Soft-tissue Aanges associated with,

maxillary incisor retraction Dr. Rains

Michael D. Rains, D.D.S.,* and Ravindra Nanda, B.D.S., M.D.S., Ph.D.**

Farmingmn, Corm.

The nature of incisor retraction and lip adaptation is still controversial. The present study was undertaken to
determine the response of upper and lower lips to maxillary and mandibular incisor movement. Cephalometric
head films of thirty late-adolescent and early-adult female patients were analyzed for changes in the integumental
profile with treatment. Sample selection was intended to reduce variables caused by growth and sex differences.
A stepwise multiple regression analysis (forward) revealed a complex interaction between dentition, bony
structures, and soft tissues of the perioral area. The lower lip was more variable than the upper lip to differences
In the upper incisor movement. The upper lip at labrale superius was found to be more variable with increased
retraction of the upper incisors. In the prediction equation, change of sulcus superius had a more direct
relationship with retraction of labrale superius and labrale inferius than with dental movement. Pogonion and/or
menton entered at statistically significant levels into four (LS, LI, SI, Stm I) of the six prediction equations,
indicating that mandibular position is of paramount importance in the prediction of vertical and/or horizontal
changes in the upper and lower lips. The upper lip response was related to both upper and lower incisor
movement, mandibular rotation, and the lower lip. Upper incisor point position related a moderately high
correlation for the prediction equation for change in labrale superius. Lower incisor movement did not correlate
with change of either the upper or lower lip. The equations derived were an improvement over previous prediction
methods.

Key words: Incisor retraction, lip adaptation, profile, mandibular rotation, cephalometrics

C ontemporary orthodontics includes treat- lary and/or mandibular incisor movement. Another ob-
ment of dental and skeletal disharmonies with careful jective of the study was to determine the feasibility of
consideration of the integumental features of the face. accurately predicting vertical and horizontal changes in
Past studies and clinical observations have shown that, the lip morphology with orthodontic treatment.
to obtain stability of the attained orthodontic results, a
balance between the dental and perioral muscles must REVIEW OF THE LITERATURE
be achieved. The soft-tissue covering of the face also Few studies are found in the orthodontic literature
plays an important role in facial esthetics, speech, and prior to the 1950’s in which an attempt has been made
other physiologic functions. Thus, it is recognized by to relate orthodontic treatment to the soft-tissue profile.
all clinical orthodontists that success of orthodontic In one of the first investigations of the response of the
treatment is closely related to changes in soft tissues of soft-tissue profile to orthodontic treatment, Riedel’
the face. studied facial profiles of thirty persons by means of
Numerous studies in the past have described the lateral cephalograms. He reported that the relation of
relationship of maxillary and/or mandibular incisor re- the maxillary and mandibular apical bases, the degree
traction to the changes in the upper and lower lips. of convexity of the skeletal pattern, and the relation of
Various retrospective clinical reports have tried to es- the anterior teeth to their respective apical bases have a
tablish incisor-lip retraction ratios. However, the nature marked influence on the soft-tissue profile. Several
of correlation between incisor retraction and lip adapta- years later, Holdaway proposed a method of analyzing
tion is still controversial. the soft-tissue profile both as a means of diagnosis and
The present study was undertaken to determine the as a method for determining changes in the soft-tissue
response to upper and lower lips to orthodontic maxil- profile induced by growth and treatment. He proposed
the “H” angle, formed by a line drawn from the point
From the University of Connecticut School of Dental Medicine.
of the soft-tissue chin tangent to the upper lip and the
*Resident, Department of Orthodontics. N-B line, as a measure of profile acceptability. He be-
**Professor. Department of Orthodontics. lieved that the H angle should be 7 to 9 degrees when
OOOZ-9416/82/060481+08$00.80/0 0 1982 The C.V. Mosby Co 481
482 Rains and Nanda

