Dental Materials PDF

DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE A CLASSIFICATION OF IMPRESSION CLASSIFICATION OF IMPRESSION MATERIALS MATERIALS...

DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE A CLASSIFICATION OF IMPRESSION CLASSIFICATION OF IMPRESSION MATERIALS MATERIALS A1 ACCORDING TO THE MANNER OF TOPIC OVERVIEW HARDENING OR MODE OF SETTING A. CLASSIFICATION OF IMPRESSION 1. Thermoplastic - those that set as a result MATERIALS of a change in temperature (materials a. According to the manner of that becomes soft when heated and hardening or mode of setting hardens upon cooling) b. According to use in Dentistry c. According to elasticity EX. Reversible hydrocolloid, waxes, B. DENTAL IMPRESSION COMPOUND Dental Compound a. Classification b. Uses 2. Thermoset - those that set as a result of c. Types a chemical reaction d. Composition e. Manipulation Ex. 20E impression paste, alginate, f. Precaution impression plaster, rubber impression g. Effect of kneading material h. Properties i. Dimensional stability j. ANSI/ADA specification No.3 A2 ACCORDING TO USE IN DENTISTRY C. BOXING METHOD a. Procedure 1. Impression materials used for complete b. Pouring the cast and cast denture prosthesis separation c. Advantages and disadvantages Impression plaster, impression D. ZINC OXIDE EUGENOL IMPRESSION compound and impression paste ( zinc PASTE oxide eugenol) - rigid a. Composition b. Classifications 2. Impression materials used for dentulous c. Factors that shorten/ mouths accelerate setting time d. Manipulation alginates and rubber base impressions - e. Disinfection elastics f. Other zinc oxide pastes E. AQUEOUS IMPRESSION MATERIAL F. ALGINATE A3 ACCORDING TO ELASTICITY G. AGAR 1. Elastic - flexible after setting a. Reversible (agar base) and irreversible (alginate base) hydrocolloid b. Elastomeric (rubber base) 2. Inelastic or rigid - hard after setting (for no undercuts exist) PAGE 1 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE a. Impression or modeling ○ Peripheral tracing or border compound molding. b. Impression Plasters Type 2 c. Zinc Oxide and Eugenol ○ To check undercuts in inlay impression paste preparation. d. Impression waxes ○ To make a special tray. B DENTAL IMPRESSION COMPOUND B3 TYPES Type 1 B1 CLASSIFICATION a. Low fusing - green stick b.Medium fusing - true impression Type | - Impression compound compound Type II - Tray compound 55 - 65°C Uses: Type lI Tray compound is used to 1. An impression material for preliminary prepare a tray for making an impression. impression taking A second material is then carried in it in 2. Taking an individual impression of a order to make an impression of oral prepared cavity tissues. 3. Peripheral tracing or border molding Since reproduction of the fine details is Type 2 - tray compound; high fusing not essential, it is generally stiffer and has compound less flow than regular impression Uses: compound. The use of dental tray 1. Secondary impression as an individual compound decreased with the increased tray substitution of acrylic tray materials. 2. Carry an impression material (use as a tray) Available in: 1. Sheets border molding: it is important to 2. Sticks record all the vestibules in the mouth 3. Cylinders* special tray: after taking ridge 4. Cones* impression using the modeling compound, impression material is put small sticks of modeling compound on top and back into the patient's are used in the impression of a single mouth for the final impression tooth B4 COMPOSITIONS B2 USES 1. Wax - beeswax; responsible for Type 1 thermoplastic property ○ For making a preliminary 2. Stearic acid - plasticizer (making the impression in an edentulous material tougher and less brittle, improve mouth (mouth without teeth). workability) ○ For impressions of full crown preparations where gingival tissues must be displaced. PAGE 2 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 3. Fillers - reduce the flow of the mc and reduce the adhesiveness of the softened B7 EFFECT OF KNEADING material to the oral tissues - talc, chalk, or iron oxide Kneading for 3 to 4 minutes will double 4. Pigments or coloring materials - brown, the flow of the compound gray or green Increased flow is believe to be the caused by the incorporation of water which acts beeswax is needed for thermoplastic as plasticizer in the compound property to make impressions May also caused distortion... if kneads too reversible long B8 PROPERTIES B5 MANIPULATION 1. Flow - continuous change in shape even 1. Dry Heat Method - used in small with no pressure impression (stick) - - materials are hard at 35°C but a. Direct flame is used; alcohol lamp plastic and capable of recording or bunsen burner impression at 45°C - for single impression 2. Thermal conductivity - low thermal b. Oven conductivity 2. Water bath - hot water (60°C) - During heating, the outside of the - used full mouth material will become soft while - cheapest the inside may still be hard and - for big mouth impression have low flow properties than desired dry heat method is used for a single - Don't immersed in hot water for impression, while water bath is used long time - will leached out the for a larger impression more soluble component and 45 degrees celsius is good so as to not adversely alters physical burn the patient's mouth properties incorporation of water while kneading yields bubbles in the compound B9 DIMENSIONAL STABILITY plaster of paris for modelling compound to make study casts What causes dimensional changes and warpage: B6 PRECAUTION 1. Storage in warm temperature for extended periods 2. pour the cast immediately or at least 1. Prolonged immersion in a water bath within the hour. causes the compound to become brittle 3. removal of the impression too early from and grainy because some of the the mouth before complete hardening. ingredients may be leached out. 2. Overheating in water makes the compound sticky and difficult to handle. 3. Avoid incorporating water while kneading. PAGE 3 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Excessively hot water is avoided as it can B10 ANSI/ADA Specification No. 3 for make the material sticky and difficult to Dental impression Compound remove from the cast. 1. Homogeneous C3 ADVANTAGES AND DISADVANTAGES 2. Smooth, glossy surface after flaming 3. Firm, smooth margins after trimming with a knife at room temperature ADVANTAGES: 1. The material can be reused a number of times (for the same patient only) in case C BOXING METHOD of errors. 2. Inaccurate portions can be remade The boxing wax completely encircles the without having to remake the entire impression tray and creates a temporary mold to impression. contain the plaster or the stone 3. Accuracy can be improved by flaming the surface. 4. The material has sufficient body to C1 PROCEDURE support itself especially in the peripheral portions. It does not collapse completely 1. Trim away the excess material. Removal if unsupported by the tray. of the excess helps to box the impression and maintain the anatomic landmarks of DISADVANTAGES: the final cast 1. Records less detail because of its high 2. Apply and attach a piece of beading wax viscosity. 2 to 3 mm down from the peripheral roll 2. Compresses soft tissues during of the impression impression. 3. Add the boxing wax around the entire 3. Distortion due to its poor dimensional impression and have it extend and stability. overlap 0.5 inch beyond the vestibular 4. Difficult to remove if there are severe edge of the tray undercuts. 4. Tilt the impression to wet and fill the 5. There is always the possibility of impression with gypsum overextension especially in the 5. Add more to completely fill the boxed peripheries. impression 6. Allow to set for 45 to 60 minutes 2 Ways to make a cast: 7. Remove the beading and boxing wax ○ inversion method 8. Carefully separate the gypsum cast from ○ boxing method the impression cast should be poured without 9. Trim the base and sides delay/within an hour thermoplastics are reversible; ('yong isa) are irreversible C2 POURING THE CAST AND CAST SEPARATION The cast should be poured without delay. The cast is separated from the impression by immersing it in warm water until it is soft enough. PAGE 4 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE - added if the paste is too thin or D ZINC OXIDE EUGENOL IMPRESSION lacks body PASTE - Increase the strength of the materials - Ex. Wax and inert powder (talc, For final impression lanolin) also rigid 4. Lanolin - 3% both for edentulous impressions 5. Resinous balsam- 10% - Increase the flow Mixed to consistency of a thin paste - Improve mixing properties Individual tray is used 6. Accelerator solution and color - 5% Rigid and thermoset which is used in - Can be incorporated in one or secondary impression taking both pastes Reacted material consists of a matrix of amorphous zinc eugenolate that holds the unreacted zinc oxide particles D2 CLASSIFICATIONS together. Manner