best to just have the 2 affected teeth pulled? There are so many medical risk when tooth decay goes un-noticed.

    • I had root canal and had a crown put on. I developed a cavity under the crown.In trying to understand how this could happen i happened to read an article that said when the tooth is removed or a year later the walls of the socket must be cut out with a dental burr. Is this really necessary? I have had some difference of opinion on this.

      • Phyllis,
        You can develop a cavity under a crown for many reasons. It can be due to: lack of flossing, high sugar diet, medications that make your mouth dry, changes in dexterity that make brushing/flossing challenging, and many many others. And yes, sloppy or rushed work on the dentist’s part can also contribute.
        Regarding an extraction, sometimes it is necessary to use a dental bur to cut the tooth and/or socket to get the tooth out. It varies a lot. But you can rest assured the dentist will not put his/her knee on your chest! (Dental MythBusters #1: Knee on my Chest?

  9. Dr Calcaterra, my crown (or the margins, actually) bleed when I floss them. What do you think this means? We can’t afford a new crown… thoughts on what it could be?

    • There could be a lot of reasons. Off the top of my head, some of them are:
      1. Poor shape (also called poor contours) of the crown.
      2. Generalized gum inflammation – but your gums would bleed elsewhere too.
      3. Decay – but the decay itself would not lead to bleeding. The decay could lead to more food being stuck underneath the crown leading to gum inflammation and then bleeding.
      4. Gap(s) between the crown and the adjacent tooth/teeth. Does the floss have resistance or does it pass unimpeded? If it is passing with no resistance, then you are getting food caught.
      What does your dentist say about it? That would be the first thing.

  10. John Bauernfeind says

    I am a born skeptic. My dentist says an X-ray shows a cavity under the crown. I was having some perio work done so I took the X-ray from my dentist and had him look at it. He said there was no cavity. My dentist is insistent that I have the tooth that he says has cavity re crowned. Should I get a third opinion? The margin is very tight and I have no bleeding from flossing or “soft pics”.

    • John,
      That is a tough question. To generalize though, periodontists don’t treat decay as part of their specialty procedures. But all the periodontists I work with are very good at spotting decay and alerting me (the general dentist) to it. I’m not trying to imply your regular dentist knows more than the periodontist – I just wanted you to know the distinction.
      A third opinion would likely be warranted. It’s tough when two professionals give conflicting opinions. Sorry I can’t be of more help.

  11. Hi Dr Calcaterra,

    I had a crown fall off during flossing last night. This crown has had issues historically, and the last dentist used amalgam to fill a couple of small cracks after looking to make sure the tooth was okay beneath. He seemed to look very thoroughly, and he used some equipment (I can’t recall that). I had crowns due to treatment for recapturing a disc with functional denistry. It left my teeth in a state of being unable to close, so crowns, etc. were used to make my mouth close again.

    What might one expect to see after just the crown comes off under the tooth? I know that is likely hard to say. But even with no cavity, how might the tooth look? I can’t tell what I am looking at, and I’m trying to find a dentist to have this corrected. What are the best things I can do until such time I can get in (likely within days).


    • Cheryl,

      In many cases, the underlying tooth will look downright ugly! But this does not mean there is/was a problem with the tooth. You will often see darker colors, especially if amalgam was once in the tooth. Amalgam, even after it is removed, will leave stains on the tooth. The tooth will look smaller, because tooth structure was removed to make room for the crown. I don’t know is this description helps you.
      The best thing you can do in the meantime is to get the crown back on. There are temporary cements you can purchase at the drugstore. And surprisingly, denture adhesive will actually work too until you can get in to see a dentist.

  12. Hi,

    I had a root canal and a crown put on a bottom molar around five years ago. I started getting some pain in the molar and gum stuck in between this crown and back tooth. Nothing could obviously be seen on an x-ray and I was sent to get a pocket reduction surgery. The specialist told me that he could see some decay between this crown and the back tooth. How could I feel pain if I had a root canal for this tooth? The pain went away following the pocket reduction surgery but is slowly recurring again after six months. None of my three different dentists and specialists seem to have a solution for me. What do you recommend?

    • Karyn,
      It is impossible for me to know what is going on without seeing you and looking at x-rays. Initial thoughts on what it might be could include:
      1. Decay into the nerve on the tooth that does not have the root canal.
      2. Chronic food impaction between the two teeth leading to gum pain.
      3. An issue with the bite – meaning the crown could be a little high or shaped in such a way that you make more contact with it than you should.
      4. Grinding or clenching at night.
      Just some thoughts. I hope this helps.

  13. Hi, My dentist says my tooth under a crown has a cavity and needs to be pulled. It doesn’t hurt at all and there was no mention of it at my last cleaning 6 months ago. I had x-rays one year ago and it didn’t show up then either. It’s going to cost over $2000 for the extraction and bridge. Do you think I should get a second opinion?

    • Susan,
      Many times decay under a crown is not visible without an x-ray. And to add to that, sometimes you need the x-ray to be at the ideal angle for the decay to be visible. So your story is totally plausible. However, since you are a bit hesitant, a second opinion would not hurt.