the ANB angle is 3 degrees. The angle could be ad- Bloom,” in a study of adolescent boys and girls,
justed to compensate for changes in the ANB angle reported a high correlation of the relationship of maxil-
to alter lip fullness. lary central incisor changes to the superior sulcus and
Burstone” presented a method to analyze the soft- upper and lower lips. He also found a strong relation-
tissue profile by means of angular and linear mea- ship of the lower incisor to the inferior sulcus and the
surements. He described the average morphology and lower lip. Bloom noted that it was possible to predict
the variation of acceptable profiles and reported that the perioral soft-tissue profile changes in relation to the
desirable and undesirable alterations in the facial expected amount of anterior tooth movement. In a simi-
contour could be influenced by the underlying dento- lar study, Rudee’O studied soft-tissue changes in eighty-
skeletal framework. In a later study, Burstone” de- five treated orthodontic patients. He reported that the
scribed in detail the lip posture and its role in orthodon- average ratio of upper incisor retraction to upper lip and
tics and advocated the use of the relaxed lip position lower lip retraction was 2.9: 1 and 1: 1, respectively.
for taking cephalograms and for treatment planning. Similarly, the lower incisor to lower lip retraction ratio
Nege? reported a method for evaluating the soft-tissue was 0.59: 1. However, the standard deviation ranged
profile in a quantitative manner with the help of profile from 4.20 to 7.62 mm., respectively. Furthermore, his
photographs and cephalograms. He indicated that the sample was selected regardless of age and sex, and no
straight profile does not necessarily accompany normal attempt was made to separate the effect of growth from
occlusion. changes due to treatment.
Subtelny” published a longitudinal study of the Hershey” reported on the effect of incisor retrac-
soft-tissue facial structures and their profile charac- tion on soft-tissue profile changes in thirty-six post-
teristics, defined in relation to underlying skeletal struc- adolescent female patients. He concluded that neither
tures. Using films from the files of the Bolton Study, he the simple nor the multiple correlation coefficients ob-
analyzed thirty subjects from 3 months to 18 years of tained were clinically useful in predicting soft-tissue
age. He reported a progressive increase in length of the response from incisor retraction. Similar findings were
upper lip until the age of 15 years. Thereafter, growth reported by Wisth, I2 who described lip morphology and
in length seemed to slow down appreciably. In both treatment changes in two groups of boys. He reported
male and female subjects the upper lip was observed to that the variability of the results was great and con-
increase in thickness from 1 to 14 years of age. After 14 cluded that prediction of soft-tissue changes in an indi-
years males continued to show an increase in thickness vidual case is impossible, particularly if the overjet is
of the upper lip. In contrast, the upper lip did not be- great.
come discernibly thicker in the female subjects after the Angelle’” compared soft-tissue profiles of orth-
age of 1.5years. He also noted that the vertical relation- odontically treated children to untreated “smile con-
ship of the incisal edge of the maxillary central incisors test” winners with excellent occlusions and esthetically
to the tip of the upper lip was relatively stable after pleasing faces. He reported significant sexual differ-
complete eruption of the maxillary central incisors. The ences in the response of the soft-tissue profile due to
growth of the lower lip was similar to that of the upper orthodontic treatment. He found a marked tendency for
lip in that the relationship of the lower lip to the incisal the upper lip to be retruded in the treated children. The
edge of the mandibular central incisor was established amount of retrusion was limited in boys but more sig-
when the lower incisors finished erupting at the age of nificant in girls. The upper lip was found to become
about 9 years. In a later study, Subtelny7 reported the thicker during orthodontic treatment, which was not
effect of orthodontic treatment on the lip position. He observed in the untreated group. A significant retrusion
presented five patients who showed a change in lip of the lower lip during treatment was found in girls,
position due to treatment and growth and concluded whereas in treated boys the lower lip continued to be-
that lip posture was closely correlated with the posture come more protrusive.
of the underlying dental and alveolar structures. Anderson and associates“’ studied profile changes
RickettsX proposed a line which he called the in orthodontically treated patients 10 years out of re-
“esthetic plane” to describe the relationship of the lips tention. Significant retraction of both upper and lower
to the soft tissues of the chin and the nose. In Caucasian lips relative to the esthetic plane was seen during orth-
adults the lips should be contained within this line odontic treatment. A change in distance from the upper
drawn from the chin to the tip of the nose. He also and lower lips and the chin to the ANS-B line occurred
reported that the upper lip thickened 1 mm. with 3 mm. during treatment. Before treatment, lips were approxi-
of retraction of the upper incisors. With incisor retrac- mately 1 mm. farther anterior to this reference line than
tion, the lower lip curled backward with no thickening. the chin, while after treatment the relationship re-
 VR L

