More info in a sibling comment: https://news.ycombinator.com/item?id=38758871
But interestingly in your comments here and elsewhere about brushing, I see no mention of one of the most -- if not the most-- important kinds of brushing, which is using a flossing brush with, crucially, the right technique, which is not much like other brushing, plus baking soda and a drop of 3% peroxide. Most dental offices aren't teaching this at all, but there is plenty of review of standard brushing "at the gumline and on the surfaces of the teeth", as well as plenty of new and hyped imaging types or surreptitious promotion of dental products...* https://www.youtube.com/watch?v=Cow6wNRJqoo
This is in addition to standard brushing.
I fear mixing sodium bicarbonate (baking soda) with a bit of low concentration peroxide is more or less going to cancel each other out chemically and the suspension is going to have an abrasive effect on the plaque/ tartar buildup but also your tooth enamel. However I am going to ask about it.
Hydrogen peroxide can whiten your teeth a bit but can also cause higher sensitivity. On its own it shouldn't hurt and it will act as a disinfectant but probably shouldn't be used long term on a regular basis. If you have an infection I would recommend using chlorhexidine < 2% concentration (2 % is only prescribed and is really disgusting, 0.2% can be bought in a pharmacy without prescription and is obviously not that strong but also far less disgusting). You probably should not use it for longer than ~2 weeks but as it has a hardly bearable taste you will happily stop using it as soon as possible.
The 4-6 minutes and 1-2 minutes interdental is based on an estimate by a professional dental hygienist. The most correct instruction of course being that you should brush your teeth until they are clean.
I brunch ONCE a day for 2 minutes with an electric toothbrush and have essentially perfect tooth health. I also floss every day. My dentist at my most recent checkup said “whatever you’re doing just keep doing it”
It is different in each country, but usually a dental hygienist has a slightly different viewpoint than a dentist. Some dentists don't care that much for gum health - they make money repairing/ extracting teeth after all and some are little too greedy. Dental hygienists are evaluated based on how well they prevent damage and further health issues/ heal the existing problems. They make more money initially when they perform deep scaling (if they are legally allowed to do that in that country) or later when your teeth are healthy doing clinical whitening. Regular dental hygiene is only mildly lucrative. Good deep scaling is exhausting however so you cannot do more than a 2-3 deep scaling patients per day if you are thorough. You have to fill out the day ideally with normal hygiene, ideally stabilized patients where it is more a checkup. Whitening is the best bang for the buck so to say. Not exhausting, more money per time than regular hygiene session.
The point of this timer is probably (I don't know that for a fact) to push most people to brush much longer than they would as most people still brush for only 30-45 seconds a day.