reproducibility of the condylar position indicator
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This study assessed the reproducibility of measurements made using the Condylar Position Indicator (CPI) by evaluating intra-operator and inter-operator variability. Three operators took CPI recordings of standardized acrylic models and stone models that were poured from impressions of the acrylic models. Results showed very low variability between operators in readings of the same recording strips. Intra-operator variability was also low for recordings made of both the acrylic and stone models. Variability was slightly higher for the stone models compared to the acrylic models, and transverse readings showed the least amount of variability compared to vertical and anterior-posterior readings. The findings suggest the CPI provides accurate and reproducible measurements with minimal technique-induced error.
![Reproducibility of the Condylar Position
Indicator
David Lavine, Richard Kulbersh, PerryBonner, and Frank Eric Pink
Gnathologically oriented practitioners believe that the tolerance of the hu-
man body for centric relation to maximum intercuspation discrepancies is
very small, 0.5 mm transversely and 1.0 mm anteroposteriorly and vertically.
The condylar position indicator (CPI; Panadent Corp, Grand Terrace, CA) was
designed to measure these discrepancies in 3 planes of space. To achieve
meaningful results with this instrument, there must be very little technique
and material-induced error. The purpose of this study was to assess the
nature and magnitude of such error by studying intra- and interoperator
variability using the CPI at the levels of the articulator mountings and CPI
recordings. CPI recordings were taken by 3 operators using both standard-
ized mounted acrylic and stone models. Results were compared in a descrip-
tive manner for intra- and interoperator variability using standard deviation.
CPI readings were very accurate both among and between operators. Trans-
verse recordings showed the least amount of variability. A trend of in-
creased variability was noted as the complexity, number of steps, and
materials involved increased. (Semin Orthod 2003;9:96-101.) Copyright2003,
Elsevier Science (USA). All rights reserved.
V
arious individuals have discussed occlusal
considerations that may act as sustaining
and contributing factors to temporomandibular
dysfunction (TMD). v'9 In an attempt to limit
TMD exacerbation factors, dental practitio-
ners 9,3,7-m have recommended that an important
orthodontic goal should be to diagnose from
and treat to the most physiologic seated position
of the mandibular condyle (ie, to the centric
relation [CR] position). In an effort to record
CR and jaw functional border movements, ar-
ticulators were manufactured that attempted to
duplicate the anatomic positions of the maxilla
and mandible extraorally. In addition, instru-
ments such as Panadent's condylar position in-
dicator (CPI; Pandent Corp, Grand Terrace,
From the Private Practice of Dr D. Lavine, Laurel, MD; the
Orthodontic Department, University ofDetroit MerO"Dental School,
Detroit, MI; thePrivate Practice ofDr P. Bonnet; Goithersburg, MD.
Address correspondence to Richard Kulbersh, DMD, MS', Uni-
versity of Detroit Mercy Dental School, 8200 W Outer Drive, PO Box
19900, Box 189, Detroit, M1 48219.
Copyright 2003, Elsevier ,Science (USA). All rights reserved.
1073-8746/03/0902-0001 $35.00/0
doi:l O.1053/sodo. 2003.34030
CA) were manufactured to record condylar
nlovenlents.
The CPI assesses condylar position changes at
the level of the occlusion by using models
mounted in CR on the Panadent Articulator (Fig
1A). These models are then transferred to the
CPI (Fig 1B) and related to each other using a
maximum intercuspation (MI) record. Measure-
ments can be made of the vertical, transverse,
and anterior-posterior distraction of the condyle
from CR to MI by using the CPI (Fig 1C and D).
This system can then be used to assess condylar
position in diagnosis and treatment planning for
patients. According to Roth, 7 the clinically ac-
ceptable difference between CR and MI in terms
of condylar position as measured by the CPI is
approximately 1.0 mm anteroposteriorly, 1.0mm
vertically, and 0.5 mm transversely. Discrepan-
cies greater than these may possibly contribute
to the development of clinical TMD signs and
symptoms,z0 Because of these small tolerances,
CPI variability must be less than 0.5 mm for this
instrument's measurements to be valid.
Some ~ have questioned whether there is at
least 0.5 mm of procedural error in the measure-
96 Seminars in Orthodontics, Vol 9, No 2 (rune), 2003: pp 96-101](https://image.slidesharecdn.com/7-180131210225/85/reproducibility-of-the-condylar-position-indicator-1-320.jpg)
![The Condylar Position h~dicalor 101
may be misinterpreted as clinical temporoman-
dibular joint dysflmction.
