Thesis (Ph. D.)--University of Toronto, 1997. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Toronto, 1997. / Includes bibliographical references.

Dental implants are an effective method of restoring missing teeth without compromising healthy neighboring teeth. Under proper oral hygiene and adequate care dental implants may be maintained for over 10 years. Good bone and gingival health are necessary for successful implants. In general systemic diseases may lead to lower rates of dental implant success. In spite of the risk the use of implants is not contraindicated. The effectiveness of antiretroviral therapy has increased the span and quality of life in HIV positive patients. Currently, HIV positive patients can opt for advanced dental treatments such as dental implants to restore their smile and masticatory function. Implants require a surgical approach which has the same level of invasiveness and risk of infection as tooth extraction. It is still questionable whether implants are a viable alternative for HIV positive patients as HIV infection itself and antiretroviral therapy both lead to bone loss. There are insufficient longitudinal studies to determine the success of dental implants in HIV positive patients. Recruited subjects for this study were scheduled for a single visit at GSDM to evaluate the current status of their implants previously placed at GSDM. Their medical history was updated including antiretroviral treatment. After a medical interview an intraoral radiographic image of the dental implant was used for comparison with the one taken at the date of implant placement to measure the amount of bone loss around the implant. This study aimed to determine if an unmodifiable factor such as HIV and the use of ART may affect the success of dental implants. Due to the small sample size, we may not conclude that HIV itself or the use of antiretroviral therapy affect the outcome of dental implant. The study supports the use of dental implants on HIV positive patients and the success of them is comparable to those placed on non-HIV patients.

<p>A study was carried in conjunction with the Orthodontic department at Halmstad General Hospital in Sweden to investigate the possibility of reducing cost and manufacture time of dental implant drill guides. </p><p>The current system involves sending a digital image in STL format to the Materialise factory in Belgium where information of the position of dental implants is translated onto a moulded mouthpiece. Drill guides are placed in the mouth piece which is then returned to the surgeon. The mouthpiece complete with drill guides is then placed in the patients mouth and used as a guide for the implant drill holes. The cost of 10000 sek and a turnaround time of 2 weeks gave rise to the need for a faster and cheaper solution. </p><p>A new mouthpiece was designed comprising of a solid cube which could be clearly seen on the x-ray. Linearisation of the cube faces is used to find a reference point from which to drive a 5 axis drilling platform. The mouthpiece is placed in the drill platform which is driven by stepper motors which in turn are controlled by a microcontroller. Co-ordinates are entered via a PC interface. The PC software then translates these co-ordinates into motor steps which are sent to the microcontroller. The drill platform then positions the mouthpiece in order to drill guide holes for the dental implants. </p><p>The study showed that the machine design gave an acceptable degree of accuracy and repeatability. Further enhancements could be made by automating the detection of the cube using image analysis techniques. The study was also limited by the lack of graphical and geometrical data concerning the position of the implant. For the purpose of this study the co-ordinates for the implants guides is entered by hand.</p><p>It was concluded that further software and hardware enhancement would be needed before the application could be developed commercially.</p>

