Surface characteristics of additively manufactured CoCr and Ti6Al4V dental alloys: The effects of carbon and gold thin film coatings, and alkali-heat treatment.

This study investigates the impact of surface modifications on additively manufactured CoCr and Ti6Al4V dental alloys, focusing on surface properties. Thin film carbon (C) and gold (Au) coatings, as well as alkali-heat treatment, were applied to the high- and low-polished specimens. Scanning electron microscopy (SEM) showed that thin film coatings retained the underlying surface topography, while the alkali-heat treatment induced distinct morphological changes. Energy-dispersive x-ray spectroscopy (EDS) analysis revealed that C-coating enriched surfaces with C, and Au-coating introduced detectable amounts of Au. Nevertheless, signs of coating delamination were observed in the high-polished specimens. Alkali-heat treatment led to the formation of a sodium titanate layer on Ti6Al4V surfaces, confirmed by sodium presence and Fourier transform infrared spectroscopy (FTIR) results showing carbonate bands. Surface roughness measurements with atomic force microscopy (AFM) showed that C-coating increased surface roughness in both high- and low-polished alloys. Au-coating slightly increased roughness, except for low-polished Au-coated Ti6Al4V, where a decrease in roughness was observed compared to low-polished bare Ti6Al4V, likely due to surface defects present in the latter resulting from the additive manufacturing process. Alkali-heat treatment led to a pronounced increase in roughness for both alloys, particularly for Ti6Al4V. Both thin film coatings decreased the water contact angles in all specimens in varying magnitudes, indicating an increase in wettability. However, the alkali-heat treatment caused a substantial decrease in contact angles, resulting in a highly hydrophilic state for Ti6Al4V. These findings underscore the substantial impact of surface modifications on additively manufactured dental alloys, potentially influencing their clinical performance. RESEARCH HIGHLIGHTS: Thin film coatings and chemical/heat treatment modify the surface properties of additively manufactured dental alloys. The surfaces of the alloys get rougher and more hydrophilic after alkali-heat treatment. Thin gold coatings exhibit potential adhesion challenges.

Mechanical and Plasma Electrolytic Polishing of Dental Alloys.

(1) Background: In dentistry, a reduction in surface roughness is established mostly by conventional mechanical polishing to hinder biofilm adhesion. This is time- and labor-intensive. Plasma electrolytic polishing is believed to be an effective finishing method due to the reduced treatment time and materials used for applications in dentistry. (2) Methods: Co-Cr-Mo dental alloy samples were sandblasted and prepared with either plasma electrolytic or conventional mechanical polishing. Evaluation of the polishing methods was obtained by atomic force microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. (3) Results: The sandblasted samples showed the highest surface roughness (Heraenium® Sun 991 ± 288 nm; Wironit® 1187 ± 331 nm). Our results show that with plasma electrolytic polishing, Co-Cr-Mo surfaces can be polished with a surface roughness in the nanometer range, comparable to those achieved by conventional mechanical polishing. Conventional mechanical polishing (Heraenium® Sun 134 ± 23 nm; Wironit® 114 ± 11 nm) provided lower surface roughness values compared to plasma electrolytic polishing (Heraenium® Sun 288 ± 94 nm; Wironit® 261 ± 49 nm). We anticipate our pilot study as a starting point for future studies to refine process parameters and quantitative microbiological assays. (4) Conclusions: Plasma electrolytic polishing might have a promising future for polishing dental alloys.

Identification method for dental alloy type using a cosine similarity program: A preliminary investigation.

Although dental evidence is frequently used for the identification of unidentified persons, information about the many types of alloys used in prosthetics is not utilized. If the type of alloy can be identified from a small amount of material, the scope of the search could be narrowed. In this experiment, a method was investigated for identifying the alloy type using 3 kinds of cutting points (a white point and 2 types of silicone points). Wavelength-dispersive X-ray spectroscopy (WDS) was used for elemental analysis. The elements were translated into multidimensional vectors, and the cosine similarity was calculated to compare vectors of the WDS results and vectors of the official data of alloys. According to the results, cosine similarity showed a concordance of more than 0.8. The developed program is expected to be useful as a method for identifying alloy types using only a small amount of grinding dust.

Simulating porcelain firing effect on the structure, corrosion and mechanical properties of Co-Cr-Mo dental alloy fabricated by soft milling.

