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Background: Ceramic-on-ceramic (CoC) bearings have been increasingly used in total hip arthroplasty (THA) because of their superior wear resistance and biocompatibility. However, there is a scarcity of reports on the computed tomography (CT) evaluation of CoC bearings with more than 10 years. The aim of this study was to evaluate the long-term CT results of THA using CoC bearings for more than 20 years of follow-up. We hypothesized that there would be no wear, osteolysis, or ceramic fracture., Methods: Between November 1997 and June 2003, 956 hips underwent THA using alumina-on-alumina bearings at a tertiary referral hospital. Among them, 107 hips were assessed, all of which underwent a CT examination more than 20 years after the index surgery. The mean age at the time of surgery was 41 years, and a CT scan was performed at an average of 22.0 years postoperatively (range, 20.0 to 25.1). The CT scans were thoroughly assessed for osteolysis, stem notching, and ceramic component fracture., Results: No loosening was observed in the acetabular cup or femoral stem. Stem notching was observed in 3 hips (2.8%). In the CT scan taken after a minimum of 20 years of follow-up, 1 case (0.9%) of osteolysis around the cup and 2 cases (1.9%) of osteolysis around the femoral stem were noted. Suspected chip fractures of the ceramic insert were discovered in 4 cases (3.7%). Despite these findings, the patients remained asymptomatic, and no subsequent surgical intervention was needed after close follow-up., Conclusions: Routine CT examinations for patients who underwent THA using CoC bearings over 20 years ago revealed unexpected findings, such as osteolysis and suspected chip fractures of the ceramic liner. However, routine CT scans may not be universally necessary. The CT evaluation in this cohort should be selectively performed for patients who have relevant clinical symptoms., Level of Evidence: Level III, Therapeutic study., (Copyright © 2024 Elsevier Inc. All rights reserved.)

This paper proposes a new range of diversity indexes applicable to ceramic petrographic and geochemical data and potentially to any archaeological data of both metric and non-metric nature in order to assess the degree of craft standardization. The case study is the Late Chalcolithic pottery from Arslantepe in eastern Anatolia, ideal to test the standardization hypothesis, i.e. the assumed correspondence between craft standardization and increased rates of production, which in turn correlate with economic specialization. The results suggest that the procurement and processing of raw materials are more sensible indicators of standardization than vessel shape variability. Higher standardization is connected with the scale of production rather than with the use of the wheel or its rotational speed. The socio-economic centralization marks a process of labor division within the operational sequence and, more generally, a shift from communal to more segregated potting practices. As a result, the variability of both technical procedures and end products increases. In contrast univocal trends towards standardization can be found in coeval contexts from northern Mesopotamia, where the incipient urbanization served to create bonds between vessel makers, favoring the transmission of models and practices regardless of the centralized power., Competing Interests: The author has declared that no competing interests exist.

Lack of homogeneity in the product (LHP) is a problem when customers require homogeneous units of a single product. In such cases, the optimal allocation of inventory to orders becomes much more complex. Furthermore, in an MTS environment, an optimal initial allocation may become less than ideal over time, due to different circumstances. This problem occurs in the ceramics sector, where the final product varies in tone and calibre. This paper proposes a methodology for the reallocation of inventory to orders in LHP situation (MERIO-LHP) and a model-based decision-support system (DSS) to support the methodology, which enables an optimal reallocation of inventory to order lines to be carried out in real businesses environments in which LHP is inherent. The proposed methodology and model-based DSS were validated by applying it to a real case at a ceramics company. The analysis of the results indicates that considerable improvements can be obtained with regard to the quantity of orders fulfilled and sales turnover., Competing Interests: The authors have declared that no competing interests exist.

Purpose: Ceramic bearings have been widely used in total hip arthroplasty (THA), which resulted in satisfactory clinical outcomes due to the excellent tribological characteristics of the implants. However, ceramic components are not commonly used in total knee arthroplasty (TKA) because of brittleness. This study aimed to gather and analyze information regarding the clinical outcomes (including survival without revision, causes of revision, functional outcome, and incidence of loosening) and reach a definitive conclusion about the use of ceramic femoral components in total knee arthroplasty., Methods: MEDLINE, EMBASE, Cochrane, and ClinicalTrials.gov databases were searched for studies that reported the clinical and/or radiological outcomes with or without survival data of ceramic TKA implants and that included more than 10 patients with a minimum of 1 year follow-up., Results: From an initial sample of 147, there were 14 studies that met the inclusion criteria. Overall, there was a notable enhancement of joint function after the procedure, with a satisfactory mid- and long-term survival of the ceramic components, which is comparable to that of the conventional alloy components reported previously. In addition, the revision rate was reported to be between 0% and 14.37% according to the included studies. However, revision due to aseptic loosening, wear, and component fracture appeared to be rare, demonstrating the safety of in vivo use of ceramic bearings in the TKA procedure., Conclusions: Ceramic TKA implants show similar post-operative clinical results and survival rate compared to their conventional metallic counterparts. Our results confirmed the safety of in vivo use of ceramic bearings in TKA, with rare implant breakage and aseptic loosening. Considering the excellent characteristics of the tribology of ceramics, the clinical use of ceramic prostheses in TKA could be promising.

Background: The purpose of this study was to investigate the effects of staining solutions and surface finishing on the colour stability and translucency of hybrid ceramic (HC) and resin nanoceramic (RNC) materials., Methods: Twenty four groups consisting of 10 specimens (240 specimens in total) were created out of HC and RNC, including six groups to be stored in distilled water served as the controls groups. The Vita Enamic technical set, Shofu polishers, medium and fine rubber wheels and Sof-Lex polishing discs were used as polishing instruments. Cola, tea, and coffee were used as staining solutions. The colour differences (∆E*) and translucency parameter (TP) were evaluated by a spectrophotometer. Data were analysed by a One-way Analysis of Variance (ANOVA) and Mann-Whitney U test., Results: There was a statistically significant difference between the ∆E* values of the HC specimens in the coffee groups and the ∆E* values of the other HC groups (p < 0.05). The ∆E* values of the RNC specimens in the coffee and tea groups were not different from the specimens in the cola groups (p > 0.05). The TP values of the polished groups were higher than the Sof-Lex groups and the Shofu groups on both HC and RNC materials (p < 0.05)., Conclusions: Increased ∆E* values were observed in HC specimens stored in a coffee solution compared to the specimens stored in a tea or cola solution. Both of the RNC specimens stored in coffee and tea had higher ∆E* values than the RNC specimens stored in the cola. The TP values of both HC and RNC specimens stored in the coffee solution decreased.

