- Email: [email protected]
The diagnostic facial triangle in the control of treatment objectives
The diagnostic facial triangle in the controZ of treatment objectives Charles Tucson,
H. Tweed, A rig.
D.D.S.
T
he development of the diagnostic facial triangle as a valuable adjunct in the analysis and treatment of malocclusion is, I believe, my most important rontribution to clinical orthodontics. The attainment of the FMIA requirement of the diagnostic facial triangle as a result of treatment procedures involves a working knowledge of the following : 1. The ability to measure and compare available and required arch lengths. 2. How to make the cephalogram correction to dcterminc total archlength discrepancies.? 3. Preorthodontic tooth guidance, including serial extraction of teeth.:: 4. The growth trend classification, Types A, B, and C.4 5. Anchorage preparation, first, second, and t,hird degrees.5 6. The necessity for instituting mechanical therapy in the treatment of Class I and Class II malocclusions that will maintain the normal inherent forward and downward growth vector of the middle and lower face. In other \lTords, maintaining the integrity of the oc~lusal plane in such a manner as not to allow it to drop down anteriorly.” Preorthodontic
guidance’
Analysis and treatment of malocclusion in the mixed dentition arc more complicated than in the permanent dentition because, in young children, greater growth changes occur in the dentofacial complex. A complete set of records, including photographs, casts, intraoral and lateral jaw x-ray films, and a lateral cephalogram, must be made. The patient is examined for abnormal sucking, swallowing, or other habits that might be contributing factors in causing the malocclusion. If such habits are present, the patient is referred to the speech therapist for treatment. The first decision that must be made is whether the cast is nonextraction or extraction in nature. For this, actual available space is measured between 651
Am.
J. Ovthodontics Juw1969
the mesial surfaces of the first permanent mandibular molars and recorded on line marked “available” (Fig. 1, C). The mesiodistal widths of the unerupted mandibular canine, first premolar, and second premolar teeth (right and left) are measured on the intraoral x-ray films and the data are transfered to the upper line of the analysis ca.rd, on which the actual widths of the central and late mral incisors had previously been recorded as measured directly in the pa-
A
Required
I
I
3-17-61
FM 3P.S”
IMPA 8V”
lo-2144
340
81.50
1 I
1
1
Required arch length Available arch length Arch length discrepancy Cephalogram correction Total discrepancy Fig.
1.
vol.
1.)
(From
Tweed:
Clinical
orthodontics,
St.
Louis,
1966,
The
C.
V.
HIA 11.50 b4.S”
-.._; ANN 20 So
65.5 65.5
mm. mm.
65.5 65.5 0 11 11
mm. mm. mm. mm. mm.
Mosby
Company,
lliagnostic
facial
triaagle
653
tient’s mouth. In the example shown in Fig. 1, C, required a.rch length is 65.5 mm., as is available arch length. Arch-length discrepancy, therefore, is 0 mm. The diagnostic facial triangle is then constructed as csplained in detail in my book entitled Clinicd Orthodontics.8 Cephalogram
correction
To arrive at the measurement referred to as the “cephalogram correction,” we rely primarily on the diagnostic facial triangle.g The FMA (Fig. 1, B) is 39.5 degrees, the IMPA is 89 degrees, and t,he FMIA is 51.5 degrees. The FMA is greater than 30 degrees. In such cases, the FMIA requirement is 65 degrees. However, the FMIA is only 51.5 degrees in this instance. Therefore, the mandibular incisors incline labially 13.5 degrees more than they should. Tipping the mandibular incisors lingually 13.5 degrees will require shortening bot,h sides of the dental arch. The measurement taken from the cephalogram, combined with the actual arch-length discrepancy (in this instance, arch-length discrepancy is 0 degree), and substracted from the available arch length gives the corrected arch length (Fig. 1, C) . Corrected arch length gives the amount of the total discrepancy in millimeters. Serial
extraction
sequence
If the diagnosis divulges that there is a discrepancy between teeth and basal bone structures, or that a cephalogram correction reduces available arch length appreciably, as in (Fig. 1, C), serial extraction procedures are instituted at the age of approximately 8 years.lO The sequence is as follows: 1. At approximately 8 years of age, all four deciduous first molars arc extracted. 2. Some 4 to 10 months later, the first premolar teeth will have erupted to gum level. At this time, all four erupting first premolars and all four deciduous canines arc removed. If this is done at least 4 to 6 months prior to eruption of the permanent canines, when they erupt they usually will migrate posteriorly into good positions. The irregularities of the mandibular incisors (if not too severe) correct themselves, and functional denture mechanics tip these teeth lingually to inclinations in keeping with the forces to which they are subjected during normal use (Figs. 1, B and 2, B) . In this instance, the mandibular incisors have tipped lingually 7.5 degrees during 43 months of guidance ; the irregularities of the mandibular incisors were self-corrected; the FMA was reduced 5.5 degrees, the FMIA increased 13 degrees (from 51.5 to 64.5 degrees), and there was a reduction of I..5 degree in ANB, indicating t.hat the growth trend is Type C. Obviously, the patient has been greatly benefited by serial extraction procedures, and mechanical treatment will be of short duration. Growth
trend
classification
(Fig.
