Connecting Bar Research Articles

Tensile strength of soldered gold alloy joints

Statement of problem. Little information is available about the mechanical properties of soldered gold alloys after they have undergone various heat treatments. Purpose. This study investigated the influence of heat treating on the strength properties of soldered joints of two gold alloys (NC Type IV and Sofard), which can be age-hardened at intraoral temperature. Material and methods. Dumbbell-shaped specimens were cast with each gold alloy and were cut at the center of the connecting bar for soldering. The two halves of the casting were then soldered with two different gold-based solders (Maingold and Degulor). Three different heat treatments were performed on the soldered gold alloy assemblies: solution heat treatment (ST) at 700° C for 5 minutes (treatment A); aging at 37° C for 7 days after ST (treatment B); and aging at 250° C (Sofard) or 400° C (NC type IV) for 15 minutes after ST (treatment C). The tensile strength, elongation and microhardness were evaluated after each heat treatment. Results. The hardness values of Sofard significantly ( p < 0.05) increased during aging at 37° C (treatment B) and produced adequate strengths of the soldered joints, especially with the harder solder (645.7 MPa: Degulor [222 VHN] vs. 493.3 MPa: Maingold [165 VHN]). Conclusions. The results of this study indicated the possibility of strengthening soldered joints in the oral environment, thus eliminating the necessity for any additional hardening heat treatment. (J Prosthet Dent 1997;78:260-6.)

Dissipation of heat during polymerization of acrylics used for external skeletal fixator connecting bars.

To determine the amount of heat conducted by transfixation intramedullary pins (IP) and Kirschner wires (KW) during polymerization of acrylics used for external skeletal fixator (ESF) connecting bars. Thermal conduction was measured using thermistors applied to IP and KW surfaces during the polymerization phase of acrylics. Type II ESF were created from IP or KW placed into wooden dowels and plastic tubing used to create connecting bars filled with one of two types of acrylic (Acrylic Pin External Fixation System or Technovit, Jorgensen Laboratories, Loveland, CO). Thermistors were positioned on the acrylic column surface and on IP or KW surfaces 5 or 10 mm from the acrylic column. Five ESF test groups were created. The maximum temperature (Tmax) of the acrylic column (Tmax-A), IP (Tmax-IP), KW (Tmax-KW), and duration that Tmax-IP or Tmax-KW remained greater than or equal to 55 degrees C were calculated. All IP and KW thermistors placed 5 mm from acrylic columns reached mean temperatures greater than 50 degrees C and had peak temperature ranges greater than 55 degrees C compared with all IP and KW thermistors placed 10 mm from the acrylic columns in all groups. Thermistors placed 5 mm from the acrylic column in two groups maintained temperatures greater than 55 degrees C for greater than or equal to 0.5 minute. Acrylic columns positioned 5 mm from a thermistor on a IP or KW had the potential to reach or exceed temperatures that have been reported to cause thermal necrosis of tissues. Acrylic Pin External Fixation System or Technovit acrylic connecting bars used in ESF designs have the potential to cause thermal injury to soft and bony tissue by thermal conduction along transfixation pins or wires.

Biomechanics of the Gazi type pelvis external skeletal fixator.

External skeletal fixation is an alternative method of treatment to conventional therapy and open surgical procedures in pelvis fractures. The appropriate type of frame and the configuration of the connecting bars of these fixators are under investigation. In the Gazi type pelvis external fixator (GPEF) which has been developed, a 70 degree angulation is applied to the connecting bars of the anterior quadrangular frame. This configuration, which is expected to improve the stability of the posterior column of the pelvis, was evaluated biomechanically on a phantom with various types of pelvic fractures and separations. The results suggest that the GPEF effectively controls anterior column pelvis fractures such as unilateral pubic ramus fractures, unilateral ischium pubis rami fractures and symphysis pubis separations under vertical loads. The fixator is partially capable of stabilizing the posterior column; however, loads above 700 N cause separation at the fracture site. Further studies and clinical trials are essential to determine the GPEF's effectiveness in reducing blood loss and in providing stability at the posterior column.

