Clearfil Core Research Articles

Effect of the Degree of Conversion on Mechanical Properties and Monomer Elution from Self-, Dual- and Light-Cured Core Composites.

The objective of this work was to measure and correlate the degree of conversion (DC), mechanical properties and monomer elution from self-, dual- and light-cured core composites. Five samples of each of the following materials were prepared for each test: Clearfil (Core, Photo Core, Automix), Bisco (Core-Flo, Light-Core and Bis-Core). DC was determined using FTIR, compressive and flexural strength and modulus of elasticity using a universal testing machine and microhardness using Vickers hardness. Elution was measured using HPLC. One-way ANOVA with Tukey’s post-test and Pearson’s correlation were used to statistically analyze the data. DC of Clearfil-Dual (70.1%) and Clerafil-Photo (66.8%) were higher than Clearfil-Self (55.4%) and all Bisco materials (51.4–55.3%). Flexural strength of Clearfilwas higher than that of Bisco composites. The Microhardness of Clearfil-Dual (119.8VHN) and Clearfil-Photo (118.0VHN) were higher compared to other materials. The greatest elution was detected from self-cured materials. DC positively correlated to microhardness and compressive/flexural strength and negatively to BisGMA elution. Clearfil-Photo and Automix showed higher conversion, lower monomer elution and, generally, better mechanical properties. Self-cured composites should not be recommended for routine clinical use as their performance was inferior to dual- and light-cured composites. Microhardness may be used as an indicator of elution.

Novel hollow fiber sandwich composite post system: mechanical characteristics.

There is currently no consensus on the optimal post system to provide effective long-term results. We used an engineering approach to investigate the mechanical properties of a sandwich hollow carbon fiber post in synergy with a new bonding technique. We studied two systems - a sandwich fiber hollow post (Techole®, Isasan, Como, Italy) composed of carbon fiber incorporated in a Dpp-MOR resin mix and a traditional non-hollow post (Tech 2000®, Isasan, Como, Italy). A bi-component composite (Clearfil Core®, Kuraray, New York, NY, USA) (2.2 gcm3, 12.3 GPa) and a dual cure composite with lower density and modulus of elasticity (Clearfil DC Core®, Kuraray, New York, NY, USA) (2.0 gcm3, 10.0 GPa) were also used into hollow posts. Results from three-point bending test (N.=81), compression test (N.=78) and cut test (N.=81) were achieved. In the three-point bending test there were significant differences in flexibility/bending when sandwich fiber hollow posts were filled with composite of different modulus of elasticity. Hollow sandwich posts showed also significant (P=0.000) better resistance to compression and cutting than solid posts, independently of the type of composite. Moreover, hollow posts filled plus composite with a modulus of elasticity of 12.3 GPa showed significant (P=0.000) improved resistance parameters rather than hollow posts filled with a composite of 10.0 GPa. The study confirms the favorable mechanical properties of the hollow sandwich fiber post system (Techole®) and the synergistic efficacy when used in combination with the composite Clearfil DC Core® (10.0 GPa) and, especially, Clearfil Core® (12.3 GPa).

Morphological and bond strength evaluation of different resin cements to root dentin

This study correlated the morphological characteristics with the bond strengths of various resin cements used for bonding fiber posts to root canal dentin. Fifty glass-fiber posts (FRC Postec Plus) were luted into the root canals of extracted human anterior teeth using five resin cements (n = 10): Panavia F 2.0, PermaFlo DC, Variolink II, RelyX Unicem, and Clearfil Core. Before insertion of the post, the adhesive systems were labeled with fluorescein and the resin cement was labeled with rhodamine isothiocyanate. The roots were sectioned into three slices (of 2 mm thickness), and each slice was analyzed using confocal laser scanning microscopy in dual fluorescence mode to determine hybrid layer thickness, the number of resin tags, and the number of broken tags. Bond strengths were measured using a micro push-out test. Bond strengths to root canal dentin, as well as the morphological characteristics, were significantly affected by the materials. However, these factors did not correlate. The self-adhesive resin cement, which showed the formation of a hybrid layer and resin tags only sporadically, had the highest bond strengths. These results indicate that chemical interactions between the adhesive cement and hydroxyapatite may be more crucial for root dentin bonding than the ability of the same material to hybridize dentin.

