Influence of ceramic veneer on the transdentinal cytotoxicity,degree of conversion and bond strength of light-cured resin cements to dentin

ObjectivesTo investigate the transdentinal cytotoxicity (TC), degree of conversion (DC), and micro shear bond strength (μSBS) to dentin of light-cured resin cements (LCRCs) photoactivated directly or through a ceramic veneer( ± CV).Materials and methodsThe TC was assessed using human dentin discs adapted into artificial pulp chambers. Odontoblast-like cells were seeded on the pulp surface of the discs, then three LCRCs( ± CV) were applied on their etched and hybridized occlusal surface (n = 8/group). The adhesive systems of each LCRCs and sterile phosphate-buffered saline were used as positive and negative controls, respectively. After 24 h, the viability and morphology of cells adhered on discs were assessed. The extracts (culture medium + components of the materials diffused through the discs) were applied on the MDPC-23 to evaluate their viability, adhesion/spreading (A/S), alkaline phosphatase activity (ALP), and mineralized nodule formation (MN). LCRCs( ± CV) specimens were evaluated concerning the DC and μSBS to dentin. Data were analyzed by one-, two-, or three-way ANOVA/Dunnett, Sidak, and Games-Howell tests (α = 5%).ResultsAll LCRCs( ± CV) reduced cell viability, A/S, ALP, MN, and DC. Except for μSBS, the intensity of reduction was dependent on the LCRC used. LCRCs+CV resulted in lower DC and μSBS but did not increase the TC.SignificanceBesides the presence of CV between the light source and LCRCs reduces the degree of conversion and bond strength to dentin, these materials cause variable level of transdentinal toxicity to pulp cells. Thus, the composition and curing protocols of LCRCs should be revisited and reinforced to prevent mechanical and biological drawbacks.     

Effect of surface treatments on optical,topographical and mechanical properties of CAD/CAM reinforced lithium silicate glass ceramics

ObjectivesTo investigate the effect of different surface treatments on optical, topographical and mechanical properties of CAD/CAM lithium silicate-based glass ceramics (LSC’s) and their combined effect on the output of a light curing unit (LCU).MethodsFour CAD/CAM LSC’s were investigated: Lithium Disilicate (Emax CAD; EC), Zirconia-reinforced silicates (Vita Suprinity; VS and Celtra Duo;CD) and Lithium Aluminum Disilicate (CEREC Tessera; CT). Ceramic specimens (n = 240) were divided into six subgroups according to their surface treatment: (a) Control, (b) Hydrofluoric acid (HF) 5%, (c) HF 5% + Neutralizing agent (N), (d) HF 9%, (e) HF 9% +N and (f) Self-etching ceramic primer (SEP). Irradiance, power and radiant exposure of a LCU were measured with MARC-LC following ceramic specimen interposition. Direct light transmission (T%) and absorbance (Abs%) of the specimens were measured with UV-Vis spectrophotometry. Roughness (Sa, Sq) and wettability (θ°) were measured with optical profilometry and sessile drop profile analysis, respectively. Biaxial flexural strength (σ) of the ceramic specimens was measured by the ball-on-three-balls method and ceramic specimens were examined microscopically. Statistical analyses was performed by two-way ANOVA followed by post hoc multiple comparisons (α = 0.05).ResultsAcid neutralization decreased T% and increased Abs% in all LSC’s and highest T% was exhibited with VS. Neutralized EC, VS and CD displayed higher Sa in HF9, while neutralized CT displayed higher Sa in HF5. Self-etch primer significantly reduced θ° (p < 0.001). σ was observed in the followed ascending order: HF9 +N < HF9 < HF5 +N < HF5 < SEP < Control for all LSC’s.SignificanceOptical, topographical and mechanical properties of the CAD/CAM ceramic blocks were strongly dependent on the type of surface treatment. Results of neutralization post-etching indicate promising potential for future investigations.     