This study aims at evaluating the effect of simulating porcelain firing on the microstructure, corrosion behavior and mechanical properties of a Co-Cr-Mo alloy fabricated by Metal Soft Milling (MSM). Two groups of Co-28Cr-5Mo specimens (25 × 20 × 3 mm) were prepared by MSM: The as-sintered (AS) specimens and the post-fired (PF) specimens that were subjected to 5 simulating porcelain firing cycles without applying the ceramic mass onto their surface. Phase identification by X-ray Diffraction (XRD), microstructure examination by optical microscopy and Scanning Electron Microscopy combined with Energy-Dispersive X-ray Spectroscopy (SEM/EDX), corrosion testing by cyclic polarization and chronoamperometry in simulated body fluid (SBF), the latter test accompanied by Cr3+ and Cr6+ detection in the electrolyte through the 1.5-diphenylcarbazide (DPC) method and UV/visible spectrophotometry, and mechanical testing by micro-/nano-indentation were conducted to evaluate the effect of the post-firing cycles on the properties of Co-Cr-Mo. The results were statistically analyzed by the t test (p < 0.05: statistically significant). All specimens had a mixed γ-fcc and ε-hcp cobalt-based microstructure with a dispersion of pores filled with SiO2 and a fine M23C6 intergranular presence. PF led to an increase in the ε-Co content and slight grain coarsening. Both AS and PF alloys showed high resistance to general and localized corrosion, whereas neither Cr6+ nor Cr3+ were detected during the passivity-breakdown stage. PF improved the mechanical properties of the AS-alloy, especially the indentation modulus and true hardness (statistically significant differences: p = 0.0009 and 0.006, respectively). MSM and MSM/simulating-porcelain firing have been proven trustworthy fabrication methods of Co-Cr-Mo substrates for metal-ceramic prostheses. Moreover, the post-firing cycles improve the mechanical behavior of Co-Cr-Mo, which is vital under the dynamically changing loads in the oral cavity, whereas they do not degrade the corrosion performance.

Mechanical Properties of Ti-Nb-Cu Alloys for Dental Machining Applications.

Titanium has excellent biocompatibility and good corrosion resistance and is extensively used in dental implants and denture bases. However, pure titanium lacks the strength for use in dental prostheses that require relatively high strength. We developed 15 different types of Ti-Nb-Cu alloys and investigated their alloy phases and mechanical properties, including tensile and yield strength, elongation after fracture, and Vickers hardness. The alloy phases of Ti-8%Nb-2%Cu and Ti-13%Nb-2%Cu were α + ß, while those of Ti-5%Nb-5%Cu and Ti-10%Nb-5%Cu were α + Ti2Cu. The tensile strength and hardness of these alloys were significantly higher than those of titanium; however, their elongation was less. In particular, the yield strength of these alloys was more than twice that of titanium. These differences in mechanical properties are attributable to solid-solution strengthening and precipitation strengthening. Other compositions with an alloy phase of α + ß + Ti2Cu or ß + Ti2Cu had high hardness but not high strength. These results suggest that the Ti-8%Nb-2%Cu, Ti-5%Nb-5%Cu, Ti-13%Nb-2%Cu, and Ti-10%Nb-5%Cu alloys can be applied to dental prostheses, which are subject to very high forces from accessories such as long-span bridges, clasps, implant-retained superstructures, and narrow-diameter implants.

Analytical Study Regarding the Behavior of Cr-Co and Ni-Cr in Saliva.

Background and Objectives: The interaction between dental alloys and saliva affects both its own properties and those of metallic materials. Materials and Methods: Samples made of Cr-Co and Ni-Cr were studied. It was opted for corrosion under tension, scanning electron microscopy was used to characterize the surface morphology, and the chemical composition of the surface was assessed with the help of an Energy Dispersive Spectrometer. In vitro testing of the cytotoxic impact of the study eluates was carried out by flow cytometric analysis. Results: Pitting areas appear in the mass of the Ni-Cr alloy. Nickel, Manganese, and Cobalt dissolve and go into the solution. Corrosion is superficial in the case of the Cr-Co alloy, the corrosion points are shallow, and the amount of dissolved metal is relatively small. Mostly Nickel passes into the solution, unlike Chromium and Cobalt, which remain at this level. We noticed an increase in the viability of cell cultures in the case of Cr-Co alloy and a decrease in the number of living cells (87%) for Ni-Cr alloy. Conclusions: Common alloys (Ni-Cr and Cr-Co) are prone to corrosion, because they lack structural features that would shield the alloy from corrosion agents.

