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Dentofacial and soft tissue changes in Class II, Division 1 cases treated with and without extractions
Dentofacial and soft tissue changes in Class II, Division 1 cases treated with and without extractions Samir E. Bishara, BDS, DDS, D.Ortho, MS," David M. Cummins, DDS, MS, b Jane R. Jakobsen, BS, MS, ° and Abbas R. Zaher, BChD, MS, PhD ~
Iowa Ci~ Iowa, Bellingham, Wash., and Alexandria, Egypt The purpose of this study was to compare the changes in subjects with Class II division 1 malocclusions treated with and without the extraction of four first premolars. Lateral cephalograms on 91 patients (44 extraction and 47 nonextraction) were evaluated at three stages: pretreatment, posttreatment, and approximately 2 years after treatment. The present findings indicate that before treatment, the upper and lower lips were more protrusive relative to the esthetic plane among the subjects treated with four first premolar extractions. After treatment the upper and lower lips were more retrusive in the extraction group, and more protrusive in the nonextraction groups. The extraction group tended to have straighter faces and slightly more upright maxillary and mandibular incisors, whereas the nonextraction group had the opposite tendencies. The average soft tissue and skeletal measurements for both groups were close to the corresponding averages derived from the Iowa normative standards. In general, differences between the groups after treatment were preserved into retention. The present findings indicate that the extraction or nonextraction decision, if based on sound diagnostic criteria, seem to have no deleterious effects on the facial profile. (AM J ORTHOD DENTOFACORTHOP 1995;107:28-37.)
T h e study of beauty and harmony of the facial profile has been central to the practice of orthodontics from its earliest days. At the turn of the century, orthodontics was in its infancy. There were few sources from which practitioners could learn the principles of "regulating" teeth. Followers of Angle's "new school" believed that if the teeth were in harmony, the face would be as well. 1'2 They believed that with their appliances they could make the bone grow, obviating the need for extractions. On the other hand the "rational school" contended that bone could not be encouraged to grow beyond its inherent potential, and therefore extractions were necessary to treat some malocclusions? Case and his followers believed that malocclusions were inherited, and arose from the mixing of face types and races. Both sides drew on a handful of cases in addition to "facts" and theories borrowed from biology and other sciences that seemed to support what they have From the University of Iowa. Support for this project has been received from the Council on Scientific Affairs of the American Association of Orthodontics. aProfessor, Department of Orthodontics, College of Dentistry. bin private practice, Bellingham, Wash. CAssistant professor, Department of Preventive and Community Dentistry, College of Dentistry. dAssistant Professor, Department of Orthodontics, Faculty of Dentistry, Alexandria University, Egypt. Copyright © 1995 by the American Association of Orthodontists. 0889-5406/95/$3.00 + 0 8/1/477911
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already accepted for themselves as the truth. The debate was also a clash of egos, often deteriorating into personal attacks. 4 Unfortunately, the debate is still ongoing, and some clinicians still suggest that four first premolar extractions will compromise posttreatment esthetics by "dishing in" the profile.5-9 In an attempt to determine the effects of incisor retraction on the profile, several studies were conducted to quantify and to predict the relationship between incisor retraction and lip retraction. 1°-15 With the exception of one study that found a predictable amount of soft tissue changes in response to incisor retraction, 1° the majority of the studies on both growing and nongrowing subjects concluded that the large individual variation prevents the accurate prediction of lip response to incisor retraction in any given person. 1115 Lip structure seems to have an influence on lip response to incisor retraction. Oliver 16 found that patients with thin lips or a high lip strain displayed a significant correlation between incisor retraction and lip retraction, whereas patients with thick lips or low lip strain displayed no such correlation. In addition, Wisth a4 found that lip response, as a proportion of incisor retraction, decreased as the amount of incisor retraction increased. This seems to indicate that the lips have some inherent support.
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American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 1
Perkins a7 found that decreases in upper vermilion height were positively correlated with upper lip retraction. However, changes in the upper vermilion height did not significantly correlate with the magnitude of incisor retraction. The available literature on the comparisons of the effects of extraction versus nonextraction treatment regimens on the profile is very limited. One study on high mandibular plane angle cases found that the lips were more retruded in nonextraction cases as compared with extraction cases. It was suggested that this is the result of an increase in the vertical dimension that tended to stretch the lips and decrease their prominence, is In another study, patients treated with four first premolar extractions and Begg mechanics were compared with a nonextraction group treated with activators. The upper incisors were retracted more in the Begg group, but there were no significant differences in the upper lip response between the two treatment groups. However; there was more retraction of the lower incisors in the Begg treatment group that resulted in a significantly greater amount of lower lip retraction. 19 In a comparison of four first premolar extraction cases to four second molar extraction cases, Staggers ~found no significant differences in the, amount of upper lip retraction. However, the lower lip was retracted significantly more when four first premolars were extracted. 2° The purpose of this study is to compare the profile changes in patients with Class II, Division 1 malocclusions who were treated with four first premolar extractions with a group of patients treated with similar appliances but without any extractions. MATERIALS AND METHODS Subjects
29
~GI
L Or
Ar"
)Pr
Pnu
~) LS ;LI
,Pg Me
Fig. 1. Landmarks used.
congenital anomalies, significant facial asYmmetries, or congenitally missing teeth. (4) The orthodontic records included lateral cephalograms taken before and after orthodontic treatment. In addition, a third set of records was obtained approximately 2 years after the completion of orthodontic treatment. (5) At the end of treatment, all cases were considered to be well treated, i.e., displayed a Class I canine and molar relationship, an overbite between 10% and 25%, and well-aligned and interdigitated arches. These criteria were selected to insure that the posttreatment changes were not caused by "poor" treatment results. Available records on patients with Class II, Division 1 malocclusions who were treated in the department were screened and only 91 cases met the selection criteria and also had complete records. Cephalometric landmarks
The material for this investigation was obtained from the records available in the Graduate Orthodontic Clinic at the University of Iowa. Ninety-one (91) patients were treated for their Class II, Division 1 malocclusions, 44 subjects (21 males and 23 females) had four first premolar extractions and 47 subjects (20 males and 27 females) were treated nonextraction. Case selection was based on the following criteria: (1) All cases were originally diagnosed as having a Class II, Division 1 malocclusion, i.e., Class II molar and canine relationship. (2) All cases have received comprehensive orthodontic treatment using an edgewise appliance. The cases were supervised by various clinical instructors in the graduate clinic. (3) None of the cases had
The following 18 hard tissue and 6 soft tissue landmarks were identified on each cephalogram (Fig. 1): Sella (S), sphenoidal wing point (W), nasion (N), orbitale (Or), anterior nasal spine (Ans), subspinale (A), supramentale (B), pogonion (Pog), menton (Me), gonion (Go), articulare (Ar), posterior nasal spine (Pns), potion (Po), occipitale (O), upper incisor point (U1 tip), upper incisor apex (U1 apex), lower incisor point (L1 tip), lower incisor apex (L1 apex), soft tissue glabella (G1), pronasale (Pr), subnasale (sn), labrale superius (Is), labrale inferius (li), and soft tissue pogonion (pg). The identification of the landmarks was based on the classic definitions previously described in the literature .21-26
30 Bishara et al.
American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table I. Average ages of the subjects (in years) at the different stages of treatment, also the average treatment and retention intervals Extraction Subject
Mean
11.5 14.6 16.8 3.1 2.3
Mean
1.6 1.4 1.6 0.9 0.5
12.1 14.5 16.5 2.3 2.1
11.6 14.4 16.8 2.9 2.4
1.6 1.6 1.7 0.9 0.5
10.9 13.2 15.3 2.3 2.1
SD
p Value
1.5 1.2 1.2 1.2 0.2
0.1848 0.7470 0.4973 0.0160 0.5356
1.5 1.2 1.2 1.1 0.3
0.1222 0.0003 0.0004 0.0480 0.0350
(n = 20)
(n = 23)
Females
Pretreatment Posttreatment Retention Treatment interval* Retention interval
SD
(n = 21)
Males
Pretreatment Posttreatment Retention Treatment interval* Retention interval
Nonextraction
(n = 27)
*Treatment interval includes a lag of 3 to 4 months between the time the initial records were taken and the actual treatment was initiated. n, Sample size; SD, standard deviation.
Reliability of landmark location and measurements All cephalograms were obtained on the same cephalometric unit. All landmarks were identified by one investigator and checked for accuracy o f location by a second investigator. The landmarks were digitized twice on separate occasions by two investigators. Allowable intrainvestigator and interinvestigator discrepancies were predetermined at 0.5 mm and 0.5°.
