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

Centric relation-A biological perspective of a technical concept

BACKGROUND

Few terms and concepts have been so extensively debated in dentistry as the words 'centric relation' (CR). Debates involve its biological, diagnostic and therapeutic usefulness.

METHODS

A review of the literature on the current concepts on CR as a diagnostic or therapeutic aid in dentistry was provided. Clinical trials assessing the superiority of one CR recording method over the others to identify patients with temporomandibular disorders (diagnostic use) or to manage patients with prosthodontic or orthodontic needs (therapeutic use) were tentatively included.

RESULTS

Due to the absence of literature addressing either of the above targets, a comprehensive overview was provided. The diagnostic use of CR as a reference position to identify the correct position of the temporomandibular joint condyle within the glenoid fossa is not supported and lacks anatomical support. From a therapeutic standpoint, the use of CR can be pragmatically useful in prosthodontics as a maxillo-mandibular reference position when occlusal re-organization is warranted and/or when the position of maximum intercuspation is no longer available.

CONCLUSIONS

The derived occlusal goals from a diagnostic misuse of CR are generally the result of circular reasoning, that is a technique is based on the recording of a certain condylar position that is believed to be 'ideal' and the treatment is considered successful when such position is shown by the specific instrument that was manufactured for that purpose. The term 'Centric Relation' might be replaced with the term 'Maxillo-Mandibular Utility Position'.

Temporomandibular Disorders: Implications in Restorative Dentistry and Orthodontics

Over the past several decades, the science of restorative/reconstructive dentistry and orthodontics has evolved tremendously, following sound principles passed down from robust literature and scientific rationale. These principles have been solid and instrumental in enhancing dentistry, from a single tooth restoration to complex full-mouth rehabilitations. However, it must be noted that some of the principles and philosophies followed over these decades have been questioned based on the advances in science, technology, and evidence-based medicine. The scenario became complex when clinicians were faced with the question of guidance for optimum joint and muscle health as related to restorative dentistry and orthodontics.

The Role of Maxillofacial Structure and Malocclusion on Condylar Displacement in Maximum Intercuspation and Centric Relation in Patients Seeking Orthodontic Treatment-A Scoping Review

BACKGROUND

Available knowledge about malocclusion and cephalometric variables and their connection with an increased risk of condylar displacement (CD) is scarce. This article aims to present current information on the relationship between centric relation-maximum intercuspal position discrepancies and maxillofacial morphology and malocclusion in patients seeking orthodontic treatment as well as to identify those who require expanded diagnostic evaluation for this disorder.

METHODS

This review analyzed the PubMed, Cochrane Library, Web of Science, and Scopus electronic databases up to February 2022. Keywords and additional manual searches were performed. Literature selection was based the PRISMA-ScR checklist. The JBI Critical Appraisal Tool assessed the methodological quality of included studies.

RESULTS

The databases search provided 2321 studies. A total of 10 studies were included in this review after eligibility criteria and JBI assessment. This review was separated into five parts that evaluated CD correlations depending on the following: maxillofacial structure in different vertical and sagittal skeletal patterns, vertical, horizontal, and transverse malocclusions.

CONCLUSIONS

A hyperdivergent facial skeletal structure is a risk factor for increased CD, particularly in the vertical dimension. The condylar processes are usually displaced in a posteroinferior direction. Further studies are warranted to elucidate the relationship among remaining skeletal and dental malocclusions and the occurrence of CD.

Magnetic resonance imaging assessment of articular disc position in temporomandibular disorder subjects with various bite registrations

Objective

This study aimed to evaluate the validity and reliability of three bite registrations on articular disc position in temporomandibular disorder patients using magnetic resonance imaging (MRI).

Materials and Methods

Fifteen clinically symptomatic and orthodontically untreated temporomandibular disorder patients within the age range of 17-40 years (mean age: 28.5 years) were examined. Each patient was subjected to three bite registrations, namely maximum intercuspation, initial contact bite and Roth power centric bite, and evaluated with MRI.

Results

On the right side, the mean vertical and horizontal measurement values of the point in the most posterior aspect of the posterior band of the articular disc in relation to horizontal reference line (HRL) and vertical reference line (VRL) in the sagittal view in the Roth power centric bite were lesser (2.720 ± 1.239 mm and 2.380 ± 1.185 mm, respectively), in comparison with the other two bites, and on the left side too, it was lesser in the Roth power centric bite (2.293 ± 0.979 mm and 2.360 ± 1.078 mm, respectively), when compared to the other two bites. Statistical analysis also showed the significance of Roth power centric bite over the other two bites.

Conclusions

Favourable articular disc positional changes were observed in the Roth power centric bite followed by the initial contact bite and that maximum disc recapture was observed in most patients with the Roth power centric bite rather than in initial contact bite and maximum intercuspation positions. The Roth power centric bite could be assumed to be the ideal method for articulation and fabrication of gnathological splints for treating patients with temporomandibular disorders.

Static mandibular condyle positions studied by MRI and condylar position indicator

We compared mandibular condyle positions as determined by magnetic resonance imaging (MRI) and a mechanical device, the condylar position indicator (CPI). Both methods assessed 3 mandibular positions in 10 asymptomatic males and 10 asymptomatic females, aged 23 to 37 years, free from temporomandibular disorders: maximum intercuspation, bimanually manipulated centric relation, and the unguided neuromuscular position. Bite registrations were obtained for bimanual operator guidance and neuromuscular position. 3 T MRI scans of both temporomandibular joints produced 3D data of the most superior condylar points in all 3 mandibular positions. Using mounted plaster casts and the same bite registrations, an electronic CPI displayed 3D data of its condylar spheres in these positions. The results showed interclass correlation coefficients ranging from 0.03 to 0.66 (95% confidence intervals from 0 to 0.8) and significantly different condyle positions between both methods (p = 0.0012, p < 0.001). The implications of the study emphasize that condyle position is unpredictable and variable. Its exact knowledge requires radiological imaging and should not rely on CPI assessments.