of dispensing: paste form by ADA Specification No. 16 hard and soft set 1. SOFT-SET material D1 COMPOSITION - Tougher and not as brittle - Buttery consistency when mixed - Cannot be used to record Tube 1 - base paste WHITE undercut areas 2. HARD-SET material Zinc Oxide (French Processed or USP - - More fluid consistency when 87% - white mixed - Shorter final setting time at always wipe colorgard/petroleum jelly mouth temp and humidity (max on your patient's labial area of 10 mins) filler adds strength; makes it harder and durable D3 FACTORS THAT SHORTEN/ACCELERATE SETTING TIME 1. Fixed vegetable or mineral oil - 13% a. acts as a plasticizers Presence of water b. Change ZnO2 to paste High humidity Increases in temperature Tube 2 - accelerator paste CONTRAST Incorporating a drop or two of water or ethyl alcohol into the eugenol paste 1. Oil of cloves or eugenol - 12% before it is mixed with zinc oxide paste a. Reduces burning sensation in the soft tissues of the mouth when the mixed paste is first placed in D4 MANIPULATION contact with them 2. Gum or polymerized resin - 50% 2 equal lengths of two pastes a. facilitates the speed reaction Paste should be mixed with broad b. Produces more homogenous and strokes in a sweeping motion for 30 to 45 smoother mix sec 3. Filler (silica type) 20% Then load in a dry INDIVIDUAL tray (CUSTOM IMPRESSION TRAY) PAGE 5 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE material initially sets in 3 to 5 minutes with a final setting time of less than 10 E AQUEOUS IMPRESSION MATERIAL minutes Rinse under cold running water and shaken to dispose excess water. A. ALGINATE Do not use separating medium - (Irreversible Hydrocolloid IMPRESSION Separate cast from the impression by MATERIAL) immersion in hot water at 50° to 60°C for B. AGAR 5 to 10 min - (Reversible Hydrocolloid Impression Material) there should be no streaks in the paste and it should be uniform in color materials cannot be manipulated impervious paper: laminated paper; in without water the absence of this, use glass slab alginate is the most compatible material of all RIM is a rubber impression D5 DISINFECTION cast is the representation of your px the odor should be nice, most especially the flavor The impression is rinsed and placed in thicker mix = not a good impression disinfectant solution. Rinsing removes saliva and other contaminants. F ALGINATE The recommended disinfectant solution is 2% glutaraldehyde solution. F1 ADVANTAGES OF HYDROCOLLOID saliva and other contaminants act as retarders Can wet a tooth surface that is contaminated by oral fluids D6 OTHER ZINC OXIDE PASTES - Fewer air entrapment coz they can absorb fewer amount of oral fluids SURGICAL PASTES (PERIODONTAL PACKS) Hydrophilic After certain periodontal surgeries le.. Pouring of gypsum is easier than RIM gingivectomy, i.e. surgical removal of diseased gingival tissues) where sutures - cannot be placed, a zinc oxide-based surgical paste F2 HYDROCOLLOID BECAUSE… may be placed over the wound to aid in the retention of the medicament, to Major component is water protect the wound and to promote Both change from a viscous liquid called healing (also known as periodontal pack). the sol, to a semisolid, rubbery material, called the gel Other uses for zinc oxide PASTE (but SOL STATE is a solution of one material not a zinc oxide IMPRESSION PASTE): dissolved in another ○ periodontal packs used for healing post-surgery especially if unable to suture PAGE 6 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 8. Quaternary ammonium compounds or F3 PACKAGING OF ALGINATE chlorhexidine- to provide self-disinfection Supplied as a powder in bulk or 9. Phenylalanine- to function as a preweighed individual packets sweetener A plastic scoop is provided for dispensing the bulk powder, and a plastic cylinder is F7 PROPERTIES provided for measurement of water. A wide-bladed, reasonably stiff spatula is used to mix the powder and water. American National Standards Institute-American Dental Association (ANSI-ADA) Specification No. 18 (ISO F4 IRREVERSIBLE BECAUSE… 1563)for alginates established requirements for: THEY WILL NOT REVERSE TO SOL ONCE THEY REACT AND BECOME A GEL odor, flavor, lack of irritation, uniformity, mixing and setting times, permanent deformation (alteration in shape) at the F5 ADVANTAGES OF IRREVERSIBLE time of removal from the mouth, OVER REVERSIBLE flexibility at the time of pouring the model or die, compressive strength, Ease of mixing and