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Background: To predict the long-term performance of restorative materials in the oral environment, it is important to evaluate their resistance to chemical and mechanical degradation and to know the toxic potential of the type and amount of ions eluted from the filling material. In this study, home bleaching was applied to dental materials with different contents and it was aimed to determine the type and amount of ions released from these materials. Methods: In this study, amalgam, posterior composite resin, anterior composite resin, bulk fill composite resin, indirect composite resin, hybrid ceramic and all-ceramic were used as restorative materials. 10 specimens of each material were prepared according to the manufacturer's instructions. Each material group was divided into two subgroups as the bleached group and the control group. After bleaching, all specimens were stored in 1 ml of 75% ethanol/water solution. Solutions were renewed after 1, 14 and 28 days. The type and amount of ions released from the materials were determined using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Data were analyzed using the Friedman, Wilcoxon Signed Ranks, and Mann-Whitney U tests (α = 0.05). Results: It was determined that the amount of ions release from the restorative materials decreased over time (p < 0.05). According to the results of the Mann-Whitney U test, there was no difference between the bleaching and control groups in most of the restorative materials (p > 0.05). Conclusion: Within the limits of this study, home bleaching system does not have a significant effect on ion release from restorative materials. [ABSTRACT FROM AUTHOR]

Abstract Background To predict the long-term performance of restorative materials in the oral environment, it is important to evaluate their resistance to chemical and mechanical degradation and to know the toxic potential of the type and amount of ions eluted from the filling material. In this study, home bleaching was applied to dental materials with different contents and it was aimed to determine the type and amount of ions released from these materials. Methods In this study, amalgam, posterior composite resin, anterior composite resin, bulk fill composite resin, indirect composite resin, hybrid ceramic and all-ceramic were used as restorative materials. 10 specimens of each material were prepared according to the manufacturer’s instructions. Each material group was divided into two subgroups as the bleached group and the control group. After bleaching, all specimens were stored in 1 ml of 75% ethanol/water solution. Solutions were renewed after 1, 14 and 28 days. The type and amount of ions released from the materials were determined using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Data were analyzed using the Friedman, Wilcoxon Signed Ranks, and Mann-Whitney U tests (α = 0.05). Results It was determined that the amount of ions release from the restorative materials decreased over time (p 0.05). Conclusion Within the limits of this study, home bleaching system does not have a significant effect on ion release from restorative materials.

Abstract Background Effects of ceramic translucency, layer thickness, and substrate colour on the shade of lithium disilicate glass-ceramic restorations proved to be significant in several studies, however, quantitative, numerical results on the relationship between the colour difference and these parameters are still lacking. The purpose of this in vitro study was to quantitatively determine how the colour reproduction ability of a lithium disilicate glass-ceramic is affected by its translucency, layer thickness, and substrate colour. Methods Ceramic samples were prepared from A2 shade IPS e.max CAD blocks with high and low translucencies (HT and LT) in a thickness range of 0.5–2.5 mm (+/- 0.05 mm). Layered samples were acquired utilizing composite substrates in 9 shades; transparent try-in paste was used. The spectral reflectance of the specimens was assessed under D65 standard illumination with a Konica Minolta CM-3720d spectrophotometer. The CIEDE2000 colour difference (ΔE00) between two samples was analysed using perceptibility and acceptability thresholds set at 50:50%. Statistical analysis involved linear regression analysis and the Kruskal–Wallis test. Results An increase in the thickness of 0.5 mm reduced the ΔE00 of the HT samples to 72.8%, and that of the T samples to 71.1% (p

The purpose of this article is to illustrate the clinical and technological steps of making a fixed prosthesis, using the substative method and a combination of materials – zirconia and ceramics – which are a sure guarantee for an optimal functional restoration. Digital technologies are used more and more frequently in dental practice due to their multiple advantages: reduced working time, the use of a wide range of materials, with good mechanical resistance and longevity, high precision of prostheses, increased comfort for the patient. These digital methods can be used to create a wide range of laboratory prosthetic elements, from temporary devices to metal, ceramic, or zirconia frameworks, crowns and bridges, and partial and complete dentures. Current concepts in fixed prosthetics are increasingly oriented towards all-ceramic processes becaus metal-ceramic prostheses no longer suffice to meet the demands of patients seeking aesthetic excellence and extreme perfection.

Background: Effects of ceramic translucency, layer thickness, and substrate colour on the shade of lithium disilicate glass-ceramic restorations proved to be significant in several studies, however, quantitative, numerical results on the relationship between the colour difference and these parameters are still lacking. The purpose of this in vitro study was to quantitatively determine how the colour reproduction ability of a lithium disilicate glass-ceramic is affected by its translucency, layer thickness, and substrate colour. Methods: Ceramic samples were prepared from A2 shade IPS e.max CAD blocks with high and low translucencies (HT and LT) in a thickness range of 0.5–2.5 mm (+/- 0.05 mm). Layered samples were acquired utilizing composite substrates in 9 shades; transparent try-in paste was used. The spectral reflectance of the specimens was assessed under D65 standard illumination with a Konica Minolta CM-3720d spectrophotometer. The CIEDE2000 colour difference (ΔE00) between two samples was analysed using perceptibility and acceptability thresholds set at 50:50%. Statistical analysis involved linear regression analysis and the Kruskal–Wallis test. Results: An increase in the thickness of 0.5 mm reduced the ΔE00 of the HT samples to 72.8%, and that of the T samples to 71.1% (p < 0.0001). 7 substrates with HT and LT specimens had significantly different results from the mean (p < 0.05). A thickness of 0.5 mm is not sufficient to achieve an acceptable result at any level of translucency, while the low translucency ceramic at a thickness of 1.5 mm gave acceptable results, except for severely discoloured substrates (ND8 and ND9). Conclusions: The colour reproduction ability of lithium disilicate glass-ceramics is significantly affected by their translucency, layer thickness, and 7 substrates out of 9 substrates examined. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of universal adhesives on the long-term bond strength to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Materials and Methods: Polyethylene tubes filled with composite cement containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) were adhesively luted to 60 fully sintered Y-TZP slabs (7 x 7 x 2 mm) with or without (control) previous application of a 10-MDP-based adhesive (All Bond Universal, Bisco) - ABU; Clearfil Universal Bond Quick, Kuraray Noritake - CUB; Scotchbond Universal Adhesive, 3M Oral Care - SUA) on the zirconia surface. The bonded specimens were stored in water for 24 h, 6 months, or 1 year and subjected to microshear bond strength testing. The data were analyzed by one-way ANOVA and Tukey's test (p < 0.05). The contact angle was measured after adhesive application to evaluate surface wettability. The adhesive-treated specimens were analyzed with x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) for chemical characterization. Results: The application of a 10-MDP-based adhesive significantly improved bond strength of composite cement to zirconia when compared to the control group (no adhesive application) (p < 0.05). One-year water storage significantly decreased bond strength for ABU- and CUB-bonded specimens, but not for SUA-bonded specimens. The analysis by XPS and ToF-SIMS showed peaks of carbon, phosphorus, and silicon in all adhesive-treated specimens. Conclusions: One-year water storage affected the bond strength of composite cement to zirconia when All Bond Universal or Clearfil Universal Bond Quick were used. [ABSTRACT FROM AUTHOR]

