Composites: Bonding to Dentine Flashcards
(32 cards)
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
