Enamel Bonding

Question 1

Enamel composition

Answer 1

~96 wt% mineral
hydroxyapatite crystals surrounded by firmly bound water
~4 wt% organic and water
primarily Type I collagen

Question 2

Instrumentation of enamel exposes prisms in several planes. How does this impact dentistry?

Answer 2

• perpendicular exposure of prisms vs. parallel exposure may result in ~50% loss of bond strength

Question 3

How did Buonocore contribute to esthetic dentistry?

Answer 3

• The idea of using phosphoric acid on dental surfaces was first introduced by Buonocore (1955), who observed that adhesion to metal surfaces by paints improved when acids were used.

Question 4

Effect of phosph acid on enamel

Answer 4

• it creates microporosities either w/in the center of enamel prisms or between them on the periphery

Question 5

Which of the following is the most impacted when enamel is exposed to acid?
The interprismatic structure
The prismatic structure
The water content
The collagen content

Answer 5

Prismatic structure (i think)

Question 6

How demineralization occurs as a result of etching (3)

Answer 6

i) selective because of morphologic arrangement of prisms
ii) prism angulations lead to varying demineralization at the head or periphery
iii) results in micro-morphologic difference

Question 7

The results of demineralization by etching (4)

Answer 7

i) it removes ~10 μm of surface
ii) If remineralization occurs, it will occur in the 5 μm to 50 μm porous layer
iii) surface free energy of tooth structure increased ~2x
iv) capillary attraction facilitates resin penetration

Question 8

Bonding agents used in bonding enamel are _________ in nature. Why?

Answer 8

• Hydrophobic

because enamel, although there is always that monolayer of water, is relatively hydrophobic.

Question 9

What makes bonding to dentin different?

Answer 9

• a lot more significant problem in that there is a lot more fluid in dentin

Question 10

What is the composition of Optibond Solo Plus?

Answer 10

• a combination of a hydrophilic primer and a more hydrophobic adhesive

Question 11

List 3 examples of hydrophilic primers

Answer 11

HEMA – hydroxyethyl methacrylate
BPDM – bis-phenyl dimethacrylate
4-META – 4-methacryloxyethyl trimellitate anhydride