ALGINATE.pptx

alginate

1. Alginate I RREVERSIBLE HYDROCOLLOID First BDS Lecture

2. IMPRESSION MATERIAL DEFIN I TION A negative likeness or copy in reverse of the surface or object. An imprint of the teeth and adjacent structures for use in dentistry

3. Non- ela s tic Elastic Aqueous Hydr o c o lloids Non-aqueous E lastomers Pol y s u lf i de Si l ico nes Conde n s a ti on Addition Agar ( r ever s ible) ALGINATE (IRREVERSIBLE ) Plaster Compound Waxes ZnO - Eugenol Polyether O‟Brien, Dental Materials & their Selection 1997

4. A L G I N A TE 🞭 Alginate is classified as irreversible hydrocolloid. 🞭 Hydrocolloid because it consists of particles of a gelatinous ( colloidal ) state in water ( hydro ) and irreversible because once it has jelled it cannot be returned to a liquid solution. They consist of gelatin particles suspended in water ( Lyosol ). Since water is the dispersion medium it is known as hydrocolloid.

5. IRREVERSIBLE HYDROCOLLOID—ALGINATE The word alginate comes from ‘ alginic acid’ ( anhydro -β-d- mannuronic acid) which is a mucous extract yielded by species of brown seaweed ( Phaeophyceae ) Type I — Fast setting. Type II — Normal setting

6. 🞭 The Word Alginate comes from the term “ALGIN”. 🞭 It is a peculiar mucous extract yielded by certain brown seaweed ( algae ) . 🞭 T h e t e r m „A L GIN‟ wa s coi n e d b y che m ist from scotland @ the end of 19 th century.

7. T Y P ES - Type I – Fast setting. Type II – Normal settin g.

8. M O DES OF SU P P L Y 🞭 It is supplied as a powder that is packed: In bulk or in tins or in sackets (or) In preweighed individual containers. A plastic scoop is supplied for dispensing the bulk powder, & a plastic cylinder is supplied for measuring the water .

9. APPLICATIONS Used In impression making : when there are undercuts In mouth with excessive flow of saliva For partial dentures with clasps. M aking preliminary /Primary impressions for complete denture. For orthodontic and study models. For duplicating models.

10. COMPOSITION : 🞭 Potassium alginate(15%) 🞤 Comes from seaweed; is used as a thickening agent. 🞭 Calcium sulfate(16%) 🞤 Reacts with the potassium alginate to form the gel. 🞭 Trisodium phosphate (2%) 🞤 Added to slow down the reaction time for mixing.

11. 🞭 Diatomaceous earth( 60 %) 🞤 A filler that adds bulk to the material. 🞭 Zinc oxide (4%) 🞤 Adds bulk to the material. 🞭 Potassium titanium fluoride(3%) 🞤 Added so as not to interfere with the setting and surface strength.

12. PHYSICAL PHASES OF ALGINATE 🞭 The first phase is a sol (as in solution ). In the sol phase, the material is in a liquid or semiliquid form. 🞭 The second phase is a gel . In the gel phase, the material is semisolid, similar to a gelatin dessert.

13. Setting reaction When alginate powder is mixed with water a sol is formed which later sets to a gel by a chemical reaction. The final gel, i.e. insoluble calcium alginate is produced when soluble sodium alginate reacts with calcium sulfate (reactor). However, this reaction proceeds too fast. There is not enough working time. So the reaction is delayed by addition of a retarder ( trisodium phosphate) by the manufacturer. Initially the sodium phosphate reacts with the calcium sulfate to provide adequate working time. Reaction 1 2Na3 PO4 + 3CaSO4 Ca3 (PO4 ) 2 + 3Na2 SO4

14. Next after the sodium phosphate is used up, the remaining calcium sulfate reacts with sodium alginate to form insoluble calcium alginate which forms a gel with water. Reaction 2 Sodium alginate + CaSO4 + H2 O Ca alginate + Na2 SO4 (Powder) (Gel)

15. SETTING REACTION 🞭 Reaction occurs by a chemical reaction. 🞭 Soluble alginate reacts with calcium sulphate to produce insoluble calcium alginate as a gel. 🞭 The production of calcium alginate is delayed by the addition of a third soluble salt to the solution,with which the calcium sulphate will react in preference to the soluble alginate to form an insoluble calcium salt.

