DHE132 Study Guide EXAM II

• A characteristic of gels to contract and squeeze out some liquid, which then accumulates on the surface.
• • If an alginate impression remains in the open air, moisture will evaporate from the material, causing it to shrink and distort.

• Absorb water from the air.
• • Dental Gypsum if left out and absorbed water increased setting time.

• The property of the material to have two different temperatures for melting and solidifying, unlike water, which has one temperature for both.
• • Reverse to the change of temperature that allows the colloid to go from liquid to gel.

• An attribute that allows material to tolerate the presence of moisture.
• • Polyvinyl Siloxanes(PVS), Vinyl Polysiloxane (VPS), Polyethers.
• • They should not be stored in a refrigerator because of moisture
• • But can be used around oral fluid & tissue moister

An attribute that does not allow a material to tolerate or perform well in the presence of moisture.

• The act of absorbing moisture.
• • If an alginate impression is stored in water or in a very wet paper towel, the alginate will absorb additional water and expand.
• • Avoid exposing polyether impressions to water as they will exhibit imbibition over time

• To alter the setting time of Gypsum using accelerators or retarders.
• • Slurry aka set gypsum [CaSO4]

• Feather -like excess of material that extends beyond the cavity margins.
• • Excess material (feather-like) on occlusal and proximal surfaces / done before polishing

indicates that the gypsum has reached its initial set

• Rate is known by: size; irregularity; hardness.
• • Determined by three factors: size, pressure, speed.
• • Moh’s hardness scale:

• Type 3 Dental Cement High-Strength Base- A thick layer of cement used in a cavity preparation to protect the pulp from chemical insult or to act as a thermal insulator.
• • Cements used as a base are mixed to a secondary consistency, a thick putty-like consistency between the tooth and the restoration.
• • In preparations with an estimated 2 mm or less dentin remaining, a base is often recommended.
• • Pulp Protection: Chemical irritation, Temperature changes, Electrical shock, Mechanical injury.
• • ‘thick putty’: glass slab mostly used

• Type I: Dental Luting Agent - Material that acts as an adhesive; Bonding or cementing together. To cement two components together such as an indirect restoration cemented on or in a tooth. (eg.inlays, crowns, bridges, veneers, ortho bracket and bands, post and pins.) Must have good wetability and flow to provide a thin film thickness.
• • Temporary luting cement: Used when the restoration needs to be removed: Temporary crown; bridge, Used for provisional coverage.
• • Long-term cementation of cast restorations: Inlays, Crowns, Bridges, Veneers, Fixed orthodontic appliances.
• • spatula lifts the cement 1 inch from the glass slab
• • Cool slab will increase working time .

Cements used for permanent or temporary luting of fixed prostheses, orthodontic bands, and pins and posts must have good wettability and flow to provide a thin film thickness: Luting cement.

• The ability of an object to be pulled or stretched under tension without rupture.
• • The ability of material to withstand permanent deformation under a tensile load without rupture

• Property of being easy to break or rupture (opposite of toughness).
• • Cements are brittle materials with good compressive strength but limited tensile strength.
• • The strongest cements are resin cements
• • The weakest are zinc oxide eugenols (ZOEs)

The maximum amount of stress a material can withstand without breaking.

• The time permitted to manipulate the material within the mouth.
• • The time allowed for mixing the alginate, loading the tray, and positioning the tray in the patient's mouth.
• • Cool slab will increase working time.
• • Zinc polycarboxylate cement have short working time.
• • Normal set Alginate-Working time of 2 minutes
• • Fast Alginate set- Working time of 11/4 minutes

Curing stage of Elastomeric Materials-The first stage results in stiffening of the paste without the appearance of elastic properties. The material may be manipulated only during this first stage.

Curing stage of Elastomeric Materials- The second stage begins with elasticity and changes to a solid rubberlike mass. The material must be in place in the mouth before the elastic properties of the final set begin.

Curing stage of Elastomeric Materials-The last stage occurs from 1 to 24 hours.

