| 韓国歯列矯正 |
| 韓国歯列矯正 |
Dental crowns are used to restore teeth when additional strength is needed, due to cracks or large broken down fillings. They can also be placed on a weak tooth as part of a root canal treatment.
Crowns come in various materials that have different properties. Some provide better cosmetic appearances, while others are stronger to withstand heavy forces.
Porcelain
Porcelain dental crowns sit over a damaged tooth and restore its appearance, strength, and health. They are often used to conceal cracked or broken teeth and discolored ones, but they can also be placed over a dental implant to replace a missing tooth.
Typically, porcelain is the material of choice for front teeth because it offers strength and beauty. Ceramic tooth crowns are stain-resistant, but they can chip or crack if the wear and tear on your smile is too great.
When it comes to porcelain crowns, there are several different types including traditional, empress, procera, lava, and zirconia. The most common is the traditional porcelain fused to metal crowns, which has a strong and durable supporting layer called the coping, and a lifelike top layer of porcelain that can fade with time.
Other porcelain crowns include the e max monolithic, which has the same strength as conventional porcelain fused to metal crowns and is translucent like natural teeth, and the lava crown, which has a glassy appearance. Zirconium crowns are gaining in popularity as they provide durability and a natural look with a tooth-like color, and do not create dark lines along the gum line as other porcelain crowns have done in the past.
The best option for replacing molars is a metal crown that is made of gold or base metal alloys and requires less of the original tooth structure to be removed to support it. These crowns are extremely durable and do not wear down the teeth on either side of them, so they can be a good solution for molars in the back of the mouth.
Zirconia
Zirconia dental crowns are a relatively new technology within the field. However, they are already being used for tens of millions of patients and have demonstrated excellent durability. They have superior strength and can withstand more biting and grinding forces than traditional porcelain or PFM crowns.
Additionally, these dental crowns can be fabricated and installed in the dentist’s office with same-day procedures. This saves both time and energy for the patient, while also ensuring that contacts and occlusion are accurate and stable. Zirconia is also an ideal material for CAD/CAM manufacturing. Zirconia is formed into void-free solid blocks that can be milled into precise shapes without the need for another material to create stability or rigidity.
Moreover, zirconia is very resistant to temperature changes. Traditional metal crowns expand and contract when exposed to hot or cold temperatures, which puts additional stress on natural teeth and can cause tooth sensitivity. Zirconia, on the other hand, is much more resistant to temperature changes and won’t crack or fracture over time.
Furthermore, zirconia is also very stain-resistant. It will not discolor or stain as easily as natural teeth, so it will stay bright and beautiful for the long-term. This can be an important factor in choosing a restoration that will last for the long-term, particularly for those who are concerned about how their restored smile will look over time.
Metal
Despite what you might have heard, crowns are not made out of pure metals, as these metals lack the ideal physical properties for crowns. Instead, a mixture of different types of metals is used to create dental alloys. These are blends that are able to provide the strength, durability, and appearance required.
Gold and base metal alloys are common choices for dental crowns as they are extremely strong, durable, and highly resistant to corrosion. They withstand biting and chewing forces very well, don’t wear down as quickly as porcelain crowns, and rarely break due to clenching and grinding. However, they have a metallic color and require a lot of healthy tooth structure to be removed during the preparation process.
Porcelain-fused-to-metal crowns are designed with porcelain covering all or most of the surface areas of the underlying metal framework. This provides a more natural appearance than all-metal or porcelain crowns, although the porcelain may still leave a thin dark line at the gum line.
Stainless steel crowns are often used for children as they don’t require multiple appointments and can be prefabricated to ensure they fit the child’s teeth properly. They are also very safe, cost-effective, and durable and can protect primary teeth until they fall out naturally to pave the way for permanent adult teeth. Resin crowns are made from a mixture of plastic type materials that are colour matched to the patient’s tooth and can be bonded directly onto the damaged tooth or constructed over a pre-built core of feldspathic porcelain (item 611 on treatment plans and invoicing from your dentist). These are less expensive than other types of crowns.
Ceramic
Ceramic crowns are the most lifelike and durable type of crown. They are made from a translucent porcelain that transmits the natural tooth colour to produce a more natural appearance. They look and feel very similar to your natural teeth, making them the preferred choice for front teeth (incisors and canines) and molars.
Ceramic can be used in a single layer or as the core of a multi-layered crown. We use Procera and Empress crowns, both of which are manufactured using a two-layer system. Firstly, an aluminium oxide core is custom milled on a CAD/CAM machine and then feldspathic porcelain is stacked into a superficial outer later for more translucent, lifelike aesthetics.
They are also extremely strong and can withstand biting and chewing forces. However, because of their opaque colour they can not be etched (given a rough texture to enhance the adhesion of cement) before being cemented like other crown types. This can result in a compromise in appearance if the cement line shows through.
The most popular and versatile material for a multi-layered ceramic crown is IPS e.max. This biocompatible lithium disilicate glass ceramic is optimized for translucency, strength and durability for full anatomical restorations. This makes it suitable for fabricating inlays, onlays, abutments, screw-retained implant crowns and veneers. It can be fabricated into a single-unit crown or as part of a bridge, and provides high durability and an exceptionally natural cosmetic result.