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Incisor movement in Class III malocclusions treated with the Begg light-wire technique
Incisor movement in Class 111 malocclusions treated with the Begg light-wire technique Anthony London,
J. Rodesano,
B.D.S.,
F.D.S.R.CS(Edin.1,
O.Orth.R.C.S(Eng.1
England
A
number of articles have been written analyzing features of the Class III malocclusion with classification into “types.“1-5 With the exception of Bennett,o however, few authors have attempted to assess the effects of a specific technique in the treatment of the malocclusion and its efficacy in correcting the incisor relationship, although many have described over-all changes that may have occurred as a result of treatment. Braccesi and Lucchese,7 in analyzing cephalometric changes that occurred in thirty treated eases, concluded that, treatment gave a backward shift to the condyles in relation to the skull base and increased the difference between the axial inclinations of upper and lower incisors, no details of the treatment techniques used were given. Both Parker” and Brenchley,” in their analyses of treated cases, emphasized the elimination of overclosure and consequent increase in lower face height without discussing method of treatment, Mills,l” in an over-all assessment of treated Class 111 malocclusions, was unable to support the premise that overclosure was a feature of the Class III case other than as a rare phenomenon, In the discussion within his article, Mills went on to suggest that the most satisfactory method of treatment was proclination of the upper incisors with simultaneous retroclination of the lower incisors, indicating those features that should be considered and assessed before deciding on the mode of incisor correction, although not specifying the technique to be used. In the present article four Class III malocclusions of graded severity arc illustrated, and an analysis is presented of those changes taking place during treatment, with particular emphasis on the changing incisor position. Each patient was treated according to the principles and method outlined by Begg” in his explanation of the light-wire technique, Class III intermaxillary elastic From the College.
Department
of
Child
Dental
Health,
The
London
Rospital
Xeiiic.al
355
356
Am. J. Odhod.
Rodesmo
Table
October1971
I
Case NO.
Angle
Angle
SNA (degrees)
(d:i%)
79.5 79
80 78 77
-0.5 1.5 2
33 33 35
104 98 104
2
81.5 78 79
80.5 78 75.5
1 0 0.5
35 35 36
114 Ill 109.5
3
7'0 73.5 70
73.5 75 74.5
-3.5 -1.5 -4.5
33 35 35
106 110 109
4
78 79 79
82 82 82.5
-4 -3 -3.5
22 23 21.5
112.5 121 122
79.5
1
Table
7:
II
Case No.
SNI, (degrees)
SNL,
SNI,
SNL,
(degrees)
[degrees)
(degrees)
1
81.5 79.5 80.5
74.0 74.0 73.0
84.0 77.5 78.5
78.5 77.0 76.0
2
84.5 82.0 82.0
77.0 73.5 72.5
83.0 80.0 80.0
77.0 77.0 77.0
3
75.0 77.5 76.0
67.0 67.5 66.5
76.5 74.5 75.0
72.5 73.5 72.0
4
80.5 84.5 82.5
74.0 75.0 74.5
82.5 80.0 81.0
79.5 81.5 81.0
traction being used as required. The analysis illustrates the degree and the “nature” of the movement obtained with this technique. The material is part of a series, the object of which will be to correlate a specific treatment technique to the presenting features of the malocclusion. Method
On the completion of treatment of each case, tracings were drawn of three lateral skull radiographs-one taken at commencement of treatment, another at the end of Stage II, and the third at completion. All measurements were then taken from the tracings. Over-all changes that had taken place were assessed by angular and linear measurements set out in Tables I and II. To obtain composite
Volume Number
Incisor
60 4
movement
of
in Class III
Fa&ll angle (degrees)
Y axis (degrees)
malocclusions
Lower face height (mm. j ANS -+ Gn
N.S.Ba (degrees)
Angle convexz’ty (degrees)
-1 1.5 0.5
83 82 82
63.5 65 65
63
74
124 124 125
77 73 70
130 130 130
0 -1 1.0
91 89.5 90
58 60 61
78 80 x2
83 69 74
134 133 134
-5 -3 -6
84 86 86
61 63 63
79 81 8-f
75 55 62
134 133 132
-5 -6 -6
100 98 100.5
48 51 49
.iR 64 65
iMPA (degrees)
87 67
Fig.
1. Lines
and
points
used
in the
357
69 69
investigation.
diagrams illustrating the movement of incisors, the tracings were placed on graph paper, where apical and in&al tip positions were marked with a sharp point; each tracing was localized on line NS at S. The direction of growth was recorded at gnathion and nasion. To illustrate the difference in position of the mandibular incisors, the first and third tracings were then superimposed on the shadow of the mandibular canal and the anterior-inferior outline of the symphysis of the mandible.12 Lines and points used in the investigation. Standard planes and points were traced and measured (Fig. l), together with the following:
358
Rodesano
Am. J. Orthod. October1971
Fig.
