Impression materials in prosthodontics

complete review of impression materials used in prosthodontics

1. IMPRESSION MATERIALS PRESENTED BY : DR.ANIKET SHINDE 1 ST YEAR PG STUDENT DEPARTMENT OF PROSTHODONTICS

2. CONTENTS INTRODUCTION HISTORY CLASSIFICATION IMPRESSION MATERIALS - Nonelastic - Elastic LATEST ADVANCES

3. INTRODUCTION Impression materials are used to produce the accurate replicas of intraoral tissues. There are a wide variety of impression materials available each with their own properties, advantages and disadvantages

4. DEFINITION Any substance or combination of substances used for making an impression or negative reproduction – GPT 9 An impression is an “imprint” or negative likeness of the teeth and/or edentulous areas, made in plastic material which becomes hardened or set while in contact with the tissue – Hartwell 1992 An impression is the perpetual preservation of what already exists and not the meticulous replacement of what is missing – M. Devan 1995

5. E volution of impression materials 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.

6. 1930 : JD Hart of Oklahoma began to use Agar for fabrication of cast restoration. 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

7. 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

8. Ideal requirements They should have low enough viscosity to adapt to the oral tissue, yet be viscous enough to be contained in the impression tray. Should have adequate wettability. The material must have pleasant taste and odour . It should show adequate elastic recovery with no permanent deformation. It should have adequate strength to prevent tear or breakage

9. The impression should be dimensionally stable after setting. The material must be bio-compatible. It should compatible with cast material. The material could be easily disinfected without loss of accuracy Material must have adequate shelf life for storage. Materials must be cost effective.

10. Classification CLASSIFICATION BASED ON THEIR MECHANICAL PROPERTIES

11. Based on tissue compressibility Mucocompressive Mucostatic

12. Based on their chemical composition

13. According to use materials in dentistry Materials used for making impression of dentulous mouth: Alginate Agar Non aqueous elastomers Materials used for edentulous mouth: impression compound Impression plaster Zinc oxide eugenol Waxes

14. Non elastic impression materials 1. Impression Plaster - used as mucostatic impression material for making final impressions for edentulous patients - Doesn’t compress and displace tissues during seating of tray due to its fluidity - Applicable to patients with displaceable soft tissues that should be recorded in a passive state

15. Composition ß-calcium sulphate hemihydrate Reacts with water to form calcium sulphate dihydrate W/P ratio– 0.5-0.6 Expansion and setting times controlled by incorporating compounds designed to mediate handling properties Potassium sulphate added as an anti-setting expansion agent Borax(retarder)- added to the powder to balance the setting acceleration caused by Pot. Sulphate and to bring the setting time under control

16. Alzarin red-to make clear distinction between the impression and model Custom tray constructed using 1-1.5mm spacer with acrylic resin or shellac Impression plaster can be used as wash material Techinque - “Puddling” the impression into place With remaining plaster in tray, the tray is seated in single movement Then tray is gently moved from side-to side and antero-posteriorly to take advantage of fluidity of material Hemihydrate particles absorb moisture from the surface of the oral tissues allowing intimate contact between impression material and the tissues

17. Plaster impression material –very brittle and fractures easily When undercut is involved, fracture the impression to facilitate removal from mouth Beading of the impression done Coated with separating medium and cast in fresh plaster Disinfection- achieved with a 10 min soak in sod hypochlorite solution Not used regularly due to mechanical limitations Used frequently as occlusal registration material

18. Zinc-oxide Eugenol Impression Paste Composition-2 separate pastes dispensed in tubes One tube contains zinc oxide and vegetable or mineral oil • Other tube contains eugenol and rosin

19. Composition

20. Setting reaction of ZOE Ionic in nature Requires ionic medium in which it can proceed at any desired rate 1st reaction-hydrolysis of zinc oxide to its hydroxide form When the 2 pastes are mixed, the phenol –OH of the eugenol acts as a weak acid and undergoes an acid-base reaction with zinc hydroxide Forms a salt- zinc eugenolate Two further coordinate bonds are formed by donation of pairs of electrons from methoxy oxygen to zinc

21. Manipulation : -Mixed on oil impervious paper or glass mixing slab -Proper proportion of two pastes obtained by squeezing 2 strips of paste of the same length, one from each tube onto the mixing slab -Flexible stainless steel spatula used for mixing - 2 strips of contrasting colors combined with the first stroke of the spatula ,mixing is continued for approx 1 min, until a uniform color achieved

