Operative - Written Exam 3 (W/O Liners and Bases Lecture - separate quizlet)

why is adhesion important in dentistry

? (6)

• Enables more conservative tooth preparations

• Reduces the need for macromechanical retention

• Minimizes the removal of unsupported enamel compared to amalgam preparations

• Seals the tooth-restoration interface, reducing microleakage

• Prevents recurrent caries by limiting bacterial penetration

• Allows bonding of indirect restorations, posts, orthodontic brackets, and other appliances

what happens when adhesion fails? (5)

• Marginal gaps may form, leading to microleakage and post-operative sensitivity

• Increased risk of recurrent caries

• Loss of restoration retention

• Compromised esthetics due to staining at restoration margins

• Potential fracture or debonding of indirect restorations or bonded posts

How do we reduce adhesion failures?

• Maintain strict moisture control (rubber dam isolation). Avoid contamination (saliva, blood, or water)during the bonding procedure

• Proper technique (etching time, application steps, curing time)

• Ensure proper light-curing (adequate intensity, correct distance and angle, appropriate time)

• Select materials appropriate for the clinical situation and understand their properties, indications,and limitations

the following is the definition of...

attraction force when the molecules are of the same kind

cohesion

the following is the definition of...

attraction force between different molecules

adhesion

The material that is used to cause adhesion or bonding is known as the...

adhesive

the material to which the adhesive is applied is called the...

adherend

special monomers containing functional groups (e.g., 10-MDP), such as phosphate or carboxyl groups, that interact with calcium and phosphate ions on the tooth surface to create chemical bonds is known as...

chemical adhesion

structural interlocking is known as what type of adhesion...

mechanical adhesion

what are the 3 kinds of adhesions in dentistry?

chemical

mechanical

combination of both of the above

a dental bonding system serves 3 key purposes:

1. Resistance to separation: ensures the substrate (enamel, dentin) stays securely attached to the restorative material.

2. Distributes stress across the bonded surfaces.

3. Seals the interface to enhance resistance to microleakage, reducing the likelihood of postoperative sensitivity, marginal staining, and secondary caries

what is meant by wettability?

The bonding must form intimate contact with the surface

compare the composition between bonding agents and composite resin

bonding agent:

- less filler, more solvent

composite resin:

- more filler, no solvent

compare the viscosity between bonding agents and composite resin

bonding agents:

- low viscosity

composite resin:

- high viscosity

general composition of bonding agents:

- Monomers

- Solvents

- Initiators

- Inhibitors

- Fillers

what are monors commonly found in bonding agents?

- BIS-GMA

- HEMA

- MDP

- 4-META

function of bonding agents:

form polymers that create mechanical and chemical adhesion

what are solvents commonly found in bonding agents?

- ethanol

- acetone

- water

function of solvents

◦ Dilutes monomers, initiators, inhibitors, and fillers for an even distribution.

◦ Facilitate the infiltration of monomers into the tooth structure.

◦ Assist in the removal of water

what are initiators commonly found in bonding agents?

- Camphorquinone

- TPO-Lucirin

function of initiators

trigger the polymerization reaction

what are fillers commonly found in bonding agents?

- Silica particles

- zirconia

function of fillers

◦ Reinforce the adhesive and improve its mechanical properties.

◦ Adjust viscosity

what is a thin film of debris formed on the surface of dental hard tissues (enamel or dentin) as a result of cutting or preparing the tooth with hand or rotary instruments?

smear layer

what is the smear layer composed of?

a mixture of organic and inorganic particles—such as denatured collagen and hydroxyapatite

T or F: the smear layer is restricted to the outer layer of enamel

FALSE

- and may extend into the dentinal tubules as smear plugs.

what are the the percentages of each material that makes up the enamel?

- 88% mineral

- 10% water

- 2% organic

enamel rods are composed of?

hydroxyapatite

enamel rods extend from where to where?

Extend from the dentinoenamel junction (DEJ) to the external enamel surface of the tooth

when and by who was enamel etching introduced?

Buonocore in 1955

when using scotchbond universal plus, what is the etching time?

15 seconds

generally what is enamel etching time?

15-30 seconds

enamel etching is made of...

phosphoric acid (35-37%)

rinsing time after acid etching:

10-15 seconds

What visual sign indicates that enamel has been properly etched?

