Key takeaways
- A 2024 review of maxillary fixed dentures found no significant survival difference between four and six implants.
- That same review found more marginal bone loss with four implants (1.02 mm) than with six (0.46 mm).
- A 2026 pooled review reported high survival for both All-on-4 and All-on-6, with high heterogeneity and one direct randomized trial.
- The implant count at this clinic comes from the 3D scan, bone, and the plan for that jaw.
| Review | What differed | What to read beside the number |
|---|---|---|
| Sharaf 2024, maxillary fixed dentures | Implant survival 98.5% with four vs 97% with six (p = 0.06). Prosthesis survival 99.8% vs 99.6% (p = 0.37). Mean bone loss 1.02 mm vs 0.46 mm (p < 0.01). | 53 studies, 4,713 maxillary arches, mean follow-up 3.8 years. Almost every four-implant arch used two axial and two tilted implants. This is not a mandible result. |
| Shao 2026, All-on-4 and All-on-6 | Pooled survival at 5 years or more was 98.14% for All-on-4 and 97.50% for All-on-6. Long-term bone loss was 1.28 mm vs 0.94 mm. Mechanical complications 5.91% vs 6.64%. Biological complications 6.54% vs 7.41%. | 55 studies. Survival heterogeneity was high. Only one randomized trial compared the two concepts directly. |
- Mean marginal bone loss with four implants in the maxillary fixed-denture review, compared with 0.46 mm with six (p < 0.01). Survival was not significantly different.
- 1.02 mm
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See which arch plan fits your mouthWhat did four-versus-six reviews actually find?
Sharaf, Wang, Mashrah, Xu, Haider, and He pooled 53 studies of maxillary fixed complete dentures: 20,251 implants in 4,713 arches, mean follow-up 3.8 years. Mean implant survival was 98.5% (95% CI 97.8 to 99.1) with four implants and 97% (95% CI 95.2 to 98.4) with six. That survival difference was not statistically significant (p = 0.06). Prosthesis survival was 99.8% versus 99.6% (p = 0.37). Mean marginal bone loss was 1.02 mm (95% CI 0.79 to 1.26) with four implants and 0.46 mm (95% CI 0.20 to 0.72) with six (p < 0.01).[1]
The abstract reports no significant difference in technical or mechanical complications, or in biological complications. The technical rates they calculated were 20.7 per 100 prostheses with four implants and 17.9 with six (p = 0.74). Biological rates were 2.0 and 0.8 (p = 0.20). A later conclusion sentence says six implants can decrease complications. That sentence is stronger than the tests. This page uses the tests.[1]
Shao and colleagues pooled 55 studies of the named All-on-4 and All-on-6 concepts. At one year, implant survival was 99.20% versus 100%. From one to five years it was 99.66% versus 98.55%. At five years or more it was 98.14% versus 97.50%. Short-term bone loss was 0.77 mm versus 0.85 mm. At five years it was 1.28 mm versus 0.94 mm. The authors report high long-term survival for both techniques and similar biological complications between them. They also note high heterogeneity, and only one randomized trial compared the two concepts directly.[2]
Why is a pooled percentage not your implant count?
These are different papers. Sharaf is maxillary fixed dentures, and nearly every four-implant study in it used two straight implants and two tilted ones. Shao names All-on-4 and All-on-6 and still warns that most included studies were lower-level evidence. Putting 98.5% from one paper next to 98.14% from the other, as if they were one experiment, would invent a comparison neither group ran.[1][2]
A longer mandibular series, with its own lost-to-follow-up problem, is in how long All-on-4 implants lasted in that follow-up. The original four-implant protocol is in what All-on-4 meant in the 2003 series. Replacing teeth one by one is a different comparison, covered in full arch treatment versus individual implants.
Why does Renew choose the number from the scan?
The upper jaw implant page says some people are candidates for All-on-4 and others may benefit from six or more implants, depending on bone density and anatomy. A snap-on overdenture remains a removable option on that page.[3] The treatment hub is All-on-4 dental implants. People comparing a whole arch with separate crowns can also read full arch dental implants.
The implant surgeon places the implants. Tom Szarski, DD, is the denturist who designs and fits the teeth with the on-site lab. The free consultation includes a 3D scan. The number of implants is part of that plan. It is not copied out of a pooled percentage.
Sources
- Outcomes that may affect implant and prosthesis survival and complications in maxillary fixed prosthesis supported by four or six implants: A systematic review and meta-analysis — Heliyon
- All-on-4 and All-on-6 implant concepts in edentulous patients: a systematic review and meta-analysis — International Journal of Oral and Maxillofacial Surgery
- Upper jaw implants — Renew Implant Centre
Frequently asked questions
Is All-on-6 safer than All-on-4?
Sharaf and colleagues found no significant survival difference between four and six implants in maxillary fixed dentures, and they did find more bone loss with four. Shao and colleagues reported high pooled survival for both named concepts, with high heterogeneity and only one randomized trial that compared them directly.
Do those percentages tell me how many implants I need?
No. They pool other people's jaws. Sharaf 2024 is mostly maxillary fixed dentures. Shao 2026 mixed studies and had only one randomized trial that compared the two concepts directly. Your count depends on bone, the jaw, and the prosthesis.
Can the upper jaw use more than four implants?
Yes. This clinic's upper-jaw page says some people are candidates for All-on-4 and others may benefit from six or more implants, depending on bone density and anatomy. A removable snap-on denture is a separate option.
