Influence of surface conditioning on ceramic microstructure and bracket adhesion

Influence of surface treatments on the bond strength of metal brackets to CAD/CAM materials and discoloration after various refinishing procedures : Scanning electron microscopy and atomic force microscopy study

PURPOSE

This study evaluated the shear bond strength (SBS) of a metal bracket bonded to three different computer-aided design/computer-aided manufacturing (CAD/CAM) restoration materials pretreated with different surface treatments. In addition, the surface topography and color change of the restorations after debonding with two different tungsten carbide burs were examined.

METHODS

A total of 216 plates were cut from three different CAD/CAM blocks, each of which was divided into three subgroups with different pretreatment methods: (1) acid etching, (2) sandblasting, and (3) laser irradiation. Incisor metal brackets were bonded. The SBS test was performed, and the failure types were classified. Then, samples were randomly divided into two subgroups according to the adhesive removal procedure to be used: a tungsten carbide bur with 12 blades or 24 blades (n = 12). Color change was calculated based on the ∆E00, and surface morphology was evaluated via SEM and AFM analysis.

RESULTS

The SBS data revealed that the type of CAD/CAM material and the applied surface treatment significantly affected bond strength. The highest SBS values were detected for the Grandio Blocs (VOCO GmbH, Cuxhaven, Germany; 14.3 ± 4.4 MPa), and the lowest was observed for Cerasmart (GC Europe, Leuven, Belgium; 12.0 ± 4.0 MPa). The ∆E00 results demonstrated significant differences only as a result of the applied surface treatment. The ∆E00 value in all groups was above the 1.77 threshold.

CONCLUSION

CAD/CAM material types and surface treatments affected the bond strength, but the interactions of these factors did not. The chosen surface treatment also significantly affected the ∆E00 after the polishing was done.

The effect of ceramic surface conditioning on bond strength of metallic brackets: An in vitro study

OBJECTIVE

To compare the shear bond strength (SBS) of brackets bonded to three different types of ceramic surfaces (feldspathic ceramic, lithium disilicate ceramic, and zirconia), conditioned with either hydrofluoric acid or sandblasting, using Assure® Plus All bonding agent.

MATERIALS AND METHODS

A total of 72 monolithic CAD/CAM ceramic specimens were divided into six groups of 12 samples. Three groups (G1: feldspathic ceramic, G3: lithium disilicate ceramic, G5: zirconia surfaces) were conditioned with 9.6% hydrofluoric acid, while the remaining three (G2, G4, G6; with ceramic type in the same order as the previous three groups) were prepared with 50 μm aluminum oxide sandblasting. Premolar brackets were bonded using light-cured Assure® Plus All. The SBS and adhesive remnant index (ARI) were recorded and submitted to inferential analysis using one-way analysis of variance and Kruskal-Wallis tests, respectively. The significance level was set at 5% (P ≤ 0.05).

RESULTS

The mean SBS values for the three different ceramic groups conditioned with hydrofluoric acid (G1: 7.2 ± 1.5 MPa, G3: 9.3 ± 2.3 MPa, G5: 8.5 ± 2.0 MPa) were significantly higher than those obtained for the groups prepared by sandblasting before bonding (G2: 7.5 ± 1.8 MPa, G4: 4.4 ± 2.0 MPa, G6: 4.3 ± 2.8 MPa).

CONCLUSIONS

The hydrofluoric acid treatment produced a favorable SBS for all three examined ceramic types before bracket bonding with Assure® Plus All. In comparison, sandblasting yielded a satisfactory SBS only with feldspathic surfaces. Furthermore, the ARI indicated a higher frequency of mixed-adhesive failures except for lithium disilicate conditioned with sandblasting. Therefore, using hydrofluoric acid is likely to be especially recommended when the clinician is not aware of the brand of ceramic restorative material.

Influence of different surface treatment on bonding of metal and ceramic Orthodontic Brackets to CAD-CAM all ceramic materials

BACKGROUND

Developing efficient bonding techniques for orthodontic brackets and all-ceramic materials continues to pose a clinical difficulty. This study aimed to evaluate the shear bond strengths (SBS) of metal and ceramic brackets to various all-ceramic CAD-CAM materials, such as lithium disilicate CAD (LDS-CAD), polymer-infiltrated ceramic (PIC), zirconia-reinforced lithium silicate glass ceramic (ZLS), and 5YTZP zirconia after different surface treatments and thermal cycling.

