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Biomedical subjects

E H van der Merwe

Publications and source records attributed to E H van der Merwe.

9 recordsLinked to original sources
PubMed1979

Relationships among fluoride concentration in enamel, degree of fluorosis and caries incidence in a community residing in a high fluoride area.

The caries inhibitory effect of optimally fluoridated drinking water is well documented. Communities are often exposed to naturally fluoridated water with F content exceeding the optimal level. The purpose of this study was to determine the relationship between enamel fluoride, degree of fluorosis (DEGF) and caries incidence (DMFT) in an endemic fluoride area. Eighty-five 14- to 16-year-old children (37 males and 48 females) who were born and had been living continually in the town of Kenhardt in South Africa were selected for this study. The fluoride content of the common water supply is 3.2 ppm F. The DMFT and DEGF were determined clinically. Acid etch biopsies were carried out on both maxillary central incisors of each subject. Ca and F analysis were carried out and mass enamel expressed in microgram and mass F in pg. Data transformations to loge mass F (1nF), loge mass En (1nEn) and square root DMFT were made. The 1nF values were corrected to a standardized depth of 10 micrometer (208.6 microgram enamel equivalent mass) by covariance analysis. Correlations between the parameters square root DMFT, 1nF ad DEGF were calculated, adjusting for the sex of the individual. The correlations were as follows: (formula: see text). A positive association among the three parameters was established.

Adolescent↗
PubMed1977

Relationships between fluoride in enamel, DMFT index and fluorosis in high- and low-fluoride areas in South Africa.

The DMFT Index, degree of fluorosis (DEGF), and enamel fluoride concentration (F) were determined in 88 children living in a high- and 79 children living in a low-fluoride area in South Africa. The following interrelationships between these parameters were found: in both areas there was a significant negative correlation between log F and age; in the high-fluoride area there was a significant positive correlation between log F and DEGF; and in the combined data from the two areas there were significant correlations between log F and area, log F and age, and log F and DEGF, and a significant association between DEGF and area. There were no significant correlations between DMFT and log F and between DMFT and DEGF.

Adolescent↗
PubMed1976

Pyruvic acid as an etching agent.

Phosphoric acid at different concentrations has been extensively used as an etching agent to improve bonding of dental materials to enamel surfaces. Recently attention has been drawn to the possible use of polyfunctional organic acids as conditioning agents. The object of this investigation was to determine the optimal concentration of pyruvic acid as an etching agent. A commercial composite resin with an intermediary bonding system supplied with 37% H3PO4 as an etching agent was used as the control system. In addition, a comparative study was carried out to evaluate 37% H3PO4, 20% lactic acid and the optimal concentration of pyruvic acid as conditioning solutions. Etching enamel surfaces with 10% pyruvic acid resulted in the optimal tensile bond strength of the resin to etched enamel surfaces. The use of 10% pyruvic acid did not adversely affect the bond strength of the resin system when compared to enamel surfaces etched with 37% H3PO4 for the same time period. Significantly lower tensile bond strengths were recorded on enamel surfaces etched with 20% lactic acid. The rate and depth of etching obtained with 37% H3PO4 can be considerably reduced by using 10% pyruvic acid as the conditioning agent.

Composite Resins↗
PubMedDate not supplied

Relationship between fluoride concentration in enamel, DMFT index, and degree of fluorosis in a community residing in an area with a high level of fluoride.

The object of the present study was an attempt to relate fluoride concentration in enamel, caries experience, and the degree of fluorosis in a community residing in an area with a high level of fluoride. A significant difference was found between the male and female samples for the F and D parameters. A positive correlation was established for the male participants between DEGF and F, and a negative correlation between age and F. These correlations were not found for the female participants. Because of the low and narrow range of DMFT indexes, no correlation involving this parameter could be established.

Adolescent↗