22. Types of ZOE Classified as base paste(type I) catlyst paste(type II) Final set for type I paste-10 min type II paste-15min Actual time shorter when setting occurs in mouth Shorten the setting time – by adding small amount of Zinc acetate or additional accelerator or a drop of water in the paste before mixing or by extending mixing time Prolonging the setting time- cool spatula and mixing slab

23. Disinfection 2 % alkaline glutaraldehyde solution Immersed in solution for required time, rinsed and poured immediately

24. Applications of ZOE Final impression of edentulous ridges As a wash impression with other impression As an interocclusal registration material As a temporary liner material for dentures • As a surgical dressing

25. Impression compound Also called “modelling plastic” Thermoplastic material Supplied in the form of cakes(red) and sticks (green, gray or red) Composition Types of Impression compound Type-I (Lower fusing) Type- II (Higher fusing) Material Role Mixture of waxes Principle ingredient Thermoplastic resin fillers Increase viscosity and rigidity Shellac, stearic acid and gutta percha Improve plasticity and workability Coloring agents

26. Type I (Lower fusing material) Cakes as a impression material for completely edentulous patients, the material is softened by heat, inserted into the tray and placed against the tissues before it cools to a rigid mass Sticks- as a border molding material for the custom tray ,the material is used before making the final impression

27. Type II( Higher fusing material) Used as an adaptation material which requires more viscous properties Used for making primary impression of the soft tissues and then used a tray to support a thin layer of a second impression material such as ZnOE paste, hydrocolloids or nonaqueous elastomers

28. Elastic impression materials 1. Hydrocolloids Reversible hydrocolloids: In which the bond holds the fibrils of colloid together breaks at elevated temperature and becomes re-established when it is cooled. Example : agar Irreversible hydrocolloids : fibrils of the sol is formed by chemical reaction and the process is irreversible Example : alginate

29. Basic concepts about colloids : - often classed as fourth state of matter as colloidal state. - can be considered as a compromise between the very small molecules in solution & very large particles in suspension. - Two phases : Dispersed phase or dispersed particles Dispersion phase or dispersion medium - All colloidal dispersions are termed as sols.

30. Types of colloids : Solid or liquid in air (aerosols) Gas liquid or solid in liquid ( lyosol ) Gas liquid or solid in solid

31. Colloids with a liquid as a dispersion medium can exist in two different forms known as Sol & Gel Sol- has a appearance & many characteristics of a viscous liquid. Gel- is a semisolid & produced from a sol by the process of gelation. Gelation : It is a process of conversion of sol to gel, to form fibrils, micelles of the dispersed phase which become interlocked to give characteristic jelly like consistency. Within the gel, the fibrils branch & intermesh to give a brush heap structure Gelation temperature : The temperature at which gelation occurs is known as gelation temperature

32. Dimensional effects : The Gel may lose water by evaporation from its surface or by exuding fluid onto the surface by a process known as SYNERESIS. The gel shrinks as a result of evaporation & syneresis. If a gel is placed in water, it absorbs water by a process known as IMBIBITION. The gel swells during imbibition, thereby altering the original dimensions. The effects of syneresis, evaporation & imbibition on the dimensional changes are of considerable importance in dentistry, since any change in dimension that occurs after the impressions are removed from the mouth will lead to inaccurate casts & models

33. Agar – reversible hydrocolloid It is a sulphuric ester of a linear polymer of galactose. Gelation Temperature of agar is approx - 37˚-50˚c. The temperature at which the gel changes to sol i.e. liquefaction temperature is 70˚-100˚c. Although it is an excellent impression material & yields accurate impressions, it has been largely replaced by alginates & rubber impressions because of the minimum equipment requirement and Possibility of obtaining metal dies from rubber impression. Supplied as gel Available in tray and syringe consistencies Tubes used to fill water cooled trays and cartridges used with syringes

34. Composition :

35. Fillers such as diatomaceous earth, wax, clay, silica, rubber and similar inert powders– used to control strength , viscosity and rigidity Thymol and glycerine added as bactericidal agent and plasticiser

36. Making the agar impression : - Process requires a 3 compartment conditioning unit for the agar tray material - Allows liquefaction,storage and tempering - Syringe material used only in liquefaction and storage compartments

