121
These questions are challenging because numerous combinations of blade shapes
can affect cutting effi ciency (Anderson and LaBarbera 2008 ). Additionally,
some aspects on the structural level must be taken into account. As discussed by
Frazzetta ( 1988 ).
“ The fl exible collagenous attachment of shark teeth may also facilitate cutting
during draw as the teeth may pivot anteroposteriorly around obstructions preventing
them from ‘hanging up’ on tough material. Tooth base overlap within the same jaw
may transmit forces to linked teeth, as overlapping bases are lashed together with
collagenous Sharpey’s fi bres, ” (Whitenack and Motta 2010 ).
In a recently published study, Whitenack and Motta ( 2010 ) investigated the
puncture and draw performance of tearing-type, cutting-type, and cutting–clutching
type of extant teeth from ten shark species in detail. Here, some selected results
from this study:
• “ Differences in puncturing performance occurred among different prey items;
• the majority of teeth were able to puncture different prey items;
• differences in puncture performance occurred among tooth types;
• broader triangular teeth were less effective at puncturing than narrow-cusped
teeth;
• no differences between the maximum draw forces and maximum puncture forces, ”
(Whitenack and Motta 2010 ).
During feeding sharks teeth undergo stress, strain, and potentially failure as results
of occasional extreme loads. Material properties of these teeth are also determined
by their chemistry and the micro- and nanostructure of the corresponding components. From anatomical view, shark teeth contain two zones: the crown and the root
or base. Shark teeth are typical examples of nanostructured biocomposites, “ with
two distinct structural components: a central core of dentine covered by enameloid,
an enamel-like substance formed from both odontoblasts and ameloblasts, ”
(Whitenack 2008 ).
Because of the lack of detailed knowledge, there are no doubts that the biomechanics as well as structural mechanics of the tooth itself and its biological
materials (enamel, dentine, cementum) must be studied using modern techniques
and approaches. For example, as determined by Whitenack et al. ( 2010 ) “ the hardness
of both osteodentine and orthodentine of sharks, are 125–181 % higher than the
petrodentine of both lungfi shes and 10–128 % higher than the dentine of mammals, ”
(Whitenack et al. 2010 ). Note that lungfi sh, which lack enamel, have petrodentine,
a specifi c hypermineralized dentine (Currey and Abeysekera 2003 ).
Performance testing of extant and extinct shark teeth, nanoindentation of shark
teeth, fi nite element analysis of tooth morphology, and phylogenetically informed
analyses of shark tooth morphology and ecology were employed to elucidate the
relationship between performance, ecology, and evolution in recent pioneering studies
by Whitenack and co-workers (Whitenack 2008 ; Whitenack et al. 2010 , 2011 ).
Finite element analysis (FEA) (Fig. 3.15 ) has been carried out to visualize stress
distributions of extant and fossil shark teeth during holding, cutting and puncture.
Following observations have been reported:
3.2 Teeth
These questions are challenging because numerous combinations of blade shapes
can affect cutting effi ciency (Anderson and LaBarbera 2008 ). Additionally,
some aspects on the structural level must be taken into account. As discussed by
Frazzetta ( 1988 ).
“ The fl exible collagenous attachment of shark teeth may also facilitate cutting
during draw as the teeth may pivot anteroposteriorly around obstructions preventing
them from ‘hanging up’ on tough material. Tooth base overlap within the same jaw
may transmit forces to linked teeth, as overlapping bases are lashed together with
collagenous Sharpey’s fi bres, ” (Whitenack and Motta 2010 ).
In a recently published study, Whitenack and Motta ( 2010 ) investigated the
puncture and draw performance of tearing-type, cutting-type, and cutting–clutching
type of extant teeth from ten shark species in detail. Here, some selected results
from this study:
• “ Differences in puncturing performance occurred among different prey items;
• the majority of teeth were able to puncture different prey items;
• differences in puncture performance occurred among tooth types;
• broader triangular teeth were less effective at puncturing than narrow-cusped
teeth;
• no differences between the maximum draw forces and maximum puncture forces, ”
(Whitenack and Motta 2010 ).
During feeding sharks teeth undergo stress, strain, and potentially failure as results
of occasional extreme loads. Material properties of these teeth are also determined
by their chemistry and the micro- and nanostructure of the corresponding components. From anatomical view, shark teeth contain two zones: the crown and the root
or base. Shark teeth are typical examples of nanostructured biocomposites, “ with
two distinct structural components: a central core of dentine covered by enameloid,
an enamel-like substance formed from both odontoblasts and ameloblasts, ”
(Whitenack 2008 ).
Because of the lack of detailed knowledge, there are no doubts that the biomechanics as well as structural mechanics of the tooth itself and its biological
materials (enamel, dentine, cementum) must be studied using modern techniques
and approaches. For example, as determined by Whitenack et al. ( 2010 ) “ the hardness
of both osteodentine and orthodentine of sharks, are 125–181 % higher than the
petrodentine of both lungfi shes and 10–128 % higher than the dentine of mammals, ”
(Whitenack et al. 2010 ). Note that lungfi sh, which lack enamel, have petrodentine,
a specifi c hypermineralized dentine (Currey and Abeysekera 2003 ).
Performance testing of extant and extinct shark teeth, nanoindentation of shark
teeth, fi nite element analysis of tooth morphology, and phylogenetically informed
analyses of shark tooth morphology and ecology were employed to elucidate the
relationship between performance, ecology, and evolution in recent pioneering studies
by Whitenack and co-workers (Whitenack 2008 ; Whitenack et al. 2010 , 2011 ).
Finite element analysis (FEA) (Fig. 3.15 ) has been carried out to visualize stress
distributions of extant and fossil shark teeth during holding, cutting and puncture.
Following observations have been reported:
3.2 Teeth