The Effect of Hydrofluoric Acid Etching Duration on the Surface Micromorphology, Roughness, and Wettability of Dental Ceramics

Effect of hydrofluoric acid and self-etch ceramic primers on the flexural strength and fatigue resistance of glass ceramics: A systematic review and meta-analysis of in vitro studies

This systematic review evaluated the effect of different hydrofluoric acid (HF) etching regimens and a self-etch ceramic primer (SECP) on the flexural strength (FS) and fatigue failure load (FFL) of glass-ceramic materials.The identification of relevant studies was conducted by two authors in five databases: PubMED, Scopus, Web Of Science, LILACS and Virtual Health Library (BVS) until July 2022 with no year limit. The analysis was conducted in RevMan 5.4.1 Software (Cochrane Collaboration) using Random effect model at 5 %. The risk of bias of the included studies were assessed. From the 5349 articles identified, 34 were included for quantitative analysis. Meta-analysis showed that for predominantly glassy ceramics, etching with HF 5 % had no significant impact on FS, however, HF acid etching with concentrations greater than 5 % negatively impacted FS. For lithium disilicate glass-ceramics (LDGC) HF acid etching, negatively influenced FS, while increasing the FFL. HF etching negatively affected FS of hybrid ceramics. The self-etch ceramic primer and HF acid etching showed a similar impact on FFL and FS. This meta-analysis indicates that the impact of SECP and HF acid etching on the mechanical behavior of glass ceramics is material-dependent.

Different surface treatments on recently introduced CAD-CAM resin-modified ceramics: Implications on bond strength

STATEMENT OF PROBLEM

The diverse chemical composition of recently introduced resin-modified ceramics complicates the establishment of a universally accepted clinical bonding protocol.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of different surface treatments of resin-modified ceramics on the bond strength to a resin cement.

MATERIAL AND METHODS

Sixteen 10×12×3-mm resin-modified ceramic slices were obtained from each material (Cerasmart; GC, Shofu Block HC; Shofu, Vita Enamic; Vita, Evolux hybrid; BlueDent, Alium; Alium). Slices were assigned to 4 groups based on surface treatments: Control (no treatment), airborne-particle abrasion with Al2O3 (Al2O3), conditioning with 9% HF (HF), and Al2O3+HF. After treatments and silane coupling agent (Monobond N; Ivoclar) application, 7 resin cement cylinders (Choice 2 veneer; Bisco) were built on each slice and light polymerized for 20 seconds. Half of the specimens (n=14 cylinders) were stored for 24 hours, and the other half were thermocycled (20 000 cycles, 5 °C to 55 °C, 30-second dwell time). Microshear bond strength was tested and analyzed with 3-way ANOVA and the Tukey HSD test (α=.05), and failure patterns were classified. Surface morphology after treatments was observed with scanning electron microscopy and Raman spectroscopy.

RESULTS

After 24 hours, all treatments induced higher bond strength (P<.05) than in the control in Evolux. Al2O3+HF caused higher bond strength (P<.05) than in the control in Cerasmart and Shofu, and higher bond strength than Al2O3 in Cerasmart. However, it resulted in lower bond strength (P<.05) than Al2O3 in Alium. After thermocycling, irrespective of the resin-modified ceramic, all treatments induced higher bond strength (P<.05) than in the control. HF induced lower bond strength (P<.05) than Al2O3 in Alium. Al2O3+HF caused the highest bond strength (P<.05) in Evolux and higher bond strength (P<.05) than HF in Vita Enamic. Adhesive failures were prevalent under control conditions, and mixed failures were common after treatments. Al2O3 induced surface alterations in all resin-modified ceramics. HF notably altered Vita Enamic, while it had no noticeable impact on the other resin-modified ceramics. Al2O3+HF caused a considerable alteration in Vita Enamic and modified the other resin-modified ceramics. Vita Enamic had the characteristic vibrational bands of inorganic compounds, while the other resin-modified ceramics exhibited distinct bands associated with organic compounds.

CONCLUSIONS

Airborne-particle abrasion with Al2O3 followed by HF yielded the highest bond strength, regardless of the resin-modified ceramic, except for Alium, which demonstrated better bond strength after airborne-particle abrasion with Al2O3. 9% HF for 30 seconds caused notable surface alterations in Vita Enamic, negatively impacting its bond strength. Vita Enamic was the only resin-modified ceramic displaying both organic and inorganic composition, while the other resin-modified ceramics showed predominantly organic composition.

Comparison of the shear bond strengths of two different polyetheretherketone (PEEK) framework materials and CAD-CAM veneer materials

BACKGROUND

This study evaluated the shear bond strength (SBS) of two different polyetheretherketone (PEEK) and CAD-CAM materials after aging.

METHODS

A total of 42 frameworks were designed and milled from 2 different PEEK discs (Copra Peek, P and BioHPP, B). P and B frameworks were divided into 3 subgroups (n = 7). 14 slices were prepared each from feldspathic ceramic (Vitablocs Mark II, VM), hybrid nanoceramic (Cerasmart, CS), and polymer-infiltrated ceramic (Vita Enamic, VE) blocks. After surface preparations, the slices were cemented to P and B surfaces. The samples were subjected to thermal aging (5000 cycles). SBS of all the samples was measured. Fractured surfaces were examined by SEM/EDX analysis. The Shapiro-Wilk, Two-way Robust ANOVA and Bonferroni correction tests were used to analyze the data (a = .05).

RESULTS

Frameworks, ceramics, and frameworks x ceramics had significant differences (p < 0.05). The highest SBS value was seen in B-VM (p < 0.05). VM offered the highest SBS with both P and B. The differences between P-VM, P-CS, P-VE and B-CS and B-VE were insignificant (p > 0.05). According to EDX analysis, ytterbium and fluorine was seen in B content, unlike P. While VM and CS contained fluorine, barium, and aluminum; sodium and aluminum were observed in the VE structure.

CONCLUSION

Bonding of P and B with VM offers higher SBS. VM, CS and VE did not make any difference in SBS for P, however VM showed a significant difference for B.

Can a Self-etching Primer be Effective in Bonding Aligner Attachments to Different Types of Ceramics?

Objective

This in vitro study aimed to evaluate the effectiveness of pretreatment with a self-etching primer for bonding aligner attachments to lithium disilicate (LD) and monolithic zirconia (MZ) ceramics.

Methods

Forty ceramics, including LD (n=20) and MZ (n=20), were divided into four study groups according to the surface pretreatments: LD specimens pretreated with universal primer (Monobond Plus, MP) after hydrofluoric acid etching (Group 1); MZ ceramics pretreated with MP after sandblasting (Group 2); LD ceramics pretreated with self-etching ceramic primer (Monobond etch & prime, MEP) (Group 3); and MZ ceramics pretreated with MEP after sandblasting (Group 4). The aligner composite (GC Aligner Connect) and universal adhesive (GPremio Bond) were used to prepare the resin attachments. The bond strength was evaluated by micro-shear bond strength (SBS) testing (0.1 mm/min) after thermocycling, and the remnant adhesive was scored according to the resin attachment remnant index (RARI). The SBS data were analyzed using ANOVA and Tukey tests, and the RARI scores were analyzed using the chi-square test.

Results

Group 1 had the lowest SBS, and group 2 had the highest SBS. There were significant differences between the groups in terms of bond strength (p<0.05). The RARI scores showed no significant differences, regardless of the pretreatment and ceramic type.

Conclusion

The use of a self-etching primer increased the bond strength of resin attachments on LD ceramics. For zirconia ceramics, both ceramic primers are recommended for aligner attachment bonding.

Dental silicate ceramics surface modification by nonthermal plasma: A systematic review

OBJECTIVES

Nonthermal atmospheric or low-pressure plasma (NTP) can improve the surface characteristics of dental materials without affecting their bulk properties. This study aimed to systematically review the available scientific evidence on the effectiveness of using NTP for the surface treatment of etchable, silica-based dental ceramics before cementation, and elucidate its potential to replace the hazardous and technically demanding protocol of hydrofluoric acid (HF) etching.

METHODS

A valid search query was developed with the help of PubMed's Medical Subject Headings (MeSH) vocabulary thesaurus and translated to three electronic databases: PubMed, Web of Science, and Scopus. The methodological quality of the studies was assessed according to an adapted version of the Methodological Index for Non-Randomized Studies (MINORS).

RESULTS

Thirteen in vitro study reports published between 2008 and 2023 were selected for the qualitative and quantitative data synthesis. The implemented methodologies were diverse, comprising 19 different plasma treatment protocols with various device settings. Argon, helium, oxygen, or atmospheric air plasma may significantly increase the wettability and roughness of silicate ceramics by plasma cleaning, etching, and activation, but the treatment generally results in inferior bond strength values after cementation compared to those achieved with HF etching. The technically demanding protocol of plasma-enhanced chemical vapor deposition was employed more commonly, in which the surface deposition of hexamethyl disiloxane with subsequent oxygen plasma activation proved the most promising, yielding bond strengths comparable to those of the positive control. Lack of power analysis, missing adequate control, absence of examiner blinding, and non-performance of specimen aging were common methodological frailties that contributed most to the increase in bias risk (mean MINORS score 15.3 ± 1.1).

SIGNIFICANCE

NTP can potentially improve the adhesive surface characteristics of dental silicate ceramics in laboratory conditions, but the conventional protocol of HF etching still performs better in terms of the resin-ceramic bond strength and longevity. More preclinical research is needed to determine the optimal NTP treatment settings and assess the aging of plasma-treated ceramic surfaces in atmospheric conditions.

