A dental crown is a custom-made cap placed over a damaged tooth to restore its shape, strength, and appearance. Crowns are often necessary when a tooth is severely decayed, cracked, or weakened, providing stability by covering the entire visible portion of the tooth. Orthodontic treatment, commonly involving braces, aims to shift teeth into better alignment for improved function and aesthetics. This article explores the technical considerations and specialized methods that allow for combining orthodontic treatment with existing crowns.
Feasibility of Orthodontic Treatment with Crowns
Having a dental crown does not prevent a person from undergoing orthodontic treatment. The underlying natural tooth structure and root are still present, allowing the tooth to be moved through the bone just like a tooth without a restoration. Since the root anchors the tooth in the jaw, braces can still exert the necessary forces to guide the crowned tooth into its new position. However, the success of this combined treatment relies heavily on careful planning and assessment by the orthodontist.
Before starting treatment, the orthodontist must thoroughly evaluate the condition and stability of the existing crowns. This includes checking the crown’s margins (the seal where the crown meets the natural tooth) and identifying the specific crown material, such as porcelain, metal, or zirconia. The overall health of the tooth underneath the crown is also assessed, as any existing decay or gum disease must be addressed before orthodontic forces are applied. Detailed planning ensures the restoration can withstand the mechanical forces of the braces and that the final tooth position will not compromise the crown’s integrity.
Specialized Methods for Attaching Brackets
Attaching orthodontic brackets to the smooth, non-porous surface of a crown requires specialized techniques different from those used on natural tooth enamel. Standard bonding agents rely on acid-etching to create microscopic roughness on the enamel, which does not work effectively on most crown materials. Therefore, the bonding protocol must be tailored to the specific crown material to achieve adequate bond strength that can withstand chewing and orthodontic movement.
Porcelain Crowns
For porcelain crowns, the surface typically needs a combination of mechanical and chemical preparation. Mechanical roughening may involve micro-etching or sandblasting the crown’s surface with aluminum oxide particles to create minute retentions for the adhesive. Following this, a chemical coupling agent, most often a silane primer, is applied. Silane chemically unites the silicon in the porcelain with the acrylic bonding material used to affix the bracket, ensuring a strong and reliable connection.
Metal Crowns and Bands
Metal crowns, such as those made of gold or stainless steel, also require mechanical preparation, like air abrasion, followed by the application of a metal primer. In some cases, particularly on molars that need to withstand high chewing forces, the orthodontist may opt to use orthodontic bands instead of directly bonded brackets. These bands are thin metal rings cemented around the entire circumference of the crown, providing a secure anchor point without relying solely on adhesive bonding. The choice of technique is dictated by the crown material, the tooth’s location, and the expected orthodontic forces.
Potential Risks and Protective Measures
The primary risk unique to crowned teeth during orthodontics is bracket debonding. Because the specialized adhesives used on crowns are not as permanent as the bond to natural enamel, they can occasionally fail under stress. Repeated debonding and re-bonding can be inconvenient and slightly prolong treatment time.
There is also a minimal risk of damage to the crown itself during the bonding or de-bonding process when the braces are removed. To mitigate this, orthodontists employ gentle de-bonding techniques, such as using a peel-type force to remove the bracket, which minimizes stress on the crown material. Any residual adhesive left on the crown is then carefully polished away using specific burs that do not damage the restoration’s surface.
Patient Protective Measures
Patient adherence to protective measures is important for maintaining the integrity of the crowns and the orthodontic appliances. This includes strictly following dietary restrictions, such as avoiding hard or sticky foods that can exert excessive force on the brackets. Excellent oral hygiene is also crucial, as poor cleaning around the crown and bracket can lead to gum inflammation or decay at the crown margin. Consistent monitoring by the orthodontist throughout the treatment ensures the stability of the crown and the effectiveness of the orthodontic movement.