Biomedical subjects

P J Liepins

Publications and source records attributed to P J Liepins.

5 recordsLinked to original sources

PubMed2000

A comparison of two nickel-titanium instrumentation techniques in teeth using microcomputed tomography.

AIM: The aim of the study was to compare the shaping of root canals by two nickel-titanium instrumentation techniques using microcomputed tomography (MCT). METHODOLOGY: Ten mandibular first molar teeth (30 canals) that had intact crowns and fully formed roots were scanned using MCT. Fifteen canals were instrumented using NiTiFlex hand files (Maillefer) using balanced force. The remainder were instrumented using prototype ProFile 0.04 Taper instruments (Dentsply) in a crown-down manner to an apical size ISO 25. The teeth were scanned again following instrumentation. The two instrumentation techniques were compared in a total of 27 canals. The area of dentine removed at predetermined levels (2.0, 3.0, 4.5, 6.0, 7.5 mm) from the apex was measured. Transportation and centring were recorded. Images constructed at these levels were compared with video images of equivalent physical sections created after the second scan. The volume of dentine removed in the apical 7.5 mm of the root canals of each tooth was calculated and the different techniques compared. Rendered three-dimensional images were used to assess the preparations qualitatively. The time taken for preparation was recorded. RESULTS: There was no significant difference between hand instrumentation with NitiFlex files and machine instrumentation with prototype ProFile 0.04 Taper instruments for any of the variables tested. CONCLUSIONS: Both techniques produced well centred and tapered preparations.

Dental High-Speed Technique↗

PubMed1999

Micro-computed tomography: a new tool for experimental endodontology.

AIM: Micro-computed tomography (MCT) using conebeam geometry is a method of producing true 3D images of the structure of small samples. A prototype MCT unit was adapted for imaging teeth to examine whether it could be used to quantify the instrumentation of root canals. METHODOLOGY: Ten mandibular first molar teeth that had intact crowns and fully formed roots were scanned using MCT at a resolution of 0.081 mm and 3D-rendered images created; root canals were segmented from this. Reproducibility of MCT was verified for root canal shape and size. Access cavities were prepared into the pulp space and root canals enlarged to a continously tapering preparation using a crowndown technique. Each tooth was scanned again to allow comparison of pre- and post-instrumentation images. The roots were then sectioned at five predetermined horizontal levels for video-digitized measurement of dimensions of roots and root canals. The video images had a resolution of 0.025 mm. Video-digitized images of the physical cut surfaces were compared with equivalent MCT reconstructed images. The total area of the root canals (internal) and root (external) at each level were calculated from both MCT reconstructions and video-digitized images, and compared. RESULTS: There was a highly significant correlation between MCT and video images for both external and internal areas (r = 0.94). Rendered 3D images were constructed to show the root canal systems of teeth. The total volumes of the apical 7.5 mm of root canals were calculated from rendered images of nine teeth before and after instrumentation. The mean amount of dentine removed by instrumentation was 3.725 mm3, which was 28% of the original canal volume. CONCLUSIONS: Micro-computed tomography was shown to be accurate for experimental endodontology.

Anatomy, Cross-Sectional↗

PubMed1998

A comparison of two histological validating techniques for occlusal caries.

UNLABELLED: Validation of a diagnostic technique is important to establish whether it actually measures what it is purported to measure. However, the accuracy of the validation technique per se can influence the apparent accuracy of the diagnostic technique. OBJECTIVES: The aim of this study was to describe two alternative histological validating techniques for occlusal caries and to compare quantitative depth measurements of carious lesions taken using each method. METHODS: Thirty sections (mean thickness 0.67 mm) were cut to include two to four discrete sites in 10 freshly extracted teeth. The first histological validating technique used a microfocal X-ray unit to produce magnified high definition radiographic images of the sections or 'macroradiographs'. An image analysis system was used to make quantitative measurements of the lesions (if present) with respect to the enamel-dentine junction (EDJ). The second validating technique used a confocal microscope to image beneath the cut surface of the section. Quantitative measurements were taken from the fluorescence images of both sides of each section and a mean depth measurement calculated. RESULTS: Complete agreement was found between the two validating techniques for the subjective interpretation of the presence and extent of caries. A strong positive relationship was found between the two histological validating techniques for depth measurements made of dentine caries from the EDJ (r = 0.93, P < 0.001). Depth measurements made from the macroradiographs were greater than from the confocal fluorescence images (mean difference = 0.41 mm). CONCLUSIONS: Both validating techniques enable the identification of sound sites, those with enamel caries and dentine caries. However, quantitative assessments made with each technique could result in disagreement.

Adult↗

PubMed1996

Histological validation of electrical resistance measurements in the diagnosis of occlusal caries.

Diagnosis of occlusal caries is difficult from visual and radiographic examination. The use of electrical resistance measurement has been described previously and reported to be a potentially sensitive alternative technique. This is possibly due to the decreased resistance of carious pits and fissures. The aim of this study was to validate a prototype electrical caries monitor for the diagnosis of caries in pits and fissures in vitro using a microfocal radiographic technique. Thirty discrete sites were investigated in 10 extracted molar teeth. Electrical resistance measurements were recorded at each site and thick sections (approximately 0.65 mm) prepared for microfocal radiography. Microfocal radiography indicated that six sites were sound, 10 had enamel caries and 14 dentine caries. At a resistance value of 2.2 M(OMEGA), below which a site was regarded as carious and above which it was regarded as sound, electrical resistance measurements proved sensitive (92%) and specific (100%). Quantification of mineral content indicated that mineral loss in enamel may influence resistance measurement more than lesion depth.

Adult↗

PubMedDate not supplied

A browser based image bank, useful tool or expensive toy?

DIBS, the Digital Image Banking System, is a web browser based environment for depositing and withdrawing generic medical images. These can be annotated or modified on an individual's computer for use in talks and lectures. DIBS is programmed in 'C', to query and update a database as well as producing web pages on the 'fly'. Images are deposited using an interactive form, minimizing data entry and are received in a digital format or are digitized on demand. Three interfaces allow DIBS to be searched; an image map of the human body presents a simple graphical interface, whilst more specific searches can be performed by selecting categories from predefined scrolling menus or using a full text search. When a DIBS search is performed, preview thumbnail images and descriptions are provided, linked to the full size images that can be saved locally along with the text description. DIBS offers fast and convenient access to a wide range of medical images, eliminating the time consuming process of producing one's own slides or borrowing from colleagues. It is proving to be a useful tool within our Medical School but some copyright, ethical and image security issues still need to be resolved.

Computer Graphics↗