Dental Implants: Connecting Natural Teeth

Although its a last resort for me, I have connected natural teeth and implants. ie:#21 has an existing crown site #20 was inadequate for an implant and site #19 was a good site. When I restored this particular case I fabricated a telescopic undercoping real thin for #21 then placed the conventional 3 unit bridge over 19 and 21 as abutments. This would ensure ,in theory anyway ,that if the natural tooth does submerge it still has a restoration that would seal the tooth. I cement the undercasting with a resin cement and the 3 unit bridge with duralon.The thinking is that the seal would fail on the duralon before the resin in the case of submerging and the integrity of the restored tooth is still intact.

Dr. Mosery: Did the natural tooth #21 submerge at all? How long ago did you insert the bridge? Thanks

I have one case which is about 15 yrs. A few other cases, also have existed for 5-10 years. The x-rays show no changes. If the occlusion is checked then there should be no ptoblem. I have never seen intrusion.

I use reverted attacments in the junction of implant and bridge and i have great results. It leaves the teeth with slghtly movents and the forces to the implant transmited in centric. I always do a root canal treatment before.

Statistics show that less than 10% of teeth intrude, curiously when using semiprecision attachments. Although it is the last resource I use, I've done for over 10 years using a rigid fixation, meaning that no attachments are used. The use of a coping is sound although not necessary. Interestingly, failures have ocurred in endo treated teeth, and reviewing lit, It is recommended that teeth should not have endo treatment, contrary to your experience Rui. Interesting topic but not as critical as It is believed. By the way in close to a hundred cases I have not seen a single intrusion yet, but keeping very close attention to oclussion in that area. It is desirable group function of the segment.

Has anyone had experience with failure of metal or porcelain when doing a three unit bridge as described i.e. 19 - 21? The theory being that the end supported by the tooth is essentially cantilevered off the implant. Thanks rhg

Two contributors have mentioned the importance of checking the occlusion. One factor is to insure there is adequate group function of the segment. What other occlusal factors should be checked?

I have been placing and restoring implants for the last 18 years and on occasion the best treatment of choice for various reasons is to connect an implant to a natural tooth. I have seen only one case of intrusion in my own practice. This was a case done in the "old days" when we thought implant supported prostheses might benefit by being splinted to natural teeth. The intruded tooth, #31, was connected via a non-ridgid attachment to an implant in site #30 which acted as the distal abutment to a 4 unit FPD. As far as metal or porcelain failure, I have seen this on only two cases. Both cases are 6 unit FPDs with the natural tooth being #22 and the implant abutment in site #27. Luckily both cases show only craze lines in the porcelain in the pontic #23. These cracks have been present in one case for 12 years and the other for 6 years. No other problems have been noted in these cases. Dr. Takayuki Takeda of Japan did a 10 year study and presented his findings, "The Harmony of ITI Implants and Natural Teeth". In summary his observations were that "connection distance had a significant effect on changes to teeth, i.e., intrusion or cement washout". Cases with change had a connection distance of 6.3+-3.2mm. Cases with no change had a connection distance of 13.8=-4mm. This seems to suggest that if you have to connect teeth to implants the distance between the two should be at least 10mm or so. I have had no problems when following this rule.

I would like to make it simple. If the natural tooth is moving that will transmit the movement to the implant. We know that is bad but if it lateral or tipping forces then there will be problems. So the bottom line, no movement in the natural tooth. How do you measure that?

All natural teeth move unless they are ankylosed.

One of the problems we face in dentistry, especially implant dentistry is very dogmatic approaches to situations that vary from patient to patient. Joining natural teeth to implants with rigid connections ie:fixed bridgework can at times improve the longterm success of a natural tooth, purserve certain esthic needs and possibly offer the patient a less expensive option than a totally implant reatined prosthesis. That being said is not to imply that you can in most situations join natural teeth to implants. In fact it is the less common case that you might find yourself faced with that decision. The health and stability of the tooth, it's location and distance rfron the implant and most importantly the opposing occlusion and parafunctional habits are very important considerations. I find that joining implants to natural teeth in our practice a rare occurance yet we do it at times if the right criteria are met. As an aside using implants to support removable prosthesis joined to natural teeth make great sense and can act to transitionize and prolong natrual teeth and perserve ridges.

Just curious, if the space at #20 is small enough is a cantilever off of implant #19 ok? Isn't the risk of failure less than attaching to a natural tooth?

the case i mentioned above is 3 years old and doing just fine.i'm not comfortable with cantilever off 19 for 20 .first of all as it stands ilike to keep the occlusal surface area as small as possible. this means that if implant 19 is the distal most"tooth" it will be contoured like a third premolar. the less abuse the implant is subjjected to the higher the predictability the last thing i would do is cantilever a full tooth off of a single implant. you're risking broken abutment,loosening of abutment,breaking the neck of the implant itself,bone loss and implant failure due to overload.not worth it.

I totally agree with Dr. Rosenchlit.Splinting an implant to natural tooth should not be the norm,but in situation where there is no other alternative for fixed prosthesis and all other conditons described by Dr. rosenchlits are favorable including health and root/roots morphology(molars with divergent large roots) then it souldbe ok. Periodic check of occlusion of all implant restorations is must,not just implant-natural tooth connection. To do prophylactic endo may not be a good idea after all.