OPD 2 lecture 1

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GV black 7 steps in cavity preparation

• establish outline form

• obtain resistance form

• obtain retention form

• obtain convenience form

• remove carious dentin

• finish enamel walls and cavosurface margin

• cleaning the preparation

outline form (class1)

• all pits and major developmental grooves are included

• preparation is centered on the central groove

• presence of graceful curves and smooth flowing lines

• lateral extension are correctly placed

• mesial and distal walls follow the crest of the marginal ridge ( or external tooth contour

retention form (class 1)

• presence of mesial and distal occlusal dovetails

• buccal and lingual walls are slightly convergent occlusally(but not the mesial an distal walls which are slighty divergent occlusally)

• there are undercuts on the buccal and lingual walls (none on mesial and distal walls)

outline form class 2

• all pits and major developmental grooves are included

• preparation is centered on the central groove.

• presence of graceful curves and smooth flowing lines

• lateral extension are correctly placed if indicated

• mesial and distal walls follow the marginal ridge crest ( or the external tooth contour)

• presence of reverse curve (or S currve) on the buccal proximal wall

• proximal wall (buccal, lingual, and gingival) clearance is 0.25 to 0.5mm from the adjacent tooth

• axial wall parallel the gingival cavosurface margin of DEJ and slightly convergent occlusally by 2-3 degrees to the long axis of the crown

resistance form class 2

• floors are flat and smooth

• pulpal depth is 0.5 to 1.0 mm from DEJ (1.5mm-2.0mm) for plastic tooth measured from the gingival cavosurface margin to the axiogingival line angles

• isthmus width is ¼ tje intercuspal distance

• mesial or distal wall is slightly divergent occlusally and is halfway between corresponding marginal ridge crest and pit

• axiopulpal line angle is beveled or rounded

• line and point angles are rounded and defined

• gingival floor is horizontal and is perpendicular to the long axis of the crown is about 1.0mm above the gingival margin

retention form class2

• presence of occlusal dovetail

• there are undercuts on the buccal and lingual walls none on the mesial and distal walls

• buccal and lingual walls are slightly convergent occlusally

• retention grooves on the Axio buccal and axio lingual line angles

convenience form class 2

• sufficient extension of distal, mesial, facial or lingual walls to gain adequate access to the deeper portion of the preparation

• cavosurface margin of the preparation should be related to the selected restorative material for the purpose of convenience and marginal adaption

• in class II preparation access is made through occlusal surface for convenience form

• proximal clearance is provided from the adjoining tooth during class II tooth preparation

• to make class II tunnel preparation for convenience the proximal caries in posterior teeth is approached through a tunnel initiating from the occlusal surface and ending on carious lesion on the proximal surface without cutting the marginal ridgen