  14. Hi Doc,
    The past couple of days I had food stuck in between my teeth twice…one time it stayed stuck for a couple of hours. Everything was fine then all of the sudden pain with the tooth…like I bit down on something hard but I didn’t. Then if I try to jiggle the tooth lots of pain but I’m not sensitive to cold or hot. This is a 20 year old crown. I can’t see any hole or infection but like I said there’s pain and the bone of my jaw near it hurts. Could this be infection under the crown? I have throbbing pain and I’ve been taking ibuproften. Thank you very much.

    • Mamie,
      There could be a lot of reasons for what you’re experiencing. If you’re getting food stuck, it is possible there is an issue with either the tooth with the crown or the one next to it. “Throbbing pain” is not normal. You should have your dentist evaluate it and let you know what it going on.

  15. Nancy Nowak says

    Hi Doc,

    My tooth #14 has a crown and a root canal. Tooth #15 was having a root canal done. It had a crown with decay under it and when the root canal dentist x-rayed #15 with a 3-D x-ray, he saw decay under the crown of #14. He said that it could not be repaired and would have to be extracted.

    Why would it be that tooth #14 can’t be repaired and must be extracted? I have no pain in this tooth. I hope if it is extracted, I can get an implant but my dentist thinks the bone is too thin for an implant. He called it #3 bone whatever that means.

    Thanks for any advice and opinions you can give me. This was such a disappointment. Now I am worried that my other three crowns might have decay under them too!

    • Nancy,
      From your description, #14 has had a root canal. As you are aware, it means the nerve is no longer there. Therefore, when you get decay in a tooth that no longer has a nerve, you are less likely to feel pain.
      I didn’t see the 3D image so I can’t know for sure. However, in general, when you develop decay that is deep under the gums, it becomes much more difficult to treat. It is also possible that there is decay which has led to a fracture of the tooth root. When that happens, the tooth is not saveable.
      Your dentist is probably referring to Type III bone. Dental implants are placed in Type III bone every single day. I would seek the opinion of a dentist who does dental implants on a regular basis (typically oral surgeons or periodontists).

  16. I’m a dentist skeptic and was told several weeks ago that there was decay under two crowns – they showed me the x-ray and said – see the dark spots – well I can’t read x-rays and saw some dark around the two crowns. They followed up with – the crowns will need to be replaced and we didn’t do them. Those are the only two they haven’t done! Hmmmm – should I ask them to show me the x-rays from 6 months ago and compare them with the recent ones? Can decay form that fast under crowns? I’m not having any problems, no hot cold feelings or anything. Thanks Dr.

    • Dianne,
      I was not there to perform an exam nor view your x-rays so I can only base my response using my own experiences. Remember that decay can develop underneath crowns (which was the point of this post). Sometimes you really can’t see the decay without an x-ray. Other times, the decay is visible. Sometimes, depending upon the angle that the x-ray was taken from, you can’t always see decay even when it is there. But take it again from the “right” angle and you can see it.
      Are some dentists overly aggressive in recommending things? Yes. Whether this is happening in your case I do not know. You do have a legal right to your x-rays so the best thing to do would be to seek a second opinion.

      • Dianne Olson says

        So happy that I had my crowns re-done and paid attention to what you said.! There was dark around the two teeth that already had the crowns on the x-rays and I of course was skeptical. There was decay under both crowns and they lasered tissue so that the new crowns fit tightly. I didn’t even have to have posts and build-ups and thank you so much for being the voice of reason!

  17. Dr. Calcaterra,

    I had a crown put on #19 5 years ago, and up until last week had no issues. I do go back every 6 months for regular cleanup. Some days ago I started noticing sensitivity to cold liquid, and a “sensation”, not really pain but a feeling that something is awry. I am following your (very helpful) thread and wanted to ask you – is is possible to have decay under the crown, clean it and put the same crown back? If not, should it be possible to get a new crown without RCT or is this a sign that root canal is the most likely alternative, followed by a new crown? What is the most conservative procedure you can think of in this case? Thank you so much!

    • Otavio,
      It is hard to tell what exactly is going on without x-rays and a clinical exam. I will say that according to the research, about 10 to 15% of teeth that have crowns placed ultimately need to have a root canal done. That need can occur 1 month after the crown is placed or twenty years! In most cases, a small hole is drilled through the crown, the root canal is done, and then that hole is filled. So in those cases a new crown is not needed. If I had to guess, you probably need a root canal. But I would defer to your dentist. Hope this helps.

      • Thank you for your reply, Dr. Calcaterra. I went to my dentist, took X-Rays from different angles and nothing came up, no cavities under the edge of the crown, typical place; or anything at the end of the roots. Also there were no difference between these and older x-rays. I am guessing there might be some sort of galvanic current, or something under way not enough to warrant a RCT but enough to cause discomfort. I really don’t know… old age maybe

      • Hello Dr. Calcaterra. So yes, I ended up needing a root canal, did that through the crown and next week will put in the guta percha. I am pretty much getting used to the idea that at some point I will need to get it extracted, and really dread the risk of having nerve damage when/if I have to do an implant. Hope the crown lasts for a little while more. Thank you as always for all the information.