manipulation reproduction of detail, compatibility with Minimum equipment necessary gypsum and deterioration of the Flexibility of the set impression packaged powder dur-ing storage. Accuracy if properly handled Low cost F8 MIXING AND SETTING TIME F6 COMPOSITION Alginate should develop a smooth, creamy consistency in less than 1 minute 1. Sodium or potassium alginate salt - to for normal set material. dissolve in water Normal-setting material should set in no 2. Calcium sulfate - to react with dissolve less than 2 minutes or more than 4½ alginate to form insoluble calcium minutes after the start of the mix. alginate Should be workable for up to 2 minutes 3. Sodium phosphate - to react Fast-setting alginate should set between preferentially with calcium sulfate and 1 and 2 minutes. serve as a retarder Be workable for at least 1¼ minutes 4. Diatomaceous earth or silicate powder The mixing time is 30 to 45 seconds. - to control consistency of mix and an increase in the temperature of the flexibility of impression water used - shortens the working and 5. Potassium sulfate or potassium zine setting times. fluoride- to counteract inhibiting effect The proportions of powder and water of alginate on settling of gypsum model also affect the setting time. or die material Thinner mixes increase the setting time 6. Organic glycol- to coat the powder particles to minimize dust during dispensing 7. Pigments- to provide color PAGE 7 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Alginate impressions are less likely to tear F9 FLEXIBILITY during removal from the mouth when they are removed rapidly. The relative amount of WP used Strength is increased if thick mixes are influence the flexibility of the set alginate used. Lower WP ratio (thicker mix) result in ○ The advantage is limited because lower flexibility the consistency becomes too thick and flow is so low that an adequate impression cannot be F10 GEL STRENGTH obtained. Tear and compressive strengths increase if the time of removal is delayed. Increased by the addition of certain modifiers such as fillers and chemicals strength of alginate impression materials F13 DIMENSIONAL CHANGE increases if thick rather than thin mixes are used. The advantage of the use of increasingly Accuracy is lost with increased time of thicker mixes is somewhat limited storage. because the consistency becomes too Set alginate is a hydrocolloid gel that thick, and the flow during seating of the contains large quantities of water. impression is so low that an adequate Water evaporates if the impression is impression cannot be obtained. stored in air, and the impression shrinks. If the impression is placed in water, it absorbs water and expands. F11 PERMANENT DEFORMATION Alginate gels shrink even under conditions of 100% relative humidity as a result of syneresis. Alginate material is flexible but not If the gel takes up water, it will expand or perfectly elastic. swell The amount of permanent deformation ○ Gel placed in water will absorb is increased when water by a process known as ○ The time before testing is imbibition shortened ○ The amount of deformation during removal is increased F14 REPRODUCTION OF DETAIL ○ The time that it is held under compression is increased ○ Thinner mixes are used The ADA specification recommends that alginates must have the minimum capabilities of transferring a line only F12 STRENGTH 0.075 mm wide to a gypsum model or die material Strengths of alginate are a function of the rate at which the impression is F15 DISINFECTION deformed. ○ Higher rates of deformation (removal) result in higher Guidelines recommend all impressions compressive and tear strengths. be rinsed and disinfected. ○ 0.5% Sodium hypochlorite - 10 minutes (soaking or spraying) PAGE 8 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE ○ iodophor solution diluted 1:213 - 10 minute immersion Rope-wax may be added to other ○ 2% glutaraldehyde diluted 1:4 - 20 borders of either upper or lower tray to minute soaking make sure extensions of alginate are well ○ Pheny|phenol diluted 1:32 - 20 supported and to be sure that alginate minute immersion flows into the vestibule when impression ○ Some manufacturers add is seated disinfectants to the alginate powder. Immersion of alginate impressions for 30 F19 MANIPULATION minutes did not affect their clinical accuracy. Materials: 1. Water dispensing cup 2. Powder dispensing cup F16 OBJECTIVES FOR TAKING ALGINATE IMPRESSIONS 3. Rubber mixing