Mechanical Properties and Corrosion Behavior of Thermally Treated Ti-6Al-7Nb Dental Alloy.

Ti and its alloys have the most satisfactory properties for biomedical applications due to their specific strength, high corrosion resistance, and high biocompatibility. Ti-6Al-7Nb has been approved for clinical use, proving to be a viable replacement for the Ti-6Al-4V alloy that has been used for many decades in medical applications. In our study, the Ti-6Al-7Nb alloy underwent heat treatment, was cooled in various cooling media such as mineral oil and water, and was then quenched in the oven. The microstructure was investigated, and the mechanical characterization was carried out by Vickers microhardness test. Young's modulus measurements and tensile tests were performed in order to study the effect of cooling media on the material. To study the corrosion behavior, in vitro studies were performed on the Ti-6Al-7Nb samples in simulated body conditions by using artificial saliva. It was observed that the martensitic phase changed as a function of cooling media, and a less intensive cooling medium decreases strength properties' indicators as well as hardness values. The results emphasize that the use of heat treatment improves the passive layer's resistance in the presence of artificial saliva.

Mechanical Properties of Dental Alloys According to Manufacturing Process.

The purpose of this study is to investigate the effect of the fabrication method of dental prosthesis on the mechanical properties. Casting was produced using the lost wax casting method, and milling was designed using a CAD/CAM program. The 3D printing method used the SLS technique to create a three-dimensional structure by sintering metal powder with a laser. When making the specimen, the specimen was oriented at 0, 30, 60, and 90 degrees. All test specimens complied with the requirements of the international standard ISO 22674 for dental alloys. Tensile strength was measured for yield strength, modulus of elasticity and elongation by applying a load until fracture of the specimen at a crosshead speed of 1.5 ± 0.5 mm/min (n = 6, modulus of elasticity n = 3). After the tensile test, the cross section of the fractured specimen was observed with a scanning electron microscope, and the statistics of the data were analyzed with a statistical program SPSS (IBM Corp. Released 2020. IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY, USA: IBM Corp.) and using Anova and multiple comparison post-tests (scheffe method). The yield strength was the highest at 1042 MPa at an angle of 0 degrees in the specimen produced by 3D printing method, and the elongation was the highest at 14% at an angle of 90 degrees in the specimen produced by 3D printing method. The modulus of elasticity was the highest at 235 GPa in the milled specimen. In particular, the 3D printing group showed a difference in yield strength and elongation according to the build direction. The introduction of various advanced technologies and digital equipment is expected to bring high prospects for the growth of the dental market.

Bonding behavior and chemical and mechanical properties of silver-based dental alloys.

This article presents a review of silver-based dental alloys, with a focus on their bonding behavior and their chemical and mechanical properties. The most effective pretreatment for bonding silver-based alloys involves alumina air-abrasion followed by the application of a metal adhesive primer containing both the vinyl-thione monomer and a hydrophobic phosphate monomer. Silver-based alloys are readily sulfurized, making it clinically important to limit their use to cast post and core restorations to avoid direct exposure to salivary components. Fracture of the post and core restorations can be prevented by reinforcing their mechanical properties by applying the cast joining technique with tougher metals.

The influence of laser frequency and groove distance on cell adhesion, cell viability, and antibacterial characteristics of Ti-6Al-4V dental implants treated by modern fiber engraving laser.

OBJECTIVE: Micro-nano scale surface modification of Ti-6Al-4V was investigated through the fascinated modern fiber engraving laser method. The process was performed at a high laser speed of 2000mm/s, under different laser frequencies (20-160kHz) and groove distances (0.5-50µm). METHODS: Topographic evaluations such as Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FE-SEM) were used to identify the quality and regularity of patterns. The proliferation of human osteoblast-like osteosarcoma cells (MG63) was analyzed by MTT assay for up to 72h. Also, the plate counting method was used to quantify the viability potential of the modified surface against Escherichia coli bacteria. RESULTS: The cellular viability of the sample modified at the laser frequency of 20kHz and grooving distance of 50µm increased up to 35 and 10% compared to the non-treated and control samples, respectively. In the case of the surface modification at lower grooving distances range between 0.5-50µm, the maximum laser frequency (160kHz) applied leads to lower pulse's energies and less bacterial adhesion. Otherwise, at groove distances more than 50µm, the minimum laser frequency (20kHz) applied reduces the laser pulse overlaps, increases the cell adhesion and antibacterial properties. SIGNIFICANCE: Surface modification by the fiber engraving laser process significantly enhances the cell adhesion on the surface. As a result of such roughness and cell adhesion enhancement, the surface toxicity feature diminished, and its antibacterial properties improved.

