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120 PREPARATION OF CAVITIES
Owing to the conditions under which operations are per-
formed in the mouth, it is not always possible or advisable to
extend cavity margins as described under the law of extension
for prevention. The conditions which may modify this opera-
tion are the following:
1. A family history of lack of susceptibility to caries.
2. A personal history of similar non-susceptibility.
3. Presence of a period of immunity.
4. Lowered vitality from sickness, convalescence, preg-
nancy, adolescence and similar causes.
5. Personal habits of cleanliness.
6. Lack of will power and low mentality.
7. Perfect habits of mastication.
8. Abundance of food in the dietary requiring adequate
mastication.
9. Normal, freely-flowing salivary secretion, nature's
flushing agent.
10. Regularly aligned arches.
11. Youth and old age, these conditions frequently not
admitting of extensive operations.
Cavity margins may frequently be placed in immune
areas by separating the teeth and building fillings out to full
contour, thus drawing labial, buccal and lingual margins
away from each other. This procedure often obviates the
necessity for extensive cutting of tooth structure.
Drawings
i
Draw the typical outline form of the following cavities.
1. Fissure cavity on the occlusal surface of 4 or 5 running
full length of the occlusal groove (Fig. 126).
2. Pit and fissure cavity on the occlusal surface of~4and
5, occupying the mesial and distal pit in 4 and running full
length of the groove in 5 (Figs. 127 and 128). In 5 there are
II
Owing to the conditions under which operations are per-
formed in the mouth, it is not always possible or advisable to
extend cavity margins as described under the law of extension
for prevention. The conditions which may modify this opera-
tion are the following:
1. A family history of lack of susceptibility to caries.
2. A personal history of similar non-susceptibility.
3. Presence of a period of immunity.
4. Lowered vitality from sickness, convalescence, preg-
nancy, adolescence and similar causes.
5. Personal habits of cleanliness.
6. Lack of will power and low mentality.
7. Perfect habits of mastication.
8. Abundance of food in the dietary requiring adequate
mastication.
9. Normal, freely-flowing salivary secretion, nature's
flushing agent.
10. Regularly aligned arches.
11. Youth and old age, these conditions frequently not
admitting of extensive operations.
Cavity margins may frequently be placed in immune
areas by separating the teeth and building fillings out to full
contour, thus drawing labial, buccal and lingual margins
away from each other. This procedure often obviates the
necessity for extensive cutting of tooth structure.
Drawings
i
Draw the typical outline form of the following cavities.
1. Fissure cavity on the occlusal surface of 4 or 5 running
full length of the occlusal groove (Fig. 126).
2. Pit and fissure cavity on the occlusal surface of~4and
5, occupying the mesial and distal pit in 4 and running full
length of the groove in 5 (Figs. 127 and 128). In 5 there are
II
