Resin

Question 1

Ideal properties fir adhesive resin

Answer 1

The ideal properties of a good adhesive resin would include these features listed in the above slide
Good initial and permanent bond strength, ideally to both dentine and enamel. We want it to bond quickly but also last for the expected duration of that restoration.
Good Biocompatibility- should be non-toxic, non-sensitising, it should not aggravate the pulpal complex
Need to reduce microleakage leading to recurrent caries and marginal staining by providing a good seal
Compatible with a wide range of resins so you do not need to store multiple adhesive resins.
We want a material with the least number of steps as each step introduces the risk for operator error or contamination, but we also want enough steps that it is effective

Question 2

\setting

Answer 2

Activation light
Initiation ‘propagation
Termination

Question 3

Adhesion steps

Answer 3

Tooth surface prep
-clean and polish
-clean smear layer
-for total etch adhesive apply etch at

Application of adhesive
-apply dental adhesive
-complete coverage of tooth
Use gentle air stream to thin adhesive layer

Wetting and imitate adaption
-allow adhesive to infiltrate the enamel or dentin creating strong bond

Bonding
-95% of the bonding is micromechanical with only a small portion of being chemical bonded

Polyermsion
-curing light

Final restoration placement

Question 4

Wettibility

Answer 4

Wettability: Refers to how well a dental adhesive spreads and connects with the tooth surface.
Hydrophilic Adhesives: Attract and interact with water, aiding in bonding to moist dentin surfaces.
Allows effective wetting of tooth surface and infiltration into microscopic irregularities.
Shown by a contact angle of less than 90 degrees in diagrams, indicating “mostly wetting.”
Hydrophobic Adhesives: Repel water, which can make wetting tooth surfaces challenging.
Often used in enamel bonding where moisture is less of a concern.
Superhydrophobic Surfaces: Highly water-repellent, causing water droplets to bead up and roll off.
May hinder proper wetting and adhesion in dental adhesives.
Shown by contact angle greater than 180 degrees, termed “absolutely no wetting.”
Enhancing Wettability: Achieved by increasing tooth surface energy through techniques like acid etching.
Acid etching removes contaminants and creates microporosities, improving adhesive monomer wetting.

Question 5

Etch

Answer 5

Smear Layer: Forms during tooth surface preparation, consisting of cutting debris and organic film.
Can block dentinal tubules, hindering resin tag penetration.
Loosely attached, removal or alteration necessary for strong bond.
Etching Process: Utilizes phosphoric acid etch (usually 37%) for composite resin restorations.
Agitation of etchant for approximately 20 seconds enhances smear removal and penetration.
Creates a stronger hybrid layer for improved adhesion and longevity.
Washing and Drying: Etchant may be washed away and lightly dried to create a frosted appearance.
Avoid over-drying to prevent collagen fiber desiccation.
Adhesive Resin Bond System: Agitated into porosities and lightly spread with air for even adaptation and solvent evaporation.
Allows deeper resin penetration into micro-porosities, forming resin tags in the hybrid layer.

Question 6

Etch sang

Answer 6

Used for bond strength

37 percent phosphoric acid
Bc it has good strength

Increases surface area , increases micromechanical bonding

Answer 7

Smear Layer Removal: Achieved with etchant, creating microporosities for improved retention.
Adhesive Resin Flow: Flows into porosities, ensuring intimate adaptation and chemical bond formation.
Hybrid Layer Formation: Resultant region serves as the true interface between tooth and resin adhesive.

