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Biomedical subjects

A J Coleman

Publications and source records attributed to A J Coleman.

At least 19 recordsLinked to original sources
PubMed2005

Acoustic streaming in lithotripsy fields: preliminary observation using a particle image velocimetry method.

This study considers the acoustic streaming in water produced by a lithotripsy pulse. Particle image velocimetry (PIV) method was employed to visualize the acoustic streaming produced by an electromagnetic shock wave generator using video images of the light scattering particles suspended in water. Visualized streaming features including several local peaks and vortexes around or at the beam focus were easily seen with naked eyes over all settings of the lithotripter from 10 to 18 kV. Magnitudes of the peak streaming velocity measured vary in the range of 10-40 mm s(-1) with charging voltage settings. Since the streaming velocity was estimated on the basis of a series of the video images of particles averaged over 1/60s, the time resolution limited by the video frame rate which is 1-2 orders of magnitude larger than driving acoustic activities, measured velocities are expected to be underestimated and were shown a similar order of magnitude lower than those calculated from a simple theoretical consideration. Despite such an underestimation, it was shown that, as predicted by theory, the magnitude of the streaming velocity measured by the present PIV method was proportional to acoustic intensity. In particular it has almost a linear correlation with peak negative pressures (r=0.98683, p=0.0018).

Acoustics↗
PubMed2002

Guidelines for dosimetry and calibration in ultraviolet radiation therapy: a report of a British Photodermatology Group workshop.

This report examines the dosimetry of ultraviolet (UV) radiation applied to dermatological treatments, and considers the definition of the radiation quantities and their measurement. Guidelines are offered for preferred measurement techniques and standard methods of dosimetry. The recommendations have been graded according to the American Joint Committee on Cancer classification of strength of recommendation and quality of evidence (summarized in Appendix 5).

Humans↗
PubMed2001

Macromolecular leakage beneath full cast crowns: A two-year in vitro investigation.

STATEMENT OF PROBLEM: Most microleakage studies have used low molecular weight dyes or isotopes rather than clinically relevant materials such as lipopolysaccharides (LPSs) or cell wall materials that have been shown to provoke inflammatory reactions in the dental pulp. PURPOSE: This investigation evaluated the leakage (diffusion) of fluorescently labeled LPS and dextran beneath cast-gold crowns luted with 3 cements. MATERIAL AND METHODS: Thirty extracted molars were prepared for crowns. Ten crowns with access ports (facial or lingual) were cast in gold and luted with zinc phosphate, glass ionomer, and an adhesive resin cement onto their preparations. Teeth and crowns with filters inserted into the ports were immersed in a solution of labeled macromolecules (TRITC-LPS, FITC-dextran) and evaluated for leakage every month for 24 months. Filters were retrieved and analyzed with fluorescent microscopy. RESULTS: All filters retrieved from crowns luted with zinc phosphate, glass ionomer, and adhesive resin cements demonstrated no detectable leakage and were negative for both FITC-dextran and TRITC-LPS for all evaluation periods. CONCLUSION: For the 24 months of this investigation, zinc phosphate, Ketac-Cem, and C&B-Metabond were equally effective at preventing leakage of detectable molecular concentrations of LPS and dextran to the level of the access ports.

Boron Compounds↗
PubMed2001

A multifunctional, provisional, implant-retained fixed partial denture.

This article describes the modification of a procedure for fabricating a laboratory-processed, metal-reinforced, acrylic resin provisional restoration that becomes an implant-retained fixed partial denture. The modification involves the incorporation of patrix and matrix components into a cast metal framework. The prosthesis can be used as an alternative to a removable radiologic stent and surgical guide. It can function as a surgical guide during implant placement and help retract the buccal mucogingival flap during implant placement. The prosthesis also can be used as an aid in locating the implant during stage II surgery. Finally, the pontics can be converted into an implant-supported provisional restoration immediately after the implant prosthetic components are attached to the uncovered implants.

Adult↗
PubMed2000

Traceable calibration of ultraviolet meters used with broadband, extended sources.

A calibration system has been developed to provide increased accuracy in the measurement of the irradiance responsivity appropriate for UV meters used with broadband, extended sources of the type employed in phototherapy. The single wavelength responsivity of the test meter is obtained in the wavelength range 250-400 nm by intercomparison with a transfer standard meter in a narrow, monochromatic beam. Traceability to primary standard irradiance scales is provided via the National Measurement System with a best uncertainty of 7% (at 95% confidence). The effective responsivity of the test meter, when used with broadband extended sources, is calculated using the measured spectral and angular response of the meter and tabulated data on the spectral and spatial characteristics of the source radiance. The uncertainty in the effective responsivity, independent of the source variability, is estimated to be 10% (at 95% confidence). The advantages of this calibration system over existing approaches are discussed.

Calibration↗
PubMed1998

Macromolecular leakage beneath full cast crowns. Part III: The diffusion of lipopolysaccharide and dextran.

