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Observations on the use of the Denar pantograph and articulator
RESEARCH AND EDUCATION JOHN
J. SHARRY,
Section
Observations
editor
on the use of the Denar
pantograph
and articulator R. B. Winstanley,
B.D.S., F.D.S., R.C.S.(Ed.l*
University of Shefield School of Clinical Dentistry, Charles Clifford Dental Hospital, Shefield, England
M
cCollum and Stuart1 developed the pantograph in 1930 as a research tool to study and record mandibular movements. The pantograph can also be used as a conventional face-bow to locate the maxillary cast in relation to the posterior reference points and the horizontal reference plane when transferring the maxillary cast to the articulator. The diagnostic data recorded by the Denar pantograph are expressed in millimeters and degrees in the calibrated control adjustments of the articulator. These numerical values are related to specific positions or reference planes which can be relocated precisely. Inability of the articulator to follow the recordings exactly does not necessarily discount its diagnostic value, since it can give valuable information as to what is happening in the temporomandibular joint. The value of an articulator lies in the degree to which it enables the operator to study existing dentitions during function and to construct restorations in such a way that satisfactory function results. Weinberg2 gave a detailed account of fully adjustable articulators and came to the conclusion that only the gnathologic type (such as the Denar) “reproduces three dimensional guidance of the working condyle” and is “the instrument of choice among the fully adjustable articulators.” Although many other authors recognize the benefits derived from the use of fully adjustable articulators, Watt,3 in his study of the reproducibility of articulator settings from graphic records, concluded that “the high probability of error in the use of this type of instrument made it inacceptable as a means of diagnosing occlusal disturbances.” In view of the widespread use of gnathologic instruments, it was thought important to ascertain if Watt’s criticism of these instruments, based on observations on the reproducibility of articulator settings from graphic records, was fully justified. *Lecturer 660
in Restorative Dentistry.
Volume Number
38 6
Use of Denar pantograph
(A) Articulator. (B) Pantograph. 2. (A) Styli. (B) Tracings covered
Fig.
1.
Fig. (D)
Lower
by protective
overlays.
and articulator
(C)
Central
bearing
661
screw.
clutch.
The present study was designed to investigate the reproducibility of articulator settings obtained from graphic records using the Denar pantograph and Denar articulator. A number of people who were unfamiliar with these instruments agreed to take part, and the results obtained by them were compared with those obtained by two participants familiar with the technique. This investigation was thought necessary before further work could be undertaken to determine how accurately this articulator reproduces mandibular movements. MATERIALS
AND
METHODS
The Denar D4-A articulator experiments (Fig. 1) . Experiment
and
the
Denar
pantograph*
were
used
for
all
1
Clutches were constructed on upper and lower diagnostic casts of a patient with a complete dentition. The clutches were rigidly cemented to the casts so that movement could not take place between clutch and cast. The clutches and diagnostic casts were mounted on the articulator, and the central bearing screw was adjusted in height so that there was a small clearance between the clutches. The posterior control adjustments of the articulator were set at arbitrary values which were noted. The pantograph was assembled on the articulator and connected rigidly to the clutches. A pantographic survey was carried out with, in this instance, the articulator acting as “the patient.” The upper part of the articulator was manipulated to simulate right and left lateral excursive movements and a protrusive movement. The tracings made by the styli were protected by the transparent overlays, and the articulator adjustments were set to zero (Fig. 2). Six experienced dentists, six dental laboratory technicians, and six dental students were asked to adjust the articulator so that the styli again followed the tracings. “Denar
Corporation,
Anaheim,
Calif.
662
Winstanley
J. Prosthet. Dent. December, 1977
Only two of the 18 participants were experienced in the use of the Denar articulator. Measures intended to verify if the styli were following the tracings exactly were omitted deliberately, since it was thought that this would prejudice the results. HOWever, each person was asked to repeat the adjustments, if necessary, until he was satisfied that consistent results had been obtained and the styli were following all the tracings. In this particular experiment, only the sagittal protrusive condylar inclination and the immediate and progressive side-shift adjustments were carried out; the adjustments were not included. Since the articulator “rear-wall” and “top-wall” itself was acting as the “patient” when the pantographic tracings were made, neither the vertical axes adjustments nor the sagittal orbiting condylar path adjustments were included, as they were irrelevant to this experiment. Vertical axes. The Denar manual4 outlines the procedure for transferring the pantograph from the patient to the articulator and for adjusting the articulator to the pantographic record. These instructions are taken by this author to mean that the vertical axes are set initially during the transfer procedure from the patient to the articulator by means of the telescopic mounting axis which registers the intercondylar distance. If the medial components of the anterior Gothic arch tracings are not followed exactly by the styli (after the correct sequence of prior adjustments has been carried out), a slight difference between the intercondylar distance on the patient and that on the articulator is indicated, necessitating adjustment of the vertical axes. However, when the articulator is itself the “patient,” the intercondylar distance must be correct, and when all the other adjustments are satisfactory, the styli will follow the medial components of the anterior Gothic arch tracings. The only way in which the vertical axes adjustments could have been incorporated into the present experiment would have been to move the condylar spheres (i.e., the vertical axes) laterally when the other adjustments were set to zero before asking the participants to adjust the articulator so that the styli followed the tracings. It would then have been necessary to explain to the participants that the condylar spheres should be moved medially until they make contact with the medial fossae walls while the articulator is locked in the centric position and the immediate sideshift values are set at zero. This would have set the vertical axes in the original positions from which the tracings were made, and it would have been an unnecessary part of the experiment. Sag&al orbiting condylar paths. These values were not recorded, because they were the same as the sagittal protrusive condylar inclination paths in this experiment, since both tracings on each side were obtained with the same articulator settings for that particular side. However, checks were made by those carrying out the experiments to verify that the orbiting tracings were, indeed, followed by the styli in lateral movements. If they were not, then the articulator had not been adjusted correctly, and it was necessary to repeat the experiment. Results. Results are shown in Table I in the order in which adjustments were carried out. Most participants adjusted the sagittal protrusive condylar inclination correctly on the right side, although there was a variation of between 38 and 41 degrees. There was a tendency, which was difficult to explain, to underestimate
’
Volume Number
38 6
Table
1. Results
Use of of Experiment
Adjustment
R
L
40”
30”
Progressive side shift
pantograph
Range of resettings
Mean value
and articulator
663
1
Original settings Sagittal protrusive condylar inclination Immediate side shift
Denar
Operator
Clinicians Technicians Students Over-all 1.2 mm. 0.4 mm. Clinicians Technicians Students Over-all 15O 5” Clinicians Technicians Students Over-all
R 41138 40 40138 41138 1.411.2 1.4/l .O 1.411.O 1.411.O 15 15/14 15/14 15114
L 31125 32121.5 31121 32/25 0.4 0.4/0.2 0.4fO.2 0.410.2 IO/5 5
614 1014
RIL 39.17 40.00 39.50 39.56 1.32 1.20 1.17 1.23 15 14.67 14.67 14.78
S.D. RIL
21.67 29.67 29.33 28.89 0.4 0.28 0.28 0.32 5.83 5.00 5.00 5.28
1.17 0 0.84 0.86 0.10 0.18 0.14 0.15 0 0.52 0.52 0.43
Standard error of S.&l. R[L
2.48 1.54 1.51 2.00 0 0.10 0.10 0.09 2.04 0 0.63 1.23
0.34 0 0.24 0.14 0.03 0.05 0.04 0.03 0 0.15 0.15 0.07
0.72 0.44 0.44 0.33 0 0.03 0.03 0.02 0.59 0 0.18 0.21
rather than overestimate. This was looked at more closely after completion of the experiment, because it was thought that, with a setting 5 degrees below the correct setting the stylus might follow the tracing more closely than at a setting 5 degrees above the correct setting, which might explain this tendency to underestimation. However, the stylus was found to follow a line parallel to the tracing, either above or below, by an equal amount with each setting of 5 degrees above or below. The sagittal protrusive condylar inclination on the left side showed greater variation than that on the right side, with values ranging from 25 to 32 degrees. Again, there was a tendency to underestimate which could not be explained. The immediate side shift on the right side gave a spread of 1 .O to 1.4 mm., with a tendency to overestimate. This is in keeping with the fact that, with small adjustments, there is a natural tendency to overestimate. However, nobody overestimated on the left side, these readings being between 0.2 and 0.4 mm. The line of vision when carrying out this adjustment on the left side is such that underestimation is more likely to occur, the articulator usually being positioned in front of and below, rather than directly below, a right-handed person. The progressive side-shift adjustments were accurate on both sides, apart from one reading on the left side (10 degrees). These are relatively more easy to adjust satisfactorily, since the tracings are longer and follow an almost straight line. Experiment
2
This experiment was similar to the previous one but included the “rear-wall” and “top-wall” adjustments. The pantographic survey was carried out initially on a patient, and the pantograph was transferred to the articulator. It was at first decided to let the same three groups (although not necessarily the same individuals) adjust the articulator until the styli followed the tracings. However, it was realized that this would not help in an investigation into the reproducibility of articulator settings, since there were no values with which the results obtained by the participants could
J. Prosthet. Dent. December, 1977
664
Winstanley
Table
II. Results of Experiment
Original Adjustment
Sag&al protrusive
R
2
settings I
Range L
25”
30°
Immediate side shift
0.8 mm.
