A dental crown is a fixed prosthetic restoration that covers a damaged tooth to restore its form and appearance. When the crown is significantly lighter, or “whiter,” than the adjacent natural teeth, it creates a stark contrast that is a frequent cosmetic concern. This color mismatch is primarily an aesthetic issue, indicating a failure in seamless integration rather than a structural failure.
Reasons for the Color Discrepancy
The crown may have been too white due to technical issues during fabrication and placement. A common cause is an error during the shade selection appointment, often conducted under poor lighting conditions that can distort color perception. Dentists and patients rely on visual comparisons using shade guides, a process that is highly subjective and prone to human error, such as rushing the selection or visual fatigue.
Temporary dehydration of natural teeth during the procedure is a specific technical factor. When a tooth is exposed to air for an extended period, it loses moisture, causing its enamel to become more opaque and appear temporarily lighter. If the crown shade is selected while the surrounding teeth are dehydrated, the resulting restoration will be too light once the natural teeth rehydrate and return to their true, darker color.
The underlying color of the prepared tooth, known as the “stump shade,” can also affect the final crown color. If the prepared tooth structure is unusually dark, the final crown material may not be opaque enough to mask this darkness. Furthermore, the color of the dental cement used to bond the crown can sometimes shine through, especially with highly translucent ceramic materials, subtly altering the perceived shade.
Why Natural Teeth Color Changes Over Time
The discrepancy often becomes apparent years after placement because the crown’s material is fundamentally different from natural enamel. Crowns made of porcelain, ceramic, and zirconia are color-stable and chemically inert, meaning their core shade will not change over time. However, the surrounding natural teeth continue to age and accumulate stains, leading to a gradual darkening that makes the originally matched crown appear progressively whiter.
Natural teeth are constantly exposed to chromogens, which are color-producing substances found in common foods and beverages like coffee, tea, and red wine. These molecules penetrate the porous structure of the enamel and dentin, causing extrinsic staining. Over time, the dentin layer beneath the enamel naturally thickens and yellows, a biological process that darkens the tooth from the inside.
Certain prior dental treatments can also contribute to the darkening of natural teeth. Teeth that have undergone root canal therapy, for example, may darken internally due to residual necrotic pulp tissue or materials used during the procedure. Since the crown’s color remains fixed, these changes in adjacent teeth are the primary reason the crown begins to stand out as lighter.
Options for Correcting a Whiter Crown
The simplest and least invasive option to correct a whiter crown is bleaching the surrounding natural teeth to match the restoration. Professional teeth whitening treatments use peroxide-based gels to penetrate the porous enamel and break down staining molecules, effectively lightening the natural teeth. This is a viable solution if the crown is only a shade or two lighter than the current natural tooth color.
It is important to understand that these bleaching agents will not change the color of the porcelain or ceramic crown material. Crowns are made of dense, non-porous materials that resist chemical whitening, meaning they will stay the same shade they were when initially placed. Therefore, the goal of whitening is to bring the natural teeth up to the level of the existing restoration.
If the crown is dramatically whiter, or if the patient desires a darker shade, the only permanent solution is a complete crown replacement. This involves removing the existing crown, re-preparing the tooth, taking a new impression, and sending it to a dental laboratory with a carefully selected, darker shade. Crown replacement is a two-visit procedure that is time-consuming and costly, typically ranging from $800 to $2,500 without insurance, depending on the material chosen.
For minor adjustments, an external shading or glazing process can be attempted, where a thin layer of tinted resin or ceramic glaze is applied to the crown surface and cured or fired. This is a limited and temporary fix, as the thin glaze can wear off over time due to biting forces and daily brushing, causing the original, lighter shade to reappear. This remedial action is usually reserved for slight color discrepancies.
Steps to Ensure Accurate Color Matching
Patients undergoing a future crown procedure or replacement can take proactive steps to prevent a color mismatch. Shade selection should ideally be performed at the beginning of the dental appointment, before the teeth have been exposed to air or isolated, which can cause temporary dehydration and lightening. The use of natural daylight or color-corrected lighting is important, as standard operatory lights can skew color perception.
The dentist should utilize a modern shade guide system, which often includes “bleach shades” that are whiter than the standard natural range, allowing for more precise matching. Digital photography and color-measuring devices can also provide objective data to the dental laboratory, reducing the subjectivity of visual selection.
Patients should ensure their teeth are freshly cleaned to remove any surface plaque or debris that could temporarily darken the color before shade selection. If the patient anticipates future professional teeth whitening, this must be discussed with the dentist before the crown shade is finalized. The crown can be made a shade or two lighter than the current natural teeth to accommodate the planned future whitening, ensuring they match after bleaching and preventing the need for a costly replacement.