Bacteria, in the form of biofilm, has been shown to play a critical role in the etiology and pathogenesis of periodontal and peri-implant infectious diseases. Studies have shown that distinctively different dental plaque is commonly found in healthy versus inflamed gingivae and mucosa. It should be noted, however, that in most of these studies, the healthy and diseased plaque samples were collected from different individuals. To address this important issue, in the two studies described within this thesis, I recruited subjects who were periodontally involved and/or had inflamed peri-implant tissues, and also had equivalent healthy control sites. In the first study, I analysed the subgingival microbiota of a cohort of tea labourers from Sri Lanka, who had never performed any oral hygiene practices. Within each of the 32 subjects, one ‘shallow’ (healthy) site and one ‘deep’ (diseased) site were chosen for subgingival plaque sampling. A 16S ribosomal RNA (16S rRNA) gene sequencing method was applied to investigate the diversity of the subgingival microbiome, and to compare the microbial composition between healthy and diseased sites. A taxonomically diverse subgingival microbiota was identified, with 318 operational taxonomic units (OTUs; 98% identity cut-off) from 1,887 cloned full-length 16S rRNA gene sequences. The subgingival microbiota was dominated by the phyla Firmicutes, Proteobacteria and Fusobacteria. A significant difference in the overall composition of microbial communities between shallow and deep sites was found ((-Libshuff, p<0.001) while pairwise comparisons within each subject revealed no significant differences. The absence of oral hygiene resulted in a highly diverse subgingival microbiota in this cohort. In the second study, 22 subjects who had both implants and teeth surrounded by healthy and inflamed tissues, were included for subgingival/submucosal microbiological sampling. Quantitative real-time polymerase chain reaction (q-PCR) was used to detect and to quantify six species, including putative periodontal pathogens, i.e., Porphyromonas gingivalis (P.g.), Treponema denticola (T.d.), Aggregatibacter actinomycetemcomitans (A.a.), Fusobacterium nucleatum (F.n.), Prevotella intermedia (P.i.), and Staphylococcus aureus (S.a.). Within the same subjects, putative periodontal pathogens were common to both periodontal and peri-implant sites irrespective of health status. The detection frequencies for each of the six target species at diseased tooth or implant sites were either equal to, or higher than, the respective detection frequencies at the corresponding healthy sites. Both periodontal and peri-implant sites, irrespective of their health status, were revealed to harbour S. aureus. Even though the target organisms were found in all clinical conditions, there were differences in the involvement of some of the pathogens for the diseased conditions. The prevalence and levels of P. gingivalis and F. nucleatum were significantly associated with periodontitis, but not with peri-implantitis. A. actinomycetemcomitans was associated with both disease conditions, periodontitis and peri-implantitis, but not with either gingival or mucosal health. In conclusion, results from my two studies indicated that the differences between the composition of subgingival microbial communities present in single sites within two different individuals, were always greater than the differences in microbial community composition present in two subgingival sites of differing health status within the same individual. / published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

A study was carried in conjunction with the Orthodontic department at Halmstad General Hospital in Sweden to investigate the possibility of reducing cost and manufacture time of dental implant drill guides. The current system involves sending a digital image in STL format to the Materialise factory in Belgium where information of the position of dental implants is translated onto a moulded mouthpiece. Drill guides are placed in the mouth piece which is then returned to the surgeon. The mouthpiece complete with drill guides is then placed in the patients mouth and used as a guide for the implant drill holes. The cost of 10000 sek and a turnaround time of 2 weeks gave rise to the need for a faster and cheaper solution. A new mouthpiece was designed comprising of a solid cube which could be clearly seen on the x-ray. Linearisation of the cube faces is used to find a reference point from which to drive a 5 axis drilling platform. The mouthpiece is placed in the drill platform which is driven by stepper motors which in turn are controlled by a microcontroller. Co-ordinates are entered via a PC interface. The PC software then translates these co-ordinates into motor steps which are sent to the microcontroller. The drill platform then positions the mouthpiece in order to drill guide holes for the dental implants. The study showed that the machine design gave an acceptable degree of accuracy and repeatability. Further enhancements could be made by automating the detection of the cube using image analysis techniques. The study was also limited by the lack of graphical and geometrical data concerning the position of the implant. For the purpose of this study the co-ordinates for the implants guides is entered by hand. It was concluded that further software and hardware enhancement would be needed before the application could be developed commercially.

Thesis (M.S.)--University of Michigan, 1999. / Includes bibliographical references.

Thesis (Ph. D.)--Case Western Reserve University, 1997. / Department of Mechanical and Aerospace Engineering. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Case Western Reserve University, 1997. / Department of Mechanical and Aerospace Engineering. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.