I think that is most unfair.  There are demonstrable changes in dental
techniques based on accumulated clinical experience and new research in
just about every area of dentistry.  As far as bacteria seeping into the
system from root canals or other dental procedures, bacteremia secondary
to dental treatment has been studied for many years.  Most of the known
sequellae have been demonstrated from surgical procedures.  Here we are
generally following the recommendations of the American Heart
Association, who continue to update their recommendations  for treating
patients with various cardiac maladies.  The other area of concern is
with prosthetic orthopedics, and they generally piggy-back on the AHA
recommendations.
    There is no question that bacteria enter the dentinal tubules, and that
there always exists the theoretical risk of seeding bacteria into the
circulation.  In fact, the much greater risk seems to be periodontal
disease, in which the hematogenous spread is directly into the
bloodstream.  Of course, periodontal bacteria also infect the dentin,
and this has been demonstrated.  I don't know if Dr. Meinig had any
objections to periodontally-involved teeth, but there is no doubt in my
mind that even in clinically healthy mouths, oral bacteria will enter
any exposed dentin and cementum.  They also enter the body through
extraoral injury, food, drink, bodily contact, respiration.  Some of
these challenges are well-tolerated by the healthy patient--some are not.
    There are root canals that are successful; one could argue about the
criteria for success.  But Meinig is very, very old news.  The surgeons
would probably not mind if his ideas became popular again; it would help
the implant business.  It wouldn't hurt the restorative dentists either.
 I'm not too worried about the endodontists though; these hoary ideas
have been discredited very long ago.  It becomes tiresome fighting the
same old fights.  Of course, patients may choose to extract their teeth.
 This is after all an elective procedure.

Steve