0.2 mm.
Progressive side shift
10”
5O
Rear wall
30B
30B
Top wall
15U
5U
condylar inclination
Operator
Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all
of resettings
R
L
21125 28/25 25124 28124 0.9/0.6 0.8/0.4 0.910.8 0.9/0.4 II/3 7/4 1217 12/3 3OBfO 40B/20F 39B/18F 40B/20F 24U/19D 0/21D ZSU/SU 25U/21D
30128 3 l/30 30/28 3 l/28 0.410.2 0.4/o. 1 0.4/0.2 0.4/o. I 9/O 111 II/5 II/O 40B/19B 30B/15B 39B/lOB 40B/lOB IOU/9D 15lJfZOD 15U/18D
25U/20D
be compared. It was also noticed that some of the fossa inserts would have to be replaced with curved inserts, and this could lead to confusion for the participants unaccustomed to the Denar system. To overcome this problem, the following method was adopted; the two people who had had experience with the Denar system adjusted the articulator until the styli followed the tracings as accurately as possible, using modified inserts where necessary. When both agreed that the articulator was correctly adjusted, the articulator readings were noted, and these were used as the original measurements. New tracings were then made by the pantograph on the articulator to these figures and protected by the transparent overlays. The articulator adjustments were set to zero, and the same three groups (although not necessarily the same individuals) were again asked to adjust the articulator until the styli followed all the tracings. This time, all the articulator adjustments were included, apart from the vertical axes and the orbiting path sagittal condylar inclination which were not included for the reasons already discussed in Experiment 1. Results. Results are shown in Table II in the order in which adjustments were carried out. Sagittal protrusive condylar inclination values on the right ranged from 24 to 28 degrees, with a tendency to overestimate, in contrast to the tendency found in the previous experiment. On the left side, there was a tendency to underestimate these values, although not significantly so, as in the first experiment, with a range of 28 to
Volume Number
3R 6
Mean
Use of Denar
value
pantograph
S.D.
II
and
Standard
articulator
error
665
of S. D
I
R
L
R
L
R
L
25.50 25.83 24.83 25.39
29.17 30.50 29.50 29.72
0.84 1.33 0.41 0.98
0.98 0.55 0.84 0.96
0.24 0.38 0.12 0.16
0.28 0.16 0.24 0.16
0.78 0.70 0.82 0.77
0.21 0.25 0.25 0.26
0.10 0.17 0.04 0.12
0.08 0.12 0.08 0.09
0.03 0.05 0.01 0.02
0.02 0.04 0.02 0.02
8.00 5.33 8.67 7.33
4.83 4.83 7.33 5.67
3.22 1.03 2.07 2.61
2.86 2.04 2.73 2.70
0.93 0.30 0.60 0.44
0.82 0.59 0.79 0.45
14.83B 18.67B 14.17B 15.898
32.OOB 20.50B 23.758 25.42B
11.14 20.90 20.74 17.19
7.92 5.75 10.24 9.16
3.22 6.03 5.99 2.87
2.?Y 1.66 2.Y5 I.53
5.67U IO.OOD 12.17U 2.6lU
2.OOu 0.83D 4.17u l.78U
16.45 8.74 8.45 14.65
7.32 12.42 13.96 II.09
4.15 2.52 2.44 2.44
2.11 3.58 4.03 1.85
31 degrees. More participants obtained the correct values in this experiment than in the previous one, and this may be because superior fossa wall inserts with more curvature were used and perhaps gave a tracing which, although more curved, was easier to follow. At the end of the experiment, the tendency to under- or overestimate was examined to see if the styli followed the tracings more closely with settings 5 degrees above or 5 degrees below the correct setting. No significant difference was found. The immediate side-shift values on the right ranged from 0.4 to 0.9 mm., with more participants obtaining the correct value than in the previous experiment. This time, there was a tendency to underestimate. On the left side, the same number of participants in Experiment 1 obtained the correct values but there was a tendency to overestimate (in distinction to the first experiment), with values ranging from 0.1 to 0.4 mm. This is the obvious tendency with such a low figure of 0.2 mm. i the correct setting). The results of the progressive side shift on the right side were disappointing (values ranging from 3 to 12 degrees), and only two participants obtained a correct result. This is even more surprising when compared with the progressive side-shift readings on the right side in the first experiment which were much better. The explanation for this will be discussed more fully later and is due to reciprocal action between the right progressive side-shift adjustment and the right top-wall adjustment. Although most of the participants obtained the correct value of 5 degrees on the left side, there was a variation of from 0 to 11 degrees.
666
J. Prosthet. Dent. December, 1977
Winstanley VALUES
ROUNDED
TO
NEAREST
VALUES ROUNDED
5’
22.5’
SHOWN
TO NEAREST AS
5’
20”
+
Fig. “ALES
3. Histograms
ROUNDED
TO
NEAREST
of rear-wall
results
in Experiment
2.
VALUES ROUNDEDTO NEAREST5’
5’
4
25”
t0”
IS”
IOU
5U
0
SD
IO0
Fig. 4. Histogrank
ISD
2OD
PSD
of top-wail
results
in Experiment
2.
The results obtained from the rear-wall adjustments have a range of from 20F to 40B (a spread of 60 degrees) on the right side and 10B to 40B (a spread of 30 degrees) on the left side. This can be seen more clearly in the histogram (Fig. 3). It can only be concluded that these were very inaccurate adjustments, likely due to the fact that the tracings were short and large variations in the settings cause only small deviations of the styli. In fact, it is difficult to decide if the correct setting on the right side is in front of or behind the coronal plane. The results obtained from the top wall are similarly very poor, as shown by the histogram (Fig. 4)-the right side being inferior to the left. The range on both sides is 20D to 25U (a spread of 45 degrees), but on the right side, only one participant obtained the correct result. As with the rear wall, it is difficult to decide whether the correct setting is above or below the horizontal plane. Some difficulty could be explained by the fact that gross movements of these adjustments give only small alterations to the paths of the styli and by the fact that the top-wall tracings are very short. This experiment was more difficult for the inexperienced operators to carry out, because more adjustments were included and curved fossa inserts were used. In addition, because there was some “slack” in the rear-wall adjustments, errors oft 5 to 10 degrees inevitably occurred. The rear-wall and top-wall adjustments were not easy
Volume Number
Table
38 6
Use of Denar
III. Results
of sagittal
A ‘s settings (degrees)
B’s resettings (degrees)
Right
Right 25 35 32.5 26 21.5 11
Le/ 30 25 20 25 25 20
25 35 30 25 25 IO Table
Left 30 25 22.5 25 21.5 21
IV. Results of immediate
A’s settings (mm.1 Right Left 0.4 1.6 0.4 '0.8 0.8 0.4
B’s resettings (mm.)
