Mandibular Displacement Research Articles

無歯顎患者の顎関節症に対する咬合回復による一治験例

In recent days, the so called arthrosis of the temporomandibular joint has been increased with other various kinds of syndromes seen in the mouth and jaw. Almost all of the temporomandibular joint dysfunction syndrome patients are dentulous, and on the other hand edentulous patients are rather few. We met an edentulous patient whose dentures are thought to be a certain factor to her temporomandibular joint dysfunction. This patient has a habit of mandibular displacement that is based on the bad dentures. We made new dentures to treat her dysfunctions. After inserting the dentures, we guided her a correct centric occlusion. And also we used pharmaco- and physio-therapies as an oral surgical treatment. Today 6 months after setting new dentures, we could get a good satisfactory progress. This case is very uncommon because the patient is so high a age, 77 years old, and edentulous and have no rheumatosis. The temporomandibular joint dysfunction is usually accompanied with local pain, and trismus, so we must need both systemic and oral surgical treatments. Andit is apparent that most of the dysfunctions are caused by the disordered occlusions. It is impossible to complete the treatment without performing prosthodontic treatment for occlusal improvement. Thus we should take care of the temporomandibular joint dysfunction patients from the two stand points, prosthodontics and oral surgery.

下顎の前後的位置変化に関する基礎的研究 : 特に顎関節の生物力学的性状について

Investigation of biomechanical behavior of the temporomandibular joint of persons with stabilized occlusion was made to establish a means for determining whether the mandible has stabilized in its new position after its anterior or posterior displacement due to orthodontic treatment. For this purpose, an apparatus which enables detailed measuring of the anterior or posterior positional change of the mandible was devised. Measurements with the apparatus were taken of adults with normal occlusion first and studied. The results obtained were as follows : 1. The extents of the anterior displacements brought about by the subjects' own muscles were 7.4 to 12.9mm (average : 10.8mm) on Frankfort Horizontal Plane. The posterior displacements were 0.1 to 1.9mm (average : 1.2mm). These values were 82.9 to 99.2% (average : 90.0%) and 0.8 to 17.1% (average : 10.0%) of the total mandibular displacements respectively. 2. When the mandible was pulled using a chin-retractor toward Pogonion to Porion direction, the extents of the posterior displacements of the mandible were 0.11 to 0.37mm (average : 0.27mm) on the Pogonion to Porion line with the traction load of 2, 000g. With the traction load of 4, 000g, the figures were 0.23 to 0.84mm (average : 0.59mm). With an increase in the traction load, the extents of the movements also increased. The extents of increase, however, showed individual differences. 3. As to the biomechanical behavior after the removal of the traction load, every subject showed viscoelastic movement consisting of instant and creep recovery. The behavior could be shown by 3 element model with the spring and voigt model in series. The biomechanical behavior of the temporomandibular joint showed elastic behavior in which a full recovery was made when the application time of the external force was quite short (about 2 minutes). 4. Observations of the extent of displacements (creep recovery) of the mandible after the removal of the traction load showed that individual differences in full creep recovery time were great even among the subjects with normal occlusion, and that the time varied from very short (4 to 6 seconds) to relatively long (4 to 6 minutes). 5. In every subject, the higher the traction load and the longer the traction time, the longer was the full creep recovery time after the removal of traction load. 6. The biomechanical behavior of the temporomandibular joint was similar to the behavior of the supporting tissue of the teeth, which has already been reported.

Effects of mandibular displacement on the metabolic activity of the masseter muscle in rat

The effects of changes in the moment of the superficial masseter muscle on its metabolic activity were studied. By cementation of a high inclined plane on the lower incisors, the bite was opened and the mandible was displaced posteriorly, so decreasing the moment of the muscle. A low inclined plane did not decrease the moment of the muscle but changed the pattern of normal proprioception. The high inclined plane appeared to decrease the functional activity of the muscle as revealed by fluorometric analyses of phosphocreatine, ATP. glucose. G-6-P and lactate. The low inclined plane, however, probably increased the functional activity of the superficial masseter muscle.

Facial asymmetries and mandibular displacements.

