Dental Materials Exam 3
gold foil is ______ or ______ using hand pressure or other mechanical means
compacted or condensed
in dentistry pure or nearly pure _______ is used to place small restorations
gold
components of a denture
White denture teeth and pink denture base
what is annealing gold foil
gold foil comes with a thin layer of a chemical protectant which is burned off with a 100% ethyl alcohol flame
acrylic resins as biomaterials
good material to cement artificial joints in place, still used today for this
a complete denture requires
precise adaptation to the supporting tissues and a peripheral "seal" for adequate retention
Pit and fissure sealants
preventive material applied to the susceptible pits and fissures of teeth to prevent or reduce caries
precipitation
process in which a solid is formed from the material dissolved in a liquid. EXAMPLE: freezing water, curdling of milk
Spherical alloys
sprayed molten metal into an inert atmosphere, droplets cool and produce these alloys
complete dentures are held in place by
suction, which is the result of surface tension and atmospheric pressure
Corrosion occurs both of the...
surface and in the interior of the restoration
the air inhibited layer has a ______ feel, and once final increment has been placed and no more composite is added, is removed with finishing of restoration
tacky
disadvantage of a chairside reline
that the new material is more porous and, typically, not as smooth as that of a lab reline
amalgam alloy
the Ag-Sn powdered metal before it is mixed with mercury
liners may change...
the bite or occlusion of a denture, causing trauma to the supporting tissues
Polishing can be delayed for ______ hours to allow the amalgam to set and become hard enough to withstand the polishing procedure
24
What are some indications that denture is not fitting well?
Frequent use of denture adhesives or OTC denture "cushion" materials or liners
working time of amalgam
(the time needed to condense and carve) is not directly controlled by the dentist, as it is with light activated composites
Low copper dental amalgam- (today high copper amalgams are the state of the art and dominate the market) composition
- 65% silver - 25% tin - 6% copper - 1% zinc (sometimes)
use of primers with sealants
- a primer can be used when rubber dam cannot be used - primer is believed to help the sealant wet a slightly contaminated surface and improve retention of the sealant
uses of composite cements
- able to bond restoration to the tooth surface - composite cements are the luting material of choice for ceramic restorations
esthetics
- all metal restorations may have acceptable or unacceptable esthetics depending on their location - ceramometal restorations adequately simulate the natural dentition in most situations - all-ceramic restorations reproduce the translucency of the natural dentition better than the ceramometal restorations and have the most life-like appearance of all restorative material
Manufacturer controls what of the alloy
- alloy composition - alloy particle size - Particle size - particle size distribution - also controls the rate of setting reaction by heat when treating the particles and by washing the surface of the particles with acid to remove surface oxides
aluminous porcelain
- alumina (alumina oxide) was added to porcelain to increase its strength - alumina is very strong ceramic material, and its addition slightly increases strength and clinical performance without affecting esthetics
wear
- because the ceramic materials used for ceramometal and all-ceramic restorations are very hard, they wear the opposing enamel much more than enamel or gold alloys - the softer gold alloys wear opposing enamel much like enamel does
Direct veneers
- bonded composites - these may not involve removal of significant tooth structure and in this case are considered to be a reversible treatment
requirements for ceramometal alloys
- casting alloys for ceramometal restorations have the same mechanical and biocompatibility requirements as alloys for all metal restorations - the ceramometal alloy must withstand the very high porcelain firing temperatures - it is important that the metal not melt or distort because the ceramometal alloy supports the porcelain during firing and clinical useq
margins
- casting techniques for metals result in more accurate margins than those for all-ceramic restorations - excessive gap at the margin of all-ceramic restoration increases the risk of recurrent caries; however, composite cements help to fill these gaps
four types of glass ionomer products
- chemical-cure glass ionomer products - resin-modified glass ionomer products - acid-base chemically activated resin-modified glass ionomer products - recharging fluoride in glass ionomer materials