Properly etched enamel will appear frosty or chalky white when air-dried

the following is a description of what process?

transforms the smooth enamel into an irregular surface and increases its surface-free energy.

acid etching

When the bonding agent is applied to the irregular etched surface, what does it do?

it penetrates into the surface, aided by capillary action

what is the fundamental mechanism of adhesion on enamel?

formation of resin MICROTAGS

material becomes interlocked with the enamel surface when...?

monomers in the material polymerize

describe the composition of dentin

50% - mineral

25% organic

25% water

compare bond strengths between deep dentin and superficial dentin

Bond strengths are generally less to deep dentin than superficial dentin

compare dentin tubule amounts and intertubular dentin amounts between superficial and deep dentin

superficial:

- fewer tubules, primarily intertubular dentin

deep:

- larger dentinal tubules, significantly less intertubular dentin

"total-etch" was introduced by who and in what year?

Fusayama in 1979

- phosphoric acid (35-37%), dentin etch time (15 sec.), and rinse time (10-15 sec) are all the same as standard protocol for etching

what does dentin etching do?

• Removes the smear layer and opens the dentinal tubules

• Partially demineralizes the dentin, exposing collagen fibrils

• Increases surface energy and porosity, allowing adhesive infiltration

• Creates a substrate for micromechanical retention via formation of the hybrid layer

• Requires careful moisture control to maintain the ideal moist dentin state for bonding

An intermediate layer of resin, collagen, and dentin that is produced by acid etching of dentin and infiltration of resin into the conditioned dentin describes what?

hybrid layer

goals of phosphoric acid:

• Removes the smear layer and opens the dentinal tubules

• Partially demineralizes the intertubular dentin, exposing collagen fibrils

Which one is more reliable:

dentin adhesion or enamel adhesion?

Enamel

what relies primarily on the penetration of adhesive monomers into the network of collagen fibrils left exposed by acid etching?

dental adhesion

why is dental adhesion more challenging than enamel adhesion?

due to the following characteristics of dentin:

• Less mineralized

• Complex structure

• Intrinsically hydrated

between enamel adhesion and dentin adhesion, which is more challenging?

dentin adhesion

what is the main goal of the etch-and-rinse adhesion strategy?

to remove the smear layer

what is the main goal of the self-etch adhesion strategy?

transform the smear layer

compare the goals of each adhesion strategy:

- self-etch

- etch-and-rinse

- self-etch: transform smear layer

- etch-and-rinse: remove smear layer

what steps do you perform in the self-etch adhesion strategy?

- NO etching of the dentin with phosphoric acid

- NO removal of the smear layer

- smear layer is modified and incorporated into the adhesive surface

- selectively enamel with phosphoric acid to improve bonding enamel

what is unique to the self-etch adhesion strategy?

the smear layer is NOT removed (with etch), instead smear layer is modified and incorporated into the adhesive surface and the enamel is selectively etched

between the etch-and-rinse and self-etch adhesion strategies, which is more technique sensitive?

the etch-and-rinse

- risk of over-etching, which can be detrimental to bond strength and increases the likelihood of post-operative sensitivity

what is a risk of using the etch-and-rinse adhesion strategy?

risk of over-etching, which can be detrimental to bond strength and increases the likelihood of post-operative sensitivity

T or F: enamel etching is not recommended in the self-etch adhesion strategy

FALSE

- Selective Enamel Etching is recommended. (Self-etch systems do not etch enamel as well as phosphoric acid)

what type of bonding can be used in both the etch-and-rinse and self-etch adhesion strategies?

universal bonding agent

is universal bonding agent performance dependent on the degree of dentin moisture?

NO it is independent

why are universal bonding agents rubbed? (2)

- enhances penetration of the adhesive

- improves solvent evaporation

why is solvent evaporation important?

• It is essential to remove water and/or solvents (e.g., ethanol, acetone) from the adhesive layer

• Incomplete evaporation can dilute the adhesive and interfere with polymerization

• Solvent retention may lead to decreased bond strength and increased nanoleakage

use gentle air-drying for at least 5-10 seconds or high-speed suction

what is a tooth-colored restorative material available in various shades and translucencies to mimic the natural appearance of tooth structure?

composite resin

what is composed of a resin matrix, inorganic filler particles, and a coupling agent (silane) that chemically binds the fillers to the resin?

composite resin

Composite resins hardens through what method, which is typically initiated by light (light-cure), chemicals (self-cure), or a combination of both (dual-cure) systems.?

polymerization reaction

what are the components of composite resin?

resin matrix, inorganic filler, coupling agent (silane), pigments, polymerization initiators

the following is a function of what component of composite resin?

