Effect of the incorporation of hydroxyapatite on the diametral tensile strength of conventional and hybrid glass ionomer cements.

The objective was to evaluate the effect of the incorporation of calcium hydroxyapatite particles (HAp) in the diametral tensile strength of a conventional type II glass ionomer (GC Gold Label 2) and a resin-modified glass ionomer cement (GC Gold Label 2 LC R). Two experimental HAp (E1HAp or E2HAp) were synthesized and characterized using X-ray diffraction and Confocal Raman spectroscopy. Both HAp were added into the powder of a conventional or resin-modified glass ionomer cement at 5 or 10 wt.%. A commercial HAp (CHAp) was used as reference material. For each glass ionomer cement, a group without the incorporation of HAp was used as a control. A universal testing machine was used for the mechanical test. The results were analyzed through a two-way ANOVA test followed by a complementary Tukey test. For all analyzes, the level of significance was set at α = 0.05. The average particle size for E1Hap was 15 µm, E2HAp was 35 μm and for CHAp was 1 µm. For conventional GIC, the addition of 10% E1HAp and 5% CHAp significantly increased the diametral tensile strength values (p ≤ 0.005). On the other hand, for the resin-modified GIC, except for the 5% E2HAp group, all experimental groups significantly reduced the values of diametral tensile strength (p ≤ 0.007). The addition of HAp improved the mechanical properties only for the conventional glass ionomer cement.