Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Dental cements /certified fixed orthodontic courses by Indian dental academy


Published on

Welcome to Indian Dental Academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy has a unique training program & curriculum that provides students with exceptional clinical skills and enabling them to return to their office with high level confidence and start treating patients

State of the art comprehensive training-Faculty of world wide repute &Very affordable.

Published in: Education
  • Be the first to comment

Dental cements /certified fixed orthodontic courses by Indian dental academy

  1. 1. DENTAL CEMENTS INDIAN DENTAL ACADEMY Leader in Continuing Dental Education
  2. 2. TERMINOLOGY Cement – Substance that hardens to act as a base, liner, filling material, or adhesive to bind devices and prostheses to tooth structure or to each other. Base – Layer of insulating, sometimesmedicated, cement, placed in the deep portion of the preparation to protect pulpal tissue from thermal and chemical injury.
  3. 3. Cavity Liner – Thin layer of cement, such as a calcium hydroxide suspension in an aqueous orresin carrier (after evaporation), used forprotection of the pulp; Varnish – A solution of natural gum, synthetic resins, or resins dissolved in a volatile solvent, such as acetone, ether, or chloroform.
  4. 4. Intermediate restoration – Tooth filling orprosthesis that is placed for a limited period, fromseveral days to months, and is designed to sealteeth and maintain their position until a long-term restoration is placed; Luting agent – A Viscous material placedbetween tooth structure and a prosthesis thathardens through chemical reactions to firmlyattach the prosthesis to the tooth structure.
  5. 5. CEMENT BASESDEFINITION: - A base is a layer of cement placed under thepermanent restoration to encourage recovery ofthe injured pulp and to protect it againstnumerous types of insult [thermal, chemical orgalvanic] to which it may be subjected.
  6. 6. TYPES: 1. High strength bases: are used to provide thermalprotection for the pulp , as well as mechanical support forthe restoration. 2. Low strength bases: have minimum strength and lowrigidity . Their main function is to act as a barrier toirritating and to provide therapeutic benefit to the pulp.
  7. 7. HIGH STRENGTH BASES LOW STRENGTH BASES- Zinc phosphate - Calcium hydroxide- Zinc polycarboxylate - Zinc oxide Eugenol- Glass ionomer cement [type III]- Reinforced Zinc oxide Eugenol
  8. 8. ZINC PHOSPHATE CEMENT: It is the oldest of the luting cementsINDICATIONS : - Luting of restorations - High strength bases - Temporary restorations - Luting of orthodontic bands and brackets
  9. 9. CLASSIFICATION: Type I: Fine grained for luting. Film thickness should be 25 um or less. Type II: Medium grain for luting and filling. Film thickness should not be more than40 um.
  10. 10. MODE OF SUPPLY: I. Powder and liquid system. II. Capsules of preproportioned powder and liquid
  11. 11. COMPOSITION: POWDER:- Zinc oxide : 90.2% Principal constituent- Magnesium oxide : 8.2% Aids in sintering- Other oxides : 0.2% Improves smoothness of mix [ like bismuth trioxide, calcium hydroxide, barium oxide]- Silica : 1.4% Filler, aids in sintering.
  12. 12. LIQUID: - Phosphoric acid : 38% Reacts with zinc oxide - Water : 36% Controls rate of reaction - Aluminium phosphate : 16.2% Buffers, to reduce or zinc phosphate rate of reaction - Aluminium : 2.5% - Zinc : 7.1%
  13. 13. SETTING REACTION: - When powder is mixed with liquid, the phosphoricacid attacks the surface of particles , dissolving thezinc oxide forming acid zinc phosphate. - The aluminium of the liquid is essential for cementformation. The aluminium complexes with thephosphoric acid to form a zinc aluminophosphate gel .SETTING TIME: 5 to 9 minutes.
  14. 14. CONTROL OF SETTING TIME: a) Manufacturing process- 1. Sintering temperature: Higher the temperature ,more slowly the cement sets. 2. Particle size : Finer particles react more quickly as a greater surface area is exposed to the liquid. 3. Water content of the liquid: excess water acceleratesthe reaction whereas less water retards the reaction. 4. Buffering agents : slow down the reaction.
