In case of ceramics the use of indentation to estimate its toughness owes its origins to pioneering work of S. Palmqvist (1962) on metal carbides using vickers indentor. The basic procedure since has been largely unchanged that of effecting radial cracks in brittle materials such as ceramics under the action of a penetrating vickers indentor. However the direct phenomenological relation of estimating the fracture toughness by measuring the load and the length of the radial cracks (eg. Kc = 1/bo (P*c^(-3/2))) have been replaced by deeper understanding of the crack formation mechanism by characterisiation of the elastic - plastic field using FEM. As a result the procedure has been applied to different classes of ceramics as well as biological material (eg. dental ceramics). A quick search in Google reveals the wide application of the technique. 

Dear Khalid Tayeb ,

yes you can determine the tenacity by measuring the lengths of cracks on the arrested Vickers imprint

there are several formulas

either for radial cracking mode or Palmquist

For this see the articles by K. liang or gilbert fantozzi

see RG hocine osmani, I have some articles

Article: Interaction between indentation cracks in sodalimesilica glass

Malou Z, Hamidouche M, Madjoubi M.A, Loucif K, Osmani H, Bouaouadja N

please find it in the papers below

http://scholar.google.com.au/citations?view_op=view_citation&hl=en&user=L1dSLIIAAAAJ&cstart=20&pagesize=80&sortby=pubdate&citation_for_view=L1dSLIIAAAAJ:Se3iqnhoufwC

http://scholar.google.com.au/citations?view_op=view_citation&hl=en&user=L1dSLIIAAAAJ&citation_for_view=L1dSLIIAAAAJ:9yKSN-GCB0IC

I announce that the determination of tenacity by the technique of indentation is used as comparison of the various parameters: development and treatments

On the other hand, the tests of failure under bending 3 or 4 points on notched samples are more reliable. This technique allows also the characterization at high temperature