PubMed Health⌕ Search

Biomedical subjects

D H Retief

Publications and source records attributed to D H Retief.

At least 19 recordsLinked to original sources
PubMed1992

A laboratory study of the Amalgambond Adhesive System.

The shear bond strengths (SBS) of the Amalgambond Adhesive System to several substrates were determined in vitro. Ninety extracted human permanent first and second molars were used. In 30 teeth, the occlusal surfaces were ground wet on 600-grit SiC to expose the enamel and in 60 to expose the superficial dentin. Amalgam (Tytin) restorations were placed on 15 exposed dentin surfaces and sandblasted. The Metafil-A composite was transferred in three increments and each cured for 30 seconds. The SBS of the composite to enamel were determined 1 minute (A) and 24 hours after final cure (B); to dentin 1 minute (C) and 24 hours after final cure (D); of freshly mixed amalgam to dentin (E) and to previously placed amalgam (F) after 24 hours. All of the 24 hours specimens were stored in saline at 37 degrees C or 24 hours. A shear load was applied to the base of the bonded cylinders with a knife-edged rod in an Instron machine at a crosshead speed of 0.5 mm/min. The SBS were expressed in MPa and the data analyzed by Student t-test, ANOVA and Student-Newman-Keuls test. The mean +/- SD of SBS were: A: 8.15 +/- 1.74; B: 15.69 +/- 4.50; C: 6.64 +/- 1.72; D: 17.09 +/- 4.61; E: 5.10 +/- 1.73; F: 6.54 +/- 3.78. The SBS to enamel and to dentin, respectively, after 24 hours were significantly greater than after 1 minute (P = 0.0001), the SBS of A vs C (P = 0.1783), B vs D (P = 0.2180) and E vs F (P = 0.7149) were not significantly different.

Analysis of Variance↗
PubMed1992

Enamel, cementum and dentin fluoride uptake from a fluoride releasing resin composite.

The purpose of this study was to determine the fluoride release by and the enamel, cementum and dentin fluoride uptake from a visible light-cured fluoride-containing resin composite. Seven circular discs of the composite were prepared and the fluoride release in distilled water determined at daily intervals for 14 days, and then after 30, 90, 180, 365 and 550 days. The baseline fluoride concentrations in enamel and cementum were determined in three successive depths by an acid etch biopsy procedure and in dentin by an abrasion biopsy procedure. Composite slabs were prepared and ligated to the enamel, cementum and dentin surfaces and the teeth were suspended in synthetic saliva for 7 or 30 days. After removal of the composite, similar biopsy procedures were performed. The teeth were then immersed in 1 M KOH for 24 hours and similar biopsies done. The fluoride concentrations were adjusted to standardized depths of 2.0 microns for enamel, 4.0 microns for cementum and 10.0 microns for dentin, and the total and bound fluoride uptake calculated. The fluoride release from the composite dropped sharply after 1 day and after 180 days reached a plateau which remained relatively constant up to 550 days. The results of this in vitro study indicated that the mineralized dental tissues acquired fluoride at various depths.

Analysis of Variance↗
PubMed1992

Microleakage of Vitrebond/P-50 Class II restorations.

Thirty extracted human mandibular permanent first and second molars were used in this study. Class II preparations were made extending 1 mm below the CEJ at the mesial and 1 mm above the CEJ at the distal aspects. In 15 of the teeth Vitrebond was applied to all exposed dentin (A) while in 15 teeth the gingival floor was left exposed (B). After cure, the enamel margins were etched with H3PO4 gel and the Vitrebond surfaces were treated with Scotchbond 2. The P-50 was transferred to the approximal boxes and occlusal aspects in three increments, each compressed firmly and cured for 60 seconds. The restored teeth were stored in saline at 37 degrees C for 1 week. The teeth were thermocycled x250 in 0.5% basic fuchsin between 8 degrees C and 50 degrees C with a dwell time of 15 seconds. The teeth were embedded in epoxy resin and five mesiodistal sections cut. Microleakage at the mesial and distal aspects were scored from 0 to 3 depending on the extent of the microleakage. The data were analyzed by the Wilcoxon 2-sample and the matched pair signed rank tests. Leakage above the CEJ was significantly less than below the CEJ and significantly reduced when Vitrebond was extended to the cavosurface margins.

Acid Etching, Dental↗
PubMed1992

Effect of axial load and temperature cycling on microleakage of resin restorations.