Repair of Diaphyseal Radius and Ulna Fractures Using a Modified Type I External Skeletal Fixator and Ulnar Intramedullary Pin

SummaryModified type I external skeletal fixation of the radius (using a curved connecting bar and unique pin placement) was combined with intramedullary pinning of the ulna to repair eight ipsilateral radius and ulna fractures in dogs. The intramedullary ulnar pin was placed first, aligning the radial fragments, which allowed closed application of the radial fixation. External skeletal fixation was designed to minimize soft tissue trauma and achieve a uniform boneto- connecting-bar distance. Seven of eight fractures healed in eight to twelve weeks with the technique described. The eighth case needed additional fixation following complications associated with the severity of the injury. Results of this study demonstrate that the technique is a suitable alternative for repair of the fracture types included.A modified type I external skeletal fixator and intramedullary pin was successfully used to repair radius and ulna fractures. The technique was developed in order to provide technically simple but rigid stabilization that minimized soft tissue disruption. The technique is described along with the results in a variety of fracture types.

Trichrome staining of Gyrodactylus sclerites and soft tissues following fixation in ammonium picrate-glycerin, including an improved rendition of the haptoral bars of G. turnbulli.

A simple technique using modified Mallory stain in the transferral of Gyrodactylus specimens from ammonium picrate-glycerin to a permanent mountant is described. Hamuli, their connecting bars and the penis sclerites are well defined by the technique as are muscles and tendons, cell nuclei, tegument and gland cells. As well as being useful in the study of general anatomy, the technique enhances the observation of the taxonomically important ventral and dorsal bars. In order to show this, improved illustrations of the dorsal and ventral bars of G. turnbulli are given along with explicit demonstrations of differences in morphology of the ventral bars of G. bullatarudis and G. rasini-two easily confused species.

Neocalceostoma Tripathi, 1957 and Neocalceostomoides Kritsky, Mizelle &amp; Bilqees, 1978 (Monogenea: Neocalceostomatidae n. fam.) from ariid fishes of Peninsular Malaysia

Three new species of Neocalceostomoides Kritsky, Mizelle & Bilqees, 1978 and Neocalceostoma elongatum Tripathi, 1957 were found on five species of Arius from Peninsular Malaysia. N. elongatum was collected from Arius sagor. A. venosus and A. maculatus, whereas Neocalceostomoides spinivaginalis n. sp., N. hamatum n. sp. and N. simplex n. sp. were obtained from A. thalassinus, A. sagor and A. caelatus, respectively. The three new species of Neocalceostomoides are similar to Neocalceostoma elongatum in the morphology of the soft anatomical parts and in having 14 marginal hooks, but differ in having the two anchors situated far apart without a connecting bar. The possibility that Neocalceostomoides and Neocalceostoma are synonymous is noted. The generic diagnosis of Neocalceostomoides is amended herein and a new family, the Neocalceostomatidae, is proposed to accommodate Neocalceostoma and Neocalceostomoides.

Modified Transarticular External Skeletal Fixation for Support of Achilles Tenorrhaphy in Four Dogs

SummaryAchilles tendon ruptures in four dogs were treated with tenorrhaphy using a modified Kessler locking loop suture pattern and postoperative immobilization in partial extension of the tibiotarsal joint. The temporary immobilization of the tibiotarsal joint was achieved with a modified transarticular external skeletal fixation (MTESF). After predrilling the bone, the first fixation pin was placed in the distal tibia and the second in the calcaneus; they were connected with medial and lateral connecting bars. This immobilization method was easy to apply and to maintain during the postoperative period. The modified transarticular external skeletal fixation was removed between five and eight weeks after the operation. All four tendons healed, and all of the dogs returned to normal function. Modified transarticular external skeletal fixation is an alternative method of immobilization of the tibiotarsal joint for support of healing Achilles tenorrhaphies in dogs.Achilles tendon ruptures in four dogs were treated with tenorrhaphy and postoperative temporary immobilization of the tibiotarsal joint. The immobilization was achieved using a modified bilateral transarticular external skeletal fixation connecting the distal tibia and the calcaneus. All four tendons healed, and all of the dogs returned to normal function.

