foreign [Music] students today in the dental materials section we will be discussing Dental Siemens many students have requested for this topic as this topic is long so we will be discussing all the classifications followed by zinc phosphate and zinc polycarboxylate cement in detail so let's begin so first of all what is a dental cement you know what is a cement cement is a binder which fixes or adhers to material similarly in dentistry also the dental cement is a binding element or agency used as a substance to make the objects adhere to each other or something serving to firmly Unite okay according to a new service what is a cement it is a substance that hardens to act as a base a liner a filling material or an adhesive to bind the devices and prosthesis to the tooth structure or to each other okay so these are basically the uses of the cements it can be used as a base liner filling material or an adhesive so let us discuss them in detail coming to the classification of cement you know there are various bases on which the dental cements can be classified first is based on the application or uses in dentistry second is based on the ingredients or the composition third is based on the setting reaction and fourth is the ISO standards covering the cements so let us discuss them one by one the first classification is based on the application or the users in this first is type 1 or the Looting agents what do you mean by a looting agent any indirect restoration the restoration which is prepared in the lab inlay only or a crown is attached to the prepared tooth with the help of the Looting agent okay this can be further of two types depending on the grain size type 1 fine grain for cementation and looting type 2 medium grain for bases and the orthodontic purpose okay now coming to the type 2 restorative applications what do you mean by restorative material restorative material are used for filling the tooth cavities or treating the dental caries okay now this can further BE intermediate or temporary restorative material or it can be the permanent restorative material depending on the duration we are using it type 3 liners and bases what do you mean by liner and basis they both are used between the direct restorative material and the tooth for palpal protection now what is the difference a danger liner is placed in a thin layer okay over the exposed dentine while a dental base it is placed on the floor of the cavity and it is relatively thick layer it pro it protects the pulp by providing the thermal insulation okay due to any temperature changes and it also absorbs the occlusion forces now when we are talking about the applications many questions are asked which cement you will use for a particular use okay so let us just know this first if we are going for a temporary cementation that means cementation for a short duration let it be a for a temporary crown so we will use the cements like zinc oxide eugenol or non-eugenol zinc oxide second is for the final cementation like the porcelain fuse to Crown metal crown or all metal Crown then we will use the cements like zinc phosphate zinc polycarboxylate glass animal and the resin cements resin cements we mainly use for the all ceramic rounds okay third is for the temporary restoration when the restorative material for a short duration has to be filled we can fill it with zinc oxide eugenol or reinforced zinc oxide eugenol it is zinc oxide eugenol only but a modification with increased strength then permanent restoration we can use glass dynomial modified glass animal cement or the compomers then bases as we just discussed for the thermal insulation placed on the floor we can use zinc phosphate zinc polycarboxylate glass anomal zinc oxide eugenol or calcium hydroxide then comes the liners they also solve the purpose of the pulpal protection applied in thin layer calcium hydroxide in a suspension can be used as a liner pulp therapy when we want that reparative dentine should be formed okay secondary dentine should be formed for the pulp capping direct pulp capping and the indirect pulp capping we use calcium hydroxide then opt-in effect it gives a pain relief effect there we go for zinc oxide eugenol and last is the root canal sealer when we are done with the root canal treatment and we have to seal the root canal we can use zinc oxide eugenol zinc polycarboxylate or the resin based sealers are also available now now these are very important as they are commonly asked in the Viva and in the multiple choice questions also the second classification of dental cements is based on the ingredients or the composition based on composition they can be the water-based cements in this glass animal cements zinc phosphate and zinc polycarboxylate second are the resin based cements in this the composite and the adhesive resins as well as the compomers third are the oil-based cements in this zinc oxide eugenol and the non-eutenol zinc oxide cement the next classification of dental cements is based on the sitting reaction this is a very common classification system which is asked so three types are there first is the acid-base reaction in this the cements they are supplied in liquid and powder form in which the liquid acts as the acid and powder as the base so when the powder in liquid are mixed the acid-base reaction takes place to form a solid Mass okay examples are zinc phosphate zinc oxide eugenol and the glass cylomer cement second is the polymerization reaction these type of cements they set by the polymerization mechanism okay now this polymerization can be activated either chemically some chemical initiator is present in the composition or by some light okay some photo initiators are present in this examples are the resin cements third are the Dual cure and the dry cure Siemens from the name itself dual cure means it can be set by two mechanisms Tricare means it can be hardened by three mechanisms okay so in the Dual cure cements they set by the acid base