This study evaluated the microleakage of Class V resin restorations subjected to temperature and axial load cyclings. The preparations were made at the mesial and distal aspects of 29 mandibular first and second molars. The enamel margins were beveled, acid etched, washed and dried. Kerr XR Bonding System was applied to the dentin and etched enamel and Herculite composite cured in two increments. The teeth were stored in saline for 7 days, thermocycled x500 in 0.5% basic fuchsin between 8 degrees C and 50 degrees C (A); subjected to an occlusal load of 34 MPa in the dye without thermocycling (B); or followed by thermocycling (C). The leakage was scored from 0 to 4 at both the enamel and cementum aspects of the restorations. The data were analyzed by the Kruskal-Wallis test. The microstrain of five restored teeth subjected to an occlusal load of 34 MPa was measured. Microleakage of the mesial restorations was significantly greater at the cementum aspects of the restorations subjected to both temperature and occlusal loading when compared to the restorations subjected to temperature cycling or load cycling only. The microstrain in eight of the 10 restorations was significantly greater at the cementum aspects of the restorations than at the enamel aspects.

Bite Force↗
PubMed1992

Phosphoric acid as a dentin etchant.

This study determined the effect of phosphoric acid (H3PO4) application to dentin on the shear bond strength (SBS) and microleakage of an experimental bonding system. Thirty human maxillary permanent first and second molars were used for the SBS evaluation. In 15 of the teeth the Dentin Conditioner was applied to dentin for 30 seconds (A), while in the remaining 15 teeth the smear layer was removed by the application of a 37% H3PO4 gel for 20 seconds (B). The Primers 1 and 2 were mixed and applied to the conditioned dentin followed by the application of the Dentin Bonding Resin prior to the placement in three increments of the Bisfil-M composite. The specimens were stored in physiological saline at 37 degrees C for 24 hours prior to applying a shear load at a crosshead speed of 0.5 mm. inch-1 in an Instron machine. Shear bond strengths were expressed in MPa. Circular Class V preparations were made on the roots of 30 maxillary permanent canines, 15 restored using the Dentin Conditioner (C) and 15 by removing the smear layer with the H3PO4 gel (D). Microleakage of the restorations was determined quantitatively by means of a spectrophotometric method. The quantitative microleakage was expressed as microgram dye/restoration. The data were analyzed by the Student t-test. The following results were obtained: A: 14.2 +/- 2.2 MPa; B: 7.2 +/- 4.2 MPa; C: 30.0 +/- 28.6 micrograms dye/restoration; (D) 10.3 +/- 8.2 micrograms dye/restoration. Removing the smear layer with H3PO4 reduced the SBS to dentin but decreased the quantitative microleakage significantly.

Acid Etching, Dental↗
PubMed1992

Gluma shear bond strength to enamel and dentin treated with pyruvic acid and glycine.

The purpose of this study was to determine the effect of pyruvic acid and glycine on the shear bond strength (SBS) of the Gluma Bonding System to dentin and enamel. Forty-five mandibular and maxillary permanent first and second molars and 45 maxillary permanent central incisors were used in the study. Fifteen test specimens were prepared with each of the following procedures. Dentin: using the conventional Gluma Bonding System (A); the Gluma 2 Cleanser was replaced with 10% pyruvic acid containing 10% glycine with pH 2.8 (B); or the dentin was etched with 10% pyruvic acid (pH 1.5) followed by the application of 10% glycine with pH adjusted to 9.0 (C). Enamel: etched with Gluma 1 Etchant (D); etched with 10% pyruvic acid containing 10% glycine (E); or etched with 10% pyruvic acid followed by the application of 10% glycine (F). The test specimens were disassembled 15 minutes after cure, stored in physiological saline at 37 degrees C for 24 hours, and the SBS determined in an Instron machine at a crosshead speed of 0.5 mm.min.-1 The SBS was expressed in MPa. The data were analyzed by ANOVA and the Student-Newman-Keuls test. The mean +/- SD of the SBS in MPa were: A: 8.7 +/- 5.2; B: 14.7 +/- 4.6; C: 12.8 +/- 4.8; D: 19.8 +/- 3.8; E: 18.0 +/- 3.1; F: 17.6 +/- 3.5. The application of 10% pyruvic acid containing 10% glycine, and 10% pyruvic acid followed by 10% glycine, resulted in a significant increase in SBS to dentin. The SBS to enamel treated with the three procedures were not significantly different.

Acid Etching, Dental↗
PubMed1991

A comparative study of the lead and cadmium content of surface enamel of Belgian and Kenyan children.

