A comparative study on tensile strength of various thermoplastic polymers sheets following thermoforming on a pre-treatment and post-treatment maxillary model of a patient: an in vitro study.

OBJECTIVES: Thermoplastic polymers show alteration in their mechanical properties after thermoforming on a dental model. The purpose of this in-vitro study was to evaluate the tensile strength of different thermoplastic polymer sheets thermoformed on a pre-treatment (moderate crowding) and post-treatment (well-aligned) maxillary model of a patient. MATERIALS AND METHODS: Forty maxillary models (Twenty Pre-treatment & twenty Post-treatment of uniform dimension) were made by duplicating them using alginate Hydrogum 5 (Zhermack). Samples were then divided into eight groups of 5 samples each. The thermoplastic sheets Imprelon® (Scheu-Dent), AVAC R® (Jaypee), Placa Crystal® (BioART), EZ-VAC® (3A Medes)-1.0 mm thick were thermoformed on these models respectively. The sample was retrieved using ceramic bur mounted on a straight hand-piece and subjected for testing using TINIUS Olsen 10ST micro universal testing machine and recorded. RESULTS: There was no statistically significant difference (P > .05) in tensile strength of thermoformed thermoplastic polymer sheets between pre-treatment and post-treatment maxillary model. Tensile strength of EZ-VAC (3A Medes) showed higher variation between pre-treatment and post-treatment maxillary model though it was found to be statistically insignificant (P > .05). Significant difference (P < .05) was seen between groups when they were compared separately among pre-treatment and post-treatment models. CONCLUSION: Placa Crystal (BioART) among the pre-treatment group, EZ - VAC (3A Medes) among the post-treatment group, showed highest tensile strength. CLINICAL RELEVANCE: Results of the study highlights the necessity to test materials in conditions which stands in accordance with the clinical scenario to a considerable extent and also emphasizes the need for further study in aligner.

Effect of acidic environment on color and translucency of different indirect restorative materials.

PURPOSE: The aim of the current study was to evaluate the effect of simulated gastric acid on the color and translucency of different indirect restorative materials. MATERIALS AND METHODS: A total of 36 disc-shaped samples were cut by using an isomet saw and divided into four equal groups (n = 9) according to the material type: Group Z: translucent zirconia (Ceramill® Zolid ht.+ preshade, Amann Girrbach, Koblach, Austria); Group E: lithium disilicate (IPS e.max CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein); Group C: resin nanoceramic (Cerasmart, GC, Tokyo, Japan); Group P: polyether ether ketone (PEEK) (Bettin Zirconia Dentale Italy) veneered with indirect high impact polymer composite (HIPC) (breCAM HIPC, Bredent GmbH & Co. KG, Germany). The samples were immersed in simulated gastric acid (HCl, pH 1.2) for 96 hours at 37 °C in an incubator. The color change (ΔE00) and translucency (RTP00) were measured every 9.6 hours (one-year clinical simulation) of immersion in simulated gastric acid. RESULTS: For color change (∆E00) and translucency (RTP00) among the tested materials, there was a highly statistically significant difference (P < 0.001) after every year of follow-up. The color change in both Z and G groups was the lowest after 1 year of acid immersion, followed by that in group H, and the highest change in color was recorded in group P. CONCLUSION: High translucent zirconia is recommended in patients who are concerned about esthetic, especially with acidic oral environment.

Current situation and prospects for the clean utilization of gold tailings.

Gold tailings are characterized by low-grade, complex composition, fine embedded particle size, environmental pollution, and large land occupation. This paper describes the mineralogical properties of gold tailings, including chemical composition, phase composition, particle size distribution, and microstructure; summarizes the recycling and utilization of components such as mica, feldspar, and valuable metals in gold tailings; reviews harmless treatment measures for harmful elements in gold tailings; and adumbrated the research progress of gold tailings in the application fields of building materials, ceramics, and glass materials. Based on these discussions, a new technology roadmap that combines multistage magnetic separation and cemented filling is proposed for the clean utilization of all components of gold tailings.

Percentage of patients shifting to another treatment modality: An experience-guided decision.