MATERIALS AND METHODS

The samples were divided into two groups to be bonded with ceramic and metal lower incisor brackets. Each group was subdivided into a control group devoid of any surface treatment, 10% HF acid (HFA) etching, ceramic etch & prime (MEP), Al2O3 air abrasion, and medium grit diamond bur roughening. After surface treatment, brackets were bonded with composite resin cement, thermal cycled, and tested for shear bond strength. The failed surfaces were evaluated with a digital microscope to analyse the type of failure. The data were statistically analysed using a one-way ANOVA and Tukey HSD tests at p < 0.05.

RESULTS

The highest mean bond strengths were found with HFA etching in LDS-CAD (13.17 ± 0.26 MPa) and ZLS (12.85 0.52 MPa). Diamond bur recorded the lowest mean bond strength roughening across all the ceramic groups. There were significant differences in mean shear bond values per surface treatment (p < 0.001) and ceramic materials.

CONCLUSION

Among the surface treatment protocols evaluated, HFA etching and MEP surface treatment resulted in enhanced bond strength of both ceramic and metal brackets to CAD-CAM all ceramic materials.

Effects of Three Novel Bracket Luting Agents Containing Zirconia Primer on Shear Bond Strength of Metal Orthodontic Brackets Attached to Monolithic Zirconia Crowns: A Preliminary In Vitro Study

Background

The increased use of zirconia crowns in adult orthodontic patients warrants the establishment of methods and materials to adhere orthodontic brackets properly to zirconia crowns. However, studies in this regard are scarce, and many materials remain untested. This preliminary study aimed to examine three new adhesives containing zirconia primers for the first time.

Methods

Sixty identical monolithic zirconia crowns were fabricated and randomly divided into 4 groups of 15 each (Panavia SA Cement Plus, G-CEM, TheraCem, and Transbond XT Composite (control)). After glaze removal with a diamond bur, a metal orthodontic bracket was attached to the surfaces of the crowns using the respective adhesive. Specimens were incubated at 37°C and then thermocycled for 2000 cycles. Shear bond strengths (SBS) of brackets in different groups were estimated using a universal testing machine. Mean SBS values were compared with the values 6, 8, and 10 (as acceptable SBS values) and 13 MPa (as the maximum SBS tolerable by zirconia) using the one-sample t-test. They were also compared with each other using the one-way ANOVA and Tamhane post hoc test (α = 0.05).

Results

The ANOVA indicated a significant overall difference; the Tamhane test showed that the difference between the control group and all test groups was significant (P < 0.0005); however, the 3 test groups were not significantly different from each other (P > 0.30). The SBS of the control group was significantly lower than the minimum acceptable SBS (6 MPa, P < 0.0005). The mean SBS of the TheraCem was not significantly different from 10 MPa (P = 0.902), while the mean SBS values of Panavia SA Cement Plus and G-CEM were significantly greater than 10 MPa (P < 0.05). None of the three zirconia adhesives had mean SBS values higher than 13 MPa.

Conclusion

All novel zirconia adhesives (Panavia SA Cement Plus, G-CEM, and TheraCem) generated SBS values adequate to attach metal orthodontic brackets to zirconia prostheses (at or greater than 10 MPa) without damaging the zirconia during bracket removal (not above 13 MPa).

Effectiveness of surface treatment on bond strength of ceramic brackets to two types of CAD/CAM-prepared nanohybrid composites

OBJECTIVES

The aim of this study was to assess the influence of surface treatment on the shear bond strength of two different adhesive-coated orthodontic ceramic brackets to computer-aided design/computer-aided manufacturing (CAD/CAM) nanohybrid composite.

