Biomedical subjects

G D Stafford

Publications and source records attributed to G D Stafford.

At least 19 recordsLinked to original sources

PubMed1995

Augmentation of the atrophic maxillary alveolar ridge with hydroxyapatite granules in a Vicryl (polyglactin 910) knitted tube and simultaneous open vestibuloplasty.

A modified technique for augmentation of the severely atrophic edentulous maxillary alveolar ridge is described. The augmentation was carried out using a knitted polyglactin 910 mesh tube filled with porous hydroxyapatite granules, the tube being inserted through the access achieved by an open vestibuloplasty. The results of an in-vivo animal study showed that the absorption of the mesh was complete between 49 and 70 days. The clinical study included 11 patients in all of whom there was severe maxillary ridge atrophy and major prosthetic problems; follow-up was for a mean of 25 months. The procedure was without significant complication and produced a mean immediate absolute augmentation of 5.5 mm and substantially increased vestibular depth. A gradual reduction of ridge height was found over time. Nevertheless all patients showed significantly increased ability to wear their dentures. The technique is presented as a safe and predictable alternative to the use of bone grafts and titanium implants in these severely atrophic cases.

Aged↗

PubMed1993

On clinical loading of osseointegrated implants. A methodological and clinical study.

Strain gauges were used to record in vivo and in vitro functional deformations in a fixed prosthetic appliance supported and retained by osseointegrated titanium implants. Four linear gauges were attached to each of totally 5 implant abutment cylinders and gauge signals were transferred into a computer via a digital converter. A computer program (ASYST) was used for collection, calibration and analysis of data obtained. Based on the results of a series of explorative in vitro tests, in vivo experiments were performed at maximum biting as well as during chewing on certain normally available food items. The results show fundamental differences between in vitro and in vivo testing conditions. Unexpectedly high bending of the implants was recorded in many of the in vivo loading situations.

Aged↗

PubMed1991

Boundary lubrication and maxillofacial prosthetic polydimethylsiloxanes.

Polydimethylsiloxanes exhibit hydrophobic behaviour and poor wettability. These features impose some problems with the clinical performance of the material when used for the construction of intraoral and extraoral facial prostheses. Surface active agents were added to modify the surface energy of the polydimethylsiloxane and contact angle measurements were carried out to observe wetting characteristics. Five siloxane-alkene oxide block copolymers, one organosilicon quaternary ammonium chloride and an epoxyalkyl silane ester were used as surfactants. The best surfactant in terms of permanency and contact angle lowering achieved a value of 24 degrees when added at 10% level compared with 57 degrees for the unmodified silicone. The fairly high viscosity, combined with a comb-like structure, together with the high hydroxyl number of 75 provided the correct balance of permanence and wetting characteristics.

Dimethylpolysiloxanes↗

PubMed1991

Intraoral strain gauge measurements on complete dentures: a methodological study.

This paper discusses the advantages and the limitations of strain gauge clinical research in prosthodontics. It also demonstrates the possibility of long term studies by explaining a methodological study that was undertaken on a group of 19 patients on two occasions a year apart. Of this group six were supplied with maxillary and mandibular complete dentures, five had maxillary complete dentures and mandibular osseointegrated fixed 10-12 unit bridges, and eight had maxillary and mandibular complete dentures at the first experimental session and osseointegrated fixed 10-12 unit bridges in the mandible at the second. It was found that during maximum biting the direction of functional strain was comparatively stable at a given point of a denture. It was evident that in experiments 12 months apart no major changes had taken place in the experimental dentures nor the denture bearing tissues. The accuracy of the strain gauges used was maintained and there were no failures due to loss of retention of the gauges. Loss of insulation and short circuiting was an occasional problem but instantly recognized if it occurred.

Aged↗

PubMed1990

Evaluation of the properties of a new pour denture base material utilizing a modified technique and initiator system.

A new denture base system, Provac, has been developed for complete and partial dentures, and for relining. The Provac material is methyl methacrylate, which cures with the aid of barbituric acid. In this study the physical and mechanical properties of the new resin were investigated and compared with those of a conventional autopolymerizing material (Croform) and a conventional heat polymerizing material (Trevalon). It was found that the dimensional accuracy of Provac was better than that of the conventional heat-curing material, Trevalon, and the denture was finished more easily and quickly. The physical and mechanical properties of Provac resin were found to be similar to those of the other two materials, and conformed to the International Specifications for denture base materials. The residual monomer levels in Provac material were always higher than the minimal obtainable values associated with conventional heat-cured materials when these were polymerized with a terminal boil during the curing cycle.

Acrylates↗

PubMed1990

[Mechanical properties of surface hardening polymers polymerizable by visible light].

A plastic layer polymerized on the surface of denture base material in a thickness of, in average, 40 microns by means of visible light was significantly harder with respect to industrial acrylic surfaces. At an irradiation time of 90s according to factory prescription no harder surface appeared even in case of multiple covering. The surface became significantly harder with an irradiation of 150s. Of the denture base material products the Trevalon and the QC-20 products showed the forming of significantly harder surface.

Denture Bases↗

PubMed1989

Comparison of three- and four-point flexural strength testing of denture-base polymers.

Flexural failure of denture-base materials is considered the primary mode of clinical failure. However, there are several methods of conducting flexural tests, and none has been demonstrated to be the most appropriate. Three- and four-point bend-testing were compared, with four different dental polymers used. The values for modulus of elasticity determined by the two tests were not statistically different. However, the values for flexural strength from the three-point bend test were always greater, suggesting that that parameter is dependent on the testing procedure. Modifications to the existing denture-base material specification are suggested.

Dental Stress Analysis↗

PubMed1988

The use of an electronic thermometer in intraoral temperature measurement.

The applicability of an electronic thermometer CRAFTEMP in taking intraoral temperatures was determined. Sublingal temperatures in ten young subjects with complete natural dentitions, and the temperatures at the denture base-mucosa interface and on the polished surface of both maxillary and mandibular complete dentures in ten elderly patients were measured. The results showed that there was a temperature difference between the polished surface of the maxillary denture and the denture base-mucosa interface. This was statistically significant in the female but not in the male subjects. No temperature difference could be demonstrated with any of the mandibular dentures. The CRAFTEMP was found to be a convenient and reliable method for intraoral temperature measurement.

Adult↗

PubMed1987