Comparisons of postsurgical stability of the LeFort I maxillary impaction and maxillary advancement Samir E. Bishara, DDS, D. Ortho., MS," and Gary W. Chu, DDS, MS b Iowa City, Iowa, and Racine, Wis.
The purpose of this study was to determine retrospectively the stability of the LeFort I osteotomy after a one-piece maxillary impaction or advancement. Cephalograms of 31 patients were evaluated before surgery, immediately after surgery, in fixation, and after fixation. Descriptive statistics for the absolute and the relative changes of the various linear and angular parameters were calculated for the different stages. The analysis of variance general linear models procedure was used to compare the impaction group (n = 23) with the advancement group (n = 8). The findings indicated that the two groups could be studied independent of age, sex, surgeon, the presence of pretreatment open bite, and the length of the postsurgical fixation. The findings further indicated the presence of significant differences in the postsurgical changes between the maxillary impaction and the maxillary advancement groups. As anexample, during fixation, the maxilla moved superiorly more at point A in the advancement group (x = 1.89 mm) than in the impaction group (x = 0.67 mm). The upper incisor movements showed a similar pattern, moving more superiorly for the advancement group (x = 2.30 mm) than for the impaction group (x = 0.96 mm). Therefore care should be taken to avoid "burying" the incisors beneath the lip in patients undergoing maxillary advancement, who have minimal exposure of the maxillary incisors before surgery. (AMJ ORTHOD DENTOFACORTHOP 1992;102:335-41 .)
T h e successful correction of dentofaeial deformities with orthognathie surgery is dependent, at least in part, on the stability of the surgical movements. One of the most commonly used approaches to the correction of maxillary deformities is the LeFort I osteotomy. 1.2 Willmar 3 did the first quantitative follow-up study on the LeFort I osteotomy using surgically placed metal markers. Although 106 patients were studied, only 3 had "idiopathic long face," and these cases demonstrated stability of markers and occlusion throughout the l-year observation period with an "insignificant" 10% superior settling occurring at the anterior marker. Schendel et al. 4 indicated that excellent stability was found in their sample of 30 patients who were followed an average of 13.8 months after surgery. Bell and McBride t examined 41 patients with vertical maxillary excess who underwent maxillary superior repositioning with LeFort I osteotomy. Their results indicated clinical stability with minimal relapse. Chu 5 and Bishara et al. 6 described the postsurgical skeletal and dental changes after the LeFort I maxillary impaction. They indicated that (1) after the initial sur-
'Professor, Department of Orthodontics. College of Dentistry, University of Iowa. bln Private practice of orthodontics. Racine. Wisc. 811129716
gical superior repositioning, the maxilla continued to move superiorly, and most of the upward movement occurred during fixation; (2) the anterior part of the maxilla moved superiorly more than twice that of the posterior part of the maxilla; and (3) maxillary dental movements tended to follow skeletal movements. The stability of maxillary advancement with LeFort I osteotomy has been evaluated by Kufner, 7 who reported problems with relapse and fixation. Araujo 8 found up to 68% relapse of the advancement if pterygomaxillary bone grafts were not used. He advocated overadvancement of the maxilla or the placement of bone grafts for large movements. Teuscher and Sailer, 9 on the other hand, reported stable results after maxillary advancements 5 years after treatment. In summary, a limited number of studies are available that evaluate the stability of the surgical correction after LeFort I maxillary impaction or advancement; however, some of these studies included patients who underwent various surgical modifications such as twopiece or three-piece osteotomies as well as mandibular surgery. The purpose of this study is to evaluate retrospectively the stability of the one-piece LeFort I maxillary osteotomy, from before surgery to after fixation but before the initiation of any significant postsurgical orthodontic tooth movement. Two groups will be compared; a group that predominantly underwent im335
336
Am. J. Orthod. Dentofac. Orthop. October 1992
Bishara and Chu
rims near the superior border of the inferior turbinate and in the zygomatic buttresses. All cases had intcrmaxillary fixation with an acrylic surgical splint. L a n d m a r k identification a n d c o n s t r u c t i o n of c o o r d i n a t e s
(0 is 7-15 ~ above PN) O'J
0
Horizontal axis
P~ fit"
g
! t ~Ar"
I l l I I l I
(MxP is 40mm from A)
I
'
I
L
Me
Fig. 1. Landmarks used.