0.8 0.8 I.0 0.6 0.6 0.4
protrusive
condylar
Difference (degrees)
pantograph inclination
B’s settings
side shift Difference (mm.)
(Experiment A ‘s resettings
(degrees)
Right 1 Left 0 0 0 0 2.5 2.5 1 0 2.5 2.5 1 1
and articulator
(degrees)
Right 1 Left 10 20 35 30 15 20 30 20 25 30 10 20 (Experiment
Right 8 37.5 15 32 25 10
667
3) Difference (degrees)
Leji 20 30 20 20 32 20
Right 2 2.5 0 2 0 0
1 Left 0 0 0 0 2 0
3)
B’s settings (mm.1
A’s resettings (mm.)
Right
Left
Right
Left
Right
1 Left
Right
Left
0.4 1.7 0.4 0.9 1.0 0.2
0.9 1.0 1.0 0.8 0.6 0.2
0 0.1 0 0.1 0.2 0.2
0.1 0.2 0 0.2 0 0.2
0.4 0.6 0.4 0.2 0.6 0.8
0.4 0.8 0.4 0.2 0.6 1.o
0.5 0.6 0.6 0.4 0.6 0.9
0.5 0.6 0.4 0.4 0.5 0.9
Difference (mm.) Right 1 Left 0.1 0 0.2 0.2 0 0.1
0.1 0.2 0 0.2 0.1 0.1
to manipulate, making it difficult for the styli to follow the tracings. A large movement of these controls during adjustment often made only small differences to the direction traveled by the styli. As in the first experiment, the “feel” of the articulator was so different from that of conventional articulators that many of the participants experienced difficulty in the beginning of the adjustments. Experiment
3
This experiment was undertaken to see if better results could be obtained when operators experienced in the use of the Denar system adjusted the articulator so that the styli followed the tracings. It was thought that unless a person was familiar with the articulator, consistent results could not be obtained. Before the start of this experiment, the defect in the rear-wall adjustments was eliminated. The experiment was performed in the same manner as Experiment 1 using a pantographic survey made by the articulator which was adjusted to random values, and two people participated in the experiment. The participants will be referred to as A and B. Operator A adjusted the articulator to certain values, noted the readings, made the tracings to these values, and then set each to zero. B adjusted the articulator until the styli once again followed the tracings, and the readings were noted by A. This was repeated six times, each time with different settings which were unknown to B. A and B then reversed roles, and a further six experiments were carried out. Results. Results are shown in Tables III to VII.
J. Prosthet. Dent. December, 1977
668
Winstanley
Table
V. Results of progressive
A ‘s settings (degrees)
B’s resettings (degrees)
Right
1 Left
Right
IO
5
10 10 15 15 10
5 10 10 IO 10
10 I 13 I1 I1 10
Table
VI. Rear-wall
A ‘s settings (degrees) Right
10F 15B 15F 208 20B 20F Table
1 Left
5F 5F 10B 15B 15B 10F
Right
5D 5U 10D 5U 5U 5D
5F 15B 15F 15B 20B 25F
VII. Top-wall
A’s settings (degrees) Left
15D 5U 5D 5D 5D 10D
Difference (degrees)
1 Leji
5 3 6 10 6 10 results
B’s resettings (degrees) Right
1 Left
2.5F 5F 10B 14B 15B 25F results
B’s resettings (degrees) Right
5D 5U 0 4D 2D 12D
side shift (Experiment
1 Left
25D 5D 20D 9D 14D 17D
3)
B’s settings (degrees)
A’s resettings (degrees)
Right
) Left
Right
1 Left
Right
0 3 3 4 4 0
0 2 4 0 4 0
IO
10
5 10 10 15 10
10 10 15 10 5
15 5 10
(Experiment
5 0 0 5 0 5
B’s settings (degrees) Left
10
15 10
1 Left
5 0 0 0 0 0
0 0 10 0 0 4
20F 15F IOF 10F 5F 15F
1 Left
10F 20F 15F 5F IOF 5F
A’s resettings (degrees) 1 Right
20F 20F 25F 6F 7F 12F
1 Left
10F 5F 12F 5B 6F 5F
Difference (degrees) 1 Right
I Left
0 5 15 4 2 3
0 15 3 10 4 0
3)
Difference (degrees)
0 0 10 9 7 7
Right
2.5 0 0 1 0 15 1
(Experiment
Right
10 10 20 15 10 9
Right
3)
Difference (degrees) Right
1 Left
Difference (degrees)
B’s settings (degrees) Left
Right
10 5D 10 5U 15 IOD 4 10D 9 5D 7 ( IOD
I Lef
10D IOU IOD 15D 15D 15D
A’s resettings (degrees) Right
15u 5u 7D 15D 5D 10D
Left
10D IOU 20D 13D 15D 4D
Difference (degrees) Right
20 0 3 5 0 0
I Left
0 0 10 2 0 11
The measurements for the sagittal protrusive condylar inclination and those for the immediate side shift differed from the original settings by only a small amount. Although there was some spread with some of the individual results, the range of this spread was small, and where incorrect settings had been obtained, they were close to the correct ones. The progressive side-shift results were variable. B tended to underestimate on both sides, while A was much closer to the correct settings, although there was one difference of 10 degrees, one of 5 degrees, and one of 4 degrees-all overestimated. The rear-wall measurements, although subject to variation of as much as 15 degrees, were an improvement on those in the second experiment. The top-wall results were similar to the rear-wall results, with variations of up to 20 degrees, but with much closer approximation to the correct settings than had been obtained in Experiment 2.
Volume Number
38 6
Use of Denar
pantograph
and articulator
669
These results, ,especially the latter two adjustments, indicated that familiarity with the Denar system gave more consistent results, although the elimination of “slack” in the rear-wall adjustments must have had some effect on this. OBSERVATIONS Seven observations were made during this study of the Denar system. (1) Reciprocal actions. The Denar procedure manual” states, “. . , when an articulator is adjusted to move one stylus relative to a line, that adjustment may have a mutual or reciprocal influence on other styli relative to their recorded lines.” The sequelae of adjustments recommended by Denar Corp. take into account these reciprocal influences to facilitate the most efficient adjustment of any articulator to a pantographic record. For example, the right and left sagittal protrusive condylar paths should be adjusted concurrently until both horizontal styli follow the protrusive tracings simultaneously. Other adjustments which should be undertaken concurrently are the right sagittal orbiting path with the left top wall and the left sagittal orbiting path with the right top wall. Since the sagittal orbiting path adjustments were not included in the present study, the latter two reciprocal actions were not relevant. It was noted by the participants during Experiments 2 and 3 that, although the progressive side-shift adjustments were correct initially and the styli were following their respective tracings, when they came back to the beginning to double-check, they found in many cases that the styli no longer followed the progressive side-shift tracings. Further investigation was carried out because of the poor results obtained for this adjustment, particularly the right side, compared with those obtained from Experiment 1. The rear-wall and top-wall adjustments were the only additional adjustments to those in Experiment 1, and it was thought that this might have had some bearing on the poor progressive side-shift results due to some reciprocal actions between them which are not mentioned in the Denar manual. Consequently, all the results in Experiment 2 were assessed with a computer to see if there were other reciprocal actions between any of the adjustments. The computer showed that, at the 1 per cent level, there was a definite correlation of results between the progressive side shift on the right and the top wall on the right. There was no comparable correlation between the same adjustments on the left. When subsequently evaluating these observations on the articulator more closely, it was found that, on both sides, topwall values on the “U” side gave lower immediate and progressive side-shift values, while top-wall values on the “D” side gave higher immediate and progressive sideshift values. These findings probably account for the poor progressive side-shift results found in Experiment 2. (2) Inability to follow tracings initially. When initially adjusting the immediate side shift, the line A-B is often not horizontal but is angled as shown in the diagram (Fig. 5). The stylus at this stage will only move horizontally, and so the immediate side shift has to be estimated at point B1 in the figure. After the other adjustments have been carried out, the stylus will follow line A-B and any correction can be made. (3) Extreme adjustments. The top-wall adjustments in certain extreme positions may catch the posterior vertical tables and cause inaccuracy. It was sometimes found
670
J. Prosthet. Dent. December, 1977
Winstanley
Fig. 5. Diagrammatic presentation of a tracing on the left posterior horizontal table: A-D, tracing from protrusive movement; A-B, immediate side-shift tracing; B-C, progressive side-shift tracing; A-E, tracing from rotating condyle during lateral excursion.
to be difficult to carry out certain articulator movements smoothly in extreme positions, but this “grating” could be eliminated by the use of a thin coating of lubricant on the condylar spheres. (4) Assembly and instructions. The rear-wall adjustments were incorrectly assembled initially with so much “slack” that errors of 5 to 10 degrees were present before any adjustment was carried out. The rear-wall assembly on the “B” side can be adjusted to 40 degrees, whereas, in the instruction manual, this is said to be 30 degrees. (5) Flexibility. Although great care was taken in these experiments to reduce flexibility, it is obvious that, in clinical use, the flexibility of the clutches and the pantograph itself will lead to errors. (6) Following the tracings after completion of adjustments. Originally, it was thought possible to arrive at a set of articulator adjustments which are different from the original ones but which still allow the styli to follow all the tracings. However, it was found that, in almost every instance, when checking after the settings had been noted for experimental use, at least one stylus did not follow a tracing accurately. Nevertheless, in many instances, it was extremely difficult to adjust the articulator in such a way that every stylus followed every tracing exactly. (7) Line
of vision.
Difficulties
were sometimes
encountered,
because
it was found
that the line of vision to some of the styli points following the tracings was obscured by the styli themselves. DISCUSSION The present study was undertaken to determine the reproducibility of articulator settings using the Denar pantograph and articulator and to determine what effect familiarity in the use of these instruments had on the results. Watt3 presented results he had obtained using an unnamed articulator (probably a Hanau) and graphic
Volume
38
Number
6
Use of Denar
pantograph
and
articulator
671
records (probably the Denar pantograph). Since his work suggested that the pantograph gave unreliable results, a more detailed examination of the use of a pantograph for studying mandibular movements was required. Customary statistical methods, including standard deviations and mean values, were included in the present study, although it was thought that standard deviations had little significance because of the. small number of participants-18 in each of the first two experiments in this investigation. Mean values also are probably of little significance, since it is the spread of results about the correct settings which is important. For example, in the present study, the mean value for the left progressive side shift obtained by the clinicians in Experiment 2 was 4.83 degrees. The correct values was 5 degrees, and yet the range of settings was 0 to 9 degrees (Table II) . The order in which adjustments were carried out and the influence of reciprocal actions are important aspects of this investigation. For example, the adjustments of sagittal protrusive condylar inclination were carried out concurrently as advised in the procedure manual. Moberg and associates5 also commented on this and recommended adjustment in accordance with those procedures outlined by Guichet4 in order to avoid inaccuracies. The adjustments of orbiting sagittal condylar inclination were not included in the present study, since they must have the same articulator values as the adjustments of sagittal protrusive condylar inclination when, as already explained, the articulator is used as the “patient.” When all the other adjustments have been carried out correctly, the respective styli must follow the paths of orbiting sagittal condylar inclination. The vertical axes are set initially on the Denar articulator with the immediate side-shift values at zero, as previously explained, and when the articulator is the “patient,” these adjustments cannot be introduced satisfactorily. Watt concluded that, “. . . the high probability of error in the use of this type of instrument made it inacceptable as a means of diagnosing occlusal disturbances.” This is not the conclusion that would be drawn from the present study. Since this work was concerned with the reproducibility of the articulator settings from pantographic tracings and was not undertaken on patients, no comment can be made upon their use in reproducing mandibular movements. However, the experiments in this work did show that most of the articulator adjustments were reproducible with a reasonable degree of accuracy. The rear-wall and top-wall adjustments are of questionable value in reproducing mandibular movements with this technique, since the results for these adjustments were disappointing. Familiarity with the technique increased the accuracy in reproducing the settings. Faults which were probably isolated to the instrument used in this study also gave rise to some of the inaccurate results, particularly the initial slackness in the rear-wall adjustments. SUMMARY An investigation was undertaken to determine the reproducibility of articulator settings from graphic records of simulated mandibular movement using the Denar pantograph and the Denar D4-A articulator. The results of the study showed that most of the articulator adjustments were
672
J. Prosthet. Dent. December, 1977
Winstanley
reproducible with a reasonable degree of accuracy, although not quite to the extent one would hope for. The rear-wall and top-wall adjustments are of questionable value in reproducing mandibular movements with this technique, since the results for these adjustments in the present study were unreliable. However, familiarity with the technique gave better results, as shown in the third experiment. It would, therefore, seem that much of the basis for adverse reports depended upon results obtained by operators with insufficient experience in the technique. I should like to thank Professor E. L. Hampson for his help and encouragement in the preparation of this article. Thanks are also due to Mr. G. E. White for his technical assistance; Mr. R. Cousins for the photography; Mrs. T. S. Wood for the preparation of histograms; and to the staff and students of the Dental School who participated in the experiments.
References 1.
2. 3. 4. 5.
McCollum, B. B., and Stuart, C. E.: A Research Report. Basic Text for the Postgraduate Course in Gnathology, School of Dentistry, University of Southern California, South Pasadena, Calif., 1955, Scientific Press, p. 6. Weinberg, L. A.: An Evaluation of Basic Articulators and Their Concepts. Part IV. Fully Adjustable Articulators, J. PROSTHET. DENT. 13: 1038-1054, 1963. Watt, D. M.: A Study of the Reproducibility of Articulator Settings From Graphic Records of Mandibular Movement, Dent. Pratt. Dent. Rec. 19: 119-122, 1968. Guichet, N. F.: Procedures for Occlusal Treatment, A Teaching Atlas, Anaheim, 1969, Denar Corporation, pp. 68, 19-20, 74-75, 75. Moberg, C. T., Yoder, J. L., and Thayer, K. E.: The Pantograph as a Face-Bow Transfer Instrument, J. PROSTHET. DENT. 29: 139-145, 1973. UNIVERSITY
OF SHEFFIELD OF CLINICAL DENTISTRY CHARLES CLIFFORD DENTAL HOSPITAL WELLESLEY RD. SHEFFIELD SlO 2SZ, ENGLAND
SCHOOL
ARTICLES
TO
APPEAR
IN
FUTURE
ISSUES
I 1 Histochemical and complete dentures Mahmoud
Khamis
Abdel
The prevalence population Carl
E. Rieder,
histopathologic
and
Razek,
magnitude
M.S.,
of the
alveolar
mucosa
under
N.
Shaaban,
M.B.Ch.D.,
Ph.D.
and
of mandibular
A.
displacement
in a survey
D.D.S.
