Dryness of the mouth, what we call xerostomia, is not uncommon at your age. There are various causes for xerostomia, the most common being a side effect of other medicines. Im not sure if Titrosint causes dryness though. Other common causes are infections of the salivary glands and radiation therapy.
For accurate diagnosis of xerostomia, your salivary flow rate needs to be measured.If found low, there are many ways by which salivary secretion can be stimulated.
When the saliva flow is restored to normal; the dryness and the soreness will disappear. I suggest you visit the Oral Medicine department of the dental school nearest to you for the treatment of dry mouth.
I am not in a position to prescribe you specific medications, without performing a physical examination and getting your salivary flow rates.What I can advise you for the time being, is to chew on sugar-free gum to stimulate your salivary glands to secrete more saliva. Also, visit this resource:
http://www.biotene.com/ for some great products that will help you swallow more easily.
One of the teeth being sensitive is an entirely separate issue. Were all teeth root canaled prior to getting the crowns? See your dentist regarding the sensitivity, a X ray will be needed .
Hope this answers your question.Please leave a positive rating for me if this answer has helped you. I do not get credit for it otherwise.
Good Luck !