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DEVELOPMENT OF COED FOB PERMANENT TEETH. 649
is this invariably the result of an impacted tliircl molar. The fact that
the third molars are developed during the period of childhood and
youth and while the system is liable to frequent conditions which impair
nutrition is probably one potent reason for their frequent lack of useful-
ness and durability.
" The decalcification or absorption of the roots of the deciduous teeth
is illustrated as far as practicable by Fig. 3, and in this eifort your
essayist has found it extremely difficult to do more than approximate
the time at which this interesting and somewhat obscure physiological
process is carried on. The avei-age period at M'liich it commences Mill
be sufficient to indicate the time when much care will be necessary in
the application of the arsenical paste for the devitalization of the pulp,
and in the subsequent treatment of the pulp-chamber and root-canal.
This process, usually commencing in the incisors before the close of the
fourth year, progresses gradually, when normally accomplished, from
the extreme end of the root toward the crown for about three years,
and usually releases this deciduous crown between the seventh and
eighth years, the central incisor being some months in advance of the
lateral. The absorption of the roots of the first deciduous molars may
be placed a year later than that of the lateral incisors, commencing
about the middle or close of the sixth year and terminating with the
removal of the first deciduous molars, about the tenth year, the second
molars following usually some months or a year later. The cuspids
invariably the last of the deciduous teeth to be shed—have their period
of absorption from the eighth to the twelfth year. AVhile these periods
would correspond with the absorption and removal of the teeth in the
average mouth, so variable are they in different families that many
would be widely different from the above figures.
"I have just spoken of this absorptive process as being physiological
and somewhat obscure. It certainly is both, and, in contradistinction
to the evolution of the tooth, may be termed its dissolution
What induces this molecular dissolution it is difficult to state, though
the several conditions which are always present are readily recognized ;
but the part they play is so obscure that it is not readily ascertained.
The manner of its commencement when successful—always at the end
of the root—and the presence of a vascular papilla in close proximity
to the absorbing surface are, with the retention of pulp-vitality, three
essential accompaniments, and the absence of any one of them would
militate against the completion of the process.
" The statement that the presence and pressure of the permanent
tooth are essential cannot be sustained, for frequently the decalcification
of the deciduous tooth is successfully accomplished in the absence of its
successor ; and again, how often do we find the permanent tooth im-
pacted against or within the bifurcated roots of the deciduous molar, or
pressing down by the side of its single-rooted predecessor, both being
more or less displaced by the persistence of the deciduous tooth without
absorption ! That the organ has served its purpose, and that the nour-
ishment which had previously been appropriated by it is diverted or
relegated to its successor, is probably the most plausible explanation we
can give of this interesting physiological process.
DEVELOPMENT OF COED FOB PERMANENT TEETH. 649
is this invariably the result of an impacted tliircl molar. The fact that
the third molars are developed during the period of childhood and
youth and while the system is liable to frequent conditions which impair
nutrition is probably one potent reason for their frequent lack of useful-
ness and durability.
" The decalcification or absorption of the roots of the deciduous teeth
is illustrated as far as practicable by Fig. 3, and in this eifort your
essayist has found it extremely difficult to do more than approximate
the time at which this interesting and somewhat obscure physiological
process is carried on. The avei-age period at M'liich it commences Mill
be sufficient to indicate the time when much care will be necessary in
the application of the arsenical paste for the devitalization of the pulp,
and in the subsequent treatment of the pulp-chamber and root-canal.
This process, usually commencing in the incisors before the close of the
fourth year, progresses gradually, when normally accomplished, from
the extreme end of the root toward the crown for about three years,
and usually releases this deciduous crown between the seventh and
eighth years, the central incisor being some months in advance of the
lateral. The absorption of the roots of the first deciduous molars may
be placed a year later than that of the lateral incisors, commencing
about the middle or close of the sixth year and terminating with the
removal of the first deciduous molars, about the tenth year, the second
molars following usually some months or a year later. The cuspids
invariably the last of the deciduous teeth to be shed—have their period
of absorption from the eighth to the twelfth year. AVhile these periods
would correspond with the absorption and removal of the teeth in the
average mouth, so variable are they in different families that many
would be widely different from the above figures.
"I have just spoken of this absorptive process as being physiological
and somewhat obscure. It certainly is both, and, in contradistinction
to the evolution of the tooth, may be termed its dissolution
What induces this molecular dissolution it is difficult to state, though
the several conditions which are always present are readily recognized ;
but the part they play is so obscure that it is not readily ascertained.
The manner of its commencement when successful—always at the end
of the root—and the presence of a vascular papilla in close proximity
to the absorbing surface are, with the retention of pulp-vitality, three
essential accompaniments, and the absence of any one of them would
militate against the completion of the process.
" The statement that the presence and pressure of the permanent
tooth are essential cannot be sustained, for frequently the decalcification
of the deciduous tooth is successfully accomplished in the absence of its
successor ; and again, how often do we find the permanent tooth im-
pacted against or within the bifurcated roots of the deciduous molar, or
pressing down by the side of its single-rooted predecessor, both being
more or less displaced by the persistence of the deciduous tooth without
absorption ! That the organ has served its purpose, and that the nour-
ishment which had previously been appropriated by it is diverted or
relegated to its successor, is probably the most plausible explanation we
can give of this interesting physiological process.