3)
Facial growth trends may be classified as Type A, Type B, and Type C. These types are described in detail in Clinical OrthodontGxll~ I2 A11 young patients undergoing preorthodontic guidance should have lateral cephalograms
654
Tweed
t,aken at the beginning. Some 12 to 18 months later a second cephalogram shonl(1 be taken, and tracings should bc made of both cephalograms. These tracings arc superimposed on S-N, with S as the reference point. If this is done prior to an) mechanical treatment procedure, it, is possible to determine the type of facial growth trend that must be contended with tluring treat~ment. It is important to ascertain the type of facial growth trcwtl as ear1.v as possible, for it concerns the prognosis, the time to begin treatment, and the length of treatment timo.
Fig. vol.
2. [From 1 .I
Tweed:
Clinical
orthodontics,
St.
Louis,
1966,
The
C.
V.
Mosby
Company,
Diagnostic Anchorage
facial
tria&e
655
preparation’2
The degree to which anchorage should be prepared
will vary considerably. B point downward and backward for some specific reason, the terminal mandibular molars must always be uprighted or kept upright in such positions as will prevent their being elongated when Class II intermaxillary force is used. I classify anchorage preparation into three categories : (1) first degree, (2) second degree, and (3) third clegree. A detailed account is given in Clinical Orthodontics.12
U~WS one is purposely endeavoring to move the teeth and the
TreatmentI
One of the many beneficial developments in ort,hodontic treatment that have occurred during the past decade has been the effort on the part of a majority of orthodontists to control the forces in the orthodontic appliances they use in such a manner as not to interfere with t,hc patient’s normal dentofacial growth (luring orthodontic treatment. The indications are that, in the future, the clinical orthodontist must work within the confines of the patient’s growth trend, whether growth is in the vertical direction, the horizontal direction or a combination of the two. Evidence also indicates that those operators whose treatment permits them
7.20-60 3-2-63
FM1
IMPA MIA
AWB
29.3" 29.50
91.50 w
5* 5'
580 65.5'
A
7-30.66
MA
IMPA FMIA ANB
29"
89"
62"
B
Fig.
3.
vol.
1 .I
(From
Tweed:
Clinical
C orthodontics,
St.
Louis,
1966,
The
C.
V.
Mosby
Company,
656
Tweed
to maintain the integrity of the occlusal plane are working more closely within the confines of normal growth processes t,han are those who permit great deriations of the occlusal plane to occur as a result of faulty treatment. Prevention of undesirable changes in the occlusal plane during treat.ment is important. The solution to the problems appears to concern the control of forces ut.ilized in treatment. Space will not permit me to discuss this topic in detail here, but further information will be found in Clinical Orthodontics.7 Controlled
orthodontic
forces
versus
differential
forces
To illustrate the importance of forccl control in orthodontic trcatmcnt, the tracings of two patients with similar Class II, Division 1 malocclusions are compared. The patient whose tracing is shown in Fig. 4 (left) was t,reatcd with the edgewise arch mechanism utilizing the high-pull headgear in conjunction with Class II intermaxillary force and vertical elastic force in the incisor segments t,o prevent a deviation or lowering of the anterior end of the occlusal plane. The patient shown in Fig. 4, B (right) was trcatetl with the Begg light-wire technique,
S-27-61 4-30-65
HA
IMFA
38" 33.3"
88" 81 I"
43 3
433
93
13
A Fig. vol.
4.
(From
Tweed:
Clinical
B orthodontics,
St.
Louis,
1966,
The
C.
V.
Mosby
Company,
1 .I
Table
I. Fig.
4 measurements
Heglinning Angles Tracing FMA IMPA E’MTA ANB Occlusal
A
Tracing
B
FMA IMPA FMIA ANB Occlusal
and
and
measured
(degrees)
Frankfort,
plane
angle
Frankfort
plane
angle
value
Posttlmtment (d~{JU!~S)
value
a
658
Tweed
using differential forces without extraoral appliances. A study and comparison of: the angular changes that have occurred in FMA, IMPA, FMIA, and ArU’B in these two tracings are most enlightening and should convince orthodontists that, force control is a must in all orthodontic treatment (Table I). With this brief review of the information required of those who practice preorthodontic guidance procedures and endeavor to fulfill the requirements of the diagnostic facial triangle, let us study the records of some children treated in this manner. The patient shown in Fig. 5, ~1 rcprescnts a Type A growth t,rend, as indi-
Fig.
6.
See
text.
L&gnostic
facial
triangle
659
cated by the constancy of the ANB angle, which has remained at 5 degrees during 32 months of preorthodontic guidance that included serial extraction. In tracing Fig. 5, A the mandibular incisors have tipped lingually 7.5 degrees and the FMIA has gone from 58 to 65 degrees which meets the requirements of the diagnostic facial triangle. Fig. 5, B illustrates the extent of the distal movement of the ma.xillary incisors which has reduced the ANB angle from 5 to 2 degrees. The FMIA is 65 degrees at the termination of treatment. Treatment. forces have been controlled, and the integrity of the occlusal plane has been maintained. Anchorage prepara-
Fig. cal
7.
(From
Tweed:
orthodontics,
1966, Company,
The
St. C.
vol.
