Hydrofluoric Acid Group Research Articles

Mechanical, Adhesive and Surface Properties of a Zirconia-Reinforced Lithium Silicate CAD/CAM Ceramic Exposed to Different Etching Protocols.

The aim of this investigation was to evaluate the effect of etching protocols on bond strength, surface roughness, and mechanical properties of a zirconia-reinforced lithium silicate (ZLS) CAD/CAM-ceramic. In total, 100 bars (ISO 6872), 75 plaques, and 25 cubes were cut from ZLS blocks(Vita Suprinity®). The surfaces were standardized, crystallized and divided into five groups: 1. control (no/treatment-C), 2. 5%-Hydrofluoric-acid (HF)/20 s (HF5%20s), 3.HF5%60s, 4.HF10%20s, and 5.HF10%60s. Flexural strength (FS) (three-point bending test, 1 mm/min), roughness (Pa), and micro-shear bond-strength (µSBS) tests were performed. The data were statistically analyzed with one-way ANOVA, Tukey's test (p ˂ 0.05) and Weibull (FS data). C showed higher Pa (1.176 ± 0.370 µm) than HF10%60s (0.627 ± 0.236 µm) and all other groups. Groups C and 20 s showed the most irregular surface patterns. The FS results were not influenced by etching protocols, while the Weibull modulus was, with the 5%HF groups being the most reliable (m: 5.63/6.70), while C and HF10%60s (m: 2.78/2.73) were the least reliable. All fractures originated from surface defects on the treated side of specimens. The 5%HF groups showed higher µSBS (20 s: 21.35 ± 4.70 MPa; 60 s: 23.50 ± 4.27 MPa) than the 10%HF groups (20 s: 14.51 ± 2.47 MPa; 60 s: 16.54 ± 3.12 MPa) and C (6.46 ± 2.71 MPa). The most prevalent failure pattern was "mixed" for etched groups, and "adhesive" for C. Etching protocols affect the evaluated properties by roughening materials' surface and, in some cases, regularizing surface defects. The best overall outcomes were achieved when applying 5%HF.

The shear bond strength of orthodontic brackets after surface conditioning of Zirconia, Ceramic and E. max models

The current study aims to evaluate the shear bond strength (SBS) of metal orthodontic brackets after surface conditioning by hydrofluoric acid (HF) and aluminum oxide air abrasion (Al2O3) and using two prime types and to determines the adhesive remnant index (ARI). We compared the bond strength of different types of models (full glazed zirconia, ceramic faced zirconia and E. max faced zirconia) with different surface conditioning methods for attaching metal orthodontic brackets. The study used 60 models for each material, divided into subgroups based on the type of prime material and surface preparation method. The bond strength was measured using a universal testing machine and the results were analyzed using statistical software. Shear bond strength of the Aluminum oxide was statistically (p<0.05) higher than the hydrofluoric acid and control groups in all groups (full glazed zirconia, ceramic faced zirconia and E. max faced zirconia). The Assure® Plus primer with Aluminum oxide surface treatment give rise to the highest shear bond strength than 3M™ Transbond™ XT, while there was no significant difference between Assure® Plus and 3M™ Transbond™ XT primer for both control and hydrofluoric acid groups. The highest shear bond strength was obtained with Aluminum oxide conditioning method for all types of ceramic materials used in this study.

Effect of Surface Treatments Applied to 3D Printed Permanent Resins on Shear Bond Strength.

3D-printed permanent resins have recently been introduced to produce permanent restorations. The aim of this study is to evaluate the effect of surface treatment methods on the shear-bond strength (SBS) between 3D-printed permanent resins and adhesive cement. In this study, samples were produced using digital light projection (DLP) and stereolithography (SLA) 3D printers with two permanent resins (Crowntec, Saremco and Permanent Crown, Formlabs) in accordance with manufacturer guidelines. The samples were separated into three groups: sandblasting, hydrofluoric acid and no surface treatment. The surface profile (Ra, Sa) of the samples was examined with a confocal microscope (Smartproof 5, Zeiss). Then, a self-adhesive resin cement was applied to the samples in a transparent mold (2.38 mm diameter) in accordance with ISO 29022:2013. A universal testing machine was used to perform SBS test. A stereomicroscope was used to analyze the different types of fractures. A two-way analysis of variance (ANOVA) test was used to assess the data (p<0.05). The samples with sandblasting applied to the surface showed higher surface roughness values than the samples with hydrofluoric acid (p<0.001). 3D printer technology and surface treatment methods affected SBS values (p<0.001). Sandblasting groups higher SBS values were than in the hydrofluoric acid group (p<0.001). Sandblasting revealed cohesion fractures, which indicated a stronger bond, while hydrofluoric acid displayed adhesive and mix fractures. When sandblasting was applied to the surface of the samples prepared using permanent resins, higher adhesion was achieved with adhesive cement. Key words:3D printing, Shear bond strength, Sandblasting, Stereolithography.

