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Biomedical subjects

S R Grobler

Publications and source records attributed to S R Grobler.

At least 37 records · Page 2Linked to original sources
PubMed1996

Shear bond strength, microleakage and antimicrobial properties of AElitebond.

PURPOSE: To evaluate the shear bond strength (SBS) and microleakage (ML) to dentin as well as the antimicrobial action against five strains of oral bacteria of AElitebond single primer restorative system. MATERIALS AND METHODS: Fifteen molars were tested to failure for each of the four time periods: 15 minutes, 24 hours, 7 days and 30 days, after final cure. The test specimens were prepared on the dentin surfaces of the extracted molars ground on 600 grit SiC paper. The bonded cylinders were removed from the assembly apparatus after cure, stored in physiological saline at 37 degrees C for the four different time periods and subjected to a shear bond load at 0.5 mm/minute until fractured. For the microleakage determination, Class V cavity preparations were done on the facial surfaces of the roots of 15 canines below the cemento-enamel junction and the specimens thermocycled (500x) between 8 degrees C and 15 degrees C in 2% methylene blue. The teeth were cut into 6 mm thick sections and the sections which included the restorations were separately dissolved in acid. The color intensities of the dissolved sections were measured at a wavelength of 590 nm against a standard curve which was constructed from the dye. The modified model cavity method of Meryon & Johnson (1989) was used to assess the antimicrobial properties of the restorative system. RESULTS: The mean SBS values (in MPa) were found to be 10.3, 9.8, 11.47 and 9.9 after 15 minutes, 24 hours, 7 days, and 30 days, respectively. There was no significant increase (P < 5%) in the SBS after 15 minutes. The ML of 0.76 micrograms dye/ restoration was relatively low in comparison to the SBS values. The restorative system significantly (P < 5%) inhibited the growth of Actinomyces naeslundii with 88%, Streptococcus mutans with 42%, Streptococcus sanguis with 39% and Streptococcus oralis with 9%. However, the growth of Veillonella parvula was stimulated with 49%.

Actinomyces↗
PubMed1996

Relative shear bond strength and microleakage of two dentine bonding agents.

We determined the relative shear bond strength (SBS) to dentine and cementum and the microleakage of All-Bond 2 universal dental adhesive and OptiBond multi-use filled adhesive. We found that for both systems the SBS increased significantly (p < 0.001) from 15 minutes to 24 hours and 7 days, but there was a slight significant (p < 0.001) weakening towards 30 days. At each time point the shear bond strength of All-Bond 2 and OptiBond were also compared and it was found that OptiBond had significantly higher values (p < 0.05) at all times except at 15 minutes. Optibond also had the lower value for the microleakage (p < 0.001). This study showed that OptiBond had significantly higher shear bond strengths to and lower microleakage in dentine which may increase the longevity of the material in the clinical situation.

Dental Leakage↗
PubMed1995

The resistance to deformation forces of endodontic posts manufactured from six different materials.

Twenty posts of 1.25 mm diameter and 10 of 1.0 mm diameter were cast in 4 different metals, namely, Argenco 4, Argenco 9, Wiron 99 and Rexillium V (5 each). These posts as well as pre-formed wrought stainless steel and titanium posts (5 each of the same diameter) were tested in an Instron machine to a deformation point of one millimetre. Of the cast posts, those of Rexillium proved to be the most rigid but could only withstand 68 per cent of the force that the wrought posts could resist. No statistically significant differences were found between the wrought posts of stainless steel and titanium and between gold and Argenco 9 in the 1.25 mm category and between stainless steel and titanium and Wiron 99, Argenco 9 and gold in the 1.0 mm category.

Chromium Alloys↗
PubMed1994

Alkali-soluble and insoluble fluoride in erupted and unerupted human enamel from a high fluoride area with a low fluorosis score.