These findings indicate that inter- and intra-
operator reliability of the CPI is acceptable at
least under the controlled laborato W conditions
in this study. The exact sources of error, material
or human, were not assessed; however, a trend
of increased variability was noted as the com-
plexity and number of the steps and materials
increased. The highest standard deviations at
the most complex point in this experiment (Ta-
ble 3, intraoperator variability using stone-
mounted models) are, however, still within an
acceptable range for both the transverse (0.13
ram) and x-y (0.16 ram) recordings.
Conclusions
CPI recordings were reproducible both among
and between operators. A trend of increased
variability was noted as the complexity, number
of steps, and materials involved increased.
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reproducibility of the condylar position indicator
- 1. Reproducibility of the Condylar Position Indicator David Lavine, Richard Kulbersh, PerryBonner, and Frank Eric Pink Gnathologically oriented practitioners believe that the tolerance of the hu- man body for centric relation to maximum intercuspation discrepancies is very small, 0.5 mm transversely and 1.0 mm anteroposteriorly and vertically. The condylar position indicator (CPI; Panadent Corp, Grand Terrace, CA) was designed to measure these discrepancies in 3 planes of space. To achieve meaningful results with this instrument, there must be very little technique and material-induced error. The purpose of this study was to assess the nature and magnitude of such error by studying intra- and interoperator variability using the CPI at the levels of the articulator mountings and CPI recordings. CPI recordings were taken by 3 operators using both standard- ized mounted acrylic and stone models. Results were compared in a descrip- tive manner for intra- and interoperator variability using standard deviation. CPI readings were very accurate both among and between operators. Trans- verse recordings showed the least amount of variability. A trend of in- creased variability was noted as the complexity, number of steps, and materials involved increased. (Semin Orthod 2003;9:96-101.) Copyright2003, Elsevier Science (USA). All rights reserved. V arious individuals have discussed occlusal considerations that may act as sustaining and contributing factors to temporomandibular dysfunction (TMD). v'9 In an attempt to limit TMD exacerbation factors, dental practitio- ners 9,3,7-m have recommended that an important orthodontic goal should be to diagnose from and treat to the most physiologic seated position of the mandibular condyle (ie, to the centric relation [CR] position). In an effort to record CR and jaw functional border movements, ar- ticulators were manufactured that attempted to duplicate the anatomic positions of the maxilla and mandible extraorally. In addition, instru- ments such as Panadent's condylar position in- dicator (CPI; Pandent Corp, Grand Terrace, From the Private Practice of Dr D. Lavine, Laurel, MD; the Orthodontic Department, University ofDetroit MerO"Dental School, Detroit, MI; thePrivate Practice ofDr P. Bonnet; Goithersburg, MD. Address correspondence to Richard Kulbersh, DMD, MS', Uni- versity of Detroit Mercy Dental School, 8200 W Outer Drive, PO Box 19900, Box 189, Detroit, M1 48219. Copyright 2003, Elsevier ,Science (USA). All rights reserved. 1073-8746/03/0902-0001 $35.00/0 doi:l O.1053/sodo. 2003.34030 CA) were manufactured to record condylar nlovenlents. The CPI assesses condylar position changes at the level of the occlusion by using models mounted in CR on the Panadent Articulator (Fig 1A). These models are then transferred to the CPI (Fig 1B) and related to each other using a maximum intercuspation (MI) record. Measure- ments can be made of the vertical, transverse, and anterior-posterior distraction of the condyle from CR to MI by using the CPI (Fig 1C and D). This system can then be used to assess condylar position in diagnosis and treatment planning for patients. According to Roth, 7 the clinically ac- ceptable difference between CR and MI in terms of condylar position as measured by the CPI is approximately 1.0 mm anteroposteriorly, 1.0mm vertically, and 0.5 mm transversely. Discrepan- cies greater than these may possibly contribute to the development of clinical TMD signs and symptoms,z0 Because of these small tolerances, CPI variability must be less than 0.5 mm for this instrument's measurements to be valid. Some ~ have questioned whether there is at least 0.5 mm of procedural error in the measure- 96 Seminars in Orthodontics, Vol 9, No 2 (rune), 2003: pp 96-101