Air flow and intelligibility with a prosthodontically Carl
B.Ch.D.,
studies
R. Schneiderman,
Ph.D.,
of speech of normal repaired cleft palate and
Mary
B. Mann,
Ph.D.
speakers
and
speakers
J. SHARRY,
Section
Observations
editor
on the use of the Denar
pantograph
and articulator R. B. Winstanley,
B.D.S., F.D.S., R.C.S.(Ed.l*
University of Shefield School of Clinical Dentistry, Charles Clifford Dental Hospital, Shefield, England
M
cCollum and Stuart1 developed the pantograph in 1930 as a research tool to study and record mandibular movements. The pantograph can also be used as a conventional face-bow to locate the maxillary cast in relation to the posterior reference points and the horizontal reference plane when transferring the maxillary cast to the articulator. The diagnostic data recorded by the Denar pantograph are expressed in millimeters and degrees in the calibrated control adjustments of the articulator. These numerical values are related to specific positions or reference planes which can be relocated precisely. Inability of the articulator to follow the recordings exactly does not necessarily discount its diagnostic value, since it can give valuable information as to what is happening in the temporomandibular joint. The value of an articulator lies in the degree to which it enables the operator to study existing dentitions during function and to construct restorations in such a way that satisfactory function results. Weinberg2 gave a detailed account of fully adjustable articulators and came to the conclusion that only the gnathologic type (such as the Denar) “reproduces three dimensional guidance of the working condyle” and is “the instrument of choice among the fully adjustable articulators.” Although many other authors recognize the benefits derived from the use of fully adjustable articulators, Watt,3 in his study of the reproducibility of articulator settings from graphic records, concluded that “the high probability of error in the use of this type of instrument made it inacceptable as a means of diagnosing occlusal disturbances.” In view of the widespread use of gnathologic instruments, it was thought important to ascertain if Watt’s criticism of these instruments, based on observations on the reproducibility of articulator settings from graphic records, was fully justified. *Lecturer 660
in Restorative Dentistry.
Volume Number
38 6
Use of Denar pantograph
(A) Articulator. (B) Pantograph. 2. (A) Styli. (B) Tracings covered
Fig.
1.
Fig. (D)
Lower
by protective
overlays.
and articulator
(C)
Central
bearing
661
screw.
clutch.
The present study was designed to investigate the reproducibility of articulator settings obtained from graphic records using the Denar pantograph and Denar articulator. A number of people who were unfamiliar with these instruments agreed to take part, and the results obtained by them were compared with those obtained by two participants familiar with the technique. This investigation was thought necessary before further work could be undertaken to determine how accurately this articulator reproduces mandibular movements. MATERIALS
AND
METHODS
The Denar D4-A articulator experiments (Fig. 1) . Experiment
and
the
Denar
pantograph*
were
used
for
all
1
Clutches were constructed on upper and lower diagnostic casts of a patient with a complete dentition. The clutches were rigidly cemented to the casts so that movement could not take place between clutch and cast. The clutches and diagnostic casts were mounted on the articulator, and the central bearing screw was adjusted in height so that there was a small clearance between the clutches. The posterior control adjustments of the articulator were set at arbitrary values which were noted. The pantograph was assembled on the articulator and connected rigidly to the clutches. A pantographic survey was carried out with, in this instance, the articulator acting as “the patient.” The upper part of the articulator was manipulated to simulate right and left lateral excursive movements and a protrusive movement. The tracings made by the styli were protected by the transparent overlays, and the articulator adjustments were set to zero (Fig. 2). Six experienced dentists, six dental laboratory technicians, and six dental students were asked to adjust the articulator so that the styli again followed the tracings. “Denar
Corporation,
Anaheim,
Calif.
662
Winstanley
J. Prosthet. Dent. December, 1977
Only two of the 18 participants were experienced in the use of the Denar articulator. Measures intended to verify if the styli were following the tracings exactly were omitted deliberately, since it was thought that this would prejudice the results. HOWever, each person was asked to repeat the adjustments, if necessary, until he was satisfied that consistent results had been obtained and the styli were following all the tracings. In this particular experiment, only the sagittal protrusive condylar inclination and the immediate and progressive side-shift adjustments were carried out; the adjustments were not included. Since the articulator “rear-wall” and “top-wall” itself was acting as the “patient” when the pantographic tracings were made, neither the vertical axes adjustments nor the sagittal orbiting condylar path adjustments were included, as they were irrelevant to this experiment. Vertical axes. The Denar manual4 outlines the procedure for transferring the pantograph from the patient to the articulator and for adjusting the articulator to the pantographic record. These instructions are taken by this author to mean that the vertical axes are set initially during the transfer procedure from the patient to the articulator by means of the telescopic mounting axis which registers the intercondylar distance. If the medial components of the anterior Gothic arch tracings are not followed exactly by the styli (after the correct sequence of prior adjustments has been carried out), a slight difference between the intercondylar distance on the patient and that on the articulator is indicated, necessitating adjustment of the vertical axes. However, when the articulator is itself the “patient,” the intercondylar distance must be correct, and when all the other adjustments are satisfactory, the styli will follow the medial components of the anterior Gothic arch tracings. The only way in which the vertical axes adjustments could have been incorporated into the present experiment would have been to move the condylar spheres (i.e., the vertical axes) laterally when the other adjustments were set to zero before asking the participants to adjust the articulator so that the styli followed the tracings. It would then have been necessary to explain to the participants that the condylar spheres should be moved medially until they make contact with the medial fossae walls while the articulator is locked in the centric position and the immediate sideshift values are set at zero. This would have set the vertical axes in the original positions from which the tracings were made, and it would have been an unnecessary part of the experiment. Sag&al orbiting condylar paths. These values were not recorded, because they were the same as the sagittal protrusive condylar inclination paths in this experiment, since both tracings on each side were obtained with the same articulator settings for that particular side. However, checks were made by those carrying out the experiments to verify that the orbiting tracings were, indeed, followed by the styli in lateral movements. If they were not, then the articulator had not been adjusted correctly, and it was necessary to repeat the experiment. Results. Results are shown in Table I in the order in which adjustments were carried out. Most participants adjusted the sagittal protrusive condylar inclination correctly on the right side, although there was a variation of between 38 and 41 degrees. There was a tendency, which was difficult to explain, to underestimate
’
Volume Number
38 6
Table
1. Results
Use of of Experiment
Adjustment
R
L
40”
30”
Progressive side shift
pantograph
Range of resettings
Mean value
and articulator
663
1
Original settings Sagittal protrusive condylar inclination Immediate side shift
Denar
Operator
Clinicians Technicians Students Over-all 1.2 mm. 0.4 mm. Clinicians Technicians Students Over-all 15O 5” Clinicians Technicians Students Over-all
R 41138 40 40138 41138 1.411.2 1.4/l .O 1.411.O 1.411.O 15 15/14 15/14 15114
L 31125 32121.5 31121 32/25 0.4 0.4/0.2 0.4fO.2 0.410.2 IO/5 5
614 1014
RIL 39.17 40.00 39.50 39.56 1.32 1.20 1.17 1.23 15 14.67 14.67 14.78
S.D. RIL
21.67 29.67 29.33 28.89 0.4 0.28 0.28 0.32 5.83 5.00 5.00 5.28
1.17 0 0.84 0.86 0.10 0.18 0.14 0.15 0 0.52 0.52 0.43
Standard error of S.&l. R[L
2.48 1.54 1.51 2.00 0 0.10 0.10 0.09 2.04 0 0.63 1.23
0.34 0 0.24 0.14 0.03 0.05 0.04 0.03 0 0.15 0.15 0.07
0.72 0.44 0.44 0.33 0 0.03 0.03 0.02 0.59 0 0.18 0.21
rather than overestimate. This was looked at more closely after completion of the experiment, because it was thought that, with a setting 5 degrees below the correct setting the stylus might follow the tracing more closely than at a setting 5 degrees above the correct setting, which might explain this tendency to underestimation. However, the stylus was found to follow a line parallel to the tracing, either above or below, by an equal amount with each setting of 5 degrees above or below. The sagittal protrusive condylar inclination on the left side showed greater variation than that on the right side, with values ranging from 25 to 32 degrees. Again, there was a tendency to underestimate which could not be explained. The immediate side shift on the right side gave a spread of 1 .O to 1.4 mm., with a tendency to overestimate. This is in keeping with the fact that, with small adjustments, there is a natural tendency to overestimate. However, nobody overestimated on the left side, these readings being between 0.2 and 0.4 mm. The line of vision when carrying out this adjustment on the left side is such that underestimation is more likely to occur, the articulator usually being positioned in front of and below, rather than directly below, a right-handed person. The progressive side-shift adjustments were accurate on both sides, apart from one reading on the left side (10 degrees). These are relatively more easy to adjust satisfactorily, since the tracings are longer and follow an almost straight line. Experiment
2
This experiment was similar to the previous one but included the “rear-wall” and “top-wall” adjustments. The pantographic survey was carried out initially on a patient, and the pantograph was transferred to the articulator. It was at first decided to let the same three groups (although not necessarily the same individuals) adjust the articulator until the styli followed the tracings. However, it was realized that this would not help in an investigation into the reproducibility of articulator settings, since there were no values with which the results obtained by the participants could
J. Prosthet. Dent. December, 1977
664
Winstanley
Table
II. Results of Experiment
Original Adjustment
Sag&al protrusive
R
2
settings I
Range L
25”
30°
Immediate side shift
0.8 mm.
