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218 THE TECHNICS. PROCEDtTKES IN FILLING TEETH.

incisor, or the lingual horn of an upper molar; in each case
probably the individual horn of the pulp was unusually long
and was caught early in the wear.
With the abrasion and loss of vitality in the tooth crown,
there is also a loss of strength of the dentin, and the attaclunent
of the enamel to the dentin becomes enfeebled. This fact is
important in undertaking tilling operations in these teeth. The
same thing occurs in teeth in which the pulp has been long dead.
In either case, fillings need to be more securely anchored than
in living dentin.
'\Mien teeth become badly worn, the enamel margin around
the worn area often has worn much less than the dentin. This
enamel is then liable to split olf under the force of mastication
and become ragged and rough. Sometimes this will give trouble
by cutting and irritating the lips, cheeks or tongue ; and to rem-
edy the evil, it should be ground with a stone, removing the
rough edges, and then it should be iiolished with a disk.
Often the abrasion is very uneven on the different parts of
the teeth. Frequently the occlusion is such that the wear comes
mostly on the buccal cusps of the lower teeth and the lingual
cusps of the upper teeth. Normally the upper incisors overlap
the lower and the result at first is wear from the labial of the
lower and the lingual of the upper incisors. If the wear of the
molars allows the jaws to close more, or shortens the teeth
generally, the occlusion of the front teeth tends to come directly
end to end, by the movement of the lower jaw forward as it closes
more. At the same time, it often happens that in the molars and
bicuspids the abi'asion becomes more and more one-sided on the
individual teeth. The lower molars and bicuspids are worn on
the buccal sides, while the upper are worn on their lingual sides.
This will go on until the shape of the occlusal surfaces are such
that the teeth slide together instead of meeting with each other
squarely in occlusion. This occasionally places the patient in
bad condition for mastication of food.
Treatment of abrasion. Not much can be done for this con-
dition. It has not seemed to be very amenable to treatment.
Some effort has been made, but it seems, from a review of the
literature, that this has been rather spasmodic and without suflS-
cient observation and discussion to develop reliable plans of
procedure. This subject needs further study and reports of
results, with models made when the work is undertaken, when
it is finished, and after five, ten and fifteen years of usage, in
order to arrive at satisfactory conclusions regarding the advan-