16. Setting reaction Chemical reaction named gelation Calcium sulfate  Sodium phosphate  Calcium phosphate  + Sodium sulfate   (1) Calcium sulfate  Sodium alginate  Insoluble calcium alginate  (2 ) The speed of the reaction is affected by; 2. Temperature 4. powder particle size 1. L/P ratio 3. Mixing rate 5. Additives

17. 🞭 In a nutshell , when powder is mixed with water to obtain a paste ,two main reaction occur during setting : 1) 2Na 3 P0 4 + 3CaSo4---> Ca 3 (Po4)2+3 Na 2 SO 4 First , sodium phosphate reacts with the calcium sulphate to provide adequate working time . 2) sodium alginate + -------- > Ca alginate + CaSO 4 + H 2 O Na 2 SO 4 (Powder ) (Gel) Second ,after the sodium phosphate has reacted, the remaining calcium sulphate reacts with sodium alginate to form an insoluble calcium alginate which forms a gel with water.

18. WATER-TO-POWDER RATIO 🞭 An adult mandibular impression generally requires two scoops of powder and two measures of water. 🞭 An adult maxillary impression generally requires three scoops of powder and three measures of water.

19. Manipulation of Alginate 🞭 Fluff or shake the powder to distribute the powder particles evenly 🞭 Use the specific measuring devices (water & powder) provided by the manufacturer for mixing 🞭 Follow the manufacturer‟s direction regarding the ratio of water to powder. 🞭 Use exact measurements

20. 🞭 After the water and powder have been measured, place the water in a clean dry bowl . Sift the powder into the water. Adding the powder to the water ensures the powder particles are wet evenly . If mixed in reverse ( the water is added to the powder ) the chemical reaction will start early with some particles setting faster than others.

21. 🞭 Mix the alginate for the specific amount of time and using a stiff spatula “swipe” the alginate mass against the sides of the bowl to avoid entrapment of air in the mix. figure of “8” motion 1. Remove most of the air bubbles. 2. Wipe dissolved algin from the surface of the yet undissolved algin thereby promoting complete dissolution

22. Alginate Mixing Time For fast set alginate—45 seconds. For normal set alginate—60 seconds. Working Time Fast set alginate—1¼ minutes. Normal set alginate—2 minutes.

23. SETTING TIME OF ALGINATE Since alginate reacts or gels chemically, temperature is a major factor in the setting time. The colder the temperature of the water the longer it takes to set; conversely, the higher the water temperature the faster it sets . Ideal water temperature is 68 degrees or room temperature.

24. LOADING OF TRAY 🞭 A perforated tray is used so that the material is forced out slightly through the holes in the tray during loading , thereby locking itself mechanically into the tray. 🞭 The surface of the alginate in the tray may be smoothened out by moistening the finger with water and running it over the surface of the alginate.

25. SEATING THE TRAY 🞭 Before making the upper impression, saliva should be wiped off from the palatal region. 🞭 In order to prevent the material from flowing along the throat and causing nausea to the patient , the posterior portion may be seated first and then the anterior portion seated properly. 🞭 Since the material sets from tissues towards periphery,any movement during gelation may result in distortion. 🞭 So once the tray is seated ,it must be held in place firmly without any movemnets.

26. REMOVAL OF THE IMPRESSION 🞭 An alginate impression when set develops a very effective peripheral seal. 🞭 This seal should be freed by running the finger around the periphery . 🞭 The impression must be removed suddenly with a jerk. or a snap 🞭 After removal from the mouth, - washed with water to remove saliva. -cast should be poured as soon as possible.

