Current Adhesives and Composite Bonding Flashcards
What is cohesion?
attraction between similar molecules or atoms
What is adhesion?
attraction between unlike molecules, attraction between two contacting surfaces
What is the adherend?
material bonded to another material by means of an adhesive
What is adhesive?
substance that promotes adhesion
What is adhesive bonding?
joining two materials by means of an adhesive
Is a physical bond weak or strong?
very weak
Is a chemical bond strong or weak?
Very limited with dissimilar materials
How does a mechanical bond work?
◦ Interlocking
◦ Adhesive interlocks into surface irregularities
◦ THIS IS THE DENTAL ADHESION MECHANISM
What is the main dental adhesion mechanism?
mechanical
What does microscopic intimate interface do to interlocking?
improves interlocking
What is surface wetting?
the ability of a liquid to maintain intermolecular contact with a solid surface
What does improved surface wetting do to surface energy?
increases surface energy
How do you increase the surface area?
◦ INCREASE SURFACE AVAILABLE FOR BONDING
◦ BY ETCHING
◦ Roughened surface (diamond bur for bevels)
◦ Etching transforms smooth enamel into an IRREGULAR surface
What is the dental adhesion of enamel?
~25-30 MPa
- very predictable
What is the dental adhesion of dentin?
◦ Bond strengths vary
- more challenging
What is the type I enamel etching?
- “honeycomb”
- from dissolution of prism (enamel rod) CORES
What is the type II enamel etching?
- “cobblestone”
- from dissolution of prism (enamel rod) PERIPHERIES
Where are type I and type II enamel etching areas found?
occlusal and middle thirds of teeth
What areas of enamel etching are the best bonds?
TYPE I AND II
What is the type III enamel etching?
combination of I and II
What is the type IV enamel etching?
pitted
What is the type V enamel etching?
asprismatic (flat and smooth)
What is acid etching enamel?
- chemical “drilling”
- creates porous layer 5-50 microns deep
- called conditioner
___% phosphoric acid is most effective for enamel retention
30-40%
How much enamel does acid etching remove?
10 microns
How do you apply acid etching enamel?
RINSE with water for 10 seconds after etching
◦ To remove acid and leave enamel surface clean for bonding
Etching raises the surface free energy to _______ the surface tension of bonding material
EXCEED
Etching produces spaces where resin can penetrate to form…
resin tags
After etching you should apply bond agent resin why?
- low viscosity so it can flow into microporosities
- polymerizes to micromechanical bond
What is the etch-and-rinse (total etch) system?
- Etch separately
- Prime
- Bond
- Or Prime + Bond combined
What is the self-etch system?
- No phosphoric acid-etch step
- Acid part of the primer or primer/bond agent
What is the 3-step (2-bottle) total etch system?
a.Etchant
b.Primer
c.Bond agent
(scotch bond multipurpose)
What is the 2-step (1-bottle) total etch system?
a.Etchant
b.Primer and bond agent combined
(Prime and Bond NT, PQ 1, Peak,
Optibond Solo Plus)
What is the 2 step self-etching bonding system?
- acidic primer & bonding agent
◦ Acidic primer partially dissolves smear layer, allows penetration of bond resin
◦ Clearfil SE Bond; Clearfil Liner Bond 2V
What is the 1 step self-etching bonding system?
– most variable/ least predictable
◦ Acidic primer and bond resin, one solution (Many require mixing)
◦ Examples: Xeno, i-Bond, Bond Force (no mix)
What are the advantages of the rinse and etch system?
◦ More predictable, stronger bond
◦ Enamel adequately prepared
What are the disadvantages of the rinse and etch system?
◦ Collagen collapse is possible
◦ Etched zone is often deeper than hybrid layer
◦ Exposed demineralized, collagen fibrils
◦ Post-operative sensitivity
What are the advantages of self-etch systems?
◦ 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
What are the disadvantages of self-etch systems?
◦ 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
What are the disadvantages of the self-etch adhesives (all-in-one)?
◦ Lower bond strength
◦ Long-term breakdown?
◦ Collagen degradation over time
What can you use with universal adhesives?
