What Is the Difference Between All-on-4 and All-on-6?
The fundamental difference between All-on-4 and All-on-6 is the number of dental implants supporting a fixed full-arch prosthesis in a single jaw. In an All-on-4 treatment, four implants are generally used, while an All-on-6 treatment utilizes six implants. However, this does not mean that six implants are superior for every patient, nor does it mean that four implants are inadequate.
The distinction between All-on-4 and All-on-6 cannot be explained solely by the implant count. The right choice is determined by the height and width of the jawbone, the anatomical regions available for implant placement, the length of the fixed prosthesis, masticatory forces, and load distribution.
Quick Answer: All-on-4 enables a fixed prosthetic plan with fewer implants, while All-on-6 can offer two additional support points in suitable candidates. The decision must be made based on whether the implants can be placed in cleanable, prosthetically driven positions that align with the final teeth.
Table of Contents
Differences Between All-on-4 and All-on-6
| Assessment Criteria | All-on-4 | All-on-6 |
|---|---|---|
| Number of implants per jaw | 4 | 6 |
| Support points | Distributed across four implants | Distributed across six implants |
| Bone requirements | Can be considered in cases with limited posterior bone | Requires suitable bone volume across the arch for two additional implants |
| Position of posterior implants | Angled (tilted) in suitable cases | Can be straight (axial) or tilted, depending on bone and prosthetic planning |
| Load distribution | Balanced through precise biomechanical planning | Distributes load across more contact points in select cases |
| Same-day temporary teeth | Applicable if adequate primary stability is achieved | Applicable if adequate primary stability is achieved |
| Patient candidacy | Depends on bone distribution and prosthetic design | Depends on whether six implants can be positioned correctly |
This comparison table alone is not sufficient to choose an implant technique. When evaluating All-on-4 versus All-on-6 treatments, clinicians evaluate not only the total implant number, but whether the implants can be placed at optimal sites to support the prosthesis. Likewise, using only four implants does not mean the treatment will lack durability.
Research Note: In a multicenter randomized clinical trial by Toia et al., fixed full-arch maxillary prostheses supported by four versus six implants were compared over a 5-year follow-up period. The study reported that the four-implant protocol was not inferior to the six-implant protocol regarding marginal bone level changes around the implants. This finding demonstrates that an All-on-6 plan cannot be deemed superior for every patient based strictly on implant count.
Should You Choose All-on-4 or All-on-6?
When adequate, well-distributed bone volume is present, All-on-6 may be evaluated; in patients with limited posterior bone volume or where a biomechanically balanced restoration can be achieved with four implants, All-on-4 may be preferred. This distinction is not a rigid rule, but a clinical planning strategy.
The most critical factor guiding the decision is not “How many implants can we fit?”, but rather “Can the implants be placed in the precise spatial positions needed to support the fixed prosthesis?”
The following clinical factors are evaluated simultaneously:
- Height, width, and bone density of the jaw
- Spatial distribution of available bone across the dental arch
- Anatomical landmarks (maxillary sinuses in the upper jaw, inferior alveolar nerve canal in the lower jaw)
- Anteroposterior (AP) spread of the planned prosthesis
- Patient’s masticatory forces
- History of bruxism (clenching or grinding)
Research Note: In a multicenter randomized clinical trial by Toia et al., fixed full-arch maxillary prostheses supported by four versus six implants were compared over a 5-year follow-up period. The study reported that the four-implant protocol was not inferior to the six-implant protocol regarding marginal bone level changes around the implants. This finding demonstrates that an All-on-6 plan cannot be deemed superior for every patient based strictly on implant count.
When might All-on-4 be indicated?
All-on-4 is particularly suitable for patients with reduced bone volume in the posterior jaw. Angling the posterior implants allows clinicians to maximize the use of existing native bone while widening the prosthetic support base (AP spread).
In many cases, this approach reduces the need for extensive bone augmentation procedures. However, this does not mean that bone grafting is entirely excluded with All-on-4. If localized alveolar ridge defects exist, tissue is lost following extractions, or bone volume around an implant requires enhancement, localized grafting may still be performed.
All-on-4 is often indicated when:
- Anatomical structures in the posterior jaw restrict standard axial implant placement
- Four well-distributed implants provide balanced prosthetic support
- The patient’s bone morphology and prosthetic plan favor tilted implant placement
When can All-on-6 offer an advantage?
All-on-6 can provide additional support points in patients where two extra implants can be positioned in prosthetically ideal sites. Especially along a wider dental arch, placing implants across a broader perimeter allows masticatory loads to be distributed across more contact points.
However, placing six implants does not automatically guarantee a more balanced outcome. Positioning two extra implants too close together, in locations that compromise daily oral hygiene, or outside the ideal prosthetic emergence profile offers no clinical benefit.
All-on-6 may be considered when:
- Sufficient bone volume is present not only in quantity, but also in spatial distribution across the entire arch
- The length of the planned dental arch benefits from additional posterior support points
- The two additional fixtures provide clear biomechanical value without complicating the treatment plan
Are Four Implants Enough to Support a Full-Arch Fixed Prosthesis?
Yes. Provided there is adequate bone quality, optimal implant distribution (AP spread), and a balanced prosthetic design, four implants can reliably support a full-arch fixed prosthesis. However, this should not be interpreted as “four implants are sufficient for every patient.”
The viability of a four-implant plan depends on:
- The anteroposterior distance between anterior and posterior implants
- The tilt angle of posterior implants and the length of the posterior cantilever
- Primary stability achieved during surgical placement
- The patient’s occlusal load and masticatory dynamics
Is the Same Number of Implants Used in the Upper and Lower Jaws?
