A dental crown is protective restoration that is used to protect and enhance a tooth’s structural integrity and is done to cover a relatively large cavity in the tooth. They not only further the strength of a compromised surface of the tooth but also make them look aesthetically pleasing. The dental crown fully encloses the top portion of the tooth and is cemented in place just above the gum line.
A dental bridge is a prosthetic used to replace one or more missing teeth. It is essentially a set of 3 or more prosthetic denture and basically consists of an artificial tooth in the center that is attached to crowns on either side. Shaping of the adjacent tooth is necessary so that the supporting crowns of the bridge can be cemented on them and the missing tooth can be covered by the artificial tooth in the center.
Dental crowns are teeth prosthesis that are very important in various situations. Lets us take a brief look at when they are employed.
To replace missing teeth
Bridges are great for replacing missing teeth to give the person a normal look and function. When a patient is in need of a partial removable denture, the neighboring tooth will have to function as a support and in such cases a bridge may be employed.
After endodontic treatment:
Teeth that undergo root canal treatments have a access cavity carved at the surface in order to treat the roots. Such teeth need restorations like amalgam fillings or crowns. The teeth at the rear are subject to much greater force than those at front. The posterior teeth can be subject to upto 200lb of force and as such those teeth should always be capped with a crown following a root canal treatment.
In dental implants:
Dental implants are gaining increasing popularity in recent years and a dental crown is used as the surface prostheses that is placed to enclose the implant and provide strong teeth-like surface. A bridge or denture may also be employed to provide more teeth with minimum number of implants.
In cosmetic dentistry:
Porcelain crowns maybe chosen for patients who want to cover a chipped or fractured tooth. Although veneers are the standard choice for aesthetic improvements for chipped or slightly surface-decayed teeth, the dentist may choose a crown if the teeth is deemed weak or fractured.
Video showing Before/After Dental Crown
Also, if the patient is someone who is a habitual clencher and grinder, a veneer might not hold on and in such situations porcelain crowns may be suggested. In our opinion, dental crowns as a means to only serve as a cosmetic procedure shouldn’t be encouraged and wherever possible cost effective and less invasive cosmetic procedures like porcelain veneers and dental bonding should be considered. We recommend crowns only when apart from serving as a cosmetic enhancer there are underlying benefits for the health of the tooth.
Restoration with a dental crown is usually done with 2 appointments. During the first appointment, the dentist will shape the tooth to ready it for the crown and then take an impression which will serve as a measurement for the crown. The dentist will then place a temporary crown which will allow the patient to manage that tooth during the 2 weeks that it could take for the dental laboratory to custom-make the crown as per the impression. The crown will then be cemented in place during the 2nd visit.
Step 1 – Numbing the tooth:
Anesthetizing tooth and gum is important to mask sensitivity and pain. If the crown restoration is post root canal then the tooth may not need anesthetizing, but the surrounding gums still will need to be numbed up.
Step 2 – Tooth shaping:
A dental crown cannot be made too thin to accommodate a thick tooth surface. So shaping the tooth that is to be restored is important to allow for a crown with minimum thickness of 2mm to be then placed on the tooth without making the tooth seem oversized. During the trimming process the dentist will also drill down the infected and unstable tooth bits and account for the lost thickness with a thicker crown if necessary.
The trimming shouldn’t be random or blocky in shape. The shaped tooth should have a tapered surface which will allow for a good crown-fit. A tooth that has an adequately thick tapered end going into the crown on top will get a nice fit. Sometimes, the dentist may have to taper down a lot of tooth bits and might have to make up some thickness with filling material – this is not ideal but sometimes necessary.
Step 3 – Tooth Impression:
Tooth impression is then taken using a paste like material. From this a plaster cast is made at the dental laboratory which would serve as an accurate measurement of the shaped tooth. Using this as a measurement, the crown is fabricated. Alternatively, a CAD/CAM machine may also be used to take optical imagery of the tooth and then use that as a reference to drill down a crown from a block of ceramic. This method can only be used to fabricate an all-ceramic crown. The impression-phase is important as this is what will determine the crown size that is accurate enough to fit well – A well measured and fabricated dental crown should neither be too thin which could leave spaces between the neighboring teeth thus causing possible long-term structural instabilities, nor should it be too thick so as to jut out.
Step 4 – Temporary crown:
The crown fabrication might take around 2 weeks and during this time the dentist will choose to fit you with a temporary crown made of metal or plastic and cemented with temporary cement which will facilitate reasonable strength but also easy removal when the permanent crown becomes available.
Step 5 – Placing the dental crown:
Before the crown is p-laced the dentist will place the crown on the shaped tooth and check for any imperfections and will make adjustments on the crown as necessary. The patient will also be asked to bite down on the crown after it is loosely held in place – if the feel is right, then the crown will be cemented on the tooth, else it will go through some more adjustments. The crown is cemented using a dental cement compound and is placed inside the crown before seating it on the shaped tooth. The crown will adhere to the tooth within a few minutes after which the dentist will scrape away the excess cement that could seep out.
Metal crowns are entirely fabricated using metal and gold crowns are a popular choice. A gold crown is one that is made from alloys of gold. The alloys of gold are easily mouldable and can be worked to accurately take the shape of the desired tooth. Strength and durability are the hallmarks of metal crowns and they almost never chip or break. They have some characteristics of tooth’s enamel which means they don’t exert unnatural forces on the other teeth, thus making them good materials for crowns. Their only problem is that they don’t look natural with their shiny metallic look. So perhaps the only place where they are considered is the bottom molars.
All ceramic porcelain crowns are translucent and provide a very natural lifelike appearance and have been used by dentists since many years. There is no question about their aesthetics, but they are not as durable as all-metallic crowns. The porcelain crowns can be manufactured very well in under an hour these days with milling machines, thereby allowing the dentists to fit them with single sitting – but, crowns manufactured this way are not as aesthetic as hand-made porcelain crowns that incorporates layers of translucent ceramic.
Metallic porcelain crowns:
Porcelain fused to metal dental crowns incorporates the best of both metal and porcelain. It is made by first fabricating a metal crown to which porcelain layer is fused in a high-temperature oven. They offer a middle path – they are stronger than all porcelain crowns but not as strong as all-metallic crowns as they have a more brittle outer porcelain that is susceptible. Also sometimes, with time the metal ridges can show up as dark lines on the edges and a good crown will attempt to hide these susceptible areas just under the gum-line. A little bit of wear and tear can always be polished though.