  18. Why don’t dentists seal the tooth before placing the crown? My mouth is full of crowns and I’m still having trouble with cavities I hate my teeth. I’ve spent more on my mouth than I have on my truck.

    • Carrie,
      The tooth is effectively sealed by the cement. Remember that all cements (and all other dental materials for that matter) have to be approved by various government agencies and be safe. There might be better cements and/or sealers out there, but if they’re full of harmful chemicals, we can’t use them! So even with the best cement and materials out there, if there is a combination of lots of sugar and less than ideal brushing/flossing, decay can occur.

  19. Dear Doc,
    I had a root canal in a molar a year ago.
    I then had a cap put on over it a few weeks after. The tooth has always been sensitive to the touch and dentist and Endo saw nothing wrong on X-rays. I complained a few times. Well now I have excruciating pain that tooth up to the gum.
    Last week the Endo told me he couldn’t get into one of the canals because it was so calcified. He tried again last week and still could not get through.
    I made an appt to get it pulled because I can no longer deal with the pain.
    My Endo is so confused as to what is causing this pain and he is a top rated Endo where I live. The X-rays show nothing even all the way up to my sinuses.
    Can this be because of the calcification or maybe something totally unrelated?
    45 yr old female, never had the greatest teeth but never severe problems like this.
    Please help!mim living in 600 ibuprofen every few hours, ice pack, and benzocaine paste.
    Thank you for any answer!

    • Sue,
      If your endodontist has evaluated you then he/she can give a much better diagnosis than I can. I will say that the success rate for root canal treatment on upper molars is not 100%. Depending upon which study you read, it can be from 96 to 99%. So even with a 99% success rate, that means 1 out of 100 upper molar root canals fail. Based on what you have written, you may have fallen in the 1%.

  20. if a cavity needs to be fixed under a crown can you put the same crown on or do you need a new one?

    • Lenore,
      The answer is “it depends.” Sometimes you can fill a cavity underneath a crown without disturbing the crown. Other times, the cavity is not accessible, and the crown has to come off. If the crown is removed, you generally have to do a new one.

  21. Dear Dr. Calcaterra,

    Seven years ago my dentist put a crown on a lower molar after the tooth developed a crack (there was some pain when I chewed and my dentist said the crack made the tooth very vulnerable). The crack resulted from, I assume, either chewing on something hard or grinding my teeth at night (though I wear a mouth guard at night). Last fall the tooth started to ache a little and early this year even more. My dentist ended up removing the cap and discovered to his great surprise that the tooth had rotted to the point where pulling the tooth and getting an implant was the best option, according my dentist. I am very careful with my teeth and am not happy losing my tooth. Is it acceptable that after seven years a tooth that was presumably well-cared-for has rotted to the point of needing to be pulled? I am wondering if my dentist is competent. If he isn’t, I see no option but to find another dentist. In addition to losing the tooth, the implant procedure is very expensive. It will cost five or six thousand dollars. Should I be looking for another dentist? Thank you.

    Thank you

    • Nick,

      I understand your frustration. Your question, though, can’t truly be answered without knowing and seeing all the clinical details. And even with all the clinical details, it is still hard to tell. As you can see in this post, decay can develop underneath a crown, and ultimately that can lead to loss of the tooth. Sometimes that is because the patient has poor hygiene… other times it is because the patient has severe dry mouth… other times it is because the tooth is tough to keep clean due to its location… other times it is because not all the decay was removed during the crown prep… and other times we simply don’t know why.

      To answer your question, I would suggest this: you will likely be seeing a specialist for the implant? While you are there, why don’t you casually ask the specialist, as well as the assistant, how confident they are in your dentist. In general, most specialists know who is good and who is not very talented. They won’t openly say anything negative, but watch for what they imply and look at their body language. Hope this helps.

      • Dear Dr. Calcattera,

        Thank for your reply. It is very helpful.

        I will follow your suggestion. Of course, my dentist refered me to the specialist who is in the process of putting in an implant where the tooth was pulled, so I sense the specialist will be very careful not to question my dentist’s ability. I will watch the specialist’s reaction and body language very carefully when I bring up this matter.

        (Regarding my dentist, when I came in to have my teeth cleaned– my first visit after he found the decay under the cap– his body language and that of his staff was strange, as though they were expecting me to bring up an unpleasant topic– the lost tooth. I imagine that dentists often get blamed for bad results and lose patients as a result, even when they are not responsible for the disappointing results. Thus, I am not sure what to make of the unusual body language.)

        I will ask the specialist who he recommends to put the cap on the implant stud, since he himself won’t be doing this. Does putting the cap (crown?) on the implant stud require a lot of skill? Is it a challenging procedure for a dentist?

        Thank you again.


        • Nick,

          Unfortunately, dentists get blamed for lots of things, most of which are not their fault. Many people just don’t want to accept that decay and/or gum disease can happen – and as a result they blame the messenger – and not the message. Occasionally, a less than ideal outcome can and will occur. This happens to all dentists – and the good ones are the individuals who own up to it and try to address it.

