1. Dental Cements

September 2024 Dental Cements – Properties & Manipulation 4. Pressure exerted during the placement of the filling Introduction material > Dental cements are a classification of dental materials 5. The degree of support from supp...

September 2024 Dental Cements – Properties & Manipulation 4. Pressure exerted during the placement of the filling Introduction material > Dental cements are a classification of dental materials 5. The degree of support from support from that are continually used in dentistry. The American surrounding structures Dental Association and the International Standards 6. Choice of correct operative techniques Organization (ISO) have teamed up to classify dental Classification of Cements cements according to their properties and their intended Type I: Luting agents that include permanent and uses in dentistry. temporary cement. Definition Luting Agent > any of various bonding substances that are placed in > A material that acts as an adhesive to hold together the the mouth as a viscous liquid and set to a hard mass; casting to the tooth structure. Luting agents are designed used in restorative and orthodontic dental procedures as to be either permanent or temporary. luting (cementing) agents, as protective, insulating, or Permanent Cement sedative bases, and as restorative materials. > For the long-term cementation of cast restorations such as inlays, crowns, bridges, laminate veneers, and Requirements of a Dental Cement orthodontic fixed appliances. 1. Thermal Barrier Temporary Cements 2. Chemical Barrier > Temporary cement is used when the restoration will 3. Electrical Barrier have to be removed. Most commonly, temporary cement 4. Strength and flow is selected for the placement of provisional coverage. 5. Radiopacity 6. compatibility Type II: Restorative applications > Dental restorative cements are specially fabricated 1. Thermal Barrier materials, designed for use as dental > Insulating properties of cements are characterized by restorations (fillings), which are used to its value of thermal conductivity or thermal diffusivity restore tooth structure loss, usually resulting from but > Thin residual layer of dentin has danger of thermal not limited to dental caries (dental cavities). shock to the pulp when tooth is exposed to hot or cold food. Type III: Liner or base applications > Potential cause of thermal injury to the pulp: Liners - heat from filling material liberated during setting > Dental liners provide a thin barrier that protects the - Base that sets by an exothermic reaction pulpal tissue from irritation caused by physical, mechanical, chemical and biologic elements. 2. Chemical Barrier > Suspensions of an oxide or hydroxide in an organic > Phosphoric acid in silicate materials and acrylic solvent varnish monomers in some resin-based material > lining cavities were used to reduce the passage of toxic > Cements themselves may contain irritants materials from restoration through the > Create an adhesive bond at the tooth/restoration dentinal tubules and "reduce "microleakage. interface so that leakage at the margins may be eliminated or reduced. Bases > Dental bases provide pulpal protection. 3. Electrical Barrier - Protective base: Protect the pulp before the restoration > Insulating cement helps to prevent galvanic shock. is placed. > Most of the cement material used are water-based or - Insulating base: Protect the tooth from thermal shock. contain polar organometallic compounds– not an ideal - Sedative base: Soothe a pulp that has been damaged electrical insulator by decay or irritated by mechanical means. > Varnish consisting of less polar resins (polysterene) > Stronger than a liner may be used to provide some electrical barrier > Provides thermal insulation 4. Strength and Flow > Support restorative material > Lining should remain intact during the placement of > Release fluoride filling material. > Some maybe irritating to the pulp before the setting > Factors that affect lining integrity reaction is completed 1. Degree of set achieved at the time the filling material > Maybe used in conjunction with a liner is placed > do not have adequate strength 2. Strength of set materials and its thickness > too soluble for use as a permanent cement 3. Type of cavity Dental Materials Lec - Midterm  September 2024 Classification