Hydrofluoric acid concentration and etching time affect differently the microstructure and surface properties of pressed lithium disilicate glass ceramics

OBJECTIVE

To evaluate the effect of different hydrofluoric acid concentrations and etching times on the surface, chemical composition and microstructure of lithium disilicate.

MATERIAL AND METHODS

Ninety specimens of pressed lithium disilicate (LDS) were obtained (IPS e.max Press, Rosetta SP and LiSi Press). The specimens of each material were divided in two groups according to the hydrofluoric acid concentration: 5% and 10% (n = 15/group), and subdivided according to the etching time: 20, 40 and 60 s (n = 5/group). Crystalline evaluations and chemical composition were performed through x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), respectively. Microstructural analyses were performed by scanning electron microscope (SEM), surface roughness (Ra), and material thickness removal evaluation. Thickness removal and Ra data were analyzed by ANOVA and Tukey test (p < 0.05).

RESULTS

XRD demonstrated characteristic peaks of lithium disilicate crystals, lithium phosphate and of a vitreous phase for all materials. EDS identified different compositions and SEM confirmed different surface responses to acid etching protocols. Material and etching time influenced Ra and material thickness removal (p < 0.05).

CONCLUSION

Hydrofluoric acid concentration and etching time affect the surface characteristics of LDS differently. LiSi Press presented higher resistance to hydrofluoric acid etching compared to e.max Press and Rosetta SP.

CLINICAL SIGNIFICANCE

Applying the appropriate etching protocol is pivotal to avoid excessive material removal and to prevent jeopardize the mechanical and optical properties of the material.

Surface antibacterial properties enhanced through engineered textures and surface roughness: A review

The spread of bacteria through contaminated surfaces is a major issue in healthcare, food industry, and other economic sectors. The widespread use of antibiotics is not a sustainable solution in the long term due to the development of antibiotic resistance. Therefore, surfaces with antibacterial properties have the potential to be a disruptive approach to combat microbial contamination. Different methods and approaches have been studied to impart or enhance antibacterial properties on surfaces. The surface roughness and texture are inherent parameters that significantly impact the antibacterial properties of a surface. They are also directly related to the previously employed machining and treatment methods. This review article discusses the correlation between surface roughness and antibacterial properties is presented and discussed. It begins with an introduction to the concepts of surface roughness and texture, followed by a description of the most commonly utilized machining methods and surface. A thorough analysis of bacterial adhesion and growth is then presented. Finally, the most recent studies in this research area are comprehensively reviewed. The studies are sorted and classified based on the utilized machining and treatment methods, which are divided into mechanical processes, surface treatments and coatings. Through the systematic review and record of the recent advances, the authors aim to assist and promote further research in this very promising and extremely important direction, by providing a systematic review of recent advances.

Different surface treatment strategies on etchable CAD-CAM materials: Part 1-Effect on the surface morphology

STATEMENT OF PROBLEM

Polymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials have either a high content of ceramic filler particles or a ceramic network structure. Proper etching of these materials is challenging. Therefore, it is relevant to assess different surface etching strategies and morphological alterations as a result of these techniques.

PURPOSE

The purpose of this 2-part in vitro study was to evaluate different etching strategies on the surface roughness and its relationship to the surface contact angle with a subsequent morphological characterization of different CAD-CAM materials.

MATERIAL AND METHODS

Two CAD-CAM polymer-based materials and 1 CAD-CAM ceramic material were selected for this study. The materials were treated with different strategies, including a combination of airborne-particle abrasion and an application of 9% hydrofluoric acid etching. After the surface treatment, roughness measurements (Sa) were assessed by using an optical profilometer on an area of 1.47 mm2. Subsequently, the contact angle on the surface was examined by means of the sessile drop technique and an optical contact angle meter. The data were analyzed by using a 2-way analysis of variance, the post hoc Tukey test (α=.05), and the Pearson correlation coefficient.

RESULTS

The 3 materials tested showed an increase in surface roughness when treated with surface airborne-particle abrasion. However, the materials with polymer in their composition concomitantly increased the contact angle. More hydrophilic surfaces were observed when hydrofluoric acid was applied, regardless of the composition of the materials. The surface roughness presented a strong positive linear tendency in the surface treatments used.

CONCLUSIONS

The application of airborne-particle abrasion on the surface of the polymer-based CAD-CAM materials increased the roughness and contact angle. However, the application of acid etching after the airborne-particle abrasion decreased the contact angle for polymer-based CAD-CAM materials, resulting in considerable enhancement of the surface quality for proper bonding.

Different surface treatment strategies on etchable CAD-CAM materials: Part II-Effect on the bond strength

STATEMENT OF PROBLEM

Bonding to recently launched polymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials has been challenging. Evidence regarding etching strategies for dual-phase CAD-CAM materials is sparse, but adequate bonding is crucial for the clinical success and longevity of a restoration.

PURPOSE

The purpose of this 2-part in vitro study was to evaluate and compare the effect of surface treatment strategies on the microshear bond strength and work of adhesion of polymer-based and ceramic materials. In addition, chemical elements present on the surface and the interface morphology after using those strategies were also assessed.

MATERIALS AND METHODS

Two CAD-CAM polymer and 1 CAD-CAM ceramic materials were selected for this in vitro study. The materials were subjected to different surface treatment strategies, including airborne-particle abrasion and the application of 9% hydrofluoric acid. Specimens were submitted to microshear bond strength before and after thermocycling, and the failure mode was classified. The work of adhesion was calculated based on the water-to-air surface tension of 72.8 mN.m-1 and the Young- Dupré equation. The surfaces were submitted to energy-dispersive X-ray spectroscopy, and the interfaces were analyzed using a scanning electron microscope. Data were subjected to 2-way ANOVA and the Tukey post hoc test (α=.05).

RESULTS

The highest microshear bond strength means were observed for the polymer-based materials when hydrofluoric acid or airborne-particle abrasion was applied. The 3 materials tested showed a decrease in microshear bond strength after thermocycling, except for applying airborne-particle abrasion to 1 of the polymer-based material tested. The ceramic material tested showed a high microshear bond strength with the application of airborne-particle abrasion and hydrofluoric acid combined. The work of adhesion varied across the materials and presented high means when hydrofluoric acid was used.

CONCLUSIONS

A combination of airborne-particle abrasion plus hydrofluoric acid should be considered for polymer-based or feldspathic ceramic CAD-CAM materials. In this in vitro study, both etching procedures combined produced higher bonding values for all materials tested.

Adjusting the Dose of Ag-Ion Implantation on TiN-Ag-Modified SLA-Ti Creates Different Micronanostructures: Implications on Bacteriostasis, Biocompatibility, and Osteogenesis in Dental Implants

The prevention of aseptic loosening and peri-implantitis is crucial for the success of dental implant surgery. In this study, different doses of Ag-implanted TiN/Ag nanomultilayers were prepared on the sandblasting with large grit and acid etching (SLA)-Ti surface using a multiarc ion-plating system and an ion-implantation system, respectively. The physical and chemical properties of the samples were assessed using various techniques, including scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, inductively coupled plasma atomic emission spectrometry, and water contact angle measurements. In addition, the applicability and biosafety of the SLA/1 × 1017-Ag and SLA/1 × 1018-Ag surfaces were determined via biocompatibility testing in vivo and in vitro. The results demonstrated that the physical and chemical properties of SLA/1 × 1017-Ag and SLA/1 × 1018-Ag surfaces were different to some extent. However, compared with SLA-Ti, silver-loaded TiN/Ag-modified SLA-Ti surfaces (SLA/1 × 1018-Ag) with enhanced bacteriostatis, osteogenesis, and biocompatibility have great potential for dental applications.

Bonding stability of universal adhesives to feldspathic ceramic with or without prior silane application

PURPOSE

This study aimed to assess the bonding stability of three universal adhesives to a CAD-CAM feldspathic ceramic with or without prior silane application.

MATERIALS AND METHODS

The universal adhesives tested were Ambar Universal (FGM), Single Bond Universal (3M), and Ybond Universal (Yller). Scotchbond Multipurpose Plus (3M) was used as a control. The silane used was RelyX Ceramic Primer (3M). Microtensile bond strength (μTBS) to Vitablocs Mark II was measured after 24 h or 6 months of water aging (n = 20). Failure modes were observed through scanning electron microscopy, and pH and degree of C=C conversion (DC) of the adhesives were measured (n = 3). Data were analyzed using one-, two-, and three-way ANOVA.

RESULTS

The pH values differed significantly among the adhesives (p < 0.001), while the DC was similar (p = 0.141). The universal adhesives showed significant differences in μTBS, with higher immediate results when using silane and lower results after aging. Notably, a significant decrease in μTBS was observed after 6 months when silane was applied. In contrast, the control adhesive exhibited consistent results between the 24-h and 6-month storage periods. The universal adhesives showed a decrease in μTBS ranging from 25.5% to 40.1% after prolonged storage. Adhesive failures were predominant in all groups. The presence or absence of silane in the adhesive composition did not affect the bonding performance.

CONCLUSIONS

The application of a separate silane coupling agent improved the immediate bond strength of universal adhesives to CAD-CAM feldspathic ceramic. However, this bond strength significantly decreased after 6 months of water aging. The bond strength remained stable for universal adhesives when applied without silane after 6 months of aging.

