The quick answer
Four per arch, in most cases. More implants aren't better. Extra implants sit closer together, reach further back into bone that handles chewing poorly, and each one adds another screw hole through your teeth, which makes them weaker. Adding implants doesn't add teeth, either. We look at your scan before we settle on a number.
In this answer
Where All-on-4 came from
Paolo Malo developed the idea for denture wearers who had very little bone. Four implants could hold a fixed set of teeth where there wasn't enough bone for more.
Two things surprised people. Denture wearers rarely wanted to switch once they'd got used to a denture. And the method worked just as well for people who had plenty of bone.
Why we went from six implants to four
We used to place six implants, then five, and now four. The science didn't change. Our circumstances did.
Early on, six felt safer. We had less experience, and extra implants felt like extra security.
The bigger reason was money, and it was true across the whole field. Remaking a set of teeth after an implant failed used to be slow and expensive, and most patients had already spent all they could. So surgeons added extra implants as insurance against a remake nobody could afford.
Digital design and our own in-house lab changed that. When a replacement is quick and affordable to make, there's no reason to put more hardware in your mouth than your case needs.
Four implants per arch, followed for up to 18 years
Lower jaw, 10 to 18 years
Upper jaw, 5 to 13 years
With four implants holding each arch, the implants and the teeth on top held up well. People were followed for up to 18 years in the lower jaw and 13 in the upper. A separate review of 93 studies compared fewer than five implants per arch with five or more. It found no clear difference.
Two studies that looked back at records from one group of clinics, both with four implants per arch. 471 people had the lower jaw done and 1,072 the upper. The clinics lost touch with 31.6% and 20.4% of them, so the figures are estimates made with a standard method (life tables). For the lower jaw, the teeth figure counts teeth still in use. For the upper jaw, it counts teeth working well. The review of 93 studies gives no added-up percentages in its summary, so it is a sentence here, not a bar.
- Maló P, de Araújo Nobre M, Lopes A, Ferro A, Botto J. 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. Clin Implant Dent Relat Res. 2019;21(4):565-577. doi:10.1111/cid.12769. PMID 30924309.
- Maló P, de Araújo Nobre M, Lopes A, Ferro A, Nunes M. The All-on-4 concept for full-arch rehabilitation of the edentulous maxillae: A longitudinal study with 5-13 years of follow-up. Clin Implant Dent Relat Res. 2019;21(4):538-549. doi:10.1111/cid.12771. PMID 30924250.
- Daudt Polido W, Aghaloo T, Emmett TW, Taylor TD, Morton D. Number of implants placed for complete-arch fixed prostheses: A systematic review and meta-analysis. Clin Oral Implants Res. 2018;29 Suppl 16:154-183. doi:10.1111/clr.13312. PMID 30328199.
Why more implants can be worse
Implants don't like close neighbors. Crowded implants can affect each other, and they're harder to keep clean. Over the years that adds up.
The bone further back is weaker. A fifth and sixth implant go further back in the jaw, where the bone copes less well with the twisting of chewing.
Shorter implants. More implants in the same space means each one tends to be shorter. When we placed six, we used 10 and 11mm implants. Our standard now is 11.5 to 13mm.
Every implant means a hole through your teeth. Each screw channel is about two millimeters wide. A twelve-tooth arch is about 120 millimeters across, so four implants take up about eight millimeters of it. At six or seven, close to a tenth of the arch is screw holes.
More holes mean thinner material at the weak spots and more places your teeth could crack. These materials are strong, but they aren't unbreakable.
Implants don’t like close neighbors
Bone lost at the top, between two implants
Implants set close together lost more than twice as much bone between them. It’s one reason more implants aren’t always better.
36 people who each had two implants side by side, measured on X-rays. These were pairs of implants, not full-arch bridges. The study is from 2000.
- Tarnow DP, Cho SC, Wallace SS. The effect of inter-implant distance on the height of inter-implant bone crest. J Periodontol. 2000;71(4):546-9. doi:10.1902/jop.2000.71.4.546. PMID 10807116.
The sinus lift connection
Reaching back for a fifth or sixth implant often meant lifting the sinus. We used to do it routinely, sometimes daily.
Moving to four mostly ended that. It also leaves your sinus untouched, which keeps it available later. If an implant ever needs replacing, working in a spot that's never been grafted is easier.
Read more: do I really need a sinus lift
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More implants, same number of teeth
Four, five or six implants, your new teeth come back with the same number of teeth. The upper design may differ a little, but adding an implant doesn't add a tooth.
People ask us about this more than anything else, and it's why so many assume more must be better.
After a lifetime of dental issues I decided that the all on four procedure was my choice.
How we decide the number
Your CT scan is a map. It shows where the bone is and where implants can go, and most of the plan holds. But we only know the bone quality for sure once surgery starts. Soft bone, or a spot where infection has worn bone away, can mean a planned position isn't the right one on the day.
So we start at four, the minimum you want, and place the number your bone calls for. If that turns out to be five, it doesn't mean your case was a bad one. One planned spot just wasn't the right place, and it doesn't change your overall cost.
In our experience that's very infrequent, nothing like the routine it used to be.
A good question to ask
Instead of asking how many implants, ask how do you decide how many? A surgeon who can walk you through that has thought about it. A practice that names a number before looking at your scan is telling you about its routine, and your mouth hasn't come into it yet.
Quick answers
Do more implants mean more teeth?
No. Whether an arch has four, five or six implants, your new teeth come back with the same number of teeth. It's the mix-up we hear most often.
Does an extra implant cost more?
Not here. We place the right number of implants for you at the time of surgery, and it doesn't change your overall cost.
Is a practice that recommends six doing something wrong?
Not necessarily. They may be seeing something specific in your case. The thing to watch for is a number given before anyone has looked at your scan.
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Read next
My dentist said I need a sinus lift. Do I really need one for full-arch implants?
Almost certainly not. In our own records, fewer than 1% of full-arch patients have needed a sinus lift. In a full-arch case we angle the implants so they avoid the sinus altogether. If you were told you need one, that advice was most likely for a single implant, which is a different procedure with different needs.
Answered by Dr. Daniel R. Noorthoek
Read the full answerWhat is peri-implantitis, and how is it different from gum disease?
Peri-implantitis is inflammation and bone loss around an implant. It's the implant version of gum disease, and it can move faster. A natural tooth is held in by a ligament and a root layer called cementum. An implant has neither, so the gum holds on less firmly and trouble can build more quickly. That's why your yearly check matters even more once you have implants.
Answered by Dr. Blake Hauer
Read the full answerWhy does Done In One remove your full-arch teeth once a year?
Once a year we take your teeth off, clean the side that sits against your gums, check the implants up close and put everything back. Not every practice does this. We do it because that side can't be fully cleaned at home, X-rays alone don't show enough, and problems around implants can grow faster than problems around natural teeth.
Answered by Dr. Blake Hauer
Read the full answer