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.     

Polymerization shrinkage kinetics of dimethacrylate resin-cements

ObjectivesTo determine polymerization shrinkage-strain (S_Y) and shrinkage-stress (S_Z) of six resin-cements and to compare their performance with the aid of degree of conversion (DC) data.MethodsVariolink 2 (VL2), Multilink Automix (MA), Multilink Sprint (MS, all Ivoclar-Vivadent), Nexus 2 (NX2), Maxcem (MX, both Kerr) and RelyX Unicem (RX, 3M-Espe) were investigated. MS, MX and RX were self-adhesive; others require a bonding-agent. All measurements were conducted at 23 °C for 60 min (n = 5), except 80 min for RX, with materials self-cured only (sc) and dual-cured (dc); NX2 and VL2 were additionally light-cured only (lc). S_Y was measured by the bonded-disk method [Watts DC, Cash AJ. Determination of polymerization shrinkage kinetics in visible-light-cured materials: methods development. Dent Mater 1991;7(4):281–7; Watts DC, Marouf AS. Optimal specimen geometry in bonded-disk shrinkage-strain measurements on light-cured biomaterials. Dent Mater 2000;16(6):447–51]; S_Z by the Bioman instrument [Watts DC, Satterthwaite JD. Axial shrinkage-stress depends upon both C-factor and composite mass. Dent Mater 2008;24(1):1–8 [Epub October 24, 2007]; Watts DC, Marouf AS, Al-Hindi AM. Photo-polymerization shrinkage-stress kinetics in resin-composites: methods development. Dent Mater 2003;19(1):1–11]. Light-cure was achieved by QTH at 500 mW/cm². The respective DCs were measured under the same conditions by FTIR–ATR spectroscopy. Data were analyzed by One-Way ANOVA plus Bonferroni test, and by t-test, at p < 0.05.ResultsDC by self-curing was less than the DC by dual-curing, for all cements. Shrinkage-strain ranged from 1.77 to 5.29% and shrinkage-stress from 3.36 to 10.37 MPa. NX2 and VL2 were not significantly different, when light-cured only. Except for RX, sc and dc shrinkage-strain varied maximally by 0.4%. MX showed the highest S_Y, RX the lowest. When sc, RX initially expanded by <0.5% (t ～ 5 min). For most materials, S_Y correlated with their filler loading. The highest stress with sc was exerted by MX, and when dc by MS, which was not statistically different from MX.SignificanceShrinkage data of resin-cements are of intrinsic clinical importance. Self-cure, despite a lower DC, did not necessarily result in a lower S_Y compared to dual-cure. S_Y-rate and S_Z development depend upon cure mode and S_Y upon filler fraction.     

An in vitro comparison of four intra-oral ceramic repair systems

ObjectivesThis study evaluated the effect of different surface conditioning methods on the tensile bond strength (TBS) and integrity of the leucite-reinforced glass ceramic (Cerana^® inserts)–resin composite interface, using four commercially available ceramic repair systems.MethodsTwo hundred extra-large Cerana^® inserts were mechanically treated and stored in artificial saliva for 3 weeks and subsequently randomly assigned to one of the following ceramic repair systems (n = 40/group): Group 1, Ceramic Repair^® (Ivoclar Vivadent, Liechtenstein); Group 2, Cimara^® (Voco, Germany); Group 3, Clearfil Repair^® (Kuraray, Japan); Group 4, CoJet system^® (3M ESPE, Germany); and Group 5, no surface conditioning and no adhesive system applied: the control group. Subsequently, resin composite material was added to the substrate surfaces and the ceramic–resin composite specimens were subjected to TBS testing. Representative samples from the test groups were subjected to scanning electron microscopy (SEM) to determine the mode of failure. The data were analysed statistically using a one-way multivariate analysis of variance and Kruskal–Wallis test at a 95% confidence interval level.ResultsSurface conditioning with the CoJet^® system resulted in significantly higher bond strength values (5.2 ± 1.1 MPa) than surface conditioning with the other repair systems (p = 0.03). The SEM examination of the failed interfaces revealed that all the specimens examined failed adhesively.SignificanceWhilst highest bond strength values were observed with the CoJet^® system all tested repair systems resulted in relatively weak TBS values and, as a consequence, these repair systems may be indicated only as interim measures.     