  15. 15. b) Factors under the control of operator: 1. Temperature: Higher temperature accelerates the reaction. 2. Powder/liquid ratio: More liquid employed ,slower the reaction. 3. Rate of addition of powder to liquid: The reaction is slower if the powder is incorporated into the liquid slowly. 4. Mixing time: Longer the mixing time, slower is the rate of reaction.
  16. 16. PROPERTIES: 1. COMPRESSIVE STRENGTH: Maximum strength is attained in the first day 103.5Mpa(15000Psi) Factors affecting strength are: a) Powder/ Liquid ratio: More the powder added into liquid, greater is the strength. b) Water content: A change in the water content of the liquid, either loss or gain, reduces the strength. 2. TENSILE STRENGTH: This cement is weaker in tension, thus making it brittle. 5.5Mpa(800Psi)
  17. 17. 4. MODULUS OF ELASTICITY: 13 Gpa 5. SOLUBILITY AND DISINTEGRATION: Shows relatively low solubility. 0.06% wt 6. FILM THICKNESS: The smaller the particle size,less is the film thickness. 7. THERMAL PROPERTIES: Are good thermalinsulators and may be effective in reducing galvanic effects. 8. ADHESIVE PROPERTIES: The retention is bymechanical interlocking of the set cement with the surfaceroughness of the cavity and restoration.
  18. 18. 8. BIOLOGICAL PROPERTIES: - Due to the presence of phosphoric acid , theacidity of the cement is quite high at the time they areinserted in the tooth. - 3 min after start of mixing Ph is 3.5 and laterrapidly approaches neutrality in 24 to 48 hours. Therefore damage to the pulp by acid occursduring the first few hours after insertion.
  19. 19. MANIPULATION: - A cool glass slab is used in order to delay the settingand allow more powder to be incorporated before thematrix formation occurs. - The liquid should be dispensed just before mixing. - The powder is added in small increments. Recommended ratio is 1.4gm/ 0.5ml - Mixing is initiated by addition of a small amount ofpowder at a time into the liquid. A large area is covered during mixing in order todissipate the exothermic heat. - Spatulation is carried out with a brisk, circular motionof the spatula.
  20. 20. - Each increment is mixed for 15 to 20 sec before thenext increment is added. Mixing time : 1 min 20 sec. - The field of operation should be kept dry during theentire procedure.
  21. 21. ZINC OXIDE EUGENOL - Zinc oxide eugenol (ZOE) is the mostwidely used temporary restorative material. - It seems to have been developed fromzinc oxy-chloride cements, which consisted of a powder: 75% zinc oxide and 25%pulverized glass or silica and liquid: zinc chloride and a little borax. - They were slow setting, and anotable shrinkage was generally observed.
  22. 22. - As an approximately neutral pH of7.0. - Unfortunately its strength is notsufficient enough to resist forces ofmastication, lacks resistance to wear and hasrelatively high solubility in the oral cavity.
  23. 23. APPLICATIONS :1. Base2. Temporary cementation3. Temporary restoration4. Cavity liner5. Endodontic sealer
  24. 24. Classification :ADA specification No. 30 has listed 4 typesType I: Temporary cementation.Type II :Permanent cementation.Type III :Temporary filling material and thermal insulation.Type IV : Cavity liners.
  25. 25. COMPOSITIONPOWDER:•Zinc oxide – 69.0% - Principal ingredient•White rosin – 29.3% - To reduce brittleness of set cement•Zinc Stearate – 1.0% - Accelerator, Plasticizer•Zinc Acetate – 0.7% - Accelerator, improvesstrength•Magnesium Oxide – Is added in some powders, it acts with eugenol in a similar
  26. 26. LIQUID :Eugenol – 85.0 – Reacts with zinc oxideOlive oil – 15.0 – PlasticizeSETTING : The setting reaction is a typical acid-basereaction to from a chelate. The reaction is also known asCHELATION and the product is called ZINC EUGENOLATE.
