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Principles of resistance form based on physical properties of various part of tooth.
Features: A) Occlusal surface: -
Flat pulpal floor (fig 6-29).
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Divergence of walls towards marginal ridge.
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Perpendicular walls towards crossing ridge.
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Facial and lingual walls should be perpendicular to isthmus.
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Occlusal ledging.
Other features of resistance: 1. Relatively flat floors i.e. pulpal floor, gingival seat. 2. Box shape cavity: To provide definite line angles and point angles. 3. Inclusion of weakened tooth structure. 4. Preservation of cusps and ridges. It is provided by following features -
Reverse curve.
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