Bonding: Enamel and Dentin ; Composite Bonding

True or False: Enamel is a very brittle structure having a high elastic modulus and a low tensile strength indicates its rigid structure.

TRUE

True or False: Enamel is a brittle material whereas dentin is a resilient material.

TRUE

True or False: The hardest substance of the human body is enamel. It is a highly mineralized crystalline structure containing from 95% to 98% inorganic matter by weight.

TRUE

True or False: The composition of enamel is 96-98% inorganic matter (hydroxyapatite), 1-2% organic elements, and 4% water.

TRUE

True or False: Enamel is composed of rods whereas dentin is composed of tubules.

TRUE

True or False: The density of enamel decreases from the surface to DEJ.

TRUE

Statement 1 / Statement 2: The enamel is thicker at the incisal and occlusal areas of a tooth; becomes progressively thinner until it terminates at the DEJ.

STATEMENT 1 TRUE; STATEMENT 2 FALSE

True or False: Enamel permeability decreases with age because of changes in the enamel matrix.

TRUE

True or False: The dentin composition is about 75% inorganic - 20% organic (collagen) - 5% water.

TRUE

A cuff of hypermineralized dentin called ____ lines the tubules.

PERITUBULAR DENTIN

True or False: The less mineralized intertubular dentin contains collagen fibrils with the characteristic collagen bonding

TRUE

True or False: Intertubular dentin is penetrated by submicron channels, which allow the passage of tubular liquid and fibers between neighboring tubules, forming intertubular anastomoses.

TRUE

ENAMEL BONDING / DENTIN BONDING / ETCHING

Enamel: Micropores in Enamel; Dentin: Removes/Modifies Smear Layer

BONDING AGENT (PRIMER)

Enamel: Flows into Pores + Cured; Dentin: Flows into Collagen + Cured

REQUIRES: HYDROPHILIC SOLVENT

Comp. Resin Bonds to Bonding Agent

RESULT

Comp. Resin Bonds to Bonding Agent

True or False: The gold standard is the three step etch and rinse *4th gen

TRUE

The reduction of which represents the most significant advantage of the acid-etch technique? A. Pulpal irritation B. Microleakage C. Polymerization shrinkage of matrix D. Coefficient of thermal expansion

B. Microleakage

Acid etching of enamel does what?

Creates micropores for micromechanical retention; Increases wetting; Increase surface energy; All of the above

True or False: When enamel is etched, micro porosities are formed; frosty appearance after etching is a good indication.

TRUE

The depth of enamel dissolution caused by acid etching is about 100-150 microns.

FALSE

True or False: Acid-etching transforms the smooth enamel into an irregular surface and increases its surface free energy.

TRUE

True or False: When a fluid resin-based material is applied to the irregular etched surface, the resin penetrates into the surface, aided by capillary action. Then the monomers in the material polymerize, and the material becomes interlocked with the enamel surface.

TRUE

True or False: The formation of resin microtags within the enamel surface is the fundamental mechanism of resin-enamel adhesion.

TRUE

True or False: NO correlation exists between resin tag length and enamel/resin bond length.

TRUE

What factors affect dentin bonding strength?

1. Cavity Location/Depth 2. Smear Layer 3. Quality/Type of Dentin (Abfraction Lesions/Sclerotic Dentin)

True or False: Whenever dentin has been cut or abrased, a thin altered surface is created called the smear layer

TRUE

True or False: The smear layer fills the orifices of dentin tubules, forming "smear plugs" and decreases dentin permeability by nearly 90%.

TRUE

True or False: The composition of the smear layer is basically hydroxyapatite and altered denatured collagen.

TRUE

True or False: Although the smear layer may decrease bond strength, it can provide pulp protection.

TRUE

True or False: The smear layer itself can serve as a pathway for leakage through the nano-channels within its core.

TRUE

It is more difficult to bond to dentin than to enamel because A. Dentin contains more mineralized tooth structure B. Dentin contains more water C. The presence of smear layer makes it harder for the adhesive to wet the dentin D. Two of the above E. All of the above

D. Two of the above

True or False: It's more difficult to bond to dentin than enamel because the presence of the smear layer makes it harder for the adhesive to wet the dentin.

TRUE

The conditioner (etchant) of a typical 3-step third generation dentin bonding agent does which of the following

Demineralizes dentin; Modifies smear layer; Increases dentin permeability; All of the above

In selecting a dental base, the dentist should give greatest consideration to which: A. Biocompatibility of the base B. Strength of base C. Thickness of remaining dentin

C. Thickness of remaining dentin

True or False: Adhesion can be affected by the remaining dentin thickness after tooth preparation.

