Composites: Bonding to Dentine Flashcards
Is tooth tissue hydrophobic or hydrophilic?
Hydrophilic
Are most restorative materials hydrophobic or hydrophilic?
Hydrophobic
What adhesive bonds can occur between tooth tissue and restorative material? 3
- Micromechanical
- Molecular Entanglement
- Chemical
Which bond needs to be achieved for longevity between tooth tissue and restorative material?
Chemical bond
What are 5 advantages of adhesives?
- Better aesthetics
- Conservation of tooth tissue
- Reinforcement of weak tooth structure
- Reduced marginal leakage
- Reduced potential for pulp sensitivity
- Range of techniques
What are the 5 ideal requirements for adhesives?
- Provide high bond strength to enamel and dentine
- Immediate and durable bond
- Prevent ingress of bacteria
- Safe to use
- Simple to use
Composition ENAMEL structure by weight
Mineral
Organic material
Water
96% Mineral
1% Organic material
3% Water
When would you need to bond a restoration to enamel? 2
- Orthodontic appliances
- Bridges
Comment on the surface tension of enamel compared to the adhesive resin
- Surface tension of enamel is lower
- So perfect wetting cannot take place
- (Resin won’t flow/cover the enamel surface properly)
What layer covers enamel?
Pellicle Layer
How can adhesion onto an enamel surface be achieved?
- Pellicle layer of enamel must be removed
- Enamel surface must be etched to raise surface tension
How is the pellicle layer removed and enamel etched?
Acid etch technique
- Involves using 30-50% PHOSPHORIC acid on the enamel surface
What are the 4 main effects of the acid etch technique?
- INCREASED surface roughness
- Surface energy is RAISED
- IMPROVED wet-ability
- Opens inner prism area for interlocking tag formation
What visible appearance is present when adequate etching has been achieved?
Enamel has a ‘FROSTY’ appearance
What is recommended to apply after an acid etching?
Low viscosity resin before placing composite
E.g. Unfilled Bis-GMA or dentine adhesive resin
Name 6 dental procedures where the acid-etched enamel is used for
- Fissure sealing
- Direct Composite
- Ceramic Veneers
- Resin Bonded bridges
- Orthodontic brackets
- Periodontal splinting
Why does a restorative resin have to be adhesively bonded to dentine?
- Retain restoration in the cavity
- Removed marginal gaps to stop bacterial microleakage
Composition of DENTINE structure by weight
Inorganic Hydroxyapatite
Organic Material
Water
70% Inorganic HA
20% Organic Material (Hydrated Collagen)
10% Water
What 2 things happens when dentine is cut?
- Fluid is pumped through the dentine tubules giving a wet surface
- Inorganic HA crystals are broken up, collagen stretched, torn and smeared over the cut surface
What is the organic material of dentine mainly composed of?
Hydrated Collagen
What are the 3 essential components of a dentine bonding agent?
- Conditioner
- Coupling agent
- Sealer
What is the role of the conditioner in a dentine bonding agent?
Acidic so modifies/clears smear layer
What is the role of the coupling agent in a dentine bonding agent?
What molecule does it contain?
Used as a adhesive
Hydroxyethyl Methacrylate
(HEMA)
What is the role of the sealer in the dentine bonding agent?
What agents can be used as sealers?
Seals the Dentine Tubules
Unfilled Bis-GMA or UDMA