paction and a group that predominantly underwent advancement. MATERIALS AND METHODS The sample
The study involved 31 patients (10 male patients and 21 female patients) who under,vent a LeFort I one-piece osteotomy for impaction or advancement. Mean age for the total group was 20.6 years with a range between 14.2 and 43.8 years. Cephalograms were available for each patient before surgery, immediately after surgery, (~ = 1.4 days with a range of I to 4 days), in fixation (x = 37.2 days with a range of 21 to 48 days), and after fixation (x = 132.2 days with a range of 62 to 190 days). All cephalograms were taken on the same machine. Patients were not included in the study if they had in their medical history craniofacial anomaly, maxillary downgrafting, and mandibular ramus or body surgery. Three cases had genioplasty advancement. All maxillae were fixed with suspension wir6s,'ffrid none with rigid fixation. Bone fixation was bilateral in the pyriform
Various landmarks were identified on the presurgical cephalograms (Fig. 1). Maxillary landmarks. Point A (A); point A' (A'), which is the point on the nasion-menton line from which a perpendicular intersects point A; and maxillary posterior point (MxP), which is the point on the line constructed 40.0 - 0.25 mm posterior to point A and parallel to the horizontal plane (O-N), midway between the inferior and superior cortical plates of the maxilla on the presurgical cephalogram. Points A and MxP have been chosen to quantify the changes in the maxilla at its anterior and posterior aspects rather than anterior nasal spine (ANS) and posterior nasal spine (PNS) because the tip of the ANS and PNS are often difficult to locate after LeFort I maxillary osteotomy. In addition, the ANS is often removed during maxillary surgery. Other maxillary landmarks identified are the maxillary central incisal edge (UI) and the upper molar point (UM), which is the midpoint between the two most distal points on the outlines of the second maxillary molars. Upper molar point has been chosen instead of the mesiobuccal cusp tips of the first maxillary molars because of the greater overlap of the hard tissue structures at the first molars than at the distal surfaces of the second molars. Mandibular landmarks. Mandibular central incisal edge (LI), point B (B), pogonion (Pog), menton (Me), gonion (Go), articulare (Ar), and articulare prime (Ar'), which is the point on the presphenoidale-gonionline from which a perpendicular is constructed to articulare. The definition of these landmarks were detailed elsewhere, s The construction of the horizontal and vertical axes, on which the various landmarks were projected, is detailed in Figs. 2, A-C. The angle between the constructed horizontal axis, O'N, and the anatomic reference line, P-N, differs from patient to patient, but remains constant for the serial cephalograms of the same patient. A template of the cranial base was constructed from the presurgery cephalogram with the positions of P, N, and O pinpricked, so that these landmarks could be located in subsequent cephalograms by superimposition. A similar template for the maxilla was used to determine the position of the skeletal points A and MxP. Dental points on the UI and the UM were located directly on each cephalogram. A detailed template of the mandible was also constructed with the position of skeletal points B, Pog, Me, and Go. Points LI and Ar were located directly on each cephalogram since their positions vary as a result of the postsurgical movements.
Voh,me102
Postsurgical stability of LeFort I 337
Number 4
Linear and angular parameters measured The changes in each of the 18 landmarks were determined by projecting each landmark on the constructed horizontal (O'-N) and vertical (O'-P) axes. The change in any landmark can be evaluated in both the horizontal and vertical directions. As an example, the A-O'N variable describes the horizontal i.e. anteroposterior change in point A, whereas the A-O'P variable describes the vertical change in point A. In addition to the changes in the position of the various landmarks, changes in seven linear and two angular measurements were evaluated including: N-A', N-Me, Ar'-Go, P-Go, N-A'/N-Me%, Ar'-Go/P-Go%, and P-Go/N-Me%, as well as the ANB and P-N:Me-Go angles.
STEP1
j#
P
.Reliability of measurements A Reflex Mctrograph digitizer (Ross Instruments Ltd, England) was used for measuring the changes in the various landmarks. The accuracy of the metrograph was determined to be within 0.2 mm. As a result, allowable intrarater and interrater variability was predetermined at 0.2 mm.
