Can whitening make teeth more translucent?

The outer perimeter of ones teeth have no underlying inner tooth structure (dentin).  Depending on the enamel this layer can have a natural translucency.  If this layer of translucency is evident prior to whitening then it will become more obvious after whitening.  It is not,however, thinning your enamel just brightening it.  The yellow look of the teeth should whiten nicely with teeth whitening and should blend in nicely with the layer of translucency.  I always tell my patients to Try not to look at the part of the tooth that is more translucent after a whitening procedure but instead look at the over all smile results.  Dissecting a tooth by areas and levels of each tooth in the smile will never show an "even" texture, shade or translucent after whitening.  The only way to get a white monochromatic (solid shade) on all teeth in your smile is with the use of porcelain veneers or crowns. 

WHitening does NOT thin your teeth.   It does remove stain though (oxidize stain).   Pure enamel (like a the tip of a front tooth) looks like a sheet of frosted glass in varying thicknesses.   So if the enamel has been thinned out there - you could have a lot more translucency 

Your enamel is thinned out because of your Gerd. And you may have slightly gray dentin underneath the enamel.