The first thing that comes to mind is the obvious, which usually is not so obvious to the patient in this case you.
You should bring your concerns up with your doctor.
I certainly wouldn't have stuck with a drug that made my teeth rot, and certainly wouldn't be asking this question AFTER having root canal work done!
Check if there is an alternative, can you take the drug as a pill and just swallow it? Is there a similar drug that has the same effect but is not caustic to your teeth?
Can you have something neutral or opposite to this to stop the erosion, like drink some milk to reverse the acidity, or drink a lot of water to dilute the acid in your mouth?
Other options you can look at are more holistic or lifestyle based. I know from a quick google search that Saphris is commonly used for bipolar and schizophrenia etc, but that doesn't mean that only medication will resolve your problems.
You could certainly look into seeing a psychologist or other counsellor, perhaps you may need to see several, or seek out someone that can help you with all the issues you face.
Many of the mental health issues we face tend to come from stress, our inability to cope, and chemical or biological triggers, so seeing a dietician and working out a regular exercise routine could be quite invaluable to you.
I suffered from debilitating depression that would last for weeks, months, or even years, but as I've stuck to my regular exercise routine over the past year or so, I've found my depression usually lasts less than a week now. My lows are usually not quite so low, and my general mood is somewhat better of average than it used to be.
Unfortunately there is no reliable "quick fix" for mental health problems. Pills may treat symptoms, but unless you can find the cause you will not be able to find the cure, and in most cases even finding the cause will not lead to cure.
The best thing you can do therefore is to try to keep your body in good shape, so these things don't effect you so badly.
The saying goes that a healthy mind will give you a healthy body; it's not exactly completely true, but certainly the healthier you keep your body, the more resilient you will be to any kind of stress or illness, the worst thing that will happen is you may get in better shape, and that can't be a bad thing.