OBJECTIVE: This study aimed to assess the frequency with which orthodontic patients decided to shift to another type of orthodontic appliance, among conventional metal brackets, ceramic brackets, lingual brackets and clear aligner, based on their personal experiences of pain, ulcers, bad breath, hygiene issues and social difficulties. MATERIAL AND METHODS: This study comprises of patients seeking orthodontic treatment. The sample (n = 500; age group = 19-25 years) was divided equally into four groups based on the treatment modality: conventional metal brackets, ceramic brackets, lingual brackets and clear aligner. Patients rated the questionnaire using a visual analogue scale, to assess variables (such as pain, ulcer etc) that impact various treatment modalities. Subsequently, patients from all groups provided feedback regarding their treatment experiences, and expressed their preference for an alternative modality. Intergroup comparison among the four groups was done using one-way analysis of variance with Tukey's HSD post-hoc test (p ≤ 0.05). RESULTS: Patients who received lingual brackets reported higher levels of pain and ulceration, as compared to those who received clear aligners. All four groups showed statistically significant differences for ulcers during treatment (p ≤ 0.05). Of the 125 patients who received conventional metal brackets, 28% expressed a preference for clear aligner therapy, while 20% preferred ceramic brackets. In the lingual group, 56% of 125 patients preferred clear aligner therapy, and 8% preferred ceramic brackets to complete their treatment. In the ceramic group, 83% did not want to switch, whereas 17% desired to switch to clear aligner, while in aligner group no patient desired to switch. CONCLUSIONS: A higher percentage of patients from lingual brackets group chose to shift to clear aligners, followed by conventional metal brackets group and by ceramic brackets group, in this descending order. The clear aligner group demonstrated fewer issues than the other treatment modalities.

Effect of Surface Treatment with Alkaline Agents at Two Different Temperatures on Microshear Bond Strength of Zirconia to Composite Resin.

Background: Zirconia, with its excellent mechanical properties, has become a popular choice for esthetic and durable restorations due to the increasing demand of patients. It has overcome most of the limitations of all ceramic restorations. However, bonding to zirconia remains a challenge. Objectives: This study is aimed at assessing the effect of surface treatment with alkaline agents at two different temperatures on microshear bond strength (µSBS) of zirconia to composite resin. Materials and Methods: This in vitro, experimental study was conducted on zirconia blocks measuring 2 × 4 × 8 mm. The blocks were sandblasted with alumina powder and randomly assigned to 5 groups (n = 16 each). The blocks in groups 1 and 2 underwent surface treatment with sodium hydroxide (NaOH) and groups 3 and 4 with zirconium hydroxide (Zr(OH)4) at room temperature and 70°C. Group 5 served as the control group and did not receive any surface treatment. After the application of bonding agent and its light-curing, composite cylinders in plastic tubes were bonded to the surface of each block and cured. After incubation, they underwent µSBS test. Data were analyzed by one-way ANOVA and Tukey's test (alpha = 0.05). Results: The µSBS was significantly higher in all intervention groups than that in the control group (P < 0.05). The µSBS in Zr(OH)4 groups was significantly higher than that in NaOH groups (P < 0.05). The mean µSBS of heated groups was slightly, but not significantly, higher than the corresponding room temperature groups (P > 0.05). Conclusion: Surface treatment of zirconia with NaOH and Zr(OH)4 alkaline agents can increase its µSBS to composite resin; Zr(OH)4 was significantly more effective than NAOH for this purpose, but heating did not have a significant effect on µSBS.

Functionalization of Ceramic Scaffolds with Exosomes from Bone Marrow Mesenchymal Stromal Cells for Bone Tissue Engineering.

The functionalization of bone substitutes with exosomes appears to be a promising technique to enhance bone tissue formation. This study investigates the potential of exosomes derived from bone marrow mesenchymal stromal cells (BMSCs) to improve bone healing and bone augmentation when incorporated into wide open-porous 3D-printed ceramic Gyroid scaffolds. We demonstrated the multipotent characteristics of BMSCs and characterized the extracted exosomes using nanoparticle tracking analysis and proteomic profiling. Through cell culture experimentation, we demonstrated that BMSC-derived exosomes possess the ability to attract cells and significantly facilitate their differentiation into the osteogenic lineage. Furthermore, we observed that scaffold architecture influences exosome release kinetics, with Gyroid scaffolds exhibiting slower release rates compared to Lattice scaffolds. Nevertheless, in vivo implantation did not show increased bone ingrowth in scaffolds loaded with exosomes, suggesting that the scaffold microarchitecture and material were already optimized for osteoconduction and bone augmentation. These findings highlight the lack of understanding about the optimal delivery of exosomes for osteoconduction and bone augmentation by advanced ceramic scaffolds.

Tribological Properties of Blocky Composites with Carbon Nanotubes.

A large amount of primary energy is lost due to friction, and the study of new additive materials to improve friction performance is in line with the concept of low carbon. Carbon nanotubes (CNTs) have advantages in drag reduction and wear resistance with their hollow structure and self-lubricating properties. This review investigated the mechanism of improving friction properties of blocky composites (including polymer, metal, and ceramic-based composites) with CNTs' incorporation. The characteristic tubular structure and the carbon film make low wear rate and friction coefficient on the surface. In addition, the effect of CNTs' aggregation and interfacial bond strength on the wear resistance was analyzed. Within an appropriate concentration range of CNTs, the blocky composites exhibit better wear resistance properties. Based on the differences in drag reduction and wear resistance in different materials and preparation methods, further research directions of CNTs have been suggested.

Bonding Effectiveness of Saliva-Contaminated Monolithic Zirconia Ceramics Using Different Decontamination Protocols.

Objective: This research study investigated the effect of new decontamination protocols on the bonding capacity of saliva-contaminated monolithic zirconia (MZ) ceramics cemented with two different monomer-containing self-adhesive resin cements. Materials and Methods: Standardized tooth preparations (4 mm. axial height) were performed for eighty human maxillary premolars under constant water cooling system. Eighty monolithic zirconia crowns (Whitepeaks Supreme Monolith) (n = 8/10 groups) were manufactured by CAD-CAM. Specimens were kept in the artificial saliva at pH = 7.3 for 1 minute at 37°C except control groups. The specimens have not been prealumina blasted and grouped according to cleaning methods and resin cements: control groups (C) (no saliva contamination + GPDM + 4-META (N) (CN) and 10-MDP (M) containing resin cement (CM), alumina blasted (AL) + GPDM + 4-META (ALN) and 10-MDP containing resin cement (ALM), zirconium oxide containing universal cleaning agent (IC) applied + GPDM + 4-META (N) (ICN) and 10-MDP containing resin cement (ICM), pumice (P) applied + GPDM + 4-META (PN) and 10-MDP containing resin cement (PM), and air-water spray (AW) applied + GPDM + 4-META (AWN) and 10-MDP containing resin cement (AWM)). Monobond Plus was applied to all surfaces for 40 seconds before cementation. The thermal cycle was applied at 5,000 cycles after cementation. The crowns were tested in tensile mode at a speed of 1 mm/min. The mode of failure was recorded. SEM examinations were carried out at different magnifications. Data were analyzed using rank-based Kruskal-Wallis and Mann-Whitney tests. Results: No significant differences were found between the surface treatments and between the two types of resin cements. Interaction effects between surface treatments and resin cements were found to be significant by two-way ANOVA analysis. ICM group resulted in significantly better bond strength results compared with CN. ICM was found to result in better bond strength results compared with PM. The combination of universal cleaning agent and 10-MDP containing resin cement had significantly the highest cementation bond strength values. The increasing order of mean tensile bond strength values of decontamination protocols was C < AW < P < AL < IC. The mean tensile bond strength of 10-MDP containing resin cement was slightly higher than GPDM + 4-META containing resin cement. Conclusions: Universal cleaning agents can be preferred as an efficient cleaning method with 10-MDP-containing cement after saliva contamination for better adhesive bond strength of 4 mm crown preparation height of monolithic zirconia ceramics.

Clinical outcomes of self-glazed zirconia veneers produced by 3D gel deposition: a retrospective study.

BACKGROUND: Self-glazed zirconia (SZ) restorations are made by a novel additive three-dimensional gel deposition approach, which are suitable for a straightforward completely digital workflow. SZ has recently been used as minimally invasive veneer, but its clinical outcomes have not been clarified yet. This study aimed to evaluate the preliminary clinical outcomes of SZ veneers compared with the widely used lithium disilicate glass-ceramic veneers made by either pressing (PG) or milling (MG) process. METHODS: Fifty-six patients treated with SZ, PG, and MG veneers by 2 specialists between June 2018 and October 2022 were identified. Patients were recalled for follow-up at least 1 year after restoration. Clinical outcomes were assessed by 2 independent evaluators according to the modified United States Public Health Service (USPHS) criteria. Overall patient satisfaction was assessed using visual analogue scale (VAS), and analyzed by one-way ANOVA. Chi-square test was applied to compare the difference in the success and survival rates among the 3 groups. RESULTS: A total of 51 patients restored with 45 SZ, 40 PG, and 41 MG veneers completed the study, with a patient dropout rate of 8.9%. Mean and standard deviation of follow-up period was 35.0 ± 14.7 months. All restorations performed well at baseline, except for 2 SZ veneers with mismatched color (rated Bravo). During follow-up, marginal discrepancy (rated Bravo) was found in 4 MG veneers and 1 PG veneer, and partially fractured (rated Charlie) was found in another 2 PG veneers. The survival rate of SZ, PG, and MG veneers was 100%, 95%, and 100%, with a success rate of 95.56%, 92.50%, and 90.24%, respectively, none of which were significantly different (p = 0.099 and 0.628, respectively). The mean VAS score of SZ, PG, and MG was 95.00 ± 1.57, 93.93 ± 2.40, and 94.89 ± 2.00 respectively, without significant difference (p > 0.05). CONCLUSION: SZ veneers exhibited comparable preliminary clinical outcomes to PG and MG veneers, which could be considered as a feasible option for minimally invasive restorative treatment.

The internal and marginal adaptation of lithium disilicate endocrowns fabricated using intra and extraoral scanners: An in-vitro study.

OBJECTIVES: The impression technique highly influences the adaptation of ceramic restorations. Not enough information is available to compare the marginal (MF) and internal fit (IF) of endocrowns fabricated with various digitization techniques. Therefore, this in-vitro study aimed to compare the MF and IF of lithium disilicate (LDS) endocrowns fabricated through direct and indirect digital scanning methods. MATERIALS AND METHODS: One extracted maxillary molar was used to fabricate endocrowns. The digitization of the model was performed with (G1) direct scanning (n = 10) utilizing an intraoral scanner (IOS), (G2) indirectly scanning the conventional impression taken from the model using the same IOS (n = 10), (G3) indirectly digitalizing the obtained impression using an extraoral scanner (EOS) (n = 10), and (G4) scanning the poured cast using the same EOS (n = 10). The MF and IF of the endocrowns were measured using the replica method and a digital stereomicroscope. The Kruskal-Wallis test was used to analyze data. RESULTS: The studied groups differed significantly (p<0.001). G2 (130.31±7.87 µm) and G3 (48.43±19.14 µm) showed the largest and smallest mean vertical marginal gap, respectively. G2 and G3 led to the highest and lowest internal gaps in all regions, respectively. With significant differences among the internal regions (p<0.001), the pulpal area demonstrated the most considerable misfit in all groups. CONCLUSIONS: Scanning the impression using an extraoral scanner showed smaller marginal and internal gaps.

Fabrication trueness and internal fit of different lithium disilicate ceramics according to post-milling firing and material type.