2
1,--A point depicting the incisal tip of the maxillary incisor. I&--A point depicting the incisal tip of the mandibular incisor. L,--A point depicting the apical point of the maxillary incisor. L,--A point depicting the apical point of the mandibular incisor. Case Case
summaries 1
Patient 5. S., aged 11 years, presented for treatment in November, 1968. Clinical examination showed an intact and erupted dentition up to and inclusive of the second molars. Third molars, with the exception of the upper left third molar, were developing. The maxillary labial segment was imbricated, with both central and lateral incisors in a reverse overjet position. The patient was able to obtain an edge-to-edge incisor contact before displacement forward int,o occlusion; the overbite was normal. There was mild crowding of the lower incisors, with the lower center line deviated toward the left. The right second premolars were in cross-bite and the molars were in a Class III relationship. Treatment was directed toward relief of crowding and the establishment of a correct labial segment relationship. First premolars were extracted, and bands and arches were fitted. A positive overjet was obtained within 5 weeks, and treatment was continued to completion in approximately 12 months. An auxiliary lingual root torquing arch was used on the mandibular incisors over the final 4 months of treatment. Case
intact,
2
Patient and
N. all
S., aged 12 years, teeth had erupted
was up
first examined to and including
in January, 1969. His the second molars.
dentition was There was no
Volume Number
60 4
Iwisor
motwms~at in Class III
Fig.
malocclusio~as
359
3
evidence of the upper right third molar in radiographs; the remaining third molars were developing normally. The maxillary labial segment was mildly imbricated, with both lateral incisors in a reverse overjet position; the overbite was minimal, with no displacement on closure. Center lines were not coincident, the maxillary one having moved to the right and the mandibular line to the left; the mandibular incisors were markedly crowded and retroclined. Buccal segments, although well aligned, were in a cross-bite relationship, the molars being Class III. Treatment was directed toward relief of crowding and correction of the incisor position. The maxillary second premolars and mandibular first premolars were rstracted, and bands were placed in March, 1069. Treatment progressed to completiou iu January, 1970. An auxiliary torquing arch was fitted on the lower incisors throughout the final 3 months of active treatment. Case
3
Patient R. B., aged 14 years, was accepted for treatment in October, 1967. All teeth were present with the exception of the mandibular left first molar, which had been eytracted; third molars were unerupted. The maxillary labial segment was crowded, with the left canine excluded from the arch, the center line having moved to the left. The overjet was reversed, with the patient ahle to obtain edge-to-edge incisor contact, displacing forward on closure. The overbite was reduced ; there was mild lower incisor crowding; and a bilateral posterior cross-hitc was present. The anteroposterior length of the maxillary dental base was short, and the crowding was consequently severe. Treatment was directed to relief of crowding, align-
360
Am. J. OWz,od. October 1971
Rodesano
Fig.
4
ment of the labial segments, and correction of the incisor relationship. It was thought that, unless future growth was in a favorable direction, positioning of the incisors in a “normal” relationship might place them in an unstable position. With this in mind, the maxillary first premolars and the mandibular right first premolar were extracted and bands and arches were fitted during the same month. A positive overjet and overbite were recorded the following February; treatment progressed to completion in December, 1968. Case
4
Patient T. C., aged 13 years, commenced treatment in January, 1967. The diagnosis was a skeletal Class III dental base relationship with imbricated and rotated incisors. There was a reverse overjet, minimal overbite, and bilateral lingual occlusion of the posterior teeth. The patient was unable to obtain an edge-to-edge incisor contact. A limited prognosis was held for orthodontic treatment alone; it was thought that the dental base discrepancy was too severe for the patient to obtain a stable incisor relationship labiolingually. Final surgical correction would be assessed on completion of orthodontic tooth movement. Bands and arches were fitted and treatment progressed to completion in June, 1968. An auxiliary root-torquing arch was fitted to the mandibular incisors over the final 6 months of active treatment. Results
of
cephalometric
analysis
Case 1 Changes related to the orthodontic treatment. March, 1969, the maxillary incisor axial inclination
Between October, 1968, and was reduced from 104 to 98
V&me Number
60 4
Incisor
movement
be Class III
malocclusions
361
Fig. 5
degrees and the mandibular incisor axial inclination from 87 to 67 degrees. This period corresponded to the elimination of the displacement and reverse overjet ; Class III intermaxillary traction was used throughout (Table I). Linear measurements indicated that the change of inclination was a result of distal tipping of both maxillary and mandibular incisors (Fig. 6). Between March, 1969, and the following January, during the last 4 months of which lingual root torque was applied to the mandibular incisors, the maxillary incisors returned to 104 degrees while the mandibular incisors were repositioned at ‘74 degrees to the mandibular plane. Linear measurements indicated some lingual movement of the mandibular incisor apices, with the crowns moving labially ; total movement, however, was small (Fig. 6). Challges related to growth (Table I). The SNA/SNB difference increased from -0.5 to 2.0 degrees. This difference was due to a decrease in angle SNB. The Y axis increased from 63.5 to 65 degrees, gnathion moving downward and backward. The angle of convexity increased from -1.0 to 1.5 degrees, to reduce finally to 0.5 degree. The initial change was probably related to the elimination of the displacement. The lower face height. increased from 64 to 69 mm. There was no initial change in the maxillary mandibular plane angle, although an overall increase of 2 degrees was recorded. The positional change of the incisors in this case was undoubtedly assisted by the favorable directional growth of the mandible. It would seem likely that
362
Rodesano
Am. J. Orthod. October 1971
lOIS 1170
0
7
Fig. 6. Case Fig. 7. Case
1. The
change
1. First
and
in incisor final
tracings
position
through
superimposed
treatmen’t. and
localized
on
N-S
at S.
