Assessment of Influence of Contact Time between Alginate and Type III Dental Stone on Properties of Cast Model: An in vitro Study.

INTRODUCTION: Alginate is a versatile, irreversible hydrocolloid impression material, which is cost-effective and forms an essential component in dental practice. For elevating the hardness of the cast models, hardeners are combined with stone. Hence, we planned the present study to evaluate the impact of altering the time of contact between alginate and stone after various interim periods. MATERIALS AND METHODS: The present study included the assessment of impact of time of contact between alginate and stone by the construction of 90 casts using a cylinder model. Two bisecting lines were marked and were named as y and y'. These lines were used for testing the dimensional stability. Using chemically cured acrylic resin, the construction of ten special trays was done. All the impression casts were randomly divided into two study groups, with 45 casts in each group-group I: control group, casts were removed after 60 minutes; group II: study group, casts were removed after 9 hours. A digital caliper was used for measuring the dimensional stability of the cast. All the data were collected and analyzed. RESULTS: In the specimens of the control group (group I) and the study group (group II), the mean dimensions from y to y' were found to be 17.54 and 17.95 respectively. The mean reading of hardness in the control group and study group was found to be 0.59 and 0.20 respectively. In groups I and II, the number of specimens showing clarity of two lines (X and X") was 0 and 5 respectively. CONCLUSION: There was no change in the dimensional stability of the dental stone model when the contact time was increased. CLINICAL SIGNIFICANCE: Within certain limits, the contact time between alginate and stone can be altered without significantly altering the properties of the cast.

Levels of airborne particles resulting from handling alginate impression material.

The levels of airborne particles emanating from handling alginate impression powders have been surveyed. The concentrations of powders, lead and silicious particles in the aerosol have been measured after thoroughly shaking the containers before opening. The decrease of the powder concentration in the ambient air as a function of time has been estimated. The efficiency of face masks to protect against powder exposure has been investigated.