• A change in the size of matter. For dental materials, this usually manifest as expansion caused by heating and contraction caused by cooling.
• • Wax-Bite registration Disadvanages: Dimensional changes at room temperate and in storage.
• • Polysiloxane bite registration paste: It gains dimensional stability over time.
• • Agar: reversible Hydrocolloid:Least dimensional change occurs when the impressions are stored in 100% humidity. Lacks dimensional stability.
• • Type 4:Polymerizing Silicones [PVS:Poly(Vinyl Siloxanes) and VPS: Vinyl Polysiloxane]:Dimensional change is essentially zero never changes

• Aka: Habitual Occlusion- The usual maximum contact (or intercuspation) of teeth of the opposing arch.
• • Occlusal Registration- An accurate registration of the normal centric relationship of the maxillary and mandibular arches. Also commonly referred to as the bite registration.

• Mechanical process and main causative Factor: direct friction or rubbing leads to loss of tooth structure at the occlusal level.
• • Normal process opposing teeth rub against each other.
• • Factors that influence bleaching outcome

• Mechanical process where the enamel is at its weakest and Main causative Factor: abnormal load created by bruxing.
• • Process of abfraction: Lateral occlusal forces stress the enamel rods at the cervical area.
• • Advanced stage, a wedge- or V-shaped cervical lesion
• • Minute cracks in the enamel roads may not be clinically evident, the tooth can exhibit hypersensitivity.

• A chemical process.
• • External and internal factors: GERD, vomiting, Citrus, Soda.

• Mechanical process and main causative Factor: direct friction or rubbing leads to loss of tooth structure at the occlusal level.
• • Normal process opposing teeth rub against each other.
• • Factors that influence bleaching outcome.

• Stains that are incorporated into the tooth structure, usually during the tooth’s development.
• • Location- Within the tooth substance and cannot be removed by *P&S.
• • Causes- Meds. During development: Fl2 & tetracycline, Meds. After development, Diseases during tooth development. Tissue remnants, Restorative material, Endo material, Canal obliteration Yellow, Necrosis w/ w/out hemorrhage.
• • Pulpal changes: Pulpal necrosis- Red/ Brown/ Purple. Trauma-Blue/Brn.Black

• Stains that occur on the tooth surface.
• • Location- Occur on the external surface can be removed by *P&S&TB
• • Yellow- Dull, Discolored biofilm, Food pigments, Poor OH.
• • Green- Embedded in biofilm, Fungal or chromogenic bacteria, Decomposed hemoglobin, Poor OH.
• • Black line- Biofilm pigmentation/ microorganisnms(gram +), Natural occurrence, Gingival 3rd.
• • Other Extrinsic colors- Metallic, Tobacco, Oranage/Red- Chromogenic bacteria.

originates from inside and are always inside. Affects mostly the dentin and this color penetrates through the enamel.

Originate from outside /can become internal.

• • Size of the abrasive particle- Larger particles cause deeper scratches in the material.
• • Pressure of the abrasive against the material being abraded- Heavy pressure causes deeper scratches and more rapid removal of material.
• • Speed at which the abrasive particle moves across the surface being abraded.
• 32. How does speed affect abrasion?
• Increase of speed will increase the rate of abrasion.

• • Water and saliva are common lubricants used to dilute the effects of abrasion.
• • If a lubricant is used to dilute the concentration of the particles, the abrasiveness is reduced.

• Carving Remove cavosurface flash with a sharp scaler, a #12 scalpel blade, or gold knife(finishing knife or amalgam knife)
• Finishing is the process used to correct irregularities in contour, remove excess material, and smooth the margins and external surfaces.
• Polishing takes the process a step further by removing scratches by the step-wise application of sequentially finer abrasives to produce a glossy, very smooth surface.

Carving, finishing, polishing.

• 1. Remove cavosurface flash with a sharp scaler, a #12 scalpel blade, or gold knife(finishing knife or amalgam knife)
• 2.Marginal and occlusal excesses removed in initial finishing with diamonds or multifluted carbide burs.
• 3.Intermediate finishing accomplished with flexible disks, cups, and strips, beginning with coarse and sequentially proceeding to superfine.
• 4.Final polishing accomplished with a submicron aluminum oxide–based polishing paste applied with soft cups or felt pads.
• d. What / where have we used these in dental materials lab?
• Composite restorations/ molars.

• • Debris
• • Saliva
• • Air inclusion = voids
• • Manipulation of self cure

Clean, Seal, Polish.