          In general, restoring dental implants did not become part of dental school curriculum until the mid 2000s. Many dental school graduates today have never restored one – they’ve only learned about it and watched it be done. And for many older dentists – they never received any training in dental school on implants. So the onus is on the dentist to learn about implants. Restoring dental implants is not necessarily difficult, assuming the dentist has spent time on his/her own or at classes or both learning. However, good specialists realize when the referring dentist is weak, and will guide him/her through the case. When I first graduated, I spent a LOT of time with specialists learning from them. And lastly, the specialist has a vested interest in seeing that the case goes well.

          This might not answer your question directly, but I hope it helps.

          So, I’m not really answeri

          • Thank you, Dr. Calcaterra.

            Your response to my questions is helpful.

            I’ll ask the specialist who he believes would be the best person to put the cap/crown on the implant stud.



  22. Hi Dr. Nicholas,
    My # 9 has a root canal + crown (joint with #8) of over 15 years, treatment done in an Asian region. Last week, I visited 3 docs to get it evaluated. 3D scan shows bone is cracked. Now these doctors suggested extraction, bone graft, implant or bridge. I have already paid some $$$ out of pocket (mold impression, etc). Cost and timing is a great factor because I am moving to different state. Most appreciated if you could you please advise what is best option for me? Thank you.

    • Ally,
      Each patient is unique and I can’t possibly know as much as the dentists treating you. But based on your description, it sounds like it has been confirmed without a doubt that there is a fracture of the root that makes the tooth unrestorable. In general, implants are a better option, because a bridge requires the two adjacent teeth to be modified – and as a result, if one tooth fails, the entire bridge has to be replaced. 3D scans can be emailed and read by other dentists. You’re also dealing with a front tooth which is highly esthetic. I would recommend that you do not begin treatment until after you move.

      • Dr. Nicholas,
        1) I forgot to mention that #9 has cavity, a post and now a minor bone fractured. Can the bone be restored? If not, what material is used to replace the bone? I am nervous about the procedure.
        2) If I decide to get a bridge, will the bone graft stays good for a long time?
        Thank you.

        • Ally,
          The tooth – #9 – appears to be unrestorable. It sounds like it will be extracted. Bone grafts are typically done. You should ask the specialist what type of bone he/she will place. Sometimes it is human cadaver bone; other times it is derived from cows. Most grafts are successful long term. But if you don’t have an implant placed into that sight, the bone long term may slowly resorb. Again, the specialist and/or your dentist should be able to help you.

          • Most appreciated for answering all our questions. Doc suggested cadaver bone and it also does not guarantee complete success.
            Thank you very much for taking time to reply.

  23. My husband had a root canal and a crown on his tooth, and now the dentist is telling him he has a cavity under his crown. Could this be caused by bad workmanship and incorrect placement and sealing of the crown??

    • Sue,
      Every clinical situation is different so I can’t really comment with certainty. When was the crown done? If the crown was done 10 years ago, then the development of decay under a crown over that amount of time can and will occur regardless of the workmanship. If the crown was done a year ago and decay is already there – then that is a problem. I’ve seen properly made crowns fail in a year only in very unique circumstances (such as a stroke leading to a total inability to brush teeth, radiation treatment to salivary glands and/or removal of salivary glands, severe acid reflux or bulimia, meth addiction, etc.). But absent anything major like that, if a crown fails in a year or less, it likely was not done properly, in my opinion.

  24. I had a 8-year old 3 units bridge
    Went to my dentist and he said I had decay under one of the towns
    I need retreat of root canal and lengthening of gum area and then a new bridge
    It will cost me around $2700
    If I pull out the tooth and do an implant it will cost me around $4600
    I found cement on ebay and willing to re cement the bridge temporarily till I can’t afford doing it
    Thank you for your help
    Will the decay get worse and what is the worst case scenario if I do that

    • Joseph,
      Every situation is different. But in general, decay almost always gets worse. Using cement found on ebay may help in the short term but long term will not fix the problem. If you don’t address the decay, that can lead to lots of issues – pain, infection, loss of tooth/teeth, and other issues.

  25. My dentist drilled through the MIDDLE of my crown to fill what he said was decay. Why would he do this instead of taking the crown off???

    • Jan,
      Unless the crown was cemented on with temp cement, there is NO way to remove a crown without destroying it. Based on your post, it sounds like the dentist was doing you a favor – trying to address your decay in your tooth without requiring you to invest in a new crown.

  26. I have a bad smell along the gum line of a crown I had done over 5 years ago. If I have to have the crown removed to clean underneath the tooth, can that same crown be put back on? Thanks.

