Stability of treatment results in Class II malocclusion corrected by full mandibular advancement surgery

Stability of treatment results in ClassII malocclusioncorrectedby full mandibular advancementsurgery Louis H. Guernsey, Colonel, DC, UXA WALTER

REED

ARMY

MEDICAL

CENTER,

WASHINGTON,

D. C.

Stability of treatment results in Class II malocclusion corrected by full mandibular advancement using sagittal osteotomy or C osteotomy in the rami of the mandible is studied retrospectively in six cases. Unexpectedly, relapse occurs in the immediate postoperative period and while the patient is still in intermaxillary fixation. The relapse is thought to be caused by orthodontic activator forces transmitted through the fixation devices to the teeth. These forces, by causing retrusion of maxillary incisors, tend to negate the effect of the relapse tendency of the mandible, so that a pleasing facial appearance is maintained.

W

hen Professor Hugo Obwegeser presented the many facets of European orthognathic surgery at Walter Reed Army Medical Center in 1966, he focused the attention of American oral surgeons upon the infinite number of treatment possibilities for improving severe congenital and acquired facial and occlusal deformities. Since then the American oral surgery literature has been replete with case reports and review articles detailing American experience with these newer procedures. Several authors have recently documented the postoperative sequelae and complications from such procedures,*-* while otherF’ have focused attention on a more sophisticated way to study postoperative treatment results, their stability, and the rationale for relapse through comparison tracings made over preoperative, postoperative, and postfixation cephalograms of surgically treated patients. In no area of dentofacial discrepancy is it more difficult to achieve excellent treatment results obtained by orthodontic or surgical means alone than in mandibular advancement for correction of Class II malocclusion. To complicate matters, Class II malocclusion occurs with greater frequency than any other serious dentofacial deformity.gp lo 668

Volume 37 Number 5

Full

mandibular

advancement

surgery

669

This article will record our experience with relapse in nine cases of Class II, Division I and Class II malocclusion with apertognathia which we have previously reported on and will add five cases that have been treated more recently or had not been previously reported. REVIEW OF THE LITERATURE A cursory review of the current American literature reveals that several authors comment on relapse 5, 7r I*, I* from a relatively small number of cases or from records from which it is difficult to draw valid conclusions. This is perhaps the single most important finding in our study, namely, the price of meaningful findings is excellence of well-documented standardized records taken at appropriate times during and after treatment. Poulton and Ware,7 as well as Proffit and White,s emphasize the overriding importance of orthodontist-oral surgeon cooperation in the diagnosis, planning, and eventual treatment of patients with mandibular retrognathism. The firstmentioned authors reported on two Class II cases in which presurgical orthodontic therapy was followed by sagittal splitting osteotomy to move the mandible forward. They discussed the special problem of the deficient mandible related to the number of muscles attached to it, particularly the suprahyoid group which is lengthened when the mandible is repositioned anteriorly, and caution that this very pull of the muscles would work toward posterior relapse. They also mentioned the overemphasis placed on the relapse potential from the major muscles of mastication. These author+ 7 and Wickwire and associates13 mention that any repositioning of the mandible in Class III cases, will result in a downward and forward change of position of the hyoid bone and associated musculature to protect the airway, while the change is upward and forward in Class II cases. In an effort to preclude posterior relapse, which appears to be accepted as inevitable, Poulton and Ware7 recommend : 1. Overrotation of the mandible by 12 to 15 degrees, bringing the chin upward and forward, which is done by using a thick occlusal splint in the molar region and overcorrecting forward. 2. Use of metallic bone implants to quantitate relapse tendencies. 3. Use of a postsurgical lip bumper as a prosthetic device to lessen the effect of a tight lower lip. This method is also highly recommended by Hamula.l* More emphasis was placed on a shoulder brace modified from the upper portion of a Milwaukee brace which, I believe, is called a Pitkin collar. 4. Myotomy of the anterior belly of the digastric mylohyoid, genioglossus, and geniohyoid muscles was mentioned as a solution but abandoned as a threat to the patient’s airway. Proffit and White5 caution that relapse after surgical-orthodontic therapy can be avoided by eliminating, where possible, the causes contributing to the original malocclusion and by not operating while patients are still growing. They, too, like an occlusal wafer to control the vertical dimensions and afford positive postoperative fixation control. They discussed the role of the tongue

Oral Surg. May, 1974

Table

I. Summary of Imticnt tlnta

Patient No. AB + W

(i

l/14/69

AB + W

ti

+

Cl. II, Aperto.

3/B/69

AB + w

(i

++

F

Cl. II, Aperto.

