VC Dental Blog

VC Dental Blog

Everything you need to know about dental crowns

Friday, March 11, 2016

What is a dental crown?

A dental crown is a custom-made, permanent restoration. They look like a hollow, tooth shaped “cap”, which is placed over a prepared natural tooth.
When cemented into place, crowns completely cover the entire visible portion of the tooth that lies at and above the gum line.

 


 

Crowns are also used in implant cases to replace missing teeth that have been lost due to disease, decay or an accident. A dental implant is an artificial root that is inserted into the jawbone to support and hold the crown in place, where there is no natural tooth or root structure to do so.


Why is a dental crown needed?

The main purpose of a crown is to restore strength, functionality, shape and size to a tooth, and to improve its appearance. Situations where a crown may be needed include:

  • To protect a tooth that has become weakened (for example by decay) or cracked, by holding it together and preventing it from breaking
  • To replace an old, broken or failing tooth filling
  • To restore a tooth that has already broken
  • To restore length on worn down teeth (for example from grinding)
  • To cover and support a tooth that has a large filling if there isn’t much natural tooth structure left
  • To make a cosmetic modification such as closing spaces between teeth, or reshaping or rotating teeth
  • Crowns are used to hold dental bridges in place
  • A crown is used to cover a dental implant
  • A crown is recommended to restore strength to any tooth that has undergone root canal therapy

A crown will not only enhance the appearance of the tooth, but will protect it from further wear and breakdown.

In the case of an entire missing tooth, gaps left in the mouth will eventually cause the surrounding teeth to shift or rotate into the empty space, causing malocclusion (‘bad bite’), which can have a negative impact on diet. It can also cause bone deterioration in the jaw and temporomandibular joint (TMJ) disorders. Therefore it is always advisable to discuss tooth replacement options with your dentist, such as an implant and crown, rather than leaving gaps in dentition.


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What types of crowns are available and what is the difference between them?

Permanent dental crowns can be made from: all metal, all ceramic, porcelain-fused-to-metal, stainless steel and all resin materials. I will go into further detail about these varieties below:

All-Metal Crowns

An all metal crown is referred to as an ITEM 618 (you will see this on treatment plans and invoicing from your dentist). The term “all-metal” crown literally means the entire crown is made out of metal.

Due to their 100% metal construction, these are the strongest types of crowns available (no matter which metal has been used to make them). Because they can be manufactured in a very thin layer without losing their solid and robust properties, metal crowns require the least tooth structure to be removed compared to other types of crowns, which preserves the core of the tooth for maximum strength and retention. They very rarely chip, fracture or break, and don’t wear down the teeth they bite against. Metal crowns provide a strong bond to the tooth, and withstand biting and chewing forces very well. Due to their single-component construction and the superior strength and durability characteristics they possess, they last the longest in terms of wear. They also have excellent biocompatibility properties. The drawback and disadvantage of these crowns is the metallic colour, which does not have the quality of a natural aesthetic appearance. However, they are a good choice for out-of-sight molars (the teeth at the back of your mouth), especially where space is minimal between teeth. They are also a good option if you have a severe habit of teeth grinding or jaw clenching.

Metal crowns aren’t made out of pure metals (not even gold), because none have the ideal physical properties required for dental applications. Instead, they are made using specific types of metal alloys. An alloy is basically a blend of materials. A dental alloy is created by mixing two or more pure metals (‘metallic elements’) together to create a ‘new’ metal. Alloys are useful because they combine the best characteristics of the elements used to make them, which creates a resulting metal that is more chemically stable and with superior properties than the pure elements could have alone. This means alloys can be specially engineered to possess the ideal physical qualities for specific purposes, such as in dentistry: greater strength, resistance to corrosion and wear, and the structure to be easily fabricated and adjusted by the lab technician and dentist.