Organic phase (e.g., Bis-GMA, UDMA, TEGDMA) thatforms the plastic network after curing.

resin matrix

the following is a function of what component of composite resin?

Glass, Silica, zirconia, or prepolymerized particles that improve strength, wear resistance, and reduce shrinkage. Reduce water sorption; control of viscosity;provide radiopacity. Typically ~75% by weight

inorganic fillers

the following is a function of what component of composite resin?

Bond chemically the fillers to the resin matrix, ensuring structural integrity

coupling agent (silane)

the following is a function of what component of composite resin?

Usually Camphorquinone. Absorbs blue light to start polymerization.

initiator

how are composite resins classified?

By Viscosity and Handling

By Placement Technique

By Polymerization Reaction (curing method)

By Filler Particle Size

what are the 3 curing methods?

- Light-Cured

- Self-Cured

- Dual-Cured

what is the most common light curing method in direct restorations?

light-cure with blue light

what light curing methods are used in core build-ups and cementation of indirect restorations?

self-cured

- chemical

- limited working time

dual-cured

- light and chemical

smaller filler particles means what for polishibility and strength?

HIGH polishability

LOW strength

higher filler content means what for polishibility and strength?

GREATER strength

LOW polishability

when are flowable composites indicated? (2)

• 0.5 mm-thick liner under large restorations

• Ultra-conservative class I restorations

compared to conventional composite, does flowable composite experience more or less shrinkage?

more in flowable

compare filler content in flowable and conventional composite

Lower filler content in flowable compared to conventional composites: 35% to 65% by weight

what are some characteristics of bulk-fill composites

• High filler loading for strength and reduced shrinkage

• Higher translucency to allow deeper light penetration

• Lower elastic modulus (not as stiff as conventional composites)

• Special monomers

how is bulk-fill composite is placed

in up to 4-5mm layers

what materials contain functional monomers capable of etching and bonding directly to tooth structure, eliminating the need for separate etching and bonding steps?

self-adhesive composites

what materials release beneficial ions (e.g., fluoride, calcium) to promote tooth remineralization?

Studies are needed to evaluate their long-term performance

bioactive composites

what composites are designed with agents that inhibit bacterial growth (quaternary ammonium compounds, bioactive fillers, or metal ions such as silver or zinc)?

Studies are needed to evaluate their long-term performance

antibacterial composites

what composites use advanced blending technology to match a wide range of tooth shades with one materia

single-shade composites

most modern composites experience how much polymerization shrinkage?

2.4% - 2.8%

if not manages corrected polymerization shrinkage can cause...

gaps, microleakage, cusp deflection, postoperative sensitivity, and increased risk of recurrent caries.

Polymerization shrinkage of composite resin generates what

internal stress

what is the consequence of internal stress generated by polymerization shrinkage?

This stress may concentrate at the adhesive interface, risking gap formation and marginal breakdown, or transmit to the surrounding tooth structure, potentially causing cusp deflection

how to minimize complication due to composite shrinkage:

what is the c-factor?

Ratio of bonded to unbonded surfaces

The C-factor relates to the...

configuration of the cavity walls

a high C-factor indicates what?

a greater ratio of bonded surfaces to unbonded (free) surfaces.

why does c-factor matter?

Higher C-factor = More bonded walls = Greater polymerization stress (more restriction during shrinkage)

what is the c-factor of a class 1 cavity?

5 bonded walls, 1 free surface → C-factor = 5:1 (High)

how can c-factor be controled?

incremental layering

- Horizontal layers for small isthmus and oblique layers for larger restorations

how does light curing work on composite?

Photoinitiators in the composite—such as camphorquinone (CQ) and TPO—absorb this light

- When activated, they initiate polymerization, transforming resin monomers into a solid polymer network

most composites use what photo initiator?

camphorquinone (CQ)

Some esthetic or flowable composites may include what photoinitiators for lighter shades?

TPO or PPD

CQ reacts at what wavelength? what about TPO?

CQ - 468 nm (blue light)

TPO - 380-420 (violet)