Centric Relation Position Research Articles

Reproducibility of the Obtained Centric Relation Records in Patients with Disc Displacement with Reduction.

ObjectiveThe aim of this study was to investigate reproducibility of the position of centric relation in patients with disc displacement with reduction.Materials and methodsThe test group included 30 subjects, diagnosed with disc displacement with reduction in right, left or both joints. The control group included 12 individuals with no signs and symptoms of temporomandibular disorders. Using chin point guidance with a jig, centric relation record was made three times by every participant, in a single session. Left and right condylar position for each centric relation record was determined and recorded using the electronic ultrasonic measuring device. The data were transferred to the computer, processed and analyzed. Condylar distances between centric relation records were measured (anteroposterior, vertical, transversal and linear values), and the data were statistically analyzed using the t and the F tests.ResultsNo statically significant difference was found between the test and the control groups. Two thirds of study participants demonstrated condylar position of the repeated centric relation recording within the area of 0.3 mm in diameter. For more than 90% of participants that area was within 0.4 mm.ConclusionsThere is no difference in reproducibility of the centric relation between patients with disc displacement with reduction and healthy temporomandibular joint individuals (p>0.05). When doing centric relation record on a patient with disc displacement with reduction there is no need for previous splint therapy and standard precautions are acceptable. The obtained results must be interpreted within the experimental group, and not projected on the other groups of temporomandibular disorders.

Utility of facebow in the fabrication of complete dentures, occlusal splints and full arch fixed dental prostheses: A systematic review.

The objective of this study is to assess the utility of facebow transfer in the fabrication of occlusal splints, complete dentures and full arch fixed dental prosthesis. A systematic review protocol was registered at PROSPERO registry, University of York, UK (CRD42016041919). Following databases were explored: PubMed, CINAHL, Cochrane, and Web of knowledge. The PICO model included participants who received occlusal splint or complete denture or full arch fixed dental prosthesis at the centric relation position. The intervention was the use of facebow transfer. Comparators were prosthesis made without using a facebow. Outcomes were the patient satisfaction of the prosthesis and the need for laboratory adjustments. Only randomized clinical trials were included in the present review. A customized data extraction pro forma was used to extract the data and assess its quality. A total of 505 articles were retrieved. On excluding duplicates, protocols, case reports, case series, narrative reviews, etc., only eight studies were selected for review. Six clinical trials on 249 complete dentures and two clinical trials on 65 occlusal splints were reviewed. No study on full arch crown and bridge work satisfied the inclusion criteria. The use of facebow did not yield a superior fit or comfort of the complete dentures or occlusal splints. Therefore, there is no evidence of the utility facebow transfer for these prostheses. However, no inference could be drawn for its utility in full arch fixed dental prosthesis as there were no studies to draw an inference.

Hinge axis - location, clinical use and controversies

The hinge axis is an imaginary line around which the condyles can rotate without translation. Terminal hinge position is the most retruded hinge position and it is significant because it is a learnable, repeatable and recordable position that coincides with the position of centric relation. There are many schools of thought regarding hinge axis. The proponents of Gnathology say that there is one transverse hinge axis common to both condyles which can be accurately located. The proponents of transographics claim that each condyle has a different transverse hinge axis and that a transograph is the only instrument that can duplicate this. Still others claim that an exact duplication of jaw movement is not possible on any machine. The aim of this article is to throw light on location, clinical use and controversies of hinge axis.

Reproducibility of Centric Relation Techniques by means of Condyle Position Analysis.

The aim of this study was to determine the reproducibility of clinical centric relation (CR) registration techniques (bimanual manipulation, chin point guidance and Roth's method) by means of condyle position analysis. Thirty two fully dentate asymptomatic subjects (16 female and 16 male) with normal occlusal relations (Angle class I) participated in the study (mean age, 22.6 ± 4.7 years). The mandibular position indicator (MPI) was used to analyze the three-dimensional (anteroposterior (ΔX), superoinferior (ΔZ), mediolateral (ΔY)) condylar shift generated by the difference between the centric relation position (CR) and the maximal intercuspation position (MI) observed in dental arches. The mean value and standard deviation of three-dimensional condylar shift of the tested clinical CR techniques was 0.19 ± 0.34 mm. Significant differences within the tested clinical CR registration techniques were found for anteroposterior condylar shift on the right side posterior (Δ Xrp; P ≤ 0.012); and superoinferior condylar shift on the left side inferior (Δ Zli; P ≤ 0.011), whereas between the tested CR registration techniques were found for anteroposterior shift on the right side posterior (ΔXrp, P ≤ 0.037) and superoinferior shift on the right side inferior (ΔZri, P ≤ 0.004), on the left side inferior (ΔZli, P ≤ 0.005) and on the left side superior (ΔZls, P ≤ 0.007). Bimanual manipulation, chin point guidance and Roth's method are clinical CR registration techniques of equal accuracy and reproducibility in asymptomatic subjects with normal occlusal relationship.

Influence of the Hinge Axis Transfer Modality on the Three-Dimensional Condylar Shift Between the Centric Relation and the Maximum Intercuspation Positions.

The purpose of the study was to determine whether the hinge axis registration and the transfer modality (facebow transfer vs. average mounting) from the subject to the articulator affect the three-dimensional condylar shift between the centric relation (CR) and the maximum intercuspation (MI) position. The study was comprised of 32 fully dentate subjects (16 male and 16 female). Only the asymptomatic participants with normal occlusal relations (Angle class I) aged 20 - 33 (mean age 22.6 ± 4.7) met the inclusion criteria. Three-dimensional condylar shift (anteroposterior, superoinferior and mediolateral shift) between the centric relation position (CR) and the maximum intercuspation (MI) position was analyzed by means of Mandibular Position Indicator (SAM Prazisionstechnik GmbH, Muenchen, Germany). The average three-dimensional condylar shift was 0.13 ± 0.12 mm for facebow transfer and 0.22 ± 0.23 mm for average mounting. There were no statistically significant differences noted between genders. The results of the Mann-Whitney test showed statistically significant differences for anteroposterior and superoinferior condylar shift (P < 0.001). However, the difference in the mediolateral shift was not statistically significant. In order to find discrepancies within the three-dimensional condylar shift, facebow transfer proved to be more accurate than the average mounting in the semi-adjustable articulator. However, the average value of three-dimensional shifts of the condyle did not differ from normal values and they did not have clinical significance. Thus, both ways of transfer modalities (facebow transfer and average mounting) in asymptomatic subjects with normal occlusion can be considered reliable.

An Efficient and Cost-Effective Technique to Construct an Intraoral Central Bearing Tracing Device.

Intraoral central bearing tracing has been shown to be a predictable way of recording and verifying centric relation position for patients. Existing tracing devices are challenging to use due to several significant clinical limitations. In comparison to commercially available counterparts, this article presents a technique that simplifies instrumentation and clinical steps to make an intraoral tracer for making centric relation records, determining occlusal vertical dimension, and detecting deflective occlusal contacts in edentulous patients.

Complete mouth rehabilitation after transposition osteotomy based on intraoral scanning: An experimental approach

This article describes the surgical and prosthodontic treatment of a patient with severe dysgnathia combined with amelogenesis imperfecta. To the authors' knowledge, this is the first treatment report to describe the application of intraoral scanning for a complete mouth reconstruction. After transposition osteotomy, the treatment included the simultaneous fabrication of antagonistic computer-aided design/computer-aided manufactured (CAD/CAM) long-term interim restorations for the maxilla and mandible and the establishment of a new centric relation position and adequate vertical dimension of occlusion. Particularly in complex situations, the major advantages of intraoral scanning can be identified as an extended magnification of the 3-dimensional digital data to control the preparation and impression at the dental office. However, the presented treatment revealed some deficiencies in the digital work flow that must be rectified. In combination with high-performance polymers, the CAD/CAM technology offers a wide range of new treatment options and simplifies the fabrication of long-term interim restorations. Although in the present treatment the esthetic and functional requirements of the patient were met, no published studies of this procedure have been based on intraoral scanning, and the approach has to be considered experimental.

