Biomedical subjects

S R Grobler

Publications and source records attributed to S R Grobler.

At least 19 recordsLinked to original sources

PubMed2005

Effect of saliva contamination on microleakage of a bonding system.

UNLABELLED: Saliva contamination is a major clinical problem during restorative dental treatment. Restorative systems must possess sufficient marginal sealing ability to avoid microleakage. PURPOSE: The purpose of this study was to investigate the effect of saliva contamination on the microleakage of cavities restored with Prime & Bond NT and Dyract-AP. METHOD: Cavities were prepared with occlusal margins in enamel and gingival margins in dentine on the buccal surfaces of extracted human permanent premolar teeth. The cavities were etched with phosphoric acid or a non rinse conditioner (NRC). Preparations were distributed randomly into 4 treatment groups (N = 18) consisting of two respective etching methods (phosphoric acid/NRC), each with and without saliva contamination. After the restorative process the samples were thermocycled in dye, sectioned, and scored for microleakage. RESULTS: Contamination with saliva had no significant effect on microleakage on the enamel or dentine sides where phosphoric acid was used as conditioner. Where NRC was used, significantly more microleakage was observed at the enamel sides, but significantly less at the dentine sides.

Analysis of Variance↗

PubMed2005

Cytotoxicity of a dentine bonding agent on four different cell-lines.

UNLABELLED: The aim of this study was to compare the cytotoxicity of a recently available dentine bonding agent on four different cell-lines (three human dental pulp fibroblast cell-lines and one mouse 3T3 fibroblast cell-line). METHODOLOGY: Three human dental pulp cell-lines from 3 different donors and one established 3T3 mouse cell-line were grown and sub-cultured. Cell viability following exposure to Scothbond was then compared to a similar number of controls using the MTT assay. RESULTS: Scotchbond 1 was cytotoxic to all four cell-lines. 3T3 cells showed a survival rate of about 60% as compared to two of the human dental pulp cells which showed a significantly lower survival rate (p<0.05, Kruskal-Wallis Multiple-Comparison Test). CONCLUSION: These findings indicated that is cytotoxic to both human pulp and 3T3 cell-lines. In general, the human pulp cell-lines showed higher sensitivity than the 3T3 cell-lines. CLINICAL SIGNIFICANCE: Scotchbond 1 cannot be recommended for direct pulp capping techniques and care should be taken when using this dentine bonding agent in cavities where the remaining dentine layer is minimal.

3T3 Cells↗

PubMed2005

Patterns of tooth surface loss among winemakers.

There are a few documented case studies on the adverse effect of wine on both dental hard and soft tissues. Professional wine tasting could present some degree of increased risk to dental erosion. Alcoholic beverages with a low pH may cause erosion, particularly if the attack is of long duration, and repeated over time. The purpose of this study was to compare the prevalence and severity of tooth surface loss between winemakers (exposed) and their spouses (non-exposed). Utilising a cross-sectional, comparative study design, a clinical examination was conducted to assess caries status; the presence and severity of tooth surface loss; staining (presence or absence); fluorosis and prosthetic status. The salivary flow rate, buffering capacity and pH were also measured. Thirty-six persons, twenty-one winemakers and fifteen of their spouses participated in the study. It was possible to show that there was a difference in terms of the prevalence and severity of tooth surface loss between the teeth of winemakers and those who are not winemakers. The occurrence of tooth surface loss amongst winemakers was highly likely due to frequent exposure of their teeth to wine. Frequent exposure of the teeth to wine, as occurs among wine tasters, is deleterious to enamel, and constitutes an occupational hazard. Erosion is an occupational risk for wine tasters.

Adult↗

PubMed2004

Volumetric polymerisation shrinkage of different dental restorative materials.

