| 摘要 |
A burr ( 30 ) includes a spherical cutting element ( 36 ) and a shield ( 40 ) integrally placed behind the burr. The shield is circularly configured, has a rounded periphery and is provided with a smooth tooth-engaging surface. The shield thus insures that the depth of the penetration-into the tooth is precise, as predetermined, without inflicting deleterious harm to the tooth. The present invention further relates to a method, utilizing the shield, for precise tooth preparation of porcelain veneers and porcelain crowns.
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