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Occlusion > Alginate and Dental Stone > Flashcards

Alginate and Dental Stone Flashcards

1
Q

SKIPPED

the ideal impression material

A 
EASY TO MIX AND HANDLE.
SUITABLE WORKING TIME.
SUITABLE SETTING TIME.
COMPATIBLE WITH STONE
NOT TOXIC OR ALLERGENIC TO THE PATIENT.
DIMENSIONALLY STABLE ON SETTING.
ACCURATE TO RECORD THE FINE DETAILS
HAS ACCEPTABLE ODOR AND TASTE.
ADEQUATE STRENGTH.
ADEQUATE SHELF LIFE.
ECONOMICAL
 READY TO BE DISINFECTED WITHOUT LOSS OF ACCURACY.
 FLUID OR PLASTIC WHEN INSERTED INTO THE MOUTH.
IT MUST BE AN EXACT RECORD OF ALL THE ASPECTS 
OTHER TEETH AND TISSUE SURROUNDING 
IT MUST BE FREE FROM AIR BUBBLES ESPECIALLY IN THE FINISH LINE AREA.
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2
Q

key properties of impresion materials (2)

A

accuracy

dimensional stability

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3
Q

accuracy

A

ability to replicate the intraoral surface details

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4
Q

dimensional stability

A

ability to retain its absolute dimensional size over time

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5
Q

nonelastic impression materials (4)

A

gypsum (plaster)
impression compound
zinc oxide eugenol
impression waxes

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6
Q

elastic impression material (2)

A

hydrocolloids

non aqueous elastomers

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7
Q

hydrocolloids (2)

A

agar reversible

alginate irreversible

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8
Q

non aqueous elastomers (4)

A

polysulfide
polyethers
condensation silicone
addition silicone

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9
Q

ALGINATE

(IRREVERSIBLE HYDROCOLLOID)(IRREVERSIBLE HYDROCOLLOID) was developed as a substitute for

A

AGAR IMPRESSION
MATERIAL WHEN ITS SUPPLY BECAME SCARCE DURING WORLD
WAR II.

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10
Q

ALGINATE IS BASED ON A NATURAL SUBSTANCE EXTRACTED FROM CERTAIN — —. THE SUBSTANCE IS CALLED

A

BROWN SEAWEED
ANHYDRO-Β-D-
MANNURONIC ACID OR ALGINIC ACID

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11
Q

THE PRINCIPAL FACTORS RESPONSIBLE FOR THE SUCCESS OF THIS

TYPE OF IMPRESSION MATERIAL ARE THAT IT IS (3)

A

EASY TO MANIPULATE,
COMFORTABLE FOR THE PATIENT,
AND RELATIVELY INEXPENSIVE SINCE IT DOES NOT REQUIRE ELABORATE EQUIPMENT

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12
Q

THE CHIEF ACTIVE INGREDIENT OF THE IRREVERSIBLE
HYDROCOLLOID IMPRESSION MATERIALS IS ONE OF THE SOLUBLE
ALGINATES, SUCH AS (3)

A

SODIUM,
POTASSIUM,
OR TRIETHANOLAMINE ALGINATE

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13
Q

WHEN THE SOLUBLE ALGINATES ARE MIXED WITH WATER,

THEY FORM A – QUITE READILY

A

SOL

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14
Q

alginate composition (6)

A 
potassium alginate 
calcium sulfate 
zinc oxide 
potassium titanium fluoride 
diatomaceous earth
sodium phosphate
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15
Q

potassium alginate
function:
weight percentage:

A

soluble aginate

15

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16
Q

calcium sulfate
function:
weight percentage:

A

reactor

16

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17
Q

zinc oxide
function:
weight percentage:

A

filler particles

4

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18
Q

potassium titanium fluoride
function:
weight percentage:

A

accelerator

3

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19
Q

diatomaceous earth
function:
weight percentage:

A

filler particles

60

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20
Q

sodium phosphate
function:
weight percentage:

A

retarder

2

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21
Q

THE TYPICAL SOL-GEL REACTION CAN BE DESCRIBED SIMPLY

AS A REACTION OF

A

SOLUBLE ALGINATE WITH CALCIUM SULFATE
AND THE FORMATION OF AN INSOLUBLE CALCIUM ALGINATE
GEL

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22
Q

IN THE CLINICAL SETTING, IT IS TEMPTING TO ALTER THE
SETTING TIME BY CHANGING THE W/P RATIO OR THE MIXING
TIME. THIS SLIGHT MODIFICATION CAN HAVE MARKED EFFECTS
ON THE (3)

A

PROPERTIES OF THE GEL,
THE TEAR STRENGTH,
AND THE ELASTICITY

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23
Q

THE CLINICIAN, HOWEVER, CAN SAFELY INFLUENCE THE
SETTING TIME BY ALTERING THE — OF THE
WATER.

