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Biomedical subjects

J C Slabbert

Publications and source records attributed to J C Slabbert.

At least 19 recordsLinked to original sources
PubMed1995

The use of fractal analysis to reveal remodelling in human alveolar bone following the placement of dental implants.

In order to confirm the presence of adequate bone support for implants it is necessary to examine the surrounding bone at intervals. While this may be attempted by looking for changes in serial radiographs, such comparisons are inaccurate unless standardized procedures are followed which allow subtraction of consecutive digital images. As image textures are less susceptible to magnification distortion, it was decided to examine the fractal dimensions of successive radiographs of bone after implant placement. All available panoramic radiographs for each of 18 patients who had received fixed implant-supported prostheses were digitized. A window of bone adjacent and distal to the most posterior implant was defined as the region of interest; the fractal dimension of the image was calculated. Linear regression was used to investigate whether there were any significant shifts in fractal dimension during the recall period after implantation. A significant increase in fractal dimension was found during the period up to 2 yr after implantation (p < 0.001). The most pronounced increase was in the region of bone around the neck of the implant. An increase in orientation of the image in a direction oblique to the implant was also found during the same period. These changes are consistent with models derived from finite-element analysis that predict the relation between trabecular architecture and strain. One subject's radiographs had a significant negative regression slope, which further monitoring may reveal was an early sign of implant failure. The satisfactory remodelling of bone in response to implant placement may be monitored using a texture analysis of routine orthopantomograms.

Adult↗
PubMed1994

Survival of fixed implant-supported prostheses related to cantilever lengths.

Various lengths of cantilevers for fixed implant-supported prostheses have been recommended in the literature. No scientific data are available for selecting specific lengths, and different views are reported. Authors contend that longer cantilevers lead to increased risk of failure. This study examined survival of fixed implant-supported prostheses using different cantilever lengths and offers clinical support for the contention.

Dental Implantation, Endosseous↗
PubMed1994

The effect of titanium on the growth of plaque micro-organisms in vitro.

The effect of titanium on the growth of plaque organisms was studied in vitro. Thioglycollate broth containing either titanium or glass cylinders was inoculated with plaque micro-organisms and incubated aerobically and anaerobically at 37 degrees C for 6 hours. Growth was measured by observing an increase in turbidity of the broth. Cultures grew more vigorously aerobically than anaerobically. In the presence of titanium there was also more growth aerobically than anaerobically. There was no significant difference between the turbidity values obtained in the presence or absence of titanium suggesting that titanium does not influence the growth of plaque micro-organisms significantly.

Agar↗
PubMed1993

Partial denture prosthodontic procedures employed by practising graduates of the University of the Witwatersrand, Johannesburg.

This study sought answers to the following two questions related to the teaching of partial denture prosthodontics in the Department of Prosthetic Dentistry at the University of the Witwatersrand, Johannesburg (Wits). Firstly, do practising graduates from Wits assiduously apply, or do they perhaps ignore, the concepts, principles, and practices taught to them at undergraduate level? Secondly, is there any merit in providing additional tutorials on partial denture prosthodontics to undergraduate students at Wits? A questionnaire was mailed to dentists who had graduated at Wits between 1979 and 1986. This sample of 302 subjects was divided into two groups: Group I--those who had graduated between 1979 and 1982; Group II--those who had graduated between 1983 and 1986 and had received additional tutorials on partial denture design. The results suggest that a wide gap exists between faculty beliefs about partial denture design and fabrication and the methods used in general dental practice. Moreover, additional tutorials had some effect on the attitudes and practices of the respondents.

Dentists↗
PubMed1992

The value of radiographic predictors of the rate of mandibular residual ridge resorption.

This study tested the relationships between the rate of mandibular residual ridge resorption and the following two variables: cortical thickness at the gonion, and the proportion of cortical bone at the symphysis. These parameters were also compared between men and women. Measurements of cortical thickness at the gonion on panoramic radiographs were compared with similar measurements on lateral cephalometric radiographs. The results showed that neither cortical thickness at the gonion nor the proportion of cortical bone at the symphysis could be used as radiographic predictors of the rate of mandibular bone resorption. The rate of resorption was significantly greater in men than in women, while cortical thickness at the gonion in women was significantly less than that in men. Furthermore, the authors concluded that cephalometric and panoramic measurements should not be used interchangeably.

Adult↗
PubMed1990

The effect of dust-suppressant additives on the physical properties of an irreversible hydrocolloid.

The effects of dust-suppressant additives on certain physical properties of an irreversible hydrocolloid were studied in five test specimens formulated as follows: no additives (F0); 10% Duomeen cationic surfactant in 0.5% paraffin with 0.05% zinc stearate (F1); 10% Duomeen in 0.5% paraffin with 0.10% zinc stearate (F2); 20% Duomeen in 0.5% paraffin with 0.05% zinc stearate (F3); and 20% Duomeen in 0.5% paraffin with 0.10% zinc stearate (F4). The properties tested according to ADA specifications were mixing time, setting time, compressive strength, strain in compression, and permanent deformation under fixed strain. For each property, the variances between formulations were not significantly different (Levene p less than 0.05) whereas means were significantly different for stress (ANOVA p + 0.0001; Kruskal-Wallis p = 0.0019); strain (ANOVA p = 0.0003; Kruskal-Wallis p = 0.0228); deformation (ANOVA p = 0.0166; Kruskal-Wallis p = 0.0308). For the properties stress, strain, and permanent deformation under fixed strain, the paired differences of dust suppressants were established by using Duncan's multiple range test. Duomeen, instead of zinc stearate seems to be responsible for these effects.

Alginates↗
PubMed1990

Provision of "comprehensive dental care" in various dental schools.

The purpose of this survey was to solicit information about comprehensive dental care (CDC) programmes in various dental schools. Seventy-four schools responded to a questionnaire which sought information about a range of topics pertaining to CDC. The 19 questions used were categorized under the following headings: implementation and success; physical nature of clinics; staffing; and, student involvement. The diverse nature of the responses is thought to be an expression of differing philosophies and of the presence of numerous constraints to the introduction of CDC. The various approaches to CDC make it very difficult to gauge the relative merits of the many systems reported. It appears from this study that departments will continue to play an important role in preparing students to participate in CDC programmes and that it would be safer to introduce students to CDC during the final year of study.

Comprehensive Dental Care↗
PubMed1989

The effect of complete dentures on head posture.

This study investigated possible changes in head posture after insertion of complete dentures in patients who had been edentulous for at least 6 months. The craniovertical angle was measured with a plastic ruler and protractor assembly, which was aligned with dots made on the skin over the zygomatic arch. Readings were made before denture insertion, immediately after insertion, and 15 and 30 minutes later. Two-way ANOVA was used to analyze the results. When the predenture insertion values were included, statistically significant changes (p less than 0.01) in head posture were found. However, when the predenture values were excluded, no statistically significant differences were found. The results support the conclusions that head posture is significantly altered immediately after insertion of dentures in edentulous patients but within the next 30 minutes there is no statistically significant alteration in head posture.

Denture, Complete↗
PubMed1987

Tongue position in relation to edentulous mandibular impressions.

An adjustable easily located impression tray handle was used as a device to control tongue position and muscular forces for mandibular complete denture impression-making. This technique is indicated where advanced residual ridge resorption is present. A denture made with a lingual guiding ramp conforming to such an impression is not a panacea for all mandibular denture problems, which have many complex causes. However, the lingual guiding ramp technique gains support from established physiological findings and can yield gratifying clinical results.

Dental Impression Technique↗