Current Adhesives and Composite Bonding Flashcards
Cohesion:
attraction between similar molecules or atoms
a. Cohesive failure
Adhesion:
attraction between unlike molecules, attraction between two contacting
surfaces
a. Adhesive Failure
Adherend:
material bonded to another material by means of an adhesive
Adhesive:
substance that promotes adhesion
Adhesive Bonding:
joining two materials by means of an adhesive
Physical Bonding
◦ Very weak
◦ Ex. van der Waals forces
Chemical Bonding
◦ Very limited with dissimilar materials
Mechanical Bonding
(3)
◦Interlocking
◦Adhesive interlocks into surface irregularities
◦THIS IS THE DENTAL ADHESION MECHANISM
Microscopically intimate interface=
improved interlocking
Surface wetting-
the ability of a liquid to maintain intermolecular contact with
a solid surface
Improved surface wetting=
increased surface energy
Improved surface wetting= increased surface energy
◦ HOW?
(2)
◦ INCREASE SURFACE AVAILABLE FOR BONDING BY ETCHING
◦ Etching transforms smooth enamel into an IRREGULAR surface
Enamel Bonding=
very predictable
◦~25-30 MPa
Dentin Bonding=
more challenging
◦ Bond strengths vary
Type I-
“honeycomb” from dissolution of prism CORES
Type II-
“cobblestone” from dissolution of prism PERIPHERIES
TYPES I and II are found in
occlusal and middle thirds of teeth
BEST BONDS ACHIEVED TO TYPE I AND II
Type III-
combination of I and II
Type IV-
“pitted”
Type V-
“prismless” (flat and smooth)
Acid Etching Enamel
Chemical “drilling”
—% phosphoric acid is most effective for enamel retention
30-40
◦ Different types of acid used to etch different materials (nitric for metal, hydrofluoric for feldspathic porcelain)
◦ Removes about – microns enamel
10
◦ Place for — seconds prior to rinsing
15
Creates porous layer — microns deep
5-50
RINSE with water for – seconds after etching
10
RINSE with water for 10 seconds after etching
◦ To…
◦ — minimum water is necessary
◦ To remove acid and leave enamel surface clean for bonding
◦ 25mL
Etching increases (2)
wettability and surface area of the enamel
Etching raises the surface free energy to — the surface tension of bonding
material
◦ = (2)
EXCEED
◦ = produces spaces where resin can penetrate to form resin tags
◦ = mechanical interlocking that we are trying to achieve
After etching, apply —
(2)
resin (low viscosity)
◦ FLOWS into microporosities
◦ Polymerizes to MICROMECHANICAL BOND
LOCATION OF ADHESION MATTERS
Incisal third and middle third enamel
◦Predictable, strong
Cervical enamel
(2)
◦Shorter and fewer enamel tags (compared to middle and incisal thirds)
◦Less prism delineation (de to presence of prismless enamel, found in cervical third of 70% of teeth)
Bevels and Adhesive Dentistry
(3)
Reduce microleakage at cervical and ascending walls in Class II
preparations
Bevel gingival floor of prep
NECESSARY in enamel!
Additionally, enamel prepared with a bur
(bevelled) — better
etches
◦Reveals underlying prismatic enamel
When do we NOT bevel?
Deep preparations
◦So little enamel remains that a bevel would remove it all OR
◦Gingival floor is on cementum or dentin
The goal of adhesive dentistry with composite resin
◦In enamel-
◦In dentin-
interlocking with etched enamel rods
interlocking with etched dentin collagen
Enamel is great
◦—% inorganic matter by weight
◦—% hydroxyapatite by volume
◦—% organic matter by weight
◦—% water weight
95-98
90-92
1-2
4
Bond strength to perpendicular
Enamel (ENDS of rods)=
Bond strength to parallel
enamel (SIDES of rods)=
25MPa
7-10MPa
PERPENDICULAR oriented enamel (3)
◦Cavosurface margins of class I preparations
◦Bevels of class II preparations
◦ENDS of enamel rods
PARALLEL oriented enamel (3)
◦Internal walls of occlusal preparations
◦Gingival floor of box of class II preparations (see bevelling)
◦SIDES of enamel rods
Enamel Bonding, summarized
Etch surface
◦ Increased surface area and surface energy
◦ Allows wetting by hydrophobic adhesive resin
◦ Remember- enamel has MINIMAL water (3%)
Resin tags interlock◦ Macro and micro tags into surface irregularities
Micromechanical bonding!