the mandibular torquing arch had little effect in repositioning the lower incisors. Interestingly enough, there was no reduction in overbite, which one might have expected with the amount of vertical growth recorded (Fig. 7). Case
2
Changes related to orthodontic treatment. Between January and November, 1969, the maxillary incisor axial inclination decreased by 3 degrees, and the mandibular incisor angulation was reduced by 4 degrees. A positive overjet of the maxillary lateral incisors was recorded during this period. The reduction in angulation of the maxillary incisors was a result of lingual tipping of the crown with concomitant reduction in angle SNA (Tables I and II). The mandibular incisor angulation decreased a further 3 degrees by the completion of treatment. The positional change of the mandibular incisors from commencement of treatment was recorded ; there was no change in the crown position, with the apices further forward (Fig. 8). Changes related to growth (Table I). The SNA/SNB difference was little changed throughout treatment, although an over-all reduction in both SNA and SNB was recorded. An increase of 3 degrees was recorded in the Y axis angulation. The lower face height increased by 4 mm., from 78 to 82 mm.; growth was largely in a vertical direction (Fig. 9). Case
3
Changes related
tember,
treatment. Between October, 1967, and Sepincisor axial inclination decreased from 83 to 69
to orthodontic
1968, the maxillary
Volume Number
Incisor
60 4
movement
in Class III
malocclusions
363
I 2
- 1169
.- 9po --__..
09 Fig.
8. Case
2. The
change
Fig.
9. Case
2. First
and
in incisor final
tracings
position
through
superimposed
treatment. and
localized
on N-S
at S.
degrees. Both linear and angular measurements indicated that the change was the result of simple tipping movement (Tables I and II). There was no further change in the position of the maxillary incisors. No attempt was made to root torque the mandibular incisors, and the recorded increase in the angular axial inclination was the result of the crowns moving labially. The over-all change in incisor relationship was a result of reciprocal mbiolingual tipping of incisor crowns (Fig. 10). Changes related to growth. The growth change recorded was vertically downward and marginally forward, the lower face height increasing by 5 mm. As in Case 1, there was little, if any, change in overbite, despite the less fa,vorable growth tendency (Fig. 11, Table I). Case 4 Changes related to orthodontic treatment. In the 2 years from January, 1966, to February, 1968, the maxillary incisor axial inclination increased from 112 to 121 degrees, while the mandibular incisor angle decreased from 75 to 55 degrees. This period corresponded to the correction of the incisors in a labiolingual direction. Movement was brought about through tipping, with some labial movement of the mandibular incisor apices (Table I). There was an over-all proclination of 10 degrees in the angulation of the
364
Rodesavlo
0
10
Fig. 10. Case Fig. 11. Case
Am.
J. 0,‘thod.
0ct0ber1971
SG” 3. The
change
3. First
and
in incisor final
tracings
position
through
superimposed
trea#tment. and
localized
on
N-S
at S.
maxillary incisors from commencement of treatment to January, 1969. The final axial inclination of the mandibular incisors was 62 degrees. Linear measurements indicated that this change in axis was largely the result of labial movement of the apex (Fig. 12, Table II). Changes related to growth. There was little change in the SNA/SNB difference; nor was there any significant change in the Y axis. The lower face height increased by 7 mm. Linear measurements indicated a 5 mm. forward movement of gnathion. As in the other cases reported in this article, little change in overbite was recorded, which is perhaps surprising in view of the degree of downward and forward movement at gnathion. The lower torquing arch worn during the last 6 months of active treatment would not appear to have accounted for any lingual root torque, but it may well have held the incisor axis stable while the bony chin grew forward, thereby preventing excessive labial movement of the incisor apex (Fig. 13). Superimposing first and third tracings, and localizing them on the mandibular canal and symphyseal outline (Fig. 14), illustrates the amount of mandibular incisor movement relative to the mandible. A measurable repositioning of the incisors has been obtained in all four cases. There is not, however, any obvious difference between Cases 1, 2, and 4, in which a torquing auxiliary arch was used, and Case 3, in which no torquing arch was used. The difference in position of the incisor tips and their relation to the occlusal
Volume Number
60 4
Incisor
4
movement
in Cla.ss III
malocclushrs
365
s
N
2
’
/ 3 2 %
12
I 3
l/b6 l/b9
. Gn
Of
Fig.
