Inlays, onlays and crowns are all part of what dentists term “indirect restorations.” Veneers and bridges are also considered indirect restorations. Fillings are an example of “direct restorations.”
Crowns (sometimes called “caps”) cover the entire tooth, including the sides. Crowns are meant to function like natural teeth and are used to shape, size and strengthen natural teeth as well as enhance their appearance.
Dentists use crowns when a tooth has been weakened by decay, is cracked, severely worn, or missing altogether.
· Crowns can hold a bridge in place when they’re placed over the teeth next to the gap
· They give a new surface to misshapen and/or extremely discolored teeth
· When a tooth with a large filling has very little tooth remaining, crowns are used to cover and provide support to the remaining tooth
· A crown can be attached to a dental implant and used to fill the gap left by a missing tooth
Crowns can be made from:
· All porcelain (ceramic)
· Porcelain fused to metal
· Gold alloy
The material is chosen according to where in the mouth the crown will be placed and on the patient’s budget. Temporary crowns, made by the dentist in his or her office for the patient to use while waiting on the permanent crown to come back from the lab are generally made from acrylic or stainless steel.
Inlays & Onlays
These are both types of fillings, and are made from porcelain. Inlays are not as large as crowns or onlays, fitting snugly within a tooth’s contours (cusps). They are custom made and then affixed permanently into a prepared cavity with dental cement.
Onlays cover some, but not the entire, chewing surface of the tooth and do not cover the entire tooth like a crown.
Both inlays and onlays are stronger than standard fillings, because they are bonded (cemented) to the tooth. Amalgam fillings are not cemented to the tooth, but are packed into the cavity. Being made of metal, they contract and expand in response to substances put in the mouth. This puts destructive pressure on the tooth, weakening it. By contrast, inlays and onlays hold the tooth together, strengthening it and prolonging its life.
Custom Fits Mean at Least Two Visits
Inlays, onlays and crowns are all made from a mold that is sent to a dental laboratory where the actual items are created. They’re custom made and require at least two visits to the dentist’s office: once for the mold to be taken, and then again to have the item(s) fitted.
All Materials Have Pros & Cons
The materials used to create these indirect restorations have their advantages and their disadvantages. While an all-porcelain restoration offers beautifully natural features, porcelain can fracture (crack) and also cause wear against opposing teeth if its surface is allowed to roughen. Gold alloys are extremely strong and durable; however, the metallic appearance is far from the natural look most people desire.
Crowns, inlays and overlays vary in their uses, the materials from which they are made and in their pricing. Learning more about these differences can help you and your dentist decide which is best for you.