OPERATIVE- MATERIALS

Question 1

Clinical photo shown: Both 36, 37 have amalgam restorations

a. What is smear layer and its effect on bonding? (2)

Answer 1

 Smear layer is a layer of disorganised materials which includes dentine debris with bacteria on the dentine surface after instrumentation.

 The smear layer can be detrimental to bonding as it is weakly attached to dentine.

 Etch-and-rinse will remove the smear layer.

 Self-etch technique uses resin bonding agents to penetrate the smear layer and incorporate it into bonding layer

Question 2

Clinical photo shown: Both 36, 37 have amalgam restorations

b. What is hybrid layer and its importance on bonding in composite restoration? (2)

Answer 2

 The combination of dentinal collagen and resinous materials, also known as ‘resin dentin interdiffusion zone’. Its link between undemineralised dentine and composite.

Question 3

Clinical photo shown: Both 36, 37 have amalgam restorations

c. Significance of not over-drying in self-etch system (2)

Answer 3

(Pickard’s Guide to Minimally Invasive Operative Dentistry 10th edition, 2015)
 If over dried, the dentine collagen fibres will collapse so neither the primer or bond can penetrate into the nano-spaces within the collagen network

Question 4

Clinical photo shown: Both 36, 37 have amalgam restorations

d. Major component of conditioner of GIC (1)

Answer 4

 10% polyacrylic acid

Question 5

Clinical photo shown: Both 36, 37 have amalgam restorations

e. Use of conditioner of GIC and the difference with the ‘conditioner’ in composite restoration (3)

Answer 5

 GIC polyacid allows chemical adherence to mineralised dental tissues and adheres to collage through hydrogen bond formation.

 ‘conditioner’ in composite restoration uses 32-37% phosphoric acid

Question 6

2. Operative - Patient complains for pain/sensitivity initiated by hot and cold food and biting, pain goes off quickly. Found to have deep DO composite placed last week. (Formative, 2013)
   a. State and explain the different systems in dentine bonding agent (10)

Answer 6

See page 147

Question 7

3. Conservative Dentistry (Formative, 2014)
   a. Describe different systems and component of DBA. (10)

Answer 7

look on page 148-149

Question 8

3. Conservative Dentistry (Formative, 2014)
   b. What are the difficulties of using the system? (3)

Answer 8

• Moisture control is essential
• Technique sensitive (multiple steps, instruction like time, sequences need strict following)
• Presence of smearing layer, variation in dentine substrate (e.g. sclerotic dentine) can cause significant effect on bond strength and thickness of hybrid layer
  
  • Clinically very difficult to find the correct balance of residual moisture
  • Etching time can be varied depends on dentine variation (e.g. sclerotic dentine theoretically need longer etching time to open up tubules, but how long is long?)

Question 9

3. Conservative Dentistry (Formative, 2014)
   c. What is ‘wet bonding’? (3)

Answer 9

 Wet bonding technique suggested by Kanca, which left the demineralized collagen fibers supported by residual water after washing

 This allow priming solution to diffuse throughout the collagen fiber network more successfully

 Since overdrying dentine will cause the collapse of collagen architecture, which prevent the effective penetration of primer and resin, while excessive water will compromise the bonding with resin

Question 10

3. Conservative Dentistry (Formative, 2014)
   d. What monomers are present in self-etch primer? (2)

Answer 10

CLEARFIL SE BOND

• 10-Methacryloyloxydecyl dihydrogen phosphate (MDP)
• 2-Hydroxyethyl methacrylate (HEMA)
• Hydrophilic aliphatic dimethacrylate