Based on Exam 1 Review Doc Flashcards
Why should you place composite incrementally vs bulk filling?
-Incrementally placing composite minimizes stresses placed on the material and on the tooth due to polymerization shrinkage (this may be a factor in postoperative sensitivity)
-Resin is bonded to LESS walls → relieves stress in the resin-adhesive surface
incrementally placed has a lower C factor
Basic components of Tofflemire matrix system
- Retainer: slot faces gingiva
placed on BUCCAL side
band comes out of SIDE channel
slit down so it is easier to remove - Matrix band: burnish adjacent tooth IN CONTACT AREA
- Wooden wedges: wedge properly- through the more open of the embrasures (typically the lingual)
Basic components of sectional matrix system (Palodent)
- Use provided tweezers to place wedge
- place sectional matrix band using provided tweezers
- place ring on top of wedge
can use on MOD
What are the advantages to using a rubber dam?
- better visualization
- better access
- prep walls dry and clean
- materials work better
- improved properties- direct contacts of varnish/liner/base with cavity walls
- moisture affects bond as well as materials ability to set up
- prevents injury to patient soft tissues
- prevents aspiration and swallowing of debris
- fewer aerosols
-shiny part of rubber dam on tongue side, matte side faces operator
Basic order of operations for preparing Class II
- establish initial outline form and depth
- extend proximal box
- once ideal outline form is achieved, remove caries (spoon excavator or round bur on slow speed handpiece)
- refine prep (with steps below)
- plane axiopulpal line angle (reduces stress)
- plane gingival margin (removes loose enamel rods)
- bevel gingival margin (ONLY with ideal preps)
*do not place gingival bevel on dentin or cementum
Basic order of operations for composite restoration
- place matrix
- etch, bond
- begin by placing material in box
- place composite incrementally
- cure each increment for 20 seconds
- form final anatomy BEFORE final cure
- finishing carbides for minor adjustments after curing
- polishing
Basic order of operations for amalgam restoration
- Tofflemire matrix in place
- fill box first, then occlusal
- begin carving
- marginal ridge- use explorer
- try a pre-carve burnish to remind you of your outline
- begin with HOLLENBACK carver to recreate anatomy (before set)
- remove band (from side)
- carve interproximal before sets up fully
- refine anatomy
- smooth restoration with wet cotton pellet
- dull, matte finish
Why bevel?
to reduce microleakage at cervical and ascending walls in class II preps
Where should you bevel in Class IIs?
Bevel gingival floor of prep
only if on enamel
When to bevel?
-NECESSARY when in enamel
-DO NOT bevel in deep preps (So little enamel remains that a bevel would remove it all OR Gingival floor is on cementum or dentin)
How to bevel?
Enamel prepared with a bur (beveled) etches better; exposes ends of enamel rods; reveals prismatic enamel
What walls in a class II are a flare recommended?
slight flare occlusal of prep
Type I enamel etching
- “honeycomb”; from dissolution of prism (enamel rod) CORES
- found in occlusal and middle thirds of teeth
- best bonds achieved to type I (and II)
Type II enamel etching
- “cobblestone”; from dissolution of prism (enamel rod) PERIPHERIES
- found in occlusal and middle thirds of teeth
- best bonds achieved to type II (and I)
Type III enamel etching
- combination of I and II
- not stuck very deep
Type IV enamel etching
- “pitted”
- not stuck very deep
Type V enamel etching
- “aprismatic”
- flat and smooth
- not stuck very deep
Acid etching enamel
- Chemical “drilling”
- Removes about 10 microns enamel
- Place for 15 seconds prior to rinsing
- Creates porous layer 5-50 microns deep
- RINSE with water 10 seconds after etching
- To remove acid and leave enamel surface clean for bonding
- 25mL minimum water is necessary
- Visualize a FROSTY surface after gentle air dry
Which acid is used to etch enamel?
30-40% phosphoric acid
What are the other types of acid used to etch different materials?
Nitric –> metal
Hydrofluoric –> feldspathic porcelain
What is the purpose of etching?
- Etching transforms smooth enamel into an IRREGULAR surface
- Etching increases wettability and surface area of the enamel
- Etching raises the surface free energy to EXCEED the surface tension of bonding material
What is surface wetting?
the ability of a liquid to maintain intermolecular contact with a solid surface
What type of bond are we trying to achieve with etch/bond?
MICROMECHANICAL BOND
What is etchant?
interacts with superficial dentin and there is no pulpal damage
After etching, what does bond agent resin do?
- low viscosity
- flows into mircoporosities
- polymerizes to MICROMECHANICAL BOND
What does resin interlock with in enamel?
enamel rods
What does resin interlock with in dentin?
dentin collagen
What are the types of bonding systems?
- Etch-and-Rinse (FKA Total etch)
- Self-etch
What are the basic elements of the Etch-and-Rinse (FKA Total etch) system?
- Etch separately
- Prime (3-step)
- Bond (3-step)
- or Prime + Bond combined (2-step)
What are the advantages to Etch-and-Rinse system?
- More predictable, stronger bond
- Enamel adequately prepared
What are the disadvantages to Etch-and-Rinse system?