of Bases Liquid Water Based Cement 1. Eugenol 1. Glass Ionomer > organic liquid that is a weak acid 2. Zinc Polycarboxylate Cement > major component of oil of cloves 3. Zinc Phosphate Cement > has distinctive smell and taste Oil Based Cement > phenol derivative that is antibacterial 1. Zinc Oxide Eugenol > obtundent to the pulp Resin Based Cement > inhibits free radical polymerization 1. Esthetic Resin Cement 2. Ethoxybenzoate Acid (EBA) 2. Adhesive Resin > raises the strength of the cement 3. Self-Adhesive Resin Cement 3. Cottonseed oil 4. Temporary Resin Cement Setting Reaction of ZOE Cement 5. Compomer Cements H2O + Zinc Oxide + Eugenol → Zinc Eugenolate Cement Based on Phosphoric Acid 1. Zinc Phosphate Cement Types of ZOE Cement 2. Silicophosphate Cement 1. Unreinforced ZOE 3. Copper Cement > only used when strength and solubility are not critical Cement Based on Organometallic Chelate Components > formulation for temporary restorations 1. Zinc Oxide Eugenol > Compressive strength 20 Mpa 2. Ortho-ethoxybenzoic Acid (EBA) Cements > Obtundent property 3. Calcium Hydroxide Cements > Has free eugenol – batericidal Cement Based on Polyacids > Affects polymerization of composite or resin based 1. Polycarboxylate Cements adhesive luting materials 2. Glass Ionomer/ Polyalkenoate Cement > Causes discoloration and softening of composite surface Chemistry of Dental Cements > Not suitable for luting – temporary basis A. Formulation - Leached eugenol is replaced by water which causes 1. Dental cements are typically powder and liquid hydrolysis of zinc eugenolate and disintegration of system. cement structure. 2. The liquid is an acid Uses: linings, temporary luting, Temporary filling 3. The powder is a base material, Root canal filling material 4. The powder must be insoluble in oral fluids but reactive with acids 2. Reinforced ZOE ____________________________________________________________________________________________________________ > stronger and less soluble > used for temporary and intermediate bases A. Zinc Oxide Eugenol Cement additives include alumina, rosin and polymethyl > A very old and yet useful cements methacrylate resin > Its obtundent property makes it useful for sedative and > Compressive strength is 40 MPa temporary fillings > Can withstand amalgam condensation forces 3. ZOE- EBA (Ortho ethoxybenzoic Acid) > Supports overlying amalgam restoration > stronger and less soluble > Biocompatibility is very good > Set material stronger than reinforced ZOE > May cause hypersensitivity reaction > used for intermediate bases > Small amount of water causes accelerating effect > additives include ethoxybenzoic acid > Compressive strength is 85MPa Components of ZOE Cement > Lower level of residual eugenol Powder > Use: lining, primarily used as luting 1. Zinc Oxide Powder > Zinc Oxide is the only insoluble, nontoxic, reactive Mixing of the Cement oxide or hydroxide available to react with the acid 1. The powder is measured and dispensed with a scoop. > Zinc oxide has some antibacterial effect 2. The liquid is dispensed as drops. 2. Rosin 3. A glass slab is used for mixing the powder/liquid ZOE. 3. Zinc Stearate 4. The powder is forced into the liquid using a cement 4. Zinc Acitate spatula. 5. Aluminum oxide 5. Mixing process first incorporates large increments > controls the setting rate than smaller increments. > mechanically reinforces the resulting cements 6. Clean-up Dental Materials Lec - Midterm  September 2024 > wash off material with water before the material sets 2. Set material is difficult to remove from slab and > soap assists in clean up spatula. > set ZOE can be dissolved in organic solvent (alcohol, Control of Setting Time orange solvent) > lower the temperature during mixing 7. Setting Reaction > rate of adding the powder to the liquid > water accelerates the setting reaction > the longer is the mixing time the slower the setting time 8. Removal of Excess > the more liquid employed in ratio to the powder the > remove with spoon excavator while the material has longer the setting time (not acceptable) not set. Things to Remember B. Zinc Phosphate Cement > no moisture > Has been used in dentistry for centuries > discard liquid when cloudy or forms crystals > At one time it was the strongest and least soluble > phosphoric acid solution absorbs water, do