Objective: The purpose of this study was to examine the fracture strength and surface microhardness of computer-aided design/computer-aided manufacturing (CAD/CAM) materials in vitro., Materials and Methods: Mesial-occlusal-distal inlays were made from five different CAD/CAM materials (feldspathic ceramic, CEREC blocs; leucite-reinforced ceramic, IPS Empress CAD; resin nano ceramic, 3M ESPE Lava Ultimate; hybrid ceramic, VITA Enamic; and lithium disilicate ceramic, IPS e.max CAD) using CEREC 4 CAD/CAM system. Samples were adhesively cemented to metal analogs with a resin cement (3M ESPE, U200). The fracture tests were carried out with a universal testing machine. Furthermore, five samples were prepared from each CAD/CAM material for micro-Vickers hardness test. Data were analyzed with statistics software SPSS 20 (IBM Corp., New York, USA)., Results: Fracture strength of lithium disilicate inlays (3949 N) was found to be higher than other ceramic inlays (P < 0.05). There was no difference between other inlays statistically (P > 0.05). The highest micro-Vickers hardness was measured in lithium disilicate samples, and the lowest was in resin nano ceramic samples., Conclusion: Fracture strength results demonstrate that inlays can withstand the forces in the mouth. Statistical results showed that fracture strength and micro-Vickers hardness of feldspathic ceramic, leucite-reinforced ceramic, and lithium disilicate ceramic materials had a positive correlation., Competing Interests: There are no conflicts of interest.

Background: Polymer infiltrated ceramics and nano-ceramic resins are the new restorative materials which have been developed in order to enhance the adverse properties of glass-matrix ceramics and resin composites. The aim of the present in vitro study was to evaluate the characteristics of various CAD/CAM materials through mechanical, microstructural, and SEM analysis., Methods: Five test groups (n = 22) were formed by using the indicated CAD/CAM blocks: VITA Enamic (VITA Zahnfabrik), Lava Ultimate (3 M ESPE), IPS e.max CAD (Ivoclar Vivadent), IPS Empress CAD (Ivoclar Vivadent), and VITA Mark II (VITA Zahnfabrik). Two specimens from each test group were used for XRD and EDS analysis. Remaining samples were divided into two subgroups (n = 10). One subgroup specimens were thermocycled (5 °C to 55 °C, 30s, 10,000 cycles) whereas the other were not. All of the specimens were evaluated in terms of flexural strength, Vickers hardness, and fracture toughness. Results were statistically analyzed using two-way ANOVA, one-way ANOVA, Tukey's HSD, and Student's t tests (α = .05). Fractured specimens were evaluated using SEM., Results: The highest Vickers microhardness value was found for VITA Mark II (p < .001), however flexural strength and fracture toughness results were lowest conversely (p < .05). IPS e.max CAD was found to have the highest flexural strength (p < .001). Fracture toughness of IPS e.max CAD was also higher than other tested block materials (p < .001). Lava Ultimate and VITA Enamic's mechanical properties were affected negatively from thermocycling (p < .05). Microhardness, flexural strength, and fracture toughness values of Lava Ultimate and VITA Enamic were found to be similar to VITA Mark II and IPS Empress CAD groups., Conclusions: It should be realised that simulated aging process seem to affect ceramic-polymer composite materials more significantly than glass ceramics.

Modern analytical methods play an important role in archaeological objects, including ceramics. This review focuses on the use of analytical methods such as: gas chromatography coupled mass spectrometry, Fourier transform infrared spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), powder X-ray diffraction with thermal analysis to study the chemical and mineralogical composition of archaeological samples and organic residues preserved inside. In this paper, special attention was paid to the ToF-SIMS method, which allows the determination of characteristic ions on the surface of ceramic samples.

Biphasic calcium phosphates (BCP) bioceramics have become the materials of choice in various orthopedic and maxillofacial bone repair procedures. One of their main advantages is their biodegradation rate that can be modified by changing the proportional ratio of the composition phases. For enhanced bone tissue regeneration, the bioactivity of BCP should be increased by optimizing their physicochemical properties. To date, the ideal physicochemical properties of BCP for bone applications have not been defined. This is mostly related to lack of standard study protocols in biomaterial science especially with regards to their characterizations and clinical applications. In this paper we provided a review on BCP and their physicochemical properties relevant to clinical applications. In addition, we summarized the available literature on their use in animal models and evaluated the influences of different composition ratios on bone healing. Controversies in literature with regards to ideal composition ratio of BCP have also been discussed in detail. We illustrated the discrepancies in study protocols among researchers in animal studies and emphasized the need to develop and follow a set of generally accepted standardized guidelines. Finally; we provided general recommendations for future pre-clinical studies that allow better standardization of study protocols. This will allow better comparison and contrast of newly developed bone substitute biomaterials that help further progress in the field of biomaterial science., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Introduction: The resistance of three different substructure materials - metal (Cr-Co), zirconium (Zr), and ceramics (IPS Empress II) - was measured by sticking them to dentine with two different resin cements, a dual-cure resin cement (Panavia F 2.0 Light) and a self-adhesive resin cement (BisCem)., Materials and Methods: In an in vitro study, 72 central upper front teeth were selected with no decay or apparent breakage and with complete development, removed for periodontal reasons. Labial and incisal surfaces of all teeth were prepared. Molds were obtained to prepare metal (Co-Cr), Zr, and ceramic (IPS Empress II) blocks for use in the study. The compressive strengths of the obtained material infrastructures were examined after thermal cycle processing by performing cementation to the teeth with two different cements. The data obtained were analyzed statistically. The Mann-Whitney U-test was used for comparisons of the groups with two options, and Kruskal-Wallis variance analysis was used to compare more than two groups. P<0.05 were considered statistically significant., Results: While the highest result between samples was 117.86 ± 47.94 N in the dual-cure (Panavia)-ceramic group, the lowest value was observed at 6.53 ± 3.12 N in the self-adhesive (BisCem)-metal group. There was a significant difference between dual-cure (Panavia) and self-adhesive (BisCem) groups., Conclusion: In this study, we measured the bond strength; our most durable resistance groups were found to be, in order, Panavia-ceramics >Panavia-metal >Panavia-Zr >self-adhesive-ceramics >self-adhesive-Zr >and self-adhesive-metal.

Statement of Problem: IPS e.max CAD and IPS e.max Press (Ivoclar Vivadent AG) are lithium disilicate glass ceramics marketed as interchangeable materials indicated for the same clinical uses. However, different crystal sizes of lithium disilicate are formed during the processing of each of these materials, a factor that could lead to significantly different mechanical properties. As mechanical failure is always associated with a crack-initiation/crack-propagation process, fracture toughness (K IC ) values could be useful in comparing different ceramics and possibly predicting clinical performance., Purpose: The purpose of this in vitro study was to determine and compare the K IC of IPS e.max CAD and IPS e.max Press., Material and Methods: The notchless triangular prism (NTP) specimen K IC test was used to determine and compare the K IC of IPS e.max Press and IPS e.max CAD. Twenty 6×6×6×12-mm NTP specimens of each material were prepared. IPS e.max CAD blocks were cut, ground, and then crystallized, while IPS e.max Press specimens were prepared by pressing IPS e.max Press ingots into molds obtained from 6×6×6×12-mm wax prisms, using the lost wax technique. Each specimen was mounted into a specimen holder, and custom grips were used to attach the specimen holder assembly to a computerized universal testing machine (model 4301; Instron Canada, Inc). The assembly was loaded in tension at a crosshead speed of 0.1 mm/min, and the K IC value was calculated based on the recorded maximum load at fracture. Fractured surfaces were characterized using scanning electron microscopy (SEM). Results were statistically analyzed using Weibull statistics and the Student t test (α=.05)., Results: Significantly (P<.05) higher K IC value was determined for IPS e.max Press than for IPS e.max CAD and, based on the Weibull modulus (m), IPS e.max Press was also more reliable. Fractured surfaces, characterized by SEM, showed a marked difference between the 2 materials, suggesting a more complete crystallization in IPS e.max Press, which was most likely responsible for the higher K IC determined., Conclusion: Within the limitations of this in vitro study, the results suggest that IPS e.max Press is superior to IPS e.max CAD with regard to the K IC and characteristic Weibull parameters., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Evaluation of the adhesive strength of femoral components to the bone cement is a relevant parameter for predicting implant safety. In the present experimental study, three types of cemented femoral components (metallic, ceramic and silica/silane-layered ceramic) of the bicondylar Multigen Plus knee system, implanted on composite femora were analysed. A pull-off test with the femoral components was performed after different load and several cementing conditions (four groups and n=3 components of each metallic, ceramic and silica/silane-layered ceramic in each group). Pull-off forces were comparable for the metallic and the silica/silane-layered ceramic femoral components (mean 4769 N and 4298 N) under standard test condition, whereas uncoated ceramic femoral components showed reduced pull-off forces (mean 2322 N). Loading under worst-case conditions led to decreased adhesive strength by loosening of the interface implant and bone cement using uncoated metallic and ceramic femoral components, respectively. Silica/silane-coated ceramic components were stably fixed even under worst-case conditions. Loading under high flexion angles can induce interfacial tensile stress, which could promote early implant loosening. In conclusion, a silica/silane-coating layer on the femoral component increased their adhesive strength to bone cement. Thicker cement mantles (>2 mm) reduce adhesive strength of the femoral component and can increase the risk of cement break-off.

The aim of this study is to explore the correlations between the properties of the source's material and the thoron flux produced. This means a complex procedure that involves morphological characterisation (the determination of specific surface area and pore size distribution) and thoron emanation and exhalation measurements as well. In this work, the preparation of 27 thoron sources has been carried out. Three types of ceramics with different morphological properties were used as a matrix material with three different thorium contents. Spheres were formed from the dollop, and they were fired at different temperatures (200, 600 and 900°C). The phase analysis of the samples was performed by powder X-ray diffraction. The pore size distribution was determined by mercury penetration. The thoron emanation was measured using an accumulation chamber; the measured thoron emanation coefficients were from 0.34 ± 0.03 to 7.69 ± 0.13 %. Based on the results, the preparation parameters of the thoron source optimised for the calibration procedure have been given., (© The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The aim of this study was to propose and validate a new unified method for testing dissolution rates of bioactive glasses and their variants, and the formation of calcium phosphate layer formation on their surface, which is an indicator of bioactivity. At present, comparison in the literature is difficult as many groups use different testing protocols. An ISO standard covers the use of simulated body fluid on standard shape materials but it does not take into account that bioactive glasses can have very different specific surface areas, as for glass powders. Validation of the proposed modified test was through round robin testing and comparison to the ISO standard where appropriate. The proposed test uses fixed mass per solution volume ratio and agitated solution. The round robin study showed differences in hydroxyapatite nucleation on glasses of different composition and between glasses of the same composition but different particle size. The results were reproducible between research facilities. Researchers should use this method when testing new glasses, or their variants, to enable comparison between the literature in the future.

Statement of Problem: Milling is a central and important aspect of computer-aided design and computer-aided manufacturing (CAD/CAM) technology. High milling accuracy reduces the time needed to adapt the workpiece and provides restorations with better longevity and esthetic appeal. The influence of different milling processes on the accuracy of milled restorations has not yet been reviewed., Purpose: The purpose of this study was to investigate the influence of different milling processes on the accuracy of ceramic restorations., Material and Methods: Four groups of partial crowns were milled (each n = 17): Three groups in a 4-axial milling unit: (1) 1-step mode and Step Bur 12S (12S), (2) 1-step mode and Step Bur 12 (1Step), (3) 2-step mode and Step Bur 12 (2Step), and (4) one group in a 5-axial milling unit (5axis). The milled occlusal and inner surfaces were scanned and superimposed over the digital data sets of calculated restorations with specialized difference analysis software. The trueness of each restoration and each group was measured. One-way ANOVA with a post hoc Tukey test was used to compare the data (α = .05)., Results: The highest trueness for the inner surface was achieved in group 5axis (trueness, 41 ± 15 μm, P<.05). The 4-axial milling unit exhibited trueness at settings ranging from 61 μm (2Step) to 96 μm (12S). For the occlusal surface, the highest trueness was achieved with group 5axis (trueness, 42 ± 10 μm). The 4-axial milling unit exhibited trueness at settings ranging from 55 μm (1Step) to 76 μm (12S)., Conclusions: Restorations milled with a 5-axial milling unit have a higher trueness than those milled with a 4-axial milling unit. A rotary cutting instrument with a smaller diameter results in a more accurate milling process. The 2-step mode is not significantly better than the 1-step mode., (Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: The excess material produced after heat pressing a lithium disilicate glass ceramic restoration can be either discarded or reused. The reuse of this material requires that any degradation of the material quality be investigated., Purpose: The purpose of this study was to investigate the number of times that leftover lithium disilicate material can be re-pressed and to determine the effect that repeated use has on material properties., Material and Methods: A large (6.1 g) lithium disilicate ingot (A3.5) was heat pressed to yield a ceramic disk (15 × 1.5 mm) for testing. The leftover material was reused to produce a further 3 disks, with the number of pressings increasing for each specimen. An additional unpressed group was included to investigate the properties before pressing so that, in total, 5 groups were established. Specimens were tested for biaxial flexural strength, Vickers hardness, and fracture toughness. X-ray diffraction was used to characterize the crystalline phase, scanning electron microscopy for the microstructure, and differential scanning calorimetry for the thermal properties., Results: No significant difference was found in the biaxial flexural strength of the groups. The hardness of the material decreased, and no significant difference was seen in fracture toughness with repeated pressings. An increase in grain size was observed with increased pressings. By using x-ray diffraction analysis, lithium disilicate was identified as the main crystal phase, and no difference in crystalline composition was found with repeated processing., Conclusion: This material can be reused while maintaining good mechanical properties and without significantly altering the chemical or crystalline composition in an adverse manner., (Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: To assess the survival outcomes and reported complications of screw- and cement-retained fixed reconstructions supported on dental implants., Materials and Methods: A Medline (PubMed), Embase, and Cochrane electronic database search from 2000 to September 2012 using MeSH and free-text terms was conducted. Selected inclusion and exclusion criteria guided the search. All studies were first reviewed by abstract and subsequently by full-text reading by two examiners independently. Data were extracted by two examiners and statistically analyzed using a random effects Poisson regression., Results: From 4,324 abstracts, 321 full-text articles were reviewed. Seventy-three articles were found to qualify for inclusion. Five-year survival rates of 96.03% (95% confidence interval [CI]: 93.85% to 97.43%) and 95.55% (95% CI: 92.96% to 97.19%) were calculated for cemented and screw-retained reconstructions, respectively (P = .69). Comparison of cement and screw retention showed no difference when grouped as single crowns (I-SC) (P = .10) or fixed partial dentures (I-FDP) (P = .49). The 5-year survival rate for screw-retained full-arch reconstructions was 96.71% (95% CI: 93.66% to 98.31). All-ceramic reconstruction material exhibited a significantly higher failure rate than porcelain-fused-to-metal (PFM) in cemented reconstructions (P = .01) but not when comparing screw-retained reconstructions (P = .66). Technical and biologic complications demonstrating a statistically significant difference included loss of retention (P ≤ .01), abutment loosening (P ≤ .01), porcelain fracture and/or chipping (P = .02), presence of fistula/suppuration (P ≤ .001), total technical events (P = .03), and total biologic events (P = .02)., Conclusions: Although no statistical difference was found between cement- and screw-retained reconstructions for survival or failure rates, screw-retained reconstructions exhibited fewer technical and biologic complications overall. There were no statistically significant differences between the failure rates of the different reconstruction types (I-SCs, I-FDPs, full-arch I-FDPs) or abutment materials (titanium, gold, ceramic). The failure rate of cemented reconstructions was not influenced by the choice of a specific cement, though cement type did influence loss of retention.

In ZnO-based low voltage varistor, the two essential features of microstructure determining its nonlinear response are the formation Bi-enriched active grain boundaries as well as a controlled ZnO grain size by secondary spinel-type phases. Besides, the microstructure and phase composition are strongly affected by the dopant concentration during sintering process. In this study, the optimal dopant levels of Bi2O3, TiO2, and Sb2O3 to achieve maximized nonlinear electrical property (alpha) were quantified by the response surface methodology (RSM). RSM was also used to understand the significance and interaction of the factors affecting the response. Variables were determined as the molar ratio of Bi2O3, TiO2, and Sb2O3. The alpha was chosen as response in the study. The 5-level-3-factor central composite design, with 20 runs, was used to conduct the experiments by ball milling method. A quadratic model was established as a functional relationship between three independent variables and alpha. According to the results, the optimum values of Bi2O3, TiO2, and Sb2O3 were obtained 0.52, 0.50, and 0.30, respectively. Under optimal conditions the predicted alpha (9.47) was calculated using optimal coded values from the model and the theoretical value is in good agreement with the value (9.43) obtained by confirmation experiment.

Purpose: To evaluate the load distribution of CAD/CAM mono-ceramic crowns supported with single-tooth implants in functional area., Materials and Methods: A 3-dimensional numerical model of a soft tissue-level implant was constructed with cement-retained abutment to support glass ceramic machinable crown. Implant-abutment complex and the retained crown were embedded in a Ø 1.5 × 1.5 cm geometric matrix for evaluation of mechanical behavior of mono-ceramic CAD/CAM aluminosilicate and leucite glass crown materials. Laterally positioned axial load of 300 N was applied on the crowns. Resulting principal stresses in the mono-ceramic crowns were evaluated in relation to different glass ceramic materials., Results: The highest compressive stresses were observed at the cervical region of the buccal aspect of the crowns and were 89.98 and 89.99 MPa, for aluminosilicate and leucite glass ceramics, respectively. The highest tensile stresses were observed at the collar of the lingual part of the crowns and were 24.54 and 25.39 MPa, respectively., Conclusion: Stresses induced upon 300 N static loading of CAD/CAM aluminosalicate and leucite glass ceramics are below the compressive strength of the materials. Impact loads may actuate the progress to end failure of mono-ceramic crowns supported by metallic implant abutments.

Objectives: The authors investigated the use of ceramic primers combined with self-adhesive resin composite cements on the shear bond strength (SBS) to zirconia and compared them with one conventional resin composite cement., Methods: The authors divided zirconia substrates (N = 550) into three groups: RelyX Unicem Aplicap self-adhesive universal resin composite cement (3M ESPE, St. Paul, Minn.) (group A) (n = 220); G-CEM Capsule self-adhesive resin composite cement (GC Europe, Leuven, Belgium) (group B) (n = 220); and Panavia 21 with Clearfil Porcelain Bond Activator and Clearfil SE Bond primer (n = 110) (Kuraray Dental, Tokyo) used as a standard comparison (SC). The authors examined the self-adhesive resin composite cements without (0) and with (1) the use of a ceramic primer. They measured SBS initially (37°C for three hours), after water storage (37°C for one, four, nine, 16 or 25 days) and after thermal cycling (5°C and 55°C for 1,500, 6,000, 13,500, 24,000 or 37,500 cycles). The authors analyzed data by using descriptive statistics, the Mann-Whitney test, the Kruskal-Wallis test and a χ(2) test., Results: Application of a ceramic primer did not result in a negative impact on SBS. Specimens in the A1 group (that is, RelyX Unicem Aplicap with ceramic primer) exhibited significantly higher SBS before and after water storage and thermal cycling compared with specimens that were not treated with a primer. The self-adhesive resin composite cements combined with ceramic primer exhibited similar or higher SBS values compared with those in the SC group at each aging duration (that is, water storage and thermal cycling). With respect to G-CEM Capsule, the authors observed a significantly positive effect of the primer after nine and 16 days' water storage and after one and four days' thermal cycling. They observed predominantly adhesive failures., Conclusions: Ceramic primer in combination with self-adhesive resin composite cement demonstrated a positive effect on SBS to zirconia and should be used for cementation., Practical Implications: Long-term adhesion to ceramic plays an important role in the longevity of dental restorations. Therefore, the authors recommend that clinicians use a ceramic primer when cementing zirconia restorations.

Study Design: Randomized, controlled study in a laboratory setting. Blinded observations/assessment of study outcomes., Objective: The purpose of this study was to determine the performance characteristics of MASTERGRAFT PUTTY as a bone graft extender in a rabbit posterolateral spine fusion model., Summary of Background Data: The rabbit posterolateral fusion model is an established environment for testing of fusion concepts. It offers the opportunity to obtain radiographical, histological, and biomechanical data on novel fusion materials., Methods: Thirty-six rabbits were entered into the study with 30 used for analysis. Bilateral posterolateral lumbar intertransverse fusions were performed at L5-L6. The lateral two-thirds of the transverse processes were decorticated and covered with graft material: autograft only (2.5-3.0 cc per side), 25% MASTERGRAFT PUTTY/75% autograft (3.0 cc total per side), or 50% MASTERGRAFT PUTTY and 50% autograft (3.0 cc total per side). Animals were humanely killed at 8 weeks postsurgery., Results: The autograft group had a 63% radiographical fusion rate (5 of 8) and correlated with manual palpation results (63%). The 25% MASTERGRAFT PUTTY group had a 73% radiographical fusion rate (8 of 11) and a manual palpation fusion rate of 64%. The 50% MASTERGRAFT PUTTY group demonstrated a 91% (10 of 11) radiographical fusion rate and 73% manual palpation fusion rate. Histologically, no inflammatory reactions were evident regardless of implant. The 2 MASTERGRAFT PUTTY groups had new bone in direct apposition to the MASTERGRAFT ceramic granules., Conclusion: In this commonly used rabbit posterolateral fusion model, MASTERGRAFT PUTTY in an autograft extender mode produces clinically and radiographically similar results to autograft fusion alone.