Disadvantages of a complete lower denture
- chewing problems - lack suction/retention and will float and move around in the mouth - may cause "sore spots" and make speech difficult
use of dental amalgam
- class I, II, V, and VI carious lesions - foundation for a crown to restore a severely decayed tooth (known as amalgam build up or amalgam core)
metals
- classified as noble elements based on their lack of chemical reactivity. The noble metals include gold, platinum, palladium, and other inert metals
repairing acrylic prosthesis or appliances
- clean the surface - apply monomer - Apply new material that is mixed, applied to surface, and allowed to set. Polymer chains of old material is entangled in the new. (chemical bond is called quasi-chemical) - finish and polish
hybrid composite
- combination of a macro and microfilled composite - filler content is 75-80% - filler particle size average 0.5-1um in size but with a wider range of particle size from 0.1-3um - good physical qualities as conventional macro but more polishable because of microfill - most versatile; used for strength and esthetics and are acceptable for small to medium class I and II restorations and because their surfaces finish is nearly as good as that of microfills, they are also used for class III and IV restorations
Denture teeth
- come in a variety of shapes, sizes, and shades - acrylic resin teeth- most denture teeth are made from acrylic resin much like that used to construct the denture base - chemically bonded to the acrylic denture base during processing of the denture - porcelain teeth- much harder and more stain resistant compared to acrylic teeth, rarely used
denture base
- constructed on the master cast made from the final impression - the base is the pink part of the denture that sits on the alveolar ridge
use of amalgam with a cavity varnish
- copal varnish is a resin dissolved in a solvent - varnish is painted on the cavity prep and the intent is to reduce initial leakage by sealing the margins before corrosion products form
macrofilled composite
- first type of dental composite developed - filler is quartz materials with particle size of 10-25um - filler content is 70-80% by weight - large size of the filler particles in macrofilled composites results in a restoration that feels rough to the dental explorer and can appear rough to the eye - likelihood of plaque accumulation and staining is greater with macrofilled than with other types of composites - adequate for class III, IV, and V restorations, however, they are not the material of choice for restorative dentistry and their use is minimal
flowable composites
- flow into cavity prep because of their lower viscosity - a weaker, less abrasion-resistant material results - typically used as the initial increment of a composite restoration and then covered with a hybrid material
condensable composites
- have a filler particle feature that inhibits the filler particles from sliding by one another, resulting in a thicker, stiffer feel - they are condensable, but are not an improvement over hybrid composite materials
treatment planning
- knowing the periodontal status of the patient is critical. without a stable foundation, the long-term success of any restoration is unlikely - the endodontic status of the tooth must be considered - caries risk assessment and testing is becoming more common. Efforts to reduce the risk of caries should precede extensive and expensive restorations - enough tooth structure must remain to retain the restoration. Badly broken-down teeth may require buildups (cores) to provide retention for the final restoration
veneers
- thin layer of material that covers another material "like the shell of a hard boiled egg" - placed on the facial surface of anterior teeth to treat an esthetic problem - discolorations, rotation, or spaces (diastemas) can be corrected with veneers
Name the steps of the laboratory-processed reline
- lab makes impression, existing denture acts as a tray - send to lab - cast is poured - impression and cast are separated, impression material removed from denture - new acrylic material is added to fill the space between that denture and the cast - acrylic material is cured, finished, and polished in the same manner as construction - denture is returned to the dentist and given to the patient
Particles of amalgam alloy may be formed by two methods
- lathe-cut alloys - spherical alloys - Admixed or blended alloys
diagnosis
- loss tooth structure and missing teeth result from a variety of causes including caries, periodontal disease, trauma or fracture, esthetic concerns, and congenital deficiencies - teeth can also be lost as a result of restoration and re-restoration