and any one of the polymerization mechanism let it be light activated or the chemically activated tricure they use all the three mechanisms of settings okay so this is just the according to the method of the curing okay examples are the resin modified GIC and the compomers next are the ISO standards covering the Siemens the iso double nine one seven one two thousand three these are the water-based cements part 1. they are available as powder liquid system they are acid-based systems then ISO double 9172 1998 water-based cements part 2 they are the light activated cements 2004 these are zinc oxide or eugenol and zinc oxide non-eugenol cements last are the iso 4049 2000 these are the polymer based cements like the resins used for filling restorative and the Looting if we just go back to the history and see the timeline of the dental cement silicates were the first Simmons to come okay they were invented by Fletcher in 1873 then zinc oxide in 1873 zinc oxide and the clove oil by to solve okay followed by zinc phosphate in 1879 by Dr Pierce then calcium hydroxide came in 1930 okay the calcium hydroxide based it was invented by Herman okay then this was followed by polycarboxylate cement in 1968 by Dennis Smith then in 1971 glass animals Simmons they came into the picture by Wilson and Kent okay now amongst this glass ionoma cement are commonly asked by The Examiner that who invented and when it was invented now let us discuss the ideal properties of the dental symbols first is its low viscosity and the film thickness it is a very important property especially for the Looting cements you know the film thickness should be less flow should be good so that it improves the seating of the restoration and greater flow will lead to more wetting of the tooth as well as the restoration surface okay the film thickness should not be more than 40 micron second is its long working time with rapid set at Oral temperature what does it mean that we should have enough working time we are mixing the cement and then we are loading onto the ground but once seated it should have a rapid set okay so that no contamination is there third is the low solubility the solubility in the oral fluids should be minimal okay otherwise what will happen there will be marginal leakage and it will lead to secondary caries then High compressive and tensile strength mechanical properties are very very important for a cement whether it is a base or it is a looting agent then comes High proportional limit the stiffness it should have high stiffness especially under the ceramic rounds you know it should be able to withstand the massicatory loads then adhesion to the tooth structure and the restorative material this will give the retention to the indirect restoration it will not come out okay it will properly fix the tooth with the restorative material then anti-kariogenic properties it should have fluoride release properties so that it prevents the carries further carries biological property in this we mean to say first the pH of the cement it should not be much acidic the pulpal response should be mild now let us discuss one of the oldest looting cement that is zinc phosphate in detail zinc phosphate as I just told you that it is one of the oldest of the Looting cement it has the longest clinical track record and it also serves as a standard with which the newer systems can be compared okay zinc phosphate cement was introduced by Dr Pierce in 1879. the zinc phosphate cement is available as one powder in the liquid system and second capsules of the pre-proportioned powder and the liquid next let us discuss the composition of the zinc phosphate cement as we said that it is available in the powder in the liquid form the powder mainly contains the zinc oxide which is 90.2 percent it is the principal constituent second is the magnesium oxide 8.2 percent which helps in fusing or the sintering then silica it is the filler 1.4 percent other oxides like the Bismuth trioxide calcium oxide barium oxide they improve the smoothness of the mix okay so for remembering the composition the name itself zinc phosphate so zinc zinc oxide in the powder and phosphate phosphoric acid in the liquid so the main constituent of the liquid is phosphoric acid that is present in 38.2 percent it only reacts with zinc oxide okay second is the water 36 percent that is why the zinc phosphate cement it can comes under the category of water-based cement okay then aluminum phosphate or sometimes the zinc phosphate is present 16.2 percent it buffers to reduce the rate of the reaction okay then aluminum ions 2.5 percent zinc 7.1 percent they also helps in the centering the fusing and forming the mass setting reaction of the zinc phosphate cement when the powder powder contains zinc oxide it is mixed with the liquid phosphoric acid the phosphoric acid attacks the surface of the particles and it releases the zinc ions it forms zinc phosphate then the aluminum which is present in the liquid is essential for the cement formation the aluminum it complexes with the with the zinc phosphate and the phosphoric acid and also the zinc ions to form zinc aluminophosphate gel this reaction is exothermic if we see the picture the set cement has a code structure consisting of the unreacted zinc oxide particles embedded in The Matrix of zinc aluminophosphate classification of the zinc phosphate cement Ada it classifies the cement into two types type 1 fine grained for looting its film thickness should be 25 micron or less type 2 median grain for looting and filling okay but the film thickness should not be more than 40 micrometer manipulation of the zinc phosphate cement it is one of the exercise which is done during the dental materials exam okay so the questions related to it are asked during the manipulation so for this first of all a cool mixing glass slab should be used now why cooled this will prolong the working and the setting time and it also permits the operator to incorporate