The efficacy of a specific stabilization splint

Background:The use of a Tanner type stabilization splint, fabricated on a leaf gauge articulation for the treatment of patients with disc displacement without reduction, is lacking in the literature.Objectives:The purpose of the study is to collect non-controlled, therapy-related observations; in other words, to demonstrate the efficacy of this appliance for the treatment of patients with disc displacement without reduction.Methods:The study enrolled 55 patients, 5 men, and 50 women, with the clinical diagnosis disc displacement without reduction, 42 with and 13 without limited mouth opening. All patients received a splint in the musculoskeletally stable centric relation (CR) position. Mouth opening, clinical performance, and the timeframe of splint treatment were assessed.Results:For 37 patients with a disc displacement without reduction with limited opening, the largest increase in mouth opening (9·5±5·6 mm) occurred in the first week (7·9±2·5 days). No occlusal adjustment of the splint was needed during the treatment sequence. For three patients, treatment took up to 3 months (8·1%), for 13 patients, between 3 and 6 months (35·1%), and for 17 patients, within a year (45·9%), making a total of 89·1% successfully treated patients. Out of 50 patients, 29 had a total resolution of signs and symptoms, whereas 21 patients still suffered from solitary temporomandibular disorder (TMD) signs.Conclusion:A Tanner type stabilization splint, fabricated in the musculoskeletally stable CR position, appears to be an effective and efficient means for the treatment of patients with disc displacement without reduction. Its efficacy makes it eligible to be tested in a randomized controlled trial.Clinical implications:The efficacy of this specific splint, fabricated in the musculoskeletally stable CR position, makes it a promising tool to treat TMD patients with disc displacement without reduction.

Craniomandibular Disorders and Mandibular Reference Position in Orthodontic Treatment

The aim of this paper is to bring into focus the literature on the choice of the mandibular reference position in orthodontic treatment; of a particular reference to this paper is intercuspal position, centric relation position, or therapeutic position. To give a comprehensive account of the literature review on craniomandibular disorders (CMD), we have relied on books and articles using both Google Scholar and PubMed. Selection criteria included a combination of Mesh and type of article. Article classification was made by two authors, using the following structure outline: prevalence of craniomandibular disorders, its etiology and pathophysiology, occlusion and craniomandibular disorders, orthodontic treatment and CMD, and the mandibular reference position in orthodontics. An important conclusion that emerged from the present literature review is that CMD do not seem to be directly related to orthodontic treatment, and their appearance cannot be predicted or prevented by any means. Therefore, orthodontists must adopt a mandibular reference suitable to their patients and which best respects the balance existing in the stomatognathic system.

A Positional Analyzer for Measuring Centric Slide

Centric relation (CR) has been considered mainly as a position posterior to habitual occlusion or maximum intercuspation (MI). Awareness of the tooth contacts relationship in centric relation position of the mandible and diagnosing the case from this position is essential to consistently select treatment plans that will allow to treat to or very near to centric relation occlusion. Centric slide and other occlusal relationships are conceived of as positions, which can be studied in three dimensions. Clinically, the difference between the two occlusal positions namely CR and MI (centric slide) can easily be determined, but for a more precise evaluation of its length and directions, an occlusal analysis on articulator mounted casts is necessary. Study was under taken on the mounted casts of ten subjects on a semi adjustable articulator to which a stylus and recording table was devised and attached for measurement of CR-MI slide in the three planes namely anterior-posterior, medio-lateral and superior-inferior. It was found that there was a displacement from CR to MI (centric slide) in all the three planes and numerically the mean slide was 0.688±0.623, 0.261±0.627 and 0.127±0.541mm in the antero-posterior, medio- lateral and superior-inferior directions respectively. The stylus and table attachment may be an accurate indirect method to measure positional changes of the condyle in 3D.

Osteochondroma of the Mandibular Condyle

Osteochondroma of the mandibular condyle in adults can be treated by surgical excision, condylectomy followed by costochondral graft or orthognathic surgery. Such complex treatment plan may not be appropriate for patients with old age, affected with chronic osteochondroma of the condyle. In this clinical report, we present a patient with osteochondroma of the condyle treated by surgical excision. The patient's postoperative occlusion was a contraindication for orthognathic surgery because of the severe abrasion of the teeth and the chronic compensation of the dentition to the deviated mandible. Surgical excision of the lesion was carried out under general anesthesia, and the remaining condylar head was salvaged as much as possible. No graft materials or posthodontic condyle reconstruction was carried out. Because there was no occlusal stop to secure the mandible in a centric relation position of the condyle, a stabilization splint was delivered to position the condyle in a relatively stable position. The stability of the condyle position was evaluated by follow-up cone beam computed tomographic scans of the pathologic and the contralateral condyle, along with clinical factors such as occlusal contact points and mandible movements assayed by ARCUSdigma (KaVo). After significant condylar position was achieved, full prosthodontic reconstruction was performed to both the patient's and the dentist's satisfaction.

Malfunctions and the lingual technique

In adult orthodontic treatment one of the many important parameters is the identification of a working referential goal for ultimate stabilization of the dentition, which differs from the one used for children. So orthodontists must carefully evaluate all the factors that make treatment for an adult patient desirable in relation to the patient’s needs in order to make a therapeutic decision with controlled risks. As orthodontists we have available to us a certain number of reference positions from which we can make decisions that will help us to establish, maintain, and stabilize our treatment results: • Rest position and myo-centered position neither of which can actually be used because they are not reproducible. • Therapeutic position, which is defined spatially and maintained by the orthodontist. It appears that in spite the assured stability of the final result this position is quite difficult to maintain through the vicissitudes of therapy. However, orthodontists can use phenomena of adaptation to keep it stable despite its imprecision. • Position of maximum intercuspation. ‘‘This is the most fundamental position because it establishes the end point of functional movements’’ (C. M. Valentin). Although it has exceptional reproducibility, orthodontists can utilize it only in certain special cases because the attachments of the lingual technique interfere with its completion. • Position of centric relation. This is usually the position of choice during treatment because orthodontists can assess it from a point removed from the dentition and reevaluate it and make comparisons between readings taken throughout the course of therapy. Whichever of these reference points is chosen, it becomes an essential adjunct of all prosthetic, surgical, or orthodontic reconstructive therapy. That is why in our orthodontic examinations we make a note of two important reference positions that will allow us at various stages to define the maxillo-mandibular position.

Cone-beam tomography assessment of condylar position discrepancy between centric relation and maximal intercuspation

The magnitude of occasional discrepancies between the centric relation and maximal intercuspation positions remains a controversial subject. This study quantitatively evaluated the possible discrepancies in the condyle/mandibular fossa relationship between these positions using cone-beam computed tomography. Twenty young and asymptomatic volunteers were distributed equally into normal occlusion and Angle Class I, II and III malocclusion groups. They were submitted to one tomographic scan in maximal intercuspation and one in centric relation. Measurements were performed on lateral and frontal cuts of the patients' temporomandibular joints, and the data collected were compared using Student's t test at a significance level of 5%. The results showed that there were no statistically significant differences between the centric relation and maximal intercuspation positions in young and asymptomatic patients with practically intact dentitions using cone-beam computed tomography.

Assessment of antero-posterior skeletal relationships in adult Korean patients in the natural head position and centric relation

Objective: This study aimed to verify the intra-individual reproducibility of the natural head position (NHP) in adult Korean patients in the centric relation (CR) position and to prove the inter-individual variability of the Frankfurt horizontal (FH) plane and sella-nasion (SN) line compared to the true horizontal line (THL). In addition, the study aimed to investigate the correlations between linear measurements from A-point and B-point to the nasion true vertical line (NTVL) and angular measurements from A-point and B-point to the SN line. Methods: Two lateral cephalograms were taken of 116 subjects (23 males, 93 females) with CR wax bites in a NHP at a one-week interval. Results: Method errors of three variables and intraclass correlation coefficients of six parameters proved the intra-individual reproducibility of NHP (p ＜ 0.001). The angle of the FH to the THL was not significantly different from 0˚ (p ＞ 0.05), but it was clinically variable (SD 3.89o) on the inter-individual level. Conversely, the angle of the SN line to the THL was significantly different from 7˚ (p ＜ 0.05). Very low correlation was found between the linear measurements and angular measurements of A-point and B-point (p ＜ 0.01). Conclusions: The NTVL could be a useful reference line for assessing the antero-posterior position of the maxilla and mandibleof Korean adult patients in NHP and CR. (Korean J Orthod 2010;40(6):421-431)

Position of Mandibular Joint Surface in Cenrric Relation

The position of mandible in centric relation is the initial position in prosthodontic rehabilitation. This fact is especially significant today when, due to development of implantology, the use of osseointegrated prostheses is increasingly discussed. The aim of the study is to define if the peak of the articulating surface of mandible in centric relation position is directed towards the zenith of madibular fossa, or is in the retroposition. The research was conducted on macerated human sculls in anthropometric system, based on objective measuring techniques and methods. The results showed that if the zenith of mandibular fossa is determined according to the vertical line of the Frankfurt horizontal, the peak of the mandibular caput articulating surface is in retroposition. The relation of the lower joint surface to the mandibular fossa zenith is the same on both right and left side. The correlation coefficient demonstrates a high correlation between the sides, highly significant with probability level of p<0,01. If the peak of mandibular fossa is determined according to the vertical line of the Frankfurt horizontal, the peak of the articulating surface of mandibular caput is in retroposition in relation to the peak of the upper jaw surface. This original scientific work will help better understanding of x-ray analysis and understanding of relationship of TMJ surfaces, what is necessary for treatment of TMD and occlusal imbalances.

Comparative evaluation of hight tracer, Chandra tracer, intraoral tracer, functiograph and checkbite: A clinical study

PURPOSE: Centric and eccentric relations of mandible can be recorded through check bites, graphic recordings, functional recordings and cephalometrics. These records are then transferred to a semi-adjustable articulator so that it can be set to simulate the human system. This study is an attempt to compare the relative accuracy of the checkbite and graphic recordings using cephalometrics as a standard. AIMS: • To compare the efficiency of hight tracer, Chandra tracer, Conventional intraoral tracer, Functiograph and Checkbite in determining centric relation. • To compare the efficiency of hight tracer, Chandra tracer, Conventional intraoral tracer, Functiograph and Checkbite in determining horizontal condylar guidance angle on Hanau H2 articulator with the aid of both centric and eccentric records. • To compare the horizontal angle values thus obtained on the Hanau H2 articulator with horizontal angle values in cephalometric tracings. MATERIALS AND METHODS: Hight tracer, Chandra tracer, Conventional intraoral tracer, Functiograph and Checkbite were used on 10 edentulous subjects to obtain centric and protrusive records. Lateral cephalograms were made at both centric and protrusive positions with each method and the horizontal condylar values thus obtained were compared with those obtained on Hanau H2 articulator. RESULTS: • There was no statistical difference between the cephalometric and articulator values in all the five experimental methods. • There was no significant difference between Hight tracer, Chandra tracer, Intraoral tracer, Functiograph and Checkbite methods. • Ranking the experimental methods in the order of efficiency: the first was the Intraoral tracer, second being Functiograph followed by Chandra tracer, Checkbite and Hight tracer. • Checkbite alone can be used to set the horizontal angles on the articulator in edentulous subjects, clinically. • Tracings can be used as a verificatory method. • Centric relation position was found to be the same in a subject with all the experimental methods. • Each experimental method can influence the condylar path differently in the eccentric position. CONCLUSIONS: The articulator value of horizontal condylar angle was higher than cephalometric value in majority of the subjects in all the five experimental methods.

Occlusal device for diagnostic evaluation of maxillomandibular relationships in edentulous patients: A clinical technique

Identifying and recording appropriate occlusal vertical dimension (OVD) and centric relation positions during the treatment of edentulous patients is necessary for predictable and successful therapy. When alterations of existing conditions are indicated, it is beneficial for both the clinician and patient to evaluate the esthetics, phonetics, function, and comfort associated with planned changes in maxillomandibular relationships before fabricating new prostheses. A procedure used to modify existing unacceptable maxillomandibular relationships and clinically monitor the effects of these alterations prior to fabrication of definitive complete dentures is presented. Acceptance of the new OVD position by both the patient and dentist following an initial diagnostic phase is important to predictable and successful treatment.

A simplified approach to implant-supported metal-ceramic reconstruction

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

Commentary

Commentary

Mysteries of asymmetries

I am going to discuss the treatment of asymmetries, the cause of which may be dental, functional, skeletal, or combinations of the three. I will spend minimal time reviewing dental and functional asymmetries because they have been well described in the literature. A dental asymmetry diagnosed in the mixed or transitional dentition should be intercepted early to establish more symmetric maxillary and mandibular dental arches. Orthodontic objectives may include maintaining or regaining arch length or correcting significant dental asymmetries through tooth movement. In the permanent dentition, dental asymmetries are corrected through tooth movement. Difficulty arises when the maxillary dental midline is coincident with the patient’s facial midline and the asymmetry is in the mandibular arch, which is often the case. Alteration of the well-positioned maxillary arch by treating or matching it to the asymmetric mandibular arch may result in esthetic compromise. The limit of maxillary midline deviation found to be esthetically acceptable to patients is approximately 2 mm on either side of the patient’s facial midline. For this reason, mandibular permanent tooth removal or opening space for prosthetic replacement of an additional mandibular tooth may be necessary to resolve the asymmetry in the mandibular arch. Functional asymmetries may be diagnosed by accurately determining if the patient presents with a discrepancy between centric relation and maximum intercuspal position. If a functional asymmetry is diagnosed in the mixed dentition, interception should be instituted as early as is practical to establish more ideal maxillary skeletal width and to eliminate the functional mandibular shift. The objective should be to establish coincidence of dental midlines with each dental midline centered on their respective skeletal bases while eliminating the functional component of the malocclusion. After this first phase of maxillary sutural expansion, the clinician