METHODS

A total of 120 specimens (10 mm × 10 mm × 3 mm) were prepared from each type of CAD/CAM block (Grandio [GR], VOCO Cuxhaven, Germany; Lava Ultimate [LU], 3M ESPE, St. Paul, MN, USA). For each type of CAD/CAM block, the plates were divided into four groups based on the applied surface treatment: hydrofluoric acid (HF), grinding bur (GB), silica coating with CoJet system (CS), and titanium tetrafluoride (TiF₄) 2 wt/v%. Maxillary central incisors of adhesive-coated ceramic orthodontic brackets (APC Flash-free Clarity Advanced Ceramic, 3M Unitek, Monrovia, CA, USA) were bonded using Transbond XT Primer (3M Unitek, Monrovia, CA, USA). Shear bond strength was conducted, and the modes of failure were assessed utilizing the adhesive remnant index. Surface roughness and topography of treated CAD/CAM were evaluated. Data were statistically analyzed using two-way analysis of variance (ANOVA) and Tukey's test. The Weibull analysis was conducted on shear bond strength data.

RESULTS

Surface treatment with 2% TiF₄ wt/v revealed significantly higher bond strength (GR, 14.51 ± 2.57 MPa; LU, 11.19 ± 2.17 MPa) than other groups for both types of CAD/CAM restorative materials (p < 0.05). Adhesive failures were the predominant mode of failure. Surface treatment with CS revealed higher surface roughness than other groups (p < 0.05).

CONCLUSIONS

Surface treatment with 2% TiF₄ wt/v enhanced the adhesion between orthodontic ceramic brackets to GR and LU CAD/CAM composite restorative materials. GR CAD/CAM nanohybrid composite had higher bond strength than LU to ceramic orthodontic brackets.

What Is the Most Effective Technique for Bonding Brackets on Ceramic-A Systematic Review and Meta-Analysis

Background: There has been an increase in demand for orthodontic treatment within the adult population, who likely receive restorative treatments using ceramic structures. The current state of the art regarding the most effective method to achieve an appropriate bond strength of brackets on ceramic surfaces isn’t consensual. This systematic review aims to compare the available surface treatments to ceramics and determine the one that allows to obtain the best bond strength. Methods: This systematic review followed the PRISMA guidelines and the PICO methodology was used, with the question “What is the most effective technique for bonding brackets on ceramic crowns or veneers?”. The research was carried out in PubMed, Web of Science, Embase and Cochrane Library databases. In vitro and ex vivo studies were included. The methodological quality was evaluated using the guidelines for reporting of preclinical studies on dental materials by Faggion Jr. Results: A total of 655 articles searched in various databases were initially scrutinized. Sevety one articles were chosen for quality analysis. The risk of bias was considered medium to high in most studies. The use of hydrofluoric acid (HF), silane and laser afforded the overall best results. HF and HF plus laser achieved significantly highest bond strength scores in felsdphatic porcelain, while laser was the best treatment in lithium disilicate ceramics. Conclusions: The most effective technique for bonding brackets on ceramic is dependent on the type of ceramic.

Orthodontic bonding to silicate ceramics: impact of different pretreatment methods on shear bond strength between ceramic restorations and ceramic brackets

Objective

The study aims to investigate the shear bond strength (SBS) between silicate ceramic restorations and ceramic brackets after different pretreatments and aging methods.

Material and methods

Leucite (LEU) and lithium disilicate (LiSi) specimens were pretreated with (i) 4% hydrofluoric acid + silane (HF), (ii) Monobond Etch&Prime (MEP), (iii) silicatization + silane (CoJet), and (iv) SiC grinder + silane (SiC). Molars etched (phosphoric acid) and conditioned acted as comparison group. SBS was measured after 24 h (distilled water, 37 °C), 500 × thermocycling (5/55 °C), and 90 days (distilled water, 37 °C). Data was analyzed using Shapiro–Wilk, Kruskal–Wallis with Dunn’s post hoc test and Bonferroni correction, Mann–Whitney U, and Chi² test (p < 0.05). The adhesive remnant index (ARI) was determined.

Results

LEU pretreated with MEP showed lower SBS than pretreated with HF, CoJet, or SiC. LiSi pretreated with MEP resulted in lower initial SBS than pretreated with HF or SiC. After thermocycling, pretreatment using MEP led to lower SBS than with CoJet. Within LiSi group, after 90 days, the pretreatment using SiC resulted in lowest SBS values. After HF and MEP pretreatment, LEU showed lower initial SBS than LiSi. After 90 days of water storage, within specimens pretreated using CoJet or SiC showed LEU higher SBS than LiSi. Enamel presented higher or comparable SBS values to LEU and LiSi. With exception of MEP pretreatment, ARI 3 was predominantly observed, regardless the substrate, pretreatment, and aging level.

