Dental Anatomy: Adhesion

• How does failure of bonding to tooth structure occur?

  1. Fatigue
  2. Breaking
  3. Leakage of restoration margin- where caries occurs/plaque accumulates.
• Why is adhesion needed?

  1. Prevents leakage.
  2. More conservative tooth preparations.
  3. Strengthens tooth tissue.
  4. In order for adequate bonding to enamel and dentine.
• What 2 things is enamel described as?

  1. Dry
  2. Brittle
• Why are cavities cut before adhesion?


  To prep the cavity.
• What are the 2 different types of margins produced when cutting cavities and what can both cause?

  1. Tungsten carbide causes SMOOTH margins.
  2. Diamond burs cause ROUGHER margins.
  3. They both give sub-surface cracking.
• What else can cause cracking of enamel and what can this cause?

  1. Composite shrinking.
  2. This puts strain on the cavity margin, which can pull the enamel apart.
• Why is pushing hard with an air turbine handpiece not efficient?

  1. Erratic and causes stalling.
  2. Stall → start → stall- not efficient.
• What 2 words are used to describe dentine?

  Wet and resilient
• What are the 5 materials that have adhesive properties and give 2 features of each. (1)

  1. Composite: all resin, adhesive needed. The bonding agent creates a micromechanical bond with the tooth surface and a chemical bond with the composite.
  2. Polyacid - Modified Composites: some resin, adhesive needed. Contain both resin components and glass ionomer components.
  3. Glass Ionomer Cement: no resin, self adhesive. Bond is achieved through ion exchange at the interface between the tooth and the material.
• What are the 5 materials that have adhesive properties and give 2 features of each. (2)

  4. Resin-Modified Glass Ionomer: some resin, primer needed. Combine the fluoride release and adhesion of GICs with the improved mechanical properties of resins but resin component often necessitates the use of a primer to enhance adhesion to the tooth structure.
• What are the 5 materials that have adhesive properties and give 2 features of each. (3)

  5. Calcium Tri-silicate Cements: new material known for their biocompatibility and bioactivity and hydrophilic + self-sealing. Set in the presence of moisture and form a tight seal with the tooth structure. They do not require a separate adhesive as they are self-adhesive and can induce the formation of hydroxyapatite when in contact with body fluids, promoting sealing and repair.
• What are 4 requirements for adhesion?

  1. Good, wet substrate.
  2. A low 'contact angle'- this allows the material to penetrate into the structure.
  3. A clean substrate, with high surface energy- this makes it attractive.
  4. Contamination must be avoided; especially with blood or saliva.
• What are the 3 mechanisms of bonding?

  1. Mechanical theories: involve the concept of interlocking of the solidified adhesive with the irregularities of the surface of the adhered. COMPOSITES.
  2. Adsorption theories: chemical bonding e.g. primary (ionic and covalent) and secondary (hydrogen, dipole interaction, or VDW) valence forces. GICs.
  3. Diffusion theories: mobile molecules across the interface. GICs, Calcium Tri-silicate cements.
• What was the 1st adhesive used to bond restorations to enamel and dentine?

  Sevriton cavity seal.
• How does composite adhere onto enamel?

  Via the acid etch technique where the smear layer is removed to leave a high energy surface. This is done by:

  1. Differential dissolution of prism boundaries.
  2. After 20 seconds etch with H3PO4 (phosphoric acid)
  3. This leaves a porous, high energy surface for resin to flow.
• What is a feature of enamel prisms that allows good adhesion?

  1. Prisms are parallel with cavity wall.
  2. So they can be pulled apart from each other easily by adhesive.
• What does the smear layer consist of and how does it form in the first place?

  1. Debris from cutting process and blood and saliva.
  2. Formed by pressure wielding process.
• How does composite adhere onto dentine?

  1. Dissolution of mineral phase, leaving exposed collagen network.
  2. Dentine tubules widened ready for composite adhesion.
• How is a resin bond achieved on the tooth?

  Via micro-mechanical retention into dentine.
• What type of restoration is required with composite and why?

  1. Layered restoration.
  2. Moisture affects bonding.
• What are the 4 classifications of DBAs?

  DBA= Dentine Bonding Agents.

  1. Three bottle (4th gen)
  2. Etch and rinse (5th gen)
  3. Mild self-etch (6th gen)
  4. Strong self-etch (7th gen)
• Give 2 examples of type 1 BDA and 4 features of it.