STATEMENT OF PROBLEM: Polymerisation shrinkage is a critical limitation of dental resins and may contribute to micro leakage. PURPOSE: The purpose of this study is to record and compare volumetric changes of various dental composites and compomers, exposed for 40 seconds to a commercial halogen light source. MATERIAL AND METHODS: Eleven light-polymerised composites and compomers were evaluated using a dilatometer that recorded the polymerisation shrinkage every 0.5 second. The mercury column pressure was measured electronically with a pressure-sensitive transducer, and the data recorded and stored in a computer. The computer also recorded the temperature, controlled the light-source and displayed the data in graphic format. Every material was tested ten times. The data were analysed by means of an ANOVA (P < 0.05). RESULTS: A high rate of shrinkage occurred for all materials in the first ten seconds of polymerisation. Surefil showed the lowest rate while TPH displayed the highest. Of the higher filled materials, Surefil (0.96%) showed the least shrinkage, followed by Z250 (0.99%), Dyract AP (1.18%), Herculite (1.27%), Compoglass (1.32%), Amelogen (1.34%) and TPH-Spectrum (1.6%). Overall, the flowable materials exhibited significantly more shrinkage (P < 0.05). For this group Compoglass Flow (2.3%) showed the least shrinkage followed by Filtec Flow (2.31%). Permaflo (3.6%) exhibited the most shrinkage followed by Dyract Flow (3%). CONCLUSION: Within the limitations of this study, it is concluded that significant differences exist among the polymerisation shrinkage of the most resins tested. An increase in the filler content of a material significantly lessens the polymerisation shrinkage while an increase in the monomer concentration causes significantly more polymerisation shrinkage. CLINICAL SIGNIFICANCE: The more flowable a composite material becomes, the more the restoration will shrink. Clinicians should take this into account when they decide on cavity design and materials to use.

Analysis of Variance↗

PubMed2004

Cytotoxicity of two concentrations of a dentine bonding agent on mouse 3T3 and human pulp fibroblast cell-lines.

The objective of this study was to investigate the cytotoxicity and effect of concentration of a recent dentine bonding agent on a mouse fibroblast cell-line (3T3) and four different human pulp fibroblast cell-lines. A mouse fibroblast 3T3 cell-line and 4 different human pulp fibroblast cell lines were used. The cells were grown and subcultured using standard conditions. For the testing of the cytotoxicity of the bonding agent (Prime & Bond NT) it was extracted with DMEM medium and the different cell-lines were exposed to the extraction. The MTT assay was used to establish the number of viable cells. For all 5 pairs (control vs test sample) of cell-lines for 4 microl bonding agent, the mouse and only two of the four human cell-lines showed a statistical significant difference (p < 0.05; Mann-Whitney) due to the cytotoxicity of the bonding agent. However, all 5 pairs showed significant differences (p < 0.05) at the 8 microl concentration level. To investigate the relative effect of concentration (4 microl compared to 8 microl) of a chemical agent (we used a bonding agent, Prime & Bond NT) on the cytotoxicity of these 5 cell-lines, the Kruskal-Wallis Multiple-Comparison test was used on the standardised medians. Statistically significant differences (p < 0.05) were found for various cell-lines between both concentration levels. In general, the tested bonding agent, at a higher concentration level, has an increased cytotoxic effect on all 5 cell-lines. About 69% (median) of 3T3 cells stayed viable with 4 microl (0.94cm2/ml) bonding agent and 61% when 8 microl was used. For the pulp cells the percentages were between 91% and 72% for 4 microl and between 77% and 24% for 8 microl. These findings indicated that the bonding agent Prime and Bond NT was cytotoxic and that different human pulp fibroblast cell-lines should be used in the cytotoxic testing of dental materials and secondly, if only one concentration is to be used it should be in the higher range of that suggested by the ANSI/ADA document (2000, Revision) for recommended standard practices for biological evaluation of dental materials.

3T3 Cells↗

PubMed2003

In vitro human dental enamel erosion by three different wine samples.

The aim of this study was to investigate the erosive effect of different wine samples on the enamel of human permanent teeth. Twenty-one extracted, sound, permanent human incisor teeth were imbedded in epoxy resin and seven immersed in each of the three different wine samples for 0, 2, 5, 15, 30, 45 and 60 minute periods. The Knoop hardness for each tooth at each of the immersed periods was determined as a measure of the degree of enamel erosion (demineralisation). The main finding was that all three wines eroded enamel (softer enamel) which should mainly be due to their very low pH values (3.2, 3.7, 3.8) and high total acid content. From the Wilcoxon non-parametric tests it was clear that wine 2 had the severest influence on the hardness of the teeth, and the wines differed significantly (p < 1%) from 30 minutes onwards. These tests showed that wine 1 differed significantly from wine 2 from 30 minutes onwards and so did wine 3, but wines 1 and 3 did not differ at all (p > 5%). It is concluded that all three wine samples were erosive to enamel and it is difficult to predict the relative erosion rate of different kinds of wines according to their chemical compositions, as this process is most probably governed and affected by a large number of a combination of factors. The only reliable way to know the exact degree of erosion of a specific wine is by means of a laboratory study. Possible ways to decrease the damaging effect of erosion caused by wine are provided.

