Ceramic Fracture Research Articles

Observing the crack tip behavior at the nanoscale during fracture of ceramics

Ultimately, brittle fracture involves breaking atomic bonds. However, we still lack a clear picture of what happens in the highly deformed region around a moving crack tip. Consequently, we still cannot link nanoscale phenomena with the macroscopic toughness of materials. The unsolved challenge is to observe the movement of the crack front at the nanoscale while extracting quantitative information. Here, we address this challenge by monitoring stable crack growth inside a transmission electron microscope. Our analysis demonstrates how phase transformation toughening, previously thought to be effective at the microscale and above, promotes crack deflection at the nanolevel and increases the fracture resistance. The work is a first step to help connecting the atomistic and continuous view of fracture in a way that can guide the design of the next generation of strong and tough materials demanded by technologies as diverse as healthcare, energy generation, or transport.

A 3-year clinical evaluation of endocrown restorations with two different materials using the computer-aided design/ computer-aided manufacture system

ObjectiveTo compare the clinical efficacy of resin nanoceramic and zirconia-reinforced lithium silicate ceramic endocrowns in the treatment of endodontically treated teeth by assessing the clinical performance of restorations fabricated using a chairside computer-aided design/computer-aided manufacturing (CAD/CAM) system. Materials and methodsNinety endocrown restorations were fabricated on endodontically treated teeth using a CAD/CAM system. Fifty-two restorations were fabricated using Lava Ultimate blocks (LU, 3 M Espe, Seefeld, Germany) and 38 restorations were fabricated using Celtra Duo blocks (CD, Dentsply Sirona, York, PA, USA). The performance of the endocrown restorations was evaluated over a 3-year period using the modified United States Public Health Service (USPHS) criteria by two calibrated evaluators. The data were analyzed using Chi-square (x2) and Fisher exact tests (p < 0.05). ResultsThe restoration survival rates in the two groups were 82.7 % (LU) and 86.8 % (CD) (p = 0.6). Twelve restorations failed (8 LU, 4 CD) due to debonding (n = 4, 2 LU, 2 CD), ceramic fracture (n = 2, 1 LU, 1 CD), tooth fracture (n = 5, 4 LU, 1 CD), and secondary caries (n = 1, 1 LU) during the follow-up period. There was no statistically significant difference between the two materials according to the modified USPHS criteria (p > 0.05). ConclusionResin nanoceramic and zirconia-reinforced lithium silicate ceramic endocrown restorations fabricated using a chairside CAD/CAM system demonstrated acceptable clinical performance in the treatment of endodontically treated teeth. Clinical SignificanceResin nanoceramic and zirconia-reinforced lithium silicate ceramics are potential alternative materials for the chairside fabrication of endodontically treated teeth.

Fracture behaviors and crack propagation anisotropy in multi-ions modified bismuth titanate ferroelectrics

Bismuth titanate (BIT) is widely considered a promising lead-free piezoelectric material for advanced high-temperature applications. Despite significant advances in high-performance BIT ferroelectrics, there remains little understanding of mechanical properties including fracture failure and crack propagation behaviors, hindering the optimization of stability and reliability for next-generation high-temperature ferroelectrics. In this work, we investigated mechanical fracture and crack propagation behaviors of a type of high-performance bismuth titanate-based ceramic (Bi3.96Ce0.04Ti3–2xWxNbxO12, BCTWN) with different doping contents and electric poling states. High-resolution transmission electron microscopy (HRTEM) and electron backscatter diffraction (EBSD) results reveal that the BCTWN ceramics possess a single ferroelectric phase and exhibit layered crystal structures characterized by periodic fringe features. In addition, the striped domain structures are observed on the surface of plate-like grains. Mechanical measurements indicate that fracture behaviors of BCTWN ceramics are significantly affected by doping contents. The ceramics with the largest grain size present inferior microstructure with more defects, endowing the lowest bending strength and fracture toughness. For the samples with different poling states, strong anisotropy in crack propagation and fracture toughness is observed, attributed to the different domain switching mechanisms driven by local incompatible stress fields, which is experimentally validated by the intriguing evolutions of striped domain structures around crack tips. This work advances our understanding of the fracture and crack propagation mechanisms of BIT-based ceramics and provides insight into tailoring the mechanical behaviors through doping and poling strategies.