V. 2.)
CliniLouis, Mosby
660
l’wcea
,411~. J. Orthodontics June 1969
tion was second degree. Fig. 5, C, made approximately 3 years later, shows the FMIA to be 68.5 degrees with the ANB remaining constant at 2 degrees. The patient shown in Fig. 6 is a sister of the patient shown in Fig. 5. Prrorthodontic guidance lasted 4 years and included serial extraction procedures. The growth trend in Fig. 6 is Type (>, as indicated by an ANB reduction from 4 t,o 2.75 degrees (Fig. 6, 11). The mandibular incisors have tipped lingual-
Diagnostic
facial
triangle
661
ly only 3 degrees, from 92 to 89 degrees. The face is quite protrusive. Fig. 6, B tracing was made immediately following treatment. The angular changes in the diagnostic facial triangle are considerable. The mandibular incisors have been tipped lingually 1.2 degrees, from an IMPA of 89 degrees to one of 77 degrees. The FMIA has increased 11 degrees, from 62 to 73 degrees. The maxillary incisors have been moved distally the width of a tooth, resulting in a reduction of 2.75 degrees in the ANB angle, which now reads 0 degrees. Treatment forces have been well controlled, and the integrity of the occlusal plane was maintained. Second-degree anchorage preparation was used. The patient shown in Fig. 7 presents a Type B growth trend. Treatment time was 35 months. Tremendous efforts were made to cont,rol treatment forces anal the integrity of the occlusal plane. The hart1 palate was not, allowetl to drop (lo\vn anteriorly. A high-pull headgear was used. The maxillary incisors have been intrndetl to touch the hard palate (Fig. 7, 11). Note the extent of the rearward bodily movement of the maxillary incisors, mitll B point dropping down. Note also the changes in the angular measurements of the diagnostic facial triangle. The FMA has gone from 28 to 22.5 degrees, a reduction of 5.5 degrees. The IMPA shows that the mandibular incisors have been tipped lingually 18 tlegrees, from 107 to 89 degrees. The FMIA has gone from 45 to 68.5 degrees, which is 23.5 degrees, and the ANB has been reduced from 10 to 4.25 degrees, ;L distance of 5.75 degrees, Third-degree anchorage preparation was employed. Fig. 7, B, made 21 months after treatment, rereals several changes in the diagnostic facial triangle. There has been another reduction in the FXA of 2.5 tlegrees. The total reduction in the FMA now is 8 degrees. JMPA has increased 7 degrees, from 89 to 96 degrees. The FMIA has deteriorated 4.5 degrees, from 68.5 to 64 degrees, a.nd there has been an increase of 0.25 degree in the AKB, from 4.25 to 4.~5degrees, indicating Ohat the middle face is growing forward at a slightly greater rate than the lower face and that the growth trend is Type B. Age and loss of weight improved facial esthetics. F’ig. 8 shows a patient treated almost 20 years ago, when I was unaware of of the importance of force control and knew nothing about growth-trend classification. I trust that presentation of this case will be helpful to those unfamiliar with growth trends and the importance of the control of forces used in treatment. F’ig. 8, A reveals that anchorage was not sufficiently prepared, that treatment forces were not controlled, and that the integrity of the occlusal plane was not maintained, which permitted the FMA to increase 7.5 degrees, from 33.5 to 41 degrees, resulting in a.n increase of 0.5 degrees in the ANB, from 8.5 to 9 degrees, with an increase in the occlusal plane to Frankfort plane angle of 9.5 degrees or from 15.5 to 25 degrees. The mandibular rotation was not overcome during his remaining growth, as indicated by photographs and tracings shown in Fig. 8, c. These are the records of the growth and treatment changes that have occurred in a Type A growth trend case between the ages of 9 and 21 years. Fig. 9, A reveals the angular changes that occurred in the diagnostic facial triangle over a period of 25$/, months. During this time the patient was under preorthodontic guidance and serial extraction procedures.
662
Tweed
Am.
.I. 0j~thodolztic.s
tlune1969
L)iagnostic facial hiangle
663
Fig. 9, A shows that there has been no change in the ANB, which has rcmained at 4 degrees. The middle and lower face arc growing forward and downward in unison. Tracing B reveals the angular changes that have occurred in the diagnostic facial triangle as a result of treatment and growth. FMA (degrees)
Nor. 29, 1956 Frl1. 7, 1961
Fig.
10.
See
INPA (degrees)
26 22
102.5 93
text.
6.1563 6-23.67
30”
21”
91.5” 96”
17.5” I.50
59”
3 75”
6-1561 P-5-68
30” 25”
91s” W’
515” 65”
IS” I I’
664
l’weecl
Treatment mechanics have been well controlled, as indiwted by the maintenance of integrity of the occlusal plane and the normal growth vector of the lowcl face. Observe the 4 degree reduction in the FMA. A series of tracings made of this case revealed a contjinuous flattening of the FMA. The ANB remained constant at 0 until the sercnteenth year. Fig. 9, C shows tracings made from cephalograms taken before preorthodontic guidanw at aq’ 9 and later at age 21.
Nov. ;\ug.
Fig.
11.
See
29, 1956 16, 1967
text.