Measurements obtained Twenty-six anteroposterior and vertical skeletal, dental, and soft tissue linear and angular measurements were derived and included: SNA, SNB, SWPog, SNPog, ANB, NAPog, N-Ans', N-Me, Ans'/N-Me, Ar'-Go, S-Go, Ar'-Go/S-Go, S-Go/N-Me, FH:MP, SN:MP, UI:L1, UI:SN, UI:APog, LI:MP, LI:FH, LI:NB, Pog:NB, G1SnP, Pr-Pg:NB, Ls : E-plane, and Li: E-plane.
Statistical analysis Student t tests were used to compare (1) the incremental changes between groups from before treatment to after treatment, from after treatment through retention and from before treatment through retention, (2) absolute dimensions within each sex and extraction group were recorded before treatment, after treatment, and at retention. Significance level for statistical comparisons was predetermined at p <- 0.05.
RESULTS Age comparisons The age distribution of the subjects in each treatment and sex subgroup is detailed in Table I. Student t test comparisons of the male extrac-
tion and nonextraction groups indicated that before treatment the two groups were well matched according to age. However, the length of treatment in the extraction groups was significantly longer among the male (p = 0.016) and female (p = 0.048) subjects when compared with the corresponding nonextraction groups.
Sex differences Male and female subjects have significant differences in their absolute dimensions; in addition, the treatment changes were not identical in male and female subjects, as a result the findings on both sexes will be presented separately.
Comparisons of incremental changes between groups (Tables Ila and lib) Only the significant changes between the extraction and nonextraction groups during the various treatment periods will be presented. The emphasis in the presentation will be on those findings that were consistent in both male and female subjects.
Before treatment to after treatment Soft tissue relationships. In the male and female extraction groups, there was a significantly greater decrease, in the angle of convexity (GISnP) and the Holdaway soft tissue angle (Pr-P:NB) as compared with the corresponding nonextraction groups.
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American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 1
Table Ila. Results of Student's t test indicating significant differences in the incremental changes between extraction and nonextraction male subjects Nonextraction
Extraction
x
Treatment interval
I
SD
SD
Pretreatment/posttreatment Skeletal p a r a m e t e r s SNA(°) NAPog(°) N-Ans'(mm)
- 2.5
1.5
- 1.1
1.7
**
- 6.7 4.7
3.3 2.7
- 3,2 3.0
3.4 2.2
** *
0.3 2.8
1.1 1.4
- 0.4 0.8
1.2 1.3
* **
4.3 - 4.6
12.8 2.4
- 4.6 - 1,5
10.1 2.0
* **
N-Ans'/N-Me(%) Pog:NB(mm) Dental parameters UI:LI(°) U 1: A - P o g ( m m ) LI:N-B(mm)
- 0.4
1.7
1.8
1.6
**
L1 : F H ( ° )
- 2.2
7.6
- 8.1
7.2
*
- 2.2 - 6.8
3.2 3.4
0.5 - 1.8
3.0 2.6
** **
ls-E(mm)
- 3.9
2.0
1.3
1.4
**
li-E(mm)
- 3.9
2.0
0.8
2.0
**
Skeletal p a r a m e t e r s MP:FH(°)
- 0.8
2.6
- 2.7
3.0
*
Soft tissue p a r a m e t e r s ls-E(mm)
- 0.7
1.9
1.2
1.3
**
- 0.7
1.5
0.8
2.2
**
- 2.4 0.5 - 8.4 6.5 3.6
1.7 2.5 4.0 2.3 1.5
- 0.8 - 1.4 - 4.4 4.7 1.5
1.5 3.3 3.6 2.6 1.2
** * ** * **
Soft tissue p a r a m e t e r s GISnPg(°) Pr-P:NB(°)
Posttreatment retention
li-E(mm)
Pretreatrnent retention Skeletal p a r a m e t e r s SNA(°) SWPog(°) NAPog(°) N-Ans'(mm) Pog:NB(mm)
Dental parameters UI:LI(°) Ul:A-Pog(mm) LI:N-B(mm) LI:MP(°) Soft tissue p a r a m e t e r s G1SnPg(°) Pr-P:NB(°) ls-E(mm) li-E(mm)
6.7
11.1
-0.7
9.0
*
-4.4 - 0.6 0.1
2.6 1.8 6.0
- 1.7 1.2 4.2
2.1 1.5 6.5
** ** *
-
3.7 4.0 2.4 2.3
0.3 - 3.0 2.4 1.6
4.5 3.0 1.6 1.8
* ** ** **
2.6 7.3 4.6 4.9
x, M e a n ; SD, s t a n d a r d deviation; S, statistically significant. *p ~ 0.05; **p <_ 0.01.
Similarly, the upper (1s-E) and the lower (li-E) lip prominence relative to the esthetic plane decreased in the extraction groups but increased in the nonextraction groups. Skeletal relationships. For both male and female subjects, there was a significantly greater decrease in the SNA and NAPog angles in the extraction groups as compared with the nonextraction groups. Dental relationships. In both sexes the interin-
cisal angle (U1 :L1) increased among the extraction groups, but decreased among the nonextraction groups. The upper incisor protrusion (UI:A-Pg) decreased significantly in both the male and female extraction groups, but the angulation of the upper incisors (UI:SN) decreased significantly more in the female extraction group. In both sexes, the lower incisor protrusion (LI:NB) showed a slight decrease among the
32
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American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table lib. Results of Student's t test indicating significant differences in the incremental changes between extraction and nonextraction female subjects Extraction Treatment interval
Non~ac~n
x
SD
x
SD
Pretreatment/posttreatment Skeletal parameters SNA(°) NAPog(°) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) UI:SN(°) LI:N-B(mm) LI:FH(°) LI:MP(°) Soft tissue parameters GISnPg(°) Pr-P:NB(°) ls-E(mm) li-E(mm)
- 2.0 - 5.1 1.8
1.6 3.3 1.2
-0.9 -3.0 0.8
1.3 3.1 0.8
* * **
12.3 -4.6 - 9.8 - 1.4 1.4 2.3
13.6 1.9 8.2 2.1 8.1 8.4
-1.1 1.9 -3.2 1.1 -5.5 3.8
10.5 2.5 9.2 1.6 6.9 5.2
** ** ** ** ** **
2.8 6.2 3.6 3.0
2.1 2.5 1,4 1.6
-1.1 -2.7 1.2 0.2
2.3 2.8 1.8 1.7
** ** ** **
0.1 1.3 1.5 - 0.2
1.3 2.7 2.2 2.9
0.9 2.8 3.4 -1.9
1.2 2.3 2.9 3.1
* * ** *
0.0 0.5
0.6 3.4
-0.4 3.8
0.8 3.7
* **
-0.6 - 0.8
1.2 1.4
0.9 1.2
1.1 1.1
** **
- 1.6 -0.2 4.6 6.6 7.1 2.4
1.4 1.2 3.0 3.3 3.4 1.4
-0.4 0.9 6.4 8.6 9.5 1.1
1.7 1.9 2.9 3,1 4,4 0,8
** * * * * **
13.0 4.3 9.4 1.3 2.5
12.1 2.2 8.0 2.0 7.2
2.3 -1.8 -3.0 0.7 1.8
9,2 2,2 8,6 1.4 4.5
** ** ** ** *
- 7.2 - 4.1 - 3.9
3.2 1.7 1.8
-4.1 2.1 1.4
3,0 2.1 1.8
** ** **
-
Posttreatment/retention Skeletal parameters N-Ans' (mm) Ar'-Go(mm) S-Go(ram) MP:FH(°) Dental parameters LI:N-B(mm) LI:FH(°) Soft tissue parameters ls-E(mm) li-E(mm)
Pretreatment/retention Skeletal parameters SNA(°) SNB(°) Ar'-Go(mm) S-Go(ram) N-Me(ram) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) U1 :SN(°) LI:N-B(mm) LI:MP(°) Soft tissue parameters Pr-P:NB(°) ls-E(mm) li-E(mm)
-
*p -< 0.05; **p -< 0.01.
extraction groups and an increase among subjects treated without extractions. In addition, the angulation of the lower incisors relative to the Frankfurt horizontal plane (LI:FH) became significantly more acute among the nonextraction male subjects.
