Push-out Strength Research Articles

The influence of antibiotics on the physical properties of endodontic cements

AimTo evaluate the influence of Metronidazole, Minocycline and Ciprofloxacin as a mixture or individually and of chlorhexidine on the push-out bond strength and surface microhardness of calcium silicate cements of differing particle size. Methodology120 extracted adult human premolars were decoronated and 2mm dentin slices were prepared. Specimens were divided equally into the following groups: normal saline and CHX, Metronidazole, Minocycline, Ciprofloxacin, and combination of Metronidazole, Minocycline and Ciprofloxacin. The specimens were irrigated with solutions and filled with endodontic cements. In the second part, the endodontic cements were mixed, placed in plastic tubes and then irrigated for 1 or 5min. Push-out and surface microhardness values were calculated and data were analyzed with three way ANOVA followed by Tukey's post-hoc test. ResultsThe normal saline and ciprofloxacin groups showed significantly higher and lower, respectively, push-out bond strength among the experimental groups (p<0.001 for all groups). Nano type cement showed higher push-out bond strength and microhardness than regular one at both time intervals. The mixture of antibiotics had significant effects on the push out and microhardness of calcium silicate cement. ConclusionsNano particle MTA resisted more than the conventional MTA to the effect of the irrigating solution and antibiotics in both hardness and push-out strength. Furthermore, the results of microhardness were consistent with the push-out strength in most cases. The microhardness test may be employed as a complimentary test to evaluate push-out strength of dental cements.

Effect of different adhesive systems and post surface treatments on the push-out bond strengths of fiber-reinforced post

Purpose: The purpose of this study was to evaluate the push-out bond strength of glass-fiber post cemented with different adhesive systems and surface treatments. Materials and methods: 160 tooth samples made from 48 human maxillary single-rooted teeth with similar root length were divided into 4 groups according to the adhesive system (no adhesive, Adper Single Bond 2, Clearfil SE Bond, Clearfil S3). Each group had 4 subgroups according to the post surface treatment methods (no treatment, sandblast, silane, sandblast and silane). Posts (Parapost Fiber White) were cemented with Rely X Unicem. The teeth were sectioned perpendicular to their long axis into 1-mm thick sections. The push-out tests was performed at a speed of 0.5 mm/min. The results were evaluated by 2-way ANOVA, 1-way ANOVA and multiple comparison procedures (Tukey test) (α =0.05). Results: Tukey test showed that the adhesive system significantly influenced the push-out strength. The Clearfil SE Bond group showed the highest value. Post surface treatments showed no significant effect. Conclusion: Bond strength of glass-fiber post cemented with self-adhesive resin cement using Clearfil SE Bond showed significantly higher values compared to other adhesive systems. (J Korean Acad Prosthodont 2016;54:218-25)

Enhanced bioactivity and osseointegration of PEEK with accelerated neutral atom beam technology.

Polyetheretherketone (PEEK) is growing in popularity for orthopedic, spinal, and trauma applications but has potential significant limitations in use. PEEK is biocompatible, similar in elasticity to bone, and radiolucent, but is inert and therefore does not integrate well with bone. Current efforts are focusing on increasing the bioactivity of PEEK with surface modifications to improve the bone-implant interface. We used a novel Accelerated Neutral Atom Beam (ANAB) technology to enhance the bioactivity of PEEK. Human osteoblast-like cells seeded on ANAB-treated PEEK result in significantly enhanced proliferation compared with control PEEK. Cells grown on ANAB-treated PEEK increase osteogenic expression of ALPL (1.98-fold, p < 0.002), RUNX2 (3.20-fold, p < 0.002), COL1A (1.94-fold, p < 0.015), IBSP (2.78-fold, p < 0.003), and BMP2 (1.89-fold, p < 0.004). Cells grown on these treated surfaces also lead to an increased mineralization (6.4-fold at 21 days, p < 0.0005). In an ovine study, ANAB-treated PEEK implants resulted in enhanced bone-in-contact by 3.09-fold (p < 0.014), increased push-out strength (control 1959 ± 1445 kPa; ANAB 4068 ± 1197 kPa, p < 0.05), and evidence of bone ingrowth at both the early (4 weeks) and later (12 weeks) time points. Taken together, these data suggest that ANAB treatment of PEEK has the potential to enhance its bioactivity, leading to bone formation and significantly decreasing osseointegration time of orthopedic and spinal implants. ANAB treatment, therefore, may significantly enhance the performance of PEEK medical implants and lead to improved clinical outcomes. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 531-543, 2017.

