Purpose: This study was conducted to evaluate the effect of selected disinfectants incorporated in the liquid of dental stones on material strength properties with the aim of developing a material with acceptable mechanical properties. Materials and Methods: Two types of dental stone (types III and V) were mixed with aqueous solutions of 0.525% sodium hypochlorite, 0.1% and 10% povidone-iodine, and 2% glutaraldehyde, and with water as a control. The liquid/powder ratios recommended by the manufacturer were used. These materials were subjected to further modification by adding a mixture of 1.0% gum arabic and 0.132% calcium hydroxide to the hemihydrate powders before mixing with the disinfectant solutions at 2 different liquid/powder ratios for each. Both the regular and the modified materials were tested for compressive and diametral tensile strength after 1 hour and 1 week from the start of the mix. The structure of set materials was determined by scanning electron microscopy examination of fracture surfaces. Results: The disinfectants often reduced the strength of both types of dental stone. However, using either 0.1% povidone-iodine or 0.525% sodium hypochlorite resulted in strength values comparable with that of the control. The addition of gum arabic and calcium hydroxide helped reduce the mixing liquid/powder ratios, improving the strength properties of the disinfected materials. Conclusions: Chemical disinfectants reduce the strength of dental gypsum when used as mixing water substitutes. Gum arabic and calcium hydroxide additives permit a lower liquid/powder ratio and can help offset this weakening.
Bibliographical noteFunding Information:
1Visiting Assistant Professor, Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota School of Dentistry, Minneapolis, MN, and Assistant Lecturer of Dental Materials, Faculty of Dentistry, Mansoura University, Egypt. 2Professor, Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota School of Dentistry, Minneapolis, MN. 3Senior Research Associate, Division of Biostatistics and School of Dentistry, University of Minnesota, Minneapolis, MN. Accepted May 28, 2002. Supported in part by a grant from the Government of the Arab Republic of Egypt and in part by NIDCR grant P30-DE 09737. This abstract was presented by the second author at the International Association of Dental Research/American Association of Dental Reasearch annual meeting, April 8, 2000, in Washington DC (abstract 3229). Correspondence to: Dr. Edward C. Combe, 16-212 Moos Tower, 515 Delaware St. SE, Minneapolis, MN 55455. E-mail: email@example.com. Copyright © 2002 by The American College of Prosthodontists 1059-941X/02/1103-0003$35.00/0 doi:10.1053/jpro.2002.126860
- Calcium hydroxide
- Compressive strength
- Diametral tensile strength
- Gum arabic