Butt-joint Design Research Articles

Evaluation of fracture resistance of ceramic veneers with different preparation designs and loading conditions: An in vitro study.

Purpose:The purpose of this study was to evaluate the effect of incisal butt joint and incisal overlap design on the fracture resistance of ceramic veneers under two different loading conditions, i.e., 125° and 60° representing protrusive and intercuspal movements, respectively.Materials and Methods:Thirty-two maxillary central incisors were divided into two groups of sixteen specimens each and were prepared with incisal butt joint and incisal overlap design. Ceramic veneers were fabricated and cemented. Both the groups were further divided and mechanical testing to evaluate the fracture resistance were done using the universal testing machine. The values were recorded in Newton along with the assessment of the failure mode of both veneer and the tooth.Results:Unpaired t-test showed a significant difference (P < 0.05) with butt joint design having higher fracture resistance than palatal overlap design with the mean value of 409.50N at 60° angle and 473.37N at 125° angle. Paired t-test depicted a significant difference for both the designs at 125° than at 60° angle (P < 0.05). Chi-square analysis showed more number of intact veneers with butt joint design; however, there was no significant difference (P > 0.05). Failure mode of teeth showed more number of coronal fracture followed by cervical fracture and root fracture, but there was no significant difference between the two groups (P > 0.05).Conclusion:Butt joint design had higher fracture resistance than palatal overlap design. Under functional loads for both designs, fracture resistance was higher at 125° than at 60° angle.

Butt-joint design in a uni-traveling carrier photodiode array monolithic with an arrayed waveguide grating by the selective area growth technique

Monolithic integration of an InP-based O-band 4-channel arrayed waveguide grating (AWG) to a uni-traveling carrier photodiode (UTC-PD) array is realized by the selective area growth (SAG) technique. The passive-active buttjoint design is introduced and experimentally proved to ensure both good compatibility between the PD fabrication process and the SAG technique, and high photodiode quantum efficiency under the complex butt-joint geometry. An extended coupling layer is adopted between the AWG output waveguides and the PD mesa. The extended coupling layer length, the regrowth boundary edge position and the AWG etching edge position relative to the heterogeneous butt-joint boundary, and the refractive indices of the PD collector and coupling layer are optically simulated and optimized by a finite-difference time-domain method. It is found that the extended coupling layer, compared with the un-extended situation, ensures a good matched optical field from AWG to PD and could reduce nearly 30% quantum efficiency loss when connecting seamlessly to the regrown InP AWG top cladding layer. A stable high efficiency around 80% is maintained within an extended layer length from 7.5 m to 15.0 m. The regrowth boundary edge into the coupling region will cause a drastic efficiency oscillation up to 20% period with the increase of distance. The efficiency drop is also attributed to the light scattering at the regrowth boundary edge, caused by the optical field mismatch, while the oscillation comes from the alternative light power concentration between the coupling layer and the core layer, for the light scattering is only obvious when the light power is well concentrated in the coupling layer. The AWG etching edge position deviation from the butt-joint boundary, however, exerts little influence on the PD quantum efficiency, which is believed not to bring obvious coupling loss during device fabrication. The higher UTC-PD collector refractive index is proved to be crucial for further better optical coupling from the coupling layer to the PD, with quantum efficiency rapidly increasing from around 0.1 to 0.8 when the index is increased from 3.20 to 3.42. By comparison, the efficiency is little affected by the coupling layer refractive index from 3.34 to 3.42.All things considered, we select a 10 m extended coupling layer, the refractive indices of both PD collector and the coupling layer to be 3.42, and align both the regrowth boundary edge and the AWG etching edge to the heterogeneous butt-joint boundary, and a PD quantum efficiency of 80% is expected. Owing to the extended coupling layer at the butt-joint, the SAG technique facilitates the PD fabrication process. The overgrown AWG top cladding layer ridge stretches out 4.67 m toward the PD, but not over the mesa yet, hence has little influence on the PD fabrication accuracy. The monolithic chip presents a uniform photodiode quantum efficiency of 76%, which accords well with theoretical value and confirms the butt-joint design. Central wavelengths for the four channels are 1347.0 nm, 1325.0 nm, 1308.0 nm, and 1286.5 nm, respectively. The low crosstalk level (below -22 dB) also indicates a good de-multiplexer performance.

