| Root canal therapy is considered to be the most effective andfundamental method of treating dental pulp diseases andperiapical diseases. The adaptation of the three-dimensionalfilling in the root canal system is the key factor to evaluateroot canal therapy, while the microleakage can lead to thefailure of root canal therapy after root canal filling. Coronalmicroleakage and apical leakage included in root canal leakageboth can lead to the failure of root canal therapy. Apicalleakage used to be the focus of research, but in recent years,coronal microleakage is being payed much more attention on asa potential reason of the failure of root canal therapy. Thereare fewer reports about coronal sealing materials used afterRoot canal therapy than during it.According to the amount of remaining tooth tissue and the wishesof patients,at present there are two ways to seal the corona,one is permanent filling,and the other one is restorativetreatment after temporary filling.Commonly the material usedin clinical permanent filling is resin, and used in temporaryfilling includes glass ionomer cement and zinc oxide eugenol, their closure property may affect the effectiveness andsuccessful rate of root canal therapy, and coronal microleakageafter root canal therapy may also be a reason for reinfectionin root canal after root filled.To provide an experimentalevidence of choosing coronal filling materials after root canaltherapy,this study was testing on the closure property of thesematerials.Methods:100teeth which are almost complete, without filling, not cracked are prepared standard class Ⅰ or Ⅱholes. The root canals are prepared in unified way and filled by continuous wave technique. After ensuring that the root canal is sealed tightly by X-ray, cut off gutta percha at tooth cervical.Divide all the teeth into five groups randomly. A group is Control group; B group is filledwith zinc oxide eugenol cement in2mm; C group is zinc oxide eugenol cement in3.5mm; D group is filled with glass ionomer cement; E group is filled with zinc rebased andresin. Use nail polish to seal off apical foramen and the occlusal surface beyond the edge of the prepared hole2mm by2times. All samples was immersed in the2%methylene blue solution in container completely filled and closed, and then place it in37℃box. Respectively take out five samples of each group after1,2,3,4weeks. Teethwere rinsed and dried after removed nail polish on them.Cut up teeth along the long axis of the cavity center mesiodistally. To measure methylene blue the maximum lengthbetween material and tooth under the stereoscopic microscope (16times) with a vernier caliper (0.05mm) as the dye leakage length recorded and analyzed by statistical software.results: It shows dye leakage length and its average of groupA, B, C, D, E (mm)(Table1-4) respectively, and the numberof teeth that the dye appeared in the canal after1,2,3,4weeks.The dye leakage can be detected at the first week in all thegroups. After the first week the dye leakage of group A and groupB reached root canal while group C, D, E didn’t. The dye leakageof group C reached root canals after2weeks. The dye leakageof some samples in group D and E reached root canals after4weeks.The leakage length grew over time during4weeks but notreached root apical.Conclusion: microleakage of coronal filling materials inroot-filled teeth affect long-term effects of root canaltherapy. Glass ionomer has an better coronal sealing effectamong temporary filling materials. There was no coronal microleakage in root canals with3.5mm zinc oxide eugenolcement within one week. Permanent filling material may havebetter closure than temporary filling material. The root apicalof root filled teeth without coronal filling materials may notbe infected within four weeks. Coronal microleakage of allkinds coronal filling materials increases over time. |
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