In vitro evaluation of the effects of different bone grafts on the surface microhardness of MTA-based retrograde fillings

The aim of this in vitro study is to compare the effects of three different bone graft materials (allograft, xenograft, and dentin graft) on the surface microhardness of two different retrograde filling materials (MTA Neoputty and MTA Angelus). In the study, 80 specially manufactured plastic cylinders with standardized inner diameters and heights were used. The cylinders were divided into two main groups and filled with MTA NeoPutty (n=40) and MTA Angelus (n=40). Each main group was divided into four subgroups (n=10): control (MTA only), allograft, xenograft, and dentin graft subgroups. Bone grafts were placed in direct contact with the MTA surface. The specimens were incubated in HBSS (Hank's Balanced Saline Solution) at 37°C for 14 days. Surface microhardness was measured using a Vickers microhardness tester. Data were analyzed using two-way ANOVA and Tukey's post-hoc tests, statistical significance was set at (p<0.05). Analyses showed that graft type had a statistically significant effect on microhardness (p<0.001), and MTA type had no significant main effect (p>0.05), however the MTA type and graft type interaction was significant (p<0.001). Among the groups, the highest microhardness value in MTA NeoPutty was measured in the xenograft group (70.21 ± 4.25 HV), and this difference was found to be statistically significant (p<0.05). In contrast, the dentin graft group showed the lowest microhardness values in both MTA NeoPutty (21.49 ± 5.54 HV) and MTA Angelus (33.30 ± 5.42 HV), and this decrease was statistically significant (p<0.05). Additionally, the microhardness value of the dentin graft group combined with MTA NeoPutty was found to be significantly lower compared to the dentin graft group combined with MTA Angelus (p < 0.05). Different bone grafts significantly affect the surface microhardness of MTA formulations. Clinically, since graft material selection can alter the hardness properties of the retrograde filling material, this effect should be considered in surgical planning. Keywords: Apical Resection, Bone Graft, Dentin Graft, Mineral Trioxide Aggregate (MTA),Vickers Microhardness Test