Bonding effectiveness of tooth-colored materials to resin cement provided by self-etching silane primer after short- and long-term storage

Statement of problem

Glass-ceramic materials are typically treated with hydrofluoric acid (HF) and silane to improve their bond to composite resin; however, HF may be harmful to human tissues and the integrity of the material, and its application is a technique-sensitive procedure. A novel self-etching ceramic primer has been introduced with the claim that it can solve those problems. However, independent scientific evidence regarding its performance is scarce.

The development and testing of glaze materials for application to the fit surface of dental ceramic restorations

ObjectivesThe aims of the study were to develop and test overglaze materials for application to the fit surface of dental ceramic restorations, which could be etched and adhesively bonded and increase the flexural strength of the ceramic substrate.MethodsThree glaze materials were developed using commercial glass powders (P25 and P54, Pemco, Canada). P25 (90 wt%) was mixed with P54 (10 wt%) to produce (P25/P54). P54 (90 wt%) was mixed with P25 (10 wt%) to produce (P54/P25). P25 (90 wt%) was mixed with 10 wt% of an experimental glass powder (P25/frit). Eighty-two disc specimens (14 mm × 2 mm) were produced by heat pressing a leucite glass–ceramic and were sandblasted with 50 μm glass beads. Group 1 control specimens (10) were sandblasted. Groups 2–4 (10 per group) were coated using P25/frit (Group 2), P25/P54 (Group 3) and P54/P25 (Group 4) overglazes before sintering. Groups 1–4 were etched for 2 min using 9.5% HF (Gresco, USA). Composite cylinders (Marathon^® v, Den-Mat) were light cured and bonded to the glazed and prepared disc surfaces and groups water stored for 8 days. Groups were tested using shear bond strength (SBS) testing at 0.5 mm/min. Disc specimens (42) were tested using the biaxial flexural strength (BFS) test at a crosshead speed of 0.15 mm/min. Group 1 was tested as sandblasted (21) and Group 2 (21) after coating the tensile surface with P25/frit. Xrd, Eds and Sem analyzes were carried out.ResultsMean SBS (MPa ± S.D.) were: Group 1: 10.7 ± 2.1; Group 2: 9.8 ± 1.9; Group 3: 1.8 ± 1.0 and Group 4: 2.6 ± 1.7. Groups 1 and 2 were statistically different to Groups 3 and 4 (p < 0.001), but there was no difference between Groups 1 and 2 and 3 and 4 (p > 0.05). The mean BFS (MPa ± S.D.) of the overglazed Group 2 (200.2 ± 22.9) was statistically different (p < 0.001) to Group 1 (150.4 ± 14.3).SignificanceThe P25/frit overglaze significantly (p < 0.001) increased the biaxial flexural strength of the leucite glass–ceramic substrate and produced comparable shear bond strengths to an etched and bonded control. The application of etched overglaze materials to dental glass–ceramic and ceramic substrates may be useful in adhesive dentistry.     

Effect of surface treatment and luting agent type on shear bond strength of titanium to ceramic materials

PURPOSEThis study aimed to compare the effect of different surface treatments and luting agent types on the shear bond strength of two ceramics to commercially pure titanium (Cp Ti).MATERIALS AND METHODSA total of 160 Cp Ti specimens were divided into 4 subgroups (n = 40) according to surface treatments received (control, 50 µm airborne-particle abrasion, 110 µm airborne-particle abrasion, and tribochemical coating). The cementation surfaces of titanium and all-ceramic specimens were treated with a universal primer. Two cubic all-ceramic discs (lithium disilicate ceramic (LDC) and zirconia-reinforced lithium silicate ceramic (ZLC)) were cemented to titanium using two types of resin-based luting agents: self-cure and dual-cure (n = 10). After cementation, all specimens were subjected to 5000 cycles of thermal aging. A shear bond strength (SBS) test was conducted, and the failure mode was determined using a scanning electron microscope. Data were analyzed using three-way ANOVA, and the Tukey-HSD test was used for post hoc comparisons (P < .05).RESULTSSignificant differences were found among the groups based on surface treatment, resin-based luting agent, and ceramic type (P < .05). Among the surface treatments, 50 µm air-abrasion showed the highest SBS, while the control group showed the lowest. SBS was higher for dual-cure resin-based luting agent than self-cure luting agent. ZLC showed better SBS values than LDC.CONCLUSIONThe cementation of ZLC with dual-cure resin-based luting agent showed better bonding effectiveness to commercially pure titanium treated with 50 µm airborne-particle abrasion.     