Conclusions

MEP pretreatment presented the lowest SBS values, regardless the silicate ceramic and aging level. Further research is necessary.

Clinical relevance

There is no need for intraoral application of HF for orthodontic treatment.

Effect of universal adhesive and silane pretreatment on bond durability of metal brackets to dental glass ceramics

This study aimed to investigate the effect of universal adhesive and silane pretreatment on the bond durability of metal brackets to dental glass ceramics. Eighty lithium disilicate glass ceramic specimens were randomly assigned to one of four groups (n = 20) defined by the pretreatment and adhesive used: (i) Adper Single Bond 2; (ii) silane + Adper Single Bond 2; (iii) Single Bond Universal; and (iv) silane +Single Bond Universal. Maxillary central incisor metal brackets were bonded on the ceramic surfaces with resin composite. A shear bond strength test was conducted after 24 h of water storage and after 10,000 thermocycles. Adhesive remnant index scoring and field-emission scanning electron microscopy were performed to determine adhesives remaining on the ceramic surfaces and the ceramic ultrastructure following bracket debonding, respectively. After 10,000 thermocycles, specimens treated with Single Bond Universal preserved an appropriate bond strength between brackets and glass ceramics and showed minimum ceramic surface damage following bracket debonding, which was not the case in the other three groups. The application of a silane-containing universal adhesive without silane pretreatment achieves adequate durability of the bond of metal brackets to dental glass ceramics and allows safe debonding, which may aid in optimizing the effectiveness for orthodontic treatment.

Orthodontic Attachment Adhesion to Ceramic Surfaces

Ceramic materials are constantly evolving, achieving good functionality and aesthetics. Bonding to ceramics may be difficult because of high toxicity procedures and risk of surface damage. The review aims to answer several research questions: Is there a golden standard for bonding to ceramic? Are there adhesives or types of photopolymerization lamps that produce a higher bond strength on certain types of ceramics rather than others? Articles focusing on the bonding process of orthodontic attachments to ceramic surfaces searched in Pubmed, Medline and Embase, published between 1990 and 2018 were revised. Exclusions concerned bonding to non-ceramic surfaces, bonding to ceramic surfaces that are not destined for orthodontics or laser usage. Forty-nine articles that matched the inclusion criteria were researched. The following categories of original research articles were compared and discussed: metallic brackets bonding to ceramic surfaces, ceramic brackets to ceramic surfaces, bonding to new types of ceramics, such as zirconia, lithium disilicate, different photopolymerisation devices used on bonding to ceramics. Some types of adhesive may achieve minimal bond strength (6-8 MPa) even on glazed ceramic. Ceramic surface preparation may be done by sandblasting or hydrofluoric acid (60s application and 9.6%) with generally similar results. Studies rarely show any statistical difference and there are reduced number of samples in most studies. Ceramic brackets show better adhesion to ceramic surfaces and the same bonding protocol is advised. A higher bond strength may lead to ceramic surface. Few studies focus on newer types of ceramics; additional research is necessary. There is no clear evidence that a certain type of photopolymerization device produces higher shear bond strength values.

Bond Strength of Metallic or Ceramic Orthodontic Brackets to Enamel, Acrylic, or Porcelain Surfaces

Bonding strategies within different brackets and dental materials are still a challenge concerning adhesion and dental surface damage. This study compared the shear and tensile bond strength of orthodontic ceramic and metallic brackets to enamel, acrylic, and ceramic surfaces after thermal cycling. Dental surfaces were divided into three groups: enamel, ceramic, and acrylic. Each group received stainless-steel and ceramic brackets. After thermal cycling, specimens were randomly divided into two subgroups considering tensile (TBS) or shear bond strength (SBS) test. After the mechanical testing, scanning electron and optical microscopy were performed, and the adhesive remnant index (ARI) was determined. The two-way ANOVA full factorial design was used to compare TBS, SBS, and ARI on the surface and bracket type (α = 0.05). There were significant differences in TBS, SBS, and ARI values per surface (p < 0.001 and p = 0.009) and type of bracket (p = 0.025 and p = 0.001). The highest mean SBS values were recorded for a ceramic bracket bonded to an acrylic surface (8.4 ± 2.3 MPa). For TBS, a ceramic bracket bonded to acrylic showed the worst performance (5.2 ± 1.8 MPa) and the highest values were found on a metallic bracket bonded to enamel. The adhesion of metallic or ceramic brackets is enough for clinical practice although the damage of the enamel surface after debonding is irreversible and harmful for the aesthetic outcome of the teeth.