bowl 4. spatula Record All teeth in the upper and lower arch F20 PREPARATION OF THE PATIENT The entire alveolar process The retromolar area of the lower arch A. Explain the procedure The area of the hamular notch in the B.Guard against spills upper arch C. Minimize gagging - upright position A detailed, undistorted, and bubble-free D. Dental appliance reproduction of the oral tissues E. Rinse with mouthwash 1. reduce the amount of bacteria F17 SELECTION AND PREPARATION OF 2. reduce the amount of saliva, reducing THE TRAY in a more accurate impression F. Sequence - mandibular first MAXILLARY 1. Completely cover the tuberosity 2. Be 4 mm wider than the most apical F21 DISPENSING THE ALGINATE portion of the alveolar process at the molar region The recommended amount of water 3. Cover the anterior teeth with the incisors should be measured into the rubber contacting the flat arch portion of the bowl using the liquid dispensing vial. tray about 4mm for the raised palatal ○ The water should be room part of the tray temperature 22 to 23°C The powder provided in bulk should be MANDIBULAR aerated (fluffed) by tumbling the 1. Cover all teeth and retromolar pad. container several times before opening. 2. Be 4 mm wider than the buccal and ○ The powder scoop should be lingual positions of the posterior and the dipped lightly into the powder, labial and lingual positions of the anterior then tapped to ensure a full teeth. measure. 3. Allow the teeth to be centered. ○ The excess powder is scraped off with a spatula. F18 MODIFICATION OF THE TRAY ○ The powder is sifted into the rubber bowl that contains water. PAGE 9 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 6. At final seating, the incisal edges and cuspal tips should be about 1 to 2 mm F22 MIXING THE ALGINATE from the metal surface of the tray. 7. The tray is held in position until the With a stiff, wide-bladed spatula, the alginate has set, which is about 1 minute alginate powder is stirred with water. after it has lost its tackiness, tested by ○ The mix is spatulated vigorously touching a portion with the finger. against the side of the rubber 8. The set impression is removed with a bowl until a smooth, creamy mix rapid, firm pull. results. Spatulation of a regular set product F24 STEPS FOR UPPER ARCH IMPRESSION should be in about 45 seconds. ○ Fast set products should be spatulated for about 30 seconds. 1. Rotate the filled tray into the mouth in a counterclockwise motion while you Allow the impression in the mouth for retract the right cheek of the patient. additional 2 mins because the physical 2. Start seating the tray by positioning its properties improve sharply during this posterior border, and then continue period, with increases in tear strength seating parallel to the axis of the central and decreases in permanent incisors so that most of the excess deformation alginate flows both in a labial or buccal direction but not in a palatal direction. 3. As with the mandibular impression, hold F23 FILLING THE TRAY the tray in position until the alginate sets. 4. Break the peripheral seal by running a Load the alginate material into the finger around the edge, and again spatula. (spatula in one hand and the tray remove the impression with a rapid, firm in the other) pull. A useful method is to start at the posterior and push the mix anteriorly by F25 HANDLING OF THE IMPRESSION adding more and more to the posterior. Rinse the impression with cool water. F24 STEPS FOR LOWER ARCH IMPRESSION Cut away any unsupported alginate. Disinfect alginate impression. 1. 1. Push the left corner of the mouth away Rinse disinfected impression with cold with the side of the tray. water. 2. Insert the tray with a rotary motion. 3 Remove excess water. 3. Place the left heel of the tray in contact Pour gypsum model, or if short-term followed by the anterior and then the storage is necessary, wrap loosely in a right heel. wet paper towel or seal in a plastic bag. 4. Have the patient lift the tongue, and with If stored, the impression should be the free hand pull the lip down gently. placed so that the tray supports the 5. Seat the tray in the direction of the long alginate. axis of the anterior teeth, and the alginate should flow into the vestibules. Apply the seating force moderately slowly to allow the alginate to flow properly. PAGE 10 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE F26 TROUBLESHOOTING THE TAKING OF F27 STORAGE ALGINATE IMPRESSION Never be placed