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Biomedical subjects

A C Shearer

Publications and source records attributed to A C Shearer.

At least 19 recordsLinked to original sources
PubMed2001

Computing facilities available to final-year students at 3 UK dental schools in 1997/8: their use, and students' attitudes to information technology.

OBJECTIVE: To identify computer facilities available in 3 dental schools where 3 different approaches to the use of technology-based learning material have been adopted and assess dental students' perception of their own computer skills and their attitudes towards information technology. DESIGN: Multicentre cross sectional by questionnaire. SUBJECTS: All 181 dental students in their final year of study (1997-8). RESULTS: The overall participation rate was 80%. There were no differences between schools in the students' self assessment of their IT skills but only 1/3 regarded themselves as competent in basic skills and nearly 50% of students in all 3 schools felt that insufficient IT training had been provided to enable them to follow their course without difficulty. There were significant differences between schools in most of the other areas examined which reflect the different ways in which IT can be used to support the dental course. CONCLUSIONS: 1. Students value IT as an educational tool. 2. Their awareness of the relevance of a knowledge of information technology for their future careers remains generally low. 3. There is a need to provide effective instruction in IT skills for those dental students who do not acquire these during secondary education.

Attitude↗
PubMed2001

Root canal systems of the mandibular and maxillary first permanent molar teeth of south Asian Pakistanis.

AIM: The purpose of the present ex vivo study was to investigate variations in the root canal systems of mandibular and maxillary first permanent molar teeth of South Asian Pakistanis. METHODOLOGY: The root canal systems of a sample of 30 mandibular and 30 maxillary first permanent molar teeth extracted from South Asian Pakistanis were studied using a clearing technique. RESULTS: The mesial roots of the mandibular molar teeth typically presented with two canals (97%) of type II, IV or VI configuration. The distal roots of these teeth presented with a single canal (50%) of type I or V configuration or with two canals (50%) of type II, IV or VI. The prevalence of four root canals in two-rooted mandibular first permanent molar teeth was 47%. In maxillary molar teeth the mesial roots with a single canal (47%) were type I or type V; those with two canals (53%) were type II, IV or type VI. The distal and palatal roots that presented as a single canal (100%) were type I or type V configuration. The prevalence of four root canals in three-rooted maxillary first permanent molar teeth was 53%. CONCLUSION: It is concluded that four root canals in mandibular and maxillary first permanent molar teeth of South Asian Pakistanis is a common occurrence. The distribution of the different configurations of root canal systems in this population differed from that in Caucasian groups, suggesting that variations in root canal systems may be attributed to racial divergence.

Carbon↗
PubMed2001

Three phosphor plate systems and film compared for imaging root canals.

AIM: The aim of this study was to compare three phosphor plate intraoral imaging systems (Digora (DA), Digident (DT), Denoptix (DX)) and E-speed conventional film (CF) for the imaging of root canals. METHODOLOGY: Sixty extracted permanent teeth were exposed using CF, DA, DT and DX. The length of root canal visible from its most apical extent to a line drawn at the level of the cementoenamel junction was measured and this was expressed as a percentage of the distance between the radiographic apex and the cementoenamel line. All images were examined concurrently by two examiners. Films were viewed under standardized conditions and DA, DT and DX images were viewed directly from the monitor screen. The images on the monitor were enhanced to give the subjectively clearest image. RESULTS: The mean percentage of canal visible on CF was 90%, DA 78%, DT 81% and DX 83%. The difference was significant for CF-DA (P < 0.001) and CF-DT (P = 0.001). There was no statistically significant difference for CF-DX or between any of the three phosphor plate imaging systems. CONCLUSIONS: It is concluded that a greater length of root canal was visible on conventional film than on three phosphor plate imaging systems and that this may be of clinical significance.

Analysis of Variance↗
PubMed2001

Treatment planning for the problem patient: restorative, ethical, legal and psychological perspectives. Case I: Emma.

'Emma' is the first of a series of four articles that aims to look at some of the problems patients may present with when they visit their dentist. Each article starts with a brief scenario about the hypothetical patient and his/her clinical problems. As well as the clinical problem, each case also raises ethical, legal or psychological problems. All of these issues are discussed and possible management strategies and treatment options described.

Adolescent↗
PubMed2001

Treatment planning for the problem patient: restorative, ethical, legal and psychological perspectives. Case 3: Mary.

Mary' is the third of a series of four articles that aims to look at some of the problems patients may present with when they visit their dentist. Each article starts with a brief scenario about the hypothetical patient and his/her clinical problems. As well as the clinical problem, each case also raises ethical, legal or psychological problems. All of these issues are discussed and possible management strategies and treatment options investigated.

Adult↗
PubMed2001

Treatment planning for the problem patient: restorative, ethical, legal and psychological perspectives. Case 4: Mr Lester.

'Mr Lester' is the final case study in a series of four articles that aims to look at some of the problems patients may present with when they visit their dentist. Each article starts with a brief scenario about the hypothetical patient and his/her clinical problems. As well as the clinical problem, each case also raises ethical, legal or psychological problems. All of these issues are discussed and possible management strategies and treatment options investigated.

