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Biomedical subjects

J L Sandrik

Publications and source records attributed to J L Sandrik.

At least 19 recordsLinked to original sources
PubMed1994

Disturbance of the dentinal smear layer by acidic hemostatic agents.

The pH of nine commonly used hemostatic agents was measured. Three measurements were recorded for each solution, and values ranged from 0.7 to 2.0. The effect of exposure to one hemostatic material, ferric sulfate solution (Fe2(SO4)3), on the dentinal smear layer was investigated. Prepared extracted teeth were exposed for periods ranging from 30 seconds to 5 minutes to an acidic ferric sulfate-based hemostatic agent. A smear layer was clearly demonstrated on a control specimen; however, the dentinal smear layer was rapidly removed by exposure to the hemostatic agent, and peritubular dentin was lost after prolonged exposure.

Acid Etching, Dental↗
PubMed1993

Peroxide bleaches: effect on tensile strength of composite resins.

Research concerning bleaching agents on the mechanical properties of composite resin restorative materials has produced conflicting reports. Representative brands of composite resin restorative materials were studied, including microfil, hybrid, and posterior types. The bleaching agents selected were 30% hydrogen peroxide and two commercial brands of 10% carbamide peroxide. Ten specimens of each material, prepared according to American National Standards Institute/American Dental Association specification No. 27 for diametral tensile testing, were stored in bleaching agents for 1 hour and 168 hours at 37 degrees C. An equal number of specimens stored in deionized water with identical conditions were designated controls. Qualitative examination of bleached specimens revealed a marked change in color, especially the microfilled composite resins. There was no significant difference in tensile strength between controls and exposed samples at either time except for the diminished strength of microfilled composite resins in 30% hydrogen peroxide for one week (p < 0.01).

Carbamide Peroxide↗
PubMed1992

Bond strength and accuracy of combined reversible-irreversible hydrocolloid impression systems.

This study investigated the bond strength and accuracy of irreversible and reversible hydrocolloids that were modified by the manufacturer to bond to each other for use in the combination impression technique. One conventional type irreversible hydrocolloid was used because of previously reported favorable results obtained in several investigations. Tensile strength of each individual material was tested as well as the adhesive bond between reversible and irreversible hydrocolloids. Tensile bond strength was then measured for each combination of materials. Subsequently, all the materials were tested individually and in combination for dimensional accuracy.

Alginates↗
PubMed1991

A comparative study of frictional forces between orthodontic brackets and arch wires.

An in vitro study of simulated canine retraction was undertaken to evaluate the difference in frictional resistance between stainless steel arch wires and steel and ceramic brackets with elastomeric, steel, and self-ligation. Each bracket slot was 0.018 x 0.025 inch. The arch wires used were 0.014-inch, 0.016-inch, 0.018-inch, 0.016 x 0.016-inch, and 0.016 x 0.22-inch stainless steel. A testing apparatus was designed to attempt to simulate the clinical situation in which teeth tip slightly while they slide along the arch wire. Under these testing conditions, the self-ligating steel bracket did not demonstrate less friction than the elastic or steel-ligated stainless steel brackets. For most wire sizes, elastomer-ligated ceramic brackets demonstrated the greatest friction when compared with other bracket/ligation technique combinations. The clinical significance of this study becomes apparent when stainless steel brackets are used on the posterior teeth and ceramic brackets are used on the anterior teeth. If sliding mechanics are used, the anterior teeth may be more resistant to movement than the posterior teeth because of the greater friction of the ceramic brackets. This could result in more posterior anchorage loss than would be expected if only one type of bracket were used.

Analysis of Variance↗
PubMed1991

Wettability of elastomeric impression materials and voids in gypsum casts.

Numerous factors are involved in making an accurate void-free dental artificial stone cast or die. The relationship of the wettability of an elastomeric impression material and its interaction with the gypsum slurry is an important factor. This study examined the relative "pourability" of several impression materials by counting the number of resultant voids in artificial stone casts containing 48 point angles. Those elastomers that exhibited the lowest contact angle with water produced artificial stone casts with the fewest voids. Surfactants applied to the impression material significantly reduced the number of voids in artificial stone casts, as did modified elastomers designated by the manufacturer as hydrophilic.

