Evaluation of W/P Ratio, Setting Time and Compressive Strength of Dental Stone Type III and IV Marketed in Jakarta

Abstract

Dental gypsum products in Indonesia are mainly imported from countries with non-tropical weather. Mostly, these gypsum products marketed in Jakarta are without adequate packaging, data or manipulative and maintenance instructions, which can cause misuse & abuse in the materials manipulation and handling. The purpose of this study was to evaluate the W/P ratio, setting time and compressive strength of dental stone type III and IV in relation with room temperature condition and relative humidity in Jakarta, Indonesia. One hundred and eighty dental stone Type III (unlabelled Blue Hard Stone; Giludur, Germany: Moldaroc, Germany) and Type IV (New Fujirock, Japan; Glastone, USA; unlabelled Quickstone) specimens were made as recommended by ISO 6873-1983 for setting time (with Vicat needle) and compressive strength determination (Shimadzu mechanical testing machine) with W/P ratio variables of 0.28; 0.29; 0.30 for Type III and 0.20; 0.21; 0.22 for type IV. The tests were conducted in 2 rooms with different temperature and humidity and with and without air-conditioned. Statistical analysis using T-test. The results shows that the increasing of W/P ratio will decrease the dental stone type III and IV setting time. Jakarta condition of high room temperature and relative humidity significantly shorten the setting time of Moldaroc and New Fujirock. The rest of the stones were reduced statistically insignificant. It can be concluded that the temperature and humidity in Jakarta can influence the setting time and compressive strength of dental stone type III and IV. However, since the setting time and strength values are still within the ISO standard, these stones can be accepted and used in Indonesia.