A dental crown is a custom-made cap placed entirely over a damaged or weakened tooth. This restoration fully covers the visible portion of the tooth, resting at the gum line. Crowns restore the tooth’s shape, size, and strength, and improve its overall appearance. They also provide a protective barrier for teeth compromised by extensive decay, fracture, or large fillings.
The Necessity of Tooth Reduction
The short answer is yes; controlled removal of tooth structure is mandatory for a crown. This procedure, known as tooth preparation, creates adequate space for the restorative material. Without reduction, the crown would be excessively bulky, leading to an unnatural appearance and interfering with the patient’s bite alignment (occlusion).
The crown requires a specific minimum thickness to withstand chewing forces. If the underlying tooth is not reduced, the restoration would be ill-fitting, potentially causing discomfort or premature failure. Dentists aim to remove just enough material to accommodate the crown while preserving healthy tooth structure.
The Tooth Preparation Procedure
The preparation procedure begins with local anesthetic applied to the tooth and surrounding gum tissue for patient comfort. Once numb, the dentist uses specialized instruments, typically high-speed dental handpieces with diamond burs, to precisely reshape the tooth. These instruments allow for the controlled removal of the outer layer of enamel and sometimes the underlying dentin.
The amount of tooth structure removed usually ranges from 1 to 2 millimeters, depending on the crown material chosen. All-ceramic crowns often require a slightly greater reduction for sufficient strength and aesthetics. The goal is to sculpt the tooth into a specific tapered or conical shape, often called the core.
This core shape allows the final crown to slide over it smoothly and lock into place with maximum retention. The prepared tooth must have a defined margin, or shoulder, at the gum line. This margin provides a clean edge for the crown to seamlessly meet the natural tooth structure, ensuring the final restoration blends naturally.
What Happens Immediately After Tooth Reduction
Immediately after preparation, the dentist captures the exact dimensions of the newly shaped tooth. This is done by taking an impression, using either a putty-like material or a modern handheld digital scanner to create a precise three-dimensional model. These measurements, along with the patient’s bite record, are sent to a dental laboratory where the permanent crown is custom-fabricated.
While the patient awaits the final restoration, which typically takes a couple of weeks, a temporary crown is placed over the prepared tooth. This temporary restoration, often made of resin or acrylic, protects the exposed inner tooth structure from sensitivity and bacteria. It also acts as a placeholder, preventing surrounding teeth from shifting into the newly created space, which ensures the final crown fits correctly.