All-on-Four Implant

What Is All-on-Four?

All-on-Four (All-on-4) is a treatment approach in which a fixed prosthesis for a fully edentulous jaw is supported by four implants. The four implants do not replace four teeth; they support a prosthesis carrying the whole arch. The number refers to one jaw — two jaws are planned separately.

The front implants are usually placed more upright and, where the anatomy allows, the back implants are angled. The aim is to use the bone that is there and to spread the support for the prosthesis. Implant positions and the number of teeth on the prosthesis are not the same in every patient.

Who Is Assessed as a Candidate?

It may be considered for patients who are fully edentulous, or where it has been established that the remaining teeth cannot be kept. Natural teeth that could be saved should not be extracted simply in order to carry out All-on-Four. The treatment options for the existing teeth, and their long-term outlook, are assessed first.

• Bone and anatomy. Enough support is needed for four implants to be placed in appropriate positions.
• General health. Medication, diabetic control, smoking and previous treatment all affect the surgical plan.
• Prosthetics and maintenance. The bite, the jaw relationship, lip support, your ability to clean the prosthesis and to keep attending reviews are considered together.

All-on-Four and All-on-Six

The basic difference is the number of supports: four implants in one, six in the other. But the decision cannot be reduced to a number or to a price. Bone volume and its distribution, the shape of the jaw, the opposing jaw, the prosthetic design and the chewing loads all matter.

Six implants are not better for every patient, and four are not automatically cheaper or graft-free for every patient. The appropriate number and placement are settled by preparing the surgical and prosthetic plans together.

What Are the Alternatives?

Fixed prostheses on a different number of implants, implant-supported removable prostheses and conventional complete dentures can all be discussed. A removable prosthesis is taken out by the patient for cleaning; a fixed prosthesis needs specific techniques to reach the surfaces underneath.

Manual dexterity, expectations, and bone and soft tissue support all influence the choice. A fixed prosthesis is not the single right answer for everyone. For the general picture see dental implant treatment.

Are Fixed Teeth on the Day of Surgery Possible?

In suitable patients a fixed temporary prosthesis may be used in the early period after surgery. That requires the initial stability of the implants, the distribution of support and the prosthetic conditions to be assessed together. Where the necessary conditions are not met, loading is postponed and the temporary options are planned again.

"Teeth in a day" does not mean the definitive prosthesis is finished or that healing is over. The rules for eating and for using a temporary prosthesis are explained to you individually.

Is Bone Grafting Needed?

Angled placement can, in some patients, make better use of the bone that is present and reduce the need for grafting. All-on-Four is not a graft-free procedure in every case. Additional bone or soft tissue procedures, a different number of implants or another prosthetic plan may be required.

In advanced upper-jaw bone loss, options such as zygomatic implants call for specialist assessment; they are not the same procedure as All-on-Four.

Risks and Long-Term Maintenance

Failure of an implant to integrate, infection, inflammation of the surrounding tissues and bone loss can occur. Wear or fracture of the prosthesis, loosening of the connecting screws and the need for repair can also arise. Losing one implant may mean the whole prosthetic plan has to be reconsidered.

Cleaning under the prosthesis and around the implants is needed every day. The brushes and interdental aids to use are demonstrated, and the review interval is set according to individual risk. If you notice bleeding, a bad taste, increasing pain or movement in the prosthesis, come in to be checked. Do not try to remove the prosthesis yourself or to tighten loose parts.

What the Published Evidence Reports

These are group figures, each with the limits its authors state. They describe studied populations, not an individual result.

The consistent signal across the papers below is that implants tend to stay in place while the prosthesis needs maintenance, and that follow-up losses make the headline percentages look better than an individual should assume.

• Maló and colleagues (2019) followed 471 patients rehabilitated with 1,884 implants in the lower jaw for 10 to 18 years. Cumulative implant survival was 93% and implant success 91.7%; prosthetic survival was 98.8%. In the same study the incidence of biological complications was 11.8% at implant level and of mechanical complications 36.7%, and 149 patients (31.6%) were lost to follow-up. This is a retrospective case series from a single clinic and concerns the mandible; it should not be read across to the upper jaw.
• Maló and colleagues (2012) reported on the upper jaw separately: 242 patients, 968 immediately loaded implants, with five-year survival estimated at 93% at patient level and 98% at implant level, and average marginal bone level 1.52 mm at three years and 1.95 mm at five.
• Soto-Peñaloza and colleagues (2017) reviewed 24 studies and reported a survival rate of 99.8% beyond 24 months — but state in the same conclusion that the evidence is limited by poor methodological reporting, inadequate follow-up and sample attrition, with a sample size calculation reported by only one study. Their figure is best read alongside that warning rather than on its own.

Frequently Asked Questions

Do I take the fixed prosthesis out at night?

A fixed prosthesis is not removed by the patient day to day. It can be unscrewed by the clinician when needed. An implant-supported removable prosthesis is a different option, used and cleaned differently.

Can I eat anything with the temporary teeth?

No. Dietary rules in the early period protect both the prosthesis and the healing implants. When you move on to other foods is decided by your treatment team. Even with the definitive prosthesis, excessive loading and biting hard objects can cause damage.

Is the treatment painful?

Pain during the procedure is controlled with anaesthesia. Afterwards there can be pain, bruising and swelling, to a degree that depends on the extent of the surgery. Complaints that are worse than expected, or increasing, need to be checked.

What does the All-on-Four fee cover?

Whether one jaw or both are treated, extractions, implants and abutments, the material of the temporary and definitive prostheses, anaesthesia and additional procedures all affect the cost. Establish which stages are included in the quote, and the terms for review and repair. Do not assume an insurance policy or institutional agreement covers this treatment. The cost drivers are set out in our guide to All-on-4 prices.

Scientific References

• Maló P, de Araújo Nobre M, Lopes A, Ferro A, Botto J. The All-on-4 treatment concept for the rehabilitation of the completely edentulous mandible: A longitudinal study with 10 to 18 years of follow-up. *Clinical Implant Dentistry and Related Research*. 2019;21(4):565-577. PMID 30924309. DOI
• Maló P, de Araújo Nobre M, Lopes A, Francischone C, Rigolizzo M. "All-on-4" immediate-function concept for completely edentulous maxillae: a clinical report on the medium (3 years) and long-term (5 years) outcomes. *Clinical Implant Dentistry and Related Research*. 2012;14(Suppl 1):e139-e150. PMID 22008153. DOI
• Soto-Peñaloza D, Zaragozí-Alonso R, Peñarrocha-Diago M, Peñarrocha-Diago M. The all-on-four treatment concept: Systematic review. *Journal of Clinical and Experimental Dentistry*. 2017;9(3):e474-e488. PMID 28298995. DOI
• Moraschini V, Poubel LA, Ferreira VF, Barboza ESP. Evaluation of survival and success rates of dental implants reported in longitudinal studies with a follow-up period of at least 10 years: a systematic review. *International Journal of Oral and Maxillofacial Surgery*. 2015;44(3):377-388. PMID 25467739. DOI