Accuracy of model surgery: evaluation of an old technique and introduction of a new one

This article evaluates the ability of 4th-year residents to accurately perform maxillary model surgical repositioning in the conventional manner. Using a special model surgery--measuring platform, measurements of the maxillary dental casts were recorded before and after model surgery was performed by residents in 20 bimaxillary cases. The model surgery was performed in the usual manner described in several texts, using reference lines scored on the casts and measurements made to the incisal pin and upper member of the articulator. Analysis of the differences between the planned movements and the postsurgical position of the maxillary model surgery casts showed statistically significant errors in maxillary repositioning for all measures. This indicates that the manner in which model surgery was performed by the residents, as reported in the literature, was inaccurate. A new technique and instrument for more accurately recording measurements and repositioning the maxillary cast is introduced.

Temporomandibular joint disk displacement without reduction. Treatment with flat occlusal splint versus no treatment

A flat occlusal splint has been extensively used in the treatment of patients with temporomandibular joint disk displacement without reduction, but no studies with untreated controls have assessed its effect. We randomly assigned 51 patients with temporomandibular joint pain and arthrographically verified disk displacement without reduction to be treated with a flat occlusal splint or to serve as untreated control subjects in a 12-month clinical trial. Pain symptoms disappeared in about one third of the patients in each group. Another third of the patients in the control group improved. Sixteen percent of the patients in the control group and 40% of the patients treated with a flat occlusal splint were worse at the end than at the beginning of the study. Joint pain and muscle tenderness decreased more frequently in the nontreatment controls than in the treatment group. A statistically significant benefit of a flat occlusal splint over nontreatment control subjects could not be identified in this study of patients with painful disk displacement without reduction. The use of a flat occlusal splint in this patient group should therefore be reconsidered.

Electromyographic and computer analyses of patients suffering from chronic myofascial pain-dysfunction syndrome: before and after treatment with immediate complete anterior guidance development

Seven women patients at Tufts University School of Dental Medicine were evaluated for the subjective symptoms of a myofascial pain dysfunction. Each patient was evaluated by an occlusal analysis of the T-Scan computer to determine posterior disclusion time during excursive movements, and EMG analysis of the masseter and temporalis muscles. Each patient was then treated occlusally by developing immediate complete anterior guidance. This adjustment process involved the removal of all lateral and protrusive interferences prior to habitual closure adjustments. No attempt was made to retrude the mandible in centric relation, and splints were not used to deprogram the musculature before adjustment. In this study, protrusive movements and interferences were not examined, and there was no control group. Posttreatment EMG and T-Scan computer analyses revealed that by shortening disclusion times to less than 0.5 second in any lateral excursions, muscle function returned to normal in all seven patients in approximately 1 month's time. A direct correlation seemed to exist between contractile muscle activity and disclusion time. Lengthy disclusion time leads to excessive muscle activity that introduces spasm and fatigue of the masseter and temporal muscles. These results indicated that a partial explanation of the etiology of MPDS may be the time the molars and nonworking premolars remain in contact during excursive movements--a phenomenon termed "disclusion time."

Orthodontic side-effects of mandibular advancement devices during treatment of snoring and sleep apnoea

The aims of this study were to investigate possible orthodontic side-effects following the use of mandibular advancement devices (MAD) in adults with snoring and sleep apnoea. A second objective was to analyse the effect of the appliance design. Seventy-five patients treated with MAD and 17 reference patients were studied at follow-up after 2.5 +/- 0.5 years. In the test group, 47 patients were provided with soft elastomeric devices, while the remaining 28 patients received hard acrylic devices. The treatment induced a change in overjet of -0.4 +/- 0.8 mm (mean +/- SD) and a change in overbite of -0.4 +/- 0.7 mm (mean +/- SD). These changes were larger than those found in the reference group (P < 0.01). The odds ratio (OR) for the largest quartile of reduction in overjet was 3.8 in patients using hard acrylic devices compared with those using soft elastomeric devices (P < 0.05). A large reduction in overjet in patients using the hard acrylic devices was unrelated to the degree of mandibular protrusion by the device. The OR for a large reduction in overjet in patients using the soft elastomeric devices with a protrusion of 6 mm or above was 6.8 compared with smaller mandibular protrusions (P < 0.05). The results indicate that the orthodontic side-effects are small during the treatment of adult subjects with MAD for snoring and sleep apnoea, especially in patients using soft elastomeric devices with mandibular protrusions of less than 6 mm. The follow-up of patients treated with MAD is recommended, as individual patients may experience marked orthodontic side-effects.