12.
Case
4. The
Fig.
13.
Case
4.
First
plane substantiates occurred.
change and
in incisor final
tracings
the previous
position
through
superimposed
observation
treatment. and
that
localized
on
no overbite
N-S
at S.
reduction
has
Discussion
Begg, in his textbook describing the light-wire technique, spends little time on treatment of the Class III malocclusion, stressing nothing other than mixeddentition treatment where possible. If crowding is an attendant feature, this is rarely possible, and there is no reason to suggest that the optimum time for treatment of the Class III malocclusion differs in any respect from other malocclusions. However, the principles outlined by Begg lend themselves particularly well to treatment of the Class III malocclusion. Reciprocal pro&nation of the maxillary incisors and retroclination of mandibular incisors are rapidly accomplished with this free-tipping flexible technique, as evidenced in the four cases described here. Further, it would seem reasonable that, having given consideration to the over-all growth pattern of the Class III malocclusion, apical root torque of the mandibular incisors in a lingual direction would be advantageous, continued forward growth of the mandible taking apices labially with the overbite maintaining the incisor crown position. One should set against this the possible disadvantage of closing mandibular arch space distal to the canines, which leaves no leeway space to be taken up by the lingual crown movement that would occur with this uprighting of the mandibular incisors. In addition, it is questionable whether there is sufficient bone on the lingual side of mandibular incisors to allow for apical root movement. A reduced overbite is a characteristic feature of the Class III malocclusion,
366
Am J. Orthod. October 1971
Rodesano
Fig. 14. Tracings inferior shadow
superimposed of the symphysis.
on
the
outline
of
the
mandibular
canal
and
the
anterior-
and with continued growth one might expect further reduction in overbite. In the cases illustrated here, despite considerable vertical growth, there was no reduction in overbite. It would be reasonable to suppose that the action of the Class III intermaxillary elastic traction applied to a full-banded fixed arch would help to prevent loss of overbite.
Volume
Number
60 4
Incisor
movement
in Class
III
malocclusions
367
Summaty
Four Class III malocclusions treated with the Begg light-wire technique have been presented, and for each case the changing incisor relationship throughout treatment has been described. In three cases an auxiliary torquinp arch was used for periods of 4 to 6 months. There was no measurable indication that lingual root torque was effected ; there was some indication in Cases 2 and 4 that the auxiliary arch was able to maintain the mandibular incisor axial inclination while the bony chin grew forward. Class III intermaxillary traction rapidly corrected the reverse incisor relationship and would seem to be instru. mental in preventing loss of overbite, notwithstanding continuing vertical growth. REFERENCES
1. Sanborn, R. T. S.: Differences between the facial skeletal patterns of Class III rnalolz. elusion and normal occlusion, Angle Orthod. 25: 208-221, 1955. 2. MeCallin, 8. G.: Angle Class III malocclusion, Trans. Br. Sot. Study Orthod., pp. 91. 101, 1955. 3. Maj, G., and others: Skeletal and dental behaviours in Class II, Division 1 and ilr Class III cases, Trans. Europ. Orthod. Soe. 34: 88-99, 1958. 4. Biederman, W.: Correction of the young prognathic mandible, Trans. Europ. Orthotl. Sot. 36: 332-340, 1960. 5. Hopkin, G. B.: Mesio-occlusion, a clinical and roentgenographic cephalometric stud>,, Ph.D. Thesis, University of Edinburgh, 1961. 6. Bennett, D. T.: Reinforced occipitomental traction and its effect on the incisor teeth in Class III malocclusions, Trans. Br. Sot. Study Orthod., pp. 59.66, 1968. 7. Braccesi, M. A., and Lucchese, P.: Sketetal and dental changes in 30 treated Class III malocclusion cases studied by cephalometric analysis, Trans. Europ. Orthod. Sot. 34: 211-214, 1958. 8. Parker, C. D.: Class III case with overclosure; a clinical and cephalometric study, Trans. Br. Sot. Study Orthod., pp. 59-64, 1959. 9. Brenchley, M. L.: Borderline Class III cases, Deut. Pratt. Dent. Rec. 16: 233-240, 1966. 10. Mills, J. R.: An assessment of Class III malocclusion, Dent. Pratt. Dent. Rec. 16: 452-467, 1966. Il. Begg, P. R.: Begg orthodontic t,herapy and technique, Philadelphia, 1965, W. B. Saunders Company. 12. Bj6rk, A.: Prediction of mandibular growth rotation, AM. J. ORTHOD. 55: 585-599, 1969.
J. Rodesano,
B.D.S.,
F.D.S.R.CS(Edin.1,
O.Orth.R.C.S(Eng.1
England
A
number of articles have been written analyzing features of the Class III malocclusion with classification into “types.“1-5 With the exception of Bennett,o however, few authors have attempted to assess the effects of a specific technique in the treatment of the malocclusion and its efficacy in correcting the incisor relationship, although many have described over-all changes that may have occurred as a result of treatment. Braccesi and Lucchese,7 in analyzing cephalometric changes that occurred in thirty treated eases, concluded that, treatment gave a backward shift to the condyles in relation to the skull base and increased the difference between the axial inclinations of upper and lower incisors, no details of the treatment techniques used were given. Both Parker” and Brenchley,” in their analyses of treated cases, emphasized the elimination of overclosure and consequent increase in lower face height without discussing method of treatment, Mills,l” in an over-all assessment of treated Class 111 malocclusions, was unable to support the premise that overclosure was a feature of the Class III case other than as a rare phenomenon, In the discussion within his article, Mills went on to suggest that the most satisfactory method of treatment was proclination of the upper incisors with simultaneous retroclination of the lower incisors, indicating those features that should be considered and assessed before deciding on the mode of incisor correction, although not specifying the technique to be used. In the present article four Class III malocclusions of graded severity arc illustrated, and an analysis is presented of those changes taking place during treatment, with particular emphasis on the changing incisor position. Each patient was treated according to the principles and method outlined by Begg” in his explanation of the light-wire technique, Class III intermaxillary elastic From the College.
Department
of
Child
Dental
Health,
The
London
Rospital
Xeiiic.al
355
356
Am. J. Odhod.
Rodesmo
Table
October1971
I
Case NO.
Angle
Angle
SNA (degrees)
(d:i%)
79.5 79
80 78 77
-0.5 1.5 2
33 33 35
104 98 104
2
81.5 78 79
80.5 78 75.5
1 0 0.5
35 35 36
114 Ill 109.5
3
7'0 73.5 70
73.5 75 74.5
-3.5 -1.5 -4.5
33 35 35
106 110 109
4
78 79 79
82 82 82.5
-4 -3 -3.5
22 23 21.5
112.5 121 122
79.5
1
Table
7:
II
Case No.
SNI, (degrees)
SNL,
SNI,
SNL,
(degrees)
[degrees)
(degrees)
1
81.5 79.5 80.5
74.0 74.0 73.0
84.0 77.5 78.5
78.5 77.0 76.0
2
84.5 82.0 82.0
77.0 73.5 72.5
83.0 80.0 80.0
77.0 77.0 77.0
3
75.0 77.5 76.0
67.0 67.5 66.5
76.5 74.5 75.0
72.5 73.5 72.0
4
80.5 84.5 82.5
74.0 75.0 74.5
82.5 80.0 81.0
79.5 81.5 81.0
traction being used as required. The analysis illustrates the degree and the “nature” of the movement obtained with this technique. The material is part of a series, the object of which will be to correlate a specific treatment technique to the presenting features of the malocclusion. Method
On the completion of treatment of each case, tracings were drawn of three lateral skull radiographs-one taken at commencement of treatment, another at the end of Stage II, and the third at completion. All measurements were then taken from the tracings. Over-all changes that had taken place were assessed by angular and linear measurements set out in Tables I and II. To obtain composite
Volume Number
Incisor
60 4
movement
of
in Class III
Fa&ll angle (degrees)
Y axis (degrees)
malocclusions
Lower face height (mm. j ANS -+ Gn
N.S.Ba (degrees)
Angle convexz’ty (degrees)
-1 1.5 0.5
83 82 82
63.5 65 65
63
74
124 124 125
77 73 70
130 130 130
0 -1 1.0
91 89.5 90
58 60 61
78 80 x2
83 69 74
134 133 134
-5 -3 -6
84 86 86
61 63 63
79 81 8-f
75 55 62
134 133 132
-5 -6 -6
100 98 100.5
48 51 49
.iR 64 65
iMPA (degrees)
87 67
Fig.
1. Lines
and
points
used
in the
357
69 69
investigation.
diagrams illustrating the movement of incisors, the tracings were placed on graph paper, where apical and in&al tip positions were marked with a sharp point; each tracing was localized on line NS at S. The direction of growth was recorded at gnathion and nasion. To illustrate the difference in position of the mandibular incisors, the first and third tracings were then superimposed on the shadow of the mandibular canal and the anterior-inferior outline of the symphysis of the mandible.12 Lines and points used in the investigation. Standard planes and points were traced and measured (Fig. l), together with the following:
358
Rodesano
Am. J. Orthod. October1971
Fig.