1m A (tlegrccs)
IJIPA (tle,qms)
FJf Id (tlr,l/ro s)
26 Il.5
IO”.5 -. !I;
*x1.5 7 l..j
,-1.Vli (tlc,q,x k 1.23
C’S1
Volume ~Nuvnber
55 6
Diagnostic
facial
triangle
665
Note the dramatic ramus growth and the 14.5 degree flattening of the FMA. Fig. 10 shows the records of a patient with a Type C growth trend (Fig. 10). At the end of preorthodontic guidance, which included serial extraction procedures, the changes in the angular measurements of the diagnostic facial triangle were as follows (Fig. 10, d) : FMA (degrees) June June
15, 1963 20, 1967
30 25
IUPA (degrees) 92.5 96
FKZA (degrees)
ANB (degrees)
57.5 59
5.5 3.75
The face is protrusive. Anchorage preparation was second-degree. The following changes have occurred in the diagnostic facial triangle from t,he heginning of guidance to the termination of treatment : FUA (degrees) June Sept.
15, 1963 5, 1968
30 25
ZiuPA (degrees) 92.5 90
FMIA (degrees) 57.5 65
ANB (degrees) 5.5 1.5
Controlled mechanics of treatment have maintained the integrity of both the occlusal plane and the normal growth vector. Note the 5 degree reduction in the FMA and the 4 degree reduction in the ANB, as well as the improvement in facial esthetics when the requirements of the diagnostic facial triangle are fulfilled. The records of the sister of the foregoing patient (Fig. 10) are shown in Fig. 11. This girl also has a Type C growth trend and has gone through a serial extraction procedure during preorthodontic guidance. This child is unusual in that, as a result of serial extraction, her occlusion is so beautiful that I did not treat her. The changes that have occurred in the diagnostic facial triangle arc as follows : FMA (degrees) Nov. Nov.
3, 1961 5, 1966
29 25
IMPA (degrees) 99 94
FMIA (degrees) 52 61
ANB (degrees) 4.5 3
The FMA has flattened 4 degrees ; the mandibular incisors have tipped lingually 5 degrees, to an IMPA of 94 degrees. As a result of these angular changes the FMIA now reads 61 degrees, an increase of 9 degrees in that angle. Comparing these two sisters, I regret that I did not treat this one, for if I had fulfilled the requirements of the diagnostic facial triangle and reduced the ANB angle, the face would not be so protrusive and facial esthetics wo~&l have been greatly improved. What poor decisions we all make at times! In Fig. 12 tracings A and A’ show the results of treatment of two Class I discrepancy malocclusions. The patient in tracing A was treated in the mixed dentition, and the patient represented by A’ was treated in the permanent dentition. Both present Type A growth trends, and anchorage preparation was second-degree. Note that the integrity of the occlusal plane has not been violated in either case. The anterior hard palate and the nasal spine have not been lowered in spite of the great distances that the maxillary incisors were moved
9-11 52 6-i-54
fMA IMPA HAlA ANR 34 5” 94” II I” 4.75 341” 78 67 I --.I
MA 28” 241“
IMPA
107” 90”
76”
101”
13”
0’
AN8 10”
6’
FA1 IA-2
MA
Z-26.51 4-12.61
31” 91” 32.5” 88
14” I.5” 59.5‘ 3.5’
II 20.51 335s 11-23.53 II”
16,
12’
D Fig.
12.
See
text.
IMPA 107” BB”
D’
distally by force-controlled treatment mechanics. In Fig. 12, A the mandibular incisors were tipped lingually 16 degrees, and there has been a decrease of 5.25 degrees in the ANB. The occlusal to Frankfort plane angle has decreased 2 degrees, from 13.5 to 11.5 degrees. In Fig. 12, d’ the mandibular incisors have been tipped lingually 24 dcgrccs. There has been a 2.5 degree reduction in the angle formed by occlusal and Frankfort planes; observe also that treatment mechanics have been coordinated with the normal inherent downward and forward growth vector of the middle and lower face as indicated by not even the slightest semblance of B point dropping down or backward. Compare these beautiful results of force-controlled treatment mechanics with B’, C’, and D’. These three cases demonstrate the results of lack of control of treatment mechanics which have permitted a serious deviation of the occlusal plane, with the result that B point has dropped downward and backward. Observe that the anterior nasal spine and the anterior hard palate have dropped down. Note the increases in the occlusal to Frankfort angles (6 degrees, 9.5 degrees, and 3.5 tlegrees). Compare the angular changes that hare occurred in the diagnositic facial triangle as a result of control of treatment forces in A and d’, B, C, and D with the angular changes in the diagnostic facial triangle that have occurred in tracings B’, C’, and D’ when treatment forces within the orthodontic mechanisms are not controlled. Rarely is it possible to achieve the requirement of the diagnostic facial triangle unless controlled treatment mechanics are utilized. On the other hand, it is possible to achierc its requirements in approximately 80 per cent of the cases by instituting force-control mechanics in one’s practice. It is my fervent hope that every orthodontist will take the time to find out how easy it is to practice force-control mechanics and how rich are the rewards when the requirements of the diagnostic facial triangle have been the results of his efforts. REFERENCES
1. Tm-eed, Charles H.: vol. 1, pp. 33, 252. 2. Ibid., pp. 259-260. 3. Ibid., pp. 248-268. 4. Ibid., pp. 13-30. 5. Ibid., pp. 7-12. 6. Ibid., pp. 232-247. 7. Ibid., ~01s. 1 and 2. 8. Ibid., vol. 1, pp. 252 9. Ibid., pp. 31-82. 10. Ibid., p. 261. 11. Ibid., pp. 13-30. 12. Ibid., pp. 7-12. 13. Ibid., pp. 232-248.
Clinical
et seq.
orthodont,ics,
St.
