Smad2 overexpression induces alveolar bone loss and up regulates TNF-α, and RANKL

ObjectiveThe aim of the current study was to investigate whether Smad2 overexpression in JE cells induced alveolar bone loss, and to understand the mechanisms regulating the bone loss.MethodsA mouse line was created that used a cytokeratin 14 (K14) promoter to overexpress Smad2 in the epithelium of the transgenic mice (K14-Smad2). Micro CT radiographs (μCT) were used to assess bone loss, bone volume, and bone density. The expression of Tnfα, Il1-β, Ifγ, Rankl, and Opg were assessed by RT-PCR. Western blots were used to detect the protein levels of TNF-α and IL1-β. Tartrate-resistant acid phosphatase (TRAP) was used as a marker for osteoclasts. Wild type (WT) mice were used as controls in all steps of the current study.ResultsK14-Smad2 mice had 52.5% (±4.2) root exposed compared to 32.4%(±3.2) in the WT mice. There was a significant difference in alveolar bone volume in the K14-Smad2 mice when compared to WT mice 2.65 mm³ (±0.3) and 4.3 mm³ (±0.35) respectively. K14-Smad2 mice also had reduced bone density 696.8 mg/cc (±70) at 12 months when compared to WT mice 845.9 mg/cc(±10). The mRNA levels of Tnfα and Rankl increased by 3.26- and 2.5-fold respectively in the K14-Smad2 mice when compared to controls. The protein level of TNF-α was also significantly increased to 2.8-fold in K14-Smad2 mice when compared to WT mice. Smad2 overexpression increased the total numbers of osteoclasts in K14-Smad2 mice (3.4 ± 0.2)-fold when compared to WT mice.ConclusionSmad2 overexpression induces alveolar bone loss and increases the numbers of osteoclasts. Also, Smad2 overexpression up-regulates TNF-α and RANKL.     

Structure, chemical composition and mechanical properties of coronal cementum in human deciduous molars

ObjectivesIt was hypothesized that the coronal cementum containing collagen forms a weak junction with enamel unlike the well integrated DEJ and CDJ.MethodsThe hypothesis was investigated in two parts: (1) evaluate the structure, chemical composition and mechanical properties of coronal cementum and its junction with enamel using scanning electron microscopy, micro-X-ray computed tomography, and atomic force microscopy. The chemical composition and mechanical properties were determined by evaluating the spatial variations of inorganic (PO₄^3? ν₁ mode at 960 cm^?1) and organic (C–H deformation at 1452 cm^?1; C–H stretch at 2940 cm^?1) contents using Raman microspectroscopy and elastic modulus and hardness values using nanoindentation. (2) Estimate the strength and evaluate the microstructure of coronal cementum interface with enamel using SEM and MicroXCT?.Results and conclusionsCoronal cementum is heterogeneous because it is a combination of laminar acellular afibrillar cementum and acellular extrinsic fiber cementum with relatively higher organic content. It integrates micromechanically via a scallop-like weak interface with enamel unlike the biomechanically efficient DEJ and CDJ and is continuous with primary root cementum. A single tooth could exhibit all three types of cementum enamel junctions; an overlap, butt and a gap depending on the sectioning plane. The elastic modulus of coronal cementum (11.0 ± 5.8 GPa) is significantly lower (p < 0.05; Student's t-test with 95% confidence interval) than primary cementum (15.8 ± 5.3 GPa).     

Effect of composition, viscosity and thickness of the opaquer on the adhesion of resin composite to titanium