In general, there are three basic categories of dental alloys that can be used to make crowns. They are: high noble alloys (precious metal), noble alloys (semiprecious metal) and non-noble or base alloys (nonprecious metal). The classification system is based on the metal’s composition:

High noble alloys (precious metal): >60%

Noble metals are resistant to corrosion and oxidation in moisture or air, are not easily attacked by acids, have high biocompatibility, and retain a shiny metallic surface when under heat treatment. The noble metals used in dentistry are gold and those from the platinum group, most commonly platinum (heavy category) and palladium (light category). Precious metals are defined as rare, naturally occurring and of high economic value. They are also extremely malleable (able to be bent without breaking) and ductile (able to be stretched). All the noble metals are also classified as ‘precious’ metals. Noble metals have the advantage that they are the easiest and most predictable to work with, ensuring the most accurate fit and bond.
High noble alloys have a composition that is over 60% noble metals (gold + platinum group), where at least 40% of that percentage must be gold. The rest of the alloy is made up of base metals (such as tin, copper and iron) which help form an oxide layer to provide a chemical bond to the tooth.

Noble alloys (semiprecious metal): ≥25%

Noble alloys are also called semiprecious as they have a lower proportion of precious (or ‘noble’) metals. They contain anywhere between 25% and 60% of any combination of noble metals (gold + metals from the platinum group) but unlike high noble alloys, there is no minimum gold content required.

Non-noble alloys (nonprecious metal): <25%

These are also referred to as base metal alloys. Base metals are more abundant in nature compared to precious/noble metals and are therefore cheaper. They are more reactive to atmosphere than noble metals and will oxidise, tarnish and corrode relatively easily when exposed to moisture, air or acidity. Examples of base metals include aluminium, copper, nickel and tin.
Base metals are more challenging for lab technicians and dentists to work with as they have a very high melting temperature, making soldering and casting difficult. They also exhibit shrinkage during casting which must be compensated for. An advantage of base metals is that they are much harder and stronger than noble metals, and exhibit twice the elasticity. Therefore alloys can be made into thinner crowns whilst still retaining the rigidity required for dental applications. However their hardness also makes them difficult to burnish and polish.
Non-noble alloys are made up of more than 75% base metals, and have a limited noble metal content (gold + platinum group metals) of less than 25%. Two common types are titanium alloys and alloys made from a mix of cobalt, nickel and chromium (which increases corrosion and tarnish resistance). Nickel free can be used if a patient has allergies.

 

All-Ceramic / All-Porcelain Crowns

An all ceramic crown is referred to as an ITEM 613 (you will see this on treatment plans and invoicing from your dentist). The term “all ceramic” crown literally means the entire crown is made out of a ceramic material.

All ceramic crowns are sometimes also called ‘all porcelain crowns’. To explain the terminology, “all ceramic” describes all the different types of ceramic crowns, whereas “all porcelain” describes some particular kinds of ceramic crowns that are made specifically out of porcelain (which is a type of ceramic material).

All ceramic dental crowns provide a natural appearance and colour match that is amazingly lifelike and unsurpassed by any other type of crown. The lustrous, glistening optical quality of a natural tooth is generated by the way light passes through the tooth and is then reflected out. The goal in the creation of a ceramic crown is to mimic the light handling characteristics, and therefore appearance, of a natural tooth. Generally speaking, the best way to achieve this effect is to use very translucent porcelain in a thick layer.

When it comes to aesthetics, there are two ways to create a full-ceramic crown:

1.   Dental laboratory produced crowns use different types of porcelains (each with different shades and translucencies) in multiple layers on different regions of the crown. This achieves the best colour match and optical quality when compared to natural teeth.

2.   ‘Monolithic’ (meaning solid) CAD/CAM (computer-aided design and manufactured) machine produced crowns. These are milled out of a single, uniform block of ceramic material. This results in a crown that has one standard shade and is therefore not as         translucent (but is still colour matched as closely as possible to the natural teeth). At VC Dental these are made on our CEREC machine in-house.

