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Fairbanks, Grant. Experimental Phonetics – T28

A Study Of Minor
Organic Deviations In ‘Functional’ Disorders
Of Articulation:
4. The Teeth And Hard Palate *1

Grant Fairbanks
Mary Van Horn Lintner **2

The present article reports a portion
of the results of an investigation which has
attempted to provide preliminary answers
to two questions: Are there organic differences
between persons with ‘functional’
articulatory disorders, as ordinarily classified,
and persons without disorders? If so, what
are some of the specific differences?

The first report of the series (4) included
a discussion of the problem and a
detailed description of the methods employed
in selecting the subjects, 60 young
adults who constituted the following four
groups: 15 males and 15 females with superior
consonant articulation; 15 males and
15 females with inferior consonant articulation.
Selection was at random from the extremes
of articulatory ability, as determined
by screening and testing; all ‘organic’ and
certain ‘functional’ types of speech disorders
were excluded. Subjects were brought into
the laboratory individually for a number of
measurements and estimates of (1) the rate
of movement of oral structures, (2) the lips,
(3) the tongue, (4) the teeth and hard
palate, and (5) hearing. The results, too
lengthy for a single article, are presented in
a series corresponding to these five divisions,
with summarization and interpretation reserved
for the final paper. The first three
divisions have already been reported (2,
3, 4).


The present division was concerned
with certain measurements and estimates.
Three dimensions of the hard
palate, corresponding to those of
Fymbo (5), were measured as follows:
(1) Cuspid width, the transverse diameter
between the lingual surfaces of
the cuspids at the highest points of
the gum lines; (2) molar width, the
transverse diameter between the lingual
surfaces of the first molars at the
highest points of the gum lines above
the prominences of the mesio-lingual
cusps; (3) palatal height, the midline
vertical distance from the plane of the
occlusal surfaces of the first molars to
the hard palate. An additional measurement
was made of the maximum
mouth opening, defined as the midline
distance between the cutting edges of
the central incisors with the mandible
maximally depressed.

The measurements of cuspid width
and molar width were made with an
orthodontic micrometer, 13 and their
reliability was evaluated by measuring
30 young adults twice on successive
days. Rank-difference correlation coefficients226

image scale

Figure 1. Palatometer.

between the sets of repeated
measurements were .91 and .97 for
cuspid and molar widths, respectively.

For the measurement of palatal
height the palatometer shown in Figure
1 was constructed. A Boley gauge
was modified by lengthening the two
straight arms 55 mm by means of bars.
A transverse plate, approximately
9 x 55 mm, was mounted on the end of
the fixed upper bar. From the end of
the movable lower bar a 45 mm rod
extended upward through a hole in
the transverse plate. In measurement
the transverse plate is placed against
the occlusal surfaces of the upper first
molars, and the upper fixed bar against
the upper incisors in the midline, these
three points establishing the zero
plane. The lowest bar is then elevated
until the rod touches the hard palate.
Palatal height is read from the scale by
subtracting the obtained value from 40
mm, that constant being the scale reading

Table 1. Measurements of the dental arch and of maximum mouth opening. Means, standard
deviations, and differences. All values in millimeters. Four basic groups of 15 subjects

tableau measure | superior | inferior | difference | cuspid width | male | AM | SD | female | molar width | palatal height | maximum mouth opening

* Superior — Inferior227

Table 2. Analysis of variance. Values in millimeters.

tableau measure | between groups | ability | sex | interaction | within groups | cuspid width | molar width | palatal height | maximum mouth opening

* df: Between Groups, 3
Ability, Sex, Interaction, 1
Within Groups, 56

F = Given Variance / Within Groups Variance
F, 3 & 55: 1%, 4.16; 5%, 2.78
1 & 55: 1%, 7.12; 5%, 4.02

at zero height: 2 4Reliability was examined
as above; the coefficient was

Maximum mouth opening was measured
with a Boley gauge, the subject
being instructed to open his mouth as
far as possible. The largest value obtained
in three successive trials was
used. Reliability was studied in the
same manner with a rank-difference
coefficient of .94.

The teeth of each subject were examined
and judged in four general respects:
(1) Molar occlusion, employing
the normal reference defined by
Angle (1), in which the antero-lateral
cusp of the upper first molar is aligned
with the buccal groove of the lower
first molar; (2) occlusion of the upper
and lower anterior teeth in both
antero-posterior and infero-superior
planes; (3) alignment of the individual
upper and lower incisors and cuspids;
(4) spaces (failures of proximal contact)
anterior to the bicuspids, both
upper and lower. Each of these four
items was rated on a Normal-Slight-Marked
deviation scale, and described
by the use of certain sub-categories
which will appear below. In this instance
reliability was estimated by
having one experimenter repeat the examinations
and judgments on two successive
days with 60 young adults.
Self-agreement percentages for the
above four items, including their subdivisions,
were 87, 83, 80, and 93, respectively.



Measurements. Means and standard
deviations are shown in Table 1 and
the results of analysis of variance in
Table 2. For the three palatal dimensions
the means are similar to those of
Fymbo (5) and the differences between
sexes are in the usual direction.
The differences between ability
groups, ser constant, are minor, and
228study of Table 2 will show that they
are not significant. In cuspid width
all F ratios are very small. For molar
width and palatal height the ratios
of the first column exceed the 5%
level, but the second and third
columns show that the differences
are attributable to sex and not to
ability. There is, in other words, no
basis for abandoning the hypothesis
that in palatal dimensions young adults
with inferior consonant articulation, as
defined in this experiment, do not differ
from those with superior articulation.

In maximum mouth opening the
findings are dubiously positive. The F
ratios in the first three columns of
Table 2, the second of which is for
ability, exceed the tabled 1%, 5%, and
1% values, respectively. Differences
between basic ability group means
in Table 1, however, do not exceed
the minimum of 4.12 required at the
5% level. In Table 1 it will be seen
that the means of the inferior groups
are larger than those of the superior
group in both sexes. This, finding is
not readily interpreted, since there is
no obvious direct connection between
size of mouth opening and articulatory
ability, unless it be in the opposite
direction. The latter hypothesis, in
fact, was the reason for including the
item. The most likely explanation
seems to be that the larger means of
the inferior subjects were produced
by higher incidence and severity of
openbite and overjet. Some support
for this speculation is given by the results
shown in Table 6 below, although
the data there permit no definite


Estimates. The general results of the
dental examinations are presented in
Table 3, which shows the distributions
of judgments for each of the four
main items, and, in parentheses, the
ratings of degree of severity of deviations
when present. For this section
the sex groups were combined into
two ability groups of 30 subjects each.

Study of Table 3 discloses that the
groups appear to differ in molar and
anterior occlusion, but not in anterior
alignment and spaces. Tests of significance, 35
however, provided no evidence
of anything but chance differences
and further analysis was not made of
these items as such.

The cases then were divided into
two categories: (1) Those judged to
be normal or to have only slight deviation

Table 3. Estimates of occlusion. Combined ability groups of 30 subjects each.

tableau rating | molar occlusion | anterior occlusion | anterior alignment | anterior spaces | sup. | inf. | no deviation | deviation | (slight) | (marked)229

Table 4. Relative incidence of marked dental deviations. Categories: No marked deviation
in any respect; one or more marked deviations in molar occlusion, anterior occlusion,
anterior alignment, or anterior spaces. Combined ability groups of 30 subjects each.

tableau superior | inferior | no marked deviation | one or more marked deviations

in all four of the general items,
and (2) those with one or more
marked deviations. The distributions
are shown in the two upper rows of
Table 4. The difference is substantial
and significant at the 1% level. The
conclusion is reached that marked
dental deviations are more numerous
among persons with so-called ‘functional’
disorders of consonant articulation
than among those with superior
articulation. The parenthetical portions
of Table 4 are sub-distributions
of the second category and are seen to
be consistent with the above interpretation.
Thus, for example, no superior
subject presented marked deviation in
all four items, while one inferior subject
was so judged; one superior subject
and five inferior subjects had three
marked deviations; etc.

