| BackgroudsRoot canal sealer is the auxiliary material of the root canal filling materials, which main feature is to fill the gap between the wall and the core material,connect with the core material and fill the palces such as lateral canals, gap areas and apical third of the root,which can not be filled by the core materials. A sealer is a material of the root canal filling which can provide fluid sealing ability.In some ways, a sealer is probably more important than a core material in achieving good results of root canal filling.In recent years, with the advances in the field of materials science,the development of the root canal sealer fit the monoblock concept of modern root canal therapy, This ideal three-dimensional root canal filling not only show the airtightness of the coronal and apical portion of the root canal root canal, but also have a ideal penetration and combination with the root canal wall, Thus forming a diffuse bonding interface of root canal sidewall.First,such diffuse bonding interface and the penetration depth increases the contact area of the root canal filling material and dentin tube, that is increase the bonding area of the entire root canal system, improve the entire root canal system airtightness; The second, the certain penetration depth of the root canal sealers occupation of dentinal tubules, inhibit bacterial colonization into tubule, achieve sterilization capability by closer to the bacteria in the dentinal tubules. The third, the diffuse interface and the penetration depth of the root canal sealers form a seal bolt,it increase the mechanical retention force of the root and the fracture resistance of a root after fillingjudging from the long-term effects,this improve the seal and adaptation between the root filling material and dentin walls of the root canal system. In recent years, different components of the root canal sealer constantly appeared,such as zinc oxide-eugenol-based, calcium hydroxide-based, silicone-based, resin-based and so on. At present, the research on the physical and chemical properties of these root canal sealers in laboratory mainly focuses on the solubility, mobility, X radiopacity, sealing ability, biocompatible, antimicrobial and antibacterial and so on,a hot spot of them is detecting the sealing ability, the detection methods on this regard reported by most experiments are dye infiltration experiments, fluid permeation experiments, bacterial penetration experiment, electrochemical permeation experiments, glucose permeation experiments, the fluorescent penetrant experiments and isotope penetration experiments and so on. In this experiment,it is observed by the scanning electron microscope, based on the depth of root canal sealers penetrate into the dentinal tubules and the width between the root canal wall dentin and sealers, detected the partial sealing ability of the root canal sealer by the most direct evaluation method.Objective:With the scanning electron microscope,the first part in this research was to measure the penetration depth in the dentinal tubule of four sealers which filled the root canals with cold lateral condensation of gutta-percha filling technique in the coronal, middle and apical third of the root canal walls, evaluating them the partial sealing ability of dentinal tubule.The second part was to measure the width of gaps between the sealers and the root canal wall in the apical third of the root canal walls with cold lateral condensation of gutta-percha filling technique, evaluating them adaptation of the root canal wall.evaluating them the partial sealing ability of dentinal tubule. Then provide some references of our rational selection and use these root canal sealers in clinical.Experiment Materials and Methods:Part1:Study on Penetration Depth in the Dentinal Tubules of the four sealers with cold lateral condensation of gutta-percha filling technique1. Fifty single-rooted mandibular premolars were extracted,we do root canalpreparation with the step-back technique.2. Two teeth of them were prepared to observe the dentinal tubular openings by random drawing, the residual samples were randomly divided into four Groups (Group A:Gutta-percha/cortisomol、Group B:Gutta-percha/iRoot SP、Group C:Gutta-percha/AH-Plus、Group D:resilon/Realseal SE).All specimens completed the root canal preparation and obturations with the four sealers using cold lateral condensation of gutta-percha filling technique.3. The specimens were placed in37℃and100%humidity environment for7days,then All specimens were transversely sectioned in three levels,which distance from the apical foramen were2mm,5mm and8mm.4. All specimens were prepared for SEM.5. All specimens were observed and measured the sealers penetration depth in the dentinal tubules in the coronal, middle and apical third of the four sealers with SEM. Part2:Study on adaptation between the four sealers and the root canal wall with cold lateral condensation of gutta-percha filling technique1. The he sealer adaptation to the root canal wall or the tubules was described as follows:Good:The majority of the sections showed no gaps between the