Dental Science - Original Article A newer technique to program a semi adjustable articulator R. Venkateshwaran, Suma Karthigeyan1, P. S. Manoharan2, Jagadish Konchada3, Manikandan Ramaswamy4, Bhuminathan
Departments of Prosthodontics, Sree Balaji Dental College, Bharath University, Pallikaranai, Chennai, 1 Rajah Muthaiah Dental College, Chidambaram, 4 KSR Dental College, Erode, Tamil Nadu, 2 Indra Gandhi Dental College, Puducherry, 3 Sree Sai Dental College and Research Institute, Srikakulam, Andra Pradesh, India Address for correspondence: Dr. R. Venkateshwaran, E‑mail: dr.venkateshwaran@ gmail.com Received : 30-03-14 Review completed : 30-03-14 Accepted : 09-04-14
ABSTRACT Introduction: The difficulty in reproducing accurate angle of condylar guidance in semi‑adjustable articulators. Purpose: The purpose of this study was to determine the correlation between the angle of horizontal condylar inclination obtained on a semi‑adjustable articulator and the corresponding angle traced on a temporomandibular joint (TMJ) radiograph in completely edentulous subject. Materials and Methods: The horizontal condylar inclination angle was obtained in a semi‑adjustable articulator by means of height tracer (extra oral tracing device) and interocclusal records to program the articulator in 21 subjects. TMJ radiograph were recorded by the same operator with same orthopantomogram (OPG) machine (planmeca). Tracings of inclines of articular eminence on the radiograph were compared with the angle obtained on a semi‑adjustable articulator. Each measurement was made using manual methods of measuring angle. The results were subjected to the Pearson correlation statistical analysis (α =0.01). Results: The outline of the articular eminence in a TMJ tomogram radiographic image was identified and traced. A significant correlation was found between the horizontal condylar inclination on a semi‑adjustable and the corresponding TMJ tomogram radiographic image for both right (R = 0.789; P = 0.001) and left (i = 0.747; P = 0.004) sides. Conclusion: The articular eminence traced on a TMJ tomogram image represents the horizontal condylar inclination with a mean difference of 5° in 21 subjects evaluated.
KEY WORDS: Horizontal condylar inclination, Programming, TMJ tomogram
I
n completely edentulous, radiographic image of the slopes of articular eminence on a TMJ tomogram when traced can be used in programming the semi‑adjustable articulator. A semi‑adjustable articulator allows adjustment to replicate average mandibular movements Glossary of prosthodontic terms.[1] It is possible only if the degrees of anatomical slopes are accurately recorded. The exact replication of mandibular movements has been a clinical challenge in order to achieve Access this article online Quick Response Code:
Website: www.jpbsonline.org DOI: 10.4103/0975-7406.137421
a perfectly harmonized occlusion. The anatomic slopes of articular eminence are represented as the horizontal condylar inclination in the articulator. These programming are done by means of using protrusive and lateral inter occlusal records.[2] Arbitrary setting of the condylar elements will provide an entirely satisfactory representation of condylar movements.[2] Numerous studies have shown the inconsistency in recording and reproducing these angles in a semi‑adjustable articulator.[3,4] The setting condylar inclination at a flatter than the average value to ensure disocclusion of the posterior teeth during excursions.[5] Interocclusal record material used in programming the articulator has also shown variation up to 21-64°.[6] The individual inclination of the eminence is very steep or flat, guidance obtained from the average value settings may differ sufficiently to cause problems in achieving particular clinical objectives, such as posterior disocclusion or balanced occlusion. The use of additional aids, such as dynamic registration or imaging, may resolve this potential problem.
How to cite this article: Venkateshwaran R, Karthigeyan S, Manoharan PS, Konchada J, Ramaswamy M, Bhuminathan. A newer technique to program a semi adjustable articulator. J Pharm Bioall Sci 2014;6:S135-9.
Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
S135
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
Materials and Methods A study was conducted at the Department of Prosthodontia, Rajah Muthiah Dental College and Hospitals, Annamalai University. 21 subjects requiring complete denture treatment were chosen randomly from the outpatient department. The inclusion criterion was patient should have good neuromuscular coordination to produce good tracing of mandibular border movements. All steps of complete denture procedures were done. A tentative jaw relation was performed and the maxillary cast was oriented to the articulator using a Hanau spring bow. Using the nick and notch method a static record of centric relation was obtained using Zinc Oxide Eugenol (ZOE) impression paste as interocclusal recording material. Once, the cast was oriented in articulator. Extra oral tracer height tracing device was used in this study. The patient was trained for tracing of mandibular border movements in the way as prescribed by Ney mandibular excursion guide. The completely edentulous subjects were trained for tracing of mandibular movement until a sharp arrow point tracing was obtained. Measuring 6 mm from the apex of the tracing a point is marked over the transparent sheet and this will represent the protrusive position. Once this is accomplished nick are made in the occlusal rim of both maxilla and mandible correspondingly in canine and molar region. Then the surface of the occlusal rim is coated with petrolatum and using the polyvinyl siloxane material (3M CAD BITE, ESPE, Virtual CAD bite registration material, Ivoclar, Zurich, Switzerland) as an interocclusal record centric record is obtained [Figure 1]. Then the patient is asked to close the mandible in a forward position to represent the protruded position of mandible such that the stylus is positioned on the 6 mm marking on the tracing plate. Interocclusal record material is injected to obtain a protrusive record. The interocclusal record material flows easily and should be rigid on setting.
Figure 1: Centric record and protrusive record
Figure 2: Protrusive record in position to program the articulator
Once the protrusive and centric records have been obtained, these records are used to program the semi‑adjustable articulator using Lauritzen’s split cast technique [Figure 2]. With the centric record in position, the cast oriented and articulated in exact centric position. Using the protrusive record the articulator is programmed to determine the horizontal condylar inclination. Once, the required horizontal condylar inclination has been determined in an articulator. Then the Bennett angle was obtained using the formula L = H/8 + 12.
Figure 3: Positioning light grid on patient
Then the patient is referred to Department of Oral Medicine and Radiology for temporomandibular joint (TMJ) tomogram. Radiographs were made at 70 Kv at a fixed distance in a planmeca radiograph machine. Cassettes were loaded with OPG film and the patient was positioned in the machine using head positioner. The positioning of the patient head was standardized using the positioning light grid in the machine [Figure 3]. This grid was designed to be parallel to Frankfort horizontal plane (FHP) in the patient. The anteroposterior positioning of the head was based on the correction scale provided by the manufacturer. The position of the head was confirmed with
the grid lines in the machine as the crossing point of the light is to be focused on the tip of the nose. In the midline, the mid nasal and anterior nasal spine were used to vertically align the sagittal plane. The exposure for radiograph was done at 70 Kv and 68 Kv at 10 mA in both open mouth and closed mouth position, respectively for increased contrast between the two positions. All radiographs were made by the same operator at the same time and with same panaromic radiographic unit. TMJ tomogram was made of each subject with the FHP and upper border of radiograph parallel to the floor. Due to circular
S136
Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
rotation of the radiographic recorder, this results in the upper border of radiograph being parallel to the FHP image. Once the tomograms were obtained, tracing papers were attached to the radiograph. Tracings were made of the images of each radiograph on parchment paper along the border of slopes of articular eminence. Horizontal reference lines were drawn parallel to the upper border of radiograph, contacting, and identifying the most superior and inferior point of each curve. The outline of each curvature and the flat reference line were traced. On tracing a line was drawn connecting the most superior and inferior points of curvature representing the mean curvature line. These two points were connected by a straight line representing a mean curvature line [Figures 4 and 5]. Angles made by the intersection of mean curvature line and the horizontal reference line (FHP) were measured. Each measurement was repeated twice by the operator. Data were subjected to Pearson’s correlation statistical analysis.
