Dr. B. asks:
I have a 65 year old male patient in need of implants in the lower right posterior segment. According to the CBVT scan I have adequate width and about 10mm of height in which to place my implants which oppose a complete maxillary denture. However, the inferior alveolar nerve space is quite unusual in that it is over 10mm in height and over 4mm in width. It gradually expands at the point where the 2nd molar should be and then contracts before exiting out the mental foramen. It does not have the earmarks of any type of pathology and if I knew how to post the CBVT view I would. Any anatomists know what’s going on?
Inferior Alveolar Nerve Quite Unusual: Any Ideas?
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Interesting finding. Please post results so we can see. The IAN can be bifid or even trifid in certain sections of the mandible. You should show this to an experienced practioner or a radiologist to rule out pathology. Remember that you are in a bone window, you are not actually seeing the nerve, but the boney canal.
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Yes, there can be variances with the IAN. Dr. Sharaway presents this in his lectures. I have seen bifid IAN’s clinically.
The oral surgeon is correct – the nerve must be in a bony canal to see it. if your shadow shows in cross sectional views, it does not necessarily mean it is all the nerve, the post mandible can have huge marrow cavities, through which the nerve passes. Also the nerve does not always have a bony canal associated. I have seen this in a number of dissections on cadavers.
If the shadow only shows on the OPG-type view, it could merely represent an undercut area beneath the mylo-hyoid ridge. The 3-D reconstruct should show this.
Regards pathology, you would be looking for other symptoms than merely a shadow on a cone beam view.
If you can place your implants with 2 mm clearance superiorly from the shadow, all will be well
Place however as many 8-10MM long implants as you wish and forget about the IAN being a problem. You are dealing with an opposing upper denture and the forces of mastication are a fraction of those with natural dentition. You can even cantilever one or even two molars off the natural premolars (and canine if it make you feel better) if present and with 0 degree mobility. Otherwise place two premolar area implants and cantilever enough to complete occlusion with the upper denture.
Neurofibromatosis (Von Recklinghausen’s disease) is rare, but one of its signs can be an enlarged IAN. Check the patient for signs such as light brown colored skin marks…