After treatment to retention Relatively fewer incremental a significant difference between nonextraction
groups
exhibited
during the retention
Soft tissue relationships. upper
changes
the extraction and
(1s-E) and the lower
The
protrusion
period. of the
(li-E) lips relative to
Bishara et al.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 1
the esthetic plane significantly decreased among the extraction groups but increased in the nonextraction groups. In other words, during the retention period, both lips continued to become less prominent among the extraction groups and more prominent among the nonextraction groups. Dental relationships. The protrusion of the lower incisors (LI:NB and L I : F H ) increased significantly more among the patients treated without extractions. Before treatment to retention
Soft tissue relationships. There was a significantly greater decrease in the Holdaway soft tissue angle in the extraction group in both sexes, but only male subjects had a significant decrease in the overall soft tissue convexity in the extraction subjects. Over the total observation period, the prominence of the upper (1s-E) and the lower (li-E) lips decreased among the extraction groups, but increased among the nonextraction groups. Skeletal relationships. During the overall period of observation there was a greater decrease in the SNA angle in the extraction groups and an increase in the chin prominence (Pog:NB) when compared with the nonextraction groups in both male and female subjects. Dental relationships. The interincisal angle (U1 :L1) became significantly more obtuse among the extraction groups. This change was associated with a decreased protrusion of the upper (UI:APg) and the lower incisors (LI:NB and LI:MP) in the extraction groups and an increase in these inclinations among the nonextraction groups. Comparisons of absolute dimensions between the groups (Tables Ilia and IIIb)
Before treatment. The prominence of the upper (ls-E) and the lower (li-E) lips, as well as the lower incisors, were significantly more protrusive (LI:MP) in the male extraction group. Only the prominence of the lower lip (li-E) was greater among the female patients who were treated with four first premolar extractions. After treatment. The extraction groups had a straighter skeletal (NAPog) and soft tissue (Pr-P:NB) convexities than the nonextraction groups in addition to a significantly more prominent bony chin (Pog:NB) particularly in male subjects. Although some face height dimensions were significantly different between the male extraction and nonextraction groups, the various ratios of these dimensions were not significantly different.
33
In both sexes, the upper lip prominence (1s-E) was less in the extraction groups when compared with the corresponding nonextraction groups. The interincisal angle (U1 :L1) was more obtuse among the male and female patients treated with extractions. This was accompanied by less protrusive upper (U1 :A-Pg) and lower incisors (LI:NB, L1 : FH and L1 : MP). Retention. The male extraction group, had relatively straighter skeletal (NAPog) and soft tissue (Pr-P:NB) profiles, as well as stronger chins (Pog:NB), than the nonextraction male subjects. The upper (1s-E) and the lower (li-E) lip prominence were significantly less among the extraction groups in both sexes. The interincisal angle (UI:L1) was significantly more obtuse among the male and female subjects treated with premolar extractions with the upper ( U I : A Pg) and the lower (LI:MP, LI:FH, and LI:NB) incisors less protrusive. DISCUSSION
In general, changes during the active treatment period are often the result of growth and appliance therapy, but when the changes are in the opposite direction of the expected "normal" growth o n e could assume that such changes are the result of treatment. On the other hand, changes occurring during the retention period are most likely the result of growth and/or a rebound effect after the completion of appliance therapy. Comparisons of incremental changes between groups (Tables Ila and lib)
This discussion will focus on the effects of the two different modes of treatment on specific areas of the face. Soft tissue relationships. The soft tissue facial convexity decreased more in the extraction groups during the treatment period. Also, the upper and lower lip prominence decreased relative to the nose and chin in the extraction groups. During the retention period, lip prominence decreased further among the extraction groups and increased among the nonextraction groups accentuating earlier trends. Skeletal relationships. During treatment, there was a significantly greater decrease in the facial skeletal convexity and an increase in c]hin prominence in the extraction groups as compared with the nonextraction groups in both male and female subjects. These findings suggest that during treatment planning if such outcomes are desirable, an
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B i s h a r a et al.
American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table Ilia. Results of Student's t test indicating significant differences between the absolute
dimensions between extraction and nonextraction male subjects Extraction Treatment interval Pretreatment Skeletal parameters N-Me(mm) Ar'-Go(mm) S-Go(mm) Dental parameters LI:MP(°) Soft tissue parameters ls-E(mm) li-E(mm) Posttreatment Skeletal parameters Ar'-Go(mm) NAPog(°) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) LI:N-B(mm) LI:FH(°) LI:MP(°) Soft tissue parameters Pr-P:NB(°) ls-E(mm) Retention Skeletal parameters NAPog(°) N-Me(mm) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) LI:N-B(mm) LI:FH(°) LI:MP(°) Soft tissue parameters Pr-P:NB(°) ls-E(mm) li-E(mm)
Nonextraction
I
x
SD
x
123.4 47.7 80.0
4.4 4.2 5.1
117.8 51.3 84.5
7.6 4.9 4.5
** * **
92.0
6.3
97.0
6.6
*
1.0 1.5
1.9 2.4
- 1.3 - 1.9
1.7 2.7
** **
51.8 1.4 4.9
5.5 4.9 2.4
55.4 5.8 2.8
5.4 4.5 2,3
* ** **
133.1 2.3 2.9 58.8 94.3
9.6 1.2 1.2 6.9 8.4
121.7 5.2 6.1 48.9 103.1
9,3 2.1 1.7 5.0 6.6
** ** ** ** **
10.0 - 2.9
4.6 1.6
13,9 - 0,1
3.7 1.7
** **
- 0.2 131.2 5.8
6.1 8.1 2.5
4.2 135.7 3.5
4.5 5.9 2.4
** * **
135.5 2.5 2.7 61.4 92.6
9.6 1.9 1.5 5.4 7.6
125.7 5.0 5.5 53.5 101.2
9.1 2.3 2.2 6.8 7.1
** ** ** ** **
9.5 - 3.6 - 3.4
5.3 2.3 2.2
12.6 1.1 - 0.3
4.3 2.2 2.8
* ** **
*p --- 0.05; **p -< 0.01.
extraction approach might enhance these changes. Dental relationships. The interincisal angle became significantly more obtuse among the extraction groups during the period of active treatment as a result of the greater retraction of the upper and lower incisors. Such changes help explain the greater amount of lip retraction seen among the extraction groups. During the retention period, there were no significant differences in the changes in lower incisor position or angulation between the two male
groups. On the other hand, the lower incisors among the nonextraction female subjects tended to upright during the retention period. Other facial parameters. In general, there were no significant differences in the changes in the inclination of the mandibular plane between the various treatment groups. These results support those of Staggers2° who found no significant difference in the changes in the mandibular plane angle between subjects treated with four first premolar extractions and four second molar extractions.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 1
Bishara et aL
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Table IIIb. Results of Student's t test indicating significant differences between the absolute
dimensions between extraction and nonextraction female subjects x
Extraction
SD
I
x Nonextraction SD
Treatment interval Pretreatment Soft tissue parameters li-E(mm)
1.1
2.9
- 1.0
2.2
53.7
3.0
55.5
3.5
*
134.6 2.8 98.1 3.4 58.8 94.1
10.1 1.9 7.6 2.2 8.2 7.4
125.5 5.0 102.6 5.1 54.5 98.8
8.9 1.7 5.8 1.7 6.6 7.2
** ** * ** * *
- 3.3
2.2
1.2
1.9
**
53.8 123.2 85.3
3.2 6.6 7.0
56.5 127.4 88.9
3.4 7.9 5.2
** * *
135.3 3.1 98.4 3.4
9.4 1.9 5.7 2.0
128.9 5.t 102.7 4.7
6.9 1.7 6.1 1.4
** ** * **
-3.8 - 2.8
2.1 3.1
2.1 0.3
2.3 2.4
** **
Posttreatment Skeletal parameters N-Ans'(mm) Dental parameters Ut:LI(°) Ul:A-Pog(mm) UI:SN(°) LI:N-B(mm) LI:FH(°) L1;MP(°) Soft tissue parameters ls-E(mm)
Retention Skeletal parameters N-Ans'(mm) N-Me(mm) S-Go(ram) Dental parameters UI:LI(°) Ul:A-Pog(mm) UI:SN(°) LI:N-B(mm) Soft tissue parameters ls-E(mm) i-E(mm) *p -< 0.05; **p -< 0.01.