Impact of high-speed sintering,layer thickness and artificial aging on the fracture load and two-body wear of zirconia crowns

ObjectiveTo investigate the impact of high-speed sintering, layer thickness and artificial aging in a chewing simulator on the fracture load (FL) and two-body wear (2BW) of 4Y-TZP crowns.Methods4Y-TZP crowns (Ceramill Zolid HT+, Amann Girrbach AG) in three different layer thicknesses (0.5, 1.0, 1.5; N = 192, n = 64/group) were manufactured using CAD/CAM technology and sintered at 1580 °C (high-speed sintering) or 1450 °C (control group). Specimens were polished in two-steps and bonded to standardized CoCr abutments with Multilink Automix (Ivoclar Vivadent). 2BW after 6000 thermo- and 1,200,000 chewing-cycles employing enamel antagonists was determined using best fit machining. FL was tested before and after artificial aging. Univariate ANOVAs, post hoc Scheffé, unpaired t-, Kruskal–Wallis- and Mann–Whitney-U-test were computed (p < 0.05).ResultsHigh-speed sintering resulted in less 2BW of the zirconia than the control group (p = 0.013). High-speed sintering (p = 0.001–0.006) and an increase in layer thickness (p < 0.001–0.012) resulted in higher FL values, while artificial aging led to a reduction of FL (p < 0.001).SignificanceAs high-speed sintering resulted in less two-body wear of the zirconia and comparable or even higher fracture load results than the control group, this cost- and time efficient alternative presents promising mechanical results.     

Influence of bonding surface and bonding methods on the fracture resistance and survival rate of full-coverage occlusal veneers made from lithium disilicate ceramic after cyclic loading

ObjectivesThe purpose of this laboratory study was to evaluate the influence of bonding method and type of dental bonding surface on fracture resistance and survival rate of resin bonded occlusal veneers made from lithium disilicate ceramic after cyclic loading.MethodsFourty-eight extracted molars were divided into three groups (N = 16) depending on the preparation: within enamel, within dentin/enamel or within enamel/composite resin filling. Lithium disilicate occlussal veneers were fabricated with a fissure-cusp thickness of 0.3–0.6 mm. Restorations were etched (5% HF), silanated and adhesively luted using a dual-curing luting composite resin. Test groups were divided into two subgroups, one using a only a self-etching primer, the other additionally etching the enamel with phosphoric acid. After water storage (37 °C; 21 d) and thermocycling (7500 cycles; 5–55 °C), specimens were subjected to dynamic loading in a chewing simulator (600,000 cycles; 10 kg/2 Hz). Surviving specimens were loaded until fracture using a universal testing machine.ResultsAll specimens survived artificial aging, several specimens showed some damage. ANOVA revealed that enamel etching provided statistically significantly (p ≤ 0.05) higher fracture resistance than self-etching when bonding to enamel and dentin. Self-etching provided statistically significant (p ≤ 0.05) higher fracture resistance for the enamel-composite group than for the enamel group. Enamel etching provided statistically significant (p ≤ 0.05) higher fracture resistance for the enamel and dentin group than for groups enamel and enamel-composite.SignificanceEtching enamel improved the fracture resistance of occlusal veneers when bonding to dentin and enamel and increased the survival rate when bonding to enamel.     

Effect of etching time and resin bond on the flexural strength of IPS e.max Press glass ceramic

ObjectiveTo evaluate the effect of hydrofluoric acid (HFA) etching time and resin cement bond on the flexural strength of IPS e.max^® Press glass ceramic.MethodsTwo hundred and ten bars, 25 mm × 3 mm × 2 mm, were made from IPS e.max^® Press ingots through lost-wax, hot-pressed ceramic fabrication technology and randomly divided into five groups with forty-two per group after polishing. The ceramic surfaces of different groups were etched by 9.5% hydrofluoric acid gel for 0, 20, 40, 60 and 120 s respectively. Two specimens of each group were selected randomly to examine the surface roughness and 3-dimensional topography with atomic force microscope (AFM), and microstructure was analyzed by the field emission scanning electron microscope (FE-SEM). Then each group were subdivided into two subgroups (n = 20). One subgroup of this material was selected to receive a thin (approximately 0.1 mm) layer of resin luting agent (Variolink N) whereas the other subgroup remained unaltered. Half of subgroup's specimens were thermocycled 10,000 times before a 3-point bending test in order to determine the flexural strength. Interface between resin cement and ceramic was examined with field emission scanning electronic microscope.ResultsRoughness values increased with increasing etching time. The mean flexural strength values of group 0 s, 20 s, 40 s, 60 s and 120 s were 384 ± 33, 347 ± 43, 330 ± 53, 327 ± 67 and 317 ± 41 MPa respectively. Increasing HF etching times reduced the mean flexural strength (p < 0.05). However, the mean flexural strength of each group, except group 0 s, increased significantly to 420 ± 31, 435 ± 50, 400 ± 39 and 412 ± 58 MPa after the application of dual-curing resin cement. In the present investigation, no significant differences after thermocycling on the flexural strengths were evident.SignificanceOvertime HF etching could have a wakening effect on IPS e.max^® Press glass ceramic, but resin cement bonding to appropriately etched surface would strengthen the dental ceramic.     

The evaluation of displacement resistance of glass FRC posts to root dentine using a thin slice push-out test

Aim  To investigate and compare the displacement resistance of glass fibre reinforced composite (FRC) posts to root dentine after luting with different adhesive systems.
Methodology  A total of 32 noncarious extracted human mandibular premolars were prepared for post-cementation using the FRC Postec system (Ivoclar Vivadent, Schaan, Liechtenstein) and divided into four groups ( n  = 8). The posts in each group were luted with one or other of the following materials. Group 1: Variolink II/Excite DSC (etch-and-rinse, dual-curing), group 2: Clearfil Esthetic Cement/ED Primer II (self-etch, dual-curing), group 3: Multilink/Multilink Primer (self-etch, chemical-curing) and group 4: Multilink Sprint (self-adhesive, dual-curing). Specimens were sectioned to obtain slices with the post in the centre and with the root dentine overlaid by the autopolymerizing acrylic resin on each side. The displacement resistance was measured using a Universal Testing Machine at a crosshead speed of 0.5 mm min⁻¹. The displacement resistance of the specimens were calculated and expressed in MPa. Data were analysed with one-way anova and post hoc Tukey's test ( P  < 0.05).
Results  Mean (SD) values of displacement resistance data in MPa are as follows: group 1, 12.08 (2.13); group 2, 12.39 (2); group 3, 11.3 (1.23); group 4, 14.29 (1.84). There were statistically significant differences amongst the groups ( P  = 0.021). A statistically significant difference was observed for the displacement resistance values between groups 3 and 4 ( P  = 0.015), that is between Multilink/Multilink Primer and Multilink Sprint.
Conclusions  Glass FRC posts luted with self-adhesive luting system exhibited higher displacement resistance than when luted with chemical-curing self-etch luting system.     

Polymerization shrinkage strain of interocclusal recording materials

ObjectivesThe aim of this in vitro study was to investigate the polymerization shrinkage behavior and to measure the polymerization shrinkage-strain of interocclusal recording materials.MethodsThe materials investigated in this study were five polyvinylsiloxane (Imprint? Bite, Silagum Automix Bite, O-Bite, Blu-Mousse^® Classic and Exabite II), one polyether (Ramitec) and one dimethacrylatebased (Luxabite) materials. The polymerization shrinkage values of ten specimens for each material were measured by the Bonded-disk method at 1, 3, 5, 7 and 10 min after mixing at 37 °C. The amount of shrinkage-strain (%) was derived and all data were statistically analyzed by one-way ANOVA and the multiple comparison Scheffé test (α = 0.05).ResultsThe representative shrinkage-strain kinetic graphs showed that all specimens shrank immediately, except Luxabite which expanded for the initial few seconds. After that, the shrinkage-strain values increased in the magnitude up to 10 min, but its rate decreased gradually with time. The shrinkage-strain values (0.18 ± 0.03–0.16 ± 0.03%) of O-Bite at 5, 7 and 10 min were significantly lower than the other materials, but Luxabite exhibited the highest values (3.10 ± 0.17–3.30 ± 0.16%).SignificanceThe interocclusal recording materials investigated presented significantly different polymerization shrinkage-strain kinetics and showed dimensional changes even after the setting time indicated by respective manufacturers.     

Initial fracture resistance and curing temperature rise of ten contemporary resin-based composites with increasing radiant exposure

ObjectivesThe principal objective of this study was to determine whether the bulk fracture resistance of ten light activated composites varied over a clinically realistic range of radiant exposures between 5 and 40 J/cm².MethodsTen operators were tested for clinically simulated radiant exposure delivery from a Bluephase^® (Ivoclar Vivadent, Schaan, Liechtenstein) LED light to an occlusal cavity floor in tooth 27 in a mannequin head using a MARC^®-Patient Simulator (Bluelight Analytics Inc., Halifax, NS) device. Notch disc test samples were prepared to determine the torque resistance to fracture (T) of the composites. Samples were irradiated with the same monowave Bluephase^® light for 10 s, 20 s or 40 s at distances of 0 mm or 7 mm. After 24 h, storage samples were fractured in a universal testing machine and torque to failure was derived.ResultsRadiant exposure delivered in the clinical simulation ranged from 14.3% to 69.4% of maximum mean radiant exposure deliverable at 0 mm in a MARC^®-Resin Calibrator (Bluelight Analytics Inc., Halifax, NS) test device. Mean torque to failure increased significantly (P < 0.05) with radiant exposure for 8 out of 10 products. The micro-fine hybrid composite Gradia Direct anterior (GC) had the lowest mean (S.D.) T between 10.3 (1.8) N/mm and 13.7 (2.2) N/mm over the tested radiant exposure range. Three heavily filled materials Majesty Posterior, Clearfil APX and Clearfil Photo-Posterior (Kuraray) had mean T values in excess of 25 N/mm following 40 J/cm² radiant exposure. Mean T for Z100 (3MESPE) and Esthet-X (Dentsply) increased by 10% and 91% respectively over the tested range of radiant exposures.ConclusionsIndividual products require different levels of radiant exposure to optimize their fracture resistance. Light activated composites vary in the rate at which they attain optimal fracture resistance.Clinical significanceUnless the clinician accurately controls all the variables associated with energy delivery, there is no way of predicting that acceptable fracture resistance will be achieved intra-orally.     

Effect of self-setting α-tricalcium phosphate between segments for bone healing and hypoaesthesia in lower lip after sagittal split ramus osteotomy

AimsThe aim of this study was to evaluate hypoaesthesia of the lower lip and bone formation using self-setting α-tricalcium phosphate (Biopex^®) between the proximal and distal segments following sagittal split ramus osteotomy (SSRO) with bent absorbable plate fixation.Subjects and methodsThe subjects were 40 patients (80 sides) who underwent bilateral SSRO setback surgery. They were divided into a Biopex^® group (40 sides) and a control group (40 sides). The Biopex^® was inserted into the anterior part of the gap between the segments in the Biopex^® group. Trigeminal nerve hypoaesthesia in the region of the lower lip was assessed bilaterally using the trigeminal somatosensory-evoked potential (TSEP) method. Ramus square, ramus length, and ramus width, the square of the Biopex^® at the horizontal plane under the mandibular foramen were assessed preoperatively, immediately after surgery, and 1 year postoperatively by computed tomography (CT).ResultsThe mean measurable period and standard deviation were 9.3 ± 15.7 weeks in the control group, 5.3 ± 8.3 weeks in the Biopex^® group, and there was no significant difference. Ramus square after 1 year was significantly larger than that prior to surgery and new bone formation was found between the segments in both groups (P < 0.05). In the Biopex^® group, the square of the Biopex^® after 1 year was significantly smaller than that immediately after surgery (P < 0.05).ConclusionThis study suggested that inserting Biopex^® in the gap between the proximal and distal segments was useful for new bone formation and it did not prevent the recovery of lower lip hypoaesthesia after SSRO with bent absorbable plate fixation.     