27. ALGINATE SETTINGS 🞭 Normal set alginate Working time of 2 minutes and a setting time of up to 4 1 / 2 minutes after mixing. 🞭 Fast set alginate Working time of 1 1 / 4 minutes and a setting time of 1 to 2 minutes. Working time The time allowed for mixing the alginate, loading the tray, and positioning the tray in the patient's mouth. Setting time 🞤 The time required for the chemical action to be completed .

28. MAKING AN ALGINATE IMPRESSION 🞭 Explain the procedure to the patient: 🞤 The material will feel cold, there is no unpleasant taste, and the material will set quickly. 🞤 Breathe deeply through your nose to help you relax and be more comfortable. 🞤 Use hand signals to communicate any discomfort.

29. AN ACCEPTABLE ALGINATE IMPRESSION 🞭 There is a complete "peripheral roll," which includes all of the vestibular areas. 🞭 The tray is not "overseated," which would result in exposure of areas of the impression tray. 🞭 The impression is free from tears or voids . 🞭 There is sharp anatomic detail of all teeth and soft tissues. 🞭 The retromolar area, lingual frenum, tongue space, and mylohyoid ridge are reproduced in the mandibular impression. 🞭 The hard palate and tuberosities are recorded in the maxillary impression.

30. CAUSES FOR DISTORTION AND DIMENSIONAL CHANGE OF ALGINATE 🞭 If an alginate impression is stored in water or in a very wet paper towel, the alginate will absorb additional water and expand. This condition is called IMBIBITION . 🞭 If an alginate impression remains in the open air, moisture will evaporate from the material, causing it to shrink and distort . This condition is called SYNERESIS .

31. RECENT ADVANCES IN ALGINATES Dust free alginates- De-dusting agent (glycerin or glycol) Siliconized alginates- silicon polymers are added to strengthen the material Alginates containing disinfectants- eg quaternary ammonium salts or chlorohexamine are added to alginate powder. Hard and soft set alginates- by adjusting the amount of fillers

32. PROPERTIES 1)FLEXIBILITY It is about 14% at a stress of 1000g/ cm 2. Lower w/p ratio results in lower flexibility. 2)ELASTICITY AND ELASTIC RECOVERY alginate are highly elastic but less when compared to the agar. 97.3% elastic recovery occurs. Permanent deformation is less if the impression is removed from the mouth quickly.

33. 3) STRENGTH The compressive strengths of alginate gels range from 5000 to 8000 g/ cm 2. The tear strengths vary from 350 to 700 g/cm2. Both of these properties are time dependent with higher values being obtained if the time of removal is delayed.

34. 4) DIMENSIONAL STABILITY : Alginate impression loses water by evaporation and shrinks on standing in air. If it is placed in water it absorbs water and swells. Therefore ,cast should be poured immediately after making the impression.

35. 5)SHELF LIFE Alginate impression material have a short shelf life. They deteriorate rapidly when stored at elevated temperatures in a humid environment. Therefore ,it is better not to stock more than 1 year supply .

36. ADVANTAGES OF ALGINATE 🞭 It makes an accurate impression 🞭 It allows for undercuts 🞭 The process is not time consuming 🞭 It is easy to work with, has good viscosity & is low in adhesive qualities 🞭 It is comfortable to the patient 🞭 Inexpensive to the dentist 🞭 Requires little armamentarium

37. DISADVANTAGES Can‟t be corrected. Cannot be used alone for compressing the tissues. It is not accurate enough for crown and bridge impressions.

38. Definition A dental impression is a negative record of the tissues of the mouth It is used to reproduce the form of teeth and surrounding tissues

39. PROPERTIES OF IMPRESSION MATERIAL Nontoxic and Nonirritant Acceptable to the patient – pleasant taste, odor, consistency & color. Should record accurate surface detail, elastic properties with no deformation & dimensionally stable Adequate shelf life for storage and distribution

40. PROPERTIES OF IMPRESSION MATERIAL Economical Handling properties- sufficient working time, set quickly in mouth & minimum equipment. Have adequate strength so that it will not break or tear while removing from mouth. Should be compatible with die and cast material .