  Type 1 = Three bottle.

  Examples: Scotchbond MP, Optibond FL.

  1. Smear is removed completely.
  2. Etch is separate.
  3. Primer is wet and separate.
  4. Bond is used as a seal (and by itself)
• Give 2 examples of type 2 BDA and 3 features of it.

  Type 2 = Etch and Rinse.

  Examples: Optibond solo, scotchbond universal.

  1. Smear removed completeley.
  2. Etch is separate.
  3. Primer and bond are one (mixed together).
• What does resin mix with in adhesion, and what does this form?

  HEMA (2-hydroxyethyl methacrylate) to form the hybrid zone (between restoration and tooth).
• What 2 layers are formed after resin infiltrates, and what do both do?

  1. Adhesive layer- seals collagen.
  2. Oxygen inhibition layer- allows composite to make strong bond to resin.
• What does the total-etch technique comprise of?

  1. Phosphoric acid on enamel and dentine.
  2. Etch left for short period of time on dentine- this stage is not always necessary due to modern self etch adhesives.
• What are the stages that lead towards resin forming a strong bond with dentine?

  1. Etch removes mineral in collagen.
  2. This mineral is then replaced by water.
  3. This helps hema to penetrate and displace the water, infiltrating around collagen fibrils.
  4. Bond mixes with hema and develops a strong structure in adheric interface.
  5. Then a curing light is used forming a hybrid layer that varies in thickness (0.5-8u)
  6. This makes sure the intertubular dentine is filled with resin- making a strong bond.
• What happens if the dentine surface is dry or wet?

  1. Dry

  Causes collapse of collagen- so adhesives cannot attach.

  2. Wet

  Bond gets through and dissolves- this forms a good adhesive interface:
• What are the 7 stages of wet-bonding?

  1. Enamel and dentine etched.
  2. Washed with water.
  3. Surplus water removed using cotton.
  4. Large amount of adhesive used on tooth.
  5. Solvent in adhesive is evaporated with air until there's no rippling.
  6. Then a light cure is used.
  7. Composite applied:

  
• What bond is used worldwide, and what does it contain?

  3M Scotchbond Universal Adhesive, which contains MDP (for self-etching).
• Give 2 examples of type 3 BDA and 4 features of it.

  Type 3 = mild self-etch (6th generation)

  Examples: Clearfil SE Bond/Protect Bond, Silorane SE bond (stronger self-etching primer)

  1. Smear dissolved, NOT COMPLETELY REMOVED.
  2. Etch and primer mixed, whilst bond is separate.
  3. Acidic primer and sealing resin is then light cured.
• What is the role of primer?

  Thins tooth surface, so solvents can penetrate dentine tubules.
• What is the role of the adhesive?

  Seals the bonding layer.
• What can often be confused with caries on a radiograph and why?

  Resin, as they are both radiolucent.
• Give 3 examples of type 4 BDA and 4 features of it.

  Type 4 = strong self-etch (7th gen)

  Examples: Xeno III; I Bond; One up bond F plus, Fuji Bond LC; G bond; Tri S Bond, Scotchbond Universal.

  1. Smear dissolved.
  2. Etch, prime and bond all in 1.
  3. May be split into 2 solutions though.
  4. Milder self-etching primer added, which is evaporated then light cured:
• What are the 2 types of type 4 Self-etch adhesives and give examples.

  1. Etch & Prime/Bond.

  Two parts- Two steps

  Examples: ClearFil SE, Protect Bond.

  1. Etch & Prime & Bond.

  Two parts- One step.

  Examples: Xeno IV, Tri S Bond, Scotchbond Universal.
• What are the 4 steps to achieving dentine bonding?

  1. Cavity is cut leading to the smear layer plugging into dentinal tubules.
  2. Dentine is etched, modifying the dentine and smear layer.
  3. Resin penetrates into smear layer.
  4. Solvent evaporates.
  5. Surface light cured to give a bonding layer and air inhibited layer.
  6. Composite can now bind, and makes a tight junction with the adhesive (bonding layer)
• What is 3M Universal Bond used with?

  The Total etch technique, or without phosophoric acid etch- as the monomer is acidic.
• What was the precursor to 3M U.B?

  L-Pop Prompt
• What adhesive was initially used alongside composite, what did it contain, and what was the name for the composite?

  1. Sevriton Cavity Seal.
  2. Glycerophosphoric acid-dimethacrylate.
  3. Hytac poly-acid modified composite.