I don't think the PRSI covers this, but check it out here . The tax can then be claimed back by using this form. Best if you bring it along and have it signed there and then [broken link removed].
I got a crown done, it was done with a private dentist as it was 'complicated' apparently and regular dentist wouldn't do it. It cost me 950e end of last year, and I am due to claim it back at the end of this year, my understanding is that I get 950*41% back...dentist gave me the form and all for me.