Teeth grinding is a result of abdominal pain.  This pain is commonly
from from GI ulcers, or insulinomas.  Since you said his "bloodwork was
normal" then ulcers are more likely.  Your list of previous medications
does not include "the ulcer antibiotic- Biaxin", nor does it include
how long he was on them, or the doses used.
 
You can look up my previous posts on ulcer treatments, and talk to your
vet about using Carafate, Biaxin, Amoxicillin, and the short term use of
an antacid.  He will likely need the Biaxin and Amoxicillin, Carafate,
and the Gerber's baby food or Hill's a/d for 4 weeks to clear the
Helicobacter infection from his stomach.
 
Another problem to consider in an 8+ year old is intestinal lymphoma.
Hopefully they did biopsies when they did the exploratory surgery to
look for lymphoma and inflammatory bowel disease.  If these diseases
were also ruled out, then ulcers are real likely!
 
Lets see how he does on Carafate, Biaxin, Amoxicillin, and Gerber's
baby food and/or Hill's a/d for 4 weeks.
 
Hope that helps,
Jerry Murray, DVM
[Posted in FML issue 4499]