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Biomedical subjects

T Donovan

Publications and source records attributed to T Donovan.

At least 37 records · Page 2Linked to original sources
PubMed1998

Use of provisional restorations to enhance soft-tissue contours for implant restorations.

The objective of restoring missing teeth with implant-supported restorations should not merely be achieving osseointegration with an implant and a biomechanically sound restoration. The objective must be the esthetic and functional restoration of the missing teeth. To achieve this, proper treatment planning is critical. Precise implant placement and delicate soft-tissue manipulation during surgery will allow the restorative dentist to enhance the peri-implant soft-tissue contours with the use of provisional restorations. Empirically, it seems that the earlier the provisional restoration is delivered in the treatment process the more ideal the esthetics. Several methods of using provisional restorations to enhance soft-tissue contours are presented. The concept of immediately delivering provisional restorations on placement of an implant is discussed.

Dental Implantation, Endosseous↗
PubMed1997

Subtypes of Campylobacter jejuni from sporadic cases of diarrhoeal disease at different locations in England are highly diverse.

Serotyping (heat stable antigens) was performed on 398 strains of Campylobacter jejuni from faeces of human enteritis cases in England. Strains isolated over 12 months at three locations were heterogeneous with 33 HS serotypes represented. HS1 and HS4 complex were the predominant types (34% of all strains). The monthly strain frequency distributions were similar at the three locations. The late spring peak appeared to be associated with a rise in miscellaneous serotypes rather than with the emergence of any characteristic predominant serotype. PFGE DNA restriction profiling provided evidence of a high degree of genomic diversity within the common HS1 and HS4 complex serotypes, irrespective of the geographical source, yet some subtypes were common to more than one location. The study showed that C. jejuni strain subtypes from human enteric infections in England were highly diverse, and that HS serotyping must be combined with a more discriminatory subtyping method such as PFGE DNA profiling to provide an accurate basis for epidemiological surveillance.

Campylobacter Infections↗
PubMed1995

Enterotoxigenic Clostridium perfringens as a cause of sporadic cases of diarrhoea.

The purpose of this study was to investigate the incidence of cases of sporadic diarrhoea associated with enterotoxigenic Clostridium perfringens. Cases were identified by detection of C. perfringens enterotoxin with the Oxoid RPLA kit, with confirmation by ELISA, in faecal specimens from isolated incidents of diarrhoea and from which no other enteropathogen had been isolated. In a 2-month study, 65 (18%) of 370 specimens were enterotoxin positive. There was no predominant age group or sex in the enterotoxin-positive group, but higher proportion (79%) was resident in the community than were enterotoxin-negative cases (34%). Only four of the 65 enterotoxin-positive patients had received antibiotic therapy. Spore counts in most enterotoxin-positive patients were < 10(5)/g, indicating that detection of high numbers of C. perfringens is not useful in determining the aetiology of sporadic diarrhoea. Diagnosis should be confirmed by the detection of enterotoxin, but further work is required to assess whether an acceptable accuracy is obtained with the RPLA kit or whether ELISA is needed in all cases.

Acute Disease↗
PubMed1993

Microcephalic, osteodysplastic, primordial dwarfism.

A case of microcephalic, osteodysplastic, primordial dwarfism (cephaloskeletal dysplasia of Taybi and Linder) is reported. This rare disease is characterised by unique clinical appearances and diagnostic radiographic findings. It is also associated with distinctive brain abnormalities. The latter include micrencephaly, lissencephaly, corpus callosum aplasia/agenesis and unusual histological brain abnormalities.

Abnormalities, Multiple↗
PubMed1993

Pharmacokinetics of dexamethasone following single-dose intravenous administration to extremely low birth weight infants.

The single-dose pharmacokinetics of dexamethasone were studied in 7 extremely low birth weight infants of mean (+/- SD) gestational age 25.6 +/- 0.5 weeks suffering bronchopulmonary dysplasia. A mean peak dexamethasone concentration of 250.5 +/- 70.7 ng/ml was obtained following an intravenous bolus dose (0.369 +/- 0.04 mg/kg dexamethasone) of dexamethasone sodium phosphate. Dexamethasone was measured in plasma by HPLC. Mean clearance (0.143 +/- 0.028 litres/kg/h) was approximately half that reported previously in children and adults, while the half-life (9.26 +/- 3.34 h) was 2- to 3-fold longer than in these patients. The volume of distribution (1.9 +/- 0.483 litres/kg) was larger than reported in a previous study in adults, but was similar to that determined in pediatric and adult patients in another study.

Bronchopulmonary Dysplasia↗
PubMed1989

[In vitro study of the microleakage pattern around posterior composite resin restorations using a new dentin bonding agent].