Effects of improvements of poorly fitting dentures and new dentures on patient satisfaction

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.

Diagnosis and treatment planning of patients with asymmetries

The diagnosis, treatment planning, and design of mechanics for the asymmetric patient requires the differentiation between problems of dental and skeletal origin. Although much information can be gleaned from a cephalometric analysis, the clinical examination and study models offer important clues in establishing the diagnosis of skeletal discrepancy. Abnormal and asymmetric axial inclinations can either produce a dental asymmetry or, if compensatory in nature, may mask an underlying skeletal problem. The role of axial inclination in diagnosis is applied to the following situations: subdivision cases, unilateral crossbites, midline discrepancies, arch form deviations, and frontal cants to the occlusal plane. The management of axial inclination asymmetries depends on the treatment plan. Nonextraction patients may require maintenance of asymmetric compensatory axial inclinations. Surgical and extraction patients can be treated to a more ideal symmetry.

A three-dimensional comparison of condylar position changes between centric relation and centric occlusion using the mandibular position indicator

The mandibular position indicator (MPI) was used to compare condylar position between centric relation (CR) and centric occlusion (CO) for 107 patients before orthodontic treatment. The MPI data were examined to determine frequency, direction, and magnitude of CO-CR difference; and data were analyzed for possible correlation to the patient's Angle classification, ANB angular measurement, age, or gender. Only one patient (0.9%) had no measurable CO-CR difference in all three spatial planes. Six subjects (5.6%) showed a shift in condylar position in the transverse plane without a measurable difference in the sagittal plane. Twenty patients (18.7%) experienced a superoinferior (SI) or anteroposterior (AP) condylar displacement of at least 2.0 mm on one or both sides; 17 (15.9%) displayed a transverse shift at the level of the condyles of 0.5 mm or greater. No statistical difference was found between the 31 patients with Class I malocclusions and 72 patients with Class II malocclusions when comparing the amount or direction of CO-CR change. The amount of CO-CR difference was nearly identical for right and left sides with the amount of SI displacement (x = 0.84 mm) consistently greater than AP displacement (x = 0.61 mm). Only weak correlations were found between movements of right and left condyles. The average transverse CO-CR difference was 0.27 mm. Patient age, ANB angle, gender, or Angle classification cannot be used to predict frequency, magnitude, or direction of CO-CR changes at the level of the condyles.

Reflections on the Michigan occlusal splint

Specific features related to the development, design and use of the Michigan splint have been described. Additional benefits from the Michigan splint beyond what can be expected from conventional stabilization splints and bite planes have been suggested. Important aspects of corrections and maintenance care of the Michigan splint have been stressed.

Clinical diagnosis of trauma from occlusion and its relation with severity of periodontitis

The purpose of the present study was to determine the reliability of several selected signs of trauma from occlusion and their relations with severity of periodontitis. 32 moderate to advanced chronic periodontitis patients participated in the study. All teeth present were evaluated for various abnormal occlusal contacts, signs of trauma from occlusion, and the severity of periodontitis. Standardized periapical radiographs were also taken for each tooth. The results demonstrated that: (1) no significant difference occurred in probing pocket depth (PD), clinical attachment loss (AL), or percentage of alveolar bone height (BH) between teeth with and without various abnormal occlusal contacts, i.e., premature contacts in centric relation occlusion, non-working contacts in lateral excursions, premature contacts of anterior teeth or posterior protrusive tooth contacts; (2) teeth with either significant mobility, functional mobility, or radiographically widened periodontal ligament space (PDLS) had deeper PD, more AL and lower BH than teeth without these signs, while teeth with pronounced wear or radiographically thickened lamina dura had less AL than teeth without these findings; (3) 2 combined indices, i.e., the trauma from occlusion index (TOI) and the adaptability index (AI), were proposed for the identification of occlusal trauma and the response of periodontium to excessive biting forces in heavy function, respectively; TOI-positive teeth exhibit deeper PD, more AL and less osseous support than TOI-negative teeth; however, AI-positive teeth had less AL and more osseous support than AI-negative teeth; (4) with identical attachment level, TOI-positive teeth had less osseous support than TOI-negative teeth while the magnitude of difference became greater with an increase of attachment loss.

