All-on-4 vs All-on-6: Do You Actually Need Six Implants?

All-on-4 uses four implants to support a full arch of fixed teeth. All-on-6 uses six. Long-term survival is close to equal between them, with pooled five-year rates near 98 percent for both approaches. Six implants are most often chosen for the upper jaw, where bone is softer, or for patients with heavy bite forces. The number should come from your CBCT scan, not from a price tier.

Is All-on-6 actually more reliable than All-on-4?

The evidence says the difference is much smaller than the sales pitch suggests.

A 2026 systematic review and meta-analysis in the International Journal of Oral and Maxillofacial Surgery pooled results from 55 studies comparing the two approaches. The headline numbers:

Read that bottom row again. At five years and beyond, the four-implant approach performed marginally better, not worse. The same analysis found mechanical complications in 5.91% of All-on-4 cases against 6.64% for All-on-6.

This matters because “more implants means more security” is the single most common thing patients are told, and it is not what the pooled data shows. Four well-placed implants supporting a properly designed bridge is not a compromise version of six. It is a different engineering solution to the same problem.

The reason is anteroposterior spread. The two rear implants in an All-on-4 case are deliberately tilted so they emerge further back in the arch, which widens the footprint the bridge sits on. A wide, stable four-point base can outperform a narrow six-point one. The geometry does more work than the count.

That said, marginal bone loss at five years ran slightly higher for All-on-4 in the same analysis, at 1.28 mm against 0.94 mm. Neither figure is alarming, and both sit within normal expectations. It is worth knowing rather than hiding.

Does it depend on which jaw?

Yes, and this is the qualifier that keeps the comparison honest.

The lower jaw is the easier case. Mandibular bone is dense and cortical. It grips implants firmly, allows high insertion torque, and supports immediate loading well. All-on-4 was originally developed and validated in the lower jaw, and this is where the four-implant approach performs most reliably.

The upper jaw is a different problem. Maxillary bone is softer and more porous. The sinuses sit above the back teeth and limit where implants can go. Bone resorbs faster in the upper jaw after tooth loss. A randomized clinical study comparing the two approaches specifically in the atrophic upper jaw found better outcomes in the six-implant group across plaque scores, pocket depth, implant stability and bone loss at twelve months.

So a fair summary looks like this:

• Lower jaw: four implants is well validated and often the right answer.
• Upper jaw: four implants works for many patients, but there is a real evidence base for considering six, particularly where bone is soft or heavily resorbed.
• Both arches at once: the two jaws are planned separately. Four below and six above is a perfectly normal combination.

If a practice quotes you the same implant count for both jaws without discussing the difference, that is worth a question.

What is All-on-X, and why do practices use different numbers?

All-on-X is the general term for full-arch restoration on a variable number of implants, where X stands for however many the case requires. You will see four, five, six and occasionally eight.

Some clarity on naming, because it causes genuine confusion when you are comparing offices:

• All-on-4 is a registered trademark of Nobel Biocare, tied to a specific protocol and implant system.
• All-on-6, All-on-X and teeth in a day are descriptive terms used across the industry rather than trademarked protocols.
• Different practices use these labels loosely, so two offices quoting “All-on-X” may be describing quite different treatments.

The practical takeaway: ignore the marketing label and ask two questions instead. How many implants, and which implant system? Those two answers tell you more than any brand name on the brochure.

When do four implants make more sense?

Four is often the better clinical choice, not merely the cheaper one.

Fewer surgical sites means less biological cost. Every implant is a wound. Six implants means six healing sites, more surgical time, more swelling and a longer recovery.

Four implants frequently avoid grafting entirely. The angled placement is designed to use existing bone at the front of the jaw. Pushing to six sometimes means placing implants where bone is thin, which reintroduces the sinus lift or bone graft that All-on-4 was designed to sidestep. Trading a straightforward procedure for a longer, more expensive, more invasive one to gain a number is a poor deal.

Four is well suited to the lower jaw, where dense bone provides strong primary stability.

Fewer implants means simpler maintenance. Each implant is a site where peri-implantitis can develop, and each abutment junction is another space to clean under the bridge every day.

When would we recommend six?

Six earns its place in specific situations, and they are worth naming plainly.

• Upper jaws with soft or heavily resorbed bone, consistent with the maxillary evidence above.
• Heavy bruxism or clenching. If you grind, the forces on the bridge are substantially higher, and spreading them across more anchors reduces the load on each.
• A large arch or a strong opposing dentition. A full set of natural lower teeth biting against an upper bridge generates concentrated force.
• Heavy zirconia prostheses. A monolithic zirconia bridge weighs more and transmits more force than an acrylic hybrid, which some clinicians prefer to support on more implants.
• Where an extra implant provides redundancy in a high-risk case, so that a single failure does not compromise the whole arch.