Durability of the bond between resin composite cores and prefabricated posts

Objectives. This study evaluated the effect of post surface treatment and of storage condition on the bond between resin composite cores (Clearfil Core) and posts of titanium alloy (Fysika), silica-zircon fiber reinforced epoxy resin (SiliciumPost), and zirconia (CosmoPost). Material and Methods. In the experimental groups, the coronal part of each post received sandblasting or tribochemical silicate-coating (CoJet) treatment. The coronal part of each post was embedded in a cylinder of resin composite core material with the aid of a fixation apparatus. After 15 min, the specimen was freed from the mold and stored in de-ionized water. The axial tensile strength (ATS) of posts was determined in a Universal Testing Machine when extracting the posts from the resin composite cores after: 1) 14 d water storage at 37°C, 2) 14 d water storage at 37°C followed by thermal cycling (6,000 cycles between 5°C and 55°C), or 3) 1 year water storage at 37°C. The results were statistically analyzed by three-way factorial ANOVA and Newman-Keuls’ multiple range test. Results. The ATS values were generally higher for Fysika posts and SiliciumPost posts than for CosmoPost posts. Surface treatment effectively improved the ATS values of Fysika posts and SiliciumPost posts, but not those of CosmoPost posts. Thermal cycling or long-term water storage had only minimal effect on the ATS values of the posts. Conclusion. Bonding of resin composite cores to the posts depended more on the material of the post and the surface treatment of posts than on the storage condition.

Is Adhesive Cementation of Endodontic Posts Necessary?

Recently, the appropriate, durable bond of adhesive systems and composite resin cements to retain endodontic posts was challenged. The question arises whether it would be possible to place glass fiber posts in a less technique sensitive conventional nonadhesive approach. The influence of nonadhesive, self-adhesive, and etch-and-rinse systems on load capability of postendodontic restorations was studied. Human maxillary central incisors were divided into 4 groups ( n = 10). Teeth were endodontically treated and restored by using glass fiber posts luted with different cements/composite resin combinations: (1) RelyX Unicem (3M ESPE, Seefeld, Germany)/Clearfil Core (Kuraray Europe, Duesseldorf, Germany), (2) RelyX Unicem/LuxaCore, (3) zinc phosphate cement/Clearfil, and (4) LuxaCore (DMG, Hamburg, Germany)/Clearfil. A 2mm-ferrule preparation was performed. All specimens received adhesively luted all-ceramic crowns and were exposed to thermal cycling and mechanical loading before subsequent static loading. Significant differences between the experimental groups regarding load capability and fracture patterns were observed. The conventional non-adhesive post cementation is less reliable to withstand simulated functional forces compared to adhesive approaches.

Effects of luting agent and thermocycling on bond strengths to root canal dentine

To investigate the effects of luting agent and thermocycling on bond strengths to root canal dentine. Extracted maxillary canines (n =144) were root filled and divided into six groups of 24 teeth each. Fibre posts (FRC Postec) were inserted using six luting agents: Panavia F, Multilink, Variolink II, PermaFlo DC, RelyX Unicem and Clearfil Core. Each root was sliced into six discs (thickness 1 mm) representing the coronal, middle and apical part of the root canal. Push-out tests were performed 24 h after post insertion (n = 12) as well as after thermocycling (5000x; 5-55 degrees C, 30 s) (n = 12). Statistical analysis was conducted using analysis of variance (anova) followed by post-hoc comparisons (Tukey-B). The influence of thermocycling on bond strengths was investigated for each material and region separately using t-tests. The bond strengths were significantly affected by the luting agent (P < 0.001), the root position (P = 0.003) and thermocycling (P < 0.001; three-way anova). RelyX had significantly higher bond strengths compared with all other materials (P < 0.05; Tukey-B). The apical region of the root canal had significantly higher bond strengths compared with the middle and coronal region (P < 0.05; Tukey-B). After thermocycling for RelyX a significant increase in bond strengths was detected for the middle and apical region (P < 0.01; t-test, Bonferroni factor 18). Bond strengths were affected significantly by luting agent and root position. RelyX had higher bond strengths compared with other materials. The apical region of the canals was characterized by significantly higher bond strengths.

In vitro evaluation of push-out bond strengths of various luting agents to tooth-colored posts

Different compositions of tooth-colored posts may influence the bonding capacity of various luting agents to these posts. An appropriate understanding of these interactions is presently unavailable. This study initially evaluated the effects of various pretreatment procedures on bond strengths to zirconium-oxide posts using a phosphate-methacrylate resin luting agent. Following that investigation, the bond strengths of various luting agents to tribochemically coated glass-fiber-reinforced composite (FRC) resin and zirconium-oxide posts were investigated. Two hundred zirconium-oxide posts (CosmoPost) divided into 10 groups (n=20) were luted into artificial post spaces prepared with drills provided by the manufacturer. In 4 groups the posts were luted with phosphate-methacrylate resin agent (Panavia F) after receiving one of the following pretreatment procedures: no treatment (control); airborne-particle abrasion; silica coating and silanization with an intraoral airborne-particle-abrasion device (CoJet); or silica coating and silanization with a laboratory airborne-particle-abrasion device in combination with airborne-particle abrasion (Rocatec). The other zirconium-oxide posts in the 6 remaining groups were silica coated (CoJet), silanated, and luted with 1 of 6 different luting agents (Multilink, Variolink, PermaFlo DC, RelyX Unicem, Clearfil Core, and Ketac Cem). Additionally, 60 FRC posts (FRC Postec) were silica coated (CoJet), silanated, and luted with 1 of the 6 resin luting agents (Panavia F, Multilink, Variolink, PermaFlo DC, RelyX, and Clearfil Core). Push-out tests were performed to evaluate the bond strengths between luting agents and posts. Qualitative scanning electron microscopy (SEM) analyses were performed to evaluate the effects of the pretreatment procedures on the surface of the zirconium-oxide posts. Data were analyzed using analysis of variance (ANOVA) followed by the post hoc Tukey B test (alpha=.05). Bond strengths to the posts were significantly affected by the type of luting agent and the type of post (P<.001; 2-way ANOVA). Bond strengths of all luting agents to the FRC posts were significantly higher than to the zirconium-oxide posts (P<.01), except for Multilink and PermaFlo DC, which demonstrated higher bond strength values to the zirconium-oxide posts (P<.001). Pretreatment procedures significantly increased the bond strength of Panavia F to the zirconium-oxide posts (P<.05). SEM analyses revealed distinctive irregularities on the surface of the pretreated zirconium-oxide posts compared to the untreated posts. Bond strengths of luting agents to tooth-colored posts are significantly affected by the type of luting agent and the type of post. All investigated pretreatment procedures of zirconium-oxide posts significantly increased the bond strength of Panavia F.

Contraction stress and bond strength to dentinfor compatible and incompatible combinations of bonding systems and chemical and light-cured core build-up resin composites

Recent studies have shown that adhesives containing acidic monomers combined with composites can adversely effect the polymerization reaction producing low bond strengths. This phenomenon may also occur in making composite build-ups, jeopardizing one of the key factors for a successful core build-up restoration. The aim of this study was to investigate the contraction stress development and bond strength to dentin of core build-up resin composites combined with adhesives of various acidities. In addition the hypothesis tested was that light irradiation through chemical-cured composites during curing does not influence contraction stress or bond strength to dentin. The chemical-cured (Clearfil Core) and light-cured (Clearfil Photo Core) core build-up resin composites were combined with two light-cured adhesives, Clearfil SE Bond (pH=1.8) and One-Step Bond (pH=4.3) and two dual-cured adhesives, Clearfil Photo Bond (pH=2.5) and All-Bond 2 (pH=6.1). Contraction stress development (at C=3) was determined for a period of 30 min in a universal testing machine where the opposing bonding surfaces were glass and dentin. After the 30 min period, the specimens were loaded in tension to determine the bond strength to dentin. To test the hypothesis, the combinations of the chemical-cured composites with the four bonding systems were also light irradiated for 40s right at the start of curing. For all composite-adhesive combinations tested, the adhesion to dentin resisted the developing polymerization contraction stresses. Both, dentin as a substrate to bond at and the use of adhesives, were showed to play an important role in keeping the contraction stresses low. The chemical-cured composite (Clearfil Core) combined with the light-cured adhesive SE Bond (pH=1.8) showed for both contraction stress and bond strength significant lower values than the other combinations. The hypothesis was accepted for combinations of the chemical-cured composite with All-Bond 2 and One-Step Bond, but was not supported by combinations with Clearfil SE Bond or Clearfil Photo Bond, as a significant increase in contraction stress was found. The higher values found for bond strength were not significant. Besides combinations of chemical-cured core build-up composites with light or dual-cured adhesives as recommended by the manufacturer, also combinations with adhesives of other manufacturers are compatible, provided that the pH is higher than approximately 4.3. Chemical-cured core build-up composites combined with light-cured adhesives with a pH as low as 1.8 lead to a significantly lower stress and bond strength compared to other combinations. Light irradiation during curing through a combination of a chemical-cured composite and a low pH adhesive reactivates polymerization.