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

OBJECTIVES

To 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).

METHODS

Four 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).

RESULTS

Acid 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.

SIGNIFICANCE

Optical, 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.

Microshear bond strength of resin cement to a zirconia-reinforced lithium silicate glass ceramic using different surface treatments

Background

The purpose of this study was to evaluate the effect of different surface treatments on the microshear bond strength (μSBS) of resin cement to zirconia-reinforced lithium silicate ceramic and to compare it with lithium disilicate ceramic.

Materials and Methods

In this in vitro study, 80 specimens containing two glass ceramics of IPS e.max press and VITA SUPRINITY were prepared and categorized into four groups according to the surface treatments (n = 10) as Group 1 (C): no treatment (control); Group 2 (HF): etching with 9% hydrofluoric acid (HF) for 90 s followed by silane application; Group 3 (SPH): sandblasting with Al₂O₃ particles (50 μm), etching with 35% phosphoric acid for 40 s followed by application of silane and adhesive (Clearfil liner bond F); and Group 4 (SB): sandblasting with Al₂O₃ followed by silanization. Then, a resin cement (Panavia F2) was applied to the prepared ceramic surfaces. All samples were subjected to thermal aging (5000 cycles, 5-55). The μSBS test was evaluated and failure modes were recorded. Data were analyzed using the Shapiro-Wilk, two-way analysis of variance and Tukey's Honest Significant Difference post hoc tests (P < 0.05).

Results

IPS e.max press samples revealed significantly higher μSBS values compared to VITA SUPRINITY (P < 0.001), in whole surface treatments. The HF group showed the highest μSBS value, followed by the SPH and SB groups, respectively (P < 0.001). Adhesive failure was recorded as a predominant failure mode.

Conclusion

The adhesion performance of IPS e.max press was significantly higher than VITA SUPRINITY. The common surface treatment protocol including HF application followed by silanization was the most effective surface treatment for both glass ceramics.

Surface characterization of indirect restorative materials submitted to different etching protocols

OBJECTIVES

This in vitro study aimed to evaluate the effect of different times and concentrations of hydrofluoric acid etching on the surface of indirect restorative materials obtained from blocks used in CAD-CAM technology.

METHODS

Specimens (4 mm × 4 mm × 0.8 mm) were obtained for each indirect restorative material: zirconia-reinforced lithium monosilicate ceramic (Celtra Duo), nanoceramic resin (Lava Ultimate), and polymer-infiltrated ceramic network material (Vita Enamic). The materials were submitted to etching with 5% or 10% hydrofluoric acid for 20, 40, 60, or 90 s. A control group for each material was evaluated without any surface treatment, totaling nine experimental groups for each material (n = 10). The specimens were evaluated for surface roughness (R_a and R_z), confocal optical microscopy, the contact angle (θ), surface free energy (γs), total free interaction energy (∆G) using a goniometer, and microshear bond strength to resin cement. Specimen images were obtained using scanning electron microscopy, confocal optical microscopy, and atomic force microscopy. Data on the surface roughness, the contact angle, surface free energy, total free interaction energy, and bond strength were subjected to two-way ANOVA and Tukey´s test (α=0.05).

RESULTS

In general, Celtra Duo showed better results after etching with 10% hydrofluoric acid for 40 or 60 s. Lava Ultimate showed better performance after etching with 10% hydrofluoric acid for 20 or 40 s, whereas Vita Enamic showed better results after etching with 5% hydrofluoric acid for 90 s.

CONCLUSION

Each material showed different characteristics after etching with hydrofluoric acid. Knowledge of the proper protocol for each material is essential to ensure improvements in the adhesion process and durability of indirect restorations. In general, Celtra Duo presented mechanical properties superior to those of Lava Ultimate and Vita Enamic.

CLINICAL SIGNIFICANCE

Specific etching protocols must be recommended for each indirect material because longer exposure to hydrofluoric acid can jeopardize the surface, thus affecting the mechanical and bond strength properties.

Y-TZP Physicochemical Properties Conditioned with ZrO2 and SiO2 Nanofilms and Bond Strength to Dual Resin Cement

Commercial Yttria-tetragonal zirconia polycrystalline (Y-TZP) was subjected to surface treatments, and the bond strength of dual resin cement to Y-TZP and failure modes were evaluated. Disks (12 mm × 2 mm), cylinders (7 mm × 3.3 mm), and bars (25 mm × 5 mm × 2 mm) were milled from Y-TZP CAD-CAM blocks, divided into seven groups, and subjected to different surface treatments; silicatization was used as control. On the basis of the literature, this study evaluated modifications with films containing SiO2 nanoparticles and silane; SiO2+ZrO2—SiO2 (50%) and ZrO2 (50%) nanoparticles, SiO2+ZrO2/Silane-SiO2 (50%) and ZrO2 (50%) nanoparticles, and silane. Specimens were analyzed by wettability (n = 3), surface free energy (n = 3), X-ray diffraction (n = 1), Fourier transform infrared spectroscopy (FTIR) (n = 1), roughness (n = 5), shear bond test (n = 10), and dynamic modulus (n = 3). Specimens treated with hydrofluoric acid—HF 40% presented significantly higher contact angle and lowest surface free energy (p < 0.05). The SiO2/Silane presented crystalline SiO2 on the surface. The surface roughness was significantly higher for groups treated with nanofilms (p < 0.05). Shear bond strength was significantly higher for silicatization, HF 40%/silicatization, SiO2/Silane, and SiO2+ZrO2/Silane groups. The proposed treatments with nanofilms had potentially good results without prejudice to the physicochemical characteristics of zirconia. Generally, groups that underwent silica surface deposition and silanization had better bond strength (p < 0.005).

Evaluation of The Fracture Resistance and Failure Types of Different CAD/CAM Ceramic Crowns Supported by Angled Titanium Abutment

PURPOSE

To evaluate the fatigue resistance of CAD-CAM single-ceramic crowns which were applied on angled implant abutments after thermomechanical aging.

MATERIALS AND METHODS

Titanium abutments (N = 72, MODE Medical Dental Implant, Turkey) with three different angles [0˚, 15°, 25°] were restored using different materials [Monolithic zirconia (Zir), lithium silicate ceramic reinforced by zirconia (VS), and Hybrid ceramic (VE)]. Crowns in the maxillary first premolar form were cemented to abutments using resin cement (Panavia 2.0 Introkit). Dynamic loading and thermomechanical aging were applied to the specimens (120,000 cycles, 49 N, 5°C to 55°C). Fracture resistance values were measured in the universal test machine and fracture types were determined. Two-way ANOVA and Tukey test were used for statistical analysis (Jamovi version 2.3.5).

RESULTS

Both the abutment angle and the type of material had a significant effect on fracture resistance (F = 3.295, p<0.05). The highest fracture resistance was obtained in the Group 0˚-Zir, and the lowest fracture resistance was obtained in the Group 15˚-VE. Fracture resistance showed significant differences between Group 0˚-Group15˚ for the Zir and VE materials, and between Group0˚-Group25˚ for VS (p<0.05), and no statistical significance was determined between the other groups (p>0.05). When failure types were evaluated they were seen to be full or partial crown fractures, and abutment deformation was found in some samples.

CONCLUSION

Monolithic crowns may be preferred on angled abutments. The fracture resistance of CAD-CAM materials decreases as the angle of abutments increases. Monolithic zirconia has higher fracture resistance than other materials. This article is protected by copyright. All rights reserved.

Effect of Erosive Agents on Surface Characteristics of Nano-Fluorapatite Ceramic: An In-Vitro Study

Erosive beverages cause dissolution of natural teeth and intra-oral restorations, resulting in surface characteristic changes, particularly roughness and degradation. The purpose of this study was to evaluate the surface roughness and topography of a dental ceramic following immersion in locally available erosive solutions. A total of 160 disc specimens of a nano-fluorapatite type ceramic (12 mm diameter and 2 mm thickness) were fabricated and equally distributed into two groups (n = 80) and then evenly distributed among the following five testing groups (n = 16): lemon juice, citrate buffer solution, 4% acetic acid, soft cola drink, and distilled water which served as a control. The surface roughness (Ra) and topography were evaluated using a profilometer and scanning electron microscope at baseline, 24 h, 96 h, and 168 h respectively. Data were analyzed using ANOVA and Tukey’s multiple comparisons (p ≤ 0.05). Surface changes were observed upon exposure to all acidic beverages except distilled water. Amongst all immersion media, 4% acetic acid produced the most severe surface roughness across all time periods (i.e., baseline, 24 h, 96 h, and 168 h). A statistically significant difference in the surface roughness values between all immersion media and across all four time intervals was observed. Erosive agents had a negative effect on the surface roughness and topography of the tested ceramic. The surface roughness increased with increased storage time intervals.

Adhesion to a Zirconia-reinforced Lithium Silicate Ceramic: Effects of Ceramic Surface Treatments and Resin Cements

OBJECTIVE

This study had the objective to test the effect of ceramic surface treatments on the microshear bond strength (μSBS) of different resin cements to a zirconia-reinforced lithium silicate (ZLS).

METHODS AND MATERIALS

ZLS blocks were sectioned, embedded in acrylic resin, and then allocated into nine groups considering two study factors: "ceramic surface treatment" (HF - hydrofluoric acid; EP - self-etching primer; TBS - tribochemical silica coating) and "resin cements" (nMDP - without MDP monomer; MDP - with MDP monomer; SA - self-adhesive). Starch tubes (n=36) were placed on the treated ceramic surface and the cement was applied. Starch tubes were removed after 24 hours of storage, and the specimens were thermocycled (5,000×; 5°C-55°C). Next, the μSBS test was performed using the wire-loop technique, and topographic and failure analyses were performed.

