Jin-Ho Phark, an assistant professor at the Case Western Reserve University School of Dental Medicine, says he has figured out a way to make ceramic crowns adhere better for dental patients.

Park used an x-ray photoelectron spectroscopy system to examine contaminants that clung to failed crown surfaces and found that plaster particles were interfering with bonding agents.

Crowns are typically made in a two-step process. First, the basic crown is made from blocks of either aluminum- or zirconium-oxide via a special CAD/CAM system. Then they are shaped and tinted into a final veneer form using a plaster mold of the patient’s mouth. It turns out that even though the veneers are sandblasted, they pick up some of the plaster from the mold.

This plaster, along with saliva and blood, creates gaps when the crowns are attached, leading to secondary decay.

Phark found an alternative in a new ceramic crown material developed and donated for testing by the Swedish company Nobel Biocare. The improved fabrication process, using new material, also involves three new steps. First, a sintering process leaves a rough surface texture on the inside of the crown. Next, during the veneering process, excess plaster particles are burned off. Finally, the interior crown surface is etched with an acid before attaching it to the tooth.

“This new crown comes prepared and does not need the extra sandblasting treatment by a dental technician,” says Phark. It can be also attached with normal cements.