Statistical analysis Descriptive statistics for the absolute changes of the various linear and angular parameters were calculated for the following stages: before surgery to immediately after surgery (1 to 2), immediately after surgery to fixation (2 to 3), fixation to after fixation (3 to 4), and immediately after surgery to after fixation (2 to 4). Relative changes for the same parameters were also calculated as a percentage of the surgical change. The analysis of variance general linear models procedure was used to compare the measurements of the two surgical groups, as well as for the following variables:-(1) male patients versus female patients; (2) younger ( a d v a n c e m e n t g r o u p . = Impaction g r o u p < a d v a n c e m e n t g r o u p .
1-2 2-3 3-4(s) 2-4(s)
10.5+** 7.6-* 0.0 4.4-*
N-A' (nun) 1-2 2-3 3-4 2-4
6.3+* 10.5-** 0.0 7.1
:339
340
Bishara and Chu
Am. J. Orthod. Dentofac. Orthop. October 1992
Mandibular changes
Table I. Cont'd Variable
F
P-Go (mm) 1-2
0.3
2-3
4.4 + *
3-4(s) 2-4(s)
0.0 2.9
Ar-'Go (mm) 1-2
2-3 3-4(s) 2-4(s)
0.4 4.8 + 0.5 0.6
P-Go/N-Me (%)
1-2 2-3 3-4(s) 2-4(s)
15.0- ** 14.0 + ** 0.0 8.3 + **
Me-GO:P-N (~
1-2 2-3 3-4 2-4
14.4 + ** 13.4-** 0.2 10.6 - **
The direction of mandibular changes differed between the impaction and the advancement surgeries. With impactions, the mandibular changes were mostly in the horizontal plane, whereas with advancements, the changes were mostly in the vertical plane. As an example, during fixation (stages 2 to 3), pogonion moved posteriorly 1.2 mm in the impaction group. Whereas with advancement, pogonion moved anteriorly 2.0 mm. After removal of the splint (3 to 4), pogonion moved anteriorly in both surgeries as a result of the mandibular autorotation. Regarding the changes in the vertical plane, in the impaction surgeries, pogonion moved superiorly 0.3 mm during fixation (stages 2 to 3). Whereas for advancement surgery, pogonion moved superiorly 1.5 mm. The larger mandibular change observed in the advancement group is related to the corresponding larger superior maxillary movement during fixation in that group.
Clinical implications the impaction groups show significantly different postsurgical changes in a few parameters and remarkably similar changes in many other parameters. Of 108 comparisons of the absolute changes between the two groups, only 20 were significantly different.
Maxillary changes One of the most interesting findings from the present study is the absolute maxillary skeletal vertical change from immediately after surgery to fixation (stages 2 to 3) was greater in the advancement surgery group. After advancement surgery, point A moved superiorly an additional 1.87 mm after the initial 0.51 mm average surgical impaction. In contrast, point A moved superiorly in the impaction surgery group an average 0.52 mm after the initial impaction of 3.86 mm. These postsurgical superior movements may be related to the surgical burr cut, bone resorption at the cut surfaces, the tightening of the suspension wires during fixation, and the nature of the surgical movements in the two procedures. The postsurgical absolute maxillary horizontal dental changes were greater for the impaction surgeries. The maxilla moved posteriorly an equal or greater amount than the dentition, and the majority of the posterior movements were during fixation. The dentition moved to a lesser degree in both groups, this is most likely because of the stabilizing effect of the occlusal splint on the dentition.
In the present study, it was observed that in tile advancement surgery group, the anterior maxilla tended to continue to move superiorly an average of 1.9 mm after surgery. Therefore such a change should be taken into consideration in the surgical, as well as the orthodontic, treatment planning for patients who will require a maxillary advancement. This is particularly important for patients with minimal maxillary incisor exposure behind the resting upper lip. If such a change is undesirable, precautions should be taken to avoid such superior movements either through rigid fixation, downgrafting, or other adjunctive soft tissue lip procedures, such as a V-Y closure. In addition, the clinician should realize that tightening of the suspension wires during fixation might further impact the maxilla and the maxillary incisors.
