Showing papers in "Journal of Prosthetic Dentistry in 1963"

Postextraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms

Abstract: 1. 1. Bone is a living tissue of varying size, shape, and density and is subject to constant remodeling throughout life. 2. 2. It is helpful in research, teaching, and patient care to classify adult mandibles into 6 orders of anatomic form: I, pre-extraction; II, postextraction; III, high, well-rounded residual ridge; IV, knife-edge residual ridge; V, low, well-rounded residual ridge; VI, depressed residual ridge. 3. 3. Microradiography of thin sections of bone shows clearly the variations in form and degree of mineralization of the various elements of bone. 4. 4. Microradiography of midsagittal sections of 21 edentulous mandibles revealed external resorption and an absence of periosteal bone on the residual ridges in all specimens. 5. 5. Evidence of mild to moderate osteoporosis was seen in one half of the specimens (average age of this group, 76 years). 6. 6. There are many avenues for the study of resorption of residual ridges. The possible roles of a constricting mucoperiosteum and of surgical technique are discussed.

Influence of occlusal rest position and clasp design on movement of abutment teeth

Abstract: 1. When treatment with a removable partial denture is necessary, the transition region from tooth to mucosa support must receive most careful consideration. 2. An occlusal rest placed on the mesial or anterior part of the most distal abutment tooth provides mucosa or soft tissue support more perpendicular to the residual alveolar ridge than does one on the distal side of that tooth. 3. The gingival mucosa adjacent to the most posterior tooth is less likely to be pinched when the occlusal rest is placed on the mesial side of the tooth. 4. The occlusal rest providing a mesial rotation point will tend to tip the abutment tooth anteriorly where it will be reinforced and assisted by other teeth. 5. All extracoronal retainers alter the natural tooth contour and interfere with proper stimulation of the gingivae and natural cleaning action. The infrabulge I bar design alters natural tooth contour the least and allows for more natural gingival stimulation than any other type of extracoronal retainer. The area of contact of the clasp with the tooth is minimal. 6. The I bar retentive clasp, when placed at the point of greatest circumference of the tooth and used in conjunction with a mesio-occlusal rest or anterior rotation point, will exert no adverse or torquing force on the abutment tooth. 7. The region of the junction between the tooth and the edentulous area exhibits pathosis most frequently. The tooth contact should be made with a thin metal plate which extends onto the soft tissue for at least 1 mm. This will increase cleanliness and prevent mutilation of the denture base which results in a space at the tooth-mucosa junction. 8. The metal-tooth contact at the distal gingival region must be physiologically adjusted in the patient's mouth to prevent tooth and tissue impingement.

The function and importance of incisal guidance in oral rehabilitation

Abstract: Incisal guidance is the influence on mandibular movements provided by the contacting surfaces of the maxillary and mandibular anterior teeth. The steepness of the incisal guidance is influenced by the horizontal and vertical overlap of the anterior teeth. In normal occlusion, the lingual inclines (surfaces) of the six upper anterior teeth may be considered as the incisal guide factor. The muscles of mastication and the temporomandibular joints control the movements of the mandible while the teeth are out of functional contact. From the time the first tooth contact is made until all teeth are in full functional contact, the teeth play a progressively greater role in directing the movements of the mandible. In the study of occlusion, we are more interested in the limited movements made by the condyles occurring while the teeth are in functional contact than we are in condylar movements made during the complete cycle of mastication.