Results The radiographic image of the outline of articular eminence was seen distinctly in a TMJ tomogram. The outline if this was traced to obtain the angle of horizontal condylar inclination of the respective side and compared with the values obtained after programming the articulator. Radiographic values were on average 5° greater than anatomic values [Table 1]. From the correlation analysis in the following results are arrived. Among the 21 subjects, significant correlation was found between the angles obtained in the articulator to that of the corresponding radiographic image. The calculation of articulator value versus TMJ value of right and left in the right the correlation value (r) is 0.789 and 0.747 at the level of 1%, respectively. The calculated value is higher than the table value and significant at 1% level. Hence, the angle obtained in articulator versus TMJ tomogram is very closely correlated. Hence, there is no significant variation among the both views [Table 2]. From the descriptive analysis in the following results are arrived. The 21 respondents are taken into the analysis calculation of the mean value of angle in articulator left is 25.714, standard deviation value is 10.159 and standard error is 1.822. Condylar inclination in TMJ tomogram view left value of mean 30.476 and standard deviation 8.352 in the same standard error (1.822) [Table 3].
Figure 4: Tracing done on a temporomandibular joint tomogram using a parchment paper Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
From the descriptive analysis in the following results are arrived. The 21 respondents are taken into the analysis calculation of articulator right value of the mean is 25.238, standard deviation value is 9.417 and standard error is 1.721. Condylar inclination in TMJ tomogram view right value of mean 30.476 and standard deviation 7.890 in the same standard error (1.721) [Table 4].
Discussion Among the 21 subjects, significant correlation was found between the angle obtained on the articulator and the TMJ tomogram radiographic image. The Pearson’s correlation analysis test was conducted at a confidence interval of 99%. The results show a higher correlation (r) value of articulator versus TMJ tomogram on the right and left as 0.789 and 0.747, respectively. This shows that the angles obtained on the articulator are very closely correlated to that obtained on a TMJ tomogram radiograph. There was statistically no significant variation in horizontal condylar inclination angle obtained from both methods. The high correlation value shows that it can be used as a reliable tool in programming the articulator. In terms of difference in horizontal condylar inclination angle, a mean difference of 5° was obtained between the angles obtained on an articulator to that of the TMJ tomogram. The mean value of error obtained between the left side and right side of the articulator and TMJ tomogram was 4.7° and 5.2°, respectively. Among all TMJ imaging technique, TMJ tomogram is a specialized view for imaging TMJ. It represents the composite sagittal inclination of the articular eminence of both sides in open mouth and closed mouth position. TMJ tomogram presents better image quality, as all other forms of radiographic visualization of TMJ had overlap of the image to some extent. The controlled radiation exposure at proper interval ensures that there is no image overlap and the TMJ alone is radiographed on the film. Gilboa et al.[7] have reported that the radiographic outline of the articular fossa and articular eminence provided an accurate representation of the equivalent outline in 25 human skulls
Figure 5: Angles obtained from temporomandibular joint tomogram radiograph S137
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
Table 1: The average angles, standard deviation between mean curvature line and the reference line (FHP) on the radiograph and in the subject
supporting the bases in order to achieve uniform simultaneous contact of denture.
Condylar inclination
Mean
Standard deviation
N
Articulator right Articulator left TMJ tomogram right TMJ tomogram left
25.2381 25.7143 30.4762 30.4762
9.41756 10.15944 7.89062 8.35236
21 21 21 21
FHP: Frankfort horizontal plane, TMJ: Temporomandibular joint
Table 2: The correlation between the angle of inclination in articulator and TMJ tomogram radiograph Condylar inclination
n
r
Significant at 0.01%
Articulator right versus TMJ tomogram right Articulator left versus TMJ tomogram left
21
0.789**
0.000
21
0.747**
0.000
**Correlation is significant at the 0.01 level (one‑tailed, Pearson correlation). TMJ: Temporomandibular joint
Table 3: Descriptive statistics among the condylar inclination in articulator left versus TMJ tomogram view left n
Mean
SD
Standard Degree error error
Condylar inclination 21 25.7143 10.15944 1.82263 4.7619 in articulator left and 21 30.4762 8.35236 condylar inclination in TMJ tomogram view left TMJ: Temporomandibular joint, SD: Standard deviations
Table 4: Descriptive statistics among the condylar inclination in articulator right and TMJ tomogram right n
