D.H. Retief

Enamel and Cementum Fluoride Uptake from a Glass Ionomer Cement

Class V cavities were prepared at the cemento-enamel junction on the facial surfaces of 45 extracted human central maxillary incisors. Enamel samples for analysis were obtained by means of perchloric acid etching from circular areas, 1 mm in diameter, positioned 1.5, 3.5, 5.5, and 7.5 mm from the incisal and apical margins of the restorations, respectively. The preparations were filled with Fuji Ionomer Restorative, Type II. The restored teeth were individually suspended in synthetic saliva at 37 °C and the saliva changed at regular intervals. 15 teeth were removed after 1, 3, and 6 months, respectively. Enamel and cementum samples were again obtained from the teeth from sites parallel and adjacent to the previous biopsy sites. The fluoride content of the etching solutions was determined by gas chromatography and the calcium content by atomic absorption spectrophotometry. Fluoride acquired by enamel after 1 month ( ± 2,500 ppm F) was retained after 3 and 6 months. Fluoride acquired by cementum after 1 month ( ± 15,000 ppm F) was significantly reduced after 3 months ( ± 6,000 ppm F) and maintained at this level after 6 months.

Effects of phosphoric acid concentration and etch duration on enamel depth of etch: An in vitro study****

In a previous study we reported no significant differences among the shear bond strengths resulting from the application of an orthodontic bonding resin to enamel surfaces etched with three phosphoric acid (H3PO4) concentrations, each for three etch durations. The objective of the current study was to determine the depths of etch on ground enamel surfaces exposed to the nine etching procedures. The facial surfaces of 45 extracted human maxillary permanent central incisors were ground wet on 600-grit silicon carbide paper. Annular adhesive disks of 6 mm outer diameter and 3 mm inner diameter were positioned on the ground enamel surfaces and etched with 10 mm3 of 37%, 15%, and 5% H3PO4 for 60, 30, and 15 seconds, respectively. The calcium concentrations of the etching solutions were determined and the depths of etch calculated. The depths of etch were then measured with a surface profilometer. A stepwise decrease in the calculated depths of etch with decreasing acid concentration and duration of etching was obtained. The calculated etch depths ranged from 27.1 microns by etching with 37% H3PO4 for 60 seconds to 3.5 microns by etching with 5% H3PO4 for 15 seconds. The measured depths of etch followed a similar pattern. A highly significant correlation between calculated and measured depths of etch was obtained.

Effects of phosphoric acid concentration and etch duration on the shear bond strength of an orthodontic bonding resin to enamel: An in vitro study

The purpose of this in vitro study was to determine the effects of phosphoric acid (H3PO4) concentration and duration of etching on the shear bond strength of an orthodontic bonding resin to enamel. Nine bonding procedures, each involving 18 extracted human maxillary permanent canines, were used. Ground enamel surfaces were etched with a 37% H3PO4 solution, a 15% H3PO4 gel, or a 5% H3PO4 solution for 60, 30, and 15 seconds, respectively. Cylinders of an orthodontic bonding resin, Concise, were prepared in a special device. The test specimens were disassembled 15 minutes after preparation and stored in distilled water at 37 degrees C for 24 hours. A shear load was applied to the bonded cylinders at a crosshead speed of 0.02 in.min-1 in an Instron testing machine, and the shear bond strengths were calculated and expressed in MN.m-2. A two-factor analysis of the data showed that the H3PO4 concentration had no significant effect on the shear bond strength, but the duration of etching affected shear bond strength significantly. The enamel aspects of the fractured test specimens were examined microscopically and the percent failure within the bonding resin at the bonding sites estimated. The correlation between shear bond strength and percentage failure within the bonding resin was not significant. The effects of the nine etching procedures on ground and unground enamel surfaces were studied by scanning electron microscopy. The etching procedures produced well-defined etching patterns on both ground and unground enamel surfaces.