Enamel- Adhesive- Composite Bond!◦ 20-25MPa
◦ Clinically Acceptable!
Dentin is very heterogenous
◦—% mineral by volume
◦—% collagen
◦—% water
Compare this to enamel- —% inorganic matter and —% water
55
30
15
97
1-2
Tubules
◦Fluid filled
Peritubular Dentin
◦Very INorganic
Intertubular dentin
(2)
◦Very ORGANIC
◦Collagen rich
Dentin tubules
◦ Diameter:
0.5 μm near DEJ, 2.5 μm near pulp
Dentin tubules
◦ Distribution
◦ 20,000/mm2 near DEJ
◦ 45,000/mm2 near pulp
Deeper dentin (2)
◦more & wider tubules
◦ = more fluid
◦less intertubular dentin
Smear Layer-
mixture of tooth debris, often contaminated with saliva, blood
cells, and bacteria
DO NOT BOND TO
SMEAR LAYER
◦ Bond strength- 7.4MPa
Remove smear layer with
acid etch
Hybrid Layer-
intermingled layer of collagen and resin
*What we WANT to form when bonding to dentin
Forming the Hybrid Layer
What happens when done properly
Steps:
(5)
1.Acid Etch 15 seconds dentin
2.Wash and LIGHTLY dry
= Hydroxyapatite removed, water remains to support collagen fibers
3.Apply primer
4. Apply adhesive
5. Light cure
Hybrid layer forms!
upon light curing, the unfilled resin sets within the collagen fibril network
OVERETCHING results in
underfilled restorations
OVERDRYING results in
lower bond strengths
UNDERDRYING results in
collagen that is too wet
Bonding Systems
(4)
Initial Bonding Agents
Etch-and-Rinse Bonding Agents
Self-Etching Primers
Universal Adhesives
Initial Bonding Agents
◦ No longer used, first three generations of bond agents
Etch-and-Rinse Bonding Agents (2)
◦Previously “Total Etch”
◦2 or 3 bottle system
Self-Etching Primers
(2)
◦Eliminate a step
◦ 1 or 2 bottle system
Development of Etch Systems
First:
No etch, adhesive resin only
◦ Pretty awful, 4-6MPa bond strength
◦ Bonds to smear layer
Development of Etch Systems
Second:
Etch, adhesive resin only
◦ 10-12MPa bond strength
Development of Etch Systems
Third:
Etch, primer, adhesive
◦ Now we’re talking!