7/24/69

AR

6

Wh

M

Cl. II, Div. 1

11/20/69

Ortho

7

17

F

Cl. II, Aperto.

12/18/69

AR + W

6

+t+ +t

N. b. 5 M.H.

19

F

Cl. II, Div. 7

23

F

Cl. II, Div. 1

Ia’.‘,.

25

F

BS. 17 R. T. 18 J. J.

23

U/17/68

J%. 22 J. M.

20

F

Cl. II, Div. 1

2/ 5/70

AB

8

29

F

Cl. II, Div. 1

1/ 5/71

AB

6

PA

23

M

Cl. II, Div. 1

7/ 8/71

AB

7

17

M

Cl. II, Div. 1

M

Cl. II, Div. 1

AB W AB t W

8

35

7/20/71 7/ 8/72 12/18/72

8

21

F

Cl. II, Div. 1

3/25/69

AB

s

23

M

Cl. II, Div. 1

2/18/69

AR

8

2 G.V. 3 D. C. M.45. 5 C. B.

Cases 7 to 22-Sagittal osteotomy eases previously Cases 1 to 5 -New cases not previously reported. Key to abbreviations: AB = Arch bars. W = Ocelusal wafer. Ortho. = Orthodontic appliances.

reported.

but believed that this organ retrained itself and adapted during the immobilization period. Proffit,‘j in his work on lip, cheek, and tongue pressures on teeth, believes that patients adapt better to maxillary surgery than to mandibular surgery for correction of Class II malocclusion. He further states that patients must exceed preoperative tongue, lip, and cheek pressures by two to three times normal to cause postsurgical relapse changes. This is also borne out by the excellent cineradiographic study in which SubtelnylG shows a strong relationship between form and function. When form is changed, function can be expected to change, and form and/or function can be changed little by retraining myotherapy. A recently published, authoritative, and well-conducted study on skeletal relapse during intermaxillary fixation by McNeil and associates8 presents four complex Class II cases-two Class II, Division 1 cases and two cases of apertognathia which were qualified as severe. These authors emphasize that dental structures used for intermaxillary fixation following osteotomies are not the stable bases they were thought to be and that, while teeth are examined

tt

+

Volume 37 Number 5

Training elastic.9 (weeks) None

Full

Orthodontic treatment

None

4

None

1

None Yes-2 mo. retainer

Remarks

5

None

Relapse to CL, II

1

None

Preop.

x

Postop. ortho. recommended; patient left service Recommended postop. but not done

None None

C osteotomy

X

2 1

Remarks re exclzlsion

No postfixation ceph. available No postfixation ceph. available

x x

No postfixation ceph. available No postfixation ceph. available

x

Chart

x

No postfixation ceph. available

x

No postoperative eeph. available

lost

X X

None

I

X

In fixation Married-postop.; no follow up C osteotomy

N/A

No

671

X

None

4

1

x

4

None

Yes

surgery

X

Fixed prosthesis, mouth rehab. 1 yr. postop. Relapse to CI, II, Div. 2 owl. adjust.

Tongue-thrust habit ; 6 owl. adjust.

2

ndvamzment

Case incltkded in present hay

None

2

1

nm~dibnlnr

in occlusion during fixation, concomitant skeletal relapse and tooth movements can and are taking place during fixation. To study these changes, it is necessary to take reproducible positioned cephalograms at determined times during and after fixation and to learn to interpret the skeletal and tooth position changes through superimposition of tracings from these cephalograms. In all the cases reported, the surgical treatment was preceded by varying degrees of edgewisebanded orthodontic therapy while occlusal wafers, in addition to a specially placed labial arch wire, were used as intermaxillary fixation devices after surgical intervention. These authors confirmed reports of skeletal relapse following mandibular advancement and agreed that this occurred during fixation. They believed that the active force of the lengthened ant.erior mandibular musculature was responsible for the alteration seen skeletally and in the dentition. The anterior and superior position of the hyoid bone described by Wickwire and colleagues’” was viewed as another indication of muscle tension. They discounted the role of the pterygomasseteric sling in relapse. The role of myotomy of the geniohyoid muscle was discussed and advocated. The role of the sphenomandibular ligament

Oral Burg. May, 1974

Preoperntiae U/19/68

/

Postoperative l/10/69

1 /

Postfixation J/86/69

KNA

Xl

79

81

SNH

78

78

79

3

1

2

35

37

37

131

123

124

30

25

22

8

6

7

36

29

25

AN13 G,,-GN-SN L to i

(degrees)

(degrees)

1 to NA

(degrees)

1 to NA (mm.) = 1 to NR (degrees) i to NR

(mm.)

