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Biomedical subjects

K Horner

Publications and source records attributed to K Horner.

At least 19 recordsLinked to original sources
PubMed1992

Clinical bone densitometric study of mandibular atrophy using dental panoramic tomography.

Using the dental panoramic tomogram (DPT) and a nickel stepwedge, the prevalence of mandibular osteoporosis in 99 elderly, edentulous individuals was investigated densitometrically. A site was chosen on each DPT adjacent to the mandibular mental foramen and the optical density measured using a digital densitometer. Each DPT was then independently examined by a radiologist and the patients grouped into those exhibiting osteoporosis and those not. Twenty-seven of the patients exhibited qualitative evidence of osteoporosis on the DPT, using established radiological criteria. A large majority of this group was female (25 individuals, 93 per cent). Of the remaining 72 non-osteoporotic patients, only 32 (44 per cent) were female. There was a significant difference in the quantitative, densitometrically derived measurements of mandibular bone density between the osteoporotic and non-osteoporotic groups. The osteoporotic group had a mean optical density at the mandibular measurement site (mean D = -0.773, s.d. = 0.2) which was significantly different from that of the non-osteoporotic group (mean D = -0.888, s.d. = 0.21), t = 2.432, P less than 0.02. This previously diagnosed difference supports the validity of the densitometric technique. When all 99 patients were studied, the difference between the mean mandibular, equivalent nickel thickness of the males and females was significant (t = 2.32, P = 0.022). This sex difference could not be entirely accounted for by differences in the period of edentulousness or age of males and females.

Adult↗
PubMed1992

Quality assurance: 1. Reject analysis, operator technique and the X-ray set.

Number 1 of the series, which will present the 'core knowledge' on radiography, is designed to help the dentist produce the highest quality radiographs and appears in two parts. Part 1 discusses the identification of problems and how to solve those related to operator technique and the X-ray set, while part 2 will comment on problems with the image receptor, the darkroom and processing.

Humans↗
PubMed1992

Quality assurance: 2. The image receptor, the darkroom and processing.

Number 1 of the series, which presents the 'core knowledge' on radiography, is designed to help the dentist produce the highest quality radiographs and appears in two parts. Part 1 discussed the identification of problems and how to solve those related to operator technique and the X-ray set, whilst this article will comment on difficulties with the image receptor, the darkroom and processing.

Humans↗
PubMed1991

The effects of positioning variations in transcranial radiographs of the temporomandibular joint: a laboratory study.

The relationship of the mandibular condyle to the articular fossa and eminence as seen on transcranial oblique lateral (TOL) radiographs of the temporomandibular joint is used by some clinicians as an important diagnostic sign and indicator of treatment. The literature is divided on the validity of this. The aim of this study was to consider the effects of variations in both the position of the joint and the X-ray beam orientation on the image seen on TOL radiographs. TOL radiography of a mounted block specimen of a human temporomandibular joint and associated tissues was carried out using a range of specimen rotations (+20 degrees to -20 degrees with respect to the sagittal plane) and X-ray beam angulations (20 degrees, 25 degrees, 30 degrees). Analysis of tracings of the joint images showed that most of the parameters measured varied by statistically significant amounts with changes in either specimen rotation or beam angulation. It is concluded that any convention which purports to evaluate the position of the mandibular condyle in relation to the articular fossa from TOL radiographs is invalid when the orientation of the condyle to coronal and horizontal planes is unknown.

Adult↗
PubMed1991

Measurement of mandibular bone mineral content using the dental panoramic tomogram.

The aim of this study was to determine whether bone mineral content could be estimated densitometrically using dental panoramic tomograms. A nickel stepwedge was attached to the film cassette to give a reference image on the radiographs. Four mandibles were radiographed and the optical density of a number of sites on the bone images measured. The calcium and phosphate content of the mandibles at these sites was measured by chemical analysis, using 3 mm diameter full thickness cores. The radiographically derived equivalent nickel thickness of the mandibular test sites was significantly correlated with calcium content (r = 0.62. P = 0.013), phosphate content (r = 0.633, P = 0.011), and dry bone weight (r = 0.541, P = 0.036), provided correction for soft tissue thickness was made. A clinical study is justified to determine whether the technique has sufficient accuracy to provide sequential data on individual patients and whether it may useful as a simple method of screening patients for mandibular osteoporosis.

Absorptiometry, Photon↗
PubMed1991

Quantitative assessment of a new dental imaging system.

The "Radiovisiography" dental imaging unit (Trophy UK Ltd) is a digital system using an intensifying screen and charge-coupled device in an intra-oral sensor. This paper presents a description of the system and an assessment of the original model in terms of patient dose (relative to film systems), resolution (limiting resolution and modulation transfer function), distortion and image noise (amplitude). The system does offer the possibility of reduced patient exposure and minimal distortion, although resolution and latitude are inferior to standard dental film.

Humans↗
PubMed1991

Radiovisiography for length estimation in root canal treatment: an in-vitro comparison with conventional radiography.

