Physical Properties of Newer Glass-Ionomer Restorative Materials

A new resin-modified glass-ionomer (RMGI) restorative material (Ketac Nano Quick Mix, 3M/ESPE) with nano-technology has been recently introduced in a quick-mix capsule system that does not require trituration.  Objectives: To compare the physical properties of various RMGI and conventional glass-ionomer restorative materials: Ketac Nano Quick Mix (3M/ESPE), Ketac Nano Paste-Paste (3M/ESPE), Fuji II LC (GC), Fuji Filling LC (GC), and Ketac Fill (GC).  Methods: Compressive strength, flexural strength/modulus, fracture toughness, and percent porosity were examined.  Ten specimens were fabricated per group.  For compressive strength testing, cylindrical specimens were prepared in a 6-mm thick x 4-mm diameter stainless-steel mold, light cured all sides (Bluephase 16i, Ivoclar) for 20-seconds each, stored 24-hours at 37^oC / 95% humidity, and loaded to failure in a universal testing machine (MTS).  For flexural strength/modulus and fracture toughness testing, rectangular beam and single-edge notched specimens were created in a 2x2x25mm mold (1-mm preformed notch – fracture toughness), light cured in five over-lapping segments per side, stored as before, and tested in 3-point flexure.  Flexural modulus was determined from the slope of the linear region of the load-deflection curve.  For percent porosity of closed pores, specimens were created in a 2-mm thick x 8-mm diameter stainless-steel mold, scanned with a microtomographic unit (Skyscan 1172) and analyzed with software (CT Analyzer, Skyscan).  A mean and standard deviation were determined per group.  See table below.  A 1-way ANOVA/Tukey was performed per property (alpha=0.05).  Results: Except for percent porosity, significant differences were found between groups per property (p<0.001).  Conclusions: Compared to the other glass-ionomer restorative materials, the new quick-mix capsule Ketac Nano Quick Mix had high strength properties and low flexural modulus with no significant increase in porosity.

Restorative Material	Physical Property Mean (std dev)
Glass Ionomer (Shade A-2)	Compressive Strength (MPa)	Flexural Strength (MPa)	Flexural Modulus (GPa)	Fracture Toughness (MPa m1/2)	Percent Porosity
Ketac Nano Quick-Mix (RMGI, encapsulated)	96.06 (8.57) a	114.90 (17.50) a	8.54 (0.69) c	0.41 (0.09) ab	0.12 (0.07) a
Ketac Nano Paste-Paste (RMGI, hand mixed)	84.77 (22.13) ab	108.72 (7.53) a	8.43 (1.04) c	0.30 (0.05) c	0.08 (0.05) a
Fuji 2 LC (RMGI, encapsulated)	97.14 (10.01) a	68.80 (10.40) b	11.62 (1.25) b	0.48 (0.08) a	0.08 (0.03) a
Fuji Filling LC (RMGI, hand mixed)	69.40 (5.11) bc	55.42 (6.89) b	9.14 (0.83) c	0.33 (0.05) bc	0.07 (0.06) a
Ketac Fill (GI, encapsulated)	54.50 (12.37) c	33.16 (8.11) c	17.46 (2.10) a	0.17 (0.03) d	0.10 (0.07) a
Groups with the same letter per column are not significantly different (p>0.05)

Keywords: Dental materials, Glass ionomers and Physical

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