Impression materials used in dentistry.pptx

Dental Impression material

1. Impression materials are used to produce the accurate replicas of intraoral tissues. Materials common ly use can be classified as elastic or non-elastic according to the ability of the set material to be withdrawn over undercuts. Introduction

2. An impression is a negative replica of the tissue of the oral cavity. It is used to register or reproduce the form and relation of the teeth & surrounding tissue . DEFINITION

3. 1782 : William Rae used wax with Plaster of Paris . 1940s: American dentists used Plaster OF Paris for impression & the technique was presented to the profession at large by Chaplin Harris in 1953. 1925 : Alphous Poller of Vienna was granted a British Patent for a totally different type of impression material which was later described by Skinner as Colloidal Sols of Emulsoid type . The possibility of using colloidal substance for dental impression became apparent when Poller’s Negacoll was modified & introduced into the dental profession as Dentacol in 1928. Agar hydrocolloid was introduced to the dental impression. 1930 : JD Hart of Oklahoma began to use Agar for fabrication of cast restoration.

4. 1930 : AW Ward and EB Kelly introduced ZnO Eugenol. 1890s : A chemist from Scotland noticed that Brown Seaweed yielded peculiar mucous extraction. He named it ‘Algin’. 1936-40 : S William Wilding used Algin as a dental impression material 1950s : Development of Rubber base impression materials (Polysulphides and Condensation Silicones) 1960s : Polyether impression material developed in Germany 1970s : Addition silicone was introduced as a dental impression material 1988 : Latest addition and light cure elastomers 1990-2000 : New auto devices and delivery systems

5. Ideal Requirements

6. 1. Pleasant taste & odour 2. Should not contain any toxic & irritating ingredients 3. Adequate shelf life 4 .Easy to disinfect with out loss of accuracy 5.Compatible with die and cast material 6.Dimentionally stabile 7.Good elastic properties 8.Easy manipulation 9 .Adequate setting characteristics 10.Good reproduction details 12.Adequate strength 13.Economical 14.Should not be technique sensitive

7. Classification

8. Based on the mode of setting and elasticity Rigidity material Elastic material Reversible Hydrocolloid Elastomeric Impression Material ZOE Impression Material Impression Plaster Impression compound Reversible: Agar Irreversible: Alginate Polysulfide Irreversible Polyether Addition silicones Condensation silicone

9. BASED ON THE TYPE OF IMPRESSION & AREA OF USED DENTULOUS EDENTULOUS PRIMARY SECONDARY PRIMARY SECONDARY ALGINATE ELASTOMERS AGAR IMPRESSION COMPOUND I MPRESSION PLASTER ALGINATE ZOE IMPRESSION PASTE ELASTOMERS

10. Based on manipulation

11. Based on the tray used for impression

12. Elastomeric Impression Materials

13. Soft and rubber-like known as elastomers or synthetic rubbers As per ADA Sp. No.19- non-aqueous elastomeric dental impression materials Liquid polymers when mixed with a suitable catalyst are converted into solid rubber at room temperature. TYPES :- According to chemistry –     Polysulphides Condensation polymerizing silicone Addition polymerizing silicone Polyether

14. SUPPLIED AS :- All elastomers –two paste systems(base and catalyst) Putty consistency – supplied in jars USES :- Impression material for all applications including Fixed partial dentures Dentulous and edentulous impressions Border moulding of special trays(polyether) Bite registration As duplicating material for refractory casts

15. POLYSULFIDE IMPRESSION MATERIAL This was the first elastomeric impression material to be introduced. It is also know as MERCAPTAN or THIOKOL. Mode of supply: It is supplied in collapsible tube as base & accelerator in paste form. Base in white color & accelerator is in gray color. It is available in three viscosities:- Light bodied Medium bodied Heavy bodied Commercial names: Permlastic (Kerr) Coe-flex: lead dioxide system. Omni flex: Copper hydroxide system.

16. COMPOSITION BASE PASTE 1. Liquid polysulfide polymer :- 80 -85% 2. Inert filler :- 16 – 18% Titanium dioxide, zinc sulfate, copper carbonate use as a filler 3. Plasticizer ACCELERATOR or CATALYST PASTE Lead dioxide :- 60 – 68% Sulfur :- 3% Inert oil :- 30 -35% Normally it is Paraffinic type or di-n- butyl phthalate. Tray adhesive : Butyl rubber or styrene/ acrylonitrile dissolved in a volatile solvent such as chloroform or a ketone is used with polysulfide .

17. CHEMISTRY The main component of polysulfide material is a multifunctional mercaptan or polysulfide polymer. An oxidizing agent such as lead dioxide is used to initiate polymerization through chain lengthening. The reaction starts at the beginning of mixing & reaches its maximum rate soon after the spatulation is completed. During the final set, a material of adequate elasticity & strength is formed. Moisture & temp. have a significant effect on the course of the reaction .