sealer and dentin.Reasonable:The majority of the sections showed some small gaps(<1μm) between the sealer and dentin.Poor:The majority of the sections showed many gaps (between1μm and10μm) between the sealer and dentin.No adaptation:The majority of the sections showed no adaptation between the sealer and dentin (gaps>10μm).2. Fifty single-rooted mandibular premolars were extracted,we do root canal preparation with the step-back technique.3. Two teeth of them were prepared to observe the dentinal tubular openings by random drawing, the residual samples were randomly divided into four Groups (Group A:Gutta-percha/cortisomol、Group B:Gutta-percha/iRoot SP、Group C:Gutta-percha/AH-Plus、Group D:resilon/Realseal SE).All specimens completed the root canal preparation and obturations with the four sealers using cold lateral condensation of gutta-percha filling technique.4. The specimens were placed in37℃and100%humidity environment for7days,then All specimens were transversely sectioned in this level,which distance from the apical foramen was2mm.5. All specimens were prepared for SEM.6. All specimens were observed and measure the width of gaps between the sealers and the root canal wall in the apical third of the root canal with SEM. ResultsPart1:The depth of the four sealers penetrate into the dentinal tubules under SEM1. The average penetration depth in the dentinal tubules in the coronal were Group A (33.41±8.55μm), Group B (66.30±24.46μm), Group C (69.82±21.79μm) and Group D (114.10±26.25μm). The penetration depth of Group D was significantly higher than that of others in the coronal of the root canal walls. The penetration depth of Group B and Group C were slightly higher than that of Group A.There was no statistically significant between Group B and Group C.2. The average penetration depth in the dentinal tubules in the middle third of the root canal were Group A (11.67±4.92μm), Group B (25.68±11.01μm), Group C (26.13±11.81μm) and Group D (42.82±13.14μn). The penetration depth of Group D was significantly higher than that of others in the middle of the root canal walls. The penetration depth of Group B and Group C were slightly higher than that of Group A.There was no statistically significant between Group B and Group C.3. The average penetration depth in the dentinal tubules in the apical third of the root canal were Group A (5.13±2.43μm), Group B (6.78±3.00μm), Group C (19.10±7.87μm) and Group D (31.93±10.86μm). The penetration depth of Group D was significantly higher than that of others in the apical of the root canal walls. The penetration depth of Group C were significantly higher than that of Group A and Group B. There was no statistically significant between Group A and Group B. Part2:The width of gaps between the sealers and the root canal wall under SEM1. The average width of gaps between the sealers and the root canal wall in the apical third of the root canal were Group A (25.65±8.54μm), Group B (6.86±2.87μm), Group C (0.97±0.43μm) and Group D (6.46±1.60μm). In the apical third of root canal,the width of gaps in Group C was significantly higher than which in Group A Group B and Group D. The width of gaps in Group B and Group D were significantly higher than which in Group A. There was no statistically significant between Group B and Group D.Conclusions:1. With the cold lateral condensation of gutta-percha filling technique, methacrylate resin-based sealer Realseal SE showed the deepest permeation depth of dentinal tubule in the coronal, the middle third and the apical third of the root canal among the four sealers.2. With the cold lateral condensation of gutta-percha filling technique,resin-based root canal sealer AH-Plus and Realseal SE showed the deeper permeation depth of dentinal tubule than the calcium silicate sealer iRoot SP and zinc oxide sealer Cortisomol in the apical third of the root canal walls.3. With the cold lateral condensation of gutta-percha filling technique,the calcium silicate root canal sealer iRoot SP showed the deeper permeation depth of dentinal tubule than the zinc oxide root canal sealer cortisomol in the coronal, the middle third of the root canal walls.4. With the cold lateral condensation of gutta-percha filling technique,epoxy resin sealers AH-Plus showed the good dentinal adaptation of root canal in the apical third of the root canal walls, and it had the better dentinal adaptation of root canal than the methacrylate resin-based sealer Realseal SE, the calcium silicate sealer iRoot SP and zinc oxide sealer Cortisomol. 5. With the cold lateral condensation of gutta-percha filling technique,the methacrylate resin-based sealer Realseal SE and the calcium silicate sealer iRoot SP showed the reasonable dentinal adaptation of root canal in the apical third of the root canal walls, the difference of dentinal adaptation of root canal of them was not significant.6. With the cold lateral condensation of gutta-percha filling technique,the zinc oxide sealer Cortisomol showed no adaptation dentinal adaptation of root canal in the apical third of the root canal walls. |
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