I'm going to chime in with my understanding of why a root canal is necessary on a decaying or otherwise infected tooth. Please let me preface this with that I'm not trying to argue with advice already given just adding my own understanding of the procedure from personal experience.

As I understand it when a tooth is decaying and has already either killed the tooth or will soon then a root canal is performed. This is done so that the pulp (center of tooth) where infection sets in can be removed and packed with dental material. This prevents the pulp from not only further destroying the tooth and causing pain but to prevent infection from spreading to surrounding teeth and gums. Teeth often turn brown or black when the tooth is either dead or dying or the nerve has been damaged. Medications can also cause discoloration as can other things. If your teeth are painful it is most likely decay that has caused the discoloration and why your dentist is recommending a root canal. Dental infections can cause serious medical problems so it is not something anyone should ignore. If there is an infection present most doctors will give antibiotics and some will give these for prophylactic measures. If the infection has spread beyond the root you will most likely be in significant pain with facial swelling & even tender and swollen lymph nodes in the neck and under the jaw. I don't know of a dentist who would recommend or perform a root canal without doing xrays which will show the extent of infection.

Many medications (especially those that treat nerve issues or pain) can cause dry mouth. Dry mouth breeds bacteria which in turn makes us more prone to tooth decay and loss. You can help prevent further decline by keeping your mouth moist - there are many OTC items that help this or just keep water close at hand. Obviously daily flossing, salt water rinse and mouthwash along with brushing will encourage healing of the gums and reducing the chances of future problems.

As for the bonding - bonding is not a permanent solution. In general a bond is only good for 7-10 years that of course depends on many factors. Just like a fresh coat of paint.. looks great in the beginning but eventually it will need a new coat. If the bonding is done on a patient who grinds there teeth or their bite is off then the length of time the bonding may last can be much less than what is considered normal.

I wish you the best outcome!
Tessa