Dentaltown July 2017 - 44

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It's Not Over-Etching-It Is Over-Drying
Townies talk bonding and find there's some division on what's the best practice

pjmop
Member Since: 02/15/05
Post: 1 of 49

I see under-etching as a bigger problem than over-etching. You can easily etch for 30 seconds
if dentin is left wet. Look at the SEMs of etched wet dentin and then look at over-dried etched
dentin. I'm convinced that over-drying etched dentin is the single biggest cause of sensitivity.
Just putting it out there, as I hear over-etching commonly used as the reason for sensitivity. It's
almost never over-etching. It's almost always over-drying. ■
4/12/2017

Bruce J LeBlancDDS
Member Since: 02/24/10
Post: 2 of 49

Are you saying this for all bonding agents or ones with certain solvents that over-drying
increases chances of sensitivity? I will say that in our practice we have etched deep dentin routinely without using bases with very favorable outcomes with regard to the issue of sensitivity.
We have found that adhesive bonding should solve sensitivity issues, not cause them. Yet many
clinicians seem to be fighting issues with sensitivities as well as brown line margins at recall.
Both are preventable. ■
4/15/2017

USCDDS95
Member Since: 10/05/06
Post: 3 of 49

Back in dental school, we were taught to blow bone-dry. I don't remember a lot of sensitivity
from those fillings. I think most sensitivity is caused by voids or lack of adaptation to prep. ■
4/15/2017

Triad
Member Since: 06/18/03
Post: 4 of 49

Really? When I was in school ('04 grad) they said, "Dry, but don't desiccate." I switched to
Surpass so I don't have to worry about that anymore. ■
4/15/2017

mike k
Member Since: 05/01/01
Posts: 6 and 8 of 49

If all you etched is enamel, then it's fine to dry the heck out of it. But if you etch dentin and dry
it out, you will get sensitivity because the collagen matrix will collapse and the primer won't penetrate
the dentin. That means no dentin bond. When I was in school in the early '90s we were taught to
cover the dentin with decal or GI before we etched because if you etched dentin, the world would end!
That whole air-dry but don't over-dry business is the toughest part about bonding with
a system that requires etching. Been using Surpass since it came out pretty much, gives that
total-etch-type etch pattern but not concern of over-drying. I'm shocked the other major manufacturers haven't all introduced similar products. ■
4/15/2017

pjmop
Member Since: 02/15/05
Post: 9 of 49

Hi, Bruce. I think you already know this, but I was talking about total-etch systems. After
etching and rinsing, the dentin needs to be wet. The solvent (acetone or alcohol) in the primer
chases out excess water. So, if you think the dentin is too wet, just use a little more primer.
When you see the SEMs of etched dentin, it looks like collagen fibers floating in water. It is
easy to picture the bonding agent infiltrating this. But dried etched dentin looks impermeable.
I challenge anyone using total etch to:
1. Etch for 30 seconds.
2. Rinse thoroughly and leave dentin wet. Quick suction or cotton pellet ... no air drying.
Continued on p. 46

JULY 2017 // dentaltown.com

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