ObjectivesThe objectives of this study were to determine the bond strength of powder-liquid and paste opaquers with different chemical compositions and viscosity to a metal substructure when they were applied in two thicknesses and to evaluate the failure modes after the bond strength test.MethodsTitanium plates (51 mm × 25 mm × 1 mm) (n_plates = 25, N = 80, n = 10 per group) were conditioned with chairside silica coating (CoJet-Sand, 30 μm silica coated Al₂O₃) from a distance of approximately 10 mm at a pressure of 2.8 bar for 15 s/cm² and silanized. Four types of opaquers, namely one powder-liquid (Sinfony, 3 M ESPE), and three paste opaquers [(Cimara, Voco), (Monopaque, Ivoclar Vivadent), (Cavex Experimental, Cavex)] were applied either in 0.25 or 0.50 mm thicknesses using standard polyethylene molds and photo-polymerized. Resin composite (Quadrant Posterior Dense, Cavex) was applied incrementally and photo-polymerized. The specimens were thermocycled (5–55 °C, 6000 cycles) prior to shear bond strength test (1 mm/min). Failure types were analyzed using an optical microscope and scores were given according to the modified Adhesive Remnant Index (ARI) (Score 0 = no opaquer on the surface, Score 1 = <1/2 covered with opaquer, Score 2 = >1/2 covered with opaquer, Score 3 = completely covered with opaquer).ResultsWhile thickness did not significantly affect the bond strength results (p = 0.523), type of opaquers had a significant influence on the results (p < 0.01) (Univariate ANOVA, Tukey's test). Interaction terms between thickness and opaquer type were significant (p < 0.01). Debonded specimens during thermocycling were considered as 0 MPa. At both 0.25 and 0.5 mm thicknesses, powder-liquid based opaquer (Sinfony) showed significantly higher results (8.4 ± 5.6 and 8.4 ± 4.9 MPa, respectively) than those of other opaquers (1.4 ± 1 to 4.3 ± 3.8 MPa) (p < 0.05). Only when Cimara was applied in 0.25 mm (6.9 ± 4.2 MPa), there were no significant differences with Sinfony (p > 0.05). The lowest results in both thicknesses were obtained from Monopaque (4 ± 3.8 to 1.6 ± 1 MPa, respectively) and Cavex (1.4 ± 1 to 4.2 ± 2.9 MPa, respectively) paste opaquers. In all opaquers, the incidence of Score 0 (30) was more frequent followed by Score 1 (27) and Score 2 (20).SignificanceThe use of powder-liquid opaquer in order to mask the metal in repair actions provided higher bond strength than those of the paste opaquers in both thin and thick applications. In all opaquers, the incidence of adhesive failure between the opaquer and the metal was more common implying inadequate adhesion.     

FTIR and SEM analysis of CO2 laser irradiated human enamel

ObjectivesConsidering the enamel chemical structure, especially carbonate band, which has a major role in the caries prevention, the objective of the present study was to assess the chemical alterations on the enamel irradiated with CO₂ laser by means of FTIR spectroscopy and SEM analysis.DesignThe enamel surfaces were analysed on a spectrometer for acquisition of the absorption spectrum relative to the chemical composition of the control sample. The irradiation was conducted with a 10.6-μm CO₂ laser (0.55 W, 660 W/cm²). The carbonate absorption band at 1600–1291 cm^?1 as well as the water absorption band at 3793–2652 cm^?1 was measured in each sample after the irradiation. The water band was measured again 24-h after the irradiation. The band area of each chemical compound was delimited, the background was subtracted, and the area under each band was integrated. Each area was normalized by the phosphate band (1190–702 cm^?1).ResultsThere was a statistically significant decrease (p < 0.05) in the water content after irradiation (control: 0.184 ± 0.04; irradiated: 0.078 ± 0.026), which increased again after rehydration (0.145 ± 0.038). The carbonate/phosphate ratio was measured initially (0.112 ± 0.029) and its reduction after irradiation indicated the carbonate loss (0.088 ± 0.014) (p < 0.05).ConclusionThe 10.6-μm CO₂ laser irradiation diminishes the carbonate and water contents in the enamel after irradiation.     

Diffusion-weighted imaging with histogram analysis of the apparent diffusion coefficient maps in the diagnosis of parotid tumours

The aim of this study was to investigate the role of diffusion-weighted imaging (DWI) with histogram analysis of apparent diffusion coefficient (ADC) maps in the characterization of parotid tumours. This prospective study included 39 patients with parotid tumours. All patients underwent magnetic resonance imaging with DWI, and ADC maps were generated. The whole lesion was selected to obtain histogram-related parameters, including the mean (ADC_mean), minimum (ADC_min), maximum (ADC_max), skewness, and kurtosis of the ADC. The final diagnosis included pleomorphic adenoma (PA; n = 18), Warthin tumour (WT; n = 12), and salivary gland malignancy (SGM; n = 9). ADC_mean (×10^?3 mm²/s) was 1.93 ± 0.34 for PA, 1.01 ± 0.11 for WT, and 1.26 ± 0.54 for SGM. There was a significant difference in whole lesion ADC_mean among the three study groups. Skewness had the best diagnostic performance in differentiating PA from WT (P = 0.001; best detected cut-off 0.41, area under the curve (AUC) 0.990) and in discriminating WT from SGM (P = 0.03; best detected cut-off 0.74, AUC 0.806). The whole lesion ADC_mean value had best diagnostic performance in differentiating PA from SGM (P = 0.007; best detected cut-off 1.16 × 10^?3 mm²/s, AUC 0.948). In conclusion, histogram analysis of ADC maps may offer added value in the differentiation of parotid tumours.     

