|dc.description.abstract||Implant prostheses have complications that compromise peri-implant health and marginal bone. In addition to pathogenic bacterial biofilm, other determinants, such as implant surface deterioration, Ti particulates in peri-implant tissues, and functional stress have been reported as influencing peri-implant tissue stability.
Aim: This thesis investigated the origin and presence of Ti particles in healthy and diseased peri-implant human tissues. Three trials evaluated the effect of acid-forming bacteria and mechanical instrumentation on Ti discs, and the effect of loading on implant surfaces on human participants.
Methods: Four experiments involving a combination of in vitro and in vivo trials were performed. The first identified Ti particles in peri-implantitis tissues. Tissue specimens were analyzed under polarized light-microscopy (LM), scanning-electron-microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) analysis. In the second, a microbiological protocol incubated Ti discs achieving viable biofilm, which were investigated in-vitro for microbial-induced-corrosion. The third was an in-vitro trial evaluating topographic and composition changes by ultrasonic instrumentation on TI discs. Surface changes were evaluated using SEM, confocal-laser-scanning-microscopy (CLSM), and EDS. Rinsing solutions were evaluated using induced-coupled-plasma-mass-spectroscopy (ICPMS). The fourth experiment was a human trial on single implant crowns after five years. Exfoliative cytology samples from peri-implant mucosa and junctional epithelial, and control tooth mucosa sites were evaluated using LM, SEM and EDS. ICPMS was carried out on the exfoliative cytology microbrushes. Clinical peri-implant parameters were determined.
Results: Firstly, the presence of Ti particles in peri-implantitis tissues was confirmed in 88% of the samples. Granular foreign material was scattered within the connective tissue and the epithelium layer. In most cases the inflammatory infiltrate contained a mixture of acute and chronic inflammatory cells. In the second experiment acid-forming bacterial colonisation of the disc surface was evident after 24 hours and maintained throughout the 7-day observation period. Although Ti isotopes should some variation in the inoculated growth media, ICPMS measurements were hindered due to the high concentrations of sodium (Na) and phosphorus (P) in the broth, this created backscattering during the analyses. The third experiment ultrasonic instrumentation of Ti discs demonstrated significant surface topographical alterations. ICPMS analysis of the rinsing solutions identified Ti and other metal traces. In the fourth experiment, the exfoliative internal and external cytology smears showed black scattered foreign material, which were also noted with SEM and EDS. More particles were identified at the level of the implant-abutment interface when compared to the external mucosal smears. The presence of these particles did not influence peri-implant health.
Conclusions: Peri-implantitis biopsies exhibited Ti and other metal particles. The origin of these particles could be related to biomaterials used in oral implantology. Although a consistent viable acid-forming biofilm on Ti specimens has been devised, the measurement of Ti dissolution in the surrounding environment needs further investigation. Ultrasonic instrumentation of Ti surfaces caused topographic and compositional changes, which created Ti particulate. The effect of functional loading between implant components, created wear of Ti implant surfaces. Functional wear of implant components resulted in release of metal particles into the peri-implant milieu. The presence of these particles did not affect the peri-implant health.||