Radiovisiography (RVG) and conventional film (CF) were compared in an in-vitro study for working length estimation of root canals. Hedstrom files (size 15) were placed in the root canals of 60 extracted teeth and the teeth imaged using both CF and RVG. The length of file observed was assessed on CF, RVG and enhanced RVG images. The results indicated that a greater length of file was imaged with CF than with RVG (P less than 0.05). However, enhanced RVG images were not significantly different from CF images. While clinical studies are now indicated to confirm these results, it is suggested that, when utilizing RVG for length estimation in root canal treatment, the enhancement facility should be used.

Dental Pulp Cavity↗
PubMed1990

Radiovisiography: an initial evaluation.

An initial evaluation of the latest dental radiographic imaging system, radiovisiography, is reported. Despite limitations in its possible clinical applications and problems inherent within the system design, radiovisiography has been found to be a rapid imaging system capable of producing clinically acceptable periapical images. It is suggested that this system may be of particular value in endodontics and in its present form should be considered as an adjunct rather than as a replacement for conventional intra-oral film. Further studies are now required into recent system modifications which are described.

Adolescent↗
PubMed1990

Dose reduction in dental radiography.

All exposures to ionizing radiation for medical and dental purposes carry risks to both the patient and staff. It is now accepted practice that all exposures should be kept as low as reasonably practicable to minimize these risks. The various methods currently available for dose limitation in intraoral and panoramic radiography and their effects on image quality are considered. In intraoral radiography the use of fast (E-speed) film and rectangular collimation offer dose reductions of approximately 50 per cent and 60 per cent respectively. Constant potential X-ray units, longer focus-to-skin distances and rare-earth filtration will permit further dose reductions. In panoramic radiography the radiation dose to the patients can be reduced by up to one-eighth by combining the use of constant potential X-ray units, rare-earth intensifying screens and rare-earth filtration.

Humans↗
PubMed1990

Radiovisiography for imaging root canals: an in vitro comparison with conventional radiography.

Radiovisiography is a rapid, low-dose, digital imaging system that utilizes a small, intraoral sensor in place of radiographic film. Because of these characteristics, it may be particularly suitable for use in endodontics. Consequently radiovisiography and conventional film radiography for the imaging of root canals were compared in vitro. There was no statistically significant difference between the percentage of length of root canal visible on conventional film and that visible on radiovisiographic images. Thus, radiovisiography may be considered to be of equal value to conventional film radiography for the imaging of root canal systems in vitro.

Dental Pulp Cavity↗
PubMed1989

Distortion products in early stage experimental hydrops in the guinea pig.

The swelling of the endolymphatic spaces in experimental hydrops is likely to induce mechanical changes all along the cochlea. The selective atrophy of short and middle stereocilia on the outer hair cell above the first cochlear turn is expected to alter micromechanics and transduction. Two tone stimuli were employed in the present study to investigate cochlear distortion products in hydropic ears. Despite a substantial low frequency sensitivity loss on the CAP audiogram, 2f1-f2 distortion products recorded in the RWCM and the CAP were similar in hydropic ears and normal control ears which reflect the probable common origin of these responses--the base of the cochlea where no threshold shifts can be detected. On the other hand this distortion product in the otoacoustic emissions was considerably reduced in hydropic cochleas when the primary tones lay within the pathological part of the audiogram. The reduction of CDT emissions cannot be accounted for by hair cell loss since at the early stage of hydrops described here there is only discrete hair cell loss which is restricted to the apex of the cochlea. On the other hand the reduction in the amplitude of the CDT might reflect disturbance in hair cell function and/or cochlear mechanics above the first cochlear turn.

Action Potentials↗
PubMed1989

Central giant cell granuloma of the jaws: a clinico-radiological study.

There is disagreement in the literature about the radiological appearance of the central giant cell granuloma (CGCG) of the jaws. A review of 26 cases of CGCG was undertaken with the aim of resolving this. CGCG were found over a wide age range but most occurred in the 2nd and 3rd decades. Females were more frequently affected. Radiologically CGCG were most commonly seen as round or ovoid, unilocular, well defined but non-corticated radiolucencies in the mandible anterior to the first permanent molars. Expansion, either bony or soft tissue alone, was common. Internal calcification was sometimes seen. Teeth in contact with CGCG may lose their lamina dura and become displaced but resorption was rare.

Adolescent↗
PubMed1988

Atypical simple bone cysts of the jaws. I: Recurrent lesions.

The aetiology, clinical and radiographic features and the treatment of simple bone cysts of the jaws are discussed. Recurrence of jaw lesions is unusual. Two cases are presented of simple bone cyst in the mandible which recurred following conventional treatment. The importance of clinical and radiographic follow-up is emphasised.

Adolescent↗
PubMed1988

Atypical simple bone cysts of the jaws. II: A possible association with benign fibro-osseous (cemental) lesions of the jaws.

Four cases are described of simple bone cysts of the mandible arising concurrently with benign fibro-osseous (cemental) lesions. Previous reports of such findings, and a possible relationship to the so-called 'cementoma' of the long bones, are considered. The relevance of this to the aetiology is addressed, and it is suggested that at least some cases diagnosed as simple bone cysts are closely related to the fibro-osseous lesions.

Adult↗