OBJECTIVES: To evaluate whether post-milling firing and material type affect the fabrication trueness and internal fit of lithium disilicate crowns. METHODS: A prefabricated cobalt chromium abutment was digitized to design a mandibular right first molar crown. This design file was used to fabricate crowns from different lithium disilicate ceramics (nano-lithium disilicate (AM), fully crystallized lithium disilicate (IN), advanced lithium disilicate (TS), and lithium disilicate (EX)) (n = 10). Crowns, the abutment, and the crowns when seated on the abutment were digitized by using an intraoral scanner. Fabrication trueness was assessed by using the root mean square method, while the internal fit was evaluated according to the triple scan method. These processes were repeated after the post-milling firing of AM, TS, and EX. Paired samples t-tests were used to analyze the effect of post-milling firing within AM, TS, and EX, while all materials were compared with 1-way analysis of variance and Tukey HSD tests (α = 0.05). RESULTS: Post-milling firing reduced the surface deviations and internal gap of AM and EX (P ≤ 0.014). AM mostly had higher deviations and internal gaps than other materials (P ≤ 0.030). CONCLUSIONS: Post-milling firing increased the trueness and internal fit of tested nano-lithium disilicate and lithium disilicate ceramics. Nano-lithium disilicate mostly had lower trueness and higher internal gap; however, the maximum meaningful differences among tested materials were small. Therefore, the adjustment duration and clinical fit of tested crowns may be similar. CLINICAL SIGNIFICANCE: Tested lithium disilicate ceramics may be suitable alternatives to one another in terms of fabrication trueness and internal fit, considering the small differences in measured deviations and internal gaps.

Development of ZTA (80% Al2O3/20% ZrO2) pre-sintered blocks for milling in CAD/CAM systems.

The present work aims to develop a production method of pre-sintered zirconia-toughened-alumina (ZTA) composite blocks for machining in a computer-aided design and computer-aided manufacturing (CAD-CAM) system. The ZTA composite comprised of 80% Al2O3 and 20% ZrO2 was synthesized, uniaxially and isostatically pressed to generate machinable CAD-CAM blocks. Fourteen green-body blocks were prepared and pre-sintered at 1000 °C. After cooling and holder gluing, a stereolithography (STL) file was designed and uploaded to manufacture disk-shaped specimens projected to comply with ISO 6872:2015. Seventy specimens were produced through machining of the blocks, samples were sintered at 1600 °C and two-sided polished. Half of the samples were subjected to accelerated autoclave hydrothermal aging (20h at 134 °C and 2.2 bar). Immediate and aged samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Optical and mechanical properties were assessed by reflectance tests and by biaxial flexural strength test, Vickers indentation and fracture toughness, respectively. Samples produced by machining presented high density and smooth surfaces at SEM evaluation with few microstructural defects. XRD evaluation depicted characteristic peaks of alpha alumina and tetragonal zirconia and autoclave aging had no effect on the crystalline spectra of the composite. Optical and mechanical evaluations demonstrated a high masking ability for the composite and a characteristic strength of 464 MPa and Weibull modulus of 17, with no significant alterations after aging. The milled composite exhibited a hardness of 17.61 GPa and fracture toughness of 5.63 MPa m1/2, which remained unaltered after aging. The synthesis of ZTA blocks for CAD-CAM was successful and allowed for the milling of disk-shaped specimens using the grinding method of the CAD-CAM system. ZTA composite properties were unaffected by hydrothermal autoclave aging and present a promising alternative for the manufacture of infrastructures of fixed dental prostheses.

Royal advertising toothpaste pot lids.

Royal patronage is not something new. Engraved images of British royalty were used by early toothpaste manufacturers, dentists and perfumiers to convey royal endorsement to boost their product sales in the nineteenth and early twentieth centuries. Packaged in high-quality ceramic pots, these toothpastes and powders promoted cleaning, beautifying and preserving the teeth and gums. These fascinating containers, sealed with a transfer-printed lid, feature inventive designs and typefaces and highlight sophisticated manufacturing and marketing skills to entice consumers. Many have been re-discovered from the excavation of former rubbish tips and are often the only tangible evidence of long defunct businesses that elected to use this latest form of packaging.

A comparative evaluation of the variations on the shades of pressable ceramic system with the layering technique after different number of firing cycles: An in vitro study.