Notice what is not on that list: a general preference for a bigger number, or a premium package tier.

Been quoted two different implant counts? The number of implants should be an output of your scan, not an input to your quote.

See how we plan full-arch cases

How much more does All-on-6 cost?

Typically $4,000 to $10,000 more per arch, driven by two extra implants, two extra abutments, longer surgical time, and a larger framework.

The important part is not the number. It is what the number should mean. Two extra implants should never be the reason for the recommendation. If a practice presents four and six as good-and-better packages at different prices, without reference to your scan, your bite or which jaw is being treated, you are looking at a pricing structure rather than a treatment plan.

The reverse also happens. An office quoting four implants when your upper jaw has significant resorption may be optimizing for a competitive price rather than for your anatomy. Both errors are worth watching for.

What should you ask if two practices quoted different numbers?

This happens constantly, and it is usually resolvable in one conversation. Take both plans to whichever dentist you trust more and ask these five questions.

1. Which jaw are we discussing, and what did the CBCT show about bone density and volume at each planned site?
2. What is the anteroposterior spread on this plan, and does it support the length of the cantilever at the back?
3. Does the six-implant plan require grafting or a sinus lift that the four-implant plan avoids?
4. What material is the final bridge, and does its weight influence the implant count?
5. Do I clench or grind, and has that been factored into this design?

A dentist who can answer all five with reference to your actual images is planning your case. A dentist who answers with generalities about more implants being safer is selling from a menu.

Dr. Gregory Mark plans full-arch cases at Forest Hills Dental using 3D imaging and computer-guided placement, and has trained in bone grafting and sinus lifts alongside implant placement. That combination matters here for a specific reason: a dentist who is equipped to graft has no incentive to avoid recommending it, and no incentive to recommend it unnecessarily. Our approach is that patients co-diagnose and co-plan their own treatment, so you will see what the scan shows before anyone proposes a number.

TL;DR

• Long-term survival is nearly identical. Pooled data at five years and beyond shows 98.14% for All-on-4 and 97.50% for All-on-6.
• More implants does not automatically mean more reliable. Anteroposterior spread and bridge design matter more than the count.
• The jaw matters more than the number. The lower jaw suits four well. The upper jaw has a genuine evidence base for considering six.
• Six is justified by specific findings: soft maxillary bone, heavy grinding, a strong opposing arch, or a heavy zirconia bridge.
• Four often avoids grafting, which six can reintroduce. That is a real trade-off, not a downgrade.
• Expect roughly $4,000 to $10,000 more per arch for six, and treat good-better-best pricing tiers with scepticism.
• Ask what the CBCT showed. The implant count should be an output of the scan.

If two practices gave you two different implant counts, bring both plans. Dr. Mark will explain what each one is responding to in your anatomy.

Get a second opinion on your plan

Frequently asked questions

Can you add more implants later if you start with four?

Adding implants to an existing full-arch case is possible but not straightforward, because the existing bridge was designed and fabricated around four specific anchor positions. Additional implants usually mean a new bridge as well. This is one reason the implant count is worth getting right at the planning stage rather than treating it as adjustable.

Do six implants last longer than four?

The available evidence does not support that. A 2026 meta-analysis of 55 studies found pooled survival at five years and beyond of 98.14% for All-on-4 and 97.50% for All-on-6, which is effectively equivalent. What affects longevity most is implant positioning, bite management, daily cleaning and whether the patient grinds their teeth.

What happens if one implant fails with All-on-4?

Losing one of four implants generally means the bridge cannot stay in function and a replacement implant is needed, usually after a healing period. With six implants there is more redundancy, since the remaining five may temporarily support the bridge. This redundancy is a legitimate argument for six in higher-risk cases.

Is four implants safe for the upper jaw?

Four implants are used successfully in upper jaws routinely, though the upper jaw is the more demanding case because maxillary bone is softer and the sinuses limit placement. Some clinical evidence favours six implants in heavily resorbed upper jaws. A CBCT scan of your specific bone volume and density should decide it.

What does the CBCT scan actually show your dentist?

A CBCT scan provides a three-dimensional image showing bone height, width and density at every potential implant site, plus the exact position of your sinuses and the nerve canal in the lower jaw. This is what determines how many implants your case needs and where they can safely be angled, which a flat panoramic X-ray cannot show.