The amounts of fluoroapatite and 'CaF2-like' fluoride (F) were determined in enamel of unerupted and erupted teeth that had been exposed in vivo to 1.8-2.6 parts/10(6) F in the drinking water and to brushing with F dentifrice at least once a day, and occasionally to a F mouth-rinse (0.022% F). Enamel was sampled by acid-etching and the F levels were measured with an adapted F ion-selective electrode. More F was built into the deeper enamel in the high-F area than in a similar low-F area. Unerupted enamel did not etch significantly (p > 0.05) deeper than erupted enamel. No significant differences (p > 0.05) were found in the F concentrations amongst the following: alkali-washed erupted, unwashed erupted, alkali-washed unerupted and unwashed unerupted at the outer most enamel (approx. 6 microns). However the erupted enamel (alkali-washed or not) showed higher F levels than unerupted enamel (alkali-washed or not) between approx. 6 microns and greater than 100 microns. The increase of F for this high-F area was about 100% in the deeper enamel while for a low-F area it was approx. 78% in the most outer enamel with no increase after a depth of about 20 microns. In contrast to a similar low-F area (water F < 0.10 parts/10(6)), no significant 'CaF2-like' F could be detected in erupted or unerupted enamel for the high-F area.

Dental Enamel↗
PubMed1994

The effect of honey on human tooth enamel in vitro observed by electron microscopy and microhardness measurements.

Various fruit juices with relatively low pH are known to have erosive effects on human tooth enamel in a reasonably short time. Honey, also with a relatively low pH, could do the same, but scanning electron microscopy showed no erosion of enamel by honey over a period of 30 min, neither did Knoop microhardness tests show any deterioration of enamel structure. The absence of any effect could be only partially attributed to the calcium, phosphorus and fluoride levels in honey.

Dental Enamel↗
PubMed1994

The fluoride concentration in the drinking water of towns in the Transvaal, Orange Free State and Natal.

In previous studies the water fluoride content of the larger cities in South Africa, and smaller towns in the Cape Province were recorded. This project was extended to include smaller towns (500 or more inhabitants) in the Transvaal, Orange Free State and Natal. Drinking water was collected in polypropylene containers and the fluoride content determined potentiometrically. The information obtained made it possible to compile a table setting out the fluoride content of the drinking water in these smaller towns. The study confirms a previous observation that water from boreholes has the highest (p < 0.05), and fountains the lowest fluoride content.

Fluorides↗
PubMed1994

Antibacterial action of honey on oral streptococci.

The antibacterial properties of honey against medically important bacteria have been well documented but this information is not available for the oral bacteria and specifically for the oral streptococci. We determined the minimal inhibitory concentration (MIC) of honey for oral streptococci. Honey had a MIC of 25 per cent (vol/vol) for the bacteria tested with the exception of Streptococcus anginosus and Streptococcus oralis which were inhibited by 17 per cent (vol/vol) and 12 per cent (vol/vol) honey respectively. The hypertonic sugar control had a MIC of 25 per cent (vol/vol) for all the bacteria tested. Although the results of this study indicate that there could be other antibacterial agents present in the honey, it may be assumed that the hypertonic sugar concentration played an important role in this activity.

Anti-Bacterial Agents↗
PubMed1994

The relationship between plaque index scores, fluoride content of plaque, plaque pH, dental caries experience and fluoride concentration in drinking water in a group of primary school children.

The aim of this study was to determine the relationship between fluoride in drinking water, plaque and dental caries experience in a sample of primary school children from a fruit farming (mainly grapes) area. The children who qualified for the study (n = 177) were placed into three groups according to the concentration of fluoride in their drinking water namely, less than 0.4 ppm (group A), between 0.4 and 1.6 ppm (group B) and more than 1.6 ppm (group C). Most children (78.5%) did not have a toothbrush. Plaque scores were significantly lower in groups B and C. A statistically significant inverse correlation was observed between plaque scores and fluoride content of plaque (p < 0.05). Plaque pH did not differ significantly between the groups. The concentration of fluoride in plaque was high and increased with increasing concentration of fluoride in the drinking water. Dental caries experience was relatively low in primary (dmft = 2.15; 2.07; 1.79) (p > 0.05) and permanent teeth (DMFT = 1.22; 1.43; 1.38) (p > 0.05). Paradoxically, there was also no significant inverse correlation between dental caries experience and fluoride concentration in drinking water. However, the significant inverse correlation between fluoride content of plaque and caries experience supports the contention that fluoride can be accumulated in plaque and act as a reservoir which provides prolonged elevated levels of fluoride to produce a cariostatic effect. It is postulated that the high fluoride levels in the plaque reservoir is responsible for the relatively low caries experience, the significant differences in caries experience between the groups and the poor correlation between dental caries experience and fluoride concentration in drinking water.

Child↗
PubMed1993

Effect of the reduction of petrol lead on the blood lead levels of South Africans.