AFII

(anterior

PFH

(posterior

F:\ci:ll

angle

Patient

facial facial

height) height)

N. C., operated

3

6

7

99

107

107

69

66

66

89

87

89

on 12/17/68.

in relapse and an operation to detach it are mentioned. They also believed that this tension and the extrusive forces transmitted through the fixation devices to the teeth were responsible for retrusion changes in the position of the maxillary incisors. A similar situation was noted in apertognathic cases with respect to mandibular incisor movement. McNeil and associates further believed that compensation for some of the above predictable changes could be accomplished through preoperative orthodontic retraction of the mandibular incisors and/or use of counterclockwise overrotation of the mandible and an interocclusal wafer to open the bite posteriorly. A form of anterior-positioning extraoral traction delivered through a modified shoulder-sternal brace would be helpful in preventing relapse. They concluded that modification in surgical technique and improved fixation methods would eliminate the presently observed relapses and recommended serial cephalometric films to ascertain relapse in progress and when to terminate fixation. PRESENT STUDY

Evaluations stability of treatment results and relapse, of necessity, often become retrospective studies and most frequently are not planned from inception of case analysis to completion of a prolonged follow-up unless they are a part of a planned research protocol. This study is no exception, Some cases from which we thought we could draw conclusions on the basis of our visual examinations of the occlusion in a previously reported article3 had to be deleted from the study because of the lack of postfixation cephalograms. Thus, from a total of thirteen Class II cases (Table I) (eleven treated by sagittal splitting and two treated by C osteotomy), only six cases (five of sagittal splitting and one of C osteotomy) are well enough documented from which to draw significant conclusions about stability of treatment results. In the original fourteen cases there were three cases of Class II apertognathia, none of which were adequately documented to report upon.

Full

Volume 37 Number 5

Table

III. Case 8. Cephalometric

naandibular

ndvancenzent surgery

673

values summarized Preoperative 10/H/68

Postoperative l/13/69

Postfixation U/4/69

Follow-up l/6/79

SNA

80

80

83

80

SNB

75

80

80

78

ANB

5

0

3

2

36

33

32

32

1 to i (degrees) 7 to NA (degrees)

115

113

119

110

43

40

39

37

1 to NA (mm.) = 1 to NB (degrees)

11

11

12

7

16

26

26

32

2

4

4

6

Go-GN-SN

(degrees)

i to NB (mm.) AFH

(anterior

facial

height)

115

115

116

112

PFH

(posterior

facial

height)

80

83

82

80

Facial

angle

83

83

88

93

Patient

M. H., operated

on l/7/69.

In our eases, no single surgeon or orthodontic consultant was responsible for the tracings of all the cases reported. The method for evaluating skeletal changes follows those suggested by McNeil and associates8 for superimposition of preoperative and postoperative cephalometric tracings on the planoethmoidal line registered at a point midway between the sphenoid wings. This will permit visualization of anteroposterior and superoinferior movements of the maxilla and mandible. McNeil’s8 recommendations for evaluation of tooth changes are also followed : 1. In the maxilla by superimposition of the maxillary portion of the tracing by use of the interior outline of the anterior palatal vault. ‘2. In the mandible by superimposition of the interior outline of the symphysis and the inferior mandibular border. Visual examination of the superimpositions made over a light source immediately gives a two-dimensional, directionally oriented view of whether the postsurgical result is maintained or has relapsed. Tooth-position changes are more subtle to evaluate, as in most cases tooth-outlining techniques were not standardized. In some instances, free-hand drawing of well-visualized tooth outlines was used; in others the Unitek grid was employed. A summary of case cephalometric findings is found in Tables II to VII. CASE SUMMARIES CASE 7

N. C. was a IQ-year-old white female patient with a Class II, Division 1 malocclusion 1). The treatment plan was as follows: 1. Bilateral mandibular sagittal splitting advancement osteotomy of the mandible. 2. Intermaxillary elastic and wire fixation using a posterior bite-opening occlusal wafer. 3. Correction of posterior open-bite by construction of an onlay removable prosthesis. This patient had a complex course resulting from postoperative pulmonary complications and elevated temperature, atelectasis, and pneumonitis which necessitated tracheostomy and bronchoscopy. (Fig.

674

Guernsey

Table

IV. Cast 17. L’cphalometric

Oral Surg. May, 1974

\-alncs summarieetl Preoperative 10/82/69

Postoperative

~

11/%5/69

/

Postfixation 4/l o/70

SNA

78

80

77

SNB

74

81

77

ANR

4

-1

0

43

46

47

125

122

127

26

30

26

6

4

5

27

25

4

3

4

127

129

130

85

91

SS

83

85

83

Go-GN-SN 1 to

i

(degrees)

(degrees)

1 to NA

(degrees)

1 to NA

(mm.)

i

to NR (degrees)

i to NB

(mm.)