Push-Out Bond Strength Evaluation of Glass Fiber Posts With Different Resin Cements and Application Techniques.

The purpose of this study was to evaluate the push-out strength of two different adhesive cements (total etch and self-adhesive) for glass fiber post (GFP) cementation using two different techniques (microbrush and elongation tip) of cement application. In addition, this study evaluated the effect of total-etch conditioning before the use of a self-adhesive cement. Sixty premolar specimens with a single root canal were selected, endodontically treated, and shaped for GFP cementation. The specimens were randomly placed into one of six groups according to the cement and technique used: RelyX ARC (ARC): ARC + microbrush, ARC + elongation tip; RelyX Unicem (RU): RU + microbrush, RU + elongation tip; or RelyX Unicem + 37% phosphoric acid (RUE): RUE + microbrush, RUE + elongation tip. Each specimen root was cut perpendicular to the vertical axis yielding six 1.0-mm-thick sections. Push-out strength test was performed, followed by statistical analysis using three-way analysis of variance and the Games-Howell test (p<0.05). Statistically significant differences between the groups were found (p< 0.05). The cervical third of the roots had the highest mean push-out strength values, while the apical third had the lowest mean values regardless of the technique used. The elongation technique produced higher mean push-out strength values compared to the microbrush technique. The self-etch adhesive cement had the highest mean push-out strength value in all thirds. The addition of a conditioning step before the self-etch adhesive cementation appears to be effective in enhancing push-out strength with GFPs.

Effects of Cemented Hip Stem Pre-heating on Stem Push-out Strength.

To determine the effect on ultimate push-out load and cement-stem surface shear strength of thermally manipulating the cobalt-chromium-molybdenum (CoCrMo) alloy stems of bone cement-stem constructs. Satin-finished CoCrMo alloy stems were allocated to the following three groups with the predetermined temperatures: T24, ambient (24 °C); T37, body (37 °C); and T44, pre-heated stem (>44 °C). They were then inserted into hand-mixed high viscosity bone cement. Ultimate push-out load to failure was assessed with a servo hydraulic testing machine and the surface shear strength calculated. Data were compared among groups using the Kruskal-Wallis with Dunn's test. A P value of less than 0.05 was considered statistically significant. According to Kruskal-Wallis analysis, ultimate push-out load and surface shear strength differed significantly between the groups (P = 0.001). The T37 and T44 groups had higher ultimate push-out loads and surface shear strengths than the T24 group (P = 0.04 and 0.001, respectively). However, there was no statistically significant difference in these two variables between the T37 and T44 groups (P = 0.08). Pre-heating CoCrMo alloy stems enhance the ultimate push-out load and surface shear strength in vitro. The suggested temperature is 37 °C. This technique is recommended for hip arthroplasty procedures.

Effect of endodontic sealers on push-out bond strength of cemented fiber posts.

The purpose of this study was to compare the effect of eugenol-based and resin-based endodontic sealers on the push-out bond strengths of prefabricated fiber posts luted with different resin cements. Ninety prefabricated fiber posts were luted into extracted singlerooted teeth with one of three resin cements (Variolink II, ParaCore, or Rely X Unicem). Each group was subdivided into three groups with 10 teeth each. The first two groups were obturated with gutta percha and one of two eugenol-based endodontic sealers (Endofil or TubliSeal) each. The third group was obturated with gutta percha and (AH26) resin-based root canal sealer. Push-out tests were performed in a universal testing machine by applying a load speed at 0.5 mm/min by using a 1-mm-diameter metallic plunger which induced a load in an apical to coronal direction. The maximum value for post dislodgement (in Newtons) was recorded. Data were collected and statistically analyzed using two-way ANOVA and Tukey multiple comparison tests (α = .05). The highest mean bond strength values were recorded for the AH26 sealer group (non-eugenol sealer) luted with Rely X Unicem resin cement (mean ± SD = 326.1 ± 66.1 N), while the lowest mean bond strength values were observed with posts luted with Variolink II resin cement into canals obturated with gutta-percha and Endofil (eugenol-based) sealer (90.3 ± 25.2 N). There was no significant difference between the means of push-out strengths for the Endofil and TubliSeal groups (P = .745). Eugenol-based sealers (Endofil and TubliSeal) significantly reduced the push-out bond strength of prefabricated fiber posts luted with resin cement.

Root canal flare: Effect on push-out strength of relined posts

PurposeThe aim of this study was to investigate the push-out bond strength (PBS) of resin-relined and non-relined glass fiber posts (GFP) luted to flared root canals. Material and methodsRoot canals of 80 bovine incisors were enlarged to obtain 40 mildly flared and 40 over-flared post spaces. Half of the specimens from each group had the GFP resin-relined, whilst the remainders were not relined. A further 20 root canals were minimally flared and restored with a non-relined GFP (control group). Posts were luted into the root canal space using dual-cure resin cement. Three slices were sectioned from each specimen: one from the coronal third and the others from the middle and apical thirds. PBS test was performed in a universal testing machine at a speed of 0.5mm/min. ResultsTwo-way ANOVA for repeated measures and Tukey’s test showed that PBS was affected by the root canal flare and relining procedure (p<0.001). Relining significantly increased the PBS of GFP luted in roots with mildly flared canals when compared to those with excessive widening, regardless of the relining procedure. Relining GFP for over-flared canals had a PBS equivalent to that observed in the control group (minimally flared canal/non-relined GFP). PBS values were higher in the coronal third. No difference was found between the PBS values in the middle and apical thirds. ConclusionsDepending on the extent of the root canal flare, relined fiber posts may outperform or at least perform as well as posts luted in minimally-flared canals.

The correlation between fluid transport and push-out strength in root canals filled with a methacrylate-based filling material.

To investigate the correlation between fluid transport and dislocation resistance in canals filled with a methacrylate-based filling material. The root canals in sixty-five single-rooted human teeth were prepared to size 40, 0.06 taper. Sixty roots were filled with a single-cone technique using RealSeal SE sealer and divided into 3 groups, whilst five roots served as fluid transport positive control. Group 1 (n = 20): correlation group. Specimens were consecutively tested with fluid transport for 90 min and thereafter with the push-out test at coronal and apical root levels. Group 2 (n = 20): push-out control. Specimens were only subjected to the push-out test at coronal and apical root levels. Group 3 (n = 20): fluid transport negative control. Specimens were totally covered with nail varnish. The correlation between fluid transport and dislocation resistance was assessed by Kendall's tau-b coefficient. The Mann-Whitney U-test was used to compare dislocation resistance between groups 1 and 2 and fluid transport between groups 1 and 3. Significance level was set at P < 0.05. Kendall's tau-b correlation coefficients between fluid transport and dislocation resistance were weak, being coronally 0.139 (P = 0.444) and apically -0.080 (P = 0.658). No significant difference in dislocation resistance could be detected between groups 1 and 2 at both root levels (P = 0.052 and P = 0.336, respectively). No significant correlation could be identified between fluid transport and dislocation resistance, meaning that the corono-apical sealing ability of a methacrylate-based root canal filling is independent of its adhesive properties as indicated by its dislocation resistance.

The effect of waterlase laser and herbal alternative, green tea and Salvadora Persica (Siwak) extract on push-out bond strength

Background: The bond strength of root canal sealers to dentin was important for maintaining the integrity of the seal in root canal filling in both static and dynamic situations. In a static situation, it should eliminate any space that allowed the percolation of fluids between the filling and the wall while in a dynamic situation; it was needed to resist dislodgement of the filling during subsequent manipulation. Materials and Methods: Forty mandibular premolars were selected for this study. All canals were instrumented using ProTaper rotary instruments. Instrumentation was done with copious irrigation of 5.25% sodium hypochlorite. Roots were randomly divided into four groups according to the type of cleaning and method of root canal irrigation (ten teeth for each group): Group A. The root canals were irrigated with 5 ml of 17% of EDTA for 1 minute and 5 ml of 5.25% NaOCl. Group B. Cleaning with waterlase laser. Group C. The root canals were irrigated with 5 ml of 5mg/ml of siwak (Salvadora persica) extract for one minute. Group D. The root canals were irrigated with 5 ml of 5% of green tea (camellia sinensis) extract for one minute. All groups were rinsed with distilled water and then obturated with cold lateral condensation technique and i Root sp sealer (Bioceramic sealer, the roots then stored in moist environment at 37°C for one week. Three horizontal sections were prepared at a thickness of 1 mm ±0.1 in the apical, middle and coronal parts of each root. The test specimens were subjected to the push-out test method using a Universal Test Machine that carried 1-mm, 0.5- mm and 0.3-mm plungers for coronal, middle and apical specimens, respectively. The loading speed was 0.5 mm/ min. The computer showed the higher bond force before dislodgment of the filling material. These forces were divided by the surface area to obtain the bond strength in MPa. Results: In all groups the mean value of push-out strength was greatest in apical area and least in coronal area and the middle area was in between, except in Waterlase the middle area showed the least mean push-out strength. Conclusion: Herbal extracts used in this study (Siwak and green tea) can be used safely as an intra-canal irrigant for smear layer removal with efficiency that is comparable with conventional synthetic materials (EDTA) and more complicated methods (Waterlase).

Effect of implant design and bioactive glass coating on biomechanical properties of fiber-reinforced composite implants.

This study aimed to evaluate the influence of implant design and bioactive glass (BAG) coating on the response of bone to fiber-reinforced composite (FRC) implants. Three different FRC implant types were manufactured for the study: non-threaded implants with a BAG coating; threaded implants with a BAG coating; and threaded implants with a grit-blasted surface. Thirty-six implants (six implants for each group per time point) were installed in the tibiae of six pigs. After an implantation period of 4 and 12 wk, the implants were retrieved and prepared for micro-computed tomography (micro-CT), push-out testing, and scanning electron microscopy analysis. Micro-CT demonstrated that the screw-threads and implant structure remained undamaged during the installation. The threaded FRC/BAG implants had the highest bone volume after 12 wk of implantation. The push-out strengths of the threaded FRC/BAG implants after 4 and 12 wk (463°N and 676°N, respectively) were significantly higher than those of the threaded FRC implants (416°N and 549°N, respectively) and the nonthreaded FRC/BAG implants (219°N and 430°N, respectively). Statistically significant correlation was found between bone volume and push-out strength values. This study showed that osseointegrated FRC implants can withstand the static loading up to failure without fracture, and that the addition of BAG significantly improves the push-out strength of FRC implants.

Histological, mechanical, and radiological study of osteoformation in titanium foam implants.

Titanium (Ti) is widely used for implants because of its high mechanical reliability and because it aids osteoformation. However, it also produces artifacts during radiological imaging. Further, Ti implants can sometimes cause the surrounding bone to break. Owing to recent advances, Ti can be transformed into sponge-like, porous materials having a three-dimensional network of pores; such materials are called Ti foams. These foams exhibit distinct characteristics that make them more suitable than nonporous Ti. The objective of this study was to evaluate Ti foams as implant materials. Implants based on Ti foams having porosities of 80% and 90% were embedded in the femurs of 11 rabbits. Implants based on 0% porosity Ti were used as controls. Five rabbits were sacrificed 4 weeks after implantation, while the remaining were sacrificed after 12 weeks. The femurs containing the Ti implants were harvested and analyzed. Biomechanical analyses showed that the 80% porosity implants induced greater osteoformation. There were significant differences in the average pushout strengths of the control and 80% porosity implants after 4 weeks (p = 0.048) and 12 weeks (p = 0.001). Histopathological analyses confirmed osteoformation in the case of the 80% porosity implants. Analyses of the micro-computed tomography images of the Ti foam-based implants did not suggest the presence of artifacts. The 80% porosity Ti implants did not exhibit the shortcomings associated with conventional Ti implants. In addition, they induced greater osteoformation. Finally, the Ti foams did not produce radiological artifacts.

Effect of smear layer on the push-out bond strength of two endodontic biomaterials to radicular dentin.

This in vitro study was designed to evaluate the effect of smear layer removal on push-out bond strength of white mineral trioxide aggregate (WMTA) and calcium-enriched mixture cement (CEM). Dentin discs with 3 mm thicknesses were divided into 4 groups (n=15): group 1: irrigation of the canal with normal saline and filling with WMTA; group 2: irrigation with sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA), and then filling with WMTA; group 3: same as group 1 but the lumens were filled with CEM; group 4: same as group 2 but the lumens filled with CEM. The samples were incubated at 37(°)C for 3 days after wrapping in gauze pieces moistened with distilled water. The push-out bond strengths were then measured by the universal testing machine and the failure modes were examined under a stereomicroscope at 40× magnification. Data were analyzed using two-way ANOVA and post-hoc Tukey's test for bond strength. Statistical significance was set at P<0.05. The greatest and lowest mean standard deviation for push-out bond strength were observed for groups 4 (3.13±1.46 MPa) and group3 (1.44±0.96 MPa), respectively. The effect of smear layer removal on push-out bond strength of CEM was significant (P=0.01), however, it was not significant for WMTA (P=0.52). The failure mode for all the groups was of mixed type. Under the limitations of this study, smear layer removal is recommended for CEM in order to gain higher push-out strength.