Tooth contact patterns in mastication

Abstract: T HE PHYSIOLOGY of mastication and its underlying neuromuscular mechanisms .are incompletely understood. Statements about the role of occlusion and tooth contact in these mechanisms have been made in the literature but only a few are based upon experimental evidence. The clinical experience of successful treatment of temporomandibular joint and muscle disturbances, as well as bruxisrn,lm4 by occlusal adjustment (equilibration) and splints is an indication that occlusion has a significant role in the neuromuscular mechanisms. Under experimental conditions, occlusal interferences have been shown to influence electromyographic patterns.3 These clinical and experimental observations are indirect evidence that occlusal contacts play an important role in the reflex systems of the masticatory apparatus. Controversy has surrounded the occurrence of occlusal tooth contacts per se during functional movements and there is no published evidence on the precise jaw relationship during such contacts, or on their duration. Early attempts to measure occlusal tooth contact were the investigation of Hesse5 who studied the masticatory movements of the mandible. His report was concerned with empty movements and his paper, given in Paris, described functional movements.6 He used the space of a missing tooth to contain a lead pencil with a recording layer on the opposing tooth. His experiments showed the occurrence of occlusal tooth contacts during chewing in maximum intercuspation as well as during lateral excursions. The recordings of Jankelson and othersi were the first which measured directly the occurrence of tooth contact. Their attempts to detect tooth contact by means of cinefluorography were not successful. Subsequently, they developed a method which applied an electrical potential between two antagonistic full crowns. Upon contact, the circuit was closed and the potential difference was recorded on an oscillograph. Based upon this study they state: “. . . it cannot be stressed too forcefully that it was only during the act of deglutition that functional contact of opposing teeth was demonstrated.” Anderson and Pictons recorded tooth

An evaluation of basic articulators and their concepts: Part II. Arbitrary, positional, semi adjustable articulators

Abstract: Suggestings have been made for adapting the Hanau Model H articulator for fixed restorative prosthesis. However, the shortcomings of the instrument must be understood. A more adjustable instrument would seem to be indicated in order to reduce the degree of occlusal correction necessary to harmonize biologic movement with the occlusion produced on the articulator. On the basis of the mathematical study, the instrument is of practical value and within the accuracy of the records used for complete denture prosthesis.

An evaluation of basic articulators and their concepts: Part III. Fully adjustable articulators

Abstract: A gnathologic instrument in which three-dimensional pantographs are used is extremely accurate in duplicating three-dimensional motion. Theoretically, no occlusal error is produced. However, the many variable factors discussed modify an absolute clinical application of this conclusion. This system is not applicable to the needs of simple fixed partial dentures. However, the instrument can be used with eccentric interocclusal records. When this is done, the gnathologic instrument is more accurate than the Hanau Kinoscope because it uses a curved condylar path and it is adjustable to all nonpathologic working condylar motions.

Function, placement, and reproduction of bevels for gold castings

Abstract: The function, placement, and reproduction of the bevel have been discussed. Difficulties in tissue displacement must be overcome with the use of gingival retraction, copper bands, or electrosurgery. Castings have inherent errors of a significant character. The preparation of teeth should be modified to cancel errors as much as possible, and to make use of certain specific properties of gold castings.

Prosthodontic research in progress at the School of Aerospace Medicine

Abstract: We have attempted to measure the error in and control all of the factors that we did not wish to vary in the construction of multiple complete dentures for a series of patients. The discussion has explained how we have (1) measured denture-base deformation in double processing of plastics, (2) measured error in mounting or fastening casts to an articulator, (3) established a method for accurately establishing our centric relation records and transfer prior to the placement of teeth for the dentures, (4) devised a method for checking the swallowing method to determine the lost vertical dimension of occlusion in the edentulous patient (this was inconsistent), (5) by using these methods, produced consistent dentures and proceeded with our primary purpose—a study of the contacts of teeth in function, and (6) accomplished this study of tooth contact, masticating and nonmasticating, waking and sleeping, by placing a small radio transmitter in dentures so that any selected contact area would send a recordable signal; our Bioelectronics Laboratory developed recording equipment to provide unattended day and night monitoring of tooth contact. By varying jaw relationship, cusp form, and signal areas, we were able to arrive at the following conclusions: 1. Denture teeth do contact in chewing. 2. The amount and character of contact varies with the type of patient, jaw relation, cusp form, occlusion, and type of food being eaten. 3. Nonmasticating waking contacts vary from 150 per hour for some patients to 1,500 per hour for others. 4. Sleeping contacts total from 3 to 15 minutes per night for some patients to1 1/2 to 2 1/2 hours for others. I have not succeeded in substantially reducing bruxism by altering occlusion. This may be a medical problem.

The effect of complete dentures on alveolar mucosa

Abstract: Histologic examination of biopsy specimens prior to the insertion of dentures and following the wearing of dentures for three months, revealed healthy tissue with minimal inflammatory infiltration and increased keratinization. The dentures appeared to stimulate keratinization.

A new approach to the gagging problem

Abstract: Causes of gagging may be classified into psychogenic and somatogenic. Gagging that occurs during various procedures such as intraoral examination, etc., is for the most part psychogenic. Such gagging is a result of excessive fear, apprehension, anxiety, etc., and occurs only when the patient is aware of the stimulus. This gagging can be reduced in direct proportion to the reduction of the awareness of the stimulus. If the patient's attention can be sufficiently diverted (e.g., by the effort involved in keeping the foot elevated from the footrest), intraoral procedures can be accomplished successfully. Gagging that persists after the insertion of new dentures, or develops after dentures have been worn successfully for many weeks or months, must be considered as somatogenic. A careful study of such patients showed that an exaggerated increase of the occlusal vertical dimension was the cause of gagging. When the occlusal facial height was too great, the elevator muscles no longer relaxed normally. This disturbance, in turn, most likely affected all the musculature involved in swallowing and provided the stimulus for the gag reflex. When the occlusal facial height was reduced, gagging was eliminated.

An evaluation of basic articulators and their concepts: Part I. Basic concepts

Abstract: The objective of this series of articles is to evaluate several articulators and their associated concepts. The first part deals with a review of the basic information that is necessary for evaluation of these instruments. The requirements for recording motion have been described in order to better understand the relationship of mandibular motion to the cuspal inclines. The clinical importance of establishing the correct orientation of the maxillary dental arch on the articulator has been demonstrated.

The use of speech patterns as an aid in prosthodontic reconstruction

Abstract: Speech patterns are invaluable as an aid in denture fabrication. The restoration of the oral functions is one of the major objectives in the science of prosthodontics. Therefore, a comprehension of the muscle dynamics, motor innervation, memory factors, and sensory feedback, all of which make up the neuromuscular patterns is a requirement. Since the neuromuscular patterns for speech are the least affected by the removal of the teeth, they can be incorporated, under actual functional conditions, into other record making procedures. The reason is that during speech the sensory feedback, which consists of the combined kinesthetic senses of the facial musculature, the maxillomandibular musculature, and the temporomandibular joints, is little affected by the loss of the teeth. On the other hand, in the functions of mastication and salivary deglutition, occlusion is a major component of the kinesthetic sense. Consequently, the sensory feedback emanating from the periodontium is destroyed with the loss of the teeth. Hence, the neuromuscular patterns are made inoperative. When the artificial teeth are so arranged that their position is different than that of the natural teeth, they are foreign and antagonistic to the speech patterns and to the other functional patterns as well. They become obstacles in the way of functional movements. Tongue movements are impeded and speech sounds are obscured when the normal tongue space is encroached upon. Similarly, invasion of the normal interocclusal distance causes interceptive occlusal contacts in speech, in the swallowing threshold for salivary deglutition, and in mastication. Interference with functional movements causes the dentures to be buffeted about, thereby damaging, breaking down, and altering the underlying foundations. 7 For these reasons, the integration of the artificial teeth to the functional movements takes precedence over the fit of the denture base to its foundation. When the teeth do not conform to these functional patterns, the fit of the base cannot endure. Impression making, the recording of jaw relations, and the fabrication of dentures are basically technical procedures which may be adequate for the restoration of missing teeth, but quite inadequate for the restoration of the oral functions. To disregard the functional movements is to but half treat the edentulous patient, and that is not enough.

Clinical applications of concepts of functional anatomy and speech science to complete denture prosthodontics: Part VIII. The final phases of denture construction

Abstract: The final phases of denture construction are effectively accomplished insofar as they are developed in harmony with the functioning anatomy of which the dentures are to become a part. Maxillomandibular relations which were provisionally recorded must be verified and corrected after the teeth have been positioned. Speech plays an important role in this verification, in esthetic determinations, and in the critical evaluation of the completed dentures. The muscles responsible for facial expressions in the regions of the lips and checks must be properly supported by the dentures so that natural movements of facial expression can take place. Dentures constructed in accordance with principles of occlusal harmonies must be maintained in these same harmonies to retain the anatomic foundational support.

The polished surface of complete dentures

Abstract: The development of the proper forms of the polished surfaces of dentures must be based upon accurate impressions of the tissues which limit the extent of the dentures, and the teeth must be arranged in relation to the ridges so the slopes of the soft wax pattern for the polished surface can have a favorable angle with the cheeks, lips, and tongue. By the technique described, the polished surfaces of dentures can be made to fit the soft tissues that surround them.

The mobility of artificial dentures during comminution

Abstract: A method has been described which will permit measurement of the amount and direction of denture mobility by utilizing cephalometric roentgenograms made at the rate of 5 per second during comminution of diced carrots. This measurement was made without devices attached to the dentures or wires protruding from the mouth.

Clinical applications of concepts of functional anatomy and speech science to complete denture prosthodontics

Abstract: In the first article of this series, the significance of the vitality factor of a patient was suggested, and the problems associated with attempts to “measure” functional anatomy were recognized In the recording phases of denture construction, we are confronted with such problems Necessarily, then, the development of impressions and the registrations of maxillomandibular relations involve a series of provisional steps which must be thoroughly tested and verified before acceptable final results are attained Just as the preliminary modeling compound impression was the initial step in developing an accurate, functional, final impression, so the provisional maxillomandibular registrations, made with the occlusion rims, are the first approach to establishing the final registrations With the selection of teeth and the placement of them in the occlusion rims, we continue our verifications of measurements of functional anatomy This phase will be considered in the next article which will consider esthetic factors and carry the construction phases to their completion

Magnets for the retention of a sectional intraoral prosthesis: A case history

Abstract: A possible solution to the problem of rehabilitating patients who have undergone surgical removal of both maxillae has been suggested. A method of constructing a two-section intraoral prosthesis with the use of attracting magnets as positive locking devices has been described. The potential value of magnets as useful devices in maxillofacial prosthesis has been discussed.

The influence of geometric occlusal carvings on the masticatory effectiveness of complete dentures

Abstract: A study of 20 edentulous subjects was made to evaluate the effect of 4 cuspless geometric occlusal patterns on the chewing efficiency of complete dentures and to compare the masticatory effectiveness of these grooved patterns with similar patterns of raised metal inserts. Results of the tests showed no significant difference in effectiveness among the patterns tested. However, after a year of experience with a given pattern, masticatory efficiency was significantly improved. After three months of experience with metal insert patterns, the patients showed a definite improvement in masticatory performance. Dentures with occlusal configurations on both upper and lower posterior tooth segments seemed to be more effective than dentures with one or both opposing segments free of occlusal markings.

Morphologic limiting factors in the temporomandibular joint

Abstract: T HE TEMPOROMANDIBULAR JOINT is a provocative challenge to the dental profession. Apart from the fact that this joint is ginglymoarthrodial which permits extreme latitude in its movements, its function as a simple hinge joint has never been satisfactorily explained. Every joint in the human body has anatomic structures which impart stability during function. These structures are: (1) the osseous conformation of the articulating ends of the bones of the joints consisting of two opposing curved surfaces which are approximately congruent ; (2) muscles which activate joints and stabilize the joints for power transmission1 ; (3) ligaments which help stabilize the joint by limiting movement; and (4) capsules and discs which form a part of a joint but which do not materially contribute to its stability. No discs are present in some types of joints.