GC EUROPE G-aenial Bond - Manual (Page 7)

7 G-ænial Bond Technical Manual
Disadvantages of etching with phosphoric acid
it is now common consensus that phosphoric acid etching of dentine is aggressive, resulting in
dentinal tubules that are widely opened, an excessively thick demineralised layer and leaving
collagen fibres without any minerals.
• Etching of Dentine can result in post-operative sensitivity
the major problem in this situation is sealing the dentinal tubules correctly in order to avoid
post-operative sensitivity. the collagen fibres collapse easily when drying the cavity, thereby
creating a layer of thick and dense fibres that can not be thoroughly impregnated with the
bonding agent, this can result in the dentinal tubules remaining open and the patient
experiencing post- operative sensitivity.
• Etching of Dentine induces risk of nano-leakage
it is documented in the literature that the collagen in dentine that becomes exposed by an etch-
and rinse procedure is highly vulnerable to hydrolytic and enzymatic degradation processes 1 . if
the bonding agent does not fully penetrate into the demineralised collagen network, degradation
of exposed collagen fibres can occur, leading to possible nano-leakage.
• Etching of Dentine reduces the potential for chemical interaction.
etching of Dentine dissolves hydroxyapatite crystals and removes minerals required for chemical
interaction. chemical interaction is believed to improve the bond durability 2 .
Figure 3: concerns associated with the use of acid etchants on dentine
1 Pashley Dh et al. collagen degradation by host-derived enzymes during aging. J Dent Res 2004;83:216-21.
2 Van meerbeek B. et al., State of the art self-etch adhesives, Dent. mat. 2011;27:17-28.
Before etching, the smear
layer acts as a barrier
after etching, thick collagen
layer 3-5 µ
no remaining minerals
no possible chemical
interaction
after drying: dense collapsed
collagen network
insufficient adhesive
penetration
tubules remain open: risk of
sensitivity
Fluid Flow
Wide open
dentinal tulube
induces
sensitivity
Dentinal
tulube
exposed
collagen will
degrade in
time (possible
nano-
leakage)