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      Comparative evaluation of diametral tensile strength of phosphate-bonded investment (ringless) material by using air-drying method, conventional hot air oven, microwave oven, and combination of microwave and conventional oven: An in vitro study

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          This study evaluated and compared the diametral tensile strength (DTS) of phosphate-bonded investment (PBI) material (ringless) used in removable cast partial denture fabrication.

          Settings and Design:

          Comparative - Invitro study.

          Materials and Methods:

          The PBI material, Wirovest used in this study was subjected to four different drying methods. A total of 80 specimens were prepared in a cylindrical form; 20 specimens were air dried for 2 h, 20 specimens were dried in a conventional oven at 230°C for 1 h, 20 specimens were dried in microwave oven at 600 W for 10 min, and remaining 20 specimens were dried first in microwave oven and then in conventional oven. The dried specimens were tested at 2-h interval for diametral compression at a crosshead speed of 0.5 cm/min.

          Statistical Analysis Used:

          Pairwise analysis.


          The microwave drying technique and drying by combination method resulted in greater DTS, respectively.


          Within the limitation of this study, PBI specimens dried in microwave oven at 600W for 10 min increased the diametral strength and are also a time-saving procedure.

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          Most cited references 25

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          Effect of microwave oven drying on surface hardness of dental gypsum products.

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            Investigation on the compressive strength of several gypsum products dried by microwave oven with different programs.

            Different programs in a microwave oven were selected to dry several gypsum products. A type III dental stone (Moldano), a type IV high-strength dental stone (Glastone) and a type III partial denture casting investment (Multi-vest) were selected. Specimens of the products were dried by microwave radiation set at the lowest and highest power levels for 5 and 15 minutes. The dried specimens were tested at intervals of 2, 4, 24, and 48 hours for compressive strength. Specimens dried in ambient room air were used as the control group. A statistical analysis of the test results was performed with Student's t-test at p < or = 0.05 level. Microwave radiation at the highest power level resulted in a decrease in the compressive strength of type IV dental stone (Glastone), whereas the values of the other gypsum products did not differ at any time interval from values attained for the air-dried specimens. The 2-hour low power test of the investment (Multi-vest) had a higher compressive strength than the air-dried specimens after 24 hours.
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              • Article: not found

              Microwave oven drying of artificial stone.

              The compressive strength of various artificial stones were tested using air, oven, and microwave oven drying methods to compare the three for drying refractory casts. The microwave oven can be used for rapid drying of refractory casts in removable partial denture construction. However, it should not be used for drying extremely wet casts.

                Author and article information

                J Indian Prosthodont Soc
                J Indian Prosthodont Soc
                The Journal of the Indian Prosthodontic Society
                Wolters Kluwer - Medknow (India )
                Jul-Sep 2019
                : 19
                : 3
                : 248-254
                Department of Prosthodontics, V.S.P.M's Dental College and Research Centre, Nagpur, Maharashtra, India
                Author notes
                Address for correspondence: Dr. Akhil Ghanshyamdas Rathi, 401, Shubham Enclave Rahate Colony, Nagpur - 440 022, Maharashtra, India. E-mail: drakhilrathi@
                Copyright: © 2019 The Journal of Indian Prosthodontic Society

                This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.

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