Zirconium crowns are one of the most important and highly recommended crown types recently. Individuals who want aesthetic artificial teeth prefer zirconium crowns. Patients often wonder about the composition or materials used in the production of zirconium crowns.
He includes four classifications to clarify how much tooth enamel remains after preparation, as well as how much dentin (the layer beneath the enamel) is exposed.
Class I – No-preparation or practically prep-less veneers: 95% to 100% of enamel volume remains. It is best to determine a finish line to provide a perfectly smooth margin between the porcelain and the tooth. Otherwise, there will be a bump where the porcelain begins. But so little enamel is removed with Class I preparation that the finish line may only be visible under magnification. Dr. LeSage considers this the ideal preparation.
Class II – Minimally invasive or modified prep-less veneers: 80% to 95% of enamel volume remains, and 10% to 20% of dentin is exposed. In some cases, because of tooth position or shape, the ideal Class I preparation isn’t practical. Class II, a slightly less conservative option, is used instead.
Class III – Conservative preparation: 50% to 80% of enamel volume remains, and 20% to 50% dentin is exposed.
Class IV – Conventional preparation: Less than 50% of enamel volume remains, and greater than 50% of dentin is exposed. Unfortunately, this veneer preparation type has become almost universally accepted for placing full veneers. But with so much enamel removed, the strength of the veneers is compromised and their lifespan is shortened.