Debonding Rate Research Articles

Comparison of tensile bond strength of ball attachments made of different materials to root canal dentin after chewing simulation

BackgroundDebonding of ball attachments is one of the complications that annoy teeth supported overdenture wearers. The polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) polymers are widely applied in the dental field. The purpose of the current study was to compare the tensile bond strength of ball attachments made of such materials and the commonly used titanium ones after 5 years of overdenture insertion and removal (5000 cycles) in addition to chewing simulation (1,200,000 cycle).MethodsExtracted mandibular canines (N = 60) were randomly allocated into three groups and received ball attachments; titanium (group TI; N = 20), PEEK (group PE; N = 20), PEKK (group PK; N = 20). In each group, the samples were divided into two subgroups whereas tensile bond strength was measured pre aging (T0; n = 10) and post aging (T1; n = 10). Tensile bond strength was measured by the Pull out test using the Universal testing machine. Failure mode analysis was determined by examination of the samples’ surfaces under 65X stereomicroscope. The resulting data followed normal distribution and the significance level was set at (α = 0.05).ResultsOne Way Anova showed statistically significant difference between the three groups (P < .00001). PostHoc Tukey test showed statistically significant difference between the groups TI and PE, TI and PK and no statistically significant difference between the groups PE and PK. Paired t test showed statistically significant difference in the tensile bond strength pre and post aging in each group.ConclusionsPEEK and PEKK ball attachments could be concluded to have a higher tensile bond strength compared to the titanium ones when bonded to root dentin. Tensile bond strength of such attachments may decrease with aging as well. Clinically, the higher tensile bond strength may have a lesser rate of debonding and thus reduced patient apprehension.

High rate of tibial debonding and failure in a popular knee replacement : a follow-up review.

AimsTotal knee arthroplasty (TKA) is a common and safe orthopaedic procedure. Zimmer Biomet's NexGen is the second most popular brand of implant used in the UK. The primary cause of revision after the first year is aseptic loosening. We present our experience of using this implant, with significant concerns around its performance with regards early aseptic loosening of the tibial component.MethodsA retrospective, single-surgeon review was carried out of all of the NexGen Legacy Posterior Stabilized (LPS) TKAs performed in this institute. The specific model used for the index procedures was the NexGen Complete Knee System (Legacy Knee-Posterior Stabilized LPS-Flex Articular Surface, LPS-Flex Femoral Component Option, and Stemmed Nonaugmentable Tibial Component Option).ResultsBetween 2013 and 2016, 352 NexGen TKAs were carried out on 331 patients. A total of 62 TKAs have been revised to date, giving an all-cause revision rate of 17.6% at a minimum of five years. Three of these revisions were due to infection. Overall, 59 of the revisions were performed for aseptic loosening (16.7%) of the tibial component. The tibial component was removed intraoperatively without instrumentation due to significant tibial debonding between the implant-cement interface.ConclusionWhile overall, we believe that early aseptic loosening is multi-factorial in nature, the significantly high aseptic revision rate, as seen by an experienced fellowship-trained arthroplasty surgeon, has led us to believe that there is a fundamental issue with this NexGen implant design. Continued implant surveillance and rigorous review across all regions using this particular implant is warranted based on the concerning findings described here.Cite this article: Bone Jt Open 2022;3(6):495–501.

Influence of the Titanium Base Abutment Design on Monolithic Zirconia Multiple-Unit Implant Fixed Dental Prostheses: A Laboratory Study.