Fluoride release from and tensile bond strength of Ketac-fil and ketac-silver to enamel and dentin

Abstract Silver-reinforced glass ionomer cements have recently become commercially available. The purpose of this study was to determine the fluoride (F) release from, and the tensile bond strength (TBS) of Ketac-Fil, a conventional, and Ketac-Silver, a silver-reinforced glass ionomer cement, to enamel and dentin, respectively. To determine F release, 6 discs, 20 mm in diameter and 1.5 mm thick, were prepared from each material, and suspended in 50 ml glass distilled water for 24 h. The discs were washed with 50 ml TISAB and the fluoride concentrations determined electrometrically. These procedures were repeated for 14 consecutive days. The TBS of Ketac-Fil to enamel (A) and dentin (B) and of Ketac-Silver to enamel (C) and dentin (D), respectively, were determined. Fifteen test specimens were prepared with each procedure. The test specimens were stored in water at 37°C for 24 h. The test specimens were then mounted in an Instron machine and subjected to a tensile load at a cross-head speed of 0.02 inch. min −1 . The bond strengths were calculated and expressed in MN.m −2 . The data were analyzed by ANOVA and Duncans multiple range test at the 5% level of significance. Ketac-Fil only released significantly more F (μg F. mm−2 during the first 7 days than Ketac-Silver. The following tensile bond strengths (MN.m −2 ) were obtained: A: 2.3±1.6; B: 2.0 ±2.3; C: 1.2±1.7; D: 0.5±1.3. The bond strengths of D were significantly lower than those of A and B but not significantly different from C. The addition of silver to a glass ionomer cement reduced the fluoride release and the bond strength to dentin.

The effects of thermal and occlusal stresses on the microleakage of the Scotchbond 2 dentinal bonding system

The microleakage of the Scotchbond 2 Dentinal Bonding System was evaluated under various experimental conditions. In this in vitro study, Class V restorations involving both enamel and cementum were placed on the buccal surfaces of 54 extracted human permanent canines and on the buccal and lingual surfaces of eight extracted human permanent mandibular molars. The canines were divided into three groups, each undergoing different conditions of thermocycling in 0.5% basic fuchsin or distilled water and storage time in the dye. The molars were subjected to an occlusal load of 8 MPa for 66,000 times prior to being thermocycled. There were no significant differences in microleakage of the restorations placed in the canine teeth; however, microleakage in the group of molars subjected to occlusal stresses was significantly increased. This may have been due to the increased length of the restorations placed in the molar teeth.The microleakage of the Scotchbond 2 Dentinal Bonding System was evaluated under various experimental conditions. In this in vitro study, Class V restorations involving both enamel and cementum were placed on the buccal surfaces of 54 extracted human permanent canines and on the buccal and lingual surfaces of eight extracted human permanent mandibular molars. The canines were divided into three groups, each undergoing different conditions of thermocycling in 0.5% basic fuchsin or distilled water and storage time in the dye. The molars were subjected to an occlusal load of 8 MPa for 66,000 times prior to being thermocycled. There were no significant differences in microleakage of the restorations placed in the canine teeth; however, microleakage in the group of molars subjected to occlusal stresses was significantly increased. This may have been due to the increased length of the restorations placed in the molar teeth.

Tensile bond strengths of dentin bonding agents to dentin

Abstract Several dentin bonding agents have recently become commercially available. The purpose of this study was to determine the tensile bond strengths of 4 dentin bonding agents to dentin. Seventy-two maxillary permanent central incisors were mounted in tooth cups and the facial surfaces ground on 600 grit SiC to expose the underlying dentin. The tensile bond strengths were determined by a test method developed by Kemper and Kilian (1976) . The following systems were evaluated: Scotchbond to untreated dentin, P 10 (A); Scotchbond to dentin etched with H3PO4, P 10 (B); Scotchbond to dentin conditioned with citric acid, P 10 (C); J. & J. Dentin Bonding Agent to dentin, Adaptic (D); Creation Bonding System to dentin treated with Den-Mat Cavity Cleanser, Spectrabond (E); Dentin-Adhesit System to dentin treated with Vivadent Dentin Conditioner, Isopast (F). Twelve test specimens were prepared in random order with each procedure. The tensile bond strengths were determined in an Instron machine and expressed in MN.m−2. The data were analyzed by a one-way analysis of variance and by Duncans multiple range test at the 5% level of significance. The tensile bond strengths were significantly different (P=0.0001). The tensile bond strengths (MN.m−2) in descending order of magnitude were: D=3.0; B=0.9; F=0.1; A=0.1; C=0.04; E=0. The tensile bond strength obtained with procedure D (J. & J. Dentin Bonding Agent, Adaptic) was significantly greater than those obtained with the other procedures. The tensile bond strengths of the other systems were not significantly different.

