Stability of mandibular constriction with a symphyseal osteotomy

Stability of mandibular constriction with a symphyseal osteotomy Charles D. Alexander, DDS, MSD, ~ Dale S. Bloomquist, DDS, MS, b and Terry R. Wallen, DDS, MSD ~ Arlington, Texas, and Seattle, Wash.

The purposes of this study are to determine the stability of surgical mandibular constriction with a midline osteotomy and to evaluate the periodontal and temporomandibular joint responses. A symphyseal osteotomy to facilitate mandibular constriction was performed in 15 patients to correct transverse discrepancies. At the same time a surgical anterior or posterior repositioning of the mandible was done by using a bilateral sagittal osteotomy of the vertical ramus. Tomograms in the coronal plane including the mandibular second molars were taken preoperatively (T,), immediately postoperatively (1-2) and 8 weeks postoperatively (T3). Linear measurements between the cortical borders of the mandible were assessed from the tomograms at each time period. Median surgical and postoperative changes in mandibular width were determined. When evaluating the entire group no statistically significant change in the surgical constriction was found postoperatively (-i-2 and T3), although there was some individual variability. An examination of the periodontal response at the osteotomy site revealed no statistically significant change between the initial and the 5-month postoperative examinations. No changes in joint noise were detected postoperatively, and all mandibular joint movements rettJ?ned to preoperative values except for excursive movements. Mandibular constriction with a midline osteotomy on conjunction with a bilateral sagittal osteotomy was found to be a stable modality for correcting transverse disharmonies. (AMJ ORTHOD DENTOFAC ORTHOP 1993;103:15-23.)

H i s t o r i c a l l y , correction of transverse disharmonies has involved the maxillary arch. Mechanical maxillary expansion may provide sufficient transverse correction in cases of unilateral or bilateral maxillary constriction before closure of the midpalatal suture. ~ After the suture becomes rigid, surgical maxillary ex9pansi~ is often necessary to accomplish significant improvement in the transverse dimension. "-46t4 Various surgical techniques have been described. 7:~ Surgical mandibular advancement may introduce or aggravate transverse malrelationships. Mild discrepancies can be corrected by buccal movement of the maxillary posterior teeth. However, if mere tipping occurs, balancing interferences may be introduced as the maxillary palatal cusps are rotated down and out. The amount of correction is limited with this type of tooth movement and the stability questionable.17 From the Department of Orthodontics. School of Dentistry. University of Washington. This article is based on research submitted by the senior author in partial fulfillment of the requirements for the degree of Master of Science in Dentistry. Supported in part by the Orthodontic Memorial Fund and the Orthodontic Alumni Association. "Private Practice, Arlington, Texas. bAssociate Professor, Department of Oral and Maxillofacial Surgery. 'Clinical Professor, Department of Orthodontics. 0$89-5406/93/Sl.00 + 0.10 8/1/32280

Surgical mandibular constriction has been reported in the literature. 17-'2The procedure is performed in conjunction with anteroposterior, as well as transverse correction. An ostectomy or osteotomy is performed at the midline, and the two halves are brought together. This particular procedure allows only a limited amount of constriction. In situations with bilateral sagittal split osteotomies for mandibular repositioning, 23"-7an additional midline osteotomy should allow a considerable amount of constriction. 283-" With the advent of rigid fixation, problems with relapse at the sagittal osteotomy site have been reduced) 3 Mandibular constriction with a symphysis osteotomy and rigid fixation should therefore provide a stable correction of transverse discrepancies. There is a concern that an interdental osteotomy may lead to periodontal defects. Also, several studies have documented a small but statistically significant loss of connective tissue attachment resulting from a period of orthodontic treatment) 43~ This is thought to be due to accumulation of plaque around the orthodontic appliance. 36 If done properly, a midline osteotomy does not interfere withthe periodontal attachment at the gingival crest. Accordingly, there should be no difference in attachment loss between a midline osteotomy site and other interproximal sites in the same segment. 15

16

Am. J. Orthod. Dent(~ac. Orthop.