RESULTS

The factors "ceramic surface treatment" and "resin cement" statistically influenced the μSBS results. Considering the surface treatment factor, the TBS produced statistically lower values when the MDP resin cement was applied, being only similar to the MDP plus EP group. For the resin cement factor, no difference was found for nMDP and SA groups, apart from the surface treatments. Failure analysis showed that the groups treated with EP had a greater number of pre-test failures. The surface treatments induced noteworthy topographic alterations when compared to control (no treatment).

CONCLUSION

The ZLS ceramic surface treatment with tribochemical silica coating associated with the MDP-containing resin cement resulted in lower bond strength values.

Surface Treatment and Cementation of Lithium Silicate Ceramics Containing ZrO2

Objective

To evaluate the effect of different surface treatments on the shear bond strength (SBS) of lithium silicate (LS) and lithium disilicate (LD) ceramics, after thermocycling.

Methods and Materials

For SBS test, 72 ceramic blocks (18×14×2 mm) were made (24 blocks from each ceramic material): VITA Suprinity (LSS), Celtra Duo (LSC), and Lithium disilicate (LD). The blocks were polished with sandpaper of increasing grit (#280, #400, #800, and #1200) and embedded in chemically activated acrylic resin. Afterwards, they were randomly divided into 12 groups (6 blocks per group) according to: “Ceramic” (LD, LSC, and LSS) and “Surface treatment” (HFS: hydrofluoric acid + silane; MEP: Monobond Etch & Prime/Ivoclar). From each treated surface ceramic block, four dual-curing resin cement cylinders (RelyX U200, 3M Oral Care) were prepared using a Tygon tube (Ø=3 mm and h=2 mm) and light cured for 40 seconds (1000 mW/cm2) (N=288/n=24). All specimens were submitted to thermocycling (10,000 cycles, 5°C and 55°C, 30 seconds) and then to SBS test at a crosshead speed of 1 mm/min using a 50-kgf load cell. Forty-five additional blocks were made for roughness and SEM analysis. Failure mode was also performed. The data (MPa) were statistically analyzed by oneway analysis of variance (ANOVA), Tukey test (5%), and Weibull analysis. The Ra was analyzed by Kruskal–Wallis and Dunn Test (5%). The other variables were analyzed qualitatively.

Results

ANOVA revealed that “surface treatment” was significant for all ceramic materials (p&lt;0.05). The LD-HFS (18.66±3.49), LSC-HFS (16.81±2.62), and LSS-HFS (16.33±3.08) groups had significantly higher SBS than the LD-MEP (7.00±4.2), LSC-MEP (14.12±3.51), and LSS-MEP (13.87±2.52) groups. Complete adhesive failures at the cement– dentin interface were more frequent. Weibull modulus was superior for the LD-HFS (6.22), LSC-HFS (8.8), and LSS-HFS (7.4) groups.

Conclusion

HF followed by silanization is the most suitable surface treatment for the cementation of LS and LD glass ceramics.

Surface Roughness and Bond Strength of Resin Composite to Additively Manufactured Zirconia with Different Porosities

PURPOSE

To investigate the bond strength of resin cement to additively manufactured (AM) zirconia with different porosities when compared to milled zirconia.

MATERIALS AND METHODS

A 12 × 5 mm disk virtual design file was used to fabricate a total of 48 disks divided into 4 groups: 3 groups were AM with different porosities including 0%-porosity (AMZ0 group), 20%-porosity (AMZ20 group), and 40%-porosity (AMZ40 group), and 1 milled zirconia (control or CNCZ group). The dimensions of all specimens were measured using a digital caliper. A 3D- confocal laser scanner was used to analyze surface morphology and measure the surface roughness (Sa), followed by SEM analysis. Tensile bond strength of composite resin cement to specimens was measured before and after aging procedures using a universal testing machine (n = 10). Failure modes were evaluated under a light microscope. Volumetric change data was analyzed using one-way ANOVA, and two-way ANOVA was used to compare bond strength values (α = 0.05).

RESULTS

There was a significant difference in volumetric changes among the groups. The CNCZ group showed the least changes in diameter 0.027 ± 0.029 mm and thickness 0.030 ± 0.012 mm and AM zirconia with 40% porosity showed the most volumetric changes in diameter 5.237 ± 0.023 mm. ANOVA test indicated an overall significant difference in surface roughness across all groups (F = 242.6, p < 0.001). The CNCZ group showed the highest mean Sa of 1.649 ± 0.240 µm, followed by AMZ40 group with Sa of 0.830 ± 0.063 µm, AMZ20 group with Sa of 0.780 ± 0.070 µm, and the AMZ0 group with Sa of 0.612 ± 0.063 µm. Two-way ANOVA showed significant difference in bond strength between the CNCZ group 12.109 ± 3.223 MPa and the AMZ0 group 8.629 ± 0.914 MPa, with significant pretest failures in specimens with porosities. Thermal cycling methods reduced the bond strength non-significantly in CNCZ group with no effect in the AMZ0 group.

CONCLUSION

Milled zirconia had a higher surface roughness and bond strength to composite resin cement than AM zirconia, and porosities in AM zirconia decreased the bond strength with significant pretest failures.

The Effect of Different Surface Conditioning Techniques on the Bonding between Resin Cement & Ceramic

Surface etching before cementation is a vital step that determines the clinical performance of ceramic restorations. Etching alters surface topography that contributes effective bonding between ceramic restoration and resin cement. This study aimed to compare etching techniques to determine the most effective etching method contributing the highest bond strength that helps in improving dental implants. Materials and methods: sixty discs of feldspathic ceramic measuring 10 mm diameter and 4 mm thickness were prepared. The 60 samples were divided into four equal groups based on the surface treatment technique used: group A: 9.6% hydrofluoric acid; group B: coarse diamond burs; group C: CO2 laser; and group D: no treatment. Ceramic disc specimens were examined under a Scanning Electron microscope (SEM) after surface treatment to characterize their surface morphology. Further, the specimens were luted with a resin luting agent and incubated for 24 h at a temperature of 37 °C simulating the oral environment. After 24 h, shear bond strength (SBS) and the nature of bond failure was determined for each specimen using a universal Instron testing machine. Results: significant change in surface morphology was noticed on hydrofluoric acid treatment forming larger irregular roughness (4.83 ± 1.78 µm) with multiple patterns of grooves and pores compared to other groups. Further, the highest SBS value was measured on hydrofluoric acid etching that display the highest bond strength due to the high surface roughness. In conclusion, our findings report a strong association between the surface roughness and bond strength upon hydrofluoric acid compared to other methods. Further work in this direction will enhance the utility of the etching technique on the improvement of dental implants.

Increasing Acid Concentration, Time and Using a Two-Part Silane Potentiates Bond Strength of Lithium Disilicate-Reinforced Glass Ceramic to Resin Composite: An Exploratory Laboratory Study

There is still a lack of consensus concerning the recommended etching concentration, application time and type of silane when bonding lithium disilicate-reinforced glass ceramics manufactured by CAD/CAM. The purpose of this study was thus to conduct an in vitro study which investigates the influence of hydrofluoric acid (HF) concentration, etching time and silane type on the microtensile bond strength (μTBS) of lithium disilicate to resin composites. Thirty-nine IPS e.max CAD blocks were randomly divided between thirteen groups (n = 3). The variables were HF concentration (9.5 or 4.9%), etching time (20 or 60 s) and silane type (Bis-Silane, Monobond Plus and ESPE Sil Silane). The blocks were cut into beams, aged for 10,000 cycles in a thermocycler and submitted to tensile stress to determine μTBS. A control group featuring the Monobond Etch & Prime (MEP) agent that combines etching/silanisation into a simultaneous process was also added. This group was discarded from the analysis due to only having pre-test failures. The data were analysed using a three-way ANOVA (α = 0.05). The HF concentration, etching time and silane type significantly influenced μTBS (p < 0.001). Significant interactions between time and silane type (p = 0.004), HF concentration and silane type (p < 0.001) and among the three factors (p < 0.001) were noted. Etching lithium disilicate with 9.5% HF (60 s), followed by the application of Bis-Silane, resulted in the highest μTBS (16.6 ± 9.0 MPa). The highest concentration and etching time under study, combined with a two-part silane, resulted in the highest bond strength, while the application of MEP showed a complete pre-test failure.

Bracket Bonding to All-Ceramic Materials with Universal Adhesives

The need for bracket bonding to ceramic restorations is increasing. The aim of this study was to evaluate the effect of universal adhesives on bracket adhesion to polished or glazed lithium disilicate (LDS) and monolithic zirconia (MZ) surfaces. One hundred and twenty brackets (N = 10) were bonded to either polished or glazed LDS (e.max CAD B32, Ivoclar Vivadent, Schaan, Liechtenstein) and MZ (In-Ceram^® YZ, VITA, Bad Sackingen, Germany) blocks using three different adhesives combined with Transbond™ XT Paste (3M Unitek, Monrovia, CA, USA). Tested universal adhesives were Scotchbond™ Universal Adhesive (SU, 3M St. Paul, MN, USA) and Assure Plus (AP, Reliance, Itasca, IL, USA). Transbond™ XT Primer (XTP, 3M Unitek, Monrovia, CA, USA) served as a control adhesive. Bracket bond strength was measured in shear mode (SBS). Failure type was determined by the Modified Adhesive Remnant Index (ARI). Data were statistically analyzed. On polished LDS, SU yielded bracket SBS significantly superior to those of AP and XTP. On polished MZ, the use of SU and AP significantly enhanced bracket retention as compared with XTP. Low SBS values, below the threshold of clinical acceptability, were reached by all tested adhesives on glazed LDS and MZ specimens. SBS measurements corresponded with failure type observations. Universal adhesives SU and AP could be considered for use on polished LDS and MZ surfaces.

