A Comparative Evaluation of Static and Functional Methods for Recording Centric Relation and Condylar Guidance: A Clinical Study

To evaluate and compare the centric relation and horizontal condylar guidance using interocclusal wax and extra oral Gothic arch methods and subjective evaluation of dentures thus fabricated. Centric relation and horizontal condylar guidance was recorded by using interocclusal wax and gothic arch tracing in 28 completely edentulous patients. These records were transferred to the articulator and difference in both values was recorded. After that patients were divided in two groups according to the centric relation and horizontal condylar guidance recording method used to achieve balanced occlusion. Response of the dentures was subjectively evaluated using “Woelfel subjective evaluation criteria”. Centric relation recorded by both the methods did coincide in 7.14 % of patients. Centric relation recorded by interocclusal wax was posterior to Gothic centric relation in 21.43 % of patients, and anterior to Gothic centric relation in 71.42 % patients. Gothic arch tracings gave higher mean guidance values on both the sides as compared to protrusive wax record in all the subjects, although the difference was statistically insignificant (P > 0.05). Subjective evaluation showed statistical insignificance for all the parameters in both groups. Gothic arch method records the centric relation at a more posterior position than the Static method, but it does not make any difference in clinical performance of the complete denture. Horizontal condylar guidance angle was approximately similar by both the methods.     

Comparative evaluation of sagittal condylar guidance obtained from a clinical method and with cone beam computed tomography in dentate individuals

Statement of problemProgramming semiadjustable and fully adjustable articulators involves time-consuming clinical steps which can be avoided if an accurate radiographic method can accurately determine the condylar guidance angles.PurposeThe purpose of this clinical study was to compare the sagittal condylar guidance in dentate individuals as determined by a clinical method, protrusive interocclusal record, and a radiographic method, cone beam computed tomography. If the methods show a correlation, then cone beam computed tomography can be used as a time-saving method of programming an articulator for patients requiring a cone beam computed tomography scan.Material and methodsA total of 40 participants (20 men and 20 women) within the 20 to 40 years age group were enrolled according to the inclusion and exclusion criteria. Cone beam computed tomography scans were obtained, and by using an appropriate software program, the sagittal condylar guidance was measured for both sides. A protrusive interocclusal record was obtained by using polyvinyl siloxane material. The maxillary cast of each participant was mounted on a semiadjustable articulator with a facebow transfer, and the mandibular cast was mounted with a maximum intercuspal record. The protrusive record was then transferred to the articulator for programming.ResultsThe right and left sagittal condylar guidance values obtained from both the protrusive interocclusal record and cone beam computed tomography method were comparable, with no significant differences (P>.05). The difference in condylar inclination values for both sexes obtained from both methods for both sides were not statistically different (P>.05). With increasing age, condylar inclination values obtained from both methods tended to decrease. The values for sagittal condylar guidance obtained from both methods (protrusive interocclusal record and cone beam computed tomography) were comparable and correlated.ConclusionsCone beam computed tomography measurement involves stable bony landmarks and can be standardized, whereas clinical methods are time consuming and can provide inaccurate results because of the instability of the materials used to register the maxillomandibular relationship. Thus, cone beam computed tomography can be used to obtain the sagittal horizontal guidance for programming semiadjustable and fully adjustable articulators for patients requiring a cone beam computed tomography scan.     

Condylar guidance: correlation between protrusive interocclusal record and panoramic radiographic image: a pilot study

Purpose: The purpose of this study was to compare the sagittal condylar angles set in the Hanau articulator by use of a method of obtaining an intraoral protrusive record to those angles found using a panoramic radiographic image. Materials and Methods: Ten patients, free of signs and symptoms of temporomandibular disorder and with intact dentition were selected. The dental stone casts of the subjects were mounted on a Hanau articulator with a springbow and poly(vinyl siloxane) interocclusal records. For all patients, the protrusive records were obtained when the mandible moved forward by approximately 6 mm. All procedures for recording, mounting, and setting were done in the same session. The condylar guidance angles obtained were tabulated. A panoramic radiographic image of each patient was made with the Frankfurt horizontal plane parallel to the floor of the mouth. Tracings of the radiographic images were made. The horizontal reference line was marked by joining the orbitale and porion. The most superior and most inferior points of the curvatures were identified. These two lines were connected by a straight line representing the mean curvature line. Angles made by the intersection of the mean curvature line and the horizontal reference line were measured. The results were subjected to statistical analysis with a significance level of p < 0.05. Results: The radiographic values were on average 4° greater than the values obtained by protrusive interocclusal record method. The mean condylar guidance angle between the right and left side by both the methods was not statistically significant. The comparison of mean condylar guidance angles between the right side of the protrusive record method and the right side of the panoramic radiographic method and the left side of the protrusive record method and the left side of the panoramic radiographic method ( p= 0.071 and p= 0.057, respectively) were not statistically significant. Conclusion : Within the limitations of this study, it was concluded that the protrusive condylar guidance angles obtained by panoramic radiograph may be used in programming semi‐adjustable articulators.     

A comparative study to measure the condylar guidance by the radiographic and clinical methods

PURPOSE

The study was conducted to compare the radiographic and clinical methods of measuring the horizontal condylar guidance (HCG) values.

MATERIALS AND METHODS

The condylar guidance was measured using the radiographic (CT scan) and three clinical methods i.e. the wax protrusive records, Lucia jig record and intraoral central bearing device in 12 patients aged between 20-40 years irrespective of sex. The records were taken and transferred on the semi-adjustable articulator to record the HCG values. The CT scan was taken for 3D reconstruction of the mid facial region. Frankfort horizontal plane (FHP) and a line extending from the superior anterior most point on the glenoid fossa to the most convex point on the apex of articular eminence (AE) was marked on the CT scan. An angle between these two lines was measured on both right and left sides to obtain condylar inclination angle. Three interocclusal protrusive wax and jig records were taken and transferred to the semi adjustable articulator. Three readings were recorded on each side. Similarly the records were taken and transferred to the same articulator using the intra oral central bearing device to record the readings.

RESULTS

The statistical analysis showed insignificant differences in the HCG values between the right and left sides [(P=.589 (CT), P=.928 (wax), P=.625 (jig), P=.886 (tracer)]. The clinical methods provided low Pearsons correlation values [(R = 0.423 (wax), R = 0.354 (jig), R = 0.265 (tracer)] for the right as well as the left sides when compared with the CT values. Among the clinical methods, jig and wax method showed strong level of association which is statistically significant while the intra-oral tracer showed weak association with the other two methods.

CONCLUSION

The right and left HCG values were almost similar. The CT scan showed higher HCG values than the clinical methods and among the clinical methods, values obtained from all the methods were comparable.     

Effect of interocclusal records on the condylar path of the articulator

Although there are studies on materials used for interocclusal records, there are no scientific data how the condylar path is influenced by the positional interocclusal records. The purpose of this in vitro study was to determine the effects of different interocclusal mediums on condylar inclination of the articulator. The materials selected for this experiment were: two addition type silicone pastes, two silicone putty materials and two waxes. The samples of protrusive records were performed on a Quick-Master semiadjustable articulator (FAG Dentaire). The same pre-established eminentia angles were used during the experiment for each type of materials. To improve the control of the condylar angles a protractor was mounted to the upper member of the articulator at right angels to each condylar fossa housing. A stylus moving simultaneously with the condylar fossa marked the eminentia angle on the protractor. 108 interocclusal records were performed and in 24 hours they were returned to the articulator. Then the articulator was adjusted and the settings of the eminentia angle were recorded. Numerical deviations between the pre-established and the adjusted settings in degrees were subjected to statistical analysis. The results indicated that these deviations for addition type silicones were significantly smaller than that of the other materials. The two waxes proved to be the least accurate materials. It is concluded that the condylar inclination is influenced by the properties of the registration materials, which may increase the shortcomings of the protrusive bite records.     

Evaluation of Hanau's formula in determination of lateral condylar guidance: A clinical research study

Statement of Problem:

The accuracy and reliability of the methods used for programming the semi-adjustable articulators determine the accuracy in occlusion. The current recommended average settings using the Hanau''s formula commonly used by clinicians is questionable, and thus reassessment is needed. This study was carried out to evaluate and compare the lateral condylar guidance: (1) Using the Hanau''s formula and the computerized jaw tracking device (Kinesiograph). (2) On the right and left sides using both these methods.

