The term All-on-4 refers to "all" teeth being supported "on four" dental implants, a surgical and technique prosthodontics procedure for total rehabilitation of the edentulous patient or for patients with badly broken down teeth, decayed teeth or compromised teeth due to gum disease. It consists of the rehabilitation of either edentulous or dentate maxilla and/or mandible with fixed prosthesis by placing four implants in the anterior maxilla, where bone density is higher. The four implants support a fixed prosthesis with 10 to 14 teeth and it is placed immediately, typically within 24 hours of surgery.
Implant manufacturer Nobel Biocare was among the first to identify the evolution of the All-on-4 technique as a potentially valid and cost-effective alternative to conventional implant techniques, and funded studies by Portuguese dentist Paulo Maló to determine the efficacy of this approach. During this time this technique was also used by various other clinicians around the world.
All-on-4 is not an invention
But rather a treatment technique that has evolved over time and has the following features:
- Four dental implants to support a full fixed bridge
- The use of angulated implants in the back to overcome bony deficiencies or anatomical structures
- Immediate loading
The concept itself of the total rehabilitation of a full set of teeth supported by as few as four fixtures was not a new one. Professor P-I Branemark, who discovered osseointegration, published numerous articles in the 70s with successful rehabilitation of a full arch supported by this number of fixtures. However, it was the angulation of the back implants that led to today's All-on-4, and has been trialed by numerous clinicians simultaneously in the USA, Sweden, Portugal, and South America in the 1990s.
The technique evolved when in an attempt to avoid certain anatomical limitations typically seen in the back of the upper and lower jaws have, clinicians successfully avoided bone-deficient areas with the use of angulated implants. Anatomical limitations are more prevalent in patients with full dentures, and once the back implants are placed at an angle there is often only enough room left for two more implants in the front. This has led to the use of only four fixtures to support a full set of teeth.