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Most previous research into cochlear implant (CI) mediated music listening deals with the mechanisms and efficacy of music perception and does not often account for the listeners real-world musical experience. Measurements of music perception ability are based on listening tasks such as pitch-discrimination, timbre-recognition and rhythmic-identification, and rarely (if ever) relate to the individual experience of the human subject. The exploration of musical experience, however, is based on a holistic view of the ways in which individual people experience music, which can be informed by the interaction of a multitude of factors. For the purposes of this thesis, three categories of experience are considered to coalesce to inform the general musical experience: sensory experience, cognitive experience and social/environmental experience. This thesis moves towards consideration of the real-world musical experiences of cochlear implant users (CIUs) with a view of developing strategies that can be implemented to improve those elements of the musical experience that may be problematic. The thesis comprises three main sections as follows: The first section investigates the musical experiences of CI users (CIUs) by means of a questionnaire study and the consideration of information gained from music focus groups and conversations with implant users. Results show a great deal of variability in the musical experiences of CIUs but many people report positive experiences of music despite suffering from what may be described as ‘poor’ music perception. The second section outlines the design, development and implementation of a multi-channel mixer application, which is used in a study exploring the way in which CIUs mix multi-channel music, to gain insight into their experience of musical elements. Analysing the user-generated mix data provides considerable insights into various elements of the musical experience of participants. Again, results show a large degree of variability on this issue amongst CIUs, and also that the average mixes of CIUs differ significantly from that of a control group of normal-hearing (NH) participants. The third section describes the composition, development and evaluation of a musical work specifically composed for CIUs but designed to be enjoyable for both CIUs and NH audience members alike. The aim of this composition is to promote a positive musical experience by addressing elements of the sensory, cognitive and social/environmental experience based on findings of this research. This thesis concludes by suggesting that the ideal approach for improving the musical experiences of CIUs should focus on the individual, due to the great deal of variability within this population, and presents some implications of this work and suggestions for future research in this area.

AIM: To compare the stability of a non-cylindrical implant using piezoelectric drilling (Piezoimplant) with a cylindrical implant with conventional drilling (Nobel Biocare™). MATERIALS AND METHODS: Three adult female Gottingen miniature pigs were used for the surgical implantation. Three implants on each quadrant, randomized split-mouth design using cylindrical or non-cylindrical implants (n=36). Osteotomies were prepared using either conventional drilling technique as per manufacturer’s instruction (Nobel Biocare™) or using piezoelectric drilling (Piezotome® (P2) (Satelec Acteon, Merignac, France) with new implant prototype tips (Fraunhofer Center for Manufacturing Innovation). The minipigs were sacrificed at 4, 8 and 12-weeks. Stability tests (three per implant) using wireless Periotest® “M” were done at the start point and after euthanization. RESULTS: R-square (ANOVA) test was plotted comparing implant design, weeks 4, 8 and 12, and location (mandible and maxilla) for stability analysis. In this model, the R-square is only 0.51, which indicates only 51% of the response variability can be explained by the fitted model. Among all the 3 factors, group (experiment vs control) is the most significant one, followed by week. Location significance is the least among the three factors. CONCLUSION: In mandibular and maxillary sites in minipigs where non-cylindrical prototype implants (piezoimplant) were inserted by piezoelectric site preparation, statistically significant differences were found between control and test group stability measurements, but no differences in week (4, 8 or 12) and location among the two groups (mandible and maxilla). Stability was like the cylindrical implants. Meaning that Piezoimplants could be an alternative for narrow residual ridges. / 2020-03-14T00:00:00Z

In this thesis, four experimental studies are reported. Two concern the surface structure of commercially relevant dental implant materials. Characterisation of four treated substrates supplied by Straumann AG was carried out. These include substrates equivalent to the commercially available SLA, SLActive and Roxolid implants. The materials vary in substrate alloy, commercially pure (grade 2) Ti and a TiZr alloy, and surface preparation treatments. All substrates are sandblasted and acid etched however post-etching one set are stored in air whilst the others are stored in saline. Within the work both substrate composition and surface treatment is shown to impact on the respective surface oxide thickness, crystallinity and morphology. The other two experimental studies concern calcium phosphate deposition from solution onto substrates. The first investigation is the deposition of calcium phosphate from a simulated body fluid onto implant-like substrates, shown to be structurally equivalent to the SLA and SLActive implant surfaces. The effect of surface modifications on calcium phosphate deposition is investigated; over the period investigated calcium phosphate did not deposit onto the SLA substrate, whilst deposition occurred within 3 days on the SLActive substrate. The role of Mg2+ ions in the simulated body fluid is also investigated, with increased [Mg2+] resulting in a longer induction period and modified crystallinity of the hydroxyapatite film formed. The final study is a model study of the initial calcium phosphate deposition on to substrates. TiO2 rutile (110) and Al2O3 corundum (0001) were prepared to be atomically flat and then exposed to a simple calcium phosphate solution. Changes in surface structure and surface chemistry over the first three hours of exposure were investigated. Deposition occurred rapidly on both substrates with a complete surface coverage after 3 hours.

