Clinical Applications And Experimental Study Of MTA

Objective: (1)To evaluate the success rate of root perforation repairs and apical barriers in open apices using MTA. (2)To evaluate the effect of intracanal irrigants on the bond strengths of mineral trioxide aggregate (MTA) to dentin in vitro.Methods: (1)Cases of perforation repairs and apical barriers were completed using MTA with the help of microscope. Radiographic and clinical follow-up examinations were performed for a period of at least 6 months to evaluate the outcome of treatment.(2) Standardized dentin samples 1.3mm in thickness with perforation 1.3mm in diameter were made. MTA mixed with sterile water at a powder to liquid ratio of 3:1 was used to repair these perforations. After 7-day's initial set, samples were randomly divided into five groups to be immersed in saline, 5.25%NaOCl, 17%EDTA, 2% chlorhexidine and Glyde File Prep for 2h. MTS testing machine was used to measure the force required to displace the material from the perforation. After the push-out test, one sample in each group was fractured and sputter-coated with gold for SEM observation.Results: (1)According to the criteria, 27 cases of perforation repairs and 20 cases of apical barriers completed with MTA were included in this study. In perforation repairs group, 21 cases were rated as success, 5 cases showed improvement and 1 case were failure. In open apices group, 5 cases were A-type root shape, 13 cases were B-type and 2 cases were C-type. Of the 20 cases, 15 cases were rated as success, 3 cases presented improvement and 2 cases were failure.(2)The samples were statistically significantly less resistant in retention strength when treated with 17%EDTA or Glyde File Prep, compared with the samples immersed in saline (P<0.05). The strength of MTA to resist displace was not decreased significantly when samples were immersed in 5.25%NaOCl or 2% chlorhexidine. Examination of the interface of MTA-dentin in EDTA group showed that gelatinous hydrated product of MTA was dissolved and peritubular dentin was excessive eroded. Flake-shaped crystals formed in the interfacewere observed in Glyde group. The SEM photograph of 5.25%NaOCl group was similar to control group. A plenty of fiber-type gelatinous hydrated products and a reduced amount of crystals of MTA on the dentin surface in 2% chlorhexidine group was noted.Conclusion: (1)The application of MTA in perforation repairs and apical barrier were effective in improving the prognosis of the teeth. (2)In the model of this study, 17%EDTA, Glyde File Prep and 2% chlorhexidine changed the interface structure of MTA-dentin after 2 hr immersion. 17%EDTA group and Glyde File Prep group had adverse effects on MTA-dentin bond strengths.