A comparative evaluation of the effect of eugenol exposure time on the bond strength of an etch-and-rinse and a self-etch adhesive to dentin: An in vitro study.

Aim: The study aimed to comparatively evaluate the effect of eugenol exposure time on the micro-shear bond strength (µ-SBS) of etch-and-rinse and a self-etch adhesive to dentin. Materials and Methods: One hundred and twelve teeth samples were prepared from bisectioning 56 freshly extracted human mandibular molars and were randomly divided into 14 subgroups of 8 samples each (n = 8). Three subgroups containing eugenol and a noneugenol-based restorative material were placed on the dentin surface and left for 24 h, 7 days, and 14 days, respectively, and were compared to a control. Two bonding systems were evaluated: one being etch-and-rinse and the other self-etch adhesive. The µ-SBS were calculated and expressed in MPa. Statistical Analysis: The data were analyzed using mixed model analysis of variance. The level of statistical significance was set at 5%. Results: There was a statistically significant reduction in the µ-SBS values when the self-etch adhesive was used, after the removal of eugenol-containing cement placed for 24 h. However, the reduction in the µ-SBS values after 7 days or 14 days was not significant. Conclusion: Exposure to eugenol containing temporary cement for 24 h significantly reduces the µ-SBS of self-etching adhesives to dentin. However, exposure for 1 week or more has minimal effects.

Comparative evaluation of the shear bond strength of lithium disilicate veneers using one light-cure and two dual-cure resin cement: An in vitro study.

Aim: The present in vitro study aimed to comparatively evaluate the shear bond strength (SBS) of one light-cure and two dual-cure resin cement to bond lithium disilicate veneers. Materials and Methods: Thirty maxillary central incisors (n = 30) were procured and randomly divided into three groups of adhesive/resin cement systems, into groups of 10 each (n = 10); Group A: Adper Single Bond 2/RelyX Veneer Cement, Group B: Prime and Bond NT/Calibra, and Group C: Excite DSC/Variolink II. All the tooth samples were etched and respective bonding agent was applied. Similarly, all the laminate veneer specimens were etched, silanated, and treated with respective bonding agents before cementation with the respective resin cement. The SBS was measured in a universal testing machine with a cross-head speed of 1 mm/min. Statistical Analysis: Data obtained were analyzed using the one-way analysis of variance and post hoc Tukey's test at a 5% significance level. Results: The highest SBS was demonstrated by Group C (18.8 ± 0.92 Mpa), followed by Group B (18.4 ± 0.74) Mpa, and the least by Group A (17.4 ± 0.75 MPa). Significant differences were found between Group A, Group B, and Group C, respectively. However, Group B and Group C did not differ significantly from each other. Conclusions: Dual-cure resin cement have higher SBS than the light-cure variants.

Extra-axial, dural-based atypical teratoid/rhabdoid tumor.

Atypical teratoid/rhabdoid tumors (ATRTs) are malignant central nervous system tumors that affect early childhood (< 3 years), and mostly located in the infratentorial space. Owing to an infrequent occurrence, their radiological features have not been completely defined. Nevertheless, these are characteristically intra-axial except for few instances in the cerebellopontine angle region. We describe a case of a 10-year-old boy who harbored an extra-axial, dural-based ATRT in the right parietal region. The lesion was totally excised followed by adjuvant chemo-radiotherapy. At 10-month follow-up, he was well with no recurrence. The report intends to highlight an atypical imaging presentation of ATRT in an older child, and adds to the radiological spectrum. This uncommon pathology should be borne in mind, even in a supratentorial dural-based location.

Electric field driven destabilization of the insulating state in nominally pure LaMnO3.

We report an electric field driven destabilization of the insulating state in nominally pure LaMnO3 single crystal with a moderate field which leads to a resistive state transition below 300 K. The transition is between the insulating state in LaMnO3 and a high resistance bad metallic state that has a temperature independent resistivity. The transition occurs at a threshold field (Eth) that shows a steep enhancement on cooling. While at lower temperatures the transition is sharp and involves a large change in resistance, it softens on heating and is eventually absent above 280 K. When the Mn(4+) content is increased by Sr substitution up to x = 0.1, the observed transition, although observable in a certain temperature range, softens considerably. This observation has been explained as a bias driven percolation type transition between two co-existing phases, where the majority phase is a charge and orbitally ordered polaronic insulating phase and the minority phase is a bad metallic phase. The mobile fraction f of the bad metallic phase deduced from the experimental data follows an activated kinetics as f = fo(E)exp(-Δ/kBT) with the activation energy Δ ≈ 200 meV, and the pre-factor fo(E) is a strong function of the field that leads to a rapid enhancement of f on application of field, leading to the resistive state transition. We suggest likely scenarios for such co-existing phases in nominally pure LaMnO3 that can lead to the bias driven percolation type transition.