Elastic connecting bar for a system for active control of vibrations

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Peri-implant mucosal aspects of ITI implants supporting overdentures. A five-year longitudinal study.

Sixty-six ITI implants placed in the mandible of 33 edentulous elderly patients (mean age: 69 years) were observed longitudinally for 5 years. The implants served as overdenture anchorage either by means of a connecting bar or single spherical attachments. During the study period, 2 implants failed (one because of a peri-implant lesion and one because of a fracture) and had to be removed. At the beginning of the study, all implants were osseointegrated and had successfully been in function for 3-5 months. Oral hygiene practices and the peri-implant mucosal status were assessed according to the criteria of conventional periodontal parameters. Approximately 50% of the implants had been installed into lining mucosa and hence were to surrounded by keratinized mucosa. The peri-implant mucosal tissue was maintained healthy during the whole observation period, and no or only minimal loss of attachment was observed. The probing depths averaged approximately 3 mm. At the end of the study, orthopantomographic radiographs were obtained from all patients to assess the peri-implant bony structures. Small local angular bony defects were detected on 16 implants (22%) in 12 patients. Slightly increased probing depths were observed when angular bony defects were present. Loss of attachment was significantly less frequent when the implants had been placed following a prolonged period of edentulousness (> 5 years). This study demonstrated that advanced age, reduced dexterity of elderly patients and environmental conditions of overdentures do not represent a higher risk for the development of peri-implant lesions.

Stifle Luxation Repair in a Moluccan Cockatoo and a Barn Owl

New York, New York 10021 An eight-year-oldMoluccan Cockatoo developed a severe stifle luxation after a traumatic event. Due to the severity of the injury, the decision was made to arthrodese the stifle. In order to fuse the stifle in a functional position, multiple K-wires were placed in the lateral aspect of the femur and tibiotarsus, and a type-1 external fixator with a connecting bar composed of an acrylic polymer was used. The bird was weight bearing by day 4 after surgery, and 7 months after surgery the stifle was stable with no detectable movement. A seven-month-old Barn Owl was examined because of a closed stfle luxation. The stifle luxation was reduced and stabilized by an externalfixation method similar to the one used for the cockatoo. External fixation for stifle repair in birds offers the advantages of no permanent implant, use of the limb during convalescence, and early return to function.

Multiple fragmentation in collapsing protostars*

Hydrodynamical calculations in three space dimensions of the collapse of an isothermal, rotating 1-M ○. protostellar cloud are presented. A numerical algorithm involving nested subgrids is used to resolve the region of initial binary formation in the central part of the protostar. An extensive series of numerical tests confirms the accuracy of the computer program. Comparisons are given with a standard test case of binary fragmentation in a collapsing isothermal cloud of initially uniform density. In a simulation with a 50 per cent initial perturbation a binary is clearly formed. In another simulation with a 10 per cent initial perturbation, however, calculations show the initial formation of a binary and a connecting bar, followed by fragmentation of the bar

Gas and dust in the pre-main-sequence multiple system GG Tauri

We present 1.4 and 2.7 mm aperture synthesis maps of the gas and dust continuum emission around GG Tauri, a very young component of a premain-sequence multiple star system; both GG Tau and its apparent companion, GG Tau/c, at 1500 AU separation, are themselves binaries. At 1.4 mm, dust continuum emission of about 750 AU in extent is associated with GG Tau, and a secondary peak is near GG Tau/c. Spectral line images reveal gaseous structure around GG Tau, elongated along the GG Tau-GG Tau/c axis. There is some suggestion that the gas associated with GG Tau/c alone is extended in a different direction. Marked changes in the morphology and velocity structure of the molecular emission near GG Tau/c also indicate that this system is differently oriented. Clumps between the two systems may be vestiges of a connecting bar. GG Tau and GG Tau/c appear to have originated in a common cloud; their different systemic orientations suggest that they formed from an initially prolate cloud rather than from an extensive and highly flattened disk.

