A Kinder, Gentler Bonding Technique
At first, they seemed like the perfect alternative to all-metal dental crowns, which clouded many smiles with their dull gray reflection.
Two ceramic materials, alumina and zirconia, were touted as a significant advance when they were introduced in dental crowns a decade ago, because their crystalline structure combines the rock-solid durability of metal with a translucence that brings new luster to restorations.
But their reputation has been tarnished in the past few years by growing evidence that the sandblasting process for bonding crowns to teeth bombards the surface with hard particles, creating cracks that can increase the risk of fractures and reduce the crown’s life span.
Now, a new bonding technique has been developed at NYUCD that relies on priming
the ceramic surface so that it attaches to teeth through a chemical bond, instead
of through mechanical processes associated with sandblasting. Dr. Van P. Thompson
and Dr. Grace Mendonca Dias de Souza discovered that a primer for treating
metal surfaces would stick to alumina and zirconia because their surfaces contain
metal oxides. They applied the primer to the ceramics, and then brushed a layer
of resin cement over the primer to fuse the crown to the tooth.
"The resulting bond registered up to five times the strength of sandblast-assisted
ceramic cementation,” Dr. Thompson reports. The technique offers potentially
significant benefits to patients, because unlike sandblast-assisted cementation,
the chemical bonding can be done quickly and efficiently chairside.
This research is part of a $5.9 million grant awarded to NYUCD by the National Institute of Dental and Craniofacial Research to enhance the machinability and performance of all-ceramic crowns. Over the coming year, Dr. Thompson and his coprincipal investigator, Dr. Dianne Rekow, will evaluate how the chemically bonded ceramic crowns perform under intense levels of simulated chewing and grinding. The testing will be conducted by Dr. Dias de Souza and a coinvestigator, Dr. Nelson da Silva.
A sandblasted bond with the rough surface texture of the ceramic visible at top right, the adhesive bond at center, and the cement at bottom left |
A non-sandblasted bond showing the smooth surface at right and the cement at left