Theses and Dissertations (Prosthodontics)

Permanent URI for this collectionhttp://hdl.handle.net/2263/32517

Browse

Recent Submissions

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    The prevalence of second canals in the mesiobuccal root of maxillary molars in a South African subpopulation : a cone beam computed tomography study
    (University of Pretoria, 2018) Herbst, Dirk; Postma, Thomas Corne; Bunn, B.K. (Belinda Kathleen); nelson@prosthodontist.net.za; Fernandes, N.A. (Nelson Alexander)
    Introduction: Endodontic therapy is a global routine dental therapeutic procedure. Despite recent and present advances in dentistry and particularly with the popularity of implant dentistry, it remains biologically and aesthetically advantageous for retention of one�s original dentition. Tooth extraction followed by surgical placement of dental implants should remain a last resort in management. Treatment success depends on intricate knowledge and a thorough understanding of the anatomy of the root canal system, in order to adequately debride, disinfect, and obturate teeth affected by irreversible pulpitis or pulp necrosis. High endodontic failure rates are frequent in the maxillary molar tooth owing to the complexity of their root canal anatomy, and variations in the number of mesiobuccal (MB) roots. Conventional radiographic imaging techniques are unreliable for the detection of multiple canals, whereas cone beam computed tomography (CBCT) has proven to be effective for visualization of additional canals of root canal systems. There is little published data on the prevalence of second canals in the MB roots (MB2) of permanent maxillary first and second molars in a South African subpopulation. The aim of this study is to detect the prevalence of MB2 canals by analysing axial views of CBCT scans of adult patients. Methodology: A total number of 200 patient CBCT scans, from 100 male and 100 female patients respectively, were enrolled in the study. A total of 800 teeth were analysed in-vivo on CBCT scans, comprising 200 right maxillary first molar teeth (tooth 16), 200 left maxillary first molar teeth (tooth 26), 200 right maxillary second molar teeth (tooth 17), and 200 left maxillary second molar teeth (tooth 27). Teeth displaying radiological evidence of an additional mesiobuccal canal (MB2) were identified. Results: First maxillary molar teeth showed a high prevalence of MB2 canals, 92% and 87%, for the 16 and 26 respectively. Second maxillary molar teeth showed a lower, but still significant, prevalence of MB2 canals, 69% and 65%, for the 17 and 27 respectively. An association between patient age, gender and the prevalence of MB2 canals was not noted in the study sample. Conclusion: Root morphology and anatomy of permanent maxillary first and second molar teeth is highly variable. The prevalence of additional canals in the MB roots is a frequent finding which has previously been underreported. The presence of these variations significantly impact endodontic therapy success, longevity, and retention of the natural dentition. The prevalence of these canals requires documentation for dissemination of this knowledge and greater cognizance thereof with respect to more accurate endodontic outcomes and success.
  • Thumbnail Image
    Item
    Evaluation of tooth shade in a selected sample of patients visiting the oral and dental hospital
    (University of Pretoria, 2015) Dullabh, Hemant; Vally, Zunaid Ismail; u10670310@tuks.co.za; Amari, Asma Mohamed Z.
    Background: Aesthetics is an important aspect of modern day dentistry. Shade selection is one of the primary determinations for achieving good aesthetics in restorative dentistry. Shade selection has three parameters, namely value, chroma and hue. These can be determined by using either visual or instrumental shade guides. Previous publications have shown that teeth become darker with advancing age.1 some studies suggest that tooth value and skin colour may be inversely related. People with medium to dark skin tones have lighter teeth; those with lighter skin tones have darker teeth.2 However, other studies have found no correlation between skin tone and tooth shade.3,4 there are no studies relating tooth shade to tooth number ;sex; skin tone; age and gingival pigmentation and smoking habits. Objectives: The objectives of this study were the following: ? To assess differences in tooth shade between the maxillary central incisor (11) and maxillary canine (13); between the mandibular central incisor (41) and the mandibular canine (43); between the maxillary central incisor (11) and mandibular central incisor (41) and between the maxillary canine (13) and the mandibular canine (43). ? To establish if there are any differences in the shades of teeth 11, 41, 13, and 43, and whether sex or age influenced the shade in any way. ? To determine if there is any correlation between the shades of teeth 11, 41, 13, 43 and patients skin tone, gingival pigmentation (non-pigmented, focal, diffuse) or smoking habits. Methods: The study sample comprised of 500 dental patients of which 305 were females and 195 were males. Their ages ranged from 18 to 81 years. These patients were divided into two age groups. Group one consisted of 291 patients, who were 35 years old and younger, Group two consisted of 209 patients older than 35 years of age. Their sex, skin tone (light, medium or dark), gingival pigmentation (non-pigmented, focal or diffuse) and smoking habits were recorded. The tooth shade of the middle third of the maxillary central incisor (11), maxillary canine (13), mandibular central incisor (41) and the mandibular canine (43), were taken, using the Vita Lumin Vacuum Shade Guide, Vita Linear 3 D-Master guide, as well as the spectrophotometer (Vita Easyshade Compact). Skin tone was recorded by using a specially designed skin tone guide; the skin tone of the inner aspect of the arm of the patient was recorded. The degree of gingival pigmentation was assessed by visual examination of the attached gingiva of the anterior part of the maxilla and mandible. Results: The results of this study indicate that the central incisors had a lighter value than the canines, but there was no difference in value between the maxillary central and mandibular central incisors. The maxillary