This in vitro study evaluated technical outcomes of monolithic zirconia implant-supported fixed dental prostheses (iFDPs) supported by different designs of titanium base abutments after aging and static load testing. Sixty three-unit monolithic zirconia (yttrium oxide partially stabilized tetragonal zirconia polycrystals; Y-TZP)iFDPs were produced and divided into four groups: group A-conical titanium base abutments for the prosthesis; group B-cylindrical titanium base abutments for the crown; group C-conical titanium base abutment for the prosthesis and cylindrical titanium base abutment for the crown; group D-cylindrical titanium base abutments for the prosthesis. The samples were subjected to an aging protocol and to continuous static loading until failure and analyzed visually and with specific software. The technical outcomes comprised the occurrence of debonding, screw loosening, deformation and fracture, abutment deformation and fracture, implant deformation and fracture, zirconia chipping and fracture, and bending moments. The Pearson chi-squared test (χ2) and Fischer exact test were used to compare the outcomes. The Kolmogorov-Smirnov test was used to evaluate data distribution of the bending moments. Analysis of variance (ANOVA) was used for the analysis of parametric data distribution, and the Kruskal-Wallis test was used for nonparametric data distribution. After aging, a higher percentage of debonding (P = .042) and micromovement (P = .034) was recorded in group C (P = .042). The conical titanium base abutments had a higher debonding (P = .049) and a higher macromovement rate (P = .05). The static load test showed higher bending moments in group D (P = .001) and lower bending moments in group A (P = .001). Debonding was highest in group C (P = .001) and lowest in group A (P = .002). Complete loss of retention rate was highest in group C (P = .001). The conical titanium base abutment had the highest debonding rate (P = .001) and complete loss of retention (P = .001). The micromovement rate was the highest for cylindrical titanium base abutments for the crown (P = .001). The lowest screw loosening, zirconia chipping, and fracture rate (P = .001) and the highest screw deformation (P = .004) were recorded in group A. The screw deformation rate was lowest in the cylindrical titanium base abutments for the crown (P = .008). The mixed titanium base abutment design comprising one conical and one cylindrical abutment in Y-TZP iFDPs led to the highest debonding rate. The cylindrical titanium base abutment for the prosthesis provided a lower percentage of debonding and the highest load resistance.

What are the risk factors specific to patient for debonding of orthodontic brackets?

The premature detachment of orthodontic brackets has consequences for the patient and the practitioner. While the responsibility for the bonding protocol has been widely assessed, the responsibility of the patient is poorly understood. The main objective of the study was to look for patient-specific predictors of metal vestibular attachment detachments. An historical cohort study was carried out from adolescents having benefited from a fixed vestibular appliance treatment lasting 27months +/- 3months, having all teeth from first molar to first molar on arch to pose. Univariate and multivariate analyses were performed by logistic regression. 333patients were included. In univariate analysis, boys tended to take off more than girls, patients in skeletal Class II more than those in Class I, those with at least two cooperative remarks more than those with less than two remarks. The percentage of patients with debonding increases with the number of hygiene remarks. Younger patients were more prone to debond than older patients. The "age" factor has a significant effect in multivariate analysis. Neither the vertical skeletal pattern nor the socio-economic level would intervene in the rate of debonding. The role of patient-specific factors in detachment should be put into perspective. The reliability of the results would be increased by a prospective study using validated indicators of compliance.

Three-Dimensional Modeling and 3D Printing of Biocompatible Orthodontic Power-Arm Design with Clinical Application

Three-dimensional (3D) printing with biocompatible resins offers new competition to its opposition—subtractive manufacturing, which currently dominates in dentistry. Removing dental material layer-by-layer with lathes, mills or grinders faces its limits when it comes to the fabrication of detailed complex structures. The aim of this original research was to design, materialize and clinically evaluate a functional and resilient shape of the orthodontic power-arm by means of biocompatible 3D printing. To improve power-arm resiliency, we have employed finite element modelling and analyzed stress distribution to improve the original design of the power-arm. After 3D printing, we have also evaluated both designs clinically. This multidisciplinary approach is described in this paper as a feasible workflow that might inspire application other individualized biomechanical appliances in orthodontics. The design is a biocompatible power-arm, a miniature device bonded to a tooth surface, translating significant bio-mechanical force vectors to move a tooth in the bone. Its design must be also resilient and fully individualized to patient oral anatomy. Clinical evaluation of the debonding rate in 50 randomized clinical applications for each power-arm-variant showed significantly less debonding incidents in the improved power-arm design (two failures = 4%) than in the original variant (nine failures = 18%).

