Connector Area Research Articles

Failure analysis of the suspender fracture in a railway self-anchored suspension bridge: Damage identification, fatigue mechanism and remaining life prediction

A suspender fracture accident was reported in a railway self-anchored suspension bridge, arousing intensive concern to fatigue issue in the suspender end connector area which is exposed to complex stress states and cyclic traffic loads. Some critical issues involving the fatigue mechanism, the damage identification, and the remaining life prediction were investigated on the basis of on-site and lab tests, numerical simulations, and theoretical analyses. It was found that the root of an ear-plate screw with threads becomes the fatigue-prone detail since action of stress concentration and the unexpected cyclic bending. Also, an effective crack identification scheme by the ultrasonic phased array inspection as well as a verified prediction method for remaining life were proposed. Short suspenders in the main span are significantly affected by the cyclic bending, resulting in the extremely lower fatigue life than that of a long or side-span suspender. Suggestions for a classified disposal plan are provided based on fatigue risk for individual suspender.

Equal-displacement principle-based direct seismic-design method for single-yielding precast-concrete frame

This study aims to improve the seismic performance and reduce damage of a structure using energy-dissipation connectors, while avoiding the design difficulties of existing methods. In this study, a single-yielding–precast-concrete (SYPC) frame was proposed to realize the design of a controllable bending moment at the beam end. An equal-displacement principle-based direct seismic-design method was proposed for the SYPC frame. First, using a dynamic time–history analysis, the key parameters affecting the stiffness of the frame and the adjustment strategy were explored. Subsequently, based on the equal-displacement principle, the seismic intensity control and target interstory drift were directly determined. Finally, a direct seismic-design method for the SYPC frame based on the equal-displacement principle was proposed. A six-story SYPC frame was designed according to the proposed design method. An elastic–plastic dynamic time–history analysis was performed for the designed frame to verify the effectiveness and accuracy of the proposed design method. The results show that the equal-displacement principle can rapidly and accurately determine the target elastic–plastic displacement of the underground motions of the structure and effectively avoid the iterative solution of structural plastic characteristic parameters, such as equivalent damping and ductility coefficient, encountered in traditional design methods. The proposed design method not only effectively controls the deformation pattern of the structure but also realizes an ideal beam-hinge mechanism. Additionally, by controlling the length and section area of the replaceable energy-dissipating connectors (REDCS) to satisfy the ductility requirement, the stiffness was verified to satisfy the requirements of the frame deformation mechanism.

Evaluation of different designs for posterior cantilever zirconia inlay-retained fixed dental prostheses in missing tooth replacement: Stage one results with 18-month follow-up assessment

ObjectivesThis clinical study aimed to investigate the outcomes and survival rates of different variations of inlay-retained fixed dental prostheses (IR-FDPs) composed of monolithic zirconia ceramic. The IR-FDPs with a single-retainer design were used for replacing missing mandibular second premolars. The research evaluated the effectiveness and longevity of these prostheses in clinical settings. MethodsA total of 30 IR-FDPs (n = 30) were placed for 27 female patients who presented with missing mandibular second premolar teeth. For this study, the mandibular first molar was chosen as a retainer for the cantilever IR-FDPs and the study involved a random assignment of participants into three distinct groups, each comprising 10 individuals (n = 10). The criterion for the grouping was the retainer design: inlay ring (IR), lingual coverage (LC), and occlusal coverage (OC). The three groups included mesial inlay box with the same dimensions (3 mm height, 3 mm width and 2 mm depth). All IR-FDPs were manufactured using monolithic high translucent 3Y zirconia and the connector area to the cantilever pontic was adjusted to dimensions of 3 × 3 mm for all designs. The restorations were bonded using adhesive resin cement. The clinical and radiographic evaluations of the restorations were conducted for a duration of 18 months, following the modified FDI (World Dental Federation) criteria. ResultsThe restorations were observed in stage one for a period of 18 months. Only one restoration in group LC was debonded after 10 months and re-bonded. The clinical quality of all crowns and the patient's satisfaction were high. No adverse soft tissue reactions around the crowns were observed and only one abutment in group IR was endodontically treated after 12 months. ConclusionsZirconia cantilever IR-FDPs offer a viable short-term treatment option for replacing missing posterior teeth, providing esthetic and functional benefits while minimizing invasiveness. Over an 18-month observation period, these prostheses have demonstrated a remarkable survival rate of 100% and a success rate of 96.6%. These findings suggest the effectiveness and reliability of zirconia cantilever IR-FDPs as a short-term solution for replacing missing posterior teeth. Clinical significanceZirconia cantilever IR-FDPs could present a practical solution for addressing posterior tooth loss, especially in cases where implant placement is not recommended and conventional fixed dental prostheses entail excessive invasiveness.