AFH

(anterior

PFH

(posterior

Facial

angle

Patient

26

facial facial

height) height)

R. T., operated

on U/20/69.

Table V. Case 2. Cephalometrie

values summarized

Preoperative r/so/71

Postoperative 7/67/71

Post fixation U/15/71

SNA

82

83

83

SNB

77

80

79

BNB

5

3

4

43

42

39

128

137

140

25

20

15

G

6

2

22

25

20

Go-GN-SN 1 to

i

(degrees)

(degrees)

1 to NA (degrees) 1 to NA (mm.) i to NB (degrees) i to NB (mm.) AFH

5

3

3

123

124

122

80

85

82

86

85

57

PFH Facial

angle

Patient

G. V., operated

on 7/20/71.

This was the only nrajor postsurgical complication of our series. In spite of the extensive manipulations in the immediate postsurgical stage there were no local surgical complications in the oral incisions and osteotomy sites which healed normally, rapidly, and well. The immediate postsurgical tracing showed that the mandible had moved downward X mm. and forward 6 mm. At the postfixation evaluation the mandible had already moved backw:ird and upward 3 mm. The major gains were in tooth-position changes. In the maxilla there was a net 1 mm. retrusion of the incisors with a normal 1 to NA inclination of the incisors to the maxillary basal bone of 22 degrees. In the mandible there was a 4 mm. anterior repositioning of the incisors with establishment of a normal angular inclination of the incisors to the basal bone. Anterior fsc*inl height (AFH) increased from 99 to 107 mm., while posterior facial height (PFH) declcased from 69 to 66 mm. A very pleasing facial appcarnnce resulted, with obliteration of the characteristic mentolabial crease.

Volume Number

37 5

Full

Table VI. Case 3. Cephalometric

mandibdnr

advancement

surgery

675

values summarized

Preoperative g/10/71

/ Postoperative No. I 7/.%?/7b

Postoperative No. 2 l/8/7$

Post@ation J/1$/7$

SNA

81

80

81

81

SNB

75

73

77

77

ANB

6

7

4

4

23

23

35

26

Go-GN-SN

(degrees )

1 to i (degrees)

145

129

111

111

1 to NA

(degrees)

40

33

27

26

1 to NA

(mm.)

15

9

6

8

i

(degrees)

30

to NB

3

3

32

3

3

5

7

height)

114

115

124

123

height)

86

84

80

82

85

80

85

85

i to NB (mm.) AFH

(anterior

I’FH

(posterior

Facial

facial

angle

Patient

Table

facial

D. C., operated

on 7/8/72

and 12/16/72.

VII. Case 5. Cephalometric

values summarized I

Preoperative Z/7/69

Postoperative J/12/69

Postfixation 6/9/69

SNA

85

87

84

SNB

81

90

86

ANB

4

-3

2

Go-GN-SN

(degrees)

J to i (degrees) 1 to NA

(degrees)

1 to NA

(mm.)

i i

to NB

(degrees)

to NB

(mm.)

BFH PFH Facial Patient

angle

L. B., operated

23

25

23

131

116

114

35

37

41

6

7

10

16

25

24

0

4

6

120

120

119

86

86

85

82

92

85

on Z/18/69.

CASE 3

M. II., a 23-year-old white woman, had a Class II, Division 1 malocclusion with extreme extrusion and fanning-out of the lower incisors (Fig. 2). This was further complicated by extensive bone loss and pcriodontitis, particularly in the central incisors. Inadequate jacket crowns restored the upper incisor teeth. The treatment plan consisted of the following: 1. Extraction of all four lower incisors and their replacement on a cast-Vitallium labial arch bar. 2. Bilateral mandibular sagittal splitting advancement osteotomy. 3. Intermaxillary elastic, then wire fixation using cast arch bars and an acrylic occlusal wafer. 4. Replacement of mandillulnr incisors with a fixed pnrtial denture and replacement of the defective maxillary incisor crowns.

676

Oral Burg. May, 1974

Guernsey

Fig. 1. Case 7. A, Preoperative facial operative occlusion. D, Postoperative facial showing extent of correction and relapse.

appearance. appearance.

