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Biomedical subjects

N Barghi

Publications and source records attributed to N Barghi.

49 records · Page 3Linked to original sources
PubMed1982

Optimum thickness of opaque and body porcelain.

Nine hundred specimens of six shades of two commercially available dental porcelains were made with different thicknesses of opaque and body porcelain. The color of specimens were compared with shade guide samples by seven observers. The results were as follows: 1. The thickness of opaque and body porcelain to produce optimum color varies from shade and in different porcelain systems. 2. Complete visual mask out of the alloy by the opaque may not produce the desired shade. 3. Excessive opaque will not effect the shade of porcelain noticeably, whereas excessive body porcelain influences the shade of porcelain. 4. Manufacturers' recommendations for each shade should include the optimum required thickness of both opaque and body porcelain.

Color↗
PubMed1981

Evaluation of the bonding of three porcelain repair systems.

1. Fractured porcelain bars repaired with Fusion/Concise displayed significantly greater repair strength (p less than .05) than bars repaired with Den-Mat and Cervident. 2. Comparing mean strengths of all samples before and after repair with Fusion/Concise indicated that only 18% of the original strength was regained following repair. 3. The low repair strengths of the tested materials indicate that their use is a temporary clinical procedure.

Composite Resins↗
PubMed1978

A study of various factors influencing shade of bonded porcelain.

Seventy-two specimens of four commercially used precious metals were constructed. The porcelain applied to these specimens was glazed up to nine times for shade comparison. Specimens were also studied with a scanning electron microscope prior to and after application of the porcelain. The important observations from this study were: 1. The four types of precious metals looked alike after casting and surface treatment and prior to application of porcelain. 2. Porcelain-bonded-to-metal shades were not influenced by the types of precious metals used. 3. Porcelain-bonded-to-metal shades remained stable after six glazings and changed only slightly after nine firings.

Color↗
PubMed1977

Porcelain shade stability after repeated firing.

There were no color changes detected in the first five firings for both air- and vacuum-fired porcelain. Slight changes were noticed in subsequent firings. These color changes were more noticeable in the air-fired samples than in the vacuum-fired samples. However, changes in the porcelain color after repeated firing were not sufficiently significant to cause rejection of the samples. The porcelain shade remains stable with repeated firing if the firing procedure is carefully carried out.

Color↗
PubMed1976

When to glaze--an electron microscope study.

1. A smooth porcelain surface can be obtained by glazing after grinding. There is no need for sanding or polishing with a rubber wheel. 2. A low-fusing glaze gives a slightly smoother surface than a natural glaze. The low-fusing glaze may be added at any stage of polishing, and the results will be the same.

Dental Porcelain↗
PubMedDate not supplied

Thermocycling of pit and fissure sealants.

Both sealants experience early thermocyclic failure, which is manifested as marginal breakdown or separation. From the 20 to 70% failure range (Fig 5) Nuva Seal was three times as resistant to thermocyclic stressing as was Epoxylite 9075. That is, the Nuva Seal-sealed teeth had to be cycled three times more than the Epoxylite 9075-sealed teeth to effect the same failure rates. Both Epoxylite and Nuva Seal reach the same failure rate at 7,000 cycles (75% failure rate). Extremely careful visual examination is required to detect marginal separation failures of pit and fissure sealants.

Dental Materials↗
PubMedDate not supplied

Comparing two methods of moisture control in bonding to enamel: a clinical study.

Twelve patients provided a total of 36 teeth to be used in this study. Visible-light-cured composite resin tabs were applied to a flattened, acid-etched surface of each tooth. Half of the teeth were isolated with cotton rolls in conjunction with a saliva ejector; the other conjunction with a saliva ejector; the other half were isolated using a rubber dam. An equal number of teeth were treated in each group for each subject to serve as a self-control. After extraction the teeth were mounted and shear bond strength of the composite resin to enamel was determined on an Instron Testing Machine. There was a significant difference in the shear bond strength between the two experimental groups.

Acid Etching, Dental↗
PubMedDate not supplied

Effects of two methods of moisture control on marginal microleakage between resin composite and etched enamel: a clinical study.

Visible light-polymerized resin composite tabs were bonded to the flattened, acid-etched surface of teeth that were scheduled for extraction. Half of the teeth (group I) were isolated with cotton rolls in conjunction with a saliva ejector. The remaining teeth (group II) were isolated using a rubber dam. Both methods of isolation were used for each patient so that to some extent all patients served as their own controls. Following extraction, all samples were thermocycled 500 times alternating between 6 degrees C and 60 degrees C, after which they were immersed in 5% methylene blue for 4 hours. Each tooth was then mounted in acrylic resin and sectioned on a hard tissue microtome. Microleakage was assessed using a light microscope at x 20 magnification. The use of rubber dam isolation resulted in less microleakage at the enamel resin interface.

Composite Resins↗
PubMedDate not supplied

The effect of microabrasion on restorative materials and tooth surface.

The effect of microabrasion on human enamel has been well documented; however, no information is available on its effect on dentin or restorative materials. The purpose of this study was to evaluate the effect of the microabrasion technique on the surface roughness of restorative materials and enamel and dentin surfaces. Flat disks of amalgam, composite resin, porcelain, and glass ionomer were evaluated. Labial enamel of three maxillary incisors and three molars that were flattened buccally to expose dentin were also tested. The Prema microabrasion compound was applied to each sample with a 10:1 gear-reduction, slow-speed handpiece for 5 seconds, then rinsed for 10 seconds. Roughness was determined with a profilometer. This procedure was repeated 20 times for each sample. A polyvinylsiloxane impression of the surface was taken after 0, 5, 10, 15, and 20 applications and examined under a scanning electron microscope. Enamel surface roughness did not improve as previously reported, suggesting that changes in optical characteristics may not be as important as removal of enamel in obtaining esthetic results. Dentin and glass ionomer exhibited an increase in roughness, such that their presence contraindicates the technique. Amalgam was essentially polished. Porcelain was most resistant to the effects of microabrasion. Judicious use of the technique, especially when restorative materials are present, is advised.

Analysis of Variance↗