In vivo Study on the Prevention of Postradiation Caries

Postradiation caries is usually prevented by the application of topical fluorides (F) at high concentrations. The aim of this study was to develop an optimal preventive program for postradiation caries by evaluating the effects of F concentration and application procedures in subjects with radiation-related xerostomia. Six ground enamel slabs were mounted on each side of the lower denture of each of 7 xerostomia patients. Four procedures were used: no F exposure (control), neutral F gel applied every 2nd day or weekly, and a daily rinse with a F mouthwash for a period of 6 weeks. The enamel slabs were analyzed at weekly intervals by scanning optical monitoring, longitudinal microradiography, and scanning electron microscopy. In addition, hardness measurements were performed on the slabs. F analyses of the enamel slabs were done prior to their insertion in the appliances and after 6 weeks of intraoral exposure. In the control experiments severe demineralization of enamel occurred within 6 weeks. Application of F gel or the use of the F mouthrinse resulted in a significant inhibition of the demineralization process. Of the procedures evaluated, F gel applied every 2nd day was the most effective in preventing the onset of postradiation caries.

Tensile bond strengths of orthodontic bonding resins and attachments to etched enamel

The purpose of this in vitro study was to determine the tensile bond strengths (TBS) of several orthodontic bonding systems and orthodontic brackets to enamel surfaces exposed to different etching procedures. The TBS of four bonding systems were determined by a test method developed by Kemper and Kilian. Twelve test specimens were prepared for each procedure. The test system was modified to determine the TBS of orthodontic brackets bonded to enamel surfaces by six bonding procedures and the TBS were evaluated 15 minutes and 24 hours after specimen preparation. The specimens were loaded to failure in an Instron machine operated at a crosshead speed of 0.02 inch/min. The TBS were expressed in MN.m-2. The TBS of the four bonding systems to etched enamel were not significantly different (P = 0.2528). The TBS of bonded brackets determined 24 hours after specimen preparation were not significantly different than the TBS recorded after 15 minutes except for brackets bonded with Lee Cleanse and Bond I to enamel surfaces etched with 15% H3PO4 for 30 seconds. The TBS of brackets to enamel etched with 15% H3PO4 for 30 seconds were not significantly different from the TBS to enamel surfaces etched with 5% H3PO4 for 15 seconds except for brackets bonded with Lee Cleanse and Bond II and tested 24 hours after bonding.

Enamel fluoride uptake, distribution and retention from topical fluoride agents.

The in vitro fluoride acquired by human enamel after application of APF, Duraphat (a resin varnish) and Fluor Protector (a polyurethane varnish), respectively, and subjected to various procedures was determined. Fluoride acquisition was the greatest in teeth treated with Duraphat and Fluor Protector and the least in APF-treated teeth. Fluoride uptake and distribution were not increased by extending the contact time between the topical fluoride agents and enamel from 4 to 24 h. Reapplication of the topical fluoride agents did not increase fluoride acquisition. Fluorapatite was the predominant reaction product with Duraphat and Fluor Protector and alkali-soluble fluorides with APF application.

A laboratory evaluation of three etching solutions

Abstract Solutions containing 50 m/m % phosphoric acid (A), 25 m/m % pyruvic acid (B), and 50 m/m % citric acid (C) were prepared. The tensile bond strenghs of a conventional chemically activated composite resin (Concise) and a sealant (Delton) to enamel surfaces etched with the respective etching agents were determined. The surface roughness (RA) of polished enamel surfaces etched with the respective acids was measured and the effects on the morphology of polished etched enamel surfaces evaluated by SEM. The tensile bond strengths expressed in MN.m−2 were: Concise: Etched with A=15.2± 3.5; B=19.1±3.1;C=10.7±1.8. Delton: Etched with A=13.5±2.9; B =18.6±4.7; C=8.4±1.4. Pyruvic acid etching produced significantly greater bond strengths than phosphoric acid etching which in turn produced significantly greater bond strengths than citric acid. RA values in μm were: A= 0.31±0.07; B=0.33±0.05; C=0.17±0.03. Phosphoric acid and pyruvic acid etching of polished enamel surfaces produced well-defined etching patterns.