Effect of Resin Infiltration and Various Etching Techniques on the Bond Strength of Sound and Demineralized Enamel

Purpose: The objective was to assess the effect of various etching techniques on the shear bond strength(SBS) of resin infiltrated sound/ demineralized enamel. Materials and methods: A total of 180 extracted human upper incisors' enamel surfaces were utilized. Half of these specimens underwent artificial demineralization, which involved exposing to an acidic buffer with a pH of 4.8(14 days). The remaining half of the specimens were kept in their original sound condition. Subsequently, both the sound/ demineralized specimens were divided into 6 groups according to the presence (I)/absence (NI) of resin infiltrant and etching methods (35% phosphoric acid (PA), 9% hydrofluoric acid (HFA), and Er,Cr:YSGG laser(L) (n=15): Following different etching procedures, an etch-and-rinse adhesive system was used, before the application of a nanohybrid composite to the enamel surfaces. Then all specimens were submitted to SBS test (MPa). three-way ANOVA and Bonferroni test were used for statistical analysis(p=0.05). Results: PA showed the highest SBS in the I groups compared with L and HFA groups, both in demineralized and sound enamel (p&amp;lt;0.05). On sound enamel, L showed higher SBS than HFA (p&amp;lt;0.05). On demineralized enamel, L showed similar values with HFA(p&amp;gt;0.05). In the NI groups, L showed similar SBS to HFA on both demineralized and sound enamel(p&amp;gt;0.05). Conclusion:Resin-infiltrated enamel can be etched by 35% phosphoric acid without jeopardize bond strength.

Effect of various porcelain surface treatment methods on shear bond strength of orthodontic adhesive

Objective: to evaluate the effect of different treatment methods of porcelain surfaces before bonding on the shear bond strength of orthodontic adhesive. Material and methods: This study was conducted on a sample of sixty feldspathic porcelain cylinders stored in artificial saliva for a week. The sample was divided into five equal groups twelve each according to the applied surface treatment, Gp1 diamond bur roughening, and Gp2 etching 37% phosphoric acid GP3 Laser etching Gp4 9% hydrofluoric acid etching Gp5 sandblasting 50 micron aluminum oxide particles. Randomly one specimen from each group was scanned by electron microscope while the other specimens were bonded to metal brackets and stored in artificial saliva for one week then mounted in acrylic blocks to allow measuring the shear bond strength using Instron universal testing machine. Results: Diamond bur group showed significant difference with all other groups. There is significant difference between phosphoric acid and laser on one hand and sand blasting and hydrofluoric on the other hand. But for both phosphoric acid and laser groups there is no significant difference and for both sand blasting and hydrofluoric acid groups there is no significant difference. Conclusion: The diamond bur group showed the highest bond strength, while phosphoric acid showed the least one.

Effects of Different Microstructured Surfaces on the Osseointegration of CAD/CAM Zirconia Dental Implants: An Experimental Study in Rabbits.

