Effect of oxalate desensitizer on the bonding durability of adhesive resin cements to dentin

PurposeThis study investigated whether the tubular occluding effect of oxalate desensitizer (OX) during adhesive cementation improved bonding of a self-etch and two etch-and-rinse resin cements to dentin after 6 months.MethodsA flat dentin surface was prepared on 120 extracted premolars, which were randomly divided into six groups of 20 teeth each according to the adhesive resin cement system used: ED primer II/Panavia F2.0, Excite DSC (Ex DSC)/Variolink II, and One-Step Plus (OS Plus)/Duolink, with or without OX (BisBlock) application. After cementation of an indirect composite rod, two subgroups (n = 10) were tested after 24 h and 6 months of water storage plus thermocycling, and shear bond strengths were recorded in MPa.ResultsStatistical tests showed that although oxalate had a borderline significant negative effect on initial bonding of ED primer II/Panavia F2.0, it significantly improved bonding durability (p < 0.05). OX severely compromised the initial bond strength of Ex DSC/Variolink II (p < 0.001) but had no effect on the reduction in bonding after aging. OX was compatible with OS Plus/Duolink and did not affect the loss of bonding strength after 6 months (p > 0.05).ConclusionCombining an oxalate desensitizer with three types of resin cements had different effects on bond strength to dentin after aging, depending on the interaction of oxalate with the adhesive system associated to the resin cement.     

Effect of chlorhexidine application on long-term shear bond strength of resin cements to dentin

PurposeThe purpose of this study was to investigate the effect of chlorhexidine [CH] on dentin bond strength of three resin cements after 1 year of water storage.MethodsA flat middle dentin surface was prepared on 120 extracted premolars. The teeth were randomly divided into 6 groups of 20 specimens each according to the resin cement used: Panavia F2.0, Variolink II, and RelyX Unicem, with or without CH application. After cementation of an indirect composite rod [Z250], one subgroup [n = 10] was tested after 24 h in water at 37 °C and the other subgroup [n = 10] was tested after 1 year storage in water plus thermocycling. A shear bond strength [SBS] test was performed. The data [in MPa] were analyzed with ANOVA and Tukey tests [P < 0.05].ResultsThree-way ANOVA [resin cement, CH and time] indicated that Variolink II had the highest strength [16.65 ± 3.60] and RelyX Unicem had the lowest strength [9.30 ± 4.07]. Chlorhexidine application increased SBS [13.31 ± 4.61] compared to samples without CH [12.16 ± 5.04] [P = 0.04]. Initial SBS [15.63 ± 4.37] was significantly higher than after 1 year of storage [9.85 ± 3.36] [P < 0.001]. Separate two-way ANOVA for 24-h and 1-year data showed that cement had a significant effect but CH and its interaction had no significant effect at 24 h, whereas at 1 year the two factors and their interaction differed significantly [P ≤ 0.001].ConclusionsChlorhexidine 2% can diminish the loss of bonding effectiveness over time associated to etch-and-rinse and self-etch cements, although it appears not have any effect on self-adhesive cement.     

Mechanical properties of new self-adhesive resin-based cement

PurposeThe aim of this study was to compare the bonding strength, flexural strength, elastic modulus, water absorption and the expansion after water storage of new self-adhesive resin cements to commercially available dental cements.MethodsTwo types (hand-mix and auto-mix) of new self-adhesive resin cements (SAC-H and SAC-A, Kuraray Medical), one conventional resin cement (Panavia F2.0), three self-adhesive resin cements (Relyx Unicem, Maxcem and G-Cem), and two resin-modified glass-ionomer cements (Fuji Luting S and Vitremer) were used. Shear bond strengths, flexural strengths and elastic moduli (ISO 4049), water absorption (ISO 4049), and the expansion rate after water storage were investigated.ResultsBoth SAC-H and SAC-A provided adhesion to enamel and dentin, and had the same bond strength to gold alloy and zirconia as conventional resin cements. SAC-H and SAC-A had greater flexural strengths (86.4–93.5 MPa) than commercial self-adhesive resin cements or glass-ionomer cements. The elastic moduli of self-adhesive and glass-ionomer cements were 5.2–7.4 GPa and 2.3–3.4 GPa, respectively. The water absorption of SAC-H and SAC-A (26.3–27.7 μg/mm³) were significantly lower than commercial self-adhesive resin cements. SAC-H and SAC-A showed significantly lower expansion rates (0.17–0.26%) than commercial self-adhesive cements and glass-ionomer cements after 4 weeks water storage.ConclusionsIt is suggested that the new self-adhesive resin cements exhibited a favorable bonding capability and mechanical properties.     