B, Preoperative occlusion. E, Pre- and postoperative

C. Posttracings

On the immediately postoperative tracing the mandible was seen to have moved forward 6 mm. while the postfixation cephalogram showed that it had relapsed 2 mm. posteriorly. Skeletally, SNB went from 75 to 80 degrees immediately and then, in a 4-year period, to 78 degrees, indicating a 3-degree net skeletal change in the mandible. The angular relationship of the maxillary incisors to NA decreased from 43 to 37 degrees, probably secondary to retrusion and/or the labial contour change afforded by the new jacket crowns. The i-NA position was dramatically changed from 11 to 7 mm., as was the i to NB position from 2 to G mm. The angular change of the mandibular incisors to NB was quite marked, from 16 to 32 degrees at termination of ftxed bridge insertion.

Full

Fig. operative

d. Case 8. 8, Preoperative occlusion. D, Postoperative

facial facial

mandibular

advancement

surgery

677

appearance, B, Preoperative occlusion. C, Postappearance. E, Comparison cephalograms.

Anterior facial height (AFH) decreased 3 mm. to 112 mm., while posterior facial height (PFH) remained the same at 80 mm. A most pleasing facial appearance resulted. Obliteration of the mentolabial crease was further enhanced by the extensive dental restorative procedures. CASE

17

R. T. was a 15%.year-old white boy with a Class II, Division 1 malocclusion which had been treated orthodontically with full-banded appliances for 3 years prior to the present treatment (Fig. 3). The four upper incisors had been lost in an athletic accident. Failure of forward growth of the mandible precluded a satisfactory esthetic result. The treatment plan was as follows: 1. Bilateral mandibular sagittal splitting advancement osteotomy. 2. Intermaxillary elastic, then wire fixation using the previously applied orthodontic appliances for fixation. 3. Removal of bands following 7 weeks of fixation and 12 weeks of appliance therapy

678

Oral Surg. May, 1974

Guernsey

Fig. 3. Case 17. A, Preoperative facial occlusion. D, Postoperative facial appearance.

appearance. B, At operation. E, Superimposition tracings.

C, Postoperative

for finalizing of treatment results. A maintenance appliance was applied lingually to the mandibular incisors. The mandible was moved forward 8 mm. at operation but showed :I 2 mm. posterior SNA relapsed from 78 to 80 to 77 degrees while relapse in the postfixation cephalogram. SNH increased from 7-2 to Xl degrees in the postllxation cephalogram. There was a slight steepening of the mandibuhlr plane from 43 to 47 degrees with an increase in overbite. In this csse, AFH increased from 127 to 130 mm. while, paradoxically, PFH changed from 85 to 87 degrees. Facial appearance was most pleasant, and the occlusion remained stable in maintenance. CASE 2

G. V. was a l$-year-old white boy with Class 11, Uivision 1 malocclusion who had been followed by an orthodontist for 3 years, unfortunately without benefit of treatment (Fig. 4). The treatment plan was as follows: 1. Bilateral mandibular sagittal splitting advancement osteotomy. 2. Intermaxillary elastic and wire fixation using cast arch bars and an oeclusal wafer. 3. Postoperative orthodontic treatment to round out some crowding in the mandibular incisors. lmmediately following the operation the mandible moved forward 6 mm. but had relapsed 2 mm. posteriorly when the postfixation tracing was made. Overjet improvement was 4 mm., which remained constant throughout, while overbite went from 0 to 4 mm. in the posttixation tracing. In this case AFH decreased over-all by 1 mm. and PFH increased by 2 mm. A follow-up by the orthodontist. who was to have completed the treatment orthodontically

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679

Fig. 3, D and E. For legend, see opposite page.

indicated that a significant relapse occurred but was rendered on visual evaluation without benefit of the preoperative cephalogram for comparison. In this case, the relapse was rendered less noticeable by a significant retrusion of the maxillary incisors. The i-NA decreased from 25 to 15 degrees with a concomitant, but smaller, mandibular incisor retrusion noted. Facial appearance was pleasing with obliteration of the mentolabial crease. CASE 3

D. severe follows 1.

C., a 35-year-old white man, had a severe Class II, Division 1 malocclusion with a overbite of 15 mm. and an overjet of 16 mm. (Fig. 5). The treatment plan was as : Depression of the anterior mandibular segment surgically to level the mandibular arch. 2. Bilateral mandibular sagittal splitting advancement osteotomy. 3. Intermaxillary elastic, then wire fixation using cast arch bars and an occlusal wafer for 8 to 10 weeks. The first procedure intruded the mandibular incisors and cuspids by 7 mm. but did not change i NB relationship. Overbite was decreased by 6 mm. This procedure, however, then

680

Fig. operative

Oral Surg. May, 1974

Guernsey

4. Case 2. 8, Preoperative occlusion. I;, Preoperative occlusion. facial appearance. D, Postoperative

facial

appearance.