Distraction-Lift their leg up, breathing, Nitrous oxide.

Nonaqueous Elastomeric/ Rubber type materials Type 3: Polyether can be used around oral fluid and tissue moister.

• a. Alginate?
• Stock trays- perforated or lock rim trays or solid tray with adhesive. Disposable rigid tray.

Custom tray, Plastic perforated tray.

Metal water coolant tray

• ● Advantages:
• ▪ Ease of mixing
• ▪ Minimum equipment necessary
• ▪ Flexibility of the of the set material
• ▪ Low cost.
• ● Disadvantages:
•  Low tear strength (rip easily)
•  Does not transfer much detail. Can not be used for final impressions of crowns/bridges.
•  Lacks stability due to water content.
•  Syneresis: loss of water content.

• • Impressions for study models.
• • Impressions of opposing arch.
• • To make working models to make teeth whitening trays, mouth guards, custom tray.
• • To have impression of unprepped teeth. Used to make temporary crowns.
• • *NOT USED FOR FINAL IMPRESSIONS OF CROWNS/BRIDGES.

• Then what is done to make it into powder form and then back into stone in the dental lab?
• • Gypsum is made of Calcium Sulfate Hemihydrate
• • Gypsum is mined as raw material which is a solid- hydrate
• • Gypsum is heated to extract water which is a Hemi-hydrate this produces the powder we utilize
• • Our addition of H2O in the lab to gypsum creates a di- {2} -hydrate again plus excess.

• • Altering water-to-powder ratio
• • Performing spatulation
• • Changing water temperature: Lower temperature, slower setting time. Higher temperature, faster setting time
• • Using accelerators or retarders
• • Slurry aka set gypsum [CaSO4]
• • K2SO4 [potassium sulfate]

• a. Reversible(Agar) Hydrocolloid:
•  An impression material that changes its physical state from a sol solution) to a gel and then back to a sol.
•  preliminary and final impressions(crown and bridges).
•  Agar impression- Light body material on teeth and Heavy body material on tray.
• b. Irreversible (Alginate)Hydrocolloid :
•  Study models
•  used impression material in dentistry
•  Easy to manipulate
•  Requires no special equipment
•  Reasonably accurate

• o 1)Impression plaster: Type 1. (weakest, most water) used primarily to mount casts on an articulator.
• o 2)Model plaster: Type 2. Used for sturdy models that do not require abrasion resistance.
• o 3)Dental stone: Type 3. Hemihydrate. Stone is stronger and more resistant to abrasion than plaster and is used for casts that need abrasion resistance. ›Ideal for: full or partial denture models, orthodontic models, and casts, whitening trays, mouth guards
• o 4)High-strength/low-expansion dental stone (aka: die stone). Type IV. Used to fabricate crowns and bridges. Require the highest abrasion resistance and strength.
• o 5)High-strength/high expansion dental stone. Type 5. (denser, least water). Use with newer base metals. Require the highest abrasion resistance and strength.

Altering will affect the setting time.

• ● Mandibular tray should:
• ▪ Cover all teeth and retromolar pad
• ▪ Be 4 mm wider than the buccal and lingual portions of the posterior and the labial and lingual portions of the anterior teeth
• ▪ Allow the teeth to be centered and yet comply with the previous requirement
• ● Maxillary tray should:
•  seated at the most posterior border and then continue seating parallel to the axis of the central incisors
•  the excess alginate flows both in a labial or buccal direction but not in a palatal direction
•  Palatal vault recorded
•  Break the peripheral seal by running a finger around the edge and remove the impression with a rapid, firm pull

Metals such as lithium, barium, or strontium

• a. Elastomeric Impression Materials: A material that is used when an extremely accurate impression is essential. The term elastomeric means having elastic or rubberlike qualities.
•  Nonaqueous Elastomeric/ Rubber type materials Polyvinyl Siloxanes or Vinyl Polysiloxane impression material [type 4] final impression material
•  Polyether
• b. Agar: Reversible Hydrocolloid: First successful flexible aqueous impression material used in dentistry. Not used anymore
•  Uses: Final impression for crowns and bridges. Not used for whitening trays.
•  Reversible: can liquefy when heated and return to gel when cooled and vise versa