  27. 27. Zn0 + H2O………………..Zn(OH)2 Zn(OH)2 + 2 HE ……………ZnE2 + 2H2O Base Acid the salt (Eugenol) (Zinc Eugenolate) The chelate (Zinc Eugenolate) formed is a matrixsurrounding free zinc oxide particles. The chelate thoughtto form as an amorphous gel that tends to crystallize
  28. 28. - The water formed in the settingreaction aids in biding the individual chelate unitstogether in a chain or in an octahedral structure,or the water may be merely absorbed by the excessZinc Oxide. - The free eugenol content of the setcement is probably very low.
  29. 29. PROPERTIES : 1. Mechanical Properties: a) Compressive strength: -They are relatively weak cements. Thestrength depends on the intended use of thematerials. -For example, cements intended fortemporary purposes like temporary restorationsand cementation (Type I), and cavity lining (TypeIV), will have a lower strength.
  30. 30. - Cements intended forpermanent cementation (Type II) andintermediate restorations will be morestronger. - The compressive strength rangesfrom a low of 3-4 Mpa upto 50-55Mpa. - The smaller the particle size, thestronger the cement. The strength can also www.indiandentalacademy.combe increased by reinforcing with alumina –
  31. 31. b) Tensile strength: Ranges from 0.32 to 5.8 Mpa. c) Modulus of Elasticity: Ranges from 0.22 to 5.4 Gpa.2.THERMAL PROPERTIES: a) Thermal conductivity: Their thermal insulting properties areexcellent and are approximately the same as for humandentin.
  32. 32. - The thermal conductivity of zincoxide-eugenol is in the range of insulators like corkand asbestos. 3.98 (Cal. Sec-1 cm-2 (°C/cm)-1 x 10-4. b) Co-efficient of thermal expansion: 35 x 10-6/°C.3. SOLUBILITY AND DISINTEGRATION: - The solubility of the set cement is high,the highest among the dental cements. - They disintegrate in oral fluids. This breakdown is due to hydrolysis of the zinc eugenolatematrix to from zinc hydroxides and eugenol.
  33. 33. - Solubility is reduced by increasingthe powder/liquid ratio.6. BIOLOGICAL PROPERTIES: a) pH and effect on pulp: They are the leastirritating of all dental cements. In terms of pulpal response they are classifiedas mild. pH is 6.6 to 8.0 b) Bacteriostatic and obtuandantproperties: They inhibit the growth of bacteria andhave an anodyne or soothing effect on the pulp indeep cavities, reducing pain when it is present.
  34. 34. Modified zinc oxide eugenol cements: - To improve upon the working, handlingand setting characteristics, various modificationswere tried and are still being tried. Improvedproperties have been achieved by two approaches:Partial substitution of eugenol by –ethoxy-benzoic acid (EBA) Addition of fused quartz or aluminium oxide or resin polymer to the powder component
  35. 35. Resin reinforced zinc oxide eugenol cements : - The conventional zinc oxideeugenol cements have been modified by theaddition of polymeric substances like polymethylmethacrylate to the powder component. - The degree of reinforcementappears to be dependent to a great extent upon theparticle size and on uniformity of distribution ofthe resinous and inorganic phases of the powdercomponents.
  36. 36. - 20% polymethly methacrylate isusually added to zinc oxide as powder and is mixedwith eugenol along with accelerators like zincacetate and zinc stearate. - Thymol or hydroxyquinoline asantimicrobial agents are added in traces.
  37. 37. The constituents of powder and liquid is as follows:POWDER WEIGHT %Zinc oxide 80.0%Polymethyl-methacrylate 20.0%Zinc stearate tracesZinc accetate tracesThymol tracesLIQUID:Eugenol 85 %Olive oil 15%
  38. 38. - Resin improves the strength,homogenicity and smoothness of the mix,decreases flow, brittleness and solubility. - Resin may physically bond to theother components or react chemically with theeugenol.