Alexander, Bloomquist, and Wal/en

.hmuary 1993

Fig. 1. Site of mandibular midline osteotomy. - . . . . Area of osteotome fracture. - = Area of oscillating bone saw.

Maxillofacial surgical procedures may not compromise temporomandibular health if they do not interfere with condylar position. Se,/eral studies have shown improvement postoperatively in signs and symptoms of temporomandibular disorder in patients treated with mandibular advancement. 373s To the contrary, an alteration in condylar position has been shown to increase postoperative temporomandibular symptoms and surgical problems. 39 Some tilting of the proximal segment may occur during the constriction after the midline osteotomy. As a result a slight change in condylar position may follow. However, this may be too minimal to represent a challenge to temporomandibular health. The purpose of the present study is to test the hypotheses that (1) a significant amount of mandibular constriction can be performed through combined sagittal split and midline osteotomies and that the constriction is stable when rigid fixation is used, (2) the periodontal support adjacent to the midline osteotomy site will not be compromised, and (3) mandibular constriction will not cause functional changes in the temporomandibular joint.

MATERIALS AND METHODS Sample Fifteen patie(ats (5 male and 10 female) underwent surgical mandibular constriction in conjunction with mandibular lengthening or shortening (13 advancements, 2 setbacks). Two patients also received advancement genioplastics. The mandibular constriction was performed to correct transverse occlusal discrepancies present after the anteroposterior correction. Sample selection was based on patient availability and standardization of technique. Mean age of the patients was 32 years 9 months with a range of 17 years 4 months to 45 years 5 months. All patients received preoperative and postoperative orthodontic treatment.

Fig. 2. Tomographic sections matched at T1 (A) and I"2 (B). T3 match not shown.

Surgical procedure All patients underwent an osteotomy at the symphysis allowing for mandibular constriction. Anteroposterior correction was achieved with modified bilateral sagittal split osteotomies of the ramus. -'~-2733The identical surgical technique was performed by the same surgeon with four exceptions. Three patients required alternative fixation methods, and one surgery was perfonned by another surgeon. After completion of the sagittal osteotomies, intermaxillary fixation over an ocelusal splint was used to relate the distal-and proximal fragments of the mandible to the maxilla in the correct sagittal relationship23 An intraoral incision about 1.5 cm in length was made just below the attached tissue of the mandibular incisors. The periosteum was elevated just below the mandibular border at the symphyseal region. The interdental bone between the mandibular central incisors was exposed by reflecting a mucoperiosteal flap superiorly while maintaining the gingival attachment. The vertical midline osteotomy was initiated with an oscillating bone saw penetrating the external and lingual cortical plates of the symphysis. This bone cut did not extend superior to the apices of the mandibular incisors. Above the apices, a thin osteotome

Volu,ne 103

Stability of mandibular constriction

17

Number I

was used to penetrate the facial cortex of the interdental alveolar region to complete the midline osteotomy (Fig. 1). Extreme care was taken to avoid damaging the roots of the teeth adjacent to the osteotomy site. With the mandible separated into two segments at the symphysis, the intermaxillary fixation was tightened to position the segments into their correct transverse oeclusal relationship. The two hemimandibles were then rigidly fixed at the symphysis, with a fourhole osteosynthesis plate and cortical screws (2.0 mm diameter, 8 mm length). Two screws per side were placed intraorally from the facial surface. After completion of the midline osteotomy fixation, the distal and proximal fragments of the mandible `'`"ere rigidly fixed with cortical screws2 ~ Intermaxillary fixation was then released, and the mandible manipulated to assure proper occlusal relationships and condylar position. Any discrepancies between the desired relationship and those achieved were corrected at this time. Elastic fixation held the tee!h together for approximately one day .after surgery. After release of elastic fixation, Class II or Class III elastics were worn with the final splint in place for approximately 14 hours a day for the first week. After the first week, the elastics and splint were worn for 8 hours a day until orthodontic treatment was resumed approximately 8 weeks after surgery.

