A long time ago there used to be a commercial by Oral-B touting their mechanical round toothbrush and how it was better than every other mechanical toothbrush and 4 out of 5 dentists agreed.  The reasoning Oral-B chose the round shape was that must be the best shape because that is the shape of the handpiece the hygienist uses when cleaning your teeth.  It is assumed millions of dollars and hours went into the decision to have a round shape and surely it was because that is invariably what cleaned your teeth best.  Well, I myself preferred the sonicare mechanical toothbrush thereby making me the much maligned fifth dentist.  I prefer the sonicare because it’s brush head has more surface area than the much smaller Oral-B and more surface area is better in my opinion, albeit to a point.  I also felt that it had superior oscillation versus just the rotational back and forth of the Oral-B.  Finally, my teeth felt better (cleaner) after using the Sonicare compared to the Oral-B.  But Dr. Farrell, what about the shape, you should know more than anyone that round is better because your own hygienist has a round handpiece and what about all those millions of dollars and time put into determining the best shape to clean your teeth?  The reason my hygienist has a round handpiece is solely because her instrument needs to go on the exact same unit as my dental drill. My dental drill must rotate to remove tooth structure for fillings or crowns, therefore whatever her instrument is, it must rotate as well, thereby making the shape round by default.  It is round because it simply couldn’t be any other shape because it must rotate, not because it is the shape that “best” cleans your teeth.  That isn’t to say it doesn’t clean your teeth very effectively, but other shapes such as a rectangular head can clean effectively as well.  I give Oral-B all the credit in the world because the round head was a great way to market a product but their reasoning isn’t completely accurate.  And so, Yes, I am that Fifth dentist.