Can be used in total etch, self-etch or selective-etch mode (etch
enamel only with phosphoric acid)
- we use at UMKC
What is the chemistry game changer of universal adhesives?
10-MDP
◦ Methacryloyoxy-decyl-dihydrogen-phosphate (10-MDP)
What is the mechanism of action of a universal adhesive?
A monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
What is the monomer for universal adhesives?
a phosphate ester
Should you directly etch the pulp?
nope
Why do we now use a total etch technique of etching enamel and dentin?
Etchant interacts with superficial dentin and there is no pulpal damage
The bond to dentin collagen is influenced by…
Matrix metalloproteinases (MMPs)
* collagen enzymes that metabolize unhybridized collagen
___________ inhibits MMP (matrix metalloproteinases) activation
Chlorhexidine
What is consepsis (ultradent)?
◦ 2% Chlorhexidine Antibacterial Solution
◦ Applied after acid etching
What can cause an adverse pulp reaction if using adhesive on dentin?
Adverse pulp reaction comes primarily from bacteria remaining in or penetrating the preparation
What are the requirements for clinical success of bonding?
- Knowledge of substrate
- Good cavity preparation and margins
- Rubber dam and matrix/wedge
- Correct use of the bonding agent
- Bond agent compatible with resin composite
What region of the tooth has a higher bond strength: superficial or deep?
superficial
What region of the tooth has a higher bond strength: flat or box?
flat surfaces
What can make the bond strengths to dentin vary?
-Region of tooth
-Flat surfaces higher than box cavities
-C-factor
-Adhesive system used
-Thickness of increment of composite resin
-Operator
-Intrinsic wetness of tooth
-Dryness vs wetness
What is the best place to adhere to the enamel?
Incisal third and middle third enamel
What is wrong with the adhesion near the cervical enamel?
◦ Shorter and fewer enamel tags (Compared to middle and incisal thirds)
◦ Less prism delineation
Prism delineation is found in cervical third of ___% of teeth
70%
What do bevels and adhesion do in class II preps?
Reduce microleakage at cervical and ascending walls in Class II preparations
When is a bevel gingival floor of prep necessary?
enamel
What does beveling the enamel do?
◦ Exposes ends of enamel rods
◦ Reveals prismatic enamel
What bur should you use to bevel the gingival floor?
7902 bur
When would you not bevel the gingival floor?
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 is…
- interlocking with enamel rods
The goal of adhesive dentistry with composite resin in dentin is…
- interlocking with dentin collagen
What are the percentages and components of enamel?
◦ 95-98% inorganic matter by weight
◦ 90-92% hydroxyapatite by volume
◦ 1-2% organic matter by weight
◦ 4% water weight
Where can you find perpendicular oriented enamel?
◦ Cavosurface margins of class I preparations
◦ Bevels of class II preparations
◦ ENDS of enamel rods
Where can you find parallel oriented enamel?
◦ Internal walls of occlusal preparations
◦ Gingival floor of box of class II preparations (see bevelling)
◦ SIDES of enamel rods
What are resin tags interlock?
Macro and micro tags into surface irregularities
What are the MPa of the enamel-adhesive composite bond?
20-25MPa
What are the percentage components of dentin?
◦ 55% mineral by volume
◦ 30% collagen
◦ 15% water
What are the different parts of the dentin?
Tubules
◦ Fluid filled
Peritubular Dentin
◦ Very Inorganic
Intertubular dentin
◦ Very ORGANIC
◦ Collagen rich
What part of the dentin is inorganic?
Peritubular Dentin
What part of the dentin is organic and collagen rich?
Intertubular dentin
What is the diameter of dentin tubules at the DEJ?
0.5 µm
What is the diameter of dentin tubules at the pulp?
2.5 µm
As the dentin goes deeper the tubules are…
wider and more of them
- more fluid
As the dentin goes deeper there is ______ intertubular dentin
less
What is the smear layer?
mixture of tooth debris, often contaminated with saliva, blood cells, and bacteria
Should you bond to the smear layer?