use of composites for restorations
- material of choice for directly placed esthetic restorations - one of several materials called "tooth-colored" materials - they are still considered to be inadequate for the characteristic of life-like appearance when compared to all ceramic restorations - when compared to metallic, these do not have the same fracture toughness - hybrid composites dominate composite materials currently in use. They function well in moderate stress restorations where esthetics is of importance - composites do not have the mechanical properties for long-term success in large high-stress restorations such as cusp replacement restorations (size of restoration increases=stress of materials increase)
ceramometals
- metal ceramic combo that was developed for dentistry in 1950's - the tough, strong metal supports the weak but esthetic ceramic materials - called porcelain-fused-to-metal or porcelain-bonded-to-metal restorations and are considered to be an important "workhorse" in modern restorative dentistry
Metals
- most metallic indirect restorations are made by a casting procedure - casting involved melting the metal and then pouring or forcing the liquid metal into a mold - the casting process allows custom, complex shapes to be easily produced - work well in high stress situations, but their esthetics are poor
liquid chemically activated acrylic resin
- mostly monomer, methyl methacrylate - cross-linking agent, such as glycol dimethacrylate is added - inhibitor, hydroquinone, is most common one added - methyl methacrylate is a powerful solvent, and the ability for it to dissolve acrylic resin has a significant effect on the handling properties of acrylic resin systems
microfilled composites
- particle size is much smaller than macrofilled composites 0.03-0.5um - these polish very smooth and lustrous and the surface is very similar to that of enamel - low percentage filler (40-50%); therefore, the surface area requires much more resin to wet the surface of the filler particles; and the high resin content results in an increased coefficient of thermal expansion and lower strength - polymerization shrinkage of microfilled composites is less than expected based on the total resin content - microfills have lower modulus of elasticity and flex with the tooth better than the strongest composite materials, so they can be great for class V restorations
matrix of composites have several functions
- polymerizes to form a solid mass - bonds to the tooth structure
powder chemically activated acrylic resin
- polymethyl methacrylate resin with added colorants and benzoyl peroxide
acrylic resin system and porosity
- regardless of type of activation of acrylic resin system, porosity is a major concern - methyl methacrylate and other monomers evaporate easily at room temperature, and if this occurs during handling or processing, the resulting material will be porous - porosity weakens material and denture is likely to collect debris in pores in become foul
recharging fluoride in glass ionomer materials
- release fluoride which decreases over time - topical fluoride treatments can recharge glass ionomers fluoride releasing capability - result is a significant increase in the fluoride released by "old" glass ionomer material
light activated materials for polymerization systems
- single paste systems - no chairside mixing occurs - these set when exposed to a very bright light - working time is variable and can be quite long if operator desires - because of increased working time, these have replaced chemically activated composites, which are only used in areas where light cannot reach the composite material, such as when cementing a metal crown with a composite cement
Setting reaction of amalgam
- starts during trituration and progresses while condensation and carving are taking place
improved hybrid composites
- the average particle size has decreased and nano-sized particles have been added - reduced particle size result in slight improvements in strength and polymerization shrinkage
silicate and phosphate-bonded investments
- these are used to cast high-melting partial denture framework alloys and ceramometal alloys - they can withstand much higher burnout temperatures and are more difficult to use than gypsum-bonded investments
indirect veneers
- these use ceramic materials, such as porcelain - the facial surface is prepared to provide space for the veneering material; therefore, they are not a reversible procedure - they require an impression, a second appointment, and a lab fee and they cost more than direct veneers
composites shrink about _____% when they set
2%
ceramometal that strengthen porcelain materials