EFFICACY OF INCISAL PREPARATION DESIGNS ON THE FRACTURE RESISTANCE OF TWO CAD/CAM LAMINATE VENEERS

Statement of problem: Mechanical properties are cardinal for the long-term clinical success of laminate veneer restorations. The most common failure is fracture and debonding, in which unfavorable occlusion and articulation play an important role. Nonetheless, the effect of different incisal preparations on the behavior of veneers remains controversial.Objective: The purpose of this study was to evaluate the fracture load of two different CAD/CAM laminate veneer materials: resin nano-ceramic [lava ultimate] and lithium disilicate glass ceramic [IPS e-max CAD], with two different incisal preparation designs [butt-Joint and incisal overlap]; using both in-vitro and finite element analysis studies. Materials and Methods: A total of 20 maxillary central incisors were used in this study. The samples were divided into two main groups (n=10), according to the CAD/CAM material used. Ten laminate restorations were constructed for each group following the manufacturer’s directions with the two preparation designs (5 samples each), then cemented on their corresponding teeth. Fracture load was recorded for each specimen using the universal testing machine. Meanwhile, Finite element analysis study was performed to assess the in-vitro observations. Results: The results revealed that incisal overlap design with Lava ultimate laminate veneers recorded the highest mean fracture strength value (395 ±37.18 N). This was supported by the finite element results that showed that the incisal overlap design with lava ultimate laminate veneers had the lowest Von Mises stress (30.75 MPa). Conclusions: Within the limitations of the present study, it was concluded that the butt-joint and incisal overlap designs demonstrated different mechanical behaviors with regard to the two different restorative materials. The incisal overlap design tolerated stresses better than the butt-joint design with both materials. Also, the incisal overlap design with resin nano-ceramic laminate veneers had the best stress distribution. Nevertheless, both types of CAD/CAM materials and different incisal preparation designs used could be considered strong enough to withstand the average anterior masticatory biting forces.

A three-dimensional finite element study on anterior laminate veneers with different incisal preparations

Mechanical properties are important in the long-term success of restorations, but whether different incisal preparations can affect the behavior of veneers remains controversial. The purpose of this study was to evaluate the influence of different preparation designs on stress distribution in a maxillary incisor restored with veneers and with regard to different restorative materials and loading conditions. Based on the cone beam computed tomography scanning of a maxillary incisor, 3-dimensional finite element models for 2 different designs were developed. A static load of 50 N was applied with angulations of 60 degrees and 125 degrees to the longitudinal axis at the level of the incisal margin, simulating functional movements. Both porcelain laminate veneer and composite resin veneer were considered. The maximum stress values and stress distribution of the veneer, cement layer, and tooth structure were calculated and analyzed. The maximum stress values in the veneer and tooth were higher with the butt-joint design. Stresses were distributed more uniformly in the cement layer in the palatal chamfer design for porcelain laminate veneers, whereas a better stress distribution under protrusive movement was observed in the butt-joint design for composite resin veneers. The palatal chamfer design for porcelain laminate veneers tolerated stress better, whereas the butt-joint design was favored for composite resin veneers, particularly under protrusive movement.

Effect of high-strength filler metals on the fatigue behaviour of butt joints

Welded structures made of high-strength steel offer benefits in fatigue strength for finite life applications. The high-cycle fatigue limit, however, depends mostly on the geometry, and the metallurgy of the notch is of little account. Therefore, an optimised weld process is required to achieve an improvement in the fatigue strength. This paper contributes to the field of fatigue behaviour of thin-walled, high-strength steel butt joints, with regard to an optimisation of the gas metal arc weld process. An existing methodology was extended to manufacture welded specimens with minimised production scatter. The majority of the butt joint samples were dynamically tested, with the root surface ground flush to plate, to study the effect of the weld process on fatigue. The investigated specimen were carefully analysed by metallographic studies along with hardness, distortion, and weld toe topography measurements. This facilitated in finding a relation between experimental fatigue life and the weld parameters. The nominal stress approach, including a benign, nonconservative thinness correction, and the recommended notch stress concept, were applied to assess the fatigue behaviour of the thin-walled, high-strength steel butt joints. The experimental results showed that in case of high-quality welds with negligable geometric notch factor, a small, but distinct influence of the filler metal on fatigue is observable. The highest fatigue strength for the investigated butt joint design was obtained with a high-strength metal-cored wire filler in combination with a three-component shielding gas.

Influence of the butt joint design of TIG welding on corrosion resistance of low carbon steel

The aim of this work is to study the influence of the joint design of Tungsten Inert Gas welding (TIG) on the corrosion resistance of low carbon steel (type St-37). A single V-butt joints of a low carbon steel plates are performed by the Vangles 30°,45°,60° and square butt joint (angle 90°). Corrosion behavior of welded specimens in 3.5% NaCl solution was examined using Tafel polarization measurements. The corrosion behavior of the welded joint also is determined by open circuit potential (OCP) after that the cell’s current is changed due to increasing in potential by ±100. The results shown that the corrosion rate of welded joint with V-angle of 30° was found to be less than that of other angles (45°,60° and 90°). It found that the corrosion resistance of base metal was better than that of all welded joints. From the results of the microstructure it is evident that the joint design or geometric shape of weld has an important role in the welding process, when the preparation angle value of the weld gets bigger, the faults gets less due to increase of heat quantity in the weld region.

Influence of the Butt Joint Design of TIG Welding on the Thermal Stresses

Influence of the Butt Joint Design of TIG Welding on the Thermal Stresses

Effect of repair surface design, repair material, and processing method on the transverse strength of repaired acrylic denture resin

The transverse strengths of blocks of denture base acrylic resin repaired with autopolymerizing monomer and polymer and autopolymerizing monomer and heat-cured polymer were measured with a three-point bending test. Three repair joints were studied: butt, round, and 45-degree bevel. Three processing methods were used: bench cure, hydroflask with hot water for 10 minutes, and hydroflask with hot water for 30 minutes. The strengths of repairs made with round and 45-degree bevel joint designs were similar and significantly greater than those with a butt joint design. The strengths of repairs processed in a hydroflask for 10 minutes and 30 minutes were similar and significantly greater than those cured on the bench top. There was no difference in the strength of repairs made with autopolymerizing monomer and polymer and autopolymerizing monomer and heat-cured polymer.