The Use of Multiple Pin and Methylmethacrylate External Skeletal Fixation for the Treatment of Orthopaedic Injuries in the Dog and Cat

SummaryMultiple pin and methylmethacry-late external fixation devices were applied in 74 animals to successfully treat several different types of orthopaedic injuries. The major advantages associated with use of the technique included increased versatility in the location and angle of fixation pin place-ment and greater ease in placement of the connecting bar when compared with conventional clamp and connecting bar systems, particularly with transarticular placement of a device. The major disadvantages associated with the technique included, increased difficulty compared to conventional K-E systems regarding postoperative adjustment of the device and difficulty in removing individual pins that were loose or infected. Generally, removal of the device was not a problem, provided sufficient space was left between the connecting bar and the skin surface.Complications associated with the technique were similar to studies which have evaluated other types of external fixation and include fixation pin loosening, pin tract drainage or infection, fixation failure, osteomyelitis, angular limb deformity, mal-union, delayed union and nonunion.The multiple pin and methylmethacrylate external fixator provides a useful and effective method of repair for a wide variety of orthopaedic injuries. The use of methylmethacrylate as a connecting bar is a helpful adjunct to standard external fixation systems.The use of multiple pin and methylmethacrylate external fixation (MPMF) increases the versatility of the external fixation technique in small animal orthopaedic injuries. Disadvantages include difficulty in removing or replacing individual fixation pins.

The Role of the External Bar in a 6-Pin Type 1 External Skeletal Fixation Device

SummaryExternal skeletal fixation devices are commonly used in human and veterinary orthopedics. Although external fixators have proven useful over the years, their use is still associated with complications. The most frequently encountered complication is premature pin loosening with or without pin tract infection. Occasionally, implant failure involving the transla tion pins, pin clamps or external bar is seen. Each of these complications can contribute to patient morbidity through poor limb use, pain, loss of fracture reduction, and delayed unions or nonunions. A more thorough understanding of the biomechanics of external fixation devices may reduce the incidence of complications and associated patient morbidity. The objective of this study was to determine the role of the external connecting bar in a 6-pin type 1 external skeletal fixation device with respect to the forces transmitted to the surrounding bone for an axial load on the bone.The methods used were finite element computer analysis and in vitro experimentation using a bone analog. The results obtained in both the FEA and in the in vitro experiments was that the middle pins on each bone segment experienced axial tension while the remainder of the pins experienced axial compression. Furthermore, increasing the stiffness of the external bar decreased the axial loads on all the pins, and more evenly distributed the end shear load and end moment on the pins.The role of the external bar in a 6-pin type 1 ESF device was investigated using finite element computer analysis and in vitro experimentation. The results show that increasing the stiffness of the external bar decreases the axial loads and more equally distributes the end shear loads on the pins. Therefore, increasing the stiffness of the external bar may reduce the chance of complications related to excessive pin loads, such as pin loosening, pin breakage, and pin tract infection.

Immediate mandibular stabilization following resection of advanced oral cavity carcinoma using the Joe Hall Morris external fixation device.

Internal mandibular fixation after resection of advanced oral cavity carcinoma with mandibulectomy has a significant complication rate. We placed the Joe Hall Morris (JHM) external mandibular appliance in 29 patients undergoing mandibulectomy for advanced oral cavity carcinoma. Fourteen patients received postoperative radiation therapy (RT). Three of 29 patients (10%) had complications associated with the JHM appliance: one patient had a broken connecting bar, a second had loosening of a single pin, and a third had loss of fixation requiring complete replacement of the appliance. Complications not associated with the appliance occurred in 8 patients (28%) including mandibular exposure (1), orocutaneous fistula (2), partial flap dehiscence (4), and flap necrosis (1). Oral continence was maintained in 26 patients, and occlusion was normal in 27. The appliance was removed in 12 weeks to 6 months in all patients. The JHM appliance allows for a reliable and rapid immediate fixation of the mandible with acceptable functional and aesthetic results, and no delay or interference with postoperative radiotherapy. Since the life expectancy of these patients is short, most do not require subsequent permanent fixation after removal of the appliance.