Non‐Destructive Testing of Bridge Cables using MIT

AbstractThis article presents the importance of non‐destructive testing (NDT) in maintaining the safety and functionality of bridge cables, and focuses on the practical use of magnetic‐inductive testing (MIT) and ultrasonic testing (UT) for NDT of bridge cables in free length and in the area of the end connectors. MIT is a non‐invasive method that can effectively detect defects such as broken wires, corrosion symptoms, and other imperfections, making it a promising technique for inspecting and maintaining bridge cables. A research project investigated various types of magnetic induction testing on different tension members made of single wires and evaluated the advantages and limitations of the MIT method. The study also explored the impact of factors such as cable diameter and measurement speed on the effectiveness of the technique. The results suggest that the MIT method can accurately detect defects in bridge cables and provide valuable information for maintenance and repair purposes. However, the article highlights the need for further research to optimize the MIT technique, particularly in automating the detection and characterization of signals, and to expand its applicability to a wider range of cable diameters and conditions.

New Methods for Replacing Single Missing Teeth with Non-prep Bridges (NPBs) - A Case Series.

Newly developed non-invasive methods for replace a missing tooth and closing single-tooth gaps in the poster- ior region using resin composite are presented. Four different non-invasive methods and the technical procedures, materials and instruments used are presented in a case series. These include the direct intraoral insertion of composite (with and without individual shaping aids) and indirect restorations, which are fabricated conventionally or digitally and bonded. The case series showed that all four methods can be used to replace single missing teeth in the posterior region, meeting current clinical requirements. Particular attention was paid to the design of the pontics, the dimension of the connector area, firm proximal contacts to the adjacent teeth, hygiene, and appearance of the non-prep bridges (NPBs). The advantages and disadvantages for both the direct and indirect techniques illustrated in this case series were com- pared in detail. Several direct and indirect non-invasive methods for single-tooth replacement are available today. Although the evidence is still limited, there is a potential for frugal dental interventions with NPBs. Further experimental and clinical studies are necessary to demonstrate that they reliably meet quality requirements (including sufficient survival rates), satisfy the criteria of cost-effectiveness (compared to treatment alternatives) and that there is a demand from the population.

Evaluation of Load-bearing Capacity of Interim Fixed Partial Dentures Reinforced with Glass Fibers: An In Vitro Study.

To compare the load-bearing capacity of three and four-unit fixed partial denture (FPD) with two different designs of pontics reinforced with industrial glass fibers at two different positions of the FPD. A total of 64 samples were made with Bis-acryl composite temporary material and reinforced with industrial glass fibers (E-glass). The specimens were divided into eight groups (groups I-VIII) depending on the number of units, type of pontic design and area of placement of fibers. A universal testing machine was used to evaluate and compare the load-bearing capacity of the specimens. The evaluated data were statistically analyzed using one-way ANOVA and Bonferroni post hoc tests (p ≤ 0.05). Three-unit interim FPD and modified ridge lap pontic design showed greater load-bearing capacity after reinforcement with glass fibers than a four-unit interim FPD and hygienic pontic design, respectively. Fiber placement at the occlusal plus connector area as well as the cervical plus connector area had comparable results. Industrial glass fibers (E-glass) could be used as a cheaper alternative but clinical performance and their safety are yet to be evaluated. Reinforcement with industrial-grade glass fibers can be a cheaper option for increasing the load-bearing capacity of interim partial dentures, but it needs to be studied in vivo through further studies.