AIM: The main aim of the present study was to compare and evaluate the effect of repetitive firings on different shades of a pressable all ceramic system layered with veneering porcelain. SETTING AND DESIGN: In-vitro comparative study. MATERIALS AND METHODS: An in vitro comparative study was conducted, and a total of 60 disc shaped specimens (15 mm in diameter and 0.8 mm in thickness) were made of heat pressed ceramic of shades A2, A3, and B2 (20 discs of each shade) grouped as Group I, II, and III, respectively, using the lost wax technique. The discs were subsequently layered with veneering porcelain followed by glazing and overglazing and underwent a firing cycle at each step until six times combined. CIE L*a*b* measurements were noted on each sample after the third, fourth, fifth, and sixth firing using VITA Easyshade Advance 4.0 spectrophotometer. STATISTICAL ANALYSIS USED: Statistical Analysis was done by SPSS 17.0 software. One way analysis of variance, multiple comparisons using the Tukey test, and descriptive statistical analysis were done for all the groups in the study. P <0.05 was statistically significant. RESULTS: The mean color differences for the repeated firings were imperceptible (ΔE <1.67) to the human eye for all ceramic samples tested except between the fourth and fifth firing of Group II (shade A3). CONCLUSION: The analysis revealed that although repeated firings lead to changes in L*, a*, and b* values, the mean color difference was below the clinically acceptable color change (ΔE <3.7).

The effect of deviations in sintering temperature on the translucency and color of multi-layered zirconia.

OBJECT: This study aimed to investigate the changes in the translucency and color of four different multi-layered zirconia materials when the sintering temperature were inaccurate. MATERIALS AND METHODS: Two hundred zirconia samples (11 × 11 × 1.0 mm) of four multi-layered zirconia, Upcera TT-GT (UG), Upcera TT-ML (UM), Cercon xt ML (CX), and Lava Esthetic (LE), were divided into five subgroups according to the sintering temperature: L1 (5% lower temperature), L2 (2.5% lower temperature), R (recommended sintering temperature), H2 (2.5% higher temperature), H1 (5% higher temperature). After sintering, color coordinates were measured. Then the translucency parameter (TP) values, and the color differences (between the inaccurate sintering temperature and the recommended temperature) of each zirconia specimen were calculated. Statistical analysis was performed by using three-way ANOVA tests, the one-way ANOVA, and Tukey's post hoc test. RESULTS: Three-way ANOVA results showed that material type, sintering temperature, specimen section, and their interactions significantly influenced the TP values (except for the interactions of specimen section and sintering temperature) (P < .05). TP values of zirconia specimens were significantly different in the inaccurate sintering temperatures (P < .05), except for the cervical and body sections of UG group (P > .05). Compared with recommended sintering temperature, higher sintering temperature caused higher TP values for CX, but lower for LE. Three-way ANOVA results showed that material type, sintering temperature, and their interactions significantly influenced the ∆E00 values (P < .05). There were no significant differences in ∆E00 values of UM and CX groups at different inaccurate sintering temperatures, and were clinical imperception (except for UM-L1) (∆E00 < 1.25). ∆E00 values of all zirconia specimens showed clinically acceptable (∆E00 < 2.23). CONCLUSION: The deviations in sintering temperature significantly influenced the translucency and color of tested multi-layered zirconia. The trends of translucency in the multi-layered zirconia depended on material type and the color changes of all zirconia materials were clinically acceptable at inaccurate sintering temperatures.

Bone formation by Irisin-Poly vinyl alchol modified bioglass ceramic beads in the rabbit model.

