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Why Is Zirconia the Widely Preferred Material for Dental Esthetics?
When it comes to crowns, many people choose zirconia crowns over porcelain and ceramic crowns because they look better or have superior aesthetics. Similarly, when it comes to implant abutments, ceramic and zirconia abutments unquestionably tend to have again the advantage of the prosthetic margins being more aesthetically pleasing or esthetic, in contrast to the bluish-grey colored titanium abutments that may frequently present long-term gingival discoloration. In implant dentistry, ceramic abutments are renowned for their exceptional mechanical strength, insoluble water strength, and great biocompatibility. Conversely, zirconia abutments have been found to have even higher biological qualities, which can improve chewing efficiency and overall performance by reducing the potential for bacterial adherence. Indeed, zirconia crowns or abutments can be more biocompatible with gingival/gum phenotypic than metal abutments. Most patients choose zirconia prostheses over ceramic and porcelain-incorporated crown or abutment choices due to the greater aesthetic requirements.
Is Zirconium Better Than Other Dental Materials in Implant Dentistry?
When patients have higher expectations for the dental prosthesis in terms of both appearance and functionality, fractured crowns or abutments can be disappointing to both the patients and the dental professionals. When it comes to prosthodontic applications such as crowns and bridges, zirconia has a far lower material degradation capability than other dental materials like ceramic titanium or porcelain. Zirconia is also less prone to material degradation than the other dental materials previously described since it is not susceptible to degradation or instability at low temperatures. Current scientific reports also demonstrate that, even in the case of temperature variations, zirconia failures are completely ruled out due to the crystalline structure of the material, particularly its formation or conversion from tetragonal phase to monoclinic phase when in contact with water.
Researchers studying dental implants have found that zirconium can withstand extreme strain and have a fracture load of approximately 444–738 N, which is higher than that of ceramic and titanium abutments in the field of implant dentistry or with surgical prostheses. This means that if a patient has a prosthetic made of ceramic, titanium, or porcelain, these materials are unable to withstand the high tensile or fracture forces that could cause the material to degrade, deform, or eventually crack the prosthesis when the abutment in question becomes brittle and fails from both a prosthetic and functional standpoint.
How Can a Zirconia Crown Fracture or Fail?
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Given that the surface and biological qualities of this material are so high, how would an abutment or crown fail in this situation? Dental professionals and academics believe that multiple factors may interact to determine the success of a prosthetic, rather than just the caliber of the material employed. This is dependent on several factors, including how the abutment or crown is manufactured, how the dental operator or implant dentist handles the prosthesis clinically, where the prosthesis is placed in the patient's mouth cavity, and what kind of shear or local masticatory forces the prosthesis would be subjected to, how the crown to implant ratio compares to dental implants, and the occlusal force-oriented prosthetic patterns or designs to distribute the pressures used during chewing and grinding, the prosthesis's RVH (restorative vertical height), and lastly the patient's local and systemic health considerations. Sometimes, even with extreme caution and careful evaluation of the prosthetic elements stated above, it might be difficult for the prosthodontist/implant dentist or dental surgeon to identify potential fractures in the patient's prosthesis.
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Current dental research indicates that this would also depend, in many cases, on the patient's systemic status, ability to maintain oral hygiene, and any underlying systemic factors that could cause oral health issues. Examples of these include people with type 2 diabetes, hyperthyroidism, hypertension, circulatory disturbances, gastrointestinal or esophageal diseases, renal or hepatic/liver-related disturbances, multiorgan issues, etc., all of which would have a profound impact on the patient's oral health status and their prosthetics as well.
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Errors in prosthetic manufacture have also resulted in cases of operator-induced fractures. This may be the result of severe internal stresses that the zirconia crown or abutment in question may experience. The dental operator or implant dentist would not have predicted these potential complications leading up to the fracture of the zirconia crown or the abutment if they had made common mistakes like overpreparing the tooth before crowning, thinning the lateral walls of the underlying prepared tooth, improper labial or buccal emergence profile in perspective to dental implants, or abutment/prosthetic overload occurring in dysfunctional or parafunctional habit oriented dental patients. Further dental study indicates that younger males, particularly those who visit the dentist, are more likely to have greater occlusal loads or forces, which have the potential to move or distort the abutment materials, as well as gingival stress, which increases the chance of zirconia material fractures.
What Preventive Measures Can Be Taken by the Dentist to Prevent Fracture of Crown?
In the case of zirconia crowns or abutments, dentists must take specific precautions. These include ensuring the careful seating of the prosthesis, using proper isolation techniques, and addressing any parafunctional habits in patients. For parafunctional habits, dentists should recommend preventive measures such as custom-fitted mouthguards. Maintaining a minimum tooth or abutment thickness of 0.020-0.028 inches is essential, and over-preparation of natural teeth should be avoided, whether for a single-unit crown or a multi-unit bridge. In implant dentistry, the use of zirconia abutments with internal connections is commonly recommended. These abutments help prevent screw loosening and reduce stress on both the implant and the underlying jawbone, as opposed to abutments with external connections.
Conclusion:
Zirconia abutments and crowns are gaining popularity in modern dental practice due to their exceptional aesthetics and biocompatibility. However, prosthodontists and implant dentists must exercise caution to prevent potential fractures of these materials. This involves carefully considering patient-specific factors, such as bite force and occlusal habits, and implementing fracture-resistant techniques to ensure the durability of the restorations. Regular monitoring and adjustments, as well as the use of advanced imaging techniques, can further aid in maintaining the integrity of zirconia restorations. By adopting these measures, dental professionals can significantly enhance the functional success and longevity of these restorations, ensuring optimal patient outcomes.
