How about no more nails!!
Seriously from what I remember a proper dental cement will bond with the dentine as well as forming a seal. Its when that seal goes that the crown falls out. I would think that a temporary cement is slightly different formula to one that your dentist will have as it is meant as a temporary measure to give you your handsome smile back until you can get an appointment and the dentist can remove it more easily to check that all is ok before cementing back in.
But you know all this Pete - Al has been through it many times with you. Tut tut.
Sara