Bowbeer 6 on the other hand suggested that the extraction of four first premolars results in a decrease in the mandibular plane angle. Comparisons of absolute dimensions between groups (Tables Ilia and IIIb)
Before treatment. A comparison of the absolute dimensions between the various groups will provide information on how the overall changes affect the face. This information should provide the clinician with some insight as to some of the cephalometric criteria on which the extraction decision was based. Another important clinical variable that influences the extraction decision is, of course, the presence of significant tooth size-arch length discrepancies as estimated from the dental casts. Comparisons of tooth size-arch length discrepancies (TSALD) between the extraction and nonextraction groups indicated the presence of significant differences between the groups. The extrac-
tion group had on the average, a deficiency of - 2.4 and - 2.3 mm for male and female subjects, respectively in the maxillary arch and - 1.8 and - 2 . 1 mm in the mandibular arch. The nonextraction group had an excess space of 1.0 and 1.2 mm for male and female subjects, respectively, in the maxillary arch and 0.8 and 2.1 mm in the mandibular arch (Table VI). The most significant differences between the extraction and nonextraction groups indicated that the upper and lower lips were more protrusive relative to the esthetic plane among the extraction groups. In addition, the lower incisor angulations relative to the mandibular plane were relatively more upright among the male extraction group. This finding was surprising, since upright lower incisors would seem to favor a nonextraction treatment plan in the lower arch. On the other hand, there were no differences between the two groups in any of the other 23
36
Bishara et aL
American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table IV. Descriptive and comparative statistics on the differences in tooth size-arch length
discrepancies between the extraction and nonextraction groups (in ram) Extraction
Maxillary arch Males Females Mandibular arch Males Females
Nonextraction
;c
SD
x
SD
P
- 2.4 - 2.3
5.7 5.7
1.0 1.2
3.4 3.3
0.0347 0.0138
- 1.8 -2.1
3.6 4.6
0.8 2.1
3.3 2.3
0.0291 0.0005
P, Probability.
Table V. Means for selected parameters obtained from the extraction and nonextraction groups,
as well as the Iowa normative data Males Variables Skeletal parameters NAPog(°) Dental parameters UI:SN(°) L1 :MP(°) Soft tissue parameters G1SnPg(°) Holdaway angle (°) Ls:E-plane(mm) Li:E-plane(mm)
Ext
INonextlrowanormals Ext]
Females Nonext
I
Iowa normals
1.4
5.5
6.4
4.1
4.5
6.0
99.8 94.3
102.1 103.1
101.6 97.2
98.0 94.1
102.6 98.8
102.1 95.4
164.4 10.0 2.9 2.4
166.2 13.9 0.1 1.1
167.5 12.8 2.1 1.2
166.9 10.3 3.3 1.9
167.8 11.4 1.2 0.9
169.0 11.3 3.5 1.4
Ext, Extraction group; Nonext, nonextraction group.
dentofacial parameters compared. As a result, it might be concluded that lip protrusion was an important profile characteristic on which the extraction decision was made, at least in the present sample. These findings confirm that the presence of crowding and/or lip protrusion are important factors in the extraction-nonextraction decision; at least in this study. After treatment. Posttreatment comparisons are useful in determining the presence of any differences between the extraction and nonextraction groups after completion of the orthodontic and orthopedic treatment changes. It should be emphasized that such comparisons do not determine, per se, whether one group "looks" better than the other. The skeletal and soft tissue angles of facial convexity were significantly straighter in the male extraction group as compared with the nonextraction group. Female subjects had similar trends but
the differences were not significant between the two groups. The lips were more retrusive in the premolar extraction groups when compared with the nonextraction groups. This should be expected since in the present study, as well as in other investigations,3'5 lip protrusion was one of the important parameters on which the extraction decision was based. The pertinent clinical question is whether the treatment changes are desirable or detrimental to the facial profile? One method to make such a determination is to compare these values with matched normative standards, e.g., those derived from the Iowa Growth StudyY As indicated in Table V, the extraction groups tend to have straighter faces and slightly more upright maxillary and mandibular incisors whereas the nonextraction groups have the opposite tendencies. Yet the averages in both groups are close to, but on opposite sides of, the Iowa normative standards. These comparisons further suggest that the ex-
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. I
traction or nonextraction decision, if based on sound diagnostic criteria, seem to have no systematic detrimental effects on the facial profile. Yet clinicians should be aware of the observed changes during their treatment planning of individual patients to avoid accentuating any undesirable esthetic characteristics. It also needs to be remembered that the clinician's judgement is influenced by other factors including the severity of tooth size-arch length discrepancies, as well as the diagnostic, mechanical, and esthetic biases of each orthodontist. Retention. Essentially the differences between the extraction and nonextraction groups observed in the posttreatment comparisons were also present at the end of the retention period. CONCLUSIONS
The following conclusions can be derived from the present study: 1. Lip protrusion is an important pretreatment profile characteristic that influences the extraction decision in addition to the presence of a tooth size-arch length discrepancy. 2. After treatment it was observed that (a) the soft tissue and skeletal convexities were straighter in the extraction groups more than in the nonextraction groups; (b) the upper and lower lips were more retrusive in the extraction groups and more protrusive in the nonextraction groups in both sexes; and (c) the upper and lower incisors were retracted and uprighted more among subjects treated with four first premolar extractions than in the nonextraction groups. 3. In general, differences between the groups after treatment were preserved into retention. REFERENCES 1. Angle E. Malocclusion of the teeth. 7th ed. Philadelphia: SS White, 1907. 2. Dewel BF. The Case-Dewey-Cryer extraction debate: a commentary. AM J ORTHOD 1964;50:862-5. 3. Case CS. The question of extraction in orthodontia. AM J ORTHOD 1964;50:660-91. 4. The extraction debate of 1911 by Case, Dewey, and Cryer. Discussion of Case: the question of extraction in orthodontia. AN J ORTHOD 1964;50:751-68. 5. Stoner CC. An interview: AAFO's man of the year 1984, Dr. John W. Witzig. Funct Orthod 1984;1(4):9-15. 6. Bowbeer GRN. The sixth key to facial beauty and TMJ health. Funct Orthod 1987;4:4-20.
Bishara et al.
37
7. Bowbeer GRN. The five keys to facial beauty and TMJ health. Funct Orthod 1985;2:12-29. 8. Bowbeer GRN. Saving the face and the TMJ. Funct Orthod 1985;2:32-44. 9. Bowbeer GRN. Saving the face and the TMJ-Part 2. Funct Orthod 1986;3:9-24. 10. Bloom LA. Perioral profile changes in orthodontic treatment. AM J ORTHOD 1961;47:371. 11. Rudee DA. Proportional profile changes concurrent with orthodontic therapy. AM J ORTHOD 1964;50:421-34. 12. Garner LD. Soft tissue changes concurrent with orthodontic tooth movement. AM J ORTHOD 1974;66:357-77. 13. Roos N. Soft tissue changes in Class II treatment. AM J ORTHOD 1977;72:165-75. 14. Wisth PJ. Soft tissue response to upper incisor retraction in boys. Br J Orthod 1974;1:199-204. 15. Hershey HG. Incisor tooth retraction and subsequent profile change in postadolescent female patients. AM J ORTrIOD 1972;61:45-54. 16. Oliver BM. The influence of lip thickness and strain on upper lip response to incisor retraction. AN J ORTHOD 1982;82:141-8. 17. Perkins RA. Change in lip vermilion height during orthodontic treatment. [Thesis.] Iowa City: University of Iowa, 1987. 18. Stromboni Y. Facial aesthetics in orthodontic treatment with and without extractions. Eur J Orthod 1979;1:201-6. 19. Looi LK, Mills JRE. The effect of contrasting forms of orthodontic treatment on the facial profile. AM J ORTHOD 1986;89:507-17. 20. Staggers JA. A comparison of results of second molar and first premolar extraction treatment. AM J ORTHOD DENTOFAG ORTHOP 1990;98:430-6. 2l. Riolo ML, Moyers RE, McNamara JA, Hunter WS. An atlas of craniofacial growth: cephalometric standards from the university school growth study. Ann Arbor: University of Michigan, 1974. 22. Krogman W, Sassouni V. A syllabus in roentgenograpbic cephalometry. Philadelphia: Philadelphia Center for Research in Child Growth, 1957. 23. Salzmann JA. Practice of orthodontics. Philadelphia: JB Lippincott 1966. 24. Enlow DH. Handbook of facial growth. Philadelphia: WB Saunders, 1975. 25. Bishara SE. Maxillary growth and development: method of analysis. In: Hughlett M. The Bratislava project: some results of cleft palate surgery. Iowa City: University of Iowa, 1978. 26. Meredith HW, Chadha JM. A roentgenographic study of change in head height during childhood and adolescence. Hum Biol 1962;34:299-319. 27. Bishara SE, Peterson L, Bishara EC. Changes in facial dimensions and relationships between the ages of 5 and 25 years. AM J ORTHOD 1984;85:238-52. Reprint requests to: Dr. Samir E. Bishara Department of Orthodontics College of Dentistry University of Iowa Iowa City, IA 52242
Iowa Ci~ Iowa, Bellingham, Wash., and Alexandria, Egypt The purpose of this study was to compare the changes in subjects with Class II division 1 malocclusions treated with and without the extraction of four first premolars. Lateral cephalograms on 91 patients (44 extraction and 47 nonextraction) were evaluated at three stages: pretreatment, posttreatment, and approximately 2 years after treatment. The present findings indicate that before treatment, the upper and lower lips were more protrusive relative to the esthetic plane among the subjects treated with four first premolar extractions. After treatment the upper and lower lips were more retrusive in the extraction group, and more protrusive in the nonextraction groups. The extraction group tended to have straighter faces and slightly more upright maxillary and mandibular incisors, whereas the nonextraction group had the opposite tendencies. The average soft tissue and skeletal measurements for both groups were close to the corresponding averages derived from the Iowa normative standards. In general, differences between the groups after treatment were preserved into retention. The present findings indicate that the extraction or nonextraction decision, if based on sound diagnostic criteria, seem to have no deleterious effects on the facial profile. (AM J ORTHOD DENTOFACORTHOP 1995;107:28-37.)