Incidence of Ceramic Component Fractures in Total Hip Arthroplasty Using Contemporary Ceramic-On-Ceramic Bearings: A Retrospective Study Spanning Two Decades From Two Tertiary Referral Hospitals

IntroductionCeramic-on-ceramic (CoC) bearings have been widely used in total hip arthroplasty (THA) due to their excellent wear properties. However, ceramic component fractures remain a concern. This study aimed to report the incidence of third- and fourth-generation ceramic component fracture and identify factors that might influence this complication. MethodsA total of 9,280 hips that underwent THA with third- and fourth-generation CoC bearings at two tertiary institutions between 1997 and 2023 were retrospectively reviewed, and the incidence and associated factors of CoC bearing fracture were determined. We performed a Kaplan–Meier survival analysis to assess implant survivorship. Logistic regression was applied to evaluate the influence of implant size and patient-specific factors on the risk of revision. ResultsOut of the 9,280 THA procedures, there were 33 (0.36%) revisions for CoC bearing fracture. Specifically, revisions for fracture were performed for zero out of 6,654 fourth-generation CoC heads, 26 (0.990%) of 2,626 third-generation CoC heads, two (0.030%) of 6,654 fourth-generation CoC liners, and five (0.190%) of 2,626 third-generation CoC liners. All ceramic head fractures occurred in a 28 mm head. Younger age was related to both ceramic head and liner fracture. ConclusionsTo our knowledge, this is the largest two-center retrospective study on CoC bearing fractures to date. The risk of revision for fracture of CoC bearings is low, as previously reported. Our data were comparable to recent evidence suggesting that the latest generation of ceramic components can significantly decrease the incidence of head fracture but not liner fracture. Factors such as younger age and men may be associated with an increased risk of ceramic component fractures. Level of evidenceIII, therapeutic.

Quarter Century Outcomes of Alumina Ceramic-on-Ceramic Total Hip Arthroplasty

BackgroundAlumina ceramic-on-ceramic (CoC) bearings were widely used in total hip arthroplasty (THA) due to their superior wear resistance and inert properties, making them ideal for young, active patients who require long-lasting implants. This study aimed to synthesize findings from previous reports, providing a comprehensive follow-up of at least 25 years on the clinical and radiologic outcomes, the prevalence of osteolysis, and implant survivorship in patients undergoing primary cementless CoC THA. MethodsWe have previously reported five-to-ten-year outcomes following the implementation of third-generation alumina-on-alumina bearings in a consecutive series of 100 primary cementless THAs. This report updates those results with a minimum follow-up of 25 years. Of the original cohort, 58 patients who had 67 hips were available for the latest follow-up. Clinical assessments were performed using the Harris Hip Score (HHS) and pain questionnaires. Radiographic evaluations were employed to assess implant fixation and osteolysis. ResultsAt the final follow-up, the implant survival rate was an impressive 96.3%, with revision of the implant as the endpoint. The mean HHS improved significantly from preoperative values to 90.1, indicating excellent functional outcomes. The incidence of ceramic-related noise increased over time, with three cases of ceramic head fractures requiring a change of bearings. Notably, the extent of stem notching observed in earlier reports did not show further progression. Radiologically, all implants demonstrated bony ingrowth with no signs of aseptic loosening or major osteolysis. ConclusionThe long-term (minimum 25-year) follow-up of alumina-on-alumina bearings in primary cementless THA demonstrates outstanding implant survivorship, excellent functional outcomes, and minimal adverse effects over twenty-five years. Despite some issues like ceramic-related noise and component fractures, the overall performance of CoC bearings remains highly encouraging, particularly suitable for young, active patients. Surgeons should provide appropriate education to both potential THA candidates and patients who already have THAs with CoC bearings.

Long-term clinical results and patient satisfaction of a metaphyseal-engaging anatomic cementless femoral component in total hip arthroplasty.