Mean
SD
Standard Degree error error
Condylar inclination in 21 25.2381 9.41756 1.72187 5.2381 articulator right and 21 30.4762 7.89062 condylar inclination in TMJ tomogram view right SD: Standard deviation, TMJ: Temporomandibular joint
with a mean difference in inclination of 7°. Images in a TMJ tomogram provide composite sagittal representations of the skeletal structures. TMJ tomogram presents better image quality and outline of the articular eminence of the temporal bone without any image overlap. A variety of interocclusal record materials are used in recording horizontal condylar inclination, are impression plaster, polyvinyl siloxane, waxes, acrylic resin and ZOE paste. Inter occlusal record even though they are considered as the most ideal way of programming the articulator. Preti et al. have reported that average interocclusal registration values of the condylar guidance inclination vary from 21° to 64°. Various interocclusal record material has been used in the past, the difficulty in recording wax inter occlusal record was uneven softening and uneven thickness of the recording material. Boucher recommends that the centric relation should be made with minimal pressure to prevent displacement of the tissues
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The Gothic arch tracing is considered as the most ideal method in programming the articulator. This method has some minor drawbacks like, the positioning of the tracer doesn’t allow the lip to be passive and hinders the rest position of the mandible, excessively resorbed ridges, flabby ridges, inadequate inter arch distance, large tongue. In subjects with TMJ arthropathy, there are chances of obtaining aberrant tracing that are faulty. These faulty tracings may lead to results that do not represent the actual horizontal condylar inclination of the patient and has no significance in programming the articulator. The temporomandibular X‑ray film reproduces the actual form and angles of the osseous structure of the joint. On the other hand, the functional registrations indicate the condylar path angles by means of the path traversed by the condyle along the slopes of the articular eminence. In recording horizontal condylar inclination errors up to 21-64° has been observed among the same operators, technique and material. By examining the angle of the osseous structure of the joint directly on the film, and making a transfer from the film to the instrument, a more specific condylar path angle can be determined. The articular eminence inclination in the radiographic image was traced from the most superior to the most inferior points of curvature representing mean inclination of curve. This may be different from guiding inclination with approximately 4-6 mm of protrusion, which is clinically significant range of protrusion and condylar guidance. When dynamic extraoral tracings are used, the starting point (centric relation), individual curved path, and eccentric position are recorded. With static records, only the centric relation and eccentric positions are recorded, the midpoint of the excursion produces the maximum error with a straight condylar slot. The maximum difference between a straight condylar path and one that has a 1/2 inch radius is 0.4 mm. A maximum condylar error of 0.4 mm produces a 0.2 mm error at the second molar. The sensitivity of the Hanau Wide‑Vue 183-2 closed tract semi‑adjustable articulator is of the order 5°. From the values obtained a mean difference of 5° was obtained between the angles obtained on an articulator to that of the TMJ tomogram. The mean value of error obtained between the left side of the articulator and TMJ tomogram was 4.7° and on the right side it was 5.2°. This shows that the 5° error is minimal or almost nil compared to other methods of recording horizontal condylar inclination. The current study concluded that TMJ tomogram accurately represents the outline of the articular eminence and the angle of the slopes of articular eminence traced on it can be used as an aid in setting the condylar guidance inclination on a semi‑adjustable articulator. Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
Conclusion The radiographic outline of the articular fossa and articular eminence provided an accurate representation of the equivalent outlines in 21 subjects with a mean difference in inclination of 5°. The image of the articular eminences in a TMJ tomogram may be used to provide an indication of the degree of inclination of the articular eminence and may be of value as an aid in setting the condylar guidance in semi‑adjustable articulators. A new method for programming the articulator has been suggested in this study that is more reliable, repeatable, ease of use with minimal drawbacks.
References 1. 2.
Brady AP, McDevitt L, Stack JP, Downey D. A technique for magnetic resonance imaging of the temporomandibular joint. Clin Radiol 1993;47:127‑33. Eriksson A, Ockert‑Eriksson G, Lockowandt P, Eriksson O. Clinical
Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
3. 4.
