[Diagnostic / Planning]  Enough bone for locators?

Hello again everyone (especially Dr. Ho-Young Chung!),

A patient would like to have locators for her existing denture...very resorbed mandible. 

Doesn't look like she has much room but the implants shown are 4 x 8.5mm and slightly angled (about 5 degrees).

Sorry no PAN, models, or intraoral pictures yet.

Okay to proceed or is there too much compromising going on here?

Cheers, Sokhi

by Sokhi Sandhu at Mon, Sep 25, 2017 11:19 AM

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Likes : 1

Mark Kwon Replied at Tue, Sep 26, 2017 10:13 PM

Dear Sokhi,

another challenge for me with resorbed md ridge when planning for 4 fixtures is finding inferior alveolar nerves. Canal dont exist oftentimes due to bone resorption. 

Thus must raise flap very carefully and try to tactily feel for the "remnant" of the the mental foramen. 

good luck !

Likes : 2

Bernard Jin Replied at Mon, Sep 25, 2017 4:08 PM

Hi Sokhi

From the sectional slices of the CBCT rendering - looks like you are able to place your fixtures provided you choose the proper diameter & length.  My thoughts are similar to Dr. Chung's - you get 1 shot.  If you overprep in your osteotomy you could compromise the integrity of the mandible (and in worst case - lead to mandibular fracture).  Don't want those.

To answer your positioning question - much depends on the position of the mandible when the patient is in function.  Have they been wearing dentures for a long time?  Are they getting in to a "Class III skeletal" relationship due to overclosure of the mandible secondary to posterior bone loss & lack of support + autorotation of the mandible?  How does that look? Does the patient posture their lower jaw forward to compensate for denture stability issues?  Will they fall back into a retruded posture once you provide them with a stable, "fixed" prosthesis that no longer requires them to compensate with mandibular anterior posturing?

Lots of questions.  Can you please provide photos?  Extraoral - especially side profile view (with & without prostheses)?  Intraoral?  Panorex?  Ideally - even lateral ceph?  I can't answer anything else without more information.

Lastly - yes - do be concerned about attached gingiva (or lack thereof).  Or is it mostly alveolar mucosa at this point?  Consider Acellular Dermal Matrix?  Autogenous FGG?  Again - need more information please.

Likes : 2

Ho-Young Chung Replied at Mon, Sep 25, 2017 12:55 PM

Hi Sokhi,

Thanks for posting this case.  These types of cases (resorbed mandible) can be challenging.  You have adequate amount of bone but chances are your patient may be in Class 2 skeletal classification due to resorption.  In these cases, implants have to be angled buccally but without perforating lingual plate.  The osteotomy must be done with utmost care.  Otherwise, you will have locator abutments come out outside of denture area.

More importantly, however, patient is likely missing keratinized tisssue due to resorption.  Soft tissue grafting isn't necessarily required but soft tissue manipulation will be critical in having success.  You need to have KT both lingual and buccal of your abutments for long-term success.  

bone density is also very high.  Your osteotomy should take this into account so as to not overtorque your implants and potentially lead to pressure necrosis or damaging the mandible.  

Whether you proceed depends on your experience and comfort.  You get only one chance with these cases.  

I would also be placing tissue level implants in these cases but that's just my  preference.  

Sokhi, I'll upload a similar case for you.  Looking at CBCT alone, it is difficult to notice all the challenges for this case.  I/O photos will show you how difficult or easy it will be for flap manipulation.  

Ho-Young Chung