Alas, I found the Ultrasonex SB300U for around $40.00 and jumped at the deal. The toothbrush offered an ergonomically comfortable handle, a three minute shut off feature, and three replacement brushes. In other words, just about exactly the same things as the more expensive models offer. What was left to discover was how good the performance would be.
Hence, I cannot recommend the Ultrasonex SB300U. There are just too many other options available that will do the good stuff every bit as well as this brush and that do not have the negatives. So, I would look to other electric toothbrushes rather than this one.