The Do’s and Don’ts of Zirconia Crowns

The Do’s and Don’ts of Zirconia Crowns

The October issue of Gordon J. Christensen’s Clinicians Report published an article on the common clinical mistakes to avoid when working with Zirconia, the crown material of choice. Here we provide an abbreviated version of that article, but we strongly encourage you to review the original. Visit www.CliniciansReport.org for subscription information. By following the do’s and don’ts covered here, we believe you should reduce the likelihood of zirconia failures from debonding and/or fracturing.

Properly prep the tooth

  • When possible, 4 mm of axial wall height is desired
  • Be sure you have at least 1.5 mm reduction to entire occlusal table, including cusps
  • Provide 1/2–3/4 mm axial wall reduction with ≤ 20 degree taper
  • Provide slight chamfer margin (smooth)

Use the double cord technique for the impression

  • The double cord technique is still the golden standard (none other has proven superior)
  • Digital impressions still require gingival retraction with cord for optimum marginal visibility
  • Non-impregnated cord is preferred or impregnated with styptic (avoid ferric sulfate because of staining)
  • Do not remove first cord until after seating the provisional restoration (hold temporary in place when removing the cord)

Sandblast or air abrade to increase surface roughness

  • Do not use hydrofluoric or phosphoric acid to attempt etching zirconia (it is not a conventional glass ceramic but rather a metal-oxide ceramic and will react negatively to these acids)
  • Increase the roughness and surface area of the zirconia restoration by sandblasting/air abrading followed by a thorough rinse

Decontaminate surfaces after try-in

  • When prepping the tooth, use flour of pumice for best results
  • Do not use prophy paste to clear debris as it can lead to inadvertent lubrication prior to cementation
  • Sandblast/air-abrade the zirconia surface for 5–10 seconds followed by a thorough rinse, which will help remove phospholipids in saliva attaching to the zirconia surface. The chemical reaction between saliva and zirconia prevents bonding so phospholipids must be removed adequately.

Use primers containing MDP

  • Do not use silane-only primers on zirconia. This does not work since zirconia is not a glass ceramic. (30 percent of clinicians are mistakenly doing this!)
  • Select a primer containing MDP or methacryloyloxydecyl dihydrogen phosphate as it enhances the chemical bond to cements containing resin. D&S Dental recommends Z-Prime Plus by Bisco.

Select the right cement

  • Use RMGI cements for retentive preps (≥ 4 mm axial height) and for caries-prone patients
  • Use self-adhesive resin cement for heavy opposing occlusion; short, non-retentive preps (<4 mm axial height); and thin, semi-translucent restorations (better see-through color than most RMGI cements)