Capacity of coronal dentin to increase fiberglass post retention: a pull-out test.

Purpose: To evaluate the capacity of residual dentin in the coronal part of the root canal to increase the retention of serrated fiberglass posts (Extra-glass P-6%). Methods: 40 freshly-extracted maxillary central incisors were randomly and evenly divided into four test groups (TGs) with no (TG0), one (TG1), two (TG2) and three (TG3) coronal walls, respectively. After shaping, the canals were filled with gutta-percha and prepared to receive fiberglass posts. Coronal wall dentin was etched with 38% phosphoric acid for 60 seconds, rinsed, and dried. Dentin bonding agent (Prime & Bond NT) was applied, and fiberglass posts were luted for 8 mm into the post space using a self-cure composite (ResiLute). All samples were then subjected to tensile forces in a universal testing machine. Data were analyzed with ANOVA and Student t-tests (P < 0.01). Results: The samples with residual coronal dentin showed higher bond strength than the samples without residual crown walls (TG0=100.30N; TG1=201.83N; TG2=263.54N; TG3=278.86N). The differences between the groups were all statistically significant at P < 0.01, except for the difference in tensile strength between TG2 and TG3, which was not statistically significant. Residual crown walls significantly increased the tensile load required to displace the posts.