Amazon offers the Oral-B Professional Deep Sweep Triaction 5000 Electric Toothbrush for $98.99. Clip the $20 off coupon on the product page to cut the price to $78.99. With free shipping, that's the lowest total price we could find by $20. It features five cleaning modes and a pressure sensor with indicator light.
Update: Scroll down to Special Offers and Product Promotions to find the coupon.