Dental Bridge – Adhesive Bridges

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Adhesive bridges make use of the strong bond that can be achieved by use of acid etching of tooth enamel followed by application of resin cements, and have the major advantage in that little or no tooth substance has to be sacrificed for such a bridge to be provided. This type of bridge is often referred to as a Maryland bridge after the university where it was developed.

A bridge consists of an artificial tooth that replaces a missing natural one, and is held in place and supported by one or more nearby teeth. In a traditional bridge this is achieved by constructing full crowns to fit over the supporting teeth, but in a Maryland the support is derived from wings made of a precious metal alloy that are bonded to adjacent teeth surfaces by means of a resin bonding technique. This means that the result will not be as inherently strong as a traditional fixed bridge, but, often it is strong enough, and is much easier to provide and avoids the loss of considerable tooth tissue. Your dentist will assess your bite to see if you are suitable for a Maryland bridge, depending on how much loading you are likely to put on it. Too much and the bond could be broken causing the bridge to fall off. For this reason Maryland bridges are usually suitable only in the anterior region of the mouth, perhaps extending as far as a premolar in some cases, but certainly not for molars in most.

In order to make an adhesive bridge your dentist assesses your teeth and decides on the design and where the metal alloy wing or wings are to be placed. Ideally they should cover the palatal or lingual aspect of at least two teeth in order to support one artificial tooth. The Maryland bridge is much easier to provide in the upper arch where there is room in the palate, and is not always tolerated so well by the tongue in the lower jaw.

There may need to be some slight preparation of tooth surfaces to help stabilize the bridge against vertical displacing forces where possible. The dentist then takes an impression of the teeth using a very accurate rubbery putty material and that is sent, along with other records and instructions to the dental laboratory for the bridge to be made.

The metal framework of a Maryland bridge is usually constructed in gold alloy and the wings shaped to give maximum extension over the palatal (back), surface of the adjacent teeth so that no metal shows. Often the fitting face of the metal wing or flange is specially treated by being etched with a fine reticular pattern to increase the surface area for bonding and is coated with a silane bond-enhancing coating just before fitting.

The fitting is done by first acid etching the enamel surfaces of adjacent teeth where the metal wings are to adhere. Then, after washing and drying, the framework is cemented on using a low-viscosity bonding resin cement which may be chemically or dual setting. It is essential that the bridge is held in place without movement until all the cement is set, so a dual-setting cement allows a light to be used to “tack” it in place until the complete chemical cure has taken place. Any surplus cement is removed and the bite checked and adjustments made as necessary.

The fitted bridge should look nice and be comfortable within a day or so, during which time you need to treat it carefully. After that it is simply a matter of common sense to avoid biting anything unduly hard and keeping the bridge clean as you would your own teeth. Typically such a bridge will last for several years without problems, and, even if it should be dislodged, can usually be re-bonded after careful laboratory cleaning.