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Proper management of the occlusal plane is an essential consideration when multiple long-span posterior restorations are designed. When restorations are added to an existing tooth arrangement characterized by rotated, tipped, or extruded teeth, excursive interferences may be incorporated, resulting in detrimental sequelae. The curve of Spee, which exists in the ideal natural dentition, allows harmony to exist between the anterior tooth and condylar guidance. An instrument called the Broadrick flag has been used to assist in the reproduction of tooth morphology that is commensurate with the curve of Spee when posterior restorations are designed; its use prevents the introduction of protrusive interferences. Consideration also must be given to lateral excursive movements when the occlusal plane is designed. In this article, the importance of the curve of Spee in prosthodontic and restorative dentistry is discussed, and a patient treatment demonstrating use of the Broadrick flag is described.

Statement of Problem: Understanding is needed regarding the effect that occlusal interferences have on the teeth, periodontium, and especially on jaw function., Purpose: This article summarizes research in which experimental occlusal interferences have been placed on the teeth of animals and human volunteers., Material and Methods: Data from 18 human and 10 animals studies were reviewed. Experimental occlusal interferences were grouped into those that alter intercuspal position and those contacting on lateral jaw movement only. The outcome of these interferences were analyzed according to their local pulpal-periodontal, jaw function, or bruxism effects., Results: Experimental occlusal interferences in maximum intercuspation had a deleterious effect on periodontal and pulpal tissues of the affected tooth; sometimes this produces a disruption of smooth jaw function and occasionally jaw muscle pain and clicking. Experimental occlusal interferences that contact only in a lateral jaw movement are infrequently harmful to jaw function. Furthermore, no reliable evidence demonstrates that occlusal interferences can cause nocturnal bruxism, or stop it., Conclusion: Transient local tooth pain, loosening of the tooth, a slight change in postural muscle tension levels, chewing stroke patterns, and sometimes a clicking joint can be induced by an experimental occlusal interference. Because such findings are present in relatively asymptomatic patients, these data do not prove that occlusal interferences are causally related to a chronic jaw muscle pain or temporomandibular joint dysfunction problems.

This article describes a device that is intended to prevent the clenching of the teeth. The principle involved is that to clench the teeth for an extended period, an intraoral vacuum must be formed and maintained. A tube or drinking straw held between the lips extending out of the mouth will prevent a vacuum. The article explains and illustrates how such a device can be made that will exploit this principle. Disadvantages and advantages are discussed.

The effects of four sequential modifications to improve occlusion, vertical dimension, retention, and stability of poorly fitting dentures, and of placing new dentures, on the EMG activity were investigated in 21 denture wearers with a mean age of 67.7 years. Electromyographic recordings of right and left masseter muscles were made while the subjects performed masticatory and swallowing threshold tests and applied static guided forces were measured before and after each modification and at three intervals after the delivery of new dentures. A 2-week adaptation period was allowed for each denture modification. Three- and 12-week adaptation periods were allowed for the new dentures. No significant changes were found in guided static bite force or peak bite force during chewing following any modification or insertion of new dentures. Significant decreases (p < 0.05) from the original poorly fitting denture in preferred side and nonpreferred side muscle activity were found for the preferred side tests with both foods after both the correction of occlusion and 3 mm increase in vertical dimension. Concomitant decreases (p < 0.05) in the masseter closing burst and stroke durations were found and contributed to the reduction in masseter muscle effort. Further reductions (p < 0.01) in masseter closing bursts and stroke durations were observed with new dentures. The results revealed that new dentures or the stabilization of poorly fitting dentures through occlusal correction and restoration of occlusal vertical dimension permits patients to use less muscle effort while chewing and maintaining their initial masticatory performance.

Clinicians reline or replace dentures to improve occlusion, stability, retention and facial support. They believe that well-fitting dentures will maintain supporting tissues in good health and satisfy patients by improving oral function and self-esteem. In this study, satisfaction of 21 patients with poorly fitting dentures was assessed before and after the dentures were modified to improve occlusion, vertical dimension of occlusion, and retention and stability or the dentures were replaced with new ones. More than 55% of the patients were moderately to fully satisfied with their poorly fitting dentures. Most patients perceived improvements in chewing comfort, chewing ability, eating enjoyment, food choices, security, and speech after each denture modification and with new dentures. The relative importance of the four sequential modifications could not be determined because they were made sequentially and their effects became cumulative. Chewing ability, eating enjoyment, particles under dentures, and food choices were highly correlated with chewing comfort and overall patient satisfaction. The results support the belief of many clinicians that patients benefit from relining of poorly fitting dentures or replacement with new dentures. Improvements in chewing function were perceived by most patients despite the lack of improvement in masticatory performance or masseter muscle activity with modified or new dentures. It is likely that denture wearers perceive chewing ability in terms of chewing comfort rather than ability to comminute food, an objective measure of chewing performance. The latter is not altered markedly by the clinical excellence of dentures.

Histories and clinical evaluations were obtained from 230 postmenopausal women aged 48 to 56 years to determine whether the alveolar height in the edentulous anterior region of the maxillae is adversely affected by the presence of mandibular incisors. Many of these women lost their teeth in early adulthood. When all subjects were included, the height of the ridge in the anterior region of the maxillae was not significantly altered by presence of mandibular incisors. When the ridge height was compared among those who had been edentate in the maxillae for less than 30 years, the difference between dentate and edentate subjects was significant. This study indicates that the alveolar ridges in the anterior region of the maxillae where teeth were extracted early in life during the rapid phase of bone metabolism are less disposed to bite trauma caused by the presence of the mandibular incisors than are individuals who lost their teeth in middle or old age.

A finite element analysis was conducted to study the influence of posts on dentinal stress in pulpless teeth. Three-dimensional models of an intact Chinese maxillary central incisor with and without post restoration were analyzed. When the tooth was subjected to masticatory and traumatic loads, stress distributions in dentin were similar whether or not the post was present. Maximal dentinal stresses were reduced by only 7% to 10% and 10% to 14.5%, respectively, with gold alloy and stainless steel posts. Thus the reinforcement effects from posts appeared limited in pulpless incisors.

Dental patients with parafunctional habits (clenching and grinding of the teeth) may pose unique treatment problems for the dentist. Several patients suffering from such muscle hyperactivity disorders were studied longitudinally by use of the occlusalgraph method to preserve the photocclusal data recorded by each patient. This report suggests that the use of the described technique provides a quick and simple method of visualizing the problem and long-term monitoring of the treatment.

The psychologic profiles of 98 female patients with signs & symptoms of temporomandibular disorders are compared with those of a control group having no signs or symptoms of such disorders. Scores on the Crown Crisp Experimental Index indicate a significant difference in the profiles of somatization and hysteria.

This study compared the performance of a new computerized occlusal analysis (T-Scan) system with that of Accufilm and Shimstock foil for the registration of tooth contacts on a laboratory model. Induced interceptive contacts were created on epoxy models in a mechanical closing device and the occlusal contacts were recorded for each registration method. The traditional methods were similar to the computerized analysis but the T-Scan system provided additional differential diagnostic information in force and time modes for an improved occlusal analysis.

The character of the occlusal surfaces of teeth programs the functions of muscles that move the mandible and imposes specifications upon the dentist within which he must work in manipulating the patient's mandible. If he exceeds those specifications, protective responses that inhibit his efforts are elicited in the patient's musculature. A knowledge of the laws governing functions of the muscles that move the mandible enables the dentist to acquire mandibular-manipulation skills necessary for diagnosis and effective occlusal treatment. A model in which the dentist visualizes the patient, the patient's protective reflexes, the components of the patient's gnathostomatic system, and himself as four independent personalities participating in the jaw manipulation is a useful tool in acquiring mandibular-manipulation skills. This article is Part III of a series presented in four parts on the "Biologic Laws Governing Functions of Muscles That Move the Mandible."

Twenty-two patients seeking treatment for the globus symptom were examined for the presence of symptoms and signs of TMJ dysfunction. They were randomly divided into a treatment group (N = 13) and a placebo group (N = 9) and underwent either simple occlusal adjustment or mock adjustment, respectively. The result of occlusal adjustment was assessed immediately after completion of treatment. The effect of treatment on the globus symptom was assessed 2 to 3 months later in a double-blind study design. Binomial tests showed that there was a significant association between the success of occlusal adjustment and disappearance of the globus symptom. Three patients in the placebo group subsequently received occlusal adjustment and splint therapy. When all patients were interviewed 20 to 44 months later, only two of them reported no improvement. Both had unstable occlusion when the treatment was terminated.

The effect of four different occlusal situations (group function, canine guidance, working side occlusal interference, and hyperbalancing occlusal interference) on EMG activity in jaw elevator muscles and related mandibular movement was investigated on 12 subjects. With a computer-based system, EMG and displacement signals were collected simultaneously during specific functional (unilateral chewing) and parafunctional tasks (mandibular gliding movements and various tooth clenching efforts) and analyzed quantitatively. When a naturally acquired group function was temporarily and artificially changed into a dominant canine guidance, a significant general reduction of elevator muscle activity was observed when subjects exerted full isometric tooth-clenching efforts in a lateral mandibular position. The original muscular coordination pattern (relative contraction from muscle to muscle) remained unaltered during this test. With respect to unilateral chewing, no significant alterations in the activity or coordination of the muscles occurred when an artificial canine guidance was introduced. Introduction of a hyperbalancing occlusal contact caused significant alterations in muscle activity and coordination during maximal tooth clenching in a lateral mandibular position. A marked shift of temporal muscle EMG activity toward the side of the interference and unchanged bilateral activity of the two masseter muscles were observed. The results suggest that canine-protected occlusions do not significantly alter muscle activity during mastication but significantly reduce muscle activity during parafunctional clenching. They also suggest that non-working side contacts dramatically alter the distribution of muscle activity during parafunctional clenching, and that this redistribution may affect the nature of reaction forces at the temporomandibular joints.

Accurate diagnosis and treatment of the gnathostomatic system require an understanding of both its biomechanics and its physiology. Clinically, the treatment consists of modifying the existing occlusal program to relieve stress from distressed tissues. The objective of treatment is to effect a neuromuscular release of the mandible. This may be accomplished by (1) equilibration of the natural occlusion, (2) orthodontics, (3) restorative procedures, or (4) surgery. Most frequently, however, the treatment entails some combination of these procedures. The criteria for success of treatment are not determined by the method or technique employed but by the neuromuscular response that the treatment produces. The purpose of this article is not to suggest which occlusal scheme produces the most favorable muscle response in the gnathostomatic tissues. Neither is an objective of this article to teach the mandible-manipulation techniques that are needed to identify occlusal irritants, perform occlusal equilibrations, or obtain accurate centric relation recores. The objective of this article is to emphasize that there are definite principles by which the muscles respond to occlusal contacts. Occlusal contacts can excite bruxism and the sequelae to bruxism. Knowledge of the laws which govern functions of the muscles that move the mandible enables the dentist to acquire the mandibular-manipulation skills that are necessary for the effective diagnosis and treatment of occlusal conditions.

An investigation of the neuromuscular effects of dental contact at the physiologic median occlusal position was conducted before and after occlusal adjustments. Eighteen patients with histories of functional disturbances of the masticatory system, but whose painful symptoms had subsided, were analyzed before and after occlusal adjustments. Nine of the patients with missing teeth received fixed partial dentures and occlusal adjustments. Another group of nine subjects with normal occlusions were used as controls. Electromyographic recordings of the bilateral temporal and masseter muscles enabled quantification of two reflex parameters, the EMG silent period duration, and the mechanical latency of the jaw-opening reflex. Phase-plane traces of jaw-closing velocity as a function of position displayed the repeatability of the median occlusal position. The statistical analysis disclosed that the mean duration of EMG silent periods and latency of the jaw-opening reflex were significantly reduced following the treatment procedures. Within the limits of this study it was concluded that the described occlusal adjustments will reduce the masticatory reflexes evoked at median occlusal position to within the range of normal subjects. Furthermore these changes can be monitored by electrophysical methods.

A tensile stress hypothesis for the etiology of idiopathic cervical erosions of human teeth is presented. It is proposed that when occlusion is not ideal, lateral forces cause the teeth to bend. The tensile stresses created during bending disrupt the chemical bonds of the crystalline structures of enamel and dentin. Small molecules may enter between the crystals and prevent the reestablishment of the chemical bonds. As a result, the disrupted tooth structure is more susceptible to loss through dissolution and abrasion and results in the development of the typically wedge-shaped lesions. Patients with lesions typical of hundreds examined by the authors were presented to illustrate the concept. The possible consequences of the proposed hypothesis were discussed. The hypothetical conclusions made in this article will be tested by experimentation.

The mechanical factors which are involved in the arrangement of anatomic type artificial teeth into balanced occlusion have been described. Many of the mechanical problems encountered during artificial tooth arrangement have been listed, together with suggestions for their solution. Hanau's Laws of Articulation have been utilized in a practical manner in formulating some of the solutions to tooth arrangement problems when establishing balanced occlusion. Trial dentures which present ideal occlusions in the articulator may not always do so when examined in the patient's mouth. Possible reasons for these differences are listed, and methods for making the necessary corrections are described.

Signs and symptoms in the masticatory system can be caused by several specified diseases leading to diagnostic problems. This investigation compared patients with temporomandibular joint disk displacement and patients with complaint of myogenic craniomandibular disorders. In association with the onset of the patient's problem, a physical event was found in half the number of patients with permanent disk displacement, compared with only 27% in the myogenic craniomandibular disorders group. Patients with permanent disk displacement reported more pain in the temporomandibular joint ear and jaw region in association with jaw function whereas patients with myogenic craniomandibular disorders reported more bruxism and dental discomfort.

Acomparison was made in this study of the prevalence of mandibular displacement in varying degrees of complexity with the incidence of parafunctional occlusal habits and some sequelae. The prevalence of occlusal habits in all patients was high but became greater with the increased complexity of the mandibular displacement, especially an asymmetrical slide from RCP to IP. The mulifactorial etiology of parafunctional occlusal habits and their sequelae tends to make the relationships more complex than a simple "cause and effect" and therefore must be considered.

The treatment of occlusal pathosis and associated facial pain is a difficult and complex problem. The interaction of two etiologic factors, occlusal interferences and psychologic stress, results in parafunctional activity. The most important prerequisite to selection of a treatment method is an understanding of the etiology of the problem. What dentistry needs is a mechanism by which the major etiologic factor of parafunctional activity can be identified for each patient. Treatment can then be directed toward the reduction or elimination of that factor. When treatment is directed toward the major cause of the problem, the likelihood of success will increase greatly. Continued research on this problem will yield new insights and means for the accurate determination of the etiology of parafunctional activity for each patient.