A technique for evaluation of centric relation tooth contacts. Part I: During normal temporomandibular joint function

An indirect method to locate the first tooth contacts in centric relation was described in this study. Mounted casts with an associated table and styli were used to locate the position of contact points in three planes. The method was tested using the anterior occlusal stop with chin point guidance and bimanual manipulation for recording centric relation. Ten records from one subject were analyzed statistically for each method. At the p less than .05 level of significance, the anterior occlusal stop produced a centric relation position more posterior than that found with bimanual manipulation. There was no statistically significant difference in the vertical and mediolateral planes. The anterior occlusal stop method produced more consistent tooth contacts in all three planes. The centric relation points found on the recording plates correlated well with the initial tooth contacts marked on the cast. This indirect method is an accurate means of recording and reevaluating changes in tooth contact positions in three planes.     

A technique for evaluation of centric relation tooth contacts. Part II: Following use of an occlusal splint for treatment of temporomandibular joint dysfunction

The purpose of this study was to determine the effect of TMJ dysfunction on the recording of centric relation. Centric relation was recorded using an anterior occlusal stop and by bimanual manipulation. Changes in occlusal contacts were recorded before and after occlusal splint therapy in six subjects with TMJ dysfunction. The pantographic reproducibility index and clinical signs and symptoms were used to determine the presence or absence of dysfunction. Use of the anterior occlusal stop resulted in a more posterior, superior initial tooth contact position when compared with bimanual manipulation. Occlusal contact positions were less consistent in TMJ dysfunction subjects than in control subjects. Initial occlusal contacts changed toward centric relation as the dysfunction disappeared. Final occlusal contact was found on the side where clinical signs and symptoms occurred. The condyle on the affected side appeared to be repositioned posteriorly and superiorly in most instances. Occlusal splint therapy was more effective when the splint was adjusted weekly. This study indicates the need to eliminate TMJ dysfunction before recording centric relation or adjusting the occlusion. Occlusal interferences found with TMJ dysfunction are not the same as occlusal interferences found when TMJ dysfunction is absent. Abnormal features on pantographic tracings may aid in indicating the presence of occlusal interferences. Occlusal adjustment in the presence of TMJ dysfunction would result in erroneous occlusal reduction.     

Occlusion and orthodontics.

The importance of considering the functional aspects as well as the static concepts of an occlusion was demonstrated in the case of an 11-year-old girl with postorthodontic temporomandibular joint muscle pain dysfunction. The following characteristics of an ideal occlusion were discussed as they relate to the entire masticatory system: 1. There should be no slide in centric; that is, there should be a stable jaw relationship when occlusal contact is made in centric relation closure. 2. There should be freedom in centric, that is, freedom for the mandible to move from centric relation to centric occlusion and slightly anterior to centric occlusion without interference. 3. Centric relation should be at the same contact vertical dimension as centric occlusion. 4. There should be no buccolingual thrust or impact to any tooth on closure to contact in centric relation or to centric occlusion. 5. Between centric relation and centric occlusion there should be an unrestricted glide with maintained occlusal contact. 6. Complete freedom for smooth-gliding occlusal contact movements in various excursions from both centric occlusion and centric relation. 7. Occlusal guidance should be on the working or functioning side rather than on the balancing or nonfunctioning side. 8. There should be no soft-tissue impingment from occlusal contacts. In effect, the occlusion should be related to centric relation and centric occlusion prior to, during, and at the completion of active treatment. The final occlusion should provide unhindered closure in centric relation, smooth-sliding lateral and protrusive movements, and an optimal bilateral vertical contact dimension. Orthodontic treatment must include proper occlusal adjustment procedures to obtain the goals of an ideal occlusion in most instances.     

Occlusal objectives in orthodontic treatment.

An attempt has been made to present a means for preventing the temporomandibular joint pain-dysfunction syndrome by treating to the terminal hinge position and using postreatment occlusal adjustment procedures. 1. Any postorthodontic patient who is not in centric relation and has occlusal interferences has the potential for temporomandibular joint pain-dysfunction syndrome symptoms to develop in the future. 2. The orthodontist should manipulate the mandible of every patient at each visit, placing the condyle in the terminal hinge position. He should close the mandible until initial tooth contact is reached and diagnose the patient's problems from this position and not from the centric occlusion position. 3. The case should be finished with the teeth in centric relation occlusion. 4. The orthodontist should equilibrate the occlusion of every completed case to eliminate the minute occlusal interferences which are always present. 5. The case treated to centric relation can be equilibrated effectively without mounting on an articulator. 6. If we have the concept of building an occlusion to fit the jaw mechanism, the temporomandibular joint pain-dysfunction syndrome can be virtually eliminated in the postorthodontic patient.     

A possible biomechanical role of occlusal cusp–fossa contact relationships

Summary Biomechanical features of occlusal contacts are important in understanding the role of the occlusion contributing to masticatory function. Cusp–fossa contact is the typical pattern of occlusion between upper and lower teeth. This includes static relations, such as that during clenching, and dynamic relations when mandibular teeth contact in function along the maxillary occlusal pathways, as during mastication. During clenching in the maximum intercuspal position (ICP), cuspal inclines may take the role of distributing the occlusal forces in multi‐directions thus preventing excessive point pressures on the individual tooth involved. During chewing movement on the functional side, the mandible moves slightly from buccal through the maximum ICP to the contralateral side. The part of the chewing cycle where occlusal contacts occur and the pathways taken by the mandible with teeth in occlusal contacts are determined by the morphology of the teeth. The degree of contact is associated with the activity of the jaw muscles. To obtain repeatable static and dynamic occlusal contact information provided by the morphology of the teeth, maximum voluntary clenching and chewing movements with maximum range are needed. In conclusion, in addition to the standard occlusal concepts of centric relation/centric occlusion and group function/cuspid protection relation, biomechanics in static and dynamic cusp–fossa relationships should be included to develop an understanding of occlusal harmony which includes no interfering or deflective contacts in functional occlusal contact.     

An electromyographic and roentgen cephalometric study of occlusal morphofunctional disharmony in children.

In a sample of children with dual bite and symptoms in the masticatory system, the activity of the anterior temporal and masseter muscles was studied electromyographically during clench and light tapping in the posterior occlusal contact position and centric occlusion and in protrusive bite on the incisors. The findings indicated that the optimal muscle function during maximal clench and tapping with displayed in the posterior occlusal contact position, which in the present subjects was situated, on the average, 0.5 to 1 mm. anterior to the centric jaw relation. It should therefore be recommended that, in orthodontic treatment of children with dual bite, the intercuspal position (centric occlusion) should be established in the posterior occlusal relationship. This is in accordance with the opinion of several authors who have emphasized the use of the retruded contact position (the centric jaw relation) as key reference position in orthodontic treatment and occlusal rehabilitation. These authors have further emphasized the importance of stable occlusal contacts in centric relation, centric occlusion, and the various jaw excursions in obtaining and maintaining a harmonious function between the dentition, the temporomandibular joints, and the neuromuscular system.     

A simplified chair-side remount technique using customized mounting platforms

Correct occlusal relationships are part of the successful prosthetic treatment for edentulous patients. Fabrication of complete dentures comprises of clinical and laboratory procedures that should be executed accurately for achieving success with fabricated dentures. Errors occurring during the clinical and laboratory procedures of a denture may subsequently lead to the occlusal errors in the final prosthesis. These occlusal errors can be corrected in two ways: i) in patient's mouth ii) by recording new centric relation and remounting dentures on an articulator. The latter method is more feasible because the mobility of denture base on the mucosa in oral cavity does not permit the identification of premature contacts in centric occlusion and tooth guided eccentric excursions. This article describes a modest and effective clinical chair-side remount procedure using customized mounting platforms.     

Complete Rehabilitation of a Patient with Occlusal Wear: A Case Report

Prosthodontic management of occlusal wear problems is a demanding task on the part of the prosthodontist. Various factors such as vertical dimension of occlusion, centric relation, occlusal contact pattern, esthetics and phonetics need to be considered simultaneously for both anterior and posterior teeth during occlusal rehabilitation. This may be further complicated by existing restorations, pulpal exposure, missing teeth and tooth sensitivity. Different philosophies have been documented for rehabilitation of such cases and the choice of the treatment plan depends on the skill and experience of the clinician. This case report gives an overview of the different philosophies used for rehabilitation of such cases and a report which utilises Hobo’s twin stage technique for the same.     

Comparison of the replicability of routinely used centric relation registration techniques

PURPOSE: This study was conducted to determine statistically the most repeatable mandibular position of 3 centric relation methods. MATERIALS AND METHODS: Three centric relation recording methods commonly reported in the literature were selected: bimanual mandibular manipulation with a jig, chin point guidance with a jig, and Gothic arch tracing. Fourteen healthy adult volunteers (7 males and 7 females), with an average age of 26.61 +/- 4.20 years and no history of extractions, temporomandibular joint dysfunction, or orthodontic treatment, were selected for the study. Accurate casts were mounted on an articulator (Denar D4A) by means of a facebow and maximum intercuspation silicone registration record. A mechanical 3-dimensional mandibular position indicator was constructed and mounted on the articulator enabling the operator to analyze the mandibular positions in 3 spatial axes (x, anteroposterior; y, superoinferior; z, mediolateral shift). Each centric relation method was recorded four times on each subject (at baseline, 1 hour, 1 day, and 1 week at approximately the same time of day). Records were transferred to the articulator, and data were extracted using a stereomicroscope modified to accept the mandibular position indicator. RESULTS: Variability within subjects ranged from 0.03 mm (left-side z axis for the bimanual method) to 1.6 mm (left-side y axis for the Gothic arch method). To indicate the least variable (most repeatable) method a comparison was made using the F test. The bimanual method was the most consistent, showing between 10.11 (p = 1) and 0.438 (p = 0.005) times less variation than the Gothic arch method (the least consistent). The repeatability of the chin point guidance method was somewhere between the other 2 methods. CONCLUSIONS: The results of this study showed that of the 3 centric relation methods evaluated, the bimanual manipulation method positioned the condyles in the temporomandibular joint with a more consistent repeatability than the other 2 methods, whereas the Gothic arch was the least consistent method.     

GEDAS II--new possibilities in digital contact point analysis

The following article describes a method for the clinical depiction and documentation of the strength, extent, and location of occlusal contact areas on the basis of digitized bite records. Bite records made of low-viscosity, addition-cured silicone in centric occlusion are digitized in a document scanner using incident and transmitted light scanning. Layer thicknesses < 20 microm were interpreted as occlusal contacts and classified as belonging to the anatomical structures of the occlusal surfaces. This procedure is of particular significance for epidemiological studies, but also of interest for dental practices and laboratories, since it can be used as a simple method of continuous quality control, documentation, and archiving of the patient's current occlusal contact situation.     

Pathophysiology of occlusal balance.

Functional disturbances of the masticatory system reflect a failure in the adaptive capacity of the individual to excessive structural and functional demands. Formerly, a particular type of articulation, balanced occlusion, was thought necessary for maintaining the health of the dental apparatus. Over the years the concept of stability of occlusion has evolved, however controversy still exists as to where stable tooth contact is made, centric occlusion of centric jaw relation. In order to express biological adaptability within the normal masticatory system, harmony at the anatomical median occlusal position is suggested as the prerequisite of a physiologically balanced occlusion.     