Aged↗
PubMed1999

Comparison of two stylus methods for measuring surface texture.

OBJECTIVES: The purpose of this study was to evaluate and compare two "stylus" methods for measuring surface texture of dental tissues and materials. METHODS: The two styli chosen were a contact diamond stylus and a non-contact focussed laser stylus attached to the same measuring apparatus. RESULTS: These indicate that there are significant differences between those obtained from surface texture measurements using a non-contact laser stylus and a diamond contact stylus method despite being mounted in the same profilometer. This is valid for both the test specimens of known surface texture, provided by the manufacturers, and for a "real world" simulation using contoured and finished Dicor ceramic blocks. The only significant agreement between the two styli was found for the Ra parameter. This should not be used alone to describe the roughness of a surface because the parameter is not sensitive to profile shape. Owing to the properties of the stylus used it is essential that the limitations of surface profilometry be recognised. SIGNIFICANCE: Caution should be exercised when comparing the results of surface texture studies of dental hard tissues and restorative materials using varying types of stylus attached to a surface profilometer.

Dental Equipment↗
PubMed1998

A milled ceramic inlay/onlay system: a report from a series of cases.

The aims of this study were to assess the handling properties of restorations produced by a milled ceramic system (Celay) and to evaluate by direct clinical means some of the characteristics of Celay restorations following placement and after one year of clinical service.

Adolescent↗
PubMed1996

Surface texture changes of a composite brushed with "tooth whitening" dentifrices.

OBJECTIVES: The aim of this investigation was to evaluate the significance of selected surface texture parameters used to describe and quantify the effect of tooth brushing with various "tooth whitening" dentifrices on a resin composite surface in vitro. METHODS: Specimens of a microfil resin composite were brushed with selected dentifrices. Surface texture profiles were acquired and analyzed both pre- and post-brushing using a contact diamond stylus. The selected parameters chosen to describe the surface texture were Ra, Rz, Rpm and the Rpm:Rz ratio. Differences between toothpastes were assessed using an ANOVA and a multiple comparisons test, the Student Newman-Keuls procedure. P and t values were calculated to determine if any of the surface roughness parameters were significantly changed by brushing. RESULTS: The results indicate that there were significant changes in the surface texture of the resin composite following tooth brushing with the selected dentifrices. For example, the use of Clinomyn significantly increased the surface roughness of the resin composite, as measured by the Rz parameter, from 2.19 +/- 1.67 microns to 10.02 +/- 2.57 microns (p < 0.05). In addition, the surface texture parameters chosen to describe the properties of the surface should reflect a knowledge of profile shape such as Rpm:Rz ratio, and care should be taken if measurements of surface texture of dental restorative materials are to be used as predictors of clinical performance. SIGNIFICANCE: All the toothpastes chosen for this investigation left a surface on the resin composite which may be prone to crack propagation during "vertical barrelling" movements generated during mastication. However, this may be more of a function of the rigidity of the restorative material rather than the surface left after tooth brushing.

Analysis of Variance↗
PubMed1996

The use of a radiopaque contrast medium in endodontic radiography.

A series of in vitro studies were carried out to investigate the use and application of a radiopaque contrast medium in conventional periapical dental radiography for the diagnosis and evaluation of root canal systems. The water-soluble radiopaque contrast medium was introduced into the root canals of 30 first permanent maxillary and 30 first permanent mandibular molar teeth. The radiographic images of these teeth with and without radiopaque contrast medium in the root canal systems were compared and contrasted. Further comparisons were made with the same teeth rendered transparent. The results indicate that by standardizing the diagnostic criteria the inter-examiner reliability was in good agreement; it was independent of the radiographic technique used. The validity of the radiographs was enhanced by the use of the radiopaque contrast medium. The results confirm that, with the use of a radiopaque contrast medium, images of root canal systems are easier to read and interpret than plain radiographic images of root canal systems. The use of radiopaque contrast medium in endodontic radiography may be a valuable aid in the diagnosis and evaluation of root canal systems. This system would complement rather than replace plain radiography.

Contrast Media↗
PubMed1996

Sensitometric and image quality performance of "rapid" intraoral film processing techniques.

A number of products are available to dentists for the rapid production of intraoral radiographic films but there is little information on their relative merits. This study evaluated the performance of five "rapid" film processing products commonly used by British dentists in comparison with standard Kodak manual processing. Two Perspex contrast-detail test objects were made in order to investigate threshold contrast. Film speed, film gradient, limiting resolution and threshold contrast results are presented. Rapid processing systems possessed lower film speed when compared with Kodak Ektaspeed film and standard Kodak processing. The speed of E-speed film was found to be lower than that of D-speed film when used with Westone "Rapid X-ray" processing. Overall image quality was generally similar for all film/processing combinations evaluated, with the exception of Nix QP which gave markedly poorer image quality.

Humans↗
PubMed1995

A laboratory evaluation of Ektaspeed Plus dental X-ray film.