18. The reaction is exothermic – 3-4 c. HS-R-SH HS-R-S-S-R-SH + H 2 Mercaptan+lead dioxide polysulfide+water As alternative to lead dioxide, an organic hydroxide can be used ( e.g T-butyl hydroperoxide ) & inorganic hydroxides ( e.g copper) can be used. PbO2 +S

19. PROPERTIES Setting time : - 16 min at 23 degree 12.5 min at 37 degree Working time : - 6 min at 23 degree 4.3 min at 37 degree Taste & odor :- Tasteless with sulphurous odor. Excellent quality of reproduction of surface details. Dimensional stability :- The curing shrinkage is high(0.45%). H ighest permanent deformation among the elastomers(3 – 5 %).

20. Good flexibility of 7% Hydrophobic Shelf life is 2 years. Biocompatibility :- The use of lead compound in polysulfide material has been questioned because of the know toxic effect of lead. It is unlikely that the lead contained in this material is able to exert a harmful effect as the material is in the patient mouth for only a few min. Coefficient of thermal expansion :- 270 x 10-6 degree centigrade -1 Stress relaxation at 2 min after setting time is 45 % PROPERTIES

21. SILICONE RUBBER IMPRESION MATERIAL These materials were developed to over come some of disadvantages of Polysulfide. Objectionable odor Staining of linen by lead dioxide Amount of effort required to mix the base with the accelerator Long setting times Moderately high shrinkage on setting Fairly high permanent deformation Pouring should be within one hour These are of two type:- Condensation silicone Addition silicone

22. CONDENSATION SILICONE This was the earlier of the two silicone impression material. It is also known as conventional silicones . Mode of supply :- This material is available as base & catalyst in paste form. Catalyst can also be supplied in liquid form. It is available in three viscosities – 1. Light bodies 2. Medium bodies 3. Putty Commercial names :- Sil21 & Coltex

23. COMPOSITION BASE Hydroxyl terminated polydimethyl siloxane Inert filler :- Colloidal Silica is use as a filler ACCELERATOR OR CATALYST PASTE Ortho ethyl silicate- cross linking agent. Stannous octate - catalyst t .

24. CHEMISTRY It is a condensation reaction. Polymerization occurs as a result of cross linkage between the orthoethyl silicate & the terminal hydroxyl group of the dimethyl siloxane , to form a three dimensional network. Stannous octate act as a catalyst. The ethyl alcohol formed as a by product evaporate gradually from the set rubber leading to shrinkage. Dimethylsiloxane + orthoethyl silicate silicone rubber +ethyl alcohol. Stannous octate

25. PROPERTIES Working time :- It is 3.3 min at 23 degree It is 2.5 min at 37degree Setting time :- It is 11 min at 23degree It is 8.9 min at 37 degree Odour less, tasteless Excellent quality of reproduction of surface details. Dimensional stability :- It is less due to high curing shrinkage. Curing shrinkage is 0.4 – 0.6% Permanent deformation is high with 1 – 3 %.

26. More stiffer & harder than the polysulfide Hydrophobic Biocompatibility :- Essentially considered nontoxic, despite the fact that they contain a heavy metal catalyst. The materials are hydrophobic & are in the patient mouth for only a few min. Coefficient of thermal expansion :- 190 x10-6 degree centigrade -1 Loss of weight of this material at 24 hrs is 0.9% Shelf life is 12 month . PROPERTIES

27. ADDITION SILICONE It has a better properties than condensation silicones. It is also know as POLY VINYL SILOXANE. MODE OF SUPPLY Addition silicone materials are available as Base & Catalyst in paste form. It is available in four viscosities:- Light bodied Medium bodied Heavy bodied Putty Commercial names:- Reprosil Provil President

28. COMPOSITION BASE Poly methyl hydrogen siloxane Other siloxane prepolymers Fillers CATALYST Divinyl polysiloxane Other siloxane prepolymers Platinum salt Palladium or hydrogen absorber Retarder Filler- 5-10um.

