Experimental Study On The Influencing Factor For Retention Of The Fiber Post

When restoring the remnant root and the remnant crown on clinic, root canal posts are oftenapplied to strengthen the resistance form and the retention form, preventing the tooth frombeing broken and the restoring body from dislocation. Because the metal post has its advantagesfor easily casting and machine-finishing, especially in the case of tight occlusion, inner absorptionfor root canal, thick root canal and big damage in tooth body which need to use the posts tosupport the core. The metal post play the role which did not have substitute, so they are widelyapplied on clinic and well restored. But, along with the wide application of the cosmetologyrestoring, especially of the whole-ceramic restoring technology in clinical oral cavity, proposedhigher request to the post core material. However the metal post can appear itself metal color inthe translucent whole-ceramic case, also the metal post is easily corroded, and makes the gummargin appear black, seriously breaks the aesthetic feeling, Moreover, the modulus of elasticity issomewhat bigger to easily generate the stress concentration, therefore potentially making thedanger which the root folds. The minority patients also can have the anaphylactic phenomenon;these insufficiencies have all urged the development of the new material. Although in recent yearsthe titanium post and the ceramic post have been developed, but there are also some shortcomings,hardly promoted in clinic. In recent tens of years, the posts made by the fiber reinforcementmaterial have been widely applied in oral cavity clinical.The research for fiber reinforcement material has already started in the 20 century 60's, but until the 90's, the fiber post started to apply clinically. The most research indicated that, the fiberpost's intensity, degree of hardness, esthetics performance, the corrosion resistance, the fatigueresistance and the biological compatibility are superior the traditional metal post's; Moreover, thefiber post's the modulus of elasticity is close to the dentine, can reduce the occurrence which theroot folds, after the restoring defeat, there is the special-purpose elimination device, these areadvantageous to tooth preservation and re-restoring after the defeat, also the quality is lighter,therefore it was considered to be the more ideal new post material.Although the fiber post is receiving dentists' affection by its fine performance, but by nomeans acme of perfection. So many researches had reported the defeats of the fiber postrestoration, obtained incompletely same failure rate, but generally speaking, it must be lower thanthe metal post, and its defeat pattern mainly for the post or the crown bonding defeat, theoccurrence which the root folds is rare, this has the protection significance to the tooth. Also thefallen fiber post surface has the complete resinous package, This indicated between the fiber postand the resinous cementing material has the good bonding properties. The reason for the fallenfiber post mainly is in the root canal the dentine surface treatment improper, between thecementing material and the dentine has not formed the good machinery and chemistry solidposition function. Therefore, how to enhance the fiber post's bonding strength becomes the key tothe restoring success ratio of the fiber post by clinic.At present, there are many domestic research reports regarding of the intensity of fiber post,modulus of elasticity, esthetics performance, corrosion resisting, biocompatibility, and thedifferent figure and the depth of quartz fiber post that brings about the effect of stress distributionon the root of teeth after post and crown restored. However the research about the influencingeffects of the bonding strengthen of the fiber post is relatively few, therefore, we proceed with theinfluencing effects of the bonding strengthen of the fiber post, through the experimental study,and hope that it can provide some references to the clinical work development.Objects Intensity of illumination when light-curing and the curing system when the fiberpost bonds are the important factors that affect the bonding intensity of the fiber post. This experiment is originated from the above factors: 1. Using the Spectrums with different intensity inthe fiber post bonding process to solidify then carries on the stretching test, through comparingthe fiber post dislocation strength, discussing the strength of illumination of the Spectrum whethercan have the influence to the fiber post bonding intensity. 2. After using light-curing andself-curing separately in the fiber post bonding process, carrying on the stretch test similarly,through to the fiber post dislocation strength comparison, discussing whether the different curingsystem can have the influence to the bonding strength of the fiber post. 3. Making the specimenswith the medullary cavity of the fiber post before bonding, the cross section of the fiber post afterbonding, the medullary cavity of the fiber post after being pulled out, through carrying on thescanning electron microscope observation, discussing the characteristic of the bonding fiber postinterface.Method 1. Thirty new extracted single root premolars, which the root lengthand the outer diameter were basically consistent, and had no decay and no crack.With turbine mist cooling, drilling with fissure bur at 2mm above enamelo-cementaljunction, removing each experimental crown with the tooth major axis vertical level.Root canal preparation at 40#, after the root canal backfilled, using Gates GliddenDrill(BISCO) to eliminate gutta percha point in root canal, to the cross section below9mm, keeping partial gutta percha point. All experimental teeth first used1#Pre-Shaping to prepare root canal, making the final depth of the post reach9mm. Then using 1#Finishing to complete the last step of root canal preparation toguarantee the uniform shape, length and diameter. The experimental teeth weredivided into three groups in random, each group of 10.Using A, B, C group ofSpectrum separately to carry on the light-cure. After measuring the light intensitywith the actinometer: A group Spectrum of the halogen 1amp-320mw/cm~2, B groupSpectrum of LED—1400mw/cm~2; C group Spectrum of LED—1250mw/cm~2,Completing the post following the operating instructions, and light-curing 40 seconds to accelerate the solidification. Making the embedding block with the testing teeth,then carry on the pulling force test on the MTS 858 electron mechanical testingmachine, loaded continually at the speed of 2mm/min, recording the maximumtension value, using the SPSS12.0 software to carry on one-way analysis of varianceto the data. 2. Divided into two groups in the experimental group: A group for self-curing; Bgroup for light-curing. The test data in B group of the first sectional experiment was applied inthe B group. The method of group A was: ten new extracted single root premolars, which the rootlength and the outer diameter were basically consistent, and had no decay and no crack, carryingon the conventional medullary cavity preparation according to the experiment one. The bondingprocess with ALL-BOND 2 Universal Adhesive System, POST CEMENT HI-X HighRadiopacity Post Cement. The mixing time was 10-15s. Under room temperature, themanipulation time was 2.5-3.0min, the curing time was 4.5-5.0min. Making the embedding blockwith the testing teeth, then carry on the pulling force test on the MTS 858 electron mechanicaltesting machine, loaded continually at the speed of 2mm/min, recording the maximum tensionvalue. Using the SPSS12.0 software to carry on test to the data.3, twelve new extracted singleroot premolars, which the root length and the outer diameter were basically consistent,and had no decay and no crack and divided into three groups in random, preparing thefiber post according to the manufacture step in experiment one. A group prepareduntil the medullary cavity was completed; B group prepared until bonding completed.C group pulled out the posts in pulling force testing machine after the fiber postbonded. During the bonding process, two teeth of every group used one-step Universal DentalAdhesive, ETCHANTS, DUOLINK Composite Luting Cement and 3M Elipar Free Light. Theothers of every group used ALL-BOND 2 Universal Adhesive System, POST CEMENT HI-XHigh Radiopacity Post Cement. After observation surface exposed, throwing the sampleto 52.5 g/L sodium hypochlorite solution to soak for 24 hours, eliminating organicmatter under root canal, washing with normal saline, dehydrating with alcohol progressively, evaporatirig at the critical point, plating with pure gold in perfectvacuum, Scanning under the electron microscope.Results 1. After using the SPSS12.0 software to carry on one-way analysis ofvariance to the data, it was significantly different within general mean. The maximumbonding strength was in group B, 223.32N, the minimum one was in group A,142.48N. The order was B＞C＞A. The difference between A and B, A and C wassignificant (P＜0.05), but there was no significant difference between B andC(P=0.172). 2. After using the SPSS12.0 software to carry on T test to the data, it wassignificantly different between light-curing and self-curing (P=0.002), the bondingstrength with self-curing＞light-curing one. 3. After the medullary cavity prepares,had not bonded: dentinal tubule basic blind opened which in the root tip of medullarycavity; Middle medullary cavity would see the dentinal tubule partly opens wide; inthe root cervix of medullar cavity dentinal tubule opened widely; bonding completed,not being pulled out: The fiber post and the cement bond closed, but existed betweenthe root dentine and the cement had small slit, mainly caused for the resinouspolymerism and contraction. After the fiber post was pulled out: there were still manydebris, gutta percha point. In the middle and cervix of medullary cavity, after thepost was pulled out: it can be see in the majority of dentinal tubule the cement waspulled out along with the post, partial cement blocked in orifice of dentinal tubule. Inthe surface of fiber post can be seen many small dentin permeability, it was just thecement which entered dentinal tubule, hybrid layer is approximately 2μm thick.Conclusion 1. The new type of LED Spectrum was better than the traditionalSpectrum of the halogen lamp. Using LED can enhance the bonding intensity of thefiber post effectively. 2. Self-curing was better than light-curing in the bondingintensity aspect. 3. The polymerization and contraction of the resin in light-curingmethod and in self-curing way for bonding process existed all the way. 4. This research demonstration, between the resinous cement and the root dentine forms dentinpermeability may play the function of mechanical padlock well.