Search PubMed⌕ Search

Biomedical subjects

N Barghi

Publications and source records attributed to N Barghi.

At least 19 recordsLinked to original sources
PubMed2000

Effects of timing and heat treatment of silanated porcelain on the bond strength.

This study examined the effects of postsilanization interval and heat treatment on shear bond strength of composite resin to porcelain. One hundred and eighty square-shaped specimens were fabricated and sanded flat sequentially. The specimens were then randomly placed into six groups and 18 subgroups of 10 specimens each. An experimental and three commercially available silane systems, including two one-mix and one two-mix systems, were tested in this study. No silane treatment specimen was used as control. Specimens from the experimental and one of the Mirage groups were selected for heat treatment for 60 min at 60 degrees C. Three post-silanization intervals were scheduled. After incubation, a dual cure composite resin (Mirage FLC) was placed on the silanated surfaces and light-cured. All specimens were stored in 37 degrees C, 2% saline solution for 1 week and subjected to shear test using an Instron machine with cross-head speed of 5 mm/min. ANOVA and Scheffe tests were used to analyse data with confidence level at 95%. The mean values of the shear bond strengths ranged from 2.8 to 23.3 MPa. All groups showed significantly higher bond strength than the control group at the 3 min, 24 h and 1 week post-silanization periods (P < 0.05). Heat treatment groups recorded an increase in the shear bond strength and maintained significantly higher bond strength values (P < 0.05). In conclusion, bond strength of composite resin to porcelain resulting from silanization of porcelain increased after heat treatment and during the post-silanization periods. The bond strength also varied for different silane coupling agents tested in this study especially in the one-mix system.

Analysis of Variance↗
PubMed2000

To silanate or not to silanate: making a clinical decision.

Etched porcelain-bonded restorations have become the treatment of choice for the esthetic restoration of anterior teeth. The bond strength of composite resin to properly etched and silanated porcelain exceeds the cohesive strength of porcelain. Although bonding to enamel is accomplished by only etching the surface to create micromechanical retention, bonding to porcelain is achieved both mechanically through etching porcelain and chemically through the use of a silane coupling agent. Literature supports silanization of porcelain, which provides a more reliable bond than etching with hydrofluoric acid only, although the combination of both are recommended. This article discusses the importance of proper silanization of porcelain in obtaining a durable and reliable resin composite bond with porcelain.

Acid Etching, Dental↗
PubMed1999

Effect of water storage on the silanization in porcelain repair strength.

This study examined the long-term water storage affect of silanization on shear bond strength of composite resin to porcelain. One hundred and sixty square-shaped specimens were fabricated and sanded flat sequentially with silicone carbide papers. The specimens were then placed into four groups and 16 subgroups of 10 specimens each randomly. Four commercially available silane systems, two one-mix and two two-mix, were tested in this study. Teflon tubes with an internal diameter of 2.97 mm and 2 mm in height were filled with a dual cure composite resin (Mirage FLC), placed on the silanated surfaces and light-cured for 120 s. Specimens were stored in room temperature water and subjected to shear bond strength testing after 24 h, 1 week, 1 month and 3 month periods of immersion. An Instron Universal testing machine with a crosshead speed of 0.5 mm/min was used for the testing. The mean values of the shear bond strengths ranged from 4.38 MPa (24-h period) to 23.90 MPa (3-month period). ANOVA and Scheffe' tests were used to analyse data with confidence level at 95%. All groups recorded an increase in bond strength after one week as compared with the 24-h period (P<0.05). With the exception of a one-mix system, all systems showed significantly higher bond strength at 3 weeks as compared with the 24-h and 1-week water storage periods. In conclusion, bond strength of composite resin to porcelain resulting from silanization of porcelain increased during the experimental period. The bond strength also varied for different silanes used in this study.

Analysis of Variance↗
PubMed1999

Effects of the solvents on bond strength of resin bonded porcelain.