canine was found to be darker than the mandibular canine. A statistically significant relationship was found between tooth value and the patient s age, sex and skin tone. There was no significant relationship between gingival pigmentation and tooth value for the maxillary central incisor 11. However, there were significant relationships between tooth values for teeth 13, 41, and 43 and gingival pigmentation. There was also no significant relationship between the tooth values for teeth 13 or 43 with smoking habits of the patients, although there was a significant relationship between teeth 11 and 41 with the patients smoking habits. Conclusion: The central incisor was lighter than the canine in both the mandible and the maxilla. The mandibular canine (43) was, however, lighter than the maxillary canine (13). There was a significant relationship between the age of patients and tooth value; older adults had darker and more yellow teeth than younger patients. Generally females had significantly lighter and less reddish teeth than males. There was a significant relationship between skin tone and tooth value in that lighter skin tone patients had darker teeth value while those with darker skin tone had lighter teeth value. Gingival pigmentation showed no association with the value of the maxillary central incisor (11), but was associated with lighter values for the maxillary canine (13), mandibular central incisor (41) and mandibular canine (43). Smoking darkened the incisor teeth, but had little or no effect on the value of canine teeth.
  • Thumbnail Image
    Item
    A comparison of posterior palatal seal creation in complete dentures by private practitioners and students at the University of Pretoria
    (University of Pretoria, 2015) Sykes, Leanne; Lekay-Adams, Mary-Rose
    Aims: The aim of this study was to investigate the methods used by private practitioners and students to fabricate a posterior palatal seal in dentures and determine how many clinicians carry out this procedure themselves. Materials and methods: The laboratory slips, final impressions and final casts at jaw registration, try-in and finish stages of complete dentures of 50 student cases from the University of Pretoria and 10 cases from 5 private dental laboratories respectively were examined to determine the presence, position and dimensions of the post dam. Photographs and impressions were taken with polyvinyl siloxane impression material in cases where the post dam were marked and/or scribed. The impressions were sectioned with a scalpel and measurements were recorded with the aid of an Iwansson gauge and Carl Zeiss microscope. Depth and width was recorded at the midpalatal suture, right and left posterolateral, and right and left hamular notch areas of the scribed post dams. Results: In the private laboratory cases one of the 50 cases had the post dam marked at the secondary impression stage. In the student laboratory cases, 20% were marked at the secondary impression stage, 14% at the jaw registration and 12% at the try-in stages. Only 4% were scribed, all at the try-in stages. Measurements for post dam dimensions could only be made in 2 cases. Conclusions: Results of this study revealed a dismal lack of compliance and appreciation of the importance of the post dam by both students and experienced dental clinicians.
  • Thumbnail Image
    Item
    The effect of glass fiber polysulphone composite reinforcement on flexural strength of two denture-base polymers
    (University of Pretoria, 2005-10-03) Kemp, P.L.; upetd@up.ac.za; Henning, Martha Carolina
    Statement of the Problem: Despite its popularity as a denture-base material, poly-methyl methacrylate exhibits inherently low resistance to impact and fatigue failure. This is reflected in the analyses of the prevalence of denture fracture which suggests that prosthesis failure remains an unsolved problem. Consequently, various approaches to improve the physical and mechanical properties of denture-base polymers have been proposed. These include incorporation of solid metal forms and various types of fibers to provide reinforcement to fracture prone areas. In recent years there has been considerable interest in glass fiber reinforcement of polymeric denture resins. Partial fiber reinforcement using glass fiber has been shown to improve the mechanical properties of removable prostheses. However, adequate impregnation of fibers often requires the use of excessive methyl methacrylate monomer which has a deleterious effect on the mechanical properties of the fiber composite material. Purpose: The aim of the present study was to determine the effect of glass fiber polysulphone composite reinforcement on the flexural characteristics of two commonly used denture-base polymers. Materials and methods: Prefabricated E-glass fiber polysulphone composite rods, ± 3mm in diameter, with a continuous, unidirectional, non-silanized fiber concentration of ± 55 vol %, were employed as strengtheners. The reinforcement was incorporated axial to the neutral axis in standardized cylindrical heat polymerizing conventional and high impact resin test specimens 6mm in diameter and 28mm in length. The two reinforced pattern groups (n = 10) were compared with unreinforced resin control groups. A three point loading test was performed in air after storage of the specimens in water at 37°C for a period of 8 weeks. The following values were measured : flexural modulus and flexural strength. The obtained data were subjected to relevant statistical analysis. Results: The flexural modulus of the glass fiber polysulphone reinforcement was 14,106 MPa and the flexural strength 546.6 MPa. The flexural modulus of conventional denture-base resin was 1746 MPa, reinforcement increased it to 2328 MPa, and the flexural strength increased from 164 MPa to 209 MPa. The flexural modulus of high impact polymer was 1684 MPa and reinforcement increased it to 2067 MPa. The flexural strength was increased from 171 MPa to 242 MPa with reinforcement. Statistical analysis using t test showed that reinforcement affected the flexural modulus and flexural strength of polymer brands (p < : 05). Conclusion: Novel glass fiber polysulphone composite reinforcement may considerably enhance the flexural properties of multi phase denture-base polymers.