Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Dental Materials > Dental impression materials > Flashcards

Dental impression materials Flashcards

1
Q

what are impression materials used for

A
  • to reproduce the form of the teeth, restorative treatments and the surrounding oral tissues
  • impressions are a negative reproduction of dental structures
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the 3 steps of impressions

A
  1. preliminary impressions: not highly accurate; used for study, diagnosing problems, teaching
  2. final impressions: highly accurate; main use is fabrication of indirect restorations
  3. bite registration: highly accurate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

who takes preliminary impressions

A
  • taken either by the dentist or the dental hygienist or the expanded function of the dental assistant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are common uses of alginate impressions

A
  • diagnostic casts (study models)
  • preliminary impressions for dentures
  • partial denture frameworks
  • opposing casts for crown and bridge
  • repairs of partial and complete dentures
  • provisional restorations
  • custom trays for fluoride or bleaching
  • sport protectors and occlusal splints (night guards)
  • orthodontic appliances
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are final impressions

A
  • taken by the dds

- the most accurate reproduction of the teeth and surrounding tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are final impressions used to make

A
  • indirect restorations
  • partial or full dentures
  • implants
  • veneers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are bite registrations

A
  • taken by the dentist, hygienist, or assistant
  • makes a reproduction of the occlusal relationship between the max and band teeth
  • provides an accurate registration of the patient’s centric relationship between the max and band arches
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

why must impression trays be sufficiently rigid

A
  • carry the impression material into the oral cavity
  • hold the material in close proximity to the teeth
  • avoid breaking during removal
  • prevent warping of the completed impression
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are quadrant trays

A
  • impression trays that covers on half of the arch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are section trays

A
  • impression trays that cover the anterior portion of the arch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are full arch trays

A
  • impression trays that cover the entire arch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are smooth trays

A
  • impression trays

- interior of the tray is painted or sprayed with an adhesive to hold the impression materiak

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are perforated trays

A
  • impression trays

- has holes in the tray to create a mechanical lock to hold the material in place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is tray selection criteria

A
  • must feel comfortable to the patient
  • extend slightly beyond the facial surfaces of the teeth
  • extend approximately 2-3 mm beyond the third molar, retromolar, or tuberosity area of the arch
  • depth to allow 2-3 mm of material between the tray and incisal or occlusal edges of the teeth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are 3 examples of tray adhesives

A
  • VPS adhesives (blue): for polyvinyl siloxane and polyether impression materials
  • rubber base adhesive (brown): used with rubber bae impression materials
  • silicone adhesive (orange-pink): used with silicone impression materials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are hydrocolloid impression materials

A
  • elastic impression materials
  • hydro meaning water
  • colloid meaning gelatine substance
  • reversible meaning gel changes to liquid with heal
  • *material used to obtain preliminary and final impressions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is reversible hydrocolloid

A
  • material used for final impressions

- an impression material that changes from a solid to a gel and then back to a solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is irreversible hydrocolloid

A
  • material that cannot return to a liquid state after it becomes a gel
  • alginate: the irriversible hydrocolloid most widely used for taking preliminary impressions
  • irreversible reaction
  • calcium sulfate dehydrate and sodium alginate and water = calcium alginate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is algniate

A
  • an elastic impression material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is the composite of alginate

A
  • an irreversible hydrocolloid
  • hydrocolloid is a suspension of medium sized particles in a water based solution
  • irreversible means it cannot be softened after setting (without damage to the material)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the use of alginate impressions

A
  • to take impressions that will be used to:
  • pour study models
  • models for pt education
  • make items that do not require highly accurate dimensions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

why is alginate the most widely used impression material

A
  1. easy to manipulate
  2. reasonably accurate (operator dependent)
  3. inexpensive
  4. no special equipment needed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the makeup of alginate

A
  • potassium (sodium) alginate (15-20%)
  • calcium sulfate (14-20%)
  • trisodium phosphate (2%)
  • diatomaceous earth (55-60%)
  • potassium sulfate (10%)
  • other additives: colour, flavour, disinfectants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is potassium (sodium) alginate (15-20%)

A
  • comes from seaweed; is also used in foods such as ice cream as a thickening agent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is calcium sulfate (15-20%)

A
  • reacts with the potassium alginate to form the gel
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is trisodium phosphate (2%)

A
  • added to slow down the reaction time for mixing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is diatomaceous earth (55-60%)

A
  • a filler that adds bulk to the material
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is the potassium sulphate (10%)

A
  • ensures set of gypsum materials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what are the physical phases of alginate

