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Biomedical subjects

D Gardiner

Publications and source records attributed to D Gardiner.

12 recordsLinked to original sources
PubMed1998

An experimental study of mandibular arch widening in the dog using distraction osteogenesis.

PURPOSE: This study evaluated the amount of skeletal and dental widening of the mandible in the dog produced by using a tooth-borne distraction device. MATERIALS AND METHODS: Four adult mongrel dogs had osteotomies performed in the parasymphysis region and had a tooth-borne distraction appliance placed to widen the mandible 10 mm. The interarch distance between the canines and between the fourth premolar teeth, as well as between the intrabony markers, was compared. RESULTS: The canine teeth moved 95% of the distraction device movement, whereas the bone widened 55% of the distraction device movement. Histological evaluation showed woven bone formation within the distraction gap. CONCLUSION: This study shows that a tooth-borne mandibular widening device will move the teeth significantly more than the bone.

Animals↗
PubMed1998

The effect of different membranes on onlay bone graft success in the dog mandible.

OBJECTIVE: The aim of this study was to compare resorbable membranes, nonresorbable membranes, and no coverage with respect to onlay bone graft healing in a dog. EXPERIMENTAL DESIGN: Each of four dogs had six corticocancellous blocks of ramus bone placed bilaterally as onlay grafts to the inferior lateral aspect of the mandible. On each side, one graft was left uncovered, one was covered with a collagen membrane, and one was covered with an expanded polytetrafluoroethylene membrane. Volume determinations were made at the time of graft placement and when the animals were killed. RESULTS: There were no statistically significant differences in bone volume or histologic outcome among the three groups.

Animals↗
PubMed1997

Skeletal and dental movements after anterior maxillary advancement using implant-supported distraction osteogenesis in dogs.

PURPOSE: This study evaluated skeletal and dental relapse in the dog after anterior maxillary advancement using an implant-anchored distraction osteogenesis device. MATERIALS AND METHODS: After the placement of implants into the palate, four dogs had a skeletally anchored distraction device fabricated and an anterior maxillary osteotomy performed. The distraction device was activated 0.5 mm two times each day to advance the anterior segment 10 mm in 10 days. The dental and skeletal changes were measured and compared for 26 weeks after distraction was completed. RESULTS: Tooth and radiographic measurements indicated that on the 10th day of distraction the average tooth advancement was 6.83 mm +/- 1.75 mm SD, and the average skeletal advancement, based on radiographs, was 8.67 mm +/- 1.25 mm SD. After 10 weeks, the average tooth advancement was 4.0 +/- 1.73 mm, and the average skeletal advancement was 8.67 +/- 3.59 mm. After 26 weeks, the average tooth advancement was 3.65 +/- 1.69 mm, and the average skeletal advancement was 8.0 +/- 1.98 mm. Bone healing occurred in all animals. The skeletal advancement 26 weeks after distraction was 85% of the initial advancement. The teeth adjacent to the distraction site initially moved 68% of the advancement, but the distance between the teeth subsequently decreased, with a resultant 36% advancement compared with the initial advancement. CONCLUSION: This study showed that skeletal fixation will result in bone movement greater than dental movement, indicating the need for skeletal anchorage to advance the maxilla.

Animals↗
PubMed1995

Vir typing: a long-PCR typing method for group A streptococci.

We have developed a new procedure (Vir typing) for typing Streptococcus pyogenes, by amplifying the entire 5- to 7-kb variable vir regulon by long PCR. The amplified DNA is then cleaved with HaeIII and visualized by ethidium bromide fluorescence after agarose gel electrophoresis. A simple procedure for preparing DNA of sufficiently high quality from 96 samples was employed simultaneously. This DNA was also used to develop a random amplified polymorphic DNA (RAPD) procedure. The discriminatory power of the two DNA-based procedures was compared with previous methods, M typing, and multilocus enzyme electrophoresis. Both procedures were highly discriminatory, but the stoichiometric yield of restriction fragments in Vir typing allows unambiguous interpretation of results.

Bacterial Proteins↗
PubMed1995

Multiple strains of Streptococcus pyogenes in skin sores of aboriginal Australians.

A molecular technique (random amplification of polymorphic DNA) was used to characterize group A streptococcal (GAS) strains among 194 isolates from 55 swabs from 12 Australian Aboriginal children and adults with multiple pyoderma lesions. Ninety-three percent of the lesions contained only one strain of GAS, but 8 of 12 individuals were infected with more than one strain. We conclude that accurate epidemiologic surveys require that more than one swab specimen be obtained from each person, whereas typing of more than one colony per swab is less informative. Characterization of GAS strains by random amplification of polymorphic DNA analysis should help to provide important insights into the epidemiology of GAS, particularly in tropical populations where many isolates are M nontypeable, and into the mechanisms of genetic variation of GAS in such populations.

Adult↗
PubMed1994

Two Saccharomyces cerevisiae genes which control sensitivity to G1 arrest induced by Kluyveromyces lactis toxin.