37. Liquefy the hydrocolloid gel in the tube in boiling water at 1000C for minimum 10 min tube then placed in a storage bath at 65°C to retain the sol condition until needed impression tray filled with hydrocolloid sol from the tube taken from storage bath , gauze pad placed over the top of the tray material Tray placed in water filled tempering compartment(at abt 45°C)

38. Just before tempering completed,syringe material taken directly from storage compartment and applied to the prepared teeth Note--- tempering time-3-10 min • if >10 min, partial gelation occurs syringe material doesn’t require tempering because maintained in fluid state to enhance adaptation to tissues Syringe material first applied to the base of the preparation, then remainder of the prepared tooth is covered Tip of the syringe is held close to the tooth and it remains embedded below the surface of the syringe material to prevent entrapment of air bubbles

39. Water soaked outer layer of hydrocollloid loaded tray and the gauze covering the tray impression material are removed to ensure firm bonding to the syringe hydrocolloid Tray immediately brought into position,seated with light pressure and held with a very light force Gelation accelerated by circulating cool (1821°C)through tray for 3-5 min During gelation process, tray must be held in mouth until gelation has proceeded to a point at which gel strength is sufficient to resist deformation or fracture Tray removed with a snap

40. Compatibility with gypsum : Contains borax- retarder for setting of gypsum products • Deficiency of gypsum setting can be overcome by--Immersing agar impression in a solution containing a gypsum accelerator(2% pot sulfate solution) prior to pouring of the impression • By incorporating gypsum surface hardener in the material such as sulfate Disinfection : House hold bleach or iodophors Accuracy : most accurate Uses : Full mouth impressions without deep undercuts • Quadrant impressions without deep undercuts • Single impressions • Can be used for crown and bridge impressions because of their accuracy • Cast duplication • Tissue conditioner

41. Alginate – irreversible hydrocolloid Developed as a substitute for the agar impression material when its supply became scarce during World War II. Based on a natural substance extracted from certain brown seaweed. This substance is called as anhydro-ß-d-mannuronic acid or alginic acid (sodium or potassium or triethanolamine acid) (insoluble in water) Currently, alginate is more popular than agar because : • easy to manipulate • comfortable for the patient. • relatively inexpensive • does not require elaborate equipment

42. Composition :

43. Setting reaction : Two main reactions occurs during setting – 2Na3PO4 + 3 Ca SO4 Ca3(PO4)2 + 3 Na2SO4 (Sodium phosphate) (Calcium sulphate) (Retarder) (Reactor) Sodium Alginate + CaSO4 + H2O Ca Alginate + Na2SO4 (Powder) (Reactor) (Gel)

44. Types of alginates : I. According to concentration of sodium phosphate • Fast set • Regular set Types Mixing time Working time Setting time I- Fast set 45 sec 1.25 mins 1-2 mins II- Normal set 60 sec 2 mins 2-4.5 mins

45. Making of alginate impression : Measured powder added slowly to premeasured water already poured into clean rubber bowl Powder incorporated into water by carefully mixing with a metallic spatula flexible enough to adapt well to the wall of the mixing bowl Avoid incorporating excessive air into the mix Vigorous figure of 8 stropping motion Mixing time- 45sec to 1 min Result should be a smooth creamy mixture that doesn’t drip off the spatula when raised from bowl

46. Mechanical mixing devices Include rotating mixing bowl , mechanical mixer with time-control unit, a vaccum mixer for water/powder mixing Advantages- convenience, speed and reduction of human error

47. Controlling the setting time : Ideal W/P ratio- 20 ml water/8gms of powder 40 ml water/16gms of powder Powder should be weighed not measured Approx 2.5:1 Slight modification in W/P ratio affects 2 important properties--- tear strength elasticity setting time best regulated by amount of retarder added during manufacturing Can also be influenced by altering the temperature of water Cool water in hot weather Precool mixing bowl and spatula Tap water-contains certain levels of metallic ions( Ca,Mg ) Tap water with a high hardness may accelerate setting time

48. PROPERTIES :According to ADA specification No 18: 1.Flexibility : 14% at a stress of 1000gm/cm2 2.Elastic recovery : 97.3% 3.Tissue detail reproduction : 0.075mm 4.Compressive strength : 5000-8000/cm2 5. Tear strength : 350-700gm/cm2 6.Poor dimensional stability

