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Biomedical subjects

T R Pitt Ford

Publications and source records attributed to T R Pitt Ford.

At least 19 recordsLinked to original sources
PubMed1992

Blood flow changes in the dental pulp during limited exercise measured by laser Doppler flowmetry.

The effect of limited exercise on pulpal blood flow was assessed by laser Doppler flowmetry (LDF). The primary aim of the investigation was to determine whether clinically significant changes could be induced by mild exercise when LDF was used to monitor pulpal blood flow. Blood flow readings were obtained from the coronal pulps of 17 upper central incisor teeth of 10 human volunteers before, during and after limited exercise. Readings were also obtained from the adjacent attached gingivae. Pulse rate was recorded concurrently. Pulpal blood flow was found to vary during exercise, with a mean percentage change of 38% from the level at rest; the range was from a 100% decrease to a 200% increase. The mean percentage increase in gingival blood flow was 65%, with a range of 6-300%. The main indication that blood flow was being assessed was the pulsatile nature of the output. Results were compared only within individual teeth. The pulse rate increased during exercise (mean percentage increase 54%, range 11-98%). There was no direct relationship between increased pulse rate and pulpal blood flow. It was evident that the mechanisms controlling pulpal and gingival blood flows differed. Laser Doppler flowmetry readings were only reproducible in individual teeth provided that the patient was at rest, and this should be taken into account in clinical or research measurements.

Adolescent↗
PubMed1992

The role of intracanal medication in root canal treatment.

The role of intracanal medication as a root canal dressing is re-examined. In pulpectomy and some root canal treatments, where the root canal contains vital pulp tissue, it is doubtful whether a routine intracanal medicament is needed. In infected root canals, intracanal medication has been advocated for many purposes. An intracanal medicament is used to: (i) eliminate any remaining bacteria after canal instrumentation; (ii) reduce inflammation of periapical tissues and pulp remnants; (iii) render canal contents inert and neutralize tissue debris; (iv) act as a barrier against leakage from the temporary filling; (v) help to dry persistently wet canals. However, most of the indications for intracanal medicaments are questionable. Intracanal medicaments should only be used for root canal disinfection as part of controlled asepsis in infected root canals, and their role is secondary to cleaning and shaping of the root canal. Thorough canal debridement and adequate canal preparation are more pertinent, and their importance is emphasized. Bacteriological sampling may be necessary if a tooth does not respond to treatment, to help in the choice of intracanal medicament.

Adrenal Cortex Hormones↗
PubMed1991

Immediate and delayed direct pulp capping with the use of a new visible light-cured calcium hydroxide preparation.

The pulpal response to mechanical exposure and capping either immediately or after 24 hours was investigated in 64 teeth of four cynomolgus monkeys with the use of Dycal, VLC Dycal, or Prisma-Bond. All overlying amalgam restorations were surface-sealed with zinc oxide-eugenol cement. After 2 months the teeth were removed and prepared for histologic examination; dentine bridges were present in almost all teeth filled with Dycal or VLC Dycal, and pulpal inflammation was observed in only one tooth that showed evidence of infection. Dentine bridges were usually incomplete when Prisma-Bond was used, although pulpal inflammation was only observed in 2 of 22 teeth. The success rate of pulp capping delayed for 24 hours was as high as that for immediate capping.

Animals↗
PubMed1991

Establishing a postgraduate course in endodontics.

A proposal was first made to the University of London in 1985 to establish an MSc degree in Endodontics. It was finally approved in 1988. The first course started in 1988, and is now offered by two schools of the University, the United Medical and Dental Schools of Guy's and St Thomas's Hospitals and the Institute of Dental Surgery. The course has three main components: a taught part, clinical practice and a research project. The taught part is a course common to both the schools, while clinical practice and the research are carried out at the students' respective schools.

Education, Dental, Graduate↗
PubMed1991

The adaptation and sealing ability of light-cured glass ionomer retrograde root fillings.

