Novel hydrolytic resistant antibacterial monomers for dental resin adhesive.

OBJECTIVES: To evaluate the properties of novel hydrolytic resistant antibacterial monomers and to determine the properties of resin adhesives containing these monomers. METHODS: Methacrylamide-based QAC (Quaternary Ammonium Compound) monomers, 1-(11-Methacryla-midoundecyl)pyridine-1-ium bromide (MAUPB) and 1-(12-Methacryl-amidododecyl)pyridine-1-ium bromide (MADPB), and their methacrylate-derivatives, N-(1-Methacryloylundecanyl)pyridinium bromide (MUPB) and N-(1-Methacryloyldodecanyl)pyridinium bromide (MDPB), were synthesized and characterized. The minimum inhibitory (MIC) and bactericidal (MBC) concentrations were determined against S.mutans and E.faecalis. Cytotoxicity of unpolymerized monomers were evaluated using L-929 and MDPC-23. Each monomer was incorporated into experimental resins (BisGMA/TEGDMA/CQ/EDMAB or BisGMA/HEMA/CQ/EDMAB) at 10wt%. FTIR Spectra were collected for degree of conversion (DC%) measurement. Bacterial attachment on resin disks were determined by fluorescent microscope. Mechanical properties of experimental resins were evaluated by flexural strength & modulus and shear bond strength testing. RESULTS: The antibacterial activity of MDPB≥MUPB>MADPB>MAUPB. The TC50 of MAUPB> MADPB>MUPB >MDPB. Incorporation of MAUPB in BisGMA/TEGDMA-based resin, had no significant effect on DC%, while significantly increase DC% in BisGMA/HEMA-based Resin. MUPB and MAUPB containing resins showed less viable bacterial attachment than pure resins. After 3-month storage, resins containing MAUPB illustrated higher flexural strength than their corresponding resins containing MUPB. BisGMA/HEMA-based resin containing MAUPB illustrated significantly higher resin-dentin shear bond strength than that of MUPB and pure resin. CONCLUSIONS: Methacrylamide monomer containing QAC, MAUPB, possessed antibacterial properties and superior physical and mechanical properties when incorporated in resin adhesives as compared to their corresponding methacrylate monomer, MUPB. CLINICAL SIGNIFICANCE: Methacrylamide-based QAC monomers are potentially used to formulate antibacterial hydrolytic resistant resin adhesives and enhance resin-dentin bond strength.

Fracture resistance of thin wall endodontically treated teeth without ferrules restored with various techniques.

OBJECTIVE: To evaluate the fracture resistance and failure characteristics of simulated thin wall endodontically treated teeth without ferrules restored with various techniques. MATERIALS AND METHODS: Forty-eight human mandibular single-root canal premolars were decoronated and endodontically treated. The 1 mm thick remaining root canal dentin was prepared. The roots were randomly divided into four groups of 12 roots according to the following post and core reconstruction techniques: direct resin composite post and core (CP), multiple fiber posts and resin composite core (FP), CAD/CAM anatomical post and core (AP), and metal cast post and core (MP). Full metal crowns were cemented to the cores. All specimens were subjected to thermocycling for 5000 cycles and submitted to axial compression until failure at a 45°angle using a universal testing machine. The failures were classified into one of the followings: post and/or core fractures, root fractures, and root fractures combined with post and/or core fractures. RESULTS: Average failure loads of groups CP, FP, AP, and MP were 360.0, 655.2, 402.7, and 856.1 N, respectively. MP provided the highest failure load, which was significantly higher than those of the other groups (p < 0.05). FP was second, being inferior to MP with a significance level of p = 0.039. CP exhibited the least failure load, and it was not significantly different from the AP group (p > 0.05). Root fractures were the major failure mode for most of the specimens except the CP group, in which composite fractures at the cervical level were commonly observed. CONCLUSION: Metal cast post and core provided the highest fracture resistance for reconstruction of a thin wall in endodontically treated teeth without ferrules, followed by multiple fiber posts and resin composite core. The milled anatomical post and core and a direct resin composite post and core provided significantly lower fracture resistance. CLINICAL SIGNIFICANCE: Metal cast posts and core and multiple fiber posts with resin composite core techniques were effective for restoring severely compromised endodontically treated teeth.