  27. Hi Dr. Calcaterra,

    Thank you for your terrific post. It has really helped me make the right decision. I have crowns on 14 and 15. 15 just had root canal retreatment. 14 has decay under the gum line that is clearly visible, and my dentist said to leave it until it bothers me. Now I understand why (since you said they are harder and need a new crown). The endo I just went to said I should have it addressed, and a second opinion also flagged 15 to be recrowned after removing some decay he spotted, also on the x-ray. So now I’m sure that I’m going to have my dentist do both #14 and #15 at the same time and clean them up. He is so great. I got 21 years out of #14 and 15 years out of #15. After I read your comment that decay would happen underneath the crown after 10 years, that really convinced me to take care of both of them, even though I might need a root canal on 14 when the decay is cleaned out. I was really going back and forth, as these other dentists kept saying you need to do this right away, and my two dentists (first his dad and now him) of 25 years said just leave it until it hurts, and then I’ll fix it. I think he is just very conservative like his dad was, and less hot to treat for financial reasons like the other 2 guys. But he said anytime I want it done he’ll do it.

    I go back to Los Angeles from Washington yearly to see him, and I was wondering if the temporary filling that the endo is putting on #15 on November 10th will last until my Jan. 1, 2016 appointment down there? One dentist told me 30 days, another told me you could go as long as 6 months, though sooner is always better. Do you think if I try chewing on the other side of my mouth a temporary filling in #15 would last about 65 days? I can go sooner, but I have other doctors I see down there, and i would have to move all of their appointments and try to get them to coverage on the same week again. I would prefer to leave it in January. How long do you think I can go?

    Thanks again for all the info,


    • Jim,
      A temporary filling placed into a crown after a root canal is done will usually last a couple of months at least. But the sooner the better.

      But a better idea would be to tell the endodontist (or whoever is doing the RCT) that you will need the temp filling to last a couple of months. He/she should be able to place something that will last a bit longer.

      Regarding your other issues on whether to do additional work on the upper left, it is impossible to know without an x-ray and an exam. But in general, if you wait until it hurts, the problem typically becomes worse and harder to treat.

      • Thanks doc. i let him know. the nurse said they can do an intermediate temporary that should hold 60 days. i got my xrays emailed to me; if you’d like to look at them, i’d be ok emailing them to you. i just didn’t want to post them online or anything. they are a less than 300K jpeg.

        thanks again for the advice and support.

      • Hi doctor Calcaterra,

        So 30 days prior to my final procedure i told my endodontists nurse assistant billing person that i wanted an intermediate temporary filling to last me for 70 days so i can get back to my dentist for a permanent filling. she said that would be no extra charge over a regular temporary filling. i told her if the dr had an issue with that to have them call me. never heard from them over that 30 day time period. i told her today just before they performed the last procedure i wanted an intermediate and asked her if she told the dr. she said no as the assistant does them. as the dr. was finishing my procedure the asistant and dr se started talking in code about physican o wants intermediate and dhmo this and some other stuff. he said to me with the rubbber dam on my mouth and all that he qad going to do a permanent for me as they dont cost that much and he also is doing me a favor so i dont need anothet appointment. i said thank you as best i could and thought it was free, especially since he unilaterally made the decision. i received no treatment plan or consent form for the filling. at checkout the same nurse i told twice that i wanted the internediate temporary now wants $280!!! the nurse at assisted during the procedure said he didn’t say it was free he just said that he would do it it cost which is not what I heard it all and if you would have told me it was $280 I would have absolutely categorically said don’t do it.

        I demanded to speak with the doctor but she said he wasn’t in the office anymore and this was only like 15 minutes after my treatment.

        on top of that, my retreated tooth has really hurt the last few days and still continues to hurt much more than before any retreatment began. he did some tapping and said he thinks its just my sinuses but the tooth is fine. but it sure hurts especially the gums are really sore. I can’t even sleep on that side of my face anymore because it hurts so much. it doesn’t seem to hurt too badly when I eat with it as long as I eat soft food.

        what would you suggest I do besides pull the tooth and pay the guy for a filling that I never wanted in the put in the first place if it wasn’t free?

        • Jim,
          I really can’t comment on the billing issue other than saying that in my office, if there is a change in treatment that will result in a larger out of pocket payment by more than $20 or so – we always tell the patient in advance.
          The success rate of endo re-treatments is far from 100%. But it sounds like not enough time has elapsed to determine success vs. failure. You may want to wait. If not, extraction is the only predictable option.

  28. Hi Dr. Calcaterra,

    My new dentist did full x-rays and was concerned about a root canal that was done through a crown. She said there could be a cavity underneath; it’s not visible. This was done over 10 years ago, so I can see the value in getting a look at it, but from my understanding, it seems like if the crown is put on well there’s not much to worry about. I’ve also read crowns are hard to remove and damage to the tooth is possible. Don’t want to end up needing an implant. I haven’t had any new cavities since I was a kid, I floss daily. What are your thoughts?



    • Donna,
      That’s really hard to tell without an exam and x-rays. In fact, even with an exam and x-rays, detecting decay underneath a crown can sometimes be difficult. While removing a crown can be time consuming, as long as it is done properly, the removal itself will rarely cause issues. Sometimes you remove a crown and the tooth is totally decayed underneath and the patient loses the tooth. But in those cases, the loss of the tooth is from the decay, not from the removal of the crown. Hope this helps.