Shear Bond Strengths of Different Substrates Bonded to Lithium Disilicate Ceramics

The aim of this study was to evaluate the shear bond strengths of pre- and untreated resin core materials to lithium disilicate ceramics. Bond strengths to dental hard tissues served as controls. Ceramic cubes (IPS-Empress II) were luted either with a one-step (Variolink II/Excite DSC) or multiple-step total etching bonding system (Tetric Flow/Syntac Classic) to ground surfaces of human enamel, dentin, and resin core materials (Clearfil Core, Multicore). Resin core materials were additionally pretreated with hydrofluoric acid (HF) or were silica-coated (CoJet System). Shear bond strengths were determined after 24-hour water storage (n=10) and thermocycling (TC) (n=10; 2000 cycles, 5-55 degrees C, 30 seconds). Bond strengths to enamel, dentin, and silica-coated composites were significantly higher compared to untreated and HF-pretreated composites (p<0.05; Tukey B). Indeed, silica coating of the composite resins significantly increased the bond strength to ceramics (p<0.05; Tukey B). Due to the lower bond strength values of ceramics to untreated composite resins (as compared to enamel and dentin), any indication for a resin core build-up prior to the preparation of a ceramic restoration should be considered carefully.

Survival of glass fibre reinforced composite post restorations after 2 years—an observational clinical study

The aim of this study is to provide prospective clinical data for the survival of postendodontic reconstructions of teeth with varying degrees of hard tissue loss using tapered or parallel-sided post shapes. Eighty-three patients got 105 glass fibre reinforced posts of tapered (Luscent Anchors, Dentatus, Sweden) and parallel-sided, serrated (FibreKor, Jeneric Pentron, USA) post shape. A dual curing hybrid composite Compolute (3M ESPE, Germany) was used as luting material, EBS-Multi (3M ESPE) as adhesive system and Clearfil Core (Kuraray, Japan) for core built-up. The restorations were followed for a minimum of 24 months. The statistical analysis was performed on a random sub-sample of one restoration per subject. The Fisher exact test was used to compare frequencies of failures after 12 and 24 month. A Kaplan-Meier-analysis was used to analyse time-to-failure in both groups. Differences of survival time between post types were tested with the log-rank test. 3.8% of the restorations failed after 12 month, 12.8% after 24 month, respectively. The main failure type observed was post fractures. All but one failed teeth could be restored. There was no difference in failure frequency between post types after 12 or 24 months. The log-rank test showed no differences in survival between the two types of post (p=0.37). Parallel-sided and tapered glass fibre posts result after 2 years of clinical service in an equal rate of survival.

接着性レジン 支台築造と接着 レジン支台築造法について

Immediately after development of composite resin, it was used not only as filling material but also as the core material. Clearfil core, which came on market in 1980, was widely accepted in dental practice, resulting in many failures because of insufficient bond strength to dentin.Since then, high polymer science has made rapid progress, and now a lot of adhesive resin core materials are available with high bond strength to dentin. It is time to check the efficiency of these materials in practice.In this study, each component and its mutual relationship of the composite resin core with prefabricated metal posts were examined. As a result, the resin core with prefabricated posts indicated the same bonding strength as the cast post and core. In addition, core resin could be used as luting materials with better bond strength than conventional adhesive resin cements.