Enamel and Dentine Bonding

Question 1

Sahaij is restoring a 46 with a deep carious lesion. To remove the smear layer, he uses corporation X’s ultra etch product which is made out of 37% wt phosphoric acid. He applies the etchant for 1 minute, washes it off thoroughly, and dries out the prepared tooth. Then, he adds on MDP and resin, followed by a blast of curing light to finish his restoration.

His patient, unfortunately, complains of pain in the tooth a few weeks in returns to the clinic with a dark-in-appearance 46.

Explain what you think went wrong. Why is the patient’s tooth darker in colour?

Answer 1

Sahaij over-etched the dentine, causing excessive demineralization. This leaves an unhybridized zone that allows water to permeate. This water undergoes hydrolysis reactions with the adhesive which causes bonds to break.

Question 2

Enamel etching is not technique sensitive but dentine etching is.

True or False?

Explain your answer

Answer 2

True

Dentine - over etch = unhybridized zone = failure

Dentine - Over dry = collagen collapse = failure