41. CLASSIFICATION OF IMPRESSION MATERIAL A. According to mode of setting and elasticity. B. According to tissue displacement during impression . C. According to uses in dentistry.

42. According to mode of setting and elasticity MODE OF …. SETTING RIGID ELASTIC Set by chemical reaction Irreversible / Thermoset Impression plaster Zinc oxide eugenol Alginate hydrocolloid Nonaqueous elastomers -e.g. polysulfide, silicone Set by temperature change Reversible/Thermostatic Compound, Waxes Agar hydrocolloid

43. ACCORDING TO TISSUE DISPLACEMENT 1. Mucostatic 2. Mucocompressive ( Mucodisplacive )

44. Mucostatic materials produce minimal displacement of the tissue during impression, e.g. plaster, zinc oxide eugenol , low viscosity alginates, low viscosity elastomeric materials, etc. Mucocompressive materials are more viscous and displace the tissues while recording them, e.g. compound, high viscosity alginates, high viscosity elastomers, etc

45. ACCORDING TO THEIR USES IN DENTISTRY 1. Impression materials used for complete denture prosthesis. 2. Impression materials used for dentulous mouths .

46. Impression materials used for complete denture prosthesis Impression plaster, impression compound and impression paste set to a hard rigid mass, and hence cannot be removed from undercuts without the impression being fractured or distorted. Therefore these materials are best suited for edentulous mouth.

47. Impression materials used for dentulous mouths On the other hand alginates and rubber base impressions are sufficiently elastic to be withdrawn from undercut areas. Such elastic impression materials are suitable for impressions for fabrication of removable and fixed partial denture prostheses, where the impressions of the ridge and teeth are required.

48. RIGID IMPRESSION MATERIALS 1. IMPRESSION COMPOUND- rigid, reversible impression material which sets by physical change. On applying heat, it softens and on cooling it hardens. It is mainly used for making impressions of edentulous ridges. CLASSIFICATION Type I - Impression compound Type II - Tray compound

49. APPLICATIONS 1. For making a preliminary impression in an edentulous mouth (mouth without teeth). 2. For impressions of full crown preparations where gingival tissues must be displaced. 3. Peripheral tracing or border molding. 4. To check undercuts in inlay preparation. 5. To make a special tray

50. REQUIREMENTS OF IMPRESSION COMPOUND 1. Harden at or little above mouth temperature. 2. Be plastic at a temperature not injurious or harmful to oral tissues. 3. Not contain irritating or toxic ingredients. 4. Harden uniformly when cooled without distortion. 5. Have a consistency when softened which will allow it to reproduce fine details. 6. Be cohesive but not adhesive.

51. ZINC OXIDE EUGENOL IMPRESSION PASTE Zinc oxide and eugenol based products are widely used in dentistry. ADA specification No. 16 Available as In paste form in two tubes 1.Base paste (white in color) 2.Accelerator or reactor or catalyst paste (red in color) CLASSIFICATION Type I or Hard Type II or Soft

52. COMPOSITION Base paste : Zinc Oxide 87% Vegetable or mineral oil:13% Accelerator paste : Oil of cloves or eugenol : 12% Gum or polymerized rosin 50% Filler 20% Lanolin 3% Calcium chloride and color 5%

53. SETTING REACTION SETTING REACTION The setting reaction is a typical acid-base reaction to form a chelate. This reaction is also known as chelation and the product is called zinc eugenolate . 1. ZnO + H2O Zn(OH)2 2. Zn(OH)2 + 2HE ZnE2 + 2H2O

54. ELASTIC IMPRESSION MATERIALS Two systems are used 1. Hydrocolloids 2. Elastomeric materials Hydrocolloids : They consist of gelatin particles suspended in water ( Lyosol ). Since water is the dispersion medium it is known as hydrocolloid.

