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DH 160 - Materials > LO 9/10 > Flashcards

LO 9/10 Flashcards

1
Q

What are the three uses for gypsum?

A
  1. Diagnostic casts - study models, used to plan treatment
  2. Working casts - working models, fabricate appliances or dentures
  3. Dies - replicas of individual teeth to fabricate indirect restorations
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2
Q

Describe the chemical properties of gypsum

A
  1. Gypsum is a mineral - A dihydrate of calcium sulfate; it is mined as a solid mass
  2. Heated to remove water and creates a powdered hemihydrate - process is referred to as calcination
  3. When mixed again with water it becomes flowable, then becomes a solid mass again when it dries - dihydrate
  4. Exothermic reaction
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3
Q

_______, ______, and ________ of gypsum powders determine the use of the product

A
  1. Size
  2. Shape
  3. Porosity
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4
Q

The ____, _______, and _____ the gypsum powder, the weaker the cast

A
  1. Larger
  2. More irregular
  3. Porous
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5
Q

Diagnostic casts undergo ______ stress, so ______ or ______ is used

A
  1. Little
  2. Plaster
  3. Stone
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6
Q

Working casts and dies undergo ______ stress so ______ stone is used

A
  1. Great
  2. High strength
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7
Q

Describe type 1 gypsum and its uses

A
  1. Impression plaster
  2. Final impressions for endentulous (toothless) patients
  3. No longer used
  4. Elastomers now used instead
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8
Q

Describe type 2 gypsum and its uses

A
  1. Model plaster
  2. Used for diagnostic casts
  3. Articulation of stone models on an articulator
  4. 45 mL of water is mixed with 100 g of powder
  5. Produces a durable but weaker cast
  6. Powder is white
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9
Q

Describe type 3 gypsum and its uses

A
  1. Dental Stone
  2. Used for full or partial denture models, orthodontic models
  3. Higher strength casts; 2.5 times stronger than plaster
  4. 30 mL of water is mixed with 100 g of powder
  5. Powder is usually yellow or white
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10
Q

Describe type 4 gypsum and its uses

A
  1. High strength, low expansion Stone
  2. Die stone or densite
  3. Used to create wax patterns for cast restoration
  4. Used in commercial dental labs
  5. 23 mL of water mixed 100 g of powder
  6. The powder is often pink or green
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11
Q

Describe type 5 gypsum and its uses

A
  1. High strength, high expansion Stone
  2. Also known as gypsum-based investment
  3. Can withstand extreme temperatures required by the casting process
  4. Is high expansion to compensate for the greater casting shrinkage of newer base metals used for dental castings
  5. 20 mL of water mixed with 100 g of powder
  6. Powder is blue or green
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12
Q

Dental offices typically only use type ______ and type ______ gypsum

A
  1. Type II (plaster)
  2. Type III (stone)
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13
Q

The strength of the gypsum model is related to the amount of ______ used

A

Water

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14
Q

How is gypsum mixed?

A
  1. Powder is slowly sifted into water over 30 seconds, avoiding clumps
  2. Mixed in a rubber bowl with a metal spatula
  3. Mixed for 1 minute against the sides of the bowl until smooth, homogeneous, and glossy
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15
Q

Describe the initial setting and working time of gypsum

A
  1. After mixing for 1 minute working time begins
  2. During this time the mixture is poured into the impression
  3. Initial setting occurs when the glossy appearance disappears, about 30 minutes
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16
Q

Describe the final setting time of gypsum

A
  1. Model should be cool to the touch
  2. Approximately 45 to 60 minutes to fully set, do not leave for more than an hour
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17
Q

How can you control the setting times of gypsum powders?

A
  1. Alter the water to powder ratios
  2. Increase water will retard the setting time, decrease water will hasten the setting time
  3. Usually use room temperature water - warmer water will accelerate the setting time, colder water will decrease the setting time
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18
Q

Describe the two parts of a dental model

A
  1. Anatomical - replicates hard and soft structures
  2. Art - the base, allows handling and articulation of the cast
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19
Q

How is the anatomic portion of a gypsum model created?

A
  1. Poured by vibrating small increments of gypsum mix into the impression
  2. Start at the posterior and allow the mix to flow around the entire impression until filled
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20
Q

Describe the three ways the art portion of a gypsum model can be created

A
  1. Double pour method - two separate mixes and two separate setting times, impression is overfilled and then inverted onto the art portion
  2. Single step method - one mixture of gypsum, half is poured into the anatomical portion and the other part is used to create the art portion, the impression is inverted onto the art portion and joined, excess is removed in tongue area
  3. Boxing method - a strip of wax is surrounding the impression creating a wall, gypsum is poured into the impression, art portion must be parallel to the occlusal plane
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21
Q

How should gypsum be stored?