In Table 5 the subjects are distributed
according to class of occlusion. 4 6
The basic distributions show equal incidence
of malocclusion, but the subgroupings
in parentheses show a tendency
for neutroclusion to predominate

Table 5. Distributions of classes of occlusion. Combined ability groups of 30 subjects each.

tableau class | superior | inferior | normal occlusion | malocclusion | (neutroclusion) | (distoclusion) | (mesioclusion)230

Table 6. Distributions of anterior occlusion. Combined ability groups of 30 subjects each.

tableau superior | inferior | antero-posterior relationships | normal | overjet or undershot | (overjet) | (undershot) | infero-superior relationships | openbite or closebite | (openbite) | (closebite)

in the superior group, while distoclusion
and mesioclusion are more
frequent among the inferior subjects.
Since the latter classes are ordinarily
regarded as more serious dental problems
than neutroclusion, this is in plausible
agreement with the findings presented
above, but the difference between
the distributions is not statistically

The occlusion between the upper
and lower anterior teeth in the region
of the incisors and cuspids was studied
by distributing the subjects as in Table
6. The two groups are seen to be
alike in the antero-posterior relationships,
but to differ in the infero-superior
relationships in the direction of
higher incidence of openbite or closebite
among the inferior subjects. This
difference is significant at the 1% level.
The parenthetical breakdown shows
that its primary source is openbite.


This study, involving measurements
and estimates of the teeth and hard
palate, is the fourth portion of an investigation
of minor organic factors in
articulatory ability which compared
extreme groups. The following were
the major findings:

1. In dimensions of the dental arch
and hard palate (width and height)
statistically significant differences related
to ability were not found. Sex
differences in molar width and in
height were significant.

2. In molar occlusion, anterior occlusion,
anterior alignment, or anterior
spaces the ability levels did not differ
significantly in total numbers of slight
or marked deviations from normal.

3. Marked dental deviations were
significantly more numerous among
the inferior subjects.

4. In number of atypical antero-posterior
relationships of the upper
and lower anterior teeth (overjet or
undershot conditions) the ability levels
did not differ significantly.

5. Atypical infero-superior relationships
in the same region (openbite or
closebite) were significantly more numerous
in the inferior group, openbite
being the greater factor in the difference.231


1. Angle, E. H. Treatment of Malocclusion
of the Teeth
. (7th Ed.) Philadelphia:
S. S. White Dental Manufacturing
Co., 1907.

2. Fairbanks, G. and Bebout, B. A study
of minor organic deviations in ‘functional’
disorders of articulation: 3. The
tongue. JSHD, 15, 1950, 348-352.

3. Fairbanks, G. and Green, E. M. A
study of minor organic deviations in
‘functional’ disorders of articulation: 2.
Dimensions and relationships of the lips.
JSHD, 15, 1950, 165-168.

4. Fairbanks, G. and Spriestersbach, D. C.
A study of minor organic deviations in
‘functional’ disorders of articulation: 1.
Rate of movement of oral structures.
JSHD, 15, 1950, 60-69.

5. Fymbo, L. H. The relation of malocclusion
of the teeth to defects of speech.
Arch. Speech, 1, 1936, 204-216.

6. McNemar, Q. Psychological Statistics.
New York: Wiley, 1949.

7. Snedecor, G. W. Statistical Methods.
(4th Ed.) Ames: Iowa State College
Press, 1946.232

1* Reprinted from the Journal of Speech and Hearing Disorders, Vol. 16, 1951, pp. 273-79.

2** Grant Fairbanks (Ph.D., Iowa, 1936) is
Professor of Speech, University of Illinois.
Mary Van Horn Lintner (M.A., Iowa, 1940)
is Speech Correctionist for San Joaquin
County, Stockton, California.

31 Blue Island Specialty Co., Inc., Blue
Island, III.

42 In Figure 1 the palatometer is shown
at approximately 8 mm. For measurements
of the smaller oral cavities of children a
9 x 35 mm transverse plate and a 25 mm
vertical rod are substituted.

53 Significance of the difference between
two proportions, as in McNemar (6), pp.
75-77, and Snedecor (7), pp. 431-440.

64 Normal occlusion implies the molar relationship
described above under Procedure
plus normal alignment and occlusion of the
anterior teeth; in neutroclusion the molar
relationship is normal, but there are anterior
irregularities; in distoclusion the upper first
molar is anterior to its normal position, and
in mesioclusion it is posterior (1). Each
class of malocclusion is subdivided into
‘types’ on the basis of other attributes, but
the data were inconsequential and are not