Table Of ContentNothing but the Tooth
Nothing but the Tooth
A Dental Odyssey
Barry K.B. Berkovitz
Emeritus Reader in Anatomy,
School of Biomedical Sciences,
King’s College London,
London, UK
AMSTERDAM(cid:1)BOSTON(cid:1)HEIDELBERG(cid:1)LONDON(cid:1)NEWYORK(cid:1)OXFORD
PARIS(cid:1)SANDIEGO(cid:1)SANFRANCISCO(cid:1)SINGAPORE(cid:1)SYDNEY(cid:1)TOKYO
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Dedication
To my namesake Kenneth Bradbury (cid:1) killed in the defence of Teruel, Spain in
1938,duringtheSpanishCivilWar,aged17.
BarryKennethBradburyBerkovitz
Acknowledgements
Iamextremelygratefultothefollowingfortheirhelpandconstructivecriticism:
Dr S.R. Berkovitz (Chapter 1), Dr R.P. Shellis (Chapters 2 and 9), Professor
C.S.C. Liu (Chapter 5), Dr N. Sahara, (Chapter 8), Professor P.-I. Branemark
(Chapter 10),Professor R. Palmer (Chapter 10),Professor M.C.Dean(Chapter 13),
Ms M. Farrell (Chapters 12 and 16) and my wife, Sylvia, for her assistance
throughout.
My special thanks to Mr M. Simon for his invaluable help with all the images
andillustrations.
BarryK.B.Berkovitz
Preface
Iretiredin2005afterspendingover40yearsteachingandresearchingthestructure
and function of teeth. Over that time, I have amassed a collection of information
that I thought might be of interest to a wider audience. I imagined that at some
stage someone surely would ask me to give a talk on the subject. Having time on
my hands, I decided to go ahead and prepare a non-clinical, illustrated, 45-min talk
demonstratinghowenjoyablethesubjectcouldbe.ThefirstthingIdidwastowrite
out a list of topics. However, when I looked at it, I realised that I was ignorant of
much of the finer detail of the subject matter and would have to spend time mug-
ging it up. Four years later, I finally finished preparing my talk, but as yet I have
not been invited to deliver it. Therefore, I decided to publish it in the form of this
book. If each reader finds at least one topic of interest, I will feel that my efforts
havenotbeeninvain.
BarryK.B.Berkovitz
London,June2012
About the Author
Dr Barry K.B. Berkovitz is an internationally recognised teacher, examiner and
researchworker inthe field ofdentistry, with over 40 years’ experience. This is his
14th book and he has written well over 120 major scientific articles. He qualified
at the Royal Dental Hospital, London, and undertook postgraduate research at
Royal Holloway College. He subsequently taught at the University of Bristol and
King’s College London. He is the Honorary Curator of the Odontological
Collection at the Hunterian Museum of the Royal College of Surgeons of England
and an Honorary Research Associate in the History of Dentistry Unit at the Dental
Institute,King’sCollegeLondon.
1
The Jaws of the Piranha
Natural History of the Piranha
The name ‘piranha’ conjures up an image of a steaming Amazon River in which a
hapless animal straying into it suddenly disappears underwater in a broiling mass
of blood. A few minutes later, all is calm (cid:1) the only trace remaining of the animal
is a skeleton clinically stripped of its flesh. This was the type of description given
by U.S. President Theodore Roosevelt in his 1914 book Through the Brazilian
Wilderness. He stated ‘They will snap the finger off a hand incautiously trailed in
the water...They are the fish that eats men when it can get the chance...Blood in
the water excites them to madness...’. However, this spectacle could have been
purposely orchestrated for him with a shoal of piranhas held in the river without
food for some time. This episode convinced Roosevelt that piranhas are ‘the most
ferociousfishintheworld’.
The fearsome reputation of the piranha is matched today only by that of the
greatwhite shark, allthe moreimpressive given thepiranha’s diminutive size(usu-
ally between 15 and 25cm in length; Figure 1.1) compared to several metres of
shark.Unliketheshark,piranhasusuallyattackpreylargerthanthemselves.
The piranha’s aggressive image has proved highly marketable, giving its name
to, among other things, a thirst-slaying, fizzy drink with its ‘bone-crushing citrus’
(Figure 1.2); a U.S. women’s ice hockey team, the ‘Pittsburgh Piranhas’; and two
well-knownrockbands.