Scratch test of thermoplastic denture base resins for non-metal clasp dentures

PurposeSeveral thermoplastic denture base resins have been introduced for the fabrication of non-metal clasp dentures. Although the surface of these materials is easily damaged, the surface roughness and characteristics of scratches created have not been evaluated. The purpose of this study was to evaluate the surface roughness of thermoplastic resins using a scratch test for the development of future materials.MethodsFour thermoplastic (polyamide: Valplast^®; VLP and Lucitone FRS^®; FRS, polyethylene terephthalate: EstheShot^®; ES, and polyester: EstheShot Bright^®; ESB) and two conventional acrylic (Heat-polymerizing: Urban^®; HC, and Pour type auto-polymerizing: Pro-Cast DSP^®; PR) denture base resins were examined. Eight specimens, approximately 10 mm × 10 mm × 30 mm in size, of each material were fabricated. Scratch test was performed by a scratch tester with a diamond indenter of 10-μm radius and cone angle 90°, applying a constant load of 500 mN, and 2-mm-long scratches were made. The scratch marks were studied under 3D laser measuring microscope and cross-section profiles at approximately 0.5 mm, 1.0 mm, and 1.5 mm from the starting point were extracted and measured with analysis software. Data from 24 cross-section profiles in each denture base material were analyzed.ResultsThe maximum depths of ES, ESB and FRS were greater than VLP, PR and HC, and the scratch widths of ES, ESB, FRS and VPL were greater than PR and HC.ConclusionsThe results showed that the surface of thermoplastic denture base resins was easily damaged compared to polymethyl methacrylate.     

Hyaluronic acid on collagen membranes: An experimental study in rats

ObjectiveThe aim of this study was to evaluate the effect of hyaluronic acid (HA) in the structure and degradation patterns of BioGide^® and OsseoGuard™ collagen membranes. HA mediates inflammation and acts in cell migration, adhesion, and differentiation, benefitting tissue remodeling and vascularization. These are desirable effects in guided regeneration procedures, but it is still unknown whether HA alters the barrier properties of absorbable membranes.DesignBone defects were created in the calvaria of rats, which were treated with HA gel 1% (HA group) or simply filled with blood clot (control group), and covered with BioGide^® or OsseoGuard™. The animals were euthanized after 1, 30, and 60 days, and their calvarias were processed for histological analysis.ResultsBioGide^®, in both HA and control groups, showed vascularization, intense cell colonization, bone formation, and tissue integration at 30 and 60 days. In contrast, Osseoguard™ presented minimal cellular colonization, and inflammatory reaction associated to foreign body reaction in both time points and groups. The HA group of BioGide^® showed higher cell colonization (574.9 ± 137.6) than the control group (269.1 ± 70.83) at 60 days (p < 0.05). Despite this finding, the structure and degradation pattern were similar for BioGide^® and Osseoguard™ in the HA and control groups.ConclusionThe results suggest that HA did not interfere with tissue integration and structural degradation of BioGide^® and Osseoguard™ membranes.     

