Experimental Investigation Of Cleanliness To The Smear Layer Of The Post Space And Retention Strength Of Fiber Post After MTAN Conditioning

Experiment ⅠExperimental Investigation on the Cleanliness of MTAN to the Smear Layer of Post SpaceObjective To investigate the cleaning capability of MTAN to the smear layer of post space.Methods After screening following experimental requirements,forty single-canal premolars taken off above 2mm of cemento-enamel junction were collected.The root canals were shaped and obturated. Post space were prepared and divided randomly into 5 groups of eight specimens each, and flushed by irrigation: irrigation with 10 ml of normal saline(group A);irrigation with 2.5ml of 3%Na OCl followed by 2.5ml of 18% EDTA(group B); irrigation with 5ml of 3%Na OCl followed by 5ml of 18% EDTA(group C);irrigation with 5ml of MTAN( group D);irrigation with 10 ml of MTAN( group E).All the specimens were irrigated by 10 ml of normal saline,then longitudinally split into two halves.The morphology of post space was observed under FESEM, and scored by Peters’ criterion.The data was analyzed by Kruskal-Wallis and Mann-whitney U tests using soft ware SPSS 19.0.Results The smear layer existed throughout the entire post space wall in group A; A large amounts of smear layer were present and more dentin tubules were obturated in group B;The smear layer was removed almost in group C、D and E,and the most of dental pulps were patent.Comparison of the five groups showed significant difference(P<0.05).Inter-group comparison showed that there was significant difference in group A and B,C,D,E(P<0.05),showing the post space in group B,C,D and E is clear than group A.there was significant difference in group B and C,D,E(P<0.05),showing the post space in group C,D,E is clearer than group B.There was no significant difference in the cleanliness of the post space among group C,D and E,showing the efficacy of the irrigation was similar.Conclusions 1. MATN is effective to remove the smear layer after post space instrumentation. 2.The efficacy of removing the smear layer using 5ml MTAN is similar to that with10 ml MTAN. Experiment Ⅱ Experimental Investigation on Retention Strength between Fiber-Post and Dentin Wall after MTAN ConditioningObjectives To evaluate the influence of retention strength between dentin wall after MTAN conditioning and fiber-post.Methods After screening according to experimental requirements, Forty-eight extracted single-canal premolars were selected.The crowns were cut above 2mm of the cemento-enamel junction.The root canals were shaped and obturated.Following the post space preparations,the teeth were divided randomly into 3 groups of sixteen specimens each and flushed by irrigation:irrigation with 10 ml of normal saline(group A);irrigation with 5ml of 3.0%Na OCl+5ml of 18%EDTA(group B);irrigation with 10 ml of MTAN(group C).All the specimens were irrigated by 10 ml of normal saline.The post space were completely dried paper points.The fiber post were luted. One week later all the specimens were embedded in self-curing resin.Three slices about 2mm were obtained each specimen.The morphology of interface between resin cement and dentin under SEM.The retention strength was measured using the universal loading device and the fracture mode was analyzed under the stereomicroscope.The statistical analysis were analyzed using soft ware SPSS19.0.Two-way analysis of variance was used for retention strength and the fracture mode was analyzed with Fisher exact test.Results1.Under SEM, hybrid layer were observed in group A(normal saline) and group B(3.0% Na OCl+18%EDTA),The interface between adhesive and dentin wall was continue and cohesive in group C(MTAN).The resin tags were present..2.The significant difference of retention strength was observed after different conditioning(P<0.05).The retention strength value was much higher in group C(MTAN) than group B(3.0%Na OCl+18%EDTA),and group A(normal saline).In addition the retention strength was significantly affected by different regions of the post space(P<0.05).The cervical third obtained much higher retention strength than middle third.Meanwhile,the retention strength of middle third was higher than that of apical third.3. Fracture modes were statistically different in three groups(P<0.05),Adhesive failure between resin cement and dentin was most observed in group A and group B,and the cement cohesive failure of present in group C.Conclusions The retention strength between fiber post and dentin after MTAN conditioning was improved.