Objective: To evaluate the shear bond strength (SBS) between alumina-toughened zirconia (ATZ) cores and veneering ceramics, investigate the effect of aging in artificial saliva on SBS and compare it with that of yttria-stabilized tetragonal zirconia polycrystals(Y-TZP)., Methods: Bars of ATZ and Y-TZP were layered with veneering ceramics in accordance to the recommendation of the manufacturer. Half of each group (n = 10) was aged at 134 °C (under 2 bar pressure) in an autoclave for 48 h. Subsequently, all specimens were subjected to shear force in a universal testing machine. The interface and fractured surface of the specimens were evaluated using scanning electron microscopy and X-ray energy dispersive spectroscopy., Results: The initial mean SBS values in MPa±SD were 28.9±8.0 for ATZ and 26.2±7.6 for Y-TZP. After aging, the mean SBS values for ATZ and Y-TZP were 22.9±4.9 MPa and 22.8±6.9 MPa, respectively. Neither the differences between the SBS values of the ATZ and Y-TZP groups nor the influence of aging on all groups were statistically significant., Conclusions: The SBS between the ATZ core and the veneering ceramics was not affected by aging. The SBS of ATZ to veneering ceramics was not significantly different compared with that of Y-TZP., (Copyright © 2012 Hainan Medical College. Published by Elsevier B.V. All rights reserved.)

Purposes: The aim of this study was to assess the effect of differences in the thermal expansion behaviour of veneering ceramics on the adhesion to Y-TZP, using a fracture mechanics approach., Methods: Seven veneering ceramics (VM7, VM9, VM13, Lava Ceram, Zirox, Triceram, Allux) and one Y-TZP ceramic were investigated. Thermal expansion coefficients and glass transition temperatures were determined to calculate residual stresses (σ(R), MPa) between core and veneer. Subsequently, the veneering ceramics were fired onto rectangular shaped zirconia specimens, ground flat and notched on the veneering porcelain side. Then specimens were loaded in a four-point bending test and load-displacement curves were recorded. The critical load to induce stable crack extension at the adhesion interface was evaluated to calculate the strain energy release rate (G, J/m(2)) for each system., Results: Residual stresses ranged from -48.3±1.5MPa (VM7) to 36.1±4.8MPa (VM13) with significant differences between all groups (p<0.05). The strain energy release rate of the Y-TZP/veneer specimens ranged from 8.2±1.7J/m(2) (Lava Ceram) to 17.1±2.8J/m(2) (VM9). Values for G could not be obtained with the VM7, Allux and VM13 specimens, due to spontaneous debonding or unstable crack growth. Except for Triceram and Zirox specimens, strain energy release rate was significantly different between all groups (p<0.05)., Conclusion: Thermal residual stresses and strain energy release rates were correlated. Slight compressive stresses in the region of -20MPa were beneficial for the Y-TZP/veneer interfacial adhesion. Stresses higher or lower than this value exhibited decreased adhesion., (Copyright © 2011 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Zirconia (Y-TZP) is used as material for components of implants and prostheses because of its high short-term strength. The mechanical long-term reliability, however, is limited for Y-TZP because of hydrothermal aging effects and a pronounced tendency for subcritical crack growth. The hypothesis of this study was that a substantial amount of alumina in a zirconia matrix can help to significantly suppress subcritical crack growth and thereby improve the mechanical long-term reliability. The Weibull parameters as well as the parameters of the subcritical crack growth were determined for Alumina, Y-TZP, and two dispersion ceramics, that is Alumina Toughened Zirconia (ATZ, 20% alumina/80% Y-TZP), and Zirconia Toughened Alumina (ZTA, 75% alumina/25% Y-TZP). The long-term failure probability as a function of service time was predicted for the four ceramics. The parameter n of the subcritical crack growth was approx. 80% higher for ATZ compared to Y-TZP. In consequence, the estimated lifetime revealed a significant better mechanical long-term reliability for ATZ. It can be concluded that tailored dispersion oxide ceramics can address the aging problem of monolithic zirconia. This makes ATZ very interesting for components of joint replacement as well as for dental prostheses and implants.

Zirconia-based ceramics with high strength have been identified as a material of choice for sliding components in a variety of biomedical and engineering applications. Despite the high flexural strength, zirconia prostheses are still vulnerable to wear and surface damage. We hypothesize that such tribological damage may be substantially mitigated by an engineered grading of elastic modulus at the ceramic surface. In this study, graded structures were fabricated by infiltrating glass into the top and bottom surfaces of zirconia plates, with resulting diminished modulus in the outer surfaces. The plates were then subjected to frictional sliding tests using a hard spherical indenter. Compared with noninfiltrated controls, infiltrated specimens showed a significant increase in the fracture loads, by over a factor of 3. The increase in the sliding contact resistance is attributed to the diminishing tensile stresses at the graded lower modulus surface. The results confirm that suitably graded structures can be highly beneficial in the design of next-generation orthopedic and dental prostheses.

Diarrhoeal diseases cause an estimated 1.87 million child deaths per year. Point-of-use filtration using locally made ceramic filters improves microbiological quality of stored drinking water and prevents diarrhoeal disease. Scaling-up ceramic filtration is inhibited by lack of universal quality control standards. We investigated filter production variables to determine their affect on microbiological removal during 5-6 weeks of simulated normal use. Decreases in the clay:sawdust ratio and changes in the burnable decreased effectiveness of the filter. Method of silver application and shape of filter did not impact filter effectiveness. A maximum flow rate of 1.7 l(-hr) was established as a potential quality control measure for one particular filter to ensure 99% (2- log(10)) removal of total coliforms. Further research is indicated to determine additional production variables associated with filter effectiveness and develop standardized filter production procedures prior to scaling-up.

Several variations of microelectrode arrays are used to record and stimulate intracortical neuronal activity. Bypassing the immune response to maintain a stable recording interface remains a challenge. Companies and researchers are continuously altering the material compositions and geometries of the arrays in order to discover a combination that allows for a chronic and stable electrode-tissue interface. From this interface, they wish to obtain consistent quality recordings and a stable, low impedance pathway for charge injection over extended periods of time. Despite numerous efforts, no microelectrode array design has managed to evade the host immune response and remain fully functional. This study is an initial effort comparing several microelectrode arrays with fundamentally different configurations for use in an implantable epilepsy prosthesis. Specifically, NeuroNexus (Michigan) probes, Cyberkinetics (Utah) Silicon and Iridium Oxide arrays, ceramic-based thin-film microelectrode arrays (Drexel), and Tucker-Davis Technologies (TDT) microwire arrays are evaluated over a 31-day period in an animal model. Microelectrodes are compared in implanted rats through impedance, charge capacity, signal-to-noise ratio, recording stability, and elicited immune response. Results suggest significant variability within and between microelectrode types with no clear superior array. Some applications for the microelectrode arrays are suggested based on data collected throughout the longitudinal study. Additionally, specific limitations of assaying biological phenomena and comparing fundamentally different microelectrode arrays in a highly variable system are discussed with suggestions on how to improve the reliability of observed results and steps needed to develop a more standardized microelectrode design.

