Normal daily routine:
Brushing - this should go without saying. AT MINIMUM twice daily, preferably three times a day (morning, Noon, night). Use a baking soda based toothpaste. Brush gently in small circles and be sure to BRUSH YOUR TONGUE (Most bacteria hides there).
Flossing - should be done once a day, realistically I do this about 5 times a week. If you don't floss and you have continual bad breath, you need to start. Most of the reason for bad breath is people not flossing.
Antiseptic mouthwash - I use it after I brush, but I would use it a minimum of once a day. Use it after you floss to flush out all the crap the floss loosens up.
Dental appointments - You should get a cleaning twice a year; once a year is the absolute MINIMUM. They should do x-rays to check for hidden cavities and do a thorough cleaning. Do not skimp on visiting the dentist as it will cost you more in the long run when things start to "hurt".
Supplies to have on hand for the SHTF:
Extra toothbrushes - you should change your toothbrush at least every six months.
Plenty of toothpaste - Baking soda can be substituted, just make sure you stockpile some.
Plenty of floss - has a myriad of uses beside dental so keep plenty on hand.
Some type of painkiller - like Tylenol or Advil, you'll thank me when the toothache starts. If you can stock some topical anesthetic like Ambesol or something...it will help.
Dental wax - have some on hand to use a filling replacement should a filling fail. Place and form the wax to keep debris out of the sensitive area of your tooth.
...that is all.