Analysis of Variance↗

PubMed2002

Dentine bonding agents--a review of adhesion to dentine.

Although constant innovation has improved the performance of dentine adhesives, the true mechanism of resin adhesion to dentine is still not clear and the optimal dentinal surface pretreatment has yet to be determined for adhesive integrity of resin to dentine. The integrity of the collagen fibrils left exposed upon acid etching seem to play a major role in the mechanism of adhesion and intermingling of the adhesive monomers with the filigree of collagen fibers or hybrid layer should be considered the paramount dentine bonding mechanism. Definite trends are emerging but more research is necessary before general conclusions can be made about the functions of different bonding agents. The all-in-one self-etching/self-primer bottle systems are relatively new to the market and need more research before they can be advocated as the agent of choice.

Acid Etching, Dental↗

PubMed2001

[Polymerization shrinkage by 4 different types of dental materials].

Forces developing during polymerisation of dental resins cause tension in the material to increase, with possible subsequent distortion of the bond. This study was undertaken to determine and compare polymerisation shrinkage in four different light-cured dental resins. A modified dilatometer was used to determine volumetric changes during polymerisation in 60 seconds of Z250 and Filtec flow from 3 M, and DyractAP and Dyract from Dentsply. Statistical analysis revealed that Dyract Flow shrinks significantly more (P < 0.05) during polymerisation in the first, as well as the last 10 seconds when compared with the other three materials and Z250 significantly less. An increase in the amount of fillers in the composition of the material leads to a decrease in polymerisation shrinkage, while an increase in the monomer concentration gives rise to more shrinkage. Stress, that builds up during the polymerisation process, is reduced by the elasticity of the material. The shrinkage of the flowables is therefore counteracted by their reduced rigidity.

Aluminum Silicates↗

PubMed2001

Drinking water in South Africa: implications for fluoride supplementation.

During the extremely heavy rainfall period in the first half of 2000 in certain summer rainfall regions of South Africa a similar investigation as in 1983-1984/1985 was done but on a smaller scale, and compared to the previous results. A greater reduction (P < 0.05) of the fluoride levels in the drinking water than previously recorded has recently been demonstrated, thus strongly accentuating the effect of heavy rains. Presently, for fluoride prescription we recommend that the prescriber should decide whether it is a dry or wet period for his area and then read the fluoride content for that area, from the higher or lower end of the water fluoride content range from the tables published in 1988, 1991 or 1994. When in doubt the higher fluoride level should be used as a measure of safety against overprescribing. If only one value exists it should be used until further notification. An extended study is in process to set a single table for South Africa.

Adolescent↗

PubMed2001

[Microleakage of four different amalgam binding systems].

This-study was undertaken to evaluate and compare microleakage in class V cavities in human teeth which were lined with Amalgambond Plus with HPA (Parkell, USA), Optibond Solo (Kerr, U.S.A.), Fuji Plus (GC Corporation, Japan) and Prime & Bond 2.1 (Dentsply, Switzerland), and then restored with Logic amalgam (SDI Australia). The restored teeth were thermocycled in basic fuchsin dye, sectioned, and evaluated for dye penetration. The interdiffusion zones were viewed in a confocal laser scanning microscope (CLSM). The results showed that no bonding system could totally eliminate microleakage. Statistical analysis revealed significant differences between Amalgambond Plus with HPA and Prime & Bond 2.1, Fuji Plus as well as Optibond Solo, for both the enamel and dentine sides. No significant differences were found between Prime & Bond 2.1, Fuji Plus and Optibond Solo, for both the enamel and dentine sides. Amalgambond Plus showed significantly more leakage at dentine sides while Prime & Bond 2.1 showed significantly more leakage at enamel sides. The CLSM revealed hybrid layers of different thicknesses, resin penetration into tubules, as well as resin incorporation within the spherical particles of the amalgam. Optibond Solo, Fuji Plus and Prime & Bond 2.1 can serve to improve the marginal seal of amalgam restorations.

Acetone↗

PubMed2000

The relation between lead concentrations in human dental tissues and in blood.