Development and Validation of 3D Finite Element Models for Prediction of Orthodontic Tooth Movement.

OBJECTIVES: The aim of this study was to develop and validate three-dimensional (3D) finite element modeling for prediction of orthodontic tooth movement. MATERIALS AND METHODS: Two orthodontic patients were enrolled in this study. Computed tomography (CT) was captured 2 times. The first time was at T0 immediately before canine retraction. The second time was at T4 precisely at 4 months after canine retraction. Alginate impressions were taken at 1 month intervals (T0-T4) and scanned using a digital scanner. CT data and scanned models were used to construct 3D models. The two measured parameters were clinical tooth movement and calculated stress at three points on the canine root. The calculated stress was determined by the finite element method (FEM). The clinical tooth movement was measured from the differences in the measurement points on the superimposed model. Data from the first patient were used to analyze the tooth movement pattern and develop a mathematical formula for the second patient. Calculated orthodontic tooth movement of the second patient was compared to the clinical outcome. RESULTS: Differences between the calculated tooth movement and clinical tooth movement ranged from 0.003 to 0.085 mm or 0.36 to 8.96%. The calculated tooth movement and clinical tooth movement at all reference points of all time periods appeared at a similar level. Differences between the calculated and clinical tooth movements were less than 0.1 mm. CONCLUSION: Three-dimensional FEM simulation of orthodontic tooth movement was achieved by combining data from the CT and digital model. The outcome of the tooth movement obtained from FEM was found to be similar to the actual clinical tooth movement.

In vitro fracture resistance of composite-resin-veneered zirconia crowns.

AIMS: The aim of this study is to investigate the fracture load to failure and damage mode of the composite resin-veneered zirconia crowns preparing with two different zirconia surface treatments compared conventional porcelain-veneered zirconia crowns. MATERIALS AND METHODS: Metallic molar-shape dies prepared with 10° convergence angle a 1.5 mm deep chamfer finish line were used. Two groups of composite-resin-veneered zirconia crowns were prepared using different surface treatment (Group A - sandblasting and Group B - glaze-on technique). Group C (conventional porcelain-veneered zirconia crowns) was served as control. Load to failure test was performed to evaluate the fracture resistance of the crowns using a universal testing machine. One-way ANOVA was used to evaluate the differences of mean values (P < 0.05) followed by Tukey's honest significance test multiple comparisons. RESULTS: The mean fracture load to failure of Group A was 1078.45 ± 72.3, Group B was 1215.68 ± 100.76, and Group C (control) was 1203.67 ± 88.05. Modes of failure are 100% bulk fracture of the core through the veneering materials for Group B and C. However, Group A showed 40% delamination of composite veneering leaving zirconia coping exposed. CONCLUSIONS: Group B and C showed significant higher load to failure than Group A. Four specimens of Group A revealed the delamination of composite resin veneering.

Effects of various etching protocols on the flexural properties and surface topography of fiber-reinforced composite dental posts.

The purpose of this study was to evaluate the flexural properties and surface topography of fiber posts surface-treated with various etching protocols. Seventy each of three types of fiber posts: RelyX Fiber Post, Tenax Fiber Trans, and D.T. Light-Post Illusion X-Ro, were randomly divided into 7 groups: no surface treatment, surface treated with hydrofluoric acid (HF) 4.5% for 60 s, HF 4.5% for 120 s, HF 9.6% for 15 s, HF 9.6% for 60 s, HF 9.6% for 120 s, and treated with H2O2 24% for 10 min. The specimens were then subjected to a three-point bending test. Surface topographies of the posts were observed using a SEM. The results indicate that fiber post surface pretreatments had no adverse effects on the flexural properties. However, the fiber posts treated with high HF concentrations or long etching times seemed to have more surface irregularities.

Effects of C-factor and resin volume on the bonding to root canal with and without fibre post insertion.