TRUE

True or False: Dentin adhesion relies primarily on the penetration of adhesive monomers into the network of collagen fibers left exposed by acid etching

TRUE

The current consensus is that dentin bonding agents bond primarily ____ to tooth structure.

MECHANICALLY

This refers to interlocking of the adhesive with irregularities in the surface of the substrate, or adherend:

MECHANICAL ADHESION

Dentin bonding agents can be used for

A. Dentin desensitization

True or False: Dentin bonding agents are being recognized as beneficial for dentin sealing under any type of restorative material.

TRUE

The hybrid layer (interdiffusion zone) is in:

dentin bonding, a layer in which hydrophilic resin surrounds the collagen fibers.

Bonding to dentin requires ____ components that can penetrate into spaces left by the decalcification process.

HYDROPHILIC

True or False: The dentin bond strength varies in relation to distance from the pulp - in which the relative area occupied by dentin tubules decreases with increasing distance from the pulp.

TRUE

Dentin that provides the highest bond strength would be which:

a. Intertubular dentin close to DEJ

True or False: The bond strengths are generally LESS in deep dentin (closer to pulp) than in superficial dentin (closer to DEJ).

TRUE

True or False: Dentin that produces the highest bond strengths would be near the intertubular dentin close to the DEJ.

TRUE

True or False: The bond strengths for superficial dentin close to the DEJ are greater than those for deep dentin; because in deep dentin, the greater number of tubules and larger diameter of tubules reduce the amount of intertubular dentin available for bonding.

TRUE

True or False: The intertubular dentin is more important for bond strength than resin tags for dentin bonding, as compared to enamel.

TRUE

Give two variables that might account for the difference in dentin bond strength at the DEJ and pulp.

There is more moisture at the pulp and moisture will interfere with the bonding strength and mechanism. The intertubular dentin is better for bonding, but there is less near the pulp as compared to the DEJ.

True or False: The clinical aspect of moist dentin is a glistening appearance without accumulation of water.

TRUE

True or False: The act of re-wetting dentin after air drying to check for the enamel frosty aspect is an acceptable clinical procedure.

TRUE

True or False: The "wet bonding" technique has been shown to enhance bond strengths because water preserves the porosity of collagen networks available for monomer interdiffusion.

TRUE

True or False: The "wet bonding" technique prevents the spatial alterations (i.e., collagen collapse) that occur on drying demineralized dentin.

TRUE

True or False: If the dentin surface is dried with air, the collagen undergoes immediate collapse and prevents resin monomers from penetrating.

TRUE

True or False: The use of etch-and-rinse adhesive systems on moist dentin is made possible by incorporation of the organic solvents acetone or ethanol in the primers or adhesives. Because the solvent can displace water from the dentin surface and the moist collagen network, it promotes the infiltration of resin monomers throughout the nanospaces of the dense collagen web.

TRUE

True or False: Dentinal tubules enclose cellular extensions from the odontoblasts and are in direct communication with the pulp

TRUE

True or False: It is important not to dehydrate the tooth by overuse of air as this may damage the odontoblasts associated with the desiccated tubules.

TRUE

True or False: Air alone as coolant is not effective in preventing pulpal damage since it needlessly desicates the dentin and damages the odontoblasts

TRUE

Using only air as a coolant during cavity preparation does not cause pulpal damage because the dentinal tubules are effectively sealed by reparative dentin during rapid progression of various lesions.

FALSE

Which of the following is the most effective way to reduce injury to the pulp during a restorative procedure? A. Prepare dentin with slow-speed bur B. Use anesthetics without vasoconstrictors C. Minimize dehydration of dentinal surface D. Keep dentinal surface clean by frequent irrigation

C. Minimize dehydration of dentinal surface

True or False: The acid-etching demineralizes dentin and may leave a layer of exposed collagen at the bottom of the hybrid layer. It has been reported that when demineralized dentin is restored with an adhesive system, the demineralized layer might undergo remineralization within 4 months.

TRUE

Marginal leakage, a persistence problem when bonding resin to dentin, can result in: A. Sensitivity B. Marginal staining C. Recurrent caries D. All of above E. A and C

D. All of above

When bonding a composite restoration it is important to acid etch long enough to remove the smear layer and open up the dentin tubules. Opening the dentin tubules allows the formation of longer resin tags, which provide the majority of bond strength to dentin.

FALSE

MICROLEAKAGE is defined as

the passage of bacteria and their toxins between restoration margins and tooth preparation walls.

