Evaluation of the Microshear Bond Strength of MDP-containing and Non-MDP-containing Self-adhesive Resin Cement on Zirconia Restoration.

OBJECTIVES: The purpose of this study was to measure the microshear bond strength (µSBS) of four different self-adhesive resin cements with/without 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primer to zirconium ceramics and to evaluate the effect of zirconia primers on these self-adhesive resin cements (SARCs). METHODS AND MATERIALS: Zirconia blocks (20 × 20 × 8 mm3) were prepared and divided into eight groups (n=20). They were sandblasted (50 µm Al2O3) and treated as follows: no primer or primer (Z-Primer Plus). Four self-adhesive resin cements (MDP-containing: Permacem 2.0 [PC], Clearfil SA luting [CS]; non-MDP-containing: Rely-X U200 [RU], Maxcem Elite [ME]) were bonded to the zirconia surface. After thermocycling, a µSBS test was performed. The failure mode was analyzed using light microscopy. Statistical analysis of µSBS was performed using one-way analysis of variance and two-sample t-test with post hoc Tukey test. The loss rate was evaluated using the Fisher's exact test and χ2 test with post hoc Tukey test (p<0.05). RESULTS: Within the no primer groups, the PC and CS groups showed higher bond strength than the RU and ME groups. Comparing the µSBS of the no primer and primer groups in the same SARCs, the RU/P group was higher than the RU group, and the ME/P group was higher than the ME group. No significant difference was observed between the PC and PC/P groups and between the CS and CS/P groups. CONCLUSIONS: Non-MDP-containing SARC showed the increased bonding value with MDP-containing primer to zirconia ceramics. The bond strength of MDP-containing SARCs was not affected significantly by the use of zirconia primer.

Immunohistochemical analysis of pulpal regeneration by nestin expression in replanted teeth.

AIM: To investigate dental pulp healing after tooth replantation in rats using nestin as an odontoblastic marker for immunohistochemical analysis. METHODOLOGY: Twenty-five maxillary right first molars from 25 female Sprague-Dawley rats, aged 4 weeks post-natally, were extracted and immediately repositioned in the original socket within 5 s. Five rats each were later killed on days 3, 5 and weeks 1, 2 and 4. The maxillae were removed en bloc and the tissue samples containing the maxillary right first molars were decalcified, sectioned, mounted and stained with anti-nestin antibody to be observed under a light microscope. RESULTS: At 3 days after replantation, there was a localized inflammatory reaction, but pulp revascularization and healing had begun in the root area. At 5 days after replantation, odontoblast-like cells were observed. Reparative dentine deposition was observed beneath the pulp-dentine border from 1 week after replantation, and gradually increased until 2 weeks after replantation. The presence of odontoblast-like cells and the formation of reparative dentine continued from the first week throughout the experimental period. At week four, deposition of osteodentine and cementum-like tissues were observed. CONCLUSIONS: Pulpal mineralization after replantation initially occurred via the deposition of reparative dentine, followed by the deposition of osteodentine and cementum-like tissues in rat teeth.