217
These as well as some salivary proteins and milk caseins have a common ancestor that arise by gene duplication to form the secretory calcium binding phosphoprotein (SCPP) family (Kawasaki et al. 2004 ), some representatives of which are
unusually acidic (Kawasaki 2011 ).
The difference between chemical content of fi sh teeth and scales’ enameloid
might be signifi cant. For example, presence of iron in some fi sh teeth enamelloid
has been reported (see for review Suga 1984 ; Motta 1987 ; Suga et al. 1989 , 1991 ).
Interestingly, that strong defi nition of enameloid is still absent, partially because
of diversity of this specifi c structure. The history of enameloid terminology was
discussed in the work by Baume ( 1980 ). Below are some examples of specifi c
enamelloids.
Coronoin is enameloid of elasmobranch fi sh (Bendix–Almgreen 1983 ). The
inner dental epithelium (IDE) cells play crucial role in development of this type of
enameloid. The detailed analysis of coronoin is given by Bendix-Almgreen and
Bang ( 1997 ). Scleroblasts during their ‘movement’ inwards in the dental papilla, are
responsible for deposition of collagen-rich pre-coronoin that is exclusively mesenchymatically derived. The change in shape of the IDE cells (they becomes elongated in the superfi cial direction) is performed synchronously with the phase of
pre-coronoin formation. These specialized cells secrete enamelin and some proteins
which participate in the degradation of the collagens, when coronoin forms out of
the pre-coronoin. The IDE cells are apparently also responsible for the supply of the
calcium constituents and even seem to participate in the removal of degraded collagens. During the fi rst steps of calcifi cation, biogenic HAP crystallite rudiments
are laid down in alignment with the partially degraded pre-coronoin collagen fi bres.
Here, the specifi c properties of the recent coronoin:
1. absence of collagen remains (similar to acrodin and enamel);
2. the mineral phase is represented by the carbonate-fl uorapatite crystallites;
3. the crystallites are oriented epitaxial to the original collagen fi bre-bundles of the
pre-coronoin (Bendix–Almgreen 1983 ).
In contrast to dentin, elasmobranch enameloid showed sharp diffraction peaks
which indicated a high crystallinity of the enameloid. The lattice parameters of
enameloid were close to those of the geological fl uoroapatite single crystal. The
inorganic part of shark teeth consisted of fl uoroapatite with a fl uoride content in the
enameloid of 3.1 wt.% (Enax et al. 2012 ). The enameloid in fi sh teeth is 4–5 times
harder than the dentine as has been recently evaluated by nanoindentation (Chen
et al. 2011 ).
Adameloid is the term of elasmobranch enameloid proposed by Sasagawa
( 2002 ): “the origin of ectodermal enamel is older than that of enameloid. It is therefore likely that the enameloid in elasmobranchs is not a direct precursor of the
ectodermal enamel in terrestrial vertebrates, but that enameloid is an analogous
structure to enamel,” (Sasagawa 2002 ; see also Smith 1995 ). Correspondingly,
Sasagawa introduced the specifi c term for this enameloid of the elasmobranchs as
“ adameloid ”.
4.1 Enamel and Enameloid
These as well as some salivary proteins and milk caseins have a common ancestor that arise by gene duplication to form the secretory calcium binding phosphoprotein (SCPP) family (Kawasaki et al. 2004 ), some representatives of which are
unusually acidic (Kawasaki 2011 ).
The difference between chemical content of fi sh teeth and scales’ enameloid
might be signifi cant. For example, presence of iron in some fi sh teeth enamelloid
has been reported (see for review Suga 1984 ; Motta 1987 ; Suga et al. 1989 , 1991 ).
Interestingly, that strong defi nition of enameloid is still absent, partially because
of diversity of this specifi c structure. The history of enameloid terminology was
discussed in the work by Baume ( 1980 ). Below are some examples of specifi c
enamelloids.
Coronoin is enameloid of elasmobranch fi sh (Bendix–Almgreen 1983 ). The
inner dental epithelium (IDE) cells play crucial role in development of this type of
enameloid. The detailed analysis of coronoin is given by Bendix-Almgreen and
Bang ( 1997 ). Scleroblasts during their ‘movement’ inwards in the dental papilla, are
responsible for deposition of collagen-rich pre-coronoin that is exclusively mesenchymatically derived. The change in shape of the IDE cells (they becomes elongated in the superfi cial direction) is performed synchronously with the phase of
pre-coronoin formation. These specialized cells secrete enamelin and some proteins
which participate in the degradation of the collagens, when coronoin forms out of
the pre-coronoin. The IDE cells are apparently also responsible for the supply of the
calcium constituents and even seem to participate in the removal of degraded collagens. During the fi rst steps of calcifi cation, biogenic HAP crystallite rudiments
are laid down in alignment with the partially degraded pre-coronoin collagen fi bres.
Here, the specifi c properties of the recent coronoin:
1. absence of collagen remains (similar to acrodin and enamel);
2. the mineral phase is represented by the carbonate-fl uorapatite crystallites;
3. the crystallites are oriented epitaxial to the original collagen fi bre-bundles of the
pre-coronoin (Bendix–Almgreen 1983 ).
In contrast to dentin, elasmobranch enameloid showed sharp diffraction peaks
which indicated a high crystallinity of the enameloid. The lattice parameters of
enameloid were close to those of the geological fl uoroapatite single crystal. The
inorganic part of shark teeth consisted of fl uoroapatite with a fl uoride content in the
enameloid of 3.1 wt.% (Enax et al. 2012 ). The enameloid in fi sh teeth is 4–5 times
harder than the dentine as has been recently evaluated by nanoindentation (Chen
et al. 2011 ).
Adameloid is the term of elasmobranch enameloid proposed by Sasagawa
( 2002 ): “the origin of ectodermal enamel is older than that of enameloid. It is therefore likely that the enameloid in elasmobranchs is not a direct precursor of the
ectodermal enamel in terrestrial vertebrates, but that enameloid is an analogous
structure to enamel,” (Sasagawa 2002 ; see also Smith 1995 ). Correspondingly,
Sasagawa introduced the specifi c term for this enameloid of the elasmobranchs as
“ adameloid ”.
4.1 Enamel and Enameloid