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Biomedical subjects

R G Jagger

Publications and source records attributed to R G Jagger.

At least 19 recordsLinked to original sources
PubMed1999

Wettability of silicone rubber maxillofacial prosthetic materials.

STATEMENT OF PROBLEM: Maxillofacial prosthetic materials that contact skin or mucosa should have good wettability. A material that is easily wetted will form a superior lubricating layer between the supporting tissues and, thus, reduce friction and patient discomfort. The surface energy of a maxillofacial prosthetic material will give an indication of the amount of energy available for adhesion and of the susceptibility of the material to bacterial adhesion. PURPOSE: This study evaluated the wettability and surface energies of a range of commercially available silicone rubber maxillofacial prosthetic materials. MATERIAL AND METHODS: Contact angles and surface energies were measured by using a dynamic contact angle measuring technique. Four commonly used silicone maxillofacial materials were tested and their properties compared with those of an acrylic resin denture base material and a widely used denture soft lining material. RESULTS: There were no significant differences in the wettability of the silicone rubber materials. All materials were significantly less wetted than the denture acrylic resin material. There were no significant differences in the surface energies of the silicone rubber materials, but all were significantly lower than denture acrylic resin material. CONCLUSIONS: The Cahn dynamic contact angle analyzer was a quick and reproducible method for determining the contact angles and surface energies of maxillofacial materials. Further work is needed to improve the wettability of silicone rubber materials used for maxillofacial prostheses, thus, reducing their potential to produce friction with tissues.

Acrylic Resins↗
PubMed1999

Mechanical properties of an experimental denture soft lining material.

OBJECTIVES: The objective of the present study was to evaluate the mechanical properties of an experimental formulation (Exp. 1) in order to assess its potential as a denture soft lining material. The same properties of a popular commercially available denture soft lining material (Molloplast-B) were determined and compared with the properties of Exp. 1. METHODS: Exp. 1 specimens were obtained by curing for 24 h at room temperature after the addition of the appropriate amounts of catalyst and cross-linker. Molloplast-B specimens were obtained after curing according to the manufacturer's instructions. The properties measured in the study were hardness, tear resistance, tensile strength and the bond strength of the material to a heat-cured acrylic denture base material. RESULTS: Exp. 1 had a significantly greater tensile strength, percent elongation, tear resistance and peel strength (p < 0.0001) than Molloplast-B. There was no significant difference in the hardness values of the two materials, although Molloplast-B had a significantly higher tensile bond and shear bond strength (p < 0.05). CONCLUSIONS: It was concluded that there was no significant difference in the hardness of Exp. 1 and Molloplast-B. Exp. 1 had superior tensile and tear properties. Its peel bond strength was superior to that of Molloplast-B, although its tensile bond strength and shear bond strength were less.

Acrylic Resins↗
PubMed1997

In at the deep end--an insight into scuba diving and related dental problems for the GDP.

Scuba diving is one of the fastest growing sports in the world. It is inevitable that the general dental practitioner (GDP) will have patients who participate in this sport and they should be aware of a number of problems that a diver can experience that are associated with the teeth and related structures. The aim of this article is to introduce the GDP to the dental problems associated with diving and make recommendations on dental care for scuba divers.

Barotrauma↗
PubMed1997

Adherence of Candida albicans to experimental denture soft lining materials.

STATEMENT OF PROBLEM: Colonization of denture soft lining materials by Candida albicans can result in clinical problems. Two experimental silicone soft lining materials have been developed and demonstrate good physical properties. PURPOSE OF STUDY: The aim of this study was to determine the extent of candidal adherence to these materials compared with a commercially available soft lining material and an acrylic resin denture base. MATERIAL AND METHODS: The experimental materials were constructed in a stainless-steel mold, and their surface energies were determined with a dynamic contact angle analyzer. The adherence of three strains of C. albicans was determined with an in vitro assay. In addition, one test strain was used to determine the effect on adherence of precoating the materials with whole saliva. RESULTS: Adhesion to all materials was strain variable, with the lowest adherence recorded for the two experimental materials. Decreased adherence was also apparent after precoating the materials with saliva. Correlation between surface energy of the material and the degree of candidal adhesion was seen for one strain, but no correlation was seen for the other two strains. CONCLUSION: Adherence of C. albicans to the two experimental silicone soft lining materials was significantly less than that for an acrylic resin denture base and a commercially available soft lining material.

Acrylic Resins↗
PubMed1997

A combined orthodontic/restorative clinic. Rationale, evolution, and experience.

The rationale for running combined clinics between orthodontics and restorative dentistry is given, together with the history of the development and experience of such a clinic at the Dental School and Hospital in Cardiff. Brief details of the organization of the combined clinic and possible future developments are also given.

Adolescent↗
PubMed1997

A bimaxillary sports mouthguard: a modified technique.

The bimaxillary mouthguard provides enhanced protection for a participant in contact sports. This article describes the fabrication of a polyvinylacetate-polyethylene (PVAc-PE) bimaxillary mouthguard in which the connection of the maxillary and mandibular components is reinforced by pressure thermoforming a 2-mm PVAc-PE sheet over the labial and buccal portions of the mouthguard.

Athletic Injuries↗
PubMed1996

Mouthguards.

Explore the source record for details and available documents.

Airway Obstruction↗
PubMed1996

Cyclical deformation behaviour of denture soft lining materials.

