A night guard, often called an occlusal splint, is a custom-fitted device designed to protect teeth and jaw joints from the forces of bruxism, which involves unconscious clenching or grinding during sleep. A dental crown is a full-coverage restoration that permanently covers a damaged or decayed tooth, restoring its shape and function. The dilemma arises when a patient who relies on a night guard receives a new crown: the existing protective appliance was precisely molded to the teeth’s original contours. The question is whether this old, custom device can still effectively protect the newly restored tooth structure.
Why a Dental Crown Requires a New Night Guard
Night guards are custom-fabricated from an exact impression of the teeth to ensure maximum surface contact and even distribution of pressure across the entire dental arch. This precise fit is necessary to achieve occlusal harmony, which is a balanced bite relationship between the upper and lower teeth. The rigid acrylic material of the guard cannot adapt to significant changes in tooth shape.
A new crown fundamentally changes the “landscape” of the dental arch, even if placed on a tooth not directly covered by the guard. Preparing a tooth for a crown involves reducing the tooth structure, and the final restoration adds a new contour and height. Although the crown is designed to fit your bite, its precise three-dimensional shape will invariably differ from the original tooth structure captured by the initial impression.
This difference in shape or height disrupts the delicate balance the night guard was built upon. The appliance is custom-molded to the microscopic contours and angles of the teeth present at the time of fabrication. If the crown is placed on a tooth the guard fits over, the old appliance is rendered obsolete because it cannot accommodate the new restoration. Without a perfect fit, the night guard cannot perform its function of stabilizing the jaw and distributing grinding forces.
Dangers of Using an Ill-Fitting Night Guard
Attempting to wear a night guard that no longer fits over a new crown can lead to several specific negative outcomes. One immediate risk is damage to the new restoration itself, as an ill-fitting guard applies uneven, concentrated pressure. This pressure can compromise the cement seal holding the crown in place or cause microfractures, particularly in all-porcelain or ceramic materials. The tight, focused pressure acts as a wedge, stressing the bond and leading to premature failure of the dental work.
A second significant danger is occlusal instability, where the misaligned device acts like an unintended orthodontic appliance. The uneven pressure can place unwanted force on surrounding teeth, potentially leading to localized tooth sensitivity or minor shifting of the bite over time. This phenomenon, sometimes called “tooth migration,” is a consequence of persistent, unbalanced forces.
Finally, a guard that forces the jaw into an incorrect or strained position can exacerbate temporomandibular joint (TMJ) symptoms and muscle pain. The purpose of the splint is to relax the jaw muscles and guide the jaw into a comfortable, stable position. If the appliance is prevented from seating correctly, it can instead strain the muscles, leading to increased morning headaches, jaw tenderness, or joint dysfunction.
The Timeline and Process for Obtaining a Replacement
The appropriate time to fabricate a replacement night guard is strictly after the permanent crown has been cemented and the dentist has verified that the bite is stable and comfortable. It is advised not to begin the process while wearing the temporary crown. These provisional restorations have different shapes and are not fixed with permanent cement, meaning the temporary shape would compromise the final guard’s fit.
The process begins with a new dental impression or a digital scan of the dental arch, which captures the newly restored tooth structure. This updated model is then sent to a specialized dental laboratory for the custom fabrication of the new acrylic splint. This fabrication step typically takes one to three weeks.
When the new crown is being planned, inform the dental team that an existing night guard is in use. This allows the dentist to factor the appliance into the treatment plan, ensuring the new crown is designed with appropriate clearance and contour. The old night guard may even be sent to the lab for reference during manufacturing.
Once the new guard is returned, a final adjustment appointment is necessary to ensure the appliance seats perfectly and establishes proper, even contact with the opposing arch. This adjustment phase prevents high spots that could introduce unwanted pressure or bite instability. Patients should also inquire about insurance coverage for the replacement, as coverage for replacement devices can vary significantly.