All ceramic crowns are the most natural looking option for front teeth. They are also a good choice for patients who have allergies to particular metals used in other types of crowns.

Some disadvantages of ceramic crowns are that they wear down opposing teeth more than metal and resin crowns do, but they are still less abrasive than porcelain-fused-to-metal crowns (which I will discuss later). They also require more tooth structure to be removed (than for example metal crowns) because of the thickness of porcelain required for sufficient crown strength (with the exception of Zirconia crowns which are explained below). The major risk with ceramic crowns is that they can fracture, which can lead to infection and failure if not treated appropriately by a dental surgeon.

Types of ceramic crowns:

There are many different types of ceramic crowns and brands of materials available. I will explain some of the main kinds below:

Feldspathic Porcelain Crowns:

Feldspathic porcelain is the traditional, standard porcelain material that has been used to create crowns for many years. It is a luminous material that offers a very natural and translucent appearance. These crowns are created by custom layering the porcelain and can either be bonded directly to the natural tooth surface (which transmits the underlying tooth colour through the porcelain), or layered over a pre-built core (for example from Zirconia – see point #2 below).

Zirconia Crowns:

Zirconia crowns are the hardest and strongest type of ceramic crown available. Zirconia is a type of crystal that is extremely durable and virtually indestructible, which is why these crowns are so long wearing and withstand biting and chewing forces exceptionally well. They are colour matched to the natural teeth, however are not as translucent and light-reflecting as other porcelain crowns due to the very opaque colour of the ceramic. Because Zirconia is such a hard material, it is impossible to "etch” the crowns before cementation (given a rough texture to enhance adhesion to the natural tooth, similar to roughing up a surface with sandpaper to help paint stick better) so they are bonded differently to other ceramic crown types. They can also be abrasive and there is greater risk of them wearing down the opposing teeth.
Zirconia can be used to make two different types of crowns:

1.   ‘Monolithic’ (solid) crowns made entirely of Zirconia, which are computer designed and milled from a single uniform block on a CAD/CAM machine. The advantage of these is that they are extremely hard and long lasting, and don’t require much tooth structure to be removed (compared to most ceramic crowns) as the material is very strong in thin sections. However, due to the dense singular material, it can be hard to get an excellent shade match and they have minimal light reflective properties.

2.   Zirconia core-only crowns. This is where Zirconia is only used to build the core (inside part) of the crown that sits over the natural tooth, and standard transparent porcelain is then layered over the top to create and build up the rest of the crown. These types of crowns are not as strong as full zirconia, but have translucent properties that more closely match a natural tooth. However, because the zirconia core is such a strong opaque colour they will never look as lifelike as porcelain crowns that are bonded directly onto a natural tooth core.

Aluminous Crowns – Procera, Empress and Emax:

Aluminous crowns get their name by being made predominantly from the porcelain material ‘alumina’. Unlike Zirconia, this material is more porous and can therefore be acid etched before cementation, which creates a chemical bond between the crown and tooth making the adhesion very strong. They are also the most aesthetic type of porcelain crowns available as they have excellent translucent light-reflective properties, which results in the closest match to natural teeth. Procera, Empress and Emax are three different kinds of aluminous crowns and I will discuss them each below:

Procera Crowns

Procera crowns are made through a two-layer system. Firstly, their aluminium oxide core is custom milled on a CAD/CAM (computer-aided design and manufacturing) machine. Then felspathic porcelain is stacked in a superficial outer later to give the crown more translucent, lifelike aesthetic properties. Procera crowns are exceptionally strong.

Empress Crowns

Empress is more like glass than porcelain. Unlike normal feldspathic porcelain which is baked, Empress crowns are cast and give a more precise fit. They are made through a two-layer system exclusively in a dental laboratory (instead of in a CAD/CAM machine like Procera). The inner core is made out of medium-strength pressed ceramic, and then a highly customisable, superficial glass is layered over the top.