Influence of surface treatments on bond strength of metal and ceramic brackets to a novel CAD/CAM hybrid ceramic material

This study evaluated the effect of four different surface treatments methods on the shear bond strength (SBS) of ceramic and metal brackets to Vita Enamic (VE) CAD/CAM hybrid ceramic. A total of 240 plates (10 mm × 10 mm × 3 mm) were cut from VE ceramic blocks and divided into two groups. In each group, four subgroups were prepared by hydrofluoric acid (HF); phosphoric acid (H₃PO₄); diamond ceramic grinding bur; and silica coating using CoJet system (CJ). Maxillary central incisor metal (Victory Series) and ceramic (Clarity) brackets were bonded with light-cure composite and then stored in artificial saliva for 1 week and thermocycled. The SBS test was performed, and the failure types were classified with adhesive remnant index scores. Surface morphology of the ceramic was characterized after treatment using a scanning electron microscope. Data were analyzed using two-way ANOVA, Tukey HSD test, and Weibull analysis. SBS was significantly affected by the type of bracket and by type of treatment (P < 0.001). Specimens treated with CJ presented with significantly higher SBS compared to other groups (P < 0.05). Improvements in SBS values (MPa) were found in the following order: CJ > HF > Bur > H₃PO₄. Ceramic bracket showed higher SBS compared to metal bracket. Adhesive failures between the ceramic and composite resin were the predominant mode of failure in all groups. Surface treatment of VE CAD/CAM hybrid ceramic with silica coating enhanced the adhesion with ceramic and metal brackets.     

Examination of ceramic/enamel interfacial debonding using acoustic emission and optical coherence tomography

ObjectiveThis study investigates monitored micro-crack growth and damage in the ceramic/enamel adhesive interface using the acoustic emission (AE) technique with optical coherence tomography (OCT) under fatigue shear testing.MethodsShear bond strength (SBS) was measured first with eight prepared ceramic/enamel adhesive specimens under static loads. The fatigue shear testing was performed with three specimens at each cyclic load according to a modified ISO14801 method, applying at 80%, 75%, 70%, and 65% of the SBS to monitor interface debonding. The number of cycles at each load was recorded until ceramic/enamel adhesive interface debonding occurred. The AE technique was used to detect micro-crack signals in static and fatigue shear bond tests.ResultsThe results showed that the average SBS value in the static tests was 18.07 ± 1.72 MPa (mean ± standard deviation), expressed in Newton's at 56.77 ± 5.40 N. The average number of fatigue cycles in which ceramic/enamel interface damage was detected in 80%, 75%, 70% and 65% of the SBS were 41, 410, 8141 and 76,541, respectively. The acoustic behavior varied according to the applied load level. Events were emitted during 65% and 70% fatigue tests. A good correlation was observed between the crack location in OCT images and the number of AE signal hits.SignificanceThe AE technique combined with OCT images as a pre-clinical assessment tool to determine the integrity of cemented load bearing restored ceramic material. Sustainable cyclic load stresses in ceramic/enamel bonded specimens were substantially lower than the measured SBS. Predicted S–N curve showed that the maximum endured load was 10.98 MPa (about 34.48 N) passing 10⁶ fatigue cyclic.     

Bond strength between temporary 3D printable resin and conventional resin composite: influence of cleaning methods and air-abrasion parameters

Objectives

The influence of different cleaning methods, air-abrasion parameters, and aging on shear bond strength (SBS) and tensile bond strength (TBS) of 3D resin luted to composite resin.

Materials and methods

Nine hundred resin substrates were 3D printed (D20II, Rapid Shape) and cleaned with either isopropanol (ISO), butyldiglycol-based solution (BUT), or centrifugation (CEN). After 24-h storage in 37 °C water, specimens were air-abraded (mean particle size 50 µm; n?=?60) with either alumina at 0.1 MPa (AL0.1) or 0.4 MPa (AL0.4) and glass pearls at 0.1 MPa (GP0.1) and 0.4 MPa (GP0.4) or conditioned with visio.link (control) and luted with PanaviaV5. Initially (24 h, 37 °C water storage) or after aging (10,000 thermal cycles), SBS and TBS were measured, and fracture types were examined. Surface free energy (SFE) and roughness (Ra) were determined after air-abrasion. Kolmogorov–Smirnov, Kruskal–Wallis H, Mann–Whitney U, chi-square, and partial eta-squared were computed.

Results

SBS measurements presented higher values than TBS (p?<?0.001–0.033). Within the pretreatment groups, CEN showed the highest SBS and TBS values compared to cleaning with ISO or BUT (p?<?0.001–0.040). Pretreatment with GP0.1 displayed the lowest bond strength values (p?<?0.001–0.049), and mostly adhesive fractures occurred. The highest Ra values (p?<?0.001) were observed for AL0.4 pretreatment.

Conclusions

Pretreatment with AL0.4 and the control group mainly presented the highest bond strength values. Thermocycling had a positive effect on the bond strength.

Clinical relevance

According to this study, 3D-printed restorations should be pretreated with AL0.4 or with visio.link before adhesive luting, regardless of their cleaning.

     

Effect of different surface treatments on the biaxial flexure strength,Weibull characteristics,roughness, and surface topography of bonded CAD/CAM silica-based ceramics

ObjectiveTo investigate the influence of different surface treatments on biaxial flexure strength, roughness, and surface topography of lithium silicate/disilicate-based ceramics.Methods225 discs (?: 12 mm; 1.2 mm – ISO 6872) were made from three ceramics: IPS e.max CAD (LD – Ivoclar Vivadent), Suprinity (LSS - Vita) and Celtra Duo (LSC - Dentsply). The samples were randomly divided into 5 groups (n = 15): no treatment (C); 10% hydrofluoric acid + silane (HF); sandblasting Al₂O₃ + silane (SB); silicatization + silane (SC); and self-etching ceramic primer (SEP). After surface treatment, a resin cement layer was applied to the disc surface (RelyX U200, 3M ESPE), mechanical cycled (1.2 × 10⁶ cycles, 50 N, 3.8 Hz) and submitted to biaxial flexural strength test (1 mm/min, 1000 Kgf). Roughness, EDS and SEM were also performed. Data were analyzed by one-way ANOVA, Tukey test (5%) and Weibull.ResultsANOVA revealed that the “surface treatment” factor was significant for all ceramics (p < 0.05). The groups LD-HF (289.30 ± 40) LD-SEP (298. 87 ± 53.29), LSC-HF (195.51 ± 42.12), LSS-HF (269.58 ± 27.07) and LSS-SEP (207.45 ± 28.63) presented significantly higher biaxial flexure strength than respective control groups, except for the LSC-SEP (165.41 ± 33.86), which was statistically similar to the control. The Weibull modulus was significantly higher for the LD-SB, LSC-SC groups. Additionally, the LD-SB, LSC-SC and LSS-HF groups showed higher roughness compared to the other treatments.SignificanceHF etching followed by silanization and self-etching ceramic primer are the most suitable surface treatments for lithium silicate/disilicate-based glass-ceramics.     

Manufacture,characterisation and properties of novel fluorcanasite glass–ceramics

ObjectiveThe aim of this study was to investigate the manufacture and characterisation of different compositions of fluorcanasite glass–ceramics with reduced fluorine content and to assess their mechanical and physical properties.MethodsThree compositional variations (S80, S81 and S82) of a fluorcanasite glass were investigated. Differential thermal analysis (DTA) and X-ray diffraction (XRD) identified crystallisation temperatures and phases. X-ray fluorescence (XRF) determined the element composition in the glass–ceramics. Different heat treatments [2 h nucleation and either 2 or 4 h crystallisation] were used for the glasses. Scanning electron microscopy (SEM) examined the microstructure of the cerammed glass. The chemical solubility, biaxial flexural strength, fracture toughness, hardness and brittleness index of S81 and S82 fluorcanasite were investigated with lithium disilicate (e.max CAD, Ivoclar Vivadent) as a commercial comparison. Statistical analysis was performed using one-way ANOVA with Tukey's multiple comparison tests (P < 0.05). Weibull analysis was employed to examine the reliability of the strength data.ResultsAll compositions successfully produced glasses. XRD analysis confirmed fluorcanasite formation with the S81 and S82 compositions, with the S82 (2 + 2 h) showing the most prominent crystal structure. The chemical solubility of the glass–ceramics was significantly different, varying from 2565 ± 507 μg/cm² for the S81 (2 + 2 h) to 722 ± 177 μg/cm² for the S82 (2 + 2 h) to 37.4 ± 25.2 μg/cm² for the lithium disilicate. BFS values were highest for the S82 (2 + 2 h) composition (250 ± 26 MPa) and lithium disilicate (266 ± 37 MPa) glass–ceramics. The fracture toughness was higher for the S82 compositions, with the S82 (2 + 2 h) attaining the highest value of 4.2 ± 0.3 MPa m^1/2(P = 0.01). The S82 (2 + 2 h) fluorcanasite glass–ceramic had the lowest brittleness index.ConclusionThe S82 (2 + 2 h) fluorcanasite glass–ceramic has acceptable chemical solubility, high biaxial flexural strength, fracture toughness and hardness.Clinical significanceA novel glass–ceramic has been developed with potential as a restorative material. The S82 (2 + 2 h) has mechanical and physical properties that would allow the glass–ceramic to be used as a machinable core material for veneered resin-bonded ceramic restorations.     

Comparison of shear test methods for evaluating the bond strength of resin cement to zirconia ceramic

Objective. This study compared the sensitivity of three shear test methods for measuring the shear bond strength (SBS) of resin cement to zirconia ceramic and evaluated the effects of surface treatment methods on the bonding. Materials and methods. Polished zirconia ceramic (Cercon® base, DeguDent) discs were randomly divided into four surface treatment groups: no treatment (C), airborne-particle abrasion (A), conditioning with Alloy primer (Kuraray Medical Co.) (P) and conditioning with Alloy primer after airborne-particle abrasion (AP). The bond strengths of the resin cement (Multilink N, Ivoclar Vivadent) to the zirconia specimens of each surface treatment group were determined by three SBS test methods: the conventional SBS test with direct filling of the mold (Ø 4 mm × 3 mm) with resin cement (Method 1), the conventional SBS test with cementation of composite cylinders (Ø 4 mm × 3 mm) using resin cement (Method 2) and the microshear bond strength (μSBS) test with cementation of composite cylinders (Ø 0.8 mm × 1 mm) using resin cement (Method 3). Results. Both the test method and the surface treatment significantly influenced the SBS values. In Method 3, as the SBS values increased, the coefficients of variation decreased and the Weibull parameters increased. The AP groups showed the highest SBS in all of the test methods. Only in Method 3 did the P group show a higher SBS than the A group. Conclusions. The μSBS test was more sensitive to differentiating the effects of surface treatment methods than the conventional SBS tests. Primer conditioning was a stronger contributing factor for the resin bond to zirconia ceramic than was airborne-particle abrasion.     

Effects of different pre-treatment methods on the shear bond strength of orthodontic brackets to demineralized enamel

Objective. To compare the effects of different treatment methods used for the enamel damage, on the shear bond strength (SBS) and fracture mode of orthodontic brackets. Materials and methods. Freshly-extracted 140 premolars were randomly allocated to seven groups: Group I was considered as the control of other groups. The remaining groups were exposed to demineralization. In group II, brackets were directly bonded to the demineralized enamel surface. CPP-ACP paste (GC Tooth Mousse), fluoride varnish (Bifluorid 12), microabrasion with a mixture prepared with 18% hydrochloric acid and fine pumice powder, microabrasion with an agent (Opalustre) and resin infiltrant (Icon®) were applied in Groups III, IV, V, VI and VII, respectively. The specimens were tested for SBS and bond failures were scored according to the Adhesive Remnant Index (ARI). Analysis of variance and Tukey tests were used to compare the SBS of the groups. ARI scores were compared with G-test. The statistical significance was set at p < 0.05 level. Results. Statistically significant differences were found among seven groups (F = 191.697; p < 0.001). The SBSs of groups I (mean = 18.8 ± 2.0 MPa) and VII (mean = 19.1 ± 1.4 MPa) were significantly higher than the other groups. No statistically significant difference was found between groups IV (mean = 11.5 ± 1.2 MPa) and V (mean = 12.6 ± 1.5 MPa). The differences in ARI scores of the groups were statistically significant (p < 0.01). Conclusions. All demineralization treatment methods improve bonding to demineralized enamel. Resin infiltrant application after demineralization showed similar bond strength values as intact enamel.     

Effect of different cleansing agents and adhesive resins on bond strength of contaminated zirconia

PurposeThis study was observed the effect of cleansing agents and adhesive resins on shear bond strength (SBS), surface morphology and phase transformation of saliva and silicone disclosing medium contaminated zirconia.MethodsThe 110 zirconia specimens size 5 × 5 × 1 mm were fabricated and randomly divided into 5 surface treated groups: Non-contaminated (PC) Saliva and silicone disclosing medium contaminated without cleansing (NC) Surface contaminated and cleansing with Phosphoric acid (PO) Ivoclean (IC) or Hydrofluoric acid (HF). The twenty of each surface treated specimens were selected and bonded with Panavia F2.0 (P) and Superbond C&B (S) for SBS test (n = 10). The data was analyzed by Kruskal–Wallis H and Mann–Whitney U test. The remaining specimens of each surface treated groups were examined by SEM and XRD.ResultsThe saliva and silicone disclosing medium contaminated zirconia without cleansing group (PNC) had the lowest SBS when Panavia F2.0 was used for cementation (p < 0.05). The SBS of surface cleansing groups (PPO, PIC and PHF) were not different from the non-contaminated group (PPC) (p > 0.05). However, there were no difference in SBS among groups when cementation with Superbond C&B (SPC, SNC, SPO, SIC and SHF) (p > 0.05). There was no morphologic changing that could be observed by SEM. The XRD showed little phase transformation when surfaces were contaminated and cleaned.ConclusionsThe saliva and silicone disclosing medium contaminated zirconia should be cleaned with Phosphoric acid, Ivoclean or Hydrofluoric acid for 20 s prior to cementation with Panavia F2.0. However, the surface cleansing was not necessary when cementation with Superbond C&B.     

Biomechanical evaluation between orthodontic attachment and three different materials after various surface treatments: A three-dimensional optical profilometry analysis

Objectives:To determine the best bonding method of orthodontic attachment among monolithic zirconia, feldspathic porcelain, hybrid porcelain, and the impact of surface-conditioning methods using a three-dimensional optical profilometer after debonding.Materials and Methods:56 feldspathic porcelain, 56 monolithic zirconia, and 56 hybrid porcelain samples were divided into four surface treatment subgroups: (1) hydrofluoric (HF) acid etch + silane, (2) Al₂O₃ sandblasting + silane, (3) silicoating (SiO₂), and (4) diamond bur + silane. The specimens were tested to evaluate shear bond strength (SBS). Residual composite was removed after debonding. Three-dimensional white-light interferometry was used to obtain quantitative measurements on surface roughness.Results:The highest SBS value was found for the HF acid–etched feldspathic porcelain group. The average surface roughness values were significantly higher in all material groups in which diamond bur was applied, while roughening with Cojet provided average surface roughness values closer to the original material surface.Conclusions:Variations in structures of the materials and roughening techniques affected the SBS and surface roughness findings.     