STATEMENT OF PROBLEM: Most microleakage studies have used low molecular weight dyes or isotopes rather than clinically relevant materials, such as lipopolysaccharides or cell wall materials, that have been shown to provoke inflammatory reactions in the dental pulp. PURPOSE: This study evaluated the leakage (diffusion) of lipopolysaccharide and dextran beneath cast gold crowns luted with 3 cements. MATERIALS AND METHODS: Thirty extracted molars were prepared for crowns. Ten crowns with access ports (facial or lingual) were cast in gold and luted with zinc phosphate, glass ionomer, and an adhesive resin cement onto their preparations. Teeth and crowns with filters inserted into the ports were immersed in a solution of labeled macromolecules (TRITC-LPS, FITC-dextran) and evaluated for leakage at 2 weeks, and 1, 2, 3, 4, 5, and 6 months. Filters were retrieved and analyzed with fluorescent microscopy. RESULTS: All filters retrieved from crowns luted with zinc phosphate, glass ionomer, and adhesive resin cements demonstrated no detectable leakage and were negative for both FITC-dextran and TRITC-lipopolysaccharide at all evaluation periods. CONCLUSION: Leakage of lipopolysaccharides and dextran did not occur during the period of this study. For the length of this investigation, zinc phosphate, Ketac-Cem, and C&B-Metabond were equally effective at preventing leakage of detectable molecular concentrations of lipopolysaccharide and dextran to the level of the access ports.

Crowns↗
PubMed1998

Acoustic performance and clinical use of a fibreoptic hydrophone.

Initial clinical experience with the use of an optical fibre hydrophone for in vivo ultrasound dosimetry is reported. The hydrophone, originally described by Beard and Mills (1997), operates as an extrinsic, low-finesse Fabry-Perot optical sensor where acoustically-induced thickness changes in a polymer film modulate the phase difference between light beams reflected from the two surfaces of the film. The pressure waveforms from the sensor are compared with those from a calibrated piezoelectric polymer membrane hydrophone. The sensor is found to have a frequency resonance at around 12 MHz, corresponding to the thickness mode of the 50-micron polymer film. The directional responses at 0.16 MHz, 1.0 MHz and 5.0 MHz are found to be similar to those predicted for a plane piston receiver with the same diameter as that of the polymer film (400 microns). The performance of the sensor as a broad-band hydrophone is degraded by the relatively low acoustical impedance of the adhesive used in the fibre-film bond. The hydrophone was used in the clinic for measurement of acoustic pressures within the ureter of 4 patients undergoing clinical extracorporeal shock-wave lithotripsy on a Dornier HM3 lithotripter. Pressures in the range 0.5 to 5.0 MPa were recorded in the ureter at positions over 10 cm from the renal pelvis. Problems related to the clinical use of the sensor, including instability in the sensitivity of the sensor following handling and its mechanical strength in high-amplitude acoustic fields, are discussed.

Acoustics↗
PubMed1997

Restorations using osseointegrated implants with resilient attachments.

This article presents a clinical report of the prosthodontic treatment of a patient with a partially edentulous mandible. Osseointegrated titanium implants and resilient attachments for overdentures were used to retain and stabilize a mandibular overdenture that restored the patient's occlusion. This provided a simple and economical solution to retention and stability problems for a patient with a partially edentulous mandible.

Aged↗
PubMed1996

Macromolecular leakage benath full cast crowns. Part II: The diffusion of lipopolysaccharide and dextran.

Fifteen extracted molars were prepared for crowns. Crowns with access ports (one facial, one lingual) were cast in gold. Teeth and crowns luted with provisional cement with filters inserted into the ports were immersed in a solution of labeled macromolecules (FITC-dextran, TRITC-LPS) and evaluated for leakage. Filters were retrieved and analyzed by use of fluorescent microscopy. Leakage of LPS and dextran occurred as early as 2 weeks beneath crowns luted with a provisional cement (NoGenol).

Crowns↗
PubMed1996

Detection of acoustic emission from cavitation in tissue during clinical extracorporeal lithotripsy.

A 1-MHz focused hydrophone has been used to search for acoustic emission expected to arise from cavitation occurring in tissue during clinical extracorporeal shock-wave lithotripsy (ESWL). The hydrophone is acoustically coupled to the patient's skin and the focus directed at depth in tissue under ultrasound guidance. The measured amplitude-time variation of the acoustic emission from tissue near the shock-wave focus of the Storz Modulith SL20 lithotripter has been examined in four patients. There is evidence of increased amplitude acoustic emission at 1 MHz from regions within tissue that also appear hyperechoic in simultaneously acquired ultrasound images. The acoustic emission from these regions decays from an initial peak to the noise level in about 500 microseconds following each shock-wave pulse. Within this period, a second peak, often of higher amplitude than the first, is typically observed about 100 microseconds after the shockwave. The time between the initial and second peaks is found to increase with increasing shock-wave amplitude. The results are similar to those previously observed from cavitation induced by shock-wave exposure in water and indicate that the 1-MHz acoustic emission arises from inertial cavitation in tissue during clinical ESWL.

