Introduction: One of the most important considerations in cavity preparation is undesirable encroachment to pulpo, that is sometimes evident and  touchable by catheter accompanied with bleeding and in some cases, it  is clinically unable to be distinguished. The dentist's  awareness of the remaining dentin thickness as well as presence or absence of microscopic exposures in the cavity can assist in selecting an appropriate treatment. The aim of this study was to determine the incidence of  pulp microexposures in deep class V cavities in the human premolars.

Methods: In this descriptive study, 30 human premolar teeth were used scheduled for extraction due to orthodontic reasons. After signing the consent form, deep class V cavities were prepared on the buccal surface of each tooth for amalgam restoration. Then the teeth were extracted and the roots as well as lingual portion of the teeth were sectioned. The samples were immersed in 2% methylene blue solution, then the presence or absence of microscopic exposure was evaluated in the axial wall using light microscopy. Besides, the remaining dentine thickness  was measured by a digital caliper. The study data were analysed using SPSS  software (ver, 16) via  ANOVA and T-test.

Results: Presence of microscopic exposure was confirmed in one tooth (3.2%), and the mean remaining dentin thickness in all samples was 0.67mm.

Conclusion: In 96.8% of deep class V cavities without clinical symptoms, about 0.67 mm of dentin remained, which may be regarded as a good criteria to predict remaining dentin thickness.