Understanding the Difference Between טירחא יתירה (Tircha Yeseira, Major Exertion) and טירחא סתם (Tircha Stam, Minor Exertion) on Shabbos;
Making a Bruise or Using a Toothbrush When One's Gums Might Bleed. Using Floss, Toothpicks, and Dealing with Blood from a Cut;