Louis,
1966,
The
C. V.
Mosly
Company,
H. Tweed, A rig.
D.D.S.
T
he development of the diagnostic facial triangle as a valuable adjunct in the analysis and treatment of malocclusion is, I believe, my most important rontribution to clinical orthodontics. The attainment of the FMIA requirement of the diagnostic facial triangle as a result of treatment procedures involves a working knowledge of the following : 1. The ability to measure and compare available and required arch lengths. 2. How to make the cephalogram correction to dcterminc total archlength discrepancies.? 3. Preorthodontic tooth guidance, including serial extraction of teeth.:: 4. The growth trend classification, Types A, B, and C.4 5. Anchorage preparation, first, second, and t,hird degrees.5 6. The necessity for instituting mechanical therapy in the treatment of Class I and Class II malocclusions that will maintain the normal inherent forward and downward growth vector of the middle and lower face. In other \lTords, maintaining the integrity of the oc~lusal plane in such a manner as not to allow it to drop down anteriorly.” Preorthodontic
guidance’
Analysis and treatment of malocclusion in the mixed dentition arc more complicated than in the permanent dentition because, in young children, greater growth changes occur in the dentofacial complex. A complete set of records, including photographs, casts, intraoral and lateral jaw x-ray films, and a lateral cephalogram, must be made. The patient is examined for abnormal sucking, swallowing, or other habits that might be contributing factors in causing the malocclusion. If such habits are present, the patient is referred to the speech therapist for treatment. The first decision that must be made is whether the cast is nonextraction or extraction in nature. For this, actual available space is measured between 651
Am.
J. Ovthodontics Juw1969
the mesial surfaces of the first permanent mandibular molars and recorded on line marked “available” (Fig. 1, C). The mesiodistal widths of the unerupted mandibular canine, first premolar, and second premolar teeth (right and left) are measured on the intraoral x-ray films and the data are transfered to the upper line of the analysis ca.rd, on which the actual widths of the central and late mral incisors had previously been recorded as measured directly in the pa-
A
Required
I
I
3-17-61
FM 3P.S”
IMPA 8V”
lo-2144
340
81.50
1 I
1
1
Required arch length Available arch length Arch length discrepancy Cephalogram correction Total discrepancy Fig.
1.
vol.
1.)
(From
Tweed:
Clinical
orthodontics,
St.
Louis,
1966,
The
C.
V.
HIA 11.50 b4.S”
-.._; ANN 20 So
65.5 65.5
mm. mm.
65.5 65.5 0 11 11
mm. mm. mm. mm. mm.
Mosby
Company,
lliagnostic
facial
triaagle
653
tient’s mouth. In the example shown in Fig. 1, C, required a.rch length is 65.5 mm., as is available arch length. Arch-length discrepancy, therefore, is 0 mm. The diagnostic facial triangle is then constructed as csplained in detail in my book entitled Clinicd Orthodontics.8 Cephalogram
correction
To arrive at the measurement referred to as the “cephalogram correction,” we rely primarily on the diagnostic facial triangle.g The FMA (Fig. 1, B) is 39.5 degrees, the IMPA is 89 degrees, and t,he FMIA is 51.5 degrees. The FMA is greater than 30 degrees. In such cases, the FMIA requirement is 65 degrees. However, the FMIA is only 51.5 degrees in this instance. Therefore, the mandibular incisors incline labially 13.5 degrees more than they should. Tipping the mandibular incisors lingually 13.5 degrees will require shortening bot,h sides of the dental arch. The measurement taken from the cephalogram, combined with the actual arch-length discrepancy (in this instance, arch-length discrepancy is 0 degree), and substracted from the available arch length gives the corrected arch length (Fig. 1, C) . Corrected arch length gives the amount of the total discrepancy in millimeters. Serial
extraction
sequence
If the diagnosis divulges that there is a discrepancy between teeth and basal bone structures, or that a cephalogram correction reduces available arch length appreciably, as in (Fig. 1, C), serial extraction procedures are instituted at the age of approximately 8 years.lO The sequence is as follows: 1. At approximately 8 years of age, all four deciduous first molars arc extracted. 2. Some 4 to 10 months later, the first premolar teeth will have erupted to gum level. At this time, all four erupting first premolars and all four deciduous canines arc removed. If this is done at least 4 to 6 months prior to eruption of the permanent canines, when they erupt they usually will migrate posteriorly into good positions. The irregularities of the mandibular incisors (if not too severe) correct themselves, and functional denture mechanics tip these teeth lingually to inclinations in keeping with the forces to which they are subjected during normal use (Figs. 1, B and 2, B) . In this instance, the mandibular incisors have tipped lingually 7.5 degrees during 43 months of guidance ; the irregularities of the mandibular incisors were self-corrected; the FMA was reduced 5.5 degrees, the FMIA increased 13 degrees (from 51.5 to 64.5 degrees), and there was a reduction of I..5 degree in ANB, indicating t.hat the growth trend is Type C. Obviously, the patient has been greatly benefited by serial extraction procedures, and mechanical treatment will be of short duration. Growth
trend
classification
(Fig.