To assess different microstructured surfaces created by sandblasting and acid etching in an effort to optimize the osseointegration performance of dental zirconia implants with an optimized surface. Sixty CAD/CAM zirconia implants were divided into four groups. The control group had no surface treatment after sintering. The other groups had three different types of surface modifications: sandblasting; sandblasting and etching with hydrofluoric acid; and sandblasting and etching with an experimental hot etching solution composed of methanol, 37% hydrochloric acid, and ferric chloride, heated to 100°C and applied for 60 minutes. Commercially available titanium implants with sandblasted and etched surfaces and identical dimensions were employed as a positive control. Surface micromorphologies of implants from the five groups were evaluated. The osseointegration performance of all the implants was assessed in adult New Zealand rabbits based on microcomputed tomography (micro-CT) and histologic analysis. Sandblasting and acid etching with hot etching solution or hydrofluoric acid exhibited moderately rough surfaces with microstructures in both microscale and nanoscale. The sandblasting and etching with hydrofluoric acid group showed the highest surface roughness. Micro-CT revealed a significantly lower mean bone volume/total volume for the control group compared with the other four groups (P < .05). Among the groups, the sandblasting and hydrofluoric acid etching group was the highest, significantly higher than the titanium implant and sandblasting groups (P < .05). The sandblasting and etching with hot etching solution (P = .006) group also showed a significantly higher bone volume/total volume value than the titanium implant group. Histologic analysis revealed significantly higher boneto- implant contact for implants with modified surfaces compared with a sintered surface (P < .05), and no significant difference was found with respect to the sandblasted and etched titanium implants. The microstructured surfaces created by sandblasting and acid etching show osseointegration comparable to that of commonly used titanium implants.

Shear bond strength of cemented zirconia-reinforced lithium silicate ceramics (Celtra Duo) with two surface treatments (in vitro study)

Enhance the bonding of cement to ceramic surface with a variety of ceramic surface modifications have been established. Air-abrasion using alumina particles, hydrofluoric acid has been shown to provide micromechanical interlocking at the ceramic-resin interface. The aim of the present study was to evaluate the effect of two surface treatments; acid etching and sandblasting; on the shear bond strength of cemented newly introduced zirconia-reinforced lithium silicate ceramics following thermocycling. Methods: 24 discs of Zirconia- reinforced glass ceramics (Celtra Duo) were tested using 10% hydrofluoric acid for 20 s (control group) and 50 µm aluminum oxide for 60 s at 10 mm distance from the nozzle tip of sandblasting machine. Subsequent to the surface treatments, both groups were salinized and cemented to composites background discs using self-adhesive dual cure resin cement (BisCem). All sample were subjected to 2500 thermal cycle shear bond strength and failure mode was evaluated. The results of the t-test indicated that the bond strength value is significantly influenced by the surface treatment method. It was found that hydrofluoric acid group recorded statistically significantly higher shear bond strength mean value (10.81 MPa) than aluminum oxide sandblasting group (7.76 MPa) as indicated by t-test (t = 2.9, p = 0.0109 < 0.05). Conclusion: failure mode showed a relation between the bond strength and the failure type mixed failure showed with higher bond valves and cohesive failure accompanied with lowest bond strengthen values. The shear bond strength of zirconia reinforced lithium silicate (Celtra Duo) ceramic cemented to resin cement was affected by the type of surface treatment.

Influence of different surface treatments on resin nano ceramic-resin cement bond strength

This work aimed to evaluate the effect of different surface treatments on the shear bond strength of resin nano ceramic to resin cement, thereby providing a theoretical basis for the improvement of clinical application. A total of 150 specimens (10 mm×10 mm×3 mm) were milled from resin nano ceramic blocks (Lava Ultimate) using computer-aided design/computer aided manufacturing(CAD/CAM) technology. The specimens were randomly divided into five groups according to the surface treatment performed, as follows: control, sandblasted, sandblasted+silane, hydrofluoric acid, and hydrofluoric acid+silane groups. After the corresponding surface treatment, the specimens were cemented using Single Bond Universal Adhesive and RelyXTM Ultimate ClickerTM adhesive resin cement. All cemented specimens were placed in distilled water for 24 h and 30 days and subjected to a shear bond strength test in a universal testing machine. The surface treatment and water storage periods showed significant effects on bond strength. Surface treatment with sandblasted+silane showed the highest shear strength values among all tested groups, and the difference was statistically significant (P<0.05). A difference was observed between the control and hydrofluoric acid groups, and both had significantly difference compared with other groups (P<0.05). Sandblasted and hydrofluoric acid+silane groups were not statistically different, and both had significantly difference compared with other groups (P<0.05). The surface of resin nanoceramic treated by sand-blasted, sandblasted+silane, and hydrofluoric acid+silane can improve the bond strength. The sandblasted+silane group had the best the shear bond strength among the groups.

Impact of different surface treatment methods on bond strength between fiber post and composite core material

PurposeTo assess the impact of different surface treatments on the push-out bond strength between fiber post and a composite resin core material. Material and methodsSeventy-two glass-fiber posts were randomly assigned into six groups according to the method of surface treatment: Control (no treatment), silane, sandblasting, hydrofluoric acid, hydrogen peroxide, and hydrogen peroxide with sandblasting. Two posts from each group were inspected under a scanning electron microscope to assess the surface modifications and 10 posts were employed for the push-out test. Each post was placed vertically in the middle of a cylindrical putty matrix and a dual-cure composite resin material was applied for core build-up. Two discs of each specimen were cut using a low-speed diamond saw (total 120 discs). The push-out test was executed using a universal testing machine at a crosshead speed of 0.5 mm/min. Statistical analysis was performed using one-way ANOVA and Tukey’s test (p ≤ 0.05). The mode of failure of each disc was evaluated under SEM. ResultsThe sandblasting and hydrofluoric acid groups presented significantly higher bond strength than control and hydrogen peroxide groups. The hydrogen peroxide groups exhibited significantly the lowest bond strength of all groups. There was no significant difference between the control and silane groups. All groups showed predominantly adhesive failure except the hydrogen peroxide with sandblasting, where the cohesive failure of the post was predominant. ConclusionsSandblasting and hydrofluoric acid surface treatments demonstrated superior results to silane and hydrogen peroxide. The combined method of hydrogen peroxide and sandblasting could weaken the fiber post and lead to clinical fractures.

The Effect of Different Plasma Treatments on the Surface Properties and Bond Strength between Lithium Disilicate and Resin Cement.

To evaluate the roughness, surface energy, and the bond strength of lithium disilicate yielded by two different types of nonthermal plasma (NTP), oxygen- or argon-based, compared to the conventional method. Ninety-three lithium disilicate (IPS e.max Press) samples were divided into 3 groups: HF (hydrofluoric acid group); ONTP (oxygen-based NTP group); ANTP (argon-based NTP group). Surface energy and roughness analyses were performed before and after surface treatment, and bond strength testing was performed before and after 5000 thermocycles. Scanning electron microscopy (SEM) was used to characterize the surface treatments. Data were submitted to ANOVA and Bonferroni's test with statistical significance set at 5%. The ONTP group presented the highest surface energy values, followed by ANTP and HF. In addition, the ONTP group had higher surface roughness. SEM revealed exposed lithium disilicate crystals in the HF group, but a homogeneous film coverage in both NTP groups. Regarding bond strength, ANTP presented statistically significantly higher values than the other groups before thermocycling, and statistically significantly lower values than the other groups after thermocycling. The HF and ONTP groups presented statistically similar values after thermocycling. The bond strength of resin cement to lithium disilicate obtained after oxygen-based NTP was comparable with that obtained after conventional hydrofluoric acid treatment.

Repair Success of Two Innovative Hybrid Materials as a Function of Different Surface Treatments.

To evaluate surface treatments for chipping in order to avoid bonding problems between hybrid materials and composite resin and to determine the optimal surface treatment method during intraoral repair of restorations to achieve clinical success. A total of 96 samples were prepared from computer-aided design/computer-assisted manufactured (CAD/CAM) blocks: 48 polymer-infiltrated ceramic (PIC) and 48 resin nano-ceramic (RNC). Prior to application of the surface treatments, the two test groups were each divided into four subgroups: control group; hydrofluoric acid group; hydrofluoric acid with silane group; and air-abraded with silica-coated aluminum oxide (Al2O3) sand with silane group. Each subgroup contained 12 samples. A shear bond strength (SBS) test was performed after artificial aging (5,000 cycles, 5°C to 55°C). For both types of ceramic used, all subgroups showed significantly higher SBS values than the control groups (P < .05). The highest SBS values for both types of ceramic were observed in the air-abraded with silica-coated Al2O3 particles group. Each of the surface treatment methods increased the SBS, with the most effective method being air abrasion with silica-coated Al2O3.