Acid etch surface enamel microbiopsies were performed on teeth from 378 children aged 6-12 years; 318 of the children lived in Belgium, an industrialized country, and 60 lived in a rural part of Kenya. In addition to lead and cadmium, calcium and phosphorus were also quantitatively determined in the etch solutions. Calcium was chosen as an internal reference for the expression of the lead and cadmium concentrations and for the assessment of the etch depth. The mean lead level in surface enamel of the Belgian children was approximately eight times higher than that of the Kenyan children. The cadmium levels were not significantly higher. An appropriate regression model taking into account differences in etch depth showed that a significant decrease of lead and cadmium with etch depth occurred and that a significant correlation between lead and cadmium in surface enamel existed for the Belgian cohort. Moreover, the same mean calcium/phosphorus ratios were obtained for the Belgian and Kenyan surface enamel samples, and were found not to play a significant role in the calibration of the lead and cadmium levels.

Belgium↗
PubMed1991

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.

Composite Resins↗
PubMed1991

Model for assessment of lead content in human surface enamel.

Acid etch surface enamel microbiopsies were taken in vitro and in vivo and analyzed for lead using electrothermal atomic absorption spectrometry. The in vitro samples were obtained from subjects resident in an urbanized region in Belgium or from a region close to a nonferrometal industrial plant. The smaller set of in vivo samples were all from subjects resident in an urbanized region. Using a regression tree approach it was possible to identify in a stepwise manner factors that contributed to the variation of lead in the samples. For the in vitro as well as in vivo samples, the etch depth, tooth type, and age of the subjects were identified as significant factors but sex and dental arch quadrant were not. The residual lead levels obtained after regression with the significant factors were better distributed with much lesser variance. Moreover, a significant higher lead concentration could be demonstrated in the in vitro samples from the region close to the nonferrometal industrial plant.

Dental Enamel↗
PubMed1991

Relation between lead in surface tooth enamel, blood, and saliva from children residing in the vicinity of a non-ferrous metal plant in Belgium.

Two groups of schoolchildren between seven and 12 years old residing in the vicinity of a non-ferrous industrial plant and exposed to lead (Pb) at a concentration that could cause health problems, were monitored. Concentrations of Pb in blood (blood-Pb), which were determined at regular six monthly intervals, were related to the Pb concentrations in surface tooth enamel (enamel-Pb). Acid etch biopsy samples of surface enamel were taken at the end of the five year study period in the first group (A) and after two years in the second group (B). Salivary Pb (saliva-Pb) concentrations were determined for the first study group on the same day that the enamel biopsies were performed. Calibration of the data was necessary--that is, blood-Pb concentration with respect to age and sex and enamel-Pb concentration with respect to etch depth and age. The blood-Pb concentrations declined with time. Surface enamel Pb concentrations correlated with blood-Pb concentration for the period starting with the pre-eruptive development of the incisors, related to blood-Pb concentration for a long time, and corresponded partly to the exposure at the time of pre-eruptive development and/or eruption. Through the correlation with enamel-Pb concentration, the seasonal behaviour of blood-Pb concentration became apparent. Saliva-Pb concentrations related to blood-Pb concentrations only in the short term.

Biopsy↗
PubMed1991

In vivo use of a dual acid etch biopsy for the evaluation of lead profiles in human surface enamel.

Two successive acid etch biopsies were performed on the permanent maxillary right central incisors of two age-groups of children resident in an urban area in Belgium. Lead was determined in the biopsy solutions and the concentrations were related to etch depths which were calculated from the calcium and phosphorus concentrations in the biopsy solutions. The mean lead concentration of the first enamel biopsy layer was five times higher than in the second biopsy layer. A strong relation was observed between the two biopsies. It was shown that calibration of the lead values with respect to etch depths and Ca/P ratios was desirable and that a robust regression analysis approach was needed instead of classic least-squares regression analysis. However, the second biopsy provided more reliable lead estimates. In this study no increase in lead concentration in surface enamel could be demonstrated with age. Therefore, it was concluded that for these children the presence of lead in surface enamel had to be attributed primarily to preeruptive uptake.

Acid Etching, Dental↗
PubMed1991

Standardizing laboratory adhesion tests.

Laboratory adhesion tests are performed as screening tests prior to the clinical evaluation of dentin bonding restorative systems. These tests include the determination of the bond strength to dentin and the evaluation of microleakage and marginal gap dimensions at the tooth-restoration interface. No standardized adhesion tests are available as the methodologies vary tremendously from one laboratory to another. The variable factors are reviewed in this manuscript and laboratory studies to standardize these procedures are proposed.