Materials and Methods:

A total of 20 completely edentulous patients (14 male and 6 females) within 40–60 years of age were selected. Jaw relation was recorded followed by face bow transfer. Extraoral Gothic arch tracing was recorded; three protrusive records were obtained and condylar guidance was calculated. Lateral condylar guidance was then calculated using Hanau''s formula, followed by the computerized jaw tracking device. A comparative evaluation was done of the obtained values. The same investigator worked with each of the study participants for the purpose of standardization.

Results:

The lateral condylar guidance values obtained using the Hanau''s formula ranged from 14 to 17° while those obtained using the computerized K7 jaw tracking device ranged from 8 to 40°. Bennett angle values, obtained using the jaw tracking device and Hanau''s formula showed statistically significant differences (P < 0.05) using paired t-test (at 95% confidence interval). Bennett angle values of the right and left sides found using the Hanau''s formula were almost similar. Difference in the Bennett angle values of the right and left sides were found using the jaw tracking device. However, this difference was not statistically significant (P > 0.05).

Conclusion:

Based on the results, dentist and dental technicians should consider reassessing the current recommended average settings and use of the Hanau''s formula for programming the semi-adjustable articulators.Key Words: Articulator, condylar guidance, temporomandibular joint     

A study of the acceptability of lateral interocclusal records by the Hanau H-2 articulator

The acceptability of lateral interocclusal records by the Hanau H-2 articulator was studied on 28 edentulous patients. Acceptability was determined in both right and left lateral jaw movements. Of the 56 lateral interocclusal records made, 39 (70%) were accepted by the Hanau model H-2 articulator.     

Age Changes in Horizontal Condylar Angle: A Clinical and Cephalometric Study

Determination of condylar inclination is important when restoring the occlusal surfaces of teeth. It is important to know the changing trends in horizontal condylar inclination with age so as to have an idea about the cuspal morphology. Aims and objectives: a) to determine the effect of age changes in horizontal condylar inclination using articulator method and radiographic method (cephalometry) b) to compare the values of horizontal condylar inclination obtained using articulator method with that of cephalometric method c) to ascertain the symmetry of horizontal condylar angle on both right and left side on an articulator. 40 dentulous individuals with Angle’s class I occlusion were selected for the study. They were divided into four groups Group I: 20–29 years, Group II: 30–39 years, Group III: 40–49 years, Group IV: 50–59 years. Horizontal condylar inclination was determined on right and left side for each individual using protrusive interocclusal record in a Dentatus (ARL) semiadjustable articulator. Cephalometric recording was carried out twice on the left side, once in centric occlusion position and then in protrusive position. The two radiographs were superimposed to draw a line connecting the shifting position of condylion on an acetate tracing paper. This line when joined with Frankfurt horizontal plane gives the horizontal condylar inclination. Analysis of variance (ANOVA) revealed that there was a significant difference in horizontal condylar angle values in all the four groups which were statistically significant. There is a decrease in horizontal condylar angle values from Group I to Group IV. Horizontal condylar values obtained by articulator method and cephalometric method showed no significant difference for all the four groups tested. When horizontal condylar values obtained on right and left sides of Dentatus articulator were compared there was not much of a significant difference. Horizontal condylar values showed a decreasing trend with increasing age, i.e, as age advances there is a flattening of condylar head. Both articulator and cephalometric method yielded no significantly different values and hence both the methods can be used for determining condylar inclination. The difference in values of horizontal condylar angle on right and left sides were insignificant.     

Comparison of condylar guidance setting obtained from a wax record versus an extraoral tracing: a pilot study

STATEMENT OF PROBLEM: Protrusive condylar angles can be determined by use of wax protrusive records (WPR), pantographic tracings (PT), and occlusal wear facets. These methods generate different angles in the same patient. PURPOSE: The purpose of this study was to compare the condylar inclination angles found by use of the WPR in a Hanau articulator with those found by use of the Whip-Mix PT quick-set recorder. The occlusal wear facet method was not part of this study. MATERIAL AND METHODS: Ten subjects were chosen at random from a dental school patient population. All subjects had a majority of maxillary and mandibular teeth present and according to the examination criteria used in the school's Division of Occlusion, they were healthy with no signs/symptoms of temporomandibular disorders. The WPR was accepted when it was evident that the patient had protruded straight forward at least 6 mm anterior to centric relation, as shown on the Hanau articulator by the condylar spheres having moved anteriorly an equal distance of 6 mm on both sides. The condylar inclination on the articulator was adjusted accordingly. The PT was used according to the manufacturer's directions, which included the use of an intraoral clutch adapted to the mandibular arch, connected to an extraoral facebow with bilateral inscribing pointers. A holder frame was adapted to the face with bilateral flags where the inscribing pointers traced the protrusive movement of the jaw. All the readings were in degrees. No control was used in this project. To test whether there was a significant difference between the 2 independent samples, a Mann-Whitney U test was performed (P=.01). RESULTS: The mean results for the WPR were as follow: right side (28.1 degrees, SD 8.94); left side (31.50 degrees, SD 9.73). For the PT, results were: right side (41.10 degrees, SD 7.53); left side (35.5 degrees, SD 6.43). When right and left side protrusive condylar angles were combined, the values were: WPR (29.80 degrees, SD 9.25); PT (38.30 degrees, SD 6.98). The differences on the right condylar values were significant (P=.01). There was no statistical difference on the left side. CONCLUSIONS: Within the limitations of this study, it was concluded that the PT technique yielded greater values for the protrusive condylar inclination than the WPR.     

Sagittal condylar guidance as determined by protrusion records and wear facets of teeth.

The maxillary and mandibular casts of 45 healthy and dentulous subjects, with conspicuous wear facets on canines and molars, were mounted on a semiadjustable articulator. The sagittal condylar guidance was determined by two methods: (1) using a protrusion wax interocclusal record and (2) by matching the wear facets of opposing canines and contralateral molars. There was a substantial bilateral symmetry of the right and left sagittal condylar guidance angles using both methods. There were, however, significant differences between the mean angles of the two methods, about 31 degrees (protrusion record) versus about 24 degrees (wear facets). This, in association with rather low coefficients of linear determination, suggested that the two methods of recording the sagittal condylar guidance angle were based on totally different phenomena.     

Analysis of rotation centers of various mandibular closures

Wax interocclusal records of five subjects made during three types of mandibular closing movement at various degrees of jaw opening were successively placed between mandibular and maxillary casts that were mounted on an articulator. Recording pins inserted into the lateral sides of the casts were used to record the amount of movements. The rotation centers were then calculated and the following results were obtained. (1) For the terminal hinge closure in which the mandible was guided by the chinpoint, no statistically constant rotation center was observed. (2) For the most retruded closure of the mandible in which each subject was asked to make the most retruded position by his own effort, a constant rotation center was found in two of five subjects. (3) For habitual closure of the mandible no constant rotation center was observed, and where the interocclusal distance was less than 1 mm the mandible seemed to close perpendicular to the occlusal plane.     

Jaw relation records for fixed prosthodontics

This article discusses and reviews general principles of jaw relation records, including the purpose of a jaw relation record and the concept of a tripod of vertical support with adequate horizontal stability to allow opposing dental casts to be mounted accurately on an articulator. The use of the maximum intercuspal position for the vast majority of patients is favored when the goal of restorative treatment is to maintain a patient's pretreatment intercuspation and vertical dimension of occlusion. In addition, articulator choice, purpose of a face bow, and materials for jaw relation records are discussed. Common errors in making impressions, pouring impressions,mounting casts, and making interocclusal records are elucidated, providing the practitioner important information with which to avoid inaccuracies that may lead to additional time spent making intraoral occlusal adjustments at the insertion of fixed restorations.     

A study of the acceptability of lateral records by the Whip-Mix articulator.

1. Of 50 lateral condylar settings made, 10 were not accepted by the Whip-Mix articulator. 2. An improved method of obtaining lateral interocclusal records was described. 3. The Whip-Mix articulator is considered useful in diagnosis and treatment in prosthodontic procedures if one is aware of its limitations.     

A comparison of lateral interocclusal records to pantographic tracings

Many techniques exist to record patients' lateral jaw movements, but they have not been thoroughly investigated. This study compared recordings of immediate sideshift by using a pantograph and two intraoral registration materials. Pantographs were completed on 20 healthy participants by using chinpoint guidance and a kinematic hinge axis. Three lateral interocclusal records were completed on each participant and averaged for right and left sides. The average immediate sideshift recorded by a pantograph (0.54 mm) was less than that recorded by the two intraoral registration materials. The standard deviations were similar for all materials. An analysis of variance test identified significant statistical differences between a pantograph and one of the intraoral registration materials, but not between the pantograph and the other registration material. Immediate sideshift recorded with one material compared favorably with a pantograph recording when three records using the chinpoint guidance were averaged.     

A comparison of articulator settings obtained by using an electronic pantograph and lateral interocclusal recordings

Articulator settings were obtained for two subjects 10 times in a 2-week period by using both a lateral interocclusal record technique and a Pantronic pantograph. The ORB and PSS articulator settings obtained from the two techniques were compared and the following conclusions drawn. 1. Over a 2-week period, the variance in the Pantronic pantograph ORB and PSS articulator settings was less than the variance in the setting obtained by using lateral interocclusal records. For the Pantronic pantograph technique, 95% of any ORB settings were within 2.5 degrees of the Pantronic pantograph mean and 95% of any PSS settings were within 1.9 degrees of the Pantronic pantograph mean. For the interocclusal record technique, 95% of the ORB settings made with interocclusal records were within 11.9 degrees of the mean for one subject and 13.4 degrees of the mean interocclusal records setting for the other subject. For the PSS settings, 95% of the interocclusal record settings were within 10.1 degrees of the mean setting for one subject and 11.6 degrees of the mean interoccusal record setting for the other subject. 2. In adjusting the ORB and PSS articulator settings, the maximum potential occlusal errors that may be produced by using the Pantronic pantograph are smaller than the maximum errors that may be produced in using the lateral interocclusal record technique.     

Jaw movements'' in young adult men during chewing

Jaw movements of a selected group of subjects were studied by clinical observation, examination of wax occlusal records and mounted casts, photoelectric mandibulography, and oscilloscopic tracings. Subjects were found to have substantially consistent and reproducible patterns of jaw movement during empty and functional chewing exercises. However, the individual patterns could not be predicted from analysis of occlusal status.Mean values of (1) the chewing cycle time, (2) the pause at centric occlusion, (3) maximum opening, (4) maximum movement to the right and left of the midline, and (5) maximum jaw point velocity while opening, closing, and moving to the right and left were obtained for 22 subjects chewing a single peanut on the right and the left sides. Great diversity in chewing patterns was observed, but in general, individual subjects exhibited specific and repetitive patterns.All subjects exhibited a pause in centric occlusion at the end of a closing masticatory stroke. A substantially constant jaw point velocity was observed for most of a chewing cycle when the open-close, close-open, left-right, and right-left components of jaw movements were analyzed separately.     

Relationship between condylar and incisor point displacement during habitual maximum open-close movements

SUMMARY The relationship between condylar movements and incisor point movements during habitual maximum open-close movements were studied in 10 healthy male and 10 healthy female subjects. Jaw movements were recorded by means of an opto-electronic jaw movement recording system, OKAS-3D, capable of recording the six degrees of freedom at a sample frequency of 300 Hz. The lower jaw position of the lateral pole of the condyles was found by means of palpation. In order to analyse the movements, the opening and closing path of the incisor point were divided into ten equal intervals and the corresponding condylar displacement in each interval was calculated. A displacement index was obtained by normalizing the condylar displacement with respect to the maximum condylar displacement. Due to the normalization, the displacement index is not sensitive to possible errors in the location of the lateral condylar point. A clear condylar displacement was already recorded in the first movement interval, right at the start of opening (average displacement index in the first opening interval was significantly greater than zero, P < 0.0005). The condylar displacements in the start and the end interval of opening and closing were smaller than in the intermediate movement intervals ( P < 0.00005).     

