Relationship between granulometric distribution and compressive strength of heat-treated Toarcian-Bajocian gypsum, Tunisia: implications for casting teeth in molds

  • Fatma Hassaïri-Krid
  • Mongi Felhi
  • Nabil Fattah
  • Ali TliliEmail author
Original Paper


Toarcian-Bajocian gypsum deposits of the Mestaoua formation (southern part of Tunisia) correspond to very thick gypsum layers. The natural gypsum and their heat-treated products were investigated to assess their utilization in dental field (cast plaster into molds for dental prosthesis). XRD data show that the Mestaoua sample (GMes) constituted of gypsum. However, the commercial product (PXETD) is made up of bassanite. Powder X-ray diffraction combined with chemical and infrared analyses reveals that heat-treated GMes samples at different temperatures (200 °C, 220 °C, 240 °C, 260 °C) are dominantly bassanite with minor amounts of anhydrite, particularly, in the samples heated at 240 °C and 260 °C. The data obtained revealed that the sample heated at 220 °C and 240 °C are distinguished by satisfactory values of compressive strength, which are close to the value observed for a commercial product, and are suitable for use in dentistry. The slight decrease in the compressive strength is commonly due to the less abundant water molecules and the two divergent modes of particle distribution, which enhance pore space. Bulk properties of the sample heated at 240 °C are generally appropriate for use as a material to prepare molds in dental fields, as confirmed by the casting of plaster into mold teeth, where teeth revealed clearly steaks and showed even small details.


Gypsum Bassanite Mold teeth Compressive strength Particle distributions 



The authors are thankful to the Engineers of Research Center of Métlaoui for XRD analysis. We thank Abdelfattah Affes for compressive strength measurement and Hafedh Gargouri for laser granulometry analysis. We are very thankful to Mr. Ridha Krid (head of dental prosthesis laboratory) for making autoclave and casting teeth in molds.

Funding information

This work was supported by the “Laboratoire Géoressources, Matériaux, Environnement et Changements Globaux, Département des Sciences de la Terre, Faculté des Sciences, Université de Sfax Tunisie.”


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Copyright information

© Saudi Society for Geosciences 2019

Authors and Affiliations

  • Fatma Hassaïri-Krid
    • 1
  • Mongi Felhi
    • 2
  • Nabil Fattah
    • 3
  • Ali Tlili
    • 1
    Email author
  1. 1.Department of Earth Science, Faculty of Science of SfaxSfax UniversitySfaxTunisia
  2. 2.Department of Geological Engineering, National School of Engineers of SfaxUniversity of SfaxSfaxTunisia
  3. 3.Gafsa Phosphate Company, Research Center Metlaoui 2130GafsaTunisia

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