OBJECTIVES: The aim of this study was to evaluate the effects of C-factor and resin volume on the regional bond strength of dual-cure luting resin to root canal dentine. METHODS: Twelve single-root human premolars were decoronated and post space prepared to a depth of 8 mm, with a diameter of 1.5 mm for six roots and 1.75 mm for the other six. Root canal dentine was treated with a dual-cure bonding system and light-cured for 20 s. Specimens were filled with a dual-cure resin composite with or without insertion of 1.4-mm-diameter light-transmitting glass fibre posts, followed by light-curing for 60s from the coronal direction. After 24 h water storage, each specimen was serially sliced into eight 0.6 mm × 0.6 mm thick beams for a microtensile bond strength test. Failure modes were observed using SEM. Bond strength data were divided into coronal and apical regions and statistically analysed. RESULTS: For both sizes of post space, bond strengths dramatically decreased when fibre posts were inserted. There were no significant differences in microtensile bond strength between 1.5 mm and 1.75 mm canal width, regardless of fibre post insertion. Regional differences in bond strength were found only in the resin-filled canals. CONCLUSIONS: The increase of C-factor of the root canal system by insertion of a fibre post had a detrimental effect on the bond strength to root canal dentine. On the other hand, the change of resin volume had no significant effect on bonding.

Effects of photocuring strategy on bonding of dual-cure one-step self-etch adhesive to root canal dentin.

This study evaluated the effects of light power density and light exposure time on regional bond strength of Clearfil DC Bond to root canal dentin. Post spaces were prepared in extracted premolars. Root canal dentin was treated with a dual-cure bonding system, Clearfil DC Bond, and light-cured for 10, 20, or 30 seconds using two halogen light curing units: Optilux 501 (830 mW/cm2) and Hyperlightel (1350 mW/cm2). Following which, all post spaces were filled with a dual-cure resin composite. After 24-hour storage, microtensile bond strengths (microTBS) at the coronal and apical regions were measured. At the coronal region, microTBS values were similar among all the experimental groups. At the apical region, bond strength improved when the curing time was extended to 30 seconds with Optilux 501, and likewise with Hyperlightel when curing time was extended to 20 or 30 seconds. In addition, significant differences in microTBS between the coronal and apical regions disappeared with prolonged curing times.

Regional bond strengths and failure analysis of fiber posts bonded to root canal dentin.

This study evaluated the regional bond strengths of fiber posts to root canal dentin luted with dual-cure resin composite. Twelve extracted human premolars were decoronated and post spaces prepared to a depth of 8 mm. The root canal dentin was treated with Clearfil SE Bond and light-cured for 20 seconds. Three posts from each of the following four types of fiber posts-Snowlight, FibreKor, DT Light-Post and GC Fiber Post-were surface-treated with a mixture of Porcelain Bond Activator and Photobond, then luted into the post spaces with Clearfil DC Core Automix and light-cured for 60 seconds. After 24-hour water storage, each specimen was serially sliced into eight 0.6 x 0.6 mm-thick beams for the microtensile bond strength (microTBS) test. Failure modes were observed using SEM. The microTBS data were divided into coronal and apical regions and statistically analyzed. The highest bond strengths were obtained from FibreKor posts. Regional factors had no effect on bond strength. FibreKor and DT Light-Post specimens primarily failed at the post-resin composite interface, whereas Snowlight and GC Post cohesively failed within the post.

Effect of adhesion to cavity walls on the mechanical properties of resin composites.

OBJECTIVES: To evaluate the regional mechanical properties of resin composite under free and constrained conditions during polymerization. METHODS: Forty cavities (8mm diameter and 5mm depth) were fabricated in resin blocks. Half of the cavities were bonded and the other half left un-bonded. The cavities were bulk-filled with one of the following composites: flowable composite (Palfique Estelite LV, Unifil Lo Flo), and Universal composites (Clearfil AP-X, Palfique Estelite Sigma), followed by photo-curing for 30s. After 24h storage, each specimen was sliced parallel to the long axis to harvest three slabs. The middle slab was serially sliced to harvest five sticks, which were trimmed to an hour-glass shape for measurement of regional ultimate tensile strength (UTS). The remaining semi-circular slabs were polished for microhardness measurement (KHN). Data were analyzed using three-way ANOVA followed by Tukey's HSD test and t-test (alpha=.05). RESULTS: The KHNs of all the resin composites were not significantly different between the bonded and unbonded groups at each cavity depth (p>0.05). The Ucapital TE, CyrillicS of the bonded group of flowable composites was significantly lower than those of the un-bonded group at the upper regions (p<0.05), while for universal composites, there were no significant differences in UTS between the bonded and un-bonded groups (p>0.05), although Clearfil AP-X had a trend toward lower UTS under the constrained condition at the upper regions. SIGNIFICANCE: The UTS of resin composite decreases due to polymerization shrinkage stress when polymerized under a constrained condition, however, these effects were dependent upon regions in the cavity and the resin materials.

Mechanical properties and bond strength of dual-cure resin composites to root canal dentin.

OBJECTIVES: To evaluate the regional mechanical properties of dual-cure resin composites and their regional bond strengths to root canal dentin. METHODS: One of the following dual-cure resin composites was placed in artificial post spaces: Unifil Core (UC), Clearfil DC Core (DC), Build-It FR (BI), Clearfil DC Core-automix (DCA), and photo-cured for 60s. After 24h storage, each specimen was serially sliced to harvest eight hour-glass shaped specimens for measurement of regional ultimate tensile strength (UTS), and the remaining eight semi-circular slabs were polished for the measurement of Knoop Hardness Number (KHN). For the microtensile bond strength (muTBS) test, post cavities were prepared in human premolar roots, and the cavity surfaces treated with Clearfil SE Bond and photo-cured for 10s. The post spaces were then filled with one of the above resin composites and photo-cured for 60s. After 24h storage, each specimen was serially sliced into 8, 0.6x0.6 mm-thick beams for the muTBS test. The data were divided into coronal and apical regions and analyzed using ANOVA and post hoc test (alpha=0.05). RESULTS: UTS and KHN were affected by the type of dual-cure resin composite and region (p<0.0001). There was no relationship between UTS and KHN for each material. The auto-mix type of resin composite possessed superior UTS to that of the hand-mix type. muTBS among the four composite materials were not significantly different at both apical and coronal regions (p>0.05). Regional differences in bond strengths were found for all materials (p<0.05). SIGNIFICANCE: The UTS and KHN of the dual-cure resin composites varied among each material, however, differences in the mechanical properties of the resin core materials did not affect their adhesion to root canal dentin.

Effect of simulated pulpal pressure on all-in-one adhesive bond strengths to dentine.

OBJECTIVES: To evaluate the durability of all-in-one adhesive systems bonded to dentine with and without simulated hydrostatic pulpal pressure (PP). METHODS: Flat dentine surfaces of extracted human molars were prepared. Two all-in-one adhesive systems, One-Up Bond F (OBF) (Tokuyama Corp., Tokyo, Japan), and Fluoro Bond Shake One (FBS) (Shofu Co., Kyoto, Japan) were applied to the dentine surfaces under either a PP of 0 or 15cm H(2)O. Then, resin composite build-ups were made. The specimens bonded under pressure were stored in 37 degrees C water for 24h, 1 and 3 months under 15cm H(2)O PP. Specimens not bonded under pressure were stored under zero PP. After storage, the specimens were sectioned into slabs that were trimmed to hourglass shapes and subjected to micro-tensile bond testing (muTBS). The data were analysed using two-way ANOVA and Holm-Sidak HSD multiple comparison tests (alpha=0.05). RESULTS: The muTBS of OBF fell significantly (p<0.05) when PP was applied during bonding and storage, regardless of storage time. In contrast, although the muTBS of OBF specimens bonded and stored without hydrostatic pressure storage fell significantly over the 3 months period, the decrease was less than half as much as specimens stored under PP. In FBS bonded specimens, although there was no significant difference between the muTBS with and without hydrostatic pulpal pressure at 24h, by 1 and 3 months of storage under PP, significant reductions were seen compared with the control group without PP. CONCLUSION: The muTBS of OBF bonded specimens was lowered more by simulated PP than by storage time; specimens bonded with FBS were not sensitive to storage time in the absence of PP, but showed lower bond strengths at 1 and 3 months in the presence of PP.