The Role of Maxillofacial Structure on Condylar Displacement in Maximum Intercuspation and Centric Relation

Purpose

This study is aimed at evaluating the impact of the craniofacial structure and occlusal conditions on the position of the articular heads of the mandibular condyles in the maximum intercuspal position (MIP) and comparing the centric relation (CR) and MIP of the mandibular condyles prior to orthodontic treatment.

Methods

The studied group consisted of 33 women and 15 men (median age of 17.75 years). Contact points of opposing teeth in the MIP were assessed by hand-held casts. Condylar displacement (CD) in three spatial planes on both sides was measured on models mounted in an articulator using a mandibular position indicator (MPI). Patients were divided into groups according to craniofacial structures (vertical and horizontal growth directions). The Mann-Whitney, Kruskal-Wallis, post hoc Dwass-Steel-Critchlow-Fligner, and Pearson's χ² independence tests as well as Spearman's nonparametric correlations were used in the statistical analyses.

Results

Within the limitations of this study, no statistically significant correlation of CD with certain cephalometric measurements from a lateral cephalometric radiograph (ANB, SN-ML, and SGo/NMe) was observed. Correlation, however, was found between condylar displacement in the transverse axis and the mandibular plane angle SN-ML (p = 0.033) and also between condylar displacement in the anteroposterior axis and a midline shift of the mandible (p = 0.041). The results revealed a relationship between Angle's classification of molar position on the right side and anteroposterior CD values (p = 0.006).

Conclusions

Cephalometric measurements cannot be used to predict CD at the level of the condyles. Analysis of occlusal conditions of models mounted in an articulator is desirable for patients with Angle's class I and lower jaw asymmetry.

The Relationship Between Centric Occlusion and The Maximal Intercuspal Position and Their Use as Treatment Positions for Complete Mouth Rehabilitation: Best Evidence Consensus Statement

PURPOSE

The purpose of this Best Evidence Consensus Statement was to evaluate the existing literature relative to two focus questions: How often does centric occlusion coincide with maximal intercuspal position in dentate and partially dentate populations?; and should centric occlusion or maximal intercuspal positions be equivalent for dentate and partially dentate patients undergoing complete mouth rehabilitation?

MATERIALS AND METHODS

Keywords used in the initial search were: intercuspal position, centric occlusion, centric relation, maximal intercuspal position, prosthodontic rehabilitation, and occlusion. The search was then limited to Systematic Reviews, Randomized Controlled Studies, Meta-analyses and Clinical Trials.

RESULTS

The initial search strategy related to the selected search terms resulted in more than 15,000 articles. When the subsequent search was limited to Systematic Reviews, Randomized Controlled Studies, and Meta-Analysis and Clinical Trials, 313 articles were selected for further analysis.

CONCLUSIONS

Review of the literature reveals that most dentate and partially dentate patients do not have coincident centric occlusion and maximal intercuspal position. There is support for coincidence between centric occlusion and maximal intercuspal position as the preferred occlusal relationship in complete mouth rehabilitations. The literature does not report conclusive evidence of adverse prosthodontic outcomes with complete rehabilitations in centric occlusion or maximal intercuspal position in a healthy population. However, there is support for an association between centric occlusion-maximal intercuspal position discrepancies and occlusal instability as well as temporomandibular joint disorders. Hence, it is concluded that partially and completely dentate patients requiring complete mouth rehabilitation should be restored in centric occlusion.

Orthodontic Treatment and Craniocervical Posture in Patients with Temporomandibular Disorders: An Observational Study

Orthodontic treatment acts through the application of forces and/or by stimulating and redirecting the functional forces within the craniofacial complex. Considering the interrelationship between craniomandibular and craniocervical systems, this intervention may alter craniocervical posture. Thus, our aim is to (a) compare craniocervical posture, hyoid bone position, and craniofacial morphology before, after, and also in the contention phase at least one year after the orthodontic treatment, in patients with temporomandibular disorders and (b) to verify whether the presence of condylar displacement, the skeletal class, or the facial biotype interferes with the abovementioned outcomes. To do so an observational, analytical, longitudinal, and retrospective design study was carried out. A non-probabilistic convenience sampling method was applied. The sample consisted of clinical records of patients diagnosed with temporomandibular disorders in order to compare pre-orthodontic treatment with post-orthodontic treatment (n = 42) and contention phase data (n = 26). A cephalometric analysis of several variables was performed. The p-value was set as 0.05. When the pre- and post-orthodontic treatment data were analyzed, there were statistically significant changes in variables concerning craniocervical posture (CV angle, C0-C1, and AA-PNS) and also concerning hyoid bone position (C3-Rgn). When pre- and post-orthodontic treatment and contention phase data were analyzed the variables concerning craniocervical posture (C0-C1, CVT/Ver, NSL/OPT, NSL/CVT, NSL/Ver; OPT/CVT, OPT/Ver) and facial biotype had statistically significant changes. This allowed us to conclude that in the sample studied, there were significant differences regarding hyoid bone position (pre- versus post-orthodontic treatment) and craniocervical posture (pre- versus post-orthodontic versus contention), with the craniocervical posture being prone to return to basal values. The presence of condylar displacement was found to significantly increase the H-H1 distance in the three moments of evaluation. Facial biotype was found to significantly increase the NSL/Ver angle on hypodivergent compared to hyperdivergent in the contention phase.

The evolution of temporomandibular disorders: A shift from experience to evidence

After over 80 years of much obsession as well as avoidance of the subject of temporomandibular disorders (TMDs), the dental profession is still divided over what they are and how to deal with them. Over this period, nearly every discipline in dentistry has played some role in the development of this field. Unfortunately, a significant amount of this information has been based on personal opinion, experience-based philosophies, or poorly conducted research. Furthermore, each dental specialty has been responsible for contributing to the concepts of the etiology and management of TMDs with their own professional bias; for example, orthodontists describe these problems in orthodontic terms and offer orthodontic treatments or solutions for their patients. As various treatment approaches were found to be effective at least some of the time, this has further led to misinformation and confusion within the profession. Advances in research from diverse fields, including neurophysiology, pain pathophysiology, genetics, endocrinology, behavioral sciences, and psychology, have significantly altered our understanding of TMDs and how they should be managed. The rigid mechanical and dental-based model of the past has been gradually replaced by a biopsychosocial medical model for the diagnosis and treatment of TMDs as well as other acute and chronic pain disorders. This paper discusses the evolution of our understanding of TMDs since they were first described 85 years ago. Contemporary scientific findings and their implications are presented in some detail for clinicians who wish to provide the appropriate management for their orofacial pain patients.

