A dental crown is a custom-made cap designed to cover a damaged or weakened tooth, restoring its natural shape, size, and function. Crowns are constructed from highly durable materials to withstand the significant forces of chewing, but they are not impervious to damage. While strong, crowns are not indestructible and can break or fail under certain conditions. Their resilience depends largely on the material chosen and the environment within the mouth.
Expected Durability and Lifespan
The longevity of a dental crown typically falls within a range of 5 to 15 years, though many restorations last longer with proper care. This lifespan is heavily influenced by the specific material used, as different substances offer varying degrees of strength and aesthetic appeal. Metal alloys, such as gold, often offer the longest durability, sometimes lasting 15 to 30 years due to their superior resistance to fracture.
Modern materials like zirconia also provide high strength and durability, often lasting 10 to 15 years, making them a popular choice for back molars where chewing forces are greatest. In contrast, all-ceramic or porcelain crowns offer the best aesthetic match to natural teeth but are generally more susceptible to chipping or fracture under concentrated stress.
Primary Causes of Crown Failure
Crown failure often results from a combination of mechanical stress and underlying biological issues. One significant mechanical cause is chronic teeth grinding or clenching, known as bruxism. Bruxism can generate forces exceeding 500 to 600 Newtons, subjecting the crown material to repetitive stress far greater than normal chewing, leading to fractures or structural fatigue over time.
Another common mechanical failure involves acute trauma, such as biting down forcefully on extremely hard objects like ice, hard candy, or non-food items. Even strong materials have limits, and sudden, high-impact force can cause immediate chipping or cracking, particularly in porcelain or ceramic layers. Failure can also stem from biological factors, most commonly the development of secondary decay beneath the crown margin.
The natural tooth structure beneath the crown remains susceptible to bacterial invasion, especially where the crown meets the tooth near the gumline. If poor oral hygiene allows decay to progress, the underlying support structure weakens, compromising the crown’s seal and leading to loosening or fracture. Furthermore, a poorly fitted or improperly cemented crown can create uneven pressure distribution, making it more prone to early fracture.
Protecting Your Crown from Damage
Protecting a crown requires careful habits and preventative dental maintenance to mitigate risks of mechanical and biological failure. Individuals who grind or clench their teeth must use a custom-fitted nightguard, which acts as a protective barrier to absorb and redistribute the intense forces generated during sleep. This intervention is the primary defense against bruxism-related wear and fracture.
Dietary modifications are important to prevent acute mechanical damage. Patients should strictly avoid chewing on extremely hard foods, such as popcorn kernels, ice cubes, or hard candies. They should also refrain from using their teeth to open packages or tear materials. These actions subject the crown to shear forces that can cause immediate, irreversible damage, especially to aesthetic ceramic materials.
Diligent oral hygiene is necessary to prevent the biological threat of decay at the crown margin. Brushing twice daily and flossing around the crown’s base helps remove plaque and bacteria that could infiltrate the gap between the restoration and the natural tooth. Regular dental check-ups allow the dentist to examine the crown’s margins and surrounding tissue, ensuring signs of decay or wear are detected before structural failure occurs.
What to Do If a Crown Breaks
If a crown cracks, chips, or falls off entirely, the immediate priority is to protect the underlying tooth and contact a dental professional without delay. If the crown is still largely intact, attempt to retrieve the piece and keep it safe, as the dentist may be able to recement it or use it to determine the cause of the failure. The exposed underlying tooth may be highly sensitive to temperature changes or pressure, so carefully rinsing the mouth with warm water can help clean the area.
Temporary relief for sharp edges or exposed areas can be achieved by applying a small piece of dental wax or sugar-free gum over the rough surface to prevent irritation. Over-the-counter pain relievers can be used to manage any discomfort or sensitivity until the dental appointment. It is crucial to avoid attempting to glue or fix the crown yourself, as this can cause further damage or interfere with professional repair. The dentist will determine the best course of action, which may involve recementation, repair of a minor chip, or fabrication of a complete replacement crown.