Old school MCer with new school questions...

I am starting another Master-Cleanse tomorrow. I've been doing these for two years or more now, once every season (10 - 14 days). This time I'm going for 21 DAYS! I have a couple of questions concerning the length of this thing. For starters, on my last MC, my teeth hurt SO UNBELIEVABLY BAD...especially when brushing my teeth (I use a natural bristle toothbrush and Tom's toothpaste). Will using a straw while drinking the lemonade make that much of a difference? If not...any other recommendations? I had to finish 2 days early last time b/c my teeth honestly hurt that bad. Also, I tend to get really sick of the drink after 10 days...so basically this question is just a request for some long term type encouragement. Some testimonials of people who have done 3 weeks would be great. And my last question is simple...I have some senna tea that's been in a drawer for probably a year...is it still potent enough to use?

So...to sum up:
1. Will using a straw for the lemonade lessen the tooth pain?
2. Any other suggestions for decreasing tooth pain/sensitivity?
3. Requesting testimonials of anybody who has gone for 3 weeks (I usually do 10-14 days)
4. Is senna tea still ok to use if it's been in my drawer for about a year?

Thanks so much in advance for your encouragement and answers. Again, I have done about 10 of these, but this is my longest attempt.

Jennifer