Biomedical subjects
Publications and source records attributed to A A Grant.
In this final article of the series, the clinical and technical aspects of a range of similar forms of immediate prosthesis are discussed. Similarly, copy denture and reline/rebase procedures are detailed.
In this section, guidelines to the diagnosis of complete denture problems are presented in tabular form. Suggestions to the management of these problems are listed.
This article deals with technical aspects of complete dentures as well as the importance of good communication between the clinician and the technician. The objectives for technicians for each component are discussed.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The provision of satisfactory complete dentures requires that dentist, technician, and patient adequately fulfill their respective roles in the provision of, and adaptation to, these dentures. The clinician should combine clinical skills and appropriate patient management, in addition to an appreciation of postextraction resorptive changes in the alveolar ridges, if clinically acceptable dentures are to be prescribed. An increasing number of replacement dentures are being prescribed for older patients; thus, the need to utilize functional factors to determine tooth placement is reviewed.
This paper presents the results of a study to observe the effect on bone resorption and residual alveolar ridge form, of placement of dense non-resorbable hydroxyapatite granules into fresh canine sockets, at the time of immediate denture provision. Thirty five subjects were randomly divided into two groups cross matched for age and sex. All subjects required bilateral extraction of at least a lower canine and an adjacent tooth. Results demonstrate that six months post-extraction the control group had lost four times more bone than the implant group. These results were highly significant (P=0.000, LHS and P=0.001, RHS).
Experiments have been carried out on the curing of poly(methyl methacrylate) denture base material in a microwave oven, using conventional dental flasks and flask clamps. It has been shown that it is important (a) to maintain sufficient pressure on the materials, (b) to avoid gaseous porosity by not heating too rapidly initially, and (c) to ensure that all metal is protected from exposure to microwaves. When the appropriate conditions of polymerisation were used, microwave-cured samples had satisfactory physical and mechanical properties according to American Dental Association specification number 12.
The bases of occlusal rims and trial dentures should fit both the cast and the mouth accurately. The retention of shape and dimension of strips and sheets of grey and pink shellac, filled cold cure acrylic resin and wax were tested following moulding over stylised upper edentulous casts. The thermoplastic materials were softened over a flame or in a water bath. Specimens were prepared with and without folding along the long axes of the strips. The angles formed by the strips, the gap between the palate of the baseplates and casts and the linear dimension of the sheets were measured after moulding, after immersion in water at 37 and 45 degrees C and after 24 h at room temperature. The least angular change was shown by unfolded grey shellac, softened over a flame and moulded by finger pressure over an unwarmed cast, followed by folded specimens softened in water and moulded with the fingers over a prewarmed cast. The least gap developed beneath pink shellac softened in water and moulded by finger pressure over a warmed cast. The smallest dimensional change was shown by grey shellac softened in water and moulded by finger pressure over a warmed cast. Thus, optimally manipulated shellac materials exhibit less change after moulding than cold cure acrylic resin or modelling wax.
Three techniques have been used to assess the shear rate dependence of the viscosity of mixed alginate impression materials prior to setting. Two methods used a cone-plate viscometer, and one method was a capillary extrusion technique. Data from the three sets of experiments have been critically compared. It has been shown that an unset alginate material exhibits Bingham behaviour.
The bases of occlusal rims and trial dentures may sorb water during disinfection procedures, adjustment in the mouth and rinsing and cooling under running water. Such sorped water may adversely affect the properties of the baseplate materials. The room temperature water sorption of sheets of grey and pink shellac and cold cure acrylic resin was determined over 10 weeks by weighing. The Wallace surface hardness, linear dimension and transverse strength were also measured each week. Specimens were reweighed each week as they dried at room temperature. At the conclusion of the tests, the materials showed a change after soaking in weight, hardness, linear dimension and transverse strength, and change after drying relative to original mass for grey shellac of +1.5%, -48%, +0.7%, -58%, +0.33%; for pink shellac of +2.0%, -56%, +0.9%, -65%, +0.4%; and for acrylic resin of +1.2%, +10%, +0.4%, -30%, -2.1% respectively. The acrylic resin material was thus less affected by water sorption than the grey and pink shellac materials.
The baseplate material that best reproduced the most grooves in a gypsum cast was filled cold cure acrylic resin, followed in turn by modelling wax, grey shellac and finally the pink shellac material. These latter three thermoplastic materials performed best when softened in a water bath and subsequently adapted to a prewarmed cast.