Challenges in luting fibre posts: Adhesion to the post and to the dentine

Objective

To investigate the relationship between physicochemical interactions of resin luting cements with dentine and retention of fibre posts in root canals.

Tensile bond strength of cast commercially pure titanium dowel and cores cemented with three luting agents

PurposeThe purpose of this study was to compare the tensile strength of commercially pure titanium dowels and cores cemented with zinc phosphate or resin cements.MethodsTwenty-one extracted human canines were endodontically treated. The root preparations were accomplished using Largo reamers (10 mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the dowel and cores were made, and specimens were cast in commercially pure titanium (n = 7) and divided in three groups: TZ–CP Ti dowels luted with zinc phosphate luting agent, TP–CP Ti dowels luted with Panavia F and TR–CP Ti dowels luted with RelyX U100. Tensile strengths were measured in a universal testing machine at a crosshead speed of 0.5 mm/min. The results (N) were statistically analyzed by ANOVA and Tukey tests (α = 0.01).ResultsThe ANOVA indicated that there were significant differences among the groups tested. A Tukey multiple comparison procedure was performed and revealed statistically significant higher retention values for the dowel luted with RelyX U100 when compared with zinc phosphate or Panavia F.ConclusionCast commercially pure titanium dowels and cores fixed with RelyX U100 cement presented superior bond strength retention when compared to zinc phosphate and Panavia F.     

Cytotoxicity of polymerized resin cements on human dental pulp cells in vitro

ObjectivesThis study was designed to evaluate the cytotoxicity of several resin-based cements (Panavia F, Super-Bond C&B, Chemiace II) after polymerization on cultured human dental pulp cells.MethodsAfter polymerization, specimens from three resin-based cements were eluted with fresh Dulbecco's modified Eagle's medium (DMEM) without serum for 72 h, at 37 °C, using 0.4 g of each substance per milliliter of fresh medium. Elutes obtained during this step were passed through a 0.22-μm filter and diluted with the culture medium by a ratio of 75%, 50%, 25% (v/v). Cytotoxicity of elutes were evaluated by the relative growth rates (RGR) of pulp cells with a modified 3-(4, 5-dimethyl-thiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay. The RGR of pulp cells were statistic analyzed by the one-way analysis of variance among the groups.ResultsThe RGR of cells exposed to 100% concentration of elution of Panavia F, Super-Bond C&B, and Chemiace II were 74.42%, 85.54%, and 82.39%, respectively. The RGR increased along with the elution of cements diluted. There was significant difference between the Panavia F group and Super-Bond C&B group (p < 0.01), but there was no significant difference in the cytotoxicity between Chemiace II and Super-Bond C&B.ConclusionsAfter polymerization, three resin-based cements (Panavia F, Super-Bond C&B, Chemiace II) induced slight cytotoxicity. The sensitivity of cytotoxicity to human pulp cells depended on the resin-based cements and the concentration of the elution. Super-Bond C&B is the least cytotoxic agent among the three resin-based cements.     

