A dental crown restores a damaged or weakened tooth, protecting it and restoring its original function. When a crown is newly placed, patients often notice that its shape, or contour, does not feel or look like a natural tooth, frequently describing it as “flat.” This lack of proper anatomical shape is more than just an aesthetic concern, as the crown’s contour is fundamental to the health of the surrounding gum tissue and the function of your bite. Understanding why a crown might be made flat is the first step toward correcting the issue.
Understanding Proper Crown Anatomy
A healthy, natural tooth possesses intricate surface features that serve specific biological functions. A properly contoured dental crown should closely mimic this original anatomy, which includes distinct cusps, grooves, and ridges on the biting surface. These features, collectively known as occlusal anatomy, are necessary for efficiently grinding and shearing food during chewing.
The side profile, or axial contour, of the crown is equally important, particularly where it meets the gums. This contour should be slightly convex to gently deflect food away from the gum margin, protecting the delicate tissue. A good crown also establishes a precise contact point with the adjacent tooth, creating V-shaped spaces known as embrasures, which are self-cleansing and allow space for the interdental gum tissue.
When a crown is described as “flat,” it usually means it lacks these distinct occlusal features or has a bulky, featureless axial profile. This failure to mimic natural anatomy compromises both chewing function and gum protection.
Technical Reasons for Reduced Contour
The primary reason a dental crown ends up flat relates to the amount of tooth structure removed during preparation. When the dentist removes insufficient tooth material, particularly on the biting surface, the dental laboratory technician is left with minimal space to create the restoration. To ensure the crown has the necessary thickness for strength, especially with materials like porcelain, the technician must flatten the biting surface and reduce the height of the cusps, compromising the natural anatomy.
Errors can also occur within the dental laboratory during fabrication. These issues might include an inaccurate impression of the prepared tooth, which misrepresents the available space, or simply prioritizing the crown’s structural integrity over its biological contour. Some materials, particularly certain ceramic types, require a minimum thickness to prevent fracture. This leads the technician to simplify the anatomy to meet strength requirements.
In some cases, the flattening may be an intentional clinical choice made by the dentist to manage a complex bite. If the opposing tooth is severely worn or if there are concerns about excessive biting force, a dentist might request a crown with reduced cuspal height to prevent hyper-occlusion, or premature, heavy contact. While this can stabilize the bite, it results in a less efficient chewing surface and is often a compromise to avoid immediate bite interference.
The Impact of Flat Crowns on Oral Health
A crown that lacks proper contour can lead to functional and biological complications. On the side surfaces, a flat or over-contoured axial profile fails to deflect food during chewing, causing food particles to be pushed directly into the gum line. This chronic irritation promotes the accumulation of plaque, which can lead to gingival inflammation and periodontal disease around the crown margin.
Functionally, the absence of natural cusps and fossae on the biting surface reduces the crown’s ability to effectively grind food. This decreased chewing efficiency can force the patient to shift the chewing load onto other teeth, leading to uneven wear patterns across the dental arch. Furthermore, an improper occlusal surface can destabilize the patient’s bite, potentially contributing to discomfort or pain in the temporomandibular joint (TMJ) due to misdirected forces.
The lack of precise contact with the adjacent tooth, or a poorly designed embrasure space, can also create a “food trap.” This causes food to become wedged between the teeth, increasing the risk of decay on the adjacent tooth surface and localized gum inflammation. Ultimately, a flat crown compromises the long-term health of the surrounding soft tissues and the stability of the entire chewing system.
Correcting a Crown That Lacks Contour
Correcting a flat crown depends on the severity of the contour deficiency and the crown’s fit. For minor issues, particularly with a slightly simplified biting surface, a dentist may be able to perform chairside adjustments. This involves re-contouring the surface to introduce more anatomical detail, followed by polishing to ensure the surface remains smooth.
If the crown is only slightly flat and the deficit is marginal, the dentist may be able to add a small amount of composite resin material to restore a portion of the missing anatomy. This is only possible provided the material can be bonded securely and withstand chewing forces. However, if the crown’s flatness is severe, affecting the axial contour or the integrity of the gum margin, a complete replacement is usually necessary.
Replacing the crown allows the dental team to start over, ensuring that the underlying tooth preparation provides adequate space for a properly contoured restoration. The dentist will communicate with the laboratory technician to specify the correct anatomical details, contact points, and axial contour needed to promote gum health and restore optimal chewing function. Patients should discuss their concerns with their dentist to determine if a minor adjustment is sufficient or if a replacement is necessary for long-term oral health.