49. Advances in alginate Dust free alginate : no diatomaceous earth Two paste system: prevents contamination of the powder Chromatic alginate : determines the setting time Self disinfected alginate Extended pour : cavex – 100 hrs extend a pour 4 weeks storage solution is available Aliginate with polyacrylamide : to create smooth mix Alginate with improved wettability

50. Laminate technique: The hydrocolloid in the tray is replaced with a mix of chilled alginate that bonds to the syringe agar. Alginate gels by a chemical reaction whereas agar gels by means of contact with the cool alginate rather than with the water circulating in the tray. Since the agar, not the alginate is in contact with the prepared tooth, maximum detail is produced.

51. Elastomeric impression materials Soft and rubber-like & known as elastomers or synthetic rubbers Types : According to chemistry – Polysulphides Condensation polymerizing silicone Addition polymerizing silicone Polyether Visible light curable polyether urethane dimethacrylate ( a new class added recently)

52. According to Viscosity(ISO 4823) Type 0—Putty consistency (very heavy) Type 1—Heavy-bodied consistency (tray consistency) Type 2—Medium-bodied consistency (regular bodied) Type 3—Light-bodied (syringe consistency) Extra low and putty available only for condensation and addition silicones • Polysulfide provided only in light body and heavy body • No heavy body for condensation silicone

53. Polysulphides: First synthetic elastomeric impression material introduced in 1950 It is also known as Mercaptan or Thiokol. Interestingly, they were first developed as an industrial sealant for gaps between sectional concrete structures. Supplied as : 2 paste system Available in low, medium and high consistencies Made up of a base and accelerator/reactor Brands- COE-FLEX,PERMALASTIC,NEOPLEX

54. Composition :

55. CHEMISTRY AND SETTING REACTIONS When the base and accelerator pastes are mixed, it undergoes a chemical reaction, whereby the liquid polymer sets to form a solid, but highly elastic and flexible rubber like material. The lead dioxide reacts with the polysulfide polymer causing Chain lengthening by oxidation of terminal—SH groups Cross-linking by oxidation of the pendant—SH groups The reaction is exothermic with a 3–4 °C rise in temperature. It is accelerated by heat and moisture.

56. 1. Unpleasant odor and color. It stains linen and is messy to work with 2. These materials are extremely viscous and sticky. Mixing is difficult. However, they exhibit pseudoplasticity, i.e. if sufficient speed and force is used for spatulation, the material will seem easier to handle. 3.The mixing time is 45 seconds. 4. It has a long setting time of 12.5 minutes (at 37 °C). 5. Excellent reproduction of surface detail.

57. 6. Dimensional stability The curing shrinkage is high (0.45%) and continues even after setting. It has the highest permanent deformation (3–5%) among the elastomers. Elastic recovery improves with time and so pouring of the model should be delayed by half an hour 7. It has high tear strength It is hydrophobic so the mouth should be dried thoroughly before making an impression. Care should also be taken while pouring the stone to avoid air pockets.

58. Making of polysulphide impression: Each paste supplied in a dispensing tube with approx sized bore diameters at the tip Equal lengths of paste extruded from each tube to provide the correct ratio of polymer to cross-linking agent Reaction starts at the beginning of mixing and reaches its maximum rate soon after spatulation is complete Resilient network started to form During final set, a material of adequate elasticity and strength is formed that can be removed past undercuts

59. Advantages Disadvantages - High tear strength - Dimensionally unstable - Long working time - Unacceptable odor - Established precision - Untidy and stains clothing - Economic - Long setting time - Extensive shelf life - Least elastic recovery - Subsequent pours are less accurate.

60. Silicones 1. Condensation Silicone 2. Addition Silicone

61. Condensation silicone Followed in 1955 Supplied as two-paste system or base-paste and a low viscosity liquid catalyst or a two-putty system Putty used as tray material in conjunction with a low-viscosity silicone Referred to as the Putty-wash technique Brands- Speedex

62. Composition :

63. Working time: 3 min Setting time: 6-8 min Impression must be poured as soon as possible within first 30 min Curing involves a reaction of tri- and tetrafunctional alkyl silicates in the presence of stannous octoate as a catalyst Sets by cross-linking between terminal groups of the silicone polymers and the alkyl silicate to form a 3-D network Condensation polymerisation of alpha-omega hydroxy – terminated poly(dimethyl siloxane) with tetraethyl orthosilicate in the presence of stannous octoate(catalyst) This reaction results in the release of ethanol molecules