Frequency of Bonded Bracket Failure in Patients, Undergoing Fixed Orthodontic Treatment

OBJECTIVE: The objective of our study is to determine frequency of bracket bond failure in relation to age, gender, most commonly involved tooth and quadrant. METHODOLOGY: In this descriptive cross-sectional study, a total of 100 patients with ages ranging from 10 to 30 years needing corrective orthodontic treatment were selected for the study. This survey was conducted at Altamash Institute of Dental Medicine, Karachi. The survey was initiated on 30th November 2019 and was concluded on 30th May 2020. A questionnaire was used to evaluate the frequency of bonded bracket failure in patients undergoing orthodontic treatment. The bonded metallic brackets were light cured for 40 seconds, and initial alignment arch wires were inserted. Bonded bracket failure was recorded over a period of six months. RESULTS: The initial debonding results of the present study demonstrated a high number of debonded brackets in mandibular dentition as compared to the maxillary dentition. Whereas, when the teeth were debonded for the second time, a greater number of maxillary teeth were found to be affected by the debonding of the brackets. Both genders demonstrated a greater rate of bracket debonding in the second premolar area and lowest in the molar area. In our study, age and gender had no significant relationship with bracket bond failure and teeth involved in debonding. CONCLUSIONS: The frequency of bonded bracket detachment during orthodontic treatment is very common. Our study concluded that females were more affected by the bracket bond failure as compared to the males along with the second premolar being the most commonly associated tooth during an active orthodontic treatment. KEYWORDS: Bonded brackets, Bracket failure, Frequency, Orthodontic treatment, Orthodontics

Impact of Prolonged Exposure of Eleven Years to Hot Seawater on the Degradation of a Thermoset Composite.

This paper presents a long-term experimental investigation of E-glass/epoxy composites’ durability exposed to seawater at different temperatures. The thermoset composite samples were exposed to 23 °C, 45 °C and 65 °C seawater for a prolonged exposure time of 11 years. The mechanical performance as a function of exposure time was evaluated and a strength-based technique was used to assess the durability of the composites. The experimental results revealed that the tensile strength of E-glass/epoxy composite was reduced by 8.2%, 29.7%, and 54.4% after immersion in seawater for 11 years at 23 °C, 45 °C, and 65 °C, respectively. The prolonged immersion in seawater resulted in the plasticization and swelling in the composite. This accelerated the rate of debonding between the fibers and matrix. The failure analysis was conducted to investigate the failure mode of the samples. SEM micrographs illustrated a correlation between the fiber/matrix debonding, potholing, fiber pull-out, river line marks and matrix cracking with deterioration in the tensile characteristics of the thermoset composite.

Micromechanical modeling of loading rate–dependent tensile damage and fracture behavior in fiber-reinforced ceramic-matrix composites

In this paper, the loading rate–dependent tensile damage and fracture behavior of fiber-reinforced ceramic-matrix composites (CMCs) are investigated. A micromechanical tensile constitutive model is developed considering multiple tensile damage mechanisms. A new parameter of the interface debonding rate is proposed to characterize the strain rate–dependent tensile damage evolution in fiber-reinforced CMCs. Experimental tensile stress-strain curves, composite’s tangent modulus, interface debonding ratio, and probability of fiber’s breakage in unidirectional SiC/CAS-II, 2D plain-woven CVI C/SiC and SiC/SiC, 2.5D woven CVI C/SiC, and 3D woven CVI and PIP SiC/SiC composites are predicted for different strain rates at room and elevated temperatures. Effects of fiber’s preforms, testing temperature, and fabrication method on the loading rate–dependent tensile damage and fracture behavior of fiber-reinforced CMCs are analyzed. Relationships between composite’s microstructure, mechanical behavior, and strain rate for different CMCs are established. The rate of interface debonding increased with increasing strain rate and was the highest for unidirectional SiC/CAS-II, and the lowest for 3D woven SiC/SiC, and the rate of interface debonding was independent of testing temperature. For unidirectional SiC/CAS-II and 2D plain-woven CVI SiC/SiC composites, when the loading rate increased, the proportional limit stress, tensile strength, and fracture strain increased; and, for 2.5D woven CVI C/SiC and 3D woven CVI SiC/SiC, when the loading rate increased, the proportional limit stress, composite tensile strength, and fracture strain decreased.

Effect of Seawater Ageing on Fracture Toughness of Stitched Glass Fiber/Epoxy Laminates for Marine Applications

Composite materials are used in various industries such as marine, aircraft, automotive, etc. In marine applications, composites are exposed to seawater, which can affect their mechanical properties due to moisture absorption. This work focuses on the durability of composite materials under the short-term effect of seawater ageing. The specimens were prepared from glass fiber/epoxy using a hand lap-up method and stitched in the z-direction with Kevlar fiber. The specimens were submerged in seawater for 24 and 35 days. A significant decrease in maximum load was found as specimen immersion time in seawater increased. The seawater ageing also affected fracture toughness with a reduction of 30% for 24 days immersion and 55% for 35 days. The ageing also caused the swelling of composites due to moisture absorption, which increased the weight of the specimens. Compared to the dry specimens, the weight of the specimen for 24 days increases to 5.2% and 7.89% for 35 days’ seawater ageing. The analysis also showed that due to seawater ageing, the de-bonding rate increased as the number of days increased.

An 8-Year Clinical Outcome of Posterior Inlay Retained Resin Bonded Fixed Dental Prosthesis Utilizing High Performance Polymer Materials: A Clinical Report.

This clinical report presents the use of a modified polyetheretherketone (PEEK) Inlay Retained Resin Bonded Fixed Dental Prosthesis (IRRBFDP) framework, veneered with indirect high impact composite for the bilateral restoration of mandibular first molar teeth, as the most conservative treatment option for a medically compromised patient. When used as a framework, PEEK's elastic modulus (approximately 4 GPa), could result in the reduction of stresses transferred to the abutment teeth and the cementation interface accordingly, therefore it could result in lower de-bonding rates and higher success rates. Furthermore, the high bond strength with the veneering composite material and the luting cements permit its use for resin-bonded restorations. Preparation guidelines, indications and advantages for the fabrication of IRRBFDPs are described in this clinical report. No technical complications such as de-bonding of the framework, connector or retainer fracture of the adhesive frameworks or loss of retention were observed during the course of 8 years. Prosthetic replacement of single missing posterior mandibular teeth utilizing IRRBFDPs with high performance polymer materials could potentially offer long-term high survival rate outcomes. Further clinical evidence is required in order to justify the above statement.

Mechanical performance of monolithic materials cemented to a dentin-like substrate

Statement of problemStudies on the mechanical behavior of restorative materials bonded to tooth structure and considering the properties of the material and the bonding between both substrates are lacking. PurposeThe purpose of this in vitro study was to evaluate the hardness, fracture toughness, load-to-failure, cyclic fatigue, and stress distribution of 4 computer-aided design and computer-aided manufacturing (CAD-CAM) materials when bonded to a substrate similar to dentin (G10). Material and methodsDisks (11×1.2 mm) of lithium disilicate (LD), feldspathic ceramic (FC), polymer-infiltrated ceramic (PC), and a nanohybrid composite resin (NC) were fabricated (n=45) and had their surfaces polished. Microhardness was measured by the Knoop indentation (19.61 N, 12 seconds, n=5). Indented specimens were subjected to biaxial flexural strength testing, and the fracture origin defect was measured to calculate fracture toughness (n=5). Forty disks from each material were adhesively bonded to G10. Half of the specimens were subjected to load-to-failure testing, and remaining specimens (n=20) were subjected to cyclic fatigue (400 N, 106 cycles). The test was suspended every 200 000 cycles, and specimens were examined for cracks, debonding, or catastrophic failure. Obtained data were evaluated by analysis of variance and the Tukey post hoc test (α=.05). Weibull analysis was also performed. A 3D model of the tested specimens was constructed in a design software program, and the stress distribution was evaluated by finite element analysis, with the application of a 100-N load normal to the restoration surface. ResultsHardness values with statistically significant differences were LD (540.4)>FC (474.6)>PC (176.6)>NC (58.26). Fracture toughness vales (MPa.m1/2) and statistical significance were as follows: LD (2.25)=NC (2.46)>FC (1.14)=PC (1.18). Load-to-failure values (N) were LD (2881.6)=FC (2881.6)=PC (3200.6)>NC (2367.5). A specimen each of LD and NC fractured during the fatigue test, and LD and PC had a high percentage of subsurface cracks (55% and 75%, respectively). The FC had the lowest debonding rate after load-to-failure testing and no catastrophic fractures or cracks during fatigue. ConclusionsThe materials tested had different mechanical behaviors depending on the tests performed. Feldspathic ceramic had the best fatigue behavior when cemented to a dentin-like substrate.