- Collagen collapse is possible (result of user error)
- Etched zone is often deeper than hybrid layer (exposed demineralized, collagen fibrils; post-operative sensitivity)
- Too many steps (more chances for operator error)
What are the basic elements of the self-etch system?
- No phosphoric acid-etch step
- Acid part of the primer or primer/bond agent (acidic primer partially dissolves smear layer, allows penetration of bond resin)
What are the types of self-etch systems?
- 2 step: acidic primer & bonding agent
- 1-step: most variable/least predictable (acidic primer and bond resin, one solution)
What are the advantages of the self-etch system?
- No separate etch: overdried, collapsed demineralized collagen not a problem
- Etched zone and hybrid layer comparable width; however, some exposed collagen
- Low postoperative sensitivity
- Time efficiency
What are the disadvantages of the self-etch system?
- Not compatible with self-cure, dual-cure composite (acidic monomers, low pH, “kills” the basic amine activator)
- Will not etch unprepared enamel
- Self-etch primer systems have long-term bond strength?
- Self-etch adhesives (all-in-one) have lower bond strength, long-term breakdown (collagen degradation over time)
- Insufficient penetration of smear layer
What effects longevity in bonds?
- Bond to dentin collagen is influenced by Matrix metalloproteinases (MMPs)
- MMPs are present on collagen fibrils and can be seen at 100,000X on SEM
- Chlorhexidine inhibits MMP activation –> leading to longer lasting bonds
What are MMPs?
collagen enzymes that metabolize unhybridized collagen
What is Consepsis?
2% Chlorhexidine Antibacterial solution applied after etching —> leads to longer lasting bonds
What are the clinical success requirements of bonding?
- Knowledge of substrate
- Good cavity preparation and margins
- Rubber dam and matrix/wedge
- Correct use of the bonding agent (follow directions; Wet/Moist bonding, total etch, self-etch)
- Bond agent compatible with resin composite
What are the bond system components?
- Etchant (Phosphoric acid gel (30-40%))
- Primer
- Adhesive Bonding Resin/Agent
- Filler (Mostly unfilled resins, some 0.5-40% by weight)
What does the primer do in bonding systems?
- HYDROPHILIC (draws the bond agent in) monomers in HEMA solvent
- Acetone, ethanol/water, water
What does the adhesive bonding resin/agent do in bonding system?
- HYDROPHOBIC dimethacrylate monomers (BisGMA)
- Initiators and Activators (Camphorquinone in light activated systems
Benzoyl Peroxide (BPO) tertiary amine in chemical and dual cure systems)
When can Universal adhesives be used?
Can be used in total etch, self-etch or selective-etch mode (etch enamel only with phosphoric acid)
What adhesive do we use at UMKC?
Universal adhesive
What is the chemistry game changer of universal adhesives?
10-MDP
Mechanism of action: a monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
Would you ever directly etch the pulp?
NO
What is dentin adhesive?
- Well tolerated by dentin
- Do NOT want to apply it directly to the pulp
- Adverse pulp reaction comes primarily from bacteria remaining in or penetrating the preparation
What location for adhesive is predictable and strong?
Incisal ⅓ and middle ⅓ enamel
What is makes cervical enamel less favorable for adhesive?
- Shorter and fewer enamel tags (compared to middle ⅓ and incisal ⅓)
- Less prism delineation (due to presence of prismless enamel)
- Bad news: this is where deep class II preps usually end
What is the Makeup of enamel?
95-98% inorganic matter by weight
90-92% hydroxyapatite by volume
1-2% organic matter by weight
4% water weight
What is the bond strength to perpendicular enamel (ENDS of rods)?
25MPa
What is the bond strength to parallel enamel (SIDES of rods)?
7-10MPa
Examples of perpendicular oriented enamel
- Cavosurface margins of class I preps
- Bevels of class II preps
- ENDS of enamel rods
Examples of parallel enamel
- Internal walls of occlusal preps
- Gingival floor of box of class II preps (see beveling)
- SIDES of enamel rods
Summary of enamel bonding
- Etch surface
- Resin tags interlock (macro and micro tags into surface irregularities)
- Micromechanical bonding
- Enamel-adhesive-composite bond
What is the makeup
of dentin?
55% mineral by volume
30% collagen
15% water
Basic dentin anatomy
- Tubules (fluid filled)
- Peritubular dentin (very INorganic)
- Intertubular dentin (very ORGANIC, collagen rich, where you want to bond)
What is the top arrow pointing to?
peritubular dentin
What is the bottom arrow pointing to?
intertubular dentin
How does the diameter of the dentin tubules change as they get closer to the pulp?
larger
- 0.5 micrometers near DEJ
- 2.5 micrometers near pulp
How does the distribution of the dentin tubules change as they get closer to the pulp?
more near pulp
- 20,000/mm2 near DEJ
- 45,000/mm2 near pulp
How does deeper dentin differ from less deep dentin?
- more & wider tubules (=more fluid)
- less tubular dentin
What is the basic dentin bonding mechanism?
- Acid-etched, demineralized collagen fibrils (2-5 micrometers deep)
- Water supports collagen network
- Dentin bond agent applied, polymerized