Reproducibility of lateral excursive tooth contact in a semi-adjustable articulator depending on the type of lateral guidance

The purposes of this study were (i) to compare the reproducibility of lateral tooth contacts of casts mounted in a semi-adjustable articulator when condylar guidance was set by different methods and (ii) to assess the margin of error of the variations of condylar guidance without changing lateral tooth contacts, depending on the type of lateral guidance. In subjects with different types of lateral guidance, intraoral lateral tooth contacts identified with occlusal registration strips were compared with those identified by use of a semi-adjustable articulator, setting the condylar guidance in four different ways: using protrusive wax wafers, by axiography and by adding and subtracting 5 degrees from the value of condylar guidance obtained by protrusive wax wafers. Tolerance to variations of condylar guidance without changing lateral tooth contacts was determined by increasing and decreasing the value of condylar guidance until lateral tooth contacts changed. Different ways of setting condylar guidance on a semi-adjustable articulator give rise to different values of condylar guidance in the same subject. The occlusal repercussions of these variations of condylar guidance values depend on the type of lateral guidance. Canine protection had the greatest tolerance to variations in the setting of condylar guidance without changing lateral occlusal contacts.     

Comparing condylar positions achieved through bimanual manipulation to condylar positions achieved through masticatory muscle contraction against an anterior deprogrammer: a pilot study

STATEMENT OF PROBLEM: The condylar position can vary depending on several factors. One factor is the influence of occluding teeth. If the influence from occluding teeth could be eliminated, it might be possible to evaluate the condylar position obtained from masticatory muscle contraction. PURPOSE: The purpose of this pilot study was to determine the placement of the condyles by contracted masticatory muscles without influence from occluding teeth. MATERIAL AND METHODS: For a group of 11 participants, 3 dentists were assigned, in turn, to fabricate a centric relation interocclusal record using bimanual manipulation on each member of the group. After obtaining the centric relation interocclusal records using bimanual manipulation, the records were stored in room temperature water. Subsequently, each of the 11 patients had an anterior deprogrammer fabricated and were given instructions to wear the anterior deprogrammer for 60 minutes. The anterior deprogrammer was designed with the contacting surface perpendicular to the arc of close of the mandibular incisors. In addition, the anterior deprogrammer was relined to eliminate any movement under force, and the occluding surface of the deprogrammer was free of any indentations. After wearing the deprogrammer, 4 interocclusal records (3 in a reclined position and 1 in an upright position to ensure the condylar position did not change in the upright position) were made by having the patient squeeze and close into a properly adapted, trimmed, and warmed interocclusal record. The condylar position in centric relation recorded in interocclusal records using bimanual manipulation was compared to the condylar position recorded by the contraction of the masticatory muscles against an anterior deprogrammer using a condylar position indicating device. The data were analyzed with a 2-independent-samples test of proportions, alpha=.05 (1-tail). RESULTS: The condylar positions obtained using bimanual manipulation repeated the condylar position within the 0.11-mm tolerance of the Centri-Check instrument in 33 out of 33 opportunities (100%). The condylar positions obtained by using the anterior deprogrammer technique repeated the condylar position within the 0.11-mm tolerance of the Centri-Check in 43/44 opportunities (97.7%). The sample size used in this pilot study was not large enough to detect a very small actual difference (5 percentage points or less) between the 2 methods, should such a difference exist. CONCLUSION: The results of this pilot study indicate that, without influence from occluding teeth, the contraction of the masticatory muscles places the condyles into the same position as centric relation.     

Setting the Sagittal Condylar Inclination on a Virtual Articulator Using Intraoral Scan of Protrusive Interocclusal Position and Cone Beam Computed Tomography

The articulator is a prerequisite device for the analysis of occlusion and prosthodontic treatment, and it is required to simulate patient jaw movements. This article describes the technique to obtain sagittal condylar inclination (SCI) using cone beam computed tomography (CBCT) data and intraoral scan of the protrusive interocclusal position. The SCI can be used on a virtual articulator in a computer‐aided design software, and it can assist in the fabrication of prosthesis which is harmonious with the mandibular movement of individual patient.