Critical energy release rate for interface delamination of asymmetrical specimen

The interface debonding is a major failure mode of composite structures. In this paper, the debonding behavior of the structurally asymmetric interfaces is studied, and the calculating method of the critical energy release rate of such debonding interfaces is proposed. The experimental results show that the critical energy release rate calculated in this paper is more in line with its intrinsic physical attribute of being a material constant, which proves the effectiveness of the proposed method.

High rate of tibial debonding and failure in a popular knee replacement: A cause for concern

BackgroundTotal knee arthroplasty (TKA) is a common orthopedic procedure with 975,739 performed in the UK between 2003 and 2016. The two most common prosthetics used are P.F.C. Sigma and NexGen. The aim of this study is to compare the experience of a single fellowship-trained arthroplasty surgeon at a single dedicated orthopedic hospital using both of these prosthetics over a 17-year period. MethodsThis study was carried out as a retrospective review. Information was gathered from a database of primary TKAs and revision TKAs, as well as medical records, correspondence and operative notes. ResultsA total of 1,511 TKAs were performed between 1999 and 2015 – with a further follow-up period of 2 years. There were 1,161 consecutive P.F.C. primary TKAs done from 1999 to April 2013, after which, 350 consecutive NexGen primary TKAs were performed. Between 2015 and 2017, 26 NexGen revisions were required. 23 (6.6%) of the NexGen knees were carried out for aseptic loosening. The average time for revision from the NexGen index surgery was 30.4 months. The failures all presented similarly – with the tibial component having collapsed into varus and radiographic lucency noted under the implant. ConclusionIn spite of changes in orthopedic practice and advances in implant technology over the time period of this study, we would not expect this level of implant failure from a surgeon who had no previous significant issues with aseptic loosening using a different prosthetic. Usage of the NexGen knee has been discontinued at this center.

Predicting the bracket bond failure rate in orthodontic patients: A retrospective cohort study

The aim of this study was to determine the risk factors associated with orthodontic bracket bond failure and to develop a prediction equation for orthodontic bracket bond failure rate using the risk factors. This was a retrospective cohort study conducted on a sample of 690 brackets in orthodontic patients aged 10 to 28 years old (mean age 17.97±5.11 years old) visiting a dental hospital. The effect of various parameters of orthodontic bond strength was assessed on bracket failure rate using survival analysis. Parametric (exponential) regression analysis was used to determine the risk factors associated with bracket failure and a prediction equation was formulated to predict the bracket failure rate. The overall mean survival time for the brackets was 3.04 (2.9-3.17) years. The univariate analysis showed a statistically significant (P<0.05) association of bracket material, site, overjet, overbite, incisor and molar classification and age. The multivariate analysis showed a significant interaction between site and side along with bracket material, jaw, overjet and overbite in the model. The risk of bracket failure on the right posterior region is 7.7 times that in the right anterior region when adjusted for all other variables in the model (HR: 7.7; 95% CI: 4.3-13.6). The model including bracket material, jaw, overjet, overbite and interaction between site and side can be used as a predictor of hazard rate for orthodontic bracket failure. Care should be taken in bonding brackets in the posterior region, as their debonding rate is higher as compared to anterior region.

Acetabular Debonding: An Investigation of Porous Coating Delamination in Hip Resurfacing Arthroplasty.

Background To date, there have been no published investigations on the cause of acetabular debonding, a rare failure phenomenon in metal-on-metal hip resurfacing where the acetabular porous coating delaminates from the implant while remaining well fixed to the pelvic bone. Purposes This study aims to summarize the current understanding of acetabular debonding and to investigate the discrepancy in rate of debonding between two implant systems. Patients and Methods To elucidate potential causes of debonding, we retrospectively analyzed a single-surgeon cohort of 839 hip resurfacing cases. Specifically, we compared rate of debonding and manufacturing processes between two implant systems. Results Group 1 experienced significantly more cases of debonding than Group 2 cases (4.0% versus 0.0%, p value<0.0001). Implant manufacturing processes differed in surface coating, heat treatment, postmanufacturing treatment, and apex thickness. Debonded implants were more likely to have missed RAIL guidelines (p=0.04). Conclusions We identified implant system, postoperative time, and acetabular component placement as variables contributing to rate of debonding. We recommend minimizing acetabular inclination angle according to RAIL guidelines. Further, we evaluated manufacturing differences between the two implant systems but did not have access to proprietary data to identify the cause of debonding. Both implants met ASTM standards, yet only the Group 1 implant debonded. This suggests the second implant had greater fatigue shear strength. Because the Group 2 implant achieved a more durable interface that did not debond, we suggest the ASTM F1160 standard for fatigue shear strength be increased to that achieved by its manufacturer. Level of Evidence II A retrospective evaluation of prospectively collected data.