Influence of hydrostatic pulpal pressure on the microtensile bond strength of all-in-one self-etching adhesives.

PURPOSE: To evaluate the microtensile bond strength (microTBS) of two all-in-one self-etching adhesive systems and two self-etching adhesives with and without simulated hydrostatic pulpal pressure (PP). MATERIALS AND METHODS: Flat coronal dentin surfaces of extracted human molars were prepared. Two all-in-one self-etching adhesive systems, One-Up Bond F (OBF; Tokuyama) and Clearfil S3 Bond (Tri-S, Kuraray Medical) and two self-etching primer adhesives, Clearfil Protect Bond (PB; Kuraray) and Clearfil SE Bond (SE; Kuraray) were applied to the dentin surfaces according to manufacturers' instructions under either a pulpal pressure (PP) of zero or 15 cm H2O. A hybrid resin composite (Clearfil AP-X, Kuraray) was used for the coronal buildup. Specimens bonded under PP were stored in water at 37 degrees C under 15 cm H2O for 24 h. Specimens not bonded under PP were stored under a PP of zero. After storage, the bonded specimens were sectioned into slabs that were trimmed to hourglass-shaped specimens, and were subjected to microtensile bond testing (microTBS). The bond strength data were statistically analyzed using two-way ANOVA and the Holm-Sidak method for multiple comparison tests (alpha = 0.05). The surface area percentage of different failure modes for each material was also statistically analyzed with three one-way ANOVAs and Tukey's multiple comparison tests. RESULTS: The microTBS of OBF and Tri-S fell significantly under PP. However, in the, PB and SE bonded specimens under PP, there were no significant differences compared with the control groups without PP. CONCLUSIONS: The microTBS of the two all-in-one adhesive systems decreased when PP was applied. However, the microTBS of both self-etching primer adhesives did not decrease under PP.

Regional bond strengths of a dual-cure resin core material to translucent quartz fiber post.

PURPOSE: To evaluate the microtensile bond strength (muTBS) of a dual-cure resin core material to different regions of translucent quartz fiber post in a post cavity using different surface treatments. METHODS: 30 translucent quartz fiber posts (Light-Post) were used and divided into six groups according to the surface treatments: (1) no surface treatment (Control); (2) photo-cure bonding agent, Clearfil Liner Bond 2V Bond A (PLB); (3) dual-cure bonding agent, Clearfil Liner Bond 2V Bond A+B (DLB); (4) BdA+B followed by light-cured for 20 seconds (DLB & LC); (5) silane coupling bonding agent, Clearfil Photobond with Porcelain Bond Activator (PB+PBA); (6) PB+PBA followed by light-cure for 20 seconds (PB+PBA&LC). Treated post were cemented into artificial post cavities using a dual-cure composite core material (Clearfil DC Core) and light-cured for 60 seconds from the top of the cavity. After 24-hour storage in water, each specimen was serially sliced into twelve 0.6 x 0.6 mm-thick beams for the muTBS test. The data were divided into three regions (upper/middle/bottom) and analyzed using two-way ANOVA and Dunnet's T3 multiple comparisons (alpha = 0.05). RESULTS: The highest bond strength was present in the silane coupling bonding agent group for all regions (P < 0.05). Application of the bonding agent to the post surface significantly improved the bond strength compared with control (P < 0.05). There were no significant differences in muTBS at all regions between the photo and dual-cure type bonding agents (P < 0.05). The bond strength significantly decreased at the bottom region when the post surface was treated with bonding agents (P < 0.05), whereas no regional differences in bond strength were found in the silane coupling bonding agent group (P > 0.05).

Effect of prolonged photo-irradiation time of three self-etch systems on the bonding to root canal dentine.