C, Post-

made it possible for the sagittal splitting procedure to achieve a satisfactory anterior occlusal relationship. The second procedure advanced the chin 12 mm. while further reducing the overbite by 6 mm. more. Overjet was reduced by 11 mm. from this procedure. The postfixation cephalogram tracing showed that the mandible had relapsed 3 mm. posteriorly, for a net forward movement of 8 mm. Overbite and overjet remained stable at 3 mm. and 5 mm. each. AFH increased markedly from 114 to 124 mm., while PFH decreased from 86 to 82 mm. There was a decrease in the interincisal angle from 145 to 110 degrees, which was achieved by a 13-degree l-NA change from 40 to 27 degrees and a es-degree increase in T-NB from 3 to 32 degrees. In this case there was a most dramatic facial improvement with obliteration of the mentolabial crease and a significant elongation of the previously foreshortened lower face. CASE 5

L. B., a 23-year-old white man, had a severe Class II, Division 1 malocclusion for which he underwent conventional banded orthodontic therapy with removal of only two premolar teeth, one from each arch (Fig. 6). When the patient was referred for surgery, the maxillary

Volume 37 Number 5

Full. n~a~~dibulnr trdvancement

Fig. 4, C rind D. For legend, see opposite

surgery

681

page.

arch was well aligned, but there was an overbite of 8 mm. and an overjet of 9 mm. Fanning up and out of the lower incisors was noted. The treatment plan was as follows: 1. Bilateral C osteotomy mandibular advancement surgery. Premaxillary oateotomy to correct the overjet was not considered, as extraction of another maxillary premolar would lead to a maxillary cuspid-to-first-molar tooth relationship. 2. Intermaxillary elastic and wire fixation, using east arch bars and an occlusal wafer for 6 weiks. Immediately following the surgical procedure there was an 8 mm. advancement of the mandible, with a 2 mm. relapse noted in the postfixation tracing comparison. SNA changed from 85 to 84 degrees. SNB changed from 80 to 90 to 86 degrees in the same period. Interestingly, the overbite decreased by 7 mm. without an increase in AFH. This can be explained by the increase in l-NA from 35 to 41 degrees, the increase of l-NA from 6 to 10 mm., and the forward movement of the lower incisors as noted in i-NB of 76 to 24 degrees with a concomitant increase in i-NB from 0 to 6 mm. A pleasant facial appearance and profile with minimal scarring were noted. The patient was particularly pleased to have a long treatment plan, started in adolescence, brought to a successful completion.

682

Fig. operative

Oral Surg. May, 1974

Guernsey

5. Case 3. A, Preoperative facial facial appearance. D, Postoperative

appearanee. occlusion.

B, Preoperative

occlusion.

C, Post-

Volume Number

37 5

E’ig. 6. Case 5. A, Preoperative operative occlusion. D, Postoperative superimposition tracings.

Full

mandibular

advancement

surgery

683

facial appearance. B, Preoperative occlusion. C, Postappearance. E, Pre- and postoperative cephalometric

DISCUSSION

The results in these cases indicate that significant forward mandibular repositioning can be accomplished surgically using predominantly the intraoral sagittal osteotomy introduced by Obwegeser and the C osteotomy of the ramus with coronoid-process detachment. In all cases, as was observed in previous reports,5-8’ I2 some skeletal relapse occurred following surgical intervention, although in this series the magnitude does not appear to be quite as great as previously reported. This relapse occurs during the period of intermaxillary fixation, confirming the reports of Poulton and Ware7 and McNeil and co-authors,s and most unexpectedly while the