5. 6. 7.
factors and clinical variation influencing the reproducibility of interocclusal recording methods. Br Dent J 2002;192:395‑400. Celar AG, Tamaki K. Accuracy of recording horizontal condylar inclination and Bennett angle with the Cadiax compact. J Oral Rehabil 2002;29:1076‑81. de Freitas A. A comparison of the radiographic and prosthetic measurement of the sagittal path movement of the mandibular condyle. Oral surgery, oral medicine, and oral pathology 1970;30:631‑8. Pullinger AG, Solberg WK, Hollender L, Guichet D. Tomographic analysis of mandibular condyle position in diagnostic subgroups of temporomandibular disorders. J Prosthet Dent 1986;55:723‑9. Pullinger AG, Hollender L, Solberg WK, Petersson A. A tomographic study of mandibular condyle position in an asymptomatic population. J Prosthet Dent 1985;53:706‑13. Gilboa I, Cardash HS, Kaffe I, Gross MD. Condylar guidance: Correlation between articular morphology and panoramic radiographic images in dry human skulls. J Prosthet Dent 2008;99:477‑82.
Source of Support: Nil, Conflict of Interest: None declared.
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Departments of Prosthodontics, Sree Balaji Dental College, Bharath University, Pallikaranai, Chennai, 1 Rajah Muthaiah Dental College, Chidambaram, 4 KSR Dental College, Erode, Tamil Nadu, 2 Indra Gandhi Dental College, Puducherry, 3 Sree Sai Dental College and Research Institute, Srikakulam, Andra Pradesh, India Address for correspondence: Dr. R. Venkateshwaran, E‑mail: dr.venkateshwaran@ gmail.com Received : 30-03-14 Review completed : 30-03-14 Accepted : 09-04-14
ABSTRACT Introduction: The difficulty in reproducing accurate angle of condylar guidance in semi‑adjustable articulators. Purpose: The purpose of this study was to determine the correlation between the angle of horizontal condylar inclination obtained on a semi‑adjustable articulator and the corresponding angle traced on a temporomandibular joint (TMJ) radiograph in completely edentulous subject. Materials and Methods: The horizontal condylar inclination angle was obtained in a semi‑adjustable articulator by means of height tracer (extra oral tracing device) and interocclusal records to program the articulator in 21 subjects. TMJ radiograph were recorded by the same operator with same orthopantomogram (OPG) machine (planmeca). Tracings of inclines of articular eminence on the radiograph were compared with the angle obtained on a semi‑adjustable articulator. Each measurement was made using manual methods of measuring angle. The results were subjected to the Pearson correlation statistical analysis (α =0.01). Results: The outline of the articular eminence in a TMJ tomogram radiographic image was identified and traced. A significant correlation was found between the horizontal condylar inclination on a semi‑adjustable and the corresponding TMJ tomogram radiographic image for both right (R = 0.789; P = 0.001) and left (i = 0.747; P = 0.004) sides. Conclusion: The articular eminence traced on a TMJ tomogram image represents the horizontal condylar inclination with a mean difference of 5° in 21 subjects evaluated.
KEY WORDS: Horizontal condylar inclination, Programming, TMJ tomogram
I
n completely edentulous, radiographic image of the slopes of articular eminence on a TMJ tomogram when traced can be used in programming the semi‑adjustable articulator. A semi‑adjustable articulator allows adjustment to replicate average mandibular movements Glossary of prosthodontic terms.[1] It is possible only if the degrees of anatomical slopes are accurately recorded. The exact replication of mandibular movements has been a clinical challenge in order to achieve Access this article online Quick Response Code:
Website: www.jpbsonline.org DOI: 10.4103/0975-7406.137421
a perfectly harmonized occlusion. The anatomic slopes of articular eminence are represented as the horizontal condylar inclination in the articulator. These programming are done by means of using protrusive and lateral inter occlusal records.[2] Arbitrary setting of the condylar elements will provide an entirely satisfactory representation of condylar movements.[2] Numerous studies have shown the inconsistency in recording and reproducing these angles in a semi‑adjustable articulator.[3,4] The setting condylar inclination at a flatter than the average value to ensure disocclusion of the posterior teeth during excursions.[5] Interocclusal record material used in programming the articulator has also shown variation up to 21-64°.[6] The individual inclination of the eminence is very steep or flat, guidance obtained from the average value settings may differ sufficiently to cause problems in achieving particular clinical objectives, such as posterior disocclusion or balanced occlusion. The use of additional aids, such as dynamic registration or imaging, may resolve this potential problem.
