Implant bridges: replacing several teeth in a row

The span is the whole design problem

A bridge on implants is an engineering question dressed up as a dental one. Two fixed points, a load across the middle, and a material that has to survive several hundred kilograms of biting force a day for fifteen years.

That is why the number of implants is not simply the number of teeth. Two implants at either end of a three-tooth gap carry the middle tooth between them without difficulty, in the same way a beam bridges two piers. Stretch it to four teeth and the forces on the metal and on the bone at each end rise sharply. Stretch it further and something eventually gives — usually the screw, occasionally the bone.

So the scan is not just checking whether there is bone for implants. It is checking whether there is bone in the right two places, far enough apart to be stable and close enough together that the span is sensible.

Where the teeth went matters

Two missing teeth in the lower back of the mouth and two missing upper front teeth are entirely different problems, and it is worth knowing which you have.

At the back, the bone is generally more generous in width but the nerve running through the lower jaw sets a ceiling on depth, and in the upper jaw the sinus sits directly above the molar roots and drops lower as the years pass. Those two structures are the reason a CBCT scan is not optional. A flat X-ray shows you a picture; it does not show you how much room you have.

At the front, the surgical part is often easier and the aesthetic part far harder. The gum line across two or three adjacent teeth has to look continuous, and the little triangles of gum between the teeth are the most difficult tissue in dentistry to recreate once lost. That is a case we plan slowly and where we are candid about what is achievable.

The alternative most people arrive holding

A great many patients come to us with a partial denture in a case in their pocket rather than in their mouth. It is worth understanding why they so often fail.

A partial rests on the gum and clips onto the remaining teeth. Those clasps pull on teeth that were not designed to be pulled on, which is why long-term partial wearers often lose the clasped teeth eventually. It moves when you eat, it traps food beneath it, and it does nothing at all to stop the bone in the gap from shrinking — in fact it accelerates it by pressing on the ridge.

None of which makes a partial the wrong answer for everybody. It is a quarter of the cost and available in a few weeks, and for someone who needs teeth before an event, or who is not well enough for elective surgery, it is a perfectly reasonable thing to have. But it should be chosen knowing what it is, and it is very often chosen because nobody explained the alternative.

What we will check before agreeing

Gum disease first. An implant placed into a mouth with active periodontal disease is an implant placed into a bacterial reservoir, and the failure rate reflects it. If your gums need treating, that happens before anything else and it is not a delaying tactic.

Then the bite. If you grind your teeth — and many people do without knowing — a bridge takes that force every night for years. It does not rule treatment out, but it changes the material we choose and it means you leave with a night guard.