Purpose: This systematic review aims to explore and compile the effect of adhesive luting on the mechanical properties of dental ceramics used as restorative materials. Materials and Methods: The PubMed/MEDLINE, Web of Science and Scopus databases were searched on January 31st, 2021 to select laboratory studies written in English, without publishing-date restrictions, which compared the mechanical properties of commercially available dental ceramics as restorative materials luted using adhesive vs non-adhesive strategies. A total of 20 (out of 2039) studies were eligible and included in the analysis. Two authors independently selected the studies, extracted the data and assessed the risk of bias. Mean differences (Rev-Man5.1, random effects model, a = 0.05) were obtained by comparing resistance values of adhesive and non-adhesive conditions (global analysis). Subgroup analyses were performed considering ceramic composition and aging. Results: In the global analysis, adhesive luting induced higher mechanical resistance values compared to non-adhesive luting (p = 0.01). The same effect was observed for glass and alumina ceramics (p = 0.01), but not for zirconia polycrystals (p = 0.83). Adhesive luting was favorable in both the aged and non-aged subgroup analysis (p = 0.01). High heterogeneity was found in all meta-analyses. All analyzed studies in the systematic review scored negatively for risk of bias in most of the factors considered. Conclusions: Adhesive luting reinforces the mechanical properties of dental ceramics used as restorative materials, with the exception of zirconia polycrystals. [ABSTRACT FROM AUTHOR]

This study examined how Er,Cr:YSGG laser surface conditioning affected the adhesion of lithium disilicate ceramic to the dentin tooth structure. Forty samples were divided into four groups (n=10). The first group was untreated, whereas the second was etched with hydrofluoric acid. The third group was treated for 2 minutes with a 7 W, 25 Hz Er,Cr:YSGG laser. The fourth group received the same Er,Cr:YSGG laser treatment at 5 W. The untreated group had the lowest shear bond scores. Laser-irradiated Group 3 at 7 W had a higher maximum shear bond strength than the hydrofluoric acid-etched group. The laser-irradiated groups also had a more uniform, non-invasive surface roughness pattern. The samples were tested by atomic force microscopy, scanning electron microscopy, and a universal shear bond testing machine. Surface treatment with the Er,Cr:YSSG laser at 7 W improves lithium disilicate ceramic adhesion to dentin. The laser outperforms hydrofluoric acid as the gold standard. [ABSTRACT FROM AUTHOR]

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The aim of this study was to investigate the low-temperature degradation (LTD) kinetics of tetragonal zirconia with 3 mol% yttria (3Y-TZP) dental ceramic using two degradation methods: hydrothermal degradation and immersed degradation. To study transformation kinetics, we prepared 3Y-TZP powders. We pressed these powders uniaxially into a stainless mold at 100 MPa. We then sintered the compacted bodies at intervals of 50 °C between 1300 °C and 1550 °C and immersed the specimens at various temperatures from 60 °C to 80 °C in 4% acetic acid or from 110 °C to 140 °C for the hydrothermal method. We used a scanning electron microscope (SEM) to confirm crystalline grain size and used X-ray diffraction to analyze the zirconia phase. As the sintering temperature increased, the calculated crystalline grain size also increased. We confirmed this change with the SEM image. The higher sintering temperatures were associated with more phase transformation. According to the Mehl–Avrami–Johnson equation, the activation energies achieved using the hydrothermal method were 101 kJ/mol, 95 kJ/mol, and 86 kJ/mol at sintering temperatures of 1450 °C, 1500 °C, and 1550 °C, respectively. In addition, the activation energies of the specimens immersed in 4% acetic acid were 60 kJ/mol, 55 kJ/mol, 48 kJ/mol, and 35 kJ/mol, with sintered temperatures of 1400 °C, 1450 °C, 1500 °C, and 1550 °C, respectively. The results showed that a lower sintering temperature would restrain the phase transformation of zirconia because of the smaller crystalline grain size. As a result, the rate of LTD decreased. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To compare the shear bond strength (SBS) of orthodontic brackets bonded to three different types of ceramic surfaces (feldspathic, lithium disilicate, and zirconium) using Assure® Plus All and Transbond™ XT adhesives. MATERIALS AND METHODS: The sample comprised 72 monolithic computer‑aided design and computer‑aided manufacturing (CAD/CAM) ceramic samples that were randomly divided into six groups of 12 specimens each. Three groups (G1, feldspathic ceramic; G3, lithium disilicate ceramic; G5, zirconium surfaces) were bonded to metal brackets using Assure® Plus All adhesive, whereas the remaining three groups (G2, G4, G6; with the ceramic type in the same order as that in the previous groups) were bonded to metal brackets using Transbond™ XT. The samples were then subjected to 10,000 thermocycles. The SBS was calculated using the shear tests. The site of bonding failure was classified using the adhesive remnant index (ARI) score. One‑way analysis of variance (ANOVA) and Kruskal–Wallis tests were used for statistical analyses at a 5% significance level. RESULTS: Statistically significant differences were observed in the mean SBS values of the groups (P < 0.001). The mean SBS for G6 (zirconium plus Transbond™ XT) (2.52 MPa) was significantly lower than that for all other groups. Furthermore, statistically significant differences were found in the ARI score distribution among the groups (P < 0.001). Differences were identified between G6 and G3 (lithium disilicate Plus All Assure® Plus All) and G5 (zirconium plus Assure® Plus All). CONCLUSIONS: The mean bonding strength of brackets with Assure® Plus All was higher than that with Transbond™ XT for all three types of ceramics. However, all groups, except the zirconium plus Transbond™ XT group, showed acceptable bonding strength for orthodontic purposes. The application of hydrofluoric acid followed by silane and finally the Assure® Plus All adhesive system is adequate for bonding brackets to any of the ceramic tested surfaces. [ABSTRACT FROM AUTHOR]

Chipping of implant-supported molar crowns (iSCs) is a frequently reported complication. This study aimed to investigate the in-vitro aging and fracture resistance of iSCs with a CAD/CAM resin composite veneer structure fabricated with the Rapid Layer Technology (RLT) approach. Eight iSCs per group were fabricated by using two different CAD/CAM resin composites (Shofu Block HC: SH; Grandio blocs: GB) for veneer structures, and zirconia (ZrO2), polyetheretherketone (PEEK), and cobalt–chromium (CoCr; control) as framework materials. The surfaces to be bonded were sandblasted, cleaned in an ultrasonic bath, and a coupling agent was applied. A self-adhesive resin luting composite was used to adhesively lute the veneer structures to the frameworks. The crowns were semi-permanently cemented to the abutments. After storage in deionized water, iSCs were loaded in a chewing simulator (TCML, 10,000 thermal cycles 5 °C to 55 °C for 20 s, 1.2 million, loading force 50 N). Four ZrO2 and one CoCr crown did not survive the TCML. The fracture force was determined after 24 h storage in deionized water and yielded values of ≥974 N. Lowest fracture forces were yielded in the PEEK-SH group in comparison to CoCr or ZrO2 groups (p ≤ 0.031). For identical framework materials, no significant influence of the veneering material was observed. All PEEK-GB frameworks fractured, and chipping occurred for ZrO2-SH and all CoCr frameworks. PEEK-SH and ZrO2-GB presented both chipping and framework fractures. Within the limitations of this in-vitro study, the RLT with a CAD/CAM resin composite veneer structure might be a promising approach to veneer iSCs. Yet, the choice of the CAD/CAM resin composite and of the framework material determine the fracture resistance. [ABSTRACT FROM AUTHOR]

