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WELCOME TO
DENTAL MATERIALS IRESD2012
Dr. Fred Berry
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WELCOME TODENTAL MATERIALS I
RESD 7022012
Dr. Fred Berry
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Hope you had aMERRY CHRISTMAS
HAPPY NEW YEARand a
Restful Time off
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PLEASE WRITE YOUR NAME ONTHE FRONT OF YOUR MANUAL
NOW!!
THANKS!!!!
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Manual PAGE # 1
Schedule Page # 3
Course Texts Page # 6
PLEASE WEAR LAB JACKETSAND NAME TAGS
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Why Dental Materials?
Learn the basic materials utilized infuture lab courses and on clinic prior tograduation
Questions on National Board Part II Exam Daily / hourly use in dental practice
Familiarity with materials is essential to
quality dental treatment Using a material incorrectly = FAILURE
loss of income & unnecessary trauma to
your patient
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REVERSIBLE AGARHYDROCOLLOID
(will be discussed later with theElastomeric Impression Materials)
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I. Introduction(terminology)
A. Impression material: Used to make anaccurate replica ofthe oral tissues
B. Impression: A negativereproduction of the
oral tissues
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C. Impression Tray: A metal or plastic device into which the material
is placed, carried to the mouth, allowed to set,supported and then removed.
Types:
All plastic perforated or non-perforated Metal rim-lock or perforated
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D. Model or Cast A POSITIVE produced by filling an
impression with a hard setting gypsummaterial
Used in the evaluation and fabrication of
restorations or prostheses
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II. Desirable Properties of anImpression Material
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(1) should be elastic:
exceptions: Impression Plaster, ZOE,Compound
(2) pleasant odor, taste, and color
(3) non-toxic or irritating (4) adequate shelf life
(5) economical
(6) easy to use with minimum equipment (7) good setting characteristics
(8) good consistency and texture
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(9) readily wets the oral tissues
(10) removed without permanent
deformation or damage (11) adequate strength
(12) dimensionally stable
(13) compatible with various cast and diematerials
(14) accurate
(15) able to be disinfected
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III. Composition of Alginate Powder
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III. Uses of Alginate Material:
Impressions and Models for: diagnostic (study) models construction of custom trays & bite
blocks construction of prosthetic temporary
crowns,bridges or appliances
fabrication of a quick model to check the
progress of a crown/bridge preparation simple transfer impressions
and many other uses where needed
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IV. Setting Reaction Potassium Alginate + Calcium Sulfate Dihydrate
(POWDER)+ H20 =Calcium Alginate GEL + SodiumSulfate
Sol to Gel Phase POWDER + WATER
IRREVERSIBLE REACTION
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V. Physical Properties
A. WORKING TIME:time you haveto work with the material before it
sets
Regular set:2 minutes (60 sec. mix time) Fast set:1 minute (45 sec. mix time)
Affected by:
increase temp colder temp
mixing time
w/p ratio
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B. Setting Time: Regular set = 4 minutes from start of mix
Fast set= 2 minutes from start of mix Affected by:
increase water temp 10 degrees = 1/2
set time (setsfaster) decreasewater temp(cold) = longer setting time(sets slower)
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C. Flexibility(elasticity): able to be removed after set (elastic)
Is limited - should block out major undercuts
D. Strength: tendency to tear - remove with SNAP motion
avoid thin areas - need 3 - 4 mm thickness
E. Compatible withmost Gypsum
Products suchas
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F. Dimensional Stability(Loss ofaccuracy with time of storage)
Syneresis: water collects on the surface
evaporates causing shrinkage Avoid by:
pouring ASAP
storingcorrectly
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Imbibition:
absorption of water causes expansion or swelling
avoid by:
pouring ASAP
storing correctly
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G. Permanent Deformation Once seated no pressure should be
exerted Needs adequate thickness (3-4 mm)
Tray size very important
Tends to slump - build up with wax forhigh palates
highest deformation
of allimpressionmaterials
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H. Surface Reproduction
Registers the detail of the soft tissue,restorations and fractured teeth
Not adequate for fine detail of
preparations
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I. Summary:
Slight initial expansion Slight initial contraction
Loss of accuracy with time of storage
STORAGE--up to 2 hrs @ 100% humidity: Cover with moistpaper towel
Place in plastic bag & seal
POUR ASAP Powers & Wataha; Dental Materials Properties and
Manipulation 9th edition: modern materials usuallycan be stored at 100% humidity for up to 5 days
without serious dimensional changes.