T h e study of beauty and harmony of the facial profile has been central to the practice of orthodontics from its earliest days. At the turn of the century, orthodontics was in its infancy. There were few sources from which practitioners could learn the principles of "regulating" teeth. Followers of Angle's "new school" believed that if the teeth were in harmony, the face would be as well. 1'2 They believed that with their appliances they could make the bone grow, obviating the need for extractions. On the other hand the "rational school" contended that bone could not be encouraged to grow beyond its inherent potential, and therefore extractions were necessary to treat some malocclusions? Case and his followers believed that malocclusions were inherited, and arose from the mixing of face types and races. Both sides drew on a handful of cases in addition to "facts" and theories borrowed from biology and other sciences that seemed to support what they have From the University of Iowa. Support for this project has been received from the Council on Scientific Affairs of the American Association of Orthodontics. aProfessor, Department of Orthodontics, College of Dentistry. bin private practice, Bellingham, Wash. CAssistant professor, Department of Preventive and Community Dentistry, College of Dentistry. dAssistant Professor, Department of Orthodontics, Faculty of Dentistry, Alexandria University, Egypt. Copyright © 1995 by the American Association of Orthodontists. 0889-5406/95/$3.00 + 0 8/1/477911
28
already accepted for themselves as the truth. The debate was also a clash of egos, often deteriorating into personal attacks. 4 Unfortunately, the debate is still ongoing, and some clinicians still suggest that four first premolar extractions will compromise posttreatment esthetics by "dishing in" the profile.5-9 In an attempt to determine the effects of incisor retraction on the profile, several studies were conducted to quantify and to predict the relationship between incisor retraction and lip retraction. 1°-15 With the exception of one study that found a predictable amount of soft tissue changes in response to incisor retraction, 1° the majority of the studies on both growing and nongrowing subjects concluded that the large individual variation prevents the accurate prediction of lip response to incisor retraction in any given person. 1115 Lip structure seems to have an influence on lip response to incisor retraction. Oliver 16 found that patients with thin lips or a high lip strain displayed a significant correlation between incisor retraction and lip retraction, whereas patients with thick lips or low lip strain displayed no such correlation. In addition, Wisth a4 found that lip response, as a proportion of incisor retraction, decreased as the amount of incisor retraction increased. This seems to indicate that the lips have some inherent support.
Bishara et al.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 1
Perkins a7 found that decreases in upper vermilion height were positively correlated with upper lip retraction. However, changes in the upper vermilion height did not significantly correlate with the magnitude of incisor retraction. The available literature on the comparisons of the effects of extraction versus nonextraction treatment regimens on the profile is very limited. One study on high mandibular plane angle cases found that the lips were more retruded in nonextraction cases as compared with extraction cases. It was suggested that this is the result of an increase in the vertical dimension that tended to stretch the lips and decrease their prominence, is In another study, patients treated with four first premolar extractions and Begg mechanics were compared with a nonextraction group treated with activators. The upper incisors were retracted more in the Begg group, but there were no significant differences in the upper lip response between the two treatment groups. However; there was more retraction of the lower incisors in the Begg treatment group that resulted in a significantly greater amount of lower lip retraction. 19 In a comparison of four first premolar extraction cases to four second molar extraction cases, Staggers ~found no significant differences in the, amount of upper lip retraction. However, the lower lip was retracted significantly more when four first premolars were extracted. 2° The purpose of this study is to compare the profile changes in patients with Class II, Division 1 malocclusions who were treated with four first premolar extractions with a group of patients treated with similar appliances but without any extractions. MATERIALS AND METHODS Subjects
29
~GI
L Or
Ar"
)Pr
Pnu
~) LS ;LI
,Pg Me
Fig. 1. Landmarks used.
congenital anomalies, significant facial asYmmetries, or congenitally missing teeth. (4) The orthodontic records included lateral cephalograms taken before and after orthodontic treatment. In addition, a third set of records was obtained approximately 2 years after the completion of orthodontic treatment. (5) At the end of treatment, all cases were considered to be well treated, i.e., displayed a Class I canine and molar relationship, an overbite between 10% and 25%, and well-aligned and interdigitated arches. These criteria were selected to insure that the posttreatment changes were not caused by "poor" treatment results. Available records on patients with Class II, Division 1 malocclusions who were treated in the department were screened and only 91 cases met the selection criteria and also had complete records. Cephalometric landmarks
The material for this investigation was obtained from the records available in the Graduate Orthodontic Clinic at the University of Iowa. Ninety-one (91) patients were treated for their Class II, Division 1 malocclusions, 44 subjects (21 males and 23 females) had four first premolar extractions and 47 subjects (20 males and 27 females) were treated nonextraction. Case selection was based on the following criteria: (1) All cases were originally diagnosed as having a Class II, Division 1 malocclusion, i.e., Class II molar and canine relationship. (2) All cases have received comprehensive orthodontic treatment using an edgewise appliance. The cases were supervised by various clinical instructors in the graduate clinic. (3) None of the cases had
The following 18 hard tissue and 6 soft tissue landmarks were identified on each cephalogram (Fig. 1): Sella (S), sphenoidal wing point (W), nasion (N), orbitale (Or), anterior nasal spine (Ans), subspinale (A), supramentale (B), pogonion (Pog), menton (Me), gonion (Go), articulare (Ar), posterior nasal spine (Pns), potion (Po), occipitale (O), upper incisor point (U1 tip), upper incisor apex (U1 apex), lower incisor point (L1 tip), lower incisor apex (L1 apex), soft tissue glabella (G1), pronasale (Pr), subnasale (sn), labrale superius (Is), labrale inferius (li), and soft tissue pogonion (pg). The identification of the landmarks was based on the classic definitions previously described in the literature .21-26
30 Bishara et al.
American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table I. Average ages of the subjects (in years) at the different stages of treatment, also the average treatment and retention intervals Extraction Subject
Mean
11.5 14.6 16.8 3.1 2.3
Mean
1.6 1.4 1.6 0.9 0.5
12.1 14.5 16.5 2.3 2.1
11.6 14.4 16.8 2.9 2.4
1.6 1.6 1.7 0.9 0.5
10.9 13.2 15.3 2.3 2.1
SD
p Value
1.5 1.2 1.2 1.2 0.2
0.1848 0.7470 0.4973 0.0160 0.5356
1.5 1.2 1.2 1.1 0.3
0.1222 0.0003 0.0004 0.0480 0.0350
(n = 20)
(n = 23)
Females
Pretreatment Posttreatment Retention Treatment interval* Retention interval
SD
(n = 21)
Males
Pretreatment Posttreatment Retention Treatment interval* Retention interval
Nonextraction
(n = 27)
*Treatment interval includes a lag of 3 to 4 months between the time the initial records were taken and the actual treatment was initiated. n, Sample size; SD, standard deviation.
Reliability of landmark location and measurements All cephalograms were obtained on the same cephalometric unit. All landmarks were identified by one investigator and checked for accuracy o f location by a second investigator. The landmarks were digitized twice on separate occasions by two investigators. Allowable intrainvestigator and interinvestigator discrepancies were predetermined at 0.5 mm and 0.5°.