OBJECTIVES: The aim of this study was to make a laboratory evaluation of the image quality of a new dental X-ray film, Ektaspeed Plus, compared with Ektaspeed and Ultraspeed films. METHODS: Films of each emulsion type underwent a range of exposures at both 50 kVp and 70 kVp, and characteristic curves were constructed to give a comparison of fog, speed and contrast. Line pair and contrast detail test objects were used to assess the resolution of radiographs and the ability of the two film types to reproduce minor differences in subject contrast. The sensitivity of the emulsions to safelighting for a range of times was also tested. RESULTS: Ektaspeed Plus had the same speed, a slightly higher base plus fog density but a higher contrast (50 and 70 kVp) than Ektaspeed. The speed of Ektaspeed Plus was higher and the contrast similar to that of Ultraspeed film. Limiting resolutions of the three films were the same. There was a slightly better imaging of one contrast detail phantom with Ektaspeed Plus compared to Ektaspeed at 70 kVp only. All three emulsions were insensitive to recommended safelighting conditions. CONCLUSION: The improved image contrast of Ektaspeed Plus may be more acceptable to dentists than Ektaspeed and lead to a greater acceptance of E-speed film, contributing to dose reduction.

Emulsions↗
PubMed1995

An in vitro comparison of 10 radiographic methods for working length estimation.

The aim of this in vitro study was to assess the efficacy of 10 currently available methods of producing radiographic images, two conventional and eight rapid, in working length estimation. Thirty extracted teeth comprising 42 root canals were mounted in blocks of poly(methylmethacrylate) and access cavities prepared. A size 15 Hedstrom file was inserted into each root canal and sealed into position. Each tooth was imaged by 10 methods: combinations of conventional (D- and E- speed) film processed with conventional manual chemistry of two proprietary brands of rapid processing chemistry (Westone Rapid Dental and Kodak 'Rapid Access'), Super X30 packet processed film, Hanshin Hi-Fi and Nix NF45-100 films processed using their respective manufacturers' monobath solutions, and the Sens-A-Ray digital X-ray system. Comparisons of length of file visible were made between the D-speed films (conventionally processed using Kodak chemistry) and the nine other radiographic methods. No significant differences in percentage length of file seen were found between D-speed film processed with conventional chemistry and E-speed film processed with the same chemistry or between D-speed film processed with with conventional chemistry and six of the rapid imaging systems studied. The percentage length of the file visible was significantly less for Sens-A-Ray (P=0.02) and for Nix NF45-100 film (P<0.005) when compared with D-speed film processed with conventional chemistry. This difference in file length is probably not of clinical importance for the Sens-A-Ray images but may be so for the Nix images.

Dental Pulp Cavity↗
PubMed1995

Comparison of methods for measuring surface roughness of ceramic.

The aim of this investigation was to compare two methods of assessing the surface texture of finished dental ceramic; a laser reflectivity method (LSR) and a contact stylus tracing method. Identical ceramic blocks (Dicor MGC) were finished using a variety of techniques and devices, and the surface texture characterized by LSR and contact stylus tracing to enable comparisons to be made between the two methods. The results indicate that there is little correlation between the two measuring methods. Therefore, laser reflectivity should not be exclusively used to measure the surface texture of contoured and finished ceramic materials. The development of sophisticated surface characterization parameters suggest that the surface characteristics of dental restorations and other related surfaces should be described using more than one surface measurement parameter. Surface parameters should be chosen which can both quantify surface roughness and provide information on the shape of the surface under investigation.

Dental Polishing↗
PubMed1993

Confidence limits on the branching order of phylogenetic trees.

We describe a confidence test for branching order that can aid protein phylogeny reconstruction as well as the evaluation of the optimal tree. It is proposed that the process resulting in the observed amino acid residue differences, which is the basis for the identification of the order and relative times of divergence events, is appropriately described by a modification of the negative binomial distribution. The relative total numbers of mutations (accepted and nonaccepted), which result in a given number of amino acid differences, may be obtained as the expectation of this distribution. The associated variances enable significant differences in tree branching order to be established. If the total rates of mutation of the genes encoding the compared proteins are equal, the expected total mutations and their associated variances map identically to their relative times of divergence. In addition, significantly different rates of change (due to differences in total mutation rate and/or acceptance rate) may be identified without the requirement of outlying reference group. The method is equally applicable to phylogenies derived from DNA or RNA sequence information.

Amino Acid Sequence↗
PubMed1993

Use of 'rapid' processing techniques by a sample of British dentists.

Knowledge of current practices amongst general dental practitioners (GDPs) is important in planning postgraduate and undergraduate teaching curricula and in ensuring the relevance of clinical research. A number of methods are available to dentists for the rapid production of intraoral radiographic images, including concentrated and monobath chemistry. No current data exists about the use of such 'rapid' systems in the UK. The aim of this study was to obtain this data, including the relative popularity of the different systems. A questionnaire on 'rapid' processing of radiographs was distributed to all 855 GDPs in four Family Health Services Authorities in North West England. Responses were received from 326 GDPs (38.1%). 29.4% of GDPs used some kind of 'rapid' system, with 'packet processed' films being the most popular. 6.1% of all GDPs used 'rapid' systems routinely, while the remainder used them for specific situations, typically emergencies and endodontics.

England↗
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↗