SUMMARY AND CONCLUSIONS The purpose of this study was to determine retrospectively the stability of the LeFort I osteotomy after a one-piece maxillary impaction or advancement. Cephalograms of 31 patients were evaluated before surgery, immediately after surgery, in fixation, and after fixation. The findings indicated the presence of significant differences in the vertical maxillary postsurgical changes between maxillary impaction and advancement. Therefore, with patients needing a maxillary advancement and who express minimal exposure of the
rob,me 102
Postsurgical stability of LeFort I
Number 4
maxillary incisors before surgery, care should be taken to avoid burying the incisors beneath the lip, since the maxilla moves superiorly an additional 2.0 mm during fixation. REFERENCES 1. Bell WH, McBridge KL. Correctionsof the long face syndrome by Le Fort I osteotomy. J Oral Surg 1977;44:493-520. 2. Bell WH, Jacobs JD. Tridimensionalplanningfor surgical/orthodontic treatment of mandibular excess. AM J ORTItOD 1981;80:263-88. 3. Willmar K. On Le Fort I osteotomy. Scand J Plast Reconst Surg Suppl. 12, 1974. 4. SchendelSA, EiscnfeldJ, Bell WH, Epker BN, MishelevichDJ. The 10ngface syndrome:vertical maxillaryexcess. Ast J ORTtr 1976;70:398-408. 5. Chu GW. Stabilityofthe Le Fort lone-piece maxillaryosteotomy. [Thesisl. Universityof Iowa, 1986.
341
6. BisharaSE, Chu GW, JakobsenJR. Stabilityof the Le Fort I onepiece maxillary osteotomy. AM J ORTtlODDENTOFACORTttOP 1988;94:184-200. 7. Kufnei"J. Four-yearexperience with major maxillaryosteotomy for retrusion, J Oral Surg 1971;29:549-83. 8. AraujoA, SchendelSA, WolfordLM, Epker BN. Total maxillary advancement with and without bone grafting. J Oral Surg 1978;36:849-58. 9. TeuscherU, Sailer HF. Stabilityof Le Fort I osteotomy in Class III cases with retropositioned maxilla. J Oral Maxillofac Surg 1982;10:80-3.
Reprint requests to: Dr. Samir E. Bishara Department of Orthodontics Universityof Iowa College of Dentistry Iowa City, IA 52242
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The purpose of this study was to determine retrospectively the stability of the LeFort I osteotomy after a one-piece maxillary impaction or advancement. Cephalograms of 31 patients were evaluated before surgery, immediately after surgery, in fixation, and after fixation. Descriptive statistics for the absolute and the relative changes of the various linear and angular parameters were calculated for the different stages. The analysis of variance general linear models procedure was used to compare the impaction group (n = 23) with the advancement group (n = 8). The findings indicated that the two groups could be studied independent of age, sex, surgeon, the presence of pretreatment open bite, and the length of the postsurgical fixation. The findings further indicated the presence of significant differences in the postsurgical changes between the maxillary impaction and the maxillary advancement groups. As anexample, during fixation, the maxilla moved superiorly more at point A in the advancement group (x = 1.89 mm) than in the impaction group (x = 0.67 mm). The upper incisor movements showed a similar pattern, moving more superiorly for the advancement group (x = 2.30 mm) than for the impaction group (x = 0.96 mm). Therefore care should be taken to avoid "burying" the incisors beneath the lip in patients undergoing maxillary advancement, who have minimal exposure of the maxillary incisors before surgery. (AMJ ORTHOD DENTOFACORTHOP 1992;102:335-41 .)
T h e successful correction of dentofaeial deformities with orthognathie surgery is dependent, at least in part, on the stability of the surgical movements. One of the most commonly used approaches to the correction of maxillary deformities is the LeFort I osteotomy. 1.2 Willmar 3 did the first quantitative follow-up study on the LeFort I osteotomy using surgically placed metal markers. Although 106 patients were studied, only 3 had "idiopathic long face," and these cases demonstrated stability of markers and occlusion throughout the l-year observation period with an "insignificant" 10% superior settling occurring at the anterior marker. Schendel et al. 4 indicated that excellent stability was found in their sample of 30 patients who were followed an average of 13.8 months after surgery. Bell and McBride t examined 41 patients with vertical maxillary excess who underwent maxillary superior repositioning with LeFort I osteotomy. Their results indicated clinical stability with minimal relapse. Chu 5 and Bishara et al. 6 described the postsurgical skeletal and dental changes after the LeFort I maxillary impaction. They indicated that (1) after the initial sur-
'Professor, Department of Orthodontics. College of Dentistry, University of Iowa. bln Private practice of orthodontics. Racine. Wisc. 811129716
gical superior repositioning, the maxilla continued to move superiorly, and most of the upward movement occurred during fixation; (2) the anterior part of the maxilla moved superiorly more than twice that of the posterior part of the maxilla; and (3) maxillary dental movements tended to follow skeletal movements. The stability of maxillary advancement with LeFort I osteotomy has been evaluated by Kufner, 7 who reported problems with relapse and fixation. Araujo 8 found up to 68% relapse of the advancement if pterygomaxillary bone grafts were not used. He advocated overadvancement of the maxilla or the placement of bone grafts for large movements. Teuscher and Sailer, 9 on the other hand, reported stable results after maxillary advancements 5 years after treatment. In summary, a limited number of studies are available that evaluate the stability of the surgical correction after LeFort I maxillary impaction or advancement; however, some of these studies included patients who underwent various surgical modifications such as twopiece or three-piece osteotomies as well as mandibular surgery. The purpose of this study is to evaluate retrospectively the stability of the one-piece LeFort I maxillary osteotomy, from before surgery to after fixation but before the initiation of any significant postsurgical orthodontic tooth movement. Two groups will be compared; a group that predominantly underwent im335
336
Am. J. Orthod. Dentofac. Orthop. October 1992
Bishara and Chu
rims near the superior border of the inferior turbinate and in the zygomatic buttresses. All cases had intcrmaxillary fixation with an acrylic surgical splint. L a n d m a r k identification a n d c o n s t r u c t i o n of c o o r d i n a t e s
(0 is 7-15 ~ above PN) O'J
0
Horizontal axis
P~ fit"
g
! t ~Ar"
I l l I I l I
(MxP is 40mm from A)
I
'
I
L
Me
Fig. 1. Landmarks used.
paction and a group that predominantly underwent advancement. MATERIALS AND METHODS The sample
The study involved 31 patients (10 male patients and 21 female patients) who under,vent a LeFort I one-piece osteotomy for impaction or advancement. Mean age for the total group was 20.6 years with a range between 14.2 and 43.8 years. Cephalograms were available for each patient before surgery, immediately after surgery, (~ = 1.4 days with a range of I to 4 days), in fixation (x = 37.2 days with a range of 21 to 48 days), and after fixation (x = 132.2 days with a range of 62 to 190 days). All cephalograms were taken on the same machine. Patients were not included in the study if they had in their medical history craniofacial anomaly, maxillary downgrafting, and mandibular ramus or body surgery. Three cases had genioplasty advancement. All maxillae were fixed with suspension wir6s,'ffrid none with rigid fixation. Bone fixation was bilateral in the pyriform
Various landmarks were identified on the presurgical cephalograms (Fig. 1). Maxillary landmarks. Point A (A); point A' (A'), which is the point on the nasion-menton line from which a perpendicular intersects point A; and maxillary posterior point (MxP), which is the point on the line constructed 40.0 - 0.25 mm posterior to point A and parallel to the horizontal plane (O-N), midway between the inferior and superior cortical plates of the maxilla on the presurgical cephalogram. Points A and MxP have been chosen to quantify the changes in the maxilla at its anterior and posterior aspects rather than anterior nasal spine (ANS) and posterior nasal spine (PNS) because the tip of the ANS and PNS are often difficult to locate after LeFort I maxillary osteotomy. In addition, the ANS is often removed during maxillary surgery. Other maxillary landmarks identified are the maxillary central incisal edge (UI) and the upper molar point (UM), which is the midpoint between the two most distal points on the outlines of the second maxillary molars. Upper molar point has been chosen instead of the mesiobuccal cusp tips of the first maxillary molars because of the greater overlap of the hard tissue structures at the first molars than at the distal surfaces of the second molars. Mandibular landmarks. Mandibular central incisal edge (LI), point B (B), pogonion (Pog), menton (Me), gonion (Go), articulare (Ar), and articulare prime (Ar'), which is the point on the presphenoidale-gonionline from which a perpendicular is constructed to articulare. The definition of these landmarks were detailed elsewhere, s The construction of the horizontal and vertical axes, on which the various landmarks were projected, is detailed in Figs. 2, A-C. The angle between the constructed horizontal axis, O'N, and the anatomic reference line, P-N, differs from patient to patient, but remains constant for the serial cephalograms of the same patient. A template of the cranial base was constructed from the presurgery cephalogram with the positions of P, N, and O pinpricked, so that these landmarks could be located in subsequent cephalograms by superimposition. A similar template for the maxilla was used to determine the position of the skeletal points A and MxP. Dental points on the UI and the UM were located directly on each cephalogram. A detailed template of the mandible was also constructed with the position of skeletal points B, Pog, Me, and Go. Points LI and Ar were located directly on each cephalogram since their positions vary as a result of the postsurgical movements.