- to strengthen porcelain it is bonded to metal - advantage of metals include tough mechanical properties and ability to obtain a precise fit of the crown to the preparation - disadvantage is that metals are opaque to light even when used in very thin layers and light is not transmitted through the restoration as it is through tooth structure - a ceramometal restoration is not as natural or life-like in appearance compared to an all-ceramic crown
Advantages of using dental amalgam
- toughness and wear resistant - long-lasting, cost-effective restorative material (Class I=15-18 years, Class II= 12-15 years) - Amalgam has capability of sealing its margins during service, as the margins corrode, the tooth/restoration interface fills with corrosion products so that microleakage is reduced - Amalgam is the least technique-sensitive permanent restorative material that is available to the dentist - only material that might work when placed in a wet, contaminated environment - As the restoration increases in size, the stress within the restoration also increases, and the life expectancy of the restoration decreases
crowns
- used to restore teeth that have lost a significant amount of tooth structure - they are used when intracoronal retention is unavailable or when the tooth needs to be surrounded and held together by the restoration
ceramic materials
- used when esthetics are important - ceramic materials can simulate the natural colors and translucency of teeth - porcelain is the ceramic material most commonly used in dentistry - ceramic materials lack the toughness and fracture resistance required by bridges, but their esthetics can be excellent
air inhibition
- when composite materials are placed in increments, each increment chemically bonds to the previous one
steps in creating a denture
1. a baseplate and wax rims are constructed from chemically activated acrylic (or similar material) and baseplate wax, made precisely to fit on patient's ridge 2. the wax rims on the baseplates are used to determine the patient's midline, "plane of occlusion" and size of the denture teeth, plane of occlusion is the plane where the upper and lower teeth meet when a patient bites 3. At the same appt, the patient's bite is recorded and is used to position the upper and lower casts in the same relationship as the supporting tissues in the mouth 4. With the aid of baseplates and rims, the casts are mounted on an articulator using dental plaster 5. Denture teeth are "set" in the wax. When all the denture teeth are set in wax, it is called a denture setup. a setup stimulates proper bite (relationship of the two arches), the vertical dimension, and esthetics of final denture 6. Before processing, the setup (the baseplates with the teeth set in wax) is placed in the patients mouth. The procedure is called the "wax try-in" this wax try-in allows the dentist to check function, occlusion, and phonetics before the actual denture is processed
Placement of a composite restoration
1. dentist diagnosis the lesion 2. a determination of the shade that will be used is made 3. dentist cuts cavity preparations, including beveling of margins 4. area is isolated with cotton rolls, dry aids, or preferably a rubber dam 5. Determine need for cavity liner 6. etch, prime, place, and cure adhesive 7. Incremental placement and curing of composite material 8. Finish (proper anatomical contours) 9. Check for proximal contacts 10. examine for voids and marginal defects with a mirror and explorer. Use dental floss to detect any overhangs 11. Polish (lustrous surface) 12. Remove rubber dam or other isolation materials 13. check occlusion
Processing the denture
1. embedding the master cast and the denture setup in a denture flask filled with gypsum material. The mold is opened, and wax/baseplate are removed while denture teeth stay in position. Acrylic resin is placed when doughy, mold is closed, and acrylic forms denture base 2. The closed mold is heated in a water bath to activate the heat-cure acrylic resin. The heating rate is controlled to reduce porosity. The application of pressure minimizes loss of the volatile monomer; loss of monomer results in porosity and weak spots 3. After processing, the denture is removed from the mold by breaking the surrounding gypsum materials. It is then finished, polished, disinfected, and delivered to the patient.
technique to placing dental sealants
1. isolation 2. surface cleaned with slurry of pumice 3. tooth is etched and rinsed with water 4. sealant is placed 5. if chemically activated, allowed to set, if light activated, which is most common type of sealant placed today, then a light is used to cure 6. floss is used to ensure no materials flowed into interproximal areas 7. occlusion is checked and adjusted if needed
improper relationship to teeth results in...