A

Gypsum absorbs moisture from the environment, and moisture will accelerate setting. Gypsum must be in a closed container, and after each use, the container must be closed

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22
Q

Describe the cleanup process for gypsum

A
  1. It is imperative that all equipment be cleaned immediately after each use, set gypsum on the equipment will affect the fresh mix
  2. Do not put gypsum down the drain, remove excess and place it in the garbage, wash all equipment and dry and store
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23
Q

Describe trimming a stone dental model

A
  1. Once separate the tray and cast, do not rock the tray back and forth due to the possibility of teeth fracturing off
  2. Soak the model in water for 5 to 10 minutes
  3. The art portion should be 1/3, the anatomic portion should be 2/3, and the occlusal plane should be parallel to the base
  4. Trim the base first, followed by the sides - the outer border should be trimmed to the depth of the vestibule
  5. Anterior is trim next - maxillary is trimmed to a point from canine eminences to the midline, mandibular trimmed on a curve from 3-3
  6. Heels trimmed last (45s at the back)
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24
Q

Describe infection control and safety for pouring impressions

A
  1. Impressions must be disinfected prior to pouring - this will allow for a clean cast after it is poured
  2. Cast can be sprayed with disinfectant after 24 hours
  3. It is extremely important to wear PPE
  4. When using the trimming wheel, hair must be tied back and no bangs hanging down
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25
Q

Describe what fluoride is

A

It is a naturally occurring mineral found in well water, food that has absorbed it from the soil, and it is additive and many dental products

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26
Q

Excess fluoride during tooth formation may cause ______, which appears as ______ or ______ depending on severity

A
  1. Flourosis
  2. White spots/bands
  3. Mottled enamel
27
Q

Fluoride has proven to be the best ______ agent

A

Anti-carogenic

28
Q

Enamel and dentin are composed of tiny crystals known as ______

A

Hydroxyapatite

29
Q

Between crystals of hydroxyapatite, enamel and dentin is filled with ______, ______, & ______, allowing these three things to pass

A
  1. Protein; lipids; and water
  2. Acid, calcium, and phosphate
30
Q

There is a constant ______ of minerals between the tooth surface and saliva, which is usually in balance

A

Interchange

31
Q

The ______ in hydroxyapatite is soluble in acid

A

Carbonate

32
Q

Describe the process of caries formation

A
  1. Went bacteria and biofilm on the tooth metabolized sugars, they produce acids and these acids cause demineralization
  2. When this process is repeated over time, the tooth becomes more porous, allowing bacteria to enter the tooth
  3. This is the beginning of the caries process
33
Q

How do developing teeth obtain fluoride?

A

From drinking water, foods, beverages, or supplements

34
Q

Topical fluoride is _______ effective after teeth have erupted

A

More

35
Q

Describe saliva’s involvement in remineralization

A

Fluoride from saliva surrounds the tooth and is incorporated into the surface hydroxyapatite crystals actively remineralizing it

36
Q

What is fluorapetite?

A

Tooth mineral that results when fluoride is incorporated into the tooth - surface veneer, which has a much lower solubility than the original tooth mineral

37
Q

Describe erosion

A

Loss of tooth mineral caused by dietary or gastric acids, not by bacterial metabolism

38
Q

Can fluoride protect against dental erosion?

A

Yes

39
Q

Fluoride can ______ bacteria and cause death to bacterial cells

A

Disrupt the function of

40
Q

Describe antibacterial rinses

A
  1. Used in conjunction with fluoride
  2. Chlorhexidine at 0.12% is effective against many microbes
  3. These antibacterial rinses are prescription-based
  4. Kills bacteria by binding to the cell membrane
  5. Excellent substantivity - prolonged effect, slow release over several hours to a few days
  6. Can create brown stains on the teeth and restorations, which can only be cleaned professionally
41
Q

What are the dietary methods of fluoride delivery?

A
  1. Water
  2. Supplements in the form of tablets, drops, or lozenges
  3. Food
42
Q

What are the in-office (topical) methods of fluoride delivery?