29. CHEMISTRY It is an addition reaction. In this case the base polymer is terminated with Vinyl group & is cross linked with silane . This reaction is activated by the platinum salt. There is no by product as long as there is proper balance between the Vinyl siloxane & the silane siloxane . If proper balance is not there hydrogen is produced causing air bubbles in the stone models . Vinyl siloxane + silane siloxane silicon rubber

30. PROPERTIES Working time :- It is 3.1 min at 23degree It is 1.8min at 37degree Setting time :- It is 8.9 min at 23degree It is 5.9min at 37degree Reproduce excellent surface details Dimensional stability :- Best in all elastomers. Low curing shrinkage with 0.17% & lowest permanent deformation of 0.05 – 0.3%

31. Hydrophobic , some manufactures add a surfactant to make it hydrophilic. Low flexibility & is harder than polysulfide. Coefficient of thermal expansion :- 190 x10-6 degree-1 Weight loss of material at 24hrs is 0.05% Shelf life is 1 – 2 year Biocompatibility : - No allergic response to this material. Tray adhesive: The adhesive for silicones contain poly dimethyl siloxane & ethyl silicate . PROPERTIES

32. Complications from latex gloves :- Contact of polyvinyl siloxanes with latex gloves should be avoided Mechanism :- When mixing by hand, mechanism of inhibition is thought to be contamination of chlorplatinic acid catalyst with free sulfur left in glove Residues from acrylics,methacrylates and petroleum jelly lubricants may interfere with setting reaction of material Contact of internal surface of impression with gloved hands :- Failure of the material adjacent to the tray to polymerize Separation of the tray from the impression material

33. Prevention :- Use vinyl or nitrile gloves to eliminate the problem Preparations should be cleaned after temporary prosthesis before making final impression Avoid handling retraction cords with latex gloves

34. POLYETHER IMPRESSION MATERIAL This was introduced in Germany in late 1960’s. It has good mechanical properties & dimensional stability. MODE OF SUPPLY It is available as a base & accelerator in paste. It is available in three viscosities :- Light bodied Medium bodied Heavy bodied COMMERCIAL NAME Impregum Ramitec

35. COMPOSITION BASE Polyether polymer :- Inert filler :- Colloidal silica is used plasticizer :- Phthalate or Glycol ether ACCELERATOR or CATALYST PASTE Aromatic sulfonate ester Inert filler :- Silica is used Plasticizer :- Phthalate or Glycol ether used

36. CHEMISTRY It is cured by the reaction between aziridine rings which are at the end of branched polyether molecule. The main chain is a copolymer of ethylene oxide & tetrahydrofuran . Cross linking is brought about the aromatic sulfonate ester via the imine end group. The reaction is exothermic (4 to 5 c). POLYETHER + SULFONIC ESTER CROSS LINKED RUBBER

37. PROPERTIES Working time :- It is 3.3 min at 23 degree It is 2.3 min at 37 degree Setting time : - It is 9 min at 23 degree It is 8.3 min at 37 degree Bitter taste with no smell. Dimensional stability :- It is very good. Curing shrinkage is low with 0.24%. The permanent deformation is low with 1 – 2% It is extremely stiff & flexibility is 3 %.

38. Hydrophilic Biocompatibility :- The Sulfonic ester component may cause skin allergy. Coefficient of thermal expansion :- 300 x10degree-1 Shelf life is 20 -24months . PROPERTIES

39. LIGHT ACTIVATED IMPRESSION MATERIAL With the increase used of light activated restorative materials, light activated impression materials were developed during the late1980’s. The advantages of such a material is there unlimited working time, eliminating one of the primary challenge in clinical impression making for complex multi – abutment fixed partial dentures. Its used chemistry is similar that used by light cured composite. Available in two viscosities :- Lighted bodied Heavy bodied

40. COMPOSITION Polyether urethane dimethacrylate Photo initiator Photo accelerator Silica dioxide filler:- 40 – 60 %

41. PROPERTIES L ong working time but short setting time. Blue light is used for curing. Tear strength :- 6000 – 7500 gm /cm D imensional stability, flow, detail reproduction, permanent deformation, compatibility with cast is similar to addition silicone.

42. MANIPULATION OF ELASTOMERIC MATERIAL SPATULATION :- Impression materials dispensed in tubes require spatulation on disposable pads. Dispending on the specific material, one or both paste may adhere tenaciously to the spatula. Wiping the spatula clean & continuing to mix will minimizing the presence of streaks of unmixed base or catalyst. AUTOMIXING TECHNIQUE :- Most silicone & polyether impression material are available in auto mix cartridge. Auto mix has been shown to result in few voids. Direct syringe tips that fits into the auto mixing tube are available. MIXING MACHINES :- With in the last few years, a mixing machines was introduced for use with polyether impression materials. Among its advantages is reduction of voids in the resulting mix & tray. Rather than rely on small cartridge, larger bulk package of impression paste are available.

43. DISINFECTION OF ELASTOMERIC MATERIALS POLYSULFIDE IMPRESSION MATERIAL :- Glutaraldehydes , chlorine compounds, iodophor , phenolics are the recommended disinfectant. Impression should be immersed in this disinfectant for 30 sec . POLYETHER IMPRESSION MATERIALS :- Chlorine compounds or iodophors are the recommended disinfectant. Immerse the impression in to disinfectant, not more than for 10 min . SILICONE IMPRESSION MATERIAL :- Glutaraldehydes , chlorine compounds, iodophors , phenolic are the recommended disinfectant for Addition & Condensation silicon impression material. Impression should be immersed in the disinfectant for 30 min .

