Development of novel bioactive restorative materials

Abduallah, Diana Mohamed Abdelazeem ORCID: 0009-0000-0812-1083 (2025). Development of novel bioactive restorative materials. University of Birmingham. Ph.D.

Abduallah2025PhD.pdf
Text - Accepted Version
Restricted to Repository staff only until 31 July 2029.
Available under License All rights reserved.
Download (83MB)

Abstract

Subgingival defects/root lesions are becoming increasingly prevalent as life expectancy is increasing globally (WHO) and teeth are retained for longer. These lesions result from attrition/abrasion or caries following the root surface exposure due to gingival recession. Restoring such defects is challenging because of the difficult isolation and the proximity to gingival tissues which could trigger periodontal inflammation due to biofilm formation and/or material toxicity. The current understanding of the interaction between resin-based restorative materials and the soft tissue is still limited. Therefore, the present work aimed to provide a deeper understanding of cellular and bacterial interaction with commonly used resin-based materials and a novel restorative material by performing a wide range of long and short-term bulk/surface characterisation, before correlating these properties -together with the material leaching profile- with epithelial and bacterial attachment to the material surfaces. Thereafter, bioactive surface coats to be applied on commercial materials were proposed and investigated for their ability to improve cellular interaction with the material and exerting an anti-bacterial effect. Viable H400 cell attachment on fresh/aged specimens was determined quantitatively (using the trypan-blue dye exclusion assay) and qualitatively using SEM. The indirect effect of the test materials leachate concentrations on cell attachment to tissue culture wells were also investigated. Attachment of Streptococcus oralis (S. oralis) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) was investigated quantitatively using a direct contact test and morphologically using SEM.
Significantly more viable cells were found attached to the Sr-prototype compared with other materials for both fresh and aged samples. SEM revealed higher number of attached cells on the Sr-prototype which showed more spread and cellular processes extending to neighbouring cells. Spearman’s correlation revealed positive association between the number of viable cells attached
to the material surfaces and pH of the media, surface roughness values, surface Si wt.% and Si4- and Sr2+ ion release. For all materials leachate concentrations, cells exposed to the Sr-prototype leachates showed significantly higher attachment to the cell culture wells compared with other materials. Two-way ANOVA revealed that the interaction between material type and leachate concentration significantly affected viable cell attachment (F(10,144)=38.99, P<0.0001). Spearman’s correlation revealed a strong negative relationship between viable cells attached to the well plates and the Al3+ released from the material (100% leachates) as well as the leachate concentration.
Sr-substituted bioglass coatings (SrC) significantly increased surface roughness and changed the surface of the RMGI as SEM-EDS demonstrated decreased Al wt.%, a higher C-O wt.% ratio and the absence of fluoride on the modified surfaces. Poorly crystalline strontianite was formed on SrC after 48 h immersion in culture media. SrC surfaces did not cause the acidity induced by non-modified surfaces (NC) in the culture media. Significantly more cells were attached to Sr-modified surfaces than to NC. Spearman’s correlation revealed positive correlation between viable cells attached to material surfaces and the media pH, surface roughness and Si4-\Sr2+ ion release while negative correlations were found with the Al3+ released and F surface wt.%. In regard to antibacterial properties, the Sr-prototype caused a significant reduction in both S. oralis and A. actinomycetemcomitans colonies compared with control. Likewise, SrC surfaces caused a statistical reduction in both bacterial species counts compared with NC.
The Sr-substituted bioglass could provide a promising potential as a filler for dental composite/surface coat for root restorations as it promoted epithelial attachment (in both direct and indirect contact tests) which can offer a mechanism to prevent gingival recession and at the same time exert an antimicrobial effect.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):