Effect of pulpal pressure on the microtensile bond strength of luting resin cements to human dentin

ObjectivesThe objectives of this study were to examine the effect of pulpal pressure on the microtensile bond strength (mTBS) of luting resin cements to human dentin and the permeability of dentin surfaces pre-treated with an adhesive and a self-etching primer.MethodsCylindrical composite blocks were luted with resin cements (RelyX ARC, 3M ESPE: ARC; Panavia F, Kuraray Medical Inc.: PF; RelyX Unicem, 3M ESPE: UN) in the absence or presence of simulated pulpal pressure. The application of Adper Single Bond 2 (3M ESPE) and ED primer 2.0 (Kuraray) was performed under 0 cm H₂O. After each resin cement was applied, the pulpal pressure group was subjected to 20 cm H₂O of hydrostatic pressure for 10 min during the initial setting period. Testing for mTBS was performed on 0.9 mm × 0.9 mm sectioned beams after 24 h water-storage. Scanning electron microscopy was performed to investigate the fractured surfaces after mTBS testing and additional dentin surfaces that were treated by an etchant, ED primer 2.0 and UN. Fluid permeability was measured on dentin surfaces that were applied with Adper Single Bond 2 and ED primer 2.0.ResultsApplication of pulpal pressure reduced mTBS significantly in groups ARC and PF. Porous bonding interfaces due to water permeability through the cured adhesive were observed on fractured surfaces. Dentin surfaces that were applied with the adhesive and the primer were more permeable than smear layer-covered dentin. The mTBS of UN was significantly lower than ARC and PF regardless of the absence/presence of pulpal pressure.SignificanceFluid permeation during the initial setting period deteriorated the bonding quality of resin cements.     

Polymerization efficiency through translucent and opaque fiber posts and bonding to root dentin

PurposeTo investigate the polymerization efficiency through translucent and opaque glass fiber posts and the bond strength of a self-adhesive resin to root dentin.MethodsTranslucent and opaque silanated conical posts, identical in length, diameter and shape (n = 8), were cemented to incisor bovine roots using RelyX Unicem Clicker. Photoactivation was performed only through the posts. The roots were transversally sectioned (cervical, middle and apical thirds) and the push-out test was carried out. Data were analyzed using two-way ANOVA and Fisher's LSD method (5%). Failure modes were classified under magnification. An elastomer mold of a bovine incisor root was filled with flowable composite and the posts inserted into the mold. After photoactivation through the post and removal of unpolymerized material, the polymerization efficiency was estimated by percentage of mass gain (n = 5). Data were analyzed using t-test (5%).ResultsThe bond strength of the translucent post was higher than the opaque post for all root thirds. For both posts the bond strength at the cervical third was higher than at the middle and apical thirds. A predominance of adhesive failures was detected for all conditions. Mixed failures were more frequently observed for the opaque post. Almost all the composite polymerized and bonded to the extension of the translucent post, whereas polymerization of the composite was restricted to the cervical area of the opaque post.ConclusionsThe use of translucent post may positively influence the polymerization efficiency and bond strength of resin cement to intraradicular dentin.     

Probability of interface imperfections within SEM cross-sections of adhesively luted GFP

ObjectivesTo calculate the probability of interface imperfections within SEM cross-sections of adhesively luted GFP depending on the level of analysis and the cement application method by means of LOM (light-optical microscopic evaluation method).Material and methodsFour groups of artificial root canals received GFPs (n = 5) under following experimental conditions: I = RelyX? Unicem, applied with application aid, II = RelyX? Unicem, III = Panavia F 2.0 and IV = Variolink II. In groups II–IV only posts were loaded with cement (i.e. conventional post cementation). After GFP cementation, standardized photographs were taken perpendicularly to post surface under light-optical microscope from two opposite sides. The length of homogenous cement interface areas were measured using surface-analyzing software. The homogenous areas were related to length of apical, middle, cervical post section and to complete post length to generate the probabilities (%) of hitting imperfections when using SEM cross-section analysis.ResultsThe probabilities (%) of hitting imperfections within SEM cross-sections for cervical, middle, and apical level of analysis were: I = 78, 64, 82; II = 89, 98, 99; III = 72, 91, 99; and IV = 85, 91, 97, respectively. For complete post length median values of probabilities (%) were: I = 75; II = 95; III = 87; and IV = 91.SignificanceThe probabilities show, that SEM cross-section evaluation concerning detection of cement interface imperfections of adhesively luted GFPs depends on the cement application method and the level of analysis and seeming therefore not always unrestricted representative for the whole specimen.     