In the aging society, slow bone regeneration poses a serious hindrance to the quality of life. To deal with this problem, in this study, we have combined irisin with the bioglass regular beads to enhance the bone regeneration process. For this purpose, highly porous bioglass was obtained as spherical beads by using sodium alginate. The bioglass was evaluated by various analytical techniques such as SEM, EDS, XRD, and pore size distribution. The results depicted that porous bioglass was prepared correctly and SEM analysis showed a highly porous bioglass was formulated. On this bioglass, irisin was loaded with the assistance of polyvinyl alcohol (PVA) in three concentrations (50 ng/ml, 100 ng/ml, and 150 ng/ml per 1 g of bioglass). SEM analysis showed that pores are covered with PVA. The irisin release profile showed a sustained release over the time period of 7 days. In vitro, biocompatibility evaluation by the MC3T3E1 cells showed that prepared bioglass and irisin loaded bioglass (BGI50, BGI100, and BG150) are highly biocompatible. Alizarin Red staining analysis showed that after 2 weeks BGI50 samples showed highest calcium nodule formation. In vivo in the rabbit femur model was conducted for 1 and 2 months. BGI150 samples showed highest BV/TV ratio of 37.1 after 2 months. The histological data showed new bone formation surrounding the beads and with beads loaded with irisin. Immunohistochemistry using markers OPN, RUNX, COL, and ALP supported the osteogenic properties of the irisin-loaded bioglass beads. The results indicated that irisin-loaded bioglass displayed remarkable bone regeneration.

INFLUENCE OF AGING, BEVERAGES, AND MOUTH WASH SOLUTIONS ON THE MICROSTRUCTURAL AND COLOR STABILITY OF DIFFERENT DENTAL CERAMICS: AN IN VITRO STUDY.

Рurроse - to evaluate the influence of aging, beverages, and mouthwash solutions on the microstructural and color stability of three CAD/CAM ceramic materials. In total, 87 specimens (7×5×1.5 mm) were prepared from 3 CAD/CAM ceramic groups, Lithium Disilicate glass ceramic (IPS e.max CAD), Extra translucent zirconia (VITA YZ), and Resin Nanoceramic (Cerasmart 270). All the materials were A2 or equivalent shades. After hydrothermal aging in distilled water at 5 C to 55 C for (10.000 cycles). The samples were randomly allocated into 3 groups (n=27) and immersion (staining) for one week in 3 different solutions coffee, green tea, and chlorhexidine. The baseline measurements of ceramic discs were recorded for color change and 2 samples of each group sent for SEM (microstructure) images before aging and staining. The second measurement was recorded after 10000 thermocycling and immersion in staining agents for 7 days. Statistical analysis were performed with an independent Kruskal-wallis test . The significant level was set at P≤0.05. ∆E values for lithium Disilicate after immersion in coffee, green tea and chlorhexidine gluconate were 3.167, 1.847 and 2.022, respectively. corresponding ∆E values for VITA XT were 3.438, 4.201 and 2.267. meanwhile Cerasmart shows more sensitivity for staining than LD and VITA of 4.454, 2.926 and 2.933. Within limitation of this study lithium disilicate showed the best color stability with values less than perception threshold. VITA and Cerasmart show higher sensitivity for staining with VITA more affected by green tea (Higher than clinically accepted threshold) and Cerasmart more affected by coffee (higher than clinically accepted threshold).

The Effect of Different Ageing Protocols on the Shear Bond Strength of the Ceromer Indirect Composite on Two Different Substructure Materials.

BACKROUND: The evolution of restorative materials in prosthodontics has led to the emergence of indirect composite resins, including ceromers, as alternatives to traditional metal-ceramic restorations. However, research gaps exist regarding the impact of ageing protocols on the bond strength of ceromer composites to different metal substructures, necessitating further investigation in this area. AIM: This study aimed to determine the effect of five different ageing protocols on the shear bond strength (SBS) of ceromer indirect composites on two different substructures. METHODS: In this in vitro study, 120 metallic discs (10 × 2 mm) were cast from cobalt-chromium (Co-Cr) alloy (n = 60) and spark erosion treated from grade V titanium (n = 60). Each sample was sandblasted. The M.L. primer (Shofu, Germany) and layers of opaque were applied to the surface following the manufacturer's instructions. A special jig (6 × 2 mm) was placed on each disc. The ceromer was condensed in it and light-cured separately for 90 s. Following polishing, specimens were separated into five ageing groups: distilled water (as a control), thermal cycling, tea, coffee, and gastric acid immersion. All samples were placed in 37°C incubation for 28 days for distilled water, coffee, and tea, and 7 days for gastric acid immersion and thermal cycling for 5000 cycles (5-55°C). A universal test machine was used to measure the SBS. The samples were evaluated for failure modes using stereomicroscopy. Data were analyzed using one-way analysis of variance (ANOVA) (P < 0.05). RESULTS: According to one-way ANOVA, the mean SBS (MPa) between the two groups was compared in each ageing protocol, and there were no significant differences between the Co-Cr-C and Ti-C groups (P > 0.05). The most frequent mode of failure in all groups was mixed. CONCLUSIONS: Applying the ageing protocols, the type of substructure material had no significant effect on the SBS of the ceromer indirect composite except for tea immersion.

