ZBrushCentral

repair gaps and cracks

Hi,

I am only working with zbrush and made up models partly by sculpting and merging with a 3d scanned object. I used dynamesh the decimate master and the zbrush exporter to make up a file to be printed.
After sending it to the printer I got a reply back that there were too many gaps and cracks in the model to be able to print.
My question are:
How can I find out if there are gaps and cracks in the model in zbrush?
How do I repair them in zbrush?:confused: