Effects Of Length And Content Of Glass Fiber Posts On The Fracture Resistance Of Teeth

Objective:To explore the influence of different lengths and contents of glass-fiber post on the fracture resistance of teeth, and to investigate the optimal length and content of glass-fiber post used for restorative treatment.Method:Forty-two intact single canal mandibular premolars were collected.The crowns were cut off the crowns from the2mm above cemento-enamel junction,keep the root part.And then they were randomly divided into three experimental groups (A, B and C)(n=14). Use a vernier caliper to record root length (cemento-enamel junction to the anatomic foramen), buccal-lingual dimension and mesial-distal dimension of each sample.All root canals were prepared to size25using1.0,0.8,0.6taper TF engine file.Between each instrument change,root canals were alternately irrigated with5ml5.25%sodium hypochlorite and5ml17%EDTA solution1min,and then irrigated with physiological saline.All teeth were obturated using the vertical condensation technique with gutta-percha and a root canal sealer (AH-PLUS).Evaluate effect of root canal filling with X-ray films.All specimens were sealed with zinc phosphate of2mm. Post insertion depths werelOmm in A group,8mm in B group, and6mm in C group,every group were randomly assigned into two subgroups (n=7) of two different content of glass-fiber post(42%and75%),The42%glass fiber post was used in Al, B1and C1groups. The75%glass fiber post was used in A2, B2and C2groups. Gutta-percha was progressively removed with a drill sequence until Tenax Fiber drill1.3mm.A self-adhesive resin cement (3M ESPE RelyXTM Unicem) was applied into the post space, posts were seated into the root canals, Resin cement was light-cured.Core was built up using a universal resin composite(Spectrum), Teeth were prepared into ferrule width1mm, height2mm, height of the core6mm, using a parallel grinding instrument control polymerization degree of6°. Teeth were restored with Ni-Cr alloy metal full crown of8mm height,30°tooth tip, the casting crowns adhered to teeth with glass ionomer cement.The sample were mounted in PVC tube (20mm high and30mm in diameter) filled with self-curing resin exposing4mm of the coronal.The fracture resistance was measured with universal testing machine and recorded the root fracture pressure data and the mode of all the teeth.The resulteds were subjected to statistical analysis using factorial analysis of variance,multiple comparison between groups using SNK-q.The level of significance was0.05.Results:1, The fracture resistance was significantly higher in group A than that of group B and group C (P<0.05), and the fracture resistance was significantly higher in group B than that of group C(P<0.05). The fracture resistance was significantly higher for75%glass fiber post than that of42%glass fiber post (P<0.05).2, all specimens without casting crowns dislocation, fracture and fracture of the resin core, in addition to group A2(glass fiber pile length10mm, fiber content of75%of the group) one case of specimens broken in the apical1/3, the remaining specimens were broken in the neck1/3.Conclusion:1, Within a certain range, the longer the length of glass fiber post, the greater the tooth fracture resistance.2, The fracture resistance of fiber content is better for75%glass fiber post than that of42%glass fiber post.