A
  • first phase: sol (as in solution). in the sol phase, the material is in a liquid or semiliquid form
  • second phase: gel in the phase, the material is semisolid, similar to a gelatine dessert
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

how do you package and wrote alginate

A
  • containers

- pre-measured packages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what are causes for distortion and dimensional change

A
  • imbibition: alginate impression stored in water or very wet paper towel will absorb the additional water and expand
  • syneresis: alginate impression remains in the open air, moisture will evaporate causing it to shrink and distort
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what are alginate settings

A
  • normal set alginate: working time of 2 minutes and a setting time of up to 4.5 minutes after mixing
  • fast set alginate: working time of 1.25 minutes and a setting time of 1 to 2 minutes
  • colour set alginate: mixing colour, thoroughly mixed and ready to be put in o.c. colour, set colour
33
Q

what is the working time

A
  • the time allowed for mixing the alginate, loading the tray, and positioning the tray in the patient’s mouth
34
Q

what is the setting time

A
  • the time required for the chemical reaction to be completed
  • setting time may be changed by varying the water temperature
35
Q

how can we alter the setting times of alginate

A
  • cooler water: can increase the setting time if additional time is needed for the procedure
  • warmer water: can reduce or shorten the setting time of the procedure (sensitivity)
36
Q

what is the water to powder ratio for an adult mandibular impression

A
  • two scoops of power and two measures of water
37
Q

what is the water to powder ratio for an adult maxillary impression

A
  • three scoops of powder and three measures of water
38
Q

what are the objectives impression taking

A
  1. accurate impression: tray size, tray placement in oc, tray removal
  2. patient comfort: tray selection, positioning - post to ant, explanation prior to placement
  3. infection control
39
Q

how do you select the proper size and shape tray (width and length)

A
  • width: adequate thickness of material on facial and lingual surfaces
  • length: allow coverage of retromolar areas (mn) and tuberosity (mx). anterior area needs 1/4 inch clearance
40
Q

how do you explain the procedure to the patient

A
  • the material will feel cold, will have or not have a specific flavour, and the material will set quickly
  • breathe deeply through your nose to help you relax and be more comfortable
  • refraining from talking after the tray has been placed will help make a good impression
  • raising their hand is best if they need to communicate during the procedure
41
Q

what is fluffing

A
  • before measuring powder, it should be fluffed 2-3 times before opening the container
  • fluffing = turning the powder container upside down, then right side up
  • fluffed alginate should be left to sit for 2-3 seconds after fluffing to ensure most of the dust created has resettled, so you do not breathe it in
42
Q

what are cautions before beginning to mix

A
  • be sure to wear a mask while spending and mixing alginate. alginate dust is potentially hazardous to inhale because it contains silicone dioxide in the diatomaceous earth fillers, as well as other chemicals
43
Q

what is the impression procedure

A
  1. alginate powder is mixed with water in a flexible bowl to a soft paste consistency
  2. load it into a tray to carry it to the mouth
  3. place tray over the patient’s teeth and allow to set
  4. when set, remove from the mouth
  5. rinse to remove any adherent saliva, blood, or debris
  6. disinfect before pouring stone into impression
44
Q

how to mix alginate

A
  • the powder and liquid must be mixed throughly by stropping to achieve a creamy consistency without bubbles
  • begin by stirring: tip of spatula is submerged and moves in circles
  • when most of powder is wet begins stropping
45
Q

what is stropping

A
  • using the flat side of the spatula, sweep back and forth across a surface (the side of the bowl). lift the spatula slightly when switching directions. try not to remove tip from material
46
Q

what is bowl gathering

A
  • gather from the bowl the alginate
  • scrape spatula along side of the bowl to pick up all material
  • scrape both sides of spatula on edge of bowl
  • repeat pickup and placement process
47
Q

how do you load the tray

A
  • the material is loaded onto the tray in large increments with the spatula
  • it can be smoothed out prior to insertion into the mouth. run under water
  • always take the impression first since gagging less likely which will enhance trust in the clinician
48
Q

what are voids

A
  • areas of air in the mix
  • internal voids weaken the material
  • surface voids do not record anatomy
49
Q

how do we prevent voids

A
  • powder is added to the water, not vice versa

- key to avoiding voids: keep the spatula tip submerged throughout the wetting and stropping process

