Bone loss: the single biggest factor in four or six
Once teeth are lost, the bone that held them slowly shrinks. How much is left, and where, shapes almost every full-arch plan.
Medically reviewed by Dt. Hüseyin Yavuz Özbek, implant surgeon · Updated October 2026If there's enough bone along the jaw, six implants are often possible. If bone at the back has shrunk, four implants with the back two tilted can often reach good bone without a graft. The other route is a bone graft or sinus lift first, so more implants can be placed, which adds time, cost and surgery. Only a 3D (CBCT) scan shows which applies to you.
Why bone shrinks
Tooth roots keep the jawbone around them in use. When teeth are lost, that bone is no longer needed in the same way and slowly shrinks, in height and width. Wearing a denture for years can add to it. Gum disease, which is often why teeth were lost, may have taken bone too.
The shrinking is usually greatest at the back of the jaw. In the upper jaw, the sinus above the back teeth can also expand downwards, leaving even less height.
How bone decides four or six
| What the scan shows | Common options |
|---|---|
| Good bone along the whole jaw | Six implants are often possible; four may also work |
| Good bone at the front, little at the back | Four implants with the back two tilted; or a graft/sinus lift first, then six |
| Very little bone anywhere in the upper jaw | Grafting first, or zygomatic implants; sometimes a removable implant denture is more sensible |
| Soft bone (common in the upper jaw) | Many dentists prefer more implants to share the load |
Grafting or angling: the trade-off
Angled implants (four)
- Uses the bone you already have
- Often avoids an extra procedure and healing time
- Fewer supports
Graft or sinus lift, then six
- Builds bone where implants are wanted
- Allows more implants, spread further back
- Adds surgery, cost, and sometimes months of waiting
Neither route is "right" in general. A graft to make room for six isn't automatically better than four well-angled implants, and avoiding a graft isn't automatically better either. It depends on how much bone is missing and what you're willing to go through.
Questions to ask about your bone
- Can you show me on my scan where each implant would go?
- Would I need a graft or sinus lift for six? For four?
- Would grafting change how many trips or how long it takes?
- If you'd use tilted implants, why, and how long are they?
- What would you do if the bone looks different during surgery?
If a graft or sinus lift is quoted separately, it changes the total. Our sister site allon6cost.co.uk helps you add up a full quote.
Common questions
I've been told I have no bone. Can I still have implants?
Often, yes. 'No bone' usually means not enough for standard implants in some places. Angled implants, grafting, a sinus lift or zygomatic implants may be options. Ask to see the scan and what each option would involve.
Does a bone graft mean extra trips?
It can. Some grafts are done at the same time as the implants; others need months to heal before implants go in. Ask whether yours would change the timeline.
Why do I need a 3D scan?
A normal X-ray is flat. A CBCT scan shows the height, width and density of the bone, and where the sinus and nerves are, so the dentist can plan where each implant goes.
Sources
- Oral Health Foundation — Understanding dental implants (bone check)
- Nobel Biocare — All-on-4® treatment concept
- Sharaf et al. (2024), Heliyon — Four or six implants for maxillary fixed prostheses: systematic review and meta-analysis
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.