Week 3- Bonding to Enamel and Dentin

Question 1

what is bonding

Answer 1

an adhesive material frequently a viscous fluid that joins two substrates together and solidifes and is able to transfer load from one surface to another

Question 2

in dentistry the bonding of resin to tooth structure is the result of 4 possible mechanisms:

Answer 2

• mechanical: penetration of the resin and formation of resin tags within the tooth surface
• adsorption: chemical bonding to the inorganic components (hydroxyapatite) or to the organic components (mainly type I collagen) of tooth structure
• diffusion: precipitation of substances on the tooth surfaces to which resin monomers can bond mechanically or chemically
• a combination of the previous three mechanisms

Question 3

what are the requirements for good adhesion

Answer 3

• the surface should be clean
• the adhesive should wet the substrate well
• there should be intimate adaptation between the adhesive (bonding agent) and the adherent (tooth structure)
• the bond strength between the adhesvie(bonding agent) and adherent (tooth structure) should be strong and resist debonding
• the adhesive should be well cured

Question 4

what are the adhesive restorative techniques in dentistry

Answer 4

• restore class I, II, III, IV, V carious or traumatic defects
• change the shape and color of teeth
• bonding of ceramic restorations
• bonding of indirect resin based restoration
• sealants
• bonding orthodontic brackets
• bonding of periodontal splints
• bonding of conservative tooth replacements
• core build ups for crowns and onlays
• bond cast and prefabricated posts
• seal apical restorations placed during endodontic surgery

Question 5

describe enamel bonding

Answer 5

-acid etching of the enamel for 15 seconds with 37% phosphoric acid
- converts the smooth enamel into a very irregular surface with high surface energy

Question 6

describe enamel bonding

Answer 6

-when a fluid based material is applied to the irregular etched surface, the resin penetrates into the enamel aided by capillary action
- the monomers undergo polymerization when cured and the material becomes interlocked with the enamel
- this formation of resin microtags within the enamel surface is the fundamental mechanism of enamel bonding

Question 7

describe dentin bonding

Answer 7

• dentin bonding primarily relies on the penetration of adhesive manomers into the filigree of collagen fibers left exposed by etching with the 37% phosphoric acid for 15 seconds
• dentin bonding does not have the strength of enamel bonding
• whereas enamel is mostly mineralized tissue (85%), dentin is half organic tissue and water and mineralized tissue

Question 8

what forms the smear layer and what is it

Answer 8

• cut dentin surface from the bur in the handpiece
• composed of debris of hydroxyapatite crystals and denatured collagen

Question 9

what does the smear layer fill

Answer 9

the orifices of dentin tubules forming smear plugs and decreases dentin permeability by 85%

Question 10

what are the 3 types of etching/bonding

Answer 10

• total etch
• self etch and selective etch

Question 11

describe total etch

Answer 11

when you use etchant on the dental and enamel you remove the smear layer- can cause more sensitivity

Question 12

describe self etch and selective etch

Answer 12

they leave the smear layer in place because you are not etching the dentin