Light transmittance and surface roughness of a feldspathic ceramic CAD-CAM material as a function of different surface treatments

BackgroundThe aim of the present study was to determine the effect of different surface treatments on light transmission of aesthetic feldspathic ceramics used in CAD-CAM chairside restorations.MethodsForty eight feldspatic ceramic test specimens were prepared from prefabricated CAD-CAM blocks by using a slow speed diamond saw. Test specimens were prepared and divided into 4 groups (n = 12). In the control group, no surface treatments were applied on the feldspathic ceramic surfaces. In the hydrofluoric acid group, the bonding surfaces of feldspathic ceramics were etched with 9.5 % hydrofluoric acid. In the sandblasting group the feldspathic ceramic surfaces were air-abraded with 30-μm alumium oxide (Al2O3) particles and Er:YAG laser was used to irradiate the ceramic surfaces. The incident light power given by the LED device and the transmitted light power through each ceramic sample was registered using a digital LED radiometer device. Each polymerization light had a light guide with 8-mm-diameter tips. Light transmission of feldspathic ceramic samples was determined by placing it on the radiometer and irradiating the specimen for 10 s at the highest setting for each light polymerization. All specimens were coated with gold using a sputter coater and examined under a field emission scanning electron microscope. Surface roughness measurement each group were evaluated with 3D optical surface and tactile profilometers.ResultsOne-way ANOVA test results revealed that both surface conditioning method significantly affect the light transmittance (F:412.437; p < 0.001) and the surface roughness values (F:16.386; p < 0.001). Al2O3 and Er-YAG laser application reduced the light transmission significantly (p < 0.05).ConclusionsThe laser and Al2O3 applications reduced the light transmission of 1.5 mm thickness feldspathic ceramic material below the value of 400 mW/cm2 which is critical limit for safe polymerization.

EFFECT OF DIFFERENT REPAIR PROTOCOLS ON BOND STRENGTH TO DIRECT AND INDIRECT RESIN COMPOSITE

Objective: This study was carried out to investigate the effect of different surface treatment protocols on bond strength of nano-composite as a repair material to two types of resin composite either direct composite or indirect resin composite blocks for CEREC system. Materials and methods: Total of 80 composite discs were prepared and were divided into two main groups (40 each) according to the type of composite used (C), nano-filled composite (C1) and composite blocks for CEREC system (C2). All specimens were aged for one month in a distilled water solution at 370C. Each group was sub-divided into four subgroups (10 each) according to the surface treatment protocol (T) that was done on the discs, either no treatment (T0) (control), application of Ortho phosphoric acid (T1), Hydrofluoric acid (T2) and Sandblasting(T3) . Each sub group was subdivided into two classes (5 each) according to silane application (S1) or without (S0). Nanofilled resin composite (Filtek Z350 XT, 3M ESPE) was used as a repair material. Microshear bond strength testing (μ-SBS) was done using Universal testing machine. Failure modes of the fractured specimens were analyzed using scanning electron microscope (SEM). μ-SBS results were analyzed using ANOVA, Tukey’s post-hoc and Student t-tests. Results: The indirect resin composite of the hydrofluoric acid group with silane showed the highest µ-Shear bond strength mean value (31.35±5.1) while the direct composite of the etchant group with no silane showed the lowest µ-Shear bond strength mean value (20.8±4.5). Regarding the composite type, C2 recorded statistically significant (P 0.05) highest µ-shear bond strength mean value (26.72±0.78 MPa) followed by T1 (25.77±2.55 MPa) then T2 (24.71±1.44 MPa) while T0 recorded statistically non- significant (P>0.05) lowest µ-shear bond strength mean value (24.54±1.7 MPa). Regarding the silane application, S1 recorded statistically non-significant (P>0.05) higher µ-shear bond strength mean value (26.28±1.57MPa) than S0(24.59±1.66MPa). Conclusions: The Cojet treatment of the resin composite improved the bond strength of different types of resin composite .The type of resin composite used for repair influences the bond strength to the repaired resin composite. Silane application to repaired resin composite affects the bond strength to it with different treatment protocols.