0.2 mm.
Progressive side shift
10”
5O
Rear wall
30B
30B
Top wall
15U
5U
condylar inclination
Operator
Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all Clinicians Technicians Students Over-all
of resettings
R
L
21125 28/25 25124 28124 0.9/0.6 0.8/0.4 0.910.8 0.9/0.4 II/3 7/4 1217 12/3 3OBfO 40B/20F 39B/18F 40B/20F 24U/19D 0/21D ZSU/SU 25U/21D
30128 3 l/30 30/28 3 l/28 0.410.2 0.4/o. 1 0.4/0.2 0.4/o. I 9/O 111 II/5 II/O 40B/19B 30B/15B 39B/lOB 40B/lOB IOU/9D 15lJfZOD 15U/18D
25U/20D
be compared. It was also noticed that some of the fossa inserts would have to be replaced with curved inserts, and this could lead to confusion for the participants unaccustomed to the Denar system. To overcome this problem, the following method was adopted; the two people who had had experience with the Denar system adjusted the articulator until the styli followed the tracings as accurately as possible, using modified inserts where necessary. When both agreed that the articulator was correctly adjusted, the articulator readings were noted, and these were used as the original measurements. New tracings were then made by the pantograph on the articulator to these figures and protected by the transparent overlays. The articulator adjustments were set to zero, and the same three groups (although not necessarily the same individuals) were again asked to adjust the articulator until the styli followed all the tracings. This time, all the articulator adjustments were included, apart from the vertical axes and the orbiting path sagittal condylar inclination which were not included for the reasons already discussed in Experiment 1. Results. Results are shown in Table II in the order in which adjustments were carried out. Sagittal protrusive condylar inclination values on the right ranged from 24 to 28 degrees, with a tendency to overestimate, in contrast to the tendency found in the previous experiment. On the left side, there was a tendency to underestimate these values, although not significantly so, as in the first experiment, with a range of 28 to
Volume Number
3R 6
Mean
Use of Denar
value
pantograph
S.D.
II
and
Standard
articulator
error
665
of S. D
I
R
L
R
L
R
L
25.50 25.83 24.83 25.39
29.17 30.50 29.50 29.72
0.84 1.33 0.41 0.98
0.98 0.55 0.84 0.96
0.24 0.38 0.12 0.16
0.28 0.16 0.24 0.16
0.78 0.70 0.82 0.77
0.21 0.25 0.25 0.26
0.10 0.17 0.04 0.12
0.08 0.12 0.08 0.09
0.03 0.05 0.01 0.02
0.02 0.04 0.02 0.02
8.00 5.33 8.67 7.33
4.83 4.83 7.33 5.67
3.22 1.03 2.07 2.61
2.86 2.04 2.73 2.70
0.93 0.30 0.60 0.44
0.82 0.59 0.79 0.45
14.83B 18.67B 14.17B 15.898
32.OOB 20.50B 23.758 25.42B
11.14 20.90 20.74 17.19
7.92 5.75 10.24 9.16
3.22 6.03 5.99 2.87
2.?Y 1.66 2.Y5 I.53
5.67U IO.OOD 12.17U 2.6lU
2.OOu 0.83D 4.17u l.78U
16.45 8.74 8.45 14.65
7.32 12.42 13.96 II.09
4.15 2.52 2.44 2.44
2.11 3.58 4.03 1.85
31 degrees. More participants obtained the correct values in this experiment than in the previous one, and this may be because superior fossa wall inserts with more curvature were used and perhaps gave a tracing which, although more curved, was easier to follow. At the end of the experiment, the tendency to under- or overestimate was examined to see if the styli followed the tracings more closely with settings 5 degrees above or 5 degrees below the correct setting. No significant difference was found. The immediate side-shift values on the right ranged from 0.4 to 0.9 mm., with more participants obtaining the correct value than in the previous experiment. This time, there was a tendency to underestimate. On the left side, the same number of participants in Experiment 1 obtained the correct values but there was a tendency to overestimate (in distinction to the first experiment), with values ranging from 0.1 to 0.4 mm. This is the obvious tendency with such a low figure of 0.2 mm. i the correct setting). The results of the progressive side shift on the right side were disappointing (values ranging from 3 to 12 degrees), and only two participants obtained a correct result. This is even more surprising when compared with the progressive side-shift readings on the right side in the first experiment which were much better. The explanation for this will be discussed more fully later and is due to reciprocal action between the right progressive side-shift adjustment and the right top-wall adjustment. Although most of the participants obtained the correct value of 5 degrees on the left side, there was a variation of from 0 to 11 degrees.
666
J. Prosthet. Dent. December, 1977
Winstanley VALUES
ROUNDED
TO
NEAREST
VALUES ROUNDED
5’
22.5’
SHOWN
TO NEAREST AS
5’
20”
+
Fig. “ALES
3. Histograms
ROUNDED
TO
NEAREST
of rear-wall
results
in Experiment
2.
VALUES ROUNDEDTO NEAREST5’
5’
4
25”
t0”
IS”
IOU
5U
0
SD
IO0
Fig. 4. Histogrank
ISD
2OD
PSD
of top-wail
results
in Experiment
2.
The results obtained from the rear-wall adjustments have a range of from 20F to 40B (a spread of 60 degrees) on the right side and 10B to 40B (a spread of 30 degrees) on the left side. This can be seen more clearly in the histogram (Fig. 3). It can only be concluded that these were very inaccurate adjustments, likely due to the fact that the tracings were short and large variations in the settings cause only small deviations of the styli. In fact, it is difficult to decide if the correct setting on the right side is in front of or behind the coronal plane. The results obtained from the top wall are similarly very poor, as shown by the histogram (Fig. 4)-the right side being inferior to the left. The range on both sides is 20D to 25U (a spread of 45 degrees), but on the right side, only one participant obtained the correct result. As with the rear wall, it is difficult to decide whether the correct setting is above or below the horizontal plane. Some difficulty could be explained by the fact that gross movements of these adjustments give only small alterations to the paths of the styli and by the fact that the top-wall tracings are very short. This experiment was more difficult for the inexperienced operators to carry out, because more adjustments were included and curved fossa inserts were used. In addition, because there was some “slack” in the rear-wall adjustments, errors oft 5 to 10 degrees inevitably occurred. The rear-wall and top-wall adjustments were not easy
Volume Number
Table
38 6
Use of Denar
III. Results
of sagittal
A ‘s settings (degrees)
B’s resettings (degrees)
Right
Right 25 35 32.5 26 21.5 11
Le/ 30 25 20 25 25 20
25 35 30 25 25 IO Table
Left 30 25 22.5 25 21.5 21
IV. Results of immediate
A’s settings (mm.1 Right Left 0.4 1.6 0.4 '0.8 0.8 0.4
B’s resettings (mm.)
