Bonded bridge (Maryland bridge): who it suits, how it is done and its limits

What is a bonded bridge?

A bonded bridge replaces a missing tooth, most often an incisor, with an artificial tooth attached to one or two thin wings that are bonded to the inner surface of the neighbouring teeth. Unlike a conventional bridge, it does not require those teeth to be cut down for crowns: preparation is limited to the enamel, or not needed at all. It is a fixed, discreet and minimally invasive solution, suited to carefully selected cases.

It is also called a Maryland bridge, after the American university where the technique was developed, or a cantilever bridge when it is supported by a single tooth. Its retention relies entirely on adhesion, in other words on the quality of the bond between the wing material and the enamel.

For a general comparison of bridges and implants, see our article on implant or bridge. Here we focus on this particular variant, which many patients have never heard of even though it can be very useful.

From the metal Maryland bridge to the ceramic cantilever

The first bonded bridges had a metal framework with two wings, one on each neighbouring tooth. They made it possible to replace many incisors without damaging healthy teeth, but they had two drawbacks. The metal could make the edges of the teeth look grey through the enamel. More importantly, linking two teeth that each move slightly differently put strain on the bond: one wing could come loose without the patient noticing, plaque would then collect under the free wing, with a risk of decay.

Practice has moved towards the single-wing cantilever bridge: the artificial tooth is attached to just one wing, bonded to just one neighbouring tooth. This design removes the conflict between two abutments, and the clinical experience gathered over recent decades has led many teams to favour it for incisors.

The materials most used today:

• zirconia, very strong, which allows a thin wing but requires a specific bonding protocol;
• lithium disilicate, more translucent, which bonds very well but needs a fairly thick connector;
• metal, still useful in some cases, for instance when space is very limited.

The choice depends on the space available, the shade of your teeth and the way you bite. Our article on e.max or zirconia describes the properties of these two ceramics.

Typical indications for a bonded bridge

A bonded bridge has its place in specific situations:

• A missing incisor, upper or lower, especially an upper lateral incisor or a lower incisor: these narrow teeth often leave little room for an implant.
• Dental agenesis, meaning a tooth that never developed, which is common for upper lateral incisors. After orthodontic treatment has opened or kept the space, a bonded bridge is a well established option.
• A young patient whose jaws are still growing. An implant placed too early stays put while the neighbouring teeth keep moving slightly, which over the years can create a visible step. A bonded bridge makes it possible to wait until growth is complete, and can also remain as a long-term solution.
• A tooth lost through trauma, in a teenager or young adult.
• A patient who does not want or cannot have an implant, for health reasons, lack of bone or personal preference.

Because it leaves the neighbouring teeth almost untouched, it also keeps the door open to an implant later if circumstances change.

The conditions for it to stay in place

Modern bonding is very effective, but it is only reliable when certain conditions are met. The dentist checks in particular:

• a healthy supporting tooth, or one with only small restorations, with enough enamel to bond the wing. A tooth with large fillings or an existing crown is a poor candidate;
• a stable tooth, with no mobility caused by gum disease;
• the bite, that is, how the upper and lower teeth meet. If the lower incisors press hard against the back of the upper incisors, there may be no room for the wing, or the forces may dislodge it;
• no severe bruxism, because clenching or grinding puts the bond under heavy strain;
• a suitable space for the width of the tooth to be replaced, and healthy gum in the gap.

For molars, chewing forces are much greater: a bonded bridge is rarely the first choice there, and other options are usually discussed.

How is a bonded bridge made and fitted?

Treatment is usually short, and an injection is often unnecessary because preparation stays within the enamel. The usual steps:

• Examination and X-ray, to check the supporting tooth, its root and the gum.
• Minimal preparation: a slight reshaping of the enamel on the inner surface of the supporting tooth, sometimes with a small rest, to guide the position of the wing and give it enough thickness without an awkward bulge. In some cases, no preparation is needed.
• Impression, preferably digital with an intraoral scanner, and shade selection.
• Fabrication by the dental technician, with particular care for the shape of the artificial tooth and its base, which should sit harmoniously on the gum and remain easy to clean.
• Bonding: the tooth is isolated from saliva, often with a rubber dam, the surfaces are treated according to the material (gentle air abrasion and a primer for zirconia, etching and silane for lithium disilicate), then the bridge is bonded with an adhesive resin cement. Excess is removed and the bite is checked.

The rigour of this bonding protocol is decisive: it often makes the difference between a bonded bridge that stays in place and one that comes off.

Limits, debonding and care

A bonded bridge has limits that you should know about honestly before deciding:

• Debonding is the main risk. It usually follows a knock, biting into something hard or a bonding failure. With a cantilever, the tooth generally comes off in one piece, so you notice straight away. If the bridge and the supporting tooth are intact, it can often be rebonded.
• Fracture of the wing or connector, especially when thickness is limited. A fractured bridge usually has to be remade.
• A change in shade of the supporting tooth, for example when a metal wing shows through a thin tooth.
• The bone under the missing tooth is not stimulated and may continue to shrink slowly, as under any bridge.

If it comes off, keep the bridge in a small box, do not try to glue it back with a household adhesive, and call the practice. Day to day, it is cleaned like your natural teeth, passing floss or an interdental brush under the artificial tooth to remove plaque. Avoid biting directly into very hard foods with that tooth.

The assessment at German Dental Clinic in Agdal

Deciding whether a bonded bridge is right for you takes a careful examination: condition and shade of the neighbouring teeth, available space, bite, gums and sometimes the orthodontist's opinion in a young patient. At German Dental Clinic in Agdal, intraoral scanning and digital X-rays help prepare this decision, and the dentist also presents the alternatives, an implant or a conventional bridge, so you can compare clearly.

If you are missing an incisor, or your child has a congenitally missing tooth, and you live in Rabat, you can book an appointment to talk it through. Our dental bridge page also gives an overview of the different types of bridge.