Why six implants?

What a sixth pair of supports adds

• Load sharing. Biting force is split between six points rather than four, spread along more of the jaw.
• A margin for problems. If one implant ever fails, five remain under the bridge. With four, losing one usually means the bridge can't be used until it's fixed.
• Shorter overhangs. With implants further back, less of the bridge hangs unsupported behind the last implant.

What the research says

A 2024 systematic review and meta-analysis in Heliyon pulled together 53 studies on fixed bridges in the upper jaw supported by four or six implants. It found:

• no significant difference in implant survival or bridge survival between the two groups;
• no significant difference in technical or biological complications;
• significantly more marginal bone loss (bone loss around the top of the implants) in the four-implant group.

The authors concluded that more implants can mean less bone loss and fewer complications, and that a CAD/CAM-milled frame and a good front-to-back spread of implants helped survival in the six-implant group.

In short: both work. Six may give a little more margin, if your bone allows it.

When six isn't possible

Six implants need enough bone along the jaw, including further back. In the upper jaw, the sinuses sit above the back teeth; in the lower jaw, a nerve runs through the bone. Where bone is thin, the choices are usually:

• four implants, with the back two angled forwards to avoid the sinus or nerve (the idea behind Nobel Biocare's All-on-4® concept);
• a bone graft or sinus lift first, then six implants;
• in severe bone loss, zygomatic (cheekbone) implants.

A 3D scan decides this, not a preference. Ask for the reason in writing if your plan says four, six or anything else.

Common questions

Do six implants last longer than four?

The research doesn't show a clear survival difference. A 2024 meta-analysis found implant and bridge survival similar with four or six implants in the upper jaw, but less marginal bone loss with six.

Why would a dentist suggest four instead of six?

Usually because there isn't enough bone at the back of the jaw. Four implants, with the back two angled, can often avoid a bone graft or sinus lift.

Is All-on-6 more surgery than All-on-4?

Yes, slightly: two more implants per jaw, so a little more surgery time and more parts. Most people have the same anaesthetic and a similar recovery.

Sources

1. Sharaf et al. (2024) — Outcomes in maxillary fixed prostheses supported by four or six implants: systematic review and meta-analysis. Heliyon
2. Nobel Biocare — All-on-4® treatment concept
3. British Society of Periodontology — Patient FAQs: dental implants

Checked October 2026. Where we give our own view as a clinic, we say so.