2
1,--A point depicting the incisal tip of the maxillary incisor. I&--A point depicting the incisal tip of the mandibular incisor. L,--A point depicting the apical point of the maxillary incisor. L,--A point depicting the apical point of the mandibular incisor. Case Case
summaries 1
Patient 5. S., aged 11 years, presented for treatment in November, 1968. Clinical examination showed an intact and erupted dentition up to and inclusive of the second molars. Third molars, with the exception of the upper left third molar, were developing. The maxillary labial segment was imbricated, with both central and lateral incisors in a reverse overjet position. The patient was able to obtain an edge-to-edge incisor contact before displacement forward int,o occlusion; the overbite was normal. There was mild crowding of the lower incisors, with the lower center line deviated toward the left. The right second premolars were in cross-bite and the molars were in a Class III relationship. Treatment was directed toward relief of crowding and the establishment of a correct labial segment relationship. First premolars were extracted, and bands and arches were fitted. A positive overjet was obtained within 5 weeks, and treatment was continued to completion in approximately 12 months. An auxiliary lingual root torquing arch was used on the mandibular incisors over the final 4 months of treatment. Case
intact,
2
Patient and
N. all
S., aged 12 years, teeth had erupted
was up
first examined to and including
in January, 1969. His the second molars.
dentition was There was no
Volume Number
60 4
Iwisor
motwms~at in Class III
Fig.
malocclusio~as
359
3
evidence of the upper right third molar in radiographs; the remaining third molars were developing normally. The maxillary labial segment was mildly imbricated, with both lateral incisors in a reverse overjet position; the overbite was minimal, with no displacement on closure. Center lines were not coincident, the maxillary one having moved to the right and the mandibular line to the left; the mandibular incisors were markedly crowded and retroclined. Buccal segments, although well aligned, were in a cross-bite relationship, the molars being Class III. Treatment was directed toward relief of crowding and correction of the incisor position. The maxillary second premolars and mandibular first premolars were rstracted, and bands were placed in March, 1069. Treatment progressed to completiou iu January, 1970. An auxiliary torquing arch was fitted on the lower incisors throughout the final 3 months of active treatment. Case
3
Patient R. B., aged 14 years, was accepted for treatment in October, 1967. All teeth were present with the exception of the mandibular left first molar, which had been eytracted; third molars were unerupted. The maxillary labial segment was crowded, with the left canine excluded from the arch, the center line having moved to the left. The overjet was reversed, with the patient ahle to obtain edge-to-edge incisor contact, displacing forward on closure. The overbite was reduced ; there was mild lower incisor crowding; and a bilateral posterior cross-hitc was present. The anteroposterior length of the maxillary dental base was short, and the crowding was consequently severe. Treatment was directed to relief of crowding, align-
360
Am. J. OWz,od. October 1971
Rodesano
Fig.
4
ment of the labial segments, and correction of the incisor relationship. It was thought that, unless future growth was in a favorable direction, positioning of the incisors in a “normal” relationship might place them in an unstable position. With this in mind, the maxillary first premolars and the mandibular right first premolar were extracted and bands and arches were fitted during the same month. A positive overjet and overbite were recorded the following February; treatment progressed to completion in December, 1968. Case
4
Patient T. C., aged 13 years, commenced treatment in January, 1967. The diagnosis was a skeletal Class III dental base relationship with imbricated and rotated incisors. There was a reverse overjet, minimal overbite, and bilateral lingual occlusion of the posterior teeth. The patient was unable to obtain an edge-to-edge incisor contact. A limited prognosis was held for orthodontic treatment alone; it was thought that the dental base discrepancy was too severe for the patient to obtain a stable incisor relationship labiolingually. Final surgical correction would be assessed on completion of orthodontic tooth movement. Bands and arches were fitted and treatment progressed to completion in June, 1968. An auxiliary root-torquing arch was fitted to the mandibular incisors over the final 6 months of active treatment. Results
of
cephalometric
analysis
Case 1 Changes related to the orthodontic treatment. March, 1969, the maxillary incisor axial inclination
Between October, 1968, and was reduced from 104 to 98
V&me Number
60 4
Incisor
movement
be Class III
malocclusions
361
Fig. 5
degrees and the mandibular incisor axial inclination from 87 to 67 degrees. This period corresponded to the elimination of the displacement and reverse overjet ; Class III intermaxillary traction was used throughout (Table I). Linear measurements indicated that the change of inclination was a result of distal tipping of both maxillary and mandibular incisors (Fig. 6). Between March, 1969, and the following January, during the last 4 months of which lingual root torque was applied to the mandibular incisors, the maxillary incisors returned to 104 degrees while the mandibular incisors were repositioned at ‘74 degrees to the mandibular plane. Linear measurements indicated some lingual movement of the mandibular incisor apices, with the crowns moving labially ; total movement, however, was small (Fig. 6). Challges related to growth (Table I). The SNA/SNB difference increased from -0.5 to 2.0 degrees. This difference was due to a decrease in angle SNB. The Y axis increased from 63.5 to 65 degrees, gnathion moving downward and backward. The angle of convexity increased from -1.0 to 1.5 degrees, to reduce finally to 0.5 degree. The initial change was probably related to the elimination of the displacement. The lower face height. increased from 64 to 69 mm. There was no initial change in the maxillary mandibular plane angle, although an overall increase of 2 degrees was recorded. The positional change of the incisors in this case was undoubtedly assisted by the favorable directional growth of the mandible. It would seem likely that
362
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Am. J. Orthod. October 1971
lOIS 1170
0
7
Fig. 6. Case Fig. 7. Case
1. The
change
1. First
and
in incisor final
tracings
position
through
superimposed
treatmen’t. and
localized
on
N-S
at S.
