Physiologic Rest Position Research Articles

Letter: Vocal frequency and vertical larynx positioning by singers and nonsingers.

Measurements were taken from lateral still photographs of the vertical larynx position of four professional singers and four nonsingers. Subjects sustained phonation at seven discrete intervals between 90 and 350 Hz. Nonsingers generally positioned their larynx upward with increased voice frequency and tended to maintain a level at or above the larynx physiologic rest position throughout their vocal range. Singers usually maintained a laryngeal position below the physiologic rest level throughout their vocal frequency range. Subject Classification: 70.20; 75.70.

隣接面接触関係から見た歯列の近遠心方向の生力学的挙動

Generally, the teeth are considered to perform a sound function as one of the masticatory organs by forming the dental arch maintaining mesio-distal contact relation with the neighbour teeth. There have been, however, few stadies done on interdental proximal contact relation investigated from a functional standpoint. The author, therefore, made clear the bio-mechanical behaviors in mesio-distal direction of the dentition, with the focus on the interdental proximal contact of the teeth. In the static experiments, measurements with regard to the items listed as follows were taken when load was applied on the teeth and the dentition in the oral cavity kept in a state of rest. a. Displacement of the individual tooth. b. Displacement of a number of the neighbour teeth. c. Displacement of the dentition and the interdental contact force. In the dynamic experiments, measurements regarding the items listed as follows were taken of the dentition in the oral cavity functioning. a. Changes of the interdental contact force. b. Changes of the interproximal distance. The following conclusions were obtained as a result. 1. Mesio-distal displacement of the teeth and the dentition : a. The mesio-distal displacement of the individual tooth did not vary greatly from those of the labio (bucco)- lingual displacement. b. When load was applied on the buccal dentition, the degree of displacement of the dentition decreased as the number of the neighbour teeth increased. It is, therefore, considered that by maintaining the interdental proximal contact of the teeth, reciprocal function of supporting of the teeth occurs, and the mesio-distal displacement and the degree of separation of the teeth decreases. When separation of the teeth occurs, and if the cause is of a temporary nature, it is considered that physiologic rest position of the teeth is restored in a relatively short span of time by the visco-elastic behaviors of the periodontal tissues and the forces of the oral soft tissues which affects the crowns. 2. Interdental Contact Force : The interdental proximal contact state of the buccal dentition was in passive state in most cases. In some cases, however, drag existed on the interdental proximal surfaces. The author termed this force exerted between the teeth 'interdental contact force'. In such cases, the interdental proximal contact state of the dentition under non-occlusal rest position is considered to be in active contact state. The interdental contact force of occlusion is 100g order and temporary at work, but those of the posterior soft tissues and the lips are 10g order. and they are considered temporary in some cases and continuous in others. 3. It is necessary to evaluate the mesio-distal stability of the dentition with an emphasis on the functions of the lips, tongue, and posterior soft tissues. Interdental contact force is considered to be a force derived mainly from the posterior soft tissues. 4. Dento-alveolar discrepancy, a term heretofore in use, should be evaluated, taking into consideration not only the local balances between the lips and the tongue and between the cheeks and the tongue, but also the balance between the lips and the posterior soft tissues, Dento-muscular discrepancy, therefore, is perhaps a more appropriate nomenclature.

Determination of physiologic rest position by electronic measurement

A means of determining the vertical dimension of physiologic rest position has been described. The method is based upon the principle that oral physiology permits the patient to automatically seek his mandibular rest position between acts of swallowing and to maintain this mandibular position during the greater portion of any given time period. By placing an electronic device employing the principle of a rheostat between the jaws, the precise point of the vertical dimension of physiologic rest position may be determined by correlation with readings on an ammeter.

Morphology of Liberian Negro deciduous teeth. II. Arch dimensions and occlusion.

AbstractLiberian Negro deciduous dentitions have arch dimensions which significantly exceed those of a variety of White populations. Winged incisors were present in 14.3% of the Negro population, again exceeding White values. No differences were noted in incisal overbite or overjet. Diastemal spaces were greater in the Negro dentitions than in the White, but the significance of this is as yet unknown. An exceptional finding was the absolute lack of Class II (distocclusion) in the Negro series. A discussion of functional occlusion stressed the necessity for the inclusion of such dynamic factors as dental abrasion, mesial migration and physiological rest position in future studies of comparative dental anthropology.

Role of the external pterygoid muscles in temporomandibular articulation

An analysis of temporomandibular articulation reveals that: 1. 1. The interarticular fibrocartilages prevent direct contact of the condyles with the surfaces of the fossae during all mandibular movements. This precludes any possible condylar guidance by the shape of the bony fossae. 2. 2. Physiologic rest position is a definite mandibular position which maintains airways and is controlled by the neuromuscular system. 3. 3. Centric relation is a definite mandibular position which is assumed in the function of deglutition. This position is the starting point of all mandibular movement, because the mandible continually returns to this position in the course of the swallowing reflex. 4. 4. Lateral mandibular movement is a rectilinear movement forward toward the midline and parallel to the occlusal plane. This movement is not translation. 5. 5. Protrusion of the mandible is a rectilinear forward movement parallel to the occlusal plane. Protrusion is translation. 6. 6. The horizontal axes of certain mandibular movements are in the necks of the condyles. 7. 7. The Bennett movement is the lateral shift of the mandible coincident with lateral mandibular movement.

Vertical Dimension, Jaw Relation Records and Occlusion

The problems of vertical dimension, jaw relation records and occlusion are complex, and they involve a complete study of what is commonly called the stomatognathic system. There are many methods available for the determination of the correct vertical dimension. Some are dependent on measurements, some on phonetics, others on cephalometrics and still others on tactile sense. The reliability of any of these methods may be questioned because there is no scientific proof of their accuracy, but their true value lies in the fact that they are aids which will help to resolve the problem of vertical dimension. Free-way space and physiologic rest position are the most sought-after aids in the establishment of the desirable vertical dimension for the edentulous patient. The use of jaw relation records is predicated on the fact that the maxillary cast has been properly oriented to the articulator so that the maxillary cast has the same relation to the temporomandibular articulation as it does in the mouth. This is accomplished through the use of the facebow. Jaw relation records generally fall into two main classifications, the interocclusal method and the tracing device method. To obtain the most accurate results from either method necessitates a knowledge of their limitations, advantages, and disadvantages. The complexity of the problem of occlusion has been stressed. The more important factors in the development of the occlusal scheme have been emphasized. Some of the more important points are these: 1. The movements of the temporomandibular articulation are many and varied. 2. The muscles of the body, to be in a state of equilibrium, must be at their true physiologic resting position or in a state of isotonic contraction. 3. Vertical dimension of rest and vertical dimension of occlusion are not one and the same. 4. The composition of bone is such that it cannot withstand a sustained force. Dentures must be constructed with a separation of the teeth when the mandible is at rest, and the teeth must be so positioned as to create forces of occlusion that are favorable to the bone, to prevent rapid resorption. 5. The plane of occlusion should be so positioned that favorable leverages will be exerted on both arches. 6. Centric relation and the hinge axis are considered a terminal position, but to call the rest relation a terminal position would be incorrect. 7. Centric relation is found at the apex of the needlepoint tracing. Patients may also have formed a habit, or functional relationship. With patients who have an acquired or functional eccentric relationship it is not advisable to lock the occlusion to the apex. This may be accomplished by allowing the teeth to gain an additional range of horizontal movement without engaging the inclined planes. 8. Cusp teeth, with their thickness of occlusal pattern and cuspal inclinations, lend themselves well to the establishment of occlusal balance and the reduction of traumatic forces to the underlying bone. 9. Flat teeth, lacking cusp height and inclination, will not be a factor in the reduction of trauma in denture construction. 10. Balanced occlusion means an equalized contact between masticating surfaces within their functional range, which will include centric and eccentric movements. 11. The eccentric movements of the mandible are controlled by condylar guidance, incisal guidance and Bennett movements. 12. The balancing factors for eccentric movements are the plane of orientation, compensating curve, cusp height and inclination. 13. Each patient is an individual in regard to age, sex, physical, mental, and physiologic factors. This obviously means that no one stereotyped pattern of tooth with an arbitrary degree of cuspal inclination will satisfy the needs of all patients.

Conservative occlusal rehabilitation

Mathematics, engineering principles, precision, and uniformity of procedures must not dictate the physiology of occlusion. Failures in occlusal rehabilitation do not result from the use of, or the failure to use, a particular brand of instrument, a hinge-axis recording, or any other registration. Rather, they result from three basic errors. Unsuccessful results are often caused by increasing the vertical dimension of occlusion beyond the limits of the physiologic rest position, by disregarding the limitations in and around the mouth, and by rehabilitating natural dentitions in every case along the lines and principles recommended for complete denture construction. A “balanced” occlusion in a natural dentition is a fallacy. It is important to duplicate the functional curve of occlusion in patients who have the habit of bruxism. Ten unfavorable types of occlusion and their management should be understood by the dentist so that he will recognize the limitations of treatment and thereby avoid difficulty.

Vertical, centric and functional dimensions recorded by gnathodynamics

An intraoral gnathodynamometer was used to register maximum biting force at various vertical dimensions. Men average 60 to 65 pounds of biting force and women produce 25 to 30 pounds. Physiologic rest position and the vertical dimension that permits maximum biting force are the same. With the aid of the intraoral gnathodynamometer, the functional area of intermaxillary relations also may be determined. The functional area may be the predominating factor in determining correct maxillomandibular relations.

Methods of obtaining vertical dimension and centric relation: a practical evaluation of various methods

All of the methods utilized to determine vertical dimension and centric relation have value if those who use the methods are aware of the problems involved. The determination of vertical dimension is largely empirical. Vertical dimension should be within the patient's physiologic limits. The vertical dimension at centric occlusion is about 3 mm. less than the vertical dimension of the physiologic rest position. Centric relation can be determined graphically or by means of wax check-bites. The hinge axis cannot be determined as a single point, but only within an area of 1.5 to 2.0 mm. diameter.

An electromyographic analysis of the function of the buccinator muscle as an aid to denture retention and stabilization

R ECENTLY, MUCH NEW INFORMATION relative to the musculature of the masticatory apparatus has been obtained through the use of the electromyograph. Research on mandibular movement, physiologic rest position and centric position, hinge axis, and pathologic conditions l 7 have contributed to an ever increasing knowledge of muscular function. The electromyograph has become another valuable instrument in aiding dental research, Jarabak7 and Pruzanskys describe the electromyographic equipment and the physiologic basis for the recordings.

Physiologic denture technique

1. Many conditions which affect denture construction require diagnosis and treatment before the impression procedures are started. 2. Conditioning the tissue and the musculature provides a more normal anatomic structure and physiologic function. 3. Principles of nondisplacement, functional denture borders, and tissue detail are included in the impression technique. 4. Vertical dimension, centric relation, and bilateral balance are determined for maxillomandibular relations. The needle-point tracing and physiologic rest position are used as reference positions for diagnosis. 5. Condyle paths are recorded by tracings and roentgenograms. 6. Tooth arrangement follows a physiologic principle. 7. The available denture base materials require careful processing and checkstep procedure. 8. Final instructions of hygiene and psychology are made at the time the finished dentures are placed in the patient's mouth.

A study of physiologic rest position and centric position by electromyography

A study of physiologic rest position and centric position by electromyography

Basic anatomic factors of jaw position

In normal cases, the occlusion, the temporomandibular joint, the bone and soft tissue, and the musculature all produce the same relations of each to the others, and any one of many registration techniques could be used. In other words, we could employ most techniques and obtain a satisfactory record of jaw relations if normal conditions were present. In addition, there is quite a functional tolerance of all of the factors of jaw relations. However, to develop a technique which could be applied to all types of patients, normal and those where the factors of jaw relation have been disturbed, we must select a predominating factor which is most nearly normal. Apparently, the musculature is the predominating basic factor of jaw position. It provides the motivation and the power for the jaw and determines the rest position. The physiologic rest position of the jaw may be used as the diagnostic reference position.

A radiographic study of the positions of the mandibular condyle at physiologic rest position and at occlusion of the teeth in individuals possessing cleft palate deformity: By A. P. Arnstine, D.D.S., M.S.D., Northwestern University, Chicago, Ill.

A radiographic study of the positions of the mandibular condyle at physiologic rest position and at occlusion of the teeth in individuals possessing cleft palate deformity: By A. P. Arnstine, D.D.S., M.S.D., Northwestern University, Chicago, Ill.

Restoring the Lost Vertical Dimension of the Cleft Palate Patient

One of the great problems of abnormal development is the cleft palate and its associated deformities. This paper will be concerned with the restoration of the lost vertical dimension in patients with cleft palates who have mutilated growth patterns subsequent to extensive surgery. Graber1 has pointed out that the man­ agement of the cleft palate in the past has been largely surgical. Yet the surgical manipulation of growing parts, traumatic interference with growth centers, and forceful mechanical closure o f palatal insufficiency have produced results which often are worse than the original dis­ orders. What may appear as a successful surgical closure of the palate in infancy may result in an extreme maxillomandib­ ular discrepancy after potential growth patterns have been fulfilled. Thompson,2 in his studies of normal groups, found that the physiological rest position of the mandible is established in infancy and remains constant into senes­ cence. A normal freeway space or interocclusal clearance o f 3 to 4 mm. in infancy will remain constant and if no growth aberrations occur and no trau­ matic interference takes place within the growth centers, the interocclusal clear­ ance in adulthood will still be 3 to 4 mm. Another observation is that of Graber3 who, in a comparison of cleft palates which had been operated on with ones which were not operated on, found a difference in growth pattern. In the cleft which had not been operated on, growth proceeded along normal lines. In the instance where an operation had been performed, however, the freeway space was not constant. Immediately after surgery, freeway space may be normal. Ten years later, however, a maxilloman­ dibular discrepancy may be pronounced and freeway space may have increased to 10 or even to 18 mm. (Fig. 1). Often in the instance where an opera­ tion has been performed and there is excessive freeway space, there is little or no occlusion. Mastication is difficult. There is an overclosure of the mandible resulting in condylar displacement (Fig. 2 ). Speech often is impaired, particularly in the production of sibilant sounds. The appearance of the patient when the teeth are fully closed is poor. The child whose appearance is incongruous often is sub­ jected to ridicule by his more fortunate schoolmates. Psychosocial conflicts fre-

