Dental crowns are customised shells made from various dental materials to fit over cracked or broken teeth in order to rebuild them to its original form. In the past, metal or gold was often used but in today's age of social media, tooth-coloured materials such as porcelain or zirconia which are strong, yet aesthetic is the popular choice. They are also known as “caps” and besides protecting teeth that are weak, can also be used to change the shape, size and colour of teeth for cosmetic dental purposes.
What Is a Dental Crown Used For?
Dental crowns are used for both functional and aesthetic reasons, for example:
to build-up a chipped, cracked or worn tooth
to protect weak teeth (teeth with large fillings or after root canal treatment)
as part of support for a dental bridge to replace missing teeth
for cosmetic dental purposes, like covering misshapen or discoloured teeth
What are the Different Types of Dental Crowns?
A dental crown can be made from different materials depending on function and budget. Traditional crowns using metal alone, or in combination with porcelain (porcelain-fused-to-metal) generally cost less. While it is still commonly used, the trend is towards using tooth-coloured materials such as full-ceramic (porcelain) or zirconia that look more natural. In addition, through the use of 3D computer technology to design and make these new generation crowns, the waiting time is far less as they can now be made within a day or two, and in some cases within 3 hours.
Pros and Cons of metal and metal-bonded crowns
Metal crowns are strong and long-lasting but because of their colour, their use is usually restricted to the back teeth, and when the patient has very strong bite forces.
Porcelain-fused-to-metal crowns provide a fair colour-match as tooth-coloured porcelain is layered over metal and then fused together in a laboratory.
They have a proven track record and in general last for between 7-10 years. However, there is a tendency for some of the porcelain to chip off, or for the margin of the crown to stain over time. They are a suitable long-term moderately priced solution.
Pros and Cons of porcelain and zirconia crowns
All Porcelain crowns provide the most aesthetic and natural looking solution. Recent advances in technology have increased the strength of porcelain significantly and they can now be used even for back teeth. A popular option is E.max made of Lithium Disilicate by Ivoclar.
Zirconia crowns are an even stronger option and is suitable for patients who grind their teeth but is more opaque. The recent introduction of multi-layer Zirconia has made the cosmetics comparable to all-porcelain crowns. They are also used when the underlying tooth is very discoloured.
What are post crowns?
Post crowns utilise the root canal of a tooth to provide the necessary retention and stability needed for a crown. In a badly broken down root-treated tooth, a post made of carbon fibre, a strong lightweight material, can be inserted into the root canal to provide a scaffold for a resin core to be built around it so that a crown can attach onto it. Alternatively, a mould of the canal can be made and a specially casted metal post made to fit into the canal. In either case, the tooth is then rebuilt sufficiently to receive the final crown.
What is crown lengthening surgery
Teeth may sometimes be too short to retain a crown or extensively damaged to below the level of the gum. A surgical procedure will be required to extend the crown margin or expose the edge of the defect. The gums are first pushed back to expose the underlying bone. A clearance of 3 mm is required between the level of the bone and the margin of the crown and the dentist may need to gently remove some bone before suturing. This procedure is known as crown lengthening and is required to enable the new crown to achieve a proper marginal fit. After healing a crown can be made.
Facial Symmetry, Proportion and the Golden Ratio
Cosmetic surgeons and dentists use the same concepts as artists in determining what is a pleasing appearance. The face can be divided into three equal parts based on imaginary horizontal lines drawn through the forehead, the brow, the base of the nose, and the tip of the chin. As the resting position of the teeth determine the lower facial height, tooth wear will lead to the lower third of the face being shorter and out of proportion. This can be corrected by crowning the teeth to increase the height of teeth and at the same time increase the facial height to the desired dimensions.