Treatment of Fractures in Avian Species

External fixation, with coaptation or Kirschner-Ehmer splints, is a viable treatment for many fractures in captive and wild birds. Important considerations in selecting a device are the weight and size of the device, location of the fracture relative to joints, and prognosis associated with location of the fracture(s). A variety of materials, not limited to traditional medical materials, may be used in coaptation splinting. Straws, plastic spoons, and rubber balls can serve as effective splints. Type I and II Kirschner splints are typically used in birds, although large birds may require a type III splint on leg fractures. The most useful configuration for wing fractures is the type Ia single bar splint using epoxy or acrylic for the connecting bar. This splint is lightweight, positioned close to the patient, and stable for most fractures. The type II splint is an excellent choice for leg fractures at the level of the tibiotarsus and below. The destructive character of psittacines requires all splints be protected from the beak of the bird. Clavicular-furcular and coracoid fractures in small birds may be effectively managed with coaptation splinting. In birds over 400 g body weight, open reduction is needed for best results. Since fractures of the foramen triosseum are usually not surgically repairable, they can be stabilized with coaptation splints. Although humeral fractures may be managed with coaptation in some circumstances, firm stabilization with a type I Kirschner-Ehmer splint or internal fixation is best. Single bone fracture(s) of the radius or ulna can usually be managed with minimal treatment, brailling, or figure-of-eight wraps. Fractures of both the radius and the ulna require a type I Kirschner-Ehmer splint for internal fixation. Coaptation splinting alone is usually indicated for carpal or carpometacarpal injuries. Femoral fractures in small birds may be managed with coaptation splinting, although fractures in large birds or unstable fractures require internal fixation or a type I Kirschner-Ehmer splint. Tibiotarsal fractures, in many species, may be managed with internal fixation or a type II Kirschner-Ehmer splint. Tarsometatarsal fractures can be cast or stabilized with a type II Kirschner-Ehmer splint. Phalangeal fractures are best managed with coaptation splinting.

リンク機構による変位の拡大と縮小

A planar linkage is described which was devised primarily for micropositioning stages. It functions both as a magnifying or reducing mechanism and a guidance system for a rectilinear motion. Two input bars, which are coupled to a driving element such as a piezoelectric stack, two output bars, one of which is mounted on a base plate and the other performs the function of a moving platform, and four connecting bars, eight bars in total are connected together by flexure pivots. A displacement amplification or reduction is effected according as the angle between the input and connecting bars is larger or less than 45°. Design formulae are given for the linearity between the input and output displacements and a decrease in magnification caused by an elongation of the flexure pivot. A differential linkage, which combines a pair of linkages, is presented for improving the linearity. Description of the experiments performed for evaluat-ing the validity of design formulae, is included.

A strain-gauge study of the effect of external fixation on the canine tibia.

Electrical resistance rosette strain gauges bonded directly to the surface of the midshaft of the normal canine tibia were utilized to study the effect of the AO external skeletal fixator on the magnitude and orientation of the peak strain values recorded during locomotion. The application of the fixator in a single lateral bar configuration resulted in a significant decrease in surface bone strain magnitude but in only minor changes in the orientation of those strains. However, in only one of three dogs tested did the addition of a second external connecting bar result in significant further decreases in bone strain.

Talo-calcaneal coalition treated with resection.

Three cases of symptomatic talocalcaneal coalition (medial or posterior) have been treated successfully with resection of the connecting bar and fat interposition without fusion. At follow-up (ranging from 1 1/2 to 14 years), the patients had no pain, good function, good range of joint motion, and no regeneration of the bar. Computed tomography scanning was the method of choice for roentgenological diagnosis of talocalcaneal coalition.

Infinitesimal rigidity of cone-like and cylinder-like frameworks

Cone-like respectively cylinder-like frameworks in 3-space are constructed from plane frameworks by displacing the knots along collinear respectively parallel straight lines to at least two different positions for each knot and taking appropriate connecting bars. In [2] ist has been shown that this construction preserves shakiness. The aim of this paper is to prove that we get an infinitesimally rigid framework in space, if the plane base is assumed to be infinitesimally rigid.