1. overworked muscles of mastication 2. poor phonetics 3. unsatisfactory esthetics
placement of PRR
1. suspicious pit is opened with a bur by the dentist, and existing caries is removed 2. tooth is etched and primed, and adhesive is placed 3. prepared pit is filled with a hybrid composite material 4. any pits and fissures not filled by the composite or adhesive are filled with sealant 5. a great deal of tooth structure is preserved by placing a PRR
air abrasion system
1. used to remove debris and decay from pits and fissures and then placing sealants and preventive resin 2. high velocity stream of air carries very hard ceramic particles (aluminum oxide) and abrades the tooth 3. these systems are different from the prophy jet that uses baking soda to remove stains from surfaces of teeth 4. air abrasion systems can effectively cut enamel and dentin, cut cavity preparations, and remove composite materials 5. a rubber dam is recommended to protect patient's airway from the dust and debris that result from an air abrasion system
process of lost-wax casting technique
1. wax pattern with the sprue attached 2. wax pattern attached to the sprue base (also called the crucible former) and the casting 3. Wax pattern and casting ring with a paper liner. the casting ring slips over the wax pattern and fits into sprue base 4. Sprued and invested wax pattern inside a sectioned casting ring 5. cross section through a casting ring after burnout and a completed casting 6. Completed casting on the die
Admixed or blended alloys
A mixture of both lathe-cut and spherical particles
What is the process of relining?
Add a small amount of new materials to the inside tissue area of the denture base to replace the additional alveolar ridge that has been lost since the denture was made
gold foil is limited to small class _____, ____, _____, and _____ restorations because it lacks strength compared to other metallic restorations
I, II, III, and V
why would we need to reline?
Ill fitting dentures due to alveolar ridge atrophy and resorption
preventive resin restoration (PRR)
a conservative approach to treating pit and fissure decay
considered by many to be the "state of the art" material for luting metal and porcelain fused-to-metal crowns
acid-base chemically activated resin-modified glass ionomer products
Mesh
acrylic resin flows into and ground when the partial denture is processed
______ ______ were first introduced in dentistry for denture bases
acrylic resins
polymerization systems
all dental composites use addition polymerization and two polymerization systems are used to convert matrix-filler paste to a solid composite material
fracture
all-metal restorations are least likely to fracture - mechanical failure of the metal substructure of ceramometal crowns almost never occurs, however fracture of porcelain is the most common type of mechanical failure
Powdered metal is called an...
amalgam alloy - predominantly silver (Ag) and tin (Sn)
the mixing process of amalgam is called
amalgamation or trituration - mechanical device called an amalgamator or triturator is used
fixed indirect restorations can be classified in two ways:
amount of tooth structure they restore - by the materials from which they are made
CAD/CAM
an "optical" impression, rather than a physical impression of the preparation is made, and the restoration is machined out of a solid piece of high-strength ceramic material through computer control in the dental office or lab
a complete denture or full denture replaces
an entire arch of missing teeth, alveolar bone, which absorbs when teeth are missing
high copper amalgam was introduced when
around 1960, increasing the copper reduced the percentage of the weakest phase of the resulting dental amalgam
polymerization shrinkage
atoms and molecules become packed much closer together when polymerized, and the resulting material is smaller in volume than the starting components
______ ______ to tooth structure reduces the potential for these gaps and the resulting microleakage
bonding materials
Detecting composite restorations
can be difficult due to good shade match or excellent margins - do feel a bit softer than enamel to a sharp explorer - they can appear radiopaque or radiolucent on radiographs, depending on filler particle; however, they have evolved to be more radiopaque, which aids in the detection of these
thermoplastic polymers
can be heated (thermo) and molded or shaped (plastic) after the polymerization reaction, similar to wax
fixed restorations
cannot be removed from the oral cavity, they are luted (cemented) in place
tin
causes setting contraction and decreases strength and corrosion resistance
silver
causes setting expansion and increases strength and corrosion resistance
sintering
changes the porcelain from a powder to a solid - after sintering, the final shape of the restoration is refined by grinding
what is the first true adhesive restorative materials
chemical-cure glass ionomers products
framework is composed of
clasps, connectors, and mesh
precious metals
classified based on their cost. Noble metals and silver
hard tissue lasers are ideal for what?