Influence of Sandblasting and Chemical Etching on Titanium 99.2-Dental Porcelain Bond Strength

The metal-ceramic interface requires proper surface preparation of both metal and ceramic substrates. This process is complicated by the differences in chemical bonds and physicochemical properties that characterise the two materials. However, adequate bond strength at the interface and phase composition of the titanium-bioceramics system is essential for the durability of dental implants and improving the substrates' functional properties. In this paper, the authors present the results of a study determining the effect of mechanical and chemical surface treatment (sandblasting and etching) on the strength and quality of the titanium-low-fusing dental porcelain bond. To evaluate the strength of the metal-ceramic interface, the authors performed mechanical tests (three-point bending) according to EN ISO 9693 standard, microscopic observations (SEM-EDS), and Raman spectroscopy studies. The results showed that depending on the chemical etching medium used, different bond strength values and failure mechanisms of the metal-ceramic system were observed. The analyzed samples met the requirements of EN ISO 9693 for metal-ceramic systems and received strength values above 25 MPa. Higher joint strength was obtained for the samples after sandblasting and chemical etching compared to the samples subjected only to sandblasting.

Comparison of Silane Heat Treatment by Laser and Various Surface Treatments on Microtensile Bond Strength of Composite Resin/Lithium Disilicate

In the current study, we evaluated the effects of heat treatment (by Er:YAG or furnace) and various surface treatments on the microtensile bond strength (μTBS) of silanized lithium disilicate ceramic. Seventy lithium disilicate (IPS e. max Press; Ivoclar Vivadent) and composite resin (Tetric N-Ceram; Ivoclar Vivadent) blocks were made and distributed into seven groups (n = 10) at random: S: silanization alone; ALS: airborne particle abrasion (APA) and silanization; SC: APA modified with silica and silanization; SHT1: silanization and heat treatment by Er:YAG; SHT2: silanization and heat treatment performed in the furnace (100 °C, 1 min); HF: etching with HF; and HFS: etching with HF and silanization. Every ceramic specimen was cemented to a composite resin block after surface treatment. Cemented specimens were embedded into acrylic resin and were tested with the μTBS test. Data were analyzed using one-way ANOVA and Tamhane T2 tests (α = 0.05). The SHT1 group had the highest bond of strength compared to the other groups (27.46 MPa). The ALS group had the lowest strength of the groups (15.56 MPa). Between SHT2 and HFS (p = 1), the comparison of the mean µTBS values showed no significant differences. It was concluded that silane heat treatment increased the resin composite–ceramic bond strength; however, within the terms of μTBS, the Er:YAG laser treatment was more successful than other surface treatment applications.

Evaluation of Micro-Shear Bond Strength of Four Different CAD-CAM Polymer-Infiltrated Ceramic Materials after Thermocycling

PURPOSE

To evaluate the bond strength of three monolithic hybrid ceramics/resin nanoceramics and a zirconia-reinforced lithium silicate to resin cement after thermocycling.

MATERIALS AND METHODS

Using four materials, including Vita Enamic (VITA Zahnfabrik), Lava Ultimate (3M ESPE), Crystal Ultra (Digital Dental), and Vita Suprinity (VITA Zahnfabrik), 64 specimens were prepared with dimensions of 4mm×3mm×1.5mm. Vita Suprinity samples were sintered at 840°C for 8 min. After polishing and cleaning all the samples in each group (n = 16), they were subjected to their recommended surface treatment: 10% hydrofluoric acid for Vita Enamic (60s) and Vita Suprinity (20s); air abrasion of Lava Ultimate and Crystal Ultra with 50μ Al₂ O₃ particles. Then, tygon tubes were filled with dual cure resin cement (Panavia F2.0), cured and then subjected to thermal cycling (2000 cycles; 5-55°C). The micro-shear bond strength was measured using micro-tensile testing machine. The data were analyzed using Welch and Games-Howell tests (α = 0.05). The mode of failure was also evaluated using a stereomicroscope.

RESULTS

The highest and the lowest mean micro-shear bond strength belonged to the Crystal Ultra (7.71 ±1.54 MPa) and Vita Suprinity (4.73 ±1.87 MPa) groups, respectively. The differences between groups were significant and Crystal Ultra had higher bond strength in comparison to all three materials (p<.05).

CONCLUSION

Hybrid ceramics showed higher bond strength to resin cements in comparison to resin nanoceramics and zirconia-reinforced lithium silicate materials. This article is protected by copyright. All rights reserved.

Surface Characterisation of Dental Resin Composites Related to Conditioning and Finishing

Due to the little information related to surface processing and conditioning of resin matrix ceramic materials previous glazing, the main purpose of this in vitro study was to investigate the effect of different surface treatments on the surface morphology of different resin composite materials. Five types of resin composite CAD-CAM materials: a resin composite ceramic Vita Enamic (E) and four types of nanoparticle-filled resins, like Lava Ultimate (L), Cerasmart (C), Shofu HC (S), Hyramic (H) were taken into consideration. Specimens received the following surface treatment protocols: conventional polishing [p], polishing and glazing [pg], conditioning with CoJet [c], conditioning with CoJet and glazing [cg], sandblasting [s], sandblasting and glazing [sg], etching [e], etching and glazing [eg]. Surface roughness was analyzed for all samples and nanosurface topographic characterization was made by Atomic Force Microscopy. The highest roughness was registered for sandblasted surfaces [s], followed by tribochemical silica airborne particle abrasion [c], and etching [e]. A very strong correlated conditioning behavior of resin nanoceramic materials, like L, C and S samples was found. The microroughness decreased thus [s] > [c] > [e]. These are moderate correlated with H, and are moderate negative correlated to E, where e is more efficient. Three-dimensional images indicated visible grain boundaries after conditioning, for all materials. After polishing and glazing, surfaces became smoother. For all tested conditioning and finishing methods, surface roughness values were within clinically acceptable limits. Finishing by polishing was proved to be a good choice for all materials taken into consideration, polishing and glazing likewise, excepting Hyramic. For Enamic and Shofu HC sandblasting or tribochemical conditioning and glazing and for Hyramic polishing and glazing are not the best options, related to nanoroughness values. Referring to the nanosurface topography, for Enamic, Cerasmart and Hyramic, glazing would be the method of choice, associated with the adequate conditioning method for each material.

Surface roughness and shear bond strength to composite resin of additively manufactured interim restorative material with different printing orientations

STATEMENT OF PROBLEM

Additive manufacturing (AM) is a technology that has been recently introduced into dentistry for fabricating dental devices, including interim restorations. Printing orientation is one of the important and influential factors in AM that affects the accuracy, surface roughness, and mechanical characteristics of printed objects. However, the optimal print orientation for best bond strength to 3D-printed interim restorations remains unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of printing orientation on the surface roughness, topography, and shear bond strength of AM interim restorations to composite resin.

MATERIAL AND METHODS

Disk-shaped specimens (Ø20×10 mm) were designed by a computer-aided design software program (Geomagic freeform), and a standard tessellation language (STL) file was obtained. The STL file was used for the AM of 60 disks in 3 different printing orientations (0, 45, and 90 degrees) by using E-Dent 400 C&B material. An autopolymerizing interim material (Protemp 4) was used as a control group (CNT), and specimens were fabricated by using the injecting mold technique (n=20). Surface roughness (Sa, Sz parameters) was measured by using a 3D-laser scanning confocal microscope (CLSM) at ×20 magnification. For shear bond testing, the specimens were embedded in polymethylmethacrylate autopolymerized resin (n=20). A flowable composite resin was bonded by using an adhesive system. The specimens were stored in distilled water at 37 °C for 1 day and thermocycled 5000 times. The shear bond strength (SBS) was measured at a crosshead speed of 1 mm/min. The data were analyzed by 1-way ANOVA, followed by the Tukey HSD test (α=.05).

RESULTS

The 45-degree angulation printing group reported the highest Sa, followed by the CNT and the 90-degree and 0-degree angulations with significant difference between them (P<.001). The CNT showed the highest Sz, followed by the 45-degree, 90-degree, and 0-degree angulations. The mean ±standard deviation SBS was 28.73 ±5.82 MPa for the 90-degree, 28.21 ±10.69 MPa for the 45-degree, 26.21 ±11.19 MPa for the 0-degree angulations and 25.39 ±4.67 MPa for the CNT. However, no statistically significant difference was found in the SBS among the groups (P=.475).

CONCLUSIONS

Printing orientation significantly impacted the surface roughness of 3D-printed resin for interim restorations. However, printing orientation did not significantly affect the bond strength with composite resin.

