A text-book of dental histology and embryology, including laboratory directions . e wall may be in the axial plane;if it has reached B, the wall must be inclined as indicated by the dotted line.(About 30 X) 132 AREAS OF WEAKNESS FOR ENAMEL MARGINS Figs. 98, 99, and 100 show the distal marginal ridge in a sec-ond molar. Notice the inclination of the rods from the tip ofthe dentine ridge. If decay has reached this point the wall Fig. 97 ;;^xv: JwKK <«»,afliBg^B Br. ? *jP- r • -?? ^•^^wHHpUte - iff A higher magnification of Fig. 96, showing enamel rod directions in the regionof the marginal ri
A text-book of dental histology and embryology, including laboratory directions . e wall may be in the axial plane;if it has reached B, the wall must be inclined as indicated by the dotted line.(About 30 X) 132 AREAS OF WEAKNESS FOR ENAMEL MARGINS Figs. 98, 99, and 100 show the distal marginal ridge in a sec-ond molar. Notice the inclination of the rods from the tip ofthe dentine ridge. If decay has reached this point the wall Fig. 97 ;;^xv: JwKK <«»,afliBg^B Br. ? *jP- r • -?? ^•^^wHHpUte - iff A higher magnification of Fig. 96, showing enamel rod directions in the regionof the marginal ridge. must be inclined distally, so as to reach the rod direction,or a frail margin will be left and one which will not sustainthe force of mastication. Neglected caries in the lingual AREAS OF WEAKNESS FOR ENAMEL MARGINS 133 pits of incisors often present the same conditions. Fig. 65shows a section through such a pit in a lateral incisor, andFig. 66 shows the gingival wall. If this were prepared byinclining the gingival wall only slightly, a very frail wall Fig. 98. An upper molar, showing the position of the section shown in Figs. 99 and 100. Fig. 99 ?J{ ?-? ?Hi o ia*ys ^^H I^HH^B The section ground from Fig. 98. would be left. It should be cut down to the horizontal plane,as indicated, and the marginal ridge restored by the fillingmaterial. The same conditions are often encountered inthe preparation of simple cavities in the mesial or distalsurfaces of incisors, when caries has followed the dento- 134 AREAS OF WEAKNESS FOR ENAMEL MARGINS Fig. 100
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