The upper and lower jaws differ significantly in bone density, anatomical contours, and structural boundaries. Consequently, a patient may receive six implants in the upper jaw and four in the lower jaw, or vice versa, or the same number across both arches.
In the maxilla (upper jaw), bone is generally less dense (cancellous), and the proximity of the maxillary sinuses affects posterior implant placement, which may require evaluating sinus floor elevation. In the mandible (lower jaw), bone is typically denser (cortical), with planning guided primarily by the position of the mental foramen and inferior alveolar nerve.
There is no universal rule mandating six implants for the upper jaw and four for the lower jaw.
Can Same-Day Teeth Be Fitted in All-on-4 and All-on-6 Treatments?
In both protocols, if the necessary clinical prerequisites are met, immediate fixed provisional teeth can be delivered on the day of surgery or shortly thereafter. However, patients should understand that this provisional restoration is not the definitive permanent prosthesis.
Immediate fixed provisional loading requires:
- Achieving high primary stability ($> 30\text{–}35\text{ N}\cdot\text{cm}$ insertion torque) on all supporting implants
- Rigid splinting of the implants through the provisional framework
- Controlled, protected occlusal contacts during the osseointegration period
Research Note: In a systematic review published in the Journal of Prosthodontics, Gallardo et al. reported high survival rates for full-arch fixed implant-supported prostheses across various loading protocols. However, they concluded that no single loading protocol is universally superior for every clinical scenario.
Having four or six implants does not automatically guarantee that immediate provisional teeth can be placed. The surgical stability achieved intraoperatively remains the decisive factor.
Why Is There a Price Difference Between All-on-4 and All-on-6?
Because All-on-6 requires two additional implant fixtures, multi-unit abutments, and corresponding prosthetic components, the total cost is generally higher than an All-on-4 treatment. However, implant count is not the sole factor determining treatment fees.
Overall costs are influenced by:
- Single-arch versus dual-arch rehabilitation
- Number of extractions and socket debridement required
- Need for bone grafting, guided bone regeneration, or sinus lifting
- Material selection for provisional and definitive prostheses (e.g., PMMA, monolithic zirconia, titanium-reinforced acrylic)
- Surgical complexity and sedation requirements
Most Common Misconceptions in Treatment Selection
All on 4 ve All on 6 karşılaştırılırken en sık yapılan hata, implant sayısını doğrudan tedavi kalitesiyle eşitlemektir.
Gerçekte şu kabuller yanıltıcıdır:
“Altı implant her zaman daha iyidir.”
Altı implantın avantaj sağlayabilmesi için doğru konumlara yerleştirilebilmesi gerekir.
“Dört implant dayanıksızdır.”
Araştırmalar, uygun planlanmış dört implantlı sabit tam çene protezlerinin başarılı sonuçlar verebildiğini göstermektedir.
The most common error when comparing All-on-4 and All-on-6 is equating the number of implants directly with treatment quality.
The following assumptions are misleading:
“Six implants are always better.”
Six implants only provide an advantage if they can be placed in anatomically and prosthetically sound positions.
“Four implants are fragile or temporary.”
Clinical trials and long-term data demonstrate high success rates and longevity for appropriately planned four-implant complete-arch prostheses.
“All-on-4 completely eliminates the need for bone grafting.”
While tilted posterior implants reduce the need for extensive vertical augmentation, localized bone grafting may still be required to manage ridge defects.
How Is the Decision Made at ON7 Clinic?
At ON7 Clinic, the choice between All-on-4 and All-on-6 is never made solely by counting how many implants can fit on a 3D radiograph. Final tooth positions, emergence profiles, bite registration, masticatory loads, and long-term cleanability are evaluated in coordination with the surgical plan.
Surgical execution is led by Dr. Emre Çimen, specialist in oral and maxillofacial surgery and implantology, while the prosthetic design and full-mouth rehabilitation are coordinated interdisciplinarily by Mohammad Meniawi, DDS, PhD.
Our objective is not to maximize the number of implants placed, but to position the precise number of implants required to ensure the long-term biological, biomechanical, and functional success of your fixed smile restoration.
Frequently Asked Questions About All-on-4 and All-on-6
What is the main difference between All-on-4 and All-on-6?
How many teeth are placed on an All-on-4 restoration?
Does All-on-6 require more bone?
What happens if one of the four implants fails?
Can an All-on-4 treatment be converted to an All-on-6 later on?
References
- Gallardo, Y. N. R., da Silva-Olivio, I. R., Gonzaga, L., Sesma, N., & Martin, W. (2019). A systematic review of clinical outcomes on patients rehabilitated with complete-arch fixed implant-supported prostheses according to the time of loading. Journal of Prosthodontics, 28(9), 958–968. doi:10.1111/jopr.13104
- Polido, W. D., Aghaloo, T., Emmett, T. W., Taylor, T. D., & Morton, D. (2018). Number of implants placed for complete-arch fixed prostheses: A systematic review and meta-analysis. Clinical Oral Implants Research, 29(Suppl. 16), 154–183. doi:10.1111/clr.13312
- Toia, M., Stocchero, M., Corrà, E., Becktor, J. P., Wennerberg, A., & Cecchinato, D. (2025). Fixed full-arch maxillary prostheses supported by four versus six implants with a titanium CAD/CAM milled framework: 5-year results of a multicenter randomized clinical trial. Clinical Implant Dentistry and Related Research. Advance online publication. doi:10.1111/cid.13397
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