Surface characterization of different surface treatments associations with plasma and bonding analysis of Y-TZP and the veneering ceramic

ObjectivesTo characterize the surface of zirconia (Y-TZP) submitted to different surface treatments (with and without plasma associations) and to evaluate the shear bond strength (SBS) between veneering ceramic (VC) and Y-TZP after different aging methods.Methods301 Y-TZP specimens were fabricated and distributed into 7 groups: C (control): no treatment; Al: airborne abrasion with 27 μm Al₂O₃ particle; L: liner; P: plasma; Al + L: airborne + liner; Al + P: airborne + plasma; P + L: plasma + liner. The Y-TZP surface was characterized by SEM, EDS, AFM, surface profilometry, surface-free energy (SFE), and XRD. SBS between Y-TZP and VC was verified after three aging protocols: initial, after hydrothermal aging (autoclave for 5 h), or thermal fatigue (30,000 baths – 5–55 °C). One- (profilometry, SFE) and two-way ANOVA (SBS), and Tukey’s HSD test were used.ResultsFor the plasma groups, a full globular surface coverage was observed (SEM, AFM). Si was found for Al, L, Al + L, and P + L. Roughness was lower for C, P, and Al + P. For SFE, the highest values were found when the liner was applied (>74.59 nm/Nm). The highest monoclinic content was observed for Al + L (6.96%) and Al + P (5.86%). For the initial period, Al and P + L presented the lowest SBS values (<5.85 MPa; P > 0.331). The highest SBS values were found for L, P, and P + L (hydrothermal aging) and for P, L, Al + L, and Al + P (thermal fatigue).SignificanceChanges in Y-TZP topography and the SBS with the VC were found, according to treatments performed. Plasma treatment improved SBS and did not cause phase transformation.     

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.     

Intra‐oral adhesive systems for ceramic repairs: a comparison

The aim of this investigation was to compare the bond strength of restorative composite resin to dental ceramic conditioned with primers and adhesives of various commercial repair kits. Three intra‐oral ceramic repair systems—Silistor (Heraeus Kulzer), Cimara (Voco), Ceramic Repair (Vivadent)—were used on all‐ceramic (IPS Empress 2, Ivoclar‐Vivadent) substrate. Shear bond strength of restorative composite resin to substrate was tested after thermocycling and without thermocycling (n=10). Substrate surfaces of the specimen after loading were examined microscopically (SEM). The highest bond strengths in both water‐stored (7.0±5.7 MPa) and thermocycled conditions (2.5±1.8 MPa) were obtained with the Vivadent repair system, while the lowest values were observed with the Cimara system (0.6±1.4 MPa and 0.0±0.0 MPa, respectively). Shear bond strengths appeared to be significantly affected by thermocycling (ANOVA, P<0.05). It is concluded that there are significant differences in the bond strengths of resin composites and ceramic substrate. The roughened surface does not necessarily provide a better bond strength; the bond strength of composite decreases with storage in water and after thermocycling. Bond strength values were generally low for all of the tested materials.     

Adhesive strength of self-adhesive resins to lithium disilicate ceramic and dentin: effect of dentin chelating agents

The aim of this study was to test the effect of different chelating agents on microtensile bond strength (MTBS) of self-adhesive resin cements to dentin. The occlusal surfaces of extracted human mandibular molars (N = 80) were cut horizontally to expose sound dentin. The teeth were randomly divided into four groups (n = 20 per group) and dentin surfaces were conditioned according to one of the following methods: group C: no treatment (control group); group CH: 0.2 % chitosan; group E: 17 % ethylene diamine tetra acetic acid (EDTA) and group P: 25 % polyacrylic acid (PAA). Lithium disilicate glass ceramic (e.max CAD) blocks were cemented to conditioned dentin surfaces with self-adhesive cements (RelyX Unicem or Clearfil SA) and photo-polymerized. Specimens were stored in distilled water at 37 °C for 24 h and thermocycled for 6,000 times. The beams were obtained from bonded ceramic–cement–tooth assemblies and were subjected to the MTBS test (1 mm/min). Failure types were analyzed and selected beams were examined under scanning electron microscope. Data (MPa) were analyzed using two-way ANOVA and Tukey’s test (P < 0.05). While cement type significantly affected the MTBS results (P < 0.05), no significant difference was observed between the dentin chelating agents (P = 0.785). Interaction terms were not significant (P = 0.114). Control group with no dentin conditioning presented significantly lower results with both cements (RelyX Unicem: 8.1 ± 1.9^a, Clearfil SA: 8 ± 1.6^a) than those of conditioned groups (19.3 ± 4.2^b–24.5 ± 5.2^b) (P < 0.05). Failure types were predominantly adhesive in all groups. Chitosan (2 %), EDTA (17 %) or PAA (25 %) could all be used as dentin chelating agents in conjunction with self-adhesive resin cements tested.     