  29. Harris Freedman says

    I have decay under my crown, when the crown is removed to fix the decay can the same
    crown be used again?

    • Harris,
      Unless the crown was cemented with temporary cement AND the decay is very small – both of which are probably unlikely – the old crown cannot be used. The old crown typically has to be cut off to be removed.

  30. Can I just have the cavity filled and put the crown that came off back on. It is in good condition and fits snug!

  31. I had several crowns put in a couple years ago. Today I was eating pizza and one of my crowns popped off. When I went to look at it in the mirror. It look like the tooth that was under the crown was rotten and have broken off. The two that was under the Crown had a root canal done probably about 20 years ago. My question is what could be done to get a new tooth in place and crown put back on? Can this be fixed. Will the tooth need to pulled? the tooth is in the front of my mouth. What cane done to restore my smile. Just like most people here, i believed that you could not get a cavity/decay under a crown. What should I ask my dentist when Ih go in to have this fixed? Spent a lot of money on crowns and can not afford to have this happen with the rest of the crowns.

    • Edward,
      Every case is difficult. But, generally speaking, if there’s very little tooth structure remaining above the gums, the long term outlook for the tooth is pretty grim. The key question to ask your dentist is whether that tooth is restorable. And if yes, what the long term outlook is. Hope this helps.

  32. I recently was told by my dentist that his crown failed BC the margin was bad and food got caught under it and the tooth under my crown decayed. He said it’s never happened to him before and he guarantees his crowns so I came back in to get a new one. Then he said that the decay was too bad and there is no tooth left so I have to get an implant. He is covering the cost of the crown but not the implant surgery. Is this fair or normal? I asked if this would have happened had the crown been done right and he said no so I’m a bit confused why I’m stuck with the bill. Thanks for any advice

    • Christel,
      Your question is impossible for me to answer without evaluating x-rays (past and current), chart notes, and seeing you in person. There are too many variables and without knowing the true history I can only speculate.

  33. Sandra Coffman says

    I had my top 8 teeth capped 9 years ago and have never had any problems with any of them since then. I have always had a problem with weak enamel, several of my baby teeth had to be pulled when I was young because of the problem so it was just something that has continued in my life regardless of brushing and flossing regularly. Anyways, this past Friday I had one of them come loose, the one to the immediate right of my front teeth. I got into the dentist that same day and much to my dismay they found decay underneath the cap due to X-rays and by the exam. My main question is, since my cap is already lose what are the odds of them being able to reuse the same crown? I understand this depends on the tooth underneath and the shape it is in. If they have to do a new crown, what are the odds of it matching my other ones? I have seen a lot of people that have mismatched caps/crowns and that is not at all what I want.
    Thanks for any help!

    • Sandra,
      Each and every case is different. But generally speaking, if there is decay observed on the tooth under the crown, usually the crown cannot be placed back on and expected to last for a long a time.
      Getting a new single crown done that matches the adjacent teeth is difficult but not impossible. Nearly all of it depends on the dentist and his/her choice of labs. I do this quite frequently in my office. It is time consuming as it requires many photos and lots of communication with the lab. Some dentists are up for this – and have the training and facility and staff to do so – while others are not. The key is to find a dentist who does this often. Hope this helps.

  34. Quick question, I have a cavity under an old temp crown. My dentist wants to remove the existing post as well. Is that normal? From what I have been reading on here is seems like the crown was removed, tooth cleaned, and a new crown put on. No one has mentioned anything about the post. Thank you.

    • Jessica,
      Posts often times need to be redone/removed. This can be due to decay around the post, fracture of the post, insufficient length of the post, the existing post loosening up, the existing post being metal and causing staining or shadowing, and/or many other reasons.

  35. I am having sensitivity pain lower right back teeth. (I am not sure if it’s the last tooth or one in front of it). It only hurts on occasion to extreme cold such as ice cream or if i bite a certain way. Although i can eat almonds, crackers, meats just fine regularly. just every now and then i get a quick “zing” I regularly visit the dentist (every 6 months) and last June when this started my dentist did an xray, blew air, cold water and tapped and tested both tooth, but did not find anything. My one tooth does have a 15 yr old crown, that he said looked in good health. I returned for my checkup this past January and mentioned it again, but again, they found nothing wrong. (although no new xray’s ) It’s now April and seems like the cold sensitivity / pain (very quick) happens a little more often. Do I ask them to xray again or not sure what to do? wait until my next checkup in july? I’m not in constant pain, and it only happens on occasion, but worried there is something else starting to go wrong with back tooth, or if maybe the crown on the one next to it is starting to fail. thank you.

    • Kim,
      You certainly can mention it again, and indicate that it’s happening more frequently. You could also ask if you think you should be evaluated by an endodontist (and endodontist is a root canal specialist). When a tooth has had a crown placed over it, there is always the possibility it will end up needing a root canal, even 15 years after the crown was placed.