684

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Oral Surg. May, 1974

surgeon observes no clinical change on examination of the teeth in fixation or in the occlusion obtained at surgery. This lack of observation is probably aggravated by the obscuring effect of the various occlusal wafers inserted at surgery to verify the desired new occlusion. In several of our cases changes were noted to be occurring during fixation and were attributed to the wafers. This resulted in a policy of early removal of wafers, usually after a week of intermaxillary fixation. In general, whenever an occlusal wafer can be dispensed with in full mandibular advancement cases, these wafers are no longer inserted at surgery. In the light of our present knowledge, the movement blamed on the wafer may very well have been the recently described and expected movement and adjustment of the maxillary and mandibular incisor teeth which occurs during fixation. Universally, all author@ 7*x, I3 have attributed this skeletal relapse to the elongation and tension of the suprahyoid musculature with the attendant upward and forward changes in position of the hyoid bone noted on postoperative cephalograms. The change in hyoid bone position is the presumptive evidence for this elongation71 I3 and subsequent muscle imbalance. We also have noted the described hyoid bone position changes in our postoperative cephalograms. The elongation of muscle fibers, with their normal tendency to return to their resting length, serves as the active force which is responsible for the skeletal relapse and observed changes in tooth position. There must, however, be some degree of adaptation by the suprahyoid muscle group, as hyoid position is noted to change back toward normal during and after treatment, and complete relapse is not the rule in anterior surgical repositioning of the mandible. To minimize the muscle effect, several authors suggest muscle detachment as a possible solution. Selective muscle myotomy is now being performed by Steinhauser” to evaluate this procedure on relapse tendency. In our view, this offers great promise and myotomies of the anterior belly of the digastric and geniohyoid muscles will be added to our future procedures to help minimize relapse. Oral surgeons to date have devoted their efforts to minimizing the relapsing effect of the major masticatory muscles. Particular attention has been paid to release of the pterygomasseteric sling in sagittal osteotomy by use of specially designed strippers. More emphasis, I believe, should be placed on the actual release of the periosteum surrounding the mandible as proposed by Rowe,ls who advocates an actual sectioning of the periosteum from as high as can be accomplished posterior to the condyle, downward between the split segments, and as far anteriorly as can be accomplished in the molar and premolar region where the periosteum has been stripped away from the body of the mandible. This will permit maximal unimpeded forward motion at surgery as far as the major muscles of mastication are concerned. We routinely detach the temporalis attachment to the tip of the coronoid process to facilitate placement of the ramus retractor. We further believe that detachment of the pterygomasseteric sling and sectioning of the periosteum will limit the posterior facial height decrease predicted by White and co-workers.ls This seems to be a finding in our series.

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The role of the sphenomandibular ligament as discussed by McNeil and associates8 cannot be evaluated from our experience, other than to note that this ligament is very frequently traumatized enough to be severed in the medial retraction of tissues and the placement of the gutter retractor. The role of intermaxillary fixation in surgical orthognathic cases, heretofore presumed to provide a stable base since it was distributed over a large number of teeth, has been shown by McNeil and co-authors8 to be a contributory vehicle and force to individual tooth movement. They postulate that the effects of extrinsic forces mediated via the appliances on the labile circummaxillary suture system are responsible for the observed retraction and retrusion of the maxillary incisors. Armed with this knowledge and the understanding that foward positioning of the mandible acts similar to the activator orthodontic appliance used in Europe to correct Class II malocclusion in children, we can now, as surgeons, more fully understand and study the individual tooth changes which occur during fixation, In this series we noted maxillary incisor retrusion with lessening of l-NA’ in four cases, with one case remaining unchanged. In the C osteotomy case, 1 to NA increased from 35 to 41 degrees, indicating a. slight increase in procumbency of the maxillary incisor. Since becoming more discerning, we see that the position of the lower incisors also benefited from these forces. Three cases of sagittal osteotomy had concomitant retraction of lower incisors, one case3 had significant retraction of the maxillary incisors with concomitant significant protrusion of the i-NB from 3 to 32 degrees; This was in the mandibular segmental repositioning case. The C ostectomy case5 again did not follow the standards noted by showing procumbency of both the maxillary (l-NA, 35 to 41 degrees) and mandibular (i-NB, 16 to 24 degrees) incisors. In studying our results with AFH, we noted that three cases (Cases 7, 17, and 3) showed an over-all increase, with a concomitant PFH decrease in two while one increased in both dimensions. One Case (Case 8) had a decrease in AFH with an increase in PFH. One (Case 2) had a slight decrease in both AFH and PFH. From this, we cannot make any general comment other than that it would be logical to expect, and in most cases one would obtain, an increase in AFH with surgical advancement procedures of the mandible. A few general comments concerning the group of treated patients are appropriate. Previous studies have been reported by groups of authors composed of orthodontists and oral surgeons treating younger patients who are followed from late infancy to early adulthood. These are frequently cases in which cornbined orthodontic-surgical management is employed only after a relatively protracted period of banded orthodontic therapy. The patients in our group, on the other hand, are usually not seen for treatment until they are young adults and, with one exception, do not have the benefit of early orthodontic care. This results in previously cast arch bars and acrylic occlusal wafers being used as immobilization devices as compared to modified orthodontic labial arch wires for intermaxillary fixation.

