| OBJECTIVE: To understand the biological activity of a new bioceramicbased root canal sealer,the iRoot SP sealer.There may be two forms of iRoot SP in the root apex based on the clinical application of the iRoot SP sealer with the single-cone technique:(1)The iRoot SP sealer and gutta percha exist simultaneously;(2)only the iRoot SP sealer exists,and the two modes were simulated in vitro to observe the crystal formation and crystal composition of the iRoot SP in different liquids to assess its biological activity.METHODS: Permanent teeth removed due to periodontal disease or orthodontic treatment were collected.After the root canals were cleaned and formed,they were filled with different materials according to the research design.After filling,the root canals of different teeth were sectioned to determine their status according to the following four groups:(1)root canals filled with the iRoot SP sealer and a single-cone gutta purcha.Cross-sectional root canals were selected as the sealer wrapping the gutta purcha of a single tooth(SPGP group);(2)cross-sectional root canals filled with iRoot SP alone(SPS group);(3)crosssectional root canals filled with mineral trioxide aggregate(MTA)alone(MTA group);and(4)the root canal left empty without filling after root canal preparation(blank control group).The root blocks were divided and soaked in simulated body fluid(SBF)or distilled water for 7 days.The surface morphology and chemical composition of the root blocks were analyzed using scanning electron microscopy(SEM)and energy dispersive X-ray spectroscopy(EDS).RESULTS: The surface morphology of the root cross-sections differed according to the filling material used in the root canals.After SBF treatment,highpower electron microscopy showed spherical crystals with similar shapes,with a uniform and orderly arrangement on the surface of the iRoot SP and MTA in the SPGP,SPS,and MTA groups.The crystals formed on the surface of the iRoot SP and MTA materials were consistent in shape and size with those formed on the dentin surface of the root section.Moreover,the dentin showed a continuous and orderly arrangement.In the SPGP group,the crystals on the iRoot SP surface were interrupted at the junction with the gutta purcha and did not extend to its surface.No crystals were observed on the surface of the gutta section.The surface of the blank control group showed amorphous sediment.After treatment with distilled water,crystal formation was observed on the surface of the SPGP and SPS groups;however,their morphology and distribution were irregular.Polygonal crystals approximately 10–15 μm in diameter were scattered on the surface of the filling and tooth tissue of the MTA group,with no crystal formation observed on the gutta purcha surface in the SPGP group.The crystals on the iRoot SP surface did not extend to the gutta surface,and there was an obvious boundary between the dental glue and iRoot SP.The surface morphology of the blank group treated with distilled water did not differ significantly from that of the untreated group.No crystal or sediment formation was observed.EDS analysis showed the same crystal element composition on the discontinuous surface of the SPGP,SPS,and MTA groups after SBF treatment,higher calcium and phosphorous contents,and comparable calcium and phosphorous molar mass ratios(1.35,1.40,and 1.35,respectively).After treatment with distilled water,the surface element composition of each group was the same;however,the molar ratios of calcium to phosphorus differed significantly.The composition of the amorphous substance on the surface of the blank control group treated with SBF was similar to that of the SBF solution,containing sodium,magnesium,calcium,phosphorus,chlorine,and a few other elements.CONCLUSION: The crystal formation phenomenon of the iRoot SP sealer in the SBF solution suggested that the material surface results in biological activity including apatite crystal formation under appropriate in vitro conditions,which is beneficial for the healing of apical lesions. |
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