Page 282 - My FlipBook

is but one, except as buccal pits in some of the molars fur-
nish a second. Therefore, if the liability were equal the
proximate cavities would be double the numl^er of either
the first or second classes.
These are all smooth surface cavities; that is, they occur
'in surfaces on which the enamel of the tooth is perfect and
smooth, presenting neither fissures, pits nor grooves, which
serve as starting points for decay. The conditions are there-
fore radically different from those presented in pit and fis-
sure cavities. The beginnings of decay in these smootli sur-
faces is not confined to a single minute point in the enamel^
as when beginning in pits and fissures, but the surface of the
lenamel is attacked and the area will be great or small, coin-
ciding with the local areas of liability occasioned by un-
cleanness. The close examination of a large number of
cases shows that this depends mainly upon the forms of
the proximate surfaces. When these are well rounded, the
contact points small and the embrasures wide and deep, de-
cay is less apt to occur and its beginning is confined to a
narrower area of surface or possibly to a small point, while
if the proximate surfaces are flat, the contacts broad and
the embrasures shallow, decay is more liable to occur and
the area of enamel surface attacked will be proportionately
broad. Other things being equal, this matter of forms of
the surfaces, their contact points and the depth of the em-
brasures control the cleanliness of these surfaces and their
liability to decay. All of this will be modified by the degree
of susceptibility to decay and by personal cleanliness. The
susceptibility of the person will constantly be the principal
factor, modified and controlled to some extent by the con-
ditions above detailed. At the present time we are unable
to control in any direct way this principal factor—suscepti-
bility ; in prophylactic treatment our attention must be di-
rected to the removal, modification or improvement of those
^conditions giving opportunity for its manifestations.
The key to the rules of management in these classes of
cases is found by noting these conditions, and in the study
of the influences they exert for limiting, increasing or modi-
fying the opportunities for the beginning of caries.
The forms of the areas of liability to decay are different
in the molars and bicuspids from the forms presented in the

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