Kinematic Hinge Research Articles

The Effect of Hinge Axis Position on Mandibular Movements

The objective of this study was to evaluate the effect of an arbitrary and true hinge axis on the Bennett shift and the horizontal condylar path inclination. Ten completely edentulous subjects were selected for this study. For each subject, true and arbitrary hinge axis positions were located. Whip Mix Quick Set Recorder was used to measure the Bennett shift and the horizontal condylar path inclination. The Bennett shift and condylar path inclinations were recorded two times, first using the arbitrary and secondary using the kinematic hinge axis as the starting point for recording. The resultof this study showed that there were no statistical differences between the two measures of the Bennett shift and horizontal condylar path inclination.

Magma flow paths and strain patterns in magma chambers growing by floor subsidence: a model based on magnetic fabric study of shallow-level plutons in the Štiavnica volcano–plutonic complex, Western Carpathians

The Miocene Stiavnica volcano–plutonic complex, Western Carpathians, exposes two nearly coeval intra-caldera plutons, their roof (basement of a stratovolcano), and associated volcanic rocks. The complex thus provides insights into mechanisms of magma chamber growth beneath large volcanoes. As inferred from the anisotropy of magnetic susceptibility (AMS), these plutons were emplaced through significantly different processes: the diorite as a discordant stock with steep fabric and the granodiorite as a tabular, bell-jar pluton. In detail, we interpret that the latter was assembled in two stages. First, an upper “layer” intruded as a thin sill along a major subhorizontal basement/cover detachment. The subhorizontal magnetic fabric and strongly oblate AMS ellipsoid in this layer record intrusive strain where the magma flow paths were subparallel to the pluton roof. Second, in the lower “layer” of the pluton, magnetic foliations dip moderately to the ∼NW and ∼WNW to vertical and are associated with down-dip to subhorizontal lineations and prolate to weakly oblate shapes of the AMS ellipsoids. Such a fabric pattern is compatible with piecemeal floor subsidence, where magma flowed along multiple subsiding fault-bounded blocks. Based on this case example, we develop a conceptual model for magma flow paths and strain patterns for four main modes of floor subsidence: (1) piston (cauldron) subsidence is characterized by convergent flow and radial principal stretching above the magma chamber floor; (2) the piecemeal floor subsidence leads to steep to inclined magma flow paths in conduits along fault-bounded blocks; (3) asymmetric (trapdoor) subsidence produces first divergent flow paths near the conduit sides, changing into convergent paths in the narrower space near the kinematic hinge; and (4) symmetric cantilever (funnel) subsidence will lead to divergent flow from a central feeder and thus circumferential principal stretching of the magma. If the growing pluton develops a “two-layer” structure, all the flow paths and associated strains are affected by the flat-lying pluton roof and will convert into horizontal flattening as the roof is approached.

Failure of CFRP airframe sandwich panels under crash-relevant loading conditions

New aircraft fuselage concepts have to prove equivalent crashworthiness standards compared to conventional metallic fuselages for certification. Brittle failure mechanisms of CFRP structures make the verification of equivalent crashworthiness for novel CFRP fuselage concepts challenging since conventional metal fuselages absorb a significant part of the kinetic energy by plasticization. In this context, the damage initiation and failure of twin-walled fuselage panels were investigated under crash relevant bending–compression loads. Since the sandwich failure is initiated by core failure, a trigger concept for CFRP composite sandwich panels was developed based on local modifications in the fold pattern of the core for controlled failure initiation. By locally adjusting the collapse strength of the core in normal direction, the failure position and failure load can be adapted according to the defined kinematic hinge requirements. The core trigger concept was validated in experiments with triggered and untriggered sandwich panels under identical loading conditions.

Cenozoic pure-shear collapse of the southern Menderes Massif, Turkey

Abstract A transition from construction to collapse of the Alpine orogen in Middle to Late Eocene time is recorded in the structural fabrics of gneissic rocks in the southern Menderes Massif, western Turkey. Augen gneiss in the southern Menderes Massif indicates a spatial switch of shear sense along a north–south section through the complex (top-to-north shear in the north and top-to-south in the south). This ‘kinematic hinge’ corresponds to a broad zone of dominant pure shear where crust underwent vertical thinning and approximate north–south extension. During this extension, foliation became corrugated with fold axes parallel to lineation, indicating inflow from neighbouring crust to the east and the west. Published geochronologic work suggests a Middle to Late Eocene age for this dominant fabric. Thermal weakening of felsic Menderes crust beneath Alpine nappes may have triggered this orogenic collapse. Deformation fabrics developed at temperatures of c. 550 °C, and progressive cooling during collapse generated strain localization within a kilometre-thick shear zone at the southern margin of the Menderes Massif. In the southern Menderes, the corrugation of foliation indicates that Middle to Late Eocene flow was constricted into an orogen-perpendicular direction. This behaviour is similar to the collapse and orogen-parallel extension of the European Alps (Lepontine dome, Tauern Window).

