OPERATIVE Restoration of Teeth Flashcards
___ are effective disinfectants, provide cross-linking of any exposed dentin matrix and occlude dentinal tubules by cross-linking tubular proteins
sealers (aka desensitizers)
sealers provide occlusion of the dentinal tubules which limits the potential for ___
tubular fluid movement and resultant sensitivity
sealers are typically ___ solutions
aqueous
historically, ___ was used as a liner under amalgam restorations
copal varnish
what are some examples of desensitizers that some sealers contain?
gluteraldehyde, hydroxyethylmethacrylate (HEMA), benzalkonium chloride, or chlorhexidine
___ are thin layers of material used primarily to provide a barrier to protect the dentin from residual reactants diffusing out of a restoration, from oral fluids, or from both, which may penetrate leaky tooth-restoration interfaces
liners
what are some ways liners act as barriers?
- contribute initial electrical insulation
- generate some thermal protection
- some formulations provide pulpal treatment
___ are used to cover a direct or near pulpal exposure and to line very deep areas of a tooth preparation in vital teeth
liners
___ and ___ are examples of typical liners used with direct restorations
calcium hydroxide and RMGI
___ are used to provide thermal protection for the pulp and to supplement mechanical support for the restoration by distributing local stresses from the restoration across the underlying dentin surface
bases
how thick should bases be?
1-2mm typically
additional bulk from a base affords ___ and ___ protection to the pulp under metal restorations
mechanical and thermal
___ or ___ are recommended as a base to overlay any calcium hydroxide liner that has been placed
RMGI or conventional glass ionomer cement
RMGI or conventional glass ionomer cement base provides additional strength to resist ___ in amalgam restorations, as well as protection of the liner from dissolution during ___ procedures
- amalgam condensation pressure
- bonded
describe how to use bases and/or liners in amalgam restorations with shallow excavations
- shallow excavation = remaining dentin thickness >2mm
- use a dentin sealer/desensitizing agent such as gluma or G5
- sealers/desensitizers replace the traditional use of copal varnish
describe how to use bases and/or liners in amalgam restorations with moderately deep excavations
- remaining dentin thickness is 0.5-2mm
- use light cured RMGI base, followed by a dentin sealer/desensitizing agent
- objective is to provide 2mm of insulation between the restorative material and the pulp
- this replaces the traditional approach of using a zinc oxide eugenol base material followed by a copal varnish
describe how to use bases and/or liners in amalgam restorations with deep excavations
- noncarious (or mechanical) pulpal exposure less than 1mm in diameter or excataions where the remaining dentin thickness is <0.5mm
- use a thin (0.5-0.75mm) layer of calcium hydroxide liner on the suspected exposure site followed by RMGI base to seal immediate site of exposure
- objectives are to prohibit bacterial infiltration and protect the liner from dissolution
- a dentin sealer/desensiziting agent or an appropriate amalgam bonding agent is placed on the remaining dentin
describe how to use bases and/or liners in composite restorations with shallow to moderately deep excavations
- remaining dentin thickness is 0.5mm or more
- no liner or base material is indicated
- only a dentin bonding system along with the composite restorative material is needed
describe how to use bases and/or liners in composite restorations with deep excavations
- noncarious (or mechanical) pulpal exposure <0.1mm in diameter or excavations where the remaining dentin thickness is judged to be <0.5mm
- use a thin (0.5-0.75mm) layer of calcium hydroxide liner placed on the suspected exposure site followed by RMGI base and the proper application of a bonding agent along with the composite restorative material
- objective is to prevent bacterial infiltration while avoiding dissolution of the liner
describe how to use bases and/or liners in indirect restorations with shallow excavations
- remaining dentin thickness is 2mm or greater
- no sealer, liner, or base is needed
- RMGI cement or a resin-based cement may be used for cementation, providing excellent dentinal sealing
describe how to use bases and/or liners in indirect restorations with moderately deep excavations
- remaining dentin thickness 0.5-2mm
- RMGI or conventional glass ionomer cement may be used to restore axial or pulpal wall contour and to ensure an adequate thermal barrier
- objective is to provide 2mm of insulation between the restorative material and the pulp
- RMGI or resin based material is recommended for cementation
describe how to use bases and/or liners in indirect restorations with deep excavations
- noncarious (mechanical) pulpal exposure less than 1mm in diameter or excavations where remaining dentin thickness is <0.5mm
- use a thin (0.5-0.75mm) layer of calcium hydroxide liner placed on the suspected exposure site followed by RMGI base to restore axial or pulpal wall contour, ensure an adequate thermal barrier, and seal the exposure site
- objective is to prevent bacterial infiltration while avoiding dissolution of the base
in indirect restoration cases where pulp exposures occurred during preparation, where there is an increased risk of endodontic complications secondary to the pulp exposure, strong consideration should be given to performing ___ before completion of the indirect restoration
endodontic therapy
what are the two types of amalgams?