Data on bond strength of methyl methacrylate-based resin cement to dental restorative materials.

A methyl methacrylate (MMA) -based resin cement is one of the popular luting agents to bond a dental restorative material in dental treatments. Bond strength of the MMA-based resin cement with adhesive primer to each restorative material is important for clinical success in prosthodontic treatments without debonding or fracture failures of the restoration such as a dental crown and post. However, open data on the bonding properties of combined use of the MMA-based resin cement and appropriate primers is limited. This article provides data on the bond strength and fracture mode of the 4-META/MMA-TBB resin cement (MMA-based resin cement) to the restorative materials (silver alloy, gold alloy, feldspathic porcelain, and zirconia) with four types of primer. Each restorative material was applied with the adhesive primer and bonded with the MMA-based resin cement. The cement-bonded samples were subjected to a thermocycling in which the materials were immersed alternately in water baths at 5 °C and 55 °C for 10,000 cycles. The bond strength between the resin cement and each restorative material was measured by means of a conventional tensile bond strength test. The fracture modes of the examined samples were observed and determined. The measured tensile bond strengths were statistically analysed using one-way analysis of variance (ANOVA), followed by Tukey's multiple comparison test.

Functional, compositional, and regulatory analyses of imported and non-imported single dental crowns.

The aims of the study were to investigate functional and esthetic properties, the composition of the alloy, and the content of hazardous elements of single dental crowns with metal skeleton and fired porcelain. Epoxy models made from full mouth impressions taken of a patient with a crown preparation of the right maxillary first permanent molar were used for production of identical polyether impressions, which were distributed to dentists in Norway. The dentists sent the impressions to their regular dental laboratories. All 55 crowns collected were anonymized and examined. Of the crowns received, 35 were made in Norway, 12 were imported, and 8 were of unknown origin. The evaluation of functional properties revealed that 50% of the Norwegian, 42% of the imported, and 25% of the unknown-origin crowns were considered unacceptable. The composition of the alloy was not in accordance with that stated by the manufacturer for 17%, 13% and 20% of the crowns, where this information was provided. The lead content of the alloy exceeded the limit set by the ISO 22674: 2016 for 18% of the crowns in total. The statement that shall follow the work according to EU-regulations was not complete for approximately 75% of the works received.

Adhesive bonding of alumina air-abraded Ag-Pd-Cu-Au alloy with 10-methacryloyloxydecyl dihydrogen phosphate.

The aim of this paper is to study changes in the Ag-Pd-Cu-Au alloy surfaces by alumina air-abrasion process and effect of those changes on the adhesive bonding characteristic. Surface roughness, surface composition and chemical state of the alumina air-abraded alloys were analyzed by a confocal laser scanning microscope, an energy dispersive X-ray spectroscopy and an X-ray photoelectron spectroscopy. The results showed that the alumina air-abrasion changed the alloy surface by mechanical roughening, alumina remain and copper oxidation. Effect of the changes in the alloy surface on the adhesive bonding characteristic was examined by using a methyl methacrylate/tri-n-butylborane derivative (MMA/TBB) resin cement with the 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained primer. The shear bond strength test results indicated that the surface oxidation by the abrasion is the main contributor that improved the adhesive bonding rather than other effects such as mechanical roughening or alumina remain.

Removal of dental alloys and titanium attenuates trace metals and biological effects on liver and kidney.