50
Q

how do we take mandibular impressions

A
  • 7/5 oclock position standing in front of the patient
  • right handed: right side of tray is used to retract left corner and a finger or mouth mirror retracts the right corner of the mouth
  • left handed: left side of tray used o retract right corner of mouth and a finger retracts the left corner of the mouth
  • rotate tray into the mouth
  • align over the teeth with tray handle at the midline
  • seat in the posterior first
  • as the tray is seated anteriorly the lower lip is pulled out of the way to allow alginate to flow into the anterior vestibule
  • ask Pte to lift the tongue to the roof of the mouth momentarily and then relax it. this allows alginate to flow into the lingual vestibule and define the lingual frenum attachment
  • stabilize tray by placing the index and middle fingers of the right/left hand over the right and left sides of the arch
51
Q

how do we take maxillary impressions

A
  • 11/1 o’clock position standing just behind patient
  • retract right/left side of the mouth with the tray and the left/right side of the mouth with a gloved finger or mouth mirror
  • align at midline and over teeth
  • seat posterior first, gently to anterior to allow the alginate to flow anteriorly and not back into the palate and down the throat
52
Q

how do we remove impression trays

A
  • leave in the mouth for 1-2 mins after it sets because it gains in tearing strength
  • alginate has poor tensile strength therefore remove in one motion DO NOT ROCK
  • use a finger at the side of the tray to apply pressure to break the seal while pulling the tray quickly away from the teeth with a snap
53
Q

how do we care for the finished impression

A
  • alginate has poor compressive strength
  • never place impression side down on a counter top
  • always place it tray side down
  • rinse gently
  • disinfect (10 mins), rebound will occur
54
Q

what is an acceptable alginate impression

A
  • impression tray is centered
  • complete “peripheral roll” , including all of the vestibular areas
  • tray is not ‘overseated’
  • impression is free from tears or voids
  • sharp anatomic detail of all teeth and soft tissues
  • retromolar area, lingual frenum, tongue space, and mylohyoid ridge are reproduced in the mandibular impression
  • the hard palate and tuberosities are recorded in the mx impression
55
Q

what is elastomeric impressions

A
  • final impression
  • a material that is used when an extremely accurate impression is essential. the term elastomeric means having elastic or rubberlike qualities
56
Q

what are characteristics of elastomeric impression materials

A
  • base: packaged as a paste in a tube, cartridge, putty in a jar
  • catalyst: ‘accelerator’ packaged as a paste in a tube, cartridge, liquid in a bottle with a dropper top
57
Q

what are forms of elastomeric materials

A
  • light bodied: also referred to as a syringe type or wash type. used because of its ability to flow in and around the details of the prepared tooth. a special syringe, or extruder, is used to place the light-bodied material on and immediately around the prepared teeth
  • regular and heavy bodied: ‘also referred to as tray type’ materials they are much thicker. as the name implies, used to fill the tray. stiffness helps to force the light bodied material into close contact with the prepared teeth and surrounding tissues to ensure a more accurate impression of the details of a preparation
58
Q

what is the basic impression technique

A
  1. the material selected depends upon the dentist’s preference and the type of impression required for the procedure
  2. the dentist prepares the tooth or teeth for the impression
  3. the light-bodied material is prepared and loaded into the syringe and transferred to the dds
  4. the DDS places the light bodied material over and around the prepared teeth and onto the surrounding tissues
  5. the heavy bodied material is prepared and loaded into the tray and transferred to the dds
  6. when the impression material has reached final set, the impression is removed and inspected for accuracy
  7. the impression is disinfected, placed in a biohazard bag, labeled and readied for the laboratory technician
59
Q

what are the curing stages for elastomeric materials

A
  • initial set: the first set results in stiffening of the paste without the appearance of elastic properties. the material may be manipulated only during this stage
  • final set: the second stage begins with the appearance of elasticity and proceeds through a gradual change to a solid rubber like mass. the material must be in place in the mouth before the elastic properties of the final set begin to develop
  • final cure: the last stage occurs from 1-24 hours
60
Q

what are the 4 types of elastomeric materials

A
  • polysulfide
  • polyether
  • silicone
  • polyvinyl siloxane
61
Q

what is occlusal registration

A
  • an accurate registration of the normal centric relationship of the maxillary and mandibular arches. also commonly referred to as the bite registration
62
Q

what are the 4 purposes of the bite registration

A
  1. proper occlusion for cementation
  2. orientation of the bite: open bite, cross bite, edge to edge, edentulous areas
  3. place between casts during: trimming, transportation, storage; to prevent breakage
  4. essential when mounting casts on an articulator
63
Q

what are different types of occlusal registration

A
  • wax bite: useful when the diagnostic casts are trimmed; the most common technique is to use a softened baseplate wax (bite into wax)
  • polysiloxane bite registration paste: supplied both as a paste system and also as a cartridge. the material is fast setting. there is no resistance to biting forces. there is no odor or taste for the patient. it gains dimensional stability over time. it is convenient to use
  • zinc oxide eugenol: bite registration paste. Zoe paste has little to no resistance to bite closure and if taste setting material. material is supplied in a paste system and is a fast setting material. material is supplied in a paste system and dispensed onto a paper pad, mixed, and placed onto a gauze tray for the patient to bite into
64
Q