The paper is divided into two parts. In the first part Facial Asymmetries are classified with special reference to the mandible, and mandibular displacements. In the second part the diagnosis of mandibular displacement associated with facial asymmetry is discussed, including the clinical and radiographic interpretation and the treatment problems involved. In the conclusion the main points of the article are summarized.

Cellular responses of condylar cartilage induced by mandibular displacement in rats (author's transl)

幼若ラット, 成熟ラットの下顎切歯唇面に斜面板を装着し, その結果誘起させる下顎遠心咬合に対して, 下顎頭軟骨がどのように反応するかについて定量的に検討した。すなわち, 3H-thymidine, 3H-prolineを用いたオートラジオグラフィー, ならびにHE染色標本により, 軟骨細胞数, 軟骨層厚径, 軟骨細胞増殖, 軟骨基質形成, 軟骨基質吸収の各々について検討を加え, 次のような結果が得られた。1.幼若, 成熟個体ともに, 斜面板による外的刺激を与えた場合には, 下顎頭軟骨における細胞数は, わずかな減少を示したが全般に大きな変動は認められなかった。2.外的刺激を受けた場合の下顎頭軟骨の各層の厚径は, 幼若個体では著しい減少がみられ, とくにhypertrophic zoneで顕著であった。しかし, transitional zoneの厚径には余り変動がなかった。一方, 成熟個体の厚径はhypertrophic zoneに減少がわずかに観察されたにすぎず, ほとんど変動しなかった。3.下顎頭軟骨の標識指数は, 幼若個体では下顎頭軟骨の中央部および後方部で著しい低下を認めたのに対し, 成熟個体では中央部に低下を認めたが, 幼若個体にみられたような大幅な低下はなかった。4.外的刺激は, 軟骨細胞分裂のみならず, 軟骨基質形成にも多大の影響を与えた。すなわち, 軟骨に取込まれた3H-prolineによる銀粒子数は, 幼若個体では全領域で著しく減少し, 基質内線維形成の低下を示した。成熟個体では後方部で減少が観察されたのみで, 幼若個体のような大きな変動はなかった。5.Erosion zoneにおいて軟骨の吸収に関与していると思われるchondroclastの出現数は, 幼若個体, 成熟個体ともに減少した。6.成熟個体は幼若個体に比し, 細胞増殖, 基質形成, 基質吸収のすべての面で活性が著しく低下しており, 外的刺激に対する反応は幼若個体と同様に低下を示したが, その変動量は僅少であった。

Histochemical study of mandibular joint adaptation in experimental posterior mandibular displacement in the rat

The effect of experimental retrusion of the mandible on the mandibular joints was studied in young and old white Sprague-Dawley rats with substance and enzyme histochemical methods. The posterior displacement of the mandible resulted in enhanced metabolic activity in the posterior parts of the condyle indicating increased cartilage formation. Marked remodelling activity and bone deposition were found in the anterior part of the condyle at the insertion of the pterygoid muscle. Remodelling activity was found also in the most anterior part of the glenoid fossa, where the cartilage was replaced by bone, while cartilage formation occurred in the posterior part of the fossa. The tissue reactions were more pronounced in young animals than in older ones, but the results show that the capacity for articular remodelling is preserved also in old animals.

Variations in Mandibular Displacement, Velocity, and Acceleration as a Function of Phonetic Context

Continuous displacement, velocity, and acceleration of the mandible were recorded along with intraoral air pressure and audio to provide some initial data on mandibular dynamics as a function of place of articulation (p, t, k) and vowel height (i, æ). The muscle-forcing-function interpretation of acceleration, reported at the last meeting of this society by the present investigators, is incorporated. Relative timing between airstream valving, glottal onset-offset, and mandibular activity provides some basic data on patterns of system coordination as they vary with phonetic context. These results also provide some additional information on the coupling between the mandibular and lingual movement systems for speech.