Effect of proteoglycans at interfaces as related to location,architecture, and mechanical cues

IntroductionCovalently bound functional GAGs orchestrate tissue mechanics through time-dependent characteristics.ObjectiveThe role of specific glycosaminoglycans (GAGs) at the ligament–cementum and cementum–dentin interfaces within a human periodontal complex were examined. Matrix swelling and resistance to compression under health and modeled diseased states was investigated.Materials and methodsThe presence of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs at the ligament–cementum and cementum–dentin interfaces in human molars (N = 5) was illustrated by using enzymes, atomic force microscopy (AFM), and AFM-based nanoindentation. The change in physical characteristics of modeled diseased states through sequential digestion of keratin sulfate (KS) and chondroitin sulfate (CS) GAGs was investigated. One-way ANOVA tests with P < 0.05 were performed to determine significant differences between groups. Additionally, the presence of mineral within the seemingly hygroscopic interfaces was investigated using transmission electron microscopy.ResultsImmunohistochemistry (N = 3) indicated presence of biglycan and fibromodulin small leucine rich proteoglycans at the interfaces. Digestion of matrices with enzymes confirmed the presence of KS and CS GAGs at the interfaces by illustrating a change in tissue architecture and mechanics. A significant increase in height (nm), decrease in elastic modulus (GPa), and tissue deformation rate (nm/s) of the PDL-C attachment site (215 ± 63–424 ± 94 nm; 1.5 ± 0.7–0.4 ± 0.2 GPa; 21 ± 7–48 ± 22 nm/s), and cementum–dentin interface (122 ± 69–360 ± 159 nm; 2.9 ± 1.3–0.7 ± 0.3 GPa; 18 ± 4–30 ± 6 nm/s) was observed.ConclusionsThe sequential removal of GAGs indicated loss in intricate structural hierarchy of hygroscopic interfaces. From a mechanics perspective, GAGs provide tissue recovery/resilience. The results of this study provide insights into the role of GAGs toward conserved tooth movement in the socket in response to mechanical loads, and modulation of potentially deleterious strain at tissue interfaces.     

Effect of thermal expansion mismatch on the Y-TZP/veneer interfacial adhesion determined by strain energy release rate

PurposesThe aim of this study was to assess the effect of differences in the thermal expansion behaviour of veneering ceramics on the adhesion to Y-TZP, using a fracture mechanics approach.MethodsSeven veneering ceramics (VM7, VM9, VM13, Lava Ceram, Zirox, Triceram, Allux) and one Y-TZP ceramic were investigated. Thermal expansion coefficients and glass transition temperatures were determined to calculate residual stresses (σ_R, MPa) between core and veneer. Subsequently, the veneering ceramics were fired onto rectangular shaped zirconia specimens, ground flat and notched on the veneering porcelain side. Then specimens were loaded in a four-point bending test and load-displacement curves were recorded. The critical load to induce stable crack extension at the adhesion interface was evaluated to calculate the strain energy release rate (G, J/m²) for each system.ResultsResidual stresses ranged from ?48.3 ± 1.5 MPa (VM7) to 36.1 ± 4.8 MPa (VM13) with significant differences between all groups (p < 0.05). The strain energy release rate of the Y-TZP/veneer specimens ranged from 8.2 ± 1.7 J/m² (Lava Ceram) to 17.1 ± 2.8 J/m² (VM9). Values for G could not be obtained with the VM7, Allux and VM13 specimens, due to spontaneous debonding or unstable crack growth. Except for Triceram and Zirox specimens, strain energy release rate was significantly different between all groups (p < 0.05).ConclusionThermal residual stresses and strain energy release rates were correlated. Slight compressive stresses in the region of ?20 MPa were beneficial for the Y-TZP/veneer interfacial adhesion. Stresses higher or lower than this value exhibited decreased adhesion.     