what are the 3 types of impressions

A
  • preliminary impressions: irreversible hydrocolloid (alginate)
  • final impressions: reversible hydrocolloid, elastomeric
  • bite registration (3 type): wax, polysiloxane, zinc-oxide eugenol
65
Q

what are the criteria for custom impression trays

A
  • be sufficiently rigid
  • fit and adapted well to the arch
  • provide accurate adaptation to an edentulous or partially edentulous arch
  • maintain an even distribution of impression material
  • max tray must cover the teeth, hard palate and extend slightly beyond the gingival margin
  • mand tray must cover the teeth and extend beyond the gingival margin
66
Q

what are custom tray materials

A
  • self-curing acrylic resins
  • provides a strong and easily adaptable material to create a custom tray
  • disadvantage: hazards of working with the liquid monomer is very volatile
67
Q

what are the 3 custom tray materials

A
  1. light cured resin tray materials

2. vacuum-formed thermoplastic resin

68
Q

what are light cured resin trays materials

A
  • a premixed, prefabricated light cured tray material not containing methylmethacrylate monomer
  • properties of this material provide excellent adaptation to the model
  • used for any impression situation: dentulous, edentulous, or partially edentulous
69
Q

what are vacuum-formed thermoplastic resin

A
  • a vacuum former uses heat and vacuum to shape a sheet of thermoplastic resin to a diagnostic model
  • uses: impression tray; making a provisional; vital bleaching tray; mouth guard
70
Q

what is the chemical makeup of polysulfide impression material

A
  • base: mercaptan polysulfide
  • cross linking agent: sulfur and/or lead peroxide
  • catalysts: copper hydroxides, zinc peroxide, organic hydro peroxide
  • fillers: zinc sulfate, lithopone, or calcium sulfate dihydrate
71
Q

how do you manipulate and use technique considerations for polysulfide material

A
  • dispense pastes at the top of the mixing pad
  • mix pastes with he tip of a spatula to incorporate the material first
  • transfer the material to the fresh surface of the mixing pad
  • water, saliva, and blood affect polysulfide material
  • impression should be removed quickly after setting – do not rock the tray
  • adhesive must be thin and dry before adding the impression material
  • wait 20-30 mins before pouring the impression for the stress relaxation to occur in the material
  • be careful of globe powder contamination
72
Q

what is the chemical makeup of polyether impression material

A
  • base: polyether
  • cross-linking agent: sulfate
  • catalysts: glycol-based plasticizers
  • filler: silica
73
Q

what are manipulation and technique considerations for polyether material

A
  • material is very stiff, which makes it difficult to remove without rocking
  • when removing the impression, break the seal and rock slightly to prevent tearing
  • water, saliva, and blood affect polyether material
  • added moisture will increase the impression’s marginal discrepancy
  • increased water absorption occurs if a thinning agent is used
74
Q

what are reversible hydrocolloid

A
  • takes accurate impression of the mouth and easily removed for Pte comfort
  • main used is crown and bridge
75
Q

what is the chemical makeup of reversible hydrocolloid

A
  • 85% water
  • 13% agar
  • agar is an organic substance derived from seaweed
  • additional chemical modifiers are added to aid in the handling characteristics
76
Q

what are the 3 compartments for reversible hydrocolloid

A
  1. ‘conditioner’ bath, liquefies the semi solid material at 212 Fahrenheit, the cools to 150 fahrenheit
  2. ‘storage’ bath, readies the material for the impression in their tubes
  3. ‘tempering’ bath, keeps the material at 110 Fahrenheit in syringe and tray
77
Q

what are the 2 different types of reversible hydrocolloid

A
  • tray material: packages in plastic tubes. each tube has enough material to fill a full arch, water-cooled tray
  • syringe material: packaged in plastic or glass cartridges that fit a syringe or in a preloaded syringe or preformed sticks that refill special hydrocolloid inlay syringes
78
Q

what is the application process of reversible hydrocolloid impression material

A
  1. a stock water-cooled tray is selected
  2. plastic stop care placed in the tray
  3. tubing is connected to the ray and to the water outlet for drainage
  4. the material is liquefied and moved to the storage bath
  5. the light bodied material is placed in the syringe, and heavy bodied material is placed in the tray
  6. the light bodied material is expressed around the prepared tooth and the dds seats the tray

Dental Materials (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions