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Results for “Condylar position”

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At least 37 records · Page 2Linked to original sources
PubMed1978

[Geometric-mathematical analysis of errors during transfer to the articulator and their practical consequences. II].

With the aid of a computer faults are examined which result in the occlusal surfaces when several articular parameters are simultaneously wrongly applied in laterotrusion. The calculations which are derived from the geometrical relations of the Dentatus articulator refer to a circular field of 3 mm radius on a molar tooth. Vertical deviations, which are caused by faulty setting up of a preferred articulator size, evidently depend on the angle of the joint on the balancing side and depend on the working side on the sagittal position of the model in relation to the condylar axis and on the length of the condylar axis. In the most unfavourable case, errors of the order of 1.3 mm on the balancing side and of 0.75 mm on the working side were demonstrated. As regards horizontal deviations, all articulator sizes were shown to be independent of one another. The effects of faulty setting up on periodontal strain is presented in a practical example.

Computers↗
PubMed1977

Posterior unilateral condylar displacement: its diagnosis and treatment.

The treatment procedure for posterior unilateral condylar displacement has been described. An acrylic resin repositioning prosthesis may be used to decrease trismus. Occlusal adjustment permits lateral freedom for mandibular movement to the opposite side which provides a dual, or a therapeutic, centric occlusion as well as the existing dysfunctional centric relation. This permits the patient's physiologic adaptive mechanism to choose between the existing dysfunctional centric relation, which resulted in unilateral condylar retrusion and pain, or a therapeutic centric occlusion which is aimed at anterior unilateral condylar repositioning. Over long period of time, muscle reprogramming produces maximum intercuspation of teeth in the planned therapeutic centric occlusion rather than in the original dysfunctional position. No explanation has been established for this phenomenon. It is important, however, to provide a technique that permits physiologic adaptability over a period of time. It should be emphasized that this is not TMJ "remodeling" but a functional change in the position of the jaw. The treatment objectives of bilateral and unilateral posterior condylar displacement are similar, but the clinical techniques are completely different. In either instance, TMJ radiographs are necessary to establish the diagnosis and treatment, as well as to document the postoperative results.

Acrylic Resins↗
PubMed1975

[Arthroplasty of the knee. Prosthesis without uni- or bicondylar hinge].

The prosthesis has two components. The femoral component is metallic surfacing the condyle and a tibial plateau in polyethylene replaces the original one. The prosthesis can be uni or bi-condylar. Operative technique has to be very precise and the position of the prosthesis needs accuracy. The advantages are: minimal bone resection, small implant harmonic action with the knee joint as a whole. 20 patients with I8 months follow up are reviewed, problems are infections and pain in the patello-femoral joint. The results on pain and walking are good. Stability depends on accurate indications.

Aged↗
PubMed1977

Condylar fractures of the mandible. I. Classification and relation to age, occlusion, and concomitant injuries of teeth and teeth-supporting structures, and fractures of the mandibular body.

In 123 individuals, 138 fractures of the mandibular condyle were classified with respect to fracture level, dislocation at the fracture level, and condylar head relation to the articular fossa. The age of the patient and the location of the most distal occlusal contact were recorded as well as teeth injuries and concomitant fractures of the mandibular body. The position of the most distal occlusal contact did not influence the dislocation of the condylar fragment. Teeth injuries such as fractures and luxation were found to be associated with condylar head or neck fractures, whereas the concomitant fractures of the mandibular body were mostly seen with the subcondylar fractures. Teeth injuries as well as concomitant fractures of the mandibular body were found more frequently in patients with bilateral than unilateral condylar fractures. Fractures of teeth in the molar and bicuspid regions were most frequent on the condylar fracture side, while the concomitant fractures of the mandibular body were located to the contralateral side. Medial angulation of the condylar fragment with lateral override at the fracture level was the typical fracture in adults, and angulation without override the characteristic fracture in growing individuals. Medical override occurred both in children and in adults and seemed to be the result of more severe trauma to the chin.

Accidents↗
PubMed1977

Condylar translation and the function of the superficial masseter muscle in the rhesus monkey (M. mulatta).

The relationship between translation of the mandibular condyle during symmetrical mandibular rotation, i.e., symmetrical jaw depression and elevation, and the function of the superficial masseter muscle was examined in light of relative torque and the length-tension relationship for muscle. Lateral cephalograms of live adult rhesus monkeys (Macaca mulatta) were analyzed using two models: (1) Model A, normal symmetrical jaw rotation accompanied by condylar translation; and (2) Model B, mandibular rotation about an axis fixed at the position of the condyles during centric occlusion. The decrease in relative torque and the excursion of the superficial masseter at mouth-open positions are significantly greater in Model B than in Model A. Symmetrical rotation of the jaw about a fixed axis would result in a 35% greater loss of maximum producible tension at maximum gape than rotation associated with condylar translation. These results suggest that condylar translation during mandibular depression and elevation functions to minimize reduction in relative torque and excursion of superficial masseter muscle, thereby maintaining optimal potential for exerting maximum tension during jaw closure.

Animals↗
PubMed1977

A new articulator emphasizing centric occlusion and the anterior determinants.

A new articulator is described which has the advantages of the rigidity of a simple articulator in the upper member and the flexibility of an adjustable articulator in the lower member. A link between the members and the frame along with the posterior controls establishes a full range of functional chewing movements and defines the extreme lateral or border paths. The articulator has condylar element controls which permit releasing and remounting the mandibular cast in a manner that serves the same function as the split-cast technique, but this method is faster and shows the amount of discrepancy. The condylar element control is an improvement over existing devices for comparing interocclusal records in that it not only indicates differences in position but it also provides quick remounting of the casts in a working articulator. Other features of the articulator are: (1) a condylar lock mechanism which is activated by only a half turn, (2) adjustable spring tension, (3) precise long centric and wide centric controls, (4) an incisal pain which can be removed and replaced on the articulator without changing its setting, (5) a Bennett movement carefully selected to avoid the complication of a pantograph type of face-bow, and (6) a new sponge wall type of mounting plate which supports both casts for simultaneous mounting.

Dental Articulators↗
PubMed1977

[Quantitative interpretation of graphs from Stuart pantography. II. Geometrical bases].

In an experimental investigation, Stuart pantographic records are geometrically analyzed. The influence of the parameters' inclination and curving of condylar guidance, intercondylar distance, Bennett angle, distance of the plate, and position of the recording pencil are studied. Further quanitative analysis was not performed, as Stuart pantography is only meant for transmission to the respective articulator and is nto suitable for metric recording.

Dental Articulators↗
PubMed1978

Mechanics, growth, and class II corrections.

Growth of the orofacial region is quantitatively described by locating the center of mandibular rotation relative to the cranial base. The center of mandibular rotation is positioned by the ratio of vertical facial growth (AFH/PFH) and the direction of condylar growth. Appliance therapy is associated with changes in the means of both of these parameters. These changes reduce or stop favorable anterior mandibular rotation and redirect the mean condylar growth vector more posteriorly. When appliance therapy is stopped, these parameters return toward their resting values. The mean direction of the condylar growth vector became even more anteriorly directed after treatment than the pretreatment mean value. These data support the hypothesis that orthodontic appliances significantly alter the facial growth pattern and when they are stopped, the growth pattern tends to rebound to or beyond the pretreatment values.

Activator Appliances↗
PubMed1975

Radiographic changes in the temporomandibular joint subsequent to vertical ramus osteotomy.

The position of the mandibular condyle in patients treated for mandibular protrusion by the oblique vertical osteotomy of the mandibular rami was studied on temporomandibular joint radiographs exposed according to the oblique transcranial projection. Forty-four adults participated in the study, and the radiographs were taken before the operation, 6 weeks postoperatively and 1 year postoperatively. At the 6-week postoperative control all the variables measured indicated a significant downward and forward displacement of the condylar fragment of about 1mm. The changes did not increase the variability of the joint morphology. At the 1-year postoperative control there were still significant differences in the position of the condyle compared with the pretreatment recording. A slight tendency to normalization was, however, observed. The mobility of the condyle, which was greatly restricted at the 6-week postoperative control, was fully restituted 1 year after the operation.

Adolescent↗
PubMedDate not supplied

[A method of osteosynthesis in supracondylar transverse fracture of the humerus in children].

A new surgical technique is described for the osteosynthesis of the supra-condylar transversal fracture of the humerus in children with an unique central transolecranian and transcondylar brooch. Intra-operative radiography is indispensable. The position for immobilization is very important. Temporary perforation of the diarthrodial cartilage and of the conjugation cartilage does not lead to functional or osteogenesis disturbances.

Child↗
PubMed1979

A reassessment of the mandibular transverse horizontal axis therory.

1. Within the limits of accuracy imposed by individual operators, equipment, and patient variations, a single transverse horizontal axis can usually appear to be located. 2. Location of a kinematic axis is worthwhile clinical procedure to transfer an arc of rotation in the sagittal plane from the patient to an articulator. 3. Past experiments have been useful, but none have proved or disproved the presence of colinear or noncolinear condyle arcs. Only the arc of the rigid clutch and its associated mechanism is located. Such an apparent arc may result from the resolution of compound condylar movements. 4. The right angle-nonright angle concept is misleading and generally is not applicable to clinical procedures. 5. The anatomic asymmetries of the axis transfer procedure may result in cast dislocations that may produce undesirable alterations in esthetic tooth positions. 6. The single transverse horizontal axis as a fact in articulating instruments and as a theory in the human craniomandibular complex. 7. The terms "transverse horizontal mandibular axis" and "intercondylar axis" should not be confused or used as synonyms. The term "transverse horizontal mandibular axis" ("hinge axis") should be used instead of "condylar" or "intercondylar" axis.

Cephalometry↗
PubMed1978

Size of variables in mandibular movements in autopsy material.

