Project submitted by:

2. Project submitted by: • A S ARYA ( 11D001 ) • ADISHA L V ( 11D004) • AISHWARYA A V ( 11D007) • AMEENA INAS (11D010) • AMEENA SALIH (11DO11) • AMEERA T P (11D012) • AMINA ABDUL SALAM (11D013)

3. Objectives • Provide general review of types of dental impression materials • Provide general information on physical and handling properties and indication for dental impression materials

4. INTRODUCTION IMPRESSION MATERIALS are very important auxiliary materials used to obtain exact replica of the oral structures from this positive hard (cast) can be prepared for construction procedure of oral appliances or study models or diagnostic purposes.As the procedure for fabrication of prosthesis like a acrylic dentures ,metal and ceramic applianceare complicated and involve,hightemperatures,sophisticatedequipments and laboratries,such positive duplicates are used bythe technician or dentist in the absence of patient. DEFENITION An impression can be defined as an exact negative replica of the teeth and its associate oral tissues with accurate reproduction of all finer details maintaining correct spatial dimensions

5. Impressionmaterials Used to register and reproduce the form and relationship of the tooth and oral tissues. Recorded of a portion of a tooth,a single tooth,severaltooth,entire dentulous or edentulous arches or even peri oral and extraoral structures. Impression materials are generally carried to the patients mouth by an impression tray.After the material sets in patients mouth impression is pulled out with the help of the tray .This gives negative replica of patients mouth which is poured with gypsum material to get a positive replica on which the oral appliance are fabricated.Therefore impression stage is the first stage and very important stage involving the fabrication of dental appliaces.

6. Ideal requirements 1.Biocompatibility and chemical properties Non poisonous,nonirritant,non allergic to oral tissues Acceptable taste and odour Chemically inert in oral condition Compatible with die

7. 2.Rheological- low viscosity-viscosity should increase quickly-pseudoplastic nature3.mechanical properties-high elasticity and complete elastic recovery-adequate compressive strength-high tear strength-high flexibility or strain in compression4.thermal properties-thermoplastic materials should have low softeningtemparatures.-very low or zero coefficient of thermal expansion-high thermal conductivity

8. 4.aesthetics.-good color contrast is required-fairly good color stability5.other minor requirements-good diamensional stability -long shelf life,easily available-able to sterilize and reuse

9. Classification of impression materials According to chemical composition: 1.Impression compound 2.Impression waxes 3.Impression plaster 4.Zinc oxide eugenol impression paste

10. Mechanical properties • Elastic imprssion material eg:hydrocolloids .Non elastic impression materials: eg:impressioncompound,impr.waxes,impr.plaster

11. The force extered on soft tissues • Mucostaticimpression materials-not exert any forceswhich distort the soft tissues durringrecordind impression. • Mucocompressive :force cause distortion;impreesioncompound,viscous alginates

12. The nature of setting : .Material set by physical change Eg:impressioncompound,agar agar .Dispensing system: POWDER-ALGINATE 2 Paste System –ZNOE impression paste;poly silicones single paste-light acti.poly ether Gels-agar agar

13. Special uses: syringe materials:eg:light body elastomer .Tray mateials:HEAVY BODY ELASTOMERS,TRAY COMPOUND,PUTTY LIKE ELASTOMER .Bodermouldingimpressoin material-Green stick compound

14. IMPRESSION TRAYS

15. Impression trays are rigid metallic or plastic devices used for supporting the unset impression material for carrying to the mouth, recording the impression, allowing to set or harden, removal of impression without distortion, pouring the cast or model materials.

16. Classification of Impression Trays • Availability a) stock trays of standard sizes b) special, custom made, individualised secondary impression trays c) special rim-lock trays(metals) d) Reusable and disposable trays

17. Depending on retention a) Perforated trays b) Non perforated trays • Depending on the impression materials/ technics a) Perforated for alginates b) Non perforated for impression compound c) Special trays for ZnOE and elastomers d) Rim lock trays for agar- agar

18. According to patients arch-size a) Maxillary(upper) arch- U1,U2,U3,U4 b) Mandibular (lower) arch- L1,L2,L3,L4 • Type of impression a) Full length ( complete) impressions b) Sectional trays ( perforated, reusable, disposable)

19. Oral conditions a) Dentulous impression trays- perforated for hydrocolloids, adhesive coated for elastomers b) Edentulous impression- non perforated trays

20. Impression trays..

21. STOCK TRAYS • Stock trays are available in standard sizes. There are two varieties; • Reusable stock trays are supplied with or without perforations and usually made out of stainless steel. • Disposable stock trays are usually perforated and made up of polymer such as nylon or polystrin.