Objective: The aim of this in vitro study is to evaluate the masking ability of polymer‐infiltrated ceramic‐network materials (PICN) with different translucencies and thicknesses on multiple types of substrates. Materials and Methods: Ceramic samples were prepared of VITA ENAMIC blocks in two different translucencies (2M2‐T, 2M2‐HT) in a thickness range of 0.5–2.5 mm (±0.05 mm). Layered specimens were obtained using composite substrates in nine shades and transparent try‐in paste. Spectral reflectance of specimens was measured using a Konica Minolta CM‐3720d spectrophotometer and D65 standard illumination. CIEDE2000 color difference (ΔE00) between two samples was evaluated using 50%:50% perceptibility and acceptability thresholds. Specular component of the reflection was examined with Specular Component Excluded (SCE) and Included (SCI) settings. Statistical evaluation was performed by linear regression analysis, Kruskal–Wallis test, and multiplicative effect analysis. Results: An increase in thickness of 0.5 mm reduces ΔE00 of HT samples to 73.5%, of T samples to 60.5% (p < 0.0001). Five substrates with HT specimens, and three substrates with T specimens had significantly different results from average (p < 0.05). There is a significant difference between SCE and SCI data depending on the wavelength (p < 0.0001). Conclusions: Masking ability of PICN materials is influenced by the thickness and translucency of the ceramic, and by the substrate. Reflection of the examined PICN material is characterized by both diffuse and specular reflection. Clinical Significance: Although PICN materials have been available on the market for 10 years now, there is a lack of information regarding their masking ability. Acquiring in‐depth data and thereby practical experience of the factors affecting the esthetics of PICN materials is essential for creating perfectly lifelike restorations. [ABSTRACT FROM AUTHOR]

Conventional surface roughening treatments used for silica-based ceramics in order to improve subsequent adhesion become unreliable for zirconia ceramics. Laser conditioning can be a good alternative. The purpose of this in vitro study was to compare conventional (macro) shear bond strength (SBS) values obtained between resin composite and zirconium oxide ceramic samples grouped according to different micromechanical treatments received, and examine differences in surface roughness. One-hundred and fifty disks of sintered zirconia were randomly divided into 5 groups and roughened as follows: (1) Group NOT, no surface treatment; (2) Group APA, abraded with 50-μm aluminum-oxide (Al2O3) particles; (3) Group TBS, abraded with 30-μm aluminum-oxide particles covered with silica; (4) Group CO2, irradiated with a CO2 laser which emitted in continuous wave mode at 3 W of power; and (5) Group FEM, irradiated with a pulsed femtosecond laser, with an incident energy of 10 μJ, a frequency of 1000 Hz, and a fluence of 1.3 kJ/cm2. All surfaces were treated with a MDP-containing adhesive/silane coupling agent mixture upon which were prepared and light polymerized composite resin cylinders. Shear bond strength was measured and samples were observed by scanning electron microscopy (SEM). Statistically significant differences (p < 0.05) were found among all groups, except between CO2 and FEM, which showed the highest adhesion values (15.12 ± 2.35 MPa and 16.03 ± 2.73 MPa). SEM revealed differences in surface patterns. CO2 laser irradiation can be an alternative to sandblasting, although it could also weaken the ceramic. Suitable surface patterns on zirconia ceramics can be obtained with ultrashort pulsed radiation emitted by a pulsed femtosecond laser. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate whether the composite cement tensile bond strength is affected by different firing cycles or etching conditions on zirconium-incorporated lithium-silicate glass ceramics. Materials and Methods: Specimens (N=53) were prepared from blocks of zirconium-incorporated lithium-silicate glass ceramic (ZLS, Dentsply Sirona) with specimen dimensions of 12.5 x 14 x 2 mm (L x W x H, respectively). The specimens were subjected to different firing cycles and etching conditions. They were subsequently cemented onto titanium rods (grade V Ti-alloy, 4.8 mm in diameter, and 25.4 mm in length) with self-adhesive composite cement (TheraCem, Bisco), and then tested for tensile bond strength (TBS). The least-square means linear regression model was used to analyze the effects on TBS using JMP Pro 14 (SAS) and the post-hoc Tukey test with α=0.05. Results: The TBS was significantly affected by etching duration (p<0.001) and firing cycles (p<0.001), but was not significantly affected by etchant concentration (p=0.31). The highest TBS peak (4.83 MPa) on the fit curve was observed at 45 s of etching time. The lowest TBS was observed at 20 s (3.02 ± 0.28 MPa) etching time. In terms of firing cycles, 1 firing cycle (4.00 ± 0.71 MPa) provided the highest TBS. In contrast, the lowest TBS was observed for as-machined ZLS specimens but without a firing step (3.29 ± 0.53 MPa). Conclusions: Changing the etching time and firing conditions of the specimens had a significant effect on the compos- ite cement tensile bond strength to zirconium-incorporated lithium-silicate glass ceramic. In contrast, etching the specimens with different acid concentrations, 5% or 9.6% of HF, did not significantly change the composite cement tensile bond strength. [ABSTRACT FROM AUTHOR]

Purpose: To systematically review studies that investigated the consequences of various polishing protocols on the mechanical properties of zirconia. The effects on the roughness and crystalline phase transformation were also evaluated. Materials and methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) was followed. The electronic searches were conducted via OVID MEDLINE (R) and Scopus for publications between 1996 and August 2022. The search strategy was limited to full texts in the English language and in vitro studies. The influences on flexural strength, hardness, fracture strength, fracture toughness, wear resistance, roughness and phase transformation were collected. Various methodologies to measure these properties were also outlined and compared. The risk of bias for included studies was evaluated according to a modified Consolidated Standards of Reporting Trials (CONSORT) checklist. Results: After removing duplicates, the systematic search identified a total of 419 studies. Nineteen studies satisfied the inclusion criteria and were selected for final analysis. Fifteen of the included studies observed the changes in surface roughness along with the mechanical properties and ten studies detected the tetragonal (T) to monoclinic (M) phase transformation. Eight studies also investigated the change in properties after polishing the ground surface. Testing parameters were not consistent among studies due to the varying methods. Conclusions: To a certain extent, polishing influences the strength, hardness, toughness and wear resistance. The damage in some mechanical properties, as well as the roughened surface, from grinding can be restored via an appropriate polishing treatment. The polishing process itself barely induces the transition from the tetragonal to monoclinic phase of zirconia, while this commonly occurs after grinding. If the subsequent polishing is adequate, the transformed monoclinic phase can be eliminated with the removal of the outermost surface layer. In dentistry, polishing is an imperative step to maintain the superior functions and service life of zirconia for patients.

Objectives: To investigate the clinical performance of chairside fabricated tooth-supported posterior single crowns from lithium disilicate ceramic. Materials and methods: Thirty-four crowns (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein) were inserted between 2006 and 2007 and again evaluated after 15 years. Survival and success rates were calculated according to Kaplan–Meier, and the quality of the crowns was evaluated by using modified United States Public Health (USPHS) criteria. Results: Twenty-two crowns were available for recall; six patients were defined as dropouts. The mean observation period was 15.2 years (± 0.2). Six failures occurred (1 technical/5 biological) resulting in a survival rate of 80.1%. The success rate was 64.2%. The roughness of the crowns increased (p = 0.021) and the majority of adhesive gaps were discolored (p = 0.001) in comparison to baseline. The color, tooth, and crown integrity remained stable over the follow-up period (p ≥ 0.317). Conclusion: The fabrication of tooth-supported lithium disilicate crowns using a chairside approach yielded acceptable long-term survival and success rates. Due to discoloration, the long-term use of dual-cure self-adhesive resin cements might result in unpleasing esthetic results. Clinical relevance: The performance of posterior lithium disilicate single crowns revealed excellent to good clinical quality and an acceptable number of events after 15 years of clinical service. [ABSTRACT FROM AUTHOR]