Adhesiveness↗
PubMed1990

Effect of dentin surface roughness on shear bond strength.

The aim of this investigation was to evaluate the effect of dentin surface roughness on the shear bond strength of a dentin bonding agent. Seventy-five dentin samples were divided into five surface preparation groups: (1) 60-grit SiC; (2) 320-grit SiC; (3) 600-grit SiC; (4) 600-grit SiC followed by AI2O3, and (5) 320-grit SiC followed by a #245 carbide bur. The prepared dentin was treated with a dentin primer, and one coat of dentin bonding agent was applied and light-cured for 30 s. Each dentin specimen was mounted in a device with a split Teflon mold (I.D. = 3.5 mm, depth = 5.0 mm). Three increments of a restorative composite were placed, compressed firmly, and light-cured for 30 s in the mold. After 24 h of storage, the bonds were stressed to failure in a mechanical testing machine at a cross-head speed of 0.5 mm/min. Weibull analysis was used to obtain a shape factor and characteristic level for each group. The results showed that, with the possible exception of the 600-grit SiC and AI2O3 group, the grit size used for preparation of dentin specimens for shear bond strength testing in this study did not significantly affect bond strength.

Dental Bonding↗
PubMed1990

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.

Acid Etching, Dental↗
PubMed1990

Effects of calcium hydroxide paste as an intracanal medicament on apical seal.

Seventy-six extracted human permanent canines and premolars with single canals were used in this study. The crowns were removed, the canals were instrumented, and the roots were randomly divided into four groups of 18 each. Three groups were medicated with Ca(OH)2 USP, Calasept, and Vitapex, respectively, while the control group was not medicated. The roots were incubated in 100% relative humidity at 37 degrees C for 1 wk, after which the medicaments were removed and the canals were enlarged to the next file size. One tooth in each group was examined in the scanning electron microscope while the remaining roots were filled with gutta-percha using a lateral condensation technique. The roots were placed in 2% methylene blue solution for 2 wk and both linear and volumetric dye penetration evaluated. A highly significant correlation between linear and volumetric leakage was observed. The leakage among the experimental groups was not significantly different, but was significantly less than in the control group.

Bicuspid↗
PubMed1990

Four-year in vivo evaluation of the composite/bonding resin-tooth interface.

The objective of this study was to evaluate the color match, marginal discoloration, recurrent caries, anatomic form, and marginal adaptation of 41 paired Class III and Class V preparations restored with a conventional chemically cured resin composite with and without a low-viscosity bonding resin (LVBR). In addition, the wear of the restorations was evaluated from scanning electron micrographs of epoxy replicas of the restorations. The subjects were re-called 48 months after placement of the restorations. The marginal discoloration and wear of the composite restorations placed without a LVBR were significantly greater than in restorations placed with a LVBR. The results of this clinical study suggest that a LVBR should be applied prior to the placement of a conventional chemical-activated resin composite.

Color↗
PubMed1990

Shear bond strength of ceramic orthodontic brackets to enamel.

The recent introduction of ceramic orthodontic brackets has generated interest among orthodontists. The aim of this investigation was to evaluate the in vitro shear bond strengths to enamel of four ceramic orthodontic brackets and one stainless steel bracket in trials with two separate acid-etching times for enamel. Eighty extracted human central incisors were prepared for bonding to Starfire, Allure, Transcend, Quasar, and stainless steel (in the control group) orthodontic bracket systems. Enamel etching times of 15 seconds and 60 seconds were used. There was a total of 10 groups. After acid etching, one coat of low-viscosity bonding agent was applied and the brackets were bonded to etched enamel with Concise orthodontic bonding resin. The bonded test specimens were stored in distilled water at 37 degrees C for 14 days, after which they were thermocycled for 500 cycles (5 degrees C to 60 degrees C). The bonds were stressed to failure in an Instron machine at a crosshead speed of 0.02 inch per minute. The shear bond strengths were calculated and Weibull analysis was used to obtain a shape factor (the slope of the straight line and a measure of predictability) and the characteristic level (the 63.2% bond strength value of median rank on the strength line) for each group. Predictability and high bond strength, along with other factors, are important in the clinical selection of a bracket system. When either predictability or bond strength was considered independently, several bracket systems, coupled with a particular etch time, had either high predictability or high bond strength. The highest predictability and the highest bond strength were both found with the Allure bracket system.

Acid Etching, Dental↗