Estimated functional space of centric condyle positions in temporomandibular joints of asymptomatic individuals using MRI

Magnetic resonance imaging (MRI) studies on centric condyle positions lack 3D comparisons of guided and unguided methods, which are used for accomplishing centric relation reference positions. The purpose of this study was to describe the space, in which mandibular condyles are placed in vivo by dental intercuspation, Dawson’s bimanual manipulation, and neuromuscular position. Twenty asymptomatic individuals aged 23 to 37 years underwent separate bite registrations using bimanual manipulation and the unguided neuromuscular technique. Subsequent 3-Tesla MRI scans of both temporomandibular joints yielded 3D data of the most superior condylar points at maximum intercuspation and both centric relation positions. We found concentric condyle positions in maximum intercuspation but considerable variation of condyle position after bimanual manipulation and neuromuscular technique. Their 95% predictive confidence ellipses overlapped substantially and created a space of reference positions. Its smallest volume averaged 2 mm³ for a minimal convex hull (95% confidence interval 1.1–3.2) and 3.5 mm³ for a minimal ellipsoid hull (95% confidence interval 1.8–5.4). Visualized in vivo by MRI, condyle positions at bimanual manipulation and neuromuscular position were not predictable and showed substantial variation in asymptomatic subjects. Clinicians should be aware of the functional space and its effect on dental intercuspation.

The Use of Mini-Plates for the Treatment of a High-Angle, Dual Bite, Class II Malocclusion

To present a case report of an orthodontic treatment of a high-angle, dual bite, Class II malocclusion without extractions and with the use of mini-plates. Class II malocclusion treatment protocols vary according to the morphological component of the malocclusion and the magnitude and direction of craniofacial growth. It is generally agreed that the cooperation of the patient and careful planning of anchorage are the key determinants of successful treatment. Protrusion of the upper and lower lip and a retrognathic mandible were the patient's chief concerns. The patient had learned to project her mandible forward to disguise the overjet. The patient's parents elected to correct the malocclusion with the use of bilateral infrazygomatic mini-plates. Pre-treatment condylar stabilization with an orthotic established a stable centric relation position, followed by mounting of the models on a semi-adjustable Panadent articulator. This allowed diagnosis and treatment planning from a stable condylar position and eliminated possible misdiagnosis due to the dual bite. Distal retraction and vertical control of the upper teeth enabled correction of the Class II malocclusion with minimal patient cooperation. Mini-plate-assisted treatment corrected the excessive overbite and overjet. The patient completed treatment with a stable occlusion and no longer postured her jaw forward. The parents and patient were completely satisfied with the positive treatment outcome. A 2-year follow-up confirmed the clinical stability.

Effects of Dental Occlusion on Body Sway, Upper Body Muscle Activity and Shooting Performance in Pistol Shooters

Occlusal splints, to some extent, have been related to reduced body sway in a static position and increased muscle activity in the upper limbs. However, how dental occlusion status affects sports performance remains unclear. Here, we investigated whether occlusal splints that reposition the temporomandibular joint (TMJ) influenced body posture, muscle activity, and performance in 10-meter pistol shooters. Thirteen national-level male shooters (age = 38.8 ± 10.9 yrs) were recruited for this study, and cleared of any cervical pathology. An occlusal splint (OS) and a placebo splint (PS) were fabricated for each of the subjects, with the mandibular and maxillary position verified by an expert dentist, with the aid of an adjustable articulator. Surface electromyography (EMG) was assessed in the upper limb that holds the pistol while the subjects were standing on a force platform. Subjects performed two series of 10 shots for each of the three experimental conditions (OS, PS, N (no splint)) in randomized order, with the mandible in a rest position. Results revealed similar centre of pressure (COP) parameters in all conditions, despite a reduction in the average oscillation area caused by the OS. There were also no significant differences in EMG activity between conditions in the five upper limb muscles monitored. Consistent with this, shooting performance was similar in all conditions, despite a reduction in shot dispersion in subjects using OS. Thus, changes in dental occlusion status induced by OS do not affect body posture, upper limb EMG muscle activity, or shot performance in healthy male pistol shooters.

The importance of the posterior joint space for functional mandibular movements: A laboratory cross-sectional study

Background

The search for the ideal, healthy and reproducible position of the condyles is of utmost importance for dental diagnosis and treatment. Thus, the objective of this laboratory cross-sectional study was to verify the relationship between the posterior joint space and the mandibular lateral movements.

Material and Methods

Dental casts from 15 women and 15 men with normal mastication, 28 natural teeth and no history of temporomandibular disorders or pain, were fabricated and mounted on a fully adjustable articulator. From the maximum intercuspal position, condylar displacement was evaluated and measured on the working and nonworking sides during mandibular lateral movement, both to the right and left sides.

Results

The correlation between the measures of interest was assessed with the Pearson correlation coefficient (α=.05). Condylar displacement on the working side and nonworking side condyle was 0.88±0.71 mm and 3.57±1.11 mm (right mandibular lateral movement); and 0.91±0.58 mm and 3.51±0.78mm (left mandibular lateral movement), respectively. No significant correlation in the condylar displacement between the working side condyles on the right and on the left sides was observed (r=.22; P=.248). The condylar poles of the articulator moved posteriorly, simulating the functional movements of the mandible during mastication. In all cases, condylar displacement during mandibular lateral movement both to the right and left occurred posteriorly on the working side condyle.

Conclusions

The condylar poles of the articulator moved posteriorly simulating the functional movements of the mandible during mastication. Moreover, left and right working condyles may require slightly different spaces to function, suggesting minor anatomical asymmetries.

Key words:Mastication, dental occlusion, prosthodontics.

Centric relation-intercuspal position discrepancy and its relationship with temporomandibular disorders. A systematic review

OBJECTIVE

The objective of this study is to assess the relationship between centric relation-intercuspal position discrepancy (CR-ICP discrepancy) and temporomandibular disorders (TMDs), by systematically reviewing the literature.

MATERIALS AND METHODS

A systematic research was performed between 1960 and 2016 based on electronic databases: PubMed, Cochrane Library, Medline, Embase, Scopus, EBSCOhost, BIREME, Lilacs and Scielo, including all languages. Analytical observational clinical studies were identified. Two independent authors selected the articles. PICO format was used to analyze the studies. The Newcastle-Ottawa Scale (NOS) was used to verify the quality of the evidence.

RESULTS

Four hundred and sixty-seven potentially eligible articles were identified. Twenty studies were analyzed, being grouped according to intervention in studies in orthodontic patients (n = 3) and studies in subjects without intervention (n = 17). Quality of evidence was low, with an average score of 3.36 according to Newcastle-Ottawa Scale. In most studies, the presence of CR-ICP discrepancy is associated with the presence of muscle (pain) and joint disorders (noise, disc displacement, pain, crepitus, osteoarthritis and osteoarthrosis). However, the lack of consistency of the results reported reduces the validity of the studies making it impossible to draw any definite conclusions.

CONCLUSIONS

Because of the heterogeneity of the design and methodology and the low quality of the articles reviewed, it is not possible to establish an association between CR-ICP discrepancy and TMD. The consequence of CR-ICP discrepancy on the presence of TMD requires further research, well-defined and validated diagnostic criteria and rigorous scientific methodologies. Longitudinal studies are needed to identify CR-ICP discrepancy as a possible risk factor for the presence of TMD.

Articulated dental cast analysis of asymptomatic and symptomatic populations

Dental instrumentation has long provided insight into the mechanism of musculo-skeletal function of the gnathic system. While large population studies associate dental arch displacement (DAD), especially laterally, with symptoms, mandibular condyle displacement (CD) resulting from DAD has not been targeted as possibly etiologic in the production of common muscle contraction headache (CMCH) and temporo-mandibular dysfunction (TMD). The objective was to evaluate the three-dimensional nature of DAD and CD between the seated condylar position (SCP) and the intercuspal position (ICP) and to compare results derived from large deprogrammed asymptomatic and symptomatic populations. A total of 1 192 sets of dental casts collected from asymptomatic and symptomatic populations were articulated in the SCP. The initial occlusal contact, DAD, and condylar displacement were evaluated for frequency, direction, and magnitude of displacement between the SCP and ICP. The data revealed significant displacement between the SCP and ICP of the condyles (displaced most frequently inferior (down) and posterior (distal)) and substantially increased frequency and magnitude of displacement of the dental arches (with posterior premature occlusal contacts, increased overjet, decreased overbite, midline differences, and occlusal classification changes) in symptomatic subjects. These discrepancies were statistically significant and clinically significant. The data support the concept of increased DAD and CD with dysfunction. Transverse condylar displacement, commonly presenting with dental cross bite, may be associated with CMCH and TMD. Displacement of the mandibular condyle may be an etiologic factor in CMCH and dysfunction of the temporo-mandibular joint.

Cone-Beam Computed Tomographic Assessment of Mandibular Condylar Position in Patients with Temporomandibular Joint Dysfunction and in Healthy Subjects

Statement of the Problem. The clinical significance of condyle-fossa relationships in the temporomandibular joint is a matter of controversy. Different studies have evaluated whether the position of the condyle is a predictor of the presence of temporomandibular disorder. Purpose. The purpose of the present study was to investigate the condylar position according to gender in patients with temporomandibular disorder (TMD) and healthy controls using cone-beam computed tomography. Materials and Methods. CBCT of sixty temporomandibular joints in thirty patients with TMD and sixty joints of thirty subjects without TMJ disorder was evaluated in this study. The condylar position was assessed on the CBCT images. The data were analyzed using Pearson chi-square test. Results. No statistically significant differences were found regarding the condylar position between symptomatic and asymptomatic groups. Posterior condylar position was more frequently observed in women and anterior condylar position was more prevalent in men in the symptomatic group. However, no significant differences in condylar position were found in asymptomatic subjects according to gender. Conclusion. This study showed no apparent association between condylar positioning and clinical findings in TMD patients.

Treatment of a mandibular functional shift in an adolescent boy with temporomandibular disorder and crossbites

A mandibular functional shift usually poses a challenge for orthodontists, especially when it is accompanied by a temporomandibular disorder (TMD). Accurate diagnosis and complete elimination of the etiologic factors are the keys to an esthetic and stable outcome. This article describes the treatment of a teenager with a mandibular functional shift, TMD symptoms, and facial asymmetry resulting from an asymmetric maxillary arch form and multiple crossbites as occlusal interferences. The treatment alternatives and effective orthodontic techniques are described. To optimize the treatment results and prevent the recurrence of the TMD after treatment, the displaced mandible was repositioned by full-time wearing of a splint for 10 months. Adhesive bite-blocks were used to maintain the newly acquired mandibular position during fixed appliance treatment. A series of nickel-titanium and stainless steel rectangular archwires was placed in the maxillary arch to reshape it for 8 months after alignment. Finally, the displaced mandible was steadily seated into its physiologic position with fine occlusion. The TMD symptoms disappeared and never relapsed after treatment. At 2 years 3 months of retention, there was good stability. The combined splint and fixed appliance approach resolved an intractable clinical problem and avoided using additional appliances. An esthetic, functional, and stable outcome was achieved that satisfied both the patient and his parents.

Comparison of condylar displacement between three biotypological facial groups by using mounted models and a mandibular position indicator

Objective

Facial-type-associated variations in diagnostic features have several implications in orthodontics. For example, in hyperdivergent craniofacial types, growth imbalances are compensated by displacement of the condyle. When diagnosis and treatment planning involves centric relation (CR), detailed knowledge of the condylar position is desirable. The present study aimed to measure condylar displacement (CD) between CR and maximum intercuspation in three facial types of an asymptomatic orthodontic population.

Methods

The study was conducted in 108 patients classified into three groups of 36 individuals each (27 women and 9 men; mean age, 20.5 years), based on the following facial patterns: hyperdivergent, hypodivergent, and intermediate. To quantify CD along the horizontal and vertical axes, the condylar position was analyzed using mounted casts on a semi-adjustable articulator and a mandibular position indicator. The Student t-test was used to compare CD between the groups.

Results

Vertical displacement was found to be significantly different between the hyperdivergent and hypodivergent groups (p < 0.0002) and between the hyperdivergent and intermediate groups (p < 0.0006). The differences in horizontal displacement were not significant between the groups. In each group, vertical CD was more evident than horizontal displacement was.

Conclusions

All facial types, especially the hyperdivergent type, carried a significantly high risk of CD. Therefore, the possibility of CD should be carefully evaluated and considered in the assessment of all orthodontic cases in order to accurately assess jaw relationships and avoid possible misdiagnosis.

The influence of different registration positions on condyle displacement in symptomatic patients

OBJECTIVE

This study aimed to evaluate effects of different registration positions on the condyle-disk position changes in the mandibular fossa in symptomatic individuals.

STUDY DESIGN

Vertical and sagittal condyle position and thickness of the bilaminar zone were measured by magnetic resonance imaging during maximal intercuspation (MI) and with jigs in Gothic arch tracing guided centric relation (DIR method [Dynamics and Intraoral Registration]) and retruded contact position (RCP). Participants were 26 patients seeking treatment for temporomandibular disorders. Condyle and disk position in the fossa were calculated in the parasagittal plane.

RESULTS

Significant differences were found for MI, DIR, and RCP for thickness of bilaminar zone and sagittal condyle position, dependent on diagnosis and registration position for vertical and sagittal condyle position and thickness of bilaminar zone.

CONCLUSIONS

DIR position ensures the widest posterior space for the retrodiskal tissues and the slightest sagittal difference between condyle zenith and glenoid fossa.

Condylar position assessed by magnetic resonance imaging after various bite position registrations

INTRODUCTION

In this study, we evaluated the reliability and validity of 3 bite registrations in relation to condylar position in the glenoid fossae using magnetic resonance imaging in a symptom-free population.

METHODS

Nineteen subjects, 14 men and 5 women (ages, 20-39 years) without temporomandibular disorders were examined. Three bite registrations were taken and evaluated on each subject: centric occlusion, centric relation, and Roth power centric relation. The differences in condyle position among the 3 bite registrations were determined for the left and right condyles: centric occlusion-centric relation, centric occlusion-Roth power centric relation, and centric relation-Roth power centric relation for each plane of space.

RESULTS

The results indicated that (1) all measurements collected had large standard deviations and ranges with no statistical significance, and (2) of the 19 subjects and 38 condyles assessed, 33 condyles (87%) were concentric in an anteroposterior plane. In the transverse anatomic plane, all condyles were concentric.

CONCLUSIONS

The clinical concept of positioning the condyles in specific positions in the fossae with various bite registrations as a preventive measure for temporomandibular disorders and as a diagnosis and treatment planning tool is not supported by this study.

Discrepancy of coronal morphology between mandibular condyle and fossa is related to pathogenesis of anterior disk displacement of the temporomandibular joint

OBJECTIVE

To evaluate whether morphological discrepancy between the mandibular condyle and fossa of the temporomandibular joint (TMJ) is related to disk displacement on magnetic resonance imaging (MRI).

STUDY DESIGN

This study included 61 patients with unilateral internal derangement based on both MRI and clinical examination. Coronal morphologies of the condyle and fossa were divided into four groups based on Öberg's classification. According to the coronal morphology of the condyle and fossa, all joints were dichotomized into either harmonized group or a discrepancy group (e.g., angled condyle and concave fossa). The incidence of discrepancy and the relationship of the discrepancy to other findings on MRI were statistically evaluated.

RESULTS

The discrepancy had a significantly higher incidence on the affected side. The discrepancy correlated with incidence of disk deformity on the affected side.

CONCLUSION

Morphological discrepancy between the condyle and fossa is related to development of anterior disk displacement in the TMJ.

Assessing joint space and condylar position in the people with normal function of temporomandibular joint with cone-beam computed tomography

BACKGROUND

The optimal position of the condyle in glenoid fossa is a fundamental question in dentistry. There is no quantitative standard for the optimal position of mandibular condyle in the glenoid fossa in our population. The purpose of this study is to assess the position of the condyle by cone beam computed tomography (CBCT) images in patient with normal function of temporomandibular joint (TMJ).

MATERIALS AND METHODS

In this cross-sectional study, CBCT images of 40 class I skeletal patients (15 males and 25 females) without history of TMJ disorders were selected. Next, the anterior, superior and posterior joint spaces (Ajs, Sjs, Pjs) were measured on the two true central sagittal slices. Then medial (M) and lateral (L) joint spaces on true coronal view were measured in the right and left sides, separately. After that, P/A ratio, S/A ratio and M/L ratio were calculated. Finally, a paired t-test and independent samples t-test were employed for analysis.

RESULTS

The centric position of the condyle in glenoid fossa was more common (92.5%) than other positions. Significant differences in Ajs, Sjs, Pjs, Mjs and Ljs values between two sides were observed (P ≤ 0.05). Additionally, Sjs showed statistically significant differences between the sexes (P = 0.05). P/A ratio and S/A ratio had significant differences between two sides but not between those sexes.

CONCLUSION

The assessment of joint spaces in right and left sides should be done independently. Overall, the measured joint spaces except Sjs are not different in two sexes. The data from this study could be a useful and comparable reference for the clinical assessment of condylar position in patients with normal functional joints.

Guided and unguided mandibular reference positions in asymptomatic individuals

OBJECTIVES

To determine the difference between guided and unguided mandibular reference positions assessed by articulator simulation.

SETTING AND SAMPLE POPULATION

This study was carried out at the Division of Orthodontics at Vienna Medical University. The sample population consisted of 19 men and 18 women aged 23-32 years and without temporomandibular disorder.

MATERIALS AND METHODS

Three examiners used bimanual operator guidance and unguided mandibular stationary hinging at final jaw closure before occlusal contact and made occlusal wax recordings. The examiners repeated both techniques after 8 and 17 days on the same subjects. Condylar positions were assessed using articulator-mounted casts and a three-dimensional electronic condylar position indicator.

RESULTS

Bimanual guidance positioned the condylar spheres, on average, 0.1 mm more right and 0.6 mm more posterior and superior to unguided hinging (p < 0.04). The repeatability of bimanual guidance by three operators and on 3 days resulted in inter-repetition standard deviations ranging from 0.19 to 0.4 mm and from 0.41 to 0.76 mm for unguided hinging. The highest fraction of the total variance came from the individuals, followed by days, then intra-operator and interoperator variability. Both methods showed considerable overlap of condylar sphere positions at the 95% confidence level.

CONCLUSION

Within the limits of an articulator study, the spatial variability of condylar sphere positions suggested a statistically but not clinically relevant methodological difference between bimanual guidance and unguided stationary hinging.

The relationship between malocclusion, benign joint hypermobility syndrome, condylar position and TMD symptoms

The current study investigated the association between temporomandibular disorders, malocclusion patterns, benign joint hypermobility syndrome and the initial condylar position. One hundred sixty-two subjects were analyzed using the Rocabado Temporomandibular Pain Analysis; Helkimo Index parameters; the Carter-Wilkinson modified test; and a mounting cast with condylar position indicator registration (MPI). The study revealed a significant association between: 1. Delta H, skeletal pattern (p = 0.034); 2. Delta Y, transversal malocclusion (p = 0.04); 3. right and left, Delta Z, right and left posteroinferior synovial pain (p < 0.05); 4. hypermobility scale, gender (p < 0.001), malocclusion pattern (p = 0.021); 5. TMJ function impairment, gender (p = 0.043); 6. sagittal malocclusion pattern, right temporomandibular pain analysis joint (TPAJ) (p = 0.0034); 7. TMJ function impairment, left and right TPAJ (p = 0.007); and 8. mandibular motion, left and right TPAJ (p = 0.035, p = 0.015). The conclusion was that anterior crossbite and condylar displacements in the vertical plane are risk factors in developing TMJ symptoms.

Comparative analysis between mandibular positions in centric relation and maximum intercuspation by cone beam computed tomography (CONE-BEAM)

This research consisted of a quantitative assessment, and aimed to measure the possible discrepancies between the maxillomandibular positions for centric relation (CR) and maximum intercuspation (MI), using computed tomography volumetric cone beam (cone beam method). The sample of the study consisted of 10 asymptomatic young adult patients divided into two types of standard occlusion: normal occlusion and Angle Class I occlusion. In order to obtain the centric relation, a JIG device and mandible manipulation were used to deprogram the habitual conditions of the jaw. The evaluations were conducted in both frontal and lateral tomographic images, showing the condyle/articular fossa relation. The images were processed in the software included in the NewTom 3G device (QR NNT software version 2.00), and 8 tomographic images were obtained per patient, four laterally and four frontally exhibiting the TMA’s (in CR and MI, on both sides, right and left). By means of tools included in another software, linear and angular measurements were performed and statistically analyzed by student t test. According to the methodology and the analysis performed in asymptomatic patients, it was not possible to detect statistically significant differences between the positions of centric relation and maximum intercuspation. However, the resources of cone beam tomography are of extreme relevance to the completion of further studies that use heterogeneous groups of samples in order to compare the results.

Condylar displacement between centric relation and maximum intercuspation in symptomatic and asymptomatic individuals

OBJECTIVE

To measure condylar displacement between centric relation (CR) and maximum intercuspation (MIC) in symptomatic and asymptomatic subjects.

MATERIALS AND METHODS

The sample comprised 70 non-deprogrammed individuals, divided equally into two groups, one symptomatic and the other asymptomatic, grouped according to the research diagnostic criteria for temporomandibular disorders (RDC/TMD). Condylar displacement was measured in three dimensions with the condylar position indicator (CPI) device. Dahlberg's index, intraclass correlation coefficient, repeated measures analysis of variance, analysis of variance, and generalized estimating equations were used for statistical analysis.

RESULTS

A greater magnitude of difference was observed on the vertical plane on the left side in both symptomatic and asymptomatic individuals (P = .033). The symptomatic group presented higher measurements on the transverse plane (P = .015). The percentage of displacement in the mesial direction was significantly higher in the asymptomatic group than in the symptomatic one (P = .049). Both groups presented a significantly higher percentage of mesial direction on the right side than on the left (P = .036). The presence of bilateral condylar displacement (left and right sides) in an inferior and distal direction was significantly greater in symptomatic individuals (P = .012). However, no statistical difference was noted between genders.

CONCLUSION

Statistically significant differences between CR and MIC were quantifiable at the condylar level in asymptomatic and symptomatic individuals.

Effects of 2 types of facemasks on condylar position

INTRODUCTION

The aim of this study was to compare Delaire and Grummons protraction facemasks with a new articulator system (Amtech MG1, American Technologies, Brazil) that can record condylar positions.

METHODS

Thirty-four patients treated with protraction facemask therapy were divided into 2 groups; 18 were treated with the Delaire facemask (DFM) and 16 with the Grummons facemask (GFM). The observation periods were 8.5 months for the DFM group and 10 months for the GFM group. Mandibular position indicator (MPI) recordings were taken with the new articulator system and evaluated before and after the protraction facemask therapies.

RESULTS

MPI recordings in the sagittal plane showed forward and downward movement from centric relation to maximum intercuspal position for both condyles at the beginning of treatment for most patients. After treatment, the discrepancy between centric relation and maximum intercuspation was less in the DFM group than in the GFM group. However, more compressive movement of the condyles through the glenoid fossa was observed in the DFM group.

CONCLUSIONS

Although the centric slide amount decreased more with the Delaire facemask compared with the Grummons facemask, patients treated with the Delaire facemask must be monitored for signs and symptoms of temporomandibular joint disorder.

Three-dimensional analysis of models articulated in the seated condylar position from a deprogrammed asymptomatic population: a prospective study. Part 1

INTRODUCTION

The seated condylar position (SCP), also known as centric relation (CR), is considered the most reliable and reproducible reference point for accurately recording the relationship of the mandible to the maxilla. Therefore, a determination of the SCP/CR is a prerequisite for the analyses of the dental interarch, condylar position, and skeletal relationships. The purpose of this prospective study was to statistically evaluate the 3-dimensional nature of dental interarch displacement and condylar displacement between the SCP/CR and maximum intercuspation or centric occlusion (MIC/CO).

METHODS

The records of 596 consecutive asymptomatic patients having routine orthodontic treatment in a private practice were used. The initial premature occlusal contact and 3-dimensional dental interarch displacement were measured by the analysis of models, mounted on an articulator (Panadent, Grand Terrrace, Calif) in the SCP/CR, by using the modified (nonmanipulated) 2-piece wax SCP/CR recording method with deprogramming. Three-dimensional condylar displacement was measured by analysis of the graphic registrations, produced by condylar position instrumentation, and evaluated for frequency, direction, and magnitude of displacement.

RESULTS

The dental interarch discrepancy in the SCP/CR was significantly different from that observed in MIC/CO, with posterior premature contacts (94.0%), increased overjet, decreased overbite, midline differences, and Angle classification changes. A difference in condylar position between the SCP/CR and MIC/CO in at least 1 plane was detected for every asymptomatic patient and every condyle. The most prevalent types of directional change in condylar position were inferior (down) (97.0%) and distal (posterior) (66.7%) when the teeth were brought into MIC/CO. The mean difference in condylar position between the SCP/CR and MIC/CO was .86 mm in the horizontal plane, 1.80 mm in the vertical plane, and .26 mm in the transverse plane. No correlation was found between a patient's age or sex and the magnitude of condylar displacement.

CONCLUSIONS

There is a significant difference in the occlusion when it is dictated by the teeth and when it is dictated by the condyles. This difference is quantifiable at both the occlusal and condylar levels.

Centric relation

BACKGROUND

Centric relation (CR) has been a controversial subject in dentistry for more than a century. For at least the past four decades, issues involving CR have been of interest to orthodontists. The definition of CR has changed over the past half-century from a retruded, posterior and, for the most part, superior condyle position to an anterior-superior condyle position.

TYPE OF STUDIES REVIEWED

The authors addressed the historical and contemporary orthodontic perspective of CR. The source material for this review came mainly from literature and searches the lead author accumulated over the last 30 years. As there is no evidence-based (EB) model level 3 (systemic) review on the topic of CR, the best evidence on this subject was gleaned only from a thorough examination and evaluation at EB model level 2 (experience plus best available sample studies). There was, however, enough high-quality EB model level 2 information on the topic of CR for the authors to draw conclusions on the basis of a scientific appraisal of relevant research.

RESULTS

Although the reliability of CR records has been substantiated, the records' validity has little to no evidentiary support. In addition, population-based sample studies and consensus statements from national conferences support the view that the positions of the temporomandibular joint (TMJ) condyles in relation to the glenoid fossa or CR position are not diagnostic of temporomandiblar disorders. There appears to be little to no benefit of using gnathologic records and articulator-mounted dental casts to discern discrepancies in maximum intercuspation of the teeth coincident with TMJ condyles in an anterior-superior CR position in orthodontic patients.

CLINICAL IMPLICATIONS

The benefit of using gnathologic CR records and articulators in orthodontics has not been substantiated by scientific evidence.

The influence of the leaf gauge and anterior jig on jaw muscle electromyography and condylar head displacement: a pilot study

BACKGROUND

A leaf gauge and an anterior jig may be used to assist the recording of a reproducible jaw position for restorative and prosthodontic treatment. This study investigated possible condylar displacement using an opto-electronic jaw-tracking device and a leaf gauge or anterior jig. The effect of a leaf gauge and anterior jig on jaw muscle electromyography was also examined.

METHODS

Five healthy adults without symptoms of temporomandibular disorders were selected. Condylar displacement during clenching were recorded simultaneously with electromyographic activity of superior and inferior heads of the lateral pterygoid, anterior and posterior temporalis, masseter, and suprahyoid muscles. Subjects were trained to bite at maximum and half-maximum bite-force using an anterior jig incorporating a force transducer.

RESULTS

No consistent condylar displacement was observed in x, y and z axes between different bite-forces although there was a trend towards superior displacement. Comparison of maximum intercuspal clench and maximum clench on a leaf gauge and an anterior jig produced significant decrease in anterior temporalis activity (p < 0.05), whilst an anterior jig with maximum clench significantly decreased posterior temporalis muscle activity.

CONCLUSION

Within the limits of this pilot study, no consistent change in condylar position was identified with these appliances.

Relationship of condylar position to disc position and morphology

INTRODUCTION/OBJECTIVE

The purpose of this study was to assess whether condylar position, as depicted by magnetic resonance imaging, was an indicator of disc morphology and position.

METHODS AND MATERIAL

One hundred and twenty two TMJs of 61 patients with temporomandibular joint disorder were examined. Condylar position, disc deformity and degree of anterior disc displacement were evaluated by using magnetic resonance imaging.

RESULTS AND DISCUSSION

Posterior condyle position was found to be the main feature of temporomandibular joints with slight and moderate anterior disc displacement. No statistical significance was found between the condylar position, and reducing and nonreducing disc positions. On the other hand, superior disc position was found to be statistically significant for centric condylar position.

CONCLUSION

It was concluded that posterior condyle position could indicate anterior disc displacement whereas there was no relation between the position of condyle and the disc deformity.

Disk position and the bilaminar zone of the temporomandibular joint in asymptomatic young individuals by magnetic resonance imaging

OBJECTIVE

The purpose was to study the disk position of the temporomandibular joint (TMJ) in young individuals without any clinical signs or symptoms or history of internal derangement or degenerative joint disease and to study the features of the bilaminar zone of the TMJ in sagittal magnetic resonance (MR) images and the behavior of the bilaminar zone during jaw opening.