3)
Facial growth trends may be classified as Type A, Type B, and Type C. These types are described in detail in Clinical OrthodontGxll~ I2 A11 young patients undergoing preorthodontic guidance should have lateral cephalograms
654
Tweed
t,aken at the beginning. Some 12 to 18 months later a second cephalogram shonl(1 be taken, and tracings should bc made of both cephalograms. These tracings arc superimposed on S-N, with S as the reference point. If this is done prior to an) mechanical treatment procedure, it, is possible to determine the type of facial growth trend that must be contended with tluring treat~ment. It is important to ascertain the type of facial growth trcwtl as ear1.v as possible, for it concerns the prognosis, the time to begin treatment, and the length of treatment timo.
Fig. vol.
2. [From 1 .I
Tweed:
Clinical
orthodontics,
St.
Louis,
1966,
The
C.
V.
Mosby
Company,
Diagnostic Anchorage
facial
tria&e
655
preparation’2
The degree to which anchorage should be prepared
will vary considerably. B point downward and backward for some specific reason, the terminal mandibular molars must always be uprighted or kept upright in such positions as will prevent their being elongated when Class II intermaxillary force is used. I classify anchorage preparation into three categories : (1) first degree, (2) second degree, and (3) third clegree. A detailed account is given in Clinical Orthodontics.12
U~WS one is purposely endeavoring to move the teeth and the
TreatmentI
One of the many beneficial developments in ort,hodontic treatment that have occurred during the past decade has been the effort on the part of a majority of orthodontists to control the forces in the orthodontic appliances they use in such a manner as not to interfere with t,hc patient’s normal dentofacial growth (luring orthodontic treatment. The indications are that, in the future, the clinical orthodontist must work within the confines of the patient’s growth trend, whether growth is in the vertical direction, the horizontal direction or a combination of the two. Evidence also indicates that those operators whose treatment permits them
7.20-60 3-2-63
FM1
IMPA MIA
AWB
29.3" 29.50
91.50 w
5* 5'
580 65.5'
A
7-30.66
MA
IMPA FMIA ANB
29"
89"
62"
B
Fig.
3.
vol.
1 .I
(From
Tweed:
Clinical
C orthodontics,
St.
Louis,
1966,
The
C.
V.
Mosby
Company,
656
Tweed
to maintain the integrity of the occlusal plane are working more closely within the confines of normal growth processes t,han are those who permit great deriations of the occlusal plane to occur as a result of faulty treatment. Prevention of undesirable changes in the occlusal plane during treat.ment is important. The solution to the problems appears to concern the control of forces ut.ilized in treatment. Space will not permit me to discuss this topic in detail here, but further information will be found in Clinical Orthodontics.7 Controlled
orthodontic
forces
versus
differential
forces
To illustrate the importance of forccl control in orthodontic trcatmcnt, the tracings of two patients with similar Class II, Division 1 malocclusions are compared. The patient whose tracing is shown in Fig. 4 (left) was t,reatcd with the edgewise arch mechanism utilizing the high-pull headgear in conjunction with Class II intermaxillary force and vertical elastic force in the incisor segments t,o prevent a deviation or lowering of the anterior end of the occlusal plane. The patient shown in Fig. 4, B (right) was trcatetl with the Begg light-wire technique,
S-27-61 4-30-65
HA
IMFA
38" 33.3"
88" 81 I"
43 3
433
93
13
A Fig. vol.
4.
(From
Tweed:
Clinical
B orthodontics,
St.
Louis,
1966,
The
C.
V.
Mosby
Company,
1 .I
Table
I. Fig.
4 measurements
Heglinning Angles Tracing FMA IMPA E’MTA ANB Occlusal
A
Tracing
B
FMA IMPA FMIA ANB Occlusal
and
and
measured
(degrees)
Frankfort,
plane
angle
Frankfort
plane
angle
value
Posttlmtment (d~{JU!~S)
value
a
658
Tweed
using differential forces without extraoral appliances. A study and comparison of: the angular changes that have occurred in FMA, IMPA, FMIA, and ArU’B in these two tracings are most enlightening and should convince orthodontists that, force control is a must in all orthodontic treatment (Table I). With this brief review of the information required of those who practice preorthodontic guidance procedures and endeavor to fulfill the requirements of the diagnostic facial triangle, let us study the records of some children treated in this manner. The patient shown in Fig. 5, ~1 rcprescnts a Type A growth t,rend, as indi-
Fig.
6.
See
text.
L&gnostic
facial
triangle
659
cated by the constancy of the ANB angle, which has remained at 5 degrees during 32 months of preorthodontic guidance that included serial extraction. In tracing Fig. 5, A the mandibular incisors have tipped lingually 7.5 degrees and the FMIA has gone from 58 to 65 degrees which meets the requirements of the diagnostic facial triangle. Fig. 5, B illustrates the extent of the distal movement of the ma.xillary incisors which has reduced the ANB angle from 5 to 2 degrees. The FMIA is 65 degrees at the termination of treatment. Treatment. forces have been controlled, and the integrity of the occlusal plane has been maintained. Anchorage prepara-
Fig. cal
7.
(From
Tweed:
orthodontics,
1966, Company,
The
St. C.
vol.
V. 2.)
CliniLouis, Mosby
660
l’wcea
,411~. J. Orthodontics June 1969
tion was second degree. Fig. 5, C, made approximately 3 years later, shows the FMIA to be 68.5 degrees with the ANB remaining constant at 2 degrees. The patient shown in Fig. 6 is a sister of the patient shown in Fig. 5. Prrorthodontic guidance lasted 4 years and included serial extraction procedures. The growth trend in Fig. 6 is Type (>, as indicated by an ANB reduction from 4 t,o 2.75 degrees (Fig. 6, 11). The mandibular incisors have tipped lingual-
Diagnostic
facial
triangle
661
ly only 3 degrees, from 92 to 89 degrees. The face is quite protrusive. Fig. 6, B tracing was made immediately following treatment. The angular changes in the diagnostic facial triangle are considerable. The mandibular incisors have been tipped lingually 1.2 degrees, from an IMPA of 89 degrees to one of 77 degrees. The FMIA has increased 11 degrees, from 62 to 73 degrees. The maxillary incisors have been moved distally the width of a tooth, resulting in a reduction of 2.75 degrees in the ANB angle, which now reads 0 degrees. Treatment forces have been well controlled, and the integrity of the occlusal plane was maintained. Second-degree anchorage preparation was used. The patient shown in Fig. 7 presents a Type B growth trend. Treatment time was 35 months. Tremendous efforts were made to cont,rol treatment forces anal the integrity of the occlusal plane. The hart1 palate was not, allowetl to drop (lo\vn anteriorly. A high-pull headgear was used. The maxillary incisors have been intrndetl to touch the hard palate (Fig. 7, 11). Note the extent of the rearward bodily movement of the maxillary incisors, mitll B point dropping down. Note also the changes in the angular measurements of the diagnostic facial triangle. The FMA has gone from 28 to 22.5 degrees, a reduction of 5.5 degrees. The IMPA shows that the mandibular incisors have been tipped lingually 18 tlegrees, from 107 to 89 degrees. The FMIA has gone from 45 to 68.5 degrees, which is 23.5 degrees, and the ANB has been reduced from 10 to 4.25 degrees, ;L distance of 5.75 degrees, Third-degree anchorage preparation was employed. Fig. 7, B, made 21 months after treatment, rereals several changes in the diagnostic facial triangle. There has been another reduction in the FXA of 2.5 tlegrees. The total reduction in the FMA now is 8 degrees. JMPA has increased 7 degrees, from 89 to 96 degrees. The FMIA has deteriorated 4.5 degrees, from 68.5 to 64 degrees, a.nd there has been an increase of 0.25 degree in the AKB, from 4.25 to 4.~5degrees, indicating Ohat the middle face is growing forward at a slightly greater rate than the lower face and that the growth trend is Type B. Age and loss of weight improved facial esthetics. F’ig. 8 shows a patient treated almost 20 years ago, when I was unaware of of the importance of force control and knew nothing about growth-trend classification. I trust that presentation of this case will be helpful to those unfamiliar with growth trends and the importance of the control of forces used in treatment. F’ig. 8, A reveals that anchorage was not sufficiently prepared, that treatment forces were not controlled, and that the integrity of the occlusal plane was not maintained, which permitted the FMA to increase 7.5 degrees, from 33.5 to 41 degrees, resulting in a.n increase of 0.5 degrees in the ANB, from 8.5 to 9 degrees, with an increase in the occlusal plane to Frankfort plane angle of 9.5 degrees or from 15.5 to 25 degrees. The mandibular rotation was not overcome during his remaining growth, as indicated by photographs and tracings shown in Fig. 8, c. These are the records of the growth and treatment changes that have occurred in a Type A growth trend case between the ages of 9 and 21 years. Fig. 9, A reveals the angular changes that occurred in the diagnostic facial triangle over a period of 25$/, months. During this time the patient was under preorthodontic guidance and serial extraction procedures.
662
Tweed
Am.
.I. 0j~thodolztic.s
tlune1969
L)iagnostic facial hiangle
663
Fig. 9, A shows that there has been no change in the ANB, which has rcmained at 4 degrees. The middle and lower face arc growing forward and downward in unison. Tracing B reveals the angular changes that have occurred in the diagnostic facial triangle as a result of treatment and growth. FMA (degrees)
Nor. 29, 1956 Frl1. 7, 1961
Fig.
10.
See
INPA (degrees)
26 22
102.5 93
text.
6.1563 6-23.67
30”
21”
91.5” 96”
17.5” I.50
59”
3 75”
6-1561 P-5-68
30” 25”
91s” W’
515” 65”
IS” I I’
664
l’weecl
Treatment mechanics have been well controlled, as indiwted by the maintenance of integrity of the occlusal plane and the normal growth vector of the lowcl face. Observe the 4 degree reduction in the FMA. A series of tracings made of this case revealed a contjinuous flattening of the FMA. The ANB remained constant at 0 until the sercnteenth year. Fig. 9, C shows tracings made from cephalograms taken before preorthodontic guidanw at aq’ 9 and later at age 21.
Nov. ;\ug.
Fig.
11.
See
29, 1956 16, 1967
text.
1m A (tlegrccs)
IJIPA (tle,qms)
FJf Id (tlr,l/ro s)
26 Il.5
IO”.5 -. !I;
*x1.5 7 l..j
,-1.Vli (tlc,q,x k 1.23
C’S1
Volume ~Nuvnber
55 6
Diagnostic
facial
triangle
665
Note the dramatic ramus growth and the 14.5 degree flattening of the FMA. Fig. 10 shows the records of a patient with a Type C growth trend (Fig. 10). At the end of preorthodontic guidance, which included serial extraction procedures, the changes in the angular measurements of the diagnostic facial triangle were as follows (Fig. 10, d) : FMA (degrees) June June
15, 1963 20, 1967
30 25
IUPA (degrees) 92.5 96
FKZA (degrees)
ANB (degrees)
57.5 59
5.5 3.75
The face is protrusive. Anchorage preparation was second-degree. The following changes have occurred in the diagnostic facial triangle from t,he heginning of guidance to the termination of treatment : FUA (degrees) June Sept.