There is relatively little information on the long-term clinical results of patients aged < 50 years with a contemporary total hip arthroplasty (THA), although a high rate of revision is projected for this group. Therefore, the purpose of this study was to evaluate the long-term results (a minimum of 21 years) of a metaphyseal-engaging anatomic cementless total hip prosthesis in patients aged < 50 years at the time of their THA. This study included 360 patients (498 hips), specifically 212 men and 148 women. The mean age of the patients at the time of their THA was 45.8 ± 8.1 years. The predominant diagnosis was osteonecrosis (56%). Demographic data, the Harris hip score, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the University of California, Los Angeles (UCLA) activity score were recorded. Radiographic evaluation and dual-energy X-ray absorptiometry (DEXA) scanning were used to evaluate implant fixation, bone remodelling, and osteolysis. The mean follow-up was 25.2 year (range 21-28 years). At the latest follow-up, the mean Harris hip, WOMAC, and UCLA activity scores were 93, 10, and 6.7 points, respectively. No patients had thigh pain. All hips had osseous integration of the acetabular and femoral components. No patient had grade 3 stress shielding. The 28-year survival rate was 98.2% (95% confidence interval [CI] 95-100%) for the acetabular components and 98.8% (95% CI 95-100%) for the femoral components. Overall, 90% of the patients were satisfied with the THA results. The results suggest that a metaphyseal-engaging anatomic cementless femoral stem with alumina-on-alumina ceramic articulation provide outstanding long-term fixation and substantial pain relief well into the 3rd decade after surgery. Furthermore, there was no alumina ceramic fracture or osteolysis. Moreover, approximately 90% of the patients were satisfied with the results of their THA.

Constitutive model of high-temperature rapid fracture of Si3N4 ceramics for engine turbine discs and their pore insensitivity parameters

ABSTRACT The metallic materials used to manufacture turbine components can potentially be replaced with ceramics such as Si3N4, but the stress on turbine discs is difficult to determine experimentally, which hinders the development and optimization of ceramics. The finite element method solves this problem, but it requires an accurate constitutive model and parameters. Existing methods for determining model parameters lack versatility and do not consider the internal pores of ceramics. This work proposes a method for determining the parameters of the high-temperature rapid fracture constitutive model of ceramics with internal pores based on the results of industrial computed tomography (CT) and high-temperature fracture toughness experiments. The constitutive model for a ceramic with internal pores was selected based on the typical service conditions of turbine discs. Industrial CT was used to measure pore information. A finite element preprocessor was developed to create simulated specimens with pores. The high-temperature fracture toughness of the ceramics was measured. Pore insensitivity was the parameter obtained from the high-temperature constitutive model of ceramics with pores using this method. The maximum relative error between the predicted and experimental flexural strengths was 6.8%. It provides a new idea for determining the parameters of constitutive models for materials with pores.

Why Are Contemporary Primary Ceramic–on–Highly Crosslinked Polyethylene Total Hip Arthroplasties Failing? An Analysis of Over 5,500 Cases

BackgroundCeramic–on–highly crosslinked polyethylene (HXLPE) has become the most common bearing surface utilized in primary total hip arthroplasty (THA). The purpose of this study was to determine the implant survivorship and clinical outcomes of THAs with ceramic-on-HXLPE in a large single-institutional series. MethodsWe identified 5,536 primary THAs performed from 2007 to 2017 using a ceramic-on-HXLPE bearing through our total joint registry. The mean age was 60 years, 51% were women, and the mean body mass index was 30. A cementless femoral component was used in 98% of cases, and a head size of ≥ 36 was used in 75%. Kaplan-Meier survivorship analyses were completed to assess survivorship free of any revision or reoperation. Clinical outcomes were assessed via Harris Hip Score. The mean follow-up was four years. ResultsThe 5-year survivorship free of any revision was 97%. The most common indications for revision were dislocation (41 hips), periprosthetic joint infection (39 hips), and periprosthetic femur fracture (18 hips). The 5-year survivorship free of any reoperation was 96%. There were an additional 70 reoperations, with the most common indications being wound dehiscence (32 hips), iliopsoas impingement (11 hips), and periprosthetic femur fracture (11 hips). There were only two bearing surface failures: one HXLPE liner fractured and one dissociated. There were no ceramic head fractures or failures. The mean Harris Hip Score increased from 57 to 92 (P < 0.0001). ConclusionsIn over 5,500 THAs completed with modern ceramic-on-HXLPE bearings, failures of the bearing surface were nearly eliminated at midterm follow-up, and overall 5-year survivorship free of revision was excellent. Dislocation, periprosthetic joint infection, and periprosthetic femur fracture were the most common causes of failure. As bearing surfaces have evolved, traditional failure mechanisms such as polyethylene wear, corrosion and metal reactions, and ceramic fractures have become nearly extinct. Level of EvidenceIII (Case-Control Study), Therapeutic.