A Systematic Review of the Survival and Complication Rates of All-Ceramic Resin-Bonded Fixed Dental Prostheses.

The aim of this systematic review was to investigate the survival and complication rates of all-ceramic resin-bonded fixed dental prostheses (RBFDPs). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied. A systematic search was conducted by an electronic search in PubMed, EMBASE, Cochrane Library, and CNKI databases complemented by a manual search. Only clinical studies on all-ceramic RBFDPs with a mean follow-up period of at least 3 years qualified for data analyses. Among 1503 screened articles, one randomized controlled trial (RCT) and seven prospective or retrospective cohort studies were included in this study. The estimated 5-year survival rate of all-ceramic RBFDPs was 91.2%. Debonding and framework fracture were the two most frequent technical complications, and the estimated 5-year debonding rate and fracture rate were 12.2% and 4.8%, respectively. Additionally, cantilevered all-ceramic RBFDPs had a higher survival rate (p < 0.01), lower debonding rate, (p < 0.05), and fracture rate (p < 0.01) compared with two-retainer all-ceramic RBFDPs. Zirconia ceramic RBFDPs had a lower incidence of failure but a higher debonding rate compared with glass-ceramic RBFDPs (p < 0.01). Within the limitations of this systematic review, although all-ceramic RBFDPs have a favorable 5-year survival rate, this rate cannot represent the complete success of the treatment, since it may include typical complications such as debonding and fractures. There is an urgent need for long-term clinical studies, especially for well-designed RCTs on all-ceramic RBFDPs.

Unusually High Rate of Early Failure of Tibial Component in ATTUNE Total Knee Arthroplasty System at Implant-Cement Interface.

AbstractA novel design total knee arthroplasty (TKA) system has been introduced to improve patient outcomes and increase longevity. However, we have encountered a high rate of debonding of tibial implant–cement interface. In addition, multiple reports have been filed in Manufacturer and User Facility Device Experience database (MAUDE) with the same mechanism of failure. Therefore, we evaluated: clinical, radiographic, and intraoperative findings of patients who received this system and required a revision surgery, and findings from MAUDE database compiled to this date. We reviewed three hospital databases for patients who had revision TKA for tibial loosening at the implant–cement interface. This yielded 15 cases with a mean age of 61 years (range, 47–84). All patients received a novel knee system at another institution. Radiographic analysis was performed by treating orthopaedist. The MAUDE database was reviewed for reports of aseptic failure. Patients presented with pain on weight bearing, effusion, and decreased range of motion (ROM) within 2 years after surgery. Radiographic evaluation demonstrated loosening of the tibial components in 2 of 15 knees. This included cruciate retaining, posterior stabilized, fixed bearing, and rotating platform bearing designs. Intraoperative findings demonstrated gross loosening of the tibial component at the implant–cement interface. Femoral and patellar components were well fixed. There were 21 reports of tibial loosening at the implant–cement interface in MAUDE database in the past 2 months alone. Numerous other tibial failures were reported; however, the mechanisms of failures were not specified. Tibial component loosening is a rare complication of cemented TKA at short-term follow-up. Several possible reasons include increased constraint, reduced cement pockets, and reduced keel rotational stabilizers. The tibial component, which has greater torsional loads, has lower surface roughness than femoral component. We believe that this complication is underreported due to failure of radiographs to assess loosening. In addition, MAUDE database reporting is not consistent and competing companies cannot provide data on the revised components. In patients who have negative workup for a painful joint, one must consider the diagnosis of debonding.