- 2. The Condylar Position indicator 97 Figure 1. Panadent Articulator (A). Panadent Condylar Position Indicator (B). Condylar Position Indicator Recording-Right (C). Condylar Position Indicator Recording Graph (D). inent technique and/or materials. Possible sources of error include the following: 1. Impression materials: expansion and con- traction 2. CR and MI records: improper trimming of the records, dimensional changes of the waxes over time, and distortion of the waxes 3. Dental stone and dental plaster: expansion, contraction, water-powder ratio, and bub- bles on models 4. Face-bow transfer: variation in technique, distortion in transferring ti-om patients to models, and improper trimming of the im- pression compound 5. Placement of the adhesive recording strips 6. Width of the recorded dots 7. Variability of recording the exact CR posi- tion within and between individual opera- tors 8. Improper positioning of the adhesive re- cording strips on the CPI 9. Width of the dots on the CPI adhesive re- cording strips 10. Film thickness of separating agent 11. Disinfecting agents causing distortion of iin- pression material The reliabilib7 of the CPI is dependent on the proper transfer of anatomical information ti'om the patient to the articulator and finally to the CPI. The purpose of this study was to test the consis- tency and accuracy of the CPI hy assessing both intra- and inte.roperator variability at the levels of the articulator mounting and CPI recording. Methods and Materials The CPI is a delicate instrument. When not in use, the upper and lower members of the CPI
- 3. 98 Lavine et al are related using an aluminum support column provided by Panadent. When related using the aluminum support column, all CPI readings should equal zero. To assure that no change in the CPI instrument occurred during the exper- iment, each operator made CPI recordings with the column in place before and after the mea- surement sessions. In an effort to remove the possible error as- sociated with CR and MI assessment in a human model, a set of standardized mounted acrylic models were used as the gold standard from which all other test models were made. Also, CR and MI were coincident for this experiment; therefore, any change measured reflected mate- rial or technique error and not CR-MI distrac- tion. To study intra- and interoperator variability on the acrylic models, each of the three partici- pants took 10 consecutive CPI recordings on the acrylic models using a standardized CR Delar blue wax 2-piece bite record (Delar Corp, Lake Oswego, OR). To study intra- and interoperator variability on separate mounted models the following pro- cedures were performed. Ten maxillary and 10 mandibular impressions of the mounted acrylic models were made. Alginate impressions were taken using rim-lock metal trays (Dentsply, Mil- ford, DE), and the manufacturers' recom- mended water-powder ratio was used. The im- pressions were not rinsed, and no surfactant was applied before being poured. All impressions were poured immediately after being taken as recommended by the manufacturer of the algi- nate. The models were poured using whip- mixed Velmix pink stone (Kerr Co, Romulus, MI) using the manufacturers' recommended wa- ter-powder ratio. The split cast technique was used on the maxillary models. The models were then trimmed and all bubbles removed from the occlusal surfaces. The maxillary models were mounted using a standardized face-bow transfer jig. Snow White #2 plaster (Kerr Co) was used for the mountings and was mixed using the manufacturers' sug- gested water-powder ratio. In this study, the CR Delar blue wax 2-piece bite record was obtained from the original mounted models. Also, the anterior pin on the articulator was set so that there was 1.0-mm dis- clusion between the first contact at the posterior molars. The CR bite was taken until the pin touched the anterior table. This procedure en- sured that the wax bite thickness would remain standardized and the vertical distraction would be constant unless there was procedural or ma- terial induced error. Each operator took 10 2-piece Delar blue wax CR records on the mounted models. Each ante- rior CR record was taken using 2 thicknesses of softened (138°F) Delar bite registration blue wax extending from maxillary cuspid to cuspid. The CR recording was then registered by closing the upper member of the articulator until the anterior pin touched the table. The anterior bite record was then chilled in ice water and trimmed so that only cusp tip registrations re- mained. This anterior wax bite was then placed back on the upper arch and the second piece or posterior portion of the bite, extending from first molar to first molar, was taken using one thickness of the softened Delar