Emax Crowns

Emax crowns are made out of a lithium discilicate glass ceramic that has exceptional strength, translucency and durability properties. They are very biocompatible in the mouth and have excellent long term wear characteristics similar to that of natural enamel (the outer layer of your teeth). They are strong enough to be made into very thin layers and still easily withstand biting and chewing forces. Emax crowns can be made either on a CAD/CAM machine or in a dental laboratory.

 

Porcelain-Fused-To-Metal Crowns

A porcelain-fused-to-metal crown is referred to as an ITEM 615 (you will see this on treatment plans and invoicing from your dentist).

Porcelain-fused-to-metal crowns are commonly abbreviated to either PFM or VMK crowns. VMK is an abbreviation of the German words ‘Vita Metal Keramik’ which is the process of firing the ceramic onto the metal base.

PFM crowns are made up of two components. Their core is made out of metal (metal alloys to be specific, which you can read more about under ‘all-metal crowns’ above). This is the inside part of the crown (also known as the ‘substructure’) which sits over and is cemented to the natural tooth. Porcelain (which is a type of ceramic) is then layered over and bonded to the metal base to give the crown its tooth-like shape and colour.

In a way a PFM crown gives the best of both worlds for strength and aesthetics, which means they are a suitable choice for either front or back teeth. Next to all-metal crowns, they are the second most long-wearing choice. The metal core is very hard and durable, and is able to be acid etched (unlike Zirconia cores, which you can read about above) for strong adhesion to the natural tooth. The porcelain that is layered on top to make up the visible portion of the crown creates a very attractive, lifelike result that is matched to the natural teeth colour. PFM crowns also have excellent biocompatibility properties.

Next to all-ceramic crowns, PFM crowns most closely resemble natural teeth. However there is still quite a difference in similarity, because in comparison to a full-ceramic crown, PFM crowns are almost non-transparent. The way all-ceramic crowns look so lifelike is by imitating the way light passes through and is reflected off a natural tooth, through the use of very translucent porcelain. Because the metal core of a PFM crown is so dark, it needs to be covered in very opaque porcelain as a mask so that none of the metal colour shows through. As a result, only a comparatively thin layer of translucent porcelain can be fit on the top, which reduces the ability to truly mimic the lustrous look of a natural tooth.

Some other disadvantages of PFM crowns are that over time, especially as the gums recede, the underlying metal can show through as a dark line. The type of porcelain used is also quite abrasive and can wear down opposing teeth. The major risk with PFM crowns is that the porcelain layer can fracture, which can lead to infection and failure if not treated appropriately by a dental surgeon.

 

Stainless Steel Crowns

A stainless steel crown is referred to as an ITEM 576 (you will see this on treatment plans and invoicing from your dentist).

For adult dentition, prefabricated stainless steel crowns are primarily used as a temporary measure, protecting the tooth or filling until the permanent crown has been manufactured. For more information on temporary crowns click here to jump to the section below.

However, stainless steel crowns are commonly used for primary (baby) teeth in children. The crown fits over a prepared primary tooth, covering it entirely and protecting it from further decay. When the primary tooth eventually falls out (when the permanent tooth is erupting), the crown naturally comes out with it. Stainless steel crowns are favourable in children’s dentistry as they require minimal dental visits to fit and cement, and are a more cost-effective option for a primary tooth that will eventually be lost anyway.

 

All-Resin Crowns

An all resin crown is referred to as an ITEM 611 (you will see this on treatment plans and invoicing from your dentist). The term “all resin” crown literally means the entire crown is made out of a resin material.

All resin crowns are also referred to as ‘composite resin’ crowns as they are made from composite resin material, which is a combination of plastic type materials that are colour matched to the natural teeth. Common resin varieties used in the creation of these crowns include: silicon dioxide resin, Polymethyl Methacrylate resin, or acrylic polymer resin (these are also referred to as ‘acrylic resin crowns’).

