Use of Air Abrasion to coat Model Mixed Strontium-Calcium Bioactive glasses on Implant surfaces

UoM administered thesis: Phd

  • Authors:
  • Fatema Al Mansour

Abstract

Peri-implantitis is one of the main causes of late dental implant failures. Due to the progressive bone loss around a functioning implant, surgical intervention may be required to expose the implant surface and remove the biofilm mechanically using rotary burs, in order to prevent the progression of disease. This technique, known as implantoplasty, introduces titanium debris at the surrounding soft tissues, and also weakens the strength of the implant; which compromises the long-term clinical success of dental implant. Given the clinical problem, early detection of peri-implantitis during clinical follow-up of the peri-implant tissues could provide an immediate chairside treatment for preventing bone loss. Strontium containing bioactive glasses are of a special interest due to their ability to enhance bone formation, but also provide anti-bacterial potential against gram negative bacteria. The first aim of this Thesis was to explore the parameters affecting air abrasion on dental implants. Then, the use of novel bioactive glasses was explored as air abrasion agents. Therefore, formulating a series of strontium containing bioactive glasses could be an effective air abrasive media to coat dental implants and regenerate lost bone at peri-implant sites. Finally, their cytotoxicity was explored. As the majority of current dental implants are moderately roughened (Sa:1.5-2 µm), coating these surfaces at low pressure is important to minimize an increase in surface roughness (> 2 µm), which has shown to induce peri-implantitis. Chapter 4 investigates the effectiveness of using low bar pressure air abrasion to coat bioactive glass particles on to titanium surfaces. Bioactive glass 45S5 (BG 45S5) particles were air abraded at varying clinical distances (2-4 mm) and durations (5, 10, 15 s) as well as abrading at a non-clinical distance of 12 mm for 15 s. Changes in surface roughness parameters (Sa, Sv, Sds, Sdr, Ssk) were measured before and after air abrasion, and the presence of bioactive glass was qualitatively confirmed via SEM-EDX analysis. In general, an increase in clinical distances (2, 3, and 4 mm) and exposure durations (5, 10, and 15 s) at a pressure of one bar resulted in a significant increase in mean surface roughness (Sa). However, the increase was minimal (< 0.2 µm) and suggests that this is effective for coating dental implants in vitro. For chapter 5, strontium containing bioactive glasses were designed and air abraded on to titanium surfaces using the optimum air abrasion parameters investigated in chapter 4. In addition, some glass physical properties and the glass apatite forming ability (bioactivity) was also explored. Three novel melt-derived mixed strontium calcium (Sr/Ca) bioactive glasses based on (SiO2-CaO-P2O5-SrO) with increased strontium for calcium substitution (20, 30, 40%) were designed and formulated. The glasses were characterized extensively by particle size analysis, XRD, FTIR, ICP, SEM-EDX, glass density and glass packing density. XRD and FTIR confirmed that the as received glasses were amorphous. The glass density and glass packing density of the glasses showed a similar trend, with Sr 20 showing the highest values, followed by Sr 40 and Sr 30. This is related to the proportion of strontium for calcium which affects the packing of cations, affecting glass packing density and glass density. The Sr 40 formulation, with nearly equivalent proportions of dissimilar sized cations, demonstrated a clear mixed alkaline earth effect, and hence showed the lowest concentrations of ions released in tris buffer solution. With regards to the glass bioactivity, only the Sr 30 glass formed a mixed Sr/Ca apatite and HCA phase at 3 days. Finally, chapter 6 investigates the pH rise and in vitro cytotoxicity from the mixed alkaline earth glass Sr 40 glass when compared to the well-known 45S5 glass on gingival fibroblast cells (GF). The high sodium oxide content released from the 45S5 glass composition caused a significant rise in pH, which resulted in a significant increase in LDH cytotoxicity at day 1 and day 3 in vitro when compared to normal culture media. However, the reduced and slow ion exchange from the Sr 40 glass resulted in minimal change in Ph, and therefore no LDH cytotoxicity on GF cells in vitro.

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Original languageEnglish
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Award date1 Aug 2020