44. COMMON FAILURE THAT OCCUR WITH USE OF ELASTOMERIC IMPRESSION MATERIAL Rough or uneven surface on impression Incomplete polymerization Improper ratio Presence of oil or other organic material on teeth Rapid polymerization Bubbles :- it occur due to Too rapid polymerization Air incorporated during mixing Irregular shaped voids :- it occur due to Presence of moisture or debris on the surface of teeth Rough & chalky :- it is due to Inadequate cleaning of impression Excess water left on surface of the impression Excess wetting agent on impression Premature removal of cast Distortion :- it is due to Lack of adhesion on tray Lack of mechanical retention for material Excessive bulk of material Movement of tray during polymerization Premature or improper removal of impression

45. ADVANTAGES & DISADVANTAGES MATERIALS ADVANTAGES DISADVANTAGES 1. Polysulfide 1.Long working time 2.High tear resistance 3.Margins easily seen 4.Comparativey More costly 1.Poor patient acceptance 2.Long setting time 3.Require custom tray 4.Hydrophobic 5.Pour with in hr. 2. Condensation silicone 1.Short setting time 2. Easy to use High polymerization shrinkage Low tear strength Low dimensional stability More difficult to pour

46. MATERIALS ADVANTAGES DISADVANTAGES Addition silicone 1.Excellent dimensional 2.Short setting time 3.Auto mixing cartridge 4.Easly seen margin 1.Hydrophobic 2.No flow if sulcus is moist 3.Low strength 4.Difficult to pour 5. High cost Polyether 1.Auto mix dissensions 2. Easily seen margin 3.Good stability 4.High tear strength 1.Stiff, high modulus 2.Bitter taste 3.Absorb water 4.High cost

47. IMPRESSION TECHNIQUES CLASSIFICATION . Based on the type of impression tray used as follows: Stock tray/ Putty-wash impression Double Single. 2. Custom tray impression 3. Closed bite Double Arch method or triple tray technique .

48. Impression making using a stock tray Putty-Wash technique Indications: It is used for most clinical situations where a combination of medium to heavy bodied elastomer and light bodied elastomer is necessary . Advantages: Tray are readily available (no need to fabricate). Metal trays are rigid and do not distort . Disadvantage: Need to sterilize the trays. More impression material is required. Technique: There are two methods to make a putty wash impression namely: Double mix putty-wash technique. Single mix putty was technique.

49. Double putty-wash technique: Suitable stock tray is selected. Tray adhesive applied uniformly. Putty impression material is mixed and made into rope and loaded onto the tray. A space for light body material, (sheet of polythene) should be placed. The loaded tray along with the spacer is used to make a full mouth impression. After impression making remove the spacer carefully. The impression is additionally relieved by scraping the areas, which needs to be recorded , of the tooth preparation. The light body material is then syringed over the putty impression and also over the tooth preparation. Once the material is set the impression is removed from the mouth .

50. Single putty wash impression In this procedure both the materials ( light & putty) are used simultaneously. The putty material is loaded into the stock tray. The light body material is syringed around the tooth preparation. A full mouth impression is made using the loaded stock tray.

51. Impression making using a custom tray This is an elaborate procedure where in a custom tray is fabricated over the primary cast made using a primary impression . Advantages: Lesser amount of impression material is required. More hygienic as it is used for a single patient. Uniform thickness of impression material reduces the chances of distortion . Disadvantages: Increased time required for fabrication. Cannot be used in patients sensitive to acrylic .

52. An acrylic special tray is constructed over the cast with two sheets (2-4mm) of wax spacer to provide space for the impression material . T echnique : Tray adhesive is applied over the acrylic tray. Medium viscosity elastomer is loaded on the tray. Light bodied elastomer is syringed around the tooth preparation. The tray with the impression material is then seated over the tooth surface.

53. Advantages: 1. Less impression material is required. 2 . Less time is taken as both the arches are recorded simultaneously. 3. Maximum intercuspation position can be recorded more accurately as it is recorded during function. Disadvantages: Distortion is possible because the tray is not rigid. Uneven distribution of impression material. Double arch/Triple tray/Closed Mouth impression

54. Technique : The syringe material injected into the area to be recorded. The high viscosity material mixed and placed in excess on both the sides of the tray. The tray is placed in between the arches. Patient is asked to inter- digitate (bite) slowly. After making the impression, the patient is instructed to open his/her mouth, the tray will adhere to one arch. Bilateral pressure should be applied to remove the tray as it helps to minimize distortion. TRIPLE TRAYS