I kinda think that if the kids, who are teenagers, are at the point where they fight with their parents about toothbrushing and fake brushing their teeth then the problem is bigger than can be cured with more lectures. How about you ask them why they don't brush their teeth, listen to the answer, and then try to find a cure?

(My guess is sensory issues, in which case I'd recommend the kids be evaluated to see if occupational therapy can help. Alternatively, google can get you started with suggestions while you try to wrangle insurance to cover this.)

Also, all the commenters at Arcamax are framing this as "the kids are disrespectful, they need to learn to obey, you should punish them in some painful or embarrassing way until they shape up" which is not a solution to this problem. God, I'd like to smack all those people with a dead fish until they shape up.