Tomographle procedure and analysis

"

Tomograms were taken in the coronal plane through the right and the left mandibular molar areas to evaluate the surgical and the postoperative changes. All tomograms were taken by the same radiologist on a Philips Polytome Universal 3 machine (Massiot/Phillips, Paris, France) with a hypocycloidal pattem in a cephalostat headholder. Included in the t o m , r a m s were the second molars, the supporting bony structures and the inferior border of the mandible (Fig. 2). Three tomographic series were taken for each patient with the identical technique. The tomographic series were obtained at the following intervals: before surgery after preoperative orthodontics (TO, within 10 days after surgery (T:), and at least 8 weeks postoperatively (Tj). A tomographic series consisted of six tomographic sections of the mandible. Each section was 2.8 mm in anteroposterior width. The six tomographic sections were exposed approximately 3 mm apart starting at the most distal part of the second molar and progressing anteriorly through the first molar area. Three tomographic sections from each time interval were matched according to anatomy. With the aid of the radiologist, the sections were matched while viewing the radiographs on a large viewb6x. Anatomy of the teeth and mandible, as well as existing restorations and orthodontic brackets, were used in the matching process. The end result in most cases was three sections of the mandible matched at all three time periods (Fig. 2). In five subjects, only two sections of the mandible could be matched at all three time periods. Once the matched sections were obtained in the T,, T,, and Tj tomograms, changes in the transverse direction of the mandible were measured between these time periods. This was accomplished by digitizing eight landmarks defined in

d

d

b

8 a

Fig. :3. Tracing of tomogram with identifying landmarks, a, Most 9prominent point on buccal cortical plate, b, most prominent point on lingual cortical plate, c, molar root apex, and d, molar crown midpoint representing long axis of molar. Fig. 3. Two linear parameters were assessed between the corresponding points to determine mandibular width. One angular measurement, representing the intersection of the long axis of the mandibular molars, was calculated to determine angular changes in the mandible because.of the constriction. Cor(esponding measurements from the three matched sections at each time interval were then averaged. Each subject had a single value for the two linear parameters and one angular measurement at the T,, T2, and T~. The principal investigator performed all tomographic evaluations.

Periodontal and temporomandibular joint examinations Preoperative (T,), 8-week postoperative (T~), and 5month postoperative (T,) periodontal and temporomandibular joint (TMJ) examinations were conducted on all patients by the same examiner. The pcriodontium around the surgical site was evaluated on each patient. This was accomplished by measuring six gingiyal areas on each mandibular central incisor: facial, mesiofacial, distofacial, lingual, mesiolingual, and distolingual. An electronic, pressure sensitive probe (Electronic Periodontal Probe, Vine Valley Research, Middlesex, N.Y.) standardized at 0.50 N with a special machined tip, 0.5 mm in diameter and caibrated in I mm increments, was used to measure the pocket depths. 4~ These same measurements ,.,,'ere also taken on the mandibular right canine to establish a control. The following measurements were included in the periodontal examination: pocket depth, measured from the free gingival margin to the gingival attachment; "git!gival attachment level, measured from orthodontic arch wire to the gingival attachment; gingival recession, measured from orthodontic archwire to the free gingival margin; gingival bleeding index, 4j and plaque index. ~:4~ The TMJ examination as described by Howard" consisted of three parts: the amount of mandibular movement including maximum opening, assisted maximum opening, protrusive opening, protrusion, and right and left excursions; the presence of joint noise in each movement; and the sensitivity to

18 Alexander, Bloomquist. and Wallen palpation of the TMJ (lateral, posterior and loaded force) and related muscles (posterior and anterior temporalis and superior and deep massctcr). Statistical and error analysis