Evaluation of Time Consumption for Debonding Brackets Using Different Techniques: A Hospital-Based Study

Materials and Methods

A total of 80 human premolars were included in this study. The samples were first arranged following a standard protocol for bracketing and then debonded using the ultrasonic scaler (US), debonding plier (DP), ligature cutter (LC), and thermal method (TM). Depending on the technique applied for debonding, the specimens were randomly divided into four groups with 20 samples, each keeping a 1 : 1 ratio. During the debonding process, the time taken for each bracket removal was recorded using a stopwatch. To assess the difference in mean time required for debonding among the four techniques, one-way ANOVA test was applied along with Tukey's HSD to compare the two methods.

Results

The time range and the mean time required for the four techniques analyzed show that the DP method has the highest range of time needed for debonding with 0.97-2.56 seconds, while LC methods have the least time range taking 0.46 to 1.79 seconds. TM's mean time to debond is the highest at 1.5880 seconds. LC method has the lowest mean debonding time of 0.9880 seconds. The one-way ANOVA test has shown the mean debonding time required by the four techniques to be significantly different (p < 0.001). Tukey's HSD multiple comparisons also show that the mean time to debond using the LC method is substantially less than the other three methods (p < 0.001).

Conclusion

The mean debonding time for the TM was substantially the highest, followed by the US and DP. Debonding with the LC technique required the least time. This study shows some limelight towards the effectiveness of the LC method as it is the least time-consuming technique.

Visualizing and Quantifying Wettability Alteration by Silica Nanofluids

An aqueous suspension of silica nanoparticles or nanofluid can alter the wettability of surfaces, specifically by making them hydrophilic and oil-repellent under water. Wettability alteration by nanofluids has important technological applications, including for enhanced oil recovery and heat transfer processes. A common way to characterize the wettability alteration is by measuring the contact angles of an oil droplet with and without nanoparticles. While easy to perform, contact angle measurements do not fully capture the wettability changes to the surface. Here, we employed several complementary techniques, such as cryo-scanning electron microscopy, confocal fluorescence and reflection interference contrast microscopy, and droplet probe atomic force microscopy (AFM), to visualize and quantify the wettability alterations by fumed silica nanoparticles. We found that nanoparticles adsorbed onto glass surfaces to form a porous layer with hierarchical micro- and nanostructures. The porous layer can trap a thin water film, which reduces contact between the oil droplet and the solid substrate. As a result, even a small addition of nanoparticles (0.1 wt %) lowers the adhesion force for a 20 μm sized oil droplet by more than 400 times from 210 ± 10 to 0.5 ± 0.3 nN as measured by using droplet probe AFM. Finally, we show that silica nanofluids can improve oil recovery rates by 8% in a micromodel with glass channels that resemble a physical rock network.

The Influence of Different Surface Cleansing Agents on Shear Bond Strength of Contaminated Lithium Disilicate Ceramic: An In Vitro Study

Materials and Methods

Seventy LDS specimens were randomly divided into seven groups. The first group was noncontaminated surface (PC). The six other groups were contaminated with the saliva and silicone disclosing medium and treated with no surface cleansing agent (NC); phosphoric acid (PO); Ivoclean (IV); sodium hydroxide solution (NA); Restorative Cleansing Agent (RC); and hydrofluoric acid (HF). Then, LDS specimens were cementated with Panavia V5 to resin composite rod. Each specimen was subjected to an SBS test. The modes of failure was inspected under light microscope. The surface element of each group was examined by SEM-EDS.

Results

The results were analyzed with one-way ANOVA and Tamhane's T2. The mean SBS value of NC was significantly lower than others (p < 0.05), and HF was significantly higher than others (p < 0.05). However, PC, PO, IV, NA, and RC were not significantly different from each other (p > 0.05). The mode of failure was mostly adhesive failure in every group. The surface showed similar amount of elements in every group.

Conclusions

The SBS of LDS was reduced by saliva and silicone disclosing medium contamination which can be restored using acid- and alkaline-based surface cleansing agents before the cementation procedure.

Examining the effects of acid etching duration on the bond strength between two CAD/CAM materials and one composite resin

This study aimed to evaluate the effect of three hydrofluoric acid (HF) etching periods on the micro-tensile bond strength between two CAD-CAM ceramic systems [Vita Suprinity (VS) and feldspathic CEREC blocs (CB)] and a composite resin. The ceramics were categorized into six groups based on the surface conditioning protocol used, as follows: G1: CB-HF 5% for 20 s; G2: CB-HF 5% for 40 s; G3: CB-HF 5% for 60 s; G4: VS-HF 5% for 20 s; G5: VS-HF 5% for 40 s; G6: VS-HF 5% for 60 s. Scotchbond Universal was applied onto the pretreated ceramic surfaces and covered with Filtek Z350 XT composite resin. After 24 h, the specimens were cut into microbars (n = 16) and a micro-tensile bond strength test (μTBS) was carried out. An optical microscope was used to examine the fractured microbars. The results showed statistically significant differences between the factors tested (p < 0.01). Moreover, the mean MPa of G1(17.27), G2(13.03), G3(12.82), G4(15.83), G5(21.66), and G6(14.50) was seen to significantly differ. The predominant failure type observed was adhesive, and all three periods of HF etching produced satisfactory bonding between the composite resin and CB. An etching time of 40 s provided the highest μTBS value for VS.

The impact of different surface treatments on the shear bond strength of orthodontic metal brackets applied to different CAD/CAM composites

Background

To investigate the shear bond strength (SBS) of orthodontic metal brackets applied to different CAD/CAM composites treated with different surface treatments.

Material and Methods

Specimens of two CAD/CAM composites were obtained of Lava Ultimate (LU; n=60) and Brilliant Crios (BC; n=60) which were randomly separated into six subgroups (n=10) according to the surface treatment: control (CTL); sandblasting (SB); sandblasting and silane (SBSL); hydrofluoric acid (HF); hydrofluoric acid and silane (HFSL); and Monobond Etch&Prime (MEP). The mandibular central incisor metal brackets were bonded with a light-cure adhesive. The SBS data were analyzed using the two-way analysis of variance and Turkey’s test, while the adhesive remnant index (ARI) by the Kruskal–Wallis, all the significance was set at 5%.

Results

A higher SBS was found for BC in comparison with LU (p< 0.05). All the surface treatments increased the SBS in comparison with CTL (p< 0.0001). Treatment with HF, SBSL and HFSL (p> 0.05) showed a higher SBS, which was followed by MEP and SB (p> 0.05), all in comparison with CTL (p< 0.0001). For ARI, a significant effect was detected only for the surface treatment (p< 0.01), and not for CAD/CAM resin (p> 0.05). Significant differences were detected between CTL to HF, and HF to MEP, as well.

Conclusions

The SBS is highly affected by the surface treatment and also by the CAD/CAM composite. The surface treatment improves the SBS and should be encouraged when orthodontic brackets are bonded to CAD/CAM composites.

Key words:CAD/CAM composite resin, brackets, shear bond strength, surface treatment, bonding.

Optical behaviors, surface treatment, adhesion, and clinical indications of zirconia-reinforced lithium silicate (ZLS): A narrative review

OBJECTIVES

The present narrative review was focused on the optical properties, surface treatment, adhesion, and clinical indications of zirconia-reinforced lithium silicate ceramics (ZLS) for Computer-aided design / Computer-aided manufacturing (CAD/CAM) technologies.

DATA/SOURCES

A literature search was performed by 3 calibrated independent researchers on PubMed, Scopus, Embase, Google Scholar, Dynamed, and Open Grey. The criteria for inclusion were: 1) papers addressing at least one of the following variables about ZLS: optical properties, surface treatment, adhesion, and clinical indications; 2) in vitro, in silico, or in vivo studies; 3) case reports; 4) systematic reviews. The exclusion criteria were: 1) animal studies; 2) non-dental studies; 3) studies only focusing on ZLS used in the heat-pressed process.

STUDY SELECTION

98 records among in vitro studies and case reports were included.

CONCLUSIONS

Despite the promising microstructure characteristics of ZLS, increased translucency compared to lithium disilicate ceramics (LS₂) was not proven, but acceptable color changes and stability were reported. Mechanical polishing was the most effective method to reduce surface roughness. Moreover, machinability and handling of ZLS resulted harder than LS₂. Conventional acid etching procedures seemed effective in conditioning ZLS surface, but no protocol has been established yet. Besides, silane-coupling and dual-curing resin cements were recommended.

CLINICAL SIGNIFICANCE

ZLSs can be used for anterior and posterior fixed single-unit CAD/CAM restorations onto both natural teeth and implants, but do not seem to represent a viable treatment option for endocrowns onto posterior teeth or fixed dental prostheses.

Development of hydrofluoric acid-cleaned silicon nitride implants for periprosthetic infection eradication and bone regeneration enhancement

Orthopedic implant is commonly associated with occurrence or relapse of osteomyelitis. This study developed a hydrofluoric acid (HF) cleaned silicon nitride (Si₃N₄) implant Si₃N₄_AC for osteomyelitis control and established a rat tibial osteomyelitis model to evaluate its efficacy on eradicating periprosthetic infection and enhancing bone regeneration. In vitro studies revealed Si₃N₄_AC had improved biocompatibility and inhibited Staphylococcus aureus adhesion. A custom-made Si₃N₄_AC implant was prepared and inserted into the rat tibia longitudinal cavity inoculated with Staphylococcus aureus. The in vivo bacteriostatic and osteogenic efficacies of Si₃N₄_AC implant were evaluated by histological, microbiological and Micro-CT analyses and compared with implants of pure Ti and Si₃N₄ . Si₃N₄_AC implant group revealed 99.5% inhibition of periprosthetic Staphylococcus aureus compared to the osteomyelitis group after 14 days post-operation. Implant-adhering bacteria density of Si₃N₄_AC was also much lower than pure Ti and Si₃N₄. In addition, micro-CT evaluation of peri-implant bone formation under the condition of periprosthetic osteomyelitis after 30 days post-surgery confirmed the osteogenic ability of Si₃N₄_AC. Taken together, Si₃N₄_AC can be an effective orthopedic biomaterial to eradicate periprosthetic infection and enhance bone regeneration.