In-vitro cytocompatibility of self-adhesive dual-curing resin cements on human mesenchymal stem cells (hMSC) and periodontal ligament cells (PDL-hTERT)

ObjectivesSelf-adhesive dual cured resin cements provide easier clinical application than conventional resin cements but release higher amounts of unreacted monomers, potentially affecting their biocompatibility. This study aimed to compare the cytotoxic effects of self-adhesive dual cured resin cements with two conventional resin cements.MethodsSamples of four resin cements, two self-adhesive dual cured cements (group A: RelyX Unicem, group B: SmartCem), and two conventional resin cements (group C: Panavia 2.0, group D: Variolink Esthetic DC) were prepared with a similar dimension under standardized polymerization conditions and stored in water. For each material 18 samples were used and cell cultures of human mesenchymal stem cells (hMSCs) or periodontal ligament cells (PDL-hTERT) were added under appropriate conditions. One experimental group (group E) was left untreated as control. A cell viability WST test, was performed in each experimental group at day 1, 7, 14 and 21. Moreover, microscopic examination of cells was performed using cell viability staining.ResultsViability of both cell types as determined by WST test was significantly impaired at all time periods by the four different cement materials compared to the untreated control. Comparison between the four materials revealed different inhibition of the viability of both, PDL-hTERT and hMSC cells (group C > group B > group A > group D; p < 0.0001).SignificanceAll resin-based cements caused significant impairment of cell viability, reflecting considerable cytotoxicity. Variolink caused significantly smaller changes of viability than the other tested materials.     

Influence of surface treatments and resin cement selection on bonding to densely-sintered zirconium-oxide ceramic

ObjectivesTo evaluate the effect of surface conditioning on the microtensile bond strength of zirconium-oxide ceramic to dual-cured resin cements.MethodsEighteen cylinder-shaped zirconium-oxide ceramic blocks (Cercon^® Zirconia, Dentsply) were treated as follows: (1) Sandblasting with 125 μm aluminum-oxide (Al₂O₃) particles; (2) tribochemical silica coating using 50 μm Al₂O₃ particles modified by silica; (3) no treatment. Each ceramic cylinder was duplicated in composite resin (Tetric Evo Ceram, Ivoclar-Vivadent) using a silicon mold. Composite cylinders were bonded to conditioned ceramics using: (1) Calibra (Densply Caulk); (2) Clearfil Esthetic Cement (Kuraray); (3) Rely × Unicem (3 M ESPE). After 24 h bonded specimens were cut into microtensile sticks that were loaded in tension until failure. Data were analyzed using two-way ANOVA and Student–Newman–Keuls test for multiple comparisons (p < 0.05). Failure mode was recorded and the interfacial morphology of debonded specimens was observed using a scanning electron microscope (SEM). Surface topography and ceramic average surface roughness were analyzed under an atomic force microscope (AFM).ResultsSignificant changes in zirconia surface roughness occurred after sandblasting (p < 0.001). Bond strength of Clearfil cement to zirconia was significantly higher than that of Rely × Unicem and Calibra, regardless of the surface treatment (p < 0.001). When using Calibra, premature failures occurred in non-treated and silica coated zirconia surfaces.SignificanceThe phosphate monomer-containing luting system (Clearfil Esthetic Cement) is recommended to bond zirconia ceramics and surface treatments are not necessary.     

