Full mouth dental implants in Singapore – is All-on-4 better?

Traditionally, patients who have lost all their teeth and want to replace them with implant-supported prostheses require fairly extensive surgery to rebuild the bone to support the implants. Typically, six to eight implants are needed for the upper jaw and five to six implants for the lower jaw. The cost of a full mouth reconstruction with dental implants in this way typically ranges from $100,000 to $150,000. All-on-4is a treatment protocol developed by Portuguese dentist Paulo Malo whereby a full arch prosthesis is supported only by four implants placed without bone grafting. The elimination of bone grafting and the use of fewer implants bring cost down significantly. But is it as good as the traditional approach? Can it replace the traditional protocol completely? 

The availability of bone

In order to serve the function of supporting a dental prosthesis, dental implants must be firmly integrated in bone. The common problem with edentulous upper jaws is that bone is usually deficient both quantitatively and qualitatively, i.e. the bone is often thin and porous. Patients who have been wearing a denture for many years often have thinner bones due to the pressure of the denture over the front of the upper jaw. At the back, the bone thins out because of the expansion of the sinus above it. Traditionally, the bone mass is augmented by grafting bone onto the jaw. The bone may be harvested from the patient’s hip bone (ideally) or it may be sourced commercially. In the front, the bone graft is usually added to the surface of the bone while at the back, bone is typically added on the floor of the sinus, after lifting up the sinus lining. While the physical dimensions of the jaw bone can be augmented by grafting, the porosity of the bone remains. As dental implants in porous bone have lower success rate, a bit of over-engineering is usually practiced by placing more implants than absolutely necessary to cater for non-integration of some implants.

Tilted Implant Placement 

All-on-4 protocol requires less bone as only four implants are used. It is able to use four implants only because the implants are inserted strategically into the four corners of the jaw and angulated in such a way as to engage as much bone as possible. This is in contrast to the traditional way whereby implants are placed perpendicular to the bone. This is the traditional way of placing implants because it allows for axial loading of the implants. However, studies have shown that implants need not be placed perpendicular to the jaw if they are joined together rigidly by a fixed prosthesis, thereby providing a splinting effect.

There are many publications reporting equal success rate of the All-on-4 protocol vs the traditional approach. Given that the cost is significantly lower, is there still a need to have the traditional approach of using 6-8 implants for one jaw? The answer is an emphatic yes.

Limitations 

Firstly, not all patients are suitable for All-on-4. There must be bone available at the strategic locations on the jaw for placement of long implants. In the Asian patient, the jaw anatomy is quite different from the Caucasian patient, the patient population that are used in the All-on-4 research. In the Asian patient, the roots of the front teeth are usually not positioned squarely in the alveolar process of the jaw. Instead, they are usually seated in a more forward position, leaving a very thin plate of bone on the outside. When the tooth is extracted, this thin bone often undergoes a lot of shrinkage which progresses with time. As such, Asian patients who have had their teeth missing for years often present with so little bone that even placement of four implants is challenging.

Secondly, patients who smoke have poorer healing ability and using only four implants gives no room for failure of implant integration. If just one of the implants fails, the whole prosthesis fails and the treatment need to be repeated almost entirely. Having extra implants will help to minimize the need to go back to square one.

Patients who have very heavy biting forces subject their implants to extraordinary load and having the bare minimum number of implants leaves no room for contingency. Furthermore, the angulated placement of implants in the All-on-4 protocol also places the implant in a less favourable position to withstand high biting forces.

So, how do we decide between the traditional approach or All-on-4? The major advantage of the latter is the reduced surgery as well as cost. Its main disadvantage is the lack of contingency options and the angulated placement of the implants. Therefore, if cost is significant factor and the bone is available, the All-on-4 protocol is preferred. However, the patient need to know that it does not have the track record of the traditional full mouth implant reconstruction and that should there be a single implant failure, the prosthesis must be repeated at significant cost.