Dental Articles
Our clinicians do not recommend 'All-on-4' for all patients
With conventional implant restorations, typically 8 to 10 implants are required to support a full dental bridge. The All-on-4 system reduces the number of implants needed by using longer implants towards the front of the jaw, to provide an increased bone-to-implant contact area.
Additional stability has to be gained by placing the rear implants at an angle to compensate for lack of bone depth in the region of the sinuses. The placing of implants at an angle creates extra stresses however, which makes the 'All-on-4' system prone to failure. Our clinicians usually prefer to use 6 implants instead of 4.
The Disadvantages on "ALL ON 4" Implant Restorations
- We naturally have one or more roots for every tooth; molar teeth have two, three or even four roots, so just imagine having 12 or 14 teeth in an arch supported by only four roots. It is difficult to imagine that natural tooth roots would support all that strain without breaking, so that is why implants (that are only artificial roots) should not be expected to last.
- Having 12 or 14 teeth supported on four implants puts a great strain on the implants themselves, and will often cause the structural integrity of the implants to fail at an early stage. As the back part of a dental bridge will usually overhang the final implant, there is also a greater chance that these large bridges could break fairly soon after the conclusion of the treatment.
- Implants assist in maintaining the bone depth, width and density in a similar way to natural teeth. Although the bone in the region of each of the four implants will be maintained and not resorb, the bone in the other regions where there are no implants, will continue to resorb at a natural rate, and failure of the implants into the future is possible.
- If an "ALL ON 4" restoration did fail, it may not be possible to place new implants in the previous implant regions. The bone in the other regions may already have resorbed too much for new implants to be placed, unless extensive bone grafting was undertaken to anchor the new implants successfully. Placing new implants may indeed be impossible.
Conclusion:
The prognosis for longevity "All on 4 Implants" is not so good.
If your preference is to have a fixed bridge restoration then this should ideally be supported on six to eight dental implants per arch. This would mean greater longevity, and when proper aftercare and hygiene is maintained this type of restoration could last a lifetime.
In the case of implant supported over-dentures the pressure of biting and chewing is taken on the gums, and the implants are there just to hold the over-denture in place, so if your budget will only really allow for four implants then the better option may be to have this type of restoration.