Mechanism and seismic performance of a novel precast concrete beam-to-very short shear link joint: Experimental and numerical simulation

This paper introduced a novel precast concrete beam-to-very short shear link (PCB-VSSL) joint with the separation from shear force and bearing moment. The mechanism and seismic performance of the PCB-VSSL joint were detailed investigated. In the present study, four specimens were investigated by cyclic loading tests, including a very short shear link-1 (VSSL-1), a novel joint with basic shear connectors (PCB-VSSL-1), and two improved joints (PCB-VSSL-2 and 3), and the influencing factors including the length of cross-bilinear-type (CBT) shear connector and lateral plate height in the CBT shear connector were analyzed by experimental and numerical simulation. The test results showed that the PCB-VSSLs had excellent bearing capacity and energy dissipation capacity, and maximum overstrength and inelastic rotation of VSSLs in the specimens PCB-VSSL-1, 2, and 3 were 1.85 and 0.15, respectively, which were the same as the specimen VSSL-1. The concrete cracks of the precast concrete beam could be minimized by enlarging the length and area of shear connectors. The results also indicated that the high-strength bolts would only transfer the bending moment from the VSSL to PCB-VSSL. The shear connectors only sustained the shear force, so the bending moment and the shear force of the novel PCB-VSSL could be effectively separated with the advantage of high bearing capacity, reasonable mechanics, ease of installation, and seismic resilience capacity. Furthermore, based on the finding of on failure mechanism of the PCB-VSSL joint, a simplified design methodology of the novel PCB-VSSL joint was proposed.

Fracture resistance of 3-unit monolithic ZrO2 ceramics FPDs with different preparation designs of the distal abutment - an in-vitro study

Masticatory pressure increases in the distal areas of the dentition. This should be considered when restoring partially edentulous patients with a metal-free fixed partial denture (FPD). An alternative abutment preparation design can be used in order to increase the materials' volume in the most fracture-prone "connector area" of an FPD. The increased size of the connection might positively influence the constructions' mechanical durability, thereby increasing its success and survivability. The aim of the present study was to investigate the influence of two preparation designs of the distal abutment on the fracture resistance of three-unit, monolithic, ZrO2 FPDs. 3D printed replicas of a partially edentulous mandibular segment and a ZrO2, milled in full-contour, three-unit FPDs were used for this investigation. Two experimental groups (n=10 ) were defined based on the preparation design of the distal abutment tooth - classical shoulder preparation 0.8mm deep, and endocrown preparation with a 2-mm retention cavity. The bridge - mandibular segment replica assembly was done with relyXU200(3M ESPE, USA), light-cured for 10 seconds per side with D-light Duo (GC, Europe). After cementation the test specimens were subjected to loading in a universal testing machine Zwick (Zwick-Roell Group, Germany). Statistical analysis was performed using R and includes descriptive statistics, t-test for quantitative and chi-squared test for qualitative variables. The results showed no difference between the two studied groups in the maximum force required to fracture the test specimens [t=-1.8088 (17.39), p-value=0.087; P>0.05]. 95% of the fracture lines were located in the distal connector. Within the limitations of this study, it can be concluded that both tested preparation designs show similar results in terms of the load required to fracture the test specimens. Furthermore, it is confirmed that the distal connector is the weakest area of an all-ceramic 3-unit FPD in the posterior area.