A simplified approach to implant-supported metal-ceramic reconstruction

Restoring the edentulous patient with an implant-supported fixed complete denture prosthesis is a challenging procedure. The patient's occlusal vertical dimension, centric relation position, esthetics, and phonetics should be maintained throughout the restorative process, while the patient is traditionally wearing a removable prosthesis. This article presents an alternative treatment philosophy that addresses these concerns and guides the restorative process using a fixed provisional restoration made from the patient's removable complete dentures.     

Prosthodontic correction of severe deep vertical overbite combined with dimensional discrepancy of the upper and lower dental arch. 31 years follow-up

Sz. S. a 39-years-old patient was referred to our department in 1968. Patient's masticatory dysfunction, orofacial pain syndrome and substantial weight loss was due to a combined genuine and acquired deep vertical overbite aggravated by a marked difference between the size of the lower and upper jaw bones. The premolars and molars had already been extracted. The lower incisors bit onto the palatal gingiva in centric occlusion causing direct mechanical irritation on the palate. Consequently the centric occlusion position of the mandible was only defined by the contact between the lower central incisors and the palatal soft tissue. According to the literature this kind of defect can only be corrected by a combined surgical prosthodontic therapy (increasing the mandibular arch by vertical osteotomy combined with bone grafting followed by complex prosthodontic reconstruction). Because patient refused any kind of surgical treatment a special upper full arch bridge was constructed with an extended occlusal surface on the palatal surfaces of the front crowns to provide full occlusal contact for the mandibular anterior teeth. The OVD was raised by 11 mm. The present paper reports the history of a 31 years long prosthodontic treatment and patient's follow up. It is shown how the correct centric occlusion, the masticatory functions, the phonetics and also the esthetics could have been maintained by a series of gradually changing fixed restorations meeting the demands imposed by the continuing tooth loss.     

Assessment of occlusal stability by measuring contact time and centric slide

The aim of the present study was to evaluate two different methods for the assessment of the positional stability of occlusion. The time taken from first contact on closure to full intercuspation was measured by the T-scan(R), and the length of the slide between centric relation (CR) and maximum intercuspation was clinically assessed in a sample of healthy adolescents and young adults undergoing a clinical trial which involved repeated occlusal adjustment. The T-scan(R) readings and the clinical assessments of the centric slide were obtained at baseline and at the third and fourth annual examination. There was an overall, but statistically not significant, decline in the contact time. The length of the centric slide did decrease significantly. However, there was no systematic correlation between the two variables. They appear to describe different qualities of occlusion, and their validity as a measure of 'goodness' of occlusion remains an unanswered question.     

Centric relation. Its effect on occluso-muscle harmony.

The most common cause of pain in the region of the temporomandibular joint is occluso-muscle imbalance. This results most often from disharmony between the articulation of the teeth and the centric relation of the condyles. Muscle tenderness of palpation indicates that muscle is involved. An examination must then be done to determine the cause of the muscle tenderness. Before the condyle-occlusion relationship can be evaluated, an accurate centric relation must be determined and verified. The condyles are in centric relation when they are in the most superior position possible in the fossae. From that apex of force position, the condyle can travel neither forward nor backward without moving downward. This position can be located with careful bilateral manipulation and then verified if it can resist firm pressure with no tension or tenderness. Until this correct centric relation is located and verified, it is not possible to properly evaluate the occlusal relationship to the temporomandibular joints. If the occlusion is harmonized to a centric related condyle that can resist firm pressure with pressure with no discomfort, there will be no reason for the muscles to protect either the teeth or the joints. If an occlusion is adjusted to a malrelated condylar position, the occluso-muscle imbalance will be perpetuated and often intensified. Centric relation is the starting point of occlusal contact. Incline interferences in excusive movements must also be eliminated and the occlusion must be harmonized to the envelope of function for each patient. If centric relation is not properly located, occlusal interferences will remain regardless of what procedures are used to record or adjust excursive movements.     

正中关系位记录方法

正中关系位对全口义齿的修复、咬合重建、牙合关系紊乱的检查与治疗、牙体修复、正畸矫治及颞颌关节功能紊乱综合征的检查与治疗等都有重要意义。传统正中关系位的记录方法包括哥特式弓描记法、吞咽咬合法、卷舌后舔法、功能反射法、颏区诱导法、双侧扶持下颌法、下颌运动轨迹描记法、肌监测仪法等,这些方法均需要患者的极大配合,而且灵活性较大,可重复性较差,初学者不易掌握。文章在概述了传统正中关系位记录方法之后,介绍了一种新的记录方法——Leaf Gauge（正中关系咬合片）法,该方法的使用无需太多临床经验,初学者容易掌握,且重复性强、精确度高。     

���й�ϵλ��¼����

??Centric relation is a vital factor in the prosthodontics of full denture?? occlusion reconstruction?? checkup and treatment of occlusion dysfunction?? dental prosthodontics?? orthodontic treatment?? temporomandibular joint disorder and so on. Traditional methods to construct the centric relation mainly include gothic arch tracing??swallowing and occluding method??retroflex licking method ??functional reflex method??Chin-point guidance method??bimanual manipulation method??recording of mandibular movement?? Myo-monitor?? and so on. All of them are quite flexible and difficult to repeat the same position??which is not suitable for the beginners. Patients' active cooperation is also necessary. This review summarized traditional methods to construct the centric relation?? and introduced a new tool named Leaf Gauge which can be used to record the accurate centric relation. It does not need sufficient clinical experience and is easy to grasp.     

Computer aided gnathosonic analysis: distinguishing between single and multiple tooth impact sounds

Watt developed a classification of tooth contact sounds that distinguished between the short sharp, reproducible sounds heard when the teeth meet simultaneously and the dull prolonged, poorly reproducible sounds heard when tooth contacts are sequential. However, when a large occlusal prematurity, for instance a high restoration, is introduced, tooth contact sounds are also short sharp and highly reproducible. In this study, a method of distinguishing single from multiple tooth contact sounds is described, based on an analysis of the phase and amplitude of sounds detected by headphones placed over the ears.     

Terminal hinge contact in dentitions

A cephalometric-electromyographic method to analyze tooth contacts in centric occlusion and at terminal hinge contact has been presented. A positional difference between centric occlusion and centric relation was demonstrated in all subjects. However, temporal and masseter muscle activity during maximal isometric contraction did not differ significantly at these two positions. The study is being continued employing young male subjects with complete dentitions as subjects.     

Influence of occlusal contacts on tooth displacement

During function, the tooth displacement path depends on occlusal contacts of the upper and lower teeth. Therefore, we must reconstruct occlusal relation carefully so as not to disturb physiological tooth displacement. In this investigation, tooth displacements were measured with the Displacement Transducer type M-3 in varying occlusal contact. The following conclusions were obtained. 1. The location of occlusal contacts influenced the tooth displacement of the upper first molar. Especially, an occlusal contact on the lingual inclination of the lingual cusp, buccal cusp had great influence. The tooth showed displacement toward the buccal direction, and it differed from the physiological tooth displacement path during clenching at the intercuspal position. 2. The location of occlusal contacts had little influence on the tooth displacement of the lower first molar. The tooth showed displacement toward the lingual direction. It was similar to the physiological tooth displacement. 3. On the upper first molar, the location of occlusal force influenced the Stress-Strain curve. Especially, the occlusal force on the buccal cusp had great influence on the amount of tooth displacement. 4. On the lower first molar, the location of occlusal force influenced the Stress-Strain curve. Especially, the occlusal force on the lingual cusp brought much displacement and a 2-phase displacement path, at times. Therefore, occlusal contacts have close relation to tooth displacement, and any occlusal reconstruction should harmonize with tooth displacement representing periodontal tissue distortion.