How to cite this article: Venkateshwaran R, Karthigeyan S, Manoharan PS, Konchada J, Ramaswamy M, Bhuminathan. A newer technique to program a semi adjustable articulator. J Pharm Bioall Sci 2014;6:S135-9.
Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
S135
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
Materials and Methods A study was conducted at the Department of Prosthodontia, Rajah Muthiah Dental College and Hospitals, Annamalai University. 21 subjects requiring complete denture treatment were chosen randomly from the outpatient department. The inclusion criterion was patient should have good neuromuscular coordination to produce good tracing of mandibular border movements. All steps of complete denture procedures were done. A tentative jaw relation was performed and the maxillary cast was oriented to the articulator using a Hanau spring bow. Using the nick and notch method a static record of centric relation was obtained using Zinc Oxide Eugenol (ZOE) impression paste as interocclusal recording material. Once, the cast was oriented in articulator. Extra oral tracer height tracing device was used in this study. The patient was trained for tracing of mandibular border movements in the way as prescribed by Ney mandibular excursion guide. The completely edentulous subjects were trained for tracing of mandibular movement until a sharp arrow point tracing was obtained. Measuring 6 mm from the apex of the tracing a point is marked over the transparent sheet and this will represent the protrusive position. Once this is accomplished nick are made in the occlusal rim of both maxilla and mandible correspondingly in canine and molar region. Then the surface of the occlusal rim is coated with petrolatum and using the polyvinyl siloxane material (3M CAD BITE, ESPE, Virtual CAD bite registration material, Ivoclar, Zurich, Switzerland) as an interocclusal record centric record is obtained [Figure 1]. Then the patient is asked to close the mandible in a forward position to represent the protruded position of mandible such that the stylus is positioned on the 6 mm marking on the tracing plate. Interocclusal record material is injected to obtain a protrusive record. The interocclusal record material flows easily and should be rigid on setting.
Figure 1: Centric record and protrusive record
Figure 2: Protrusive record in position to program the articulator
Once the protrusive and centric records have been obtained, these records are used to program the semi‑adjustable articulator using Lauritzen’s split cast technique [Figure 2]. With the centric record in position, the cast oriented and articulated in exact centric position. Using the protrusive record the articulator is programmed to determine the horizontal condylar inclination. Once, the required horizontal condylar inclination has been determined in an articulator. Then the Bennett angle was obtained using the formula L = H/8 + 12.
Figure 3: Positioning light grid on patient
Then the patient is referred to Department of Oral Medicine and Radiology for temporomandibular joint (TMJ) tomogram. Radiographs were made at 70 Kv at a fixed distance in a planmeca radiograph machine. Cassettes were loaded with OPG film and the patient was positioned in the machine using head positioner. The positioning of the patient head was standardized using the positioning light grid in the machine [Figure 3]. This grid was designed to be parallel to Frankfort horizontal plane (FHP) in the patient. The anteroposterior positioning of the head was based on the correction scale provided by the manufacturer. The position of the head was confirmed with
the grid lines in the machine as the crossing point of the light is to be focused on the tip of the nose. In the midline, the mid nasal and anterior nasal spine were used to vertically align the sagittal plane. The exposure for radiograph was done at 70 Kv and 68 Kv at 10 mA in both open mouth and closed mouth position, respectively for increased contrast between the two positions. All radiographs were made by the same operator at the same time and with same panaromic radiographic unit. TMJ tomogram was made of each subject with the FHP and upper border of radiograph parallel to the floor. Due to circular
S136
Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
rotation of the radiographic recorder, this results in the upper border of radiograph being parallel to the FHP image. Once the tomograms were obtained, tracing papers were attached to the radiograph. Tracings were made of the images of each radiograph on parchment paper along the border of slopes of articular eminence. Horizontal reference lines were drawn parallel to the upper border of radiograph, contacting, and identifying the most superior and inferior point of each curve. The outline of each curvature and the flat reference line were traced. On tracing a line was drawn connecting the most superior and inferior points of curvature representing the mean curvature line. These two points were connected by a straight line representing a mean curvature line [Figures 4 and 5]. Angles made by the intersection of mean curvature line and the horizontal reference line (FHP) were measured. Each measurement was repeated twice by the operator. Data were subjected to Pearson’s correlation statistical analysis.