blue wax. These posterior bites were chilled and also trimmed so that only cusp tips indentations remained. The lower models were then related to the upper casts and mounted using these CR records. After the mounting plaster had set, the upper models were separated from the mounting plates at the level of the split cast. The Delar CR blue wax bite records were then interposed be- tween the upper and lower dentitions and the upper arm of the articulator with the mounting plate lowered onto the maxillary cast. A correct fit, judged by the fact that .005 shim stock (Great Lakes Co, Tonawanda, NY) could not be pulled out at the split cast level, indicated no mounting error at this point. Casts that did not split cast check were discarded. At this point, the mounted models were trans- ferred to the CPI. Using the CR Delar blue wax bites interposed between the models, measure- ments were made of the AP, vertical, and trans- verse distractions. In addition, each operator read the strips of another operator to test for interjudge reliability of reading the same strips. Results Initial and Final Readings With the Storage Block in Place All operators found CPI readings did not zero as expected before or after treatment, except in 3
- 4. The Condylar Position indicator 99 instances (Table 1). The range in the right x axis was -0.15 mm to 0.10 ram. The range in the right y axis was -0.25 mm to 0.15 ram. For the left x axis, the range was 0.15 mm to 0.25 ram. For the left y axis, the range was 0.0 mm to 0.20 ram. For the transverse plane, the range was -0.05 mrn to 0.1 ram. Interoperator Variability of Reading Same Recording Strips As shown in Table 2, standard deviations were extremely low among operators reading the same recording strips. Intraoperator Variability Using Acrylic and Individually Mounted Stone Models Although means did not approach zero in most cases, an extremely low standard deviation was found within all operators' individual readings for both the acrylic mounted models and the individually mounted stone models (Table 3). The transverse readings had consistently lower standard deviations than the vertical x or y read- ings. &s expected, standard deviations were greater for the trials with the individually mounted stone models than the acD,lic models. Interoperator Variability on the Acrylic and Individually Mounted Stone Models &s shown in Table 4, variability among operators reading their own recordings of the same mod- els was also quite low. Discussion Because CR is coincident with MI for this exper- iment, all recordings should have equaled zero. There are several factors that might explain why this was not so. At the most basic level, the CPI Table 2. Interoperator Variability of Reading the Same CPI Recording Strips (Standard Deviation in ram) Rig~z/ 1.eft x* 3'? x ~: 7"ran~$ A1 0.02 0.02 0.00 0.02 0.00 A2 0.05 0.17 0.04 0.16 0.02 A3 0.02 0.08 0.00 0.06 0.02 A4 0.04 0.07 0.02 0.{}4 0.02 A5 0.09 0.05 0.02 0.08 0.04 A6 (}.09 0.05 0.07 (}.10 0.06 A7 (}.05 0.13 0.{}0 0.07 0.02 A8 0. I 3 (}.02 0.02 l).02 ().(}{i A9 0.08 0.18 0.14 0.11 0.02 AI{} 0.02 0.09 (}.{}4 (}.(){i 0.02 Mean 0.06 (}.(}9 0.04 0.(}7 (}.03 SI (}.04 0.{}2 (}.05 {}.14 0.06 $2 0.07 0.00 0.08 0.i2 0.12 SB (}.0{.) 0.05 0.05 0.05 (}.12 $4 {}.05 0.(}7 0.24 0.02 0.1 I $5 0.04 0.02 0.02 0.02 0.08 $6 0.07 0.02 0.14 0.05 0.09 $7 (}.09 O.11 0.04 O.13 0.0(} $8 0.12 0.09 0,06 0.02 0.02 $9 0.06 0.02 0.(}9 0.04 (}.(}6 S10 0.04 0.02 0. I 1 0.(}4 0.02 Mean 0.07 0.04 0.09 (}.06 0.07 Abbreviations: A, acD'lic models; S, stone *Rel{ers to horizontal CPI axis tReR~rs to vertical CPI axis +Rctbrs to hansversc CPt axis models. should zero with the storage block in place, h did not. Attempts were made by Panadent to correct the placement of the crosshairs before the experiment. The placement, however, was never exactly correct as shown in Table 1. If the CPI is not zeroed ti-om the start, the resuhs may be misinterpreted nnless the initial amount of machine CPI distraction error is known and sub- tracled from the readings. Because diagnostic issues were not a tactor in this experiment, exact CPI numbers were not as important as was re- peatability; therefore, the differences were not subtracle(t. In addition, there was some "play" in Table 1. Initial and Final CPI Readings With the Storage Block in Place (ram) Operator 1 Operator 2 Operator 3 Right l.dt flight l.d~ Rt¢t+/ Ldt Axis: x* y'[- x y Tran,s¢ x y x y Tmn,~ x 3 x y Trans hilt. 0.10 -0.25 0.20 0.00 -0.05 0.15 0.20 0.15 0.15 0.10 0.05 0.15 0.20 0.20 0.00 Final -0.10 -0.20 0.25 0.20 -0.05 0.00 0.20 0.20 0.15 0.05 0.05 0.15 0.20 0.20 0.00 *Refbrs to horizontal CP1 axis. /Refers to vertical CPI axis. +Rcfi'rs to transverse CPI axis.