Performance of high-translucent zirconia CAD/CAM fixed dental prostheses using a digital workflow: A clinical study up to 6 years

Background/purposeZirconia has recently become a popular material for fixed restorations. The purpose of this study was to use a digital workflow to fabricate monolithic zirconia fixed dental prostheses (FDPs) and assess the connection between variable connector sizes compared to their clinical performance. Materials and methodsClinicians evaluated monolithic zirconia FDPs in 58 patients. After definitive impressions were made, stone casts were obtained. The stone casts were scanned to a standard triangle language (STL) file. A digital wax up was fabricated, and corresponding provisional restorations were milled. Final FDPs were fabricated from a high-translucent zirconia material. During digital fabrication, the connector area of each FDP was recorded while meticulous attention was paid to ensure that the connector cross-sectional area was ≥9 mm2 for the 3-unit restorations (pontic to retainer) and ≥12 mm2 for the 4-unit restorations (pontic to pontic). Biological an technical outcomes of the FDPs were performed at 1 week, 6 months and then annually for 6 consecutive years. ResultsA total of 23 men and 35 women received a total of 63 full-contour zirconia FDPs in the posterior regions and were observed for a time period ranging between 50 and 70 months. No decementation occurred and no caries were detected during the observation period, however signs of gingivitis were detected in 4 patients. The dimension of the connector areas was 12 mm2 in the two broken 4-unit FDPs. ConclusionThe results of this study suggest that the use of digital scanning and milling to fabricate monolithic zirconia FDPs of posterior regions may be an acceptable alternative restorative approach to traditional metal-ceramic restorations.

Effects of selective laser melting process parameters on the accuracy of the intaglio surface of maxillary removable partial denture frameworks

PurposeThis in vitro study aims to explore the effects of selective laser melting (SLM) process parameters on the accuracy of the intaglio surface of cobalt–chromium alloy (Co–Cr), commercially pure titanium (CP Ti) and titanium alloy (Ti–6Al–4V) maxillary removable partial denture (RPD) frameworks and optimize these process parameters.Design/methodology/approachMaxillary RPD framework specimens designed on a benchmark model were built. The process parameters, including contour scan speed and laser power, infill scan speed and laser power, hatch space, build orientation and metallic powder type, were arranged through the Taguchi design. Three-dimensional deviations of the clasps area, connector area and overall area of maxillary RPD frameworks were analyzed by using root mean square (RMS) as a metric. One-way analyses of variance with the above RMSs as the dependent variable were carried out (α = 0.05).FindingsMaxillary RPD frameworks built horizontally had a more accurate intaglio surface than those built at other orientation angles; CP Ti or Ti–6Al–4V maxillary RPD frameworks had a more accurate intaglio surface than Co–Cr ones; the Maxillary RPD framework built with a higher infill scan speed and lower infill laser power had the more accurate intaglio surface than the one built with other levels of these two process parameters.Originality/valueA novel benchmark model for evaluating the accuracy of the intaglio surface of maxillary RPD frameworks manufactured by SLM is proposed. The accuracy of the intaglio surface of maxillary RPD frameworks can be improved by adjusting SLM process parameters. The optimal setting of process parameters concerning the accuracy of the intaglio surface of maxillary RPD frameworks was given.

Fracture Resistance and Fracture Behaviour of Monolithic Multi-Layered Translucent Zirconia Fixed Dental Prostheses with Different Placing Strategies of Connector: An in vitro Study

PurposeTo evaluate the effect of different placing strategies performed in the connector area on fracture resistance and fracture behaviour of monolithic multi-layered translucent zirconia fixed dental prostheses (FDPs).Materials and MethodsThirty 3-unit monolithic FDPs were produced and divided into three groups (n = 10) based on the different strategies for placing the connector area of FDPs in multi-layered zirconia blank with varying contents of yttria ranging from 4 to 5 mol%. The groups were as follows: FDPs with connectors placed in dentin layer with 4 mol% yttria content, FDPs with connectors placed in gradient layer, and FDPs with connectors placed in translucent layer with 5 mol% yttria content. A final group (n = 10) of conventional monolithic zirconia with a monolayer of yttria content (4 mol%) has been used as a control group. The specimens were artificially aged using thermocycling and pre-loading procedures and subsequently loaded to fracture using a universal testing machine. Fracture loads and fracture behaviour were analyzed using one-way ANOVA and Fisher’s exact tests and statistically evaluated (p ≤ 0.05).ResultsThere were no significant differences in fracture loads among the groups based on the placing strategies of the connector area of the FDPs in the multi-layered translucent zirconia blank (p > 0.05). There was no significant difference in fracture loads between monolithic multi-layered translucent zirconia and conventional monolithic translucent zirconia materials (p > 0.05). Fracture behaviour of FDPs with connector area placed in translucent layer differed significantly compared to FDPs with connector area placed in dentin layer and FDPs in control group (p = 0.004).ConclusionThe placing strategies of the connector used in the computer aided design and manufacturing procedures do not considerably affect fracture resistance of monolithic FDPs made of multi-layered translucent zirconia. Monolithic FDPs made of multi-layered translucent zirconia show comparable strength to FDPs made of conventional translucent zirconia, but with different fracture behaviour.

