A patient seeking full-arch rehabilitation most commonly encounters two terms: All-on-4 and All-on-6. The first impression tends to be straightforward — since the difference is two additional implants, "more" must mean "better". In clinical practice the picture is more complex. The choice of implant number depends on bone conditions, the planned prosthesis, the biomechanics of loading and the long-term prognosis. This article explains what actually distinguishes the two protocols, when four abutments are sufficient, and when even six may prove too few. It sets aside the question "which method is better" — because no universal answer exists. It presents instead the criteria by which the implantologist qualifies the patient for each protocol.
How do the All-on-4 and All-on-6 protocols differ?
All-on-4 is a full-arch rehabilitation protocol based on four implants: two placed upright in the anterior part of the ridge and two tilted distally at an angle of usually 30–45° relative to the occlusal axis (so-called tilted implants), anchored anterior to the maxillary sinus wall in the maxilla or anterior to the mental loop of the inferior alveolar nerve in the mandible. All-on-6 uses six implants distributed evenly along the arch — most commonly four upright and two tilted. The difference, however, does not come down to the number of abutments alone. It affects the distribution of loading, the possibility of avoiding bone augmentation, and the design of the prosthesis itself.
Biomechanics — why the distribution of forces can matter more than the number of abutments
In full-arch rehabilitation the durability of the restoration depends not so much on the absolute number of implants as on the length of the cantilever arm of the prosthesis and the distribution of masticatory forces across the individual abutments. In All-on-4 the distal implants are deliberately tilted — this shortens the cantilever and makes use of available bone without the need for maxillary sinus floor elevation. Six implants distributed more widely provide more anchorage points and shorter spans of prosthesis between them.
The practical consequence: when bone quantity and quality are very good, All-on-4 is a predictable solution. When bone density is reduced — typical in patients who have worn a complete removable denture for many years, especially in the mandible — a greater number of abutments reduces the risk of overloading individual implants and allows occlusal forces to be distributed more safely.
When are 4 enough, and when are 6 implants needed?
Four implants are usually considered sufficient when several clinical conditions are met:
- sufficient bone height in the anterior and lateral parts of the ridge to achieve primary stability at a level that permits immediate loading (usually an insertion torque above 35 Ncm for each implant or ISQ ≥ 60 by resonance frequency analysis),
- the patient maintains controlled oral hygiene and is not an active smoker,
- the planned prosthesis does not require a long cantilever arm,
- the overall health status (diabetes, periodontal disease, medications) is stable and does not introduce additional risk factors.
Six implants are worth considering when:
- bone in the posterior region has reduced density (type III/IV in the Lekholm–Zarb classification — cancellous bone with a thin cortical layer),
- the arch is exceptionally long, which applies more often to the maxilla than the mandible,
- the patient has strong masticatory force, parafunctions (bruxism) or an asymmetric loading pattern,
- a metal or zirconia framework is planned, which loads the abutments more heavily than a lighter acrylic-titanium construction.
The Modern Dental & Orthodontics team points out that this distinction requires careful assessment on a cone-beam computed tomography scan (CBCT — a three-dimensional low-dose radiographic examination). Bone height alone is not enough — density, quality and geometry also matter, and these parameters cannot be assessed on a panoramic radiograph alone.
Decision table — bone conditions and the recommended number of implants
| Bone conditions | Suggested number of implants | Clinical notes |
|---|---|---|
| Good bone quantity and density in both segments (type I–II) | All-on-4 or All-on-6 | Both protocols have a good prognosis; the choice often depends on the type of prosthesis. |
| Reduced bone density in the posterior segment (type III–IV) | Consider All-on-6 | A greater number of abutments distributes the load and reduces the risk of overloading. |
| Extreme maxillary ridge resorption | Augmentation before implant placement or a specialist protocol: zygomatic / pterygoid implants | Conventional implant placement may not be possible even after sinus floor elevation. |
| Bruxism, strong masticatory force | Consider All-on-6 | More abutments + an occlusal splint. |
| Patient with stable diabetes or a history of periodontal disease | Individual decision | The number of implants is one of many factors; the maintenance phase is equally important. |
When even six implants are not enough — zygomatic and pterygoid implants
In cases of extreme maxillary bone resorption — when conventional implant placement is not possible even after augmentation — specialist protocols are considered. Zygomatic implants are anchored in the zygomatic bone and bypass the alveolar ridge. Pterygoid implants are anchored in the pterygoid process of the sphenoid bone. Both protocols require advanced surgery, precise digital planning and are not standard in every clinic.
These are specialist solutions — for patients in whom conventional implant placement in the alveolar ridge is impossible even after augmentation and augmentation itself carries a high risk of failure. In a typical clinical practice they account for a fraction of full-arch rehabilitations and require referral to a centre that performs such procedures routinely.