The adaptation and sealing ability of a light-cured glass ionomer cement when used as a retrograde root filling was assessed using a confocal optical microscope with and without a fluorescent dye. This material was compared with a conventional glass ionomer cement and amalgam. The root canals of 60 extracted human single-rooted teeth were prepared and filled with gutta-percha and sealer. All the teeth were apicected, retrograde cavities were prepared, and then divided into three groups of 20 teeth each and filled with the test materials. The light-cured glass ionomer cement was well adapted to the retrograde cavity and apicected root surface. Within the retrograde cavity the cement was often well adapted to one wall, but gaps were found on the opposite cavity wall. This was probably caused by the polymerization contraction of the material. In contrast, the amalgam retrograde root fillings were poorly adapted to the cavities, with gaps between the cavity walls and amalgam. This group exhibited the poorest sealing ability as measured by the extent of dye penetration. The conventional glass ionomer cement was often found smeared over the root face, and there were unfilled voids at the base of some retrograde cavities. The results of the dye leakage study were analysed statistically. The sealing ability of the light-cured glass ionomer cement was significantly better than that of amalgam (P less than 0.001). The dye penetration around the light-cured glass ionomer cement and the conventional glass ionomer cement was not significantly different (P greater than 0.05). However, the sealing ability of the conventional glass ionomer cement was significantly better than that of amalgam (P less than 0.05).

Analysis of Variance↗
PubMed1991

Perialveolar interstitial resistance and compliance in isolated rat lung.

We have developed a method to characterize fluid transport through the perialveolar interstitium using micropuncture techniques. In 10 experiments we established isolated perfused rat lung preparations. The lungs were initially isogravimetric at 10 cmH2O arterial pressure, 2 cmH2O venous pressure, and 5 cmH2O alveolar pressure. Perialveolar interstitial pressure was determined by micropuncture at alveolar junctions by use of the servo-null technique. Simultaneously a second micropipette was placed in an alveolar junction 20-40 microns away, and a bolus of albumin solution (3.5 g/100 ml) was injected. The resulting pressure transient was recorded for injection durations of 1 and 4 s in nonedematous lungs. The measurements were repeated after gross edema formation induced by elevated perfusion pressure. We model the interstitium as a homogeneous linearly poroelastic material and assume the initial pressure distribution due to the injection to be Gaussian. The pressure decay is inversely proportional to time, with time constant T, where T is a measure of the ratio of interstitial tissue stiffness to interstitial resistance to fluid flow. A linear regression was performed on the reciprocal of the pressure for the decaying portion of the transients to determine T. Comparing pressure transients in nonedematous and edematous lungs, we found that T was 4.0 +/- 1.4 and 1.4 +/- 0.6 s, respectively. We have shown that fluid transport through the pulmonary interstitium on a local level is sensitive to changes in interstitial stiffness and resistance. These results are consistent with the decreased stiffness and resistance in the perialveolar interstitium that accompany increased hydration.

Airway Resistance↗
PubMed1990

Effectiveness of ultrasonic files in the disruption of root canal bacteria.

The physical mechanisms of ultrasound, namely cavitation and acoustic streaming, generated by the Enac-Osada ultrasonic unit were investigated for effectiveness in disrupting Streptococcus mitis. In addition, the bactericidal effect of ultrasound in the presence of 2.5% sodium hypochlorite was examined. Bacterial suspensions were irradiated directly with ultrasound in simulated root canals, and the viability of bacteria was examined after growth on a blood agar medium under anaerobic conditions at 37 degrees C for 5 days. The results indicated that ultrasound per se failed to disrupt bacteria but resulted in increases in the viable counts; the former was considered to be because of the lack of cavitation and the latter because of the dispersal effects of acoustic streaming. The 2.5% sodium hypochlorite solution demonstrated powerful bactericidal activity.

Colony Count, Microbial↗
PubMed1990

The assessment of pulpal vitality.

This is a review of methods of assessing dental pulp vitality in order to assist the clinician in diagnosis and treatment planning. It covers the patient's history, clinical examination, assessment of radiographs, thermal tests, electrical tests, test cavities, use of anaesthesia, and the recent application of laser Doppler flowmetry.

Dental Pulp Diseases↗
PubMed1990

Tissue response to glass ionomer retrograde root fillings.

The periapical tissue response to glass ionomer cement retrograde root fillings was investigated both in the presence and in the absence of fillings in the root canals of eight upper incisor teeth of four monkeys. The pulps of the teeth were extirpated and one canal in each pair was filled with laterally condensed gutta-percha immediately after canal preparation. The other canal was prepared but left open to oral contamination. Apicectomies were performed on both teeth in each pair 1 week later, and glass ionomer cement retrograde root fillings were placed. After 5 months, the teeth and surrounding tissues were removed and prepared for histological examination. All four of the teeth without root canal fillings showed severe periapical inflammation, and bacterial were present in the interface between the dentine and the retrograde root filling. The teeth with root canal fillings showed little or no periapical inflammation. This study showed that adhesive retrograde root fillings were successful when the root canal was completely filled, but in the absence of a gutta-percha canal filling they failed to provide a seal.

