An Updated Classification of Hydraulic Cements Used in Dentistry

Mineral trioxide aggregate (MTA) was the first hydraulic cement used in endodontics. It is composed of Portland cement, a binder in concrete, and bismuth oxide to enhance the radiopacity. MTA was introduced in dentistry to be used as a root-end filling material and also to repair root perforations. The specific use was motivated by the well documented hydraulic nature of Portland cement used in construction. Currently, dental hydraulic cements are used for all endodontic procedures. They are composed of a hydraulic cement with various additives and the material chemistry changes when placed in different clinical fields. These characteristics influence the clinical performance of the materials. A classification of hydraulic cements used in dentistry has already been published, but it is unfortunately already outdated due to the rapid changes in the market and material availability. The aim of this publication is to guide the users of hydraulic cements in dentistry in choosing the right material for the clinical technique being undertaken. The new classification being proposed subdivides the components into the cement which is the binder, the radiopacifier, vehicle, and additives. Irrespective of the cement chemistry, the cements are either calcium hydroxide releasing or not, the vehicle is water or alternative, and the additives are cementitious or non-cementitious. This new classification identifies the reaction byproduct as the main classifier of the material type since it is the most significant component that affects the clinical interactions. The presence of water and hydration is important; thus, it is also listed as part of the classification. Alternative vehicles that react with moisture from the environment require updated clinical protocols to ensure the hydration can proceed. The updated classification of hydraulic cement used in dentistry focuses on the clinical effect rather than on the material chemistry; thus, it is more suitable for material identification.