Humans↗
PubMed1996

A technique for shielding electron beams used in radiotherapeutic management of head and neck cancer.

One of the major complications of radiation therapy in the management of maxillofacial tumors is the postradiation damage to the healthy tissues adjacent to the tumors. The success of radiation therapy is often limited by the treatment sequelae. The use of shielding prostheses reduces the number of potential treatment sequelae caused by the administration of therapeutic radiation for head and neck tumors. A technique for shielding uninvolved tissues from external electron beams used in therapeutic radiation treatment of head and neck cancer is described. The materials required are readily available and the shielding prosthesis can be easily fabricated by any dentist with a thorough understanding of radiation therapy, dosimetry, and the goals of treatment with radiation therapy.

Acrylic Resins↗
PubMed1996

A conservative fixed partial denture: a clinical report.

The restoration of a patient's edentulous area with a three-unit fixed partial denture is described. The denture consisted of an etched-metal bonded retainer and metal ceramic pontic with a nonrigid connector in combination with a conventional inlay retainer. The incorporation of a nonrigid connector permitted the use of dissimilar metals and cements with retainers of different retention potentials. This technique provides minimal reduction of tooth structure with supragingival margins for improved periodontal health.

Adult↗
PubMed1996

An injection technique for generating direct resin post and core patterns.

An injection technique can be used to rapidly generate direct post and core patterns with autopolymerizing acrylic resin. The technique uses an autopolymerizing acrylic resin, a serrated plastic pin, and a syringe with a disposable needle tube and plug to inject acrylic resin into the root canal. The technique is simple, accurate, and faster than the bead-brush technique and eliminates some of its shortcomings.

Acrylic Resins↗
PubMed1995

The cavitation threshold of human tissue exposed to 0.2-MHz pulsed ultrasound: preliminary measurements based on a study of clinical lithotripsy.

Evidence of acoustic cavitation was identified in the form of transient echoes in ultrasound B-scan images of patients receiving extracorporeal shock-wave lithotripsy treatment on a Storz Modulith SL20. This lithotripter generates 10-microseconds duration pulses with a centre frequency of 0.2 MHz at a pulse repetition frequency of 1 Hz. The visual appearance of B-scan images was examined in a total of 30 patients and a quantitative analysis of echogenicity changes was carried out in six cases involving lithotripsy treatment of stones in the renal pelvis. In these patients new echoes were identified in images unaffected by movement artefacts and were found to occur in perinephric fat and adjacent muscle and kidney tissue at positions close to the axis of the shock-wave field between 1 and 2 cm in advance of the indicated beam focus of the lithotripter. The echogenicity within each region increased significantly above the background level when the output of the lithotripter was increased above a threshold value. The acoustic pressures corresponding to this threshold were measured in water using a calibrated PVDF membrane hydrophone. After correction for attenuation in tissue the cavitation thresholds, in terms of the temporal peak negative pressure, are found to lie between 1.5 MPa and 3.5 MPa in all six cases. Interpretation of the measured values in terms of the likely threshold at the higher frequencies used in diagnostic ultrasound is considered using a theoretical model.

Acoustics↗
PubMed1995

Macromolecular leakage beneath full cast crowns. Part I: The diffusion of lipopolysaccharide and dextran.

Fifteen extracted molars were prepared for crowns. Crowns with access ports (one facial, one lingual) were cast in gold. Teeth and crowns with filters inserted into the ports were immersed in solutions of different concentrations of labeled and unlabeled macromolecules (fluorescein isothiocyanate-dextran, tetramethylrhodamine isothiocyanate-lipopolysaccharide [LPS], unlabeled LPS) and were evaluated for leakage. Retrieved filters were analyzed with fluorescent microscopy. At 10 micrograms/ml, only LPS leaked beneath the crowns in 24 hours (p = 0.0002), but after a 1-week immersion, both LPS and dextran leaked beneath the crowns. LPS scores were higher (p = 0.0002) than dextran scores. Slightly more LPS leakage occurred at 1 week than at 24 hours. LPS appeared to inhibit dextran diffusion beneath the cast crowns. Neither LPS nor dextran influenced LPS diffusion. Factors other than molecular size and weight may play a more important role in the microleakage occurring beneath crowns.

Crowns↗
PubMed1995

A two-stage impression technique for custom facial prostheses.

A two-stage impression technique that uses polyvinyl siloxane and irreversible hydrocolloid in a custom impression tray is described. The technique records the tissues to be contacted by the facial prosthesis with minimal distortion with the patient in an upright position and facial musculature at rest. The procedure is simple, accurate, and it eliminates some of the shortcomings of other techniques.

Acrylic Resins↗
PubMed1995

Restoration of posterior edentulous areas when space precludes conventional treatment: a case report.

Interarch space is sometimes severely restricted, precluding the use of a conventional removable partial denture design. The treatment of a patient with bilateral posterior edentulous spaces and insufficient interarch space is described. A modified removable partial denture with metal bases and metal pontics covered with facial veneers of tooth-colored resin was used to provide a functional and esthetic restoration.

Dental Occlusion, Traumatic↗