Who needs four implants and who needs six
The number is not a matter of taste. It follows from a handful of things a dentist can see on your scan and learn from your history.
Medically reviewed by Dt. Hüseyin Yavuz Özbek, implant surgeon · Updated October 2026Four implants usually suit people with good bone at the front of the jaw but too little at the back, because the back two can be tilted to avoid the sinus or the nerve without a graft. Six usually suit people with enough bone along the jaw, especially in the softer upper jaw, those with a strong bite or who grind, and anyone who values a spare support if one implant fails. Health, smoking and the opposing jaw also play a part.
The five things that decide it
When a dentist looks at your scan and asks about your health, they are really answering five questions. The answers usually point clearly one way.
| Question | Points towards four | Points towards six |
|---|---|---|
| How much bone is there at the back of the jaw? | Little height under the sinus or above the nerve | Enough height and width for implants further back |
| Which jaw? | Common in the lower jaw, where front bone is dense | Often preferred in the upper jaw, where bone is softer |
| How strong is the bite? | Average bite, denture or bridge opposite | Strong bite, natural teeth or a fixed bridge opposite |
| Do you grind or clench? | No sign of grinding | Signs of grinding or clenching |
| Do you want to avoid extra surgery? | Yes, if six would need a graft first | Willing to have a graft if needed for six |
None of these is a rule on its own. A patient with soft upper bone and a strong bite but almost no bone at the back may still be better off with four tilted implants than with a sinus lift. The two-minute quiz walks through the same questions.
Bone: the deciding factor
Implants need bone around them. After teeth are lost, the bone that held them shrinks, and the back of the jaw usually loses the most. In the upper jaw the sinus sits just above the back teeth; in the lower jaw a nerve runs through the bone further back. Both limit where an implant can go.
Four-implant plans handle this by tilting the back two implants so that their tips stay in front of the sinus or the nerve while their heads come out further back in the mouth. A meta-analysis of 44 studies found tilted and upright implants failed at similar rates overall (1.6% and 1.8%), with no difference in bone loss around them. It did find a higher failure rate for tilted implants in studies that looked only at the upper jaw, which is one reason many dentists prefer more implants there when bone allows.
Six-implant plans need bone further along the jaw. If it is there, six spreads the support over a wider area. If it is not, the choice becomes four tilted implants, or a sinus lift or bone graft first and six later. More on that trade-off is on bone loss and grafting.
The upper and lower jaws are different
Upper-jaw bone is usually less dense than lower-jaw bone. A 2024 review of 53 studies on upper-jaw bridges found implant and bridge survival similar with four or six implants, but less bone loss around the implants when six were used. In practice, that is why six is often the first choice on top and four is common underneath. Our page on the upper and lower jaw goes into the detail.
Bite force and grinding
Each implant in a four-implant bridge carries a larger share of the bite. That matters most for people who bite hard or grind their teeth at night. A 2024 meta-analysis of 27 studies found that implants in people with probable bruxism (grinding or clenching) were about twice as likely to fail as implants in people without it. Six implants do not cure grinding, but a dentist treating a grinder will usually want more support and a night guard. Our article on grinding and four or six implants explains why.
Health and habits
Health affects whether implants are wise at all more than it decides four or six. The factors that matter most:
- Smoking: raises the risk of implant failure and infection. Stopping before surgery helps.
- Diabetes: well-controlled diabetes is compatible with implants; poorly controlled diabetes slows healing.
- Gum disease: a history of it raises the risk of infection around implants later, so cleaning and check-ups matter more.
- Bone medicines: high-dose drugs for osteoporosis or cancer, such as some bisphosphonates and denosumab, need discussing with the dentist and your doctor before any surgery.
A review of patients aged 75 and over found implant survival of about 97% after one year and 96% after five, so age on its own is not a reason to rule treatment out. See four or six over 70.
What you want from the result
Some preferences are legitimate reasons to lean one way. If you would rather avoid a graft and an extra few months, four tilted implants may be the better plan. If you want the reassurance that one failed implant will not leave you without fixed teeth for a while, six gives that margin, as explained on what if an implant fails. Tell the dentist what matters to you; it is part of the decision.
When neither is right
A full fixed arch is not for everyone. If you still have several healthy teeth, a smaller bridge or individual implants may keep more of your own mouth. If bone is very thin in the upper jaw, zygomatic implants or a removable denture on implants may be safer. If you cannot clean under a fixed bridge every day, for example because of arthritis in the hands, a removable option can be easier to live with.
Common questions
Can I choose six even if my dentist suggests four?
You can ask, and a good dentist will explain why they suggested four. If six would need a sinus lift or graft, the choice is really between four implants now and extra surgery first. If your bone already allows six, many dentists are happy to place them.
Am I too old for All-on-4 or All-on-6?
Age alone is rarely the issue. A large review of patients aged 75 and over found high implant survival. General health, medicines and how well you can clean matter more than the date of birth.
Does it matter what is on the other jaw?
Yes. A full arch biting against natural teeth or another fixed bridge takes more force than one biting against a removable denture. Dentists factor that into how many implants they want.
What if neither option is possible?
If bone is very thin, especially in the upper jaw, the choices are grafting first, zygomatic implants anchored in the cheekbone, or a removable denture on implants. A CBCT scan shows which apply.
Do I need a CBCT scan to know?
Yes, for a final answer. A panoramic X-ray gives a good first idea of bone height, but only a 3D scan shows width and the exact position of the sinus and nerve.
Sources
- Sharaf et al. (2024), Heliyon — Four or six implants for maxillary fixed prostheses: systematic review and meta-analysis
- Chrcanovic, Albrektsson, Wennerberg (2015), Journal of Dentistry — Tilted versus axially placed dental implants: a meta-analysis
- Schimmel et al. (2018), Clinical Oral Implants Research — Effect of advanced age and/or systemic medical conditions on dental implant survival
- Häggman-Henrikson et al. (2024), Journal of Oral Rehabilitation — Bruxism and dental implants: systematic review and meta-analysis
- Polido et al. (2018), Clinical Oral Implants Research — Number of implants placed for complete-arch fixed prostheses
Checked October 2026. Where we give our own view as a clinic, we say so.
Only a scan can settle it.
Send us an X-ray or scan if you have one. A dentist will tell you which option suits your bone, and say so honestly if neither is the right step.