A randomized trial of occlusal adjustment in the treatment of periodontitis patients

The purpose of the randomized clinical trial was to test; (1) the influence of occlusal adjustment (OA) in association with periodontal therapy on attachment levels, pocket depth, and tooth mobility, (2) whether OA was of greater significance in non-surgically treated periodontal defects, and (3) whether initial tooth mobility or disease severity had an affect on post-treatment attachment levels following OA. After hygienic-phase therapy, 50 patients received OA/No OA according to random assignment; 22 patients received an OA and 28 were not adjusted. 2 months after OA, either modified Widman flap surgery or scaling and root planing by a periodontist were done according to random assignment within each patient in a split-mouth design. Following active treatment patients were maintained with prophylaxis done every 3 months and scored annually. For the analysis of this two-year data, a repeated measures analysis of variance was performed using attachment level change and pocket depths as outcome indicators. There was significantly greater gain of clinical periodontal attachment in patients who received an OA compared to those who did not. Both the surgically and non-surgically treated sides of the mouth responded similarly to OA. There was no affect of OA on the response in pocket depth, nor did initial tooth mobility or initial periodontal disease severity influence the response to OA.

Mandibular condyle position: comparison of articulator mountings and magnetic resonance imaging

This study evaluated the reliability of jaw positions, the existence of distinct jaw positions, and condyle-disk-fossa relationships in a symptom-free population by using articulator mountings and magnetic resonance imaging (MRI). The subjects examined included 28 men, 22 to 35 years of age, all having Angle Class I molar relationships and no discernible TMJ dysfunction. Records taken included the following: an axiographic face-bow to locate retruded hinge axis position, an interocclusal registration of retruded position (RE), a series of interocclusal registrations for centric occlusion (CO), a leaf gauge-generated centric relation (CR), a series of interocclusal registrations for CR, and MRI. The mandibular position indicator of the SAM articulator (Great Lakes Orthodontics, Ltd., Tonawanda, N.Y.) was used to determine reliability and existence of distinct jaw positions. Magnetic resonance imaging also evaluated jaw positions and anatomic relationships. The results indicate: (1) The articulator analysis of CO and CR is statistically replicable. (2) A distinct jaw position could be demonstrated for CO that was separate from RE and CR. It was not possible to discriminate between RE and CR. (3) Condylar concentricity was observed in half of the sample and remained consistent in RE, CO, and CR. (4) Of the sample 13% demonstrated anteriorly displaced disks that were not influenced by posterior condyle placement. (5) The clinical concept of treating to CR as a preventive measure to improve disk-to-condyle relationships was not supported by this study.

Accuracy of contacts calculated from 3D images of occlusal surfaces

OBJECTIVES

Compare occlusal contacts calculated from 3D virtual models created from clinical records to contacts identified clinically using shimstock and transillumination.

METHODS

Upper and lower full arch alginate impressions and vinyl polysiloxane centric interocclusal records were made of 12 subjects. Stone casts made from the alginate impressions and the interocclusal records were optically scanned. Three-dimensional virtual models of the dental arches and interocclusal records were constructed using the Virtual Dental Patient Software. Contacts calculated from the virtual interocclusal records and from the aligned upper and lower virtual arch models were compared to those identified clinically using 0.01mm shimstock and transillumination of the interocclusal record. Virtual contacts and transillumination contacts were compared by anatomical region and by contacting tooth pairs to shimstock contacts. Because there is no accepted standard for identifying occlusal contacts, methods were compared in pairs with one labeled "standard" and the second labeled "test". Accuracy was defined as the number of contacts and non-contacts of the "test" that were in agreement with the "standard" divided by the total number of contacts and non-contacts of the "standard".

RESULTS

Accuracy of occlusal contacts calculated from virtual interocclusal records and aligned virtual casts compared to transillumination were: 0.87+/-0.05 and 0.84+/-0.06 by region and 0.95+/-0.07 and 0.95+/-0.05 by tooth, respectively. Comparisons with shimstock were: 0.85+/-0.15 (record), 0.84+/-0.14 (casts), and 81+/-17 (transillumination).

