Dental crown, dental bridge. Structure
Fixed dental restorations include two classes of prosthetic constructions: dental crowns and dental bridges. Their main characteristic is they are permanently fixed on natural teeth, posts or dental implants and do not have to be removed for cleaning.
Dental crowns and dental bridges are closely linked. Basically, dental crowns are the building blocks of dental bridges. These crowns are permanently cemented on the abutment teeth to ensure proper support.
Over the years, many manufacturing materials have been suggested. They have constantly improved their qualities, leading to materials with excellent strength and aesthetics.
Mainly, the materials used for dental restorations must have two qualities :
- strength and durability
Unfortunately, up to this moment, a material that has at the same time both these qualities has not been discovered. However, there are materials that are very close to these goals :
Zirconium or zirconia is an extremely durable material that has a white color. Large dental restorations can be manufactured using zirconium, but because of its restricted range of shades, it cannot be used, alone, in areas where aesthetics is a very important factor.
Dental ceramics or porcelain is a tough and durable material with a rich range of shades. It has excellent aesthetic properties ; therefore, the smallest details on the surface of a tooth can be reproduced. However, it cannot support, alone, a large dental restoration.
For this reason, porcelain is usually fused on other materials (zirconium, metal alloys) that are able to provide proper support for the restoration. However, there are some special situations where it is possible to construct full porcelain restorations without a supporting frame.
Therefore, in most of the cases a fixed dental restoration is constructed with 2 different materials, one on top of the other.
Supporting frame (shell or core)
The framework gives strength and durability to the entire restoration and provides support for the aesthetic materials. The frame must perfectly fit on the prepared teeth. (more on that)
The frame can be constructed from various materials:
Metal alloys : gold, palladium, titanium, chromium-nickel, chromium-cobalt, other base metal alloys. The type of alloy will influence the final price of the restoration.
Zirconium : it is used only when porcelain reconstructions are designed. (more)
The aesthetic materials aim to restore physiognomy and aesthetics. They are placed over the supporting frame using various techniques.
Some of the materials are placed all around the supporting core so that no part of it remains visible. Other materials, because of the lower resistance, can only be placed in specially prepared areas inside the metal frame and never on the side where chewing forces directly act.
The most important aesthetic materials are :
Dental ceramics or porcelain : is the best aesthetic material available at the moment...more
Dental composite resins : are types of synthetic resins which are used as restorative materials...more
Acrylic base resins : are polymeric materials with low resistance and poor aesthetics. However, they are very cheap...more
metal acrylic restoration
dental composite restoration
Crowns and bridges without frame support
In some clinical situations, it is possible to construct dental crowns or small bridges without a supporting frame. To avoid unwanted accidents, these restorations should be carefully planned.
All porcelain restorations
Anterior dental crowns or small dental bridges may be manufactured entirely of porcelain. These prosthetic restorations have excellent aesthetic properties.
They are not indicated in the back part of the mouth cavity where chewing pressures are very high because there is a risk of porcelain fractures or chipping.
These restorations do not need any frame because they are designed for a limited period of time. Usually, they are made from acrylic or composite materials...more
Dental restorations without aesthetic materials
Such restoration may be indicated only in posterior (back) parts of the mouth where areas are less visible.
Full zirconium restorations
They have excellent strength and durability and a white color. They can be successfully constructed when aesthetics is not the primary factor. When aesthetics is important, a layer of aesthetic porcelain will be fused on top.
Full metal restorations
Full metal crowns and bridges have great resistance but aesthetics is extremely poor. They are indicated only in less visible areas of the mouth cavity. Full gold restorations are still widely used. Various metal alloys may be utilized (gold, titanium, other base metal alloys)...more
full zirconia crowns and bridges
full metal crown
In following chapters, we will provide detailed information about each of the materials with advantages and disadvantages. You will also see how dental crowns and bridges are manufactured at the dental laboratory.
Last review and update: November 2020