not leave cement available bottle open > Used mainly for retention of cast metallic restorations, bases, and for cementing orthodontic bands C. Polycarboxylate Cement > pH is 2-4 and increases to nearly neutral after 48 hrs. > powder liquid system, powder mixed with water > Set material is opaque > cement which has evidence of adhesion to the tooth > Not effective as chemical barrier > not as acidic as zinc phosphate cement and is > Retention of cement is mechanical interlocking biocompatible > not as strong as other cements and has a moderate Components of Zinc Phosphate Cement solubility Powder > Compressive strength 80MPa 1. Zinc Oxide > acidic 2. Magnesium Oxide > Difficult to handle in clinical setting 3. Silicone dioxide - It tends to be rubbery during setting reaction 4. Other oxide (e.g. Bismuth and Silica) - Adhere to stainless steel Liquid > Bonds with enamel and dentin 1. Water solution of phosphoric acid (40%) - Weak with gold 2. Metallic salts – slows down the setting reaction, - No predictable bond with porcelain buffers - Bonds to non-precious metal 3. aluminum phosphate - Strong bond with stainless steel (orthodontic band) > Set material is opaque Properties of Zinc Phosphate Cement > Uses: luting cements for crowns, bridge and inlay, > cement is strong and has low solubility compared to cavity base material, occasionally used for attachment other cements of orthodontic bands > has low pH > irritating to the pulp Components of Polycarboxylate Cement > cement set into a hard brittle material Powder > can support amalgam condensation forces 1. Zinc oxide > can support overlying amalgam restoration 2. Magnesium oxide 3. Calcium hydroxide Setting Reaction 4. Fluoride Zinc Oxide + Phosphoric Acid → Zinc Phosphate + Heat 5. Metallic salts- modify the setting reaction Mixing the Zinc Phosphate Cement *Freeze dried polyacrylic acid (powder mixed with water) 1. Dispensed as scoop of powder and drops of liquid Liquid 2. A cement spatula and glass slab is used to mix the 1. Aqueous solution of polyacrylic acid material. 2. Copolymers 3. Powder is divided into portion Setting Reaction 4. Powder is added to the liquid in increments Zinc Oxide + Polyacrylic Acid → Zinc Polyacrylate 5. Adding the powder slowly at 15 sec intervals for a total mixing time of 1 1/2 min. Manipulation 1. Dispensing of powder and liquid Clean Up 2. Powder is rapidly incorporated into the liquid in large 1. Glass slab and cement spatula and washed with tap quantities water and soap before the material sets. 3. Mix should be completed in 30-40 sec Dental Materials Lec - Midterm  September 2024 4. Mix will appear thicker than the other cement mixtures 5. Meticulous clean surface is necessary to provide Clean Up intimate contact with the cement and tooth. > clean-up with water is very easy and should be done before the material sets. Properties of Polycarboxylate Cement > set material will chemically bond with stainless steel. > pH of the cement is 1.7 > produce minimal irritation to the pulp (biocompatible) E. Resin Modified GI Cement > adhesion occurs by the chelation of the calcium of the > Powder/ liquid mixing prior to light activation of apatite in enamel and dentin by the carboxyl group of the polymerization polyacrylic acid > Encapsulated form Theories explaining the reaction of Pulp to the Component of RMGI Cement Polycarboxylate cement Powder – ion leachable glass 1. Large size of the polyacrylic acid molecule Liquid 2. Polyacrylic acid molecule tendency to complex with 1. Methacrylate resin – allows polymerization protein limiting its diffusion through the dentinal tubules 2. Poly Acid- reacts with ion leachable glass 3. Hydroxyethylmetharylate (HEMA)- enables both the D. Glass Ionomer Cements resin and acid component to co-exist in aqueous > similar in both composition and handling solution characteristic to the silicate cement 4. Water – essential component required to allow > become popular as result of their physical and ionization of acid component so that the acid-base mechanical properties and clinical performance reaction can occur Components of GI Cements 5. Activators Powder 6. Stabilizers 1. Calcium alumino silicate glass particle Development of GI Cement 2. Fluoride 1. Traditional glass Ionomer Liquid - Hybrid formulation of silicate and polycarboxylate. 