Effect of a single-component ceramic conditioner on shear bond strength of precoated brackets to different CAD/CAM materials

OBJECTIVES

To compare the shear bond strength (SBS) of the CAD/CAM material-bracket interface using three surface treatments: following manufacturers' instructions (MI), Monobond Etch & Prime (MEP) and 9.6% hydrofluoric acid plus silane (9.6% HF), after 24 h of water storage (24 h) and 10,000 cycles of thermocycling (TC).

MATERIALS AND METHODS

A total of 126 crowns with four identical buccal surfaces were fabricated using seven different CAD/CAM materials: CEREC Blocs unglazed (CBU), CEREC Blocs glazed (CBG), IPS Empress CAD (EMP), IPS e.max CAD (EMA), VITA SUPRINITY PC (SUP), inCoris TZI (TZI) and VITA ENAMIC (ENA). A total of 504 APC Flash-Free (APC FF)-precoated brackets were bonded applying three surface treatments: (1) MI; (2) MEP and (3) 9.6% HF. SBS was performed after 24 h and TC. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests (p < 0.05).

RESULTS

MEP conditioning yielded lower SBS results compared with MI and 9.6% HF for CBG (24 h and TC) and EMA (TC) materials. EMP conditioning with MEP after 24 h obtained lower SBS values compared with MI; however, after TC, SBS was similar to MI group and higher than with 9.6% HF. After TC for TZI ceramic, MI protocol (sandblasting) obtained higher SBS scores than MEP, but similar than 9.6% HF. Treatment of ENA with MI and MEP produced higher results than 9.6% HF after TC. SBS results were similar for CBU and SUP, regardless of the treatment.

CONCLUSIONS

Although each CAD/CAM material requires specific surface treatment to obtain the highest SBS of APC FF brackets, the treatment with MEP is a valid orthodontic alternative for most of the materials tested. TC significantly decreased SBS for most of the materials.

CLINICAL RELEVANCE

MEP can be considered a valid and promising product to condition most of the CAD/CAM ceramics evaluated for APC FF bracket bonding purposes, allowing a faster and safer procedure.

Adhesive luting of orthodontic devices to silica-based ceramic crowns-comparison of shear bond strength and surface properties

OBJECTIVES

The aim of this study was to analyse the impact of different clinical conditioning approaches and an ammonium polyfluoride- and trimethoxysilylpropyl methacrylate-based experimental primer for intraoral luting of buccal tubes on silica-based ceramic surfaces.

MATERIALS AND METHODS

A total of 60 leucite-reinforced glass ceramic molar crowns were conditioned using different methods (n = 10): I-roughening, hydrofluoric acid, silane; II-roughening, silane; III-roughening, experimental coupling agent; IV-experimental coupling agent; V-roughening; VI-no treatment. A buccal tube was adhesively luted to the ceramic surface. Subsequently, water storage, thermocycling and chewing simulation were carried out. The shear bond strength (SBS) was determined, and changes in the surface were assessed.

RESULTS

All tubes of the control group (group VI) debonded after incubation. The conditioning methods using coupling agents revealed mean values for SBS of 61.56 MPa (group I), 45.53 MPa (group III), 41.65 MPa (group II), and 23.14 MPa (group IV). In groups I-III, both composite residues and cracks/tear-outs were detected.

CONCLUSIONS

The conditioning of silicate ceramic surfaces with a suitable coupling agent system appears to allow sufficient adhesive luting of buccal tubes. The intraoral luting of fixed appliance elements on silicate ceramic surfaces using an ammonium polyfluoride- and trimethoxysilylpropyl methacrylate-based ceramic primer can withstand orthodontic forces.