Operator vs. material influence on clinical outcome of bonded ceramic inlays

ObjectiveThe aim of the present study was to clinically evaluate the suitability of Definite Multibond and Definite ormocer resin composite for luting of Cergogold glass ceramic inlays in a two-center trial involving two dentists.MethodsThirty-nine patients received 98 Cergogold inlays with at least one inlay luted with Definite Multibond/Definite (n = 45) and at least one inlay luted with Syntac/Variolink Ultra (n = 53) in a split mouth design. Treatments were carried out in two private practices by two operators (Operator A: n = 38; Operator B: n = 60). Forty-four cavities required caries profunda treatment, 23 cavities exhibited no enamel at the cervical margin. At baseline (2 months), and after 6, 14, 27, and 51 months of clinical service, the restorations were investigated according to modified USPHS criteria.ResultsThe drop-out rate was 3% after 4 years. After 48 months of clinical service, 21 restorations in 16 patients (9 luted with Definite, 12 with Variolink; 2 placed by operator A and 19 by operator B) had to be replaced due to inlay fracture (n = 11), tooth fracture (n = 4), hypersensitivities (n = 3), or marginal gap formation (n = 3). Seventy-seven inlays were in good condition (survival rate 89.9%, median survival time 4.2 years (95% confidence interval ±0.25; survival analysis by Kaplan–Meier algorithm). Survival rate after 4 years was 97.4% for operator A, and 75.4% for operator B (p = 0.002; Log Rank/Mantel-Cox) resulting in annual failure rates of 0.6% and 6.2%, respectively. The operators did not differently judge the clinical behaviour of the luting procedures (Mann–Whitney U-test, p > 0.05). Independent of the operator and the used luting system, the following criteria significantly changed over time: color match, marginal integrity, tooth integrity, inlay integrity, sensitivity, hypersensitivity, and X-ray control (p < 0.05; Friedman test). Significant differences between operators over the whole period were computed for the criteria marginal integrity, tooth integrity, and inlay integrity (p < 0.05, Mann–Whitney test). Differences between luting materials were only present during single recalls.SignificancesFor luting of ceramic inlays, only slight differences between the two luting systems were detectable. The operator influence on clinical outcome was clearly proven.     

Effects of different radiation doses on the microhardness,superficial morphology,and mineral components of human enamel

ObjectiveTo evaluate the effects of three different radiotherapy doses (20, 40, and 70 Gy) on the microhardness, superficial morphology, and mineral content (based on Ca and P values) of three different depths of human enamel (cervical, middle, and occlusal).DesignThirty-four third molars were cut, separated, and prepared. Microhardness samples (n = 30) were embedded in acrylic resin and then polished, and depths were delimited. Microhardness tests were performed on cervical, middle, and occlusal enamel pre- and post-radiotherapy with a load of 50 g for 30 s. For the scanning electron microscopy (SEM) analysis (n = 4) and energy dispersive X-ray spectroscopy (EDS) (n = 12), samples were fixed in a 3% glutaraldehyde solution, washed in 0.1 M cacodylate solution, and dehydrated in crescent concentrations of ethanol. Microhardness data were tested for significant differences using a two-way analysis of variance (ANOVA) and Tukey’s test (p < 0.05), while SEM and EDS were evaluated qualitatively.ResultsThe results showed a decrease in microhardness values only in the cervical enamel, regardless of the radiation dose used; no morphological or mineral change was observed.ConclusionRadiotherapy can affect the microhardness values of only cervical enamel without compromising the morphological or mineral (Ca and P) content at any depth.     

The efficacy of Salvadora persica extract in the elimination of the intracanal smear layer: A SEM study

AimTo evaluate the efficacy of an ethanolic Salvadora persica extract in removing the smear layer following a root canal procedure.MethodsSixty extracted, single-rooted human teeth were cleaned, shaped, and divided into four groups. Experimental groups 1 (n = 20) and 2 (n = 20) were irrigated with 1 mg/ml and 5 mg/ml of S. persica, respectively. The positive controls (n = 10) were irrigated with 17% ethylenediaminetetraacetic acid (EDTA), while the negative controls (n = 10) were irrigated with saline. Approximately 5 ml of the irrigating solution was delivered into the root canals for 5 min, and the final rinse was performed with 5 ml of 1% sodium hypochlorite. Scanning electron microscopy was used to evaluate the endodontic smear layer removal at the coronal, middle, and apical thirds of the specimens.ResultsA significant difference in smear layer removal between groups 1 and 2 at the coronal and middle thirds of the canal was observed, and no significant difference was seen between group 2 and the positive control at the coronal third. At the apical third, both concentrations of S. persica had similar effects and were less effective than the positive control in removing the smear layer.ConclusionThe 5 mg/ml S. persica solution was significantly more effective than the 1 mg/ml solution. In addition, the 5 mg/ml S. persica solution was as effective as 17% EDTA in removing the smear layer from the coronal third of the canal wall.     

