Development and Physicochemical Analysis of SrO/Hydroxyapatite Modified Mineral Trioxide Aggregate Synthesized from Calcium Carbonate and Tetraetyl Ortosilicate as an Endodontic Material

Abstract

Mineral trioxide aggregate (MTA) is utilized in endodontics for root fracture repair, apexification, and as a root canal filling material. MTA possesses favorable sealing capability and biocompatibility. However, its clinical performance is limited by low mechanical performance at the early stage of hydration. In the present study, the limitations of MTA were addressed by incorporating SrO and hydroxyapatite (HA) into its formulation. MTA was synthesized using calcium carbonate as the calcium oxide precursor and tetraethyl orthosilicate as the silica source. The synthesis employed a sol–gel method followed by a solid-state calcination process at 1000 °C. The hydration of material was performed with water at a powder-to-liquid ratio of 3:1 (w/v). The study found that incorporation of 5% SrO into MTA enhanced the formation of calcium silicate hydrate (C–S–H) phases, as evidenced by increased X-ray diffraction peak intensity at 2θ = 29.3°. This modification also increased the compressive strength after seven days of hydration, sustaining an alkaline pH environment. MTA composite containing 5% SrO combined with 6% HA further amplified the intensity of C–S–H formation. Morphological analysis showed that the development of hydration reaction reduced porosity and voids, yielding a more regular microstructure. An increase in HA concentration leads to a decrease in the pH of the material, trending toward neutrality by days 7 and 28. Such pH modulation can reduce the localized acidity and thereby minimize inflammatory responses when the material is applied in biological settings.