cleaning debris from pits and fissures when placing sealants and preventive resin restorations
acrylic resin systems used in dentistry
cold-cure or chemically activated acrylic resins (supplied as powder/liquid)
composite materials
combination of two materials resulting in a material that is superior to either component alone
complex restoration
combine the features of inlay, onlay, and crown restorations
_____ ______ replaced both acrylic resins and silicate restorative materials
composite materials
Mercury toxicity
concern in dentistry because mercury and its chemical compounds are toxic to the kidneys and the CNS - not a problem for patients, except for patients who may have an allergy to mercury and very few cases, <0.1% have been reported - not ethical for dentist to urge patients to replace them
temporary restoration
constructed and cemented at the time of the preparation
most dental resins are ____ _____ and therefore thermoset
cross-linked
overtriturated amalgam tends to
crumble and is difficult to condense. In addition, voids will likely result in the restoration
there is a limit to the amount of filler that can be added, as it can cause a _______ ______
defective product
when _____ _____ became available, direct acrylic restorative materials were made obsolete
dental composites
Immediate denture
denture that is placed at the same appointment during which the remaining teeth are extracted
final step in the treatment plan
determine the recall status of the patient based on periodontal concerns, caries risk, chronic problems, and oral hygiene home care practices
filler size
determines surface smoothness or resulting restoration - composites are classified by the size of their filler particles - There are three categories that will be discussed in the book: macrofill, microfill, hybrid; however, it is important to know a new category has been introduced known as a nanofilled composite
gold foil is also called...
direct gold or cohesive gold
Lathe-cut alloys
done by grinding an ingot of metal to produce fillings
a partial denture uses a cast metal ________ for retention
framework
additional polymerization is an ______ reaction
exothermic it means they release heat
true or false: dental hygienists cannot place dental sealants
false, they can
true or false: polymeric materials have low coefficients of thermal expansion compared to tooth structure
false; high coefficients
true or false: an immediate denture does not protect the extraction sites during healing
false; it does protect
true or false: fiber-reinforced composites are much more brittle and weaker than particle-reinforced composites
false; much tougher and stronger
true or false: composites do not chemically bond to primers and adhesives
false; they do
sintered
firing porcelain causes the powder to become sintered
special use composite materials
flowable and condensable composite materials
The triturated material is reacting or setting while it is...
forced, or condensed, into the cavity prep
crazing
formation of many shallow surface cracks
acrylic resin
hard, brittle, glassy polymers - handled more like a thermoset material, after it sets, it is not heated and molded - most common is methyl methacrylate
undertriturated amalgam
has a mushy-grainy feel because not all of the particles are broken up. The mass is difficult to properly condense
Thermoset polymers
have cross-linked rather than linear structures and tend not to melt; rather, they decompose
Most dentists use ______ _____ alloys
high copper
why are dental composites placed in layers and cured after each layer
if not fully cured, pulpal irritation and post-operative sensitivity are more likely to occur
procedure of immediate dentures
impression is made, denture constructed in lab, remaining teeth are extracted, denture is placed, post op instruction given to patient
fillers
in beginning, fillers in dental composites were naturally occurring quartz materials (sand). Recently, manufacturers have "engineered" glass materials for dental composites - these glass materials are formulated to have the proper strength, hardness, and chemical as well as optical properties for use in dental composites
as filler content ______, the resin content _____, therefore, polymerization shrinkage decreases, and the coefficient of thermal expansion becomes more like that of tooth structure. Hardness and abrasion resistance increases as well
increases, decreases
CAD/CAM equipment is utilized to fabricate ______ restorations
indirect
reactions of chemically activated material is initially delayed for several minutes by the presence of a chemical reaction called an
inhibitor
inlays
intracoronal (inside the crown) restorations that replace small to medium amounts of tooth structure - they are most commonly used to restore pits, fissures, and grooves (class I) as well as proximal surfaces (class II) or posterior teeth, however, they do not restore the cusps - they are retained by using luting cement
Properly triturated amalgam
is a cohesive mass that might be slightly warm to the touch. The surface is smooth and this mix is easy to condense and exhibits the proper working time
Poor condensation with defects at the margin increases
likelihood of recurrent decay
dentistry has used the "______-______ _______ technique" for a century to produce metal restorations
long-wax casting
Shades and opacities of dental composites
manufactured in several shades to match the color or translucency of teeth - by layering materials, with different shades and translucencies a more natural result can be obtained - opaque composites are used to hide stained or discolored dentin
Polymers
materials that are made of large, long molecules formed by chemically reacting molecular building blocks called monomers, together to produce a polymer via polymerization
elongation
measure of the ability of a material to be stretched before it breaks - used to predict the ability of an alloy to be burnished, which when burnishing occurs it pushes the metal against the tooth to close any gap between the tooth and the casting, therefore, a margin or gap between the restoration and the tooth becomes smaller when it is burnished
What is dental amalgam?