Introduction: The survival of dental implants depends on osseointegration. Modifications to the implant surface are attractive for promoting the success of the implant. Abrading the surface of the implant with bioactive glass is an attractive option for improving the speed of osseointegration. Aims: To develop a bioactive glass that has the ability to enhance the surface roughness of the implant by embedding particles into the surface and to investigate the effect of grit blast parameters on the removal of the titanium from the surface. Methods: Three glasses based on SiO2-CaO-Na2O-P2O5-CaF2 were synthesized by a melt quench technique. The glasses were characterised and investigated for their bioactivity. Titanium discs were abraded with coarse glass particles by using a grit blast technique with different parameters, such as, distance, air pressure and speed. The depth, width of the abraded line and surface roughness (Ra) were measured by light profilometer. The distribution of the glasses on the titanium surface was measured by SEM-EDX. The biocompatibility of the abraded discs was tested in vitro using MC3T3-E1 cell line. Results: All glasses exhibited an amorphous structure with varied bioactivity. Changing the abrasion parameters influenced the amount of titanium removed and the surface coverage. The harder the glass the lower the amount of titanium removed and the wider the width of the abraded area. The Ra was significantly increased from 0.1μm to 1.6μm. The SEM-EDX analysis confirmed that the glasses were widely distributed and a higher coverage was seen with the harder glass. The abraded discs showed good biocompatibility in vitro. Conclusions: The designed compositions were successfully modifying the surface of the titanium. They are abrasive enough to significantly embed into the titanium surface by using the grit blast technique and increase their surface roughness. TheIntroduction: The survival of dental implants depends on osseointegration. Modifications to the implant surface are attractive for promoting the success of the implant. Abrading the surface of the implant with bioactive glass is an attractive option for improving the speed of osseointegration. Aims: To develop a bioactive glass that has the ability to enhance the surface roughness of the implant by embedding particles into the surface and to investigate the effect of grit blast parameters on the removal of the titanium from the surface. Methods: Three glasses based on SiO2-CaO-Na2O-P2O5-CaF2 were synthesized by a melt quench technique. The glasses were characterised and investigated for their bioactivity. Titanium discs were abraded with coarse glass particles by using a grit blast technique with different parameters, such as, distance, air pressure and speed. The depth, width of the abraded line and surface roughness (Ra) were measured by light profilometer. The distribution of the glasses on the titanium surface was measured by SEM-EDX. The biocompatibility of the abraded discs was tested in vitro using MC3T3-E1 cell line. Results: All glasses exhibited an amorphous structure with varied bioactivity. Changing the abrasion parameters influenced the amount of titanium removed and the surface coverage. The harder the glass the lower the amount of titanium removed and the wider the width of the abraded area. The Ra was significantly increased from 0.1μm to 1.6μm. The SEM-EDX analysis confirmed that the glasses were widely distributed and a higher coverage was seen with the harder glass. The abraded discs showed good biocompatibility in vitro. Conclusions: The designed compositions were successfully modifying the surface of the titanium. They are abrasive enough to significantly embed into the titanium surface by using the grit blast technique and increase their surface roughness. The glass abraded discs show both good bioactivity and biocompatibility in vitro.

Objective: To determine the long-term prosthodontic maintenance requirements of mandibular unsplinted, two-implant overdentures, using different attachment systems and loading protocols. Materials and Methods: An original total of 106 participants were randomly allocated to one of four different implant systems (Brånemark, Steri-Oss, Straumann and Southern Implant systems). Three different loading strategies were used (2-weeks, 6-weeks and 12-weeks). A total of six different unsplinted attachment systems for mandibular two-implant overdentures were used with the four implant systems. These attachment systems included; the Brånemark gold matrix, Straumann gold matrix, Straumann titanium matrix, Southern Implants plastic matrix, Southern Implants palladium matrix and the Steri-Oss rubber matrix. Each matrix group was allocated to one or more loading strategies and data related to prosthodontic maintenance events was collected prospectively from overdenture insertion (baseline) to year eight, according to predefined categories. Data were analysed using SPSS, and levels of statistical significance were set at P < 0.05. To test for significance between multiple groups, ANOVA was used. Where a statistically significant difference existed, a one way ANOVA with Post Hoc tests was performed. Results: A total of 90 participants from all matrix groups were followed for six-years and loading comparisons could only be made up to this time. The Southern palladium matrix was followed for only six-years therefore it could not be included in the eight year analysis. A total of 69 participants remained in the randomised controlled trial after eight years. Mandibular two-implant overdentures fitted with the Steri-Oss rubber matrix displayed the highest mean number of maintenance events at 32.2 (SD 14.5) followed by the Brånemark matrix group at 28.8 (SD 12.6), the Straumann titanium matrix group at 24.9 (SD 10.7) and the Straumann gold matrix group at 12.8 (SD 8.2), over an eight year period. The Southern plastic matrix group had the lowest average number of maintenance events (8.7 SD 4.2) over the eight-year period and this was significant compared with all other groups (P < 0.05). Over six years, there were no significant differences found between the number of prosthodontic maintenance events and the loading strategy used. On average, the Straumann gold matrix lasted for 3.9 (SD 2.1) years which was significantly longer than all other matrices (P < 0.05) over six years. The Southern palladium (3.1 SD 1.7), Brånemark gold (2.7 SD 1.5) and Southern plastic (2.5 SD 1.4) matrices all lasted significantly longer than the Straumann titanium (1.7 SD 0.8) and the Steri-Oss rubber (1.4 SD 0.7) matrices over six years. Conclusions: Mandibular two-implant overdentures using the Southern Implants plastic cap required significantly less prosthodontic maintenance events compared with all other matrix groups. The Straumann gold matrix required significantly less prosthodontic maintenance compared with the Steri-Oss rubber matrix (P<0.05). The Straumann gold matrix also demonstrated the greatest longevity compared with all other matrices (P<0.05). There was no significant difference in the number of prosthodontic maintenance events of two-implant overdentures when loaded at 2, 6 or 12-weeks after implant placement. The prosthodontic maintenance requirements of unsplinted mandibular two-implant overdentures are dependant upon the attachment system chosen.