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I can only believe that cast stainless steel arch bars, ligated to the teeth with 0.018 inch stainless steel wire, will be more positive fixation appliances than the lighter orthodontic wire ligature. Furthermore, the positioning of fixation lugs in the casting permits a more precise orientation of elastic traction placed at surgery to encourage the forward position of the mandible, thus decreasing the relapse tendency during fixation. Our group, unfortunately, is a very transient population, which explains the small number of postfixation cephalograms available for this study. To this of records, have end, it would appear most logical to effect a standardization several (two or more) tracings made by the same person when the preoperative tracing is first made, and to practice prediction tracing advocated by McNeil8 and by Proffit and White.5 It would further seem logical to do a comparison study on the stability of treatment results when surgical correction of Class II, Division 1 malocclusion consists of premaxillary osteotomy as opposed to full mandibular advancement. Although modification in surgical procedures will inevitably evolve with time and ingenuity of surgeons, it seems logical to assume that myotomy of selected muscles of the suprahyoid musculature will minimize relapse from full mandibular surgical advancement procedures. The use of the modified Milwaukee brace advocated by Poulton and Ware7 and McNeil and associate@ shows the greatest promise for preventing relapse over an entire postoperative surgical procedure. The difficulty of having young adults voluntarily wear such a device over a protracted period is immediately apparent. A modified bumper suggested by HamuIa,14 if it could be shown to be effective in preventing relapse, would be much more desirable than the shouldersternal brace suggested above. SUMMARY A retrospective study of six mandibular advancement osteotomies for surgical correction of Class II, Division 1 malocclusion indicates that in all cases a degree of skeletal relapse and minor tooth movement can be expected during the intermaxillary fixation period, The cast fixation devices used in our group may tend to decrease this relapse when compared to modified orthodontic labial arch wire fixation. Modification in surgical technique, including myotomy in selected suprahyoid muscles, along with the use of orthopedic skeletal appliances to prevent relapse may be the only way to improve the present inevitable skeletal relapses noted. Further study of these modalities is clearly needed. REFERENCES

1. Shira, R. B.: Personal Communication. 2. White, R. P., Jr., Peters, P. B,, Costich! E. R., and Page, H. L., Jr.: Evaluation of Sagittal Split Ramus Osteotomy m 17 patients, J. Oral Surg. 27: 85?,1969. of the Intraoral 3. Guernsey, L. H., and DeChamplain, R. W.: Sequalae and Complicatrons Sagittal Osteotomy of the Mandibular Rami, J. Oral Burg. 32: 176, 1971. 4. Behrman. 5. J.: Comnlications of Saaittal Osteotomv of the Mandibular Ramus. J. Oral Rurg. sol 554, 1972. a of Severe Malocclusions by Correlated 5. Proffit, W. R., and White, R. P., Jr.: Treatment Orthodontic-Surgical Procedures, Angle Orthod. 40: 110, 1970.

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6. Poulton, D. R., Taylor, R. C., and Ware, W. II.: Cephalometric X-ray Evaluation of the Vertical Osteotomy Correction of Mandibular Prognathism, ORAL SURO. 16: 1907, 1973. 7. Poulton, D. R., and Ware, W. H.: Surgical-Orthodontic Treatment of Severe Mandibular Retrusion, Am. J. Orthod. 59: 244, 1971. 8. McNeil, R. W., Hooley, J. R., and Sundberg : Skeletal Relapse During Intermaxillary Fixation. J. Oral Sure. 31: 212. 1973. 9. Clement& B. 8.: The-Orthodontic Approach to Class II, Division 1 Malocclusions, J. Am. Dent. Assoc. 82: 789, 1971. 10. Hunter, W. S.: The Vertical Dimension of the Face and Skeletodental Retroguathism, Am. J.‘Orthod. 53: 586. 1967. Surgical Procedures for Correction of 11. Murphy, P. J., and tialker, R. V.: Orthodontic Severe Oral and Facial Malformation, J. Am. Dent. Assoc. 79: 1431, 1969. 12. Bell, W. H.: Surgical Correction of Mandibular Retrognathism, Am. J. Orthod. 52: 518, 1966. 13. Wickwire, N. A., White, R. P., Jr., and Proffit, W. R.: The Effect of Mandibular Osteotomy on Tongue Position, J. Oral Surg. 30: 184, 1972. 14. Hamula, W.: Surgical Alteration of Muscle Attachments to Enhance Esthetic and Denture Stability, Am. J. Orthod. 57: 327, 1970. 15. Proffit, W. R.: Personal Communication. 16. Subtelny, J. D. : Malocclusions, Orthodontic Corrections and Orofacial Muscle Adaptation, Ande Orthod. 40: 170, 1970. 17. SteTnhauser, E. W.: Personal Communication, September, 1972. 18. Rowe, N.: Personal Communication. 19. White, R. P., Jr., Proffit, W. R., Cramer, J. R., and Kohu, M. W.: A Study of Facial Height Changes After Mandibular Osteotomy in Forty-six Patients, ORAL SURO. 29: 858, 1971. Reprint requests to: Colonel Louis H. Guernsey Walter Reed Army Medical Washington, D. C. 20012

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