Adhesion properties in systems of laminated pigmented polymers,carbon–graphite fiber composite framework and titanium surfaces in implant suprastructures

ObjectiveFor long-term stability the adhering interfaces of an implant-retained supraconstruction of titanium/carbon–graphite fiber-reinforced (CGFR) polymer/opaquer layer/denture base polymer/denture teeth must function as a unity. The aim was to evaluate adhesion of CGFR polymer to a titanium surface or CGFR polymer to two different opaquer layers/with two denture base polymers.Materials and methodsTitanium plates were surface-treated and silanized and combined with a bolt of CGFR polymer or denture base polymer (Probase Hot). Heat-polymerized plates of CGFR polymer (47 wt% fiber) based on poly(methyl methacrylate) and a copolymer matrix were treated with an opaquer (Sinfony or Ropak) before a denture base polymer bolt was attached (Probase Hot or Lucitone 199). All specimens were heat-polymerized, water saturated (200 days) and thermally cycled (5000 cycles, 5/55 °C) before shear bond testing.ResultsSilicatized titanium surfaces gave higher bond strength to CGFR polymer (16.2 ± 2.34 and 18.6 ± 1.32) MPa and cohesive fracture than a sandblasted surface (5.9 ± 2.11) MPa where the fracture was adhesive. The opaquer Sinfony gave higher adhesion values and mainly cohesive fractures than the opaquer Ropak. Different surface treatments (roughened or polished) of the CGFR polymer had no effect on bond strength.SignificanceThe fracture surfaces of silicatized titanium/CGFR polymer/opaquer layer (Sinfony)/denture base polymers were mainly cohesive. A combination of these materials in an implant-retained supraconstruction is promising for in vivo evaluation.     

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.     

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.     

Bonding of acrylic denture teeth to MMA/PMMA and light-curing denture base materials: the role of conditioning liquids

ObjectivesThe connection between resin denture teeth and the denture base is essential for the integrity of partial and full dentures. The aim of the present study was to analyse the bond strength of acrylic denture teeth to two light curing denture base materials compared to the gold-standard (MMA/PMMA) using different conditioning liquids.MethodsThe ridge laps of 220 identical denture teeth were ground and pre-treated using different conditioning liquids (MMA, an experimental conditioning liquid as well as the two commercially available liquids Palabond and Versyo.bond). The denture base materials (PalaXpress, Versyo.com, Eclipse) were applied using a split mould to obtain tensile bond strength specimens of identical shape. Ten specimens per test group were either stored in water for 24 h or thermocycled (5000×, 5–55 °C) prior to tensile bond strength testing (cross-head speed 10 mm/min). Data was subjected to parametric statistics (α = 0.05).ResultsThe three-way ANOVA revealed a significant influence of the material, pre-treatment as well as the storage. PalaXpress showed the highest bond strength (24.3 MPa) of all materials tested after TC, whereas the use of MMA led to the most constant results. Lower values were recorded for Versyo.com (17.5 MPa) and Eclipse (10.4 MPa) bonded with Versyo.bond.ConclusionsThe results indicate that MMA/PMMA based denture base resins provide reliable and durable bond strength to acrylic denture teeth. Using light-curing denture base materials requires the application of appropriate conditioning liquids to obtain acceptable bond strength. The use of MMA affects bond strength to light-curing denture base materials.Clinical significanceThe pre-treatment of denture teeth is critical regarding their bond-strength to denture base materials and in turn for the integrity of removable full and partial dentures. Light-curing denture base resins are more sensitive to the correct tooth pre-treatment compared to conventional MMA/PMMA materials, requiring specific conditioning liquids.     

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.     

Effects of biglycan on physico-chemical properties of ligament-mineralized tissue attachment sites

Matrix proteoglycans define matrix structure, mineralization, and resulting biomechanics of tissues and their attachment sites.ObjectiveWe therefore investigated physical and (bio)chemical differences in enamel and periodontal tissues/attachment sites from mice that lack a specific nanoscale small leucine-rich proteoglycan (SLRPs) named biglycan (BGN).DesignExperimental groups consisted of N = 4, biglycan knockout (BGNKO) and N = 5 wildtype (WT) 8-week-old, male C3H mice. Morphology, histochemical and mechanical analyses were performed through micro X-ray computed tomography (Micro XCT?), immunohistochemistry, and microindentation. Unless mentioned otherwise, all differences between BGNKO and WT were demonstrated to be statistically significant through Student's t-tests with a 95% confidence interval (P ≤ 0.05).ResultsHistomorphometry performed by using Micro XCT? images indicated significantly higher BGNKO-enamel (0.46 ± 0.03 mm³) and BGNKO-root (1.81 ± 0.10 mm³) volumes compared to WT-enamel (0.37 ± 0.02 mm³) and WT-root (1.65 ± 0.07 mm³). BGNKO tooth size was relatively larger than WT mice, with no significant difference between skull sizes. Immunohistochemistry indicated BGN expression in the periodontal ligament (PDL), alveolar bone (AB), at the bone–PDL and cementum–PDL attachment sites in WT mice. Deeper AB resorption pits within interdental region of BGNKO specimens compared to WT resulting in significant differences in PDL-space of BGNKO (93 ± 13 μm) and WT (74 ± 11 μm) were observed. Microhardness of BGNKO-enamel (2.46 ± 0.60 GPa) and BGNKO-AB (0.52 ± 0.10 GPa) was significantly lower than WT-enamel (2.67 ± 0.60 GPa) and WT-AB (0.54 ± 0.10 GPa).ConclusionResults indicate that BGNKO-mice exhibit significant differences in tissue properties compared to WT-mice.     

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.     

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.     

Fracture strength of CAD/CAM composite and composite-ceramic occlusal veneers

PurposeTo determine the effect of material type and restoration thickness on the fracture strength of posterior occlusal veneers made from computer-milled composite (Paradigm MZ100) and composite-ceramic (Lava Ultimate) materials.Methods60 maxillary molars were prepared and restored with CAD/CAM occlusal veneer restorations fabricated from either Paradigm MZ100 or Lava Ultimate blocks at minimal occlusal thicknesses of 0.3, 0.6, and 1.0 mm. Restorations were adhesively bonded and subjected to vertical compressive loading. The maximum force at fracture and mode of failure were recorded. 2-Way ANOVA was used to identify any statistically significant relationships between fracture strength and material type or thickness. Spearman's rank correlation coefficient was used to analyze mode of failure with regard to fracture strength.ResultsThe average maximum loads (N) at fracture for the Paradigm MZ100 groups were 1620 ± 433, 1830 ± 501, and 2027 ± 704 for the material thicknesses of 0.3, 0.6, and 1.0 mm, respectively. The Lava Ultimate groups fractured at slightly higher loads (N) of 2078 ± 605, 2141 ± 473, and 2115 ± 462 at the respective 0.3, 0.6, and 1.0 mm thickness.Statistical analyses revealed that, while no significant difference existed among the various restoration thicknesses in terms of fracture strength (P > 0.05), the material type was found to be influential (P = 0.04). The maximum load at fracture (N) for Lava Ultimate averaged over all thicknesses (2111 ± 500) was significantly higher than that of the Paradigm MZ100 (1826 ± 564). No correlation between mode of failure and fracture strength was found.ConclusionsUnder the conditions of this study, the maximal loads at fracture for these “non-ceramic” occlusal veneer restorations were found to be higher than human masticatory forces. Occlusal veneers made from the two materials tested are likely to survive occlusal forces regardless of restoration thickness, with those fabricated from the composite-ceramic hybrid material being more likely to survive heavier loads.     

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.     

New insight into the "depth of cure" of dimethacrylate-based dental composites

ObjectivesTo demonstrate that determination of the depth of cure of resin-based composites needs to take into account the depth at which the transition between glassy and rubbery states of the resin matrix occurs.MethodsA commercially available nano-hybrid composite (Grandio) in a thick layer was light cured from one side for 10 or 40 s. Samples were analyzed by Vickers indentation, Raman spectroscopy, atomic force microscopy, electron paramagnetic imaging and differential scanning calorimetry to measure the evolution of the following properties with depth: microhardness, degree of conversion, elastic modulus of the resin matrix, trapped free radical concentration and glass transition temperature. These measurements were compared to the composite thickness remaining after scraping off the uncured, soft composite.ResultsThere was a progressive decrease in the degree of conversion and microhardness with depth as both properties still exhibited 80% of their upper surface values at 4 and 3.8 mm, respectively, for 10 s samples, and 5.6 and 4.8 mm, respectively, for 40 s samples. In contrast, there was a rapid decrease in elastic modulus at around 2.4 mm for the 10 s samples and 3.0 mm for the 40 s samples. A similar decrease was observed for concentrations of propagating radicals at 2 mm, but not for concentrations of allylic radicals, which decreased progressively. Whereas the upper composite layers presented a glass transition temperature – for 10 s, 55 °C (±4) at 1 mm, 56.3 °C (±2.3) at 2 mm; for 40 s, 62.3 °C (±0.6) at 1 mm, 62 °C (±1) at 2 mm, 62 °C (±1.7) at 3 mm – the deeper layers did not display any glass transition. The thickness remaining after scraping off the soft composite was 7.01 (±0.07 mm) for 10 s samples and 9.48 (±0.22 mm) for 40 s samples.SignificanceAppropriate methods show that the organic matrix of resin-based composite shifts from a glassy to a gel state at a certain depth. Hence, we propose a new definition for the “depth of cure” as the depth at which the resin matrix switches from a glassy to a rubbery state. Properties currently used to evaluate depth of cure (microhardness, degree of conversion or scraping methods) fail to detect this transition, which results in overestimation of the depth of cure.     

Thermo and mechanical cycling and veneering method do not influence Y-TZP core/veneer interface bond strength

ObjectivesThe purpose of this study was to evaluate the influence of thermal and mechanical cycling and veneering technique on the shear bond strength of Y-TZP (yttrium oxide partially stabilized tetragonal zirconia polycrystal) core–veneer interfaces.Materials and methodsCylindrical Y-TZP specimens were veneered either by layering (n = 20) or by pressing technique (n = 20). A metal ceramic group (CoCr) was used as control (n = 20). Ten specimens for each group were thermal and mechanical cycled and then all samples were subjected to shear bond strength in a universal testing machine with a 0.5 mm/min crosshead speed. Mean shear bond strength (MPa) was analysed with a 2-way analysis of variance and Tukey's test (p < 0.05). Failure mode was determined using stereomicroscopy and scanning electron microscopy (SEM).ResultsThermal and mechanical cycling had no influence on the shear bond strength for all groups. The CoCr group presented the highest bond strength value (p < 0.05) (34.72 ± 7.05 MPa). There was no significant difference between Y-TZP veneered by layering (22.46 ± 2.08 MPa) or pressing (23.58 ± 2.1 MPa) technique. Failure modes were predominantly adhesive for CoCr group, and cohesive within veneer for Y-TZP groups.ConclusionsThermal and mechanical cycling, as well as the veneering technique does not affect Y-TZP core–veneer bond strength.Clinical significanceDifferent methods of veneering Y-TZP restorations would not influence the clinical performance of the core/veneer interfaces.     

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.     

Effects of blood and saliva contamination on shear bond strength of metal orthodontic brackets and evaluating certain methods for reversing the effect of contamination

The background and purposeContaminations may reduce shear bond strength (SBS) of orthodontic brackets. For reversing such effects, certain surface treatments are suggested. This study was conducted to evaluate (1) effects of saliva and blood contamination on SBS of metal brackets, (2) the efficacy of three surface treatments, while (3) using two adhesives (37% phosphoric acid etchant (Ivoclar/Vivadent) + RMGIC (Fuji Ortho LC), and self-etchant primer (iBonD GI) + composite resin (No-Mix, Dentaurum)).MethodsThe sample was categorized into 12 experimental subgroups (2 contaminations × 3 treatments × 2 adhesives, n = 12 × 10) and 2 control subgroups (n = 2 × 10). Experimental specimens underwent different treatments according to their group. They were incubated (37 °C, 96 h) and thermocycled (3000 cycles, 5–55 °C, dwell time = 30 s). SBS was tested at 1 mm/min crosshead speed.ResultsSEP–composite produced significantly lower SBS rates (P < 0.05) according to Mann–Whitney. ANOVA indicated a significant difference between blood contamination and both control and saliva contamination. According to Wilcoxon signed rank test, comparing with SBS = 7, drying failed to achieve appropriate SBS rates (except drying saliva when using RMGIC). On RMGIC, re-etching and rinsing–drying methods might provide sufficient SBS levels. All treatments (except rinsing–drying saliva contamination) did not produce appropriate SBS levels when using SEP–composite.ConclusionsBlood contamination reduced the SBS much greater than saliva. Using etchant–RMGIC is strongly recommended. Drying may only suffice when RMGIC is used over saliva contamination. The efficacy of re-etching depends on the etchant type. Rinsing–drying may produce appropriate SBS levels.     

Soft tissue, skeletal and dentoalveolar changes following conventional anchorage molar distalization therapy in class II non-growing subjects: a multicentric retrospective study

ObjectivesThe purpose of this retrospective prolective study is to evaluate soft tissue, dentoalveolar and skeletal vertical changes following conventional anchorage molar distalization therapy in adult patients.Materials and methodsForty-six patients (34 females, mean age 25 years 6 months; and 12 males, mean age 28 years 4 months) were recruited from 4 specialists Board Certified. All subjects underwent molar distalization therapy according different distalization mechanics. Cephalometric headfilms were available for all subjects before (T0) and at the end of comprehensive treatment (T1). The initial and final measurements and treatment changes were compared by means of a paired t-test or a paired Wilcoxon test.ResultsMean total treatment time was 3 years 3 months ± 8 months. Maxillary first and second molars distalized 2.16 ± 0.84 mm and 2.01 ± 0.69 mm respectively, but also maintained a slight distal tipping of 1.45° (min 2.22°, max -6.45°) and 3.35° (min 0.47°, max -15.48°) at the end of treatment. Distal movement of maxillary first molar contributed 57.6% to molar correction, and 42.4% was due to a mesial movement of mandibular first molar (1.59 ± 0.46 mm). Dentoalveolar changes contributed to overjet correction; maxillary incisors retroclined 5.78° ± 3.17°, lower incisors proclined 7.49° ± 4.52° and occlusal plane rotated down and backward 2.32° ± 2.10°. A significant clockwise rotation of the mandible (1.97° ± 1.32°) and a significant increase in lower facial height (3.35 ± 1.48) mm were observed. Upper lip slightly retruded (-1.76 ± 1.70 mm) and lower lip protruded (0.96 ± 0.99 mm) but these changes had a negligible impact on clinical appearance.ConclusionsAlthough maxillary molar distalization therapy can be performed in adult patients, significant proclination of the lower incisors, clockwise rotation of the occlusal plane and increase in vertical facial dimension should be expected. Nevertheless, in absence of maxillary third molars and in presence of mandibular third molars this procedure could be recommended.     

Effects of aging procedures on the topographic surface,structural stability,and mechanical strength of a ZrO2-based dental ceramic

