A tooth consists of the clinical crown and the roots firmly gripping the alveolar bone invisible to the eyes. The crown either being incisor, canine or molar have the exact composition. The strongest layer is the outer most layer called the enamel, the layer underneath the enamel which gives it the color is dentine. The color of the tooth is dependant on the underlying dentine. People with slightly darker dentine have a darker shade of off white or yellow-colored teeth whereas, people with lighter colored dentine have lighter shade teeth. The cementum is usually found within the roots of the tooth and is most prominent at the apex of the roots. It is most important for binding the tooth to the alveolar bone and helping in reparative functions in case of root resorption. The core of the crown is composed of pulp which carries main nerves to the teeth. It is the pulp where the pain originates from. The pulp extends from the underneath of dentine till the apex of the root. Any part of the pulp being affected within this region of the tooth is of great concern.
There are certain reasons why pulp involvement takes place which will require pulpectomy and hence a crown fabrication. A pulpectomy is synonymous with Root Canal Treatment (RCT).
Few main reasons for pulp damage could be:
- Irreversible Pulpitis: Usually, poor oral hygiene is responsible for the caries occurrence. Long-lasting caries that have not been treated can reach the pulp and then results in pulp involvement. The pulp then becomes inflamed, inflammation of pulp is called pulpitis. Pulpitis pain is unbearable. Especially in case of irreversible pulpitis because it is a condition in which the pulp has been damaged to an extent that it is beyond repair. The patient is kept awake due to the excruciating pain at night time. There is a lingering pain that lasts for 10 minutes to a couple of hours to cold and hot or sometimes on bitting. The treatment for this tooth is RCT and crown placement.
- Enormous cavity close to pulp proximity: A tooth having a huge cavity that is very close to the pulp, makes the tooth structure weak because the bacteria release acids which destroy the bulk of the tooth. Due to which bitting on something hard could instigate a tooth crack that would propagate further leading to pulp exposure.
- Trauma: On another occasion, tripping down could chip off the upper incisor or incisors thus exposing the pulp. Usually seen in patients with Class 2 Div 1. A blow to the jaw could also lead to partial fracture of the posterior upper or lower molars, hence, exposing the pulp.
In such instances, Root Canal Treatment is required for the complete dissolution of the infection. The procedure of root canal treatment requires a lot of coronal tooth reduction to locate the orifice or the canals of the tooth. These canals are then obturated/cleaned and prepared by removing any remaining pulp or nonvital tissue to prevent any further infection in the future. All of this preparation and shaping the tooth causes extensive loss of natural tooth structure. In addition to the weakening of the tooth structure, there is a marked reduction in the stress-bearing capacity of the tooth. This means that to reproduce the natural tooth form and function while preventing any fracture of the tooth, a crown will have to be placed.
The main functions of placing a crown are:
- Reproducing the natural tooth form: there is none better replacement than a natural tooth itself, however, in these instances, when a tooth is root canal treated, the crown placement becomes essential. A crown that is compensating for the loss of tooth structure will replicate the original tooth, allowing healthy maintenance of the crown to root ratio. Reproducing a crown with similar tooth morphology as the original tooth also provides better occlusal adaptability.
- Reproducing the tooths function: a crown placement maintains the function of a tooth. For instance, after completing RCT, a filling is placed which replicates the anatomy of the tooth which is restored. This tooth still requires proper coverage to tolerate the masticatory forces, hence a crown must be placed. The crown shows impeccable strengths against the forces of mastication and allows ease of chewing without the risk of tooth fracture.
- Increases RCT success rate: The tooth without a crown is like an empty box, which can easily be damaged. As mentioned earlier, crown coverage prevents the fracturing or chipping of the treated tooth. Sometimes, the filling material can shrink due to polymerization shrinkage, which can then allow fluids to enter the pulp chamber and accumulate there. This may lead to RCT failure. A crown prevents such occurrence.
- In orthodontic correction: Before initiating an orthodontic tooth correction such as; placing brackets to correct a rotated molar, crown placement is important. Because the root canal treated tooth is not strong enough to bear the orthodontic forces required for tooth correction. This strength is provided mainly by placing a crown on the tooth if it has not already been placed. This way, the crown will maintain arch stability during the tooth correction process.
- Aesthetics: To several patients, aesthetics is a major concern, it’s the duty of a dentist to choose the right crown for these patients. For anterior teeth, such as incisors or canines, all-ceramic can or zirconia provides good aesthetic and strength. Furthermore, for posterior whether aesthetic is a concern or not, posterior zirconia can be placed.
A tooth that can be saved by root canal treatment and crown placement is perhaps the best option up to date. Instead of placing a bridge, or extracting and then replacing it with a partial denture or a dental implant.