Diagnosis and Reconstruction Technic in Full Mouth Rehabilitation

O n e of the primary objectives of good dentistry is the maintenance of healthy teeth and their supporting structures. A great impediment to achiev­ ing this goal is malocclusion, which is responsible for the loss of teeth through trauma. It is also responsible for the resorption of the bony support ridges under both partial and full dentures. There are three ways of overcoming this handicap of malocclusion and securing a functional occlusal balance: by ortho­ dontia, by grinding to eliminate the trauma caused by cusp interference, and by full mouth reconstruction. In this paper, we are chiefly interested in the discussion of the last of these methods; namely, full mouth reconstruction as it pertains to the securing of a functional occlusal balance. To understand the problems involved in complete rehabilitation of the masti­ cating mechanism, one requires a thorough knowledge of the associated dental sciences of anatomy, physiology, histology, biology and physics. The causes of the various conditions which are present must be recognized, as must be the limitation in the use of the three methods of treatment mentioned above. In order to secure the best results it is frequently necessary to combine ortho­ dontics and grinding in cases in which full mouth reconstruction is being under­ taken. Full mouth reconstruction may be em­ ployed ( i ) when the patient has lost vertical dimension, (2) in cases in which restorative work is necessary although vertical dimension has not been lost, and (3) for purely cosmetic reasons. There are definite symptoms of lost vertical dimension, objective and subjective. The objective symptoms are plainly visible; teeth show attritional wear, there is a marked change in facial expressions upon swallowing, a sagittal displacement of the mandible in closure is apparent, or . there may be found a deep overbite of the anterior teeth. The subjective symptoms are pain or soreness in the mandibular joint, crack­ ing noise in the joint, dizziness (fre­ quently after eating), localized head­ aches, subluxation of the mandibular joint, and a burning sensation of the sides of the tongue. One of the chief causes of failure of so-called “bite open­ ing” technics has been due to a disregard of the importance of maintaining a normal freeway space. “Freeway space” is a term which defines the space that exists between the teeth when the jaw is at the physiologic rest position. Niswonger1*2 first recognized that this physiologic rest position was constant throughout life. Thompson and Brodie3 have confirmed his findings. Thompson4 examined many cases in which the verti­ cal dimension had been increased by means of full dentures but no allowance

A study of spontaneous fulminant shock in a heart-lung-dog preparation: Wégria, R., Rojas, A. G., and Wiggers, C. J.: Am. J. Physiol. 138: 212, 1943

Vertical dimension has been defined in relation to the clinical rest position of the mandible, the vertical dimension of occlusion, and the interocclusal space between the two. The physiologic rest position has been attributed to three possible mechanisms: postural tonicity of the muscles, myotatic (stretch) reflexes, and gravity-elasticity, and/or a combination of all three. There is general agreement that it varies due to head position and many other extrinsic and intrinsic stimuli.The myotatic (stretch) reflex is produced by stimulation of the stretch receptors in the elevator muscles producing a simple two-neuron reflex arc which causes reflex muscle contraction. Its function is to give proprioceptive information to the central nervous system concerning position and movement. The proprioception of mandibular position is determined for the most part by the joint receptors, muscle spindles, pressoreceptors (in the periodontal membrane), and exteroceptors in the oral mucosa.Minimal EMG activity has been demonstrated at the clinical rest position and slightly beyond, at an increased vertical dimension which eliminates the interocclusal space. However, experimental evidence has been shown with adult monkeys that long-term increases in the vertical dimension of occlusion result in intrusion of the posterior teeth with the return almost to the original vertical dimension of occlusion. Several clinical examples of intrusion of the posterior teeth were shown when long-standing occlusal splints were used. Since both occlusal adjustment and vertical dimension increases can cause a reduction in EMG activity, it is recommended that the treatment of TMJ dysfunction is best accomplished by occlusal correction.A treatment prosthesis is recommended for trismus and/or joint injury but it should be accomplished within the interocclusal space. Most treatment prostheses, except those for condylar repositioning, are utilized for the control of symptoms and do not treat the cause of TMJ dysfunction pain.