The  gold  is  allowed  to  overlap  the  margin  of  the  cavity,  so  as  to  per-
fectly protect  all  of  the  exposed  —  or  what,  in  the  ordinary  method,
would  be  the  exposed  —  surface  of  the  root.
"  The  gold  filling,  besides  protecting  the  root,  retains  the  square
cylinder  in  the  centre  of  it.  In  placing  the  cylinder  in  the  root  with
the  pivot  in  it,  preparatory  to  inserting  the  gold  filling  around  it,  the
split  in  the  pivot  should  range  directly  back  from  the  labial  to  the
palatine  surfaces,  and  not  transversely.  The  pivot,  after  the  filling  is
inserted,  is  drawn  out  of  the  cylinder,  which  remains  firmly  fixed  in
the  root,  and  that  part  of  the  cylinder  which  projects  beyond  the  gold
is  filed  down  to  a  level  with  the  surface  of  the  filling.  An  impression
of  this  surface  is  then  taken  with  wax  or  gutta-percha,  and  die  and
counter-die  made  of  fusible  metal,  by  iiieans  of  which  a  disk  of  plati-
num plate  is  swaged  to  fit  accurately  the  concave  surface  of  the  gold
filling  in  the  root.
"  When  this  is  done,  the  convex  surface  of  the  disk  is  thinly  covered
with  wax.  and  the  disk  placed  in  its  proper  position  over  the  gold  fill-


520       PREPARATION    OF    A    NATURAL    ROOT,    ETC.