55. Based on the mode of gelation Reversible hydrocolloids They are called reversible because their physical state can be reversed. This makes them reusable. Irreversible hydrocolloids Once these set, it is usually permanent, and so are known as irreversible. Reversible hydrocolloids—Agar Classification BASED ON VISCOSITY Type 1 — Heavy bodied (for use as tray material) Type 2 — Medium bodied (for use as tray or syringe material) Type 3 — Light bodied (for syringe use only) Type 3A — Light bodied for agar-alginate combination technique

56. AGAR SUPPLIED AS Gel in collapsible tubes (for impressions) As cartridges or gel sticks (syringe material) In bulk containers (for duplication)

57. AGAR INGREDIENT FUNCTIONS AGAR 13-17% Basic constituent BORATES 0.2-0.5% Improves strength and retards setting of plaster Potassium sulphate 1–2% It counters retarding effect of borates Wax, hard 0.5–1% It acts as a filler Thixotropic materials 0.3–0.5% It acts as plasticizer Alkylbenzoates 0.1 % It acts as preservative. Coloring and flavoring agents Traces For patient comfort and acceptance Water B alance (around 84%) It acts as the dispersion medium

58. Gelation or setting of agar Agar changes from the sol to the gel state (and vice versa) by a physical process. As the agar sol cools the dispersed phase groups to form fibrils called micelles. The fibrils branch and intermesh together to form a brush-heap structure.

59. AGAR The fibrils form weak covalent bonds with each other which break easily at higher temperatures resulting in gel turning to sol. The process of converting gel to sol is known as liquefaction which occurs at a temperature between 70 and 100 °C. On cooling agar reverses to the gel state and the process is called gelation. Gelation occurs at or near mouth temperature which is necessary to avoid injury to oral tissue.

60. PROPERTIES OF AGAR HYDROCOLLOIDS Gelation , liquefaction and hysteresis Syneresis and imbibition (dimensional stability) Flexibility Elasticity and elastic recovery Gel strength including tear and compressive strengths

61. ADVANTAGES 1. Accurate dies can be prepared, if the material is properly handled. 2. Good elastic properties help reproduce most undercut areas. 3. It has good recovery from distortion. 4. Hydrophilic, moist mouth not a problem. It also gives a good model surface.

62. Disadvantages of agar 1. Does not flow well when compared to newly available materials. 2. It cannot be electroplated. 3. During insertion or gelation the patient may experience thermal discomfort. 4. Tears relatively easily. Greater gingival retraction is required for providing adequate thickness of the material.

63. IRREVERSIBLE HYDROCOLLOID—ALGINATE The word alginate comes from ‘ alginic acid’ ( anhydro -β-d- mannuronic acid) which is a mucous extract yielded by species of brown seaweed ( Phaeophyceae ) Type I — Fast setting. Type II — Normal setting

64. ALGINATE As a two paste system One contains the alginate sol, while the second contains the calcium reactor. One product is supplied in low density for use with syringe Dust free alginates Concern over the inhalation of alginate dust have prompted manufacturers to introduce ‘dust free alginates’ Chromatic alginates Alginates which change color on setting Commercial names: Zelgan (DPI), Jeltrate ( Dentsply ), Hydrogum ( Zhermack ), etc.`

65. APPLICATIONS 1. It is used for impression making – When there are undercuts. – In mouths with excessive flow of saliva. – For partial dentures with clasps. 2. For making preliminary impressions for complete dentures. 3. For impressions to make study models and working casts. 4. For duplicating models.

