All-on-4 Dental Implants

All-on-4 is a way of placing four implants in a jaw that has no teeth, or whose remaining teeth can no longer be saved, and attaching a single-piece fixed bridge to them. The two front implants go in upright; the two back implants are tilted backwards. The bridge is screwed to the implants: you cannot take it out — only your dentist removes it, for check-ups and cleaning.

The problem it solves is this: when teeth were lost a long time ago, the bone at the back of the jaw has usually shrunk. Planning an implant for every missing tooth would mean major grafting there. All-on-4 largely bypasses that area and uses the front of the jaw, where the bone is better preserved. For a general comparison of full-arch options, see our All-on-4 and All-on-6 page; this page goes into the detail of the four-implant plan.

Why are the back implants placed at an angle?

In the upper jaw, the sinus sits above the molars; in the lower jaw, a nerve runs through the bone and gives feeling to the lip. In these areas an upright implant either ends up too short or comes too close to these structures. When it is tilted — usually at an angle of 30–45 degrees — the implant runs along the front wall of the sinus in the upper jaw, and in front of the point where the nerve leaves the bone in the lower jaw.

The angle has three consequences:

• A longer implant can be used, so more of its surface is in contact with bone.
• The implant emerges further back in the mouth, so the bridge is supported further back.
• The part of the bridge that extends unsupported beyond the last implant (the cantilever) is shorter. The shorter the cantilever, the less leverage acts on the implants.

Can it be done without a bone graft?

That is the aim of the technique, but it is not possible in every case. Thanks to the angled implants, a sinus lift or major bone augmentation at the back of the jaw is often unnecessary. Even so, the front of the jaw needs bone of enough height and width to hold four implants. If the front has also thinned considerably, a small bone graft may be added during placement, or the plan changes. A 3D CBCT scan shows this — it is not a matter of guesswork.

There is another detail that is rarely discussed: some bone at the front may be reshaped to make room for the bridge and to hide the line where the bridge meets the gum behind your lip. If a lot of gum shows when you smile, this is an important part of planning and should be discussed before surgery.

Who is it suitable for, and who not?

We most often consider it for patients who have worn dentures for years and find them loose, for those whose teeth are mostly loose from advanced gum disease and cannot be saved, and for those whose bone loss at the back would make an implant-by-implant plan very long.

There are also situations where we need to be more cautious. Diabetes with uncontrolled blood sugar, heavy smoking, bone-strengthening drugs given intravenously, or a history of radiotherapy to the jaw all make healing harder. Severe clenching increases the load on the four implants. And if you will not be able to make time every day to clean under the bridge, a fixed solution can become a burden — we tell you that from the start, too.

What is prepared before surgery?

Whether a temporary bridge can be fitted quickly depends on preparation done before the operation. Alongside the scan, we take impressions of your existing teeth or denture and photographs of your face; these records are used to plan the length of the teeth, the support they give your lip, and your smile line. Tell us at the first examination about any medicines you take, especially blood thinners and bone medication; if necessary, we liaise with the doctor who prescribes them. If you have diabetes, your blood sugar needs to be under control before surgery.

Surgery day and the temporary bridge

Any teeth that need to come out are extracted in the same session, and the implants are placed under local anaesthetic; you usually feel no pain during the procedure. The key decision is made during surgery: if the implants are held firmly enough in the bone (primary stability), a fixed temporary bridge is fitted the same day or within a few days in most cases. If the hold is not sufficient, we do not rush: either a fifth implant is added, or you wear a removable temporary denture while the implants fuse with the bone.

Expect swelling and tenderness for the first two or three days. For the first 2–3 months with the temporary bridge, eat soft foods you could mash with a fork; while the implants are fusing with the bone, a hard bite puts them under strain. If the swelling in your face keeps getting worse, or you develop a fever or difficulty swallowing, contact us or go to the nearest emergency department without waiting.

What is the final bridge made of?

Once fusion is complete — usually after 3–6 months — impressions are taken and the final bridge is made. There are two common options: acrylic or composite teeth on a titanium framework, and a zirconia bridge. The first is lighter and easier to repair, but it wears and picks up stains over the years. Zirconia is more durable and does not stain; if it breaks, however, it is difficult to repair. Our zirconia crowns page gives an idea of the material's properties.

The bridge usually carries 10–12 teeth. The second molars at the very back are often left off the bridge; this keeps the cantilever within a safe limit, and most patients notice no real shortfall when chewing.

The limits of four implants

A bridge on four implants has no spare. In long-term studies the great majority of implants stay in place; but if one of the four is lost, the bridge usually cannot be safely loaded on the remaining three, and a temporary solution is needed until a new implant is placed. Bone in the upper jaw is softer; if the bone allows it and your bite is strong, All-on-6 gives a wider safety margin. At our clinic in İzmir we go through the scan with you to work out which makes sense in your case.