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Biomedical subjects

C H Jooste

Publications and source records attributed to C H Jooste.

17 recordsLinked to original sources
PubMed1996

Designing a transmandibular implant with the aid of biostereometric analysis.

A biostereometric survey of severely resorbed dry mandibles was used to determine whether it was possible to design a transmandibular implant that could be used for the majority of clinical situations. Computerized profiles of the relevant mandibular areas were generated and superimposed to examine the feasibility of a universal shape. It would appear that the crestal shape of the mandible between the mental foramina is on the circumference of a circle and that the surface of the inferior border is so variable that a flat surface would have to be used for a transmandibular implant. A design of a transmandibular implant is proposed on the basis of the common anatomic features of the mandible.

Cephalometry↗
PubMed1996

Biostereometric quantification of clinical denture tooth wear.

In this study the wear of mandibular acrylic resin teeth opposed by porcelain maxillary teeth arranged in a lingualized occlusal scheme over a period of 3 years was measured. Six edentulous subjects received complete dentures as above and with three baseline markers of amalgam. At yearly intervals casts were made of the mandibular occlusal surfaces, including markers, and plotted by stereophotogrammetry. Volumetric loss of material was quantifiable. Ranges of 0.62-3.33 mm3/mm2 on the left side and 0.71-1.64 mm3/mm2 on the right were recorded. Friedman two-way ANOVA test indicated significant wear on teeth 35, 36, 45 and 46 but not on 34 and 44. A one-sided chewer displayed greater wear on the contralateral side, a finding difficult to explain.

Acrylic Resins↗
PubMed1995

Compression implants: case report of a surgical, prosthetic, and cosmetic failure.

A case involving the use of non-submergible compression-type implants in an effort to rehabilitate a patient who had experienced tooth loss as a consequence of a motor vehicle accident is reported. The implants were placed in the maxillary arch without consideration of their contribution to subsequent prosthetic rehabilitation. The literature pertaining to compression-type implants is reviewed, and the difficulties related to their correct usage are delineated.

Accidents, Traffic↗
PubMed1994

Biostereometric measurement of oral tumour growth. Description of the technique and case report.

Following radiotherapy, it may be difficult to determine clinically whether tumour regression, stabilization or growth has occurred. Traditional diagnostic imaging may not be possible due to the small size of the tumour and the proximity of metallic restorations. A case of squamous cell carcinoma of the mandibular alveolar process in which these problems arose is presented. A computer-assisted biostereometric technique was used to identify volumetric change of the tumour. Polyvinylsiloxane impressions were obtained to record the anatomy of the tumour site. From these, stone models were made at four and eight weeks following radiotherapy. Using optical mapping techniques, tumour growth was demonstrated which was not evident on follow-up examinations. The methodolgy of biostereometry is presented and its advantages and potential applications are discussed.

Carcinoma, Squamous Cell↗
PubMed1993

A comparison of the bond strengths of microwave- and water bath-cured denture material.

A comparison was made of the shear bond strengths between microwave-polymerized and conventional water bath-cured polymethyl methacrylate (PMMA) bonded to denture teeth. Four groups of 15 specimens were prepared and shear bond strengths obtained by use of standardized laboratory testing methods. The results showed that microwave-cured PMMA demonstrated significantly (p 0.0001) higher bond strengths than conventional PMMA, and priming of the denture tooth surface with monomer liquid yielded significantly higher bond strengths than other surface treatment (p 0.0001).

Analysis of Variance↗
PubMed1992

Complete mandibular denture stability when posterior teeth are placed over a basal tissue incline.

Six patients with previous denture experience were provided with new dentures. Metal indicators were placed on either side of the mandibular denture and a cobalt-chromium alloy marker was inserted in the left bucco-posterior area of the mandible in each case. In the new dentures posterior teeth were positioned up to the retro-molar pad, over the basal tissue slope of the posterior mandibular alveolar ridge. After habituation had taken place, a cineradiographic recording was made of chewing. Prior to the second recording the mandibular teeth were removed to a point where the remaining teeth were not over inclined residual alveolar ridges. Denture movement was observed by measuring the distances between the markers on an analytical projector. The results show a significant difference between the cranial values of the two chewing experiences. Values for all denture movements were less after removal of the teeth over an incline. These results support the clinical observation that teeth placed over a basal tissue incline have a destabilizing effect during complete mandibular denture function.

Adult↗
PubMed1989

The effect of a custom edentulous impression tray on lingual sulcus depth.

An acrylic resin custom edentulous impression tray and standardized irreversible hydrocolloid impression technique were used. Ten impressions were made, after which the lingual border of the tray was reduced by 1.5 mm before the next series of impressions was made. This was done three times. Impressions were cast in a miter box. The plaster blocks so obtained were sectioned in the (a) retromylohyoid region, (b) 10 mm anterior, and (c) in the region of the mental foramen. In the retromylohyoid region there was a significant difference between the flange length after each reduction of the custom tray (p less than 0.01). Ten millimeters anteriorly the differences after each reduction except between the first and second reduction were less significant. In the region of the mental foramen there was a significant difference after the first reduction, but there was no significant difference between the flange lengths obtained thereafter.

Adult↗
PubMed1989

An indirect in vivo method for quantification of wear of denture teeth.

A method using a reflex microscope to undertake direct and highly precise three-dimensional measurements of denture casts for the purpose of mapping and determining the volumetric loss of material over a period of time has been developed. The wear that occurred in tooth 46 after clinical use for one year was measured and found to be 7.2 mm3. This technique has proved to be an accurate and objective quantification of what has previously often been a subjective impression.

Denture, Complete↗
PubMed1984

A method for orienting the ocular portion of an orbital prosthesis.

The success of an orbital prosthesis depends largely on the correct orientation of the pupil and ocular bulb. The method presented in this article uses a transparency projection from which a tracing of prominent facial features is made. The transfer of these dimensions to the facial cast reduces the chairside time that is necessary to position the pupil and orbital bulb.

Eye, Artificial↗
PubMedDate not supplied

The influence of the retromylohyoid extension on mandibular complete denture stability.

It has been a clinical impression that the retromylohyoid extension in complete mandibular dentures contributes to stability. This hypothesis was tested in six individuals by means of cineradiography and placement of a metal marker in the mandible and dentures during chewing exercises, with and without the relevant denture extension. Analysis of tracings of the movements of the markers revealed that statistically significant differences existed between first and second chewing experiences. Movement in a horizontal plane around a vertical axis, however, was common to all dentures during all chewing. It is concluded that the retromylohyoid extension has a stabilizing effect on complete mandibular dentures.

Adult↗
PubMedDate not supplied

Three-dimensional finite element model of a human mandible incorporating six osseointegrated implants for stress analysis of mandibular cantilever prostheses.

The three-dimensional finite element stress analysis method was used to determine the distribution of stresses in and around a model of six implants which supported a typical fixed complete-arch prosthesis in a simulated human mandible. A load of 100 N was applied at different intervals along the cantilever segment. There was a decrease of stress that reached a minimal level at 15 mm along the cantilever segment. Thereafter, a progressive increase of stresses in the lingual and buccal plates was demonstrated.

Biomechanical Phenomena↗