STUDY DESIGN

MR imaging examinations of 80 TMJs of 40 symptom-free healthy subjects (20 women and 20 men) with a mean age of 26.9 years formed the basis of this study.

RESULTS

In 33 of the 40 symptom-free subjects (82.5%), there was a normal relationship between disk and condyle at occlusion, whereas 5 individuals had unilateral disk displacement and 2 had bilateral disk displacement. The superior part of the bilaminar zone could be identified in all of the 40 symptom-free subjects. The inferior band of the bilaminar zone was identified bilaterally in 57.5% of individuals and unilaterally in 20%. In 9 subjects, the inferior band of the bilaminar zone could not be identified in any of the TMJs.

CONCLUSIONS

Disk displacement of the TMJ occurred in approximately 20% of the young individuals in this sample. The use of both sagittal and oblique coronal MR images is of importance for classification of the position of the disk in that the oblique coronal imaging plane rendered significant complementary information to that of the sagittal images. The identification of both the superior and the posterior band of the bilaminar zone must be considered new information. The superior band remained consistently in contact with the fossa at the open-mouth position.

Multifactorial modeling of temporomandibular anatomic and orthopedic relationships in normal versus undifferentiated disk displacement joints

STATEMENT OF PROBLEM

There is persistent dispute about the diagnostic value of hard tissue anatomic relationships in predicting temporomandibular joint disorders and normals.

PURPOSE

The goal of this study was identification of multifactorial temporomandibular hard tissue relationships that differentiate asymptomatic normal joints.

MATERIAL AND METHODS

Central section lateral tomograms of 162 female temporomandibular joints with pooled diagnoses of unilateral disk displacement with and without reduction were compared to 42 female asymptomatic normal joints using 14 linear and angular measurements and 8 ratios. A validated classification tree model was tested for accuracy with sensitivity, specificity, goodness of fit, and the amount of the log likelihood accounted for. The tree model was compared with a multiple logistic regression model and univariate testing.

RESULTS

The classification tree model consisted of 3 asymptomatic and 4 disk displacement terminal nodes consisting of interactions of condyle position with measures of fossa size and shape, of which mainly average non-extreme measurements and more frequent concentric ranges typified the asymptomatic joints. The logistic regression and univariate models also incorporated condyle position and size, but the logistic regression accounted for less of the log likelihood than the tree (23.3% vs. 32.6% Rescaled Cox and Snell R(2)). The tree and the logistic regression models were moderately good predictors for distinguishing normals from disk displacement joints (sensitivity 67.9% and 72.2%, specificity 85.7% and 76.2%, respectively). Although the univariate analysis showed that the asymptomatic joints had smaller mean fossa width to fossa depth ratios (P<.0005), shorter mean eminence length (P<.007), and more concentric to anterior mean condyle position (P<.049), overlap in most of the ranges limited the predictive value.

CONCLUSION

Within the limitations of this study, multifactorial analysis revealed that several subsets of asymptomatic temporomandibular joints could be distinguished from joints with disk displacement according to hard tissue measurements taken from central section tomograms. In general, asymptomatic normal joints were typified by interactions of less extreme ranges of fossa size, shape, and condyle position.

Multifactorial analysis of differences in temporomandibular joint hard tissue anatomic relationships between disk displacement with and without reduction in women

STATEMENT OF PROBLEM

Without multifactorial models, it is difficult to resolve whether hard tissue tomographic relationships can distinguish differences between temporomandibular joint (TMJ) internal derangement diagnoses.

PURPOSE

The purpose of this study was to use multifactorial models to examine whether there are hard tissue anatomic and orthopedic characteristics that distinguish temporomandibular joints with disk displacement with reduction from disk displacement without reduction.

MATERIAL AND METHOD

. TMJ tomograms from female patients who had unilateral disk displacement diagnosed with (n = 84) or without (n = 78) reduction were compared with the use of 14 linear and angular measurements and 8 ratios. A representative classification tree model was tested for fit with sensitivity, specificity, accuracy, and likelihood accountability, and the results were compared with a multiple stepwise logistic regression model and univariate analysis.

RESULTS

Disk displacement without reduction joints had longer mean postglenoid fossa heights (P<.0005), greater mean fossa depth (P<.017), and narrower mean absolute superior joint spaces (P<.041) than disk displacement with reduction joints (univariate t test). The classification tree had 4 terminal nodes; to differentiate the joints, it used the eminence radius and the absolute superior joint space to anterior joint space ratio subordinate to the postglenoid process height. The tree model accounted for 31.4% of the likelihood (Rescaled Cox and Snell R(2)) with 73.5% accuracy (sensitivity 82.6% and specificity 65.4%). Disk displacement without reduction joints had either deeper posterior fossa walls or posterior walls of average length combined with a superior-to-anterior joint space ratio of less than 0.83; this suggests a more open-wedge-shaped anterior joint space combined with a less-rounded articular eminence. In contrast, most disk displacement with reduction joints had shorter posterior fossa wall height combined with more equal or larger superior-to-anterior joint spaces. The logistic regression model was less accurate than the classification tree model (sensitivity 60.9%, specificity 66.7%) and accounted for only 9.9% of the likelihood (Rescaled Cox and Snell R(2)) and 63.6% accuracy. The postglenoid process height was the strongest differentiating factor in all models.

CONCLUSION

Hard tissue relationships revealed by central tomogram sections were able to model notable differences between disk displacement with and without reduction joints when examined as contingency-based multifactorial systems.

Functional occlusion: II. The role of articulators in orthodontics

Opinion is divided on whether there is a place for the use of semi-adjustable dental articulators in orthodontics. In this review we explore the validity and reproducibility of the techniques involved in mounting study models on a semi-adjustable dental articulator. We also look at the role of articulated study models in orthodontic diagnosis and treatment planning, in the finishing stages of orthodontics and in planning for orthognathic surgery. We report that each of the many stages involved in mounting study models on a semi-adjustable articulator is a potential source of error and that only if the technique is carried out with a high degree of accuracy is it worth the additional chairside time.