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Biomedical subjects

D Eng

Publications and source records attributed to D Eng.

7 recordsLinked to original sources
PubMed2006

Comparative study of torsional and bending properties for six models of nickel-titanium root canal instruments with different cross-sections.

This study investigated the influence of cross-section profile on the mechanical behaviors of six commercial nickel-titanium (NiTi) root canal instruments using the finite element method. The nonlinear mechanical characteristics of the NiTi alloy were taken into account. The six root canal instruments studied were ProTaper, Hero642, Mtwo, ProFile, Quantec, and NiTiflex. Mathematical models for these instruments were constructed and their performances were analyzed under equal torque conditions. The ProTaper and Hero642 models achieved the lowest stress levels that made them the most torque-resistant while the NiTiflex model was the poorest. The maximum stress value and the stress distribution in a model were found strongly influenced by the cross-section profile. Factors affecting the stress distribution include the cross-sectional inertia, depth of the flute, area of the inner core, radial land, and peripheral surface ground. As the area of the inner core of the cross-section increased, the model was more torque-resistant.

Dental Alloys↗
PubMed2000

Brachial plexus catheter reservoir for the treatment of upper-extremity cancer pain: technical case report.

OBJECTIVE AND IMPORTANCE: Infiltration of the brachial plexus with anesthetics can provide relief of upper-extremity pain from invasive cancer. Because the analgesia is short-lived, however, repeated invasive treatments are necessary. We describe the implantation of a catheter reservoir system, in which anesthetic injections through a subcutaneous port resulted in anesthetic infiltration of the brachial plexus. CLINICAL PRESENTATION: A 47-year-old Hispanic man with squamous cell carcinoma of the larynx had undergone surgical resection, radiation treatment, and chemotherapy. Two years later, he had locally recurrent disease involving the brachial plexus, neck, and chest wall. The patient's pain was minimally responsive to narcotics, which also caused severe nausea and anorexia. TECHNIQUE: The brachial plexus was localized percutaneously with a needle electrode stimulator. Contrast injection under fluoroscopy confirmed entry into the plexus sheath. With use of the Seldinger technique, two Silastic catheters were placed within the brachial plexus and attached with a "Y" connector to a reservoir. The patient experienced complete relief of upper-extremity pain after a test injection with xylocaine. Thereafter, serial injections of bupivacaine with triamcinolone at 1-week intervals provided complete pain relief. After the treatments were initiated, the patient reported improved sleep and an improvement in his quality of life. CONCLUSION: A catheter reservoir system for brachial plexus analgesia can provide safe and effective analgesia for upper-extremity pain. This technique negates the need for repeated invasive procedures and avoids the complications of neurolysis.

Anesthetics, Local↗
PubMed1987

A simple quantitative analysis system for coronary cineangiograms using a personal computer.

We have developed a simple quantitative analysis system for coronary cineangiograms using a personal computer and a standard projector-video camera system. The selected frame of cinefilm was projected onto the target area of a CCD video camera. To decrease spatial fluctuations due to quantum noise, the digital data were smoothed spatially by applying a moving averaged filter and a median filter. Following the smoothing process, the digital data with gray level were transformed to binary data by quantifying the threshold property of their gray level. To minimize the geometric influence, mainly pincushion effect, a cinefilm of a 1 cm grid was placed against the input screen of the image intensifier to correct the distortion by using 3rd degree polynomials. The accuracy of the contour detection procedure was validated on the basis of phantom models filled with a contrast medium. Despite the potential influence of many radiographic variables on computerized diameter measurements, the overall accuracy was found to be 0.26-0.33 mm over a wide range of clinically relevant artery diameters and radiographic conditions. Using this system we demonstrated one method of examining the effects of acetylcholine and nitroglycerin on coronary artery diameter in adult humans.

Acetylcholine↗
PubMed1976

Neonatal narcotic abstinence: Effects of pharmacotherapeutic agents and maternal drug usage on nutritive sucking behavior.

An uncoordinated and ineffectual sucking reflex is a major manifestation of neonatal narcotic abstinence and may have important consequences for the infant's subsequent well being. Measures of nutritive sucking were used to monitor the severity of neonatal narcotic abstinence in a series of infants born to narcotic-dependent mothers who were either attending the methadone clinic or else were "street addicts." In all these infants, sucking measures were significantly reduced relative to normal control subjects. Furthermore, the sucking behavior of infants born to mothers attending the methadone clinic was significantly more depressed than that of infants born to street addicts. In regard to the salutary effects of pharmacotherapy for neonatal narcotic abstinence, infants treated with paregoric approached normal control levels and showed significantly better sucking than those treated with phenobarbital or diazepam. The latter drug practically eliminated all spontaneous nutritive sucking behavior.

Diazepam↗
PubMedDate not supplied

Tumor response to interferon inducer and radiation effect of serum interferon levels.

The effect of interferon inducing complex of polyriboinosinic, polyribocytidylic acid with poly-L-lysine and carboxymethylcellulose - Poly (ICLC) - on the response of Lewis lung carcinoma in C57B1 mice to radiation treatments was studied. Improved tumor response was obtained in mice receiving 1.5 mg/m2 or higher of Poly (ICLC). Such doses have induced more than 1000 mu/ml of serum interferon. The same doses of Poly (ICLC) potentiated the epilation effect of radiation. The injection of 0.15 mg/m2 of Poly (ICLC) led to protection of the tumor and the stimulation of it's growth. It also did not potentiate the epilation effect. In this study, one weekly administration of Poly (ICLC) was as effective as three times per week treatment. The cellular mechanism of the increased radiosensitivity caused by Poly (ICLC) was reflected in the reduction of the width of the shoulder on the cell survival curve, which was dependent on the dose of the drug. In cell cultures, doses of 100 micrograms/ml synchronized the cell division, thus contributing to the increase in radiosensitivity.

Animals↗