Mechanical and physical properties of silorane and methacrylate-based composites

ObjectivesThis study measured the degree of conversion (DC), sorption, solubility and microhardness of methacrylate (Filtek Z250 and Filtek Z350XT) and silorane-based composites (Filtek P90).MethodsDC was measured using near infrared spectroscopy immediately and 24 h after the photoactivation. Sorption and solubility measurements were performed after 24 h, 4 weeks and 12 weeks of storage in water. Knoop microhardness was measured after 24 h and after thermal cycling. The data were statistically analyzed using ANOVA followed by Tukey's, Tamhane or paired t-tests (α = 0.05).ResultsThe DC for P90 (37.22 ± 1.46) was significantly lower than the Z250 (71.44 ± 1.66) and Z350 (71.76 ± 2.84). Water sorption was highest in the Z250 and lowest in the P90. All the tested composites exhibited similar values after 24 h of immersion, and no significant differences were observed. No significant differences were observed between the solubilities of the P90 composite (12 weeks) and the Z250 or Z350 composites (4 weeks). KHN values were less elevated for the P90 composite and similar for the Z250 and Z350 composites. An effect of thermal cycling on KHN values was observed for all the composites (p < 0.001).ConclusionsSilorane produced the lowest DC and KHN values and exhibited lower water sorption and solubility compared to methacrylate-based composites. These differences suggest that silorane composites exhibit better hydrolytic stability after 3 months of water immersion compared to conventional methacrylate-based composites.Clinical significanceSilorane had higher hydrolytic stability after 3 months of water immersion than the methacrylate-based resins, despite the lower values of DC and KHN recorded.     

Effect of types of luting agent on push-out bond strength of zirconium oxide posts

ObjectiveThe aim of this study was to investigate the effect of different luting agents on the bond strength of zirconium oxide posts in root canals after artificial ageing.Material and methodsThirty single-rooted extracted teeth were collected. Post spaces were prepared. Custom milled zirconium oxide posts (Cercon, Degudent) were fabricated. Specimens were divided into 3 groups (n = 10), according to the luting agents used: group RA, conventional resin luting agent (RelyX ARC); group RU, self-adhesive resin luting agent (RelyX Unicem); and group Z, zinc phosphate luting agent (DeTrey). Specimens were subjected to thermocycling and water storage at 37 °C. Specimens were horizontally sectioned into three sections and subjected to a push-out test with 0.5 mm/min crosshead speed. The failure mode was assessed by scanning electron microscopy. Data were analysed by using 2-way ANOVA.ResultsThe following bond strength values were obtained: group RA – 8.89 MPa, group RU – 10.30 MPa and group Z – 9.31 MPa. There was no significant difference in bond strength among the groups (P = 0.500). Adhesive failure mode at the cement/post bonded interface was seen in 100%, 66.67% and 83.3% of examined sections in groups RA, RU and Z, respectively. There was no significant difference in bond strength among different root regions (P = 0.367).ConclusionThe type of luting agent had no significant effect on the push-out bond strength of zirconium oxide posts after artificial ageing.Clinical significanceConventional luting agents, such as zinc phosphate cement, seem to provide comparable retention to resin luting agents for cementing custom milled zirconium oxide posts.     

A comparison of stress relaxation in temporary and permanent luting cements

PurposeThe stress relaxation and compressive strength of resin, resin-modified glass ionomer, glass ionomer, polycarboxylate, and zinc oxide eugenol cements were measured to determine the characteristics of these materials after setting.MethodsA total of 19 luting cements including 12 permanent cements and 7 temporary cements were used. Cylindrical cement specimens (10 mm long and 6 mm in diameter) were obtained by chemical setting or light curing. The specimens were stored for 24–36 h in water at 37 °C and were then used for the stress relaxation and compression tests. The stress relaxation test was carried out using three constant cross-head speeds of 5, 50, and 100 mm/min. Upon reaching the preset dislocation of 0.5 mm, the cross-head movement was stopped, and the load was recorded for 60 s. Fractional stress loss at 1 s was calculated from the relaxation curves. The compressive strength and modulus were measured at a cross-head speed of 1 mm/min. Data were analyzed with the Kruskal–Wallis test and Holm's test.ResultsA zinc oxide eugenol cement [TempBOND NX] exhibited the largest fractional stress loss. A resin cement [ResiCem] showed the largest compressive strength, while a glass ionomer cement [HY-BOND GLASIONOMER CX] showed the largest compressive modulus among all tested cements (p < 0.05).ConclusionThe fractional stress loss could not be classified by the cement type. Two implant cements [Multilink Implant and IP Temp Cement] showed similar properties with permanent resin cements and temporary glass ionomer cements, respectively. Careful consideration of the choice of cement is necessary.     