64. Addition silicone Commonly referred to as Polyvinyl siloxanes(PVS) Tubes The base and catalyst pastes come in equal sized tubes (unlike condensation silicones). The different viscosities usually come in different colors like orange, blue, green, etc. Cartridge form with static mixing tips For use with a dispensing gun. Putty jars Two equal sized plastic jars—containing the base and catalyst. A larger electric driven autodispenser and mixing device is also available ( Pentamix — ESPE). This machine stores larger quantities. At the press of the button, it dispenses and mixes the material. Brand name- Aquasil

65. Composition :

66. Working time: 2-4.5 min Setting time: 3-7 min Cast can be poured upto 1 week after making the impression Reaction activated by a platinum salt catalyst (chloroplatinic acid) without the release of byproducts In presence of impurities or moisture, secondary reaction takes place between the residual hydrides and moisture leading to evolution of hydrogen gas This can cause minute gaseous voids in the gypsum casts and reduce the effectiveness of cross-linking polymer structure Automatic mixing systems simplified their manipulation, reduced voids in impressions, reduced the amount of material wasted and reduced the sensitivity of their mixing technique

67. Advantages : Most elastic of currently available materials Virtually negligible distortion upon removal from undercuts Exceptional accuracy in reproducing anatomic details Dimensional stability allows pouring long after impression making Excellent occlusal record registration material

68. Disadvantages : Inherent hydrophobic nature Non-ionic surfactant wetting agent added to silicone paste rendering the surface of the impression more hydrophillic and called hydrophilized addition silicone Sulfur contamination from natural latex gloves inhibits the setting of addition silicone Touching the tooth with latex gloves before seating the impression can inhibit the setting of critical surface next to tooth

69. Polyether Introduced in Germany in late 1960s Good mechanical properties and dimensional stability, but short working time, very stiff material and expensive Supplied as two-paste system in low, medium and high consistencies 2 types: 1. based on ring-opening polymerization of aziridine rings which are at the end of branched polyether molecules . based on an acid-catalyzed condensation polymerization of polyether prepolymer with alkoxysilane terminal groups Brands- IMPREGUM

70. 1 st type :Main chain probably a copolymer of ethylene oxide and tetrahydrofuran Cross-linking and setting promoted by an initiator and an aromatic sulfonate ester R alkyl group • Produces cross-linking by cationic polymerisation via the imine end groups Supplied as 2 pastes: base and accelerator

71. Composition :

72. Working time: 2.5 min Setting time: 4.5 min Poured upto 1 week of storage

73. Type 2 nd : Based on an acid-catalyzed condensation polymerization of polyether prepolymer with alkoxysilane terminal groups Mechanism similar to condensation silicones Material often called hybrid Behave very much like the 1st type due to ether linkages High degree of wettability Inherent hydrophillic nature Relative stiffness Excellent material for good duplication of fine details and rigid support for pick-up copings

74. Advantages Disadvantages Dimensional stability - Set material very stiff Accuracy - Imbibition Shorter setting time - Short working time. Automix available - Allergic hypersensitivity in some cases.

75. Making of impression with elastomeric materials Fabrication of gypsum models ,casts and dies involves 6 major steps: 1. Preparing a tray 2. Managing tissue 3. Preparing the material 4. Making the impression 5. Removing the impression 6. Preparing stone casts and dies

76. Impression trays Custom tray recommended to reduce the quantity of material required In case of severe undercuts, custom tray avoided Prior to impression making, uniform thickness of tray adhesive applied

77. Soft tissue management Displace the gingival tissues, control gingival haemorrhage and control sulcular fluids to ensure access for the tooth preparation and making impression Gingival retraction cord- most commonly used

78. Manipulation of impression materials The 5 main mixing techniques are 1. Hand or manual spatulation 2. Manual kneading 3. Rotary table assisted mixing 4. Static or extrusion mixing 5. Dynamic mechanical mixing

79. Hand mixing : Dispense the same length of materials onto a mixing pad or glass slab • Catalyst paste first collected on stainless steel spatula and then spread over base paste • Mixture is then spread over the mixing pad • Mass is then scraped up with the spatula blade and spread uniformly back and forth on the mixing pad Process continued until the mixed paste is uniform in color with no streaks of the base or catalyst appearing in the mixture • 2 putty systems(condensation and addition silicone) dispensed by volume using equal number of scoops of each material • Knead the material with fingers until a uniform color is obtained