Animals↗
PubMed1990

Therapeutic efficacy of recombinant tumor necrosis factor alpha in an experimental model of human prostatic carcinoma.

Prostatic carcinoma represents the second leading cause of cancer mortality in men and is responsible for over 25,000 deaths each year. Currently, no curative therapy is available for metastatic carcinoma of the prostate. The present studies were undertaken to assess the efficacy of recombinant tumor necrosis factor alpha (TNF) in the therapy of experimental prostatic carcinoma. TNF was cytotoxic to the prostate cancer cell lines PC3, DU145, and LNCAP but not benign prostatic epithelial and stromal cells in vitro. The sensitivity of the prostatic carcinoma lines to TNF-mediated cytotoxicity was enhanced by the presence of actinomycin D. Intravenous administration of TNF (50-100 micrograms/kg) to nude mice bearing subcutaneous PC3 tumors resulted in significant inhibition of primary tumor growth compared to control. TNF was also effective in reducing the growth of intraabdominal PC3 tumors induced by intrasplenic injection of PC3. Furthermore, the incidence of microscopic PC3 foci in the spleen, liver, lung, and diaphragm was diminished in mice receiving TNF therapy. These studies demonstrate the potential of TNF in the therapy of human prostatic carcinoma.

Animals↗
PubMed1989

Comparison of two ultrasonic units in shaping simulated curved canals.

The effects of ultrasonic instrumentation on the preparation shape of curved simulated canals were investigated. Measurements of the displacement amplitudes of the files were made to examine the possible relationship between displacement amplitude and the cutting ability of the file. Twenty-five simulated canals in clear resin blocks were instrumented using a Cavi-Endo unit at a power setting of 1 with differing times of instrumentation and with water as irrigant. Another group of 25 canals received similar treatment but were instrumented with an Enac unit at a power setting of 1. The canal shape and the incidence of elbow formation were evaluated using various measurements taken from photographic prints of the canals. All canals exhibited unequal removal along the canal with more removal occurring coronally. The Enac group exhibited a higher incidence of elbows which occurred further apically than those in the Cavi-Endo group. There was no significant difference between groups in the amount of apical canal enlargement. Coronally, the Enac appeared to cut significantly better. The Enac also caused significantly greater apical deviation and change in width. In both units more elbows were formed following instrumentation, with less flexible files having smaller displacement amplitudes.

Dental Cavity Preparation↗
PubMed1989

A new root canal sealer based on calcium hydroxide.

A new root canal sealer based on calcium hydroxide has been developed and two properties, sealing ability and biocompatibility, have been investigated in this study. Sealing ability was assessed by the extent of dye penetration along root fillings in extracted teeth. The sealing ability was good and similar to that of a control zinc oxide-eugenol sealer. Biocompatibility was assessed by histological examination of the periapical tissues of monkey teeth, either 1 or 6 months, after vital pulpectomy and immediate root filling with gutta-percha and sealer. Zinc oxide-eugenol was used as the control sealer. Normal periapical tissues were observed around all 24 teeth filled with the experimental root canal sealer. The study established that the new root canal sealer had acceptable properties of biocompatibility and sealing ability.

Animals↗
PubMed1989

A comparison using macroradiography of canal shapes in teeth instrumented ultrasonically and by hand.

Forty teeth with severely curved canals were divided into two groups and the root canals were prepared either ultrasonically or with hand instruments. Canal shapes were compared qualitatively and quantitatively using subtraction macroradiography; this allowed the pre- and postinstrumented canal shapes to be viewed on the same print. The times to carry out instrumentation and the incidence of elbows were recorded. In addition, the following measurements were taken from the radiographs using a digitizer: apical and coronal areas, distance of elbow from canal curvature, change in width at elbow and 0.5 mm apical to it, and apical transport width. Subjective evaluation revealed that no difference was apparent between the methods as to the places where the dentin was removed; both instruments exhibited unequal dentin removal along the canal length with more removal occurring coronally. The quantitative results indicated an absence of differences in the following: the time of instrumentation, the incidence of elbows, the distance of elbow from the point of curvature, the change in width at the region of the elbow, and the apical transport width. These findings indicated that ultrasonic files behaved similarly to hand instruments when used in a filing action.

Dental Pulp Cavity↗