Crowns on Implants: Proper Length for Biting Surface?

Joyce, a dental implant patient, asks:

I currently have 7 dental implants and I’m getting surgery Tuesday for 2 more. I take well to the implants and love them, but I don’t like the implant crowns.

My dentist says that the crowns should be a bit shorter so there is not direct contact on the biting surface and this will make them last longer. The problem is I have so many implants now that none of my molar’s biting surfaces touch and I feel like only my teeth more in the front touch. This is putting excessive pressure on those teeth and I’m afraid, over time, I’ll lose them too. Also, this has caused my bite to get tighter and has changed the tension on my temperomandibular jaw joints [TMJ].

My question is, is it correct that the implant crowns should not touch? If they can touch, should I have my implant crowns redone to be longer so they touch. This is driving me crazy and I’ve already spent a fortune on this stuff. Certainly, if you get enough implants, some of your teeth have to touch each other on the biting surface, right? What’s the deal here?

5 Comments on Crowns on Implants: Proper Length for Biting Surface?

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Ryan Dunlop DMD
2/25/2009
Hi Joyce, You've described a very common problem I see in implant crowns. As patients receive more and more dental implant crowns, the force of their bite is distributed on less and less natural teeth, causing overloading of these (usually anterior or front) teeth and possible accelerated tooth loss in the front of their mouth. The original implant crowns should have been placed in regular occlusion with the opposing tooth, albeit the occlusion should be 'slightly lighter' than full, tight occlusion. You should absolutely be able to clench the implant crowns with natural teeth, but you shouldn't be able to create excessive forces on the implant or opposing tooth. What's much more important for the health of the implant, implant crown, and opposing tooth is what I like to call "implant centric occlusion." This means that the majority of the biting force should be focused directly over the implant itself and not at an off angle from the angle of the implant post. Implants love compressive forces (biting straight down) but hate tensile forces (sideways chewing). So as long as when you chew side to side you don't overload the implants, you can have a tighter bite on your implant crowns. I have treated patients with "chronic TMJ" where all I had to do was redo 4 implant crowns (2 on each side) and their symptoms disappeared. I don't think your dentist did anything wrong, unless he left the bite totally open from the onset. All implant dentists try to protect their patients' implants by lightening the bite, especially when implants oppose natural teeth. Hope this helps
A:Romano dr med, dr dent
2/27/2009
when i build a circular prosthesis over six or 8 or 10 implants, the first problem to solve is the maintaining of the original (quasi original) height and maintaining or reproducing the best centric occlusion and centric relation. to do that, for me, the best method is to create on the fixed circular bar, some thicknesses in centric position (4 to 6 ) so that the technician can modellating porcellain quietly good, naturally after my golden fusion trial. in this way, at finished work i can, during the temporary placing on the implants, fine retouching the contact or miscontact, till i have, and the patient too, naturally, the best balance between natural denture and the fixed overdeture.
prof.Dr.Hossam Barghash
3/4/2009
one of biggest mistake,if we keep the implant out of occlusion & the opposing tooth is natural one what well happen is over eruption of the opposing & the implant well be the first to meeet & well be verloaded .
R. Hughes
3/5/2009
Good point Dr. Barghash.
Paul D.
3/14/2009
Dr. Bargash hit the nail on the head, leaving implants out of occlusion will open the door for the apposing teeth super eruption (migrating toward the available space). A well balanced and protected bite especially from lateral sheer forces as one of the Docs stated is the proper way to build the bite. To protect my implants I always use a T-Scan a computerized occlusion analysis to measure the amount, and the timing of occlusion in centric and lateral excursions

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