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Biomedical subjects

H S Cardash

Publications and source records attributed to H S Cardash.

14 recordsLinked to original sources

Post-irradiation polymerization of different anterior and posterior visible light-activated resin composites.

The Knoop hardness number was measured for bottom and top surfaces of 2 mm thick specimens of different anterior and posterior visible light-cured composites. The variables for this study included various exposure times and a series of time intervals from immediately after curing up to 72 h. Post-irradiation microhardness at the bottom and top surfaces increased rapidly over the first hour, was slower during 24 h and showed no further increase after 24 h. Increasing exposure time resulted in higher microhardness values at both surfaces. Magnitudes of change were larger for the bottom surface. Exposure times longer than those recommended by the manufacturers were needed, especially for the anterior microfilled composites, to achieve adequately photo-activated resin that had an optimum bottom/top surface microhardness of 80-90%. Maximum hardness values were found to be dependent on the volumetric fraction but not on the average inorganic filler size. The post-irradiation increase in hardness value was independent of composite parameters and is probably commensurate with polymerization kinetics.

Analysis of Variance

A clinical evaluation of materials used in registering interjaw relationships.

Three recording media used to relate stone casts for 15 dentate patients were compared for accuracy. Interjaw relationships at the maximum intercuspation position and the retruded contact position were recorded using impression plaster, wax, and Duralay acrylic resin. A Lucia programming jig was used in the retruded contact position. The vertical distance and horizontal deviation between the casts were measured from reference points on the casts using each recording material. The average percentage differences between the recording materials were calculated. Hand articulation was the most accurate method of relating the casts at maximum intercuspation. The most accurate recording medium was impression plaster, followed by dental wax and Duralay resin at the maximum intercuspation and retruded contact positions.

Acrylic Resins

The fluid-filled gap under amalgam and resin composite restorations.

This article discusses the factors involved in the formation of marginal gaps between amalgam or resin composite restorative materials and cavity walls. The fluid that penetrates the microspace from the oral cavity and from the dentinal tubules is followed by bacterial invasion. This process can lead to secondary caries and irritation of the dentin/pulp complex. The bacterial growth is controlled by effective sealing at the tooth/restoration interface, partial obliteration of the gap, accumulation of solids at the cavosurface margins of the restorations, and by antibacterial linings.

Animals

Effect of retention grooves on tooth-denture base bond.

The bond strength of acrylic resin teeth with and without retention grooves processed onto standard and high-impact denture base resin was investigated. A shear compressive force was applied at an angle of 130 degrees to the lingual surface of the teeth until fracture occurred. The values were subjected to a two-way analysis of variance with repeated measures. Canine teeth bonded better than central or lateral incisors (p less than 0.01). A significantly greater force was required to fracture teeth from high-impact resin (p less than 0.01). Vertical retention grooves enhanced bond strength (p less than 0.01).

Acrylic Resins

A combined amalgam and composite resin restoration.

Difficulties with restoring class II cavities with posterior composite resin are enumerated. The problem is especially acute when a gingival margin lies close to or apical to the cementoenamel junction. A technique is described whereby the proximal portion of class II cavities is restored with amalgam to the contact area and composite resin inserted in the remainder of the cavity. Microleakage was studied by dye penetration tests. At the composite resin/cementum interface microleakage was significantly greater than at the amalgam/cementum and amalgam/composite resin interfaces (p less than 0.001). No statistically significant difference was observed in microleakage between the amalgam/cementum and amalgam/composite resin interfaces.

Bicuspid

An innovative method of monitoring denture hygiene.

A simple and rapid test for measuring oral hygiene was recently developed. It is based on the rate of oxygen consumption of oral expectorates of milk. This investigation modified the test to study denture hygiene. The dentures of 20 patients were immersed in 10 mL of sterile milk. After a 2-minute agitation, 3 mL of milk was added to test tubes containing methylene blue. The time required for color change at the bottom of the test tube, which is indicative of the rate of oxygen consumption, was recorded. For comparison with visual plaque accumulation, the dentures were coated with disclosing solution and the extent of plaque was scored by three examiners. A correlation was found between the plaque index scores and results of the milk test (r = -0.64; p less than 0.005). The data suggests the use of this test to monitor denture hygiene.