Introduction: A general trend in all ceramic systems is to use veneering ceramics of slightly lower thermal expansion coefficients compared with that of the framework resulting in a positive mismatch in thermal expansion coefficient (+DeltaTEC). The concept behind this TEC mismatch is to generate compressive stresses in the weaker veneering ceramic and thus enhance the overall strength of the restoration. This technique had excellent results with porcelain fused to metal restorations (PFM). However, there are concerns to apply this concept to all-ceramic restorations. The aim of this research was to determine the stresses in bilayered all-ceramic restorations due to the mismatch in TEC., Materials and Methods: Two commercial veneering ceramics with a TEC lower than that of zirconia (+DeltaTEC); NobelRondo zirconiatrade mark and Lava Ceramtrade mark, plus one experimental veneering ceramic with an identical TEC that matches that of zirconia (DeltaTEC = 0) were used to veneer zirconia discs. The specimens were loaded in biaxial flexure test setup with the veneer ceramic in tension. The stresses due to load application and TEC mismatch were calculated using fractography, engineering mathematics, and finite element analysis (FEA)., Results: In this study, the highest load at failure (64 N) was obtained with the experimental veneer where the thermal mismatch between zirconia and veneering ceramic was minimal. For the two commercial veneer ceramics the magnitude of the thermal mismatch localized at the zirconia veneer interface (42 MPa) exceeded the bond strength between the two materials and resulted in delamination failure during testing (ca. 50 MPa)., Significance: For all-ceramic zirconia veneered restorations it is recommended to minimize the thermal mismatch as much as possible., ((c) 2008 Wiley Periodicals, Inc.)

Calcium silicate (CaSiO(3)) is regarded as a potential bioactive material. However, its poor chemical stability and cytocompatibility limits its biological applications. The aim of this study is to incorporate Titanium (Ti) into CaSiO(3) to produce a ceramic with improved chemical stability and biological properties. Sphene (CaTiSiO(5)) ceramics were prepared by sintering sol-gel-derived CaTiSiO(5) powder compacts and their chemical stability was assessed by measuring the ions released and weight loss after soaking CaTiSiO(5) in simulating body fluid for 1, 3, 7, and 14 days. Results indicated that CaTiSiO(5) has a significantly improved chemical stability, compared with CaSiO(3). The ability of CaTiSiO(5) ceramics to support human bone-derived cells (HBDC) attachment, proliferation, and differentiation was assessed using scanning electron microscopy, MTS, and alkaline phosphatase activity assays, respectively. CaTiSiO(5) ceramics supported HBDC attachment and significantly enhanced their proliferation and differentiation, compared with CaSiO(3) ceramics. Taken together, this study demonstrates that the newly developed CaTiSiO(5) ceramics possess excellent chemical stability and bioactivity, suggesting their potential use in skeletal tissue regeneration and as coating onto currently available orthopedic/dental implants.

The aim of this work was to study, in vitro, cell colonization of two biomaterials currently used for bone and cartilage repair, this step being important to understand the function of engineered tissues. Current methods that use histological approaches are not always suited to tissue-engineering analysis. We, therefore, set up a protocol to assess cell distribution, utilizing noninvasive confocal microscopy and fluorescent labels with a far red emission wavelength to optimize scaffold transparency and minimize light scattering. Hard (ceramic substitute) and soft (collagen sponge) biomaterials were seeded respectively, on one side of the scaffold, with human fibroblasts and bovine chondrocytes labelled with carbocyanine dyes (DiD and DiR). The mean penetration depth for DiR labelled fibroblasts and chondrocytes in the two scaffolds, around 270 m, was greater than for DiD (136-218 microm) labelled cells. These depths were independent of cell origin but were influenced by the nature of the scaffolds. Collagen sponge is transparent in contrast to ceramic substitutes where measurements could only be made in opened macropores. Besides the limits of the equipment, the limits of the supports were diffusion for collagen sponges and transmission for ceramic substitutes. Confocal microscopy techniques could thus be used to address the question of cell colonization of porous biomaterials in a noninvasive manner., ((c) 2006 Wiley Periodicals, Inc.)

Study Design: Retrospective analysis of 36 cases of degenerative disc disease treated by interbody fusion with polyetheretherketone (PEEK) cages., Objective: To determine the safety and efficiency of PEEK cages for anterior cervical fusion (ACF)., Summary of Background Data: ACF with autologous bone has been reported since over 50 years ago. The recent development of cages housing materials inducing osteogenesis simplifies the technique of interbody fusion. The main purposes of bone substitutes for ACF are immediate biomechanical support, osteo-integration of the graft, and elimination of local side effects at the donor site. This report shows our results using PEEK cages., Materials and Methods: During an 18-month period, 36 consecutive patients had cervical fusions at 43 levels between C3 and C7. All operations involved one or two disc spaces for degenerative disc disease. We implanted all disc spaces with PEEK cages (Stryker Corporation, Kalamazoo, MI) containing granulated coralline hydroxylapatite (Pro-Osteon 200, Interpore Cross International, Irvine, CA) or deantigenated pig bone in a gel solution (Gen-Os, Tecnoss, Torino, Italy)., Results: About 97% of patients had a good to excellent outcome; the result in one myelopathic patient was fair. The cervical fusion rate was 16.7% at 3 months, 61.1% at 6 months, and 100% at one year., Conclusions: PEEK cages appear to be safe and efficient for ACF. In order to confirm our preliminary impressions studies on larger series with long term follow-up are warranted.

The aim of this study was to test the utilization of a generally accepted quality criteria system (United States Public Health Services Modified Quality Criteria) in the authors' practice, in the cases of all ceramic inlays and onlays. 41 ceramic inlays/onlays--29 pressed and 12 laminated--were made for 28 patients. Restorations were controlled after 2 years of cementation. According to the USPHS criteria system the following characteristics were controlled: anatomic contour, marginal integrity, marginal discoloration, color match, secondary caries, and surface roughness. In addition, postoperative sensitivity, patient's satisfaction and tooth vitality were examined as well. The USPHS quality criteria system together with the complementary data proved to be an objective examination method that was easily applicable to our clinical practice. On the basis of these studies the utilization of this system together with patient's satisfaction, tooth vitality and sensitivity records appeared a good basis for a regular quality control system of ceramic inlays and onlays.