Results The radiographic image of the outline of articular eminence was seen distinctly in a TMJ tomogram. The outline if this was traced to obtain the angle of horizontal condylar inclination of the respective side and compared with the values obtained after programming the articulator. Radiographic values were on average 5° greater than anatomic values [Table 1]. From the correlation analysis in the following results are arrived. Among the 21 subjects, significant correlation was found between the angles obtained in the articulator to that of the corresponding radiographic image. The calculation of articulator value versus TMJ value of right and left in the right the correlation value (r) is 0.789 and 0.747 at the level of 1%, respectively. The calculated value is higher than the table value and significant at 1% level. Hence, the angle obtained in articulator versus TMJ tomogram is very closely correlated. Hence, there is no significant variation among the both views [Table 2]. From the descriptive analysis in the following results are arrived. The 21 respondents are taken into the analysis calculation of the mean value of angle in articulator left is 25.714, standard deviation value is 10.159 and standard error is 1.822. Condylar inclination in TMJ tomogram view left value of mean 30.476 and standard deviation 8.352 in the same standard error (1.822) [Table 3].
Figure 4: Tracing done on a temporomandibular joint tomogram using a parchment paper Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
From the descriptive analysis in the following results are arrived. The 21 respondents are taken into the analysis calculation of articulator right value of the mean is 25.238, standard deviation value is 9.417 and standard error is 1.721. Condylar inclination in TMJ tomogram view right value of mean 30.476 and standard deviation 7.890 in the same standard error (1.721) [Table 4].
Discussion Among the 21 subjects, significant correlation was found between the angle obtained on the articulator and the TMJ tomogram radiographic image. The Pearson’s correlation analysis test was conducted at a confidence interval of 99%. The results show a higher correlation (r) value of articulator versus TMJ tomogram on the right and left as 0.789 and 0.747, respectively. This shows that the angles obtained on the articulator are very closely correlated to that obtained on a TMJ tomogram radiograph. There was statistically no significant variation in horizontal condylar inclination angle obtained from both methods. The high correlation value shows that it can be used as a reliable tool in programming the articulator. In terms of difference in horizontal condylar inclination angle, a mean difference of 5° was obtained between the angles obtained on an articulator to that of the TMJ tomogram. The mean value of error obtained between the left side and right side of the articulator and TMJ tomogram was 4.7° and 5.2°, respectively. Among all TMJ imaging technique, TMJ tomogram is a specialized view for imaging TMJ. It represents the composite sagittal inclination of the articular eminence of both sides in open mouth and closed mouth position. TMJ tomogram presents better image quality, as all other forms of radiographic visualization of TMJ had overlap of the image to some extent. The controlled radiation exposure at proper interval ensures that there is no image overlap and the TMJ alone is radiographed on the film. Gilboa et al.[7] have reported that the radiographic outline of the articular fossa and articular eminence provided an accurate representation of the equivalent outline in 25 human skulls
Figure 5: Angles obtained from temporomandibular joint tomogram radiograph S137
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
Table 1: The average angles, standard deviation between mean curvature line and the reference line (FHP) on the radiograph and in the subject
supporting the bases in order to achieve uniform simultaneous contact of denture.