Aged

RLS--the lingually retained clasp assembly for distal extension removable partial dentures.

The design of clasp for a distal extension removable partial denture that helps preserve both the abutment teeth and the tissues of the edentulous ridge is described. The clasp assembly takes advantage of surveyed lingual undercuts to provide support, retention, and stability. It consists of a mesio-occlusal rest, a distolingual L-bar direct retainer that is located on the abutment tooth adjacent to the residual ridge, and a distobuccal stabilizer (RLS).

Denture Design

Rigidity of major connectors when subjected to bending and torsion forces.

Rigidity tests were performed on maxillary major connectors of different designs and mandibular major connectors of the lingual bar-type with different cross-sectional shapes and thicknesses. Each major connector was clamped on one side while the other side was subjected to bending, torsion, and bending under torsion forces. Deformation was measured with a micrometer microscope. The most rigid maxillary major connector was the design incorporating the anterior-posterior palatal bar. The most flexible was the U-shaped palatal bar. The full pear-shaped lingual bar (4 x 4 mm) was the most rigid of the major connectors. Among the more conventional lingual bars, the semielliptical bar (3.75 X 1.75 mm) was the most rigid, and the narrow semielliptical bar (4 x 1.5 mm) was the most flexible.

Chromium Alloys

Transferring anterior occlusal guidance to the articulator.

Anterior disclusion has become accepted as an optimal therapeutic model in the restoration of the anterior dentition. The ability to achieve anterior disclusion is influenced by the anterior determinants of esthetics, phonetics, skeletal relation, tooth position, abutment distribution, and alveolar bone support in addition to the posterior condylar determinants. Temporary restorations are made to incorporate these factors and it becomes necessary to transfer the information to working models of the articulator. A technique is described whereby a wax or silicone index fixed partial denture is made at chairside, duplicating the temporary restoration that is directly transferable to the working casts of the articulator. This technique allows the technician to make final restorations according to the index fixed partial denture, thus incorporating the anterior determinants of occlusion in conjunction with the posterior condylar determinants specific to each patient.

Dental Articulators

An analysis of rotational movement of asymmetrical distal-extension removable partial dentures.

An axis of rotation is created through the most distally placed occlusal rests when a distal-extension removable partial denture is loaded. If the residual ridges are of unequal lengths, this axis of rotation may not be perpendicular to the residual ridges. The resultant movement of asymmetric denture bases and their effect on the tissues are discussed. Movement of I-bar retainers located on the mesiobuccal aspect of asymmetrical abutment teeth may torque the abutment teeth as the denture base moves tissueward. Use of L-shaped direct retainers on the distobuccal surveyed undercut will create a more favorable class II lever effect on the abutment tooth.

Dental Abutments

Prevalence of Candida albicans in denture wearers in an Israeli geriatric hospital.

Thirty-seven patients wearing complete dentures were investigated for Candida albicans. Twenty-five of the patients suffered from denture stomatitis and twelve had clinically normal mucosa. Candida albicans was isolated and identified from Sabouraud dextrose agar culture medium models constructed from impressions of the maxilla and from the upper dentures. The presence of Candida albicans was demonstrated in all denture wearers suffering from denture stomatitis and in 82% of denture wearers in a control group. A higher concentration of Candida was found in the denture stomatitis group. Large quantities of Candida resided in the denture base and not in the palate. Candida was also found in the denture base in areas not related to the lesion. The concentration of Candida was related to denture cleanliness.

Aged

The overdenture: a concept.

Teeth that are unsuitable as abutments for a fixed bridge or removable partial denture may be retained as roots under an overdenture. While these roots remain, the vertical height of the bony ridge is preserved. In addition, the roots give support to the denture and reduce stress on the alveolar ridge.

Alveolar Process