Calcium Sulfate↗
PubMed1989

Tensile strength of elastomeric impression materials, adhesive and cohesive bonding.

Numerous factors are known to effect the accuracy of elastomeric impression materials. Factors often overlooked are the quality of the bond between low-viscosity and high-viscosity elastomers and the presumed cohesive bond between materials during an impression reline procedure. This study examined the bond strength of condensation polymerization polysiloxanes, addition polymerization polysiloxanes, polyethers, and a light-cured polyether urethane dimethacrylate. Of the tested materials, light-cured polyether urethane dimethacrylate exhibited the greatest bond strength. The reline technique, light-body cured to previously cured heavy-body putty, yielded results similar to the simultaneous-cure technique. In terms of bond strength there is no advantage of one technique over the other. The corrective reline technique yielded acceptable results in bond strength. In general, the tested materials exhibited greater tensile strength than bond strength.

Dental Bonding↗
PubMed1984

Force measurement and design of a torquing high-pull headgear.

The dynamic extraoral force analyzer (DEFA) was found to be capable of measuring linear deflection as a function of force created by a headgear. Ten standard nontorqued face-bows with a cervical and a high-pull direction were tested to determine the reliability of the DEFA. Statistical analysis showed the DEFA to be reliable and accurate in differentiating various directions and deflections of maxillary molars. Doubled-over distal ends of the inner bow with 0 degree of torque and a parietal direction of pull were used as controls. The same face-bows with 9 degrees of buccal root torque were tested on the DEFA. These face-bows were tested to determine whether transverse translation without buccal crown tipping of the maxillary first molar will occur. Statistical analysis showed that transverse translation occurred at a force of 200 to 347 gm.

Dental Stress Analysis↗
PubMed1984

Clinical evaluation of the accuracy of interocclusal recording materials.

The importance of accurate, reliable recording mediums cannot be understated. Function and esthetics are directly related to this critical step. Dental recording materials must be accurate, easily manipulated, and economical for effective use. Five types of intraoral records of 31 patients were registered and placed on an arcon, semiadjustable articulator to measure the magnitude and direction of distortion. The results were the following. Polyether interocclusal recording medium without a carrier was the most accurate. Polyether and zinc oxide-eugenol pastes with carriers were the next most accurate recording mediums, but they required a disciplined technique. Recording waxes were consistently unreliable. Distortion occurred more frequently in a vertical direction, followed by an anteroposterior direction.

Clinical Trials as Topic↗
PubMed1984

Acid and water solubility and strength of calcium hydroxide bases.

The solubility in water and 37% phosphoric acid, and compressive strength of four brands of hard-setting calcium hydroxide base materials were studied. Results were highly variable among brands and no correlations appeared to exist between properties studied. One product was significantly different from the others with regard to acid solubility and compressive strength.

Calcium Hydroxide↗
PubMed1982

Rotation of rectangular wire in rectangular molar tubes. Part II. Pretorqued molar tubes.

Buccal tubes from five manufactures producing the new generation of preadjusted (straight wire type) appliances were tested to determine the amount of rotation various-sized rectangular wires produced prior to binding within the tube. This rotation reflected the amount of torquing force dissipated because of the interaction of the wires and tube. In addition, it indicated the degree of compensatory third-order bends needed in the wire to deliver the desired torque force to the tooth. Wire and tube dimensions were measured and compared to manufacturers' stated specifications. The amount of rotation for each manufacturer's tube was compared to the theoretical values based on calculations. Theoretical calculations and published charts of deflection angles based on these calculations give a false impression in that they do not revealed a true expression of the amount of torque dissipated through rotation of the rectangular wire in that tube. There is variation between the manufacturer's stated lumen dimension and the actual lumen size, even beyond the manufacturer's stated tolerances. Rectangular wire will rotate within a rectangular buccal tube to varying degrees, depending upon the size of the wire used and the manufacturer of the appliance. This means that additional torsion or angulation may need to be placed in the wire prior to application intraorally. The amount of this additional torquing of the arch wire will depend upon the manufacturer of the appliance used and will vary from tube to tube of the same manufacturer.