0.8 0.8 I.0 0.6 0.6 0.4
protrusive
condylar
Difference (degrees)
pantograph inclination
B’s settings
side shift Difference (mm.)
(Experiment A ‘s resettings
(degrees)
Right 1 Left 0 0 0 0 2.5 2.5 1 0 2.5 2.5 1 1
and articulator
(degrees)
Right 1 Left 10 20 35 30 15 20 30 20 25 30 10 20 (Experiment
Right 8 37.5 15 32 25 10
667
3) Difference (degrees)
Leji 20 30 20 20 32 20
Right 2 2.5 0 2 0 0
1 Left 0 0 0 0 2 0
3)
B’s settings (mm.1
A’s resettings (mm.)
Right
Left
Right
Left
Right
1 Left
Right
Left
0.4 1.7 0.4 0.9 1.0 0.2
0.9 1.0 1.0 0.8 0.6 0.2
0 0.1 0 0.1 0.2 0.2
0.1 0.2 0 0.2 0 0.2
0.4 0.6 0.4 0.2 0.6 0.8
0.4 0.8 0.4 0.2 0.6 1.o
0.5 0.6 0.6 0.4 0.6 0.9
0.5 0.6 0.4 0.4 0.5 0.9
Difference (mm.) Right 1 Left 0.1 0 0.2 0.2 0 0.1
0.1 0.2 0 0.2 0.1 0.1
to manipulate, making it difficult for the styli to follow the tracings. A large movement of these controls during adjustment often made only small differences to the direction traveled by the styli. As in the first experiment, the “feel” of the articulator was so different from that of conventional articulators that many of the participants experienced difficulty in the beginning of the adjustments. Experiment
3
This experiment was undertaken to see if better results could be obtained when operators experienced in the use of the Denar system adjusted the articulator so that the styli followed the tracings. It was thought that unless a person was familiar with the articulator, consistent results could not be obtained. Before the start of this experiment, the defect in the rear-wall adjustments was eliminated. The experiment was performed in the same manner as Experiment 1 using a pantographic survey made by the articulator which was adjusted to random values, and two people participated in the experiment. The participants will be referred to as A and B. Operator A adjusted the articulator to certain values, noted the readings, made the tracings to these values, and then set each to zero. B adjusted the articulator until the styli once again followed the tracings, and the readings were noted by A. This was repeated six times, each time with different settings which were unknown to B. A and B then reversed roles, and a further six experiments were carried out. Results. Results are shown in Tables III to VII.
J. Prosthet. Dent. December, 1977
668
Winstanley
Table
V. Results of progressive
A ‘s settings (degrees)
B’s resettings (degrees)
Right
1 Left
Right
IO
5
10 10 15 15 10
5 10 10 IO 10
10 I 13 I1 I1 10
Table
VI. Rear-wall
A ‘s settings (degrees) Right
10F 15B 15F 208 20B 20F Table
1 Left
5F 5F 10B 15B 15B 10F
Right
5D 5U 10D 5U 5U 5D
5F 15B 15F 15B 20B 25F
VII. Top-wall
A’s settings (degrees) Left
15D 5U 5D 5D 5D 10D
Difference (degrees)
1 Leji
5 3 6 10 6 10 results
B’s resettings (degrees) Right
1 Left
2.5F 5F 10B 14B 15B 25F results
B’s resettings (degrees) Right
5D 5U 0 4D 2D 12D
side shift (Experiment
1 Left
25D 5D 20D 9D 14D 17D
3)
B’s settings (degrees)
A’s resettings (degrees)
Right
) Left
Right
1 Left
Right
0 3 3 4 4 0
0 2 4 0 4 0
IO
10
5 10 10 15 10
10 10 15 10 5
15 5 10
(Experiment
5 0 0 5 0 5
B’s settings (degrees) Left
10
15 10
1 Left
5 0 0 0 0 0
0 0 10 0 0 4
20F 15F IOF 10F 5F 15F
1 Left
10F 20F 15F 5F IOF 5F
A’s resettings (degrees) 1 Right
20F 20F 25F 6F 7F 12F
1 Left
10F 5F 12F 5B 6F 5F
Difference (degrees) 1 Right
I Left
0 5 15 4 2 3
0 15 3 10 4 0
3)
Difference (degrees)
0 0 10 9 7 7
Right
2.5 0 0 1 0 15 1
(Experiment
Right
10 10 20 15 10 9
Right
3)
Difference (degrees) Right
1 Left
Difference (degrees)
B’s settings (degrees) Left
Right
10 5D 10 5U 15 IOD 4 10D 9 5D 7 ( IOD
I Lef
10D IOU IOD 15D 15D 15D
A’s resettings (degrees) Right
15u 5u 7D 15D 5D 10D
Left
10D IOU 20D 13D 15D 4D
Difference (degrees) Right
20 0 3 5 0 0
I Left
0 0 10 2 0 11
The measurements for the sagittal protrusive condylar inclination and those for the immediate side shift differed from the original settings by only a small amount. Although there was some spread with some of the individual results, the range of this spread was small, and where incorrect settings had been obtained, they were close to the correct ones. The progressive side-shift results were variable. B tended to underestimate on both sides, while A was much closer to the correct settings, although there was one difference of 10 degrees, one of 5 degrees, and one of 4 degrees-all overestimated. The rear-wall measurements, although subject to variation of as much as 15 degrees, were an improvement on those in the second experiment. The top-wall results were similar to the rear-wall results, with variations of up to 20 degrees, but with much closer approximation to the correct settings than had been obtained in Experiment 2.
Volume Number
38 6
Use of Denar
pantograph
and articulator
669
These results, ,especially the latter two adjustments, indicated that familiarity with the Denar system gave more consistent results, although the elimination of “slack” in the rear-wall adjustments must have had some effect on this. OBSERVATIONS Seven observations were made during this study of the Denar system. (1) Reciprocal actions. The Denar procedure manual” states, “. . , when an articulator is adjusted to move one stylus relative to a line, that adjustment may have a mutual or reciprocal influence on other styli relative to their recorded lines.” The sequelae of adjustments recommended by Denar Corp. take into account these reciprocal influences to facilitate the most efficient adjustment of any articulator to a pantographic record. For example, the right and left sagittal protrusive condylar paths should be adjusted concurrently until both horizontal styli follow the protrusive tracings simultaneously. Other adjustments which should be undertaken concurrently are the right sagittal orbiting path with the left top wall and the left sagittal orbiting path with the right top wall. Since the sagittal orbiting path adjustments were not included in the present study, the latter two reciprocal actions were not relevant. It was noted by the participants during Experiments 2 and 3 that, although the progressive side-shift adjustments were correct initially and the styli were following their respective tracings, when they came back to the beginning to double-check, they found in many cases that the styli no longer followed the progressive side-shift tracings. Further investigation was carried out because of the poor results obtained for this adjustment, particularly the right side, compared with those obtained from Experiment 1. The rear-wall and top-wall adjustments were the only additional adjustments to those in Experiment 1, and it was thought that this might have had some bearing on the poor progressive side-shift results due to some reciprocal actions between them which are not mentioned in the Denar manual. Consequently, all the results in Experiment 2 were assessed with a computer to see if there were other reciprocal actions between any of the adjustments. The computer showed that, at the 1 per cent level, there was a definite correlation of results between the progressive side shift on the right and the top wall on the right. There was no comparable correlation between the same adjustments on the left. When subsequently evaluating these observations on the articulator more closely, it was found that, on both sides, topwall values on the “U” side gave lower immediate and progressive side-shift values, while top-wall values on the “D” side gave higher immediate and progressive sideshift values. These findings probably account for the poor progressive side-shift results found in Experiment 2. (2) Inability to follow tracings initially. When initially adjusting the immediate side shift, the line A-B is often not horizontal but is angled as shown in the diagram (Fig. 5). The stylus at this stage will only move horizontally, and so the immediate side shift has to be estimated at point B1 in the figure. After the other adjustments have been carried out, the stylus will follow line A-B and any correction can be made. (3) Extreme adjustments. The top-wall adjustments in certain extreme positions may catch the posterior vertical tables and cause inaccuracy. It was sometimes found
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J. Prosthet. Dent. December, 1977
Winstanley
Fig. 5. Diagrammatic presentation of a tracing on the left posterior horizontal table: A-D, tracing from protrusive movement; A-B, immediate side-shift tracing; B-C, progressive side-shift tracing; A-E, tracing from rotating condyle during lateral excursion.