ObjectiveTo determine the effects of different aging methods on the degradation and flexural strength of yttria-stabilized tetragonal zirconia (Y-TZP)MethodsSixty disc-shaped specimens (∅, 12 mm; thickness, 1.6 mm) of zirconia (Vita InCeram 2000 YZ Cubes, VITA Zahnfabrik) were prepared (ISO 6872) and randomly divided into five groups, according to the aging procedures (n = 10): (C) control; (M) mechanical cycling (15,000,000 cycles/3.8 Hz/200 N); (T) thermal cycling (6,000 cycles/5–55 °C/30 s); (TM) thermomechanical cycling (1,200,000 cycles/3.8 Hz/200 N with temperature range from 5 °C to 55 °C for 60 s each); (AUT) 12 h in autoclave at 134 °C/2 bars; and (STO) storage in distilled water (37 °C/400 days). After the aging procedures, the monoclinic phase percentages were evaluated by X-ray diffraction (XRD), and topographic surface analysis was performed by 3D profilometry. The specimens were then subjected to biaxial flexure testing (1 mm/min, load 100 kgf, in water). The biaxial flexural strength data (MPa) were analyzed by 1-way ANOVA and Tukey's test (α = 0.05). The data for monoclinic phase percentage and profilometry (Ra) were analyzed by Kruskal–Wallis and Dunn's tests.ResultsANOVA revealed that flexural strength was affected by the aging procedures (p = 0.002). The M (781.6 MPa) and TM (771.3 MPa) groups presented lower values of flexural strength than did C (955 MPa), AUT (955.8 MPa), T (960.8 MPa) and STO (910.4 MPa). The monoclinic phase percentage was significantly higher only for STO (12.22%) and AUT (29.97%) when compared with that of the control group (Kruskal–Wallis test, p = 0.004). In addition, the surface roughnesses were similar among the groups (p = 0.165).SignificanceWater storage for 400 days and autoclave aging procedures induced higher phase transformation from tetragonal to monoclinic; however, they did not affect the flexural strength of Y-TZP ceramic, which decreased only after mechanical and thermomechanical cycling.     

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.     

Bridging the gap between clinical failure and laboratory fracture strength tests using a fractographic approach

ObjectiveThe aim of this study was to analyze and to compare the fracture type and the stress at failure of clinically fractured zirconia-based all ceramic restorations with that of morphologically similar replicas tested in a laboratory setup.MethodsReplicas of the same shape and dimensions were made for 19 crowns and 17 fixed partial dentures, all made of veneered zirconia frameworks, which fractured during intra-oral service. The replicas were statically loaded by applying axial load in a universal testing machine. The principles of fractography were used to identify the location and the dimensions of the critical crack and to estimate the stress at failure. Failure was classified according to origin and type (P < 0.05 was considered significant).ResultsClinically fractured restorations failed due to either: delamination of the veneer ceramic (28.2 ± 9 MPa), defects at core veneer interface (27.7 ± 6 MPa), the generation of Hoop stresses (884.3 ± 266 MPa), radial cracking (831 MPa), or fracture of the connector (971 ± 343 MPa). The replicas failed by mainly by cone cracking of the veneer ceramic (52.4 ± 34.8 MPa) or by fracture of the connector (1098.9 ± 259 MPa). The estimated stress at failure was significantly higher for the replicas compared to the clinically fractured restorations (F = 6.8, P < 0.01).SignificanceWithin limitations of this study, careful design of fracture strength test would lead to more clinically relevant data. The performance of zirconia veneered restorations could be further improved with careful design considerations.     

Evaluation of interface characterization and adhesion of glass ceramics to commercially pure titanium and gold alloy after thermal- and mechanical-loading