The Kluyveromyces lactis toxin causes an arrest of sensitive yeast cells in the G1 phase of the cell division cycle. Two complementary genetic approaches have been undertaken in the yeast Saccharomyces cerevisiae to understand the mode of action of this toxin. First, two sequences conferring toxin resistance specifically in high copy number have been isolated and shown to encode a tRNA(Glu3) and a novel polypeptide. Disruption of the latter sequence in the yeast genome conferred toxin resistance and revealed that it was nonessential, while the effect of the tRNA(Glu)3 was highly specific and mediated resistance by affecting the toxin's target. An alpha-specific, copy number-independent suppressor of toxin sensitivity was also isolated and identified as MATa, consistent with the observation that diploid cells are partially resistant to the toxin. Second, in a comprehensive screen for toxin-resistant mutants, representatives of 13 complementation groups have been obtained and characterized to determine whether they are altered in the toxin's intracellular target. Of 10 genes found to affect the target process, one (KTI12) was found to encode the novel polypeptide previously identified as a multicopy resistance determinant. Thus, both loss of KTI12 function and elevated KTI12 copy number can cause resistance to the K. lactis toxin.

Adaptor Proteins, Signal Transducing↗
PubMed1992

The handwriting on the wall. Warning signs of impending job loss.

Can nurse executives read the handwriting on the wall when they or another nurse executive are facing a forced resignation or termination? What are the warning signs of an eroding job position, including the relationship between the chief nurse executive and the chief executive officer? How much time does a nurse executive typically have in the job once the warning signs begin to show? The authors discuss these questions and specific tactics and strategies suggested by warning signs.

Decision Making, Organizational↗
PubMedDate not supplied

Hydroxyapatite-coated cylindrical implants in the posterior mandible: 10-year observations.

A total of 443 hydroxyapatite-coated cylindrical implants were placed into the posterior mandibles of consenting patients from July 1985 through December 1991. Implants were placed into ridges that had sufficient bone volume. Implants were also placed in ridges with thin bone, grafted bone, or immediate extraction sites, which occasionally resulted in increased morbidity. All were followed yearly with clinical and radiographic examinations. Life table analyses were performed using SAS software. Ten-year cumulative survival and nonmorbid (based on bone loss criteria) rates were determined for the four posterior tooth locations and for all posterior locations combined. Cumulative survival for implants was 0.858 +/- 0.056 in the first premolar region, 0.833 +/- 0.041 for the second premolar region, 0.785 +/- 0.041 for the first molar region, and 0.718 +/- 0.064 for the second molar region. When all posterior mandibular locations were taken together, the cumulative survival was 0.793 +/- 0.025. Cumulative nonmorbid rates were 0.816 +/- 0.056 for the first premolar, 0.729 +/- 0.049 for the second premolar, 0.600 +/- 0.046 for the first molar, and 0.507 +/- 0.066 for the second molar. The cumulative nonmorbid rate was 0.646 +/- 0.028 for all sites combined. Comparisons between sites indicated that the second molar site had statistically more morbidity than did the other three sites. Most of the problems were identified with 8-mm-long implants, especially in the second molar location. Clinical parameters, including the presence of keratinized gingiva and a hygienic restoration, were associated with survival. Both mechanical and inflammatory compromise were found to be reasons for implant failure.

Bicuspid↗
PubMedDate not supplied

Bone response to functioning implants in dog mandibular alveolar ridges augmented with distraction osteogenesis.

The specific aim of this study was to determine the response of alveolar bone after it was augmented vertically using distraction osteogenesis and subsequently loaded with implant restorations. Four dogs each had four implants placed horizontally into an edentulous mandibular quadrant and, after integration, a distraction osteogenesis device was fabricated in the laboratory. An osteotomy was made to allow the crest of the alveolar ridge to be distracted vertically. After 10 mm of vertical distraction, the device was stabilized with light cured resin. Following bone fill confirmation of the distraction gap at 10 weeks, two implants were placed into the ridges, one in distracted bone and one in nondistracted bone. After 4 months for implant integration, freestanding prostheses were fabricated. Crestal bone levels were evaluated throughout the period of function. Animals were sacrificed after 1 year of loading, for histologic evaluation of the bone. The vertical ridge augmentation averaged 8.85 +/- 1.05 mm after 10 weeks of healing following distraction, without change over 1 year of implant loading. Histologic examination showed that bone had formed between the distracted segments, creating an augmented ridge. The average thickness of the labial cortex in the distraction gap was significantly thinner than the lingual cortex in distracted bone and the lingual and labial nondistracted cortical bone. The presence of the dental implant did not significantly affect cortical bone thickness. Serial sections showed that implants remained integrated and functional without soft tissue inflammation. Dental implants placed into alveolar ridges augmented with the technique of distraction osteogenesis maintained bone and were functional for the length of this study.

Alveolar Ridge Augmentation↗