Zirconia, a crystalline oxide of zirconium, holds good mechanical, optical, and biological properties. The metal-free restorations, mostly consisting of all-ceramic/zirconia restorations, are becoming popular restorative materials in restorative and prosthetic dentistry choices for aesthetic and biological reasons. Dental zirconia has increased over the past years producing wide varieties of zirconia for prosthetic restorations in dentistry. At present, literature is lacking on the recent zirconia biomaterials in dentistry. Currently, no article has the latest information on the various zirconia biomaterials in dentistry. Hence, the aim of this article is to present an overview of recent dental zirconia biomaterials and tends to classify the recent zirconia biomaterials in dentistry. This article is useful for dentists, dental technicians, prosthodontists, academicians, and researchers in the field of dental zirconia. [ABSTRACT FROM AUTHOR]

Introduction: Marginal adaptation highly affects the long-term success of crowns. This study intends to investigate the marginal adaptation of monolithic zirconia and veneered zirconia crowns. Methods: Based on our searches in PubMed and Google Scholar from 2011 to 2020, 22 articles were obtained, and after studying their full-texts. Five articles that were most related to our subject were selected. Results: In almost all articles, the greatest mean marginal gap value was recorded for monolithic zirconia, whereas layered zirconia crowns demonstrated the lowest mean marginal gap values. Conclusion: Based on finding of the current study, monolithic zirconia restorations had a superior marginal adaptation than layered zirconia restorations. However, clinically both restorations have an acceptable marginal fit

Purpose: To systematically review studies that investigated the consequences of various polishing protocols on the mechanical properties of zirconia. The effects on the roughness and crystalline phase transformation were also evaluated. Materials and methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) was followed. The electronic searches were conducted via OVID MEDLINE (R) and Scopus for publications between 1996 and August 2022. The search strategy was limited to full texts in the English language and in vitro studies. The influences on flexural strength, hardness, fracture strength, fracture toughness, wear resistance, roughness and phase transformation were collected. Various methodologies to measure these properties were also outlined and compared. The risk of bias for included studies was evaluated according to a modified Consolidated Standards of Reporting Trials (CONSORT) checklist. Results: After removing duplicates, the systematic search identified a total of 419 studies. Nineteen studies satisfied the inclusion criteria and were selected for final analysis. Fifteen of the included studies observed the changes in surface roughness along with the mechanical properties and ten studies detected the tetragonal (T) to monoclinic (M) phase transformation. Eight studies also investigated the change in properties after polishing the ground surface. Testing parameters were not consistent among studies due to the varying methods. Conclusions: To a certain extent, polishing influences the strength, hardness, toughness and wear resistance. The damage in some mechanical properties, as well as the roughened surface, from grinding can be restored via an appropriate polishing treatment. The polishing process itself barely induces the transition from the tetragonal to monoclinic phase of zirconia, while this commonly occurs after grinding. If the subsequent polishing is adequate, the transformed monoclinic phase can be eliminated with the removal of the outermost surface layer. In dentistry, polishing is an imperative step to maintain the superior functions and service life of zirconia for patients. [ABSTRACT FROM AUTHOR]

Zirconia, a crystalline oxide of zirconium, holds good mechanical, optical, and biological properties. The metal-free restorations, mostly consisting of all-ceramic/zirconia restorations, are becoming popular restorative materials in restorative and prosthetic dentistry choices for aesthetic and biological reasons. Dental zirconia has increased over the past years producing wide varieties of zirconia for prosthetic restorations in dentistry. At present, literature is lacking on the recent zirconia biomaterials in dentistry. Currently, no article has the latest information on the various zirconia biomaterials in dentistry. Hence, the aim of this article is to present an overview of recent dental zirconia biomaterials and tends to classify the recent zirconia biomaterials in dentistry. This article is useful for dentists, dental technicians, prosthodontists, academicians, and researchers in the field of dental zirconia.

The aim of this study was to investigate the low-temperature degradation (LTD) kinetics of tetragonal zirconia with 3 mol% yttria (3Y-TZP) dental ceramic using two degradation methods: hydrothermal degradation and immersed degradation. To study transformation kinetics, we prepared 3Y-TZP powders. We pressed these powders uniaxially into a stainless mold at 100 MPa. We then sintered the compacted bodies at intervals of 50 °C between 1300 °C and 1550 °C and immersed the specimens at various temperatures from 60 °C to 80 °C in 4% acetic acid or from 110 °C to 140 °C for the hydrothermal method. We used a scanning electron microscope (SEM) to confirm crystalline grain size and used X-ray diffraction to analyze the zirconia phase. As the sintering temperature increased, the calculated crystalline grain size also increased. We confirmed this change with the SEM image. The higher sintering temperatures were associated with more phase transformation. According to the Mehl–Avrami–Johnson equation, the activation energies achieved using the hydrothermal method were 101 kJ/mol, 95 kJ/mol, and 86 kJ/mol at sintering temperatures of 1450 °C, 1500 °C, and 1550 °C, respectively. In addition, the activation energies of the specimens immersed in 4% acetic acid were 60 kJ/mol, 55 kJ/mol, 48 kJ/mol, and 35 kJ/mol, with sintered temperatures of 1400 °C, 1450 °C, 1500 °C, and 1550 °C, respectively. The results showed that a lower sintering temperature would restrain the phase transformation of zirconia because of the smaller crystalline grain size. As a result, the rate of LTD decreased.

New monolithic multi-layered zirconia restorations are gaining popularity due to their excellent aesthetic properties. However, current knowledge of these newest multi-layer ceramics in terms of mechanical properties is scarce. Three monolithic, multi-layered zirconia materials (Katana, Kuraray Noritake, Japan) were selected for comparison: High Translucent Multi-layered zirconia (HTML), Super Translucent Multi-layered zirconia (STML) and Ultra Translucent Multi-layered zirconia (UTML). Fifteen specimens per group were cut from pre-sintered blocs in each of the four layers (L1, L2, L3, L4) and in different thicknesses (0.4 mm, 0.8 mm and 1.2 mm). Critical fracture load (Fcf) was recorded in 3-point-bending. Flexural strength (σ) in MPa, Vickers hardness (HV) in N/mm2, fracture toughness (KIc) in MPa*m1/2, Weibull Modulus (m) and characteristic Weibull strength (σw) in MPa were assessed. Statistical analysis was performed using ANOVA analysis. FS and KIc were significantly higher (p < 0.05) for Katana™ HTML (652.85 ± 143.76–887.64 ± 118.95/4.25 ± 0.43–5.01 ± 0.81) in comparison to Katana™ STML (280.17 ± 83.41–435.95 ± 73.58/3.06 ± 0.27–3.84 ± 0.47) and UTML (258.25 ± 109.98–331.26 ± 56.86/2.35 ± 0.31–2.94 ± 0.33), with no significant differences between layers and layer thicknesses. The range of indications should be carefully considered when selecting the type of monolithic zirconia for fabrication of dental restorations, as materials widely differ in mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract This study evaluated how the background (white or gray) affects the color parameter measurements and color difference calculations (∆Eab and ∆E00) of dental ceramics. Disc-shaped feldspathic ceramic specimens were prepared with two shades (enamel and dentin) and stained in red wine (7-day immersion). A spectrophotometer was used to perform color measurements (CIEL*a*b* coordinates) over gray and white backgrounds after the specimen preparation and after staining. The color difference was calculated with CIEDE2000 (ΔE00) and CIELAB (ΔEab) formulae. Initial L*a*b* coordinates, ΔE00, and ΔEab data were analyzed with t-tests separately for each ceramic shade. White background led to higher values of L* and b* coordinates from the enamel shade, and of L*, a*, and b* coordinates from the dentin shade. However, ΔE00 and ΔEab results from white and gray backgrounds were similar in both ceramic shades. Therefore, background color did not affect the color difference results of the slightly stained feldspathic ceramic samples.