OBJECTIVES: The purpose of the study was to examine and describe the deformation behaviour of five denture soft lining materials under dynamic cyclic loading over a range of applied forces using apparatus designed to simulate masticatory performance. METHODS: Five lining materials were tested over 5-min periods using an Instron tensile testing machine that was modified to measure load and strain semi-continuously during cyclic loading. RESULTS: Strain energy and strain energy densities and moduli values for each material were calculated. The strain energy absorbed at separate times during the cycling period demonstrated the elastic behaviour of the materials over the 5-min simulated chewing cycle. CONCLUSIONS: All materials demonstrated elastic but not perfectly linearly elastic behaviour over the chosen loading and cycling frequency. Molloplast B absorbed most energy at the lower testing loads and Novus absorbed most energy at the higher loads.

Acrylic Resins↗
PubMed1996

Effect of surface modified fillers on the water absorption of a (RTV) silicone denture soft lining material.

OBJECTIVES: The purpose of the present study was to modify the filler content of an experimental room-temperature vulcanizing (RTV) lining material that demonstrated high water sorption in order to produce a material with low sorption properties. METHODS: Three new formulations were prepared, each containing different hydrophobic silane-treated silica fillers. Water sorption properties for specimens obtained from these formulations were determined using standard experimental techniques. RESULTS: All formulations demonstrated greatly reduced water absorption and low volume change. CONCLUSIONS: An experimental RTV poly(dimethylsiloxane) denture soft lining material having low water sorption properties has been produced.

Absorption↗
PubMed1996

Effect of test method on the bond strength of a silicone resilient denture lining material.

The purpose of this study was to compare the peel, tensile, and shear bond strength values of a commonly used heat-cured denture soft-lining material (Molloplast-B) bonded to a polymethyl methacrylate denture base material. A further purpose was to evaluate the effect of liner thickness and deformation rate on the bond strength. Results showed that recorded failure and the mode of specimen failure are affected by the type of the test method. The highest tensile and shear strengths were obtained by specimens having the lowest liner thickness. The deformation rate had a significant effect on Molloplast-B tensile and shear strengths. Bond strength results must be interpreted with caution. Cohesive failure of soft lining material during testing provides information regarding the material itself instead of an accurate measure of bond strength.

Analysis of Variance↗
PubMed1996

Dimensional accuracy of thermoformed polymethyl methacrylate.

Thermoforming of polymethyl methacrylate sheet is used to produce a number of different types of dental appliances. The purpose of this study was to determine the dimensional accuracy of thermoformed polymethyl methacrylate specimens. Five blanks of the acrylic resin were thermoformed on stone casts prepared from a silicone mold of a brass master die. The distances between index marks were measured both on the cast and on the thermoformed blanks with an optical comparator. Measurements on the blanks were made again 24 hours after processing and then 1 week, 1 month, and 3 months after immersion in water. Linear shrinkage of less than 1% (range 0.37% to 0.52%) was observed 24 hours after removal of the blanks from the cast. Immersion of the thermoformed specimens in water resulted in an increase in measured dimensions, but after 3 months' immersion these increases were still less than those of the cast (range 0.07% to 0.18%). It was concluded that it is possible to thermoform Perspex polymethyl methacrylate accurately.

Dental Materials↗
PubMed1995

The bimaxillary mouthguard.

The bimaxillary mouthguard provides enhanced protection for the participation in contact sports. This article describes the bimaxillary mouthguard and outlines construction techniques.

Humans↗
PubMed1995

Wettability of denture soft-lining materials.

Data on the wettability of long-term resilient denture base lining materials have previously been obtained by static methods. This study determined the dynamic contact angle of a range of long-term resilient lining materials and the surface free energy properties of these materials. This method was a rapid and convenient method for determining wettability parameters. The equilibrium contact angle revealed the Flexor and Novus materials to be the least wetted with the Molloplast-B material, and CoeSuper-Soft material was wetted similarly to Trevalon material. The contact angle hysteresis indicated that all the soft-lining materials tested would improve denture stability under dislodgment forces. The surface-free energies appeared to be similar for all the soft-lining materials but were significantly lower than that of Trevalon.

Acrylic Resins↗
PubMed1995

Thermoforming polymethyl methacrylate.

This study characterized a range of commercially available polymethyl methacrylate sheets with respect to molecular weight, residual monomer content, and glass transition temperature and then developed a thermoforming procedure that produced visually satisfactory thermoformed polymethyl methacrylate specimens. Molecular weight values of Perspex material were considerably greater than those of the other materials. All materials but Diakon had residual monomer concentrations of less than 1% and glass transition temperature values greater than 100 degrees C. Perspex material was selected for further investigation. It was necessary to preheat Perspex sheets in an oven at 160 degrees C for at least 30 minutes before heating and forming on the thermoforming apparatus to obtain acceptable specimens.

Acrylic Resins↗
PubMed1995

Heat-cured silicone bimaxillary mouthguard.

A laboratory procedure for the construction of a heat-cured, silicone, custom-made bimaxillary mouthguard for contact sports is described. Contours and vertical dimension are easier to control than with the conventional thermoformed product, and there is no danger of injury from contact between the maxillary and mandibular components.

Dental Prosthesis Design↗
PubMed1992

The effect of cross-linking chain length on mechanical properties of a dough-molded poly(methylmethacrylate) resin.

Three different cross-linking agents which provide a range of cross-linking chain lengths and flexibilities were added to the monomer component of a dough-molded poly(methylmethacrylate) resin in various concentrations, and their effects on the impact strength, transverse bend strength, and tensile strength of the cured polymer were investigated. Increase in the chain lengths of cross-linking agents led to a decrease in the properties of transverse bend strength and tensile strength and an increase in the property of impact strength.

Acrylic Resins↗