Tricalcium silicate cements: in-vitro comparative studies of mechanical and biological characteristics of relevance to regenerative endodontics
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Tricalcium silicate cements (TSC), are bioactive ceramic materials with a wide range of clinical applications in the field of “regenerative endodontics”, i.e. tissue engineering concepts applied to regeneration of damaged or lost dental tissue. This broad definition includes both vital pulp therapy (VPT) and regenerative endodontic procedures (REP) in immature permanent teeth with necrotic pulps. Both procedures involve direct contact between stem cells and TSC: the ensuing interaction is an essential determinant of regeneration and/or repair. It is therefore important to determine the bioactivity and biocompatibility properties of TSC. In REP moreover, the application of TSC should take into account potential mechanical effects on teeth at greater risk of fracture because of the thin dentinal walls. In this thesis three commercially available TSC were compared: White MTA-Angelus (MTA), Biodentine and TotalFill BC Root Repair Material PUTTY (TotalFill). The surface microhardness of MTA, Biodentine and TotalFill was evaluated by the Vicker’s Hardness Test. Biodentine showed the highest microhardness whereas TotalFill, which failed to achieve a measurable level, had the lowest. Based on the Vicker’s test results, the potential effect of MTA, Biodentine and TotalFill on tooth resistance to fracture was investigated. The aim of Study 1 was to compare the fracture resistance of immature teeth treated with REP and MTA, Biodentine or TotalFill applied to the cervical area. The study utilized an acknowledged bovine tooth model. The teeth were prepared to simulate immature permanent teeth, then treated with REP and tested for fracture resistance. No differences in fracture resistance were observed in relation to the three TSC tested. Cellular responses to MTA, Biodentine and TotalFill were evaluated and compared in cell culture experiments. Cell proliferation was assessed by MTT assay and osteogenic/angiogenic/ inflammatory responses were assessed with qRT-PCR, ELISA, ALP quantification and Alizarin red staining. In Study 2 the effect of TSC on human bone marrow stem cells (hBMSC) was investigated. Compared to MTA and TotalFill, Biodentine had the least inhibitory effect on hBMSC proliferation. The osteogenic and angiogenic responses to the materials varied. Biodentine and TotalFill induced earlier changes at gene level. All TSC induced mineralization after 14 days, with MTA possibly demonstrating the greatest eﬀect. In Study 3 the effect of TSC on human dental pulp stromal cells (hDPSC) was investigated. Biodentine exhibited the least inhibitory effect on proliferation and induced upregulation of most osteogenic markers. TotalFill had an anti-inflammatory effect, expressed as downregulation of IL6. Moreover, TotalFill induced increased gene expression and production of VEGFA and had a long-lasting effect on the inhibition of ALP production. The results indicate that although the TSC tested tend to be used interchangeably in clinical practice, these materials have not only different mechanical properties but also different biological effects. The microhardness levels of TSC differed, but there were no associated differences in fracture resistance. With respect to cellular responses, Biodentine was the most inert. It had the least effect on cell proliferation and induced pronounced expression of osteogenic markers in both hBMSC and hDPSC. TotalFill exhibited enhanced angiogenic and anti-inflammatory effects on hDPSC. The results of these studies have potential clinical implications and further investigation is therefore warranted.
Består avPaper I: Mohamed Raouf W. Ali, Manal Mustafa, Asgeir Bårdsen, Athanasia Bletsa. Fracture resistance of simulated immature teeth treated with a regenerative endodontic protocol. Acta Biomater Odontol Scand. 2019; 5(1): 30–37. The article is available at: https://hdl.handle.net/1956/23208
Paper II: Mohamed Raouf W. Ali, Manal Mustafa, Asgeir Bårdsen, Athanasia Bletsa. Tricalcium silicate cements: osteogenic and angiogenic responses of human bone marrow stem cells. Eur J Oral Sci. 2019 Jun;127(3):261-268. The article is available in the main thesis. The article is also available at: https://doi.org/10.1111/eos.12613
Paper III: Mohamed Raouf W. Ali, Manal Mustafa, Asgeir Bårdsen, Maryam Alizadeh Gharaei, Inge Fristad, Athanasia Bletsa. Differential Responses of Human Dental Pulp Stromal Cells to Bioceramic Materials: a comparative in-vitro study. Full text not available in BORA.