Crowns
Chipped or fractured teeth, broken down fillings or teeth that are malformed or discoloured are all conditions which can affect your smile. A crown is a cap that is used in order to help restore or hold together a tooth that has been chipped or damaged.
Crowns can also cover a large filling to help keep it in place, and they can protect a tooth recovering from root canal treatment. Multiple crowns are also used to hold a bridge in place. Their purpose is to restore each tooth to its normal shape and size, while both strengthening and improving its appearance.
A crown is recommended for a number of reasons:
- To restore fractured teeth
- To protect weak teeth from fracturing
- To repair a tooth when there is not enough original tooth remaining
- To conceal badly shaped or discoloured teeth
- To protect teeth from fracturing following root canal treatment
- To disguise extensive damage caused by decay
- To attach a bridge
- To cover a dental implant.
Natural looking porcelain attached to a durable metal shell is the most common construction used to create a crown because of its strength. However, a crown can also be made of gold alloys or non-precious alloys, ceramic, acrylic (plastic) or composite resin, or any combination of these.
Tooth location, the position of the gum tissue, the amount of tooth that shows in the smile, the colour and shade of the tooth, and the function of the tooth are all taken into consideration when choosing which material to use.
Having a crown fitted may require two or three dental visits. At the first appointment, the tooth to be crowned will be numbed and reduced in size to accommodate the crown, and then a mould of your tooth will be taken for the laboratory to use in the manufacture of the crown. A temporary crown will be placed over the tooth until the custom (final) crown is available.
Crowns are permanent fixtures, but they can occasionally come loose and need to be replaced. Caring for a crown requires proper dental and gum care as instructed by a dentist or hygienist.
Inlays/Onlays
When cavities become too large, an ordinary filling is not strong enough to cope with the normal biting forces. The dentist will need to have stronger fillings made in a laboratory. An inlay is used for this purpose and as the name suggests it fits inside the tooth. An onlay covers the top of the tooth and is used for worn teeth, or where the remaining tooth needs strengthening to prevent it breaking away. Sometimes a combination of both is used. They are either cemented or bonded to the natural tooth.
They can be made of gold, non-precious metals, porcelain or special plastics. The choice depends on the position in the mouth in which they are to be placed, the strength of the bite, whether the patient grinds their teeth, and to some extent the wish to have a tooth coloured filling.
There are two stages in fitting these devices: The first is the preparation of the cavity and the taking of an impression of the cavity and of the opposing teeth so the bite can be made correctly. A temporary filling is then fitted. The impression is sent to a laboratory and the filling is constructed. The second is the fitting. The tooth may need to be numbed to prevent discomfort during the fitting. There could also be a need for some minor adjustments to the bite but that is all.
As there are two stages and some quite complex laboratory work they are more expensive than ordinary fillings but less than crowns. They last between ten and 15 years, which is probably longer than ordinary fillings and about the same as crowns.
Bridges
A bridge is a device that is used as one of the ways of replacing a missing tooth. There are two types of bridge: a conventional bridge or an adhesive bridge.
Conventional bridge
A false tooth is attached to a crown on one or both sides of a gap. It involves quite extensive drilling of the tooth (or teeth) to which the false tooth will be attached. The crowns are either made of gold, a non-precious metal, or a combination of metal and porcelain. The false tooth is usually made out of tooth-coloured porcelain.
Once the teeth have been prepared, a mould (impression) of the affected teeth is made. This is sent to a laboratory for the bridge to be made; it usually takes two weeks. In the meantime, to prevent any sensitivity, a temporary bridge covers the drilled teeth.
Once it has been manufactured, the bridge will be tried in place. It may require some adjustments before it is cemented in permanently.
The advantages of a conventional bridge are that it is strong and not removable. The disadvantage is that it involves extensive drilling of the adjacent teeth.
Adhesive bridge
A false tooth is attached to a wing of metal and the wing is then glued to the adjacent tooth.
With this type of bridge there is no (or only a small amount of) drilling of the adjacent teeth. An injection is normally not required. Once the teeth have been prepared, a mould is made and sent to a laboratory which makes the bridge. The bridge usually takes two weeks to make. No temporary bridge is required.
When using an adhesive bridge to replace a front tooth, the metal wing is stuck on to the back of the adjacent tooth and so cannot be seen from the front. An adhesive bridge replacing a back tooth will have metal wings on one or both sides of the gap. These may be visible if the mouth is opened wide.
The adhesive bridge is stuck on with a very strong glue. The process requires that the teeth be dry whilst gluing.
The advantages of an adhesive bridge are that it is not removable and requires very little drilling of the adjacent teeth. The disadvantage is that it sometimes falls off (though it is easily stuck back on). An adhesive bridge might not be suitable for those who grind their teeth or who play contact sports.
A bridge is not always possible or suitable, for example if there are too many teeth missing or if the remaining teeth or gums are not healthy. In some instances, it may be best to leave a gap.
Alternative treatments to bridges include removable dentures (false teeth) or dental implants (screw-in teeth).
