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J Perdigao

Publications and source records attributed to J Perdigao.

12 recordsLinked to original sources
PubMed1999

Effect of acid etching and collagen removal on dentin wettability and roughness.

It was recently reported that removal of the collagen network from etched dentin does not affect dentin bond strengths. The aim of this study was to determine if the removal of the collagen fibers results in changes in dentin roughness and wettability. Twenty cary-free extracted human third molars were sectioned parallel to the occlusal surface to expose either superficial or deep dentin. Dentin was ground flat through 600-grit SiC abrasive paper under water to provide uniform surfaces. Observed contact angle measurements were performed to assess wettability by using the axisymmetric drop shape analysis technique using water and a water-based primer. Average roughness was determined with a profilometer. The specimens were analyzed just after being ground, after etching with 35% H(3)PO(4) gel for 15 s, and after etching and deproteinization with 5% NaOCl for 2 min. Data were analyzed with two-way ANOVA and Newman-Keuls multiple comparison t test procedure. Etching resulted in an increase in surface roughness and dentin wettability. For deep dentin, collagen removal did not influence the average roughness, but it resulted in a significantly greater degree of wettability. The degree of wettability for deep dentin was greater than for superficial dentin.

Acid Etching, Dental↗
PubMed1995

Field emission SEM comparison of four postfixation drying techniques for human dentin.

Critical-point drying (CPD) is generally considered essential for the preparation of biologic specimens for electron microscopy. Several attempts have been made to introduce alternative techniques. More recently, this problem has arisen in dentistry, because of the new developments in dentin bonding. The present study focuses on three alternative techniques to CPD: hexamethyldisilazane (HMDS) drying, Peldri II drying, and air drying. Twenty-four dentin disks were obtained from noncarious extracted human molars by microtome sectioning parallel to the occlusal surface. The dentin surfaces were etched with polymer-thickened, silica-free, 10% phosphoric acid semigel, fixed, dehydrated, and dried with one of the four techniques. The specimens were observed in two perpendicular planes, showing dentinal tubules in longitudinal view and cross-section, using a field emission scanning electron microscope. The intertubular demineralized dentin zone was composed of three different successive layers, which did not substantially differ between CPD and Peldri II drying, but were more evident in HMDS-dried specimens: first, an upper layer of denatured collagen and residual smear layer particles, with sectioned collagen fibrils and few open intertubular pores; second, an intermediate layer of closely packed cross-sectioned collagen fibers; and third, a deeper layer with unfilled spaces, scattered hydroxyapatite crystals, and few collagen fibers. HMDS drying seemed to preserve better the collagen network and the microporosity of the demineralized dentin surface. Moreover, HMDS drying is easy to perform. The air-drying method caused some artefacts, such as surface collapsing and thickening of the denatured collagen layer.

Air↗
PubMed1994

In vitro bond strengths and SEM evaluation of dentin bonding systems to different dentin substrates.

In comparison to enamel, bonding to normal dentin is a greater challenge because of its organic constituents, fluid-filed tubules, and variations in intrinsic composition. Bonding to sclerotic dentin is even more difficult. To evaluate the shear bond strengths of four adhesive systems to dentin substrates with different levels of mineralization, 120 extracted human teeth were randomly assigned to three groups (n = 40). After mid-coronal dentin was exposed, groups of specimens were artificially hypermineralized by immersion in a remineralizing solution, demineralized by means of an acetic acid demineralizing solution, or stored in distilled water to model sclerotic, carious, and normal dentin, respectively. Resin composite was bonded to dentin by use of commercial adhesive systems. After the specimens were thermocycled, shear bond strengths were determined in an Instron universal testing machine. Dentin substrates and resin/dentin interfaces were examined by SEM. For each adhesive system, the mean shear bond strength to normal dentin was significantly higher than that to either of the other substrates. Shear bond strengths to hypermineralized dentin were significantly higher than those to demineralized dentin with all adhesives except Prisma Universal Bond 3.

Analysis of Variance↗
PubMed1994

Analysis of dental adhesive systems using scanning electron microscopy.

This study used scanning electron microscopy (SEM) to evaluate the effects of various acid conditioners (etchants) on dentine surfaces. The conditioners completely removed the smear layer from dentine and opened the dentinal tubules, but some also left debris or a reaction product on the surface. The study also evaluated the resin-dentine interfaces produced by five new-generation dentine bonding systems: All-Bond 2, Amalgambond, Gluma 2000, OptiBond, and Scotchbond Multi-Purpose. All-Bond 2, Amalgambond, OptiBond, and Scotchbond Multi-Purpose formed acid-resistant hybrid layers and intra-tubular resin tags when they were applied to visibly moist dentine.

Acid Etching, Dental↗
PubMed1994

Silica contamination of etched dentin and enamel surfaces: a scanning electron microscopic and bond strength study.