Mechanical properties and multi-field ferroelastic response of Nb/Mn Co-doped CaBi4Ti4O15 high-temperature ferroelectric ceramics

CaBi4Ti4O15 (CBT) ceramics are promising piezoelectric materials that have been widely studied for high-temperature applications. Despite significant advancements in the electrical performance of CBT ceramics, the understanding of their mechanical behaviors remains limited, which is unfavorable for designing ceramics with high stability and reliability during high-temperature service. This work investigated the mechanical properties and fracture behaviors of Nb/Mn co-doped CaBi4Ti4O15 (CBTNM) with various doping levels, focusing on stress-strain responses and ferroelastic deformation behaviors under uniaxial compression and multi-field coupling conditions. HRTEM analysis reveals small-scale layered domain wall structures on the surface of plate-like grains. The fracture and compressive strengths of CBTNM ceramics initially decrease and then increase with an increase in doping content, and the underlying mechanisms are related to grain size, defects, and densification. CBTNM ceramics exhibit nonlinear stress-strain responses due to ferroelastic deformation under compressive loading, and the resultant irreversible domain switching strain increases with an increase in doping content, while poling can further increase the residual strain. Under multi-field loading conditions, CBTNM ceramics undergo more ferroelastic deformation events and exhibit larger residual strain. The micro-cracks, pores, complicated fracture modes, and degraded fracture surfaces with fragmental and rough features are mainly responsible for the lower elastic modulus and inferior mechanical response. This work enhances our understanding of the mechanical behaviors of high-temperature piezoelectric ceramics and provides guidance for designing high-performance piezoelectric materials for complex environmental applications.

Decoding ceramic fracture: Atomic defects studies in multiscale simulations

Microstructural atomic defects, including voids, cleavage, and inclusions, are commonly observed in alumina materials, and their impact on mechanical properties, such as fracture stress and toughness, is significant. In this paper, we introduce novel alumina models that incorporate experimentally observed void features. An atomic model is established to study the effects of micro-structural void features on fracture properties and atomic structure changes using molecular dynamics simulations. The electron backscatter diffraction and scanning electronic microscopy analysis of experimental samples are used to evaluate microstructural features that are used as inputs to the simulations (e.g., void aspect ratio, void angle). We apply an innovative Atomistic-to-Continuum (ATC) method based on Riemann sums to bridge atomic and continuum mechanics theories, evaluating the resistance of materials with atomic defects to crack propagation. The results show the greatest effects of pore angles on weakening mechanical properties such as peak strength and fracture energy density. The accuracy and efficiency of the ATC method in evaluating stress intensity factors are used to calculate the mechanical responses. Additionally, we establish a multiple layer perceptron neural network to evaluate the complex relationship between void features (aspect ratio, pore angle, relative distance) and typical fracture properties (fracture stress, critical stress intensity factor). A meta-analysis of these results from both machine learning methods and molecular dynamics simulations reveals the significant impact of each void feature on the sensitivity of typical fracture properties (peak strength, critical stress intensity factor at peak strength) and highlights the critical role of aspect ratio on fracture properties.

Explosive welding of TA2-SiC-AW5083 composite armor

This study investigates the use of explosive welding to encapsulate SiC between TA2 and 5083, aiming to achieve large-area, high-efficiency, and low-cost fabrication of ceramic composite armor. A new weldability window was established, and six configurations of ceramic composite armor were devised. Ten sets of experiments were conducted to explore the influence of explosive welding parameters, ceramic fracture, and different configurations of composite complate on mechanical properties, macro-deformation, welding interface morphology, and energy absorption and conversion. The research revealed that the fracture of ceramic influences the welding quality, the propagation of the blast wave, and the kinetic energy utilization of the flying plate, while the crevices between the ceramic and the groove on the base plate do not influence the welding quality. When the ceramic remains intact, the kinetic energy utilization rate of the flying plate can be calculated using the η = E1(1-A1/A)/Ef, and when the ceramic penetratively fractures, the kinetic energy utilization rate of the plate can be calculated using the η=(E1-E4) (1-A1/A)/Ef. Finally, we recommend adding a suitable interlayer as a buffer between the flying plate and the ceramic, and the static parameters for explosive welding should strictly adhere to the “Lower bound principle."By analyzing the energy conversion and absorption during the explosive welding process, the macro-deformation and mechanical properties of the composites, the interface morphology, and the level and characteristics of the ceramic fracture, the energy source of the ceramic fracture was found, and the effects of ceramic fracture and structural characteristics of composites on gap airflow, kinetic energy utilization of face plate, explosive wave propagation path, and welding quality were analyzed. Finally, we propose that the explosive welding static parameters of ceramic composite armor should strictly adhere to the " The principle of lower explosives limit."