Effect of the interfacial area measurement parameters on the push-out strength between fiber post and dentin

PurposeTo verify the influence of different instruments and operators on the bonding interfacial area and on the push-out bond strength values. Material and methodsFifteen anterior human teeth (n=15) were selected, cleaned and standardized to 15mm length. Root canals were prepared in 12mm and the fiber posts were cemented using the RelyX U-100 cement. Three slices were obtained per tooth (N=45) and submitted to the push-out bond strength test. The bonding interfacial area (mm2) of each specimen was calculated based on the disc slice dimensions: coronal and apical diameter and height. The bonding area of each specimen was used to calculate the bond strength (Mpa). The dimensions were analyzed by different operators, using two instruments: G1 – Operator A with a digital caliper; G2 – Operator A with a stereomicroscope; G3 – Operator B with a digital caliper; G4 – Operator B with a digital stereomicroscope; G5 – Operator C with a digital caliper; G6 – Operator C with a stereomicroscope. The mean area was submitted to inter-operator and intra-operator analyses, while the mean area and mean of bond strength were submitted to the 2-way ANOVA with repeated measures and the Tukey test (α=0.05). ResultsThe inter-operator kappa was 0.83 to the digital caliper and 0.91 to the stereomicroscope, while the intra-operator kappa was 0.76. The operator and the measurement instrument influenced the interfacial bonding area (p=0.000 and p=0.001) and the push-out bond strength values (p=0.000 and p=0.000, respectively) of the disc slices. ConclusionThe final push-out bond strength values are influenced by the measuring instrument and by the measurer operator.

Influence of Surface Conditioning Protocols on Glass-Fiber Post Adhesion Performance After Aging and Flexural Strength

The effect of surface-conditioning of fiber-posts on the flexural strength of the post and on the adhesion between the root dentin and cement and between the fiber-post and the composite core were assessed. The fiber-posts were subjected to cleaning with alcohol (AL), treatment with AL + silane (SIL), sandblasting with Al2O3 particles + SIL, H2O2 etching + SIL, hydrofluoric acid etching + SIL, and H3PO4 etching + SIL. For comparison, another group of specimens was left unconditioned (control group). The conditioned fiber-posts were cemented to bovine roots, and standardized cylindrical resin cores were fabricated. The specimens were subjected to 106 mechanical pulses and then sectioned perpendicular to the long axis of the root. Push-out tests were conducted on the sliced root sections, and microtensile testing was applied to the trimmed sliced core sections. The posts were also subjected to three-point bending tests. The surface-conditioning did not have any significant effect on the push-out strength. However, silanization increased the microtensile strength at the resin core. Sandblasting significantly decreased the flexural strength as compared to other surface treatments. Our study indicates that post surface-conditioning did not improve the post retention in the root canal, although silanization enhanced the adhesion to the core resin. Sandblasting with 125-µm alumina particles should be avoided.

Mixing with Propylene Glycol Enhances the Bond Strength of Mineral Trioxide Aggregate to Dentin

IntroductionMixing mineral trioxide aggregate (MTA) with different proportions of propylene glycol (PG) improves its handling property. The aim of this study was to evaluate the effect of PG on MTA-dentin push-out bond strength. MethodsSeventy-five 2-mm-thick midroot sections were prepared from single-rooted human extracted teeth. The lumen of each slice was enlarged with Gates-Glidden burs. The slices were randomly divided into 3 groups (n = 25). In each group, 0.3 mL of the liquid was mixed with 1 g MTA (Angelus, Londrina, Brazil). The liquid vehicles used in groups 1–3 were 100% distilled water (DW), 20% PG–80% DW, and 100% PG, respectively. After incubation, the push-out strength of the samples was measured using a universal testing machine. The samples were then cut in halves and examined under a stereomicroscope to determine the failure pattern. One-way analysis of variance followed by the Tukey post hoc test was used to compare the push-out strength among groups. ResultsThere were statistically significant differences between groups (P < .001). The push-out strength in group 1 (DW) was significantly lower than groups 2 and 3 (P < .001 and P = .022, respectively). However, there was no significant difference between groups 2 (DW-PG) and 3 (PG). ConclusionsMixing MTA with PG increased its push-out bond strength to dentin. In the present study, the most suitable ratio was 80% DW–20% PG.