S-N

CFH

A-7 LIP
B

Fig. 2. Hard-tissue landmark points and reference lines used.

moved nearer to the facial plane as a result of the

hard-tissue remodeling caused by orthodontic treatment.
Female patients reportedly showed a relationship be-
tween upper incisor retraction and reduction in promi-
nence of the upper and lower lips. The male patients
showed no correlation between the upper incisor and lip
position. They attributed this to continued mandibular
growth in the males.
Fig. 1. Soft-tissue landmark points used in the investigation. In yet another study, which was not controlled for
the effects of growth, ROOSTS examined pre- and post-
versed. All of the soft-tissue changes that occurred fol- treatment records of thirty patients. The ages in the
lowing treatment had the effect of flattening the dental sample varied widely, from 8 years 8 months to 16
area of the facial profile because of continued nose and years 7 months for pretreatment records. There was a
chin growth in maturing faces. Thickness of the upper range from 10 years 9 months to 18 years 8 months of
lip increased 1 mm. for every 1.5 mm. of maxillary age at the time of posttreatment records. Both sexes
incisor retraction during treatment. This change was were included in the study. Roos established a refer-
related to maxillary retraction. During and after reten- ence line perpendicular to the S-N line at sella for all
tion the lip thickness decreased, but not back to the soft-tissue and hard-tissue measurements. He reported
original dimension. A significant increase remained 10 a relatively good correlation between the retraction of
years postretention. Thickness of the lower lip was not skeletal points and soft-tissue landmarks subspinale,
affected by orthodontic treatment. incision inferior, and supramentale. The correlations
Garner’” analyzed soft-tissue changes in ten female between the retraction of incision superior and labrale
and six male American Negroes following orthodontic superior or labrale inferior were relatively poor.
treatment. He found reduction in lip protrusion corre- As can be seen from this brief review, the contro-
lated to incisor retraction approximately to the same versy still exists as to the ability of an orthodontist to
degree as reported by Rudee’O and Hershey. l l predict soft-tissue changes at the time treatment is
In 1975 Huggins and McBride16 reported a study of planned for a patient. Previous investigations have relied
thirty-three randomly selected Class II, Division 1 pa- on simple ratios of hard-tissue to soft-tissue changes.
tients with overjet ranging from 3.0 to 12.0 mm. It was The perioral apparatus is much too complex for this
not reported whether the lips were relaxed or closed dur- approach; therefore, a sophisticated analysis was em-
ing the radiographic exposure. Their analysis showed ployed in this study to improve our understanding of
that subnasale, labrale superius, and labrale inferius soft-tissue changes in response to orthodontic treat-
484 Ruins md Nun&

