Enamel bonding

Question 1

Enamel composition %

Answer 1

96% HAP (mineral)
1% organic proteins
3% water

Question 2

Enamel composition description

Answer 2

• Hexagonal rods of mineral (prisms)
• Prismatic arrangement perpendicular to tooth surface
• Naturally covered in pellicle and usually plaque

Question 3

How to acid etch enamel

Answer 3

• Need to make retentive surface for micromechanical bonding –> > SA for resin to flow in and polymerise
• Use ~35% phosphoric acid
• ~40s etch for fresh enamel
• ~20s for burred/ milled enamel

Question 4

Clinical procedure for acid etch

Answer 4

1. Px selection
2. Enamel prophylaxis (keep it clean)
3. Application of etchant

Question 5

Patient selection

Answer 5

• Bonding area must be kept free of contaminants e.g. saliva or water
• Pxs who will re-wet dried surface should not be selected for acid etch (elderly, children, mentally ill)
• Do not use if dentine is exposed
• Isolate with rubber dam if possible

Question 6

Enamel prophylaxis

Answer 6

• Need to bond to enamel, not pellicle/ plaque
• Clean with slurry of pumice and H2O for 30s using bristle brush
• Wash thoroughly to remove debris and dry

Question 7

What is pumice?

Answer 7

Aluminium oxide powder

Question 8

Application of etchant

Answer 8

~35% phosphoric acid

• Comes as liquid (fissure sealing) or gel (ortho breackets, veneers)
• Apply with cotton pledget
• Do not rub etchant onto surface
• Wash etched surface thoroughly (to remove salts and excess acid)
• Dry, to frosty white appearance

Question 9

Treatment possibilities for enamel acid etch

Answer 9

Resin bonded bridges

Direct restorations