All resin crowns are primarily used as a temporary measure, protecting the tooth or filling until the permanent crown has been manufactured. They are a metal-free alternative to stainless steel temporary crowns and can therefore be mixed in a number of shades to match the natural teeth colour. Patients may find this a more aesthetically pleasing option. For more information on temporary crowns click here to jump to the section below.

The reason resin crowns are often only used as a temporary measure is because they wear down easily over time and do not withstand biting and chewing forces very well. They are also relatively vulnerable to fractures compared to other crown types, which does not make them a very appropriate permanent option. They also require a large part of the natural tooth structure to be removed if they are being placed as a permanent option, to give the crown as much strength as possible. However, they are relatively inexpensive compared to the other more durable crown types, and are quite easy-going on opposing teeth (they do not wear them down easily).

If they are to be used as crowns, they are most suitable for restoring the front teeth. They are also a good alternative to straight fillings as they can be wrapped around the entire tooth surface to give it more strength and durability.

 

Post and Core

In some instances, a core or a post-and-core may be required before a crown is cemented.

Successful placement of a dental crown depends on the amount of tooth structure that exists in the natural tooth to extend into its centre. A solid core provides adequate stability for the crown to ensure it can effectively resist all the forces that will be placed on it in future (such as biting and chewing). If very little natural tooth structure is available, there is risk that the crown will easily become loose and be dislodged.

Reasons why there may be diminished natural tooth structure left include: decay, fracture, the loss of a previous filling (where natural tooth was drilled away before placement) and if the tooth has already undergone root canal therapy.

The term ‘core placement’ refers to a procedure where missing natural tooth structure is replaced with a filling before cementation of the restoration (crown). By rebuilding the tooth with an artificial core (so it is closer to its original dimensions) and creating an optimal foundation, we can greatly increase the stability of the crown, therefore maximising the long-term prognosis for the new restoration.

A core filling can be made out of any type of permanent dental restorative material. Common options include amalgam (metal filling material), composite resin (a combination of plastic type materials that are colour matched to the natural teeth) or glass ionomer cement (another tooth coloured restorative material made predominantly from silicon).

If sufficient lower tooth structure remains to support it, a core filling is all that is needed to provide a suitable foundation for the crown. However, if there is not enough structure to secure it to, it will be a very weak bond and risk the filling fracturing off inside the crown. If this is the case, to combat the problem a metal ‘post’ is inserted into the root canal first to help anchor the core filling to the tooth. There are many different types of dental post systems available, including parallel sided, tapered, threaded and serrated which are made from metals such as titanium or stainless steel. Your dentist will select the most appropriate post variety for your individual case.

To reiterate, a core filling can be placed on its own if there is sufficient tooth structure to support it. If there isn’t and a dental post is required, it is always used in combination with a core filling (never on its own); this is called a post –and-core.

While a dental core can be created for any tooth, a post and core can only be used on a tooth that has had root canal treatment. This is because the post must extend deep into a hollow root canal of the tooth in order to get adequate grip to hold the core. Sometimes the tooth will have already undergone root canal therapy, in which case the post can be placed immediately. In other cases, the root canal treatment must be completed first. As a side note, a tooth has already undergone root canal therapy will always need a post inserted (never just a core) to provide sufficient stability for a crown.

There are two kinds of post-and-core varieties available. The first type is called the direct method. This is where prefabricated posts are used, which can be placed in one dental visit. The core filling will then be attached to the post. The other option is called the indirect method. This is where an impression of the root canal is taken and a custom made post and core is created in a dental laboratory. In this instance, the post and core will be made as one piece (so there is no need to attach core filling material to the post like in the direct method). An indirect post and core will require more dental visits, however they are generally stronger as there is no join between the materials.