ment. In the present study, several variables which traced at the same sitting to minimize tracing errors.
have affected the results of other studies were mini- Figs. 1 and 2 show the landmarks and reference
mized. Our study used only female patients who were lines used for the study. The positional changes of the
past adolescence at the start of treatment. All patients cephalometric landmarks between the two tracings
were treated according to a carefully executed treat- were measured by a Cartesian coordinate system. A
ment plan. horizontal reference line (CFH) constructed by reduc-
ing 7 degrees from the sella-nasion line was used as the
MATERIALS AND METHODS X axis. Because of problems with reproduction of the
Sample conventional Frankfort horizontal (FH) plane, the Uni-
Orthodontic records of thirty patients were analyzed versity of Connecticut computerized analysis uses a
to determine the correlation between the maxillary in- constructed FH plane. A vertical line (VRL) passing
cisor retraction and the integumental profile changes. through sella and perpendicular to the X axis served as
The effect of mandibular rotation on the results was the Y axis. All measurements were taken to the nearest
also studied. All patients were Caucasian females rang- 0.5 mm.
ing in age from 15 to 23 years, with a median age of The following skeletal, dental, and soft-tissue land-
16.6 years, at the start of orthodontic treatment. Care marks were identified for the study (Figs. 1 and 2):
was taken to select only postpubertal patients with neg- Skeletal:
ligible amounts of facial growth remaining. Sella (S)-Center of the contour of sella turica.
Since the major objective of the study was to de- Nasion (N)-Most anterior point of the nasofrontal
termine soft-tissue changes following the maxillary in- suture in the midsagittal plane.
cisor movement, no attempt was made to select the Point A (A)-Deepest point in the midsaggital plane
sample on the basis of dental and skeletal malocclusion between the anterior nasal spine and prosthion.
or according to whether extractions were performed to Point B (B)-The deepest point in the midsaggital
achieve treatment goals. The present sample had nine plane between infradentale and pogonion.
Angle Class 1 and twenty-one Class II, Division 1 Soft tissue:
malocclusions according to the dental classification. Subnasal (Sn)-The point of convergence of the
Four patients were treated on a nonextraction basis, and nose and the upper lip.
in the remaining twenty-six various teeth were ex- Superior sulcus (SS)-The point of greatest con-
tracted. Maxillary and mandibular first premolars were cavity in the midline between the upper lip (Ls) and
extracted in ten cases, only maxillary first premolars in subnasale (Sn).
nine, maxillary first and mandibular second premolars Upper incisor point (UIP)-The most anterior point
in five, maxillary second premolars and mandibular on the crown of the upper incisor.
first premolars in one, and only maxillary first molars in Labrale superius (LS)-The most anterior point on
one. All patients were treated with edgewise appliances, the convexity of the upper lip.
and the average treatment time was 28.3 months. Lower incisor point (LIP)-The most anterior point
on the crown of the lower incisor.
Radiographs Labrale inferius (LI)-The most anterior point on
Lateral cephalograms taken prior to and after treat- the convexity of the lower lip.
ment were used for the study. None of the patients had Sulcus inferius (SI)-The point of greatest concav-
any appliance in the mouth at the time the cephalo- ity in the midline between the lower lip and soft-tissue
grams were taken. All cephalograms were taken with chin.
patients in a standing position with relaxed lips. The Soft-tissue pogonion (Pg’)-The most anterior point
relaxed lip position has been suggested as the best of the soft-tissue chin.
posture for cephalometric soft-tissue evaluation.“. 8 Stomion superius (Stm”)-The lowermost point of
Each pre- and posttreatment cephalogram was taken on the upper lip.
the same cephalostat to eliminate the need for correc- Stomion inferius (Stm’)-The uppermost point on
tion of radiographic magnification. All posttreatment the vermilion border of the lower lip.
cephalograms were taken within 1 month of appliance
removal. Measurement reliability
The reliability of the method was determined by
Cephalometric analysis randomly selecting five patient records, each of which
Pre- and posttreatment lateral cephalograms were was traced three times and measured as previously de-
carefully traced for each patient on 8 by 10 inch ace- scribed. Since repeated measurements were taken on
tate paper. Each pair of radiographs of a patient was each subject in this set of data, and because subjects
Vohmr 81 Soft-tissue changes with maxillary incisor rotation 405
Number 6

Table I. Change (in millimeters) of the landmark points with treatment (n = 30)
Corrected Coeficient of
Landmark Mean Standard deviation standard deviation* variationt Standard error

Horizontal measurements
Soft-tissue points
Sulcus superius -1.1 1.2 0.6 60 0.22
Labrale superius -1.9 1.6 0.5 32 0.29
Labrale inferius - 1.3 2.0 0.7 66 0.37
Sulcus inferius -2.8 1.2 0.7 326 0.23
Soft-tissue pogonion 0.1 0.9 0.7 334 0.16
Hard-tissue points
Point A -0.4 0.5 0.5 15.5 0.08
Upper incisor point -3.1 2.2 1.1 49 0.41
Lower incisor piont -1.1 1.7 0.3 44 0.31
Point B -0.3 0.8 0.7 35 0.15
Pogonion 0.1 0.9 0.5 266 0.16
Vertical measurements?
Soft-tissue points
Stomion sup&us 0.3 1.4 0.5 131 0.25
Stomion inferius -0.6 1.8 0.6 137 0.33
Hard-tissue points
Menton 0.8 1.1 0.4 58 0.20
Growth
Articulare 0.5 0.6 0.3 67 0.10

*Calculated from two-way ANOVA repeated measures of one factor subjects X trials to control for repeated measures variation.
t&efficient of variation percent = S/X X (100).
$Positive number indicates inferior movement.

differed significantly from each other, it was necessary RESULTS

to perform a two-way ANOVA (repeated measures on The amount and direction of change of the land-
one factor) to determine the actual standard deviation of mark points with treatment are summarized in Table I.
each variable. The corrected standard deviations were The relationship of the soft-tissue landmarks to the
smaller than the noncorrected ones. The coefficient of hard- and soft-tissue variables is summarized in
variation and the standard error indicate a degree of Tables II and III. Between one and four independent
precision similar to other cephalometric studies. The variables were found to be significant predictors, at
results are given in Table I. the 0.05 level, for the soft-tissue landmarks inves-
tigated. The multiple r coefficients ranged from 0.49
Statistical analysis to 0.90.
The mean and standard deviations were calculated Mean retraction of the upper incisors was 3.1 mm.
for each measurement. A stepwise multiple regression with a range from 0 to 9.5 mm. The upper lip retracted
analysis (forward) was performed for each of the seven at labrale superius an average of 1.9 mm., giving a
soft-tissue measurements investigated. A SPSS com- ratio of 8: 5 for uper incisor to labrale superius re-
puter package was used on a UNIVAC 1100 series traction.
computer. The upper lip response was related to both upper
The multiple regression equation by stepwise is: and lower incisor movement, mandibular rotation, and
the lower lip. Upper incisor point entered stepwise into
Y = B, + BdX,) + B.dXd + BaWs) B&G)
the multiple regression equation at the 0.01 level of
with B, as a constant. This formula is used to predict significance. A multiple r coefficient of 0.75 indicates a
the amount of change of the dependent variable Y moderately high correlation for the prediction equation
due to changes of the independent variables B at the (Table III) for change of labrale superius. The response
level of significance desired. For this study, all vari- of sulcus superius was more complex. It was related to
ables greater than the 0.05 level of confidence were three independent variables, namely, labrale superius,
used. labrale inferius, and lower incisor point. The change of
Selected significant hard-tissue to soft-tissue ratios sulcus superius was found to be more directly related to
were also calculated. change in labrale superius position than to point A,
486 Rains and Nanda