Voh,me102
Postsurgical stability of LeFort I 337
Number 4
Linear and angular parameters measured The changes in each of the 18 landmarks were determined by projecting each landmark on the constructed horizontal (O'-N) and vertical (O'-P) axes. The change in any landmark can be evaluated in both the horizontal and vertical directions. As an example, the A-O'N variable describes the horizontal i.e. anteroposterior change in point A, whereas the A-O'P variable describes the vertical change in point A. In addition to the changes in the position of the various landmarks, changes in seven linear and two angular measurements were evaluated including: N-A', N-Me, Ar'-Go, P-Go, N-A'/N-Me%, Ar'-Go/P-Go%, and P-Go/N-Me%, as well as the ANB and P-N:Me-Go angles.
STEP1
j#
P
.Reliability of measurements A Reflex Mctrograph digitizer (Ross Instruments Ltd, England) was used for measuring the changes in the various landmarks. The accuracy of the metrograph was determined to be within 0.2 mm. As a result, allowable intrarater and interrater variability was predetermined at 0.2 mm.
Statistical analysis Descriptive statistics for the absolute changes of the various linear and angular parameters were calculated for the following stages: before surgery to immediately after surgery (1 to 2), immediately after surgery to fixation (2 to 3), fixation to after fixation (3 to 4), and immediately after surgery to after fixation (2 to 4). Relative changes for the same parameters were also calculated as a percentage of the surgical change. The analysis of variance general linear models procedure was used to compare the measurements of the two surgical groups, as well as for the following variables:-(1) male patients versus female patients; (2) younger ( a d v a n c e m e n t g r o u p . = Impaction g r o u p < a d v a n c e m e n t g r o u p .
1-2 2-3 3-4(s) 2-4(s)
10.5+** 7.6-* 0.0 4.4-*
N-A' (nun) 1-2 2-3 3-4 2-4
6.3+* 10.5-** 0.0 7.1
:339
340
Bishara and Chu
Am. J. Orthod. Dentofac. Orthop. October 1992
Mandibular changes
Table I. Cont'd Variable
F
P-Go (mm) 1-2
0.3
2-3
4.4 + *
3-4(s) 2-4(s)
0.0 2.9
Ar-'Go (mm) 1-2
2-3 3-4(s) 2-4(s)
0.4 4.8 + 0.5 0.6
P-Go/N-Me (%)
1-2 2-3 3-4(s) 2-4(s)
15.0- ** 14.0 + ** 0.0 8.3 + **
Me-GO:P-N (~
1-2 2-3 3-4 2-4
14.4 + ** 13.4-** 0.2 10.6 - **
The direction of mandibular changes differed between the impaction and the advancement surgeries. With impactions, the mandibular changes were mostly in the horizontal plane, whereas with advancements, the changes were mostly in the vertical plane. As an example, during fixation (stages 2 to 3), pogonion moved posteriorly 1.2 mm in the impaction group. Whereas with advancement, pogonion moved anteriorly 2.0 mm. After removal of the splint (3 to 4), pogonion moved anteriorly in both surgeries as a result of the mandibular autorotation. Regarding the changes in the vertical plane, in the impaction surgeries, pogonion moved superiorly 0.3 mm during fixation (stages 2 to 3). Whereas for advancement surgery, pogonion moved superiorly 1.5 mm. The larger mandibular change observed in the advancement group is related to the corresponding larger superior maxillary movement during fixation in that group.