Lead has no metabolic role in the human body and its presence is associated with various toxic effects. Several countries have responded to this health hazard reducing petrol lead additives or entirely eliminating them. Studies have shown that there has been a resultant fall in blood lead levels of the particular populations. This study reports on the progressive decline in blood lead levels of South Africans during the period 1984-1990 which coincided with a stepwise reduction in petrol lead additives from 0.8 g/l to 0.4 g/l. During this period the blood lead levels of Cape Town city dwellers decreased significantly (P < 0.01) from 9.7 micrograms/dl to 7.2 micrograms/dl. This blood lead level compares favourably with that of other more industrialized countries with less lead in their petrol. Therefore, the authors question the need for further reduction of petrol lead content bearing in mind the considerable financial burden that such a step will entail and the dubious health advantage that may be gained.

Adult↗
PubMed1991

The effect of airborne lead on lead levels of blood, incisors and alveolar bone of rats.

Groups of 20 inbred rats were exposed to: (1) "clean air" (0.05 micrograms Pb/m3) for 70 days; (2) 77 micrograms Pb/m3 for 70 days; (3) 249 micrograms Pb/m3 for 28 days; and (4) 1546 micrograms Pb/m3 for 50 days. Half the rats in each group were then killed and the other half kept in "clean air" until the blood lead of groups 1-3 had returned to normal. That half of the incisors which had been completely renewed during the experimental period, as well as the alveolar bone of each rat, were analysed for lead by atomic absorption spectrophotometry. In the rats killed immediately after exposure, the lead levels by atomic absorption alveolar bone showed significant differences (p less than 0.05) among all four groups, except between groups 2 and 3, indicating the importance of the combined effect of airborne lead concentration and length of exposure. For blood, significant differences (p less than 0.05) were found among all groups. For the post-exposure rats, the incisors and blood showed no significant differences (p greater than 0.05) among groups 1, 2, and 3. For alveolar bone, significant differences were not found (p greater than 0.05) between groups 2 and 3. It can be concluded that during lead exposure the alveolar bone transformation was the highest and that of incisor tissue just lower, and that blood lead became supplemented through the process of remobilization from alveolar bone, as reported for other bones.

Aerosols↗
PubMed1991

[Fluoride concentration in drinking water in small villages in the Cape province].

The purpose of the study was to update existing tables on the fluoride content of drinking water and thereby help curb its fluoride overdose from the use of fluoride containing tablets. The fluoride concentration in the drinking water of 57 villages in the Cape Province was determined by a combination fluoride ion selective electrode. This investigation showed that the number of available water sources decreased as follows: boreholes greater than dams greater than fountains = canals. Furthermore, boreholes contained more fluoride in the drinking water than fountains, dams or canals (p less than 0.10). Five out of 41 boreholes have less than or equal to 0.10 parts per million (ppm) fluoride in the drinking water, while 17 out of 26 dams, 4 out of 13 rivers and 3 out of 5 fountains and canals contained less than or equal to 0.10 ppm fluoride.

Fluoridation↗
PubMed1990

Alkali-soluble and insoluble fluoride in erupted and unerupted sound enamel of human third molars in vivo.

The amounts of firmly and loosely bound fluoride were determined in sound enamel of unerupted and erupted teeth which had been exposed in vivo for 1-16 yr to brushing at least once a day, and occasionally to mouth rinsing and the application of sealers. Enamel was sampled by an acid-etch procedure, and the fluoride levels were measured with an adapted fluoride ion-selective electrode. Unerupted enamel was etched significantly (p less than 0.05) deeper than erupted enamel up to a depth of at least 8 microns. Significant differences (p less than 0.05) were found between the mean enamel fluoride concentrations of unwashed and alkali-washed, erupted teeth up to a depth of at least 3 microns and also between unwashed or washed, erupted versus unwashed or washed, unerupted teeth. At a depth of 3 microns, the fluoride treatments of enamel had increased the total amount of fluoride by approx. 78% of which approx. 53% was loosely bound fluoride (like CaF2) and 47% firmly bound (like fluorapatite). No increase in sound enamel fluoride as a result of topical treatments over a period of up to 16 yr could be found at a level deeper than 20 microns.

Acid Etching, Dental↗
PubMed1990

In vitro demineralization of enamel by orange juice, apple juice, Pepsi Cola and Diet Pepsi Cola.