Performance of Bonded Lithium Disilicate Partial-coverage Crowns in the Restoration of Endodontically Treated Posterior Teeth: An Up to Seven-Year Retrospective Study.

To evaluate the clinical performance of adhesively bonded lithium disilicate glass-ceramic (LDG) partial-coverage crowns in restoring posterior endodontically treated teeth (ETT). A total of 121 morphologically compromised posterior ETT were restored with LDG partial-coverage crowns between October 2015 and January 2018. The restorations were fabricated in the laboratory or at the chairside. Two adhesive systems and resin cements were used to cement the restorations. Tooth and restoration survival rates were calculated. The restorations were evaluated clinically using the modified United States Public Health Service (USPHS) criteria for an observation period of 5-7 years. The Cox proportional hazards model was used to estimate relative failure risks such as tooth type, resin cements, gender, and sleep bruxism. The standard chi-squared test was used to compare the survival of different tooth types for significant differences (α=0.05). In addition, survival probability was calculated using the Kaplan-Meier algorithm. Among seven failed cases, one was a tooth fracture, and six were restoration fractures. According to the Kaplan-Meier analysis, the estimated survival rate of the teeth was 99% for seven years, while the estimated survival rate of the restorations was 94.8% for 5 years and 92.8% for 7 years. Tooth type and resin cements did not influence restoration survival rates (p>0.05), while sleep bruxism and male patients might increase the risk of failure (p<0.05). The indirect adhesively bonded LDG partial-coverage crowns of posterior ETT exhibited favorable clinical outcomes. Ceramic fracture was the most common failure pattern.

May the 4th be with you: mixed-methods best-evidence synthesis on 4th-generation alumina-zirconia ceramic bearings in total hip arthroplasty.

To assess utility, benefits, and risks of 4th-generation alumina-zirconia ceramic pairings in elective total hip arthroplasty (THA). A comprehensive mixed-methods best-evidence synthesis using data from systematic reviews, randomized controlled trials (RCTs), prospective and retrospective cohort studies, as well as joint replacement registries, was conducted to estimate overall revision and survival rates, periprosthetic infection, bearing fractures, and noise phenomena with 4th-generation alumina-zirconia ceramic versus other tribological couplings in elective THA. The systematic review part across multiple databases was registered with PROSPERO (CRD42023418076), and individual study data were extracted for statistical re-analysis. Twenty overlapping systematic reviews, 7, 17, and 8 references from RCTs, cohort studies, and joint replacement registries form the basis of this work. According to current best evidence, it is (i) 15-33 times more likely that 4th-generation alumina-zirconia pairings avoid a revision for infection than causing a revision for audible noise, (ii) 38-85 times more likely that 4th-generation alumina-zirconia pairings avoid a revision for infection than causing a revision for ceramic head fractures, and (iii) three to six times more likely that 4th-generation alumina-zirconia pairings avoid a revision for infection than cause a revision for ceramic liner fractures. Fourth-generation alumina-zirconia pairings in THA show a favorable benefit-risk ratio, with rare compound-specific adverse events and complications significantly outbalanced by long-term advantages, such as a markedly lower incidence of revision for infection.

Computed Tomography Evaluation of Alumina Ceramic-on-Ceramic Total Hip Arthroplasty With More Than 20 years of Follow-Up: Is a Follow-Up Computed Tomography Scan Necessary?

BackgroundCeramic-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. MethodsBetween 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. ResultsNo 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. ConclusionsRoutine 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 evidenceLevel III, Therapeutic study.

Alternating load failure analysis under the high-temperatures vibration of thermal barrier coatings

During thermal barrier coatings (TBCs) service, high-temperature and vibration are environmental factors that cannot be ignored. The vibration fatigue damage mode of TBCs under operating conditions that couple vibrations with high temperatures is unclear. In this paper, a high-temperature vibration coupled environment simulator was developed to investigate the evolution of high-temperature vibration fatigue damage modes of LaZrCeO/7-YSZ(LZC/YSZ) TBCs under alternating loads by employing acoustic emission detection. The results show that in the initial fatigue stage, the damage appears as discrete micro-cracks formed by the initial defects in the TBCs. With the increase in the number of cycles, the initiation of transverse microcracks began to occur inside the LZC layer and at the LZC/YSZ interface. When the transverse microcracks accumulate to the critical value, the applied alternating loads accelerate the propagation of opening interfacial cracks. Finally, the columnar crystal structures of the ceramic layers fracture at different heights under cyclic loading by high-temperature vibrations.

Bearing-Related Complications of Total Hip Arthroplasty Using Fourth-Generation Ceramic-On-Ceramic Articulations: Does Articular Noise Increase Over Time?

BackgroundWe previously reported the mean 6-year outcomes of total hip arthroplasty (THA) using fourth-generation ceramic-on-ceramic (CoC) articulations. With extended observations, this study aimed to report the mean 12-year outcomes focusing on bearing-related complications of CoC THA. MethodsWe reviewed primary CoC THAs performed between May 2009 and April 2012 at a single institution. Of the 831 hips (739 patients), 716 hips (635 patients) that satisfied a minimum 10-year follow-up were included. The mean age at operation was 54 years (range, 16 to 83). The occurrence of bearing-specific complications, including ceramic fractures and noise generation, was evaluated. The mean follow-up duration was 12 years (range, 10 to 14). ResultsA total of 2 (0.3%) ceramic liner fractures occurred, as previously reported. No additional ceramic fractures were observed during the extended follow-up period. However, the cumulative incidence of audible noise increased from 6.4 (48 of 749) to 8.2% (59 of 716). Of the 59 hips with noise, 26 (44.1%) developed noise within 1 year, whereas 13 (22.0%) presented with noise more than 5 years after THA. The noise was described as clicking in 35 hips (4.9%) and as squeaking in 24 hips (3.4%). No revision surgeries were performed for noise, except in 2 cases of concomitant liner fractures. The implant survivorship free of any revision was 98.1% at 12 years. ConclusionsNo additional ceramic fractures were identified in this extension study at a minimum follow-up of 10 years. However, the prevalence of articular noise has increased from 6.4 to 8.2% since the previous report. Possible late-onset noise should be considered when performing CoC THA in younger patients.

Long-term performance of ceramic in/-onlays vs. cast gold partial crowns – a retrospective clinical study

ObjectivesTo assess the long-term clinical performance of ceramic in-/onlays (CIOs) and cast gold partial crowns (CGPCs) in posterior teeth in terms of success, survival, complications (biological, technical) and quality.Material and methodsIn a retrospective study, a total of 325 patients were recorded after up to 24.8 years (mean 13.9 ± 3.8 years) having (pre-)molars restored with CIO (Empress I, Ivoclar Vivadent, n = 161) and CGPC (Degunorm, DeguDent, n = 164) by supervised undergraduate students. A total of 296 restorations were assessed clinically and radiologically in healthy and endodontically treated teeth using modified United States Public Health Service (USPHS) criteria. Cumulative success and survival rates of the restorations were calculated using Kaplan–Meier estimates. Biological and technical complications were recorded. Status of oral health comprising caries risk and localized periodontitis were assessed.ResultsThe cumulative success rates of CIOs were 92.1% and of CGPCs 84.2% after mean service times of 14.5 years. The annual failure rates of total service times were 0.5% in teeth restored with CIO (n = 155) and 0.7% in teeth restored with CGPC (n = 163). The cumulative survival rates of CIOs were 93.9% after a mean service time of 15.2 years and decreased to 91.7% after 23.5 years. The cumulative survival rates of CGPCs were 92.6% after a mean service time of 14.9 years and 91.8% after 23.5 years. Complications in CIOs (n = 149) were ceramic fracture (6.7%), secondary caries (4.7%), endodontic complication (2.7%) and tooth fracture (1.3%) compared to CGPCs (n = 147) with endodontic complication (8.8%), secondary caries (4.8%) and decementation (2.0%). Endodontically treated teeth restored with CIO or CGPC revealed significantly less often success compared with corresponding vital teeth (p = .02). CIOs and CGPCs revealed clinically and radiographically good and excellent qualities with 71.8% (107/149) and 68% (100/147) without any significant differences regarding type of restoration.ConclusionsBoth CIOs and CGPCs achieved high survival rates up to 24.8 years when performed by supervised undergraduate students. The longevity of the restorations may benefit from the intraoral repair of accessible defects and, in case of pulp infection or necrosis, an adequate endodontic management.Clinical relevanceCIOs and CGPCs made by supervised undergraduate students are proper restoration types in posterior teeth in the long-term. An adequate preparation design, meticulous care in the inserting technique and constant biofilm removal due to proper oral hygiene combined with professional maintenance care are substantial. The clinical long-term performance was mostly limited by ceramic fractures in CIOs and endodontic complications in CGPCs.