Influence of various irradiation processes on the mechanical properties and polymerisation kinetics of bulk-fill resin based composites

ObjectivesTo assess the effect of irradiation time and distance of the light tip on the micro-mechanical properties and polymerisation kinetics of two bulk-fill resin-based composites at simulated clinically relevant filling depth.MethodsMicro-mechanical properties (Vickers hardness (HV), depth of cure (DOC) and indentation modulus (E)) and polymerisation kinetics (real-time increase of degree of cure (DC)) of two bulk-fill resin-based composites (Tetric EvoCeram^® Bulk Fill, Ivoclar Vivadent and x-tra base, Voco) were assessed at varying depth (0.1–6 mm in 100 μm steps for E and HV and 0.1, 2, 4 and 6 mm for DC), irradiation time (10, 20 or 40 s, Elipar Freelight2) and distances from the light tip (0 and 7 mm). Curing unit's irradiance was monitored in 1 mm steps at distances up to 10 mm away from the light tip on a laboratory-grade spectrometer.ResultsMultivariate analysis (α = 0.05), Student's t-test and Pearson correlation analysis were considered. The influence of material on the measured mechanical properties was significant (η² = 0.080 for E and 0.256 for HV), while the parameters irradiation time, distance from the light tip and depth emphasise a stronger influence on Tetric EvoCeram^® Bulk Fill. The polymerisation kinetics could be described by an exponential sum function, distinguishing between the gel and the glass phase. The above mentioned parameters strongly influenced the start of polymerisation (gel phase), and were of less importance for the glass phase.ConclusionsBoth materials enable at least 4 mm thick increments to be cured in one step under clinically relevant curing conditions.Clinical significanceThe susceptibility to variation in irradiance was material dependent, thus properties measured under clinically simulated curing conditions might vary to a different extent from those measured under ideal curing conditions.     

The influence of various light curing units on the cytotoxicity of dental adhesives

ObjectivesThe objective of this study was to test the hypothesis that various light curing units (LCUs) have an influence on the cytotoxic action of adhesive systems.MethodsSamples of the dental adhesives (Syntac^®, iBondTM, Clearfil? Protect Bond, Prime & Bond? NT, Adper? Prompt? L-Pop?) were prepared in microwell plates, making use of the LCUs Voco Polofil Lux (VPL), EMS Swiss Master Light^® (SML) and the LED prototype developed by the IMT of Jena University. To obtain extracts, the samples were topped with cell culture medium, which was changed daily on the 1st to 7th days and then on the 14th, 21st and 28th day, and stored for further use at ?20 °C. Human gingival fibroblasts (HGFs) were cultivated in the extract-containing medium for 48 h. The viability of the HGFs was determined by the neutral red (NR) uptake test. The statistical test was performed by one-way ANOVA according to Bonferroni.ResultsDuring the first few days, reduction of the viability rates of the HGFs by 85–90% were observed in all adhesives. A rise up to a plateau phase was observed at different times depending on the materials. The influence of the LCUs on the cytotoxic action of the dental adhesives was clearly evident for the adhesives Syntac^® and Clearfil? Protect Bond. In case of the Syntac^® extracts, cytotoxicity after polymerization with the VPL was statistically significant reduced compared to the other LCUs used (p < 0.001). A comparison between all the adhesives used proved that Adper? Prompt? L-Pop? and Prime & Bond NT^® had the lowest overall cytotoxicities.SignificanceIn practice, one should use combinations of dental adhesive and LCU in which the material has the least toxic influences.     

Maxillary sinus floor augmentation and dental implant placement using dentin matrix protein-1 gene-modified bone marrow stromal cells mixed with deproteinized boving bone: A comparative study in beagles