- 5. 100 Lavine et al Table 3. Intraoperator Variability for Reading CPI Recording Strips Using Acrylic Versus Stone Models (Standard Deviation in nun) Operator 1 Operator 2 Operator 3 Right Left t¢~¢ht Left Right Left Axis x y x y Trans x y x y Trans x y x y Tram Mounted acD,lic models Mean -0.20 -0.07 -0.09 0.32 (1.14 0.19 -0.05 0.10 0.30 -0.16 0.18 -0.22 0,18 0.17 -0.28 SD 0.08 0.12 0.10 0.09 0.04 0.07 0.07 0.11 0.08 0.06 0.06 0.05 0.02 0.02 0.03 Mounted stone models Mean -0.10 0.11 0.06 0.43 0.00 0.05 0.11 0.06 0.29 0.10 0.03 0.04 0.14 0.15 0.05 SD 0.15 0.13 0.13 0.13 0.05 0.14 0.12 0.12 0.13 0.06 0.16 0.14 0.10 0.11 0.13 Abbreviations: SD, standard deviation. x - Refers to horizontal CPI axis. y -Reters to vertical CP1 axis. Trans - transverse CPI axis. the recording styli as they were moved to mark the strips. This "play" error was observed to range from 0.01 to 0.05 mm. The next level of possible technique error was interoperator variability in reading the same strips. Although the means did not equal zero, the largest standard deviation mean was remark- ably low, (+_ 0.09 mm) indicating good repeat- Table 4. lnteroperator Variability for Reading CPI Recording Strips Using Acrylic and hldividually Mounted Stone Models (Standard Deviation in ram) R~t L~ Axis x y x y Trans A1 0.08 0.11 0.12 0.00 0.12 A2 0.04 0.06 0.07 0.06 0.06 A3 0.02 0.07 0.08 0.02 0.04 A4 0.07 0.09 0.07 0.04 0.06 A5 0.06 0.06 0.11 0.06 0.02 A6 0.05 0.08 0.14 0.11 0.05 A7 0.05 0.12 0.09 0.09 0.07 A8 0.02 0.12 0.18 0.08 0.08 A9 0.04 0.15 0.24 0.13 0.08 A10 0.04 0.09 0.19 0.06 0.08 Mean 0.05 0.10 0.13 0.07 0.07 S1 0.20 0.07 0.12 0.05 0.21 $2 0.05 (/.07 0.05 0.18 0.09 $3 0.07 0.05 0.05 0.16 0.13 $4 0.00 0.05 0.11 0.25 0.08 $5 0.00 0.05 0.02 0.08 0.08 $6 0.07 0.07 0.12 0.02 0.08 $7 0.05 0.04 0.11 0.02 0.07 $8 0.15 0.18 0.06 0.09 0.02 $9 0.12 0.05 0.12 0.02 0.11 S10 0.08 0.05 0.02 0.11 0.08 Mean 0.08 0.07 0.08 0.10 0.10 Abbreviations: A, acrylic models; S, stone x = Refers to horizontal CPI axis. y - Refers to vertical CPI axis. Trans - transverse CPI axis. models. ability. The ability to locate the center of the recorded dot with the magnifying loops was also apparent in these readings. The error associated with positioning the graph paper recording strips on the CPI was small. This was shown by the low standard deviations in interoperator variability of reading operator-marked strips in the same category (Table 2). Finally, intraoperator variability was smaller using the aclylic-mounted models than the stone-mounted models (Table 3). Trials with the acrylic-mounted models showed lower standard deviations than those with the stone models. This indicates that some operator and/or mate- rial error was certainly incorporated as the list of tested variables increased. Standard deviations approaching 0.16 were recorded. In the authors' ()pinion, this may be considered the outer limit of acceptability. Transverse standard deviations were generally smaller than x or y standard de- viations. These results seem credible since the transverse reading is a midline structure and, therefore, less sensitive to error than the more laterally located x and y parameters. Most recordings showed very low standard deviations. There were a few, however, that were considerably different from the others. When the strips for these aberrant readings were re- read, some were found to be grossly in error. The wrong recordings were not replaced with the correct ones and are presented here as op- erator error. This emphasizes the fact that me- ticulous attention to detail is required using these techniques because erroneous readings