Autopsy was performed on the right temporomandibular joint in eleven individuals with a mean age of 71 years. Standard positions indicative for protrusion, laterotrusive border movement and posterior opening movement were photographed in the sagittal plane. Size of movements of the disc and condylar head were recorded, as well as movements of a reference point in the mental region. The slope of the anterior discal movement was estimated and mandibular rotation during posterior opening was registered. Centre of rotation during the hinge movement was in all cases located to the craniodorsal part of the condylar head. Attempt to construct centres of rotation in the eminence and condylar head for the horizontal movements was in vain. The discussion deals with the influence of the specific kind of material on the results and the possible systematic differences to clinical material.

Aged↗
PubMed1979

Experimental tests concerning the biomechanical behaviour of pertrochanteric osteosyntheses.

The biomechanical behaviour of pertrochanteric fractures stabilized by means of an angled plate or flexible condylar nails was characterized by mechanical testing. The stability and the types of motion occurring under dynamic load in the vicinity of the fracture and the effect on the implant were examined. The mechanical test results corroborated clinical experiences. In the case of extramedullary anchorage of implants, stability under load is possible only if an intact cortex on the medial side of the fracture guarantees the bearing of compressive load. With flexible condylar nails, however, it is possible to achieve a permanent load capacity up to approximately 100 kp, even if medial support is lacking, by putting the fracture in a valgus position so that the load-bearing arm is shortened. It was also possible to estimate the actual loading on the operated leg within the immediate postoperative phase by means of the "stabilization effect".

Biomechanical Phenomena↗
PubMedDate not supplied

The mechanical testing of a sliding meniscus knee prosthesis.

A 3-component sliding meniscus knee prosthesis was tested mechanically to evaluate the direct loads and the anteroposterior and mediolateral bending moments on the prosthetic components during the loading phase on a pendulum prosthesis testing machine. The bending moments changed with variation of the component positions. Tilting the tibial plateau produced the greatest change in lateral bending moment on the femoral component but alteration in plateau rotation or femoral tilting produced little change in the low values of the 2 bending moments. It is necessary to ensure that the tibial component is positioned horizontally on the tibial plateau, but it is not necessary to be concerned about the angle of the femoral component to the vertical or the misalignment rotationally of the tibial component. The load ideally passes through the condylar component to the tibia much more centrally than if it were a constrained prosthesis system during the loading range, reducing the likelihood of displacement of the 2 fixed components.

Biomechanical Phenomena↗
PubMed1979

Inferior joint space arthrography and characteristics of condylar paths in internal derangements of the TMJ.

Inferior joint space arthrography and measurements of the condylar path provide scientific documentation of derangement of the TMJ disc and condyle. These derangements are described as an anterior displacement of the disk associated with posterior-superior displacement of the condyle when the teeth are closed into the intercuspal position. Clinical studies demonstrate that approximately 70% of a TMJ patient population present with some type or stage of these derangements. These observations have far-reaching implications regarding contemporary dental curriculum, particularly concerning exegesis of the MPD syndrome theory and concepts of dysfunctional dental occlusion.

Cartilage, Articular↗
PubMed1978

Craniofacial adaptations after total maxillary osteotomy in Macaca irus: a cephalometric and histologic study.

Five Macaca irus monkeys were used in this study to determine cephalometric and histologic changes after total maxillary impactions. In the three experimental animals, the maxilla was impacted 5 to 7 mm. and lateral cephalograms were taken over a 150-day period. By superimposing on craniofacial implants, osseous and dental changes were measured. Excellent skeletal stability was demonstrated during the postoperative period. Histologically, there was normal osseous healing of the osteotomized maxillas. Accompanying the counterclockwise rotation (overclosure) of the mandible, there was extensive change in the temporomandibular joint. In the experimental monkeys, the fibrous articular covering of the temporal fossa was thin and irregular. The condylar cartilage appeared atrophic and showed considerable aging; also, the articular disc was much thicker in the experimental animals. The study showed the superiorly repositioned total maxillary osteotomy to be a stable procedure after 150 days of postoperative observation. However, further studies are needed to investigate the neuromuscular and adaptive response of temporomandibular articulation and mandibular rest position after maxillary surgical procedures.

Animals↗
PubMed1979

Effects of orthodontic intermaxillary class III mechanics on craniofacial structures. Part II - computerized cephalometrics.

The relation between active growth and induced anatomic changes was examined using a computerized cephalometric analysis of ten Class III cases treated with intermaxillary traction. The following can be concluded from this investigation: 1. Mandibular growth was redirected and mandibular opening was observed due to maxillary molar extrusion and counterclockwise rotation of the maxilla. 2. Condylar repositioning was noted to occur in all cases due to the effect of the external pterygoid muscle and a possible translatory movement during mandibular rotation. 3. Counterclockwise palatal development occurred in most of the treated cases through vertical action of the Class III mechanism. 4. The effect of the Class III traction was also observed in the mandibular incisor and molar teeth. The incisors retruded and the molars either were located in the predicted position or farther distally. 5. The soft tissue profile was less concave than the predicted value due to less mandibular growth and more retruded incisors in the treated cases. 6. Evidence was shown that a positive relationship exists between computerized cephalometrics and photoelastic techniques in the analysis of ten treated cases. This relationship is based on the fact that specific changes which took place during treatment were found to be consistent with the results of the photoelastic analysis.

Cephalometry↗