Aims and Objectives: This study evaluated the surface roughness of three dental ceramics after polishing with three types of extraoral ceramic polishing sets. Materials and Methods: One hundred and twenty specimens were fabricated from feldspathic porcelain, lithium disilicate, and zirconia ceramics. The specimens were randomly allocated into four subgroups (n = 10). Group one was glazed (control) and the other three groups were ground using fine diamond burs and then sequentially polished by two rubber wheels from three polishing sets: feldspathic porcelain, lithium disilicate, and zirconia sets. The surface roughness measurement was performed with a profilometer and the surfaces were analyzed using scanning electron microscopy. Elemental compositions of three polishing sets were examined using x-ray powder diffraction. The surface roughness values of three polishing systems were compared by one-way analysis of variance with Dunnett's T3 post hoc test. The significance level was set at p < 0.05. Results: There was no significant difference in surface roughness when polishing ceramics with the lithium disilicate and zirconia polishing sets. In addition, those two sets provided lower roughness compared with the feldspathic porcelain polishing set and glazing. The main component of all polishing wheels was carbon, and only zirconia polishing wheel had more additional trace elements, which were titanium and silica. Conclusion: Lithium disilicate and zirconia extraoral polishing sets achieved superior results compared to feldspathic polishing set and glazing. [ABSTRACT FROM AUTHOR]

Introduction: Marginal adaptation highly affects the long-term success of crowns. This study intends to investigate the marginal adaptation of monolithic zirconia and veneered zirconia crowns. Methods: Based on our searches in PubMed and Google Scholar from 2011 to 2020, 22 articles were obtained, and after studying their full-texts. Five articles that were most related to our subject were selected. Results: In almost all articles, the greatest mean marginal gap value was recorded for monolithic zirconia, whereas layered zirconia crowns demonstrated the lowest mean marginal gap values. Conclusion: Based on finding of the current study, monolithic zirconia restorations had a superior marginal adaptation than layered zirconia restorations. However, clinically both restorations have an acceptable marginal fit [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction: This article gives a brief history of dental ceramics and discusses recent research targeted at improving ceramics for clinical usage, evaluating and selecting them, and, most importantly, their clinical performance. It has been discovered that there are strong scientific and collaborative grounds for continuing to study and enhance dental ceramic systems.

The threat of serious radiation exposures to members of the public from radiological incidents and nuclear events has led to intensive study of a number of emergency dosimetry techniques for purposes of triage. As such, a national laboratory of retrospective dosimetry was established in our institute. The purpose of this work is to provide a summary of the well-established and already implemented retrospective physical dosimetry techniques based on thermoluminescence (TL), optically stimulated luminescence (OSL) and neutron activation including their specifics. Moreover, we present some new results of the experimental work, in which we compared dosimetry potential of various dental repair materials and human teeth. At first, an overview of already established retrospective physical retrospective methods including their main features was compiled. As regards recent research, an experimental comparative study was performed under defined conditions. The materials used were aliquots prepared from both pure and repaired teeth and aliquots of unused dental ceramics of known type. Following irradiation, we compared TL and OSL curves of the materials. We also compared dosimetry characteristics of OSL signal as reproducibility, dose dependence and fading. After irradiation, the teeth aliquots of dental enamel and dentin exhibited very low OSL and TL signals compared with aliquots containing some dental repair materials or aliquots of pure dental ceramics. With a few exceptions, the OSL signal of dental enamel and dentin aliquots irradiated to 2 Gy was hardly distinguishable from OSL signal corresponding to unirradiated aliquots. In contrast, aliquots of teeth containing some dental repair material and aliquots of pure dental ceramics provided a well reproducible OSL signal exhibiting linear dose response. All the materials tested exhibited a significant fading of the OSL signal. The loss of OSL signal during the first 24 hours after irradiation was from 20 to 99% of its original value obtained immediately after the irradiation. The already established physical methods of retrospective dosimetry use a spectrum of verified materials and techniques for dose assessment in the aftermath of serious radiological incidents and nuclear events. In the comparative study, we found that the dosimetry potential of teeth in natural state is much worse compared to teeth repaired with dental ceramics or dental cement fillings. Teeth restored with dental repair materials exhibited relatively favorable dosimetry characteristics. However, they can be usable for a dose reconstruction only on condition that the main practical problems connected with fading and optical bleaching were solved. [ABSTRACT FROM AUTHOR]

Currently, a significant challenge in the fabrication of ceramic dental prostheses via vat photopolymerization lies in the utilization of slurries composed of organic monomers, which compromises environmental sustainability and impedes commercial viability. In this research, we successfully develop a low-viscosity aqueous zirconia ceramic suspension with a solid loading of 40 vol% and 20 vol% deionized waters, incorporating 3 wt% dispersant and 0.5 wt% photoinitiator for printing dental crowns using vat photopolymerization. The resulting green bodies require only water washing to remove unreacted material. The printed ceramics demonstrate an average flexural strength of 708 MPa, a relative density of 98.3 %, and a Vickers hardness of 14.7 GPa. A dental crown is ultimately fabricated with an accuracy of 92.8 %. This study demonstrates that zirconia ceramics fabricated by vat photopolymerization with aqueous suspension exhibit excellent mechanical properties and accuracy, highlighting their potential for broad applications in dental restorations through an environmentally sustainable approach. [ABSTRACT FROM AUTHOR]

Tooth wear is an inevitable process during mastication and para-functional movements. It is indispensable to find a restorative ceramic to match the wear rates between dental ceramic and natural enamel, which are usually used in clinical after surface treatment to modify surface properties. There are some researches on the wear of the teeth antagonist caused by ceramics after surface treatment, however, they mainly focus on the wear caused by zirconia and the heterogeneity of in vitro wear tests is significant, with different simulated mastication methods, resulting in complex and even contradictory conclusions. In this review, we conclude the influencing factors, summarize the existing research, and provide valuable insights for future surface treatment strategies in dental ceramics. [ABSTRACT FROM AUTHOR]

This study evaluated how the background (white or gray) affects the color parameter measurements and color difference calculations (ΔEab and ΔE00) of dental ceramics. Disc-shaped feldspathic ceramic specimens were prepared with two shades (enamel and dentin) and stained in red wine (7-day immersion). A spectrophotometer was used to perform color measurements (CIEL*a*b* coordinates) over gray and white backgrounds after the specimen preparation and after staining. The color difference was calculated with CIEDE2000 (ΔE00) and CIELAB (ΔEab) formulae. Initial L*a*b* coordinates, ΔE00, and ΔEab data were analyzed with t-tests separately for each ceramic shade. White background led to higher values of L* and b* coordinates from the enamel shade, and of L*, a*, and b* coordinates from the dentin shade. However, ΔE00 and ΔEab results from white and gray backgrounds were similar in both ceramic shades. Therefore, background color did not affect the color difference results of the slightly stained feldspathic ceramic samples. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To compare the shear bond strength (SBS) of orthodontic brackets bonded to three different types of ceramic surfaces (feldspathic, lithium disilicate, and zirconium) using Assure® Plus All and Transbond™ XT adhesives. MATERIALS AND METHODS: The sample comprised 72 monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic samples that were randomly divided into six groups of 12 specimens each. Three groups (G1, feldspathic ceramic; G3, lithium disilicate ceramic; G5, zirconium surfaces) were bonded to metal brackets using Assure® Plus All adhesive, whereas the remaining three groups (G2, G4, G6; with the ceramic type in the same order as that in the previous groups) were bonded to metal brackets using Transbond™ XT. The samples were then subjected to 10,000 thermocycles. The SBS was calculated using the shear tests. The site of bonding failure was classified using the adhesive remnant index (ARI) score. One-way analysis of variance (ANOVA) and Kruskal–Wallis tests were used for statistical analyses at a 5% significance level. RESULTS: Statistically significant differences were observed in the mean SBS values of the groups (P < 0.001). The mean SBS for G6 (zirconium plus Transbond™ XT) (2.52 MPa) was significantly lower than that for all other groups. Furthermore, statistically significant differences were found in the ARI score distribution among the groups (P < 0.001). Differences were identified between G6 and G3 (lithium disilicate Plus All Assure® Plus All) and G5 (zirconium plus Assure® Plus All). CONCLUSIONS: The mean bonding strength of brackets with Assure® Plus All was higher than that with Transbond™ XT for all three types of ceramics. However, all groups, except the zirconium plus Transbond™ XT group, showed acceptable bonding strength for orthodontic purposes. The application of hydrofluoric acid followed by silane and finally the Assure® Plus All adhesive system is adequate for bonding brackets to any of the ceramic tested surfaces.

New monolithic multi-layered zirconia restorations are gaining popularity due to their excellent aesthetic properties. However, current knowledge of these newest multi-layer ceramics in terms of mechanical properties is scarce. Three monolithic, multi-layered zirconia materials (Katana, Kuraray Noritake, Japan) were selected for comparison: High Translucent Multi-layered zirconia (HTML), Super Translucent Multi-layered zirconia (STML) and Ultra Translucent Multi-layered zirconia (UTML). Fifteen specimens per group were cut from pre-sintered blocs in each of the four layers (L1, L2, L3, L4) and in different thicknesses (0.4 mm, 0.8 mm and 1.2 mm). Critical fracture load (Fcf) was recorded in 3-point-bending. Flexural strength (σ) in MPa, Vickers hardness (HV) in N/mm2, fracture toughness (KIc) in MPa*m1/2, Weibull Modulus (m) and characteristic Weibull strength (σw) in MPa were assessed. Statistical analysis was performed using ANOVA analysis. FS and KIc were significantly higher (p < 0.05) for Katana™ HTML (652.85 ± 143.76–887.64 ± 118.95/4.25 ± 0.43–5.01 ± 0.81) in comparison to Katana™ STML (280.17 ± 83.41–435.95 ± 73.58/3.06 ± 0.27–3.84 ± 0.47) and UTML (258.25 ± 109.98–331.26 ± 56.86/2.35 ± 0.31–2.94 ± 0.33), with no significant differences between layers and layer thicknesses. The range of indications should be carefully considered when selecting the type of monolithic zirconia for fabrication of dental restorations, as materials widely differ in mechanical properties.

Objective: The purpose of this systematic review was to compare the survival and complication rates of all-ceramic restorations after a minimum follow-up time of 5 years. Data Sources: A comprehensive search of studies published from 2005 to November 2015 and listed in the PubMed/MEDLINE, Scopus, and Cochrane Library databases was performed in accordance with the PRISMA statement. Two reviewers independently analyzed the abstracts. Relevant studies were selected according to predetermined inclusion criteria. Results: Twenty-nine studies were selected for the final analysis from an initial yield of 514. Only four studies fulfilled the requirement of having a randomized design, and 25 studies were prospective with a mean follow-up period of 5 to 16 years. Overall, the 5-year complication rates were low. The most frequent complications were secondary caries, endodontic problems, ceramic fractures, ceramic chipping, and loss of retention. Conclusion: This systematic review showed that all-ceramic restorations fabricated using the correct clinical protocol have an adequate clinical survival for at least 5 years of clinical service with very low complication rates. Minor ceramic chipping and debonding did not affect the longevity of the restorations. Clinical Relevance: Long-term clinical performance of all-ceramic restorations manufactured using various ceramic systems provides clinical evidence of complications and long-term management of these restorations. Available evidence indicates the effectiveness of many ceramic systems for numerous clinical applications. Correct planning and a rigorous technical execution protocol increase clinical success. Studies of ceramic prostheses indicate more problems with ceramic failure and debonding. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of different bonding strategies on short- and long-term bis-GMA-based resin cement bond strengths to zirconia. Materials and Methods: One hundred twenty samples of fully-sintered zirconia (Prettau Zirconia) were sandblasted and randomly distributed into 5 groups (n = 24): UA: Scotchbond Universal Adhesive; SZP: Signum Zirconia Bond I + II; ZPP: Z-Prime Plus; EXP: MZ experimental primer; CO: no primer application (control). After performing these surface treatments, translucent tubes (0.8 mm diameter and 1.0 mm height) were placed on the zirconia specimens, and bis-GMA-based cement (Duo-Link) was injected into them and light cured. Specimens were tested for microshear bond strength either 24 h or 6 months (m) after water storage (37°C) and surfaces were characterized by SEM and EDX. Two-way ANOVA and Tukey's post-hoc test (p < 0.05) were used to evaluate bond strength results. Results: The mean bond strengths (MPa ± SD) were: UA=14.6 ± 4.7a (24 h); 16.0 ± 4.8a (6 m); SZP = 14.0 ± 5.4ab (24 h); 11.9 ± 2.6ab (6 m); ZPP=8.0 ± 1.8b (24 h); 8.6 ± 3.3b (6 m); EXP = 1.2 ± 0.5c (24 h); 0.6 ± 0.7c (6 m); CO=1.0 ± 1.2c (24 h); 1.3 ± 1.2c (6 m). Bonding strategy significantly influenced bond strength (p = 0.0001), but storage time did not (p = 0.841). Groups UA and SZP showed a homogeneous layer covering the zirconia surface. In these groups, EDX demonstrated the presence of phosphorus. Group ZPP resulted in a nonhomogeneous layer, exposing the zirconia substrate underneath. EXP application resulted in an undetectable layer. Conclusion: Water storage did not affect resin cement bond strengths to zirconia irrespective of the surface treatment. Bis-GMA-based resin cement bond strengths to zirconia are affected by specific bonding strategies. [ABSTRACT FROM AUTHOR]

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.

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.

Purpose: This study investigated and compared the surface roughness achieved by glazing porcelain samples in a conventional and a microwave oven. Materials and Methods: Two commercial brands of metal ceramics were used, VITA VMK MASTER and IPS CLASSIC. Sixty samples were fabricated, 30 for each type of ceramic. The samples were sintered in the conventional oven and hand-polished to remove any irregularities. Samples (n = 10) from each type of ceramic were further divided into three groups as follows: hand-polished (Group A), conventional oven glazed (Group B), and microwave glazed (Group C). Each specimen was evaluated for surface roughness by atomic force microscope. Data were statistically analyzed using two-way analysis of variance (ANOVA) and Tukey's post hoc test (a = 0.05). Results: Two-way ANOVA indicated a highly significant difference in surface roughness based on the type of glazing (P < 0.001), there was a significant difference based on the metal ceramics (P = 0.002). There was also a significant interaction between the type of glazing and metal ceramics (P = 0.009). The images obtained from the atomic force microscope corroborated the measured values. Conclusions: All the results indicate that microwave glazing can be a feasible option for glazing porcelain specimens. It was concluded that surface topography is influenced by surface treatment and microwave glazed ceramic is superior to conventional oven glazed ceramic and hand-polishing showed greater surface roughness when compared to glazing. IPS CLASSIC ceramic showed relatively smooth surface when compared to VITA VMK MASTER irrespective of the surface treatment.