Bond strength durability of a resin composite on a reinforced ceramic using various repair systems

ObjectivesThis study compared the durability of repair bond strength of a resin composite to a reinforced ceramic after three repair systems.MethodsAlumina-reinforced feldspathic ceramic blocks (Vitadur-α^®) (N = 30) were randomly divided into three groups according to the repair method: PR-Porcelain Repair Kit (Bisco) [etching with 9.5% hydrofluoric acid + silanization + adhesive]; CJ-CoJet Repair Kit (3M ESPE) [(chairside silica coating with 30 μm SiO₂ + silanization (ESPE^®-Sil) + adhesive (Visio?-Bond)]; CL-Clearfil Repair Kit [diamond surface roughening, etching with 40% H₃PO₄ + Clearfil Porcelain Bond Activator + Clearfil SE Bond)]. Resin composite was photo-polymerized on each conditioned ceramic block. Non-trimmed beam specimens were produced for the microtensile bond strength (μTBS) tests. In order to study the hydrolytic durability of the repair methods, the beam specimens obtained from each block were randomly assigned to two conditions. Half of the specimens were tested either immediately after beam production (Dry) or after long-term water storage (37 °C, 150 days) followed by thermocyling (12,000 cycles, 5–55 °C) in a universal testing machine (1 mm/min). Failure types were analyzed under an optical microscope and SEM.ResultsμTBS results were significantly affected by the repair method (p = 0.0001) and the aging conditions (p = 0.0001) (two-way ANOVA, Tukey's test). In dry testing conditions, PR method showed significantly higher (p < 0.001) repair bond strength (19.8 ± 3.8 MPa) than those of CJ and CL (12.4 ± 4.7 and 9.9 ± 2.9, respectively). After long-term water storage and thermocycling, CJ revealed significantly higher results (14.5 ± 3.1 MPa) than those of PR (12.1 ± 2.6 MPa) (p < 0.01) and CL (4.2 ± 2.1 MPa) (p < 0.001). In all groups when tested in dry conditions, cohesive failure in the composite accompanied with adhesive failure at the interface (mixed failures), was frequently observed (76%, 80%, 65% for PR, CJ and CL, respectively). After aging conditions, while the specimens treated with PR and CJ presented primarily mixed failure types (52% and 87%, respectively), CL group presented mainly complete adhesive failures at the interface (70%).SignificanceHydrolytic stability of the repair method based on silica coating and silanization was superior to the other repair strategies for the ceramic tested.     

Evaluation of physical properties of fiber-reinforced composite resin

ObjectivesThis study aimed to investigate physical properties of a fiber-reinforced CAD/CAM resin disc, which included woven layers of multi-directional glass fibers.MethodsFiber orientations of CAD/CAM specimens (TRINIA, SHOFU) were specified as longitudinal (L), longitudinal-rotated (LR), and anti-longitudinal (AL). A fiber-reinforced composite (everX posterior, GC (E)) and a conventional composite (Beauti core flow paste, SHOFU (B)) were also tested.A three-point bending test and a tensile test with notchless prism-shaped specimens were conducted using a universal testing machine (AUTOGRAPH AG-IS, Shimadzu). A water absorption test was also carried out after the specimens were stored in water for 24 h or 1 week. Flexural strength and fracture toughness were obtained by conducting a three-point bending test.ResultsTRINIA L and LR groups showed significantly high flexural strength (254.2 ± 22.3 and 248.8 ± 16.7 MPa, respectively). Those were approximately 2.5 times higher than those in AL, E, and B groups (96.8–98.0 MPa) (p < 0.05, ANOVA and Tukey HSD test). No significant difference was shown in flexural modulus among the experimental groups. The fracture toughness in L group (9.1 ± 0.4 MPa/m^1/2) was found to be significantly higher than those in other groups (1.9–3.0 MPa/m^1/2; p < 0.05). TRINIA group demonstrated significantly lower water absorption (4.7 ± 1.9 μg/mm³) than did E (16.1 ± 3.1 μg/mm³) and B (17.3 ± 3.7 μg/mm³) groups (p < 0.05).SignificanceTRINIA demonstrated distinct anisotropy. TRINIA can be used as a superior restorative material when specifying directions of its fiber mesh layers.     

Salivary levels of antimicrobial peptides Hnp 1-3, Ll-37 and S100 in Behcet's disease

BackgroundOral ulcer is the cardinal clinical sign and increased neutrophilic activity is a part of the pathogenesis in Behcet's disease (BD). Saliva, as a part of the innate immune response, contains antimicrobial peptides (AMPs) that are derived from both oral epithelial cells and neutrophils. The aim of this study was to investigate the associations between salivary levels of AMPs HNP 1-3, LL-37 and S100 and disease course in patients with Behcet's disease (BD).MethodsFifty-three patients with BD and 44 healthy controls (HC) were included in the study. Disease severity score reflecting organ involvement was calculated. Salivary HNP 1-3, LL-37 and S100 levels were measured in unstimulated saliva samples by ELISA.ResultsSalivary HNP 1-3 and S100 levels in BD patients (2715.2 ± 1333.4 μg/ml and 430.6 ± 203.9 ng/ml) were significantly higher compared to HC (1780.6 ± 933.2 μg/ml and 365.3 ± 84.7 ng/ml) (p = 0.000 and p = 0.004, respectively). Although LL-37 levels were also higher in BD than HC (190.9 ± 189.1 vs 143.1 ± 128.9 ng/ml), no significant difference was observed (p = 0.53). Salivary HNP 1-3 and LL-37 levels were associated with the severity of BD (mild disease: 1975.1 ± 1174.2 μg/ml and 115.9 ± 109.4 ng/ml vs severe disease: 2955.7 ± 1305.6 μg/ml and 215.3 ± 203.8 ng/ml, p = 0.020 and p = 0.031, respectively). Salivary LL-37 levels also correlated with the number of monthly oral ulcers (r = 0.5 p = 0.000).ConclusionAn increase in salivary HNP 1-3 and S100 levels might be associated with enhanced local and systemic innate responses in BD.     

Metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting

ObjectivesThis study was to evaluated the metal–ceramic bond strength of a Co–Cr dental alloy prepared using a selective laser melting (SLM) technique.MethodsTwo groups comprised of twenty Co–Cr metal bars each were prepared using either a SLM or traditional lost-wax casting method. Ten bars from each group were moulded into standard ISO 9693:1999 dimensions of 25 mm × 3 mm × 0.5 mm with 1.1 mm of porcelain fused onto an 8 mm × 3 mm rectangular area in the centre of each bar. Metal–ceramic bonding was assessed using a three-point bending test. Fracture mode analysis and area fraction of adherence porcelain (AFAP) were determined by measuring Si content of specimens by SEM/EDS.ResultsStudent's t-test within the groups demonstrated no significant difference for the mean bond strength between the SLM and traditional cast sample groups. While SEM/EDS analysis indicated a mixed fracture mode on the debonding interface of both the SLM and the cast groups, the SLM group showed significantly more porcelain adherence than the control group (p < 0.05).ConclusionsThe SLM metal–ceramic system exhibited a bonding strength that exceeds the requirement of ISO 9691:1999(E) and it even showed a better behaviour in porcelain adherence test comparable to traditional cast methods.     

Improving the standard of the standard for glass ionomers: An alternative to the compressive fracture strength test for consideration?

ObjectivesThree strength tests (compressive, three point flexure and biaxial) were performed on three glass ionomer (GI) restoratives to assess the most appropriate methodology in terms of validity and reliability. The influence of mixing induced variability on the data sets generated were eliminated by using encapsulated GIs.MethodsSpecimen groups of 40 (eight batches of n = 5) cylinders (6.0 ± 0.1 mm height, 4.0 ± 0.1 mm diameter) for compressive fracture testing, bars (25.0 ± 0.1 mm length, 2.0 ± 0.1 mm height, 2.0 ± 0.1 mm width) for three point flexure testing and discs (13.0 ± 0.1 mm diameter, 1.0 ± 0.1 mm thickness) for biaxial flexure testing were randomly prepared by an operator. The strength data sets for each GI restorative were pooled and one-way analyses of variance (ANOVAs) were conducted to compare between GI restoratives (p = 0.05). The coefficient of variation (CoV) values for each test were pooled and a one-way ANOVA was conducted to test for differences between the reliability of the three tests.ResultsFor the GI restoratives, the one-way ANOVA showed significant differences when tested in compression (p = 0.001) but not when tested in three point (p = 0.271) or biaxial (p = 0.134) flexure. The pooled CoV values showed no significant difference between the three strength tests (p = 0.632).ConclusionsThe compressive fracture strength test specified for GIs in the International Organisation for Standardisation (ISO 9917-1: 2003) should be replaced and should no longer be advocated for the predictive performance modelling of GI restoratives.     

Bis-GMA co-polymerizations: Influence on conversion,flexural properties,fracture toughness and susceptibility to ethanol degradation of experimental composites

ObjectivesThe aim of this study was to evaluate the influence of monomer content on fracture toughness (K_Ic) before and after ethanol solution storage, flexural properties and degree of conversion (DC) of bisphenol A glycidyl methacrylate (Bis-GMA) co-polymers.MethodsFive formulations were tested, containing Bis-GMA (B) combined with TEGDMA (T), UDMA (U) or Bis-EMA (E), as follows (in mol%): 30B:70T; 30B:35T:35U; 30B:70U; 30B:35T:35E; 30B:70E. Bimodal filler was introduced at 80 wt%. Single-edge notched beams for fracture toughness (FT, 25 mm × 5 mm × 2.5 mm, a/w = 0.5, n = 20) and 10 mm × 2 mm × 1 mm beams for flexural strength (FS) and modulus (FM) determination (10 mm × 2 mm × 1 mm, n = 10) were built and then stored in distilled water for 24 h at 37 °C. All FS/FM beams and half of the FT specimens were immediately submitted to three-point bending test. The remaining FT specimens were stored in a 75%ethanol/25%water (v/v) solution for 3 months prior to testing. DC was determined with FT-Raman spectroscopy in fragments of both FT and FS/FM specimens at 24 h. Data were submitted to one-way ANOVA/Tukey test (α = 5%).ResultsThe 30B:70T composite presented the highest K_Ic value (in MPa m^1/2) at 24 h (1.3 ± 0.4), statistically similar to 30B:35T:35U and 30B:70U, while 30B:70E presented the lowest value (0.5 ± 0.1). After ethanol storage, reductions in K_Ic ranged from 33 to 72%. The 30B:70E material presented the lowest reduction in FT and 30B:70U, the highest. DC was similar among groups (69–73%), except for 30B:70U (52 ± 4%, p < 0.001). 30B:70U and 30B:35T:35U presented the highest FS (125 ± 21 and 122 ± 14 MPa, respectively), statistically different from 30B:70T or 30B:70E (92 ± 20 and 94 ± 16 MPa, respectively). Composites containing UDMA or Bis-EMA associated with Bis-GMA presented similar FM, statistically lower than 30B:35T:35U.SignificanceComposites formulated with Bis-GMA:TEGDMA:UDMA presented the best compromise between conversion and mechanical properties.     

Effects of regular and highly fluoridated toothpastes in combination with saliva substitutes on artificial enamel caries lesions differing in mineral content

ObjectiveFor patients with hyposalivation fluorides are supportive to prevent caries lesions. Remineralization of subsurface lesions might be improved by toothpastes containing 5000 μg F^?/g compared with those having 1400 μg F^?/g. This could be influenced by the degree of baseline mineralization. Therefore, this in vitro study evaluated the effects of fluoride toothpastes differing in fluoride concentration in combination with de- and remineralizing saliva substitutes using two lesion types.DesignSpecimens with shallow (SL; ΔZ (SD): 1915 (543) vol% × μm) or deep lesions (DL; 5804 (427) vol% × μm) were either stored in mineral water [saturation with respect to octacalcium phosphate (S_OCP): 0.5], demineralizing experimental (Exp, S_OCP: 0.3), demineralizing commercial (Glandosane, S_OCP: 0.3), or remineralizing saliva substitute (modified Saliva natura; S_OCP: 1.9) for five weeks (37 °C). Either one of three brushing procedures was performed additionally three times daily: no brushing, Elmex anticaries toothpaste (E; 1400 μg F^?/g), Duraphat toothpaste (D; 5000 μg F^?/g). Mineral parameters before and after storage were evaluated using microradiographs.ResultsStorage in Exp as well as Glandosane induced a significant demineralization (p < 0.05; relatively more pronounced in SL than DL). Additional brushing in particular with D reduced these effects. Storage alone in modified Saliva natura remineralized specimens (p < 0.05).ConclusionsUnder the in vitro conditions chosen shallow lesions seem to be more susceptible for demineralization compared with deeper ones when stored in an undersaturated (with respect to OCP) saliva substitute. The highly fluoridated toothpaste seemed to be more beneficial than a regular one.     

The crushing truth about glass ionomer restoratives: exposing the standard of the standard

ObjectivesThe compressive fracture strength (CFS) test is the only strength test for glass ionomers (GIs) in ISO 9917-1: 2003. The CFS test was the subject of much controversy in 1990 and has been challenged over its appropriateness and reproducibility and the study aimed to revisit the suitability of the CFS test for GIs.MethodsGroups of 20 (four batches of n = 5) cylinders (6.0 ± 0.1 mm height, 4.0 ± 0.1 mm diameter) of three encapsulated GIs were prepared for CFS testing using two mechanical mixing regimes and two operators. The CFS data for each GI restorative were pooled, three-, two- and one-way analyses of variance (ANOVAs) were conducted (p = 0.05) for operator, mixing regime and batch to assess reliability. The data was also analysed according to ISO 9917-1: 2003.ResultsThe three-way ANOVAs showed a significant interaction of operator × mixing regime × batch (p < 0.017) for two of the three encapsulated GIs. However, no significant effects of operator × mixing regime (p > 0.042), operator × batch (p > 0.332), mixing regime × batch (p > 0.056), operator (p > 0.094), mixing regime (p > 0.118) or batch (p > 0.054) were evident. When examined in batches of five (or ten where appropriate) as specified in ISO 9917-1: 2003, inter- and intra-operator variability were evident.ConclusionsThe use of batch-censoring in accordance with ISO 9917-1: 2003 is unsafe when the data scatter reflects a homogenous flaw distribution as it misidentifies operative variability. Despite demonstrating that the CFS test can be performed reliably, the validity of the CFS test for GIs remains under scrutiny.     

Color stability of silorane-based composites submitted to accelerated artificial ageing--an in situ study

ObjectivesTo assess the in situ color stability, surface and the tooth/restoration interface degradation of a silorane-based composite (P90, 3M ESPE) after accelerated artificial ageing (AAA), in comparison with other dimethacrylate monomer-based composites (Z250/Z350, 3M ESPE and Esthet-X, Dentsply).MethodsClass V cavities (25 mm² × 2 mm deep) were prepared in 48 bovine incisors, which were randomly allocated into 4 groups of 12 specimens each, according to the type of restorative material used. After polishing, 10 specimens were submitted to initial color readings (Easyshade, Vita) and 2 to analysis by scanning electronic microscopy (SEM). Afterwards, the teeth were submitted to AAA for 384 h, which corresponds to 1 year of clinical use, after which new color readings and microscopic images were obtained. The values obtained for the color analysis were submitted to statistical analysis (1-way ANOVA, Tukey, p < 0.05).ResultsWith regard to color stability, it was verified that all the composites showed color alteration above the clinically acceptable levels (ΔE ≥ 3.3), and that the silorane-based composite showed higher ΔE (18.6), with a statistically significant difference in comparison with the other composites (p < 0.05). The SEM images showed small alterations for the dimethacrylate-based composites after AAA and extensive degradation for the silorane-based composite with a rupture at the interface between the matrix/particle.ConclusionIt may be concluded that the silorane-based composite underwent greater alteration with regard to color stability and greater surface and tooth/restoration interface degradation after AAA.     

Influence of age and gender on trigeminal sensory function and magnetically evoked masseteric exteroceptive suppression reflex

ObjectiveThe present study explored the effect of age and gender on trigeminal sensory function and masseteric exteroceptive suppression (ES) reflex responses.MethodsYoung healthy men (n = 12) and women (n = 12) (age: 23.5 ± 3.0 years) and older healthy men (n = 12) and women (n = 12) (age: 58.5 ± 5.2 years) participated. Sensory function was assessed on the skin overlying the mental foramen using mechanical stimuli. Surface EMG was recorded from the left masseter muscle to assess ES reflex responses evoked by a magnetic stimulus applied to the skin above the left mental nerve.ResultsThe older group had significantly higher tactile detection thresholds. Early ES1 was present in all subjects. Onset latency of ES1 was significantly delayed in older subjects. ES2 was present in all young subjects, but only in 5 of the 12 men and 8 of the 12 women in the older group. Significant gender differences were found for sensory and pain thresholds to mechanical stimuli as well as for duration of ES.ConclusionsAgeing affects tactile detection thresholds, onset latency of ES1 responses, and appearance of ES2. The present results indicate that trigeminal sensory function and brainstem reflex responses differ between genders and age groups. These findings may have implications for assessment of craniofacial pain conditions.     

Influence of the application of a pre-sintered surface augmentation on zirconia and lithium disilicate bonding using an adhesive composite resin cement

ObjectiveThe purpose of this laboratory study is to evaluate the application of a pre-sintered surface augmentation to zirconia (Zir) and lithium disilicate (LDS) ceramics on the delamination strength of adhesive resin cement. The applied surface augmentation was the ruling of lines to the pre-sintered surface of the ceramics.MethodsNinety milled Zir and sixty pressed LDS specimens (3 mm × 0.5 mm × 25 mm) were created and divided into five groups (n = 30). Group 1: Zir no surface treatment (control Zir-NT); Group 2: Zir airborne particle abraded (Zir-APA) with 30 μm CoJet; Group 3: Zir pre-sintered surface augmentation (Zir-SA); Group 4: LDS etched (control LDS-etched) and; Group 5: LDS with pre-sintered surface augmentation and etching (LDS-SA). A resin adhesive cement (3 mm × 1 mm × 8 mm) was then applied and cured to the ceramic specimens. The delamination strength values of the resin cement from the ceramic were recorded. The delamination strength data were analysed statistically using one-way ANOVA and Turkey post hoc analysis.ResultsThe mean delamination strength and standard deviation, when comparing only the Zir-SA to the resin cement were statistically different (p < 0.001); Zir-SA 63.42 ± 11.85, Zir-NT 26.82 ± 12.07, and Zir-APA 48.11 ± 17.85 MPa. Comparison between LDS groups were not significantly different (p = 0.193); LDS-etched 33.49 ± 16.07 and LDS-SA 28.83 ± 10.15 MPa. The delaminated Weibull modulus was highest for surface augmentation Zir specimens (m = 13.56) but decreasing to less than half for Zir-APA (m = 6.27) and Zir-NT (m = 5.68). The Weibull values for the LDS-SA and LDS-etched specimens was 5.63 and 3.38 respectively.SignificanceIncorporating the pre-sintered surface augmentation to zirconia improved the delamination strength and reliability of Zir to the resin cement but not for LDS.     

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.     

Erosive-abrasive tissue loss in dentine under simulated bulimic conditions

ObjectivesThe eroded organic dentine matrix is remarkably resistant to mechanical impacts. Additional brushing abrasion of eroded dentine has only limited influence on tissue loss. Digestive enzymes (e.g., pepsin, trypsin) that can reach the oral cavity during reflux or vomiting can partially degrade the matrix. This degradation may have an influence on both the stability of the matrix against mechanical forces and the susceptibility of eroded dentine to combined chemo-mechanical impacts. Both were investigated in the present study.MethodsDentine samples of four groups were cyclically demineralised (6 × 2 min/day, 9 days) with an HCl-pepsin-solution (pH 1.6, 1.5 mg/ml pepsin) and treated with a trypsin-solution (6 × 10 min/day, 2000 BAEE units/ml) directly afterwards. One group served as control; specimens of three groups were additionally brushed (2 × 15 s/day) directly after the first and last trypsin treatment with forces of 200 g, 300 g, and 400 g. Loss of demineralised and mineralised tissue was determined profilometrically. Additionally, an SEM analysis was performed.ResultsLoss of mineralised tissue (μm, mean ± SD) was: 135.7 ± 10.9 (control), 165.2 ± 30.8 (200 g), 168.0 ± 16.3 (300 g), and 174.9 ± 17.1 (400 g). Tissue loss was increased significantly (p ≤ 0.001) by brushing independently of the force used (n.s. between brushed groups). SEM revealed that in all groups, the matrix was equally thinned through enzymatic activity, but it was still present as a continuous band.ConclusionThe results indicate that brushing of dentine after impact of acid and enzymes resulted in an increased tissue loss; however, the matrix persisted on the surface despite enzymatic treatment and brushing with forces of up to 400 g.