Nano-cellulose Reinforced Glass Ionomer Restorations: An In Vitro study

ObjectiveVarious modifications in formulation of glass ionomer cements (GICs) have been made in order to improve the clinical performance of these restorations. The aim of this work was to evaluate the microleakage and microshear bond strength (μSBS) of bacterial cellulose nanocrystal (BCNC)–modified glass ionomer cement (GIC) restorations in primary dentition.MethodsA total number of 60 freshly extracted primary molar teeth were selected. Half of the samples were used for μSBS testing (in 2 groups, n = 15). In group 1, conventional GIC (CGIC) of Fuji IX (GC) was placed in cylindrical molds on dentinal surfaces. In group 2, CGIC of Fuji IX containing 1% wt of BCNCs was used. μSBS was evaluated using a universal testing machine. In another part of the study, microleakage of class V restorations was assessed according to the mentioned groups (n = 15). The sectioned samples were observed under stereomicroscope, and microleakage scores were recorded. SPSS version 16.0 (SPSS), independent samples t test, and Mann–Whitney U test were used for statistical analysis at a significance level of P < .05.ResultsResults showed statistically significant differences between the μSBS of CGIC and modified GIC groups (P < .0001). The BCNC-modified GIC group recorded significantly higher bond strength values (3.51 ± 0.033 vs 1.38 ± 0.034 MPa). Also, microleakage scores of CGIC and BCNC-modified GIC restorations were not significantly different (P = .57).ConclusionsBased on our findings, it was concluded that incorporating BCNCs (1% wt) into the CGIC of Fuji IX significantly increased the μSBS to the dentin structure of the primary teeth.     

Effect of staining on the mechanical,surface and biological properties of lithium disilicate

PurposeTo simulate biodegradation and wear of stained and glazed CAD lithium disilicate ceramic, and evaluate their effects on the microbial adherence and mechanical and surface properties of lithium disilicate ceramicMaterials and methods160 lithium disilicate ceramic discs were fabricated and divided in eight groups according to manual stain and glaze application with a fine paint brush (without stain and glaze; with stain and glaze) and aging procedures (no aging; wear at 30 N load, 1.7 Hz, 3 × 10⁵ cycles; biodegradation by exposure to microcosm biofilm; biodegradation + wear; biodegradation + wear). Profilometry was performed to determine the surface roughness and the wear consequences. Biaxial flexural strength test was performed, and a Streptococcus mutans adherence test was conducted to evaluate the number of colony forming units.ResultsUnaged samples with and without stain and glaze presented the lowest values of surface roughness (p < 0.001), but after aging (wear, biodegradation, or both), the samples in the stain and glaze groups were rougher than those in the no stain and glaze groups (p < 0.001). The stain and glaze groups showed the highest volume of wear after aging (p = 0.04), and had the lowest flexural strength values (p < 0.01), irrespective of the aging method. The aging method did not affect the flexural strength (p = 0.06). The number of colonies forming units was higher for biodegradation + no stain and glaze, biodegradation + wear + no stain and glaze, no aging + stain and glaze, biodegradation + stain and glaze, and biodegradation + wear + stain and glaze. The lowest values were observed for no aging + no stain and glaze.ConclusionThe staining and glazing of lithium disilicate increased the surface wear and bacterial adherence, and decreased biaxial flexural strength of the material. When exposed to S. mutans, surface roughness increased, and biodegradation favored bacterial adherence.