The effects of different surface finishing procedures on the translucency of yttria stabilized zirconia ceramics (ZrO 2) were evaluated. ZrO 2 -3mol.%Y 2 O 3 (designed Zr3) or ZrO 2 -5mol.%Y 2 O 3 (Zr5) specimens with thickness varying between 0.5 and 1.5 mm were obtained by sintering at 1500 °C for 2 h. Surface finishing of the sintered specimens was done in three distinct manners: polishing with diamond pastes, blasting with Al 2 O 3 particles and blasting with Al 2 O 3 –SiO 2 particles, according to the preparation protocol for dental prostheses. These sample groups were characterized by X-Ray diffraction analysis, scanning electron microscopy, surface roughness and spectrophotometry. The sintered ceramics exhibited relative densities higher than 99% and were composed of 68.5% and 31.5%of tetragonal (t)-ZrO 2 and cubic(c)-ZrO 2 for composition Zr3 and 25.2% and 74.8% for composition Zr5, respectively. Furthermore, 1.5 to 1.8% of monoclinic (m)-ZrO 2 , has been found in the blasted surfaces. The average grain size varied from 0.5 μm for Zr3 to 1.45 μm for the Zr5 samples. After polishing, all samples presented a surface roughness R a of about 0.05 μm, while blasting resulted in an increased roughness ranging between 1.24 μm and 1.49 μm.Samples rich in (c)-ZrO 2 phase (Zr5) are more translucent than samples rich in (t)-ZrO 2 (Zr3) because of their larger grain size and because the cubic phase is less anisotropic than (t)-ZrO 2. Furthermore, the translucency of thinner samples is more affected by abrasive blasting because they also present the highly anisotropic monoclinic(m)-ZrO 2 phase and, therefore, the reduction of translucency is more pronounced. Parameters such as grain size, crystalline phase composition, porosity and grain boundary density are used to explain the phenomena involved in the differences of translucency of these materials. [ABSTRACT FROM AUTHOR]

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Nowadays, there are two different approaches to the treatment of defects of hard tissues of anterior teeth. There is a direct recovery method with composite materials and an indirect method with the usage of ceramic restorations. The issue of choice an optimal method of the preparation of hard tissues for appropriate types of restorations is relevant. Some scientists raised the question of choice between direct composite resin restorative techniques and indirect ceramic techniques. The choice of many authors leaned towards indirect ceramic restoration because of their better physical, mechanical and esthetic properties. Aim. Working on this publication, we wanted to highlight some physical properties of the most commonly used composite resin restoration materials and dental ceramic materials. Object and methods. For the experiment intact teeth (premolars, incisors) were selected (extracted according to orthodontic prescriptions). For the experiment selected teeth were prepared from the vestibular surface to a corresponding depth, within enamel or dentine. Totally 60 teeth were selected (30 prepared within to dentin, 30 with the depth of preparation within the enamel). The technique of determining of the tensile strength means the determining of the destructive force value on the sample. The tests were performed on the universal AUTOGRAPH AGS-J tearing machine, which provides an effort of 0-12 kN. The speed of the clamps of the machine is (5 0,5) mm / min. The tensile strength was calculated by the formula: A = F / S * 0,0981, where: F - the destructive force at which the sample is destroyed, kgf; S - the surface area at which the destruction occurs, cm?. Results and discussion. The results of the studies have shown that the average tensile strength (kgf / cm2 in samples, which have been thermocycled, and prepared within the dentin, for the EsthetX and V generation adhesives was 35.07 6.08; VII generation adhesive - 16,92 1,99; EX3 -32.24 2.83; IPS Empress - 25.86 3.34. In samples prepared without dentine exposure: for the EsthetX and V generation adhesives, on average, was 51.9 5.53; with the VII generation of adhesive - 33.08 2.27; EX 3 - 49.61 8.82; IPS Empress - 34.34 3.84. Conclusions. According to our research, the most effective bonding relationship with hard tooth tissues was present is the composite resin Esthet X in combination with the adhesive of the V generation, and the EX3 fieldspatic ceramics if the preparation was performed within the enamel. The strength of all investigated materials is in the same range, but taking into account the factor of water absorption and aesthetic stability, field-spatic ceramic and leucite glass based ceramic should be considered as the material of choice. Prospects for the further research. This study is promising and requires an augmentation of samples quantity for studying in order to get a greater reliability. Also a promising tactic seems to be further studies of other physical and chemical properties of materials (shear strength, abrasion resistance, color stability etc.).

Objective: To evaluate the changes in surface roughness of dental ceramics with various substances/instruments and polishing methods during the course of repeated firings. Method and Materials: Three types of dental ceramic (IPS Classic, Empress Esthetic, and Empress 2 [all by Ivoclar Vivadent]) were used to form three groups, respectively. The samples from the first group were subjected to glaze, the second group to natural glaze, and the third group to mechanical polishing. As many as seven firings were performed on each sample, and surface roughness measurements of the samples were carried out at certain stages. Statistical evaluation was performed through repeated-measures ANOVA, and the Duncan test proved that the differences among the mean values were by no means a coincidence. Results: The interaction among the substrates, the method used, and the time was statistically significant (P < .05). Mechanical polishing significantly increased surface roughness (P < .05), and the greater number of firings significantly decreased the amount of surface roughness (P < .05). Conclusion: In terms of surface roughness, the best method available is the glaze method and the best material is IPS Classic. The mechanical polishing process generates rough surfaces. Repeated firings should be avoided as much as possible because they have a destructive effect on the glaze layer and deform the surface. [ABSTRACT FROM AUTHOR]

Introduction: Badly broken or structurally compromised posterior teeth are frequently associated with crown/root fracture. Numerous restorative materials have been used to fabricate indirect full-coverage restorations for such teeth. This study aims to evaluate and compare the effect of restorative materials on the stress distribution pattern in a mandibular first molar tooth, under varying loading conditions and to compare the stress distribution pattern in five commonly used indirect restorative materials. Materials and Methods: Five three-dimensional finite element models representing a mandibular first molar tooth restored with crowns of gold, porcelain fused to metal, composite (Artglass), alumina-based zirconia (In-Ceram Zirconia [ICZ]), and double-layered zirconia-based materials (zirconia core veneered with porcelain, Lava) were constructed, using a Finite Element Analysis Software (ANSYS version 10; ANSYS Inc., Canonsburg, PA, USA). Two loading conditions were applied, simulating maximum bite force of 600 N axially and normal masticatory bite force of 225 N axially and nonaxially. Results: Both all-ceramic crowns allowed the least amount of stress distribution to the surrounding tooth structure. In maximum bite force-simulation test, alumina-based all-ceramic crown displayed the highest von Mises stresses (123.745 MPa). In the masticatory bite force-simulation test, both all-ceramic crowns (122.503–133.13 MPa) displayed the highest von Mises stresses. Conclusions: ICZ crown displayed the highest peak von Mises stress values under maximum and masticatory bite forces. ICZ and Lava crowns also allowed the least amount of stress distribution to the surrounding tooth structure, which is indicative of a favorable response of the underlying tooth structure to the overlying full-coverage indirect restorative material. These results suggest that ICZ and Lava crowns can be recommended for clinical use in cases of badly damaged teeth.