The purpose of this study was: (1) to measure the lead concentrations in various parts of the teeth (enamel, dentine and circumpulpal dentine) and in blood from individuals of a remote rural South African community; (2) to investigate any correlation between the lead concentrations in these various dental tissues and in blood; and (3) to estimate blood lead from the tooth lead concentrations reported in other studies. Primary teeth and blood were collected from 48 children and analysed by graphite-furnace atomic absorptiometry. The following median concentrations (expressed in mg/kg) of lead were found: blood, 0.025; enamel, 0.25; dentine, 2.04; circumpulpal dentine, 6.71. The tooth lead concentrations were similar to those from other studies from remote rural areas but comparisons of blood lead were not possible in the absence of previous data. Blood lead in other studies could be calculated from the ratios here reported.

Child↗

PubMed2000

In vitro evaluation of two adhesive systems used with compomer filling materials.

AIM: To evaluate and compare the in-vitro shear bond strength, microleakage and dentine-restorative interface of a self-etching/self-priming dentine bonding agent with a three-component dentine-bonding agent. METHOD: For shear bond strength (SBS) testing 30 non-carious human molars were used of which 15 were tested with Non-Rinse Conditioner (NRC)/Prime&Bond NT (PBNT) and Dyract AP and 15 were tested with Scotchbond Multi-Purpose Plus (SBMP) and F2000. For the microleakage evaluation cavity preparations were made on the facial surfaces of 30 non-carious human premolars of which 15 were restored with NRC and PBNT with Dyract AP and 15 were restored with SBMP and F2000. The dentine-restorative interface was examined through a confocal scanning laser microscope (CSLM). RESULTS: The mean SBS of PBNT and SBMP were 12.8 and 18.1 MPa, respectively. The microleakage scores showed NRC/PBNT leaked on the dentine side in 13 of the 15 specimens examined. On the enamel side two of the 15 specimens showed microleakage. With SBMP no microleakage was observed on either enamel or dentine sides. The CSLM images show clear resin tag and hybrid layer formation for both the materials examined although SBMP showed better and deeper penetration into the dentine with longer resin tags. SBMP showed resin tags measuring about 150 mm while the hybrid layer measured about 5 mm. The length of the resin tags as well as the thickness of the hybrid layer for PBNT were 20 mm Pounds and 2 mm Pounds, respectively. CONCLUSIONS: The acid-etch technique of SBMP produced higher bond strength and no microleakage when compared with the self-etching/self-priming 'non-rinse technique' of NRC with PBNT. Thus it can only be speculated that SBMP should be the superior in the clinical situation.

Compomers↗

PubMed1999

In vitro, relative microleakage of five restorative systems.

The purpose of this study was to determine the relative microleakage of five restorative systems when bonded to dentine/cementum. For the microleakage determination Class V cavity preparations were prepared on the facial surfaces of 65 teeth (10-15 for each material) below the cemento-enamel junction and restored. The root apices were sealed, the teeth coated with nail varnish except for 1 mm surrounding the restorations and the specimens were thermocycled (x500) in 2 per cent methylene blue solution. Root sections including the restorations were dissolved in acid and the concentrations of the dye determined spectrophotometrically. The sequence of the microleakage values were: Dyract < OptiBond < AeliteBond < All-Bond 2 < ScotchBond. It is concluded that Dyract had the lowest microleakage at dentine/cementum interface, which may increase the longevity of the restorative in the clinical situation, with no, or less secondary caries.

Acid Etching, Dental↗

PubMed1999

The effects of extreme temperatures on composite, compomer and ionomer restorations.

The composite resin, compomer and glass ionomer restorative materials used in modern dental practice are fire resistant and remain radiopaque. They shrink significantly and are likely to fall out of the cavities after being burnt, but they remain extremely important for identification purposes and it may be possible to identify the white filling materials used to restore teeth by their radiopacity and morphology. The radiographic density of these filling materials do not change significantly when exposed to heat and although they may be difficult to see with the naked eye, they will remain visible when radiographed. Furthermore, special care has to be taken when handling heated materials as their compressive strengths decrease significantly depending on temperature and time of exposure and damage is possible.

Analysis of Variance↗

PubMed1998

A comparison of fluoride release from various dental materials.