The item numbers for these are as follows (you will see this on treatment plans and invoicing from your dentist):

ITEM 627 – Core (where just a core filling is required, without the use of a post)

A direct post and core (prefabricated post) has two separate parts and therefore two item numbers:
          ITEM 597 – Post
          ITEM 627 – Core

ITEM 625 – Indirect post and core (as these are made in a lab as one piece, there is only one item number)

Post and Core procedure animation:

 

 

Temporary Crowns

The kind of permanent crown you will have determines whether or not you need a temporary crown.

If you have a ‘monolithic’ (solid) ceramic crown, which is made on a CAD/CAM (computer-aided design and manufacturing) machine at your dental surgery, you will not need a temporary crown as these are created and cemented during one appointment.

If you have any other type of crown that is made in a dental laboratory, you will need a temporary crown. This is because firstly the tooth is prepared (ground down) and shaped to fit the crown, and impressions are taken and sent off to the dental laboratory. Then there is a delay while your permanent restoration is being manufactured before you receive it to be cemented. A temporary dental crown protects the tooth and gum, allows for continued chewing function and provides an aesthetic appearance during this waiting period.

Temporary crowns can either be made at your dental surgery, or ahead of time in a dental laboratory. They are usually made out of either stainless steel or acrylic resin (which is a metal free alternative that is matched to the natural teeth colour). These days most patients will choose resin as a more aesthetically pleasing option. Stainless steel temporary crowns are a good option for out-of-sight back teeth.

The temporary crown is attached to the prepared tooth with an adhesive called temporary cement. This is a special material designed provide a weak bond, so the temporary crown can be easily removed when your permanent crown arrives.

 

What is involved in the procedure?

Dental crown procedures will vary depending on your individual case, however I will provide a general overview of what to expect.

Before commencing any preparation work for your crown, the dentist will perform an initial examination of your tooth and overall mouth, which may include taking x-rays. If there is extensive decay found in the tooth, or a risk of infection is diagnosed, you may require a root canal treatment first. Alternatively, there may not be enough natural tooth structure left to securely hold the crown in place, and it could be decided that you need a core, or a post-and-core first (you can read more about this procedure above). If you require either of these procedures, you will be given a treatment plan and on-booked accordingly. However, if everything is examined to be satisfactory the appointment will proceed as planned. The procedure for your crown will vary depending on whether your crown is going to be made at your dental surgery or in a dental laboratory:


CAD/CAM CEREC single-appointment ceramic crowns:

If you are having a ‘monolithic’ (solid) ceramic crown, which are made on a CAD/CAM (computer-aided design and manufacturing) machine at your dental surgery, the procedure will be completed in one dental appointment. At VC Dental these crowns are made on our CEREC machine system, which consists of a blue camera, a 3D computer and a diamond milling machine.
Firstly the natural tooth and gum surrounding it will be numbed. Next any decay or old filling material is removed. Then the tooth is filed down along the chewing surface and sides to make room for the crown to fit on top. Reflective powder is then sprayed over the prepared tooth and neighbouring teeth. A small camera takes a 3D image.
The restoration is then digitally custom-designed by an experienced team member to match your natural dentition and bite (‘occlusion’). While you rest, the crown is manufactured using an in-house milling machine with diamond coated burs.
The fitting is confirmed, and the custom made crown is then cemented to the tooth using an advanced luting cement.

 


Dental Laboratory made crowns:

Generally, a laboratory-manufactured dental crown will require two appointments. The first appointment involves examining and preparing the tooth, making impressions and placing a temporary crown. Your impressions are then sent off to the dental laboratory. The second appointment is when the permanent crown is cemented (bonded to the tooth). I will go into more detail below:

Firstly, the natural tooth and gum surrounding it will be numbed. Then the tooth receiving the crown is filed down along the chewing surface and sides to make room for the crown to fit on top. The amount of filing required depends on the type of crown you are receiving. For example, all-metal crowns are the thinnest type available and therefore need the least amount of natural tooth structure to be removed, whereas PFM (porcelain-fused-to-metal) crowns are much thicker and require more filing of the tooth.