ObjectiveThe aim of the study was to evaluate the effects of the combined use of dentin matrix protein-1 (DMP1) gene-modified bone marrow stromal cells (BMSCs) and Bio-Oss^® for maxillary sinus floor augmentation (MSFA) implant placement in dogs.Materials and methodsBMSCs were derived from bone marrow of six beagles and cultured. The cells were transduced with a lentiviral vector overexpressing the DMP1 gene and enhanced green fluorescent protein (EGFP) gene (Lenti-DMP1/EGFP) in test group, and with a lentiviral vector encoding EGFP gene (Lenti-EGFP) in control group. Six dogs received sinus augmentations using the bilateral approach with a simultaneous implant placement at each site respectively. At the same concentration, 2 × 10⁷ cells/ml, one sinus was grafted using a mixture of autologous DMP1/EGFP gene-modified BMSCs and Bio-Oss^® (DMP1 group), and the contralateral sinus was grafted with autologous EGFP gene-modified bMSCs and Bio-Oss^® (EGFP group). After a 3 month healing period, bone regeneration and osseointegration were evaluated using histologic and histomorphometric methods.ResultsThe bone-implant contact (BIC) and the bone area fraction in the DMP1 group (BIC: 34.67% ± 8.23%, bone area fraction: 35.16% ± 3.32%) were significantly greater compared with the EGFP group (BIC: 26.06% ± 5.16%, bone area fraction: 20.74% ± 1.63%) (P < 0.05). No significant difference between the residual bone substitute material volume (BSMV) in the DMP1 group (35.86 ± 7.35) and the EGFP group (32.16 ± 9.16) was found in our study (P > 0.05).ConclusionBMSCs modified with the DMP1 gene can be used as an adjunct to Bio-Oss^® to enhance new bone formation and the osseointegration of dental implants in MSFA of dogs.     

Treatment outcome of the two-part semi-rigid oral appliance in obstructive sleep apnea

AimThe aim of this study was to assess the effectiveness of the two-part semi-rigid oral appliance, Silensor^® (Erkodent, Tuttlingen, Germany) which prevents the mandible from retracting during mouth opening.Materials and methodsTen patients with mild or moderate obstructive sleep apnea (2 males and 8 females; mean age = 62.5 ± 10.0 years) were recruited and lateral cephalometric radiographs were taken. The patients underwent polysomnography before and after 3 months of receiving treatment with the Silensor^®. The relationship between the improvement in the polysomnographic variables after the therapy and the cephalometric features was analyzed.ResultsA significant difference was observed in the apnea–hypopnea index after 3 months of Silensor^® therapy (1st (baseline), 17.1 ± 5.5; 2nd (therapy of Silensor^®), 11.0 ± 7.2, p = 0.011). Furthermore there was a significant positive correlation between the improvement in the degree of slow wave sleep (%) and the mandibular plane angle (R = 0.662, p = 0.037), as well as between the improvement in degree of slow wave sleep (%) and the lower face height (R = 0.845, p = 0.002). A significant negative correlation was observed between the improvement in degree of sleep efficiency (%) and the soft palate area (R = ?0.809, p = 0.005).ConclusionThese results suggested that keeping the nasopharyngeal airway space during mouth opening improves apnea–hypopnea index of some patients with mild or moderate obstructive sleep apnea and quality of sleep in obstructive sleep apnea patients with a long lower face height and a small soft palate.     

Effectiveness of pretreatment with phosphoric acid,sodium hypochlorite and sulfinic acid sodium salt on root canal dentin resin bonding

PurposeThe purpose of this study was to evaluate the effect of pretreatment using phosphoric acid, sodium hypochlorite and sulfinic acid sodium salt on the bonding of one-step self-etching adhesives to root canal dentin.MethodsThirty-six single-rooted sound human premolars were randomly assigned into three groups before applying the one-step self-etching adhesive. These comprised a control group with no pretreatment, an NC group that received phosphoric acid and subsequent sodium hypochlorite gel pretreatments, and an NC + AC group that received an additional treatment with sulfinic acid sodium salt following the same pretreatment applied to the NC group. Microtensile bond strength measurements, bonding interface observations by scanning electron microscopy (SEM), elemental analyses by X-ray photoelectron spectroscopy (XPS) and degree of polymerization (DOP) analyses by Raman spectroscopy were subsequently performed.ResultsThe bond strength was significantly higher in the NC + AC group than in the other two groups (Control: P = 000.1 and NC: P = 0.004). SEM observations showed that resin tags were present in the dentinal tubules in the NC and NC + AC groups. Compared to the control group, the adhesive resin layer had a lower DOP in the NC group, while the DOP for the NC + AC group was higher than that of the NC specimens.ConclusionsBonding to root canal dentin was improved by applying sulfinic acid sodium salt in addition to treatment with phosphoric acid followed by sodium hypochlorite. The DOP of the adhesive resin was reduced by sodium hypochlorite and subsequently restored by applying sulfinic acid sodium salt.     