Most acid-etchant gels are thickened with silica, which can leave a particulate residue on dentinal surfaces. Some newer etchants are thickened with polymers, which reportedly leave no surface residue. This study used scanning electron microscopy to examine dentinal and enamel surfaces that had been etched with either silica- or polymer-thickened gels. The silica gels left particulate debris on dentinal surfaces, and this debris was not removed by rinsing with water. There was little evidence of this contaminant on enamel surfaces. Enamel and dentinal surfaces treated with the polymer-thickened gels appeared to be clean and uncontaminated. Shear bond strengths of composite resin to enamel and dentin etched with the different types of gel etchants were also evaluated. Silica contamination did not adversely affect bonding. In fact, etching with silica-thickened gels resulted in slightly higher bond strengths to both substrates. However, the differences were not statistically significant.

Acid Etching, Dental↗
PubMed1994

Adhesion of a total-etch phosphate ester bonding agent.

This study evaluated the shear bond strengths of a phosphate ester bonding agent, Clearfil Photo Bond, using different phosphoric acid gels to etch dentin. The study also tested the shear bond strength of the Clearfil Liner Bond system. Sixty extracted human molars were ground to expose mid-coronal dentin and were randomly assigned to six treatment groups. The first group was left unetched as a control. In the next four groups, dentin was etched with phosphoric acid gels: K-etchant (40% with silica thickener); Uni-Etch (polymer-thickened 32%); All-Etch (10%, polymer thickener); or Ultra-Etch (10%, silica thickener). Specimens in the sixth group were etched with 10/20 Ca, a gel with 10% citric acid and 20% calcium chloride. All specimens were bonded with Clearfil Photo Bond and XRV Herculite resin composite. Specimens in the final group also received SA Primer and Protect Liner. After thermocycling, shear bond strengths were determined using an Instron universal testing machine. Mean shear bond strengths ranged from 1.3 MPa (control) to 15.9 MPa (Clearfil Liner Bond). The shear bond strengths of specimens that had been etched with phosphoric acid gels were in the range of 5-8 MPa, and were not significantly affected by either acid concentration or thickener type. SEM examination showed that phosphoric acid demineralized dentin to a depth of 5 microns, while 10/20 Ca demineralized dentin to a depth of only 1-1.5 microns.

Acid Etching, Dental↗
PubMed1994

Effects of chlorhexidine on dentin surfaces and shear bond strengths.

This in vitro study examined the effects of chlorhexidine on dentin surfaces and on the bond strengths of composite to dentin. Scanning electron microscopy revealed that the chlorhexidine solution deposited debris on the surface and within the tubules of etched dentin but chlorhexidine had no significant effect on the shear bond strengths of composite to dentin using the All-Bond 2 adhesive system.

Analysis of Variance↗
PubMed1993

Effects of surface treatment and bonding agents on bond strength of composite resin to porcelain.

This study evaluated porcelain repair by use of various surface treatments and hydrophilic bonding resins. The surface treatments were air abrasion (sandblasting), roughening with a diamond, etching with 9.6% hydrofluoric acid, and a combination of the latter two methods. A silane coupling agent was applied to all porcelain surfaces, and composite resin was bonded to porcelain with All-Bond 2, Amalgambond, or Clearfil Porcelain bonding agents. Shear bond strengths were determined on a universal testing machine. The most effective surface treatment was the combination of diamond roughening and hydrofluoric acid etching, but it was not significantly better than the other methods. The Clearfil Porcelain Bond system showed a greater repair strength than the other two materials but was statistically different only from Amalgambond resin.

Acid Etching, Dental↗
PubMed1993

Effects of etchants, surface moisture, and resin composite on dentin bond strengths.

This in vitro study evaluated the effects of etchant type, surface moisture, and resin composite type on the shear bond strength of dentin adhesives. Three adhesives which bond to etched dentin were used in the study: All-Bond 2, Amalgambond, and Clearfil Photo Bond. Occlusal enamel was removed from 200 human molars to expose dentin. The dentin surfaces were etched, treated with a dentin adhesive system, and bonded with resin composite. After thermocycling and storage, the composite columns were fractured from dentin using an Instron machine. Bond strengths were calculated and subjected to a statistical analysis. Etchant type, surface moisture, and resin composite type all had significant effects on dentin bond strengths. Overall, the highest bond strengths were obtained with 10/3 etchant, moist dentin, and hybrid composite. The highest bond strengths for All-Bond 2 and Amalgambond were obtained by using the manufacturer's recommended etchant, moist dentin, and a hybrid composite. The mean bond strengths for All-Bond and Amalgambond under these conditions were 22.5 and 19.0 MPa, respectively. Clearfil Photo Bond had significantly lower bond strengths, but was relatively unaffected by changes in experimental conditions.

Acid Etching, Dental↗
PubMedDate not supplied

The State of an Art.

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Curriculum↗