Assessment of stress transfer in laminated structural power composites produced with mechanically-connected electric double-layer capacitors

Enabling energy-storing functions in structural composites is an appealing strategy to reduce the weight of systems in electric transport. Structural power composites (SPC) can be made by introducing energy-storing layers in traditional composite laminates, either as embedded devices or as thin integrated interleaves simultaneously performing load-bearing and electrochemical energy storage functions. However, the solid electrolyte in these layered architectures is typically a soft polymer, thus making the SPC very prone to delamination. Mechanical interconnection using structural matrix bridges between plies, analogous to metal connectors, provides a solution to alleviate delamination risks while maintaining the structural integrity of the SPC even under the most unfavourable combinations of loads. This paper reports on the use of experimental tests and FEM simulations to study the micromechanics of interlaminar polymer connectors in SPCs. It explores the effect of the connector area on the shear strength and energy density. The results provide a validated methodology to design laminated structural composites with a tailored balance of multi-functional properties of wide application to SPC of different constituents, with electrochemical energy storage either as capacitors or batteries.

Influence of the Connector Area on the Chipping Rate of the VM9 Veneering Ceramic in a Posterior Four-Unit Yttria-Stabilized Tetragonal Zirconia Polycrystal Fixed Dental Prostheses: A Pilot Study

Abstract Objective The purpose of this study was to evaluate the influence of the connector area on the chipping rate of the VM9 veneering ceramic in a 4-unit yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) framework, using a novel sonographic technique. Materials and Methods The framework was designed as a 4-unit fixed dental prostheses (FDP) with two abutment teeth at the first mandibular premolar and second mandibular molar. The cross-sectional area of the connector was 7.5, 8, or 9 mm2. The prepared teeth were scanned using CAD/CAM technology, and five frameworks were prepared for each design, making a total of 15. The frameworks were divided according to the veneering ceramics: Y-TZP FDPs using Vita VM9 (12 frameworks), and porcelain fused to metal (PFM) FDPs using Vita VM13 (3 frameworks). The specimens were statically loaded until failure. To capture the initiation of the failure within the specimens, a novel sonographic technique, designed for this research, combining acoustic emission and visual monitoring during live load bearing tests, was used to determine the failure load value. Failed frameworks were inspected using a microscope, and failure patterns were identified. One-way ANOVA and Tukey HSD tests were applied for statistical analysis of the results (p-value ≤ 0.05). Results Despite the fact that the chipping strength is proportional to the cross-sectional area of the connector, the effect of the cross-sectional area on chipping load revealed no statistically significant differences, while PFMs showed superior chipping strength relative to the zirconia frameworks regardless of the connector's size. A high rate of catastrophic fracture occurred while loading the specimens. Conclusion The effect of the cross-sectional area on chipping load revealed no statistically significant differences in Y-TZP frameworks. The novel sonographic technique may be a potential method to study the behavior of dental ceramics, including chipping and fracture.

Framework Fracture of Zirconia Supported Full Arch Implant Rehabilitation: A Retrospective Evaluation of Cantilever Length and Distal Cross-Sectional Connection Area in 140 Patients Over an Up-To-7 Year Follow-Up Period.

