I honestly think if you have teeth problems with breath problems also - I would go if not twice a year - once a year - Yorkies can be prone to dental problems and you want him to have teeth his whole life - so I would think about a cleaning/scaling and they'll make them all sparkly and pretty again - and no icky breath -
I love the way both my girls breath smells but have a feeling Cheri will be the one who needs more dental visits...after she had her's cleaned & baby teeth pulled....her breath was lovely again.