Long-term prognosis — what does the evidence say?
Current systematic reviews indicate that both protocols achieve high implant survival rates at 5 and 10 years (usually above 95% under controlled clinical conditions). Implant survival itself and the frequency of mechanical and biological complications are comparable between the two protocols. A 2024 meta-analysis (Sharaf et al., Heliyon), however, demonstrated significantly less marginal bone loss (MBL) in the 6-implant group (p<0.01) — a clinically relevant difference over many years.
More importantly, the factors with a stronger influence on success are: oral-hygiene control, the absence of smoking, stability of diabetes (if present), regular follow-up appointments and an appropriately designed prosthesis. At Modern Dental & Orthodontics we emphasise to patients that full-arch rehabilitation is the beginning of a long-term commitment, not its culmination.
What can be more important than the number of implants
- The team's experience in full-arch protocols — the learning curve is long.
- The quality of digital planning (CBCT, a designed surgical guide).
- The implant and prosthetic system — component compatibility over many years.
- The protocol for post-operative care and the maintenance phase (recall every 6 months, screw checks, occlusion assessment).
An implant is a tool. The treatment outcome depends on the plan, its correct execution and the patient's cooperation during the maintenance phase.
Key takeaways
- All-on-4 and All-on-6 are different protocols, not different versions of the same procedure — they are based on different biomechanical distributions.
- The choice is determined by bone conditions, biomechanics and the type of planned prosthesis, not the assumption that "more means better".
- In cases of extreme bone resorption, zygomatic or pterygoid protocols are considered — these are specialist solutions, not a standard alternative.
- Long-term success depends not only on the number of implants but also on the treatment plan, hygiene control and post-operative care — all of these factors work together.
- The decision should be made after thorough 3D diagnostics, not on the basis of a panoramic radiograph or a telephone consultation alone.
Frequently asked questions
Is All-on-6 better than All-on-4?
There is no universal answer. Both protocols have documented high efficacy in the appropriate indications. All-on-4 works well with good bone quality and a typical arch length; All-on-6 is considered when bone density is reduced, the arch is long, bruxism is present or a heavier prosthesis is planned. The choice is made after CBCT analysis, not on the basis of a preference regarding the number of implants.
How long does All-on-4 or All-on-6 treatment take?
Under favourable conditions the patient leaves the clinic with a temporary prosthesis on the day of the procedure (so-called immediate loading). The definitive prosthesis is made after full osseointegration — usually after 4–6 months in the mandible and 5–7 months in the maxilla. If bone augmentation is required or anatomical conditions are challenging, the total treatment time may extend to 9–12 months.
Is All-on-4 possible with significant bone resorption?
In many cases, yes, although thorough 3D diagnostics are required. In the maxilla, tilting the distal implants makes it possible to use the available bone before the sinus without the need for a sinus lift. In the mandible, tilted implants allow the mental foramen to be bypassed. In cases of extreme resorption, zygomatic or pterygoid implants may be considered.
How long do implants in a full-arch protocol last?
Current systematic reviews indicate that implant survival in All-on-4 and All-on-6 protocols at 5- and 10-year follow-up usually exceeds 95%. The key to durability is not the protocol itself but the quality of prosthetic design, oral-hygiene control, the absence of smoking and regular follow-up visits every 6 months.
Is the All-on-4 procedure painful?
The procedure is performed under local anaesthesia, optionally with inhalation or intravenous sedation — the patient does not experience pain during it. In the first 3–5 days moderate swelling and discomfort are typical, which respond well to standard analgesics (paracetamol, ibuprofen). The full-arch procedure is more extensive than a single-implant placement, so the post-operative period may be somewhat longer.
When can I eat normally after All-on-4?
First 24 hours — a cool, semi-liquid diet. For the following weeks soft foods are recommended, avoiding hard and sticky items. A full diet can usually be resumed after the definitive prosthesis has been fitted — i.e. after 4–7 months, depending on the protocol. On the day of the procedure the temporary prosthesis allows speech and basic eating, but it should not be loaded with hard foods.
Read more:
- Dental Implants: https://klinikamdo.pl/en/offer/implantology/
- What to avoid with dental implants? https://klinikamdo.pl/en/blog/what-to-avoid-with-dental-implants/
- How much does a tooth implant cost in Poland in 2026? https://klinikamdo.pl/en/blog/dental-implant-cost-poland-2026/
- How long does it take to heal after a dental implant? Osteointegration step by step https://klinikamdo.pl/en/blog/healing-time-after-dental-implant-osseointegration/
- Dental implant vs bridge — which is better? https://klinikamdo.pl/en/blog/dental-implant-vs-bridge/
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