Measurements obtained Twenty-six anteroposterior and vertical skeletal, dental, and soft tissue linear and angular measurements were derived and included: SNA, SNB, SWPog, SNPog, ANB, NAPog, N-Ans', N-Me, Ans'/N-Me, Ar'-Go, S-Go, Ar'-Go/S-Go, S-Go/N-Me, FH:MP, SN:MP, UI:L1, UI:SN, UI:APog, LI:MP, LI:FH, LI:NB, Pog:NB, G1SnP, Pr-Pg:NB, Ls : E-plane, and Li: E-plane.
Statistical analysis Student t tests were used to compare (1) the incremental changes between groups from before treatment to after treatment, from after treatment through retention and from before treatment through retention, (2) absolute dimensions within each sex and extraction group were recorded before treatment, after treatment, and at retention. Significance level for statistical comparisons was predetermined at p <- 0.05.
RESULTS Age comparisons The age distribution of the subjects in each treatment and sex subgroup is detailed in Table I. Student t test comparisons of the male extrac-
tion and nonextraction groups indicated that before treatment the two groups were well matched according to age. However, the length of treatment in the extraction groups was significantly longer among the male (p = 0.016) and female (p = 0.048) subjects when compared with the corresponding nonextraction groups.
Sex differences Male and female subjects have significant differences in their absolute dimensions; in addition, the treatment changes were not identical in male and female subjects, as a result the findings on both sexes will be presented separately.
Comparisons of incremental changes between groups (Tables Ila and lib) Only the significant changes between the extraction and nonextraction groups during the various treatment periods will be presented. The emphasis in the presentation will be on those findings that were consistent in both male and female subjects.
Before treatment to after treatment Soft tissue relationships. In the male and female extraction groups, there was a significantly greater decrease, in the angle of convexity (GISnP) and the Holdaway soft tissue angle (Pr-P:NB) as compared with the corresponding nonextraction groups.
Bishara et al. 31
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 1
Table Ila. Results of Student's t test indicating significant differences in the incremental changes between extraction and nonextraction male subjects Nonextraction
Extraction
x
Treatment interval
I
SD
SD
Pretreatment/posttreatment Skeletal p a r a m e t e r s SNA(°) NAPog(°) N-Ans'(mm)
- 2.5
1.5
- 1.1
1.7
**
- 6.7 4.7
3.3 2.7
- 3,2 3.0
3.4 2.2
** *
0.3 2.8
1.1 1.4
- 0.4 0.8
1.2 1.3
* **
4.3 - 4.6
12.8 2.4
- 4.6 - 1,5
10.1 2.0
* **
N-Ans'/N-Me(%) Pog:NB(mm) Dental parameters UI:LI(°) U 1: A - P o g ( m m ) LI:N-B(mm)
- 0.4
1.7
1.8
1.6
**
L1 : F H ( ° )
- 2.2
7.6
- 8.1
7.2
*
- 2.2 - 6.8
3.2 3.4
0.5 - 1.8
3.0 2.6
** **
ls-E(mm)
- 3.9
2.0
1.3
1.4
**
li-E(mm)
- 3.9
2.0
0.8
2.0
**
Skeletal p a r a m e t e r s MP:FH(°)
- 0.8
2.6
- 2.7
3.0
*
Soft tissue p a r a m e t e r s ls-E(mm)
- 0.7
1.9
1.2
1.3
**
- 0.7
1.5
0.8
2.2
**
- 2.4 0.5 - 8.4 6.5 3.6
1.7 2.5 4.0 2.3 1.5
- 0.8 - 1.4 - 4.4 4.7 1.5
1.5 3.3 3.6 2.6 1.2
** * ** * **
Soft tissue p a r a m e t e r s GISnPg(°) Pr-P:NB(°)
Posttreatment retention
li-E(mm)
Pretreatrnent retention Skeletal p a r a m e t e r s SNA(°) SWPog(°) NAPog(°) N-Ans'(mm) Pog:NB(mm)
Dental parameters UI:LI(°) Ul:A-Pog(mm) LI:N-B(mm) LI:MP(°) Soft tissue p a r a m e t e r s G1SnPg(°) Pr-P:NB(°) ls-E(mm) li-E(mm)
6.7
11.1
-0.7
9.0
*
-4.4 - 0.6 0.1
2.6 1.8 6.0
- 1.7 1.2 4.2
2.1 1.5 6.5
** ** *
-
3.7 4.0 2.4 2.3
0.3 - 3.0 2.4 1.6
4.5 3.0 1.6 1.8
* ** ** **
2.6 7.3 4.6 4.9
x, M e a n ; SD, s t a n d a r d deviation; S, statistically significant. *p ~ 0.05; **p <_ 0.01.
Similarly, the upper (1s-E) and the lower (li-E) lip prominence relative to the esthetic plane decreased in the extraction groups but increased in the nonextraction groups. Skeletal relationships. For both male and female subjects, there was a significantly greater decrease in the SNA and NAPog angles in the extraction groups as compared with the nonextraction groups. Dental relationships. In both sexes the interin-
cisal angle (U1 :L1) increased among the extraction groups, but decreased among the nonextraction groups. The upper incisor protrusion (UI:A-Pg) decreased significantly in both the male and female extraction groups, but the angulation of the upper incisors (UI:SN) decreased significantly more in the female extraction group. In both sexes, the lower incisor protrusion (LI:NB) showed a slight decrease among the
32
Bishara et al.
American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table lib. Results of Student's t test indicating significant differences in the incremental changes between extraction and nonextraction female subjects Extraction Treatment interval
Non~ac~n
x
SD
x
SD
Pretreatment/posttreatment Skeletal parameters SNA(°) NAPog(°) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) UI:SN(°) LI:N-B(mm) LI:FH(°) LI:MP(°) Soft tissue parameters GISnPg(°) Pr-P:NB(°) ls-E(mm) li-E(mm)
- 2.0 - 5.1 1.8
1.6 3.3 1.2
-0.9 -3.0 0.8
1.3 3.1 0.8
* * **
12.3 -4.6 - 9.8 - 1.4 1.4 2.3
13.6 1.9 8.2 2.1 8.1 8.4
-1.1 1.9 -3.2 1.1 -5.5 3.8
10.5 2.5 9.2 1.6 6.9 5.2
** ** ** ** ** **
2.8 6.2 3.6 3.0
2.1 2.5 1,4 1.6
-1.1 -2.7 1.2 0.2
2.3 2.8 1.8 1.7
** ** ** **
0.1 1.3 1.5 - 0.2
1.3 2.7 2.2 2.9
0.9 2.8 3.4 -1.9
1.2 2.3 2.9 3.1
* * ** *
0.0 0.5
0.6 3.4
-0.4 3.8
0.8 3.7
* **
-0.6 - 0.8
1.2 1.4
0.9 1.2
1.1 1.1
** **
- 1.6 -0.2 4.6 6.6 7.1 2.4
1.4 1.2 3.0 3.3 3.4 1.4
-0.4 0.9 6.4 8.6 9.5 1.1
1.7 1.9 2.9 3,1 4,4 0,8
** * * * * **
13.0 4.3 9.4 1.3 2.5
12.1 2.2 8.0 2.0 7.2
2.3 -1.8 -3.0 0.7 1.8
9,2 2,2 8,6 1.4 4.5
** ** ** ** *
- 7.2 - 4.1 - 3.9
3.2 1.7 1.8
-4.1 2.1 1.4
3,0 2.1 1.8
** ** **
-
Posttreatment/retention Skeletal parameters N-Ans' (mm) Ar'-Go(mm) S-Go(ram) MP:FH(°) Dental parameters LI:N-B(mm) LI:FH(°) Soft tissue parameters ls-E(mm) li-E(mm)
Pretreatment/retention Skeletal parameters SNA(°) SNB(°) Ar'-Go(mm) S-Go(ram) N-Me(ram) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) U1 :SN(°) LI:N-B(mm) LI:MP(°) Soft tissue parameters Pr-P:NB(°) ls-E(mm) li-E(mm)
-
*p -< 0.05; **p -< 0.01.
extraction groups and an increase among subjects treated without extractions. In addition, the angulation of the lower incisors relative to the Frankfurt horizontal plane (LI:FH) became significantly more acute among the nonextraction male subjects.