- low copper (generally inferior, seldom used)
- high copper (spherical and admix)
is spherical or admix amalgam better? why?
- admix
- less leakage and less postoperative sensitivity
the linear coefficient of thermal expansion of amalgam is ___ than that of tooth structure
greater
the compressive strength of high copper amalgam is ___ than tooth structure
similar
the tensile strength of high copper amalgam is ___ than tooth structure
lower
amalgams are brittle and have ___ edge strength
low
high copper amalgams exhibit ___ creep or flow
no clinically relevant creep or flow
is amalgam a high or low thermal conductor?
high
what are the clinical disadvantages of amalgam?
marginal fracture, bulk fracture, and secondary caries
what are the uses for amalgam restorations?
- nonesthetic cervical lesions
- large class I and II preparations where heavy occlusion would be on the material
- class I and II preparations where isolation problems exist for bonding
- temporary or caries-control restorations
- foundations
- patient sensitivity to other materials
- where cost is a factor
- inability to do a good composite
what are the advantages of amalgam?
strength, wear resistance, easy to use, less technique-sensitive, self-sealing margins over time, history of use, lower fee, long-term clinical longevity
what are the disadvantages of amalgam?
not esthetic, conductivity, tooth preparation more demanding and less conservative
is there scientific evidence that amalgam poses health risks to humans?
- no, with the exception of rare allergic reactions
- there is actually no evidence ensuring that alternative materials pose a lesser health hazard
true amalgam allergies are rare. how many have been reported since 1900?
50
what is the estimate of human uptake of mercury vapor from amalgams?
5 ug/m^3
which amalgam type is likely to produce a more successful restoration?
high copper
how thick does amalgam need to be to increase its success?
1-2mm
after the tooth preparation for most amalgam restorations, a ___ is placed on the prepared dentin before amalgam insertion to ___
- sealer
- occlude the dentinal tubules
- this step may occur before or after the matrix application
what are the 4 objectives of a matrix?
- provider proper contact
- provide proper contour
- confine the restorative material
- reduce the amount of excess material
what are the 4 characteristics a matrix needs to be effective?
- be easy to apply and remove
- extend below the gingival margin
- extend above the marginal ridge height
- resist deformation during material insertion
in terms of trituration, what two features affect the setting reaction of the material?
the speed and time of the mix
of spherical and admixed (lathe-cut) amalgam, which is easier to condense?
spherical
how is floss used to to check the proximal contact of an amalgam restoration?
- insert floss inter proximally first by wrapping the floss around the adjacent tooth and pulling it through
- wrap floss around restored tooth and move it occlusally and gingivally to determine if excess material exists and to smooth it
how do you repair an amalgam restoration?
-the defective area must be prepared again as if it were a small restoration, with appropriate depth and retention form
what are the causes of postoperative sensitivity from amalgam restorations?
- lack of adequate condensation, especially lateral condensation in the proximal boxes
- lack of proper dentinal sealer or pulp protection
what are the causes of marginal voids from amalgam restorations?
- inadequate condensation
- material pulling away or breaking from the marginal area when carving bonded amalgam
what are the causes of marginal ridge fracture of amalgam restorations?
- axiopulpal line angle not rounded in class II tooth preparations
- marginal ridge left too high
- occlusal embrasure form incorrect
- improper removal of matrix
- overzealous carving
are amalgam restorations safe?
- yes, as reported by the US Public Health Service
- proper handing of amalgam is of vital importance
which type of high-copper amalgam provides higher earlier strength and permits the use of less pressure? which one permits easier proximal contact development because of higher condensation forces?
- spherical
- admixed
are bonded amalgam restorations recommended?
- not any longer
- however, if bonding an amalgam, the use of typical secondary retention form preparation features are still required
- small to moderate amalgam restorations should not be bonded
what are the indication for proximal retention locks?