To determine whether the potential effects on liver and kidney caused by dental alloys could be reduced or terminated by the removal of nickel-chromium (Ni-Cr) alloy, cobalt-chromium (Co-Cr) alloy, and commercially pure titanium (CP-Ti), they were placed in the cheek pouches of Syrian hamsters according to ISO 10993-10. Then, the peak/plateau and end times of trace metals in the blood were determined with or without the removal of the dental alloys. Based on these time points, the trace metals and their effects on liver and kidney were examined. We found that trace metals released from these dental alloys and titanium were accumulated transiently in the blood, liver, and kidney but had no effect on the histopathology of the liver or kidney. Although the functions of the liver and kidney were compromised, the function of these tissues seemed to be clinically acceptable compared to those in control Syrian hamsters. In addition, the apoptotic effect on renal cells was terminated by removing the Ni-Cr and Co-Cr alloys, and that on hepatocytes was also eliminated by removing the Ni-Cr alloy. In contrast, the effect of the Co-Cr alloy on hepatocytes was temporary and recovered by itself. Taken together, Ni- and Co-based dental alloys and titanium have no effect on the histopathology or function of liver and kidney. Moreover, Ni-Cr and Co-Cr alloys induce transient trace metal accumulation and apoptotic effects in liver and kidney, which can be reduced or terminated by the removal of the alloys, while CP-Ti shows favorable biocompatibility.

Investigation of the Microstructure, Hardness and Corrosion Resistance of a New 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn Dental Alloy.

Higher-noble dental alloys (Au, Ag, and Pd) are the most desirable for dentistry applications, but they are expensive. Low-noble (Ag, Pd, Cu) dental alloys are alternatives to higher-noble ones due to their lower price. In this regard, the paper supports the price lowering of dental alloy by increasing the Cu content, i.e., a new 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn dental alloy. The increasing addition of the Cu leads to a complex structure consisting of a solid solution that engulfs compounds of micrometric and nanometric sizes. The 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn has demonstrated a much better electrochemical corrosion behavior in artificial saliva compared to the Paliag and Unique White dental alloys. The improved corrosion behavior of the new alloy is supported by the diminishing of the Cu selective diffusion into the electrolyte due to its retaining into compounds and into Ag-Pd solid solution. Also, the synergic effects of Cu, Zn, In, Sn may improve the corrosion resistance, but they have strengthened the 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn matrix. The main finding addressed in the paper consists in a new 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn dental alloy with improved corrosion resistance in artificial saliva.

Evaluation of Topographical Co-Cr-Mo Alloy Surface Changes After Various Finishing Treatments.

PURPOSE: To quantify the influence of three different finishing treatments on the cobalt-chromium-molybdenum (Co-Cr-Mo) alloy surface based on stereometric analysis parameters. MATERIALS AND METHODS: Eighteen specimens were casted from an extra-hard alloy (Wironit®, BEGO, Bremen, Germany). The samples were distributed into three groups (n = 6 samples per group) dependent on different polishing techniques applied, as follows: A group, only electropolished (EP) samples; B group, after EP, an additional mechanical polishing process was applied to the surface by rubber discs and a polishing paste (RP); C group, after EP, an additional mechanical polishing process was completed by rubber discs, polishing paste and finally by a rotating deer leather wheel (RPDL). Samples were imaged by atomic force microscopy (AFM) in a contact mode, in air, at room temperature. RESULTS: The evaluation of the microtexture of the sample surface was made based on the 3-D roughness parameters. The lowest statistical surface roughness parameters were found in the RP samples, whereas the highest values were obtained from the EP samples. CONCLUSIONS: The experiments described can help manufacturers identify the most appropriate parameters and their ranges within which optimal surface characteristics can be achieved.

Human Stem Cell Responses and Surface Characteristics of 3D Printing Co-Cr Dental Material.

Recently, the selective laser melting (SLM) method of manufacturing three dimensional (3D) dental prosthetics by applying a laser to metal powder has been widely used in the field of dentistry. This study investigated human adipose derived stem cell (hADSC) behavior on a 3D printed cobalt-chrome (Co-Cr) alloy and its surface characteristics and compared them those of a nickel-chrome (Ni-Cr) alloy. Alloys were divided into four groups according to the material and manufacturing methods. Co-Cr disks were manufactured with three different methods: a conventional casting method, a metal milling method, and an SLM method. Ni-Cr disks were manufactured with a conventional casting method. The surface roughness and compositions of the disks were assessed. hADSCs were then cultured on the disks. Cell morphologies on the disks were analyzed by a field emission scanning electron microscope (FE-SEM). Cell proliferation was assessed with a bromodeoxyuridine (BrdU) assay kit. Cell viability was evaluated with a water-soluble tetrazolium salt (WST) assay kit. There were no differences in surface roughness between all groups. The cells were well attached to the disks, and morphologies of the cells were similar. The cell proliferation and viability of the Ni-Cr disks were significantly lower than the other groups. However, the Co-Cr disks showed no differences in their different fabricating methods. In conclusion, the biocompatibility of 3D printed Co-Cr alloys showed comparable results compared to that of the conventional casting method, and these alloys were more biocompatible than Ni-Cr alloys.