Condylar inclination
Mean
Standard deviation
N
Articulator right Articulator left TMJ tomogram right TMJ tomogram left
25.2381 25.7143 30.4762 30.4762
9.41756 10.15944 7.89062 8.35236
21 21 21 21
FHP: Frankfort horizontal plane, TMJ: Temporomandibular joint
Table 2: The correlation between the angle of inclination in articulator and TMJ tomogram radiograph Condylar inclination
n
r
Significant at 0.01%
Articulator right versus TMJ tomogram right Articulator left versus TMJ tomogram left
21
0.789**
0.000
21
0.747**
0.000
**Correlation is significant at the 0.01 level (one‑tailed, Pearson correlation). TMJ: Temporomandibular joint
Table 3: Descriptive statistics among the condylar inclination in articulator left versus TMJ tomogram view left n
Mean
SD
Standard Degree error error
Condylar inclination 21 25.7143 10.15944 1.82263 4.7619 in articulator left and 21 30.4762 8.35236 condylar inclination in TMJ tomogram view left TMJ: Temporomandibular joint, SD: Standard deviations
Table 4: Descriptive statistics among the condylar inclination in articulator right and TMJ tomogram right n
Mean
SD
Standard Degree error error
Condylar inclination in 21 25.2381 9.41756 1.72187 5.2381 articulator right and 21 30.4762 7.89062 condylar inclination in TMJ tomogram view right SD: Standard deviation, TMJ: Temporomandibular joint
with a mean difference in inclination of 7°. Images in a TMJ tomogram provide composite sagittal representations of the skeletal structures. TMJ tomogram presents better image quality and outline of the articular eminence of the temporal bone without any image overlap. A variety of interocclusal record materials are used in recording horizontal condylar inclination, are impression plaster, polyvinyl siloxane, waxes, acrylic resin and ZOE paste. Inter occlusal record even though they are considered as the most ideal way of programming the articulator. Preti et al. have reported that average interocclusal registration values of the condylar guidance inclination vary from 21° to 64°. Various interocclusal record material has been used in the past, the difficulty in recording wax inter occlusal record was uneven softening and uneven thickness of the recording material. Boucher recommends that the centric relation should be made with minimal pressure to prevent displacement of the tissues
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The Gothic arch tracing is considered as the most ideal method in programming the articulator. This method has some minor drawbacks like, the positioning of the tracer doesn’t allow the lip to be passive and hinders the rest position of the mandible, excessively resorbed ridges, flabby ridges, inadequate inter arch distance, large tongue. In subjects with TMJ arthropathy, there are chances of obtaining aberrant tracing that are faulty. These faulty tracings may lead to results that do not represent the actual horizontal condylar inclination of the patient and has no significance in programming the articulator. The temporomandibular X‑ray film reproduces the actual form and angles of the osseous structure of the joint. On the other hand, the functional registrations indicate the condylar path angles by means of the path traversed by the condyle along the slopes of the articular eminence. In recording horizontal condylar inclination errors up to 21-64° has been observed among the same operators, technique and material. By examining the angle of the osseous structure of the joint directly on the film, and making a transfer from the film to the instrument, a more specific condylar path angle can be determined. The articular eminence inclination in the radiographic image was traced from the most superior to the most inferior points of curvature representing mean inclination of curve. This may be different from guiding inclination with approximately 4-6 mm of protrusion, which is clinically significant range of protrusion and condylar guidance. When dynamic extraoral tracings are used, the starting point (centric relation), individual curved path, and eccentric position are recorded. With static records, only the centric relation and eccentric positions are recorded, the midpoint of the excursion produces the maximum error with a straight condylar slot. The maximum difference between a straight condylar path and one that has a 1/2 inch radius is 0.4 mm. A maximum condylar error of 0.4 mm produces a 0.2 mm error at the second molar. The sensitivity of the Hanau Wide‑Vue 183-2 closed tract semi‑adjustable articulator is of the order 5°. From the values obtained a mean difference of 5° was obtained between the angles obtained on an articulator to that of the TMJ tomogram. The mean value of error obtained between the left side of the articulator and TMJ tomogram was 4.7° and on the right side it was 5.2°. This shows that the 5° error is minimal or almost nil compared to other methods of recording horizontal condylar inclination. The current study concluded that TMJ tomogram accurately represents the outline of the articular eminence and the angle of the slopes of articular eminence traced on it can be used as an aid in setting the condylar guidance inclination on a semi‑adjustable articulator. Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1
Venkateshwaran, et al.: A newer technique to program a semi adjustable articulator
Conclusion The radiographic outline of the articular fossa and articular eminence provided an accurate representation of the equivalent outlines in 21 subjects with a mean difference in inclination of 5°. The image of the articular eminences in a TMJ tomogram may be used to provide an indication of the degree of inclination of the articular eminence and may be of value as an aid in setting the condylar guidance in semi‑adjustable articulators. A new method for programming the articulator has been suggested in this study that is more reliable, repeatable, ease of use with minimal drawbacks.
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Source of Support: Nil, Conflict of Interest: None declared.
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