face down on the bench. If alginate is setting before a satisfactory Alginate not supported by the tray impression is obtained, the following should be cut away since the weight of may be contributing factors: the excess material can cause ○ Incorrect dispensing of powder deformation. and liquid Storage can be in a humid in a plastic ○ An unusually high room bag for longer that 1 hr. do not wrap too temperature tight so that alginate is not placed under ○ Too much time used in loading stress. the tray and inserting the impression retromolar area: distal to the third The best solution is to reduce the molar temperature of the mix water. rinse with mouthwash (bring this If the alginate impression contained during impressions; also bring several voids in critical areas: toothbrush) ○ Initial wetting of the powder is mandibular first before upper accomplished by squeezing the polish excess off the scoop alginate between the blade of the water before powder spatula and the side of the rubber explain to the patient how the process mixing bowl. will go on ○ When filling the tray, add alginate load alginate on the tray first with the at one location and force the posterior area alginate to flow into other portions of the tray. ○ A portion of alginate can be E AGAR spread over occlusal surfaces of the teeth before the loaded tray is inserted. Reversible hydrocolloid impression material If the alginate impression had a large The first successful elastic impression amount of material in the posterior material used in dentistry palatal area and did not record Alginate hydrocolloid and rubber adequately the area of the vestibule: impression materials have largely ○ The posterior of the tray may not replaced it. have been seated first followed by Preference for alginates is a result of the the anterior. minimum equipment required in their ○ Inadequate alginate may have clinical application. been placed in the tray. Advantage of rubber impressions has ○ The lip may not have been pulled been their greater dimensional stability, out gently to allow alginate to improved quality of gypsum models, and flow into the vestibule. the option of obtaining metal or epoxy dies. PAGE 11 CHESKA NOREEN ALAY– DDM 3B  DENTAL MATERIALS PPT-BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 3rd compartment - tempering is done in F23 SUPPLIED AS 110°F (45°C) water bath several minutes before used gel in a collapsible tube for impression As cartridges or gel sticks (syringe F23 EQUIPMENT USE material) Bulk containers (for duplication) requires special equipment to heat, store and temper the materials F23 COMPOSITION special impression tray that circulate cooling water 12% to 15% agar - basic constituent though inexpensive and very accurate 0.2% borax - as a strength improver accurate, special equipment limits the 1% to 2% potassium sultate - to ensure popularity of the material proper setting of the gypsum model and die materials F23 MANIPULATION 0.1% benzoates - as preservatives Other additives to control the flow of the material when heated After the tray is properly positioned in the Flavoring patient's mouth, water at 13°C is 80% to 85% water circulated throughout the tray. Syringe materials have a lower When the agar has gelled, the peripheral concentration of agar. seal around the impression is broken, and the impression removed rapidly from the mouth. F23 PROPERTIES The impression is rinsed with water, disinfected, and rinsed again. Agar gel is converted to sol by heating in The impression is poured in plaster or water, usually boiling (100°C). stone. ○ Shrink when stored in air or 100% ○ Prolonged contact of the agar relative humidity impression with plaster and stone ○ Expand when stored in water results in a rougher than normal Prompt pouring is recommended. surface on the model. F23 MANIPULATION ADVANTAGES AND DISADVANTAGES ADVANTAGES DISADVANTAGES A tube of tray material is placed in one of the water baths of a hydrocolloid Works well in wet Require special conditioner at 100°C for 10 to 15 minutes. environment when equipment The conditioner has three the margins of a temperature-controlled water baths. crown preparation 1st compartment - boiled to change the are subgingival or not rubbery material ( the gel) into a viscous easily kept dry liquid (the sol) 2nd compartment - storage; 150°F (65°C) Poor tear strength water bath until needed. This can be done at the beginning of the day or week PAGE 12 CHESKA NOREEN ALAY– DDM 3B