Prosthodontic rehabilitation of a patient using a swing-lock lower denture after segmental mandibulectomy

A swing-lock denture is useful in partially dentate patients where the configuration of the remaining teeth means that either the retention or stability available for a conventional removable partial denture is compromised. Such removable prostheses can also prove to be extremely useful when providing prosthodontic rehabilitation following surgical resection of oral cancer. A 20 year-old patient was referred to the Restorative Department of Cork University Dental Hospital following segmental mandibulectomy to treat a calicifying epithelial odontogenic tumour (Pindborg Tumour). Initial treatment using a conventional lower partial denture failed. This paper outlines the successfully rehabilitation using a lower Cobalt-Chromium swing-lock partial denture.

Durability and water absorption properties of surface treated concretes

Durability of concrete can be improved by applying surface treatments. Pore-lining treatments prevent or delay the ingress of water-borne salts while allowing vapour transfer across the concrete surface. The most common pore-liners are silanes and siloxanes; both reported to give good results. One area of concern, however, is variability in effectiveness of the treatment. This variability may be due to inconsistent coverage or extreme drying conditions. With care these can be controlled but another source of variability which is difficult to control is the moisture profile within the concrete at the time of application of the treatment. This paper describes a test programme to assess the sensitivity of three different surface treatments to moisture gradient in the concrete at the time of application of treatment. The test programme included durability parameters such as chloride ingress, corrosion due to chloride ingress, freeze-thaw salt scaling resistance. Water absorption (sorptivity) of treated and untreated concretes was also measured with a non-distructive test technique called Autoclam with the aim of determining if the Autoclam sorptivity test can be used to assess the effectiveness of surface treatments. Using these results it is possible to avoid, or allow for, moisture conditions which would adversely affect the success of a pore-liner. However there are advantages in specifying an expected performance of the surface treatment rather than specifying the conditions in which it must be placed. By this method a treatment would have to achieve a specified value of sorptivity or a specified reduction in sorptivity. Failure to do so would be an objective basis on which to make a decision of whether or not to reject the treatment. The Autoclam is a device capable of measuring sorptivity values down to the range typical of surface treated concrete. The paper assesses if the device can be used to discriminate between acceptable treatment and unsatisfactory treatments.

Impact of Testing Procedure on Permeability of Compacted Soils

The commonly used British Standard constant head triaxial permeability (BS) test, for permeability testing of fine grained soils, is known to have a relatively long test duration. Consequently, a reduction in the required time for permeability test provides potential cost savings, to the construction industry (specifically, for use during Construction Quality Control (CQA) of landfill mineral liners). The purpose of this article is to investigate and evaluate alternative short duration testing methods for the measurement of the permeability of fine grained soils.

As part of the investigation the feasibility of an existing method of short duration permeability test, known as the Accelerated Permeability (AP) test was assessed and compared with permeability measured using British Standard method (BS) and Ramp Accelerated Permeability (RAP). Four different fine grained materials, of a variety of physical properties were compacted at various moisture contents to produced analogous samples for testing using three the three different methodologies. Fabric analysis was carried out on specimens derived from post-test samples using Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscope (SEM) to assess the effects of testing methodology on soil structure. Results showed that AP testing in general under predicts permeability values derived from the BS test due to large changes in structure of the soil caused by AP test methodology, which is also validated using MIP and SEM observations. RAP testing, in general provides an improvement to the AP test but still under-predicts permeability values. The potential savings in test duration are shown to be relatively minimal for both the AP and RAP tests.

Measurement of permeability using a bench-top centrifuge

The commonly used British Standard constant head triaxial permeability test for testing of fine-grained soils is relatively time consuming. A reduction in the required time for soil permeability testing would provide potential cost savings to the construction industry, particularly in the construction quality assurance of landfill clay liners. The purpose of this paper is to evaluate an alternative approach of measuring permeability of fine-grained soils benefiting from accelerated time scaling for seepage flow when testing specimens in elevated gravity conditions provided by a centrifuge. As part of the investigation, an apparatus was designed and produced to measure water flow through soil samples under conditions of elevated gravitational acceleration using a small desktop laboratory centrifuge. A membrane was used to hydrostatically confine the test sample. A miniature data acquisition system was designed and incorporated in the apparatus to monitor and record changes in head and flow throughout the tests. Under enhanced gravity in the centrifuge, the flow through the sample was under ‘variable head' conditions as opposed to ‘constant head' conditions as in the classic constant head permeability tests conducted at 1 g . A mathematical model was developed for analysis of Darcy's coefficient of permeability under conditions of elevated gravitational acceleration and verified using the results obtained. The test data compare well with the results on analogous samples obtained using the classical British Standard constant head permeability tests.

Implant-retained overdentures did not have a significant improvement in dietary intake

DESIGN: Randomised controlled trial.

INTERVENTION: Patients aged 65 or above edentate for a minimum of five years, with sufficient bone for two implants in the anterior mandible, were recruited. Those with systemic disease that contraindicated implants or had a low mini-mental state evaluation score were excluded. Patients in both groups had a standard maxillary complete denture fabricated. Patients randomised to the treatment group received a two-implant mandibular overdenture while those in the control group received a standard mandibular complete denture. Three 24-hour dietary recalls were collected by telephone interviews at baseline and at 12 months.

RESULTS: 255 patients were randomised: 128 received a standard complete denture (CD) and 127 a two-implant mandibular overdenture (IOD). 127 patients were available at 12-month follow up, 114 in the CD group and 103 in the IOD group. No significant between-group differences were found.

CONCLUSIONS: Although there is much evidence supporting the adoption of two-implant mandibular overdenture (IOD) treatment as the standard of care for edentate patients, this evidence does not include an improvement in dietary intake at one year for medically healthy independent edentate elders when given no specific dietary counselling.