Determination of Fracture Toughness of Provisional Dental Materials

Objectives:   To determine and compare the fracture toughness of five provisional dental materials. 

Methods:   Five groups of ten samples each of provisional materials were tested in this study. The samples were made using a stainless steel mold 2 mm in height, 4.95 mm in width, and 25 mm in length.  After 24 hours of polymerization,  a notch (2.6 ± .05 mm) was inserted into the middle of each sample using a separating disc (thickness 320 µm) attached to an immobilized low speed handpiece .  Microscope examination was used to observe any defects.  The three-point bending test was performed using a universal testing machine (Instron, 5566A) at a cross-head speed of 1mm/min (load cell 500 N).   The notch was positioned centrally beneath the contact and the distance between the two supports was 20 mm. The radius of each support was 1 mm.

The fracture toughness (K_1C) was calculated according to ISO 13586.  The Kolmogorov-Smirnov test was used to determine normal distribution and the homogeneity of the samples was checked using the Levene test.  A one-way ANOVA was used to test the mean fracture toughness between groups.  Statistical significance was predetermined at level p<0.05.

 

Results:  

Group (n=10)	Material	Mean Fracture Toughness (MPa ∙ m0.5)
1	Structur Premium (Voco)	1.36 ± .14b
2	Protemp Plus (3M)	1.66 ± .22c,d
3	Luxatemp (DMG)	1.05 ± .11a
4	Luxatemp Ultra (DMG.)	1.54 ± .17b,d
5	Experimental (Dentsply Caulk)	1.35 ± .17b

 

Conclusions:   Group 3 exhibited a statistically lower resistance to crack propagation than all other groups, whereas Group 2 exhibited a statistically higher resistance than Group 1, Group 3, and Group 5.  No statistical difference is evident between Groups 1, 3, and 5.