To my understanding the issue with chemo and dental work is the risk of infection as your immunity will be compromised.
If the crowns are urgent or leave you at risk of infection, you should probably have them done first but if not, and they are not going to cause you problems for a few months while you are having chemo, it is probably not so important.
The chemo I was having, FEC and Docetaxol, affected my gums, making them rough, tender and in the case of FEC, receded around the teeth while I was on it.
You just don't want to be going in for major dental work while having chemo if you can avoid it.
There are a lot of articles on here regarding tips with chemo if you have a look, I found that reading through them gave me lots of good advice so I put together a coping kit with medications to deal with the side effects.
While you are having chemo, you can also come on with questions if you are struggling to deal with something.
Give your Oncologist and your chemo nurses LOTS of feedback about what side effects you are experiencing, you can ring them for advice at all hours, I had an email address for the Pharmasist at the hospital (Gosford Private) to ask questions and had a foolscap list of side effects I ran through with the Onco every review.
Get a thermometer, and monitor your temperature regularly.
If you start before chemo you will know what your regular temp is usually.
Mine is always below the "usual" 37 degrees, so if it started to climb towards 37 I was wary and started to monitor.
I ended up in hospital with two of the Docetaxol doses because of high temperatures. If you catch them early it is a shorter stay!
Chemo is horrid, but doable and once you know how your body reacts you can manage the side effects better.
Good luck, Jennie