  36. I had a root canal performed and a crown put on a molar in Oct. 2015. I still have sensitivity on the outside near the gum and if I tap on the crown. It almost feels like the crown might not be completely secure or the tooth is cracked and I’m concerned I might get food particles or bacterial up there and decay may begin. The dentist says it looks fine. Also, I have a crown that was put on 30 years ago that has some nerve sensitivity now. I don’t know what’s going on…I figured I needed a new crown. The dentist says it’s secure, so it should be fine. Is there something that I might be missing here….I figured if I have nerve sensitivity maybe it’s cracked, or there’s cavity…I’m not sure. The dentist did x-rays and didn’t notice decay I’m assuming since she isn’t feeling it needs treatment.

  37. Was randomly googling facts about teeth and found this site. Started reading through the comments and I admire the fact you are here answering questions, for years at that!

  38. Hello Doctor, If you get decay underneath your cap, and its close to the nerves as my Doctor has said, and he said I need a root canal, what is the best thing to do, an implant with zirconium, or just pull it and be done with it?

    • Also, he said the tooth is not infected, and that the pulp is alive? I’m just having pain when the food compacts between the chipped cap.

    • Greg, the whole decision of saving the root with a root canal vs. getting an implant is a complex decision relying on many factors. There is no one size fits all approach. But, in general, if a tooth has a good prognosis, most would recommend a root canal over an implant – myself included.

  39. I had a crowns put on two teeth, one on each side of my mouth, the crown on the left side has a large gap between the gum and the tooth(I noticed it within 2 months of the placement). My dentist told me that my gum had receded(even though a crown next to it (gold)is fine,,he put both on…..Now the second tooth on the other side of my mouth has a small gap,,, I have a total of 4 crowns, 3 he placed and of the 3, 2 have gaps that appeared in less then 3 months of placement,,,,I have a hip replacement and am diabetic and worry about infections,,,,,,Should I change dentist???

    • Barb,
      Your situation is tough to diagnose without seeing you and doing a complete exam. Generally speaking though, if significant changes are occurring so quickly after the crowns were placed, that could mean something is wrong. If you attempt to floss and the floss encounters no resistance as it passes between the teeth (this is called an open contact), then that is not supposed to happen. If I placed a crown and 3 months later there was an open contact, I would be doing a new crown – at no charge – ASAP.

  40. I had an emax crown placed 3-4 months ago (after a root canal). The past two months, the gums around that tooth have been somewhat sensitive and very slightly puffy to the touch (and on one occasion started bleeding while flossing). The gums around the rest of my teeth feel fine/normal. I also sometimes feel slight pain in this particular tooth, that shoots up the face, but I didn’t think that would be possible since it has a root canal? Are these symptoms normal in new crowns as the mouth adjusts, or should I be concerned?

  41. I had a top molar extracted about 10 months ago. After I had the extraction done I went to my dentists office two weeks later to get the bridge started. Just as he started to remove a crown, the dental drill slipped and cut my lip open pretty bad-I was pretty traumatized by the drill accident but I like my dentist and he’s human, and these things just happen…To make a long story short-I ended up waiting for awhile to go back to get it done.
    Is it too late for me to get a bridge since its been 10 months? Also the drill mark on the crown,can that compromise the tooth underneath? (Had a root canal on that tooth over ten years ago) He had just started the procedure when the drill slipped.

    Thank you for your help.

    • Amy,

      Generally speaking, waiting awhile after an extraction to do a bridge is not an issue. In general, I like to wait at least a month, sometimes more. But each case is different.

      Regarding the drill mark, that’s hard to tell, but if it was just when he started the procedure, it is unlikely to have compromised the tooth.

  42. I had a root canal and crown put on back molar 3 years ago. It popped off a few weeks back, went to the dentist, and he said there was decay and that crown no longer fits.

    I’ve taken very good care of my teeth since I had those procedures done- it was such a financial struggle that it gave me great motivation to do so! I read a comment above that a crown that fails after a year is not normal. What about 3 years? I am yet another dentist skeptic because I’ve had a few fillings fall out within one years time, so my confidence in this dental office is lacking.

    Thanks so much!

    • Aubrey,
      Every case is unique. A crown that fails after 3 years is fairly unusual. There could be many reasons for this. I don’t know the specific circumstances. But, generally speaking, crowns typically don’t fail that quickly and neither should fillings be coming out so readily.

      • Thank you. I just needed to know if it falling off is unusual for most people so I don’t sound like an idiot when I speak with my dentist about the cost to replace it.

  43. Hello Doctor,
    About ten days ago a very old gold crown (from the 70’s!) fell off while I was eating, and luckily I spit it out rather than swallowed it. It’s the rear left last lower molar. My dentist is of course on vacation but I’m hoping to get an emergency appointment next week when she’s back. Under where the crown was, the remaining tooth seems to have a dark crevice running from the ouside surface towards the center of the tooth. Maybe this is the cause of it falling off. I am hoping I won’t have to have a new crown made (so expensive!) and that if decay is present, it can be cleaned up and the crown re-sealed back onto the (possibly repaired) tooth. Does this sound like a possibility to you? Or is it obligatory to get a new crown when the shape of the tooth it’s on has been changed? And should I get some temporary dental glue from the pharmacy in the meantime and stick it back on? I’m being really careful to keep it clean and not eat anything hard! There’s no pain or sensitivity.