1. Polyacryli-itaconic acid copolymer Using alumniosilicate powder of silicate cement and the Properties of GI Cements polyacrylic acid liquid of polycarboxylate. > strongest and least soluble dental cements - ASPA – Aluminosilicate polyacrylic Acid > adheres to the tooth and releases fluoride 2. Amalgam Substitute > good biocompatibility - “miracle mixture” (amalgam alloy admixed with > bonds to stainless steel and alloys for ceramometal cement) > Compression strength is 130MPa - Cermet-particle reinforced > More translucent-unreacted glass rather than zinc 3. Light-Cured GI oxide > liners and bases > Radiopaque – barium salts or metallic silver > HEMA (Hydroxyethyl methacrylate) added to liquid component Setting Reaction of GI Cement > Modified by: Polyacrylic acid + Aluminosilicate Glass → Metal * Adding comonomers (maleic acid, itaconic acid and/or fluoride ions +Polyanions → Salt gel matrix tartaric acid) to polyacrylic acid Mixing of GI Cement * Smaller powder particle size 1. The powder is dispensed with a scoop and the liquid 4. Hybrid or resin-modified Glass Ionomer is dispensed in drops. > cements, restorative filling, cores 2. A cement spatula and mixing pad is typically used. > HEMA and other monomers added to liquid - the plastic coating prevents the paper from absorbing components the liquid > polymers added to powder components 3. Follow manufacturers recommended powder/liquid 5. Polyacid-modified Resin ratio > Composites (Compomers) 4. Mixing should be completed 60 sec or less. - cements, restorative material, cores 5. The cement should be seated within 2 mins. from start - similar to hybrid of mix. - with exception of water 6. The powder is mixed into the liquid in two increments 7. The mixed material must be placed while the cement F. Calcium Hydroxide surface appears glossy, if there is loss of gloss adhesion > at one time very popular is reduced or lost. > placed under most composite resin restoration Dental Materials Lec - Midterm  September 2024 > promote formation of tertiary dentin > maybe applied to the surface of new metallic > recommended when cavity preparation leaves little > restorations to reduce galvanic action. dentin covering the pulp (indirect pulp capping) or > Components of Varnish when a micro pulp exposure (direct pulp capping) is > Natural gum – copal, rosin or synthetic resin suspected > organic solvent – acetone, chloroform or ether Types of CaOH Application of Varnish 1. Liner- has thinner consistency than base. Oldest > varnishes are fluid substance that is readily painted on calcium hydroxide was weak and was used a liners. the surface of the prepared cavity 2. Bases – layer of material that acts as insulator and > solvents rapidly evaporate leaving a film that protects protective barrier beneath restorations. Has thicker the underlying tooth structure consistency and stronger than the liner > two application of the varnish is required Components of CaOH > calcium hydroxides are supplied in paste-paste system > one paste contains calcium hydroxide in distilled water > second paste contains salicylate (weak acid similar to eugenol) > titanium oxide – filler Paste 1 Calcium Hydroxide (50%) - primary reactive; ingredient Zinc Oxide (10%) - primary reactive; ingredient Zinc Stearate (.5%) - Accelerator Ethyl toluene sulphonamide (39.5%) –Oil compound, act as carrier Paste 2 Glycol salicylate (40%) – primary reactive; ingredient Titanium dioxide Calcium sulfate inert fillers, pigments Calcium tungstate Mixing of CaOH 1. the pastes of the same amount are dispensed on a mixing pad 2. an applicator is used for mixing the paste 3. mixing should achieve a homogeneous color of the paste Properties of CaOH > setting reaction of calcium hydroxide is accelerated by water > moisture present in dentin causes material to set in a few seconds. > Very low viscosity- hard to apply to cavity in thick section > set material relatively weak 8-20 Mpa > Antibacterial property > Calcium hydroxide is readily leached out generating an alkaline environment Clean Up > allow to set and scrape the material with any metallic instrument. G. Varnish > serves as protection against acids of dental cements > reduce leakage of mouth fluids around the restorations Dental Materials Lec - Midterm  September 2024 Dental Materials Lec - Midterm  September 2024 End. Dental Materials Lec - Midterm