◦ 20-30MPa bond strength
Disadvantages of bonding systems
(3)
Too many steps
Or insufficient penetration of smear layer
Delicate treatment of dentin necessary
Bonding System Components
(4)
Etchant
Primer
Adhesive Bonding Resin/Agent
Filler
Etchant
◦ Phosphoric acid gel (30-40%)
Primer
(2)
◦ HYDROPHILIC monomers in HEMA solvent
◦ Acetone, ethanol/water, water
Adhesive Bonding Resin/Agent
(4)
◦ HYDROPHOBIC dimethacrylate monomers (BisGMA)
◦ Initiators and Activators
◦ Camphorquinone in light activated systems
◦ Benzoyl Peroxide (BPO) Tertiary amine in chemical and dual cure systems
Filler
◦ Most unfilled, some 0.5-40 % by weight
Adhesive/primer monomers–> polymers
◦Chemical reaction
Activator
(3)
◦Converts Initiator (chemical) into a free radical
◦Free radical starts polymerization reaction
◦Light or chemical
◦ Light
(2)
◦ Blue light (~47-nm)
◦ Camphorquinone→free radical→polymerization reaction
◦ Chemical (tertiary amine)
(1)
◦ Benzoyl peroxide (initiator)→free radical→polymerization reaction
Bonding Procedure
steps (6)
Step 1. Acid etch
◦ 15 seconds
Step 2. Rinse
◦ 10 seconds
◦ GENTLY dry- enamel should be dry, dentin should be slightly moist
Step 3. Apply Primer
Step 4. Apply Bond
Step 5. Light cure (= polymerize)
(Step 6. Place composite)
Dentin Bonding Mechanism
(4)
- Acid-etched,
demineralized collagen fibrils
(~2-5 m deep) - Water supports collagen
network - Hydrophilic Primer
applied - Hydrophobic Dentin Bond
agent
applied, polymerized
Bonding Procedure
Step 1. Acid Etch
◦Dentin-
15 seconds at MOST
◦ Acid demineralizes dentin, leaving collagen
Bonding Procedure
Step 1. Acid Etch
◦Enamel-
15-30 seconds
◦ Removes hydroxyapatite
Bonding Procedure
Step 1. Acid Etch
◦Or
SELECTIVE ETCH
◦ Only etch enamel
Bonding Procedure
Step 1. Acid Etch
◦Removes
smear layer
◦Denatured collagen, hydroxyapatite
crystals, debris from cutting tooth
~2 microns thick
Held on tooth by van der Waals forces
(4-6MPA)
Step 2: Gently rinse and air dry
(4)
◦Rinse 10 seconds, air dry gently
◦DO NOT DESSICATE
◦Enamel should be dry
◦Dentin should be slightly moist
Step 3: Apply Primer
(6)
◦Hydrophylic
◦Low viscosity
◦2-hydroxyethyl methacrylate (HEMA)
◦Penetrates water filled spaces in demineralized collagen network
◦Promotes bonding to dentin
- Attracts hydrophobic bond agent
Step 4: Apply Bonding Agent Resin
(4)
◦Hydrophobic
◦Follows primer into spaces in demineralized collagen
◦Bisphenol A diglycidyl methacrylate (~70%)
◦Triethylene glycol dimethacrylate (~30%)
Bisphenol A diglycidyl methacrylate (~70%)
◦ Bis-GMA- viscous, rigid
Triethylene glycol dimethacrylate (~30%)
(2)
◦ TEGDMA- flexible, decreases viscosity
◦ Crosslinking
Step 5- Light cure
(3)
◦Polymerization reaction
◦ Blue light ACTIVATES
◦ Camphorquinone INITIATES
Step 6- Place composite resin
(2)
◦Incrementally
◦Light cure between increments
Primary dentin bond mechanism is from — LAYER
HYBRID
Hybrid layer-
micromechanical interlocking of resin with demineralized
collagen
◦ Collagen from intertubular dentin
Factors affecting bond to dentin
(3)
cavity depth
caries
moist vs dry dentin
Cavity depth
◦ Better bond strength in superficial dentin
\
Caries
◦ Lower bond strength in carious dentin
Moist vs. Dry dentin
◦ Moist is better!
