Crowns are designed to restore the shape and colour of compromised teeth. If a tooth is heavily filled and prone to fracture a crown covers the tooth to restore its shape and function. They also help to prevent further fracture of the underlying tooth. Crowns require reshaping of the tooth so as to provide space for the crown. They are fabricated from a variety of materials including porcelain, metal or a combination of both porcelain and metal.
Veneers are a thin layer of either porcelain or resin bonded to the front surface of a tooth to improve their colour, shape and appearance. Porcelain is considered the most aesthetic and more durable material. The amount of tooth removal required for porcelain veneers is less than crowns. Bonding of veneers requires enamel and therefore heavily filled teeth or worn teeth are more ideally restored with crowns. Crowns are generally considered stronger than veneers. Veneers are a conservative option in cases where the teeth are not overly compromised.
A bridge allows missing teeth to be replaced by placing crowns on the adjacent teeth to the gap. The crowns are connected to the replacement tooth and hold it in place. Bridges are glued into place and are therefore not removable. Bridges are generally used to replace one to two teeth, although more teeth can be replaced in certain situations. If the adjacent teeth that are supporting the bridge are heavily filled and require crowns, a bridge is a reasonable alternative. However, if the adjacent teeth are in good order, then an implant supported crown would be the preferred option so as to avoid the need to place crowns on the adjacent teeth to the gap.
Resin Bonded Bridges (Maryland Bridges)
A Resin Bonded Bridge is a conservative type of bridge that requires minimal tooth preparation on the back surface of one of the adjacent teeth to the missing tooth. Small grooves are prepared onto the back surface of the adjacent tooth. The bridge has a metal wing that is bonded to the back of the adjacent tooth. This metal wing is attached to the replacement tooth. This type of bridge is not considered as strong as a conventional bridge, but is an ideal alternative to replace missing teeth with a fixed solution if implants need to be delayed.
Full or partial dentures can be used to replace multiple teeth. Dentures not only replace teeth but also provide lip support in cases where there has been increased bone loss often as a result of long term tooth loss. Implants can be used to create far more stable dentures by providing retentive anchors similar to press studs. These type of dentures are called overdentures. Full upper dentures generally require four upper implants to achieve adequate stability. Full lower dentures can be improved with as few as two implants although three to four implants is sometimes required. The advantage of overdentures is that they are relatively easy to clean and provide lip support.
Implants are titanium screws that are placed into the bone to act as a support for a crown, bridge or overdenture. Implants require adequate bone volume to be successful. Often implants can be placed at the same time as the extraction of the tooth, if there is adequate bone and tissue. This is often the case in the front part of the mouth. In the back part of the mouth implants cannot be placed immediately following extraction because of the lack of bone. Implant placement is often delayed for at least three months in the back part of the mouth to allow the bone to reform following extraction of a tooth.
Grafting is required when there is a lack of bone or tissue to create a favourable situation for implant placement. Grafting is sometimes done at the time of implant placement if the amount of grafting is minimal. If extensive grafting is required then it will require a separate procedure. A comprehensive assessment prior to surgery will be undertaken to determine the need for grafting.
The implant will take 6 to 12 weeks to integrate to the bone. A crown can then be attached. Multiple implants can be used to support bridges to replace several teeth. A complete upper or lower set of teeth can be attached to 4 to 6 implants. Whilst crowns on natural teeth are glued, implant crowns and bridges are in most cases screwed into place and designed to be able to be removed by a dentist or specialist prosthodontist. The ability to retrieve implant crowns and bridges allows for easier future maintenance.