All-on-4 is a treatment approach in which four implants placed in one jaw support a fixed full-arch prosthesis in selected patients who have lost all their teeth or whose remaining teeth cannot be preserved. Placing the posterior implants at particular angles may help make use of existing bone where anatomical conditions are suitable.
However, All-on-4 is not a standard solution for every patient without teeth. Bone structure, general health, oral hygiene, chewing forces and the design of the planned prosthesis affect the treatment decision.
In my Biofunctional Dentistry approach, what matters is not only implant placement. How the teeth prepared on the implants will work within the patient's chewing system is also an important part of planning.
What Is All-on-4?
All-on-4 is an implant treatment concept intended to support a fixed full-arch prosthesis with four implants.
In this approach, implant positions and angles are determined according to the patient's bone structure and planned prosthesis.
In some cases, angling the posterior implants can allow the use of available bone regions where there are particular anatomical limitations.
However, using four implants does not automatically mean treatment is easier or more reliable.
The bone where implants will be placed, prosthesis dimensions and forces that may arise during chewing should be assessed together.
Who Is Suitable for All-on-4?
All-on-4 may be considered particularly in the following situations:
- Patients who have lost all the teeth in one jaw;
- Patients whose remaining teeth do not appear to be maintainable in the long term;
- People who struggle with removable complete dentures;
- Patients seeking a fixed implant-supported prosthesis who meet the necessary clinical conditions.
Nevertheless, not every case of complete tooth loss is suitable for All-on-4.
Bone volume, possible implant positions, general health and the patient's ability to clean the prosthesis are important.
Active infections, certain uncontrolled systemic diseases and use of particular medicines can change the treatment plan.
Smoking is also a factor that needs assessment in relation to healing and peri-implant disease.
What Is Assessed Before All-on-4?
General health
Existing medical conditions, medicines and risks that may affect surgery are assessed.
Jawbone
Bone volume and anatomical structures in the possible implant sites are examined.
Cone beam computed tomography (CBCT) may be used where necessary.
Oral and gum health
The remaining teeth, infections and periodontal health are assessed.
Relationships between the jaws
The relationship between the upper and lower jaws, existing bite height and space required for the planned prosthesis may be examined.
Patient expectations
Expectations for a fixed prosthesis, aesthetic preferences, speech and chewing needs are assessed.
For me, it is important that implant positions are not determined solely by surgical convenience.
The design of the prosthesis to be placed on them should be considered from the outset.
How Is All-on-4 Treatment Carried Out?
1. Examination and treatment planning
Oral health, bone structure and general health are assessed.
Necessary imaging and prosthetic planning are carried out.
2. Assessment of remaining teeth
Where teeth cannot be preserved, the need for extraction is determined.
However, extracting all the teeth should not automatically be preferred solely to enable All-on-4 treatment.
The condition of natural teeth that could be preserved should be assessed carefully.
3. Implant placement
Four implants are placed in one jaw according to the treatment plan.
Surgical technique and implant angles are determined by the patient's anatomy.
4. Temporary prosthesis
An early fixed temporary prosthesis can be prepared if suitable conditions are met.
However, this stage may not be possible for every patient.
5. Healing and follow-up
Integration of the implants with bone and healing of surrounding tissues are monitored.
6. Definitive prosthesis
The definitive prosthesis is prepared after appropriate healing and clinical assessment.
Its design should consider appearance, speech, chewing and ease of cleaning together.
Can Teeth Be Fitted on the Same Day With All-on-4?
One of the expressions most frequently encountered in relation to All-on-4 is “same-day teeth”.
In selected suitable patients, a fixed temporary prosthesis can be fitted on the day of implant placement or shortly afterwards.
This approach is called immediate loading.
However, immediate loading requires suitable implant stability at placement and appropriate other clinical conditions.
Fitting a temporary prosthesis on the same day does not mean treatment is completely finished.
Healing, reviews and preparation of the definitive prosthesis may continue in later stages.
It is therefore incorrect to claim that All-on-4 gives everyone permanent teeth on the same day.
How Long Does All-on-4 Treatment Take?
Treatment duration varies according to the patient's existing condition.
Surgery, the temporary prosthesis, healing and the definitive prosthesis may be planned as separate stages.
Some patients may need additional surgery or infection treatment.
Integration of implants with bone is generally assessed over weeks or months.
When the definitive prosthesis is prepared depends on healing and the chosen treatment protocol.
Why Does Function Matter in All-on-4 Prostheses?
A full-arch implant-supported prosthesis replaces most or all of the natural teeth.
How chewing forces are transmitted through the implants and prosthesis is therefore important.
Natural teeth have a connective tissue called the periodontal ligament.
This structure contributes to the response of teeth to forces and to sensory feedback.
Implants do not have the same structure.
The biomechanical behaviour of full-arch implant-supported prostheses therefore differs from natural teeth.
Tooth anatomy of the prosthesis
The shapes of the prosthetic teeth, their chewing surfaces and contact relationships should be planned.