A

TEMPERATURE

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24
Q

ALGINATE IMPRESSION MATERIALS ARE —, SO

MOIST TISSUE SURFACES ARE NOT A PROBLEM

A

HYDROPHILIC

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25
Q

GENERALLY, ALGINATES ARE USED AS A

A

FIRST PRELIMINARY
IMPRESSION TO CONSTRUCT A CUSTOM TRAY FOR A MORE
ACCURATE SECOND IMPRESSION OR TO MAKE STUDY MODELS
TO HELP WITH TREATMENT PLANNING AND DISCUSSIONS WITH
THE PATIENT.

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26
Q

SKIPPED

MAKING AN ALGINATE IMPRESSION (7)

A
  1. THE MEASURED POWDER IS SIFTED INTO PREMEASURED WATER THAT
    HAS ALREADY BEEN POURED INTO A CLEAN RUBBER BOWL.
  2. THE POWDER IS INCORPORATED INTO THE WATER BY CAREFULLY
    MIXING WITH A METAL OR PLASTIC SPATULA THAT IS SUFFICIENTLY
    FLEXIBLE TO ADAPT WELL TO THE WALL OF THE MIXING BOWL. ALL OF
    THE POWDER MUST BE DISSOLVED.
  3. THE RESULT SHOULD BE A SMOOTH, CREAMY MIXTURE THAT
    DOES NOT READILY DRIP OFF THE SPATULA WHEN IT IS RAISED
    FROM THE BOWL.
  4. BEFORE SEATING THE IMPRESSION, THE MATERIAL SHOULD HAVE
    DEVELOPED SUFFICIENT BODY SO THAT IT WILL NOT FLOW OUT OF
    THE TRAY AND GAG THE PATIENT.
  5. THE MIXTURE IS PLACED IN A SUITABLE TRAY, WHICH IS THEN
    PLACED IN THE MOUTH. IT IS IMPERATIVE THAT THE IMPRESSION
    ADHERE AND BE RETAINED TO THE TRAY SO THAT THE
    IMPRESSION CAN BE WITHDRAWN FROM AROUND THE TEETH.
  6. ALGINATE IS VERY WEAK; THEREFORE THE TRAY MUST
    FIT THE PATIENT’S ARCH SO THAT THERE IS A
    SUFFICIENT BULK OF MATERIAL. THE THICKNESS OF THE
    ALGINATE IMPRESSION BETWEEN THE TRAY AND THE
    TISSUES SHOULD BE AT LEAST 3 MM.
  7. ALGINATE HYDROCOLLOID MATERIALS ARE STRAIN-
    RATE DEPENDENT. THUS THE TEAR STRENGTH IS
    INCREASED WHEN THE IMPRESSION IS REMOVED
    WITH A SNAP.
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27
Q

mixing time

A

45 s to 1 min

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28
Q

THE THICKNESS OF THE
ALGINATE IMPRESSION BETWEEN THE TRAY AND THE
TISSUES SHOULD BE AT LEAST - MM.

A

3

29
Q

impression disinfection

A

disinfectant soaked paper towel/plastic bag, 10 min

30
Q

does disinfection affect VPS?

A

not adversely affected

31
Q

HYDROCOLLOIDS

•• IMBIBITION:

A

EXPANSION AFTER 10 MIN

32
Q

POLYSULFIDE, POLYETHER

•• POTENTIAL EXPANSION,

A

increase exposure time

33
Q

digital impressions (2)

A
  • LESS FOCUS ON RESEARCH AND DEVELOPMENT OF IMPRESSION MATERIALS
  • DIGITAL IMPRESSIONS, SCAN AND THEN SEND ELECTRONIC FILE
34
Q

SOME CURRENT digital impression SYSTEMS: (3)

A

crerec
itero element
LAVA

35
Q

which digital impression system will we use in lab?

A

cerec

36
Q

CHEMICALLY, THE GYPSUM PRODUCED FOR DENTAL APPLICATIONS

IS NEARLY PURE

A

CALCIUM SULFATE DIHYDRATE

37
Q

DIFFERENT — FORMS OF GYPSUM HAVE BEEN USED FOR
CENTURIES FOR CONSTRUCTION PURPOSES AND FOR MAKING
ARTIFACTS.

