All-on-4 and All-on-6 both give you a fixed full-arch bridge, a complete row of teeth screwed onto implants. Six implants are usually preferred when there is enough bone and the bridge must carry strong chewing forces, especially in the upper jaw. Four can be enough when bone is limited or dense. An examination decides.
What All-on-4 and All-on-6 have in common
Both techniques replace all the teeth of one jaw with a single fixed bridge, which is screwed onto a small number of dental implants. An implant is a titanium post placed in the jawbone that acts as an artificial root. Unlike a denture, it stays in day and night; only the dentist removes it for maintenance.
The real difference is the number of implants and where they sit. In All-on-4, two implants are placed upright at the front and two at the back are tilted, so that they avoid the sinus or the nerve and use the bone that is already there. In All-on-6, six implants are spread along the arch, most of them more upright. For the full step-by-step procedure, see our guide to All-on-4 dental implants and a fixed full set of teeth. For the basics of a single implant, read our complete patient guide to dental implants.
Why the number of implants matters: load and bite force
Chewing forces pass through the bridge into the implants and the bone. With six implants, that force is shared between more supports, so each implant carries a smaller part of the load. With four, each implant works harder, which is fine when the bone and the plan are right.
The part of the bridge that extends beyond the last implant is called a cantilever: it is supported on one side only, like a small balcony. Long cantilevers put extra stress on the implants and the bridge. Because six implants can be placed further back, the cantilevers are usually shorter.
Bite force varies from person to person. Strong jaw muscles, clenching or grinding the teeth (bruxism), and a bridge that bites against natural teeth or another fixed bridge all increase the load. Dentists then often lean towards more implants.
Upper jaw versus lower jaw
- Upper jaw: the bone is usually softer and less dense, and the sinuses (air spaces above the back teeth) often limit the bone height at the back. Many dentists therefore prefer six implants, sometimes more, for a fixed upper bridge.
- Lower jaw: the bone at the front, between the two nerves that exit near the premolars, is usually dense and strong. Four well-placed implants in this area are often enough to support a full lower bridge.
When bone is missing, it can be rebuilt or the plan can be adapted to the bone that remains. Our article on bone grafting and sinus lift explains when rebuilding is needed. The tilted implants of All-on-4 are one way of avoiding a graft; six implants usually need more bone, which sometimes means grafting first.
Bridge design and materials
A fixed full-arch bridge usually carries around ten to twelve teeth. With six implants, the bridge can be longer at the back, which may give better chewing on the molars. It can sometimes be made in two or three sections, so that one area can be repaired without touching the rest.
Full-arch bridges are generally made either of resin teeth on a rigid metal framework, or of zirconia or ceramic materials, each with its own balance of strength, appearance and ease of repair. Design and material are chosen after the examination, according to your bite and the opposing teeth, and the underside is always shaped so you can clean beneath it.
Four or six: how the decision is made
When six (or more) implants are usually preferred
- for a fixed bridge in the upper jaw, where bone is softer;
- when there is enough bone, or it can be rebuilt, along the whole arch;
- for a strong bite, clenching or grinding;
- when a longer bridge with molars and short cantilevers is wanted;
- when a sectioned bridge is planned.
When four implants may be enough
- in the lower jaw, where the front bone is often dense;
- when the bone at the back is limited and you wish to avoid a graft;
- when general health makes a shorter surgery preferable;
- when the bite forces are moderate.
| Point | All-on-4 | All-on-6 |
|---|---|---|
| Number of implants | Four, the back two tilted | Six, mostly upright |
| Bone needed | Less; uses the front bone | More, along the whole arch |
| Need for grafting | Often avoided | Sometimes needed |
| Load per implant | Higher | Lower, spread out |
| Cantilevers at the back | Usually longer | Usually shorter |
| Typical use | Often the lower jaw | Often the upper jaw or a strong bite |
The process in brief, comfort and aftercare
The journey is similar for both options: a consultation with X-rays and usually a 3D scan, any extractions or gum treatment, placement of the implants under local anaesthesia, a healing period of several months while the bone bonds to the implants, and finally the definitive bridge. Six implants take a little longer to place than four, but recovery is similar for most people: a few days of soreness and swelling.