15, 1963 5, 1968
30 25
ZiuPA (degrees) 92.5 90
FMIA (degrees) 57.5 65
ANB (degrees) 5.5 1.5
Controlled mechanics of treatment have maintained the integrity of both the occlusal plane and the normal growth vector. Note the 5 degree reduction in the FMA and the 4 degree reduction in the ANB, as well as the improvement in facial esthetics when the requirements of the diagnostic facial triangle are fulfilled. The records of the sister of the foregoing patient (Fig. 10) are shown in Fig. 11. This girl also has a Type C growth trend and has gone through a serial extraction procedure during preorthodontic guidance. This child is unusual in that, as a result of serial extraction, her occlusion is so beautiful that I did not treat her. The changes that have occurred in the diagnostic facial triangle arc as follows : FMA (degrees) Nov. Nov.
3, 1961 5, 1966
29 25
IMPA (degrees) 99 94
FMIA (degrees) 52 61
ANB (degrees) 4.5 3
The FMA has flattened 4 degrees ; the mandibular incisors have tipped lingually 5 degrees, to an IMPA of 94 degrees. As a result of these angular changes the FMIA now reads 61 degrees, an increase of 9 degrees in that angle. Comparing these two sisters, I regret that I did not treat this one, for if I had fulfilled the requirements of the diagnostic facial triangle and reduced the ANB angle, the face would not be so protrusive and facial esthetics wo~&l have been greatly improved. What poor decisions we all make at times! In Fig. 12 tracings A and A’ show the results of treatment of two Class I discrepancy malocclusions. The patient in tracing A was treated in the mixed dentition, and the patient represented by A’ was treated in the permanent dentition. Both present Type A growth trends, and anchorage preparation was second-degree. Note that the integrity of the occlusal plane has not been violated in either case. The anterior hard palate and the nasal spine have not been lowered in spite of the great distances that the maxillary incisors were moved
9-11 52 6-i-54
fMA IMPA HAlA ANR 34 5” 94” II I” 4.75 341” 78 67 I --.I
MA 28” 241“
IMPA
107” 90”
76”
101”
13”
0’
AN8 10”
6’
FA1 IA-2
MA
Z-26.51 4-12.61
31” 91” 32.5” 88
14” I.5” 59.5‘ 3.5’
II 20.51 335s 11-23.53 II”
16,
12’
D Fig.
12.
See
text.
IMPA 107” BB”
D’
distally by force-controlled treatment mechanics. In Fig. 12, A the mandibular incisors were tipped lingually 16 degrees, and there has been a decrease of 5.25 degrees in the ANB. The occlusal to Frankfort plane angle has decreased 2 degrees, from 13.5 to 11.5 degrees. In Fig. 12, d’ the mandibular incisors have been tipped lingually 24 dcgrccs. There has been a 2.5 degree reduction in the angle formed by occlusal and Frankfort planes; observe also that treatment mechanics have been coordinated with the normal inherent downward and forward growth vector of the middle and lower face as indicated by not even the slightest semblance of B point dropping down or backward. Compare these beautiful results of force-controlled treatment mechanics with B’, C’, and D’. These three cases demonstrate the results of lack of control of treatment mechanics which have permitted a serious deviation of the occlusal plane, with the result that B point has dropped downward and backward. Observe that the anterior nasal spine and the anterior hard palate have dropped down. Note the increases in the occlusal to Frankfort angles (6 degrees, 9.5 degrees, and 3.5 tlegrees). Compare the angular changes that hare occurred in the diagnositic facial triangle as a result of control of treatment forces in A and d’, B, C, and D with the angular changes in the diagnostic facial triangle that have occurred in tracings B’, C’, and D’ when treatment forces within the orthodontic mechanisms are not controlled. Rarely is it possible to achieve the requirement of the diagnostic facial triangle unless controlled treatment mechanics are utilized. On the other hand, it is possible to achierc its requirements in approximately 80 per cent of the cases by instituting force-control mechanics in one’s practice. It is my fervent hope that every orthodontist will take the time to find out how easy it is to practice force-control mechanics and how rich are the rewards when the requirements of the diagnostic facial triangle have been the results of his efforts. REFERENCES
1. Tm-eed, Charles H.: vol. 1, pp. 33, 252. 2. Ibid., pp. 259-260. 3. Ibid., pp. 248-268. 4. Ibid., pp. 13-30. 5. Ibid., pp. 7-12. 6. Ibid., pp. 232-247. 7. Ibid., ~01s. 1 and 2. 8. Ibid., vol. 1, pp. 252 9. Ibid., pp. 31-82. 10. Ibid., p. 261. 11. Ibid., pp. 13-30. 12. Ibid., pp. 7-12. 13. Ibid., pp. 232-248.
Clinical
et seq.
orthodont,ics,
St.
Louis,
1966,
The
C. V.
Mosly
Company,