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V. Clinical Technique
A. Patient position & instruction: Upright position, have saliva ejectorready
Brush, rinse one minute with mouthrinse Wipe teeth & soft tissue of excess saliva
with a gauze pad
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B. Tray Selection
Correct size:
Comfortable - not impinge on the tissuecheck:
Maxillary Molars (facial)
Mandibular Molars (lingual) Always better to be slightly larger
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Adapt & Extend with wax when needed
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Wax extends tray borders & allows for border molding
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C. Equipment Needed
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D. Water Temperature & Amount
70-75 degrees
Add water to the bowl first
1 - Full cylinderper pack
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E. Dispensing
Read Instructionson the productfirst Accurate water powder ratio is critical
Alterations will affect the strength,viscosity, setting time, consistency,flexibility, tear strength and surface
detail It is no longer necessary to fluff thebulk container.
Do not pack the scoop tightly
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F Mi i
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F. Mixing Add powder to measured water
Use a clean bowl as gypsum particles will cause adecrease in the setting time of the alginate
Regular set:Mix 45 to 60 seconds
Fast set:Mix 30 to 45 seconds Under mix= weak gel, poor surface
texture, loss of detail, unmixedpowder
Over mix= decrease workingtime, loss of detail, incompleteseating of the tray
Th hl i i th id f
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Thoroughly mix using the side ofthe rubber mixing bowl
Have separate bowl and spatula only foralginate
Particles of gypsum products will affect
the working and setting times (lessworking time and faster set)
G L din th tr
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G. Loading the tray Avoid trapping air if using a solid tray
Place more in the anterior Apply excess in areas of common voids
Maxillary molars, palate, anteriors under the
lip, occlusal surfaces Linguals of Mandibular molars, anteriors
under the lip, occlusal surfaces
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Incorrect w/p ratio produces runny mix = discard
Correct w/p ratio
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Seat tray fully allowing the alginate to moveforward
Hold in place without pressure or movementuntil fully set
2 minutes after alginate loses
its stickiness 4 minutes from
start of the
mix
( ) l
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I. Tray (impression) removal Grasp tray firmly
Support patient Remove with one snap motion
Break the posterior seal first
Avoid rocking to remove
J I i E l ti
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J. Impression Evaluation Rinse onlywith water if areas of blood or
saliva are present Rinse with slurry before the model is
poured
K C it i
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K. Criteria A. clear negative reproduction of the
teeth,gingival margins, palate,frenum attachments, facial and
lingual vestibules, hamular notches,
palatal vault B. free ofbubbles or voids
in the toothportions
C free of bubbles or voids larger than
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C. free of bubbles or voids larger than0.5 mm in diameter in other areas
D. no evidence of unmixed powder E. surface should be smooth with no
evidence of distortion
F. no tears G. impression should be completely within
the confines
of the tray H. impression
should not be
pulled
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If the Impression is unacceptable,simply remove it from the tray andtry again. It is more difficult to remove
if adhesive has been used and in mostcases a new tray must be used. Onereason for not using it in our lab
project today and Wednesday.
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VI Imp ssi n/M d l Disinf ti n
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VI. Impression/Model Disinfection
1. AntiMicrobial Alginate
2. Use Aseptisol /Water mixture in the
Plaster or Stone inorder to disinfect themodel (found in the
lab) not for our
VII Impression Storage
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VII. Impression Storage
Wrap with a MOISTpaper towel
Place in a plastic bag and seal
Can be stored for up to 2 hours in 100%humidity (Only in extreme situations)
NEVER WITH AN IMPRESSION FOR AFINAL MODEL
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VIII. Model Fabrication
Ideally pour immediately (within 10-15minutes) in the selected Gypsum product
Always keep the impression facing upright
DO NOT AIR DRY!