- may be beneficial for large amalgam restorations (not necessary for smaller restorations)
- correct placement of proximal retention locks is difficult
what are the advantages of bonding to tooth structure?
less micro leakage, less marginal staining, less recurrent caries, less pulpal sensitivity, more conservative tooth preparation, improved retention, reinforcement of remaining tooth structure, and more conservative treatment of root-surface carious lesions
what are the uses of adhesive techniques?
change shape and color of anterior teeth, restore class I-VI lesions, improve retention for metallic or PFM crowns, bond ceramic restorations, bond indirect composite restorations, seal pits and fissures, bond orthodontic brackets, bond periodontal splints, bond conservative tooth-replacement restorations, repair existing restorations, provide foundations for crowns or onlays, desensitize exposed root surfaces, impregnate dentin and enamel to make them less susceptible to caries, bond fragments of anterior teeth, bond prefabricated and cast posts, and reinforce remaining enamel and dentin after tooth preparation
what is sufficient to etch enamel?
10-15 second acid etch (30-40% phosphoric acid) is sufficient
is micro leakage common at etched enamel margins?
no, it is virtually nonexistent
enamel bonding resists ___ forces of composite
polymerization shrinkage
how is dentin bonding accomplished?
either etch and rinse (simultaneous with enamel etch) or self etch (with a self etching primer or all in one adhesive)
how does dentin bonding compare to enamel bonding?
- less reliable, less durable, and not as predictable as enamel bonding
- may have some micro leakage, especially after aging of the restoration
- may have similar or higher bond strengths than enamel
- may not resist polymerization shrinkage forces
what are the factors that affect the ability to bond to dentin vs enamel?
- microstructural features of enamel and dentin
- material factors
- preparation factors
describe the difference in composition of enamel vs dentin
- enamel is 90% mineral (hydroxyapatite)
- dentin is much less mineral and more organic (type I collagen) and water
are enamel prisms and inter prismatic areas etched and bondable?
yes
what are the 3 types of dentin tubules?
peritubular, intratubular, and intertubular channels
dentin tubules extend from the ___ to the ___
pulp to the DEJ
what do dentin tubules contain?
odontoblastic extensions and fluid
how do dentin tubules range in size/number as they near the pulp?
- much larger (2.4um) and numerous (45,000/mm^2) near the pulp
- near DEJ (0.6um, 20,000mm^2)
fluid movement inside dentin tubules is dictated by ___
pulpal pressure
dentin that is aging, below a caries lesion, or exposed to oral fluids exhibits increased mineral content (sclerosis) and is much more resistant to ___
- acid etching
- therefore, the penetration of dentin adhesive is limited
what is the smear layer?
- debris left on the surface after cutting
- consists of hydroxyapatite and altered denatured collagen and fills the orifices of the tubules (smear plugs), decreasing dentin permeability by 86%
how is the smear layer removed?
etching removes the smear layer, resulting in greater fluid flow onto the dentinal surface, which may interfere with adhesion
how is the linear coefficient of thermal expansion of dentin altered when subjected to thermal changes compared to composite?
dentin is 4x less than composite
composites shrink when they polymerize, creating stresses up to ___ megapascals
7 (1MPa = 150lb/in^2)
preparations with multiple walls or boxlike shapes (configuration) have limited ___ opportunity for the composite material (polymerization shrinkage), and the high configuration factor (C factor) may result in ___ and ___
- stress relief
- internal bond disruption and marginal gaps
C factor is determined by the ratio of ___ vs ___ within a tooth preparation
prepared (bonded) vs unprepared (unbounded) walls
high C factor may indicate increased chance for ___
postoperative sensitivity
what are the two current adhesive systems used for bonding?
etch and rinse, and self etch
etch and rinse is also called ___
total etch (etch enamel and dentin)
what are etch and rinse three step systems?
- aka multibottle or fourth gen systems
- etch, primer, and adhesive
what is the purpose of etch?
demineralizes enamel and dentin selectively, increases surface area, and cleans the surface of debris
T or F:
etched enamel and dentin appear chalky
- false
- enamel appears chalky, but dentin does not
etched dentin exposes a layer of ___
collagen
what is the purpose of etch, primer, and adhesive?
- etched dentin exposes a layer of collagen
- primer increases the collagen
- adhesive flows between the collagen and interlocks with it to form a sandwich (or hybrid or resin-reinforced) layer
most bond strength is from the formation of the ___ layer
- hybrid (aka sandwich or resin-reinforced)
- the surface layer is only a few microns thick, creating a demineralized layer of dentin intermingled with resin