In order to find a substitute for human teeth in the adhesion test, the adhesive strength to bovine teeth was compared with that to human teeth using five dental cements and two composite resins. The adhesion to enamel and the superficial layer of dentin showed no statistically significant difference between human and bovine teeth, although the mean values were always slightly lower with bovine teeth. Adhesion to bovine dentin decreased considerably with the depth of dentin.

The ultrastructure of the transparent layer of carious dentin was investigated in relation to hardness. This layer was the deeper part of the intermediately-softened inner carious dentin. Intratubular deposition of fine crystals was initially observed at the uppermost layer of normal dentin, increased in the subtransparent layer, and gradually shifted to deposition of rhomboid-shaped crystals in the transparent layer. Crystals were not seen in the tubules in the overlying discolored layer. Softening, due to demineralization of the intertubular and peritubular dentin, started at the bottom of the subtransparent layer and increased in the outward direction.

Non-pressure adhesion of a new adhesive restorative resin was investigated employing a new tensile test. The material was adhesive to both enamel and dentin as well as to carious dentin and showed strong adhesion to all substrates tested. Etching further increased the adhesion even to dentin.

SYNOPSIS IN INTERLINGUA LE RELATION INTER LE DURITATE, LE DISCOLORATION, E LE INVASION MICROBIAL IN DENTINA CARIOSE.-Frescamente extrahite dentes con carie esseva dissecate verticalmente. In un del partes le superficie sectional esseva examinate pro duritate secundo Knoop e discoloration. Sectiones histologic del altere parte esseva usate pro le detection de evidentia microbiotic. Le resultatos esseva le sequentes: In dentina cariose, mollification precedeva in omne casos le discoloration, e invasion microbial esseva semper le tertie stadio. Le duritate de dentina in le fronte discolorate o microbial esseva inferior in casos acute e superior in casos chronic. Le distantia inter ille frontes e le fronte de mollification esseva plus grande in casos acute e plus micre in casos chronic.

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