• • Additional silicones: (Polyvinyl Siloxanes: PVS or Vinyl Polysiloxane: VPS
• o Polyether
• • Elastomeric: Polysulfides

• 1. Prepare tooth [non-fl2 prophy paste or pumice]
• 2. Isolate and dry
• 3. Acid etch/condition
• 4. Rinse, dry, isolate, dry again
• 5. Apply sealant and cure
• 6. Check occlusion and contacts

Sensation felt when the nerves inside the dentin are exposed to the environment

• a. What portion registers ‘pain’?
• Pain - registered by the depolarization/neural discharge mechanism that characterizes all nerve activity.
• Sodium/potassium pump = is responsible for depolarizing the nerve as potassium leaves the nerve cell and sodium enters it

Brannstrom Hydrodynamic Theory: the outer aspect of dentin will cause fluid movement within the dentinal tubules.

• • Desensitizing agents
• • Dentifrices
• • Dental professional measures

• Pain - registered by the depolarization/neural discharge mechanism that characterizes all nerve activity.
• Sodium/potassium pump = is responsible for depolarizing the nerve as potassium leaves the nerve cell and sodium enters it

• • A. Potassium salts
•  Formulations containing potassium chloride, potassium nitrate, potassium citrate, or potassium oxalate
•  reduce depolarization of the nerve cell membrane and transmission of the nerve impulse
•  Potassium nitrate dentifrices
• • B. Fluorides
•  precipitate calcium fluoride (caf2) crystals within the dentinal tubule to decrease the lumen diameter
•  Create a barrier by precipitating caf2 at the exposed dentin surface to block open dental tubules
• • C. Oxalates
•  Oxalate salts such as potassium oxalate and ferric oxalate precipitate
•  block open dental tubules
• • D. Glutaraldehyde
•  coagulates proteins and amino acids within the dentinal tubule to decrease the dentinal tubule lumen diameter
•  Creates calcium crystals within the dentinal tubule to decrease the lumen diameter
• • E. Calcium phosphate technology
•  used for caries control
•  to reduce demineralization and to remineralize by releasing calcium and phosphate ions
• • F. Arginine and calcium carbonate
•  occludes the dentinal tubules using arginine, a naturally occurring amino acid, bicarbonate (pH buffer), and calcium carbonate

• • Intratubular and Peritubular dentin:
•  deposit of extra minerals eventually causing sclerotic dentin
• • B. Calculus
• • C. Iontopherosis:
•  Electrical current used to apply medicament to areas
• • D. Secondary dentin:
•  Slow secretion/ Protective/dentin stimulated/protect pulp from dentinal tubule flow= narrower canal and pulp wall
• • E. Smear layer: organic and inorganic:
•  Smear Plug
•  Formed from ‘grinding debris’ instrumentation consists of cementum, dentin, tissue and cellular debris = occludes tubules
• • F. Tertiary reparative dentin:
•  Formed along pulpal wall as response to trauma

• 1. Stain adheres directly to tooth surface (*P&S)
• 2. Stain is contained with in calculus and soft deposits (*P&S)
• 3. Stain is incorporated within a tooth structure or the restorative material (No*P&S)

• • Polish and scaled: Extrinsic- external surface of tooth
•  Stain adheres directly to tooth surface
•  Stain is contained within calculus and soft deposits
• • Not Polished and scaled: Intrinsic-within the tooth
•  Stain is incorporated within a tooth structure or the restorative material

• • Use of *free radicals in carbamide & hydrogen peroxide
• • Break down lrg. pigments to sm. Pigments
• • This ‘whitens’ teethO2 release of peroxide products = changes optical quality in enamel and dentin = ‘white’
• • Dentin is what causes the change of color

carbamide peroxide

• • Neutral pH
• • 10% active ingrd.
• • Breaks down into hydrogen peroxide
• • Change to High pH to facilitate bleaching
• • Slow release = lower sensitivity
• • Takes fewer days but more contact time is needed
• • Safer and more effective

• • Some patients may be allergic to components of the bleaching material
• • Sensitive teeth may exacerbate the problem
• • Teeth that are at an acceptable shade
• • Patients may have unrealistic expectations
• • Pt. Compliance
• • Pregnancy
• • Light powered bleaching contraindicated for pt. Taking photosensitive medications
• • Root canal / internal damage too severe