Enamel demineralization was studied over periods related to normal use of an orange juice, an apple juice, Pepsi Cola and Diet Pepsi Cola. Rectangular blocks of intact human enamel (3 mm x 3 mm) were cut from teeth, coated with nail varnish except for the enamel surface and exposed to the drinks for 2, 4, 5, 6 or 40 minutes. The amount of calcium released from the enamel into solution was determined with the use of an atomic absorption spectrophotometer. The results showed the following degree of enamel demineralization: Pepsi Cola = orange juice greater than apple juice greater than Diet Pepsi Cola. The results suggest that diet colas are less demineralizing than other acid drinks, and complementary plaque studies indicate that they are also less cariogenic. The study emphasized the importance of acid-type, buffer capacity, pH and the presence of other components on the degree of enamel demineralization.

Beverages↗
PubMed1988

Variations in the fluoride levels of drinking water in South Africa. Implications for fluoride supplementation.

The range of fluoride levels in the drinking-water of cities and villages in South Africa was determined during the transition from a very dry (1983) to a wet (1984/85) period. The combination fluoride ion selective electrode was employed for the determination of the fluoride concentration. It was found that fluoride levels in drinking-water changed for 93% of the cities and villages studied during the period 1983-1985. Furthermore, it became clear that when the water volume of the supplying source increased, the fluoride level decreased significantly (P less than 0.01). Boreholes showed significantly higher fluoride levels (P less than 0.01) than rivers or dams. The impact of the variation in drinking-water fluoride concentrations on supplementary fluoride dosage is discussed and recommendations made.

Fluoridation↗
PubMed1988

The relative distribution of fluoride in erupted and unerupted enamel of human third molars from a low fluoride area.

Acid-etch biopsies were taken from the centre of the mesio-lingual, disto-lingual, disto-buccal and mesio-buccal cusps of non-carious erupted (n = 16, aged 18-28 years) and unerupted (n = 21, aged 18-28 years) teeth. The donor subjects had lived continuously in a low fluoride area (F water less than 0.1 parts/10(6] from birth, and had had no systemic fluoride supplementation. Tooth brushing, mouth rinsing and the application of sealers were the only fluoride-containing anti-caries programmes practised singly or in combination. Six successive acid-etchings were taken from each of the four cusps, and the fluoride levels in the etching solution were measured with an adapted, fluoride ion-selective electrode. Up to a depth of about 10 microns, unerupted enamel was etched significantly (p less than 0.05) more deeply than erupted enamel, which might be explained by changes in its composition. Up to a depth of approximately 10 microns, significantly more fluoride was found in erupted than in unerupted enamel. This difference may mainly be attributed to the effect of fluoride from the oral environment on erupted enamel. Fluoride concentrations, up to a depth of approximately 3 microns, were (p = 0.07) higher in the buccal cusps than in the lingual cusps of erupted molars, but not at the other etch depths. There were no significant differences (p greater than 0.10) between the buccal and lingual cusps of the unerupted molars at any depth. No significant correlations between enamel fluoride concentrations and age could be found either for erupted or unerupted third molars.

Adult↗
PubMed1988

A laboratory evaluation of the tensile bond strength of some orthodontic bonding resins to enamel.

In this in vitro study, the tensile bond strengths of three two-paste and four no-mix orthodontic bonding resins applied to etched enamel were determined. One hundred ninety-six extracted human teeth were used to prepare 14 bonded test specimens for each of the seven resin systems evaluated. The tensile bond strengths were expressed in MN.m-2 and the data were analyzed by a one-way analysis of variance at the 5% level of significance and with a procedure of multiple comparisons with the best resin. The tensile bond strengths were not significantly different (P = 0.5065).

Acid Etching, Dental↗
PubMed1988

The relationship of the periodontal status to fluoride levels of alveolar bone and tooth roots.

The periodontal status and fluoride levels of alveolar bone and tooth roots were compared for subjects from a high (2.5 ppm F) and a low (less than 0.05 ppm F) fluoride area. The plaque index, gingival index, probing depth and loss of attachment were measured to determine the periodontal status. The fluoride levels were determined by the use of the fluoride ion-selective electrode. Both communities had high plaque and gingival indices. However, the mean pocket probing depths in both communities were less than 2.5 mm. No statistically significant differences could be found in the periodontal status between the 2 areas. The fluoride levels in bone and root were higher for subjects from the high fluoride area. No statistically significant difference could be demonstrated between the fluoride levels in alveolar bone and tooth roots for each area. It was found that the fluoride levels in bone and roots increased with increasing age, but to a lesser degree for subjects from the low fluoride area.

Adolescent↗