maximum amount of powder okay for this Frozen glass slab technique is also used what is that in that third glass slab it is cooled in the refrigerator at six degrees C or freezer at 10 degree minus 10 degrees Celsius okay the advantage of Frozen glass slab is that it increases the working time of the mix and it shortens the setting time of the mix after placement into the mouth it is mainly indicated for cementation of long span Bridges okay this Frozen glass slab is often asked in the Bible okay second is the stainless steel spatula is used for mixing powder liquid ratio is 1.4 gram is 2.5 ml then the liquid should not be dispensed onto the slab until the mixing is to be initiated why because the water it will be lost by to the air by evaporation okay then the powder is divided into several portions the mixing is initiated by the addition of small amount of powder then the small quantities are Incorporated initially with the brisk speculation a considerable area of the mixing slab should be used why because it is an exothermic reaction okay so we want to mix in the larger area then each increment is mixed for 15 to 20 seconds before adding another increment the total mixing time the total mixing it completes in around 1 minute to one and a half minute the maximum amount of powder should be incorporated why because it will ensure minimum solubility and maximum strength okay then the crown is loaded or filled with a cement okay it should be half loaded and then it is seated and placed in the patient's mouth it is allowed to sit setting time of the zinc phosphate cement according to EDS specification Number 96 the setting time may vary between 2.5 to 8 minutes practice controlling the setting time a very very common question which is asked during the Viva first the manufacturing process first is the sintering temperature you know when the granules they are sintered and the powder is prepared that is the sintering temperature the higher the temperature the more slowly the cement sets so the setting time will increase second is the particle size finer the particles more quickly they will mix at a greater surface area they will be exposed to the liquid so the it will fasten the reaction the setting time will decrease then water content of the liquid if there is more water excess water will accelerate the reaction and the setting time will decrease the buffering agents if they are added they slow down the reaction so the setting time will increase second the factors which are under control of the operator these are more important okay first is the temperature higher the temperature it accelerates the reaction so the setting time will decrease so that is why we cool the glass slab second is the powder liquid ratio more the liquid slower the reaction but this is not recommended as it affects the strength of the cement then rate of addition of the powder to the liquid the reaction is slower if the powder is incorporated slowly so the setting time will be increased mixing time the longer the mixing time okay the slower will be the rate of the reaction so the setting time will increase properties of the zinc phosphate cement first are the mechanical properties first is the compressive strength the fully set cement it has very high relatively High compressive strength of the range one zero four to one one nine Mega pascals and it gains 70 percent of its maximum strength in the first 30 minutes but the ultimate maximum strength is attained at the end of 24 hours okay mainly the powder liquid ratio should not be altered because more the powder greater the strength it will achieve second is the tensile strength which is the cement is weaker in tension it is 5.5 Mega pascals which makes it brittle third is the modulus of elasticity which is high 13.7 it makes the cement stiff and also resistant to the elastic deformation okay next is the solubility the zinc phosphate cement it shows low solubility of 0.06 percent weight though it shows disintegration in the oral cavity so the marginal adaptation of the crown should be good next are the thermal properties it it shows good thermal insulation that is why successfully it is used as bases and it is also effective in reducing the galvanic effects adhesion adhesion is micro mechanical that means it depends on the mechanical interlocking of the surface roughness of the tooth as well as the roughness of the restoration biological properties the cement is highly acidic at the time of mixing the pH is to then at uh after 24 hours the pH has increased to 5.5 which is still in the acidic range then comes the pulpal response it is moderate Optical properties the cement is opaque applications or the uses of the zinc phosphate cement first is Looting of the indirect Restorations like the inlays on lays then all metal crowns coarsely infused to metal crowns second it is used as a high strength base below the amalgam restoration it is used second third temporary restorative material also the zinc phosphate cement is used it is also used for Looting of the orthodontic bands and the brackets advantages of the zinc phosphate cement first it has a long track record as we just uh discussed in the beginning it has good reliability second good compressive strength that is why it is used as a base below their amalgam Restorations then disadvantages first there is no chemical adhesion it is all micro mechanical so it depends on the roughness of the restoration and the tooth surface so the retention is compromised second no anti-keliogenic property no fluoride release third acidic nature which calls the pulp irritation last is poor Aesthetics the Aesthetics are not good so that is why it cannot be used with the all ceramic rounds and The Vineyards now we will discuss about the second cement that is zinc polycarboxylate cement in detail zinc polycarboxylate cement you know the Canadian biochemist Smith he developed the zinc polycarboxylate cement in 1968. what he did he substituted