An Investigation On The Adhesion Of Fiber Posts With Root Canal Wall--Micro Push-out Test

[Objectives]:This study aimed to evaluate the effects of several factors, including four different bonding procedures,five different post-surface conditionings, three different cement film thickness and three different root regions,on the micro push-out test of fiber-reinforced composite posts.[Methods]:Test one:Four bonding procedures,i.e.three-step total etch system (LuxaBond/LuxaCore),self-etch system(iBond/ LuxaCore),self-adhesive system (RelyX Unicem),and etching+ self-adhesive system(32%phosphoric etching/RelyX Unicem),were used to cement posts cementation subgroups.We made thin-slice specimens and indented as coronal,middle,and apical.Then,the thin-slice push-out test was used to assess the adhesion of fiber posts.Test two:Five surface treatments, i.e.Silanization,iBond,Burnishing with sand paper,Etching with potassium permanganate,with no surface conditioning(control group) and 32%phosphoric etching/RelyX Unicem,were used to cement posts cementation subgroups.Then,the thin-slice push-out test was used to assess the adhesion of fiber posts after making thin-slice specimens and indenting as coronal,middle,and apical.Test three:Three RTD drills with varied diameters(i.e.1.2mm,1.4 mm and 1.6 mm) were used to cement posts with 1.2mm(diameter) cementation subgroups.Test on the adhesion of fiber posts was then conducted after making thin-slice specimens and measuring thickness with metalloscope.[Results]:1.Test one showed that bonding procedures had significant impacts on the bond strength(p＜0.05).GroupⅠ(LuxaBond/LuxaCore) had the hightest bond strength compared with GroupⅡand GroupⅢ.For the variable "root region",the coronal resulted in statistically significant difference with middle and apical region (p＜0.05).2.Test two showed that post-surface conditioning had a significant influence on bond strength of fiber posts(p＜0.05),in particular,the method of sand paper burnishing and etching with potassium permanganate which has bond strength of(17.71±4.35) MPa and(15.29±2.13) MPa.3.Test three showed that different cement film thickness(49—230μm) achieved significantly different results for each other(p＜0.05).GroupⅠhas the highest bond strength(17.03±5.95) Mpa.[Conclusion]:1.Three-steps adhesive(total etch system) is the best way to cement fiber posts compared with self-etch and self-adhesive.Coronal root region comparatively has the highest bond strength.2.Post surface treatments are useful for improving push-out bond strength involving burnishing with sand paper and etching with potassium permanganate.3.The thickness of resin cement film influences the bond strength of fiber post.The dislocation resistance of fiber posts could be significantly decreased if the thickness of cement film were too thick,and thus,we propose that 49—230μm is the best thickness.