Instead of trying to melt out paraffin, reverse processing, then decalcify,
try this first. 

Immerse trimmed face of block into decalcifier you normally use to
decalcify your cores for 15 minutes or so (HCl or formic acid will work,
HCL being stronger acid) then rinse well with water to remove acid
(damaging to metal parts of microtome and knife), chill block and recut.
DO NOT trim futher into the block, you want to get the FIRST few sections
coming off the knife as "face" decalcification only happens on a a few
micrometers into exposed bone.  

Keep doing this if you get into more calcified bone, you should have good
results without having to compromise sample with further exposure to heat
and solvents during reprocessing. 
>
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)

email: gcallis@montana.edu