  39. 39. - Zinc stearate acts as a plasticizer and zincacetate improves the strength of the cement. - Zinc stearate and zinc acetate also acts asaccelerators. - Olive oil acts as a plasticizer and masksthe irritating effects of eugenol.
  41. 41. Definition (Akinmade & nicholson, 1993) : - Water based cement where-in followingmixing, the glass powder & polyalkenoic acidundergo an acid/base setting reaction. - The acid attacks the surface of powderparticles, releasing calcium & aluminium ions, thusdeveloping a diffusion-based adhesion betweenpowder & liquid.
  42. 42. INDICATIONS: - For eroded areas like erosion, abrasion and class Vrestorations. - Anterior esthetic material for class III cavities. - As luting agent - As liners and bases - For core build-up - To a limited extend pit and fissure sealants.
  44. 44. Pits and fissures Primary Teeth restorations Bracket Bonding
  45. 45. Luting of crowns Core
  46. 46. CONTRAINDICATIONS: Class IV carious lesions of fractured incisors. Lesions involving large areas of labial enamelwhere esthetics is of major importance Class II carious lesions where conventional cavitiesare prepared; replacement of existing amalgamrestorations. Lost cusp areas.
  47. 47. CLASSIFICATION: According to skinners: Type I – Luting Type II- Restorative Type III- Liner and base According to Sturdevent:1. Traditional or conventional2. Metal modified GIC a. Cermets b. Miracle mix3. Light cured GIC4. Hybrid (Resin modified GIC)5. Polyacid modified resin composite or Compomer
  48. 48. According to clinical use as: Type I- Luting TYPE II- Restorative Type III- Liner/ Base Type IV- Pit & Fissure Sealant Type V- Luting for Orthodontic Purpose Type VI- Core build up material Type VII- High fluoride releasing GIC Type VIII- ART Type IX- Geriatric & Paediatric GIC
  49. 49. COMPOSITION OF CALCIUM FLUROALUMINOSILICATEGLASS POWDER: COMPONENT WEIGHT% SiO2 [quartz] 29 Al2O3 [alumina] 16.6 CaF2[fluorite] 34.2 Na3AlF6[cryolite] 5 AlF3 5.3 AlPO4 9.9
  50. 50. POWDER: - The composition of the glass is an acid solublecalcium aluminosilicate glass. - Formed by fusing silica[Sio2], alumina [Al2O3],calcium fluoride / fluorite(CaF2), at 11000C to 15000Ctemperature. - The glass is crushed, milled and then ground to afine powder {20u – 50u)
  52. 52. LIQUID: - The liquid was an aqueous solution of polyacrylicacid in a concentration of about 50%. - The liquid was quite viscous and tended to gel overtime. Hence, acrylic acid was copolymerised with other acidssuch as iticonic ,maleic,and tricarboxylic acid.
  53. 53. SETTING REACTION : The setting reaction of glass Ionomer cements involves three overlapping stages.Stage1: DissolutionStage2: Precipitation of salt, gelation and hardeningStage3: Hydration of salts.
  54. 54.
  55. 55. ADHESION: - Glass ionomer cements have the important propertyof adhering to untreated enamel and dentin. - It reacts with the smear layer on cut dentin and alsobonds to other reactive polar substrates such as the basemetals.
  56. 56. ADHESION OF GIC: - Polyalkenoic acid attacks the dentine andenamel and displaces phosphate and calcium (orstrontium) ions. - These migrate into the cement and developan ion enriched layer firmly attached to the toothstructure. - Dentinal tubules will remain sealed andmicroleakage can only occur into the cement.