Purpose: The purpose of this study was to clarify the effect of holding condition with different prism length on the Notchless Triangular Prism (NTP) fracture toughness test and to define the prism length as a measuring condition., Methods: Two kinds of NTP prism (ceramic and composite resin) were fabricated by CAD/CAM and each prism was adjusted to one of three lengths (8.0 mm, 12.0 mm, 16.0 mm). NTP was conducted for prism specimens made under six different conditions. The displacement of prism specimen holder gap (Delta d) and maximum fracture load (Pmax) were recorded and then a fractogram of each prism was inspected by SEM., Results: Inclined stable fracture propagation was observed on the fractogram of the 8.0-mm prism. Both Delta d and Pmax of the 8.0-mm prism were significantly higher than those of the other lengths., Conclusions: A prism length of at least 12.0 mm is needed for the NTP because the 8.0-mm prism did not have a sufficient holding condition. The fracture toughness of the ceramic (3.68+/-0.09 MPa.m(1/2)) was significantly higher than that of the composite resin (2.38+/-0.20 MPa.m(1/2)).

Different types of calcium phosphates [hydroxyapatite (HA), fluorapatite (FA), tricalcium phosphate (TCP), and their composites (HA + FA, HA + TCP)] were coated on a zirconia (ZrO(2)) porous scaffold using a powder slurry method. The ZrO(2) porous scaffold was intended for a load-bearing implant, and the apatite layers were coated to improve osteoconductivity. The insertion of an FA intermediate layer between the coating layer and ZrO(2) scaffold effectively suppressed the reaction between the calcium phosphate and ZrO(2) and maintained the coating layer at the initial powder composition. The obtained coating layer, of a thickness of approximately 30 microm, was relatively microporous and firmly adherent to the ZrO(2) scaffold. Dissolution tests in physiological solution showed typical differences depending on the coating layers, with the dissolution rate increasing in the order TCP > HA + TCP > HA > HA + FA > FA. This result suggests the functional coating of the calcium phosphates in view of tailoring the solubility. Osteoblast-like cells, MG63 and HOS, responded similarly in terms of cell growth, morphology, and proliferation rate regardless of the coating types, indicating favorable and comparable cell viability. However, the alkaline phosphatase (ALP) activity of the cells on the pure HA and HA composite coatings (HA + FA and HA + TCP) expressed at higher levels compared to those on pure FA and pure TCP coatings for both MG63 and HOS cells, suggesting a selective cell activity depending on the coating types. All the calcium phosphate-coated-ZrO(2) scaffolds showed higher ALP levels compared to pure ZrO(2) scaffold., (Copyright 2004 Wiley Periodicals, Inc.)

Porous hydroxyapatite (HA) has already been widely used as a bone substitute due to its similarity with the mineral part of the bone. In this work, cylindrical tablets with micro and macro porosity were produced from stoichiometric and deficient hydroxyapatites by using naphthalene as porosifier agent. The influence of the processing parameters such as Ca/P ratio of start material, calcination temperature, and naphthalene content on the characteristics of porous calcium phosphate tablets was evaluated. Three mineral phases-HA, alpha-TCP (alpha tri-calcium phosphate), and beta-TCP (beta tricalcium phos-phate)-with variable contents were identified by x-ray diffraction (XRD) and Fourier-transformed infrared spectroscopy (FT-IR). Image analysis and density measurements were used to characterize sample porosity. As expected, the total porosity of the calcinated material is not dependent on the stoichiometry of the precursor hydroxyapatite. For calcium-deficient hydroxyapatite, the increase in naphthalene content contributes to stabilize alpha-TCP phase, altering the relative phases content.

This study demonstrates the anti-Staphylococcus aureus properties of stainless steel surfaces coated with zeolite containing 2.5% silver and 14% zinc ions. Stainless steel panels with and without the heavy-metal-containing coatings were inoculated with S. aureus and incubated at room temperature. Survival of S. aureus was significantly reduced by the silver/zinc coatings within 1 h. Many hospital surfaces could be constructed of stainless steel with silver/zinc zeolite coatings. Such measures may reduce rates of hospital-acquired S. aureus infection., (Copyright 2002 The Hospital Infection Society)

Objectives: Prosthetic posts made of zirconia ceramics are beneficial because of their esthetic advantages. The mechanical reliability of ceramic posts is limited because of the strength level and the large scatter in strength of ceramic materials. The hypothesis of this study is that the failure of ceramic posts in vivo, which occur on low-quality posts because of critical microscopic defects can be excluded using the so-called proof test technology., Methods: The theory of the proof test technology is explained in detail in this study. In the experimental part 22 ceramic posts were tested at different proof load levels using a stepwise rotating four-point bending proof test device., Results: The experimental failures deviated from the theoretical failure probabilities by 0.24-12.69%. The deviation would be further reduced in a serial proof test using batches with a greater quantity of posts. The test eliminated those posts, which contained microscopic defects above a critical size of clinical relevance., Significance: The technology can help to reduce clinical failures of non-vital abutment teeth with ceramic posts, which are caused by critical microscopic defects of the ceramic material as a result of the industrial manufacturing process.

Bone substitute materials are very demanding with respect to their quality, in particular, a high toughness and durability are required. In case of producing the composites by sintering of mechanically generated powder mixtures, a high efficiency of mixture is demanded, too. The characterisation of such particle systems is difficult. An effective method is the image analysis supported by statistical evaluation of both the size and the shape distributions of particles and agglomerates. As it is proved by first results, powder mixtures of hydroxyapatite can be described by the geometry of voids in the agglomerate structure using the shape factor weighted by area of the respective image object. As a measure of the efficiency of mixture, the degree of reproducibility was introduced.

Results of contact tests using spherical indenters on flat ceramic coating layers bonded to compliant substrates are reported for selected dental ceramics. Critical loads to produce various damage modes, cone cracking, and quasiplasticity at the top surfaces and radial cracking at the lower (inner) surfaces are measured as a function of ceramic-layer thickness. It is proposed that these damage modes, especially radial cracking, are directly relevant to the failure of all-ceramic dental crowns. The critical load data are analyzed with the use of explicit fracture-mechanics relations, expressible in terms of routinely measurable material parameters (elastic modulus, strength, toughness, hardness) and essential geometrical variables (layer thickness, contact radius). The utility of such analyses in the design of ceramic/substrate bilayer systems for optimal resistance to lifetime-threatening damage is discussed., (Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 137--145, 2002; DOI 10.1002/jbm.10091)

Previous work has shown that lithium mica glass-ceramics were excellent potential candidates as dental ceramics. The purpose of this study was to evaluate the effect of various additives on the microstructure and thermal properties of a mica glass-ceramic in the system Li(2)O-K(2)O-SiO(2)-MgO-F. Five glass compositions were prepared: a base composition and four compositions with various additives. The compositions were melted at 1400 C for 2 h and cast into 50 x 8 mm ingots. Differential thermal analyses were performed on the glasses up to 1400 C. Bars (4 x 8 x 25 mm) were cut from the ingots and heat treated at various temperatures. The crystalline phases were analyzed by x-ray diffraction. The microstructure was investigated by scanning electron microscopy. The percent crystallinity, crystal density, and average particle size were calculated from stereology measurements. X-ray diffraction revealed that the major crystalline phase was taeniolite for all glass-ceramics. Differential thermal analyses showed that the crystallization exotherm occurred in the temperature range 600--700 C. The addition of calcium fluoride was most efficient in promoting the growth of mica crystals. Larger mica plate diameter could be beneficial to the crack-propagation resistance of the glass-ceramic. The addition of aluminum phosphate promoted nucleation rather than crystal growth and led to a significantly lower glass transition temperature and crystallization exotherm temperature., (Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 146--151, 2002; DOI 10.1002/jbm.10122)

