Does placing composite on enamel for shade evaluation causes contamination?

[Qu3stionmarx]

Hello y'all
I'm a 5th year dental student and last week I was doing an anterior restoration of a hypoplastic enamel lesion on tooth no 10. I thought it would be a good idea to test different shades on the minimal preparation I made without etching\bonding so I would be able to remove the composite after I light-cure it. One of the doctors told me that I'm introducing contamination into the preparation every time I place the composite on the enamel. She continued her scolding by saying that it could seriously affect bond strength and color. She said I would have to remove additional enamel to get rid of the supposed contamination. Obviously, everything placed on the enamel other than the definitive restoration is considered a contaminant, but is it really the case with composite? My assumption was that by etching the preparation (once I found the right shade), every contaminant would be neutralized. I tried to find research to answer the question but turned up empty handed. What do you think?

 

[honestdoc]

You're right about the etching removing contaminants. Some dentists use Chlorhexidine before acid etching. If possible, don't work with this dentist/instructor. If unavoidable, add a small amount of composite on an instrument and match it against the tooth without putting it on the tooth. You may speak with this instructor's supervisor that she has no scientific basis for her scolding.

 

[MattKW]

Have you noticed how easily the composite flicked off when you'd finished the comparison? Your tutor is wrong, go talk to the lecturer of restorative treatment. If you really wanted to be sure of cleanliness, then some plain pumice would scrub off anything.
If I have a patient with multiple diastemata I want to close using composite, I will often do a quick mock-up in composite so they can see the colours and altered sizes before committing to a treatment. I will place plain bonding liquid on the unetched surfaces for a bit more grip, but it still flicks off with slightly more effort.