Influence of Fluoride and Stress on the Mechanical Properties of Nickel-Titanium Coils

Objective: The objective of this study was to determine the influence of fluoride and stress on the mechanical properties of nickel-titanium open coil springs. Materials and Methods: Sentalloy nickel-titanium open coil springs (15 mm length) were divided into five groups. A control group was tested mechanically in as-received condition. The other four experimental groups were exposed to artificial saliva (Fusayama-Meyer solution) at 37oC for 12 weeks in a 2x2 factorial design with fluoride exposure and stress (compression) as the two factors. Those springs which were under compression were held at 5 mm in length for the entirety of the testing period. Fluoride exposure was two minutes per day in a 1500 ppm NaF solution. In each group, n=10. The experimental groups were then tested mechanically via compression on a universal testing machine following the 12-week exposure period to measure force characteristics. Results: No significant differences in activation force were seen between the coil groups, whereas significant (p\u3c0.05) differences were observed in deactivation forces between the control and compressed/fluoride group and also between the control and the non-compressed/non-fluoride group. Ranges of mean deactivation force values between all groups were less than only 6 and 14 grams of force at 4 mm and 8 mm respectively. Conclusions: Clinically relevant daily fluoride exposure (1500 ppm) and continuous compression for twelve weeks did not result in clinically significant changes in force values of the nickel-titanium open coil springs, indicating they are likely to deliver consistent forces during the course of treatment

Titanium Nitride and Nitrogen Ion Implanted Coated Dental Materials

Titanium nitride and/or nitrogen ion implanted coated dental materials have been investigated since the mid-1980s and considered in various applications in dentistry such as implants, abutments, orthodontic wires, endodontic files, periodontal/oral hygiene instruments, and casting alloys for fixed restorations. Multiple methodologies have been employed to create the coatings, but detailed structural analysis of the coatings is generally lacking in the dental literature. Depending on application, the purpose of the coating is to provide increased surface hardness, abrasion/wear resistance, esthetics, and corrosion resistance, lower friction, as well as greater beneficial interaction with adjacent biological and material substrates. While many studies have reported on the achievement of these properties, a consensus is not always clear. Additionally, few studies have been conducted to assess the efficacy of the coatings in a clinical setting. Overall, titanium nitride and/or nitrogen ion implanted coated dental materials potentially offer advantages over uncoated counterparts, but more investigation is needed to document the structure of the coatings and their clinical effectiveness

Biocolloid retention in partially saturated soils

Unsaturated soils are considered excellent filters for preventing the transport of pathogenic biocolloids to groundwater, but little is known about the actual mechanisms of biocolloid retention. To obtain a better understanding of these processes, a number of visualization experiments were performed and analyzed