I also knew I didn't have a plan to combat this habit -- apart from the occasional “serious” discussions about my daughter's future beauty and other equally unsuccessful activities.
However, this time the dentist had a plan...or at least tangible advice.
He produced a leaflet about thumb and finger guards which are sold in the UK and are apparently quite successful. Our dentist gave the product a resounding thumbs up and that’s all I needed.
I promptly went to Thumbguard and bought a finger guard for £49.99 plus the usual extras.