Anterior displacement of the mandible in adult rhesus monkeys

An anterior displacement of the mandible of about 1.5 mm. was instituted in five adult rhesus monkeys by placement of cast splints on the mandibular anterior teeth. Appropriate tissues were studied by histologic means. The monkeys could masticate well with the splints in place. No traumatic injury occurred to the functioning surfaces of the temporomandibular joints. A slight mesial or forward positioning of the condyles induced mild adaptive changes in the joints. However, these changes seemed insignificant, nonprogressive, and possibly reversible without treatment. There was evidence of severe trauma and significant adaptive changes in the periodontium of the teeth involved in the dysfunctional occlusal relationship. The main accommodation to the induced anterior mandibular displacement took place in the dentition rather than in the temporomandibular joints. The results of this experiment confirm the importance of adapting the occlusion to the temporomandibular joints rather than hoping for the joints to adapt to the occlusion.

Condylar adaptation to a change in intermaxillary relationship.

Twenty Sprague‐Dawley rats were utilized to study the effects of a distal occlusion on the mandibular joint. The experimental period varied from one to four weeks. Cellular behavior and synthesis of new bone was revealed radioautographically after the injection of tritiated thymidine and tritiated proline respectively. The following structures within the joint were studied: (1) the fibrous layer of the articular fossa, (2) the fibrous and (3) the embryonic zone of the condyle. The number of labeled cells decreased in all areas analyzed after the first week of experiment but by two weeks had increased above the control. At four weeks, while still higher than the control, the radioactive index was decreasing. Of the structures studied, the embryonic layer showed the greatest response in number of cells undergoing DNA synthesis due to: (1) growth, (2) age, and (3) distal displacement of the mandible. Within the fibrous layer of the condyle and articular fossa, however, except for the central portion of the latter, the difference in radioactive index between control and experimental groups was negligible. Concomitant with the downward and forward growth of the mandible the number of cells undergoing DNA synthesis was highest in the posterior portion of the condyle. Initially, resorption was observed in the area of the external pterygoid attachment of the condyle followed by new bone formation as evidenced by tritiated proline. From this investigation the following conclusions were drawn: (1) The cells within the embryonic zone of the condylar cartilage can be stimulated, even in the adult, to increase their rate of cellular division to adapt to changes in mandibular position. (2) The articular fossa and disc remain unaltered following distal mandibular displacement. (3) Tension within the external pterygoid muscle will result in gross morphologic alterations on the anterior border of the condyle.

The differential diagnosis and treatment of mandibular displacements and prematurities

The differential diagnosis and treatment of mandibular displacements and prematurities

Diagnosis and treatment of mandibular displacements by mandibular kinematography. The dental nociceptive reflex

Diagnosis and treatment of mandibular displacements by mandibular kinematography. The dental nociceptive reflex

Temporomandibular joint disorders

Twenty patients suffering from disorders of the temporomandibular joint were treated by correcting their occlusions; this involved the reduction of cuspal inclines that were causing mandibular displacements. All 20 patients received complete relief, generally within 24 to 48 hours. Occlusal corrections were made only in the centric position. A new procedure for the analysis and correction of traumatic occlusion utilizes a check-bite made of white alginate; interfering cusps are located by a study of the perforations in the check-bite.

A Functional Consideration of the Problems of Occlusion

Abnormal form and abnormal function of the stomatognathic system must be diagnosed and appraised in the living individual, and restoration of normal function must be consistent with the fundamental physiology of the system and its components. Three abnormal functional conditions, premature contact, functional occlusal interference, and mandibular displacement, may be present in varying degrees of severity and may be responsible for abnormal temporomandibular joint function. These conditions are not limited to adults, making it necessary that an evaluation of function be accomplished on all patients regardless of age. If dentistry is to accept the challenge and assume the additional problems of diagnosis and treatment of impaired occlusal and neuromuscular patterns, we must no longer permit our thinking to be dominated by the various mechanical techniques. A thorough knowledge and understanding of the anatomy, growth, and physiology of the stomatognathic system will enable the dentist to adapt the necessary technical procedures to the needs of the fundamental biologic principles of the living individual. As we accept science as an attitude, we will be better able to produce a greater health service.

Cephalometric appraisal of a treated mandibular displacement case in an adult patient

Cephalometric appraisal of a treated mandibular displacement case in an adult patient