A

CRYSTALLINE

38
Q

GYPSUM PRODUCTS ARE USED IN DENTISTRY FOR THE

A

PREPARATION OF STUDY MODELS FOR ORAL AND MAXILLOFACIAL
STRUCTURES AND AS IMPORTANT AUXILIARY MATERIALS FOR
DENTAL LABORATORY OPERATIONS THAT ARE INVOLVED IN THE
PRODUCTION OF DENTAL PROSTHESES.

39
Q

WHEN PLASTER IS MIXED WITH FILLERS, SUCH AS DIFFERENT

FORMS OF SILICA, IT IS KNOWN AS A

A

GYPSUM DENTAL

INVESTMENT

40
Q

THE PRINCIPAL CONSTITUENT OF GYPSUM-BASED PRODUCTS SUCH

AS DENTAL PLASTERS AND STONES IS

A

CALCIUM SULFATE

HEMIHYDRATE

41
Q

VARIOUS GYPSUM PRODUCTS REQUIRE DIFFERENT AMOUNTS OF
WATER AND THESE DIFFERENCES ARE ACCOUNTED FOR
PRINCIPALLY BY THE

A

SHAPE AND COMPACTNESS OF THE
CRYSTALS. THESE FACTORS ARE REGULATED BY THE
MANUFACTURER

42
Q

THE — THEORY PROPOSES THAT WHEN MIXED WITH
WATER, PLASTER ENTERS INTO THE COLLOIDAL STATE
THROUGH A SOL-GEL MECHANISM.

A

COLLOIDAL

43
Q

THE — THEORY SUGGESTS THAT REHYDRATED
PLASTER PARTICLES JOIN TOGETHER THROUGH HYDROGEN
BONDING TO THE SULFATE GROUPS TO FORM THE SET
MATERIAL.

A

HYDRATION

44
Q

HOWEVER, THE MOST WIDELY ACCEPTED MECHANISM IS THE — — THEORY BASED ON DISSOLUTION OF PLASTER AND INSTANT RECRYSTALLIZATION OF GYPSUM, FOLLOWED BY INTERLOCKING OF THE CRYSTALS TO FORM THE SET SOLID

A

DISSOLUTION PRECIPITATION

45
Q

THE SETTING REACTION OF GYPSUM OCCURS BY: (4)

A

DISSOLUTION OF CALCIUM SULFATE HEMIHYDRATE

FORMATION OF A SATURATED SOLUTION OF CALCIUM SULFATE

AGGREGATION OF LESS SOLUBLE CALCIUM SULFATE DIHYDRATE, AND

PRECIPITATION OF THE DIHYDRATE CRYSTALS.

46
Q

THE – RATIO IS AN IMPORTANT FACTOR IN DETERMINING
THE PHYSICAL AND CHEMICAL PROPERTIES OF THE FINAL
GYPSUM PRODUCT.

A

W/P

47
Q 
Mixing time (MT)

A

DEFINED AS THE TIME FROM THE ADDITION OF
THE POWDER TO THE WATER UNTIL THE MIXING
IS COMPLETED.

48
Q

MECHANICAL MIXING OF STONES AND PLASTERS

IS USUALLY COMPLETED IN

A

20 TO 30 SEC.

49
Q

HAND-SPATULATION GENERALLY REQUIRES AT

LEAST — TO OBTAIN A SMOOTH MIX.

A

A MINUTE

50
Q

WORKING TIME (WT)

A

WORKING TIME IS THE TIME AVAILABLE TO USE A
WORKABLE MIX, ONE THAT MAINTAINS A UNIFORM
CONSISTENCY TO PERFORM ONE OR MORE TASKS.

51
Q

SETTING TIME (ST)

A

THE TIME THAT ELAPSES FROM THE BEGINNING OF MIXING

UNTIL THE MATERIAL HARDENS

52
Q

PROBABLY THE MOST EFFECTIVE AND PRACTICAL METHOD FOR

CONTROLLING THE SETTING TIME IS THE

A

ADDITION OF CERTAIN
CHEMICAL MODIFIERS TO THE MIXTURE OF PLASTER OR DENTAL
STONE.

