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Biomedical subjects

D H Retief

Publications and source records attributed to D H Retief.

At least 127 records · Page 7Linked to original sources
PubMed1980

In vitro fluoride uptake, distribution and retention by human enamel after 1- and 24-hour application of various topical fluoride agents.

The in vitro fluoride acquisition by human enamel after a 1-hour and 24-hour application of APF, Duraphat (a resin varnish) or Fluor Protector (a polyurethane varnish) and subjection to various procedures was determined. Fluoride acquisition was the greatest in teeth treated with Fluor Protector and the least in APF-treated teeth. Fluoride uptake and distribution were increased by prolonging the contact time between the varnishes and enamel, and fluoride retention was decreased after subsequent exposure to synthetic saliva.

Acidulated Phosphate Fluoride↗
PubMed1979

Finishing of enamel surfaces after debonding of orthodontic attachments.

The finishing of enamel surfaces after removal of directly bonded attachments is essential. The following procedures are suggested: 1. The bonding of mesh-backed stainless steel brackets with a lightly filled resin system. 2. Debonding of attachments with a direct bonding bracket remover. 3. Removal of the bulk of the remaining resin with a 12-bladed tungsten carbide bur operated at high speed with adequate air cooling. 4. Finishing of the residual resin and underlying enamel with graded polishing discs or Ceramisté wheels used with light pressure and adequate air cooling. 5. Final finishing with a rubber cup and a water slurry of pumice.

Acid Etching, Dental↗
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↗
PubMed1978

The mechanical bond.

Explore the source record for details and available documents.

Acid Etching, Dental↗
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↗
PubMed1977

Pulpal response to pyruvic acid.

Etching of enamel surfaces produces a marked increase in the bond strength of dental materials to tooth structure. The results of recent studies have indicated that pyruvic acid may be used in preference to phosphoric acid, because of its milder etching effect on enamel surfaces, without adversely affecting the bond strength. The pulpal responses elicited by 10% pyruvic acid applied for 90 seconds to freshly prepared cavities in monkey teeth, were examined after 4, 14 and 42 days. The differences between some of the ariteria used to evaluate the pulpal responses in acid-treated and control teeth at the three post-operative time intervals were statistically significant. These results suggest that exposed dentin should be protected with a lining before etching adjacent enamel surfaces with 10% pyruvic acid.

Acid Etching, Dental↗
PubMed1976

A comparative study of some dental cements used in orthodontics.

It is suggested that decalcification occurring beneath orthodontic bands is, among other factors, related to the tensile bond strength of the cement to the enamel surface, its marginal leakage at the enamel-cement interface, and its solubility and and disintegration. Under the laboratory conditions described in this study the composite cement exhibited the greatest tensile bond strength to both enamel and band material. The composite cement also displayed no marginal leakage at the enamel-cement interface and showed no solubility or disintegration under the experimental conditions. It could therefore be anticipated that, of the four cements evaluated in this study, the composite cement would have the greatest potential for eliminating pathologic enamel decalcification occurring beneath orthodontic bands.

Composite Resins↗
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↗
PubMed1975

Clinical experience with the acid-etch technique in orthodontics.

The acid-etch technique and the development of improved composite resin systems have made the direct bonding of orthodontic attachments an accepted clinical procedure. This technique can be used with confidence as an adjunct in the armamentarium of the orthodontist.

Adolescent↗
PubMed1975

The use of 50 per cent phosphoric acid as an etching agent in orthodontics: a rational approach.

The chemical treatment of enamel surfaces is an approach used in obtaining increased adhesion of dental materials to tooth surfaces. One of the conditioning solutions extensively used prior to the direct bonding of orthodontic attachments is a 50 per cent phosphoric acid solution. The object of this investigation was to study the effect of various concentrations of phosphoric acid on the bond strength of an epoxy adhesive formulation developed for the direct bonding of orthodontic attachments. Furthermore, an attempt was made to quantitate the etching action of the phosphoric acid solutions by determining the depth of etch on polished enamel surfaces and recording the surface profiles of etched enamel surfaces by means of a surface-roughness measuring instrument. The use of 50 per cent phosphoric acid solution as a conditioning agent prior to the use of the epoxy adhesive formulation is advocated. The rationale supporting this recommendation includes (1) the bond strength of the epoxy adhesive system to enamel surfaces etched with 50 per cent H3PO4 is not significantly improved by the use of phosphoric acid at any other concentration; (2) the depth of etch obtained with 50 per cent H3PO4 is less than that observed with H3PO4 solution at concentrations which produce comparable bond strengths; (3) the surface roughness of enamel surfaces etched with 50 per cent H3PO4 is greater than that obtained with more dilute acid solutions. The optimal phosphoric acid concentration should be determined for each adhesive system.

Dental Bonding↗
PubMed1975

A comparative study of three etching solutions: effects on enamel surface and adhesive-enamel interface.

The chemical treatment of enamel surfaces is an approach in obtaining increased bonding of dental materials to tooth srufaces. Three etching solutions commonly used at present are 50% H3PO4, 50% H3PO4 attenuated with 7% zinc oxide and 50% citric acid. The effects of these three conditioning solutions on normal and polished enamel surfaces and on the interfaces between untreated enamel and etched enamel surfaces were studied by scanning electron microscopy. The variable etching pattern observed with each of the acids made a comparative study difficult. This was further complicated by the dependence of the etching action on prism orientation on polished enamel surfaces. Additional factors that have to be considered are the presence of prismles enamel and perikymata. Surface profile recordings of polished and acid-etched polished enamel surfaces provided some quantitative measure of the etching action of the conditioning solutions. The 50% citric acid solution had the mildest etching action while 50% H3PO4 and 50% H3PO4 attentuated with 7% zinc oxide elicited comparable responses.

Citrates↗