Hello, i am

People Brux (grind their teeth) for two reasons
One is that there are interferences in their bite which cause irritation to the chewing muscles and tooth nerves leading to a reflex attempt to "wear down" the interferences
The other reason is that is it a way for the body to deal with emotional stress

A dentist cannot help with the latter but a custom made AND CORRECTLY ADJUSTED HARD mouthguard will allow your dentist to give you a bite that has been perfected in such a way that these interferences have been eliminated while the guard is in place
This will reduce the damage done by "emotional bruxing"

When you remove the guard the interferences will again influence the facial muscles and may lead to more aggressive bruxing

With regard to your new crowns, Zirconia is abrasive against natural teeth but this can be reduced by polishing the ceramic

IF the crowns have been made in harmony with the rest of your occlusion then they should not cause you to grind more often or more aggressively but I would recommend wearing the night guard indefinitely to protect your teeth, crowns and joints

what you need is what we call an "occlusal evaluation" and for someone to work out why you are grinding . look at occlusion category on this site . You can have it treated and then it can stop if your teeth are trimmed carefully .

if you did not brux before the crowns were placed and you do now , then your new crowns have caused this as they may be too high in the bite . if the only way to stop you bruxing is this guard then you need to keep on wearing it until your crowns are adjusted and polished by the dentist who placed them .