the mandibular torquing arch had little effect in repositioning the lower incisors. Interestingly enough, there was no reduction in overbite, which one might have expected with the amount of vertical growth recorded (Fig. 7). Case
2
Changes related to orthodontic treatment. Between January and November, 1969, the maxillary incisor axial inclination decreased by 3 degrees, and the mandibular incisor angulation was reduced by 4 degrees. A positive overjet of the maxillary lateral incisors was recorded during this period. The reduction in angulation of the maxillary incisors was a result of lingual tipping of the crown with concomitant reduction in angle SNA (Tables I and II). The mandibular incisor angulation decreased a further 3 degrees by the completion of treatment. The positional change of the mandibular incisors from commencement of treatment was recorded ; there was no change in the crown position, with the apices further forward (Fig. 8). Changes related to growth (Table I). The SNA/SNB difference was little changed throughout treatment, although an over-all reduction in both SNA and SNB was recorded. An increase of 3 degrees was recorded in the Y axis angulation. The lower face height increased by 4 mm., from 78 to 82 mm.; growth was largely in a vertical direction (Fig. 9). Case
3
Changes related
tember,
treatment. Between October, 1967, and Sepincisor axial inclination decreased from 83 to 69
to orthodontic
1968, the maxillary
Volume Number
Incisor
60 4
movement
in Class III
malocclusions
363
I 2
- 1169
.- 9po --__..
09 Fig.
8. Case
2. The
change
Fig.
9. Case
2. First
and
in incisor final
tracings
position
through
superimposed
treatment. and
localized
on N-S
at S.
degrees. Both linear and angular measurements indicated that the change was the result of simple tipping movement (Tables I and II). There was no further change in the position of the maxillary incisors. No attempt was made to root torque the mandibular incisors, and the recorded increase in the angular axial inclination was the result of the crowns moving labially. The over-all change in incisor relationship was a result of reciprocal mbiolingual tipping of incisor crowns (Fig. 10). Changes related to growth. The growth change recorded was vertically downward and marginally forward, the lower face height increasing by 5 mm. As in Case 1, there was little, if any, change in overbite, despite the less fa,vorable growth tendency (Fig. 11, Table I). Case 4 Changes related to orthodontic treatment. In the 2 years from January, 1966, to February, 1968, the maxillary incisor axial inclination increased from 112 to 121 degrees, while the mandibular incisor angle decreased from 75 to 55 degrees. This period corresponded to the correction of the incisors in a labiolingual direction. Movement was brought about through tipping, with some labial movement of the mandibular incisor apices (Table I). There was an over-all proclination of 10 degrees in the angulation of the
364
Rodesavlo
0
10
Fig. 10. Case Fig. 11. Case
Am.
J. 0,‘thod.
0ct0ber1971
SG” 3. The
change
3. First
and
in incisor final
tracings
position
through
superimposed
trea#tment. and
localized
on
N-S
at S.
maxillary incisors from commencement of treatment to January, 1969. The final axial inclination of the mandibular incisors was 62 degrees. Linear measurements indicated that this change in axis was largely the result of labial movement of the apex (Fig. 12, Table II). Changes related to growth. There was little change in the SNA/SNB difference; nor was there any significant change in the Y axis. The lower face height increased by 7 mm. Linear measurements indicated a 5 mm. forward movement of gnathion. As in the other cases reported in this article, little change in overbite was recorded, which is perhaps surprising in view of the degree of downward and forward movement at gnathion. The lower torquing arch worn during the last 6 months of active treatment would not appear to have accounted for any lingual root torque, but it may well have held the incisor axis stable while the bony chin grew forward, thereby preventing excessive labial movement of the incisor apex (Fig. 13). Superimposing first and third tracings, and localizing them on the mandibular canal and symphyseal outline (Fig. 14), illustrates the amount of mandibular incisor movement relative to the mandible. A measurable repositioning of the incisors has been obtained in all four cases. There is not, however, any obvious difference between Cases 1, 2, and 4, in which a torquing auxiliary arch was used, and Case 3, in which no torquing arch was used. The difference in position of the incisor tips and their relation to the occlusal
Volume Number
60 4
Incisor
4
movement
in Cla.ss III
malocclushrs
365
s
N
2
’
/ 3 2 %
12
I 3
l/b6 l/b9
. Gn
Of
Fig.
