Dental crowns are custom-made caps designed to fit over a damaged or weakened tooth, restoring its shape, size, strength, and appearance. They serve multiple purposes, such as protecting a cracked or severely decayed tooth from further damage, covering a tooth after a root canal, or supporting a dental bridge. Crowns are crafted from various materials, including porcelain, ceramic, metal alloys, or a combination, and are fabricated to match the natural teeth, enhancing both function and aesthetics.
What is Crown Cementation?
Crown cementation is the process of securely bonding a dental crown to the prepared natural tooth structure using a specialized dental adhesive. This step is fundamental, ensuring the crown remains firmly in place for long-term function and stability. The cement seals any minute gaps between the crown and the tooth, which helps prevent bacteria from entering and causing further decay underneath the restoration.
A strong bond created by cementation is also important for evenly distributing chewing forces across the tooth surface, thereby reducing stress on both the crown and the underlying tooth. Without proper cementation, a crown could become loose, dislodged, or fail prematurely, leading to discomfort, pain, and potentially requiring additional dental interventions. This creates a durable, semi-permanent attachment that withstands daily biting and chewing.
Common Dental Cements
Different dental cements are used for crown cementation, each with unique properties suitable for specific clinical situations and crown materials. Resin cements, including self-adhesive resin cements, offer high bond strength and excellent aesthetic qualities, making them a preferred choice for tooth-colored restorations like ceramic and zirconia crowns. These cements often simplify the procedure by combining etching and bonding steps.
Glass ionomer cements (GICs) chemically bond to tooth structure and release fluoride ions, which can help prevent recurrent decay around the crown. While they may have lower bond strength compared to resin cements, their biocompatibility and fluoride-releasing properties are advantageous, especially for metal or porcelain-fused-to-metal crowns in less visible areas. Resin-modified glass ionomer cements (RMGICs) combine the benefits of GICs with improved strength and moisture resistance, offering enhanced aesthetics and wear resistance.
Traditional cements like zinc phosphate have been used for over a century and provide strong mechanical retention, often considered a permanent cement for crowns and bridges. Polycarboxylate cement offers chemical adhesion to tooth structure with minimal pulp irritation and moderate strength, often used for temporary restorations or luting applications. The selection of cement depends on factors such as the crown material, aesthetic requirements, and the specific needs of the tooth.
The Cementation Procedure
The crown cementation procedure begins with removing any temporary crown. The natural tooth surface is then thoroughly cleaned to remove debris or temporary cement, ensuring a clean surface for bonding. Simultaneously, the inner surface of the permanent crown is prepared, which might involve sandblasting to create a rougher surface for better adhesion.
The dentist selects and mixes the appropriate dental cement, ensuring a homogeneous consistency. The prepared tooth is isolated from saliva to maintain a dry field, which is important for the cement’s effectiveness. The mixed cement is then applied evenly to the inside of the crown, and the crown is seated onto the tooth with gentle pressure.
After the crown is seated, the dentist removes any excess cement that extrudes from the margins, often by tack-curing the cement with a light for a few seconds to partially harden it, making removal easier. A scaler is used to remove the excess while holding the crown in place. A final light cure, lasting about 20 seconds per surface, or allowing sufficient self-curing time, ensures the cement is fully hardened. The dentist then performs final checks for proper fit and bite alignment, making any necessary adjustments to ensure comfort and function.
Post-Procedure Care and Crown Longevity
Following crown cementation, some sensitivity around the gum line or to temperature changes may occur for a few days. Patients should wait at least an hour before eating to allow the cement to fully set. For the first 24 to 48 hours, avoid hard, sticky, or chewy foods, as these can dislodge the newly cemented crown or put undue stress on it.
Maintaining consistent oral hygiene practices is important for the longevity of a cemented crown. Brushing twice daily with a soft-bristled toothbrush and fluoride toothpaste, along with daily flossing, helps prevent plaque buildup and decay around the crown’s margins. While the crown itself cannot decay, the underlying tooth structure remains susceptible. Regular dental check-ups are also important to monitor the crown’s condition and address any issues early.
The lifespan of a dental crown ranges from 5 to 15 years, with proper care extending it further. Factors influencing longevity include the crown material, with metal and zirconia crowns offering greater durability than porcelain or resin. Oral habits like teeth grinding (bruxism) or chewing on hard objects can significantly reduce a crown’s lifespan, as can poor gum health. Avoiding sugary or acidic foods also helps protect the underlying tooth from decay.