If you are an employee of a dental firm, you would click on the income tab and scroll down to employment expenses.  You will need to get a T2200 Conditions of employment form from your employer in support of your claim for travel expense.  Uniforms are generally not deductible.

http://www.cra-arc.gc.ca/tx/ndvdls/tpcs/ncm-tx/rtrn/cmpltng/ddctns/lns206-236/229/slry/menu-eng.html

If you are a contract worker, you will be able to enter the income under self-employment, but clothing is still not deductible.  Deductible items for self-employment are here:

http://www.cra-arc.gc.ca/tx/bsnss/tpcs/slprtnr/rprtng/t2125/p13-eng.html