Glass-ceramics/composites with interesting microstructure/properties for dental restorations
|Starts:||12:30 15 Nov 2019|
|Ends:||13:30 15 Nov 2019|
|What is it:||Seminar|
|Organiser:||Faculty of Biology, Medicine and Health|
|Speaker:||Professor Bikram Basu|
Please register via the Eventbrite link below and add it to your calendar if you wish to attend.
The current choice of glass ceramic materials for ceramic restorations range from heat pressed leucite (IPS Empress), lithium disilicate glass ceramics (IPS emax.Press) to feldspathic porcelains
(VITA Mark II) and machinable IPS emax.CAD. In this talk, I will present the results of our research on SiO2-MgO-Al2O3- K2O-B2O3-F glass-ceramic system to highlight the following aspects:
a) how crystals with two different characteristic morphologies, i.e. interlocked, randomly oriented mica plates (‘house-of-cards’ morphology) or spherulitic-dendritic like crystal morphology
can develop, as a result of adopting two sets of heat treatment experiments, and b) how ZrO2 reinforcements to glass ceramics can enhance the fracture resistance.
An important result is that a maximum of around 70% of spherulitic-dendritic like crystal morphology can be obtained after heat treatment at 1000oC for 24 hours, while a lower
amount (~ 58 %) of interlocked plate like mica crystals is formed after heat treatment at 1040oC for 4 hours. The activation energy for crystal nucleation and Avrami index is computed
to be 388 kJ/mol and 1.3 respectively, assuming Johnson-Mehl-Avrami model of crystallization. The bioactivity will be discussed in reference to changes in pH, ionic conductivity and ionic
concentration of artificial saliva (AS), following in vitro dissolution experiments. Furthermore, the presence of (Ca, P, O)-rich mineralized deposits on the leached glass-ceramic surface as
well as the decrease in Ca+2 ion concentrations in the leaching solutions (compared to that in initial AS solution) provide evidences of the moderate bioactivity or mild biomineralisation
property. Also, the cytocompatibility property (cell vitality, ALP and osteocalcin assay) of the selected glass ceramics using human osteoblast cells will be presented.
Towards the end of the presentation, it will be shown how the glass ceramics reinforced with 20 % ZrO2, with comparable properties, like the commercially available IPS
emax Press and IPS emax CAD; can be obtained in terms of fracture toughness, hardness and chemical solubility. A spectrum of properties of zirconia toughened mica based
glass ceramic composites can be explored for metal free ceramic inlays, onlays and veneers.
Professor Bikram Basu
Role: IIsc Bangalore
Travel and Contact Information
Lecture Theatre B
Coupland Building 3