Equipment Design↗
PubMed1981

Rotation of rectangular wire in rectangular molar tubes. Part I.

The degree of angular rotation of rectangular orthodontic wires in rectangular molar tubes was measured using a rotatable mechanical stage on a Unitron metallograph and compared to theoretical data. It was found that square 0.016 inch wire did not bind in 0.018 by 0.022 inch or larger mandrel- or inconel-formed tubes, whereas rotations of 11 to 23 degrees were noted in cast tubes of this dimension. Although 0.016 by 0.022 inch wire did bind in these tubes, the degree of rotation was far greater than expected on the basis of theoretical calculations or clinical expectations. The results indicated that it was unrealistic to expect fine control of a few degrees of torque to occur as expected for delicate clinical control.

Dental Equipment↗
PubMed1981

Bond strength of three orthodontic adhesives.

A method was devised to study the bond strength of direct-bonding orthodontic adhesives. A shear load was applied parallel to the tooth-adhesive-bracket interface by means of an Instron Universal Testing Machine. The bond strength was found to increase for some products after 27 days. However, no significant differences could be detected 1 day after placement. The interface was studied to determine the mode of failure. In all cases bond failure occurred as mixed adhesive-cohesive phenomena.

Acrylic Resins↗
PubMed1981

Comparison of elastomeric impression materials used in fixed prosthodontics.

Five elastomeric impression materials were evaluated: two polysulfides (one lead-cure and one non-lead cure), two silicones (one condensation polymerization and one addition polymerization), and one polyether. These materials were subjected to simulated clinical conditions. Two techniques were evaluated. All materials were evaluated initially with use of a custom tray and manufacturers' adhesive. A second evaluation was performed without using the tray system. Both techniques were subjected to statistical comparison. Conclusions of the research were as follows: 1. All impression materials that were poured immediately and evaluated using a custom tray and adhesive consistently demonstrated superior results in comparison to those tested without the custom tray. 2. Polyether material consistently yielded superior results with or without a custom tray when compared to the other impression materials. The additional polymerization silicone ranked second, followed by the lead-cure polysulfide and the condensation polymerization silicone, respectively.

Dental Impression Materials↗
PubMed1981

Accuracy and dimensional stability of four interocclusal recording materials.

Four materials, zinc oxide-eugenol paste, eugenol-free-zinc oxide paste, a silicone, and polyether jaw relations registration material were studied in a controlled laboratory environment to determine their accuracy and stability in intervals over a 1-week period. The results are as follows: 1. The eugenol-free zinc-oxide paste was the only material which exhibited no statistically significant difference between the die scribes and those of the sample. 2. The setting reaction of the eugenol-free-zinc oxide paste was a saponification reaction, resulting in the production of an insoluble soap. 3. With polyether, silicone, and zinc oxide-eugenol paste, there was a statistical difference between the die and the respective samples at the immediate reading and throughout the experiment. Polyether showed the least difference, and zinc oxide-eugenol paste the greatest.

Chemical Phenomena↗
PubMed1979

The influence of preloading on stress relaxation of orthodontic elastic polymers.

The main objective of the investigation was the determination of whether prestretching would decrease the rapid force loss of the elastic polymers. The results indicated that Alastik CK chains showed a significant decrease in force loss whereas the C2 chains were unaffected. Since overextending the chain to compensate for force loss during clinical placement could result in capillary bed ischemia, increasing the force loss of the CK chains must be done before application. To accomplish this the chains should be prestretched by the manufacturer or operator. An improvement in the material component or manufacturing process would provide a more lasting solution to a material for which orthodontists have found increasing use.

Elasticity↗