metal alloy of which one of the elements is mercury - made by mixing approx. equal parts (by weight) of powdered metal alloy with liquid mercury
Clasps
metal and adjust fit
alloys
metals that are a combo of several elements
titanium
most biocompatible metal - current titanium used is limited - titanium has been used as material of choice for dental implants for decades - if handled properly, titanium can osseointegrate with bone
Restoration design
most common factor influencing the design of a restoration is the patient desire for an esthetic restoration - the attrition (wear) rate of the restoration should be considered - biocompatibility of the material must be considered - location of the margins of a restoration may be placed above the gingiva or in the gingival sulcus. Margin location affects esthetic retention, periodontal response to the restoration, and likelihood of recurrent caries
additional polymerization is called this because
one monomer at a time is added to the polymer chain as the reaction proceeds
Porcelain
porcelain jacket crowns were the first all-ceramic restorations used in dentistry- the entire crown was made of porcelain
cavity prep is always ____________ with amalgam
overfilled
a caries risk assessment should be made to determine
past history of caries, diet, salivary flow, and buffering capacity, fluoride exposure, and oral hygiene
the advantage of a chairside reline
patient does not go without his or her denture
Classification by gold content
percentage is parts per 100 - carat is parts per 24 - fineness is parts per 1,000 - Therefore: 75%=18 carat=750
surface corrosion discolors an amalgam restoration and may even lead to
pitting
incremental addition
placement of composite in layers, and not only assures adequate polymerization, but provides a secondary benefit as well
________ reactions make a few very large polymer molecules from many small monomer molecules
polymerization
microleakage
polymerization shrinkage has potential to open gaps at margins of restorations
processing a partial denture
processed much like a complete denture; however, acrylic resin must flow through and around the mesh of the framework
_____ _____ is not used because it is too soft, this is why other elements are combined to gain the strength needed
pure gold
the quality of an amalgam restoration is ______ if it is placed on a wet or contaminated environment
reduced
polishing produces a smooth and lustrous surface that...
reduces both the likelihood of corrosion and the ability of plaque to adhere to the surface
zinc
reduces the oxidation of the other metals in the alloy
if a prosthesis can be removed by patient, it is called...
removable partial denture, or simply a partial denture
excess amalgam is ___________ to restore the original anatomy of tooth
removed (carved)
percolation
repeated expansion and contraction of polymeric restorative materials can open and close gaps at the margin of a restoration - results of this are an increase in leakage resulting in greater chance of caries
onlays
replace more tooth structure than inlays - onlays restore one or more cusps and, at times, the entire occlusal surface of a tooth - these can be used when likelihood of cusp fracture is high as it protects the cusps from occlusal forces - retained by luting cement
dental bridge
replaces missing teeth - typically a bridge has a crown, called a retainer, at each end - retainers are supported by abutments - replacement teeth are called pontics - a bridge may replace one tooth or several teeth
also called resin-reinforced glass ionomers
resin-modified glass ionomer products
these are popular for class III and V restorations
resin-modified ionomer products
process of a chairside reline
same material acts as impression material, it is mixed, placed in denture, and placed in mouth. Material sets and becomes rigid. Excess is trimmed, denture is polished and returned to patient
Dual-cure materials
several dental materials have both chemical, and light activated capabilities - polymerization is started with a curing light, but materials that cannot be reached by the intense light sets via the chemical-cure mechanism
matrix
soft, weak, flexible, and prone to wear when compared to the filler - matrix of dental composite is a polymer, typically bis-GMA or a similar monomer and an organic chemical called a diluent, which is added to control the viscosity of the final product
open interproximal contacts, overhanging margins, and other improper contours increase
the likelihood of periodontal problems
Dental amalgam
the mixing of powdered metal with mercury
functional group
the part of the molecule responsible for its important chemical properties
to obtain maximum benefit from addition of filler and silane particles...