CONCLUSIONS

The virtual record, aligned virtual arches, and transillumination methods of identifying contacts are equivalent, and show better agreement with each other than with the shimstock method.

New definition for relating occlusion to varying conditions of the temporomandibular joint

Centric relation is the accepted term for defining the condylar axis position of intact, completely seated, properly aligned condyle-disk assemblies. However, some structurally deformed temporomandibular joints may function comfortably, even though they do not fulfill the requirements for centric relation. A wide range of temporomandibular disorders from partial to complete disk derangements with or without reduction may adapt to a conformation that permits the joints to comfortably accept maximal compressive loading by the elevator muscles. There has been no accepted terminology to define the condition or position of such joints. The purpose of this article is to define a new term, adapted centric posture, and to explain its rationale and how it is determined. Verification of successful adaptation is an important step in diagnosis, because it rules out structural intracapsular disorders as a source of orofacial pain and establishes responsible guidelines for initiation of occlusal treatment or prosthetic dentistry. It also establishes a much needed terminology for more specific description of temporomandibular joint position and condition for clinical research on the relationship between occlusion and the temporomandibular joints.

A common-sense approach to splint therapy

Splint therapy is a proven modality for alleviating the pain of many types of temporomandibular disorders and bruxism, though questions still remain regarding how splints work. In this article, a review of the literature is used to determine an effective splint design for the different degrees of temporomandibular problems. Sufficient credible literature exists to help provide an understanding of and a treatment protocol for the use of splints for temporomandibular disorders and bruxism problems.

A multidisciplinary approach to esthetic dentistry

Today's dentist does not just repair teeth to make them better for chewing. Increasingly, his or her work involves esthetics. With patients demanding more attractive teeth, dentists now must become more familiar with the formerly independent disciplines of orthodontics, periodontics, restorative dentistry, and maxillofacial surgery. This article provides a systematic method of evaluating dentofacial esthetics in a logical, interdisciplinary manner. In today's interdisciplinary dental world, treatment planning must begin with well-defined esthetic objectives. By beginning with esthetics, and taking into consideration the impact on function, structure, and biology, the clinician will be able to use the various disciplines in dentistry to deliver the highest level of dental care to each patient.

A new method to orient 3-dimensional computed tomography models to the natural head position: a clinical feasibility study

PURPOSE

The purpose of this study was to evaluate the clinical feasibility of a new method to orient 3-dimensional (3D) computed tomography models to the natural head position (NHP). This method uses a small and inexpensive digital orientation device to record NHP in 3 dimensions. This device consists of a digital orientation sensor attached to the patient via a facebow and an individualized bite jig. The study was designed to answer 2 questions: 1) whether the weight of the new device can negatively influence the NHP and 2) whether the new method is as accurate as the gold standard.

PATIENTS AND METHODS

Fifteen patients with craniomaxillofacial deformities were included in the study. Each patient's NHP is recorded 3 times. The first NHP was recorded with a laser scanning method without the presence of the digital orientation device. The second NHP was recorded with the digital orientation device. Simultaneously, the third NHP was also recorded with the laser scanning method. Each recorded NHP measurement was then transferred to the patient's 3D computed tomography facial model, resulting in 3 different orientations for each patient: the orientation generated via the laser scanning method without the presence of the digital orientation sensor and facebow (orientation 1), the orientation generated by use of the laser scanning method with the presence of the digital orientation sensor and facebow (orientation 2), and the orientation generated with the digital orientation device (orientation 3). Comparisons are then made between orientations 1 and 2 and between orientations 2 and 3, respectively. Statistical analyses are performed.

RESULTS

The results show that in each pair, the difference (Δ) between the 2 measurements is not statistically significantly different from 0°. In addition, in the first pair, the Bland-Altman lower and upper limits of the Δ between the 2 measurements are within 1.5° in pitch and within a subdegree in roll and yaw. In the second pair, the limits of the Δ in all 3 dimensions are within 0.5°.

CONCLUSION

Our technique can accurately record NHP in 3 dimensions and precisely transfer it to a 3D model. In addition, the extra weight of the digital orientation sensor and facebow has minimal influence on the self-balanced NHP establishment.

The effect of occlusal discrepancies on periodontitis. I. Relationship of initial occlusal discrepancies to initial clinical parameters

BACKGROUND

A causal relationship between occlusal discrepancies and periodontal disease has been postulated in the past. However, animal studies and clinical studies have not been able to clearly demonstrate or rule out this potential relationship.

METHODS

The records from a private practice limited to periodontics were reviewed to find patients who had complete periodontal examination records, including occlusal analysis, that were recorded at least 1 year apart. Patients who fit these criteria were divided into a group who had none of the recommended treatment (untreated n = 30), those that had only nonsurgical treatment (partially treated n = 18), and a control group that had complete all recommended treatment (surgically treated n = 41). The data for each tooth of each patient, including occlusal status, were placed in a database and analyzed using the generalized estimating equations (GEE) method to test for associations between initial occlusal discrepancies and various initial clinical parameters while adjusting for significant confounders.

RESULTS

Teeth with initial occlusal discrepancies were found to have significantly deeper initial probing depths (P < 0.0001), significantly worse prognoses (P < 0.0001), and significantly worse mobility than teeth without initial occlusal discrepancies. In addition, this association between initial occlusal discrepancies and initial periodontal condition was found to hold for various subsets considered as well, including posterior teeth only and when only patients with good oral hygiene were considered.

CONCLUSIONS

This study indicates that there is a strong association between initial occlusal discrepancies and various clinical parameters indicative of periodontal disease. Based on adjustments made for other known risk factors for periodontal disease, such as smoking, poor oral hygiene, etc., this study provides some evidence that occlusal discrepancy is an independent risk factor contributing to periodontal disease.

Functional occlusion: I. A review

The features that constitute an "ideal" functional occlusion have not been conclusively established. Orthodontic treatment has the capacity to change static and functional occlusal relationships fundamentally. In this article, we present the evidence on which features of the occlusion are reported to be detrimental to the teeth and masticatory system Deficiencies in this research area are highlighted, together with the need for prospective longitudinal trials to clarify the requirements of an ideal functional occlusion Based on the existing evidence this paper suggests which occlusal features may be significant in producing an "ideal" functional occlusion As no long-term studies exist to measure the impact of non-ideal occlusal relationships on the dentition, it is debatable whether orthodontic treatment should be prolonged in order to ensure that "ideal" occlusal contacts are achieved As the occlusion tends to "settle" in the period following appliance removal, we propose that it may be more appropriate to examine the functional occlusal relationships after retention has ceased rather than prolong active orthodontic treatment to achieve "ideal" functional occlusal goals.

Diagnostic criteria for pseudo-Class III malocclusion

The aim of this study is to identify the diagnostic criteria for pseudo-Class III malocclusion and compare it with Class I malocclusion in the southern Chinese population. Sixty-seven patients (mean age, 10.9 +/- 1.8 years) were included in this study; 36 patients represented pseudo-Class III malocclusion. Selection criteria included the following: (1) anterior crossbite (at least 2 incisors with negative overjet and overbite); (2) mandibular displacement; (3) all patients were southern Chinese who had been followed after the growth spurt, none had developed a skeletal Class III malocclusion; (4) the patients were treated for an average of 7 months to procline upper incisors and retrocline lower incisors. None of the cases received any treatment that might affect skeletal growth. Thirty-one patients with Class I malocclusion were included in the Class I malocclusion group for the comparison of dentoskeletal characteristics with the pseudo-Class III malocclusion group. Selection criteria included the following: (1) skeletal Class I malocclusion with normal overjet and overbite, (2) mild to moderate crowding with Class I molar relationship, (3) straight facial profile. The following were included in the assessment of pseudo-Class III malocclusion cases: (1) family history, (2) molar and canine relationships at habitual occlusion and centric relation, and (3) dentoskeletal morphology. The results were that 72% of the examined cases in the pseudo-Class III malocclusion group showed no family history and 75% showed Class I molar relationship at habitual occlusion. Compared with the Class I malocclusion group, subjects in the pseudo-Class III malocclusion group showed a significantly decreased midface length, increased maxillary-mandibular difference, more retroclined upper incisors, and a retrusive upper lip. In conclusion, a pseudo-Class III malocclusion is characterized by retroclined upper incisors, retrusive upper lip, decreased midface length, and increased maxillary-mandibular difference. Findings of this study showed that patients with a pseudo-Class III malocclusion exhibit certain morphologic, dental, and skeletal characteristics that should be of aid in the diagnosis of pseudo-Class III malocclusion.