Numerical analysis of the mechanical behavior of ZTAp/Fe composites

Composites are complex and inhomogeneous. Various factors of microstructure will affect their mechanical behaviors. Based on a systematic numerical analysis, we present a coupling effect of the volume fraction of reinforced particles and the particle-matrix interface properties on the mechanical properties of ZTAp/Fe composites. We find that for yield limit and peak stress, the particle-matrix interface properties show a dominant impact while for the critical strain the particle volume fraction is the main factor. A combined effect of the particle volume fraction and the interface properties is found on the elastic modulus. The von Mises stress distributions are investigated and the results show that the particles clustered in the direction perpendicular to tensile load have larger debonding potential. In addition, the probability of particle cracking and the number of interface debonding are investigated to analyze the damage mechanism of the composites. We find that strong bonded interface can withstand more extra stress and protect the particle from cracking. The interface debonding rate becomes smooth after some critical value as the strain increases continuously due to a steady crack propagation after crack initiation along the interface line. This paper provides a guidance towards the design of advanced ceramic particle reinforced metal matrix composite materials.

A systematic review of the survival and complication rates of resin-bonded fixed dental prostheses after a mean observation period of at least 5years.

The objective of this systematic review was to assess the 5-year and 10-year survival of resin-bonded fixed dental prostheses (RBBs) and to describe the incidence of technical and biological complications. An electronic MEDLINE search complemented by manual searching was conducted to identify prospective and retrospective cohort studies and case series on RBBs with a mean follow-up time of at least 5years. Patients had to have been examined clinically at the follow-up visit. Assessment of the identified studies and data extraction were performed independently by two reviewers. Failure and complication rates were analyzed using robust Poisson regression models to obtain summary estimates of 5- and 10-year proportions. The search provided 367 titles and 87 abstracts. Full-text analysis was performed for 22 articles resulting in seven studies that met the inclusion criteria. Five articles were found through manual search, and 17 studies were provided from (Pjetursson etal. 2008, Clinical Oral Implants Research, 19, 131), resulting in an overall number of included studies of 29. Meta-analysis of these studies reporting on 2300 RBBs indicated an estimated survival of resin-bonded bridges of 91.4% (95 percent confidence interval [95% CI]: 86.7-94.4%) after 5years and 82.9% (95% CI: 73.2-89.3%) after 10years. A significantly higher survival rate was reported for RBBs with zirconia framework compared with RBBs from other materials. RBBs with one retainer had a significantly higher survival rate (P<0.0001) and a lower de-bonding rate (P=0.001) compared with RBBs retained by two or more retainers. Moreover, the survival rate was higher for RBBs inserted in the anterior area of the oral cavity compared with posterior RBBs. The most frequent complications were de-bonding (loss of retention), which occurred in 15% (95% CI: 10.9-20.6%) and chipping of the veneering material that was reported for 4.1% (95% CI: 1.8-9.5%) of the RBBs over an observation period of 5years. Despite the high survival rate of RBBs after 5 and 10years, technical complications like de-bonding and minor chipping were frequent. RBBs with zirconia framework and RBBs with one retainer tooth showed the highest survival rate.

Statistical study on bracket debonding rate with the win lingual technique.

The aim of this study is to present the results of a statistical inquiry measuring the bracket debonding rate using the WIN lingual technique. This inquiry was performed in the Odontology Unit at the Rothschild Hospital in the framework of the Lingual Orthodontics University Diploma at Paris VII university. Results were gathered by 8 orthodontic practitioners during two years of training from all their patients treated with the WIN lingual technique. The sample study comprised 33 patients treated exclusively with the WIN lingual technique. The 8 practitioners filled in a questionnaire relating to bracket bond failure in their patients in the course of treatment. In all, sixty-two questionnaires were analyzed. The data were then computed using the statistical tool of R software version 3.1.3. The results of this analysis demonstrate the reliability of the WIN system evidenced by an average of 2.1 bracket bond failures over the two-year treatment period, i.e. approximately 1 bracket per patient per year. Given the right conditions, (precise prescription, compliance with bonding protocols), the bond failure rate can be lower still, even compared with the buccal technique or relative to other lingual techniques. The benefits of lingual appliances, particularly in the WIN system, are essential to clinicians in their daily practice in order to optimize the quality and duration of their treatments with a view to ensuring patient satisfaction.