When All-on-4 Isn’t the Right Choice, and What Is

All-on-4 has earned its reputation. Four implants, two of them tilted to catch more bone, can carry a fixed arch of teeth and often support a temporary bridge on the same day. For a great many people with failing or missing teeth, it is a sound, well-documented solution. But a technique being excellent is not the same as it being right for everyone. Part of honest implant dentistry is knowing when to reach for something else.

At Ortoimplant we plan every full-arch case from a CBCT scan before we commit to a number of implants. Sometimes that scan tells us four will do the job beautifully. Sometimes it tells us four would be a compromise the patient would come to regret. This piece walks through the situations where All-on-4 is not the first choice, and what we consider instead.

What All-on-4 does well, and where its edges are

The concept was designed to rehabilitate an atrophic or fully edentulous jaw without extensive bone grafting, by angling the back implants to make use of the bone that remains. Reviews of the technique report survival rates above 97 per cent past the three-year mark, which is why it has become a default for so many clinics.^[1]

Its limits are structural rather than mysterious. Four points of support leave less margin if one implant underperforms. The fixed bridge usually ends in a short cantilever behind the last implant, and the longer that overhang, the more stress lands on the bone at the back. In the right mouth none of this matters. In the wrong one, it does.

When four implants may not be enough

The most common reason we step up from four to six implants is load, not just bone quantity. A few patterns push us that way:

• Soft or low-density bone, often in the upper jaw, where each implant grips less firmly and spreading the load across more fixtures makes sense.
• A powerful bite or grinding habit (bruxism), which multiplies the force travelling through the prosthesis night after night.
• A long or wide arch, where six implants shorten the unsupported spans and keep the bridge more rigid.

The obvious question is whether six implants actually last longer than four. The honest answer from the evidence is that, when a case is well selected and well executed, survival is broadly similar between the two. A large comparative analysis of nearly 6,000 implants found two and five-year survival rates that were statistically comparable for four and six-implant restorations, with implant loss tied more to jaw type and patient age than to the number of implants.^[2] So the choice is rarely about chasing a higher survival figure. It is about biomechanics: distributing force, reducing cantilever length, and building in redundancy for a mouth that will be under heavy demand for decades. All-on-6 is not a better technique than All-on-4. It is a better fit for certain jaws.

When there is not enough bone even for tilted implants

All-on-4 already leans on tilted implants to avoid grafting. But there is a point of upper-jaw bone loss, after long-term denture wear, gum disease, or a failed previous graft, where even angled standard implants have nothing solid to anchor into. The back of the upper jaw is the usual problem, where the sinus sits low and the ridge has thinned to little more than a shell.

This is where the techniques we are known for come in. Rather than sending a patient away for a year of grafting, or telling them they are not a candidate, we can anchor into bone outside the usual ridge:

• Zygomatic implants, which are longer and engage the dense cheekbone rather than the resorbed jaw.
• Pterygoid implants, which reach into bone at the very back of the upper jaw.
• Subperiosteal and transnasal approaches for selected cases where standard fixation is not available.

The evidence behind zygomatic implants for the severely resorbed upper jaw is encouraging. A systematic review reported cumulative success around 98 per cent in the first year, settling near 96 per cent past five years.^[3] A separate meta-analysis found survival comparable to conventional implants placed in the front of the jaw, with the added benefit of avoiding sinus grafting and its longer recovery.^[4] These are demanding procedures that belong in experienced hands, and complications such as sinus irritation do occur, which is precisely why case selection and 3D planning matter so much. The principle we work to is straightforward: there is no patient for whom teeth cannot be fixed. The technique simply changes to match the anatomy.

When grafting or a different plan still makes sense

Not every shortfall calls for an exotic implant. For a patient with a localised bone deficit, good general health, and no rush, a staged bone graft followed by conventional implants can be the cleaner long-term answer. For someone medically unable to tolerate a longer surgery, a more conservative plan may be kinder. The right choice is a conversation about your anatomy, your health, your bite, and how much time you want the treatment to take.

How we decide

Every full-arch plan at Ortoimplant starts with a CBCT scan and guided planning, so the number and position of implants is a decision made on real bone, not a guess. For anxious patients or longer procedures we can work under analgosedation, and our recovery support, including hyperbaric oxygen therapy, ozone therapy, and pre-operative lymphatic drainage, is aimed at helping healing along. The first examination is free, and it is the proper place to find out which of these paths fits you.

All-on-4 is often the answer. When it is not, the goal does not change: fixed teeth you can rely on, built on a foundation chosen for your jaw rather than for convenience.

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