. The Dental cosmos. ods of reten-tion, but I would like to call your at-tention to a few points in regard to un-dercuts in inlays and cavities which havebeen brought out by Dr. H. W. in his book on The MetallicInlay. Dr. Bodecker states that inusing undercuts for the retention of , the undercuts in the inlay shouldbe, if possible, directly opposite those inthe cavity in order to best take advantage of the compression strength of thecement. In considering the advantageof undercuts for retention, Dr. Bodeckerclaims that the strength of the anchoragedepends upon the thickness
. The Dental cosmos. ods of reten-tion, but I would like to call your at-tention to a few points in regard to un-dercuts in inlays and cavities which havebeen brought out by Dr. H. W. in his book on The MetallicInlay. Dr. Bodecker states that inusing undercuts for the retention of , the undercuts in the inlay shouldbe, if possible, directly opposite those inthe cavity in order to best take advantage of the compression strength of thecement. In considering the advantageof undercuts for retention, Dr. Bodeckerclaims that the strength of the anchoragedepends upon the thickness of the cementin the opposing undercuts, and theamount of crushing stress it will contends that the resistance offeredby the compression strength is muchgreater than that offered by the tensilestrength of the cement, and that thestrongest anchorage can be obtained bygetting the undercuts in accurate rela-tionship, as above stated. In the accompanying diagram, pat-terned after Dr. Bodecker, we may ob- serve the advantage of securing this ap-position of undercuts. The dark linesrepresent an inlay, the lighter ones thecavity Avail, and it is evident that thefarther away the undercuts in the inlayare from those in the cavity wall the lesswe are taking advantage of the com-pression strength, and the more we aredepending upon the tensile strength andadhesiveness of the cement. Dr. Bod-ecker admits the difficulty of gettingthe undercuts in exact apposition, andsays the same results may be obtainedby a further or more general excavationof the cavity walls, thus thickening thelayer of cement and obtaining a moreuniform distribution of pressure. If Dr. Bodeckers premises are correct,it is manifest that such an anchorage asis represented in Fig. 1 would be muchmore effectual than those represented in STARR. CAVITY PREPARATION FOR I N LA Y>. 283 Figs. 2, 3, and 4. In Figs. 3 and 4, theundercuts are comparatively useless,since the cement in the cavity undercutswill not
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