A porcelain bridge is a dental bridge that is completely made of porcelain, and has the advantage of giving the most natural appearance. Porcelain is an excellent material for simulating tooth substance, since it is both strong and has similar optical properties, so can be very aesthetically pleasing. Also, technological advances have produced ways of making better and stronger porcelain to enable the construction of crowns and bridges without the need for a strengthening metal sub-structure.
Porcelain’s colour and translucency closely matches that of natural tooth enamel, making it most suitable for restorations involving front teeth. Bridges made from porcelain alone give the best aesthetic result and avoid the problem sometimes seen with porcelain fused to metal alloy types. With porcelain fused to metal types of crowns and bridges there has to be an opaque layer put over the metal to block out its colour, and this makes it impossible to have a very translucent restoration that mimics the translucency of natural teeth. Thus these types of restorations can look rather dead when compared with the lifelike, vital appearance of all porcelain crowns and bridges. In addition the metal of some fused porcelain to metal restorations is difficult to cover totally at the margins leading to a dark line at the gum line which can spoil the appearance. Sometimes the dentist can overcome this by placing the restoration margin just beneath the gum line but any subsequent gum shrinkage can expose the margin to view.
Porcelain is a strong material but biting forces can be high and sometimes cause a piece of porcelain to chip off from a porcelain bridge. This means that careful case assessment is required before a dentist will prescribe an all-porcelain bridge. They are mainly used on front teeth where biting forces are judged to be lighter, and rarely used on back teeth, like molars, where forces are much higher.
There are a number of different porcelain systems available such as Procera, for example, which is a milled ceramic on the inside to form a core with more traditional type of porcelain baked onto the outside. This gives it exceptional strength over the usual kind of porcelain, although it may not be quite so translucent. Another strong type of porcelain is InCeram which has quite good aesthetic appearance. Where the highest possible strength is needed then these may be some of the best types to use.
Some of the all-ceramic systems that have an inner ceramic core with an outer layer of porcelain baked on are very strong but are thicker and therefore require more tooth reduction. Grinding away more of the tooth may not be desirable if it might compromise retention of the bridge where teeth are small in size, or there may be a danger of damage to the tooth pulp.
Conventionally crowns and bridges may be cemented with a type of adhesive such as phosphate or carboxylate cement which are yellowish in colour and can sometimes cause a slight line to be in evidence at the margins. This can be avoided by using resin luting cements which can also give superior retention by means of acid etched bonding.
Porcelain materials are hard and abrasion resistant but they can actually cause abrasion of natural tooth enamel where they come in contact with them, and this is another factor that may need to be taken into consideration when prescribing a bridge, especially if it is all-porcelain or porcelain bonded to metal alloy.
It is the dentist’s job to carry out a full assessment in every individual case and to design a bridge to meet all the aesthetic and functional requirements with minimal risk to the rest of the dentition, and often the choice for a fixed restoration of any size such as a bridge, will be between porcelain and porcelain fused to gold alloy. Where occlusal loads allow the all-porcelain bridge can give the best aesthetic result without a doubt.