Comparison of Mechanical and Nonmechanical Failure Rates Associated With Rotating Hinged Total Knee Arthroplasty in Nontumor Patients

Rotating hinge total knee arthroplasty (TKA) has had acceptable to poor results in terms of clinical outcomes and survivorship, leading to skepticism with regard to its use. A total of 271 hinged TKAs performed between 1998 and 2008 were studied to determine survivorship and factors affecting survivorship. A median survivorship of 6.9 years was found for the best-case cohort (n = 111), and 4.1 years, for the worst-case group (n = 174). Of the 111 patients, 51 (45.9%) experienced a failure that required reoperation, with more than half of these (29/51, or 56.9%) due to nonmechanical modes of failure. Comparison of the kinematic hinge implants with the distal femoral replacements showed that the Kaplan-Meier survivorship was slightly higher for the patients with distal femoral replacements, although this was not significant (P = .962). Our study suggests that the hinge TKA is well designed and provides acceptable survivorship in healthy patients who do not have nonmechanical complications.

Flow of partially molten crust and origin of detachments during collapse of the Cordilleran Orogen

Abstract In metamorphic core complexes two types of detachments develop, coupled by flow of partially molten crust: a channel detachment and a rolling-hinge detachment. The channel detachment, on the hinterland side of the orogen, represents the long-lived interface that separates the partially molten crust flowing in a channel from the rigid upper crustal lid. On the foreland side of the core complex, a rolling-hinge detachment develops. This detachment dips toward the foreland, probably affects the whole crust, and its geometry is governed by strain localization at the critical interface between cold foreland and hot hinterland. Activation of the rolling-hinge detachment drives rapid decompression and melting, leading to the diapiric rise of migmatite domes in the footwall of the detachment. A kinematic hinge (switch in sense of shear) separates the two types of detachments. Structural, metamorphic and geo/thermochronological studies in the Shuswap core complex (North American Cordillera), combined with an anisotropy of magnetic susceptibility study of leucogranites concentrated in the detachments, suggest that this orogen collapsed rapidly through the development of channel and rolling-hinge detachments in the early Eocene. The kinematic hinge is currently located approximately 40 km west of the footwall in which it originated, corresponding to a mean exhumation rate of >5 km Ma −1 , which explains the near-isothermal decompression recorded within the migmatite dome.

A comparison of protrusive interocclusal records to pantographic tracings

The rationale for recording protrusive mandibular movement is to accurately adjust an articulator. Techniques to record condylar inclination include radiographic interpretation, extraoral tracings, and intraoral recording materials. This study compared the protrusive settings on an articular adjusted by a pantograph to protrusive settings recorded by two intraoral recording materials, one a polyvinyl siloxane material and one a laminated, metalized wax. Pantographs were completed for 20 patients by using a kinematic hinge axis and conventional pantographic techniques. The patients also had three protrusive interocclusal records made with two intraoral registration materials completed and averaged. The average condylar inclination recorded with a pantograph (29.5 degrees) was greater than the recording by either intraoral registration material. Standard deviations ranged from 4.1 degrees to 6.6 degrees. An analysis of variance showed that the condylar inclination recorded by wax was statistically less than recorded with a pantograph. A comparison between the pantograph and the polyvinyl siloxane displayed no statistically significant difference in recording condylar inclination.

A comparison of lateral interocclusal records to pantographic tracings

Many techniques exist to record patients' lateral jaw movements, but they have not been thoroughly investigated. This study compared recordings of immediate sideshift by using a pantograph and two intraoral registration materials. Pantographs were completed on 20 healthy participants by using chinpoint guidance and a kinematic hinge axis. Three lateral interocclusal records were completed on each participant and averaged for right and left sides. The average immediate sideshift recorded by a pantograph (0.54 mm) was less than that recorded by the two intraoral registration materials. The standard deviations were similar for all materials. An analysis of variance test identified significant statistical differences between a pantograph and one of the intraoral registration materials, but not between the pantograph and the other registration material. Immediate sideshift recorded with one material compared favorably with a pantograph recording when three records using the chinpoint guidance were averaged.

Technique to record the location of the kinematic hinge axis without tattooing

Technique to record the location of the kinematic hinge axis without tattooing