DS (21 months) does not want to brush his teeth. When he was about a year old, he found it fun to imitate me, putting a little toothbrush in his mouth and wiggling it around; however, the appeal of this game has long since worn off. Sometimes I can get him to brush the beak of his beloved rubber duck, or another toy. We sing toothbrushing songs. I have even gotten him some (yuck!) kiddie toothpaste, which he happily sucks off the brush and then chucks the brush into the sink or tub. On the suggestions of a more commercial parenting site, I got us matching toothbrushes (kiddie ones) and also taught him to spit into the sink or tub as a "reward." Of course this backfired and he spits everywhere else all the time
just to be mischievous. D'OH!
Any advice? Although he is still nursing and eats fairly little sugar, I still feel concerned about this.

Any advice? Although he is still nursing and eats fairly little sugar, I still feel concerned about this.