Is a deposit for a future service considered an expense when paid or when the service is rendered and paid in full?

When paying for my dentist appointment today, I also gave them a $2000 deposit for a service that is schedule on January 17, 2023. In regards to itemizing on my personal return, will the deposit be considered as paid in 2022 or in 2023 after the service is rendered and I pay the remaining balance? 

 

It's more beneficial if I can claim it in 2023. If it is not eligible to be itemized in 2023, I'm guessing I should have it refunded and wait until the appointment to pay it in full. Any advice is greatly appreciated.