Comparative analysis of bonding strength between enamel and overlay of varying thicknesses following an aging test.

Abstract: Background/purpose: Overlay restorations can be used clinically as a treatment option to preserve natural dentine. However, whether the residual enamel thickness and overlay thickness affect the adhesion between the restoration and tooth is still unknown. This study was to investigate effects of the overlay thickness and residual enamel thickness on bonding strength. Materials and methods: Overlays of different thicknesses were prepared with natural teeth which had 2, 4, and 6 mm of occlusal reduction (n = 10). Specimens were subjected to 10,000 cycles in water at 5-55 °C, and finally compressive strength tests were used to evaluate the bonding strength. Results: All groups showed good bond strength (P > 0.05). The overlay restorations of different thicknesses reduced the preparation amount by 30.3%-7.2% and significantly preserved more of the tooth structure (P < 0.005). Compared to the control group, the overlay restoration increased the marginal fitness by about 0.67-0.88 times. The thermal cycling indicated that the decrease in the maximum bearing stress was due to the aging of the ceramic itself. Therefore, the thickness of the overlay had a greater influence on the compressive strength than the bond strength. Conclusion: Based on the above this study recommends an overlay thickness of at least 2 mm in clinical practice. The aging test confirmed that adhesion between the overlay and teeth was quite firm and stable. This shows that a stable adhesive effect of the overlay can be used as a treatment option for preserving a greater amount of a tooth's structure.

A 10-year retrospective study on mandibular fractures in Northern Taiwan.

Background/purpose: The mandible is an independent and protruding bone structure in the lower third portion of the human facial skeleton. Because of its prominent and unprotected position, the mandible is a primary site of facial trauma. Previous studies have not comprehensively discussed the association between the mandibular fractures and concomitant fractures of facial bones, the trunk, or limbs. This study analyzed the epidemiology of mandibular fractures and their correlation with concomitant fractures. Materials and methods: The present study enrolled 118 patients with a total of 202 mandibular fracture sites during at any time from January 1, 2012, to December 31, 2021, in northern Taiwan. Results: According to the study results, the patients between 21 and 30 years of age had the highest occurrence of trauma, and road traffic accidents (RTAs) constituted the primary cause of mandibular fractures. Fall-related injuries were significant in patients >30 years of age. By the analysis of Pearson's contingency coefficient, the number of mandibular fractures was not significantly associated with concomitant fractures of the extremities or the trunk. However, accompanying maxillary fractures can be regarded as an indication of concomitant extremity or trunk fractures in patients with mandibular fractures. Conclusion: Three-site mandibular fractures are not necessarily accompanied by extremity and trunk fractures; however, clinicians should implement multidisciplinary examination and management in patients with mandibular fractures accompanied by maxillary fractures. Maxillary fractures can be regarded as an indication of concomitant fractures of other facial bones, the extremities, or the trunk.

Dehydroepiandrosterone (DHEA) Sensitizes Irinotecan to Suppress Head and Neck Cancer Stem-Like Cells by Downregulation of WNT Signaling.

Purpose: Current treatment options for head and neck squamous cell carcinoma (HNSCC) are limited, especially for cases with cancer stem cell-induced chemoresistance and recurrence. The WNT signaling pathway contributes to maintenance of stemness via translocation of ß-catenin into the nucleus, and represents a promising druggable target in HNSCC. Dehydroepiandrosterone (DHEA), a steroid hormone, has potential as an anticancer drug. However, the potential anticancer mechanisms of DHEA including inhibition of stemness, and its therapeutic applications in HNSCC remain unclear. Methods: Firstly, SRB assay and sphere formation assay were used to examine cellular viability and cancer stem cell-like phenotype, respectively. The expressions of stemness related factors were measured by RT-qPCR and western blotting. The luciferase reporter assay was applied to evaluate transcriptional potential of stemness related pathways. The alternations of WNT signaling pathway were measured by nuclear translocation of ß-catenin, RT-qPCR and western blotting. Furthermore, to investigate the effect of drugs in vivo, both HNSCC orthotopic and subcutaneous xenograft mouse models were applied. Results: We found that DHEA reduced HNSCC cell viability, suppressed sphere formation, and inhibited the expression of cancer-stemness markers, such as BMI-1 and Nestin. Moreover, DHEA repressed the transcriptional activity of stemness-related pathways. In the WNT pathway, DHEA reduced the nuclear translocation of the active form of ß-catenin and reduced the protein expression of the downstream targets, CCND1 and CD44. Furthermore, when combined with the chemotherapeutic drug, irinotecan (IRN), DHEA enhanced the sensitivity of HNSCC cells to IRN as revealed by reduced cell viability, sphere formation, expression of stemness markers, and activation of the WNT pathway. Additionally, this combination reduced in vivo tumor growth in both orthotopic and subcutaneous xenograft mouse models. Conclusion: These findings indicate that DHEA has anti-stemness potential in HNSCC and serves as a promising anticancer agent. The combination of DHEA and IRN may provide a potential therapeutic strategy for patients with advanced HNSCC.

Astragalus Polysaccharide (PG2) Suppresses Macrophage Migration Inhibitory Factor and Aggressiveness of Lung Adenocarcinoma Cells.

Astragalus membranaceus is the most popular traditional Chinese medicine for managing vital energy deficiency. Its injectable polysaccharide PG2 has been used for relieving cancer-related fatigue, and PG2 has immune-modulatory and anti-inflammatory effects. In this study, we explored the effects of PG2 in lung adenocarcinoma A549 and CL1-2 cells and investigated its anticancer activity, and the results were validated in severe combined immunodeficiency (SCID) mice. Although PG2 did not inhibit the growth of these cells, it dose-dependently suppressed their migration and invasion, accompanied by reduced vimentin and AXL and induced epithelial cadherin (E-cadherin) expression. Regarding the underlying molecular mechanism, PG2 treatment reduced the macrophage migration inhibitory factor (MIF), an inflammatory cytokine that promotes the epithelial-mesenchymal transition and aggressiveness of cancer cells. Consistent with the previous finding that MIF regulates matrix metalloproteinase-13 (MMP-13) and AMP-activated protein kinase (AMPK), treatment with PG2 reduced MMP-13 and activated AMPK in A549 and CL1-2 cells in this study. In SCID mice injected with A549 cells through the tail vein, intraperitoneal injection with PG2 reduced lung and abdominal metastases in parallel with decreased immunohistochemical staining of AXL, vimentin, MMP-13, and MIF in the tumor. Collectively, data revealed a potential application of PG2 in integrative cancer treatment through the suppression of MIF in cancer cells and their aggressiveness.