| Background Due to the development of the biological ceramic materials and the root canal filling technology, the emergence of biological ceramic material iRoot SP fits the monoblock concept of root canal filling integration. Root canal three-dimensional filling focuses on root canal filling material melting into root,which bears chewing force together.It not only reduces the root canal microleakage, but also is advantageous to the long-term retention of tooth. To form three-dimensional root canal filling, root canal filling material must meet some conditions: on the one hand the material has good adhesive ability,on the other hand the elastic modulus shoud be close to dentin. The monoblock filling system Proposed in the literature mainly includes:GuttaFlow filling system, Resilon/Epiphany (R/E) system, Activ GP system (glass ion filling system). The traditional root canal filling materials due to these factors such as physical and chemical properties are difficult to form three-dimensional root canal filling.iRoot SP is a new type of excluding aluminum silicate bioceramics materials, which has good adhesion, sealing ability, biocompatibility and antibacterial, etc. Compared with other root canal sealers itself has specific advantages:(1) injecting into the root canal without modulation directly. (2) using 20 percent(by volume) water in dentine to initiate the setting; (3)forming hydroxyapatite in the process of reaction, which can create a bond between dentine and the filling material; (4) with good liquidity, small grain size, particle diameter is less than 2 microns, the diameter of dentinal tubule is about 3～4 microns near pulp, about 1 micron near the surface,these characteristics benefit dentin permeability of iRoot SP; (5) hydrophilic, without contraction and expansion after curing hard solid; (6) iRoot SP can fill the root canal alone or in combination with the gutta-percha point.Based on many domestic and foreign researches,we have found that iRoot SP has good physical and chemical properties and it has the conditions to form three-dimensional root canal filling.At present, there were few researches about iRoot SP used directly filling the root canal without gutta-percha point.The study based on the research methods of the scholars at home and abroad, is aimed at evaluating the sealing ability,permeability and fracture resistance of iRoot SP,providing a new material and a new filling method for root canal filling.Objectives To evaluate the sealing ability of iRoot SP in root canal obturation with a quantitative method using glucose and micro-computed tomography (micro-CT), the penetration depth into the dentinal tubules of iRoot SP by scanning electron microscopy(SEM) and the fracture resistance of roots filled with iRoot SP.Materials and Methods 1. Sealing ability of iRoot SP (a bioceramic material) in root canal three-dimensional obturation, an in vitro study. Fifty-five mandibular premolars with single root canal were decoronated to obtain 12-mm root segments. The root canals were instrumented using Protaper Files prepared to 30#. The roots were randomly divided into 3 experimental groups A,B and C(n=15),a negative control group D(n=5),and a positive control group E (n=15). The root canals of group A were directly filled with iRoot SP without a gutta-percha point. The root canals of Group B were filled with iRoot SP using continuous wave of condensation technique.The root canals of Group C were filled with AH Plus(root canal sealer) using continuous wave of condensation technique. Models were built to measure leakage with the quantitative method using glucose. The concentration of glucose leaked from the crown to the root was measured with a glucose oxidase-peroxidase method on the 1st day and in the 1st,2nd,3rd,4th,5th and 6th weeks during the experimental period. Voids in the root canal fillings were assessed using cross-section images from micro-CT scanning.2. Penetration of dentinal tubules by root canal sealer iRoot SP(a bioceramic material) in vitro.Twenty-eight mandibular premolars with single canal were decoronated to obtain 12-mm root segments. The root canals were instrumented using Protaper Files prepared to 30#.Smear layer was removed by irrigating the root canals with 17% ethylene diaminetetraacetic acid(EDTA) solution,followed with 5.25% NaCLO. The roots were randomly divided into 2 experimental groups A, B(n=12), and a control group C(n=4). The root canals of group A were filled with iRoot SP using the continuous wave of condensation technique.The root canals of group B were filled with AH Plus(root canal sealer) using the continuous wave of condensation technique.Specimens of group A and group B were sectioned in 3 levels with hard tissue cutting grinding system transversely,which distanced from the apex were 3mm,6mm and 9mm,then measured the sealers penetration depth into the dentinal tubules under scanning electron microscope (SEM). Specimens of group C were longitudinally sectioned and viewed under scanning electron microscope (SEM)3. Fracture resistance of roots obturated with iRoot SP(a bioceramic material) by a universal testing machine.Fifty-five mandibular premolars with single canal were decoronated to obtain 12-mm root segments. Roots were randomly divided into 3 experimental groups A,B and C(n=15), and a control group(n=10). Control group 10 roots were left unprepared and unfilled.The experimental groups root canals were instrumented using Protaper Files prepared to 30#.The root canals of group A were directly filled with iRoot SP without a gutta-percha point. The root canals of Group B were filled with iRoot SP using continuous wave of condensation technique.The root canals of Group C were filled with AH Plus(root canal sealer) using continuous wave of condensation technique.Evaluate the density of samples after root canal filling with X-ray films.All samples were sealed with light-cured glass ionomer,then all samples were kept at normal temperature with 10% formalin for 2 weeks.Then all samples were placed on a universal testing machine and loaded until fractured.Results 1. During the 1st to 4th weeks, there was almost no glucose leakage in the three experimental groups,and the average daily leakage concentration was less than 0.18mmol/L. In the 5th and 6th weeks, there was glucose leakage(>0.18mmol/L) in group C,and there were significant differences between group C and group A,as well as differences between group C and group B(P<0.05). Micro-CT scanning found that voids were formed only at the apical apart (1mm) in group A,while voids are formed in the root canals in group B and group C.2. The penetration depth of group AH Plus was significantly higher than that of group iRoot SP in the apical third of the root canal walls(P<0.05). There was no significant difference in the coronal and middle third of the root canal walls(P>0.05).The smear layer was removed mostly completely in the coronal and middle third of the root canal walls and was removed partly in the apical third of the root canal walls.3. The highest fracture resistance was recorded for both the control group and group A (iRoot SP) with no significant difference between them(P>0.05), whereas the lowest value was recorded in group B and group C.There were significant differences in fracture strength between group A and group B (P＜0.05)Conclusions 1. iRoot SP as cement paste has excellent sealing ability in root canal three-dimensional obturation, and can realize primary monoblock without damage to periodontal tissue.2. iRoot SP and clinical commonly used AH Plus both has the ability to penetrate into the dentinal tubule,it can be concluded that the dentinal tubule penetration of AH Plus is significantly greater than that of iRoot SP.The ability to penetrate of AH Plus and iRoot SP was stronger in the coronal and middle third than in the apical third of the root canal walls. The dentinal tubule penetration of root canal sealers is affected by their physical and chemical properties and smear layer.3. iRoot SP (bioceramic-based sealer) is a promising sealer in terms of increasing resistance to the fracture of endodontically treated roots.It can realize primary monoblock,which excluds the wedging forces of the spreaders during lateral compaction and vertical compaction during root canal filling. |
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