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Oral Surgery/Any situations where the dental implant cannot be inserted ?


QUESTION: What are the situations where a dental implant, the last resort,  cannot be used to replace an extracted tooth ?

Is the dental implant viable in the following two cases :
1. extracted tooth was at the back e.g. lower left molar (#37)
2. not enough bone after crown lengthening

ANSWER: Dorothy - an implant cannot be utilized if an inadequate amount of bone is present.  If that is the situation, the doctor needs to initially graft bone to the area to create a proper amount of bone to receive an implant.  

In the situation you describe of tooth #37 was extracted, it is important to not only make sure an adequate amount of bone is present, but the mandibular nerve is there and if it is too close to the surface or in a position that the implant is needed, then the implant cannot be placed there.

If there is not enough bone after crown lengthening then the tooth or implant is not strong enough to be functional.  

If an implant cannot be placed and that tooth is important for a proper occlusion, replacement of a tooth to chew on in that area would be via a cantilever bridge, using the 1st molar and second bicuspid to support a cantilever tooth in that position.

---------- FOLLOW-UP ----------

QUESTION: Thank you very much for your prompt reply.

Sorry, I did not describe my situation which is as follows:

My lower L. molar at the back (#37) was badly damaged, had root canal treatment and filling and was then fitted with a crown in 2009. In 2012 this crown started to come off very often. My dentist said that my molar (height ~1 mm above gum line) was very short. Each time this crown came off it was recemented, but the last time on 24/12/2014 it was swallowed while eating. There is no LL tooth #38, and LL 1st molar (#36) had root canal treatment and was fitted with a crown in 2007 and has had no problem. The second bicuspid is perfect and does not even have a filling.

Regarding my  tooth #37, I have been thinking that crown lengthening was the only solution to keep the crown in place. I thought that if this did not work, the dental implant might be the last resort. And thanks for correcting me that the mandibular nerve is there which makes the dental implant not viable.

You mentioned the cantilever bridge. I read about it on the internet and found that it is for areas under less stress i.e. the front teeth.

I spoke with a periodontist about crown lengthening. He mentioned something about 5 mm. I don't know whether he meant removing 5 mm depth of bone or  5 mm depth of (bone + gum + other tissue). I'm worried about the consequences of removing bone/tissue, as my lower jaw beneath this tooth #37 is only about 1 inch (25 mm) high.

Dorothy - First of all, crown lengthening involves removing bone and shifting the gum tissue downwards surgically.  This exposes more tooth structure and often it is below the level where enamel is present on the tooth. Depending on the amount of lengthening that is done, that tooth could become quite sensitive if excess lengthening is performed.  

Secondly, I lost a second molar as a child and had a cantilever bridge fabricated more than 50 years ago.  The cantilever is still in place and it was made into a balanced bite without excess pressure on the area, only a normal amount of pressure.  

Usually if the situation exists like you describe, when root canal treatment has been performed on the tooth, the dentist places a post into the tooth, via into the nerve canal that is filled with root canal material, and then builds up the crown from the remaining surface of the crown with a composite material that is almost as strong as natural tooth.  This is a very common procedure and probably should have been done initially by the dentist if he had cut the tooth down and only 1 mm of tooth structure was present.

As far as crown lengthening, it is important to know the height of the remaining crown above the bone and if there is a periodontal pocket in the area.  

So you need a knowledgeable dentist to choose the proper method.  I wish I could tell you simply the correct approach, but without, at least, seeing an xray of the area it is difficult for me to tell you which technique is best for you.  Just so you know that there are options and not only one single can be done but a qualified dentist should be able to decide on the best for you.

The problem is finding a skilled and knowledgeable proper dentist to help you.  I you live in or near a large city that has a dental school, seek an evaluation by the doctor at the head of the crown and bridge department of the dental school as an evaluator and possibly refer you to a qualified dentist.

I wish you well and if you have any further questions, do not hesitate to contact me again.  

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Joel S. Teig, DMD, Diplomate ABOMS, retired


I am a board certified oral and maxillofacial surgeon available to answer questions related to tooth extractions, implant insertion, facial recontruction, facial and oral tumor removal, TMJ dysfunction and various successful treatments, including surgery if all else fails, and occlusal discrepancy requiring orthognathic or jaw surgery.


Board Certified Oral and Maxillofacial Surgeon practicing for over 20 years. Assistant Clincal Professor at State University School of Dentistry.

American Dental Association, American Association of Oral and Maxillofacial Surgeons, American Board of Oral and Maxillofacial Surgeons

BA- University of Connecticut DMD-University of Pennsylvania School of Dental Medicine Oral and Maxillofacial Surgical Residency - Roosevelt Hospital, NYC

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