Effects of various coating methods on the mechanical, physical, and aesthetic properties of GUMMETAL® archwires: In vitro study.

PURPOSE: The objective of this study was to evaluate the mechanical, physical, and aesthetic properties of GUMMETAL® (GM) orthodontic archwires after the application of various aesthetic coating materials. METHODS: This in vitro study included 180 orthodontic wires: five experimental groups used 0.016×0.022-inch GM as the core-based wire followed by the application of epoxy, polytetrafluoroethylene (PTFE), clear ceramic, white ceramic, or silicone; and four control groups: 0.016×0.022-inch GM, 0.019×0.025-inch GM, 0.016×0.022-inch stainless steel (SS), and 0.019×0.025-inch SS. Frictional forces, force deflection rate, yield strength, aesthetic colour value, corrosive and wear resistance were compared between the experimental and control groups. RESULTS: Among the coated wires, white ceramic exhibited the highest frictional force (2.06±0.20 N) and silicone showed the lowest values (0.88±0.12 N). There were significant differences in static friction between experimental and control groups (P<0.001). PTFE coating had the highest force deflection rate (9.03±0.12 N/mm) and yield strength (10.0±0.14 N/mm) among coated wires and white ceramic exhibited the lowest values (6.86±0.14 N/mm and 7.74±0.17 N/mm for force deflection rate and yield strength, respectively). Differences in force deflection rate and yield strength between experimental and control groups were statistically significant (P<0.001). All coated wire groups had a clinical difference in colour when compared to A1 shade. Coated and uncoated wires showed good corrosion resistance after one week in corrosive saliva with no detectable loss of mass. CONCLUSIONS: This study has shown that coating wires can improve some aspects of the wire properties but not all when compared to uncoated GM and SS. Future investigation of the materials used in this study is required to further characterize their properties.

Adhesive cryogel particles for bridging confined and irregular tissue defects.

BACKGROUND: Reconstruction of damaged tissues requires both surface hemostasis and tissue bridging. Tissues with damage resulting from physical trauma or surgical treatments may have arbitrary surface topographies, making tissue bridging challenging. METHODS: This study proposes a tissue adhesive in the form of adhesive cryogel particles (ACPs) made from chitosan, acrylic acid, 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The adhesion performance was examined by the 180-degree peel test to a collection of tissues including porcine heart, intestine, liver, muscle, and stomach. Cytotoxicity of ACPs was evaluated by cell proliferation of human normal liver cells (LO2) and human intestinal epithelial cells (Caco-2). The degree of inflammation and biodegradability were examined in dorsal subcutaneous rat models. The ability of ACPs to bridge irregular tissue defects was assessed using porcine heart, liver, and kidney as the ex vivo models. Furthermore, a model of repairing liver rupture in rats and an intestinal anastomosis in rabbits were established to verify the effectiveness, biocompatibility, and applicability in clinical surgery. RESULTS: ACPs are applicable to confined and irregular tissue defects, such as deep herringbone grooves in the parenchyma organs and annular sections in the cavernous organs. ACPs formed tough adhesion between tissues [(670.9 ± 50.1) J/m2 for the heart, (607.6 ± 30.0) J/m2 for the intestine, (473.7 ± 37.0) J/m2 for the liver, (186.1 ± 13.3) J/m2 for muscle, and (579.3 ± 32.3) J/m2 for the stomach]. ACPs showed considerable cytocompatibility in vitro study, with a high level of cell viability for 3 d [(98.8 ± 1.2) % for LO2 and (98.3 ± 1.6) % for Caco-2]. It has comparable inflammation repair in a ruptured rat liver (P = 0.58 compared with suture closure), the same with intestinal anastomosis in rabbits (P = 0.40 compared with suture anastomosis). Additionally, ACPs-based intestinal anastomosis (less than 30 s) was remarkably faster than the conventional suturing process (more than 10 min). When ACPs degrade after surgery, the tissues heal across the adhesion interface. CONCLUSIONS: ACPs are promising as the adhesive for clinical operations and battlefield rescue, with the capability to bridge irregular tissue defects rapidly.

Expression of osteopontin and type I collagen of hFOB 1.19 cells on sintered fluoridated hydroxyapatite composite bone graft materials.

PURPOSE: The biological effect of fluoridated hydroxyapatite (FHA) graft materials has been attributed to their fluoride ion content; but, only few studies have been conducted to explore the osteoblastic cellular response to physicochemical characteristics of them. We hypothesized that the effect of varied sintered FHA composites on osteoblastic behavior would attribute certain specified physicochemical characteristics of apatites. MATERIALS: Sintered FHA composites were prepared by sintering method with varied gravity percentages of calcium fluoride and hydroxyapatite. Scanning electron microscopic, x-ray diffraction, and Fourier-transform infrared analysis were recorded. The human fetal-osteoblast (hFOB 1.19) cells were seeded on the apatites and tissue culture plates. Responses to the apatites were assessed in terms of osteopontin (OPN) and type I collagen, COL I, gene differentiation. RESULTS: We observed the calcined hydroxyapatite (OHAp), sintered F- OHAps, and hydroxy fluorapatites (OH-FAps) with different physicochemical characteristics. The x-ray diffraction analysis showed sintered apatites to be fluorapatites. Otherwise, Fourier-transform infrared spectral patterns could differentiate the sintered F-OHAps from OH-FAps by the existence of OH, OH···F, or OH···F···OH bands. With ≤ 1 wt% CaF2 added, sintered F-OHAp composites expressed both OH and OH···F bands. With >1 wt% CaF2 added, sintered OH-FAp composites expressed both OH···F and OH···F···OH bands. Sintered F-OHAp composites could enhance OPN and COL I gene expression after 6-day culture (P ≤ 0.05). Otherwise, sintered OH-FAp composites inhibited the expression. CONCLUSION: The results revealed that sintered F-OHAp composites with both OH and OH···F bands were bioactive bone graft materials.