IS IT SAFE TO USE A CERAMIC-ON-POLYETHYLENE BEARING IN REVISIONS FOR CERAMIC FRACTURE?

Ceramic bearing fracture is a rare complication following implantation using modern day ceramic bearing materials. Revision bearing options in such cases is debated, with the choice between ceramic-on-ceramic and ceramic-on-polyethylene bearings. Revision to a hard on soft bearing raises concerns about potential catastrophic wear secondary to a third-body reaction caused by the fractured ceramic particles.Data was collected retrospectively from the NJR, electronic patient records, revision database and picture archiving and communication system. Templating software was used to determine linear wear between first post-operative radiograph and the latest available follow up. Univariate analysis was used to examine patient demographics and the wear rates for revision of ceramic bearing fractures to ceramic on polyethylene components. The intra and inter-rater reliability of wear measurements was calculated.There were twelve patients identified as meeting the inclusion criteria. The average age at revision was 62 years (54–72). There were 6 liner and 6 head fractures revised to delta ceramic heads and cross-linked polyethylene acetabular components. The most frequently used head size was 32mm. At mean follow up of 3.8 years (0.5 6.1 years), median 4.4 years, linear wear rate was calculated at 0.08± 0.06 mm/year. Both intra-rater and inter-rater reliability was excellent with ICC scores of 0.99 at all timepoints.Revision to ceramic on polyethylene (CoP) bearings following ceramic fracture does not cause early catastrophic wear at early follow up. It appears safe to use this hard on soft bearing combination, given that wear rates are comparable to what is expected in a primary hip replacement setting. Longer follow up is required to establish if this trend persists.

AB165. SOH24AB_216. Matter of prosthetic hip-associated cobalt toxicity (PHACT)?—A clinical case report, and systematic review of cases of PHACT in patients with prosthetic hip ceramic head fractures subsequently revised to metal-on-polyethylene implants

AB165. SOH24AB_216. Matter of prosthetic hip-associated cobalt toxicity (PHACT)?—A clinical case report, and systematic review of cases of PHACT in patients with prosthetic hip ceramic head fractures subsequently revised to metal-on-polyethylene implants

Microcantilever investigation of slow crack growth and crack healing in aluminium oxide

Slow crack growth (SCG) plays an important role in the fracture of ceramics and glasses. A full understanding of the long term reliability of ceramic components therefore requires knowledge not only of fracture toughness (Kc) but also characteristics of SCG such as the threshold stress intensity factor (K0) of individual microstructural features. Previous investigations have been limited by the small scale of the microstructure and low crack growth rates involved. Here, the stress intensity factors for crack propagation Kp in sapphire were measured continuously under stable crack growth using chevron-notched microcantilevers, in air and in vacuum. Kp in vacuum was considered close to the fracture toughness Kc, with a value of 2.8 ± 0.1 MPa m1/2 for the a-plane of sapphire. Kp in air at 54 % relative humidity was reduced substantially by moisture-assisted SCG to around 1.7 MPa m1/2 and, with crack velocities of ∼20 nm/s, was considered to be close to K0. Cyclic loading in vacuum enabled quantitative measurements to be made during repeated crack growth and healing for the first time. Cracks healed up along their full length when unloaded but exhibited severe degradation of toughness on reloading. The toughness fell from 2.8 MPa m1/2 on the a-plane of pristine sapphire to 1.6 MPa m1/2 after one healing cycle and to successively lower values after further cycles. This technique offers a powerful method of investigating SCG and crack healing at the microstructural scale in different environments, with greater accuracy and on shorter timescales than can be achieved in macroscopic tests.