ALL ON 4
This concept was introduced by Nobel Biocare, Sweden. But what is an all‐on‐4 technique? Who should consider it? Is it considered safe? And how is it different from common implants?
Nobel Biocare presented this treatment as a means of overcoming limitations in the human mandible. This treatment is basically immediate‐function protocols involving the use of dental implant supported prostheses for the rehabilitation of completely edentulous mandibles and are documented as having a high success rates.
The loss of alveolar bone with a relative surfacing of the inferior alveolar nerve in the mandible is a result of posterior teeth loss, particularly at an early age, thus often prohibiting placement of implants in the posterior regions. An alternative could be the use of tilted implants, which allows for maximum use of the existing bone and placement of posterior fixed teeth with minimum cantilevers in a region where bone height and nerve proximity does not allow for the placement of axial implants.
In this treatment, only 4 implants are utilized. Two are placed vertically in the anterior and the other two placed with an angle up to 45 degrees in the posterior region. Unlike other implants, multi‐unit abutments are placed and can provide soon-to-be edentulous patients with an immediate restoration.
Based on the optimal number of four implants for supporting full‐arch prosthesis in an edentulous jaw, the concept benefits from the posterior tilting of the two distal implants with a maximum of a two tooth distal cantilever in the final prosthesis. Optimized bone support with minimum bone volume is provided in this treatment.
With this said, these are not the only benefits as improved anchorage along with vital structures avoidance (such as mandibular nerve or the maxilla sinus) are also results of the tilting of implants in the maxilla optimizing load distribution and allowing for a final prosthesis with up to 12 teeth. One can conclude that there is a clear biomechanical advantage in using splinted tilted distal implants, rather than axial implants, supporting distal cantilever teeth.
The step by step procedure of the treatment.
• The first step of the procedure includes:
Wax Try‐in Denture /Re‐mount and Equilibration/ Cross Mount and Occlusal Guide / Bite Registration / Duplicate Denture and Surgical Template/ Adding ٠30-45 Degree Angulation for Posterior Implant, Indication of the Amount of Ridge Reduction and Marking the Surgical Template.
• The second step involves:
Marking Vertical Dimension of Occlusion prior to Surgery/ teeth extraction / dental implant placement / Attachment of Multi‐Unit Abutments / Index position of Multi‐Unit Abutments / Hollowing‐out space in denture for Temporary Coping Multi‐unit / Attaching Temporary Coping Multi‐unit to Multi‐Unit Abutments / Reducing the Height of Temporary Coping Multi‐Unit / Rubber Dam attachment / Picking‐up Temporary Coping Multi‐unit cylinders / Removing Prosthesis with Temporary Coping Multi‐unit cylinders processed in acrylic / Converting from Immediate Denture to Fixed Implant Bridge / Polishing and Smoothing the Surface of Fixed Implant Bridge and finally Attaching Provisional Fixed Implant Bridge Prosthesis with Prosthetic Screws.
In a research done on 245 patients with a total of 980 immediate‐function implants (four per patient) placed in the anterior region to support fixed full‐arch mandibular prostheses. The results were as follows: a total of 21 implants failed in 13 patients, giving cumulative patient‐related and implant‐related success rates of 94.8% and 98.1%, respectively, at five years, and 93.8% and 94.8%, respectively, with up to 10 years of follow‐up. The prostheses’ survival rate was 99.2% with up to 10 years of follow up.
These results support the conclusion that the All‐on‐4 immediate‐function implant concept is viable and a patient friendly long term stable treatment.