Table II. Results of stepwise multiple regression Table Ill. Soft-tissue profile prediction equations
and correlation coefficients of soft-tissue
Horizontal measurements
landmarks with independent variables Sulcus Labrale
Independent variables superius = -0.68 superius = -0.40
enter stepwise into -0.23 (ALIP) +0.70(A&)
Dependent variables, regression equations Multiple r +0.27(aLI) +os2(AuIP)
soft-tissue P = 0.01 coeficients +0.47(ALS)
Labrale Sulcus
Horizontal measurements infer& = f0.24 inferius = +0.27
Sulcus superius LS LI LIP 0.09 +O.'lO(A@) -0.37(oMe)
Labrale superius UIP Pg 0.75 -0.37(nUIP) +0.86(AB)
Labrale inferius ME UIP pg* 0.61 -0.67(AMe)
Sulcus inferius B Me* 0.75 Vertical measurements
Soft-tissue pogonion Pg 1.001 Stomion Stomion
Vertical measurements superius = +0.77 inferius = +0.21
Stomion superius LI 0.49 +0.33(nLr) +O.SO(nMe)
Stomion inferius UIP LI LS Me 0.75 +0.52(nLS)
-0.43(AL1)
*Significant only to 0.05 level
+0.25(aUIP)
tColinear.
The stepwise multiple regression equation (forward) is: Y = B(, +
B,(X,) + B,(X,) + B,(X,) B,(X,) with B(, as a constant.
lower incisor point, upper incisor point, or labrale in-
ferius.
Lower lip response, in both vertical and horizontal The change at point A was insignificant and did not
directions, was found to be influenced by change in enter into any of the multiple regression equations cal-
position of the mandible. No significant correlation was culated. Point B also changed negligibly with a mean of
found between lower incisor movement and response of -0.3 mm. Menton descended 0.8 mm. on the average,
the lower lip. Menton and upper incisor point entered with a range of 3.0 mm. superior to 2.5 mm. inferior
stepwise into the prediction equation for labrale inferius movement. In only two persons was there found to be a
at the 0.01 level with pogonion entered at the 0.05 menton change in a superior direction.
level, with a multiple r coefficient of 0.61. Mandibular Growth was determined by separate mandibular su-
rotation was found to have a greater influence on lower perimpositions as described by Bjijrk.lX The mean
lip response than incisor movement. mandibular growth of the postmenarche female sub-
Both hard- and soft-tissue pogonion had a mean jects was only 0.5 mm. Change at articulare did not
change of 0.1 mm. and a range from 2.0 to -2.0 mm. enter into any of the prediction equations, indicating
They were found to be colinear with r = 1.00. that the minimal growth was not significant.
Stomion superius descended slightly an average of
0.3 mm., with a range from 1.5 mm. superior to 0.4 DISCUSSION
mm. inferior movement. Labrale inferius was the only Careful selection of patients for the present study
independent variable found to be a significant predictor substantially reduced many of the variables, which may
of vertical change in the upper lip (r = 0.49). How- have adversely affected the results of earlier studies.
ever, step 3 of the multiple regression equation entered The sample was limited to females with a devel-
menton as significant at the 0.05 level. The F value for opmental age greater than 15 years, which significantly
labrale superius was very close to the critical number at reduced the effects of growth and possible differences
the 0.05 level, with a multiple r of 0.61. While this was in response between sexes. Most previous investigators
not significant, it did give an indication of the com- did not try to separate the effects of treatment from
plexity of the response of this landmark point. those of normal growth.“. lo, 2o Subtelny6 and Vig and
Stomion inferius experienced large movement from Cohen,ls in independent studies, have reported that
3.0 mm. inferiorly to 5.0 mm. superiorly, with a mean marked changes in the relationship of the upper incisors
ascent of 0.6 mm. Four independent hard- and soft- to the lips take place with normal growth during early
tissue landmark points (UIP, LI, LS, ME) entered into adolescence. A relaxed lip position at the time cepha-
the prediction equation at the 0.01 level for stomion lograms were taken eliminated the variability due to lip
inferius. Retraction of the maxillary incisors and man- strain caused by lip closure, especially in patients with
dibular rotation were found to correlate (Table II) with large overjet and/or open-bite.
vertical changes in the lower lip. Figs. 3, 4, and 5 clearly demonstrate that the soft-
 Soft-tissuechangest+ith muxilluyy incisor rotation 487

