Indications and Contraindications of a Dental Crown

Crown and bridges are being served to dental patients routinely as its manufacturing has become fast, readily available. It is a dependable option. 

Although, the crown & bridge is generally considered very safe and it is associated with a low incidence of complications, there are some precautions that need to be considered. 

Indications of a Dental Crown

1. Damage of crown beyond repair
2. Large filling needing replacement
3. Fractured tooth
4. Esthetic enhancement
5. Dental implant coverage
6. To fix dental bridges or dentures
7. Erosion of teeth

1. Damage beyond repair: Cases where the tooth has been damaged beyond repair: If the patient has a large cavity that cannot be fixed with a filling, but the dentist determines that the dentine and pulp are in good condition then he will recommend that a crown be placed to save the tooth.

2. Large fillings need replacing: Fillings need replacing every so often, your dentist may recommend installing a crown instead of re-filling the tooth, the reasons for this are the crown is a long term solution and it is aesthetically more pleasing.

3. Fractured tooth: In the case that a tooth gets fractured due to a dental trauma or progressive tooth decay, it is highly recommended that a procedure known as post and core be performed. The post and core procedure simply put, is the placement of an implant without extracting the root. In this procedure a small rod is inserted into the root of the affected tooth, this rod will slightly protrude and the core or crown will be attached to it. For this procedure, the tooth in question will require a root canal before the post and core can be done.

4. Esthetic enhancement: For patients who have discoloured or uneven teeth, or even for those who have large fillings the use of crowns can greatly improve the esthetic of their smile.

5. To cover dental implants: When a patient has lost a tooth for any reason, and an implant is required to maintain proper function, the implant will be covered by a porcelain crown that has been made to match your existing teeth.

6. To affix dental bridges or dentures: A dental bridge is a prosthetic used to replace missing teeth, these bridges are permanently adjoined to either dental implants or crowned teeth. The dental crowns are used to hold the prosthetic in place.

7. Dental erosion: The tooth enamel can be dissolved by the acidity in foods; when the enamel has been compromised, porcelain crowns are the ideal solution to prevent the progression of tooth decay to the dentine and pulp. Other forms of erosion include tooth abrasion which occurs from improper uses of toothbrushes, brushing too hard, improper flossing or biting on hard foods. And it also includes conditions where natural tooth to tooth friction happens, as in the case of involuntary grinding known as bruxism.

Contraindications

1. Where anaesthesia is contraindicated
2. Where filling can solve the problem
3. Insufficient tooth material
4. Chances of nerve damage
5. Bite misalignment
6. Allergy

As with any medical procedure, it is possible that complications can arise. Among the risk factors and contraindications of dental crown procedures, we can list the following:

1. Contraindication of anaesthesia: Illnesses where the use of anaesthesia is contraindicated. These may include severe heart disease, recent strokes and allergic reactions to anaesthesia.

2. The use of crowns is not indicated in cases where the problem can be solved with a filling.

3. Insufficient tooth material: There is a risk that during the preparation phase, the tooth’s surface can become too thin or be perforated by an instrument.

4. Nerve damage: During the preparation procedure, nerve damage can occur, if this should happen, it will be necessary to perform a root canal.

5. Bite misalignment, although in most cases dental crowns can correct TMJ (temporomandibular joint), if the crown is incorrectly placed, it can exacerbate the problem in some patients. Once the dental crown is in place, your dentist should check the fit taking into account the surrounding teeth as well as the whole bite.

6. Allergic reactions to one or more of the materials. Dental crowns can be made from a variety of materials, choosing the right material will minimize the chances of an allergic reaction.

7. Infections, if the dental crown is not properly sealed or if the damaged tissue was not properly removed, the area might become infected.

 

 

Crown and Bridge

Introduction

A crown is provided to protect the weakened natural tooth, regain its shape, maintain or enhance the esthetics and regain the functional ability of a person. A bridge is a prosthesis that is constructed to replace the one or more missing teeth and is supported by the neighbouring teeth.

A posterior tooth prepared for full crown (pink area)
B-Buccal aspect, L-Lingual aspect

They can be constructed in variety of the materials as follows:

1. All Metal
2. Porcelain fused to metal
3. All ceramic material
4. Pressed ceramic
5. All acrylic

There are various types of crown based on the surfaces they cover.

1. Full coverage crown
2. 3/4 crown
3. 4/5 crown
4. Inlay
5. Onlay

All metal includes precious metals like gold alloys, semi-precious that contains lesser amount of gold and non-precious alloys that are basically chrome- cobalt or nickel- chrome alloys.

Porcelain fused to metal crowns and bridges are made in any one of the above mentioned alloys. This metal crown, in the later phase of construction, is sintered with ceramic powders and chemo-mechanically fuses with metals in ceramic furnace.

“All ceramic” crown is made in Ceramic only. Aesthetically they are the best. Their con is that they are not as strong as metal ceramic or pressed ceramic.

A variety of factors have to be considered for the construction of a bridge.

1. Span of the edentulous area
2. Type of the teeth being replaced
3. Quality of supporting teeth
4. Conditions of the teeth in the opposing arch
5. Age of the patient
6. Patients’ ability to bear the treatment cost

Span of the edentulous area means how many teeth have to be replaced by bridge. The more number of teeth to be replaced, the longer will be the bridge; that in turn, will cause more stress in the bridge itself as well as onto the supporting teeth known as abutments. More stressed bridge will get more fractured ceramic from the metal part.

Type of the teeth decides as to how much masticatory load will have to be borne by the abutments. In case of the lateral incisor pontic, supported by one central incision and one canine, the masticatory load over abutments will be minimum. As we move from the Canines through Premolars to Molars, the quantity of masticatory load increases. Accordingly, we need to increase the number of abutments.

Quality of supporting teeth means how healthy the attachment apparatus of the supporting teeth is present. The healthier the apparatus, the better will be the masticatory load bearing ability of the abutments. It will result in a relatively longer life span of the bridge with minimum number of abutments. If the available healthy root surface area of the abutments will be less than the root surface area of the tooth or teeth being replaced, then more number of teeth should be used as abutment to prevent the overloading of any particular abutment tooth and ultimately bridge failure.

Conditions of the teeth present in the opposite dental arch includes the considerations of occlusal surface of the tooth and whether it is extruded. Is it causing mandible deviation during chewing?

Age wise a very young patient cannot be given crown and bridge as their pulp chambers are usually large and the trauma caused by heat during crown preparation or acids of luring agents may render the pulp tissue dead. This may lead to pulpal or periapical pathology ultimately leading to the failure of the bridge.

Preparation features for anterior crowns [1]

Treatment cost of the PFM bridges are very high. Therefore, the patient must understand the importance of the maintenance of the oral hygiene for the longer life of the prosthesis. The patient should be able to bear the cost of this treatment, otherwise a less expensive treatment needing easy maintenance should be chosen.

Preparation features of the posterior crowns [1]

Further Reading: Read BDJ article by clicking at the link

1. Crowns and other extra-coronal restorations: Preparations for full veneer crowns