The deductions for a dental office would be no different than most any other business. You have rental fees on the space you are leasing, depreciation on major equipment purchases, deductions for routine dental supplies, and supplies you purchase for your office. Utilities, phone expenses, premiums for insurance, building maintenance fees, etc.
I am giving you a link below which is a checklist of typical deductions you may take in particular connection with a medical practice. They may not all apply in the case of a dentist, but this will give you a good idea of the expenses you can deduct.
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