If you own one of those fancy rechargeable toothbrushes that cost $80 to $150, you also discovered that the replacement heads are $5 to $15 each. I own one of them and I love it. No cavities in the five years I've owned it.

But the price of the brush heads prompted me to find out which retailers in the Twin Cities sell them cheaper. See my "On Your Side" column in Sunday's Metro section (Jan. 17). One sneak preview: If you're a Costco member, you're in luck.

My real beef is with Philips Sonicare and Braun Oral-B, which indicate on the replacement head packaging that the brushes should be replaced every three months. I think they took a cue from the shampoo people whose directions said "Lather, rinse, repeat, and repeat and repeat."

I checked with Dr. Sheila Riggs, chair of the Department of Primary Dental Care at the U of M. She said that rather than blindly following the 3 month rule, ask your dentist to assess your situation. I'm replacing mine every 6-12 months without my dentist's approval. I figure a cavity-free stretch of five years is proof enough.

Now that I'm in a lather about this, I'm going to vent about Procter & Gamble. How smart were they to invent the Swiffer? Almost everyone loves it except me. The high cost of the disposable replacement pads is the gift that just keeps on giving to P&G. Same thing with the company that invented a toilet brush with disposable ends. And the toothbrush heads....

Have you found a cheaper source for the replacement heads than I did? Let me know, deal spotters.