◦ Overwet◦ Resin doesn’t penetrate well
◦ Decreased bond strength
◦ Collagen fibers collapse in dry dentin◦ Resin cannot penetrate
◦ Poor hybrid layer
◦ Decreased bond strength
Factors to improve bond to dentin
(2)
Use extreme caution when using air/water syringe to dry
dentin
◦Use brush or cotton pellet to remove excess water on dentin
Use Rubber Dam
◦Prevents saliva contamination
◦Reduces humidity in oral cavity
Systems previously described by ‘Generation’ number
(2)
a.Not a useful system
b.Describe instead by the components
Bonding Systems
(3)
Phosphoric acid used to etch
Etch-and-Rinse/Total etch
Self-etch
Etch-and-Rinse/Total etch
(2)
• Extra step
• Rinsed
Self-etch
(3)
• No phosphoric acid-etch step
• Acid part of the primer or primer/bond agent
• Not rinsed
Etch-and-Risne/Total Etch Bonding Systems
2 steps
1.3-step (2-bottle) Total Etch
a.Etchant
b.Primer
c.Bond agent
1)Example: Scotch Bond Multi-purpose
2.2-step (1-bottle) Total Etch
a.Etchant
b.Primer and bond agent combined
1)Examples
1)Prime and Bond NT, PQ 1, Peak,
Optibond Solo Plus
Self-etching primer
(3)
◦2-step: acidic primer & bonding agent
◦Acidic primer partially dissolves smear layer, allows penetration of
bond resin
◦Clearfil SE Bond; Clearfil Liner Bond 2V
Self-etching adhesive (All-in-one)
◦ 1-step –most variable/ least predictable
◦ Acidic primer and bond resin, one solution
◦ Many require mixing
◦ Examples: Xeno,
i-Bond, Bond Force (no mix)
Rinse and Etch/Total Etch Systems
Advantages
(2)
◦More predictable, stronger bond
◦Enamel adequately prepared
Rinse and Etch/Total Etch Systems
Disadvantages
(4)
◦Collagen collapse is possible*
◦Etched zone is often deeper than hybrid layer
◦ Exposed demineralized, collagen fibrils
◦ Post-operative sensitivity
Self-etch SystemsAdvantages
(4)
◦No separate etch: overdried, collapsed demineralized collagen not a problem
◦Etched zone and hybrid layer comparable width; however, some exposed
collagen
◦Low post-operative sensitivity
◦Time efficiency
Self-etch Systems
Disadvantages
(4)
◦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
-Long-term bond strength?
◦Self-etch adhesives (all-in-one)
- Lower bond strength
- Long-term breakdown?
- Collagen degradation over time
Universal adhesives
Can be used in total etch, self-etch or selective-etch mode (etch
enamel only with phosphoric acid)
What we’re using at UMKC
Adhese and Peak
Universal adhesivesChemistry game changer is
10-MDP
◦ Methacryloyoxy-decyl-dihydrogen-phosphate (10-MDP)
Universal adhesives
Mechanism of action : (3)
A monomer that chemically interacts via ionic bonding to
calcium in hydroxyapatite
Single bottle, no mix adhesive system
Monomer is a phosphate ester
Biocompatibility of acid etchEtchant
◦ Enamel was only etched up until the late 1980’s;
we thought etching dentin would harm the pulp so we used to cover the dentin with CaOH before we etched a tooth.
We now use a total etch technique of etching enamel and dentin.
◦ Etchant interacts with superficial dentin and there is no pulpal damage
Direct etch of pulp?
bad
Dentin adhesive
(3)
◦ Well tolerated by dentin
◦ Do not want to apply it directly to the pulp though
◦ Adverse pulp reaction comes primarily from bacteria remaining in
or penetrating the preparation
Bond Strengths to Dentin Vary (8)
Region of tooth
◦ Superficial higher bond strength than deeper (Prati, 1992)
Flat surfaces higher than box cavities (Bouillaguet, 2001)
C-factor (Yoshikawa, 1999)
Adhesive system used (Yoshikawa, 1999)
Thickness of increment of composite resin
◦ 1 mm better than 2 mm increment
Operator (Shono, 1999)
Intrinsic wetness of tooth (Ogata, 2001)
Dryness vs wetness (Tay, 1996)
ond to dentin collagen is influenced by
Matrix metalloproteinases (MMPs)
• collagen enzymes that metabolize unhybridized collagen
MMPs are present on
collagen fibrils and can be seen at 100,000X on SEM
— inhibits MMP activation
Chlorhexidine
Consepsis® (Ultradent)
(2)
◦ 2% Chlorhexidine Antibacterial Solution
◦ Applied after acid etching