22. Advantages: • Eliminates time and expense of fabricating trays. • Metal stock trays are rigid. • They can be sterilized and reused. • Disadvantages • Non uniform thickness of impression. • Must be sterilized before using for other patient. • Requires more bulk of material.

23. SPECIAL TRAYS • These are fabricated from a primary cast of patients mouth and these are disposable trays. • These trays are usually made out of shellac or similar thermoplastic materials and also by acrylic resins; • Heat cure acrylic resins • Cold cure acrylic resins

24. Advantages: • Less to moderate impression material required and less wastage. • Uniform thickness of impression is achieved due to spacers. • Since trays are disposable, no sterilization required. • More accurate impression. • Disadvantages: • Fabrication of trays are time consuming process.

25. Selection of trays • a) Based on relative need of retention of impression material • b) Based on type of impression material to be used • c) Based on patients arch size • d) Based on the arch length -Full arch length trays -Sectional trays

26. Properties required for impression trays: • Trays should not be too rigid, can distort or displace the soft tissues. • Trays must not be too flexible • Impression material should adhere to the tray

27. IMPRESSION COMPOUND

28. Impression compound is a muco compressive, thermoplastic,non elastic impression material used to take the preliminary impression of edentulous arches in the preparation of complete denture.

29. ALTERNATIVENAMES • IMPRESSION COMPOUND • DENTAL COMPOUND • MODEL COMPOUND • MODELLING COMPOUND

30. TYPES OF IMPRESSION COMPOUND Two types of impression are available • Type I impression compound • Type II impression compound

31. SETTING ACTION • Impression compound sets by physical change , i.e. it is softened by heating and hardened by cooling.

32. PROPERTIES • BIOLOGICAL PROPERTY It is non toxic , non irritant , non poisonous to oral tissues. • RHEOLOGICAL PROPERTY Impression compound is highly viscous and muco compressive impression material. • THERMAL PROPERTIES • Fusion temperature:Impression compound has a fussiontemperatureof 43.5°C. • Thermal conductivity:Impression compound is a poor conductor of heat. • Co- efficient of thermal expansion(COTE):They have high thermal expansion and contraction . The COTE value is 200-500 PPM/°C

33. DIMENSIONAL STABILITY : Residual mechanical stresses are commonly during heating and manipulation as well as during the actual process of recording the impression.

35. MANIPULATION • REQUIREMENTS: Temperature controlled water bath or air bath or open flame • There are 2 technique of kneading of the impression compound • Wet Kneading • Dry kneading

36. PROCEDURE TO RECORD IMPRESSION • The technique for softening consists of submerging the compound in water bath heated at about 60°C. • After the material has reached sufficient temperature to uniformly soft it is customerely kneaded with fingers to produce a uniform state of plasticity. • At this point the impression compound is placed in a non – perforated stock tray.

37. After the compound is moulded to the shape of impression tray is inserted it is inserted to mouth. • The impression is retained until it cools to body temperature of 37°C. • Since it has a rather low conductivity,it may b hardened on the surface although, the inner portion may b considerably hot and softer. • Premature removal from the mouth result in warpage or distortion. • After the impression compound hardens,the impression is removed from the mouth,washed,dried,trimmedand cast is poured.

38. PRECAUTION • When direct flame is used the compound should not be allowed to igniteor boil.so that the important constituents are not violated. • Prolonged immersing or heating in water bath, makes it brittle and grainy and some of the low molecular weight ingredient may leach out causing stickiness and grainy surface. • Undue kneading of compound in order to produce plasticity can incorporate water into the compound or mateial and flow after hardening will be increased,so it should be avoided.