OBJECTIVES: To evaluate the effect of photo-irradiation time to the adhesive on the regional bond strength of a dual-cure resin core material to root canal dentine using photo and dual-cure adhesives with self-etching primer. MATERIALS AND METHODS: Post spaces were prepared in extracted premolars and then the root canal dentine was treated with one of the following bonding procedures: (1) Clearfil SE Bond Primer/Bond (SE), (2) Nano-Bond Primer/Photo-cure adhesive (PNB), (3) Nano-Bond Primer/Dual-cure adhesive (DNB). Photo-irradiation was performed for 10 or 20s from a coronal direction. The post spaces were then filled with a dual-cure composite resin (Build-It FR) and light-cured for 60s. After 24h storage, each specimen was serially sliced into 8, 0.6 x 0.6mm-thick beams for the microTBS test. The bond strength data were divided into coronal and apical regions and analysed using three-way ANOVA and Games-Howell multiple comparison (alpha=0.05). RESULTS: The microTBS of the photo-cure adhesive resin, SE and PNB, significantly decreased (p<0.05) at the apical region when the photo-irradiation time was 10s. However, the bond strength of the SE group was significantly improved at both regions when photo-irradiation time was extended to 20s (p<0.05). There were no differences in microTBS of the photo-cure adhesive resin (PNB) cured for 20s and dual-cure adhesive resin (DNB) (p>0.05). CONCLUSION: Photo-cure adhesive was effective for application on root canal dentine when the photo-irradiation time was sufficient. Extension of photo-irradiation time to the adhesive improved the bond strength depending on the type of adhesive resin.

Regional bond strength of four self-etching primer/adhesive systems to root canal dentin.

The purpose of this study was to evaluate the regional bond strength of a dual-cure resin core material to root canal dentin using four self-etching primer/adhesive systems. Post spaces were prepared in extracted premolars, and their root canal dentin was treated with one of the following self-etching primer/adhesive systems: ED Primer II and Clearfil Photobond, photo-cure/dual-cure systems of Clearfil Liner Bond 2V, or Clearfil SE Bond. Post spaces were filled with the dual-cure resin core material, and microtensile bond strength (microTBS) at the coronal and apical regions was measured after 24-hour storage. There were no regional differences in microTBS of the photo-cure and dual-cure systems of Clearfil Liner Bond 2V, while microTBS at the coronal region of Photobond and SE Bond groups were higher than those at the apical region. At the apical region, photo-cured Clearfil Liner Bond 2V exhibited significantly higher bond strength than those of the other systems.

Microtensile bond strength of a dual-cure resin core material to glass and quartz fibre posts.

OBJECTIVES: To evaluate the microtensile bond strength (microTBS) of a dual-cure resin core material to different regions of fibre posts using different surface treatments. MATERIALS AND METHODS: Twenty-five silica zirconium glass fibre posts (Snowpost) and 25 quartz fibre posts (Aestheti-Plus) were used and randomly divided into five groups according to the surface treatments: (1) no surface treatment (Control) (2) dual-cure bonding agent, Clearfil Liner Bond 2V (LB) (3) LB followed by light curing for 20 s (LB and C) (4) silane coupling bonding agent agent, Clearfil Photobond with Porcelain Bond Activator (PB+PBA) (5) PB+PBA followed by light curing for 20 s (PB+PBA and LC). Treated posts were cemented into artificial post cavities using a dual-cure composite core material (Clearfil DC Core) and cured for 60 s from the top of the cavity. After 24 h storage in water, each specimen was serially sliced into 8, 0.6 x 0.6 mm2-thick beams for the microTBS test. The data were divided into three regions (upper/middle/bottom) and analyzed using three-way ANOVA and Dunnet's T3 multiple comparisons (alpha=0.05). RESULTS: There were no significant differences in bond strength between the three regions (p>0.05). The bond strengths were enhanced by the application of a silane coupling agent. For Snowpost, photoirradiation of the dual-cure bonding agent applied to the post surface significantly improved the bond strength (p<0.05) whereas it did not affect the bond strength of Aestheti-Plus post (p>0.05). CONCLUSION: The bond strength between fibre post and dual-cure resin core material depends upon the type of post and surface treatment. There were no regional differences in microTBS of the bonded post.