After treatment to retention Relatively fewer incremental a significant difference between nonextraction
groups
exhibited
during the retention
Soft tissue relationships. upper
changes
the extraction and
(1s-E) and the lower
The
protrusion
period. of the
(li-E) lips relative to
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American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 1
the esthetic plane significantly decreased among the extraction groups but increased in the nonextraction groups. In other words, during the retention period, both lips continued to become less prominent among the extraction groups and more prominent among the nonextraction groups. Dental relationships. The protrusion of the lower incisors (LI:NB and L I : F H ) increased significantly more among the patients treated without extractions. Before treatment to retention
Soft tissue relationships. There was a significantly greater decrease in the Holdaway soft tissue angle in the extraction group in both sexes, but only male subjects had a significant decrease in the overall soft tissue convexity in the extraction subjects. Over the total observation period, the prominence of the upper (1s-E) and the lower (li-E) lips decreased among the extraction groups, but increased among the nonextraction groups. Skeletal relationships. During the overall period of observation there was a greater decrease in the SNA angle in the extraction groups and an increase in the chin prominence (Pog:NB) when compared with the nonextraction groups in both male and female subjects. Dental relationships. The interincisal angle (U1 :L1) became significantly more obtuse among the extraction groups. This change was associated with a decreased protrusion of the upper (UI:APg) and the lower incisors (LI:NB and LI:MP) in the extraction groups and an increase in these inclinations among the nonextraction groups. Comparisons of absolute dimensions between the groups (Tables Ilia and IIIb)
Before treatment. The prominence of the upper (ls-E) and the lower (li-E) lips, as well as the lower incisors, were significantly more protrusive (LI:MP) in the male extraction group. Only the prominence of the lower lip (li-E) was greater among the female patients who were treated with four first premolar extractions. After treatment. The extraction groups had a straighter skeletal (NAPog) and soft tissue (Pr-P:NB) convexities than the nonextraction groups in addition to a significantly more prominent bony chin (Pog:NB) particularly in male subjects. Although some face height dimensions were significantly different between the male extraction and nonextraction groups, the various ratios of these dimensions were not significantly different.
33
In both sexes, the upper lip prominence (1s-E) was less in the extraction groups when compared with the corresponding nonextraction groups. The interincisal angle (U1 :L1) was more obtuse among the male and female patients treated with extractions. This was accompanied by less protrusive upper (U1 :A-Pg) and lower incisors (LI:NB, L1 : FH and L1 : MP). Retention. The male extraction group, had relatively straighter skeletal (NAPog) and soft tissue (Pr-P:NB) profiles, as well as stronger chins (Pog:NB), than the nonextraction male subjects. The upper (1s-E) and the lower (li-E) lip prominence were significantly less among the extraction groups in both sexes. The interincisal angle (UI:L1) was significantly more obtuse among the male and female subjects treated with premolar extractions with the upper ( U I : A Pg) and the lower (LI:MP, LI:FH, and LI:NB) incisors less protrusive. DISCUSSION
In general, changes during the active treatment period are often the result of growth and appliance therapy, but when the changes are in the opposite direction of the expected "normal" growth o n e could assume that such changes are the result of treatment. On the other hand, changes occurring during the retention period are most likely the result of growth and/or a rebound effect after the completion of appliance therapy. Comparisons of incremental changes between groups (Tables Ila and lib)
This discussion will focus on the effects of the two different modes of treatment on specific areas of the face. Soft tissue relationships. The soft tissue facial convexity decreased more in the extraction groups during the treatment period. Also, the upper and lower lip prominence decreased relative to the nose and chin in the extraction groups. During the retention period, lip prominence decreased further among the extraction groups and increased among the nonextraction groups accentuating earlier trends. Skeletal relationships. During treatment, there was a significantly greater decrease in the facial skeletal convexity and an increase in c]hin prominence in the extraction groups as compared with the nonextraction groups in both male and female subjects. These findings suggest that during treatment planning if such outcomes are desirable, an
34
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American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table Ilia. Results of Student's t test indicating significant differences between the absolute
dimensions between extraction and nonextraction male subjects Extraction Treatment interval Pretreatment Skeletal parameters N-Me(mm) Ar'-Go(mm) S-Go(mm) Dental parameters LI:MP(°) Soft tissue parameters ls-E(mm) li-E(mm) Posttreatment Skeletal parameters Ar'-Go(mm) NAPog(°) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) LI:N-B(mm) LI:FH(°) LI:MP(°) Soft tissue parameters Pr-P:NB(°) ls-E(mm) Retention Skeletal parameters NAPog(°) N-Me(mm) Pog:NB(mm) Dental parameters UI:LI(°) Ul:A-Pog(mm) LI:N-B(mm) LI:FH(°) LI:MP(°) Soft tissue parameters Pr-P:NB(°) ls-E(mm) li-E(mm)
Nonextraction
I
x
SD
x
123.4 47.7 80.0
4.4 4.2 5.1
117.8 51.3 84.5
7.6 4.9 4.5
** * **
92.0
6.3
97.0
6.6
*
1.0 1.5
1.9 2.4
- 1.3 - 1.9
1.7 2.7
** **
51.8 1.4 4.9
5.5 4.9 2.4
55.4 5.8 2.8
5.4 4.5 2,3
* ** **
133.1 2.3 2.9 58.8 94.3
9.6 1.2 1.2 6.9 8.4
121.7 5.2 6.1 48.9 103.1
9,3 2.1 1.7 5.0 6.6
** ** ** ** **
10.0 - 2.9
4.6 1.6
13,9 - 0,1
3.7 1.7
** **
- 0.2 131.2 5.8
6.1 8.1 2.5
4.2 135.7 3.5
4.5 5.9 2.4
** * **
135.5 2.5 2.7 61.4 92.6
9.6 1.9 1.5 5.4 7.6
125.7 5.0 5.5 53.5 101.2
9.1 2.3 2.2 6.8 7.1
** ** ** ** **
9.5 - 3.6 - 3.4
5.3 2.3 2.2
12.6 1.1 - 0.3
4.3 2.2 2.8
* ** **
*p --- 0.05; **p -< 0.01.
extraction approach might enhance these changes. Dental relationships. The interincisal angle became significantly more obtuse among the extraction groups during the period of active treatment as a result of the greater retraction of the upper and lower incisors. Such changes help explain the greater amount of lip retraction seen among the extraction groups. During the retention period, there were no significant differences in the changes in lower incisor position or angulation between the two male
groups. On the other hand, the lower incisors among the nonextraction female subjects tended to upright during the retention period. Other facial parameters. In general, there were no significant differences in the changes in the inclination of the mandibular plane between the various treatment groups. These results support those of Staggers2° who found no significant difference in the changes in the mandibular plane angle between subjects treated with four first premolar extractions and four second molar extractions.
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Bishara et aL
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Table IIIb. Results of Student's t test indicating significant differences between the absolute
dimensions between extraction and nonextraction female subjects x
Extraction
SD
I
x Nonextraction SD
Treatment interval Pretreatment Soft tissue parameters li-E(mm)
1.1
2.9
- 1.0
2.2
53.7
3.0
55.5
3.5
*
134.6 2.8 98.1 3.4 58.8 94.1
10.1 1.9 7.6 2.2 8.2 7.4
125.5 5.0 102.6 5.1 54.5 98.8
8.9 1.7 5.8 1.7 6.6 7.2
** ** * ** * *
- 3.3
2.2
1.2
1.9
**
53.8 123.2 85.3
3.2 6.6 7.0
56.5 127.4 88.9
3.4 7.9 5.2
** * *
135.3 3.1 98.4 3.4
9.4 1.9 5.7 2.0
128.9 5.t 102.7 4.7
6.9 1.7 6.1 1.4
** ** * **
-3.8 - 2.8
2.1 3.1
2.1 0.3
2.3 2.4
** **
Posttreatment Skeletal parameters N-Ans'(mm) Dental parameters Ut:LI(°) Ul:A-Pog(mm) UI:SN(°) LI:N-B(mm) LI:FH(°) L1;MP(°) Soft tissue parameters ls-E(mm)
Retention Skeletal parameters N-Ans'(mm) N-Me(mm) S-Go(ram) Dental parameters UI:LI(°) Ul:A-Pog(mm) UI:SN(°) LI:N-B(mm) Soft tissue parameters ls-E(mm) i-E(mm) *p -< 0.05; **p -< 0.01.