Introduction: Adjustments with diamond burs on the ceramic surface can affect its roughness and decrease flexural strength. This study evaluated the effect of polishing or glazing on the surface roughness and biaxial flexural strength of a zirconia-reinforced lithium silicate glass-ceramic upon adjustment with diamond burs., Methods: Seventy disks were prepared according to ISO 6872 and divided into seven groups (n = 10) according to different adjustments and finishing processes. Surface roughness was measured prior to biaxial flexural strength testing. The topography was analyzed using an atomic force microscope , fracture markings were identified using a stereomicroscope and representative specimens were analyzed using scanning electron microscopy., Results: The use of diamond burs significantly increased the surface roughness and decreased the strength of the evaluated ceramic (p⟨0.05). Polishing reduced the ceramic's roughness but resulted in flexural strength similar to that of the groups with wear (p⟩0.05). The glaze-treated specimens showed flexural strength statistically similar to the control group (p>0.05) but higher roughness, similar to those with wear., Conclusions: Polishing reduced the surface roughness but did not affect the biaxial flexural strength of the ZLS ceramic. At the same time, the application of glaze after wear increased the strength., (Copyright© 2023 Dennis Barber Ltd.)

Objective: To compare the shear bond strength (SBS) of orthodontic brackets bonded to three different types of ceramic surfaces (feldspathic, lithium disilicate, and zirconium) using Assure® Plus All and Transbond™ XT adhesives., Materials and Methods: The sample comprised 72 monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic samples that were randomly divided into six groups of 12 specimens each. Three groups (G1, feldspathic ceramic; G3, lithium disilicate ceramic; G5, zirconium surfaces) were bonded to metal brackets using Assure® Plus All adhesive, whereas the remaining three groups (G2, G4, G6; with the ceramic type in the same order as that in the previous groups) were bonded to metal brackets using Transbond™ XT. The samples were then subjected to 10,000 thermocycles. The SBS was calculated using the shear tests. The site of bonding failure was classified using the adhesive remnant index (ARI) score. One-way analysis of variance (ANOVA) and Kruskal-Wallis tests were used for statistical analyses at a 5% significance level., Results: Statistically significant differences were observed in the mean SBS values of the groups ( P < 0.001). The mean SBS for G6 (zirconium plus Transbond™ XT) (2.52 MPa) was significantly lower than that for all other groups. Furthermore, statistically significant differences were found in the ARI score distribution among the groups ( P < 0.001). Differences were identified between G6 and G3 (lithium disilicate Plus All Assure® Plus All) and G5 (zirconium plus Assure® Plus All)., Conclusions: The mean bonding strength of brackets with Assure® Plus All was higher than that with Transbond™ XT for all three types of ceramics. However, all groups, except the zirconium plus Transbond™ XT group, showed acceptable bonding strength for orthodontic purposes. The application of hydrofluoric acid followed by silane and finally the Assure® Plus All adhesive system is adequate for bonding brackets to any of the ceramic tested surfaces., Competing Interests: There are no conflicts of interest., (Copyright: © 2023 Journal of Orthodontic Science.)

The purpose of this study was to measure and correlate the fitness and trueness of a 3-unit fixed dental prosthesis (FDP) fabricated using two digital workflows. The 3-unit FDPs were fabricated using two digital workflows (N = 15). The digital workflows were divided into chairside (closed type) and in-lab (open type) groups. The scanning, computer-aided design (CAD), and computer-aided manufacturing (CAM) processes were conducted with 3shape E1 scanner, exocad CAD software, and DDS EZIS HM, respectively, in the in-lab group; and with CEREC omnicam intraoral scanner, CEREC CAD software, and CEREC MC XL, respectively, in the chairside group. The fitness of the fabricated 3-unit FDPs was evaluated by scanning the silicone replica of the cement space and analyzing the thickness of the silicone replica in the three-dimensional (3D) inspection software (Geomagic control X). The trueness of the milling unit was analyzed by 3D analysis of the CAD reference model, which is the design file of the 3-unit FDP, and the CAD test model, which is the scanned file of the 3-unit FDP. In the statistical analysis, comparison of the two groups was conducted by Mann–Whitney U test, and the correlation between the fitness and trueness was conducted by Pearson correlation test (α = 0.05). The marginal and internal fit were significantly lower in the in-lab group at all measurement positions (p < 0.001). The trueness of the milling unit was significantly higher in the in-lab group compared to the chairside group (p < 0.001). There was a positive correlation between the trueness and internal fit (correlation coefficient = 0.621) in the in-lab group (p = 0.013). The use of appropriate equipment in an in-lab (open type) digital workflow enables a better fabrication of 3-unit FDPs than a chairside (closed type) digital workflow, and poor trueness on the inner surface of the crown adversely affects the internal fit. [ABSTRACT FROM AUTHOR]

This study set out to compare the three-dimensional (3D) trueness of crowns produced from three types of lithium disilicate blocks. The working model was digitized, and single crowns (maxillary left second molar) were designed using computer-aided design (CAD) software. To produce a crown design model (CDM), a crown design file was extracted from the CAD software. In addition, using the CDM file and a milling machine (N = 20), three types of lithium disilicate blocks (e.max CAD, HASS Rosetta, and VITA Suprinity) were processed. To produce a crown scan model (CSM), the inner surface of each fabricated crown was digitized using a touch-probe scanner. In addition, using 3D inspection software, the CDM was partitioned (into marginal, axis, angular, and occlusal regions), the CDM and CSM were overlapped, and a 3D analysis was conducted. A Kruskal–Wallis test (α = 0.05) was conducted with all-segmented teeth with the root mean square (RMS), and they were analyzed using the Mann–Whitney U-test and the Bonferroni correction method as a post hoc test. There was a significant difference in the trueness of the crowns according to the type of lithium disilicate block (p < 0.001). The overall RMS value was at a maximum for e.max (42.9 ± 4.4 µm), followed by HASS (30.1 ± 9.0 µm) and then VITA (27.3 ± 7.9 µm). However, there was no significant difference between HASS and VITA (p = 0.541). There were significant differences in all regions inside the crown (p < 0.001). There was a significantly high trueness in the angular region inside the crown (p < 0.001). A correction could thus be applied in the CAD process, considering the differences in the trueness by the type of lithium disilicate block. In addition, to attain a crown with an excellent fit, it is necessary to provide a larger setting space for the angular region during the CAD process. [ABSTRACT FROM AUTHOR]

To evaluate the stress behavior of ceramic fragment restoration, varying the thickness of the cement layer and intraoral temperature variation. A solid model of a upper lateral incisor was obtained and a defect at enamel distal/incisal edge was restored with a ceramic fragment. Based on this initial model, 4 different models (M) were built: M1 – absence of cement layer (CL) (0 μm of thickness); M2 – CL with an uniform thickness of 50 μm; M3 – CL with 50 μm at the margin of ceramics and 100 μm in the inner area far from margins; M4 – CL with 50 μm at the margin of ceramics and 200 μm in the inner area far from margins. The environment temperature changed from 5 °C to 50 °C in 4 increments. The finite element analysis was performed. Increase the cement layer thickness generated higher stress levels on ceramic surface in all temperatures, as well as on cement interface. In general hot temperature was the worst scenario for ceramic fragments integrity, since tensile and compressive stress were more intense. The maximum principal stress on ceramic fragment was found 90 MPa for M4 at 50 °C, followed for M3 (87 Mpa). For CL, the peak of stress was found for M3 at 5 °C (47 MPa). Is it possible to conclude that thick resin cement layer contribute to higher stress concentration on ceramic fragment, and extremely hot temperatures increase the risk of structural failure, since both ceramic and \cl are exposed to higher compressive and tensile stresses. [ABSTRACT FROM AUTHOR]