Search PubMed⌕ Search

Biomedical subjects

R G Jagger

Publications and source records attributed to R G Jagger.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1992

Signs and symptoms of temporomandibular joint dysfunction in a Saudi Arabian population.

The signs and symptoms of temporomandibular joint dysfunction present in 219 Saudi Arabians attending a dental clinic for routine dental treatment are described. Joint sounds (36%) and muscle tenderness to palpation (34%) were common findings. Of the subjects examined, 31% reported suffering from frequent headaches. The study demonstrated a high incidence of signs and symptoms of temporomandibular joint dysfunction. Findings were similar to those of a previous study of an investigation in a bedouin community in Western Egypt (Abdel-Hakim, 1983).

Adolescent↗
PubMed1991

Effect of the curing cycle on acrylic denture base glass transition temperatures.

Glass transition temperature of a polymer is an important physical property which may have a major effect on the dimensional stability of denture base materials. Thermomechanical analysis has been used to determine the glass transition temperature of specimens of denture base materials which had been produced by various selected curing cycles. It was found that different curing cycles produced variations in glass transition temperature of up to 20 degrees C.

Acrylic Resins↗
PubMed1991

Reflected light microscopy of the human mandibular condyle--a study of a post-mortem material.

The surface characteristics of the articulating surfaces of 11 human mandibular condyles removed post-mortem were determined by the use of reflected light dark-field microscopy. Good agreement was obtained between macroscopical grading of degenerative change and appearance as observed by microscopy. Microscopical appearances believed to correspond to normal surface, fibrillation and degenerative changes are described.

Aged↗
PubMed1991

Mandibular manipulation of anterior disc displacement without reduction.

The history and clinical symptoms of anterior temporomandibular joint disc displacement without reduction are characteristic, and include limitation of mandibular movement and mandibular deviation on opening of the mouth. Twelve consecutive patients attending a clinic with such symptoms were treated by mandibular manipulation. An immediate increase in the range of mandibular movement was obtained for all patients, with a mean increase in interincisal opening of 8 mm. The method of manipulation is described, and the implications of the results for the treatment of TMJ patients are discussed.

Adolescent↗
PubMed1990

Effect of cross-linking on sorption properties of a denture-base material.

Cross-linking of the polymer of the interstitial matrix of a heat-cured resin denture base is said to provide craze resistance for the denture base. The mechanism of crazing can be related to both water sorption and solvent attack. The present study shows that the addition of ethylene glycol dimethacrylate in concentrations of 0-100% of monomer volume has little effect on water sorption properties but is an efficient method of providing solvent resistance.

Cross-Linking Reagents↗
PubMed1990

Hydrochloric acid-pumice treatment of fluorosis-stained enamel.

The management of dark staining of teeth caused by dental fluorosis is discussed. The results of treatment of 20 patients with dental fluorosis by a hydrochloric acid-pumice technique are described. All patients showed considerable improvement in colour which was maintained for review periods of (up to) two years.

Fluorosis, Dental↗