Whether a temporary fixed bridge can be attached soon after surgery depends on how stable the implants are when they are placed, so it can never be promised in advance. Afterwards, clean under the bridge every day with a water flosser or interdental brushes, attend regular check-ups, and wear a night guard if you grind your teeth.
What determines the cost
The cost of full-arch treatment depends on the number of implants, any extractions, bone grafting or sinus lift, the imaging needed, whether a temporary bridge is made, the implant system and the material of the final bridge. Six implants do not simply cost “two more”, because the bridge and preparatory work can differ too. Our article on what determines the price of dental implants in Lebanon explains these factors. A clear figure is only possible after an examination.
All-on-4 and All-on-6 at Ajam Dental Clinic in Tripoli
Ajam Dental Clinic offers both All-on-4 and All-on-6, a fixed full-arch bridge on four or six dental implants, as part of full mouth rehabilitation alongside crowns, bridges and dentures. Patients come to our clinic on Fouad Chehab Boulevard from across Tripoli — Abu Samra, Al-Qobbeh, El Mina, Al-Haddadine and the old souks — as well as from Akkar and the rest of North Lebanon.
At the consultation, the dentist examines your mouth, reviews your X-rays and explains honestly whether four or six implants suit you, or whether another option would serve you better. To book, contact us by WhatsApp or phone.
Frequently asked questions
If one implant fails, do I lose the whole bridge?
Not necessarily. Implant failure in a full-arch bridge is uncommon, and when it happens the situation is assessed case by case. With six implants, the remaining five may still be able to support the bridge for a while, which gives more time to plan a replacement implant. With four, each implant carries a larger share of the load, so losing one usually means the bridge must be adapted or a new implant placed before normal chewing can resume. Regular check-ups help detect problems early, while they are still simple to treat.
Can I have All-on-4 in the lower jaw and All-on-6 in the upper jaw?
Yes. Each jaw is planned on its own, according to the bone available, the anatomy and the forces it will receive. A common combination is four implants in the lower jaw, where the front bone is usually dense, and six in the upper jaw, where the bone is often softer. Some people need a fixed bridge in one jaw only and keep their natural teeth or a denture in the other. The dentist explains the reasoning for each jaw separately at the consultation, so you understand why a given number is suggested.
Can an All-on-4 be upgraded to six implants later?
In some cases, extra implants can be added later if there is enough bone in the right places. However, the existing bridge was designed for four supports, so adding implants usually means modifying or remaking the bridge. That is why it is better to discuss both options carefully before treatment, with good imaging, rather than planning to upgrade afterwards. If your situation is borderline, ask the dentist to explain what would change with four or with six, both now and in the long term.
Is surgery for six implants more painful than for four?
Both are done under local anaesthesia, so you should feel pressure and vibration rather than sharp pain during the procedure. Placing six implants usually takes somewhat longer, and if a bone graft is needed the treated area is larger. Afterwards, most people experience soreness and swelling for a few days, whichever option they have, and this is usually controlled with the painkillers the dentist recommends. Soft food, cold packs on the first day and good rest help. Tell the team if you are anxious so they can explain each step.
I grind my teeth at night. Does that change the choice?
It can. Grinding and clenching, called bruxism, put strong and repeated forces on the implants and the bridge, often while you sleep without noticing. In this situation, dentists often prefer more implants to spread the load, shorter cantilevers at the back and a bridge material suited to heavy forces. A night guard, a custom-made protective appliance worn while sleeping, is usually recommended after treatment. Mention grinding, jaw pain on waking or worn teeth at the consultation, because it is an important part of the plan.
Will a fixed bridge on implants feel different from a denture?
Yes, in most cases it feels much more like having your own teeth. The bridge does not move when you eat or speak, and an upper bridge does not cover the palate, so taste and temperature are often easier to feel than with a full upper denture. There is usually a short adaptation period of a few weeks, during which speech and chewing feel slightly unusual. Most people adapt well. The bridge still needs daily cleaning underneath and regular professional maintenance to stay healthy.
Have a question about your teeth?
Send a WhatsApp message to Dr. Abdel Rahman Ajam or Dr. Soumaya Ajam, or call the clinic to book a consultation.
This article provides general information for patients. It does not replace an examination by a dentist, who can advise you on your own situation.
