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Biomedical subjects

G H Evans

Publications and source records attributed to G H Evans.

At least 19 recordsLinked to original sources
PubMed1992

Effects of the Nd:YAG dental laser on plasma-sprayed and hydroxyapatite-coated titanium dental implants: surface alteration and attempted sterilization.

The Nd:YAG dental laser has been recommended for a number of applications, including the decontamination or sterilization of surfaces of dental implants that are diseased or failing. The effects of laser irradiation in vitro (1) on the surface properties of plasma-sprayed titanium and plasma-sprayed hydroxyapatite-coated titanium dental implants, and (2) on the potential to sterilize those surfaces after contamination with spores of Bacillus subtilis have been examined. Surface effects were examined by scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction after laser irradiation at 0.3, 2.0, and 3.0 W using either contact or noncontact handpieces. Controls received no laser irradiation. Melting, loss of porosity, and other surface alterations were observed on both types of implants, even with the lowest power setting. For the sterilization study, both types of implants were first sterilized by exposure to ethylene oxide and then contaminated with spores of B subtilis. After laser irradiation, the implants were transferred to sterile growth medium and incubated. Laser irradiation did not sterilize either type of implant. The spore-contaminated implants in the control group were successfully sterilized with ethylene oxide.

Bacillus subtilis↗
PubMed1990

Laryngeal mask airway and tracheal tube insertion by unskilled personnel.

After a short training programme 11 naval medical trainees inserted a laryngeal mask airway (LMA) and a tracheal tube (ETT) in random order in a total of 110 anaesthetised patients. They were allowed 40 s for each attempt. Success was defined as the detection of expired carbon dioxide within 40 s of Guedel airway removal which subsequently rose to an end-tidal value of at least 4 kPa, together with satisfactory lung expansion and ventilation, without other airway intervention by the anaesthetist. 104 LMA insertions were successful compared with 56 of ETTs (p less than 0.01). All first attempts at LMA insertion were successful, whereas satisfactory ETT placement was progressive. Insertion was also quicker with the LMA (20 s) than with the ETT (35 s) (p less than 0.01). Further studies are indicated to assess the value of the LMA in emergencies.

Airway Obstruction↗
PubMed1990

Association of magnesium deficiency with the blood pressure-lowering effects of calcium.

The role of dietary calcium and magnesium in the development of hypertension was studied in nine groups, each consisting of nine spontaneously hypertensive rats aged 8-31 weeks. The animals were fed AIN 76A semi-purified diets varying in calcium (0.075, 0.5 and 2.5%) and magnesium (0.01, 0.05 and 0.75%) concentrations according to a 3 x 3 factorial design. Dietary calcium and systolic blood pressure were inversely related, significantly (P less than 0.05) after 12 weeks. Total and ultrafilterable serum calcium concentrations were also significantly negatively correlated with blood pressure (r = -0.46; P = 0.001 and r = -0.57; P = 0.001, respectively). Repeated measures analysis of variance indicated that dietary magnesium had no effect on systolic blood pressure, and no calcium x magnesium interaction on blood pressure was observed. Signs of magnesium deficiency, calcium deposits in the kidneys, and histological lesions were observed in groups on a high-calcium diet receiving normal and low levels of magnesium. Thus a lowering of blood pressure by calcium supplementation, without concomitant magnesium supplementation, was accompanied by biochemical and histological abnormalities in this animal model.

Animals↗
PubMed1989

Effect of various graft materials with tetracycline in localized juvenile periodontitis.

Ten patients with bilateral, posterior osseous defects associated with localized juvenile periodontitis (LJP) completed the study. Following the initial therapy, osseous defects were surgically debrided and grafted with a 4:1 volume ratio combination of either Synthograft/tetracycline (b-TCP/TTC), Periograf/tetracycline (HA/TTC) or freeze-dried bone allograft/tetracycline (FDBA/TTC). Graft materials were selected randomly for each half mouth following defect debridement, with a different material used on the opposite side for that patient. Immediately following each surgery, patients were placed on doxycycline 100 mg/day for 10 days. Direct re-entry evaluation of 51 osseous defects demonstrated no significant differences among the graft materials regarding hard tissue or soft tissue changes, except for greater percent defect fill for HA/TTC compared to b-TCP/TTC. Significant decreases in defect depth and pocket depth were achieved with each graft material. No adverse reactions to the use of any of the graft materials in combination with local and systemic tetracycline were found. The results indicate all three graft materials used in conjunction with TTC are acceptable and beneficial for the treatment and repair of osseous defects associated with localized juvenile periodontitis.

Adolescent↗
PubMed1989

Dietary magnesium does not affect blood pressure in spontaneously hypertensive rats.

To determine the therapeutic effectiveness of dietary magnesium in the treatment of established hypertension, 21 male spontaneously hypertensive rats were fed altered levels of magnesium oxide from 17 to 29 weeks of age. The rats were divided into three groups of approximately equal mean baseline systolic blood pressures and fed AIN 76A purified diets containing magnesium at 0.01% (low), 0.05% (normal), and 0.40% (high) levels. Mean systolic blood pressures in the conscious SHR during the 12 week period and terminal direct blood pressures under anesthesia were not significantly different among treatment groups. Total and ultrafilterable serum magnesium concentrations reflected dietary magnesium intake. Total and ultrafilterable serum calcium levels were significantly higher (p less than 0.05) in the low magnesium-fed SHR. Histopathologic alterations indicative of aging did not differ among treatment groups. Therefore, in spite of altered serum mineral status, blood pressure and histopathology were not affected by dietary magnesium.

Animals↗
PubMed1985

Evaluation of durapatite ceramic as an alloplastic implant in periodontal osseous defects. II. Twelve month reentry results.

Thirteen patients received Durapatite, a hydroxylapatite ceramic (Periograf), as a bone implant material in various types of intrabony defects following internally beveled full thickness flaps, root planing, and defect debridement. All osseous margins and defects were measured from the cemento-enamel junction (CEJ) at specific locations using a standardized periodontal probe. Similarly debrided, nonimplanted defects served as controls. Defect selection as either experimental or control site was based on an alternating defects design after local therapy was completed. Periodontal dressing and systemic tetracycline were used for 10 days. Postsurgical visits for documentation and plaque control were at 10, 20 and 30 days, and 3, 6, 9 and 12 months. Measurements relating to defect changes were made at the 12-month surgical reentry. For evaluation purposes original defect depths were divided into three groups. In Group I (less than 3 mm) defect fill was 1.0 mm (47%) for the implanted defects and 0.3 mm (33%) for the control sites (significantly different at P less than 0.05). In Group II (3-6 mm) defect fill of 1.7 mm (44%) for implanted sites was significantly better (P less than 0.05) than the 0.8 mm (29%) found in control sites. In the deepest group (Group III, greater than 6 mm) Durapatite placement yielded 2.1 mm (32%) of defect fill while debridement alone resulted in 1.8 mm (26%) of fill (P greater than 0.05). Hard tissue responses demonstrated a substantial advantage for use of Durapatite over controls, while soft tissue changes were similar for both.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