Bowbeer 6 on the other hand suggested that the extraction of four first premolars results in a decrease in the mandibular plane angle. Comparisons of absolute dimensions between groups (Tables Ilia and IIIb)
Before treatment. A comparison of the absolute dimensions between the various groups will provide information on how the overall changes affect the face. This information should provide the clinician with some insight as to some of the cephalometric criteria on which the extraction decision was based. Another important clinical variable that influences the extraction decision is, of course, the presence of significant tooth size-arch length discrepancies as estimated from the dental casts. Comparisons of tooth size-arch length discrepancies (TSALD) between the extraction and nonextraction groups indicated the presence of significant differences between the groups. The extrac-
tion group had on the average, a deficiency of - 2.4 and - 2.3 mm for male and female subjects, respectively in the maxillary arch and - 1.8 and - 2 . 1 mm in the mandibular arch. The nonextraction group had an excess space of 1.0 and 1.2 mm for male and female subjects, respectively, in the maxillary arch and 0.8 and 2.1 mm in the mandibular arch (Table VI). The most significant differences between the extraction and nonextraction groups indicated that the upper and lower lips were more protrusive relative to the esthetic plane among the extraction groups. In addition, the lower incisor angulations relative to the mandibular plane were relatively more upright among the male extraction group. This finding was surprising, since upright lower incisors would seem to favor a nonextraction treatment plan in the lower arch. On the other hand, there were no differences between the two groups in any of the other 23
36
Bishara et aL
American Journal of Orthodontics and Dentofacial Orthopedics January 1995
Table IV. Descriptive and comparative statistics on the differences in tooth size-arch length
discrepancies between the extraction and nonextraction groups (in ram) Extraction
Maxillary arch Males Females Mandibular arch Males Females
Nonextraction
;c
SD
x
SD
P
- 2.4 - 2.3
5.7 5.7
1.0 1.2
3.4 3.3
0.0347 0.0138
- 1.8 -2.1
3.6 4.6
0.8 2.1
3.3 2.3
0.0291 0.0005
P, Probability.
Table V. Means for selected parameters obtained from the extraction and nonextraction groups,
as well as the Iowa normative data Males Variables Skeletal parameters NAPog(°) Dental parameters UI:SN(°) L1 :MP(°) Soft tissue parameters G1SnPg(°) Holdaway angle (°) Ls:E-plane(mm) Li:E-plane(mm)
Ext
INonextlrowanormals Ext]
Females Nonext
I
Iowa normals
1.4
5.5
6.4
4.1
4.5
6.0
99.8 94.3
102.1 103.1
101.6 97.2
98.0 94.1
102.6 98.8
102.1 95.4
164.4 10.0 2.9 2.4
166.2 13.9 0.1 1.1
167.5 12.8 2.1 1.2
166.9 10.3 3.3 1.9
167.8 11.4 1.2 0.9
169.0 11.3 3.5 1.4
Ext, Extraction group; Nonext, nonextraction group.
dentofacial parameters compared. As a result, it might be concluded that lip protrusion was an important profile characteristic on which the extraction decision was made, at least in the present sample. These findings confirm that the presence of crowding and/or lip protrusion are important factors in the extraction-nonextraction decision; at least in this study. After treatment. Posttreatment comparisons are useful in determining the presence of any differences between the extraction and nonextraction groups after completion of the orthodontic and orthopedic treatment changes. It should be emphasized that such comparisons do not determine, per se, whether one group "looks" better than the other. The skeletal and soft tissue angles of facial convexity were significantly straighter in the male extraction group as compared with the nonextraction group. Female subjects had similar trends but
the differences were not significant between the two groups. The lips were more retrusive in the premolar extraction groups when compared with the nonextraction groups. This should be expected since in the present study, as well as in other investigations,3'5 lip protrusion was one of the important parameters on which the extraction decision was based. The pertinent clinical question is whether the treatment changes are desirable or detrimental to the facial profile? One method to make such a determination is to compare these values with matched normative standards, e.g., those derived from the Iowa Growth StudyY As indicated in Table V, the extraction groups tend to have straighter faces and slightly more upright maxillary and mandibular incisors whereas the nonextraction groups have the opposite tendencies. Yet the averages in both groups are close to, but on opposite sides of, the Iowa normative standards. These comparisons further suggest that the ex-
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. I
traction or nonextraction decision, if based on sound diagnostic criteria, seem to have no systematic detrimental effects on the facial profile. Yet clinicians should be aware of the observed changes during their treatment planning of individual patients to avoid accentuating any undesirable esthetic characteristics. It also needs to be remembered that the clinician's judgement is influenced by other factors including the severity of tooth size-arch length discrepancies, as well as the diagnostic, mechanical, and esthetic biases of each orthodontist. Retention. Essentially the differences between the extraction and nonextraction groups observed in the posttreatment comparisons were also present at the end of the retention period. CONCLUSIONS
The following conclusions can be derived from the present study: 1. Lip protrusion is an important pretreatment profile characteristic that influences the extraction decision in addition to the presence of a tooth size-arch length discrepancy. 2. After treatment it was observed that (a) the soft tissue and skeletal convexities were straighter in the extraction groups more than in the nonextraction groups; (b) the upper and lower lips were more retrusive in the extraction groups and more protrusive in the nonextraction groups in both sexes; and (c) the upper and lower incisors were retracted and uprighted more among subjects treated with four first premolar extractions than in the nonextraction groups. 3. In general, differences between the groups after treatment were preserved into retention. REFERENCES 1. Angle E. Malocclusion of the teeth. 7th ed. Philadelphia: SS White, 1907. 2. Dewel BF. The Case-Dewey-Cryer extraction debate: a commentary. AM J ORTHOD 1964;50:862-5. 3. Case CS. The question of extraction in orthodontia. AM J ORTHOD 1964;50:660-91. 4. The extraction debate of 1911 by Case, Dewey, and Cryer. Discussion of Case: the question of extraction in orthodontia. AN J ORTHOD 1964;50:751-68. 5. Stoner CC. An interview: AAFO's man of the year 1984, Dr. John W. Witzig. Funct Orthod 1984;1(4):9-15. 6. Bowbeer GRN. The sixth key to facial beauty and TMJ health. Funct Orthod 1987;4:4-20.
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7. Bowbeer GRN. The five keys to facial beauty and TMJ health. Funct Orthod 1985;2:12-29. 8. Bowbeer GRN. Saving the face and the TMJ. Funct Orthod 1985;2:32-44. 9. Bowbeer GRN. Saving the face and the TMJ-Part 2. Funct Orthod 1986;3:9-24. 10. Bloom LA. Perioral profile changes in orthodontic treatment. AM J ORTHOD 1961;47:371. 11. Rudee DA. Proportional profile changes concurrent with orthodontic therapy. AM J ORTHOD 1964;50:421-34. 12. Garner LD. Soft tissue changes concurrent with orthodontic tooth movement. AM J ORTHOD 1974;66:357-77. 13. Roos N. Soft tissue changes in Class II treatment. AM J ORTHOD 1977;72:165-75. 14. Wisth PJ. Soft tissue response to upper incisor retraction in boys. Br J Orthod 1974;1:199-204. 15. Hershey HG. Incisor tooth retraction and subsequent profile change in postadolescent female patients. AM J ORTrIOD 1972;61:45-54. 16. Oliver BM. The influence of lip thickness and strain on upper lip response to incisor retraction. AN J ORTHOD 1982;82:141-8. 17. Perkins RA. Change in lip vermilion height during orthodontic treatment. [Thesis.] Iowa City: University of Iowa, 1987. 18. Stromboni Y. Facial aesthetics in orthodontic treatment with and without extractions. Eur J Orthod 1979;1:201-6. 19. Looi LK, Mills JRE. The effect of contrasting forms of orthodontic treatment on the facial profile. AM J ORTHOD 1986;89:507-17. 20. Staggers JA. A comparison of results of second molar and first premolar extraction treatment. AM J ORTHOD DENTOFAG ORTHOP 1990;98:430-6. 2l. Riolo ML, Moyers RE, McNamara JA, Hunter WS. An atlas of craniofacial growth: cephalometric standards from the university school growth study. Ann Arbor: University of Michigan, 1974. 22. Krogman W, Sassouni V. A syllabus in roentgenograpbic cephalometry. Philadelphia: Philadelphia Center for Research in Child Growth, 1957. 23. Salzmann JA. Practice of orthodontics. Philadelphia: JB Lippincott 1966. 24. Enlow DH. Handbook of facial growth. Philadelphia: WB Saunders, 1975. 25. Bishara SE. Maxillary growth and development: method of analysis. In: Hughlett M. The Bratislava project: some results of cleft palate surgery. Iowa City: University of Iowa, 1978. 26. Meredith HW, Chadha JM. A roentgenographic study of change in head height during childhood and adolescence. Hum Biol 1962;34:299-319. 27. Bishara SE, Peterson L, Bishara EC. Changes in facial dimensions and relationships between the ages of 5 and 25 years. AM J ORTHOD 1984;85:238-52. Reprint requests to: Dr. Samir E. Bishara Department of Orthodontics College of Dentistry University of Iowa Iowa City, IA 52242