From the way you phrased your question, it appears that your husband does not own his own dental practice, but is an employee of a practice or health system.
I that is correct, his unreimbursed employee business expenses (uniforms, licenses, continuing education, professional liability insurance, etc.) are no longer deductible, under the terms of the Tax Cuts and Jobs Act of 2017. The entire category of Miscellaneous Itemized Deductions has been suspended for tax years 2018 - 2025.
