In vitro evaluation of the effects of different bone grafts on the surface microhardness of NeoPUTTY and MTA Angelus

The interaction between bone grafts and retrograde filling materials may influence the physicomechanical properties of calcium silicate-based biomaterials used in endodontic surgery. This in vitro study evaluated the effects of allograft, xenograft, and dentin graft on the surface microhardness of NeoPUTTY and mineral trioxide aggregate (MTA) Angelus. The null hypothesis was that the type of MTA, the type of graft, and the interaction between these two factors would have no statistically significant effect on surface microhardness. Eighty custom-made plastic cylinders were used. Specimens were divided into two main groups filled with NeoPUTTY (n = 40) or MTA Angelus (n = 40). Each group was further subdivided into control (MTA only), allograft, xenograft, and dentin graft subgroups (n = 10). Bone grafts were placed in direct contact with the apical surface of both NeoPUTTY and MTA Angelus. All samples were incubated in Hank's Balanced Salt Solution (HBSS) at 37 °C for 14 days. Surface microhardness was measured using the Vickers microhardness test. Data were analyzed using two-way ANOVA and Tukey's post hoc test (p < 0.05). Graft type significantly affected surface microhardness (p < 0.001) under the conditions tested, whereas the main effect of MTA type was not significant (p > 0.05); however, a significant interaction between MTA type and graft type was observed (p < 0.001). The highest microhardness value was observed in the NeoPUTTY-xenograft group (70.21 ± 4.25 HV). No significant differences were found between NeoPUTTY and MTA Angelus in the control and allograft groups. Dentin graft groups exhibited the lowest microhardness values (NeoPUTTY: 21.49 ± 5.54 HV; MTA Angelus: 33.30 ± 5.42 HV). Additionally, microhardness was significantly lower in the dentin graft group combined with NeoPUTTY compared with MTA Angelus (p < 0.05). Within the limitations of this in vitro study, different bone graft materials were associated with differences in surface microhardness of MTA-based retrograde filling materials. The interaction between graft type and filling material may contribute to variations in surface microhardness under direct-contact experimental conditions and should be interpreted with caution.