tissue response may vary widely for a given amount of 3

tooth movement. A comparison of Fig. 3 with Figs. 4 2
and 5 demonstrates that the lower lip was more variable 1
than the upper lip to differences in upper incisor 1
movement. The upper lip at labrale superius was found 2
.= 0 . . .
E l . .
to be more variable with increased retraction of the 2 . 0. l l *
upper incisors (Fig. 3). .
2 -2- . l .
Burstone and Hershey I1 have proposed that the m .
perioral soft tissues may be self-supporting and that 2 - . . .
2 . . .
factors other than dental movement may cause the wide -4- .
variability of individual response. A stepwise multiple
.
regression analysis (forward) was performed in an at-
tempt to evaluate which factors might be responsible -tJ! , , , 1 , , , ( , ,
-10 -a -6 -4 -2 0
for changes of the upper and lower lips. The results of
the analysis indicate that dental movement, particularly Upper incisor point
of the lower incisors, does not correlate well with Fig. 3. Response of the upper lip to retraction of the upper
changes in the lips. Lower incisors point entered only incisors (in mm.).
one prediction equation at a statistically significant
level. 1 .
In the prediction equation, change in sulcus su- 2- .
.
perius had a more direct relationship with retraction l l

of labrale superius and labrale inferius than with den- *

. l
.z o-
tal movement. The prediction equation for labrale su- k
. l l l
0
perius [ALS = -0.4 + 0.7(APg) + O.S(AUIP)] was E.-
a
strongly influenced by mandibular rotation as the value a,z -2- .
. .
0.7(APg) indicates. Retraction of upper incisors did * . . . .
not have as direct a relationship, O.S(AUIP), with la- 1 . 0 0
-4-
brale super& movement as with movement of pogo-
nion. From the prediction equation [ALI = 0.2 + 0.4 - .

(AUIP) - 0.7(AME)], change in labrale was found to -6 I I I ! r I I

be more directly related to mandibular rotation [0.7 -10 -a -6 -A -2 0
(APg) and -0.7(AME)] than to upper incisor retraction Upper incisor point
[0.4(AUIP)].
Vertical changes in stomion superius and stomion Fig. 4. Response of the lower lip to retraction of the upper
inferius were both influenced by movement of the op- incisors (in mm.).
posing lip. Their prediction equations gave an insight
into the complexity of the perioral musculature and its . .
.
relationship with the underlying hard tissues. Step 3 of .
the multiple regression analysis for stomion superius . . .
entered menton as a significant variable. The F value .
for labrale superius was also very close to the critical . . . . . .
number at the 0.05 level. An interaction of a large .
. .
number of landmark points (LI, Me, LS, UIP) with .
. .
stomion superius and stomion inferius indicates that the .
.a
prediction of the interlabial gap is difficult. .
Pogonion and/or menton entered at statistically
significant levels into four (LS, LI, SI, Stm I) of the six .
prediction equations, indicating that mandibular posi-
-6; , 1 I I 1 I 1 I I I
tion is of paramount importance in the prediction of -4 -2 0 2 A
vertical and/or horizontal changes in the upper and
Lower incisor point
lower lips.
The findings revealed a complex interaction be- Fig. 5. Response of the lower lip to movement of the lower
tween dental movement, mandibular rotation, and the incisors (in mm.).
488 RainsandNanda Am. J. Orrhod.
June 1982