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VIII. Removal of the Impression fromthe Final Set Model
Remove after one hour Prolonged contact between the Alginate and
Gypsum will cause surface deterioration of the
model Alginate will absorb moisture from the model
Danger of fracture of
the teeth due to thehardness of the Alginatewhen removing theimpression from the model
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IX. Trouble Shooting
A. Short working or setting time Water temp, w/p ratio, mixing time, time
in loading the tray
B. Grainy surface, lack of detail
Not mixed well, material starting to set,removal before final set
Incorporated air when mixing
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C. Gagging Explain to patient, patient position
Take lower first, use fast set Anesthetic rinses and sprays
Avoid overloading the tray in the posterior
D. Tearing Removal
Size of the tray & presence of severe
undercuts E. Bubbles or voids
Apply some material with finger or syringe
prior to tray placement
X LABORATORY PROCEDURE
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X. LABORATORY PROCEDUREA. Preparation of the Typodont for Impression
Apply SMALL piecesof MOIST paper towelto the proximal areasof all teeth to prevent
tearing of the alginate
Clinically theseareas are usuallyoccupied bythe tissue papilla
WETTYPODONTBEFORE YOUTAKE THEIMPRESSION
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B. Tray Adaptation
Trays may be heated over a bunsen burnerto soften and allow the tray to bestretched or adapted to the arch prior toadding wax to the borders. Usually it willbe required with the Mandibular tray.
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C. Wax Addition to Impression Trays
After the tray has been tried in thepatients mouth and determined to
bethe correct size for this patient. Waxmay be added to extend or lengthen thesides of the tray in order to register
the muco-buccal fold and freenumattachments.
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Adapt & Extend with wax when needed
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Be sure to apply the adhesiveafterthe tray has been tried in
the patient and selected as theone to be used.
F l b d b f l t t
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For our lab procedure, be careful not totouch the typodont with your fingers or
gloves if you have adhesive on them as it willcause the alginate to stick to the typodontand you will not be able to remove the
impression without tearing it!!
Today we will not be using the spray
unless there is a problem with thealginate pulling loose from the tray inremoving it from the typodont
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X Impression Procedure
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X. Impression Procedure
Separate the Maxillary & Mandibulararches of the Yypodont by removing thesprings-- be careful not to lose thesprings!!
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Removalwith a
SNAPonce theJeltrateis set
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Note void areain anterior
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You will receive a Max.
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and Mand.Tray--You mayuse them for the next
lab also.so dont throwthem away!!
You will not have to useany marginal wax asthese trays extend farenough to register theborders of the typodont
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B. Model Fabrication Wrap impression in MOISTpaper towel to
avoid drying out or
Pour (using Dental Plaster) before takeMaxillary impression
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A vibrator is used to decrease air bubbles and producea denser model
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Alginate Clean-up
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WIPE WITH A PAPER TOWEL AFTER SET THEN WASH BOWL
Plaster/Stone Clean-up
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Plaster/Stone Clean upWIPE WITH A PAPER TOWEL BEFORE SET THEN WASH BOWL
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POUR IMPRESSION FIRST
Note LOSS OF GLOSS
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Second Pour = Base Fabrication
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BE VERY CAREFUL NOT TO
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Impressions may beboxed with wax inorder to pour a
one stage modelImpression must bekept upright!
BE VERY CAREFUL NOT TODISTORT THE IMPRESSIONWHEN YOU WRAP THE WAX
AROUND THE IMPRESSION
Wide masking tape may also be used
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being careful not to distort the
impression during its placement.
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Rubber modelformers mayalso be used--Be careful theimpression does notsink down into thePlaster!!
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Happy Impression Making!!!!!!!
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Happy Impression Making!!!!!!!
The
Berry
End
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