Durability of Porcelain Crowns
With the advancement of modern cosmetic dentistry into all porcelain crowns from traditional porcelain fused to metal crowns (PFM crowns), many have wondered if the
porcelain crowns would be as durable over the long term. Well, recent clinical studies have shown that they are just as strong and also have the ability to maintain their beauty over time as well.
The main differences in porcelain crowns are the type of porcelain used, and how they are fabricated in a dental laboratory. Different porcelain types and strengths are used for different reasons. Remember also, that a lab created porcelain crown, is of higher fabrication quality and fit, than an in office computer milled crown.
Long Term Study – Porcelain Crowns
The researchers at the Medical University at Innsbruck studied a little over 1,300 all porcelain crowns placed between 1987 and 2009. They were tested for predictability and strength and found to have a high,(93.5% probability of survival) success over a 10 year period. The study was published in the International Journal of Prosthodontics). The study included those with root canal teeth, and those who grind their teeth.
A total of 302 patients (120 men and 182 women) participated in the study. They were examined at the university during regularly scheduled visits for dental examination. Patient-specific data about sex, age, tooth sensitivity, smoking, and grinding were noted, as well as self-reported data regarding their level of satisfaction with their restorations: excellent, good, medium, or none. The porcelain crowns were broken down into areas of mouth as well, into front( anterior), and back( premolar, and molar) regions.
All 1,335 porcelain crowns had been placed at the university between November 1987 and December 2009. Of these porcelain crowns, 451 were observed over a 10-year period, 84 for 15 years, and 24 over 20 years.
Dental examinations were completed by two dentists in the spring of 2010. One dentist had placed the majority of porcelain crowns, whereas the other dentist involved in examinations had placed none of them. California Dental Association/Ryge criteria were used to rate each porcelain crowns as a success, relative failure, or absolute failure.
Any porcelain crowns that had severe enough issues to warrant replacement were considered an absolute failure. If a finishing procedure or polishing was able to fix the issue, the porcelain crown was labeled a relative failure.
Of the 1,300+ porcelain crowns in the study, only 95 porcelain crowns were rated as failures, 79% of which were absolute failure. Most failures occurred in the anterior region, with 65, while 19 occurred in premolars and 11 occurred in molars.
Success rates remained strong over time. The estimated survival rate was 97.3% at five years, 96% at eight years, 94% at 10 years, 85.8% at 15 years, and 78.5% after 20
years. Almost half of all porcelain crown failures happened in the first 8 years..
The most frequent reason for failure was fracture,(cracks) of the ceramic, according to the researchers, followed in order by cracks in the ceramic and decay.
Root canal teeth and patients who grind their teeth, had higher failure rates.
Patient responses to questions about satisfaction were very positive. With 96% rating it as excellent and 4% rating it as good. The surprising thing about this study was that even patients with failures thought that porcelain crowns were an ideal dental restoration and would do it all over again.
Porcelain Crowns Conclusion
Porcelain crowns are a proven part of cosmetic dentistry and with continued advances in dental porcelain (like e.max porcelain crowns) these results will be even better into the future. Porcelain crowns are an ideal restoration due to their color, shape, and light reflecting properties. The study just proves that they are a valuable asset to any dental patient’s smile.