After reshaping the tooth, a putty-like material is used to make an impression for the crown to be moulded to. Impressions of the teeth above and below will also be taken to make sure the crown fits comfortably within your natural bite (‘occlusion’). If the crown you are receiving is ceramic, your dentist will then select the custom shade that most closely matches your natural teeth. If you are interested in teeth whitening, it is important to discuss this with your dentist and have this procedure completed first, as you are not able to change the colour of a crown (i.e. whiten it) once it is made. You will then be provided with a temporary crown (you can read more about these above) to wear until you come back for your second appointment. This will be bonded to your natural tooth with temporary cement which only provides a weak adhesion, allowing it to detach easily at your next appointment.

Your teeth impressions are then sent off to the dental laboratory where your crown will be custom manufactured.

At your second dental visit, the temporary crown will be removed and the colour and fit of your permanent crown will be checked. If everything is satisfactory, your tooth and gum will again be numbed before the new crown is permanently cemented in place.

Crown procedure animation:


 

Partial Crowns: Onlays

What happens when a tooth is too damaged to support just a filling, but is not damaged enough to warrant a full dental crown? Filing down the entire top of a tooth for a crown when it doesn’t need one removes more natural tooth structure than necessary. However, placing a large dental filling in a badly damaged tooth can weaken the remaining structure and leave it very susceptible to fractures, causing worse problems in the future. In cases such as this, a dental restoration called an ‘onlay’ is usually selected.

Onlys fall somewhere between a filling and a crown, and allow large cavities to be restored while keeping as much natural tooth structure as possible. An onlay is a custom-made restoration that only covers some of the cusps of the tooth, as opposed to a crown which covers all of them, which is why they are sometimes referred to as ‘partial crowns’. They can be made from metal, composite (resin) material or ceramic/porcelain (the latter two are matched to the natural tooth colour).

There are two kinds of onlays available depending on the method in which they are made. They are called Indirect and Direct onlays.

Indirect onlays are made in a dental laboratory and generally require two dental appointments. They are usually made out of porcelain. During the first appointment after the tooth is prepared, impressions are taken which are sent to the lab for the onlay to be custom designed from. You will receive a temporary filling to wear while your permanent onlay is being made. When you come back for your second appointment, the temporary is removed and the permanent restoration is cemented.

Direct onlays are made at your dental surgery which means the procedure is completed in just one appointment, with no need for impressions. These onlays are usually made from composite resin or ceramic. There are two ways this can be done. Traditionally the filling was moulded, hardened in an oven and then cemented to the tooth. These days we have high tech CAD/CAM (computer-aided design and manufacturing) machines which digitally create the restoration. At VC Dental we make these on our CEREC machine. After the tooth is prepared, photos are taken using a 3D camera. The onlay is then custom computer designed and milled in the surgery while you wait, before being cemented permanently onto the tooth.

You may also have heard of a restoration similar to an onlay, called an ‘inlay’. These are the same kind of restoration, but they cover different areas of the tooth. A dental inlay fills the space in the middle of the tooth between the cups, whereas an onlay covers the middle area and one or more outer chewing cusps. Because of the extensive coverage onlays provide, only they are referred to as ‘partial crowns’.



Onlay procedure animation:


 

In Conclusion

Dentistry has come a long way from the old days of plain metal crowns. While they still have many useful applications, these days we are able to offer a wide variety of options to suit your individual case. Whether you are after durability, strength or the most natural aesthetic appearance, we can custom manufacture a crown to fit seamlessly into your smile. Crowns offer incredible practicality in their use. One of their most important functions is allowing patients to repair, and therefore keep, their natural teeth. They can also create the most amazing cosmetic transformations. If you are interested in how a crown may be able to benefit your smile, contact us for a no-obligation consultation.

 

By Dr Lee Woodward.


VC Dental

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