Question 8

Answer 9

Answer 10

Answer 11

Answer 12

Answer 13

Dentine Composition and Challenges: Dentine contains high water content and consists of approximately 70% inorganic material, 20% organic material, and 10% water.
Dentine Tubules and Fluid Movement: Dentine tubules act as passageways for bacteria and irritants to reach pulpal tissue. Fluid movement through tubules keeps dentine surface wet.
Risk of Pulp Damage: Adequately drying dentine poses risk of irreversible damage to vital pulp tissue due to its high water content.
Components of Dentine Bonding Agents: Include conditioners, primers, and adhesives/sealers.
Role of Conditioners: Alter appearance and quality of dentine surface, despite their acidic nature which may transiently affect pulp.
Importance of Conditioning: Necessary even with proximity to pulpal tissue, as smear layer and sclerotic dentine may be present.
Primers and Bonding: Allow resin penetration into intertubular dentine, facilitated by coupling agents displacing water.
Resin Tags Formation: Resin tags formed in dentine bonding similar to enamel bonding, enhancing adhesion.

Answer 14

Answer 15

Etch and Rinse/Total etch (5th generation) - Combines primer and adhesive resin into one step. The phosphoric etch is placed and washed away followed by primer and adhesive which are subsequently cured. The etch is placed and washed separately from the primer and adhesive

Self-etch (6th generation) - Self-etch system. This is not rinsed away and is used to condition and prime simultaneously. Considered to have and good bond strength (good chemical bonding as more carboxyl and phosphate groups but more prone to water intrusion).

1 step (7th generation) - Combination of dentine conditioner, primer and bonding resin into one single step. There is no need to wash or dry as it is an all in one, this makes it an appealing option for efficiency to clinicians. Their effectiveness continues to improve to compete with the 2 step systems.

Answer 16

Definition of composite:

A structure or an entity made up of distinct components

A complex material, such as wood or fibreglass, in which two or more distinct, structurally complementary substances, especially metals, ceramics, glasses, and polymers, combine to produce structural or functional properties not present in any individual component.

Answer 17

Question 18

Advantages of composite resins:

Answer 18

• Excellent aesthetics
• Acceptable physical properties
• Conservative cavity preparation
• Ability to repair
• Versatile
• Restorations, luting agents, endodontic core, aesthetics

Question 19

Disadvantages of composite resins

Answer 19

Reduced longevity compared to amalgam
• Lower tensile strength
• Staining
• Technique sensitive
• Polymerisation shrinkage

Question 20

Composite resin is made of

Answer 20

esin matrix (organic): Essentially binds all the components together and provides flexibility to the composite. Bis-GMA (Bisphenol A glycidyl methacrylate) is the more common monomer but a diluent is usually needed to reduce viscosity of the material, making it easier to place. Bis-GMA also undergoes significant shrinkage.
Filler (inorganic): Can be made of glasses or ceramics. Common glasses include crystalline silica, silicone dioxide, lithium/barium aluminium. A large amount of glass filler reduces polymerisation shrinkage as there is less resin; it also increases strength of the material. The filler also reduces the coefficient of thermal expansion of the resin matrix by approximately ten times. So, this means as the coefficient decreases, the material will change less in response to a change in temperature. This is quite significant as the more the material changes, the more stress is placed on the bond and the higher the risk of microleakage and fracture.
Coupling agent: The coupling agent, usually silane, binds the filler and the resin together. It also allows for stresses to be transferred between organic and inorganic phases. Silanes do age quite quickly and are very sensitive to moisture contamination, making them quite technique-sensitive.

Question 21

Setting reaction of composite resin

Answer 21

activation
initiation
propagation
termination.

Answer 22

Initiation Stage: Free radicals are formed by breaking the chemical structure of the activator. Without activator, initiation cannot occur.
Reaction Mechanism: Involves monomers containing carbon–carbon double bonds (C=C), which are relatively unstable and react easily with other molecules.
Carbon–Carbon Double Bond Splitting: When monomer approaches initiator, C=C bond splits, leaving a molecule with a carbon–carbon single bond and a free radical (unpaired electron), initiating propagation.
Bis-GMA Resin Monomer: Commonly used, with a weak double bond that breaks, creating a single bond and a free radical.
Propagation Phase: Free radical continues to react, binding with other monomers like Bis-GMA, creating more free radicals and propagating the reaction.
Continuation until Termination: Reaction continues until termination stops it.