- 6. The Condylar Position h~dicalor 101 may be misinterpreted as clinical temporoman- dibular joint dysflmction. These findings indicate that inter- and intra- operator reliability of the CPI is acceptable at least under the controlled laborato W conditions in this study. The exact sources of error, material or human, were not assessed; however, a trend of increased variability was noted as the com- plexity and number of the steps and materials increased. The highest standard deviations at the most complex point in this experiment (Ta- ble 3, intraoperator variability using stone- mounted models) are, however, still within an acceptable range for both the transverse (0.13 ram) and x-y (0.16 ram) recordings. Conclusions CPI recordings were reproducible both among and between operators. A trend of increased variability was noted as the complexity, number of steps, and materials involved increased. References 1. Creekmore TD, Cetlin NM, Ricketts RM, et al..]CO Roundtable: Diagnosis and treatment planning..I Clin Orthod 1992;26:585-606. 2. Slavicek R. Inten,iew with Dr. Slavicek Parts 1-10..J Clin Orthod 1988;22:358-370. 3. Slavicek R. Functions and dysflmctions of the mastica- tor7 organ. Diagnosis and therapy. Presented to Vienna Group IV,July 28 to August 5, 1990, Vienna, Austria. 4. Farrar WB. Diagnosis and treatment of anterior disloca- tion of the disc. NYJ Dent 1971;41:348-351. 5. Lindbloom G. Disorders of the temporomandibular joint: Causal factors and therapy. Acta Odont Scand 1953;11:61-94. 6. Ricketts TM. Clinical implications of the tcmporoman- dibular joint. Am J Orthod 1966;52:416-439. 7. Roth RH. Temporonaandibular pain-dysflmction and oc- clusal relationships. Angle Orthod 1973;43:136-152. 8. Roth RH. Functional occlusion ti)r the orthodontist. Part 1.J Clin Orthod 1981;15:32-51. 9. Roth Rtt, RolEsDA. Functional occlusion lot the orth- odontist. Part 2. J Clin Orthod 1981;15:100-123. 10. Roth RH. Occlusion and condylar position. Am,] Orthod Dentofac Orthop 1995;107:315-318. 1I. PerD' HT. Temporomendibularjoint and Occlusion. An- gle Orthod 1976;46:284-293. 12. Thompson ,JR. Abnormal function of the /emporomen- dibularjoints and related musculature: Orthodontic im- plications part 2. Angle Orthod 1986;56:181-195. 13. Jamsa T, Kirveskari P, Alanen P. Malocclusion and its association with clinical signs of craniomandibular dis- orders in 5, 10 and 15-year old children in Finland. Pro( Fins Dent Soc 1988;85:235-240. 14. Egermark-Eriksson 1, Carlsson (;1:2, Magnusson T. A long-term epidemiologic study of the relationship be- tween o~clusal tactnrs and mandibular dysfunction in (hildren and adolescents.J Dent Res 1987;66:63-71. 15. Riolo M, Brendt I), Ten Have' T. Associations between occlusaI characteristics and signs and symptoms of TMJ dysftmction in children and ~oung aduhs. Am,] Orthod Dentofac Orthoi) 1987;92:461-477. 16. Magnusson T, Carlsson GE. Occlusal ae!justmenl in pa- lienls with residual or recurrent signs of mandilmlar dyslhnction.,J Prosthet 1)enl 1983;49:706-710. 17. Wennbcrg N. Nystrom "I', Carlsson GE. Occlusal equili- bration and other stomatognathic treatment in palients with mand dvstunction and headache..] Prosthet Dclll 1988;59:478-484. 18. Wyatt WE, Prexenling adverse efI~'cts on the temporo- mandibular joint through orthodontic treatment. AM ,] Orlhod I)ento Fac Or/hop 1987;91:493-499. 19. Zarb (;A, Speck JE. The u'eatment of mandibular dvs- fimctio. In: Zarb (;A, Carlsson (;E (eds). Temporoman- dibular Joint Function and l)ysthncfion. Copenhagen, Munksgaard, 1997;373-396. 20. Crawtbrd SD. Condylar axis position, as determined by the occlusion and measured by lhe CPI instrument, and signs and symplnms of lempromandibular dysfunction. Angle Orlhod 1999;69:103-116. 21. Phillips RW. Report of committee on Scientitic Investi- gation of the American Academy of Reslorative Den- tistr)'.,}. Prosthel Dent 1986;55:736-772.