Push‐out bond strength of MTA with antiwashout gel or resins

Assessment of the push-out bond strength of four MTA-based formulations for use as root-end filling materials. MTA Plus mixed with (i) water ('MTA-W'); (ii) a proprietary water-based antiwashout gel ('MTA-AW'); (iii) Superbond C&B chemically curing resin ('MTA-Chem'); and (iv) Heliobond light-curing resin ('MTA-Light') was tested. Root slices 3 mm thick human had a 1.5 mm diameter hole drilled centrally and were treated with 17% EDTA for 60s. Forty specimens divided into groups 1-4 were prepared and filled with MTA-W, MTA-AW, MTA-Chem and MTA-Light, respectively. Groups 3 and 4 were etched with 37% phosphoric acid for 60s, and bonding agent was applied to the dentine surface. Specimens were stored for 28 days in Hanks' Balanced Salt Solution at 37 °C. Push-out strength was tested with a punch and die (punch diameter 1.3 mm, die diameter 2.0 mm, punch speed 1 mm min(-1)). Stereomicroscopy was used to classify failure mode (adhesive, cohesive or mixed type). The resulting push-out strengths were 5.1 MPa (MTA-W), 4.3 MPa (MTA-AW), 4.7 MPa (MTA-Chem) and 11.0 MPa (MTA-Light). MTA-W had higher push-out strength than MTA-AW (P = 0.022). The same was noted for MTA-Light relative to the other materials (P < 0.05). All materials exhibited adequate push-out strengths compared with MTA-W. Failure was predominantly mixed, except for MTA-Chem (predominantly adhesive). All materials exhibited adequate push-out strength. Previous studies have shown the new formulations have additional advantages including increased washout resistance and faster setting time, making them promising for future dental applications.

Push-out bond strengths of different dental cements used to cement glass fiber posts

Since the introduction of glass fiber posts, irreversible vertical root fractures have become a rare occurrence; however, adhesive failure has become the primary failure mode. The purpose of this study was to evaluate the push-out bond strength of glass fiber posts cemented with different luting agents on 3 segments of the root. Eighty human maxillary canines with similar root lengths were randomly divided into 8 groups (n=10) according to the cement assessed (Rely X luting, Luting and Lining, Ketac Cem, Rely X ARC, Biscem, Duo-link, Rely X U100, and Variolink II). After standardized post space preparation, the root dentin was pretreated for dual-polymerizing resin cements and untreated for the other cements. The mixed luting cement paste was inserted into post spaces with a spiral file and applied to the post surface that was seated into the canal. After 7 days, the teeth were sectioned perpendicular to their long axis into 1-mm-thick sections. The push-out test was performed at a speed of 0.5 mm/min until extrusion of the post occurred. The results were evaluated by 2-way ANOVA and the all pairwise multiple comparison procedures (Tukey test) (α=.05). ANOVA showed that the type of interaction between cement and root location significantly influenced the push-out strength (P<.05). The highest push-out strength results with root location were obtained with Luting and Lining (S3) (19.5 ±4.9 MPa), Ketac Cem (S2) (18.6 ±5.5 MPa), and Luting and Lining (S1) (18.0 ±7.6 MPa). The lowest mean values were recorded with Variolink II (S1) (4.6 ±4.0 MPa), Variolink II (S2) (1.6 ±1.5 MPa), and Rely X ARC (S3) (0.9 ±1.1 MPa). Self-adhesive cements and glass ionomer cements showed significantly higher values compared to dual-polymerizing resin cements. In all root segments, dual-polymerizing resin cements provided significantly lower bond strength. Significant differences among root segments were found only for Duo-link cement.

