What it involves
The All-on-4 concept rehabilitates an entire arch — the whole upper or the whole lower — on four implants rather than six, eight or ten. Two are placed straight at the front, and two are tilted backwards to use the bone that is usually preserved in front of the maxillary sinus above and in front of the alveolar nerve below.
That tilt is the central idea. Angling the rear implants lets the bridge be supported further back without invading those structures and, in many cases, without grafting bone where none is left. That is why the technique exists: not to save implants, but to avoid an extensive graft.
The result is a fixed, screw-retained full bridge that you do not take out. It is not a denture that is glued in, and not an appliance removed at night.
Who it is for
It is a solution designed for complete arches, not for isolated gaps. The usual profiles are these:
- A completely edentulous arch
- Especially the lower jaw, where a conventional full denture moves when you talk and eat because there is nothing to retain it.
- Teeth that cannot be saved
- Where what remains is mobile or has generalised bone loss, and keeping it only postpones the problem.
- Posterior resorption
- Where the bone in the molar region no longer gives any height but the front of the jaw still does. That is precisely the scenario the technique was designed for.
- People who would rather avoid an extensive graft
- Avoiding one shortens the calendar and reduces the number of surgeries, and for many patients that weighs as heavily as the final result.
What it asks of the bone and the bite
With four implants carrying twelve or fourteen teeth, each implant works harder than in a rehabilitation on six or more. That means the planning has less margin for error, not more.
There must be enough bone at the front to house the four implants with good initial stability, and that stability has to be measured at the time of surgery rather than assumed. The bite matters too: if the opposing arch is healthy natural teeth, the forces are greater than if it is another prosthesis.
Three-dimensional imaging is not optional here. Angling an implant backwards requires knowing precisely where the sinus or the nerve is, and a flat x-ray does not show that.
The temporary bridge and the definitive one
The image that circulates of All-on-4 — walking out of the clinic with teeth in place — refers to the temporary bridge, not the definitive one. Where conditions allow, a fixed temporary bridge is fitted in the hours after surgery, lighter and with the bite adjusted so it does not load the implants while they integrate.
The definitive bridge comes months later, once integration is confirmed and the gum has settled. It is made from different materials and on fresh measurements, because the gum contour changes during healing and a bridge made on day one would no longer fit the same way.
Two prostheses is not a surprise extra: it is part of the treatment and it belongs in the quote from the outset.
Its limits, stated plainly
None of this disqualifies the technique. All of it should be said before you decide.
- Little redundancy
- With four implants, losing one compromises the whole structure. With six, the bridge can sometimes be rescued. That is why All-on-6 exists, and why it is sometimes the recommendation.
- Hygiene changes
- Under a fixed full bridge there is a space that has to be cleaned every day with a water flosser and specific brushes. Anyone who does not will get inflammation, and then bone loss.
- The prosthesis needs maintenance
- Screws are checked, acrylic wears, and at some point the bridge needs repair or replacement. It is a mechanical structure under load, not a permanent part.
- Speech takes adjusting
- The volume and contour differ from your own teeth or from a previous denture. Most people adapt within days or weeks; it is worth knowing that period exists.
- It does not easily reverse
- If teeth are extracted to fit it, the decision cannot be undone. It deserves a second opinion if you have the slightest doubt.
This page is general patient information, written so that you arrive at the practice knowing what to ask. It is not a diagnosis or a treatment recommendation: those can only follow a clinical examination and the appropriate imaging.
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