A totally new product, by the name Scotchbond 2 (3M Co) appeared recently in the field of bonding agents. Grace to its improved formula, the manufacturers claim that both the bond strength and the sealing ability of the material, render it trustful for use in both anterior and posterior composite resin restorations. The purpose of this in vitro investigation was to determine the microleakage pattern around slot type cavities, restored with posterior composite resin (P-50, 3M Co) using two different generations of bonding agents. Two types of cavities were prepared in sound premolars extracted for orthodontic reasons. In the first group (10 teeth) the cervical wall was located in the enamel, above the cementoenamel junction and in the second group (10 teeth) the cervical wall was located below the CEJ. The enamel surrounding the cavity margins was etched using 37% orthophosphoric acid gel, rinsed and dried and the bonding agents were applied and cured according to the manufacturer s instructions. The posterior composite was condensed and light-cured incrementally, in three horizontal layers. The samples were thermocycled for 200 cycles of 4 minutes each between 4.37 and 60 degrees centigrade, covered with fingernail varnish and sticky wax and immersed in 0.5% basic fuchsin dye for 12 hours. The specimens were split in two halves longitudinally in a mesiodistal direction in a hard tissues microtome and the degree of dye penetration was evaluated using an optical microscope. According to the results obtained we come to the conclusions that: 1. The use of Scotchbond 2 minimized but did not eliminate the microleakage around posterior composite resin restorations, in both types of cavities.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicuspid↗
PubMed1987

Effect of electrodeposition of gold on porcelain-to-metal bond strength.

The effect of electrodeposition of two different thicknesses of gold on porcelain-metal bond strength with three different base metal alloys was determined and compared to a control high gold alloy. The following conclusions can be drawn. Mean porcelain-metal bond strengths of all four alloys were in the same range when conventional porcelain application techniques were used. However, the base metal porcelain-metal bond is clinically suspect because of adhesive failure through the porcelain-metal interface. A thin 180A gold coat increased the porcelain-metal bond strength and generally resulted in cohesive failure through the porcelain. A thicker gold coat (720A) decreased the bond strength and generally resulted in adhesive failure. The mechanism of action of the gold coat on bond strength is likely its effect on the oxide layer on the surface of the base metal alloy.

Chemical Phenomena↗
PubMed1987

Esthetic results with full restorations.

The metal-ceramic and all-ceramic esthetic restorations available today bear little resemblance to their predecessors of 2 and 3 decades ago. Metal-ceramic crowns and fixed partial dentures are successful when the dentist understands what biologic and mechanical demands will be placed on the restoration. Tissue management and tooth preparation affect long-term function and esthetic success.

Crowns↗
PubMed1986

Effect of four pretreatment techniques on porcelain-to-metal bond strength.

Porcelain bond strengths of three base metal alloys with different metal pretreatment techniques were studied. Statistically significant differences were found in bond strengths achieved between the different metals but not with the different pretreatments. Each metal displayed considerable variation in bond strength with each of the pretreatment techniques. Collectively, the base metal alloys evaluated displayed a disturbing tendency for adhesive failure through the porcelain-metal interface, although this was not universal. Manufacturers and ceramists should develop a specific regime for porcelain bonding for each alloy used. Standardized testing should demonstrate adequate bond strengths with cohesive failure through the body of the porcelains.

Crowns↗
PubMed1986

[Follow-up (4.6 years) of patients with latent cardiomyopathy].

25 patients with latent cardiomyopathy (LCM) (filling pressure elevated during exercise) were followed. After 4.6 years 15 patients were re-examined (10 female, 5 male, mean age at first examination 47 years). 6 patients could not be reexamined, but it is certain that all 6 patients lived. 3 patients of whom 2 were foreigners could not be followed. 9 of these 15 re-examined patients showed 4.6 years after the first examination a normalization of filling pressures during exercise. Findings remained constant in 4 and became worse in 2 patients. There was a tendency for arterial blood pressure to increase during the 4.6 years. This small group of retrospectively followed patients with latent cardiomyopathy showed a favourable long-term result. The findings do not support the hypothesis that LCM is an early manifestation of dilated congestive cardiomyopathy.

Adult↗
PubMed1985

An analysis of margin configurations for metal-ceramic crowns.

Major types of margin configurations for ceramometal crowns are reviewed. This is one of the most commonly misunderstood and poorly practiced aspects of fixed prosthodontics. The resultant underprepared teeth produce discolored gingiva and chalky crowns.

Crowns↗
PubMed1984

Use of paint-on die spacers in preparations with grooves.

Film thickness of paint-on die spacer materials was measured on axial walls and in grooves. Two different materials and two different modes of application were tested. From the data presented, the following conclusions can be drawn: There are potentially significant differences in film thickness produced with different die spacing materials. The technique used to apply die spacer can affect the film thickness produced. Careful application of Pactra airplane dope will not result in significant accumulation of die spacer in the groove. Tru-fit die spacer produced generally erratic film thickness and demonstrated a potentially significant amount of pooling in the groove base. Further study is warranted to determine if use of die spacer in grooves will improve the seating of castings.

Chemical Phenomena↗