Clinical trials of porcelain veneers for chairside colour modifications may require the use of a trial resin with various colours of tints. The bond strength effects of four different solvents used for removal of trial resin from etched porcelain specimens were investigated. Fifty-six porcelain specimens were fabricated, flattened by a metallurgically standard method, etched with hydrofluoric acid and silane treated. The specimens were divided into four groups at random. The trial resin material was cleaned with different solvents prior to bonding of a dual cure resin composite button. After bonding the specimens were stored in water at 37 degrees C for 7 days. Shear bond strength results were as follows: acetone (control) group, 12.9+/-2.9 MPa; ethanol group, 15.1+/-4.6 MPa; methanol group, 11.5+/-2.9 MPa; methylene chloride group, 11.3+/-2.4 MPa. No significant differences were measured (ANOVA, P>0.05). The results indicated that the resin-porcelain bond strengths were not affected by the type of solvent used to remove trial resin. This procedure is recommended for clinical cases when resin composite is used for the try-in of etched porcelain bonded restorations.

Acetone↗
PubMed1999

A predictable and accurate technique with elastomeric impression materials.

A method for obtaining more predictable and accurate final impressions with polyvinylsiloxane impression materials in conjunction with stock trays is proposed and tested. Heavy impression material is used in advance for construction of a modified custom tray, while extra-light material is used for obtaining a more accurate final impression.

Dental Impression Materials↗
PubMed1998

Porcelain for veneers.

An ideal porcelain veneer placed on a non-discolored tooth requires the least amount of tooth preparation and the use of a translucent porcelain that interferes minimally with the transmission of light. In contrast, veneering a discolored tooth requires additional tooth preparation and the use of a chromatic or opacious porcelain. This article discusses several criteria for the selection of porcelain for porcelain veneers, including some steps to enhance the esthetic properties of these restorations.

Dental Porcelain↗
PubMed1998

Making a clinical decision for vital tooth bleaching: at-home or in-office?

The dramatic increase in public demand for esthetic dentistry and tooth bleaching has encouraged development and resulted in new products and eltasdeltaues. Vital tooth bleaching, including in-office bleaching and at-home bleaching, has been adopted as an effective and safe method for whitening natural dentition. Although most dentists prefer at-home bleaching, nearly one third use in-office bleaching. Continuous improvements in bleaching products and delivery systems have made in-office bleaching more practical and predictable. This article discusses the practical applications of vital tooth bleaching, as well as the advantages and disadvantages of each method.

Adult↗
PubMed1997

Bleaching following porcelain veneers: clinical cases.

These clinical reports present two somewhat identical cases needing bleaching of the opposing teeth following placement of porcelain veneers. Using a new light-activated power bleaching gel (Opalescence Xtra) eliminated color discrepancies between veneered and non-veneered teeth. In both cases ideal esthetic results were achieved.

Adult↗
PubMed1993

A comparative study of three glass ionomer base materials.

This study compared the compressive and diametral tensile strength, compressive modulus, shear bond strength to dentin and resin composite, marginal gap between the base and tooth in Class V cavity preparation, and fluoride release of three glass ionomer base materials. In general, visible light-cured (VLC) base materials outperform the autopolymerizing glass ionomer base Ketac-Bond. The compressive modulus is significantly less for the VLC glass ionomer materials Vitrebond and Fuji LC compared to Ketac-Bond. The Fuji LC had greater diametral tensile strength, compressive strength, bond to dentin and bond to resin composite than Vitrebond or Ketac-Bond. The fluoride release of Vitrebond was greater than Ketac-Bond or Fuji LC. The marginal gap at the tooth/base interface was significantly less with the Fuji LC compared to the other two materials.

Analysis of Variance↗
PubMed1992

Marginal accuracy and geometry of cast titanium copings.

The biocompatibility of titanium with human tissue is well established; its potential as an alternate metal for crown restorations has yet to be fully investigated. This study measured the geometry and accuracy of coping margins cast in Ti, 99.5% chemically pure. Twenty castings with 45-degree facial and 90-degree palatal margins were made by indirect technique with a commercial system using recommended procedures. They were then cemented with ZnPO4 cement. The coping and die assemblies were embedded in resin, sectioned longitudinally, and measured with a microscope at x50 power. Casting shrinkage was characteristic, particularly along the horizontal axis in the plane of the shoulder. Although horizontal linear shrinkage of 45-degree margins was greater than that for the 90-degree form, the surface of marginal discrepancy was greatest with the 90-degree configuration.

Analysis of Variance↗