Chemical alteration of Ag-Pd-Cu-Au alloy surface by alumina air-abrasion and its effect on bonding to resin cement.

The goal of this study was to investigate the chemical alteration of a dental alloy surface by alumina air-abrasion and its effect on bonding to resin cement. Alumina air-abrasion was carried out on an Ag-Pd-Cu-Au alloy. The surface morphology and chemical state of the abraded alloy were characterized. The effect of the air-abrasion on the shear bond strength between the alloy and a methyl methacrylate/tri-n-butyl borane (MMA/TBB) resin cement with some primers was evaluated. The surface characterization revealed that the alumina air-abrasion mechanically roughened and chemically altered the surface. The chemical alterations had two effects: (1) abraded alumina particles remained on the alloy surface and (2) copper ions were oxidized in the alloy surface. As the result, the shear bond strength test indicated that 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained primer worked with the abraded alloy surface, whereas it did not work with the non-abraded alloy surface.

An innovative method for in-situ composition analysis of fixed metallic dental restorations.

Dental restorations made from alloys corrode during their service time. In cases of suspected toxic or allergic reactions to the corrosion products, the composition of the intraoral dental restorations has to be determined. The sample materials can be obtained intra-orally in a non-destructive manner using the chipping test. Metallic shavings are extracted with the aid of a dental stone and graphite carrier platelet, which is then transferred to an electron microscope for electro dispersive X-ray (EDX) analysis. The chipping test suffers from a rather complicated and error-prone procedure of obtaining and transferring the samples. OBJECTIVE: The objective of the present study was the validation of a simplified method for non-destructive in-situ extraction of dental alloy samples, using a newly developed dental bur made from carbon fiber reinforced polyether ether ketone (PEEK), which at the same time serves as an electrically conductive sample carrier for EDX analysis. METHODS: Fifteen burs for dental hand pieces were manufactured from carbon fiber reinforced PEEK, using two formulations. The burs were passed over precious and non-precious dental alloys with different rotation speeds. The alloy samples embedded in the burs were analyzed using EDX and compared to a control. RESULTS: The burs manufactured from PEEK containing 30% short carbon fibers proved sufficiently robust for sample extraction even from the harder non-precious metals. The results of EDX analysis were in accordance with the control,no statistical significant differences, free of contamination, and were not affected by rotation speed,higher as 20%. SIGNIFICANCE: The proposed method is valid, practical and constitutes an improvement over the traditional chipping test.

Effect of Bonding Agent on Metal-Ceramic Bond Strength between Co-Cr Fabricated with Selective Laser Melting and Dental Feldspathic Porcelain.

PURPOSE: To investigate the effect of bonding agent on the bonding strength between Co-Cr dental alloy, prepared by selective laser melting (SLM), and feldspathic porcelain. MATERIALS AND METHODS: The experiments were conducted according to ISO 9693 and the conventional protocols for the production of metal-ceramic dental restorations. After Al2 O3 air-particle abrasion, metal substrates of Co-Cr dental alloy specimens were bonded, using bonding agent (25 specimens), with dental porcelain positioned in layers (opaque, dentin, enamel). Control specimens (25) were also produced without bonding agent. Bonding strength was measured using 3-point bending tests, and the results were statistically analyzed using the t-test and Weibull statistics. Elemental (by SEM/EDS) and crystallographic analyses (by XRD) were conducted on the bonding agent, along cross sections of alloy-porcelain interfaces, and on fracture surfaces. RESULTS: Cohesive fracture occurred (on the porcelain side). The application of the bonding agent decreased the average bonding strength (from 42.27 ± 5.85 to 36.25 ± 3.26 MPa, P = 0.00006), attributed to the nonexisting reaction between the TiO2 -rich bonding agent and the Co-Cr alloy, but it increased the Weibull modulus (from 7.84 to 12.16), which reflects the reliability of the bond in the tested metal-ceramic specimens. CONCLUSIONS: Although the application of bonding agent slightly decreased the bonding strength, all the measured values of the metal-ceramic specimens produced by the SLM technique, with or without the bonding agent, are markedly higher than the minimum value required by ISO 9693 (25 MPa). Moreover, the use of bonding agent favors the increase of the Weibull modulus.