OBJECTIVE: The aim of this study was to determine, in vitro, the relative short- and long-term fluoride release from four resin-modified glass ionomers (Fuji II LC, Vitremer, Enforce & Advance), a polyacid-modified composite resin (Dyract compomer) and a bonding agent (OptiBond). METHODS: All the materials were prepared as outlined by the manufacturers. Circular discs of the materials mentioned were suspended in water for up to 300 days and the non-cumulative 24-h fluoride release was determined potentiometrically at chosen times. RESULTS: The amounts of fluoride released during the first day were Vitremer (1.46 micrograms mm-2), Advance (1.18 micrograms mm-2), Fuji (1.08 micrograms mm-2), Optibond (0.33 microgram mm-2), Dyract (0.31 microgram mm-2) and Enforce (0.15 microgram mm-2). After the second day the sequence changed slightly and remained approximately the same for the rest of the 300-day period. There was also an increase in the fluoride release during the 60-200-day period relative to the previous period. CONCLUSION: In general the most fluoride was released by Advance and not by Fuji II LC or Vitremer. For most materials, fluoride is still released after 300 days. Furthermore, even a thin layer of bonding agent released a relatively high amount of fluoride (volume-wise the most) at the beginning. It is deduced that even the release of relatively low amounts of fluoride may result in significant concentrations of fluoride in a microleakage gap.

Analysis of Variance↗

PubMed1998

Effects of honey consumption on enamel microhardness in normal versus xerostomic patients.

The aim was to investigate the effect of honey on the microhardness of enamel in normal and xerostomic patients. Normal subjects and patients who were xerostomic after neck irradiation, wearing prosthetic appliances with slabs of human enamel inserted, were asked to consume a single teaspoonful of pure honey, pH 3.9. Measurements of the saliva pH were taken before, during and after a 5 min exposure to the honey. The pH of the honey-saliva mixtures decreased significantly from about 6 to 4 in both groups, returning to the baseline pH after the mixture was swallowed. The initial microhardness of the surface of the enamel slabs decreased significantly after consumption of a teaspoonful of the honey in the subjects with a regular saliva flow, whereas in the irradiated dry-mouth patients, no enamel microhardness decrease occurred. The supposed solubility-reducing factor present in honey which, according to the literature remains active in the absence of saliva, but will be inactivated by salivary enzymes, gives some support to the hypothesis that honey is less cariogenic in dry-mouth subjects. The absence of adequate controls in the present study prevents the investigation of how specific this effect is to honey.

Adult↗

PubMed1998

A new microwave acid digestion bomb method for the determination of total fluorine.

A new microwave acid digestion method for total fluorine analysis was compared to the reliable reverse-extraction technique. The commercially available Parr bombs which are compatible with microwave heating were modified for this purpose. The Mann-Whitney statistical test did not show any significant differences (p > 0.05) in the determinations of total fluorine in various samples between the two above-mentioned methods. The microwave method also gave high fluorine recoveries (> 97%) when fluoride was added to different samples. The great advantage of the microwave acid digestion bomb method is that the digestion under pressure is so aggressive that only a few minutes is needed for complete digestion (also of covalently bonded fluorine), which reduces the time for fluorine analysis dramatically, while no loss of fluorine or contamination from extraneous sources could take place during the ashing procedure. The digestion solution was made up of 300 microliter of concentrated nitric acid plus 537 microliter of water. After digestion 675 microliter of approximately 8.5 M sodium hydroxide plus 643 microliter of citrate/TISAB buffer was added resulting in an alkaline solution (pH approximately 12) which was finally adjusted to a pH of approximately 5.3 for fluoride determination.

Acids↗

PubMed1996

Evidence of undue lead exposure in Cape Town before the advent of leaded petrol.

Lead concentrations were determined in the exhumed teeth of 28 people who lived in the Cape Town area before the combustion of leaded petrol (i.e. before 1922). The lead content of circumpulpal dentine was analysed by graphite-furnace atomic absorption spectrometry. The mean lead level in the dentine of primary teeth (N = 6) was 109 micrograms/g, while that in secondary teeth (N = 22) was 315 micrograms/g. The current lead levels in circumpulpal dentine of Cape Town residents are reported to be 74 micrograms/g and 16 micrograms/g for primary and secondary teeth respectively. It was found that lead pollution of the human body during the period 1812-1922 in the Cape Town area was substantially higher than at present. We conclude that the main reasons for this were the widespread use of lead piping and soldering of water tanks, which resulted in a higher incidence of lead poisoning than that attributable to leaded petrol.

Adolescent↗