The successful application of the concept of computer-assisted manufacturing in restorative dentistry requires that computer-assisted design (CAD) and computer-assisted machining (CAM) not only meet but actually exceed currently accepted standards for the material and clinical quality of dental restorations. In addition, the continued development of systems for polyvalent processing of disparate materials and objects must be assured. With these critical requirements in mind, the Precident system is a clinically proven and competitive system. The resolving power of the CCD chip is much improved compared to conventional cameras or charge-coupled devices. The scanner is able to scan entire casts in a fully automated process. In principle, this facilitates the production of frameworks for fixed prosthetic devices (FPD) of any size. It is also possible to create at least partial frameworks for removable prosthetic devices (RPD). A factor of great clinical and economic importance is the polyvalence of the process in materials processing: the numeric control (NC) machine can be programmed for metal alloys and ceramic materials as well as fiber-reinforced resins. At Aeskulap Klinik, the Precident System is routinely used for producing all single crowns and FPDs with up to four units. CAD/CAM all-ceramic crowns and FPDs currently cost about the same as metallo-ceramic or conventional all-ceramic restorations.

The availability of improved ceramic materials, bonding techniques, new technology and issues of amalgam safety have led to a revival of interest in ceramic inlays in dentistry over the past ten years. Clinical studies have been carried out during this time using various evaluation techniques to assess the clinical performance of these restorations. In this paper, recent clinical studies are examined and a review of the current state of knowledge regarding the clinical performance and survival statistics of ceramic inlays is presented. The major problems associated with ceramic inlay therapy appear to be fracture, hypersensitivity, degree of fit, maintenance of marginal integrity, microleakage, bond failures and cement wear. Other areas which also affect the clinical performance of ceramic inlays are ceramic wear, opposing tooth wear, plaque accumulation, gingivitis, secondary caries, colour stability, anatomic form and radiopacity. Recommendations based on the findings of clinical studies are also presented and whilst no specific material or technique has been shown to be clearly superior, certain principles which predispose to success can be identified. When compared with other forms of aesthetic intracoronal restorations, ceramic inlays perform well. However, their high cost and extreme technique sensitivity would appear to restrict their use to certain limited clinical situations.

Unlabelled: We used this material in clinic since 1995., Objective: Discussion on the prosthetic effects of the above-mentioned material to spreat it clinically., Methods: Through half to two years clinical observations to evaluate the effect of IPS Empress crowns in anterior teeth and inlays in posteriors., Results: and, Conclusion: Prosthesis made of this kind of material IPS Empress is one kind of excellent all-ceramic prosthetic material. IPS Empress also could be used in post crowns and the clinical effect was satisfactory.

Objective: To evaluate the relation between different opaque thickness and color difference., Methods: Model made of the thin plastic paper was used to control the ceramic thickness. The data of chromaticity was measured by TC-PIIG auto color difference meter and its results were processed by computer., Results: There are two thickness values which can be considered as ideal range of opaque thickness for color opaquing: one is the values of ceramic thickness which is based on the color difference values of the infinite chromaticity thickness (ICT) and the other is the values of ceramic thickness which is depended on the color difference values which is 1.5 compared with ICT. The ideal range for VITA is (0.207-0.152) mm, SHOFO is (0.190-0.160) mm, CARAT is (0.140-0.074) mm and EXCELCO is (0.169-0.144) mm., Conclusion: There is a relationship of non linear direct ratio between opaque thickness and its shadow capacity. However, no more increase of color difference values in respect to the thickness was found when the ceramic thickness reach a certain value. Different ceramic porcelain needs different ideal range of thickness.

The overall resistance to accidental blows of the many ceramic brackets that are sold today has not been explored. Facing a similar diversity, the eyeglasses industry has chosen to standardize the testing of lenses by subjecting them to the drop of a steel ball. By slightly modifying this test, 10 brands of ceramic brackets were examined. In most cases, the findings coincided with those found by other authors when duplicating debonding. Thus, polycrystalline ceramics with bulkier structures and glazed surfaces were found to be more resistant to impact than the monocrystalline brackets, the loftier real "twins," and the less dense attachments. Protruding tie wings and bases were liabilities, and domed configurations seemed to deflect the blows. Bulkier "single" designs alone did not offer a guarantee of impact resistance when not accompanied by an appropriate microstructure and a smooth surface. The ceramic brackets most resistant to impact were found to be 20/20 by American Orthodontics and Fascination by Dentaurum. Medium resistance was displayed by Lumina by Ormco, Allure III and Allure by GAC, Transcend 2000 and Transcend by Unitek/3M; the last was not as good as the other four. The least resistant were Illusion by Ortho-Organizers, Intrigue by Lancer Orthodontics, and Starfire TMB by "A"-Co. Probably because of its real twin design, the last bracket lends itself to the highest probability for accidental breakage. Although resistance to impact and accidental debonding is desirable from the point of view of treatment, the advantage should be weighted against the chance of enamel fracture. Indeed a weak bracket attached with a soft adhesive may be preferable when the chance of an increased exposure to accidental blows is probable. In such cases, the ceramic may take the brunt of the force, instead of the tooth.

The objective of this investigation is to test by common perception, the colour fidelity of laboratory-fired samples of ceramic. Thirty-two ceramic discs were constructed in a thickness similar to that used for ceramic veneers using eight shades from each of four different manufacturers. A group of 20 'adept' observers colour matched the samples in strictly controlled viewing conditions using a Vita Lumin (Vita Zahnfabrik) shade guide. Samples were categorised as 'positive matches'(matching the expected shade), 'agreed shades' (matching an unexpected shade), or as 'unidentified shades' (no match). The Vita Lumin (Vita Zahnfabrik) colour 'value' index was used as a reference to categorise colour 'value' differences between observed and expected shade. Colour 'value' selection was divided into three groups: (1) matching colour 'value', (2) shades of higher colour 'value' than expected or (3) shades of lower colour 'value' than expected. Only six of the 32 samples examined were perceived to be 'positive matches' with the recommended shade guide. Fourteen 'agreed shades' were found while the remaining 12 shades were regarded as 'unidentified shades'. The vast majority of observations disagreed with the manufacturers' designated shade. A significant trend was found favouring higher 'value' (lighter) shades than those specified by the manufactures. Significant differences in the pattern of shade matches and disagreements between brands were also found. Alternative shade determination systems and/or ceramic colour modifications are required if colour fidelity between the shade guide and the materials tested is to be improved.

Bioceramics are used in a wide range of different clinical applications, the most important being femoral heads in total hip replacement. Because of their very attractive mechanical properties, zirconia ceramics (ZrO2) have recently been used as implant material. At the present time, two medical-grade types of zirconia are available: Mg-PSZ and Y-TZP. For the Y-TZP, an international standard (ISO) was issued. The standard is discussed, and the properties that are of importance in the field of orthopaedics are identified.