Clinical implications the impaction groups show significantly different postsurgical changes in a few parameters and remarkably similar changes in many other parameters. Of 108 comparisons of the absolute changes between the two groups, only 20 were significantly different.
Maxillary changes One of the most interesting findings from the present study is the absolute maxillary skeletal vertical change from immediately after surgery to fixation (stages 2 to 3) was greater in the advancement surgery group. After advancement surgery, point A moved superiorly an additional 1.87 mm after the initial 0.51 mm average surgical impaction. In contrast, point A moved superiorly in the impaction surgery group an average 0.52 mm after the initial impaction of 3.86 mm. These postsurgical superior movements may be related to the surgical burr cut, bone resorption at the cut surfaces, the tightening of the suspension wires during fixation, and the nature of the surgical movements in the two procedures. The postsurgical absolute maxillary horizontal dental changes were greater for the impaction surgeries. The maxilla moved posteriorly an equal or greater amount than the dentition, and the majority of the posterior movements were during fixation. The dentition moved to a lesser degree in both groups, this is most likely because of the stabilizing effect of the occlusal splint on the dentition.
In the present study, it was observed that in tile advancement surgery group, the anterior maxilla tended to continue to move superiorly an average of 1.9 mm after surgery. Therefore such a change should be taken into consideration in the surgical, as well as the orthodontic, treatment planning for patients who will require a maxillary advancement. This is particularly important for patients with minimal maxillary incisor exposure behind the resting upper lip. If such a change is undesirable, precautions should be taken to avoid such superior movements either through rigid fixation, downgrafting, or other adjunctive soft tissue lip procedures, such as a V-Y closure. In addition, the clinician should realize that tightening of the suspension wires during fixation might further impact the maxilla and the maxillary incisors.
SUMMARY AND CONCLUSIONS The purpose of this study was to determine retrospectively the stability of the LeFort I osteotomy after a one-piece maxillary impaction or advancement. Cephalograms of 31 patients were evaluated before surgery, immediately after surgery, in fixation, and after fixation. The findings indicated the presence of significant differences in the vertical maxillary postsurgical changes between maxillary impaction and advancement. Therefore, with patients needing a maxillary advancement and who express minimal exposure of the
rob,me 102
Postsurgical stability of LeFort I
Number 4
maxillary incisors before surgery, care should be taken to avoid burying the incisors beneath the lip, since the maxilla moves superiorly an additional 2.0 mm during fixation. REFERENCES 1. Bell WH, McBridge KL. Correctionsof the long face syndrome by Le Fort I osteotomy. J Oral Surg 1977;44:493-520. 2. Bell WH, Jacobs JD. Tridimensionalplanningfor surgical/orthodontic treatment of mandibular excess. AM J ORTItOD 1981;80:263-88. 3. Willmar K. On Le Fort I osteotomy. Scand J Plast Reconst Surg Suppl. 12, 1974. 4. SchendelSA, EiscnfeldJ, Bell WH, Epker BN, MishelevichDJ. The 10ngface syndrome:vertical maxillaryexcess. Ast J ORTtr 1976;70:398-408. 5. Chu GW. Stabilityofthe Le Fort lone-piece maxillaryosteotomy. [Thesisl. Universityof Iowa, 1986.
341
6. BisharaSE, Chu GW, JakobsenJR. Stabilityof the Le Fort I onepiece maxillary osteotomy. AM J ORTtlODDENTOFACORTttOP 1988;94:184-200. 7. Kufnei"J. Four-yearexperience with major maxillaryosteotomy for retrusion, J Oral Surg 1971;29:549-83. 8. AraujoA, SchendelSA, WolfordLM, Epker BN. Total maxillary advancement with and without bone grafting. J Oral Surg 1978;36:849-58. 9. TeuscherU, Sailer HF. Stabilityof Le Fort I osteotomy in Class III cases with retropositioned maxilla. J Oral Maxillofac Surg 1982;10:80-3.
Reprint requests to: Dr. Samir E. Bishara Department of Orthodontics Universityof Iowa College of Dentistry Iowa City, IA 52242
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