    • Connie,
      Most of those questions are hard to answer without an exam and x-rays. Generally speaking, dark spots and crevices can be decay, but can also be staining, especially with a crown dating back to the 1970s. If you are able to maneuver the crown back on yourself, and it feels OK, then getting temporary cement at the drugstore is a good idea. That can offer protection until you can get it.

  44. Shawnna Conner says

    Dr. Calcaterra,

    My crown and the tooth next to it hurts so badly that I can’t even chew soft food without both teeth hurting. I went to my dentist to get it checked out and all he did was take an X-ray, which the crown lights up like a Christmas tree, tap the teeth, and check my bite. Then he blamed my extreme tooth pain on my TMJ. I thought it felt like I had gotten food under my crown, but he sent me on my way with absolutely no answer on the specific tooth pain problem. It was a waste of time and money and I lost a lot of confidence in him, unfortunately.

    Anyway, I flossed (again) that night to try to get the food out of my tooth and my gums were swollen and started bleeding really bad. The next day I gargled with hydrogen peroxide and the pain eased up for a few weeks. The pain recently started back up again and no matter how much I floss and gargle with hydrogen peroxide, I can’t get rid of the pain. I think there’s tooth decay. My gum line is definitely swollen and it looks like I have a small gap between the teeth. I took some pictures of my teeth last night where I noticed the small gap and swelling. The biggest problem is I can’t afford to go back to my dentist just for him to tell me it’s my TMJ, which is what he’ll tell me. For now, I’m alone in my assertion that there’s something definitely wrong under my crown and the tooth next to it. My teeth are not supposed to hurt!

    I appreciate this board. I’m glad I found it so I definitely know that it isn’t my TMJ….I think I already know that….lol.


    • Shawna,
      Sometimes diagnoses in dentistry are easy. Sometimes they are difficult. It can sometimes be challenging to ascertain what, if anything, is going on underneath a crown.
      Generally speaking, if a tooth is significantly temperature sensitive, it is not related to the TMJ. I know you didn’t mention that. A second opinion would also be valuable.

  45. Hi, I went for a check up few days ago. They did xrays, exam and cleaning. Now I feel like my tooth under crown is sensitive and painful. Is it possible they missed that there is a decay under The crown?

  46. Lisa Kuhlman says

    I have a crown on one of my back teeth.Just had a cleaning and X-rays done about a month ago.There is a black line at the gumline of the tooth that has the crown.If the dentist looked at it and didn’t think it was anything could it still be decay?Thanks

    • While I can’t answer with 100% certainty since I am not doing an exam, what you are describing is likely the metal of the crown showing through. Many crowns are porcelain overlying a dark metal. At the margin, typically at the gumline, that metal can be visible.
      Plus, if you were just at your dentist and they didn’t mention anything, that should also indicate the tooth is fine.

  47. Janice Taylor says

    Dr. I woke up with a throbbing pain in my lower jaw under my crown, #19 lower left side of mouth. I took 500mg Tylenol and 40mg Motrin for pain, but as I swallowed the pills, the cold water sent a shooting pain to my temple. I swished my mouth with salt warm water which helped. I went to see my dentist the following day, he took x-rays and found no hairline fractures or decay. The tooth has had a root canal. He did notice some swelling inside and reduced contact slightly over the crown and said we would monitor. But it is throbbing again this evening and again taking pain meds and salt water swish.

  48. I have this same thing in back of my mouth. there is a big hole and it black, beginning at the gum, same tooth on both sides of mouth but I’m scared to go to dentist, because of the last time with the palatal injection to the roof of my mouth, is there another way???

    • Virginia,
      For procedures on teeth on the upper arch, a palatal injection is sometimes needed. And yes, it can be unpleasant. However, avoiding the dentist over a possible injection like that can lead to many consequences such as pain, infection, and tooth loos. Those are far worse, in my opinion, than an injection on the palate.

  49. I had a permanent bridge in front..2 front teeth and one on the side. While eating pizza, the bridge came off. One of the prepped teeth looked fine..the other was all black and smaller than the other. Today, I called my dentists office only to find out hes away this week, so had to see another dentist in the office. She said the blacken tooth was decayed and would have to come out. In order to remake a new bridge, they have to cut another bridge and attach the whole as one. My question is why cant they clean and seal the decayed tooth and put a pulp cover on it and just replace the bridge? She temporarily cemented it back on until I see my dentist.

  50. Phyllis,
    It is not possible to answer your question without x-rays and an exam. But if one of the supporting teeth is decayed, then it can’t be used to support a bridge. That would be like standing on a deck supported by two pieces of wood – with one of the pieces decayed and falling apart. Would you want to stand on that deck?


  1. Dentists 4 Implants In 30301 says:

    […] Dental MythBuster #9 – You can’t get a cavity under a crown – Another Dental MythBuster in which the myth that a tooth with a crown cannot develop a cavity is busted. Teeth with crowns and fillngs can get dental decay. […]

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