In vitro evaluation of physical vapor deposition coated beta titanium orthodontic archwires.

OBJECTIVE: To determine in vitro the frictional properties, surface morphology, and load deflection rate with looped designs of two newly developed titanium aluminum nitride (TiAlN) and tungsten carbide/carbon (WC/C) physical vapor deposition (PVD) coated beta titanium orthodontic archwires coated with PVD. MATERIALS AND METHODS: Frictional properties with Tidy's protocol, surface evaluation before and after friction testing with the help of scanning electron microscopy (ESEM), and load deflection rate with different orthodontic loops on Instron universal testing machine were evaluated. RESULTS: The results clearly indicate reduced frictional properties for WC/C coated archwires when compared with uncoated and TiAlN coated archwires. There were no significant surface alterations upon ESEM evaluation of friction tested archwires. Low load deflection rate was exhibited by both coated archwires, the difference in load deflection rate between the coated and uncoated archwires was statistically significant. CONCLUSION: WC/C coated wires can be recommended for even sliding mechanics due to reduced frictional properties, better surface characteristics, and low load deflection rate compared with TiAlN coated and uncoated archwires.

Development and evaluation of two PVD-coated ß-titanium orthodontic archwires for fluoride-induced corrosion protection.

The present research was aimed at developing surface coatings on ß titanium orthodontic archwires capable of protection against fluoride-induced corrosion. Cathodic arc physical vapor deposition PVD (CA-PVD) and magnetron sputtering were utilized to deposit thin films of titanium aluminium nitride (TiAlN) and tungsten carbide/carbon (WC/C) coatings on ß titanium orthodontic archwires. Uncoated and coated specimens were immersed in a high fluoride ion concentration mouth rinse, following a specially designed cycle simulating daily use. All specimens thus obtained were subjected to critical evaluation of parameters such as electrochemical corrosion behaviour, surface analysis, mechanical testing, microstructure, element release, and toxicology. The results confirm previous research that ß titanium archwires undergo a degradation process when in contact with fluoride mouth rinses. The study confirmed the superior nature of the TiAlN coating, evident as many fewer changes in properties after fluoride treatment when compared with the WC/C coating. Thus, coating with TiAlN is recommended in order to reduce the corrosive effects of fluorides on ß titanium orthodontic archwires.

A cross-sectional seroprevalence survey for HIV-1 and high risk sexual behaviour of seropositives in a prison in India.

This study was conducted to know whether prisoners constitute a "high risk group" for HIV transmission in India today. A sero-epidemiological period prevalence survey was conducted in Central Prison, Bangalore, South India covering 1007 undertrials and 107 permanent convicts during January to December 1993. Twenty (1.98%) undertrials and none of the permanent convicts were seropositive for HIV infection. All of them were males and 1.6(80%) of them were in the age group of 20-30 years. Low literacy, poor income, sexual promiscuity and low condom usage were observed among the seropositives. Thus, prisoners constitute a high risk group and routine screening and counselling are recommended.

PIP: Throughout 1993, health workers took blood samples from 1007 prisoners awaiting trial and 107 convicted inmates in the Central Prison in Bangalore, India, for HIV-1 screening. All these prisoners were male and underwent pretest counseling. 20 (1.98%) prisoners awaiting trial and none of the permanent convicts tested positive for HIV-1 antibodies. Only 13 underwent post-test counseling. Many prisoners initially denied the possibility of being HIV positive. Many suffered psychologically, breaking down or becoming depressed. The HIV-1 positive prisoners tended to be illiterate (53%), poor (69%), and married (61%) and their job involved traveling (61%). All reported having had many casual sexual relationships, particularly in brothels and cheap hotels. Some prisoners had these relationships outside of Bangalore. 23% of the HIV-1 positive prisoners had had sexual intercourse with 50-60 women. 69% did not use condoms. 39% had used urine and/or soda water to wash their genitals after sexual intercourse. No one had used intravenous drugs. No one had had a blood transfusion. 30% had tatoos. 50% of the HIV-1 positive prisoners had lost weight. 15% had diarrhea, weight loss, and persistent glandular lymphadenopathy. All had used pyoderma antibiotics (e.g., penicillin and gentamicin). 90% knew nothing about HIV/AIDS. 13 of the 20 prisoners were released from the prison and lost to follow-up. Since prisoners are easily accessible and there is a steady flow of prisoners awaiting trial, it is important to routinely screen them, conduct contact tracing, and do follow-up action to prevent further HIV-1 transmission in the community. Similar surveys should be conducted in other prisons nationwide.