ObjectivesThis study evaluated the effect of thermal- and mechanical-cycling on the shear bond strength of three low-fusing glassy matrix dental ceramics to commercial pure titanium (cpTi) when compared to conventional feldspathic ceramic fused to gold alloy.MethodsMetallic frameworks (diameter: 5 mm, thickness: 4 mm) (N = 96, n = 12 per group) were cast in cpTi and gold alloy, airborne particle abraded with 150 μm aluminum oxide. Low-fusing glassy matrix ceramics and a conventional feldspathic ceramic were fired onto the alloys (thickness: 4 mm). Four experimental groups were formed; Gr1 (control group): Vita Omega 900–Au–Pd alloy; Gr2: Triceram–cpTi; Gr3: Super Porcelain Ti-22–cpTi and G4: Vita Titankeramik–cpTi. While half of the specimens from each ceramic–metal combination were randomly tested without aging (water storage at 37 °C for 24 h only), the other half were first thermocycled (6000 cycles, between 5 and 55 °C, dwell time: 13 s) and then mechanically loaded (20,000 cycles under 50 N load, immersion in distilled water at 37 °C). The ceramic–alloy interfaces were loaded under shear in a universal test machine (crosshead speed: 0.5 mm/min) until failure occurred. Failure types were noted and the interfaces of the representative fractured specimens from each group were examined with stereomicroscope and scanning electron microscope (SEM). In an additional study (N = 16, n = 2 per group), energy dispersive X-ray spectroscopy (EDS) analysis was performed from ceramic–alloy interfaces. Data were analyzed using ANOVA and Tukey's test.ResultsBoth ceramic–metal combinations (p < 0.001) and aging conditions (p < 0.001) significantly affected the mean bond strength values. Thermal- and mechanical-cycling decreased the bond strength (MPa) results significantly for Gr3 (33.4 ± 4.2) and Gr4 (32.1 ± 4.8) when compared to the non-aged groups (42.9 ± 8.9, 42.4 ± 5.2, respectively). Gr1 was not affected significantly from aging conditions (61.3 ± 8.4 for control, 60.7 ± 13.7 after aging) (p > 0.05). Stereomicroscope images showed exclusively adhesive failure types at the opaque ceramic–cpTi interfacial zone with no presence of ceramic on the substrate surface but with a visible dark titanium oxide layer in Groups 2–4 except Gr1 where remnants of bonder ceramic was visible. EDS analysis from the interfacial zone for cpTi–ceramic groups showed predominantly 34.5–85.1% O₂ followed by 1.1–36.7% Al and 0–36.3% Si except for Super Porcelain Ti-22 where a small quantity of Ba (1.4–8.3%), S (0.7%) and Sn (35.3%) was found. In the Au–Pd alloy–ceramic interface, 56.4–69.9% O₂ followed by 15.6–26.2% Si, 3.9–10.9% K, 2.8–6% Na, 4.4–9.6% Al and 0–0.04% Mg was observed.SignificanceAfter thermal-cycling for 6000 times and mechanical-cycling for 20,000 times, Triceram–cpTi combination presented the least decrease among other ceramic–alloy combinations when compared to the mean bond strength results with Au–Pd alloy–Vita Omega 900 combination.     

Effect of filler particle size and morphology on force/work parameters for stickiness of unset resin-composites

ObjectivesTo investigate the effect of variation in filler particle size and morphology within an unset model series of resin-composites on two stickiness parameters: (1) maximum probe separation-force and (2) work-of-separation. This study was to complement previously reported measurements of composite stickiness in terms of a strain-parameter, ‘peak-height’.Materials and methodsEleven experimental light cured resin-composites were selected. All had the same matrix (Bis-GMA, UDMA and TEGDMA, with 0.33% camphoroquinone) and the same filler volume fraction—56.7%, however filler particles varied in size and shape and were either unimodal or multimodal in size-distribution. Each material was placed in a cylindrical mould (φ = 7 mm × 5 mm depth) held at 26 or 37 °C. The maximum force (F_max, N) and work of probe-separation (W_s, N mm) were measured. A flat-ended stainless-steel probe (φ = 6 mm) was mechanically lowered onto and into the surface of the unset sample, until a compressive force of 1 N was reached, which was held constant for 1 s. Then the probe was moved vertically upward at a constant speed; either 2 or 8 mm/s. The tensile force produced on the probe by the sticky composite was plotted against displacement and the maximum value was identified (F_max). W_s was obtained as the integrated area. Data was analyzed by multivariate ANOVA and multiple pair-wise comparisons using a Tukey post hoc test to establish homogenous subsets (at p = 0.05) for F_max and a Games–Howell was used for W_s.ResultsAs potential measures of stickiness, F_max and W_s showed more coherent trends with fillersize when measured at the lower of the two probe speeds, 2 mm/s. For unimodal resin-composite F_max ranged from 1.04 to 5.11 N and W_s from 0.48 to 11.12 N mm. For the multimodal resin-composite they ranged from 1.64 to 4.13 N and from 2.32 to 8.34 N mm respectively. Temperature increase tended to slightly reduce F_max, although this trend was not consistent. W_s generally increased with temperature.ConclusionFiller particle size and morphology influences F_max and W_s of uncured resin-composite which partly express the handling behaviors of resin-composites.