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The chinpoint-guidance technique, using an anterior programmer, as performed in this study, seems to be a replicable method of locating centric relation. Sequential registration of centric relation was repeatable in 60% of the patients studied. The average variability found in 40% of the patients of this study was about +/- 0.20 mm at the level of the condyles.
Casts of 42 patients free from temporomandibular joint problems were mounted on an articulator in centric relation contact position. The movement of the horizontal axis of rotation was measured when the casts were moved from centric relation contact position to the intercuspal position. Measurements of the vertical and horizontal movements of the incisal pin were also made during this movement. There was a highly significant correlation between the movement of the horizontal axis in the horizontal plane and the ratio of vertical to horizontal movement as measured at the incisal pin. The greater this ratio was, the smaller the horizontal movement of the axis was; the smaller the ratio (the larger the horizontal component) was, the larger was the horizontal movement of the axis. The clinical implications are discussed.
To obtain centric relation and program recordings, a universal jig was made to be molded after adjustment to the upper incisors by means of dental plaster. The jig can be produced by means of an autopolymerizing resin mold based on the wax model. Once the jig is in position, the patient is asked to produce left and right lateral movements until muscular relaxation is obtained. This allows centric relation to be recorded by whatever method use. After plaster has been injected on the occlusal surfaces of the teeth, the patient is asked to close his jaws on the jig and to perform either a propulsion movement or left- or right-lateral movement so as to obtain two plaster "bites" ready for the programming of semiajustable articulators.
The "universal jig" described in a previous article was tested on 10 patients to check for reliability. The recording of centric relation by this method was compared with Lucia's method of recording centric relation. The results of three series of three recordings were analyzed. The influence of the universal jig on rear-determinant movement was measured by two pantographic recordings, one enabling occlusion to take place, the other using the universal jig. The results were analyzed and demonstrated that the universal jig is a reliable means of simplifying the setting up of models and the programming of semiadjustable articulators.
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.
Laminagraphs were made of each temporomandibular joint of 20 subjects (1) with the mandible forcefully retruded to centric relation and (2) with the mandible positioned by a closing force while an anterior guidance prosthesis was being used. The radiographs were compared by measurements of condylar position; results indicated the condyles to be significantly more superior in the glenoid fossa when anterior guidance was used. The difference in anterior-posterior positioning of the condyles appeared to occur randomly. Measurements of the joint spaces with the mandible in centric relation using anterior guidance indicated that mandibular condyles were not centered in the fossae. There seemed to be a range in the size of the space that could be considered normal.
Cephalometric analyses were made of forty-six preorthodontic patients with the mandibular teeth in maximum intercuspation. A Centric-Ceph was used and the analysis was repeated on these patients with the mandible in centric relation. The following conclusions are drawn: 1. No clinically useful prediction may be made from cephalometric radiographs concerning the amount of mandibular deflection from centric relation to maximum intercuspation of teeth. 2. There are differences in cephalometric measurements with the mandible in the two different positions. However, with the exception of a few cases, the differences are slight. 3. The individual cases that have the largest discrepancies tend to be Class II malocclusion cases. The orthodontist should be aware of those cases and be prepared to articulate them for diagnosis.
This study addresses the reproducibility of the centric relation, or CR, position. Using bimanual manipulation, several dentists were randomly assigned to one of five patients to clinically determine CR and record this position by using the same wax recording technique. These bite records, which were then analyzed by using the Denar Centri-Check marking system (Teledyne Water-Pik), were found to capture condylar positions with a maximum variation of 0.1 millimeter, as measured within the tolerances of the Denar Centri-Check.
Many orthodontists today are using diagnostic casts mounted in centric relation (CR) because they can reveal a completely different malocclusion than what is seen in maximum intercuspation (MI). The CR to MI slide can be measured at the condyles using a semi-adjustable articulator and a condylar position indicator device (CPI). However, before planning treatment from casts mounted in CR, the reliability of the method must be established. Therefore, the purposes of this investigation were: i) to determine the reproducibility, measured with the CPI, of the two-piece wax CR bite registration technique as described by Roth; ii) to determine the direction of the centric slide; iii) to determine differences in overjet measured from CR and MI and; iv) to evaluate the location of the initial tooth contacts in CR. The condylar displacements for 39 subjects were measured in vertical and horizontal components from mounted models. A CR bite registration was taken five times (approximately every five days) and used to remount the lower cast and record the data five times. Since there was not a significant difference between the five CPI readings (p > .05), the Roth CR bite registration is highly reproducible. The condyle moved inferiorly with a small distal component from CR to MI. A statistically significant difference (p < .001) was found in the overjet measurements between CR and MI. Thirty six out of 39 subjects had an initial tooth contact in CR on the most posterior tooth.
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For patients who require complex fixed prosthodontic oral rehabilitation, recording an accurate centric relation is often a difficult procedure. A minimal number of abutment teeth or implants may not offer adequate support for the occlusal registration material. In the described technique, Triad tray material is used as an occlusal registration supporting tray. This procedure is accurate and convenient for the restorative dentist.
The purpose of this study was to compare the electromyographic activity of masticatory muscles (temporal and masseter) with the use of an anterior repositioning splint and a centric relation superior repositioning splint. Twenty-six consecutive patients, who referred with the chief complaint of temporomandibular pain and/or headache were selected from one of the author's practices. All these subjects were diagnosed as having internal derangement of the temporomandibular joint. Ten normal subjects were used as controls. Surface electromyographic recordings were taken of each subject prior to the beginning of clinical therapy for the patients. The results show significantly less masseter and temporal muscle activity with anterior repositioning splint therapy compared to the centric relation superior repositioning splint therapy.
Measurement of the influence of the degree of applied force on the resulting retruded border position of the mandible established that the position varied significantly in all three dimensions according to variation in the amount of force. On the basis of the analysis of the t-test (sampling error of 8%), it can be concluded that increasing the manipulative force on the mandible in the general male population will result in a significant three-dimensional increase in the distance from centric occlusion to centric relation. The measurement data document the variability of the retruded centric relation position according to the different amounts of applied retrusive force. The data question the choice of the retruded border position on the basis of its clinical repetitiveness.
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When constructing a complete denture, the correct vertical dimension of occlusion (VDO) and centric relation (CR) can be difficult to determine. The aim of this study was to compare the swallowing technique used to determine the maxillomandibular relationship with a conventional technique. Fifteen edentulous patients were selected, each having a complete denture. The VDO and CR were assessed using acrylic base plates and a Boley gauge. First, the VDO was established by means of the vertical dimension of rest (VDR) and interocclusal rest space, and the CR was obtained by mandibular manipulation. Secondly, the VDO and the antero-posterior mandibular position were determined using swallowing. All measurements were repeated three times and the average was calculated. The results showed that (i). the VDO determined by means of the swallowing method was reproducible and significantly higher than the one established from the VDR (P < 0.01), and (ii). the swallowing position was located 2 mm anterior to CR (P < 0.01) and was moderately reproducible. This study suggests that swallowing can be used to determine the vertical position but no as a reference position in the sagittal plane.
The present study assessed condylar displacement between initial maximal habitual intercuspation (MHI) and centric relation (CR), recorded after using a deprogramming occlusal splint for an average period of 7.8 +/- 2.1 months prior to any orthodontic treatment. The sample consisted of 22 subjects, 11 male and 11 female, with an average age of 14.2 +/- 1.4 years, with Class II malocclusion and with no apparent signs or symptoms of temporomandibular dysfunction (TMD). Condylar displacement was measured using a Panadent axis position indicator in decimal fractions of a millimeter. The original mean vertical displacements and the corresponding standard deviations were 4.24 +/- 2.53 mm and 3.86 +/- 2.72 mm, respectively, for the right and left sides. Because a significant negative correlation was observed between original condylar displacements and age factors, the displacement values were statistically adjusted to 2.74 +/- 2.00 mm and 2.44 +/- 1.93 mm. On the horizontal plane, the mean displacements measured were -0.72 +/- 1.53 mm on the right side and -0.51 +/- 1.98 mm on the left. The mean displacement on the transversal plane was 0.03 +/- 0.87 mm. A comparison between these values and those observed in non-deprogrammed groups, as well as those published in the related literature, indicates that use of occlusal splints results in greater mean condylar displacement values, especially vertically, between CR and MHI positions, which contributed to a more accurate orthodontic diagnosis.
The authors studied the lateral positional desviations of the mandible, in relation to the facial median line in 30 (thirty) full edentulous patients, with the purpose to verify the influence of the unstrained guided (chinpoint guidance) and deglutition methods for the determination of centric relation. According the results obtained they conclude that the unstrained guided method produced a mandibular lateral desviation with a mean value of the 0.752 mm and in the deglutition method the mean value observed was 1.109 mm. The statistical analysis of the results revealed for the unstrained guided method a proportion of the "points" to the right and left of the median line not statistically significant, while for the deglutition method the difference was statistically significant at a level of 5%.
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