the polymer is bonded to the filler particle with a coupling agent
creep
the slow change in shape caused by compression
light activated additional polymerization
these are supplied in a single paste and no mixing is required - the polymerization process does not begin until the material is exposed to a very bright light source - the "set on demand" makes these materials very popular, composite restorative materials being the most common
chemically activated additional polymerization
these materials are also supplied as a powder/liquid system (temp crowns, retainers, impression trays, etc.) - powder and liquid are mixed together to start the polymerization process
heat activated additional polymerization
these materials come from manufacturer as a powder/liquid system - the polymerization does not start until the material is heated typically in a hot water bath
connectors
thicker parts of framework. Connect the mesh/clasps together
depth of cure
thickness of composite that is cured by a light source
indirect restorations
those that are constructed outside of the mouth
What can long-term use of adhesives cause:
tissue inflammation
undercarved occlusal surfaces cause
trauma to the supporting tissues
true or false: a lower partial denture with a few remaining natural teeth to hold it securely functions far better than a complete lower denture
true
true or false: chemical-cure glass ionomer products are susceptible to dehydration during the initial setting of the material and the finishing of restoration, and if not protected from dehydration, surface crazing occurs
true
true or false: curing light can only penetrate through several millimeters of composite to polymerize the underlying material
true
true or false: dental composites use ceramic filler particles with silane coupling agents
true
true or false: light activated glass ionomer restorations are easier to place and finish, and they are not as sensitive to dehydration as their chemical cure counterparts and are stronger and tougher
true
true or false: polymers without filler additives are not suitable for use as restorative materials
true
Chemically activated materials for polymerization systems
two paste systems - paste are different colors and they are mixed until the two colors blend into one - when mixing the two pastes air bubbles are incorporated during mixing, which can lead to weakness of the set material and increased staining - when pastes are mixed, inhibitor destroys the free radicals that are produced for a short period of time, which results in a limited amount of working time because when inhibitor has been reacted completely polymerization begins
filler particles
typically inexpensive, strong, hard ceramic materials
compomers
used to describe materials that bond and set like dentinal bonding/composite systems but that initially release some fluoride like glass ionomers
chairside reline
uses different material than lab-processed reline
heat-activated acrylic resins
very similar to chemically activated systems, except there is no chemical activator in the liquid - less inhibitor is present in liquid and only required as a preservative that prevents polymerization during storage - supplied as powder/liquid similar to cold-cure resins - much longer working time - after material is formed into the desired shape, material is heated in a water bath - heat breaks down benzoyl peroxide, forming free radicals - polymerization proceeds by changing dough into a rigid material - products that are heat-cured are a bit stronger and tougher than cold-cure acrylic resin
if fillers are not properly wetted by the liquid monomers, _____ and _____ between the filler particles result
voids and gaps
an inadequate mercury/alloy ratio results in...
voids and poor restorations
matrix is the _______ and least wear-resistant phase of dental composite material
weakest
When is the amalgam considered a zinc containing amalgam?
when the zinc content is greater than 0.01%
galvanic corrosion occurs when?
when two dissimilar metals exist in a wet environment - the electrical current flows between the two metals, and corrosion (oxidation) of one of the metals occurs)
silane coupling agents
work like soap - long molecules that react with polymer matrix at one end with the ceramic filler at the other end