Surface characterization of lithium disilicate ceramic after nonthermal plasma treatment

Surface transformation with nonthermal plasma may be a suitable treatment for dental ceramics, because it does not affect the physical properties of the ceramic material. The purpose of this study was to characterize the chemical composition of lithium disilicate ceramic and evaluate the surface of this material after nonthermal plasma treatment. A total of 21 specimens of lithium disilicate (10 mm in diameter and 3 mm thick) were fabricated and randomly divided into 3 groups (n=7) according to surface treatment. The control group was not subjected to any treatment except surface polishing with abrasive paper. In the hydrofluoric acid group, the specimens were subjected to hydrofluoric acid gel before silane application. Specimens in the nonthermal plasma group were subjected to the nonthermal plasma treatment. The contact angle was measured to calculate surface energy. In addition, superficial roughness was measured and was examined with scanning electron microscopy, and the chemical composition was characterized with energy-dispersive spectroscopy analysis. The results were analyzed with ANOVA and the Tukey honestly significant difference test (α=.05). The water contact angle was decreased to 0 degrees after nonthermal plasma treatment. No significant difference in surface roughness was observed between the control and nonthermal plasma groups. Scanning electron microscopy and energy-dispersive spectroscopy images indicated higher amounts of oxygen (O) and silicon (Si) and a considerable reduction in carbon (C) in the specimens after nonthermal plasma treatment. Nonthermal plasma treatment can transform the characteristics of a ceramic surface without affecting its surface roughness. A reduction in C levels and an increase in O and Si levels were observed with the energy-dispersive spectroscopy analysis, indicating that the deposition of the thin silica film was efficient.

Influence of glass particle size of resin cements on bonding to glass ceramic: SEM and bond strength evaluation

This study investigated the effect of the filler particle size (micron or submicron) of experimental resin cements on the microtensile bond strength to a glass-ceramic pretreated with hydrofluoric acid (HFA) etching or alumina airborne-particle abrasion (AA). Cements were obtained from a Bis-GMA/TEGDMA mixture filled with 60 mass% micron-sized (1 ± 0.2 µm) or submicron-sized (180 ± 30 µm) Ba-Si-Al glass particles. Ceramic blocks (PM9; VITA) were treated with 10% HFA for 60 s or AA for 15 s. Silane and adhesive were applied. Ceramic blocks were bonded to resin composite blocks (Z250; 3M ESPE) using one of the cements. Bonded specimens were sectioned into beams (n = 20/group) and subjected to microtensile bond strength tests. Data were analyzed using ANOVA and Student-Newman-Keuls' tests (5%). Failure modes were classified under magnification. Morphologies of the treated ceramic surfaces and bonded interfaces were evaluated by scanning electron microscopy. The HFA-submicron group had lower bond strengths than the other groups. All AA-submicron specimens debonded prematurely. Mixed failures were predominant for HFA groups, whereas interfacial failures predominated for AA groups. SEM revealed a honeycomb-like aspect in the HFA-treated ceramic, whereas the AA-treated groups showed an irregular retentive pattern. Continuity of cement infiltration along the bonded interface was more uniform for HFA-treated compared to AA-treated specimens. Cracks toward the bulk of the ceramic were observed in AA-treated specimens. Particle size significantly influenced the ceramic bond strength, whereas surface treatment had a minor effect.

The effects of various surface treatments on the shear bond strengths of stainless steel brackets to artificially-aged composite restorations

Abstract Objective: To compare the shear bond strengths (SBS) of stainless steel brackets bonded to artificially-aged composite restorations after different surface treatments. Methods: Forty-five premolar teeth were restored with a nano-hybrid composite (Tetric EvoCeram), stored in deionised water for one week and randomly divided into three equal groups: Group I, the restorations were exposed to 5 per cent hydrofluoric acid for 60 seconds; Group II, the restorations were abraded with a micro-etcher (50 μm alumina particles); Group III, the restorations were roughened with a coarse diamond bur. Similar premolar brackets were bonded to each restoration using the same resin adhesive and the specimens were then cycled in deionised water between 5 °C and 55 °C (500 cycles). The shear bond strengths were determined with a universal testing machine at a crosshead speed of 1 mm/min. The teeth and brackets were examined under a stereomicroscope and the adhesive remnants on the teeth scored with the adhesive remnant index (ARI). Results: Specimens treated with the diamond bur had a significantly higher SBS (Mean: 18.45 ± 3.82 MPa) than the group treated with hydrofluoric acid (Mean: 12.85 ± 5.20 MPa). The mean SBS difference between the air-abrasion (Mean: 15.36 ± 4.92 MPa) and hydrofluoric acid groups was not significant. High ARI scores occurred following abrasion with a diamond bur (100 per cent) and micro-etcher (80 per cent). In approximately two thirds of the teeth no adhesive was left on the restoration after surface treatment with hydofluoric acid. Conclusion: Surface treatment with a diamond bur resulted in a high bond strength between stainless steel brackets and artificially-aged composite restorations and was considered to be a safe and effective method of surface treatment. Most of the adhesive remained on the tooth following surface treatment with either the micro-etcher or the diamond bur.