To evaluate the relationship between different dimensional parameters in implant-supported monolithic zirconia fixed complete dental prostheses (IFCDPs) and the incidence of framework fracture in a large sample of cases in vivo. This retrospective observational study evaluated all patients rehabilitated with screw-retained zirconia IFCDPs between January 2013 and April 2019 at a private practice. The minimum follow-up period was 1 year after occlusal loading. Fractures were classified as: type I-fractures that happened between but not involving the two most posterior screw-access openings (SAOs) and type II-fractures of the distal cantilever. Cantilever length, distal connector cross-sectional area, and screw access opening length were measured using data obtained from digital scans. Logistic regression was performed to evaluate the relationship between types I and II fractures and the independent variables (dimensional parameters). Using the receiver operating characteristic curves, two parameters were identified to be useful for establishing a cut-off and predicting type II fractures. A total of 180 prostheses delivered to 140 patients were analyzed. Five implants failed in three patients: three before delivery of the definitive prostheses and two after. Ten prostheses failed (5.6% prosthetic failure rate): 2 because of implant failures, and 8 because of framework fractures. Five fractures were classified as type I and three as type II. Significant associations were found between cantilever length and type I fractures (Wald = 5.772, df = 1, p = 0.016), distal connector cross-sectional area and type II fractures (Wald = 3.806, df = 1, p = 0.051), and cantilever length and the total number of fractures (Wald = 6.117, df = 1, p = 0.013). Zirconia IFCDPs may be reliable medium-term solutions if some dimensional parameters are followed. The ratios between the cantilever length and cross-sectional connector area should be <0.51, while the ratio between the cantilever length and screw access opening length should be <1.48.

Shape optimization of a 2-unit cantilevered posterior resin-bonded fixed dental prosthesis

Statement of problemThe cantilevered resin-bonded fixed dental prosthesis (RBFDP) is a feasible and minimally invasive treatment option to restore a single missing tooth, especially when the missing tooth space is small (<7 mm) and cost-effectiveness is essential. However, its long-term survival needs to be improved by increasing its structural strength and interfacial adhesion. PurposeThe purpose of this study was to improve the interfacial bonding and to enhance the structural strength of a 2-unit inlay-retained cantilevered RBFDP with a 2-step numerical shape optimization. Material and methodsA finite element model of a mandibular first molar with a second premolar pontic was constructed. A load of 200 N simulating the average occlusal force was applied on the mesial fossa of the pontic. In the first step, an in-house user-defined material subroutine was used to generate the cavity preparation. The subroutine iteratively changed the tooth tissues next to the pontic to composite resin according to the local stresses until convergence was achieved. In the second step, the subroutine was used to optimize the placement of fibers in the pontic by placing fibers in high-stress regions. To assess the debonding resistance and load capacity of the optimized and conventional designs, further analyses were conducted to compare their stresses at the tooth-restoration interface and those within the restoration. ResultsShape optimization resulted in a shovel-shaped cavity preparation and a pontic with fibers placed near the occlusal surface of the connector region. With the optimized cavity preparation only, the maximum principal stress within the restoration and the tooth structure was reduced from 639.4 MPa to 525.4 MPa and from 381.7 MPa to 352.8 MPa, respectively. With the embedded fibers, the shovel-shaped cavity preparation reduced the maximum interfacial tensile stress by approximately 70% (conventional: 189.6 MPa versus optimized: 57.0 MPa) and the peak maximum principal stress of the veneering composite resin by 45% (conventional: 638.8 MPa versus optimized: 356.5 MPa). The peak maximum principal stress was also reduced for the remaining tooth structure by approximately 30% (conventional: 372.2 MPa versus optimized: 253.1 MPa). ConclusionsShape optimization determined that a shovel-shaped retainer with fibers placed near the occlusal surface of the connector area can collectively reduce the interfacial and structural stresses of the 2-unit cantilevered fiber-reinforced RBFDP. This may offer a more conservative treatment option for replacing a single missing tooth.