CLINICAL RELEVANCE

Ammonium polyfluoride- and trimethoxysilylpropyl methacrylate-based ceramic primers revealed promising results for the intraoral adhesive luting of orthodontic devices to silica-based ceramic crowns.

[Effect of sandblasting on the microroughness of ceramic restorations]

The influence of aero-abrasive technology on the microroughness of the ceramic samples standardized in shape, structure, and manufacturing method was studied by comparing the results obtained from the action of alumina particles of 27 and 50 μm size under a pressure of 0.5 and 2 atm for 5 seconds at a distance of 3 cm. To objectify the features of the treated surface relief its micro-roughness has been studied. With the help of a scanning electron microscope the morphology of studied samples was visualized. The data confirming the reliable absence of differences in the microroughness between the sandblasting methods under the given conditions was obtained. Microphotographs of samples surface obtained using the mode of reflected electrons detection showed no significant structural differences between all groups of samples. Thus, sandblasting can be integrated into the general algorithm as a stage of ceramics preparation for adhesive fixation since it does not cause mechanical damage to the surface, does not fundamentally change its structure and cleans the surface from contamination.

Effect of two different primers on the shear bond strength of metallic brackets to zirconia ceramic

BACKGROUND

In view of the increasing demand of adult orthodontics for esthetic purposes, adult treatment with brackets has become an important issue. One essential factor for the quality of such treatment is bracket bonding on ceramics. For testing the adhesive bond between the bracket and the ceramic surface it is important to consider the static or cyclic loading that goes along with it.

METHODS

Metallic Brackets were adhesively fixed on zirconia ceramic blocks in a simulated leveling phase using two different primers (Monobond S and Monobond Etch & Prime). Half of the metallic brackets were activated using a 0.14-nickel titanium wire, while the other half remained non-activated. Shear bond testing (SBT) was performed after thermocycling. Furthermore the Adhesive Remnant Index (ARI) was analyzed.

RESULTS

SBT resulted in significantly higher shear bond values when Monobond Etch & Prime was used compared to the use of Monobond S. Activation of the brackets did not show different results in comparison to the non-activated brackets. The ARI did not indicate cement remnants on the ceramic surface, regardless of the primer and the activation status.

CONCLUSIONS

The use of Monobond Etch & Prime has great potential for the bonding of brackets on dental zirconia ceramics.

Influence of tooth brushing on adhesion strength of orthodontic brackets bonded to porcelain

BACKGROUND

Adhesive resin composite, which is used to bond orthodontic bracket to tooth surface is exposed to the influence of wear by tooth brushing and wear may influence loosening of the bracket.

OBJECTIVE

The aim of this study was to evaluate in vitro the effect of tooth brushing on the adhesion strength of orthodontic brackets bonded to surface treated porcelain.

METHOD

A total of 90 glazed porcelain fused to metal facets (PFM) were randomly assigned into 3 groups according to the surface treatment to be received. Group 1 was conditioned with hydrofluoric acid (HF), group 2 conditioned with grit-blasting (GB) and group 3 conditioned with tribochemical silica coating (RC). The groups were evaluated for surface roughness (Ra) before and after surface treatment. Next, 15 samples from each group were subjected to brushing and remaining 15 samples served as the baseline (n=15). Adhesion strength (shear bond strength)was recorded using a universal testing machine. Data collected were analyzed by ANOVA and Tukey's multiple comparison post hoc analysis.

RESULTS

Tooth brushing decreased the bond strength in all groups. The highest adhesion strength (baseline and after brushing) was observed in group 3 (26.8 ± 1.77 MPa and 23.57 ± 1.02 MPa) and the lowest was found in group 1 (9.6 ± 1.5 MPa and 5.87 ± 0.77 MPa). Group 3 specimens exhibited the highest Ra (1.24 ± 0.08).

CONCLUSION

It was found that tooth brushing of the exposed adhesive resin composite at the bracket-bonding substrate interface lowers the bonding strength regardless of the surface treatment of the substrate.

Bond strength of metal brackets bonded to a silica-based ceramic with light-cured adhesive : Influence of various surface treatment methods

OBJECTIVE

The purpose of this work was to evaluate the effects of several surface treatment methods on the shear bond strengths of metal brackets bonded to a silica-based ceramic with a light-cured adhesive.