perioral soft tissues as well as a complex relationship REFERENCES

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cephalometric standards for skeletal and soft tissues. during orthodontic treatment, AM. J. ORTHOD. 42: 176-193,
Simple ratios of lip response to incisor movement, par- 1956.
ticularly the lower incisors, are of little value in obtain- 3. Burstone, C. J.: The integumental profile, AM. J. ORTHOD. 44:
l-25, 1958.
ing those goals when applied to an individual subject. I*
4. Burstone, C. J.: Lip posture and its significance in treatment
The equations proposed in this study represent an im- planning, AM. J. ORTHOD. 53: 262.332, 1967.
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tissue facial profile, AM. J. ORTHOD. 45: 738, 1959.
SUMMARY 6. Subtelny, J. D.: A longitudinal study of soft tissue facial struc-
tures and their profile characteristics, defined in relation to un-
Cephalograms of thirty late-adolescent and early-
derlying skeletal structures, AM. J. ORTHOD. 45: 481.507.
adult female orthodontic patients were analyzed for 1959.
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odontic treatment. Pretreatment and posttreatment lat- changes, Angle Orthod. 31: 105-122, 1961.
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AM. J. ORTHOD. 46: 330, 1960.
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9. Bloom, L. A.: Perioral profile changes in orthodontic treatment,
structed with a horizontal axis 7 degrees from the AM. J. ORTHOD. 47: 371, 1961.
sella-nasion line. A vertical reference line was drawn to 10. Rudee, D. A.: Proportional profile changes concurrent with
the nearest 0.5 mm. An SPSS computer package was orthodontic therapy, AM. J. ORTHOD. 50: 421-434. 1964.
used on a UNIVAC 1100 series computer to perform a 1 I. Hershey, H. G.: Incisor tooth retraction and subsequent profile
stepwise multiple regression analysis (forward) for change in postadolescent female patients, AM. J. ORTHOD. 61:
45-54, 1972.
each of seven soft-tissue variables (LS, SS, LI, SI, Pg’, 12. Wisth, P. J.: Soft tissue response to upper incisor retraction in
Stm S, Stm I). For each dependent variable, eleven boys, Br. J. Orthod. 1: 199-204, 1974.
independent hard and soft variables (LS, SS, LI, SI, 13. Angelle, P. L.: A cephalometric study of the soft tissue changes
Pg, Stm S, Stm I, A, UIP, LIP, B, Pg, Me, Ar) were during and after orthodontic treatment, Trans. Eur. Orthod. Sot.
used. 49: 267-280, 1973.
14. Anderson, J. P., Joondeph, D. R., and Tutpin, D. L.: A
Soft-tissue pogonion was found to be colinear with
cephalometric study of profile changes in orthodontically treated
hard-tissue pogonion (R = 1.00). The other soft-tissue cases ten years out of retention, Angle Orthod. 43: 324-336,
dependent variables (LS, SS, LI, SI, Stm S, Stm I) 1973.
were found to have between one and four independent 15. Garner, L. D.: Soft tissue changes concurrent with orthodontic
variables, significant at the 0.05 level, in the predic- tooth movement, AM. J. ORTHOD. 66: 367-377, 1974.
16. Huggins, D. G., and McBride, L. J.: The influence of the upper
tion equations. Multiple r coefficients ranged from
incisor position on soft tissue facial profile, Br. J. Orthod. 2:
0.5 to 0.9. 141-146, 1975.
The prediction equations found were an improve- 17. Roos, N.: Soft tissue profile changes in Class II treatment. AM.
ment over those previously reported in predicting soft- J. ORTHOD. 72: 165-175, 1977.
tissue response to incisor retraction. The stepwise mul- 18. Bjork, A.: Variations in the growth pattern of the human man-
dible: A longitudinal radiographic study by the implant method,
tiple regression analysis revealed a complex interaction
J. Dent. Res. 42: 400-411, 1963.
between the dentition, the bony structures, and the 19. Vig, P. S., and Cohen, A. M.: Vertical growth of the lips: A
perioral soft-tissue profile. Mandibular rotation was serial cephalometric study, AM. J. ORTHOD. 75: 405-415, 1979.
found to be one of the more significant variables in 20. Jacobs, J. D.: Vertical lip changes from maxillary incisor retrac-
predicting response of both upper and lower lips with tion, AM. J. ORTHOD. 74: 396-404, 1978.
treatment. Lower incisor movement was found to enter
only the prediction equation for sulcus superius at a
statistically significant level. It was not considered a
good predictor for changes of the lips with treatment.