When to choose All-on-4, All-on-6 or All-on-8

Patients comparing full-arch quotes run into this quickly: one clinic proposes All-on-4, another proposes All-on-6 for a few thousand more, somewhere a website mentions All-on-8, and the names start to sound like trim levels on the same car. More implants, more money, presumably more security.

The trial evidence says otherwise, and it is worth knowing before you compare a single quote. Randomized studies that directly compared four implants against six per arch found no survival advantage in the higher number. What separates the configurations is not strength as a product feature; it is which anatomy each one serves. The deciding input is your jaw, read on a CT scan, and this article walks through how that decision actually gets made.

What the numbers in the names mean

All three are fixed full-arch restorations: a complete row of teeth screwed onto implants, removable only by a dentist. All-on-4 supports the arch on four implants, with the back two placed at an angle of up to about 45 degrees, a design that uses the denser bone toward the front of the jaw and steers clear of the sinus above and the nerve below. All-on-6 adds two more implants for a wider distribution of support. All-on-8 pushes that logic further and appears mostly in upper-jaw cases where a surgeon wants maximum spread. Each gets its own section below, because they answer different anatomical situations rather than different budgets.

If you are still deciding between fixed arches, overdentures and conventional dentures, that earlier fork in the road is the subject of our implants-or-dentures decision guide. This article assumes the fixed arch won and the question is how many posts hold it up.

Where each configuration fits

All-on-4 is the workhorse of full-arch dentistry and the configuration with the deepest published record. Its design solves a specific problem: patients who lost teeth years ago usually lost bone with them, especially toward the back of the jaws, where the sinus (above) and the nerve canal (below) limit where implants can go. Tilting the two rear implants up to about 45 degrees anchors them in the denser bone toward the front while extending support far enough back to carry a full row of teeth. The result treats most full-arch cases without grafting, on four implants, which is why it dominates both the literature and the price lists. The longest follow-up published by the group that developed the concept tracked mandibular cases for 10 to 18 years, with prosthesis survival of 98.8 percent and implant survival around 93 percent over that horizon. Our All-on-4 treatment page and its price page carry the specifics.

All-on-6 adds two implants, typically in the middle zones of the arch, and surgeons reach for it when the scan shows enough bone to place six comfortably and the case benefits from a wider distribution: a larger arch to restore, an opposing row of natural teeth or fixed implants that will bite hard against it, or bone quality that makes the surgeon want the load spread across more posts. It costs a step more and requires a step more bone. What it does not do, on the trial evidence, is outlast a well-planned All-on-4, so its case has to be anatomical rather than promotional. Details live on the All-on-6 page and its pricing.

All-on-8 appears mostly in upper-jaw cases, where bone is softer and a surgeon may want maximum distribution, sometimes across a full-mouth reconstruction where both arches are being rebuilt to bite against each other. Comparative research specific to eight implants is thin, so treat it as a specialist's prescription for particular anatomy rather than a premium tier. When a case genuinely calls for it, the reasoning will be visible on the scan and the surgeon should be able to show you. The All-on-8 page covers the procedure and its price.

What happened when trials compared four and six

A multicenter randomized clinical trial published in 2025 followed patients with upper-jaw fixed arches for five years, randomly assigned to four or six implants. Survival came out at 100 percent in the four-implant group and 99.3 percent in the six-implant group; the single early failure of the study happened in the group with more implants, and bone levels around the implants showed no significant differences between groups.

An earlier randomized trial, published in 2016, ran the same comparison with guided surgery and immediate loading over five years. Implant failures reached 1.25 percent with four implants and 5 percent with six, a difference that did not reach statistical significance, and neither group lost a single prosthesis. A 2025 retrospective cohort added scale to the picture: 943 patients and 5,989 implants followed for up to 17 years, with four and six implant configurations showing high and comparable survival. In that dataset, the factors that did correlate with implant loss were the type of jaw and the patient's age. The count was not the story.

The long-term record rounds out the picture. Beyond the head-to-head trials, the All-on-4 concept itself carries followed cohorts of 5, 10 and up to 18 years, with five-year implant survival of 98.1 percent in the developer group's mandibular series and the 10-to-18-year outcomes cited above. Four implants per arch is the configuration dentistry has tested longest and hardest, which is worth remembering when a sales conversation frames it as the entry-level option.

Read those results for what they establish and no more. They do not say the number of implants never matters; they say the number alone buys no measurable survival advantage when cases are properly planned. Planning is the load-bearing word.

What actually decides the number

The deciding inputs live in your CT scan. Bone volume and where it sits determine how many implants fit, at what angles, and whether the configuration can avoid grafting. The jaw matters: upper jawbone is generally softer and interrupted by the sinus cavities, while the lower jaw offers dense bone toward the front, which is part of why the 17-year cohort found jaw type correlated with implant loss and why upper arches sometimes receive more implants, longer implants, or steeper angulations. The prosthesis weighs in too, since the spread of the implants governs how the row of teeth distributes chewing forces along its length.

The scan sometimes returns a harder answer: not enough bone for any standard configuration without preparation first. Grafting can rebuild volume at the cost of months of healing before implants go in, and severely resorbed upper jaws have specialized solutions that belong in a specialist conversation rather than a price list. A clinic that names this possibility before you fly, based on the records you send, is doing exactly what the remote-quoting process is for.

A surgeon reading your scan is balancing those variables, and different competent surgeons sometimes land on different answers for the same mouth. What separates a judgment call from a sales decision is the reasoning: a serious proposal points at your anatomy and explains why this number, in this jaw, for this prosthesis. The trials give patients one reassurance worth keeping: when a well-planned case calls for four, four is a complete answer, supported by the same survival curves as six.