MATERIALS AND METHODS

Silica-based ceramic (IPS Classic(®)) with glazed surfaces was cut into discs that were used as substrates. A total of 80 specimens were randomly divided into four groups according to the method used: 9.6 % hydrofluoric acid (group 1), 9.6 % hydrofluoric acid (HF) + silane coupling agent (group 2), sandblasting (aluminum trioxide, 50 μm) + silane (group 3), and tribochemical silica coating (CoJet™ sand, 30 μm) + silane (group 4). Brackets were bonded to the treated specimens with a light-cure adhesive (Transbond XT, 3 M Unitek). Shear bond strength was tested after bracket bonding, and the Adhesive Remnant Index (ARI) scores were quantified after debonding.

RESULTS

Group 4 showed the highest bond strength (12.3 ± 1.0 MPa), which was not significantly different from that of group 3 (11.6 ± 1.2 MPa, P > 0.05); however, the bond strength of group 4 was substantially higher than that of group 2 (9.4 ± 1.1 MPa, P < 0.05). The shear bond strength of group 1 (3.1 ± 0.6 MPa, P< 0.05) was significantly lower than that of the other groups.

CONCLUSION

Shear bond strengths exceeded the optimal range of ideal bond strength for clinical practice, except for the isolated HF group. HF acid etching followed by silane was the best suited method for bonding on IPS Classic(®). Failure modes in the sandblasting and silica-coating groups revealed signs of damaged ceramic surfaces.

Color stability of ceramic brackets immersed in potentially staining solutions

OBJECTIVE

To assess the color stability of five types of ceramic brackets after immersion in potentially staining solutions.

METHODS

Ninety brackets were divided into 5 groups (n = 18) according to brackets commercial brands and the solutions in which they were immersed (coffee, red wine, coke and artificial saliva). The brackets assessed were Transcend (3M/Unitek, Monrovia, CA, USA), Radiance (American Orthodontics, Sheboygan, WI, USA), Mystique (GAC International Inc., Bohemia, NY, USA) and Luxi II (Rocky Mountain Orthodontics, Denver, CO, USA). Chromatic changes were analyzed with the aid of a reflectance spectrophotometer and by visual inspection at five specific time intervals. Assessment periods were as received from the manufacturer (T0), 24 hours (T1), 72 hours (T2), as well as 7 days (T3) and 14 days (T4) of immersion in the aforementioned solutions. Results were submitted to statistical analysis with ANOVA and Bonferroni correction, as well as to a multivariate profile analysis for independent and paired samples with significance level set at 5%.

RESULTS

The duration of the immersion period influenced color alteration of all tested brackets, even though these changes could not always be visually observed. Different behaviors were observed for each immersion solution; however, brackets immersed in one solution progressed similarly despite minor variations.

CONCLUSIONS

Staining became more intense over time and all brackets underwent color alterations when immersed in the aforementioned solutions.

Four chemical methods of porcelain conditioning and their influence over bond strength and surface integrity

OBJECTIVE:

To assess four different chemical surface conditioning methods for ceramic material before bracket bonding, and their impact on shear bond strength and surface integrity at debonding.

METHODS:

Four experimental groups (n = 13) were set up according to the ceramic conditioning method: G1 = 37% phosphoric acid etching followed by silane application; G2 = 37% liquid phosphoric acid etching, no rinsing, followed by silane application; G3 = 10% hydrofluoric acid etching alone; and G4 = 10% hydrofluoric acid etching followed by silane application. After surface conditioning, metal brackets were bonded to porcelain by means of the Transbond XP system (3M Unitek). Samples were submitted to shear bond strength tests in a universal testing machine and the surfaces were later assessed with a microscope under 8 X magnification. ANOVA/Tukey tests were performed to establish the difference between groups (α= 5%).

RESULTS:

The highest shear bond strength values were found in groups G3 and G4 (22.01 ± 2.15 MPa and 22.83 ± 3.32 Mpa, respectively), followed by G1 (16.42 ± 3.61 MPa) and G2 (9.29 ± 1.95 MPa). As regards surface evaluation after bracket debonding, the use of liquid phosphoric acid followed by silane application (G2) produced the least damage to porcelain. When hydrofluoric acid and silane were applied, the risk of ceramic fracture increased.

