Introduction
Dental implants are among the most common services provided in dentistry. Zirconia screw-retained restorations are widely favored for their balance of strength and esthetics, making them long-lasting solutions. These restorations are typically used in combination with standard stock abutments, which often leads to failures and cracks in the Zirconia chimney. Recently, there has been a shift in utilizing a more appealing and durable alternative where a screw-retained crown is placed over a custom abutment. This viable solution enhances strength of the entire restoration and the Zirconia chimney, without compromising esthetics or versatility. This article describes the leading causes of failure of screw-retained Zirconia crowns when they are paired with a stock abutment, and describes the favored alternative of custom abutments.
Why Stock Abutments Lead to Failures in Zirconia Crowns
Poor Fit and Alignment Stock abutments are pre-manufactured to general standards, which may not perfectly fit each patient. This misfit can result in uneven distribution of stress, leading to fractures in the Zirconia chimney.
Inadequate Support and Stability Stock abutments may not ensure adequate stability, causing micromovements that contribute to cracks and possible failure of the crown over time.
Suboptimal Angulation The angulation of stock abutments may not align with occlusal forces, leading to improper force distribution. This misalignment increases the amount of stress on the Zirconia chimney, making it more susceptible to fractures.
Thin Zirconia Walls Zirconia chimneys typically have thin walls to maintain a natural appearance and fit within the prosthetic design. However, these thin walls are more prone to cracking under stress, especially when the underlying support from the stock abutment is inadequate. Excessive torque during insertion can also fracture these fragile Zirconia chimney walls.
Misalignment of the Emergence Profile Stock abutments do not allow for a natural emergence profile for the crown, thereby leading to improper gum tissue support and faulty contour of the restoration. This can create a bacteria reservoir and lead to poor oral hygiene.
Alternative Solution: Custom Abutments
Perfect Fit and Alignment Custom abutments are tailored to each individual patient, ensuring a precise fit. This eliminates the gaps and misalignments that are common with stock abutments, providing even stress distribution and reducing the risk of fractures in the Zirconia chimney.
Enhanced Support and Stability Custom abutments are designed to provide optimal support, providing a stable foundation for the crown.
Optimal Angulation By customizing the angulation of the abutment, dentists can ensure that occlusal forces are properly aligned. This reduces stress concentrations in the restoration, enhancing the durability and longevity of the crown.
Titanium Chimney in Custom Abutments Custom abutments often feature a titanium chimney, which is significantly more durable and prevents cracking, as opposed to the thin and fragile Zirconia walls of stock abutment-supported crowns.
Achieve an Ideal Emergence Profile Custom abutments allow for optimal dental implant emergence profiles. They can support the soft tissue contour, improve oral hygiene, and improve esthetics.
Conclusion
The use of stock abutments often leads to fractures and ultimately failures in the Zirconia chimney due to poor fit, inadequate support, suboptimal angulation, fragile walls, and misalignment of the emergence profile. Transitioning to custom abutments addresses and solves these issues by providing a precise fit, enhanced stability, optimal angulation, superior strength of a titanium chimney, and an ideal emergence profile. Dentistry is moving towards making customized abutments the standard of care for patient health, safety, and satisfaction. By investing in custom abutments, dentists can significantly improve the success rate of screw-retained Zirconia crowns, ensuring long-lasting and reliable restorations for their patients.
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