Acrylic or zirconia, the other decision

Alongside the implant count runs a second choice that moves the price as much as the count does: the material of the final row of teeth. Acrylic (technically a hybrid of acrylic teeth on a reinforcing frame) is the proven standard: lighter, less costly, and repairable chairside when a tooth chips, at the cost of gradual wear that typically brings a refresh of the teeth years down the line. Monolithic zirconia is milled from a single ceramic block: harder, more stain-resistant, closer to natural teeth in translucency, and priced accordingly, with repairs that generally mean lab work rather than a quick fix. At verified Costa Rican clinics the difference is explicit: All-on-4 from $8,500 in acrylic and $11,500 in zirconia, quoted as separate line items rather than a vague "premium option."

Neither material is the trick answer. Heavy grinders sometimes do better with the forgiveness of acrylic, patients prioritizing aesthetics and longevity often choose zirconia, and the constant underneath is that both materials need the same four to eight implants doing the structural work. Ask for both versions priced in writing and decide with the numbers in front of you.

What teeth in a day actually means

Full-arch marketing leans on the phrase "teeth in a day," and it describes something real with an important asterisk. What can happen in a day, when the scan supports it, is surgery plus a fixed provisional row of teeth: you leave with teeth that do not come out at night. What cannot happen in a day is the finished result, because bone needs months to fuse to titanium (osseointegration) before the definitive prosthesis should be delivered. The standard calendar at verified clinics runs 7 to 10 days for the first trip, a healing period of several months at home, then a shorter second visit for the final teeth, a structure our All-on-4 cost article lays out day by day. A clinic promising definitive teeth in one short visit is compressing biology, whatever the implant count.

The price ladder in both countries

Each step up the ladder adds implants, surgical time and prosthetic complexity, and the pricing follows.

Whichever configuration is proposed, the quote should itemize the same things: how many implants and which brand, the prosthesis material with the acrylic and zirconia versions priced separately, IV sedation as its own line ($300 to $600 at verified clinics rather than folded invisibly into a total), and both visits of the timeline. The calendar barely changes with the count: surgery and a fixed provisional on the first trip of 7 to 10 days, then the final prosthesis on a shorter second visit months later, once the bone has fused.

Cases involving both arches double the arithmetic and add a planning question: some patients restore both in one surgical trip, others stage the arches months apart, spreading cost and recovery. Staging also lets the second arch be planned against the first one's bite. Either path is legitimate; what matters is that the quote prices each arch separately so you can see the structure of what you are buying, and that the plan says which teeth the new arch will bite against during every phase.

The arithmetic consequence runs in both directions. Paying for All-on-6 when your anatomy is fully served by four buys nothing the trials could measure, and the difference at verified Costa Rican clinics is $2,500 per arch. Choosing four when your bone genuinely needs six is the more expensive mistake, because a failed or compromised arch costs more than any configuration. The number is a prescription, and prescriptions come from scans. How patients cover these amounts, including the pre-tax routes, is the subject of our article on paying for implants, and the price guide holds the complete list.

Red flags in both directions

The upsell version sounds like strength marketing: eight is stronger than six, six is stronger than four, priced per implant like toppings. If the proposal cannot point to something in your scan that motivates the higher number, you are being sold hardware. The evidence above is your polite counterargument.

The downsell version promises four implants and finished teeth for everyone, sight unseen, sometimes in a single short visit. A recommendation made before anyone has looked at your bone is a guess, and definitive same-day full-arch teeth remain a biological red flag regardless of implant count, since bone needs months to fuse to titanium. Both versions fail the same test, which makes the test easy to remember: the number must come from your image, and the reasoning must survive being written down. A CT scan in hand also makes second opinions cheap: send the same records to two clinics and compare the proposed numbers and their reasons. Two competent surgeons disagreeing about four versus six is normal and even useful, because their explanations teach you what your case turns on. Our verification article covers the rest of what to check before trusting any clinic with a full arch.

What to ask at your evaluation

Five questions extract the reasoning from any proposal, at home or abroad.

Every verified clinic on our platform takes a cone beam CT on site and quotes itemized, in writing, naming the implant brand and prosthesis material, which turns these questions into a ten-minute conversation instead of a negotiation. The planning guide shows where the evaluation fits in the trip.

The number is an output, not a menu choice

All-on-4, All-on-6 and All-on-8 are answers to anatomical questions, and the trial record shows the smallest of them holding its own wherever it is properly indicated. Walk into your evaluation knowing that, ask for the scan before the final number, and let every proposal defend its count in writing. The configuration that fits your jaw is the right one, whichever name it carries.

Sources

• Toia, M., Moreira, C. S., Dias, D. R., et al. (2025). Fixed full-arch maxillary prostheses supported by four versus six implants: 5-year results of a multicenter randomized clinical trial. Clinical Oral Implants Research, 36(3), 298-313. PMID 39581887. pubmed.ncbi.nlm.nih.gov
• Tallarico, M., Meloni, S. M., Canullo, L., Caneva, M., and Polizzi, G. (2016). Five-year results of a randomized controlled trial comparing patients rehabilitated with immediately loaded maxillary cross-arch fixed dental prosthesis supported by four or six implants placed using guided surgery. Clinical Implant Dentistry and Related Research, 18(5), 965-972. PMID 26446912.
• Four vs. six implant full-arch restorations: a direct comparative retrospective analysis in a large controlled treatment cohort (2025). Journal of Clinical Medicine, 14(12), 4237. pmc.ncbi.nlm.nih.gov
• Maló, P., de Araújo Nobre, M., Lopes, A., Ferro, A., and Botto, J. (2019). 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. doi.org/10.1111/cid.12769

This article is for general information and is not medical advice. Which full-arch configuration fits your case requires an in-person evaluation and a CT scan by a licensed dentist. Prices shown are verified starting prices and vary by case complexity.