NO
- remove smear layer with acid etch
- bond strength of smear layer is 7.4 MPa
What is the hybrid layer?
intermingled layer of collagen and resin
What is the problem with forming the hybrid layer?
Must be the perfect balance
◦ Avoid OVERetching
◦ Avoid OVERdrying
◦ Avoid UNDERdrying
What are the steps to form the hybrid layer?
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
What happens when the hybrid layer forms?
upon light curing, the unfilled resin sets within the collagen fibril network
What are some problems with forming the hybrid layer?
- overetching
- overdrying
- underdrying
What happens to the hybrid layer if you overetch?
results in underfilled restorations
-Demineralized zone is too thick
-Primer can not infiltrate far enough
-Leaves unprotected layer
subject to degradation
-leads to premature bond failure
-leads to failure over time due to hydrolysis of uninfilitrated collagen
What happens to the hybrid layer if you overdry?
results in lower bond strengths
-Collagen collapses
-lower bond strength
What happens to the hybrid layer if you underdry?
results in collagen that is too wet
◦ Excess water
◦ Poor hybrid layer formation
◦ Resin unable to infiltrate intertubular dentin
◦ “blister spaces” where primer and adhesive separate
Which type of bonding system has the self-etching primers?
self-etching primers
What type of bonding system do we primarily use in lab and clinic?
Universal Adhesives
What are the disadvantages of bonding systems?
- Too many steps
- Insufficient penetration of smear layer
- Delicate treatment of dentin necessary
What is the etchant for bonding system?
Phosphoric acid gel (30-40%)
What is the primer for bonding system?
◦ HYDROPHILIC monomers in HEMA solvent
◦ Acetone, ethanol/water, water
What is the adhesive bonding resin/agent for 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
What is the adhesive bonding resin agent for light activated systems?
Camphorquinone
What is the adhesive bonding resin agent for chemical and dual cure systems?
Benzoyl Peroxide (BPO) Tertiary amine
What are the fillers for bonding systems?
Most unfilled resins, some 0.5-40 % by weight
What is the polymerization process?
Adhesive/primer monomers–> polymers
◦ Chemical reaction
What is the activator in the polymerization process?
light or chemical
- blue light
- benzoyl peroxide
What is the polymerization process using light?
◦ Blue light (~470-nm)
◦ Camphorquinone→free radical→polymerization reaction
What is the polymerization process using chemical?
◦ Chemical (tertiary amine)
◦ Benzoyl peroxide (initiator)→free radical→polymerization reaction
What are the steps in the bonding process?
Step 1. Acid etch
◦ 20 seconds for enamel
◦ 15 seconds for dentin
Step 2. Rinse
◦ 10 seconds
◦ GENTLY dry- enamel should be dry, dentin should be slightly moist
Step 3. Apply Primer- not with Adhese Universal
Step 4. Apply Bond
Step 5. Light cure
Step 6. Place composite incrementally
How long should you etch dentin and enamel?
◦ Dentin- 15 seconds at MOST
◦ Enamel- 20 seconds
What does acid etch do?
◦ Removes smear layer
◦ Denatured collagen, hydroxyapatite crystals, debris from cutting tooth
How much should you dry enamel and dentin during the acid etch?
enamel - dry
dentin - slightly moist
What does blue light do in the polymerization reaction?
activates
What does camphorquinone do in the polymerization reaction?
initiates
Primary dentin bond mechanism is from _______ LAYER
HYBRID
What is the hybrid layer?
micromechanical interlocking of resin with demineralized
collagen
What are the factors that affect the bond to dentin?
- cavity depth
- caries
- moist vs dry dentin
- rubber dam
What helps form a better bond to dentin: moist or dry dentin?
moist
What helps form a better bond to dentin: superficial dentin or deep dentin?
superficial dentin
Do caries increase or decrease the ability to bond to dentin?
decrease
What happens if the dentin is too wet when you try to bond?
◦ Resin doesn’t penetrate well
◦ Decreased bond strength
What happens if the dentin is too dry when you try to bond?
◦ Resin cannot penetrate
◦ Poor hybrid layer
◦ Decreased bond strength
