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.

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.

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.

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.

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.

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.

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.

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.

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.

Evaluating intensity output of curing lights in private dental offices.

Dentists in private offices were using inadequate curing lights, according to these study results. Many were unaware that the output of the lights was inadequate to completely cure composite resins.

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.

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.

Postcementation marginal fit of a new ceramic foil crown system.

The in vitro marginal fit of a new foil crown was investigated. Ten standardized polycarbonate master dies filled with 30 wt% carbon having a 90-degree butt joint margin were used to evaluate the marginal fit of Sunrise porcelain foil crowns. The crown specimens were made on stone dies and treated with three coats of die spacer. After fabrication, they were adjusted, cemented with zinc phosphate cement to their respective master dies with 5 kg loading for 10 minutes and stored in water. A Gaertner traveling microscope was used to measure the marginal fit of each specimen. Readings were recorded at five locations randomly marked but equally dividing the margin on each crown, and the overall mean for the crowns was then calculated. The results from the 50 areas revealed a mean marginal discrepancy of 25.3 microns, and this compared favorably with the discrepancies reported for other ceramic crown systems.