80. Static mixing : Transforms 2 fluid(or paste-like) materials into a homogenous mixture without mechanical mixing • Device used- gun for compressing materials into a 2cylinder cartridge, which contains the base and catalyst separately, as well as mixing tip Mixing tip is made of helical mixer elements in a cylindrical housing • Mixer elements are series of alternating right and left –turn 180°helixes positioned so that leading edge of one element is perpendicular to the trailing edge of the next • Length of each material is the same as the inner diameter of the cylinderical housing

81. Dynamic mechanical mixing : Device uses motor to drive parallel plungers,forcing the materials into a mixing tip and out into an impression tray or syringe • Motor driven impeller mixes the materials as they are extruded through the tip • Materials supplied in collapsible plastic bags housed in cartridge • Polyether and addition silicone

82. Making of an impression 3 techniques: Multiple-mix technique Monophase technique Putty wash technique

83. Multiple mix technique : Syringe material(light body)and tray material(heavy body) Lighter material injected within or around the tooth preparation Filled tray then inserted in the mouth and seated over the syringe material Tray material force the syringe material to adapt to the prepared tissues

84. Monophase technique(single stage) : Medium body polyether and addition silicone Only one mixture is made and a part of the material is placed in the tray and another portion in syringe for injection in the prepared tissues Success depends on pseudoplastic (shear thinning) property of material

85. Putty wash technique (two stage): Originally developed for condensation silicone to minimize the effect of associated dimensional changes Thick putty material placed in stock tray and a primary impression made Space for light-body “wash” material provided Mixture of thin consistency wash material placed into putty impression and preparation

86. Removal of the impression Shouldn’t be removed until curing progressed sufficiently to provide adequate elasticity ,so distortion doesn’t occur • Typically impression should be ready for removal within at least 10 min from time of mixing, allowing 6-8 min for impression to remain in mouth Mechanics of removing impression– separation at the impression/tissue interface and stretching of the impression • 1st step to break the physical adhesion between the tissue and the impression • Polyether requires extra effort • 2nd step stretches the impression enough to pass under the height of contour of hard tissue to remove impression

87. Recent advances Advances in alginate Pentamix Intraoral scanners

88. Advances in alginate Dust free alginate : no diatomaceous earth Two paste system: prevents contamination of the powder Chromatic alginate : determines the setting time Self disinfected alginate Extended pour : cavex – 100 hrs extend a pour 4 weeks storage solution is available Aliginate with polyacrylamide : to create smooth mix Alginate with improved wettability

89. Pentamix : Automatic Mixing System for Impression Materials • Economical: Use only the exact amount of material you need • Reliable: Remarkably mixed material assures consistent quality • Hygienic: Direct filling of tray and syringe reduces the risk of cross-contamination • Efficient: Push button activation makes it fast and easy to handle

90. The innovative design of the Red Penta™ Mixing Tip reduces dispensing forces by up to 50 %. This also allows heavybodied pastes to be reliably conveyed and mixed without the cartridge and foil bag caps being subjected to excessive pressure. The tried and tested PentaMatic ™ Auto Open System from 3M ESPE base paste foil bag cap has been reinforced with additional struts helps to prevent breakage. The PentaMatic foil bag cap of the catalyst features a redesigned opening with a widened base helps to prevent the opening from snapping off even when under load. The new Penta™ Cartridges now include an integrated steel cylinder, designed helps to prevent the expansion or breakage of cartridges.

91. Intra oral scanners : Trios, 3Shape. Sirona, Cerec . Itero Element 2. Planmeca ® Emerald  Scanner . 3M Tru def. Carestream. Advantages: less patient discomfort time efficient simplified clinical procedure no more plaster cast

92. references Text book of phillip’s dental material sciences 12 th edition Text book of boucher 13 th edition Alaghari S, Velagala S, Alla RK, Ramaraju AV. Advances in alginate impression materials: a review. International Journal of Dental Materials. 2019 Nov 15;1(2):55-9. Mangano F, Gandolfi A, Luongo G, Logozzo S. Intraoral scanners in dentistry: a review of the current literature. BMC oral health. 2017 Dec 1;17(1):149.