The term NANOLEAKAGE has been used to describe

small porosities in the hybrid layer or at the transition between the hybrid layer and the mineralized dentin that allow the penetration of miniscule particles of a silver nitrate dye.

The term WATER TREES is associated with

porosities in the polymerized adhesive layer. It might be one of the factors responsible for degradation of the bonding interface with time.

True or False: The dentin that undergoes these compositional changes is called sclerotic dentin and is much more resistant to acid-etching than "normal" dentin.

TRUE

Inorganic Particles (Glass/Silica)

Embedded in Organic Matrix

Particles Coated with Silane

Improve Bonding

Organic Matrix (BIS-GMA)

Affects: Polymerization Shrinkage; Color Stability; Fluid Sorption; Thermal Stability

The matrix of most composite resin is composed of:

BIS-GMA resin

Base material are needed under composite resin restorations to provide thermal insulation because the BIS-GMA resin used in the manufacture of filled composite resin is a known conductor of thermal energy

FALSE

True or False: Silicate cement powder is composed of acid-soluble glasses, and the liquid contains phosphoric acid, water, and buffering agents.

TRUE

True or False: As a restoration, acrylic resin was most successful in the protected areas of teeth where temperature change, abrasion, and stress were minimal.

TRUE

True or False: Composite restorative materials consist of a continuous polymeric or resin matrix in which an inorganic filler is dispersed.

TRUE

True or False: This inorganic filler phase significantly enhances the physical properties of the composite by increasing the strength of the restorative material and reducing thermal expansion

TRUE

True or False: For a composite to have good mechanical properties, a strong bond must exist between the organic resin matrix and the inorganic filler. This bond is achieved by coating the filler particles with a silane coupling agent, which not only increases the strength of the composite but also reduces its solubility and water absorption.

TRUE

MACROFIL (PS > 1 MICRON)

Least Esthetic; Poor Polishing (Plucking Effect)

MICROFIL (PS < 1 MICRON)

Best Polishing ⇒ Best for Cervical Lesions; Reduced Strength ⇒ Limited Filler Volume

HYBRID (MIXTURE OF PARTICLE SIZES)

Strongest 'Layered' With Microfil For Esthetics

FLOWABLE

Reduced Filler Content of Traditional Hybrid Composites ⇒ Increased Resin Reduces Mixture Viscosity

PACKABLE

Stiff Composite with Handling Properties Like Amalgam ⇒ Tendency for Margin Void Formation

True or False: The upper limit of composites is the % of filler volume affects its composites.

TRUE

True or False: The amount and size of the filler particles affects polishing, flexural modulus, viscosity, color, absorption changes (amount of matrix), polymerization shrinkage and LCTE.

TRUE

This is the rate of dimensional change of a material per unit change in temperature:

LINEAR COEFFICIENT OF THERMAL EXPANSION

True or False: The closer the LCTE of the material is to the LCTE of enamel, the lower the chance for creating voids or openings at the junction of the material and the tooth when temperature changes occur.

TRUE

The linear coefficient of thermal expansion of the composite restorative material is about ____ that of the tooth structure.

3-4x GREATER THAN

The linear coefficient of thermal expansion of current used composites is approximately ____ that of tooth structure

3.0X times

The LCTE of hybrids are ____ that of tooth structure.

1.5 to 2x

This is the amount of water that a material absorbs over time per unit of surface area or volume:

WATER SORPTION

True or False: Materials with higher filler contents exhibit lower water absorption values than materials with lower filler content.

TRUE

This refers to a material's ability to resist surface loss as a result of abrasive contact with opposing tooth structure, restorative material, food boli, and such items as toothbrush bristles and toothpicks:

WEAR RESISTANCE

True or False: Esthetic restorative materials must be sufficiently radiopaque so that the radiolucent image of recurrent caries around or under a restoration can be seen more easily in a radiograph. Most composites contain radiopaque fillers such as barium glass to make the material radiopaque.

TRUE

How are composites grouped? On the basis of:

1. Primary Particle Size (Homogeneous) 2. Mixtures of Precured with Uncured Composite (Heterogenous) 3. Mixture of Major Particle Sizes (Hybrids) 4. Other Special Modifications (Chopped Fiber)

True or False: Filler particles may be clusters or agglomerates.

TRUE

True or False: The more glass particles, the more stable the material it'll be.

TRUE

True or False: Because of the relatively large size and extreme hardness of the filler particles, macrofill composites typically exhibit a rough surface texture.

TRUE

True or False: Nonetheless, microfill composites are clinically highly wear resistant.

TRUE

Because these small primary particles can be easily agglomerated, a full range of filler sizes is possible, and optimal particle packing is facilitated:

NANOFILL