All-on-4 and All-on-6: what the difference actually is

When a jaw has been without teeth for a while, the bone at the back resorbs first, and what remains solid sits towards the front. The All-on-4 design answers that by tilting the two rear implants so they travel forward through the bone that is still there, rather than being planted vertically into bone that is not. That is what removes the need for grafting in a large share of cases, and it is why the design exists at all.

The consensus report on the protocol names its main indication plainly: an atrophic upper or lower jaw, with or without remaining hopeless teeth, in patients who are otherwise healthy.^[2] That is a specific description, not a general one, and it is worth checking your own case against it rather than against a photograph of somebody else's result.

A 2026 systematic review and meta-analysis gathered 55 studies to set the two designs against each other. Implant survival at one year: 99.20% for four, 100% for six. At one to five years: 99.66% and 98.55%. Beyond five years: 98.14% and 97.50%. Marginal bone loss at short follow-up was 0.77 mm for four and 0.85 mm for six, and at five years 1.28 mm and 0.94 mm.^[1]

Read carefully, the two designs trade places depending on which window you look at, which is what a genuine absence of difference looks like in data. The authors say as much and add the caveat that matters: heterogeneity between the included studies was high, so these are pooled numbers from unlike populations rather than a head-to-head trial.^[1] Anyone presenting one design as clearly superior is going further than this evidence does.

Implant survival is the number everyone quotes, and it is the number least likely to be your problem. Both designs survive above 97% past five years. What actually generates work afterwards is the prosthesis: how the bite is arranged, whether the arch can be cleaned under, whether the material can take the load your jaw applies. The consensus guidance is explicit that the definitive prosthesis must be cleanable and biomechanically matched to the implant positions, and that occlusion should be balanced without interferences.^[2]

This is the reason the case is planned from the finished arch backwards rather than from the surgery forwards. Where the teeth need to be for your face, your speech and your bite decides where the implants can usefully go. Deciding the implant positions first and fitting teeth to them afterwards is the sequence that produces an arch which survives on paper and irritates in the mouth.

A fixed arch is easier to live with than a denture and harder to clean than natural teeth, because the whole span is joined and you cannot get between the units. Peri-implantitis is named as the second most frequent biological complication of the protocol,^[2] and the international case definitions describe it as a plaque-associated condition with inflammation and progressive loss of the bone supporting the implant.^[3] Both facts point the same way: the arch needs a scheduled professional clean and check, at an interval decided when it is fitted.