The effect of smear layer on the push-out bond strength of root canal calcium silicate cements

IntroductionThe aim of this study was to evaluate the effect of smear layer removal on the push-out bond strength between radicular dentin and three calcium silicate cements (CSC) in comparison with gutta percha and sealer. MethodsEighty human anterior extracted teeth were decoronated, cleaned and shaped to size 50/0.05 apically and randomly divided into 2 major groups: (A) smear layer preserved, and (B) smear layer removed using irrigation with 17% EDTA. Roots within each major group were further divided into 4 subgroups according to the obturation material used: (1) ProRoot MTA, (2) Biodentine, (3) Harvard MTA, (4) Gutta percha and AH-plus sealer. Obturated roots were stored in synthetic tissue fluid for 7 days to allow maximum setting of the root filling materials. Three 2-mm-thick slices were obtained from each root at different section levels (coronal, middle, apical). The canal diameters and slice thickness were measured, and the adhesion surface area for each slice was calculated. Push-out bond strength test was carried out using a universal testing machine. The bond failure mode was assessed under an optical microscope at 40×. ResultsThe mean push-out bond strength in groups 1A, 2A and 3A were 7.54 (±1.11), 7.64 (±1.08) and 8.79 (±1.55)MPa respectively, while those for groups 1B, 2B and 3B were 6.58 (±1.13), 6.47 (±1.08), 7.71 (±1.81)MPa, respectively. In the gutta percha and sealer groups the push-out bond strength means were: 1.98 (±0.48) and 2.09 (±0.51)MPa in the preserved and removed smear layer groups respectively. The push-out strength values were significantly reduced when the smear layer was removed in the CSC groups (P<0.05) while no significant difference was detected in the gutta percha and sealer groups. ConclusionsBased on the conditions of this ex vivo study, it can be concluded that smear layer removal is detrimental to the bond strength between calcium silicate cements and dentin.

Effect of Screw Insertion Torque on Push‐Out and Cantilever Bending Properties of Five Different Angle‐Stable Systems

To compare the screw push-out strength and resistance to cantilever bending of 5 different angle-stable systems using 4 different insertion torque values to tighten locking screws. In vitro mechanical testing of 5 screw-plate constructs. Screw plate constructs (n = 60) were tested; 12 of each design, 3 for each torque value. To compare push-out strength, screws were loaded in axial direction on the screw tip until loosening of the locking mechanism was recorded. For cantilever bending test, screws were loaded perpendicularly to their longitudinal axis at 2 mm of distance from the under surface of the plate. Load was applied in displacement control at 1 mm/min. There was a significant difference between the 5 different angle-stable systems regarding both push-out and cantilever bending strength. There was an influence of insertion torque value on push-out strength for 2 systems and insertion torque value influenced cantilever bending behavior only in 1 locking system. Locking mechanisms using "thread in thread" principle provided a stronger screw push-out behavior. Screws materials and core diameter of the different screws were directly related to cantilever bending strength.

Aging affects the adhesive interface of posts luted with self-adhesive cements: a 1-year study.

To examine the bond strength and interfacial nanoleakage expression of fiber posts luted to intraradicular dentin with self-adhesive cements. Six-month and 1-year aging effects were examined. Post space was created in endodontically treated human incisors. Each tooth was assigned to a self-adhesive cement/post combination: (1) Bifix SE Cement (Voco) with proprietary posts (Rebilda Post, Voco), (2) RelyX Unicem (3M ESPE) with proprietary posts (Rely X Fiber Post, 3M ESPE), (3) MaxCem (Kerr) with Rebilda Posts. Each specimen was cut into 1-mm-thick sections and either immediately stressed to failure with the push-out bond strength test or aged in artificial saliva for 6 months or 1 year before testing. Additional specimens were processed for quantitative interfacial nanoleakage analysis using ammoniacal silver nitrate. Immediate bond strength ranked in the following order: Bifix SE (7.8 ± 2.9 MPa) = RelyX Unicem (8.4 ± 2.7 MPa) > MaxCem (4.6 ± 2.4 MPa) (p < 0.05). Aging significantly reduced the bond strength of all cements after 1 year: Bifix SE (3.8 ± 1.4 MPa) = RelyX Unicem (5.8 ± 1.7 MPa) > MaxCem (1.3 ± 0.9 MPa; p<0.05). No immediate difference in interfacial nanoleakage expression was found. Nanoleakage increased after aging, and MaxCem showed the highest values. The push-out strength and interfacial nanoleakage expression of fiber posts luted with self-adhesive cements were dependent on luting material and type of post, and were significantly affected by storage time.