66. COMPOSITION -AGAR Ingredients % wt Function Sodium or potassium alginate Dissolves in water and reacts with calcium ions Calcium sulfate (reactor) Reacts with potassium alginate and forms insoluble calcium alginate Zinc oxide Acts as a filler Potassium titanium fluoride Gypsum hardener Diatomaceous earth Acts as a filler Sodium phosphate (retarder) Reacts preferentially with calcium sulfate Coloring and flavoring agent e.g. wintergreen, peppermint

67. Setting reaction When alginate powder is mixed with water a sol is formed which later sets to a gel by a chemical reaction. The final gel, i.e. insoluble calcium alginate is produced when soluble sodium alginate reacts with calcium sulfate (reactor). However, this reaction proceeds too fast. There is not enough working time. So the reaction is delayed by addition of a retarder ( trisodium phosphate) by the manufacturer. Initially the sodium phosphate reacts with the calcium sulfate to provide adequate working time. Reaction 1 2Na3 PO4 + 3CaSO4 Ca3 (PO4 ) 2 + 3Na2 SO4

68. Next after the sodium phosphate is used up, the remaining calcium sulfate reacts with sodium alginate to form insoluble calcium alginate which forms a gel with water. Reaction 2 Sodium alginate + CaSO4 + H2 O Ca alginate + Na2 SO4 (Powder) (Gel)

69. PROPERTIES OF ALGINATE HYDROCOLLOID 1. Pleasant Taste and Odor 2. Flexibility 3. Elasticity and Elastic Recovery 4. Reproduction of Tissue Detail 5. Strength -Compressive strengths  Ranges from 0.5 to 0.9 MPa . 6. Syneresis and Imbibition

70. Manipulation of Alginate Fluff or aerate the powder by inverting the can several times. This ensures uniform distribution of the filler before mixing. The proper W/P ratio as specified by the manufacturer should be used (usually one measure water with two level scoops of powder. The water is taken first. The powder is sprinkled in to the water in the rubber mixing bowl and the lid of the metal can is replaced immediately. The mixing is started with a stirring motion to wet the powder with water.

71. Once the powder has been moistened, rapid spatulation by swiping or stropping against the side of the bowl is done. A vigorous figure-eight motion can also be used. This helps 1. Remove most of the air bubbles. 2. Wipe dissolved algin from the surface of the yet undissolved algin thereby promoting complete dissolution.

72. Alginate Mixing Time For fast set alginate—45 seconds. For normal set alginate—60 seconds. Working Time Fast set alginate—1¼ minutes. Normal set alginate—2 minutes.

73. ELASTOMERIC IMPRESSION MATERIALS Elastomers are essentially polymers with elastic or rubber-like properties. They contain large molecules with weak interaction between them. They are tied together at certain points to form a three-dimensional network. On stretching, the chains uncoil, and on removal of the stress they snap back to their relaxed entangled state They are amorphous polymers existing above their glass transition temperature, so that considerable segmental motion is possible.

74. Types of polymerization reactions: In elastomers 3 types of polymerization reactions are seen: 1. Addition polymerization 2. Condensation polymerization 3. Ring opening polymerization

75. Classification : According to their chemistry, 1. Polysulfide 2. Condensation polymerizing silicones 3. Addition polymerizing silicones 4. Polyether

76. According to viscosity (ISO 4823:2015) they are further divided based on consistencies determined immediately after completion of mixing, 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)

77. According to wetting ability or contact angle, 1. Hydrophilic, if their contact angle is from 80 to 105°. 2. Hydrophobic, if their contact angle is from 40 to 70°

78. Uses: 1. In fixed partial dentures for impressions of prepared teeth. 2. Impressions of dentulous mouths for removable partial dentures. 3. Impressions of edentulous mouths for complete dentures. 4. Polyether is used for border molding of edentulous custom trays. 5. For bite registration. 6. Silicone duplicating material is used for making refractory casts during cast partial denture construction

79. Supplied as : 1. Two component (base and catalyst) systems, 2. Cartridges—light and regular body material are also supplied in cartridges to be used with static mixing tips and dispensers 3.Putty consistency is supplied in jars

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