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today AAPD Seattle May 22

n There is no denying that pre- formed zirconia crowns are now proven as an excellent choice for esthetic primary tooth full-coverage restorations, offering clinicians and their patients numerous advantages when compared to stainless-steel crowns and even other commonly used esthetic options. These advan- tages include: • More natural-looking translu- cent appearance. • Superior durability/fracture resistance. • Greater variety of sizes, shapes and shades. Zirconia crowns can also exhibit excellent retention strength, but sci- entific research indicates this reten- tionstrengthcanbeseriouslycompro- mised if saliva contamination occurs during the crown trial fit phase. Crown retention failure is something neither we nor our patients ever want to experience. During tooth preparation for any zirconia restoration, the crown must be temporarily placed over the prepared tooth structure to ensure proper fit. As a result of this trial fit- ting step, the inside of the crown will be exposed to saliva and/or blood 100 percent of the time. Phosphates in saliva and blood chemically bond to zirconia, interfering with cement-to- crown bonding. The threat of saliva contamination is recognized by many cement manu- facturers. For example, the IFU for Ketac® glass-ionomer cement, a com- monly used cement for stainless-steel crowns that is also sometimes used for ceramic restorations, states: “… for optimal adhesion, carefully clean the surfaces of the tooth and restoration to be cemented … Avoid further con- tamination by saliva.”1 Some zirconia crown manufactur- ers claim that a clean, contaminant- free intaglio surface is not required, but scientific evidence does not sup- port this position. Zirconia contamination was exam- ined in the landmark study by Kern et al,“InfluenceofSalivaContamination on Zirconia Ceramic Bonding.”2 Saliva-contaminated ceramic specimens were “cleaned” either by exhibitors6 AAPD — Friday, May 22, 2015 Don’t let saliva contamination compromise your zirconia crowns Ad By Dr. Jane A. Soxman, DDS5 (Photo/Provided by NuSmile) 8 see SALIVA, page 8

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