• Niyom Thamrongananskul D.D.S., M.Sc.D. (Prosthodontics), Ph.D. (Oral Biology)
• Natpaphat Watanasomsiri D.D.S.
• Janejira Thirawat D.D.S., M.Sc.D. (Endodontics), M.S. (Health Development)

Objective To study the diametral tensile and compressive strengths of newly developed zinc
oxide-calcium sulfate based temporary filling material.

Materials and methods The reinforcing copolymer PMMA-PS were performed by altering the ratio
of poly (methylmethacrylate) and polystyrene as 1:1, 1:2, 1:3 and 1:4 in the copolymerization process.
The copolymers were then mixed with zinc oxide, calcium sulphate, and other materials that provided
4 formulas and divided into 4 groups. Cavit^® was used as a control group. Fifteen specimens from each
group were prepared and measured diametral tensile strength that modified from Darvell. For the
compressive strength test, thirty specimens from each group were prepared and measured according to
the method modified from ISO 3107/2004. The data were statistically analyzed using one-way ANOVA
at p = 0.05.

Results Diametral tensile strength and compressive strengths of all groups of newly developed
temporary filling material were significantly different between groups. Increasing in amount of
polystyrene decreased material strength. In the group prepared with copolymer PMMA-PS ratio 1:1
showed the highest mean of diametral tensile and compressive strengths and it provided strength
significantly higher than Cavit at the 0.05 level of significance.

Conclusion The newly developed temporary filling materials from copolymer PMMA-PS ratio 1:1
had significantly higher diametral tensile and compressive strengths than Cavit^®.

(CU Dent J. 2012;35:157-66)