A resin-retained bridge (also known as resin-bonded-bridge or resin-bonded fixed dental prosthesis (RBFDP)) is a

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...

(a fixed dental prosthesis) replacing a missing

tooth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

that relies for its retention on a composite resin cement. It is one of many available

dental restoration Dental restoration, dental fillings, or simply fillings are treatments used to restore the function, integrity, and morphology of missing tooth structure resulting from caries or external trauma as well as to the replacement of such structure sup ...

methods which is considered minimally invasive and conservative of tooth tissue. The resin-retained-bridge has gone through a number of iterations. Perhaps the best known is the

Maryland bridge The Maryland Bridge is a bridge that crosses over the Assiniboine River in Winnipeg, Manitoba. It serves as a major transportation route for Winnipeg. The bridge connects Academy Road with Maryland Street and Sherbrook Street. The current struc ...

and other designs used in the past include the Rochette bridge. The five-year survival rate is around 83.6% and the ten-year rate at 64.9%. The case selection is important and as with any dental prosthesis, good

oral hygiene Oral hygiene is the practice of keeping one's mouth clean and free of disease and other problems (e.g. bad breath) by regular brushing of the teeth (dental hygiene) and cleaning between the teeth. It is important that oral hygiene be carried out ...

is paramount for success. In recent years, the indications for the use of resin-retained-bridges have diminished significantly and there have been changes in the principles underpinning their design. Resin-retained-bridges should be considered when a fixed prosthesis retained by natural teeth is required. The use has been driven by the advent of evidence-based dentistry showing the benefits to patients of reduced tooth preparation and the importance of an intact enamel structure for the long-term health of the teeth. The bridge is currently in favour in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

for these reasons. Indeed, recent contemporary research shows resin retained bridges have better success rates than implants and are a cheaper alternative.

Types of material used for resin-retained-bridges

Traditionally resin-bonded-bridges were composed of ceramic bonded to a substructure made of non-precious metal. In recent years fibre-reinforced and high strength all-ceramic resin-retained-bridges have become popular.

Metal framed

Conventionally made a substructure that is a non-perforated and sandblasted non-precious metal that is cemented with a chemically active resin cement. A disadvantage to this type of bridge is the appearance of the abutment tooth which can appear grey due to the decreased

translucency In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions ...

. The metal substructure can also be visible and will not suit every aesthetic need.

Fibre-reinforced composite

Bridges made from fibre-reinforced composite are considered to have better aesthetics and adhesion of luting agent to the framework as well as lower costs. Composite is usually fibre-reinforced with

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...

, ultra-high molecular

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including b ...

Kevlar Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...

fibres. Areas predicted to have high stress, benefit from having fibres in one direction (unidirectional) which can improve the mechanical properties. These bridges can be fabricated in the mouth during a single visit or indirectly in a dental laboratory. Fracturing and wear of the composite can sometimes be seen.

All-ceramic

Previously glass-infiltrated aluminium oxide ceramic frameworks have been used. More recently, yttrium tetragonal zirconia polycrystal-based materials such as Lava (3M ESPE) and Cercon (Degudent) have come into use. These frameworks can be designed by wax-ups or using CAD-CAM. The main advantage of this type of bridge is the aesthetics as well as good biocompatibility and lower levels of plaque accumulation. Connector dimensions however are greater than those needed for in the other types of resin-retained-bridges.

Types of designs used for resin-retained-bridges

Resin-retained bridges have a variety of designs:

Fixed-fixed

In this design the connectors are rigid and there are one or more abutments at each end of the span; allowing load to be distributed more equally on abutment teeth.

Fixed-movable

This design includes one movable connector, allowing differential movement between abutments.

Cantilevers

This design is simple without the requirement of linking abutments at each end of the bridge span. However, it is the most mechanically unsound out of all the designs as the load is transmitted to one abutment.

Complex or Hybrid

Complex bridge is the traditional term to describe fixed prosthesis with different types of bridge making up the overall prosthesis. More modernly, the term hybrid has been used as it permits the inclusion of fixed prosthesis using a variety of both designs and retainers.

Principles of design for resin-retained-bridges

A resin-retained bridge requires a very specific set of design principles. The following should be followed when designing the bridge: * Design should be kept as simple as possible * Should cover as much of the abutment tooth or teeth as possible * Be rigid * Permit the control of the occlusal contacts

Components

Framework

A resin-bonded bridge consists of a

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metal framework that is cemented with resin composite to an abutment(s) which has preparation(s) confined either entirely or almost entirely to enamel.A. Damien Walmsley, Trevor F.Walsh, Phillip J. Lumley, F.J Trevor Burke, Adrian C. Shortall, Richard Hayes-hall, Iain A. Pretty. ''Restorative Dentistry'' second edition, Churchill Livingstone, 2007

Wing or retainer

The wing or retainer must be rigid and is usually fabricated from a

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...

. The inner surface must fit closely to the

abutment An abutment is the substructure at the ends of a bridge span or dam supporting its superstructure. Single-span bridges have abutments at each end which provide vertical and lateral support for the span, as well as acting as retaining walls ...

tooth. The intaglio is treated in some way to enhance the micromechanical

adhesion Adhesion is the tendency of dissimilar particles or surfaces to cling to one another ( cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can b ...

between the prosthesis and the composite resin cement. In the past various methods have been used, ranging from metal-weave patterns to tin plating. The modern resin-retained bridge retaining wing is usually

sandblasted Sandblasting, sometimes known as abrasive blasting, is the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface or remove su ...

with an alumina powder. The metal wing needs to engage as much of the sound enamel. In the majority of cases the metal wing is taken to the incisal edge of anterior teeth and overlapping of the occlusal (biting) surface of the teeth for posterior teeth.

Pontic

The

pontic Pontic, from the Greek ''pontos'' (, ), or "sea", may refer to: The Black Sea Places * The Pontic colonies, on its northern shores * Pontus (region), a region on its southern shores * The Pontic–Caspian steppe, steppelands stretching from no ...

is usually made from dental porcelain. The whole restoration is thus a porcelain fused to metal restoration.

Cementation

Current cement brands commonly used for this procedure include Panavia and Nexus. The use of Panavia is shown to have a higher survival rate compared to other luting cements. All are either autocure or dual-cure luting cements to ensure complete polymerisation of the resin under the wing. Great care must be taken during cementation to avoid contamination of the operative field as this will lower the bond strength of the cement and lead to premature failure. For this reason rubber dam is often advocated for placement, though this can bring its own difficulties. In the majority of cases, with good four handed dentistry, rubber dam is not required and does not improve success.

Complications

One major advantage of the resin-retained bridge over a conventional bridge is the failure mode is likely to be debonding of the retainer. In conventional

bridges A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...

, the failure mode is likely to be complete fracture of the abutment tooth with difficult-to-manage sequelae, possibly requiring

root canal treatment Root canal treatment (also known as endodontic therapy, endodontic treatment, or root canal therapy) is a treatment sequence for the infected pulp of a tooth which is intended to result in the elimination of infection and the protection o ...

. With a resin-retained bridge the prosthesis can usually be cleaned off and rebonded in position with minimal inconvenience to the patient. There are a number of complications from resin-retained-bridges, the most common being debonding and porcelain fracture. * Debonding * Porcelain fracture * Caries * Framework fracture * Root resorption * Retained cusp fracture * Loss of abutment due to periodontitis * Minor rotation

References

{{Prosthodontology Prosthodontology Restorative dentistry