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Initial cavity preparation stage Step 1 Outline form and initial depth Step 3 Primary retention form Step 4 Convenience form
Initial cavity preparation stage Step 1 Outline form and initial depth Step 2 Primary resistance form Step 3 Primary retention form Step 4 Convenience form
Primary Resistance Form I Definition: The shape and placement of the cavity walls that best enable both the restoration and the tooth to withstand without fracture, masticatory forces delivered principally in the long axis of thethe tooth
Primary Resistance Form Ⅰ Definition: The shape and placement of the cavity walls that best enable both the restoration and the tooth to withstand, without fracture, masticatory forces delivered principally in the long axis of the the tooth
Primary Resistance Form I Principles I To utilize the box shape with a relatively flat floor to resist occlusal loading by virtue of being at right angles to mastication force; l To restrict the extension of the external walls(keep as small as possible)to allow strong cusp and ridge areas to remain with sufficient dentin support
Primary Resistance Form Ⅱ Principles: To utilize the box shape with a relatively flat floor to resist occlusal loading by virtue of being at right angles to mastication force; To restrict the extension of the external walls (keep as small as possible) to allow strong cusp and ridge areas to remain with sufficient dentin support;