Predictability of maxillary repositioning during bimaxillary surgery: accuracy of a new technique

The purpose of this retrospective study was to evaluate the predictability of maxillary repositioning following Le Fort I osteotomy during bimaxillary surgery using a new technique with splints to reposition the maxilla in the three planes of space. In order to assess the accuracy of horizontal and vertical maxillary movements of the maxilla, 32 consecutive patients who underwent bimaxillary surgery had their predictive tracings and model surgery measures compared to postoperative cephalograms taken 1 week after surgery. There was a strong positive correlation between model surgery and postoperative result: 53% of horizontal movements and 41% of vertical movements showed less than 0.2 mm variation. When predictive tracings were compared to postoperative results 44% of horizontal and 50% of vertical movements showed less than 0.2 mm variation. There was no significant difference (P>0.05) between the planned and actual maxillary positions in the sample evaluated. This technique for maxillary repositioning during two-jaw surgery proved to be effective and predictable, with strong agreement between predictive tracings, model surgery and postoperative results.

Using Intraoral Scanning to Capture Complete Denture Impressions, Tooth Positions, and Centric Relation Records

Intraoral scanning was used to capture the soft tissue surfaces of both maxillary and mandibular edentulous ridges and the denture borders. Additionally, an intraoral scanner was used to digitize existing dentures with their tooth positions and base forms and a centric relation record obtained with a Gothic arch-tracing device. These scans provided all the required records for fabrication of computer-aided design/computer-assisted manufacturing of complete dentures.

Occlusal adjustment and the incidence of demand for temporomandibular disorder treatment

STATEMENT OF PROBLEM

Contrary to clinical opinion, the structural risk from dental occlusion in temporomandibular disorders has been questioned or considered to be insignificant in clinical practice.

PURPOSE

This study tested the effect of elimination of occlusal interference through occlusal adjustment, on the incidence of temporomandibular disorders.

MATERIAL AND METHODS

In a controlled clinical trial of 146 healthy children and adolescents, half of the subjects underwent occlusal adjustment aimed at elimination of the presumed structural risk, and the other half underwent mock adjustment. Adjustments were repeated every 6 months over a period of 4 years. The outcome variable was the incidence of temporomandibular disorders, operatively defined as request for treatment of symptoms characteristic of the disorders with presence of clinical signs demonstrated in the muscles of mastication and/or jaw joint.

RESULTS

The cumulative incidence rate was 9/67 in the mock adjustment group and 1/60 in the real adjustment group, for a relative risk of 8.06. The difference between groups was statistically significant (p = 0.019).

CONCLUSIONS

Elimination of the presumed structural risk from the dental occlusion appeared to significantly reduce the incidence of temporomandibular disorders in a select group of young subjects.

A classification system for occlusions that relates maximal intercuspation to the position and condition of the temporomandibular joints

Interarch occlusal relationships are defined by temporomandibular joint (TMJ) position. Determination of the most physiologic joint position is a logical prerequisite for occlusal analysis. Existing classification systems for occlusion do not consider TMJ position or condition when relating the mandibular arch to the maxillary arch or the range of adaptive changes that can affect the position of the condyles or influence long-term occlusal stability. If the relationship between occlusion and TMJ position is as important as many clinicians believe, condylar position must be defined precisely as an essential control in any clinical study that purports to evaluate the relationship between occlusion and any masticatory system disorder to include temporomandibular disorders. This article presents a new classification system that defines the relationship between maximal intercuspation and the position and condition of the TMJs. The classification uses guidelines that are specific enough to be consistent and verifiably reproducible. A recently introduced term, "adapted centric posture," is used in this classification to distinguish deformed TMJs that have remodeled or adapted to a conformation that can comfortably accept maximal loading. This classification is necessary because deformed but adapted joints may within certain conditions function with the same degree of comfort as intact, properly aligned condyle disk assemblies in centric relation.