12.
Case
4. The
Fig.
13.
Case
4.
First
plane substantiates occurred.
change and
in incisor final
tracings
the previous
position
through
superimposed
observation
treatment. and
that
localized
on
no overbite
N-S
at S.
reduction
has
Discussion
Begg, in his textbook describing the light-wire technique, spends little time on treatment of the Class III malocclusion, stressing nothing other than mixeddentition treatment where possible. If crowding is an attendant feature, this is rarely possible, and there is no reason to suggest that the optimum time for treatment of the Class III malocclusion differs in any respect from other malocclusions. However, the principles outlined by Begg lend themselves particularly well to treatment of the Class III malocclusion. Reciprocal pro&nation of the maxillary incisors and retroclination of mandibular incisors are rapidly accomplished with this free-tipping flexible technique, as evidenced in the four cases described here. Further, it would seem reasonable that, having given consideration to the over-all growth pattern of the Class III malocclusion, apical root torque of the mandibular incisors in a lingual direction would be advantageous, continued forward growth of the mandible taking apices labially with the overbite maintaining the incisor crown position. One should set against this the possible disadvantage of closing mandibular arch space distal to the canines, which leaves no leeway space to be taken up by the lingual crown movement that would occur with this uprighting of the mandibular incisors. In addition, it is questionable whether there is sufficient bone on the lingual side of mandibular incisors to allow for apical root movement. A reduced overbite is a characteristic feature of the Class III malocclusion,
366
Am J. Orthod. October 1971
Rodesano
Fig. 14. Tracings inferior shadow
superimposed of the symphysis.
on
the
outline
of
the
mandibular
canal
and
the
anterior-
and with continued growth one might expect further reduction in overbite. In the cases illustrated here, despite considerable vertical growth, there was no reduction in overbite. It would be reasonable to suppose that the action of the Class III intermaxillary elastic traction applied to a full-banded fixed arch would help to prevent loss of overbite.
Volume
Number
60 4
Incisor
movement
in Class
III
malocclusions
367
Summaty
Four Class III malocclusions treated with the Begg light-wire technique have been presented, and for each case the changing incisor relationship throughout treatment has been described. In three cases an auxiliary torquinp arch was used for periods of 4 to 6 months. There was no measurable indication that lingual root torque was effected ; there was some indication in Cases 2 and 4 that the auxiliary arch was able to maintain the mandibular incisor axial inclination while the bony chin grew forward. Class III intermaxillary traction rapidly corrected the reverse incisor relationship and would seem to be instru. mental in preventing loss of overbite, notwithstanding continuing vertical growth. REFERENCES
1. Sanborn, R. T. S.: Differences between the facial skeletal patterns of Class III rnalolz. elusion and normal occlusion, Angle Orthod. 25: 208-221, 1955. 2. MeCallin, 8. G.: Angle Class III malocclusion, Trans. Br. Sot. Study Orthod., pp. 91. 101, 1955. 3. Maj, G., and others: Skeletal and dental behaviours in Class II, Division 1 and ilr Class III cases, Trans. Europ. Orthod. Soe. 34: 88-99, 1958. 4. Biederman, W.: Correction of the young prognathic mandible, Trans. Europ. Orthotl. Sot. 36: 332-340, 1960. 5. Hopkin, G. B.: Mesio-occlusion, a clinical and roentgenographic cephalometric stud>,, Ph.D. Thesis, University of Edinburgh, 1961. 6. Bennett, D. T.: Reinforced occipitomental traction and its effect on the incisor teeth in Class III malocclusions, Trans. Br. Sot. Study Orthod., pp. 59.66, 1968. 7. Braccesi, M. A., and Lucchese, P.: Sketetal and dental changes in 30 treated Class III malocclusion cases studied by cephalometric analysis, Trans. Europ. Orthod. Sot. 34: 211-214, 1958. 8. Parker, C. D.: Class III case with overclosure; a clinical and cephalometric study, Trans. Br. Sot. Study Orthod., pp. 59-64, 1959. 9. Brenchley, M. L.: Borderline Class III cases, Deut. Pratt. Dent. Rec. 16: 233-240, 1966. 10. Mills, J. R.: An assessment of Class III malocclusion, Dent. Pratt. Dent. Rec. 16: 452-467, 1966. Il. Begg, P. R.: Begg orthodontic t,herapy and technique, Philadelphia, 1965, W. B. Saunders Company. 12. Bj6rk, A.: Prediction of mandibular growth rotation, AM. J. ORTHOD. 55: 585-599, 1969.