the phosphoric acid of zinc phosphate with polyacrylic acid okay and form the polycarboxylate cement this was the first cement system that developed an adhesive bond to the tooth structure the zinc phosphate was is mechanically bonded and this is this will form the adhesive Bond okay now this cement is available as powder liquid system in the bottles then water settable cements what do you mean by water settable cement in this the polyacid it is freeze dried and it is added to the cement powder itself and then the water is used as the liquid then it is also available in the precapsulated powder liquid system composition of the zinc polycarboxylate cement it is in the powder it has zinc oxide you know the constituents of the powder is almost the same of the zinc phosphate so it contains zinc oxide which is the basic ingredient magnesium oxide which is the principal modifier and it helps in the centering the few the formation of the set cement then oxides of the Bismuth and aluminum they are added in small amounts stannous fluoride this is an addition it imparts the anti-kariogenic properties also it increases the strength and it also helps in modifying the setting time second is the liquid now the liquid is different from the zinc phosphate instead of phosphoric acid it contains the aqueous solution of polyacrylic acid okay or the copolymer of the acrylic acid okay with other uh carboxylic acids that is the itaconic acid malic acid and the tricarbolic acid setting reaction of the zinc polycarboxylate cement and this the powder and the liquid the powder zinc oxide and the liquid polyacrylic acid they are mixed the surface of the powder particles they are attacked by the acid then they release the zinc magnesium and the ten ions these ions they bind to the polymer chains okay via the carboxylic groups and they form the zinc polyacrylate okay now it forms the amorphous gel Matrix of the zinc polyacrylate in which the unreacted powder particles of the zinc oxide they are dispersed now this was the first cement to be chemically added to the tooth okay now what happens how it bonds chemically with the tooth structure the polyacrylic acid it reacts with the calcium ions on the surface of the enamel or the dainty via the carboxylic groups now this is one of the mcqs which is asked via the carboxylic groups and thereby they adhere chemically to the touch structure the bond strength of the semen to the enamel is 3.4 to 13 Mega pascals and to the dentine it is 2.07 megapascals the manipulation of the zinc polycarboxylate cement now in the dental materials practical exam you may be asked to mix the cement and show to The Examiner okay now the recommended powder liquid ratio for this is 1.5 is to 1 a glass slab or paper pad is used to mix the cement okay the paper pad should be such that it should not absorb the liquid glass lab is preferred because it can be cooled and we can go for a longer working time okay then the liquid is dispensed immediately just before mixing this will prevent the evaporation of water and subsequent thickening of the liquid okay the mixing time is 30 to 60 seconds the powder should be rapidly incorporated into the liquid in large quantities okay the consistency of the mix should be creamy and it should appear glossy why glossy so that it indicates that sufficient number of carboxylic acid groups is present on the surface that are important for the bonding with the tooth structure okay if it is a dull looking mixture it should be discarded okay now working time is around two and a half minutes the setting time is seven to nine minutes before application the conditioning of the truth is important it should be conditioned with 10 percent polyacrylic acid followed by rinsing with water or one to three percent hydrogen peroxide then the surface should be dry and isolated properties of the zinc polycarboxylate cement first the compressive strength the strength is inferior to the zinc phosphate cement and it is around 55 to 67 megapascals then the diametral tensile strength it is slightly higher than the zinc phosphate cement it is around 3.6 to 6.3 megapascals solubility solubility is slightly more than the zinc phosphate okay which is 0.6 percent weight so the marginal dissolution you know at the margins the the solution of the cement is more when we are using it for cementation purpose then biocompatibility the it is pulpal response is mild the pH of the liquid is 1 to 1.7 but it increases the pH of the freshly mixed cement when it is mixed with the powder the pH goes to three to four and after 24 hours the pH is 5 to 6. okay now how this is happening the liquid it is rapidly neutralized by the powder that is where the pH is increasing and second the pulpal response is mild because the large size of the polyacrylic acid molecule it limits its penetration into the dentinal tributes okay as compared to the phosphoric acid which was present in the zinc phosphate okay now Optical properties it is opaque in nature due to the unreacted zinc oxide particles anti-karyogenic property is present but it is very limited thermal properties they are good thermal insulators applications or the uses of the zinc polycarboxylate cement first it is used for Looting of the permanent Restorations the metal inlays on lace all metal crowns then porcelain fuse to metal crowns second it is used as a high strength basis third it is used for the cementation of the orthodontic bands advantages if we talk about of the zinc polycarboxylate cement it is less irritating to the pulp when compared to the zinc phosphate cement second it chemically bonds with the tooth okay disadvantages the fluoride release is limited as compared to the glass anomal cement second some better options are available now so these cements have become less popular that's all for this topic my dear students please like and share the video you can give your topics in the comment section 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