  57. 57. Comparative properties of glass ionomer cement Property TYPE- I TYPE- II TYPE- III P:L ratio 1.5:1 3:1 3:1 Working time 3.5 2.0 2.0 Setting time 7.0 5.0 4.0 Compressive 120 150-200 120 strength(Mpa) Tensile 9-12 15-20 6-10 sterngth(Mpa) Flexural strength 12-15 18-20 13-16 Surface hardness 160 200 120 Film thikness(uM) 20 - - Coeff.thermal - -6 -6 expansion 13x10 8x10 Solubility 0.1 0.1 0.1
  58. 58. PROPERTIES:PHYSICAL PROPERTIES – EFFECT ON PULP AND CELLS: - The glass Ionomer causes greater inflammatory response than zinc-oxide eugenol cement but less than zinc phosphate cement and the silicates - Freshly mixed materials is very acidic between (0.9 and 1.6) which causes mild inflammatory response of pulpal tissues but it resolves within 30 days and there is no enhancement of reparative or secondary dentin formation.
  59. 59. - Although the glass ionomers are acidic they are lessirritant than silicates - The acid used in glass Ionomer cement i.e. thepolyacrylic acid is weaker than phosphoric acid. - The polyacid chains are large and immobile beingfurther restricted by their affinity for calcium ions in thetooth on which the material is applied.
  60. 60. Fluoride Release: - Fluoride ions released from the restorative materials become incorporated in hydroxyapatite crystals of adjacent tooth structure to from structure such as fluorapatite that is more resistant to acid mediated decalcification. - The fluoride originates from that used in preparing the alumino silicate glass, which can contain upto 23% fluoride
  61. 61. ASTHETICS: - The glass ionomer cement is an aesthetic fillingmaterial because it has a degree of translucency which arisesbecause it’s filler is a glass. - The colour of glass ionomer remains unaffectedby oral fluids as compared to composites which tend tostain. Translucency increases as they age and is reflected by adecrease in opacity.
  62. 62. DIMENSIONAL STABILITY: A correctly manipulated and protected glass ionomer material shows a volumetric setting contraction of approximately 3% which develops slowly through the setting process.
  63. 63. Thermal Properties: The thermal diffusivity value of glass Ionomer cement ions is close to that for dentin. Hence the material has an adequate thermal insulating effect on the pulp and helps to protect it from thermal trauma.
  64. 64.
  65. 65. DISPENSING AND MIXING Glass ionomers are available commercially in two forms:- Powder and liquid supplied separately, or handmixing. Encapsulated, or mechanical mixing.
  68. 68. FINISHING & POLISHING - No finishing for 24 hours. - If essential, sharp blade to reduce gross contour - After 24 hours, fine diamond with air/ water spray for gross contour. - Rubber polishing points for refining - Polishing discs for glossy finish - sealing with resin sealant or vaseline.
  69. 69.
  71. 71. METAL – MODIFIED GLASS IONOMER CEMENTS - Glass ionomer cements lack toughness and hence,cannot withstand high-stress concentrations. - GIC have been modified by the inclusion of metalfiller particles in an attempt to improve toughnessTwo methods of modifications have been employed.
  72. 72. SILVER ALLOY ADMIX or MIRACLE MIX - Sced and wilson (1980) found that amalgamalloys could be incorporated into glass ionomer cementsand that these served to increase the flexure strength. - Spherical silver amalgam alloy powder is mixedwith Type II glass ionomer powder in the ratio 7:1.
  73. 73. - These systems have been used clinically bySimmons(1983). However, their esthetics are poor –theytend to impart a gray to blackish colour to the cementand they do not take burnish.
  74. 74. CERMET – IONOMER CEMENTS: - In an attempt to improve the abrasion resistance and strength of GIC, McLean and Gasser(1985) developed the “cermet”-ionomer. - These cements, unlike simple mixtures of alloy particles or metal fibres, contain glass-metal powders sintered to high density that can be made to react with polyacids to form a cement.
  75. 75. RESIN – MODIFIED GLASS IONOMER CEMENT: -Low early strength and moisture sensitivity of thetraditional glass ionomer was the result of slow acid-basereactions. - Hence to overcome these two inherent drawbacks, somepolymerizable resin functional groups have been added to GICto impart additional curing process and allow the bulk of the
  76. 76. POLYACID – MODIFIED COMPOSITE RESINS “COMPOMERS” A new variety of the usual composite resinscomprising resins and inorganic filler particles is thepolyacid-modified composite resin or “compomer” whichwas introduced in the early 1990s.
  77. 77. The compomer - combination of “comp” form composite and“omer” from glass ionomer was introduced as a type of glassionomer, with claims that it offered some fluoride release aswell as improved physical properties and clinicalcharacteristics.
  78. 78. Zinc polycarboxylate:INDICATIONS: 1. Primarily for luting permanent restorations. 2. As bases and liners. 3. Used in orthodontics for cementation of bands. MODE OF SUPPLY: 1. Powder and liquid in bottles. 2. Powder mixed with water (water settable cements)
  79. 79. COMPOSITION: POWDER - Zinc oxide Basic ingredient - Magnesium oxide Principle modifier and also aids in sintering. - Other oxides like Small amounts Bismuth and aluminium - Stannous fluoride Increases strength , modifies setting time and imparts anticariogenic properties.
  80. 80. LIQUID: - Liqueous solution of polyacrylic acid OR - Copolymer of acrylic acid with other unsaturated carboxylic acids i .e; iticoni c, maleic, tricarboxylic acid. SETTING REACTION: - When the powder and liquids are mixed, the surface of powder particles are attacked by the acid, releasing zinc magnesium and tin ions. - These ions bond to the polymer chain via cross – linked salts.
  81. 81. SETTING TIME: 7 to 9 minutes.PROPERTIES:1. MECHANICAL PROPERTIES: - Compressive strength: 5.5 Mpa (80000Psi) - Tensile strength : 6.2 Mpa (900 Psi)2. SOLUBILITY AND DISINTEGRATION: - More soluble than zinc phosphate 0.06% 3. BIOCOMPATIBILITY: - Pulpal response is mild. pH of liquid is 1.0 to 1.7 & the freshly mixedcement is 3.0 to 4.0.www.indiandentalacademy.com5.0 to 6.0 After 24 hrs pH of cement is
  82. 82. 4. ADHESION: - Cement bond chemically with tooth structure.The bond strength to enamel is 3.4 to 13.1Mpa & that ofdentin is 2.07Mpa. 5. THERMAL PROPERTIES: - They are good thermal insulators.
  83. 83. MANIPULATION: - Proportioning 1.5 parts of powder to 1 part of liquid by wt. - The powder and liquid are taken on glass slab. - The powder is incorporated into the liquid in large quantities (90%) MIXING TIME : 30 to 40 sec. - The cement should be used while the surface is still glossy. - When placed in the cavity do not remove the excess, as it passesthrough the rubbery stage it tends to get lifted from the cavity . Remove the excess cement only when it has hardened
  85. 85. DEFINITION: - Calcium hydroxide cements are relatively weakcements commonly employed as direct or indirect pulpcapping agents. - Due to their alkaline nature they also serve as aprotective barrier against irritants from certainrestorations.
  86. 86. INDICATIONS: - For direct and indirect pulp capping. - As low strength bases beneath silicate andcomposite restorations for pulp protection. - Root canal sealer. - In wheeping canals for exudation control. CONTRAINDICATIONS: - It cannot be used in a teeth with a degeneratingpulp tissues as this can lead to calcific type ofdegeneration.
  87. 87. MODE OF SUPPLY: 1. Two paste system containing base and catalystpastes in collpsible tubes . 2. In powder form. 3. Light cured system
  88. 88. BASE PASTE - Glycol salicylate 40% Reacts with calcium hydroxide & zincoxide - Calcium sulphate - Titanium dioxide Inert fillers,pigments - Calcium tungstate Provides radio-opacity
  89. 89. CATALYST PASTE- Calcium hydroxide 50% Principal reactive ingredients.- Zinc oxide 10%- Zinc stearate 0.5% Accelerator- Ethylene toluene- Sulfonamide 39.5% Oily compound, acts as carrier
  90. 90. MANIPULATION: Traditionally, it is formulated by dispersing calcium hydroxide in aqueous or resin carrier solutions to facilitate application to the walls of cavity preperation. The carrier evaporates and leaves a thin layer of calcium hydroxide on the cavity walls.