Clinical evaluation of monolithic zirconia multiunit posterior fixed dental prostheses

Statement of problemMonolithic zirconia restorations have been evaluated with in vitro studies, but limited clinical evidence of their longevity and reliability is available. PurposeThe purpose of this clinical study was to evaluate the clinical performance of posterior multiunit glazed monolithic zirconia fixed dental prostheses. Material and methodsA total of 20 participants received 33 monolithic posterior zirconia fixed dental prostheses (Zolid white; Amann Girrbach AG) with minimally invasive preparations. Bilaterally supported fixed dental prostheses with a connector area of at least 9 mm2 were luted with resin-modified glass ionomer cement. The clinical evaluations were performed after 1 week, 6 months, and then annually after completion of the treatment. The biologic outcomes were evaluated by assessing the pocket depth, attachment level, plaque control, bleeding on probing, caries, and tooth vitality. Esthetics and the functional performance of the prostheses (color match, cavosurface marginal discoloration, anatomic form, marginal adaptation) were evaluated as per the rating scales of Cvar and Ryge. An analysis of survival was made by using the Kaplan-Meier method. ResultsAfter 39.8 ±16.7 months of observation, the overall survival rate of the monolithic zirconia multiunit posterior prostheses was 93.9%. No caries were found on the abutment teeth, signs of gingivitis were noted in 1 participant after 24 months, and increased probing depths of the abutment teeth were detected in 5 prostheses (15.1%). No loss of retention was detected. Two prostheses had to be replaced: 1 because of a biologic complication and 1 because of a technical complication. The remaining 31 prostheses received Alfa scores for marginal adaptation, cavosurface marginal discoloration, and caries. Twenty-seven (87.1%) prostheses were rated as Alfa and 4 (12.9%) as Bravo for anatomic form. The color match was noted as Alfa in 15 (48.3%) prostheses, and 16 (51.6%) were rated as Bravo. ConclusionsMonolithic zirconia restorations demonstrated a reliable treatment option after medium-term clinical use for the replacement of missing posterior teeth.

Physicochemical and mechanical characterization of a fiber-reinforced composite used as frameworks of implant-supported prostheses

ObjectivesTo characterize the physicochemical and mechanical properties of a milled fiber-reinforced composite (FRC) for implant-supported fixed dental prostheses (FDPs). MethodsFor FRC characterization, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier-transformed infrared spectrometry, simultaneous thermogravimetric analysis and differential scanning calorimetry were performed. For fatigue testing, 3-unit FRC frameworks were fabricated with conventional (9 mm2 connector area) and modified designs (12 mm2 connector area and 2.5 mm-height lingual extension). A hybrid resin composite was veneered onto the frameworks. FDPs were subjected to step-stress accelerated-life fatigue testing until fracture or suspension. Use level probability Weibull curves at 300 N were plotted and the reliability for 100,000 cycles at 300, 600 and 800 N was calculated. Fractographic analysis was performed by stereomicroscope and SEM. ResultsThe FRC consisted of an epoxy resin (∼25%) matrix reinforced with inorganic particles and glass fibers (∼75%). Multi-layer continuous regular-geometry fibers were densely arranged in a parallel and bidirectional fashion in the resin matrix. Fatigue analysis demonstrated high probability of survival (99%) for FDPs at 300 N, irrespective of framework design. Conventional FDPs showed a progressive decrease in the reliability at 600 (84%) and 800 N (19%), whereas modified FDPs reliability significantly reduced only at 800 N (75%). The chief failure modes for FRC FDPs were cohesive fracture of the veneering composite on lower loads and adhesive fracture of the veneering composite at higher loads. SignificanceMilled epoxy resin matrix reinforced with glass fibers composite resulted in high probability of survival in the implant-supported prosthesis scenario.

Evaluation Of The Fracture Resistance And Marginal Gap Of Endocrowns Retained Bridges With Two Different Designs

Objective: The purpose of this in vitro study will evaluate marginal gap of endocrowns retained bridges replacing missing lower second molar will done by two different designs from monolithic zirconia. Material and method: twenty bridges designed from monolithic zirconia. Specimens will be divided into two groups, each of these groups contains 10 samples, the first group represents endocrown endocrown retained, and second group endocrown retained bridges. The marginal gap for the buccal, lingual, proximal and connector area were measured .scan electron microscope were used. Universal testing machine was used to detect fracture resistance for all samples. Results: Data analysis was performed by student t-tests to detect significance between groups. One way analysis of variance ANOVA test followed by pair-wise Newman-Keuls was used to detect significance between sites. Statistical analysis was performed using Graph pad Prism-4 statistics software for Windows. P values 0.05). Conclusions: Fracture resistance and marginal gap of endocrowns retained bridges with two different designs were be accepted.