Misfit and microleakage of implant-supported crown copings obtained by laser sintering and casting techniques,luted with glass-ionomer,resin cements and acrylic/urethane-based agents

ObjectivesThis study evaluated the marginal misfit and microleakage of cement-retained implant-supported crown copings.MethodsSingle crown structures were constructed with: (1) laser-sintered Co–Cr (LS); (2) vacuum-cast Co–Cr (CC) and (3) vacuum-cast Ni–Cr–Ti (CN). Samples of each alloy group were randomly luted in standard fashion onto machined titanium abutments using: (1) GC Fuji PLUS (FP); (2) Clearfil Esthetic Cement (CEC); (3) RelyX Unicem 2 Automix (RXU) and (4) DentoTemp (DT) (n = 15 each). After 60 days of water ageing, vertical discrepancy was SEM-measured and cement microleakage was scored using a digital microscope. Misfit data were subjected to two-way ANOVA and Student–Newman–Keuls multiple comparisons tests. Kruskal–Wallis and Dunn's tests were run for microleakage analysis (α = 0.05).ResultsRegardless of the cement type, LS samples exhibited the best fit, whilst CC and CN performed equally well. Despite the framework alloy and manufacturing technique, FP and DT provide comparably better fit and greater microleakage scores than did CEC and RXU, which showed no differences.ConclusionsDMLS of Co–Cr may be a reliable alternative to the casting of base metal alloys to obtain well-fitted implant-supported crowns, although all the groups tested were within the clinically acceptable range of vertical discrepancy. No strong correlations were found between misfit and microleakage. Notwithstanding the framework alloy, definitive resin-modified glass-ionomer (FP) and temporary acrylic/urethane-based (DT) cements demonstrated comparably better marginal fit and greater microleakage scores than did 10-methacryloxydecyl-dihydrogen phosphate-based (CEC) and self-adhesive (RXU) dual-cure resin agents.     

The effect of Morinda Citrifolia juice as an endodontic irrigant on smear layer and microhardness of root canal dentin

PurposeThe purpose of this study was to evaluate the effect of Morinda Citrifolia Juice (MCJ) on smear layer removal and microhardness value of root canal dentin in compared with various endodontic irrigants.Material and methodsEighty-four single-rooted human teeth were prepared to apical size of #35. Since decoronation, samples were divided into seven groups of 12 in each (n = 12). Specimens were finally irrigated by either 1: 2.5% NaOCl, 2: 6% MCJ, followed by a final flush of 17% ethylene diaminetetraacetic acid (EDTA), 3: 6% MCJ, 4: 2.5% NaOCl then17% EDTA, 5: MTAD, 6: 2% chlorhexidine (CHX), and 7: saline. After irrigation, all samples were subjected to Vickers microhardness test at 100 and 500-μm depths and then were examined under scanning electron microscopy (SEM) and ImageJ program was used to calculate open dentinal tubules. One way ANOVA and post hoc Tukey tests were used to reveal any significant differences among and between groups respectively.ResultsThe microhardness values at 100 μm and 500 μm for MTAD were significantly lower than for NaOCl + EDTA and MCJ + EDTA groups (p < 0.05). MCJ + EDTA, NaOCl + EDTA, and MTAD protocol significantly removed smear layer in compared with control group (p < 0.05), with no significant differences among these three groups.ConclusionsIt was concluded that 6% MCJ followed by a final flush of 17% EDTA can be regarded as an effective solution on smear layer removal without any adverse influence on microhardness property of root canal dentin.