Esterases affect the physical properties of materials used to seal the endodontic space

Materials used to seal the endodontic space are subjected to enzymatic degradative activities of body fluids and bacteria.ObjectivesTo assess effects of simulated human salivary, blood and bacterial esterases (SHSE) on physical properties of typical restorative material and root canal sealers.MethodsSpecimens of set methacrylate-based resin composite (Bisfil^TM2B; RC), calcium-silicate sealer (EndoSequence^®; BC) or epoxy-resin sealer (AH-Plus^®; ER) were tested after up to 28 Days exposure to phosphate buffered saline (PBS) or SHSE, using ANSI/ADA-57:2000 and ISO-6876:2012.ResultsRegardless of media, microhardness increased with time for BC remained unchanged for ER and decreased for RC (p < 0.05). SHSE moderated the increase for BC compared to PBS (28.0 ± 4.8 vs. 38.1 ± 7.9 KHN) at 7 Days, and enhanced the decrease for RC at 7 Days (55.6 ± 7.1 vs. 66.3 ± 6.5 KHN) and 28 Days (52.3 ± 9.2 vs. 62.6 ± 8.5 KHN). Compressive strength was enhanced only for BC by either media. BC expanded with time for both incubation conditions; SHSE moderated the expansion compared to PBS at 7 Days (0.026 ± 0.01% vs. 0.049 ± 0.007%). Shrinkage of ER was similar for both incubation media and was lower than that for RC (p < 0.05). Shrinkage of RC was enhanced by SHSE compared to PBS at 7 Days (0.5 ± 0.07% vs. 0.38 ± 0.08%). Weight loss was lowest for ER and highest for BC (p < 0.05). It was enhanced by SHSE compared to PBS for BC at 28 Days (2.40 ± 0.2 vs. 2.96 ± 0.19 W L%), and for RC at 7 Days (0.54 ± 0.09 vs. 0.80 ± 0.1 W L%).SignificanceSimulated body fluids and bacterial esterases affected the physical properties of test materials, suggesting potential impacts on sealing ability and resistance to bacterial ingress, and tooth strength ultimately affecting their clinical performance.     

In vitro enamel erosion and abrasion-inhibiting effect of different fluoride varnishes

ObjectiveTo investigate the erosion and abrasion inhibiting effect of CPP-ACP/NaF and xylitol/NaF varnishes.MethodsBovine enamel samples (n = 40) were exposed to the following treatments (n = 10): NaF varnish (Duraphat^®, positive control); CPP-ACP/NaF varnish (MI varnishTM); xylitol/NaF (Profluorid^®) or distilled and deionized water (MilliQ^®, negative control). The samples were submitted for 3 days to 4 cycles/day of erosion (5 min in Sprite Zero) and 2 cycles of abrasion/day after the first and last erosive challenge, with a toothbrush machine and slurries of a placebo toothpaste for 15 s (50 strokes/s). Among the cycles and after the last daily cycle, the specimens remained in artificial saliva. The change in the enamel surface was evaluated by using 3D non-contact optical profilometry with surface roughness (Ra and Sa values) and tooth structure loss (TSL) measurements. Scanning electron microscopy (SEM) assessed the enamel topographic characteristics. Differences in the Ra, Sa and TSL among treatments were tested using one-way ANOVA followed by the Tukey test.ResultsAll varnishes promoted better results for Ra and Sa values than the negative control (p = 0.0001), without difference among them (p > 0.05). However, CPP-ACP/NaF varnish stimulated fewer TSL (7.09 ± 0.70 μm) compared to NaF varnish (10.33 ± 1.36 μm, p = 0.002), xylitol/NaF varnish (9.96 ± 0.41 μm, p = 0.007) and the negative control (18.38 ± 3.32 μm, p = 0.0001).ConclusionA single-application of fluoride topical varnishes was effective in reducing enamel wear. The CPP-ACP/NaF varnish had the best effect against enamel loss from an erosion-abrasion challenge.     

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.