Impact of the Microstructure of CAD/CAM Blocks on the Bonding Strength and the Bonded Interface

PURPOSE

To investigate the relationship between the microstructure of CAD/CAM blocks and the quality of adhesion as function of the surface treatment and resin cement type.

MATERIALS AND METHODS

Two nano-ceramic composite resin CAD/CAM blocks, Lava Ultimate (LU) and Cerasmart (CS), and two Leucite-reinforced glass ceramic CAD/CAM IPS blocks, Empress^® CAD (EM) and Initial^TM LRF (IR), received either Hydrofluoric acid (HF) or sandblasting (SB) surface treatments. The blocks were then luted using two dual-cure resin cements, LinkForce (LF) and Multilink Automix (ML) with their corresponding silanes, resulting in 16 study groups. The luted blocks were then thermal-cycling (TC) for 5000 cycles and subjected to a microtensile bond strength (μTBS) test. Scanning electron microscopy (SEM) micrographs of the treated surfaces were analyzed using ImageJ software and XRD analyses were performed for the two ceramic blocks. The data obtained were submitted to Games-Howell post-hoc nonparametric test to compare combinations of groups or treatments and a linear mixed-effects model for the factors surface treatment, block type, and resin cement, together with their first-degree interactions (α = 0.05).

RESULTS

The lowest mean μTBS values were obtained with LU-HF, whereas the highest mean μTBS values were obtained with CS regardless of resin cement type and surface treatment method. IR-HF mean μTBS were significantly higher than IR-SB, EM-SB, and EM-HF. Analysis using ImageJ software demonstrated significant differences in the density and pore size after HF surface treatment.

CONCLUSIONS

The specific microstructure of each block material within the same family group impacted the micromechanical retention and the bonded interface strength.

Effect of Nd:YAG Laser with/without Graphite Coating on Bonding of Lithium Disilicate Glass-Ceramic to Human Dentin

This study evaluated the effect of different surface treatments on the tensile bond strength between lithium disilicate glass-ceramics, resin cement, and dentin. Fifty truncated cone-shape glass-ceramics were divided into five groups (n = 10): G1, control: 10% hydrofluoric acid (HF); G2, Nd:YAG laser + silane; G3, Sil + Nd:YAG laser; G4, graphite + Nd:YAG laser + Sil; and G5, graphite + Sil + Nd:YAG laser. Fifty human third-molars were cut to cylindrical shape and polished to standardize the bonding surfaces. The glass-ceramic specimens were bonded to dentin with a dual-cured resin cement and stored in distilled water for 24 h at 37ºC. Tensile testing was performed on a universal testing machine (10 Kgf load cell at 1 mm/min) until failure. The bond strength values (mean ± SD) in MPa were G1 (9.4 ± 2.3), G2 (9.7 ± 2.0), G3 (6.7 ± 1.9), G4 (4.6 ± 1.1), and G5 (1.2 ± 0.3). Nd:YAG laser and HF improve the bond strength between lithium disilicate glass-ceramics, resin cement, and dentin. The application of a graphite layer prior to Nd:YAG laser irradiation negatively affects this bonding and presented inferior results.

Chemical surface modification of lithium disilicate needles of a silica-based ceramic after HF-etching and ultrasonic bath cleaning: Impact on the chemical bonding with silane

OBJECTIVE

Recommendations to obtain the best bonding to silica-based ceramics are to prepare its surface by hydrofluoric-acid HF etching and regular application of a silane. This study investigated how the HF-etching following by ultrasonic water bath cleaning (recommended protocol to improve the bonding with a composite resin), modifies the surface chemistry of a lithium disilicate glass-ceramic and impacts the chemical bonding with silane.

METHODS

Lithium disilicate glass-ceramic discs (IPS Emax Press, Ivoclar Vivadent) were mirror polished, etched with 9% HF for 20 s and rinsed 1 min under water. Two post-etching cleaning were compared: (1) no additional cleaning and (2) immersion in water ultrasonic bath for 4 min. Morphology evolution of the surfaces was carried out by scanning electron microscopy. Chemical changes were studied using X-ray Photoelectron Spectroscopy and Nano Auger Electron Spectroscopy analyses. Identification of the compounds formed with fluorine was based on by High Resolution Transmission Tlectronic Microscopy .

RESULTS

Residues left on the surface of the discs after etching, the fluorine salts, were eliminated after the ultrasonic bath cleaning. However, analyses showed presence of fluorine on the lithium disilicate needles associated among others with the lithium. HR-TEM validates the presence of Li₂SiF₆ crystallized phased. A mechanism to explain silane bonding when Li₂SiF₆ phase is formed on the Li₂Si₂O₅ needles, is proposed.

SIGNIFICANCE

HF-etching leads to the formation of lithium and fluorine contain LiSi₂F₆ nano-precipitates on the Li₂Si₂O₅ needles which helps to improve the bonding with silane.

Effect of Hydrofluoric Acid Surface Treatments on Surface Roughness and Three-Point Flexural Strength of Suprinity Ceramic

Objectives

This study aimed to evaluate the effects of hydrofluoric acid (HF) concentration and etching time on the surface roughness (SR) and three-point flexural strength of Suprinity and to analyze the surface elements before and after etching.

Materials and Methods

To measure the SR, 70 specimens of Suprinity (2×4×5mm³) were assigned to seven groups (n=10). Six groups were etched for 20, 60, and 120 seconds with 5% and 10% HF and 7th group was the control group. Specimens were evaluated using atomic force microscopy (AFM). One specimen from each group was used to analyze the surface elements using scanning electron microscopy (SEM). For measuring the three-point flexural strength, 60 specimens were divided into six groups (n=10) and etched as previously described. The flexural strength was measured using a universal testing machine. T-test, one-way analysis of variance (ANOVA), and two-way ANOVA were used for statistical analyses (P<0.05).

Results

The 10% concentration of HF caused higher SR compared to the 5% HF. The effect of HF concentration on the flexural strength was significantly different in the 20- and 60-second etching groups. Different etching times had no significantly different effect on the SR. With 5% HF, the flexural strength was significantly higher for 20-second etching time than for the etching times of 60 and 120 seconds. With 10% HF, there was a significant difference in flexural strength between etching times of 20 and 120 seconds. The atomic percentage (at%) of silica was enhanced by increasing the etching time.

Conclusion

The best surface etching protocol comprises 10% HF used for 20 seconds.

Incorporation of Hybrid Nanomaterial in Dental Porcelains: Antimicrobial, Chemical, and Mechanical Properties

Biofilm formation on biomaterials is a challenge in the health area. Antimicrobial substances based on nanomaterials have been proposed to solve this problem. The aim was to incorporate nanostructured silver vanadate decorated with silver nanoparticles (β-AgVO3) into dental porcelains (IPS Inline and Ex-3 Noritake), at concentrations of 2.5% and 5%, and evaluate the surface characteristics (by SEM/EDS), antimicrobial activity (against Streptococcus mutans, Streptococcus sobrinus, Aggregatibacter actinomycetemcomitans, and Pseudomonas aeruginosa), silver (Ag+) and vanadium (V4+/V5+) ions release, and mechanical properties (microhardness, roughness, and fracture toughness). The β-AgVO3 incorporation did not alter the porcelain's components, reduced the S. mutans, S. sobrinus and A. actinomycetemcomitans viability, increased the fracture toughness of IPS Inline, the roughness for all groups, and did not affect the microhardness of the 5% group. Among all groups, IPS Inline 5% released more Ag+, and Ex-3 Noritake 2.5% released more V4+/V5+. It was concluded that the incorporation of β-AgVO3 into dental porcelains promoted antimicrobial activity against S. mutans, S. sobrinus, and A. actinomycetemcomitans (preventing biofilm formation), caused a higher release of vanadium than silver ions, and an adequate mechanical behavior was observed. However, the incorporation of β-AgVO3 did not reduce P. aeruginosa viability and increased the surface roughness of dental porcelains.

Influence of Low-Pressure Plasma on the Surface Properties of CAD-CAM Leucite-Reinforced Feldspar and Resin Matrix Ceramics

The introduction of new ceramic materials for dental restorations is currently a reality; however, little information is available on their surface treatment for the bonding process. Furthermore, surface treatment with plasma on ceramic materials has been recently introduced, although not many studies are available. The aim of this study was to evaluate the surface properties of a leucite-reinforced feldspar ceramic (LIC) and resin matrix ceramic (RMC) after low-pressure plasma treatment. From each material, 48 discs were prepared and subject to surface treatment. The LIC group was treated by hydrofluoric acid (HF) (LIC-HF), plasma with oxygen (LIC-O2), and plasma with argon (LIC-Ar). The RMC group was treated by sandblasting with alumina (RMC-SB), plasma with oxygen (RMC-O2), and plasma with argon (RMC-Ar). The groups whose surfaces were not subjected to treatment were considered as the control group. Surface wettability and roughness was analyzed. The results showed significant differences among the treatments for both ceramics regarding wettability and roughness. Plasma treatments increased the wettability and had a very low effect on the roughness. Plasma treatments achieved similar values for both surface properties in each ceramic group with no differences between both treatments. Plasma treatment seems to be a promising alternative for ceramic surface treatments since it increased the surface energy of the ceramics analyzed and hardly affects the roughness. Further studies are necessary to evaluate the effect of plasma treatment on the bond strength of ceramics.