Chemical adhesion rather than mechanical retention enhances resin bond durability of a dental glass-ceramic with leucite crystallites

This study aims to evaluate the effect of chemical adhesion by a silane coupler and mechanical retention by hydrofluoric acid (HFA) etching on the bond durability of resin to a dental glass ceramic with leucite crystallites. Half of the ceramic plates were etched with 4.8% HFA (HFA group) for 60 s, and the other half were not treated (NoHFA group). The scale of their surface roughness and rough area was measured by a 3D laser scanning microscope. These plates then received one of the following two bond procedures to form four bond test groups: HFA/cement, NoHFA/cement, HFA/silane/cement and NoHFA/silane/cement. The associated micro-shear bond strength and bond failure modes were tested after 0 and 30 000 thermal water bath cycles. Four different silane/cement systems (Monobond S/Variolink II, GC Ceramic Primer/Linkmax HV, Clearfil Ceramic Primer/Clearfil Esthetic Cement and Porcelain Liner M/SuperBond C&B) were used. The data for each silane/cement system were analyzed by three-way ANOVA. HFA treatment significantly increased the surface Ra and Ry values and the rough area of the ceramic plates compared with NoHFA treatment. After 30 000 thermal water bath cycles, the bond strength of all the test groups except the HFA/Linkmax HV group was significantly reduced, while the HFA/Linkmax HV group showed only adhesive interface failure. The other HFA/cement groups and all NoHFA/cement groups lost bond strength completely, and all NoHFA/silane/cement groups with chemical adhesion had significantly higher bond strength and more ceramic cohesive failures than the respective HFA/cement groups with mechanical retention. The result of the HFA/silane/cement groups with both chemical adhesion and mechanical retention revealed that HFA treatment could enhance the bond durability of resin/silanized glass ceramics, which might result from the increase of the chemical adhesion area on the ceramic rough surface and subsequently reduced degradation speed of the silane coupler, rather than the mechanical retention of the ceramic rough surface.

Hydrofluoric acid on dentin should be avoided

Hydrofluoric acid can be used for intra-oral repair of restorations. Contamination of tooth substrate with hydrofluoric acid cannot always be avoided. Objectives To investigate the bonding effectiveness to hydrofluoric acid contaminated dentin by, micro-tensile bond strength testing, SEM and TEM. Methods For this study, 15 molar teeth were used of which dentin surfaces were subjected to five, different etching procedures. Group A, 37.5% phosphoric acid (Kerr Gel) (control group); group B, 37.5% phosphoric acid followed by 3% hydrofluoric acid (DenMat); group C, 37.5% phosphoric acid, followed by 9.6% hydrofluoric acid (Pulpdent); group D, 3% hydrofluoric acid followed by 37.5%, phosphoric acid; group E, 9.6% hydrofluoric acid followed by 37.5% phosphoric acid. After the bonding procedure (OptiBond FL, Kerr) a composite resin build-up (Clearfil AP-X, Kuraray), was made. After 1 week storage, specimens were prepared for micro-tensile bond testing, SEM- and, TEM-analysis. Data were analyzed using ANOVA and post hoc Tukey's HSD ( p < 0.05). Results In the control group (solely phosphoric acid), the mean μTBS was 53.4 ± 10.6 MPa, which was, significantly higher than any hydrofluoric acid prepared group (group A versus groups B–E, p < 0.001). No, significant differences in μTBS were found between the 3% and 9.6% hydrofluoric acid groups: group B versus group C (13.5 ± 5.5 MPa and 18.7 ± 4.3 MPa, respectively) or group D versus group E (19.9 ± 6.8 MPa and 20.3 ± 4.1 MPa, respectively). Significance Due to its adverse effect on the bond strength of composite to dentin, contact of hydrofluoric acid to dentin should be avoided.