Piranhas have also inspired Hollywood. In the 1978 cult horror film Piranha, a
shoal of piranhas, genetically engineered by the military to be oversized, fast-
breeding and flesh-crazy, is accidentally released into a river leading to a holiday
resort, with predictably gory results. In the 2010, 3-D film Piranha, a shoal of pir-
anhas thought to be extinct for over 2 million years is released from an under-
ground lake into a river following an earthquake. They reach a town where a large
number of teenagers, swimming in the river, meet with a violent end. In the James
Bond film You Only Live Twice, supervillain Ernst Stavro Blofeld feeds one of his
femaleagentstohispetpiranhasasapunishmentforfailingtokillBond.
Much ferocious piranha behaviour has been wildly exaggerated. Of the more
than 30 different species, many do not kill other fish, but merely ‘graze’ off them,
taking small pieces of the fin orscales,which will later regenerate. Some are vege-
tarians. Only a few species are considered fierce and aggressive. Attacks on
humans are extremely rare, and deaths are virtually unknown. Amazonian children
swim quite safelyinstreams andriversinhabited by piranhas,ashas the occasional
NothingbuttheTooth.DOI:http://dx.doi.org/10.1016/B978-0-12-397190-6.00001-8
©2013ElsevierInc.Allrightsreserved.
2 NothingbuttheTooth
Figure1.1 A19-cmlong
piranhashowingthegeneral
bodyfeatures.Notethedeep-
bodiedoutline,theforward-
juttinglowerjawandthewide
gapeofthejaws.
Figure1.2 Acancontainingafizzydrink
calledPiranhawiththelogo‘bone-crushing
citrus’.
intrepid, documentary filmmaker. A recent exception occurred in 2002 in southeast
Brazil, where over 50 attacks were recorded (the most serious requiring a toe
amputation). This unusual aggression seemed to be a consequence of damming the
local river for flood protection, resulting in a large number of understandably
irritablepiranhas beingtrappedinthestillwaters, compared withtheflowing white
watersoftheirnativeenvironment.
The giant feeding frenzy is also a myth: some piranhas hunt individually,
whereas shoals typically contain only 20(cid:1)30 individuals. Piranhas tend to pair up
when swimming in shoals, and if there is an odd number of fish, the unlucky
unpaired single one may be eaten by its fellows. Although previously regarded as
TheJawsofthePiranha 3
an attacking strategy, recent research has suggested that shoaling behaviour may
alsorepresentadefenceagainstpredators(i.e.safetyinnumbers).
PiranhasarebonyfishbelongingtothegenusSerrasalmus,meaningsawsalmon
and referring not to the teeth but to the notched appearance of the enlarged scales
running in the midline across the belly. The origin of the word piranha is uncertain
but may be derived from a local Amazonian tribal word meaning either toothed
fishorscissors.Insupportofthelatter,piranhajawsareusedascuttingorshearing
tools,evenbeingemployedtocuthairortosharpenpoisonousdarts.
Although their main prey is other fish, piranhas are opportunistic and will eat
whatever is available. Analysis of their stomach contents reveals insects, crusta-
ceans, molluscs, lizards and rodents. As the rivers flood into the forests, piranhas
incorporate seeds and other vegetable matter into their diet. Like carnivorous pre-
dators on the African savannah, piranhas seek out and dispatch the weak and
injuredanimalsinAmazonianrivers.Theirextremesensitivitytothescentofblood
helps them in this pursuit. Birds, such as young herons and egrets, falling from
theirnestsintotheriverbelowsupplementthepiranhadiet.
Piranhas themselves have many predators such as larger fish, birds, caiman,
freshwater dolphins, turtles and the indigenous people. A new tourist attraction of
piranha fishingisbeingpromoted.Inthedryseason,piranhasmaybecomeconcen-
trated in isolated, shrinking, shallow pools that provide particularly rich pickings
forfish-eatingbirds(includingherons).
Teeth of the Piranha
The success of piranhas in obtaining food depends not only upon cooperating as a
pack, like wolves, but also in their possession of an extremely specialised set of
teeth. The unique arrangement of their teeth makes the piranha very effective as a
predator. Whereas the majority of fish have large numbers of teeth (in many
instances reaching a hundred or more, as in the barracuda; see Figure 4.10), the
piranha has an upper row of only six and a lower row of seven on each side, and
thisnumberis retained throughout theirlife. Unlikemostfish,whoseteethare con-
ical and spaced out (Figure 1.3), piranha teeth are sharp, triangular, narrow and
bladelike with razor-sharp edges and are in contact with each other (Figures 1.4
and 1.5). In addition to the central, prominent, main cusp, there is a small cusp at
Figure1.3 Theteethofthe
short-nosedgarfish.Notethe
largenumberofspaced,conical
teeth,withgapsalongthe
dentitionwherereplacingteeth
willsoonerupt.
Source:Courtesyofthe
HunterianMuseumattheRoyal
CollegeofSurgeons.
