I. Shear Bond Strength to Air-dried and Remoistened Dentin.. The effect of air-drying and remoistening of acid-conditioned dentin before priming with the primer of All-Bond 2(BISCO. INC., U. S. A.) on shear bond strength(SBS) was investigated. Ninty freshly extracted sound human molars were divided at random into 9 groups of 10 teeth each. SBSs were meaured for acid-conditioned and non-conditioned dentin to which the primer and bonding agent of All-Bond 2 and composite resin(Z-100, 3M Dental Products, U. S. A.) were applied. The following values(Mean${pm}$ SD, MPa) were obtained for the groups conditioned with 10% phosphoric acid for 15 seconds: Group l(blot dried) $6.7{pm}4.1$ ; Group 2(10 seconds dried) $16.1{pm}5.3$ ; Group 3(20 seconds dried) $15.4{pm}4.8$ ; Group 4(30 seconds dried) $15.2{pm}6.3$ ; Group 5(10 seconds dried/remoistened) $26.4{pm}2.6$ ; Group 6(20 seconds dired/remositened) $22.2{pm}2.7$ ; Group 7(30 seconds dried/remoistened) $21.5{pm}4.1$. For the non-conditioned groups the values were: Group 8 (blot dried) $13.3{pm}2.6$ ; Group 9(10 seconds dried) $12.9{pm}3.5$. The data were analyzed using ANOVA. In the acid-conditioned groups, mean values of SBS for the air-dried specimens(Grps. 2, 3 and 4) and the 20 and 30 seconds dried/remoistened specimens (Grps. 6 and 7) were significantly lower than that of blot dried specimens.(p<0.05) The value for 10 seconds dried/remoistened specimens (Grp. 5), however, was not statistically different compared to that of blot dried specimens.(p>0.05) In the non-conditined groups, there was no statistical difference between blot dried and 10 seconds dried specimens.(p>0.05) The results suggest that the acid-conditioned dentin surface is more vulnerable to dentin bonding when it is air-dried or even remoistened after long period of drying. II. Shear bond stengh to the moistened and primed enamel. The effect of moistening and priming of enamel compared to the air-drying of enamel on the shear bond strength of enamel bonding agent was investigated. The experiment was divided into 4 groups each containing 10 caries-free maxillary incisor teeth. Shear bond strength values were measured for the primed and non-primed enamel to which All-Bond 2 and Z-100 were applied. The following values(MPa) were obtained for the primed groups pretreated with 32 % phosphoric acid for 15 seconds. : Group 1 (10 seconds dried) $29.8{pm}2.2$ ; Group 2(moistened) $26.8{pm}5.4$. For the non-primed groups the values were: Group 3(10 seconds dried/primed) $27.6{pm}5.0$ ; Group 4(mostened/primed) $28.2{pm}3.5$. The data were subjected to statistical analysis using ANOVA. The results showed that mean shear bond strengths among the experimental groups were not statistically different. (p>0.05) Conclusively, It is suggested that the bonding ability to enamel is not decreased by the moistening and priming of the enamel.