39. Water bath should be lined with napkin to prevent the compound from sticking to the sides of the bowl. • Adequate time must be given for uniform softening and hardening due to low thermal conducitivity. • Premature removal from the mouth should be avoided as it may result in distortion of impression. • Cast should be poured as sson as possible,delay cause realxation of internal stresses and distortion.

40. ADVANTAGE • It can be used in combination with other material. • It is reusable and economical. • It can be added to and readopted • It has long shelf life of about 5 years • Non – toxic all well tolerated by the tissue of the mouth.

41. DISADVANTAGES • It is non- elastic and should not be used when undercut exists,or dentulous cases. • Does not reproduce all the fine sufacedetailsrequired,as it is muco compressive. • As it can not be sterilised,it tends to become unhygienic and should not be reused ideally. • Its thermal properties are not ideal ,it has large coefficient of thermal expansion (COTE), and it is a very poor conductor of heat,which leads to distortion.

42. USES • Type I impression compound is used to record the preliminary impression of edentulous arches in preparation of complete dentures. • Green stick compound(Type I) is used to tske tube impression for inlays and crowns. • Used for border moulding. • Type II impression compound is used to prepare special trays for recording secondary impression or corrective wash impressions.

43. Zinc oxide eugenol impression material

44. ZnoE • DEFINITION: • It is mucostatic,inelastic,chemically setting impression materials used for recording secondary/corrective wash impressions of edentulous arches in preparation of complete dentures

45. COMPOSITION OF ZINC OXIDE EUGENOL PASTE

46. ZnO+H₂O(moisture)→Zn(OH)₂ • Zn(OH)₂+2HE→ZnE₂+2H₂O • ↓ • (BASE) (ACID) ZINC EUGENOLATE(CHELATE PRODUCT) SETTING REACTION

47. PROPERTIES BIOLOGICAL PROPERTY • Non toxic,can be irritant giving burning sensation to the patients,mayproduce allergic sensation • RHEOLOGICAL:shouldnotbe too long as it cause inconvenience to the patient&should not be too short as the materials cannot be manipulated • Final setting time for type 1:<10 minutes • Final setting time for type 2:<15 minutes • Hardness:by Krebs Penetrometer:to find the hardness of set material • Penetration hardness for type 1<.5mm b.Penetration hardness for typ e 2 is b/w .8 &1.5 3.CONSISTENCY:has thinner consistency&good flow property • DIMENSIONAL STABILITY:very low diamensional changes during setting(<0.1%)%no diamensional changes after setting. • ELASTICITY:inelastic&cannot used for recording undercuts> • STRENGTH:7MPa.afteer 2hrs from the start of mixing. • SHELF LIFE:upto 1yr

48. MANIPULATION • INSTRUMENTS:glass slab /oil impervious paper pad.stiff stainless steel spatula • PROCEDURE: the proprotionating of two pastes obtained by squeezing outropes of pastesof same length on the glass slab.a flexible stainless spatula is to be used for mixing.the reactor paste is first collected&applied over the base&mixed with broad stokes in a sweeping motion until a uniform homogeneous color mixing is 1min. • Mix is collected &spread over the dry tissue surface of the special tray &placed in the mouth .it is held firmly in position until the material has uniform hardenedafter set impression is removed another increment of mix can be placed on the distorted area &better impression can be obtained out the old materials from the special tray &record a new impression. • The impression is well rinsedunder running cold water for the removal of saliva&cast is poured in dental stone.cast can be separated from impression by imersion in hot water of 45-60º for 5-10 minutes.

49. o ADVANTAGES: • mucostatic, • Diamensioally stable • Easily manipulated DISADVANTAGES: • Cannot be used when undercuts exists. • Requires special trays • Unpleasant to some patients USES: • For recording corrective wash impressions of edentulous • Modified ZnOE pastes can be used: • Surgical pastes • Bite registration paste • Non eugenolpaste

50. MODIFICATIONS OF ZnOE IMPRESSION PASTES 1.SURGICAL PASTES a modified ZnOE paste with longer setting time Can be used after gingivectomy as intra oral bandage to protect cut surfaces&to prevent infection of tissues POWDER &LIQUID SYSTEM