A dental crown is a custom-made prosthetic designed to completely cover a damaged or weakened tooth, restoring its shape, size, strength, and appearance. When a crown falls off, the immediate concern is whether it can be reused. The answer is often yes, but successful reuse depends entirely on a professional assessment of both the crown’s integrity and the condition of the underlying tooth. The dentist’s examination determines if simple re-cementation is possible or if a new crown is required.
Evaluating the Potential for Reuse
The initial assessment focuses on the crown’s viability. For reuse, the crown must be structurally intact, meaning there are no fractures, cracks, or chips, especially along the margins. Damage to the crown’s edge compromises the seal, allowing bacteria to penetrate after re-cementation. The inner surface must also be cleanable, requiring meticulous removal of all traces of old cement for a successful bond.
The underlying tooth structure, known as the abutment, must also be able to securely retain the crown. The tooth preparation must still have sufficient height and proper taper to provide adequate retention and resistance against chewing forces. If the tooth has fractured or been reshaped since the crown was first placed, the fit may be compromised. A successful outcome requires the crown to seat perfectly back into its original position without any movement.
Conditions That Mandate Crown Replacement
Re-cementation is not possible if issues with the crown or tooth mandate replacement. The most common reason a crown falls off is recurrent decay on the tooth underneath, near the crown margin. If significant new decay is discovered, the existing crown must be discarded. This is because the tooth structure must be drilled away and rebuilt, which changes the shape of the abutment.
Structural failure, such as a major fracture in the porcelain or metal framework, also necessitates replacement. A weakened or perforated crown cannot provide necessary protection or withstand chewing forces. An ill-fitting margin, where the crown does not perfectly seal the tooth, is another reason for replacement. An imperfect seal allows saliva and bacteria to leak underneath, increasing the risk of recurrent decay.
Inadequate Tooth Preparation
Sometimes, the original failure was due to inadequate initial preparation, such as a tooth that was too short. If the underlying tooth structure is too short to provide adequate retention, re-cementing the old crown will lead to repeated dislodgement. In these cases, the professional must create a new crown designed to compensate for the compromised shape. Additional procedures, like a core buildup, may be required before a new, custom-fitted crown can be placed.
The Clinical Process of Re-Cementation
If the crown and the tooth pass the thorough examination, the clinical process of re-cementation begins with preparation. The dental professional carefully cleans the interior of the crown, removing all residue from the old cement using specialized tools or cleaning agents. Simultaneously, the underlying tooth is cleaned, often roughened slightly, and isolated to prevent contamination from saliva.
The next step is the application of the chosen dental cement, which may be a conventional luting cement or a resin-based adhesive. The cement type depends on the crown material, remaining tooth structure, and desired retention strength. Resin cements are often preferred for their high bond strength, while glass ionomer cements offer the benefit of fluoride release. The cement is applied inside the crown, which is then carefully placed onto the prepared tooth under steady pressure to ensure full seating.
After the crown is fully seated, any excess cement that has extruded from the margins must be meticulously removed before it fully sets. Hardened remnants can irritate the gum tissue and lead to inflammation. Finally, the dentist checks the occlusion, or the bite, to ensure the re-cemented crown does not interfere with the patient’s natural bite. This final adjustment prevents premature contact, which could place excessive force on the crown and increase the risk of future bond failure.