A
  1. Gels, foams, and varnish
  2. Acidulated phosphate fluoride (APF) - popular to be used on kids before fluoride varnish took off
  3. 2% neutral sodium fluoride
43
Q

Describe over the counter rinses and toothpaste

A
  1. Rinses - contain sodium fluoride, high percentage sodium fluoride versions should be used only once daily before bed
  2. Toothpaste - contains sodium fluoride, sodium monofluorophosphate, children under 6 should use a very small amount and be supervised while brushing
44
Q

Describe prophylaxis pastes

A
  1. Contains pumice as an abrasive to remove surface stains and plaque/biofilm from the teeth
  2. In the process a small amount of enamel surface is removed
  3. Fluoride is regained after enamel removal by incorporating it in the paste
45
Q

Describe the uses of pit and fissure sealants

A
  1. Used to seal non-carious pits and fissures
  2. Used on deciduous and permanent teeth
  3. Most carries in children are found in pits and fissures
46
Q

Describe pits and fissures

A
  1. Narrow and deep channels in the teeth
  2. Can extend close to the DEJ
  3. Collect biofilm, food debris and bacteria and begin the carries process
  4. Cannot be cleaned by tooth brushing
47
Q

When a sealant is placed ______, it provides an effective barrier

A
  1. Before cavitation has begun
48
Q

What happens if caries are sealed over with pit and fissure sealants?

A

Typically, the caries process is stopped because a food source for the bacteria is not available

49
Q

What happens if the sealant is poorly placed and the margins begin to leak?

A

The caries process will likely continue

50
Q

Which teeth are not ideal candidates for pit and fissure sealants?

A

Teeth with shallow grooves

51
Q

What are the considerations before giving pit and fissure sealants?

A
  1. Age
  2. Oral hygiene
  3. Caries risk
  4. Diet
  5. Fluoride history
  6. Tooth type and morphology
52
Q

Describe deciduous teeth in relation to pit and fissure sealants

A
  1. Can reduce caries rate and prevent premature tooth loss
  2. While occlusal surfaces are generally smoother than permanent teeth, if deep fissures are present, sealants may be recommended
53
Q

When are permanent teeth sealed?

A
  1. If there is or was evidence of caries in deciduous dentition
  2. If there are very steep cuspal inclines
  3. If deep, sticky fissures are present (the molars are more susceptible)
54
Q

How are pit and fissures sealants placed?

A
  1. Tooth is isolated
  2. Tooth surface is pumiced
  3. The tooth is etched with 37% phosphoric acid
  4. The tooth is rinsed and dried
  5. The tooth is re-isolated
  6. The sealant is placed and cured
55
Q

Unsealed, etched areas will begin remineralization after _____ with saliva

A

24 hours

56
Q

Sometimes a ______ is placed after the sealant to assist and remineralization of areas that were actually not sealed

A

Fluoride gel

57
Q

Describe the mechanism of tooth sensitivity

A
  1. Gingival recession
    - dental tubules exposed
    - the cementum is worn away
    - stimuli can cause the tooth to respond with a sharp pain, such as hot, cold, sweet, and acidic foods
58
Q

What are the common causes of gingival recession?

A
  1. Root caries
  2. Toothbrush abrasion
  3. Acid erosion
  4. Abfraction due to bruxism
  5. Scaling and root planning
  6. Leaking restoration on the root
59
Q

What are the two treatments for sensitive teeth?

A
  1. Occluding the tubules-reduces fluid movement and stops pressure on nerve endings, fluoride, chemical solution containing resins
  2. Desensitizing the nerve endings - potassium nitrate, passes through the tubules to the pulp acting directly on the nerve, depolarizes the nerve, it cannot cause pain
60
Q

Sports guards are great for protecting and supporting tooth structures and can prevent some concussions, what are the three basic types?

A
  1. Stock - poorest fit, uncomfortable to wear, least amount of protection, least expensive
  2. Boil and bite - thermoplastic material, softened in boiling water and molded to the mouth, difficult to adapt to the teeth
  3. Custom fit- professionally fabricated from a preliminary impression, made in the dental office or lab, most protection
61
Q

How are custom mouth guards made?

A
  1. Cast of the client’s mouth is made
  2. Thermoplastic sheet used
  3. Vacuum former used to mold plastic for cast
  4. Trimmed for the best fit and comfort
  5. Strap can be added to attached to the helmet
62
Q

Describe night guards use and indicators for use

A
  1. Occlusal guards or bite splints
  2. Fabricated for clients that grind or clench
  3. Grinding and clenching can wear facets, chip incisal edges, cause stress cracks, fracture cusps, cracked teeth, cause mobility in teeth, and enlarge masseters, and cause some sore muscles
63
Q

Describe what night guards are made of and how they can help with grinding and clenching

A
  1. Made of acrylic (hard), or thermoplastic (soft)
  2. While they do not stop the grinding habit, they can relieve the stress placed on the TMJ and further wear and stress on the teeth
64
Q

Describe space maintainers

A
  1. Used in pediatric dentistry when deciduous tooth is lost prematurely
  2. Prevents adjacent teeth from drifting in and closing the space
  3. Allows the permanent tooth to erupt properly
  4. Can be fixed or removable

DH 160 - Materials (8 decks)

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