Flexible and Tough Superelastic Co-Cr Alloys for Biomedical Applications.

The demand for biomaterials has been increasing along with the increase in the population of elderly people worldwide. The mechanical properties and high wear resistance of metallic biomaterials make them well-suited for use as substitutes or as support for damaged hard tissues. However, unless these biomaterials also have a low Young's modulus similar to that of human bones, bone atrophy inevitably occurs. Because a low Young's modulus is typically associated with poor wear resistance, it is difficult to realize a low Young's modulus and high wear resistance simultaneously. Also, the superelastic property of shape-memory alloys makes them suitable for biomedical applications, like vascular stents and guide wires. However, due to the low recoverable strain of conventional biocompatible shape-memory alloys, the demand for a new alloy system is high. The novel body-centered-cubic cobalt-chromium-based alloys in this work provide a solution to both of these problems. The Young's modulus of <001>-oriented single-crystal cobalt-chromium-based alloys is 10-30 GPa, which is similar to that of human bone, and they also demonstrate high wear and corrosion resistance. They also exhibit superelasticity with a huge recoverable strain up to 17.0%. For these reasons, the novel cobalt-chromium-based alloys can be promising candidates for biomedical applications.

Differences in the effect of surface texturing on the wear loss of ß-type Ti-Nb-Ta-Zr and (α+ß)-type Ti-6Al-4V ELI alloys in contact with zirconia in physiological saline solution.

The effectiveness of dimple surface texturing via picosecond pulsed laser processing for reducing wear loss was investigated using two types of titanium alloys, ß-type Ti-29Nb-13Ta-4.6Zr (TNTZ) and α+ß-type Ti-6Al-4V ELI (Ti64). The two alloys showed different modes of wear against zirconia. As the sliding distance increased, the wear loss was observed to increase for Ti64, but not necessarily for TNTZ. The wear debris of Ti64 acted as abrasive particles, but that of TNTZ easily adhered to the surface, and the adhered wear debris turned into a hard wear-protective layer. Therefore, the dependence of wear loss on the sliding distance for these two titanium alloys could be attributed to the difference in the roles of wear debris between each titanium alloy and zirconia. Further, depending on this difference in wear mode, the effect of dimple surface texturing on the wear was found to be different in Ti64 and TNTZ. As the dimples can trap the wear debris, they are effective for reducing wear in Ti64 but are detrimental in TNTZ.

Retrospective clinical study of 296 patients with mass lesions of the tongue.

To better understand the clinical features of mass lesions of the tongue, we retrospectively evaluated frequency, recurrence rate, and complications in 296 patients who had undergone surgery for such lesions. The diagnoses were fibroma (43.6%), mucous cyst (14.2%), papilloma (11.8%), hemangioma (7.8%), granuloma (6.4%), lipoma (1.4%), schwannoma (1.0%), ectopic tonsil (0.7%), and other (13.2%). Recurrence was noted in two patients (0.7%). Twenty-two patients (7.4%) developed surgical complications, including lingual nerve paralysis (6.4%), glossodynia (0.6%), and postoperative infection (0.3%). Lingual nerve paralysis was observed in the ventral portion (42.1%) of the tongue, apex (36.8%), lateral border (10.5%), and dorsum (10.5%). When all sites were considered together, there was no significant difference in the number of patients presenting with lingual nerve paralysis (P = 0.075). However, there were significant differences in lingual nerve paralysis at the lateral border (P < 0.05), apex (P < 0.05), and dorsum (P < 0.001) but not at the ventral portion (P > 0.05) in the size of the patients with versus without it which suggests that the risk of lingual nerve paralysis is higher at the ventral tongue, regardless of tumor size. These results shed light on the clinical features of mass lesions of the tongue.

Nickel chloride administration prevents the growth of oral squamous cell carcinoma.

The effect of NiCl2 on oral squamous cell carcinoma-derived cell line HSC3 was examined. Incubation with 1 mM NiCl2 significantly reduced the expression of MMPs at mRNA and protein levels. The in vivo orthotopic implantation model was established by injecting highly metastatic subcell line HSC3-M3 to nude mouse tongue. After 1 week of injection, mice were fed with or without 1 mM NiCl2-containing water for two to three weeks. Immunohistochamical examination revealed that MMP9 expression was drastically reduced in NiCl2-fed mice. By CT images, cancer mass was observed as a translucent area in control mice. In NiCl2-fed mice, much highly translucent area was observed within the translucent area. Histologically, this area corresponded to the necrotic area in the tumor mass. Real-time PCR analysis revealed the reduced expression of angiogenic factors such as IL-8 and VEGF mRNA in NiCl2-fed mice. To further examine the effect of NiCl2 on metastasis, human ß-globin gene expression in regional lymphnodes was compared. The ß-globin gene was totaly absent in NiCl2-fed mice. Moreover, various cancer metastasis-related genes were inhibited in NiCl2-fed mice by PCR array analysis. The results indicated that NiCl2 might be a promising new anti-cancer therapeutics for the oral cancer treatment.

Rapid detection of Candida albicans in oral exfoliative cytology samples by loop-mediated isothermal amplification.

Loop-mediated isothermal amplification (LAMP) rapidly amplifies DNA under isothermal conditions. The aim of this study was to detect Candida albicans and compare the positivity rate in the LAMP reaction with that of conventional methods for oral exfoliative cytology (EC) samples. Sixty-eight EC samples from 53 patients were subjected to LAMP analysis. These patients had been clinically diagnosed with leukoplakia, squamous cell carcinoma, oral lichen planus (OLP), stomatitis, oral candidiasis, and other malignancies. LAMP reactions were defined as positive when the sample turbidity exceeded 0.1 (arbitrary unit). Periodic acid-Schiff (PAS) staining and microbial culture were also performed to detect Candida species in EC samples. The LAMP reaction detected C. albicans in 42.6% of EC samples. Candida species were detected in 32.4% of the same samples by culturing and in 29.4% of samples by PAS staining. C. albicans DNA was detected most frequently in samples from OLP patients. We conclude that, in comparison to conventional methods for detection of C. albicans, the LAMP method is highly sensitive and time-saving, and does not require expensive equipment or diagnostic technology. It may therefore be useful for on-site screening of C. albicans at dental clinics.