Dental Bonding Question And Answers

Bonding Important Notes

1. Bonding systems

• Enamel bonding system
• Dentin bonding system
• Amalgam bonding system

2. Enamel bonding system

• Consist of unfilled liquid acrylic BIS-GMA resin monomer mixture placed onto acid etched enamel
• Steps:
  • Acid etching by 37% phosphoric acid
    • Results in the formation of resin tags
    • A concentration greater than 50% results in the formation of monocalcium phosphate monohydrate that prevents further dissolution
    • Below 30% results in the formation of dicalcium phosphate dehydrate that cannot be easily removed
    • The length of application of the etchant is 15 seconds
    • Increased in fluoride-treated teeth and primary teeth
  • Etched enamel is rinsed with water for 20 seconds
  • Next enamel bonding agent is applied to the etched surface

3. Dentin bonding system

• Consist of unfilled liquid acrylic BIS-GMA resin monomer mixture placed onto acid-conditioned dentin surface
• Dentin bonding is difficult because
  • Dentin tissue contains plenty of fluids
  • Presence of a smear layer
  • Chemical effects on the pulp
• Steps:
  • Step 1 – Etching/ conditioning
    • Conditioners are agents that aid in the removal or modification of the smear layer
  • Step 2- Application of primer
    • Primers are hydrophilic monomers which are applied over the etched surfaces for easy flow of bonding agents
  • Step 3 – Application of bonding agent
    • Dentin bonding agents are unfilled resins that help in the formation and stabilization of hybrid layer

4. Amalgam bonding systems

• It is used to bond
  • Amalgam to tooth
  • Amalgam to amalgam
  • Amalgam to other metal substrates

5. Dentin bonding agents – generations

6. Bond strength of various bonding systems

Bonding Short Essays

Question 1. Acid etching.

Answer:

Acid etching:

• It is the process of increasing the surface reactivity by demineralizing the superficial calcium layer and thus creating enamel tags.
• These tags help in micro-mechanical bonding between the tooth and restorative resin.

Mechanism:

• Cleanses debris
• Increases enamel surface area
• Produces micropores for mechanical interlocking
• Exposes more reactive surface layer

Factors Affecting It:

• Form of acid-gel
• The concentration of acid – 37% phosphoric acid
• Time – 15-20 sec.
• Chemical nature of enamel
• Type of dentition

Technique:

• Oral prophylaxis
• Isolate the tooth
• Application of etchant for 15 seconds
• Rinse thoroughly for 5-10 seconds

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• Dry it which results in a frosty, white appearance
• Apply enamel bonding agents

Question 2. Dentin Bonding agents.

Answer:

Bonding agents:

• Denting bonding agents have both hydrophilic and hydrophobic ends
• The hydrophilic end displaces dentinal fluid while the hydro-phobic end bonds to the composite resin

Bonding Short Answers

Question 1. Hybridization.

Answer:

Hybridization:

• Given by Nakabayachi
• It is a process of the formation of resin
• Important in micromechanical bonding
• Conditioning the dentinal surface exposes the collagen fibrin network with microporosities
• These spaces are filled with low-viscosity monomers when the primer is applied.

Question 2. Hybrid Layer.

Answer:

Hybrid Layer:

• The layer formed by the demineralization of dentin infiltration of monomer and subsequent polymerization is called a hybrid layer

Zones:

1. Top layer – Loosely arranged collagen fibrils

• Interfibrillar spaces filled with resin

2. Middle layer – Replacement of hydroxyapatite crystals by resin monomer

3. Bottom layer-Unaffected dentin

Question 3. Smear Layer.

Answer:

Smear Layer:

Definition:

• It is defined as any debris calcific in nature, produced by reduction or instrumentation of enamel, dentin, or cementum.
• Depth – 1-5 pm

Components:

• Inorganic:
  • Tooth Structure
  • Nonspecific inorganic contaminants
• Organic:
  • Coagulated proteins
  • Necrotic pulp tissues
  • Saliva, blood cells
  • Micro-organism
• Role:
  • The physical barrier for bacteria
  • Diffusion of molecules
  • Resistance to fluid movement

Question 4. Types and Definition of Adhesion.

Answer:

Definition of Adhesion:

• Adhesion refers to the forces between atoms of two unlike substances when placed in intimate contact with each other

Types:

1. Micromechanical – By formation of resin tags
2. Adsorption – Chemical bonding
3. Diffusion – Precipitation of substances
4. Combinations

Question 5. Objectives of Acid Etching.
(or)
Effects of acid etching on Enamel

Answer:

Objectives of Acid Etching:

• Creates microporosity in the enamel
• Increases surface area of enamel
• Results in the selective dissolution of enamel
• Formation of resin tag through the penetration of resins
• Forms a mechanical bond to the enamel
• Allows the wetting of tooth surface with resin

Question 6. Self-Etching Primers.

Answer:

Self-Etching Primers:

• These are sixth-generation dentinal adhesives
• Etchant and primes are in the same bottle while the adhesive resin is in other
• Easy to manipulate
• Good bond strength to dentin
• Example. Prompt L-Pop

Bonding Viva Voce

1. After etching, the surface area increases up to 2000 times that of the original untreated surface
2. Maleic acid, citric acid, and oxalic acid are used to etch enamel and dentin
3. The bonding agent enhances the wettability of composites to etched enamel
4. Resin tags between enamel rod peripheries are called macro tags
5. Resin tags across the end of each rod are called micro tags
6. Length of micro tags – 2-5 mm
7. Most composites are hydrophobic
8. 2-HEMA and HEMA dissolved in acetone or alcohol are used as primers
9. Cast restorations bonding system uses luting cement
10. Buonocore discovered acid etching