Effect of different surface treatments and multimode adhesive application on the Weibull characteristics, wettability, surface topography and adhesion to CAD/CAM lithium disilicate ceramic

This paper aims to evaluate the effect of different surface treatments on surface topography, wettability, and shear bond strength of resin cement to glass ceramic.

Effect of prolonged application of single-step self-etching primer and hydrofluoric acid on the surface roughness and shear bond strength of CAD/CAM materials

This in vitro study aimed to assess the influence of different concentrations and durations of hydrofluoric acid (HF) and Monobond Etch & Prime (MEP) etching on the surface roughness (R_a ) of different CAD/CAM materials and on the shear bond strength (SBS) of a self-adhesive resin bonded to the materials. Seventy specimens of hybrid ceramic, leucite-based glass-ceramic, lithium disilicate glass-ceramic, and zirconia-reinforced lithium silicate glass-ceramic were prepared and divided into seven groups according to the surface treatments: Control (C); MEP etching for 60 (MEP₆₀ ) and 120 (MEP₁₂₀ ) s; 5% HF etching for 60 (HF-5%₆₀ ) and 120 (HF-5%₁₂₀ ) s; 9.5% HF etching for 60 (HF-9.5%₆₀ ) and 120 (HF-9.5%₁₂₀ ) s. The R_a was measured using a 3D profilometer. All groups were treated with a universal primer except for the C, MEP₆₀ , and MEP₁₂₀ groups. A self-adhesive resin cement was bonded to all specimens, and the bond strengths were measured using a universal testing machine. All surface treatments increased both R_a and SBS values compared to the control in each material. Neither the duration of surface treatments nor the HF acid concentrations had a statistically significant effect on SBS. Within the limitations of this experimental study, it can be concluded that Monobond Etch & Prime may be a preferable method to achieve high 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 potassium hydrogen difluoride in zirconia-to-resin bonding

The objective of this study was to compare potassium hydrogen difluoride (KHF₂) etching for zirconia with commonly used surface roughening and chemical bonding methods (silane, MDP-monomer primer) for resin-based luting cement bonding to zirconia. Zirconia specimens were divided into six groups (n=10) according to surface treatment and bonding procedures, with and without thermocycling (6,000 cycles, 5-55ºC): 1) air-borne particle abrasion with alumina+MDP-monomer (ABP), 2) air-borne particle abrasion with silica-coated trialuminium trioxide+silane (ABPR-S) and 3) KHF₂ etching+silane (ETC). Surface roughness and bond strength (SBS-test) for dry and thermocycled specimens were measured. SBS did not vary statistically between the dry groups, but thermocycling decreased the bond strengths of all the tested methods (p<0.05). After thermocycling, ABP had statistically significantly lower bond strength values compared to ABPR-S and ETC (p<0.05). Etching method with KHF₂ did not provide better bonding capacity to previously introduced and commonly adopted bonding methods.

Orthodontic Bonding: Review of the Literature

BACKGROUND

Patients seeking orthodontic treatment are increasing, and clinicians often have to place brackets on various surfaces aside from enamel. It is crucial to know what materials or instruments are required to bond brackets to each surface.

OBJECTIVE

This study aims to serve as a clinical guideline for the safest and most effective approaches taken to condition various surfaces for bonding to orthodontic brackets and provide background knowledge on the subject.

MATERIALS AND METHODS

PubMed and EBSCO databases were searched, along with the use of Google Scholar search engine, to obtain relevant articles published in English in peer-reviewed journals, from 1955 to 2020. Keywords used were Shear bond strength; Orthodontic bracket; Base design; Etching; Sandblasting; Laser; Conditioning; Enamel; Ceramic; Porcelain; Gold; Amalgam; Composite.

CONCLUSION

Even though orthophosphoric acid is the most widely used enamel conditioning agent, laser etching should be considered to avoid enamel decalcification. Hydrofluoric acid is the current standard for ceramic conditioning; however, its use intraorally should be minimized due to its toxicity. Orthophosphoric acid, CoJet-Sand air abrasion, and laser etching are viable alternatives for conditioning ceramic. Monobond Etch & Prime is toxic and should not be used intraorally. Composite can be conditioned by bur roughening, and the use of ceramic brackets is recommended. Amalgam and gold surfaces can be conditioned adequately by air abrasion. Despite the claims of many authors, the maximum shear forces that orthodontic brackets are subjected to are not 6-8 mega pascal (MPa). Further investigation is required in that regard. More in vivo studies need to be performed to confirm the in vitro results.

Fatigue performance of adhesively luted glass or polycrystalline CAD-CAM monolithic crowns

STATEMENT OF PROBLEM

Data comparing the fatigue performance of adhesively luted glass or polycrystalline ceramic systems for computer-aided design and computer-aided manufacturing (CAD-CAM) are scarce.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the fatigue performance of monolithic crowns manufactured from glass or polycrystalline CAD-CAM ceramic systems adhesively luted to a dentin analog.

MATERIALS AND METHODS

Fifty-four pairs of standardized preparations of dentin analog (NEMA Grade G10) and simplified ceramic crowns of 1.5-mm thickness were obtained with 3 ceramic materials: lithium disilicate (LD) glass-ceramic (IPS e.max CAD); zirconia-reinforced lithium silicate (ZLS) glass-ceramic (Vita Suprinity); and translucent yttrium fully stabilized polycrystalline zirconia (Trans YZ) (Prettau Anterior). The simplified crowns (n=15) were adhesively cemented onto the preparations and subjected to step-stress fatigue test (initial load of 400 N, 20 Hz, 10 000 cycles, followed by 100-N increment steps until failure). Collected data (fatigue failure load [FFL] and cycles for failure [CFF]) were submitted to survival analysis with the Kaplan-Meier and Mantel-Cox post hoc tests (α=.05) and to Weibull analysis (Weibull modulus and its respective 95% confidence interval). Failed crowns were submitted to fractography analysis. The surface characteristics of the internal surface (roughness, fractal dimension) of additional crowns were accessed, and the occlusal cement thickness obtained in each luted system was measured.

RESULTS

Trans YZ crowns presented the highest values of FFL, CFF, and survival rates, followed by ZLS and LD (mean FFL: 1740 N>1187 N>987 N; mean CFF: 149 000>92 613>73 667). Weibull modulus and cement thickness were similar for all tested materials. LD presented the roughest internal surface, followed by ZLS (mean Ra: 226 nm>169 nm>93 nm). The LD and ZLS internal surfaces also showed higher fractal dimension, pointing to a more complex surface topography (mean fractal dimension: 2.242=2.238>2.147).

CONCLUSIONS

CAD-CAM monolithic crowns of Trans YZ show the best fatigue performance. In addition, ZLS crowns also showed better performance than LD crowns.

Influence of different surface treatments and universal adhesives on the repair of CAD-CAM composite resins: An in vitro study

STATEMENT OF PROBLEM

The repairability of computer-aided design and computer-aided manufacturing (CAD-CAM) composite resins might be adversely affected by the high degree of matrix polymerization that occurs during their manufacturing process. However, information on their repairability is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the microtensile bond strength of CAD-CAM composite resins subjected to simulated repair procedures by using varying surface treatments and universal adhesives.

MATERIAL AND METHODS

Four different CAD-CAM blocks (Brilliant Crios, Lava Ultimate, Shofu Block HC, and Vita Enamic) were thermocycled (5000 times, 5/55 °C) and divided into 4 groups according to the surface treatment: control, 9% hydrofluoric acid etching, aluminum oxide airborne-particle abrasion, and tribochemical silica airborne-particle abrasion. After surface treatments, the surface roughness was measured with a nanoindenter and further examined with scanning electron microscopy. After the application of 3 different universal adhesives (Clearfil Universal Bond, Prime&Bond Universal, and Single Bond Universal), the specimens were subjected to a simulated repair process with composite resin. Bonded specimens were cut into 1 mm² beams, and microtensile bond strength values were determined until failure at a crosshead speed of 0.5 mm/min. The bond strength data were analyzed with 3-way analysis of variance, and surface roughness data were analyzed with 2-way analysis of variance tests. Pairwise analyses were performed with the Tukey test (α=.05).

RESULTS

All surface treatments effectively improved repair microtensile bond strength values compared with the control (P<.05). Aluminum oxide airborne-particle abrasion had similar mean bond strength values compared with tribochemical silica airborne-particle abrasion (P>.05). Among the CAD-CAM blocks treated with hydrofluoric acid etching, Vita Enamic had the highest mean bond strength values. The highest mean microtensile bond strength repair values with the highest cohesive failure rates were found with the silane-containing universal adhesive (Single Bond Universal).

CONCLUSIONS

Surface treatment with aluminum oxide airborne-particle abrasion and tribochemical silica airborne-particle abrasion produced successful repair results for aged resin nanoceramics, whereas hydrofluoric acid etching can be used for aged hybrid ceramic repair. Silane-containing universal adhesive reported increased bond strength. Application of universal adhesive after surface treatment is recommended to increase repair strength.