Effect of ceramic type and thickness on the masking ability of chairside machinable all-ceramic crowns.

OBJECTIVES: This study aimed to evaluate the influence of ceramic type and thickness on the masking ability and final aesthetic effects of chairside machinable all-ceramic crowns. METHODS: Six kinds from three types chairside machinable ceramic materials (IPS e.max CAD HT/MT/LT, IPS Empress LT, and VITA Suprinity HT/T) in shade A2 were fabricated to slice specimens into 1.0, 1.5, and 2.0 mm-thick sections (n=10). The color parameters of the specimens against black and white tiles and four resin substrates (A2, A4, B3, and C4 shade) were measured with a spectrophotometer. The translucency parameter (TP) was calculated using color parameters measured over standard white and black backgrounds. The color differences (ΔE) were calculated between there substrate shades (A4, B3, C4 ) and A2 shade (control group). Two-way analysis of variance (ANOVA) was performed on the TP values. The two va-riables were ceramic type and ceramic thickness. Three-way ANOVA was used to determine the effects of ceramic materials, ceramic thickness, and substrate shades on the ΔE values, followed by Tukey test for multiple comparisons (α=0.05). RESULTS: Ceramic type, ceramic thickness, and substrate shade significantly affected the ΔE values (P<0.001). The L* and b* values of the specimens increased with increasing ceramic thickness, except in substrate A2, whereas the ΔE values decreased. The color difference of all 1.0 mm-thick specimens or all specimens over the substrates C4 shade exceeded the clinically acceptable threshold (ΔE>3.3). CONCLUSIONS: The masking ability of chairside machinable all-ceramic crowns is influenced by ceramic type and thickness, and ceramic material. The thickness of ceramic less than 2.0 mm cannot mask the gray shade abutment.

Effect of ZrO2 paste, surface treatments, and storage on Weibull characteristics and resin bond strength to zirconia.

The objective is to evaluate the effect of different surface treatments and storage on the shear strength of ultratranslucent zirconia. 36 blocks of ultra-translucent zirconia were fabricated (7x7x2mm) and sintered. Then, divided into 12 groups according to the "surface treatment" (C -Primer; Al -Sandblasting with Al2O3 + Primer; Si -Silicate + Primer; Gl -Glaze + HF + Primer; Z -Zirlink; Zp -Zirlink + Primer) and "storage" factors (ST-with 150 days/37º and without). After surface treatment, five cylinders (Ø=2mm; h=2.0mm) of resin cement (n=15) were constructed in each ceramic block; at the end, the shear strength test was performed (1mm/min, 50Kgf), and analysis of surface failures. 60 additional samples (2x2x2mm) were made for extras analysis (surface roughness, MEV, and EDS). Bond strength and surface roughness data were statistically evaluated by ANOVA (2 factors/1 factor), Tukey test (5%), and Weibull analysis, respectively. ANOVA (2-way) revealed that all factors were statistically significant for bond strength. The silicatization groups (SiST: 30.47AMPa; Si: 29.21AMPa) showed the highest bond strength values, regardless of storage (Tukey's test). While the groups treated with Zirlink (ZST: 2.76FMPa; Z: 5.27EFMPa) showed the lowest values, just similar to the GlST group (5.14EFMPa). The Weibull modulus (m) showed a statistical difference between groups (p=0.000). ANOVA (1 factor) revealed that the "surface treatment" factor (p=0.0000) was statistically significant for surface roughness. Therefore, the application of Zirlink and Glaze on pre-sintered zirconia did not promote efficient adhesion of the ultratranslucent zirconia to the resin cement, even when associated with a primer containing MDP.