  91. 91. It can be carried in various ways: - The powder can be mixed with distilled water orsterile saline to form a thick paste. - It can also be suspended in chloroform or plasmaand can be applied with the help syringe. - It may be applied in pure powder form also.
  92. 92. SETTING TIME: 2.5 TO 5.5 minutes. Factors affecting the setting time: - The setting of cement can be accelerated bymoisture and heat. Conversely, the setting time will be retarded bydryness and cold.
  93. 93. PROPERTIES: 1. MECHANICAL PROPERTIES- a) Compressive strength: It has a low compressive strength ,however it increases with time after setting. The strength after 24 hrs ranges from 10 to 27 Mpa. b) Tensile strength: has low tensile strength – 1.0 Mpa c) Modulus of elasticity: 0.37Gpa. 2. THERMAL PROPERTIES: If used in sufficiently thick layers they provide some thermalinsulation. Thickness should not exceed 0.5 mm
  94. 94. 3. SOLUBILITY AND DISINTEGRATION: Solubility is high in water – 0.4 to 7.8% Solubility is more when exposed to phosphoric acid andether. So care should be taken during acid etching andduring application of varnish in present of this cement. 4. BIOLOGICAL PROPERTIES: a) Effect on pulp: It is alkaline in nature due to presence of freecalcium hydroxide in set cement. Ph 9.2- 11.7 b) Helps in formation of secondary dentin.
  95. 95. CAVITY VARNISHDEFINITION: Is a solution of one or more resins whichwhen applied onto the cavity walls, evaporatesleaving a thin resin film, that serves as a barrierbetween the restoration and the dentinal tubules.
  96. 96. APPLICATIONS:1.It reduces the microleakage around the margins of newly placed amalgam restorations, thereby reducing post operative sensitivity.2. It reduces passage of irritants into the dentinal tubules from the overlying restoration or base.Eg: silicate,zinc phosphate etc..3 In case of amalgam restorations it prevent the penetration of corrosion products into the dentinal tubules, thus www.indiandentalacademy.comdiscoloration. minimizing the tooth
  97. 97. 4. May be used as a surface coating over certainrestorations to prevent them from dehydration orcontact with oral fluids; eg; Silicate and GIC. 5. May be applied on the surface of metallicrestorations as a temporary protection in case ofgalvanic shock. 6. In cases where electrosurgery is to be doneadjacent to metallic restorations, varnish applied overthe metallic restorations serves as a temporaryelectrical insulator.
  98. 98. COMPOSITION:- Natural gum : Copal , rosin or synthetic resin.- Organic solvent : alcohol , acetone or ether.- Medicinal agents : Chlorbutanol , thymol or eugenol Some varnishes contains fluorides.
  99. 99. CONTRAINDICATIONS: a) Composite resins – The solvent in varnish may react with or soften the resin. b) Glass ionomer – Varnish eliminate the potential for adhesion and the biocompatibility of the cement. c) When therapeutic action is expected from the overlying cement. Eg: Zinc oxide eugenol and calcium hydroxide.
  100. 100. PROPERTIES: - Varnishes neither possess a mechanical strength norprovide thermal insulation , because of the thin filmthickness. Film thickness ranges between 2 to 40microns. - The solubility of dental varnishes is low , they arevirtually insoluble in distilled water.
  101. 101. MANIPULATION: - The varnish may be applied by using a brush , wire loop on a small pledget of cotton. - Several thin layers are applied. Each layer is allowed to dry before applying the next one. - When the first layer dries , small pinholes develop.These voids are filled in by the succeding varnish applications. The main objective is to attain a uniform and continuous coating.
  102. 102. PRECAUTIONS: - Varnish solutions should be tightly closed to prevent loss of solvent by evaporation. - Should be applied in a thin consistency. Viscous varnish does not wet the cavity walls properly. - Excess varnish should not be left on the margins of the restorations as it prevents proper finishing of the margins of the restorations. - Varnish should be confined to the dentin.