Harmful effects and acute lethal toxicity of intravenous administration of low concentrations of hydrofluoric acid in rats

The acute toxicity of hydrofluoric acid (HFA) was investigated in a 24-h lethal dose study of intravenous infusion in rats. The lethal dose lowest (LDLo) and LD50 were 13.1 and 17.4 mg/kg, respectively. Harmful systemic effects were also studied 1 h after acute sublethal exposure to HFA. The maximum dose was set at 9.6 mg/kg (LD5). Rats were injected with HFA (1.6, 3.2, 6.4 or 9.6 mg/kg), saline, sodium fluoride (NaF) or HCl solution. NaF and HCl solution concentrations corresponded to the F- and H+ concentrations of 9.6 mg/kg HFA. Blood urea nitrogen (BUN) and Cr were significantly increased in response to HFA concentrations greater than 3.2mg/kg. Acute glomerular dysfunction also occurred at HFA concentrations greater than 3.2 mg/kg. HCO3- and base excess (BE) were significantly decreased in the 6.4 and 9.6 mg/kg groups. Ca2+ was significantly decreased, and K+ was increased in the 9.6 mg/kg group. BUN was significantly increased in the NaF and HFA groups and was increased in the HFA group compared with that in the NaF group. Cr was significantly increased in the HFA group only. HCO3- and BE were significantly decreased in the NaF and HFA groups and were increased in the HFA group compared with values in the NaF group. Ca2+ was significantly decreased in the NaF and HFA groups, and K+ was significantly increased in the NaF and HFA groups. F- exposure directly affected serum electrolytes. Mortality was thought to be due to cardiac arrhythmia resulting from hypocalcemia and hyperkalemia. Metabolic acidosis and renal failure were more severe in response to HFA exposure than in response to NaF exposure because of more free F-, which has strong cytotoxicity, in the HFA group than in the NaF group. Lethal effects of HFA are promoted by exposure routes such as inhalation that cause rapid absorption into the body. Even low exposure to HFA can cause acute renal dysfunction, electrolyte abnormalities and metabolic acidosis. These complications result in a poor prognosis.

The effect of food simulants on porcelain–composite bonding

Purpose The purpose of this study was to evaluate the in vitro effects of food simulants on the bond strength of brackets to porcelain surfaces. Materials and methods One hundred and eighty porcelain-fused to metal specimens were fabricated. Samples were divided into 3 groups including 60 specimens each. Different surface treatment methods were applied to each group and these were: sandblasting (SB), etching with orthophosphoric acid (OPA) and etching with hydrofluoric acid (HFA). After the surface treatments, the brackets were bonded to the center of each sample with a light-curing orthodontic composite adhesive. Then each group was divided into five test subgroups and one control subgroup each consisting of 10 specimens. The test groups were conditioned for 90 days at 37 °C as follows: water, 0.02N citric acid, heptane, 8% ethanol aqueous solution and 50% ethanol aqueous solution. The control specimens were stored at room temperature in air. Shear force was applied to the porcelain–bracket interface by using a universal testing machine with a crosshead speed of 1 mm/min until debonding occurred. The shear bond strength was calculated by dividing the maximum load by the cross-sectional area of the bracket to give the results in megapascals (MPa). The statistical evaluations were made by using analysis of variance. Whenever a significance was detected, Bonferroni tests were performed for post hoc analyses. Results Fifty percent ethanol conditioned specimens for all surface treatment groups showed lower shear bond strength values. HFA group showed significantly higher shear bond strength values when compared with other groups ( P < 0.05). For all porcelain surface treatment groups, control groups showed statistically significant higher shear bond strength values ( P < 0.05). Conclusion The results of this in vitro study show that food simulants significantly decrease the bond strength between bracket and porcelain surface.