ADHD and Bipolarity are sooooooo close to each other, that misdiagnosis is actually quite common. Our hyperfocus can be mistaken for mania (and vice versa), our mood swings look like rapid cycling, our temper tantrums or sensory overload meltdowns look like mixed episodes, etc., etc., etc..
Honestly the blowup about the teeth is one of those classic "is it, isn't?" sorts of things. If he's adhd he could have been spinning in his head reliving some sort of emotional event, or in any other kind of sensory overload... and the first word out of anyone's mouth that in any way fed into what was spinning in his mind / emotions triggered the launch into kablawhahsudauewhlayashflkasasdf;idjakj!!! skadoosh!!!! Or it could be the bipolar equivilent.
One of the many differences between adhd & bipolarity, however, is that we adhd'ers can LEARN control over our emotional outbursts, while as you know, bipolarity doesn't. We can learn to breathe, and slow our heart rate, and recognize what's going on, and take ourselves into something blissfully calming (like really loud, really fast, music that downs out the world... i know, that just doesn't SOUND calming), and calm down. We can't stop the mental spinning out of control... but we CAN learn (and learn is such the operative word) to disconnect our mouths and bodies from the maelstrom... until we cool off and reason has a chance to elbow it's way through.
What personally concerns me the most about adhd/ bipolarity misdiagnosis... is that the meds for the wrong one REALLY make a person crazy. ADHD meds keep a bipolar person in a constant state of mania (so they look really productive, but as you know with mania's... you're just not YOU) and in a mania memory gets screwed up.. which looks even more like adhd, because things are being forgotten all the time, and about 50 other things. OTOH, if an adhd'er is on bipolar meds... it's like speedballing. They have to be on super high doses, some of the cocktail causes hallucinations (which makes it look even more like bipolar) moods get REALLY wacky... oy. The list just goes on. Simply put, medicating the wrong disorder actually makes the person LOOK like they have the opposite disorder that they actually have. The meds just don't work.
A friend of mine in the field (psychiatrist specializing in adhd, bipolarity, & addiction... who is adhd himself) says that very occasionally he gets patients who exhibit so many of both disorders (aka massive/bipolar moodswings, but everything else looks adhd or vice versa, someone who's actually bipolar but looks more adhd) that there are times he and the patient decide to do a trial run... one set of meds for a month and the other set for a month ... to see what's really going on. One thing for certain, while the disorders overlap as much as 70%, you NEVER find the two of them together.
<grinning> Meant this to be short. Whoops. Point being... if you're getting a bipolar "feel" from your kiddo, as someone who is bipolar themselves... I would REALLY trust your instincts and follow it up.
Being ADHD my radar certainly "pings" sometimes, and as yet (IRL) I've never been wrong.