CONCLUSIONS:

Acceptable levels of bond strength for clinical use were reached by all methods tested; however, liquid phosphoric acid etching followed by silane application (G2) resulted in the least damage to the ceramic surface.

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.

Surface treatment of feldspathic porcelain: scanning electron microscopy analysis

PURPOSE

Topographic analysis of treated ceramics provides qualitative information regarding the surface texture affecting the micromechanical retention and locking of resin-ceramics. This study aims to compare the surface microstructure following different surface treatments of feldspathic porcelain.

MATERIALS AND METHODS

This in-vitro study was conducted on 72 porcelain discs randomly divided into 12 groups (n=6). In 9 groups, feldspathic surfaces were subjected to sandblasting at 2, 3 or 4 bar pressure for 5, 10 or 15 seconds with 50 µm alumina particles at a 5 mm distance. In group 10, 9.5% hydrofluoric acid (HF) gel was applied for 120 seconds. In group 11, specimens were sandblasted at 3 bar pressure for 10 seconds and then conditioned with HF. In group 12, specimens were first treated with HF and then sandblasted at 3 bar pressure for 10 seconds. All specimens were then evaluated under scanning electron microscopy (SEM) at different magnifications.

RESULTS

SEM images of HF treated specimens revealed deep porosities of variable sizes; whereas, the sandblasted surfaces were more homogenous and had sharper peaks. Increasing the pressure and duration of sandblasting increased the surface roughness. SEM images of the two combined techniques showed that in group 11 (sandblasted first), HF caused deeper porosities; whereas in group 12 (treated with HF first) sandblasting caused irregularities with less homogeneity.

CONCLUSION

All surface treatments increased the surface area and caused porous surfaces. In groups subjected to HF, the porosities were deeper than those in sandblasted only groups.

Orthodontic bonding to porcelain: a systematic review

OBJECTIVE

To use a systematic review to determine which materials and technique/protocol present the highest success rate in bonding brackets to porcelain surfaces.

MATERIALS AND METHODS

Different databases were searched without limitations up to July 2013. Additionally, the bibliographies of the finally selected articles were hand searched to identify any relevant publications that were not identified earlier. In vitro and in vivo articles were included.

RESULTS

No in vivo articles were found that fulfilled the inclusion criteria. A total of 45 in vitro articles met all inclusion criteria. They were published between 2000 to July 2013.

CONCLUSIONS

The best protocol described in this review is the etching of 9.6% hydrofluoric acid for 1 minute, rinsed for 30 seconds, and then air-dried. The etching of hydrofluoric acid should be followed by an application of silane. Considering the harmful effects of etching with hydrofluoric acid, another appropriate suggestion is mechanical roughening with sandblasting followed by an application of silane.

Effect of a DPSS laser on the shear bond strength of ceramic brackets with different base designs

This study evaluated the shear bond strength (SBS) and adhesive remnant index (ARI) of ceramic brackets with different base designs using a 473-nm diode-pumped solid-state (DPSS) laser to test its usefulness as a light source. A total of 180 caries-free human premolars were divided into four groups according to the base designs: microcrystalline, crystalline particle (CP), dovetail, and mesh. For each base design, teeth were divided into three different subgroups for light curing using three different light-curing units (LCUs) (quartz-tungsten-halogen unit, light-emitting diode unit, and a DPSS laser of 473 nm). Applied light intensities for the DPSS laser and the other LCUs were approximately 630 and 900 mW/cm(2), respectively. Stainless steel brackets with a mesh design served as controls. The failure modes of debonded brackets were scored using ARI. As a result, brackets bonded using the DPSS laser had the highest SBS values (16.5-27.3 MPa) among the LCUs regardless of base design. Regarding base designs, the CP groups showed the highest SBS values (22.9-27.3 MPa) regardless of LCU. Furthermore, stainless steel brackets with a mesh design had the lowest SBS values regardless of LCU. In many cases, brackets bonded using the DPSS laser had higher ARI scores and had more adhesive on their bases than on tooth surfaces. The study shows that the 473-nm DPSS laser has considerable potential for bonding ceramic brackets at lower light intensities than the other light-curing units examined.