Prosthesis extensions
Parts of the prosthesis extending beyond the most posterior implant support points require careful mechanical assessment.
These extensions are called cantilevers.
Bite relationships
Contacts between the upper and lower prostheses during closure, and relationships during jaw movements, are assessed.
However, no particular bite arrangement can be guaranteed to prevent complications in all patients.
In my approach, what matters is designing a prosthesis suited to the patient's anatomical and functional conditions.
What Are the Advantages of All-on-4?
All-on-4 may provide various advantages in suitable patients.
A fixed prosthesis option: A fixed implant-supported prosthesis can be made for patients with complete tooth loss.
Using particular bone regions: In suitable cases, angled implants may allow use of existing bone.
Supporting chewing function: Implant-supported prostheses may improve chewing comfort compared with removable dentures in some patients.
An early temporary prosthesis option: A fixed temporary prosthesis can be fitted early under suitable conditions.
However, these advantages cannot be achieved in the same way for every patient.
What Are the Limitations of All-on-4?
Using four implants for a full-arch prosthesis may not be suitable in every anatomical and mechanical situation.
Loss of one implant can substantially affect the prosthesis support structure.
Adequate space and appropriate design are also needed for cleaning.
Planning with a different number of implants may be more suitable for some patients.
The number of implants should therefore not be determined before the treatment goals.
What Are the Risks of All-on-4?
All-on-4 involves surgical and prosthetic stages.
Possible risks include:
- Pain, swelling and bleeding after surgery;
- Infection;
- Effects on anatomical structures;
- Failure of an implant to integrate with bone;
- Inflammation in tissues around implants;
- Prosthesis fracture;
- Screw loosening;
- Difficulty adapting to speech or chewing;
- Failure to meet aesthetic expectations.
The level of risk varies according to general health and clinical conditions.
What Are the Alternatives to All-on-4?
All-on-4 is not the only treatment option for complete tooth loss.
Alternatives may include:
- Fixed full-arch prostheses supported by different numbers of implants;
- Implant-supported removable dentures;
- Conventional complete dentures;
- Treatment plans using natural teeth that can be preserved in suitable patients.
All-on-6 is also an option that may be considered for certain patients.
However, using six implants does not mean better results than four implants in every situation.
How Is All-on-4 Maintained?
All-on-4 prostheses need regular cleaning.
Cleaning the underside of the prosthesis and the tissues around implants is particularly important.
Appropriate cleaning aids and techniques may be recommended to help the patient reach beneath the prosthesis.
Regular professional reviews assess the peri-implant tissues, integrity of the prosthesis and connecting components.
Having a fixed prosthesis does not remove the need for maintenance.
When Should You Contact Your Clinician?
Contact your clinician if uncontrolled bleeding, progressively increasing swelling, fever or persistent numbness occurs after surgery.
In the longer term, movement or fracture of the prosthesis, bleeding around implants, discharge or pain requires assessment.
What Affects the Cost of All-on-4?
The cost of All-on-4 depends on the implant system, surgical procedures, characteristics of the temporary and definitive prostheses and additional treatments required.
The prosthesis material and manufacturing process may particularly affect cost.
A definite price should therefore not be determined solely from the number of implants.
Frequently Asked Questions
1. How many implants are used for All-on-4?
The All-on-4 concept involves four implants in one jaw supporting a fixed full-arch prosthesis.
2. Is All-on-4 suitable for everyone?
No. Bone structure, general health and prosthetic requirements must be suitable.
3. Can teeth be fitted on the same day with All-on-4?
A fixed temporary prosthesis can be fitted in some suitable patients. However, this is not possible for everyone.
4. Is All-on-4 permanent?
It is a treatment option that can be used over the long term. However, implants and prostheses cannot be guaranteed to remain problem-free for life.
5. Is All-on-4 painful?
The procedure is generally performed under anaesthesia. Pain and swelling may occur afterwards.
6. Does All-on-4 require a bone graft?
Some patients may need one. Using angled implants does not make all bone augmentation procedures unnecessary.
7. Can an All-on-4 prosthesis be removed?
Fixed prostheses are generally not removed by the patient. However, screw-retained designs that can be removed by the clinician may be used.
8. Can you eat hard foods with All-on-4?
Chewing capacity depends on the prosthesis design and healing status. Dietary restrictions may be necessary, particularly during the temporary prosthesis phase.
9. Is All-on-4 or All-on-6 better?
Both approaches have suitable uses. The number of implants should be determined according to bone structure and the prosthetic plan.
10. Is an All-on-4 prosthesis difficult to clean?
It may require special cleaning techniques. Prosthesis design and the patient's manual dexterity affect ease of maintenance.
11. Can All-on-4 implants fail?
Yes. As with other implant treatments, implant loss and biological or mechanical complications are possible.
12. Are regular reviews needed after All-on-4?
Yes. Regular assessment of peri-implant tissues and the prosthesis is important.