How to stop a 4-yr-old sucking his thumb? 8-yr-old DD has only just stopped sucking her thumb at night after being told by dentist it was damaging her teeth! (She apparently has something called an 'open bite' which will need correcting when she's about 11 - I feel awful about it). Am now really worried same will happen to DS - he only sucks his when he is tired and at bedtime, but objects when I suggest he stop. Any tips/advice, please?