53
Q

IF THE CHEMICAL ADDED DECREASES THE SETTING TIME, IT IS
KNOWN AS AN—; IF IT INCREASES THE SETTING TIME, IT
IS KNOWN AS A —

A

accelerator

retarder

54
Q

THE CRYSTALLIZATION PROCESS IS PICTURED AS AN

A

OUTGROWTH OF CRYSTALS FROM NUCLEI OF
CRYSTALLIZATION. ON THE BASIS OF THE ENTANGLEMENT OF
THE DIHYDRATE CRYSTALS, CRYSTALS GROWING FROM THE
NUCLEI CAN INTERMESH WITH AND OBSTRUCT THE GROWTH
OF ADJACENT CRYSTALS.

55
Q

WHEN SUFFICIENT CRYSTALS FORM TO PRODUCE THE

OUTWARD THRUST BY IMPINGEMENT,

A

SETTING EXPANSION

FOLLOWS

56
Q

SOMETIMES A SETTING EXPANSION IS ADVANTAGEOUS FOR A
DENTAL PROCEDURE; SOMETIMES IT IS DISADVANTAGEOUS,
BECAUSE IT MAY BE A SOURCE OF —.

A

ERROR

57
Q

SETTING EXPANSION MUST BE CONTROLLED TO OBTAIN THE

DESIRED — IN DENTAL APPLICATIONS.

A

ACCURACY

58
Q

THE MOST EFFECTIVE METHOD FOR CONTROLLING THE SETTING
EXPANSION IS THROUGH THE ADDITION OF CHEMICALS BY THE
MANUFACTURER. THE SETTING EXPANSION CAN BE REDUCED
BY ADDING EITHER (3)

A

POTASSIUM SULFATE, SODIUM CHLORIDE,

OR BORAX.

59
Q

IMPRESSION PLASTER (TYPE I) (2)

A

COMPOSED OF PLASTER OF PARIS, TO WHICH MODIFIERS
HAVE BEEN ADDED TO REGULATE THE SETTING TIME AND
THE SETTING EXPANSION.
RARELY USED ANYMORE FOR DENTAL IMPRESSIONS.

60
Q

MODEL PLASTER (TYPE II) (2)

A

IT IS USUALLY MARKETED IN THE NATURAL WHITE COLOR,
THUS CONTRASTING WITH STONES THAT ARE GENERALLY
COLORED.
TYPE II MODEL PLASTER IS RELATIVELY WEAK
AS EVIDENCED BY A COMPRESSIVE STRENGTH AS LOW
AS 9 MPA AND A TENSILE STRENGTH OF 0.6 MPA.

61
Q

DENTAL STONE (TYPE III)

A

TYPE III STONES ARE PREFERRED FOR CASTS USED
TO PROCESS DENTURES, BECAUSE THE STONE HAS
ADEQUATE STRENGTH FOR THAT PURPOSE AND THE
DENTURE IS EASIER TO REMOVE AFTER PROCESSING.

62
Q

DENTAL STONE, HIGH STRENGTH (TYPE IV)

A

 A HARD SURFACE IS NECESSARY FOR A DIE STONE,
BECAUSE THE CAVITY PREPARATION IS FILLED WITH
WAX THAT IS CARVED FLUSH WITH THE MARGINS OF
THE DIE.

63
Q

DENTAL STONE, HIGH STRENGTH, HIGH EXPANSION (TYPE V)

A

THE TYPE V DENTAL STONE GYPSUM PRODUCT EXHIBITS
AN EVEN HIGHER COMPRESSIVE STRENGTH THAN DOES
THE TYPE IV DENTAL STONE.

64
Q

THE SETTING EXPANSION HAS BEEN INCREASED FROM A MAXIMUM OF (TYPE V)

A

0.10% TO 0.30%.

65
Q

THE RATIONALE FOR THE INCREASE IN SETTING EXPANSION

LIMITS IS THAT

A

CERTAIN NEWER ALLOYS, SUCH AS BASE
METAL, HAVE A GREATER CASTING SHRINKAGE THAN DO THE
TRADITIONAL NOBLE METAL ALLOYS. THUS HIGHER EXPANSION
IS REQUIRED IN THE STONE USED FOR THE DIE TO AID IN
COMPENSATING FOR THE ALLOY SOLIDIFICATION SHRINKAGE.

66
Q

Maximum

Intercuspation

A

All the teeth
contact in a
stable way

67
Q

Centric Occlusion

Contact:

A

First contact when
leaf gauge is in
place on the
anterior teeth

68
Q

CR: Condyle in the most — position

A

anterior-superior

Occlusion (15 decks)

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