to be difficult to carry out certain articulator movements smoothly in extreme positions, but this “grating” could be eliminated by the use of a thin coating of lubricant on the condylar spheres. (4) Assembly and instructions. The rear-wall adjustments were incorrectly assembled initially with so much “slack” that errors of 5 to 10 degrees were present before any adjustment was carried out. The rear-wall assembly on the “B” side can be adjusted to 40 degrees, whereas, in the instruction manual, this is said to be 30 degrees. (5) Flexibility. Although great care was taken in these experiments to reduce flexibility, it is obvious that, in clinical use, the flexibility of the clutches and the pantograph itself will lead to errors. (6) Following the tracings after completion of adjustments. Originally, it was thought possible to arrive at a set of articulator adjustments which are different from the original ones but which still allow the styli to follow all the tracings. However, it was found that, in almost every instance, when checking after the settings had been noted for experimental use, at least one stylus did not follow a tracing accurately. Nevertheless, in many instances, it was extremely difficult to adjust the articulator in such a way that every stylus followed every tracing exactly. (7) Line
of vision.
Difficulties
were sometimes
encountered,
because
it was found
that the line of vision to some of the styli points following the tracings was obscured by the styli themselves. DISCUSSION The present study was undertaken to determine the reproducibility of articulator settings using the Denar pantograph and articulator and to determine what effect familiarity in the use of these instruments had on the results. Watt3 presented results he had obtained using an unnamed articulator (probably a Hanau) and graphic
Volume
38
Number
6
Use of Denar
pantograph
and
articulator
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records (probably the Denar pantograph). Since his work suggested that the pantograph gave unreliable results, a more detailed examination of the use of a pantograph for studying mandibular movements was required. Customary statistical methods, including standard deviations and mean values, were included in the present study, although it was thought that standard deviations had little significance because of the. small number of participants-18 in each of the first two experiments in this investigation. Mean values also are probably of little significance, since it is the spread of results about the correct settings which is important. For example, in the present study, the mean value for the left progressive side shift obtained by the clinicians in Experiment 2 was 4.83 degrees. The correct values was 5 degrees, and yet the range of settings was 0 to 9 degrees (Table II) . The order in which adjustments were carried out and the influence of reciprocal actions are important aspects of this investigation. For example, the adjustments of sagittal protrusive condylar inclination were carried out concurrently as advised in the procedure manual. Moberg and associates5 also commented on this and recommended adjustment in accordance with those procedures outlined by Guichet4 in order to avoid inaccuracies. The adjustments of orbiting sagittal condylar inclination were not included in the present study, since they must have the same articulator values as the adjustments of sagittal protrusive condylar inclination when, as already explained, the articulator is used as the “patient.” When all the other adjustments have been carried out correctly, the respective styli must follow the paths of orbiting sagittal condylar inclination. The vertical axes are set initially on the Denar articulator with the immediate side-shift values at zero, as previously explained, and when the articulator is the “patient,” these adjustments cannot be introduced satisfactorily. Watt concluded that, “. . . the high probability of error in the use of this type of instrument made it inacceptable as a means of diagnosing occlusal disturbances.” This is not the conclusion that would be drawn from the present study. Since this work was concerned with the reproducibility of the articulator settings from pantographic tracings and was not undertaken on patients, no comment can be made upon their use in reproducing mandibular movements. However, the experiments in this work did show that most of the articulator adjustments were reproducible with a reasonable degree of accuracy. The rear-wall and top-wall adjustments are of questionable value in reproducing mandibular movements with this technique, since the results for these adjustments were disappointing. Familiarity with the technique increased the accuracy in reproducing the settings. Faults which were probably isolated to the instrument used in this study also gave rise to some of the inaccurate results, particularly the initial slackness in the rear-wall adjustments. SUMMARY An investigation was undertaken to determine the reproducibility of articulator settings from graphic records of simulated mandibular movement using the Denar pantograph and the Denar D4-A articulator. The results of the study showed that most of the articulator adjustments were
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Winstanley
reproducible with a reasonable degree of accuracy, although not quite to the extent one would hope for. The rear-wall and top-wall adjustments are of questionable value in reproducing mandibular movements with this technique, since the results for these adjustments in the present study were unreliable. However, familiarity with the technique gave better results, as shown in the third experiment. It would, therefore, seem that much of the basis for adverse reports depended upon results obtained by operators with insufficient experience in the technique. I should like to thank Professor E. L. Hampson for his help and encouragement in the preparation of this article. Thanks are also due to Mr. G. E. White for his technical assistance; Mr. R. Cousins for the photography; Mrs. T. S. Wood for the preparation of histograms; and to the staff and students of the Dental School who participated in the experiments.
References 1.
2. 3. 4. 5.
McCollum, B. B., and Stuart, C. E.: A Research Report. Basic Text for the Postgraduate Course in Gnathology, School of Dentistry, University of Southern California, South Pasadena, Calif., 1955, Scientific Press, p. 6. Weinberg, L. A.: An Evaluation of Basic Articulators and Their Concepts. Part IV. Fully Adjustable Articulators, J. PROSTHET. DENT. 13: 1038-1054, 1963. Watt, D. M.: A Study of the Reproducibility of Articulator Settings From Graphic Records of Mandibular Movement, Dent. Pratt. Dent. Rec. 19: 119-122, 1968. Guichet, N. F.: Procedures for Occlusal Treatment, A Teaching Atlas, Anaheim, 1969, Denar Corporation, pp. 68, 19-20, 74-75, 75. Moberg, C. T., Yoder, J. L., and Thayer, K. E.: The Pantograph as a Face-Bow Transfer Instrument, J. PROSTHET. DENT. 29: 139-145, 1973. UNIVERSITY
OF SHEFFIELD OF CLINICAL DENTISTRY CHARLES CLIFFORD DENTAL HOSPITAL WELLESLEY RD. SHEFFIELD SlO 2SZ, ENGLAND
SCHOOL
ARTICLES
TO
APPEAR
IN
FUTURE
ISSUES
I 1 Histochemical and complete dentures Mahmoud
Khamis
Abdel
The prevalence population Carl
E. Rieder,
histopathologic
and
Razek,
magnitude
M.S.,
of the
alveolar
mucosa
under
N.
Shaaban,
M.B.Ch.D.,
Ph.D.
and
of mandibular
A.
displacement
in a survey
D.D.S.
Air flow and intelligibility with a prosthodontically Carl
B.Ch.D.,
studies
R. Schneiderman,
Ph.D.,
of speech of normal repaired cleft palate and
Mary
B. Mann,
Ph.D.
speakers
and
speakers