Good day, I am Professor Josette Camilleri, Associate Professor at the University of Malta. Today, we will be discussing tricalcium silicate-based endodontic cements. Tricalcium silicate-based endodontic cements can be based on Portland cement and they can also be based on tricalcium silicate. The presentation clinically, usually are cements which are presented as powder and liquid, they can be presented as pastes and putty, they can even come in sealer forms, and also as pulp-capping materials. The tricalcium silicate can be pure tricalcium silicates, which are manufactured in the labs by sintering, by sol-gel methods, or else they can be also the Portland type, which comes in sets but usually are bought from the construction industry. It is a very, very cheap material which can be used in dentistry and packaged in small packets at a higher price. The main interest with this material is that when the material is mixed with water, which is the main mixing liquid of this cement type, you form calcium hydroxide as part of the reaction. As all clinicians know, calcium hydroxide is a very important material in clinical dentistry, as it is used for most endodontic procedures and pulp-capping procedures. With this material, this calcium hydroxide is formed as part of the hydration of both Portland cement and tricalcium silicate cement. When the material hydrates, you will have the main particle which is the cement particle around which you get a reaction rim, where you get calcium silicate hydrate which is the main material mass, and also you will get soluble calcium hydroxide. If you look at an X-ray diffractogram, which is shown here, you will find that when you have the powder, you have the main peaks of bismuth oxide, you have the main peaks of the cement that can be seen at around 30 - 32 degrees on the X-axis scale, the bismuth oxide which can be seen at the 27 X-axis scale. When the powder is hydrated after 28 days, you can see a new peak of calcium hydroxide, which is viewed at 18 degrees, two-theta. This is the typical peak showing that this material has hydrated and this calcium hydroxide has been formed. The other peaks which show reduction in the level, showing material reaction, and obviously, reduction in the peaks will be shown since there will be a phase change. The difference between the Portland cement and the tricalcium silicate is that the tricalcium silicate is mostly 99.9% pure, while the Portland cement has other phases and it will be only 68% of tricalcium silicate, which is the reactive component. When the material reacts, you get the formation of the calcium hydroxide and an amorphous matrix of calcium silicate hydrate. The main uses of this material is for root-end filling, repair of root perforations, which can be surgical and non-surgical, apical plug in apexification procedures, regenerative endodontics, pulp capping, and as a root canal sealer. For all material types, we have the main composition is always a cement, radiopacifier, and a mixing liquid. For the new generation materials, the mixing liquid can be absent, which means that we have pre-mixed materials. The normal mixing liquid, which is water, but sometimes mixing liquids are placed with various resin types mostly for use as sealers and for pulp-capping materials. Again, with the second generation materials, we have a number of additives which we will be discussing, because these additives will enhance the material properties. In this lecture, we will be discussing the main material composition, the properties, and also the modifications. We will be discussing modifications in the cement type, the modifications in the radiopacifier type, modifications in the mixing liquid, and also the effect of the additives. The main modification in the cement is the use of pure tricalcium silicate instead of the Portland cement type. Pure Portland cements, since they are made from natural raw materials, have inclusions of arsenic, lead, and chromium. All these trace minerals can be found in the cements as acid-extractable trace elements, and also in the material that is leached. And obviously, when it is leached, it will be leached to the human tissues. This has raised some concerns, and the manufacturers have replaced the Portland cement with a pure tricalcium silicate, which is made from controlled materials in the labs. The main problem with the Portland cement is that the Portland cement, besides containing tricalcium silicate, also contains another phase. This other phase is the tricalcium aluminate phase, which when it reacts, you will have an aluminium phase present in close contact with the tissues. This is problematic because as recent study carried out on test animals has shown that this aluminium phase can leach aluminium to plasma and liver of test animals. Aluminium has been linked with Alzheimer's disease.