Effect of Air-Particle-Abrasion Protocols on Surface Roughness and Early Biofilm Formation of Zirconia.

The air-particle-abrasion on zirconia in the gingival area of connectors and pontics in fixed partial dentures appears to increase fracture resistance. This study evaluated 'in situ' biofilm formation on the zirconia surface after different air-particle-abrasion protocols. Ninety sintered blocks (5 × 5 × 2 mm) of yttrium partially stabilised zirconia (Y-TZP) were obtained and randomised among nine groups according to the factors 'type of particle' (Alumina 50 and 110 µm; Cojet and Rocatec) and 'pressure' (2.5 and 3.5 bar) used for sandblasting for 10 s. The surface roughness (Ra/Rz) was measured before and after sandblasting. For the in-situ analyses, custom-made removable intraoral devices n = 10 with one sample of each group attached to the buccal area were used by volunteers for 8 h at night. The specimens were analysed under confocal microscopy to quantify both biovolume and thickness of the initial biofilm formed. One-way analysis of variance (ANOVA) and Dunnett's tests were performed (5%). The roughness values ranged from 0.05 to 0.39 µm for Ra and from 0.35 to 2.11 µm for Rz, p = 0.00. Mean biofilm thickness ranged from 0.06 and 0.54 µm (p = 0.005), while the biovolume values were between 0.02 and 0.61 µm3/µm2 (p = 0.002). Values statistically significant for biofilm thickness and biovolume were found in groups sandblasted with Rocatec using 3.5 bar. In order to increase the fracture resistance of zirconia fixed partial dentures (FPDs), the air particle abrasion of zirconia with SiO2 (110 μm/3.5 bar), in the gingival area of connectors and pontics, should be avoided.

Effect of ceramic material type on the fracture load of inlay-retained and full-coverage fixed dental prostheses

Objective Ceramic inlay-retained fixed partial denture (IRFPD) is a conservative prosthetic option but the mechanical durability of new high strength zirconia reinforced glass ceramic FPDs is not investigated. The purpose of this study was to compare fracture load of 3-unit ceramic FPDs. Materials and methods Extracted premolars and molars (N = 64) were used to create three test groups (IRFPDs) and one control group (full coverage FPD) (n = 8). The teeth were embedded in PMMA resin with a mesiodistal distance of 6 mm. Premolars had a distal and molars had a mesial inlay preparation (width: 3 mm; height: 4 mm) in the test groups. IRFPDs were made from a zirconia reinforced lithium silicate (VS) or a monolithic zirconia. Zirconia IRFPDs received 2 types of surface treatments: sandblasting (Zr-IRFPD) or internal coating with feldspathic porcelain (ZrC-IRFPD). Control group was made from monolithic zirconia with the same connector size and zirconia surfaces were sandblasted (Zr-FPD). All restorations were cemented using a resin luting cement. After 5000 thermo-cycles, fracture load values (N) were determined with a universal testing machine at a crosshead speed of 0.75 mm/min. Data were analyzed using 1-way ANOVA and Tukey`s post hoc test (p ˂ .05). Result Fracture load (mean ± SD) of Zr-FPDs, Zr-IRFPDs and ZrC-IRFPDs were 672 ± 183, 672 ± 123 and 638 ± 59, respectively, being not statistically different (p > .05). VS-IRFPD exhibited statically lower values (391 ± 136). The predominant mode of failure was fracture at the connector area in all groups. Conclusion The fracture load of 3-unit IRFPD was significantly affected by types of ceramics but the retainer design and surface treatment in Zr groups did not show a significant effect.