EFFECT OF AIR-DRYING ON DEMINERALIZED AND ON SOUND CORONAL HUMAN DENTIN - A STUDY ON DENSITY AND ON LESION SHRINKAGE

Recently, several papers investigated the linear dimensional changes i n dentine after air-drying. This paper pertains to weight changes, vol ume changes, and density changes caused by air-drying of sound and dem ineralized intact dentine. The densities of sound and artificially dem ineralized human coronal dentine were measured in the wet state and af ter various drying periods of up to 24 h. The volume was assessed eith er by means of a pyknometer (wet samples) or by means of dimension mea surements. The air-drying experiments were done using a Mettler thermo balance at room temperature. The density of wet sound coronal dentine was found to be 2.24 +/- 0.12 g.cm(-3); the value of wet demineralized dentine was about 1.6 g.cm(-3). The data show that previously publish ed density values of powdered sound dentine may have been influenced b y powdering effects, air-drying, and air inclusion. In whole demineral ized air-dried dentine, air inclusion can be very severe: up to 30% by volume. The results show furthermore that in demineralized dentine we have two drying stages: during the first one (up to about 10 min of a ir-drying), the lesions shrink about 23%, while a main part of the wat er in the lesion evaporates, and air is incorporated into the tissue; during the second stage (drying longer than 10 min), the lesions hardl y shrink anymore, but water is evaporated mainly from underlying sound dentine, followed by air incorporation.