Nonparamctric tests were used for statistical analysis. Significance of change of mandibular width and angulation over time was determined by a two-sided Wilcox sign-rank test with statistical significance established atp < 0.05. Temporomandibular joint data were analyzed for change by using a one-sample binomial test. This change was taken as a ratio of the numbers of patients who experienccd an increase or a decrease in response versus the number of patients with change in response. Periodontal changes were compared with the control by using graphic and summary statistics. Error in landmark identification was evaluated by measuring every tomogram a second time after a 3-week period. glean measurement error was characterized by a mean absolute difference of the two measurements. Reliability of TMJ and periodontal examinations was determined by examining three patients twice within a l-week period. A magnification error of 1.25 was divided into all measurements obtained from the tomograms. RESULTS

Stability of surgical mandibular narowing was analyzed with the use of tomograms through the coronal plane. The most lateral and medial points of the mandibular conical plate were defined bilaterally and used to construct linear measurements of mandibular width. Angular changes in the mandible were calculated by using the intersection of the long axis of the mandibular molars. Mean measurement error was 0.42 mm with a standard error of 0.1 mm for the linear measurements and 2.1 ~ with a standard error of 0.2 ~ for the angular measurements. The periodontal and TMJ responses to t h e symphyseal osteotomy and constriction were also evaluated. Mean measurement error was 0.03 mm (SE = 0.05) for the periodontal probings and 1.5 mm (SE = 0.4) for the TMJ examination. A rate of agreement of 63% was established for the periodontal categorical measurements. The median buccal width of the mandible before surgery (T~) was 76.1 mm (75th percentile = 79.4, 25th percentile = 72.1), immediately after surgery (T2) it was 72.2 rnm (74.3, 66.8), and at a minimum of 8 weeks after surgery (T3) it was 73.1 (74.9, 65.7). The median surgical constriction (4.6 mm) between T~ and Tz was statistically significant (p < 0.05). Mandibular constriction remained stable between T, and T3 with no statistically significant change (p > 0.05) and a median value of 0.37 mm of continued constriction. Median widths from the lingual revealed similar findings. At T~ it was 36.2 mm (40.7, 32.5), T_, was 33.5 mm (35.9, 29.1)~ and T3 was 34.6 (36.8, 29.0). Again for the sample, statistically significant constriction (2.5

Am. J. Orthod. Dentofac. Orthop.

Jam mrj" 1993

mm) was shown between Tt and T2 from the lingual (p < 0.05) with no statistically significant change (p > 0.05) between the T~ and T3 time periods (median value = 0.24 mm). Figs. 4 and 5 illustrate the individual surgical change (T, to T_,) and posttreatment response (T,_ to T3) to mandibular constriction, respectively. Median values for the total sample are shown in Fig. 6. Subject nos. 2, 5, 7, and 12 requiring an alteration in surgical technique were subgrouped and compared with the median values for the total sample. Because of problems in the sagittal split osteotomy in one patient, no. 7, a plate in the remus had to be used in fixation instead of the normal three conical screws. The amount of surgical constriction measured on this patient was comparable to the median values for the group (buccal (B) = 4.76 mm, lingual (L) = 1.0 mm), and stability was shown in the postoperative analysis (B = 0.40, L = 0.24). The symphyseal osteotomy site was not fixated with an osteosynthesis plate on two patients (nos. 2 and 5) because Of the proximity of the advancement genioplasty. Instead the fixation o f the genioplasty with two 18 mm length cortical screws was used to stabilize the osteotomy site. The amount of surgical constriction (no. 2, B = 6.02, L = 1.54) (no. 5, B = 4.44, L = 3.0) and postoperative change (B = 0.28, L = - 0 . 3 1 ) (B = 0.37, L = 0.48) in these patients was consistent with the group medians. In patient no. 12 treated by the other surgeon, the amount of surgical constriction (B = 7.47, L = 4.44) was in the top 25th percentile of the sample, and T2 to T3 changes were toward the original preoperative position (B = - 0 . 9 2 , L = - 0 . 0 4 ) . Relapse of the surgical constriction was evident in five subjects, nos. 6, 10, 12, 13, and 15, and continued constriction postoperatively, was detected in three patients (nos. 1, 8, and 11). Subjects nos. 5 and 14 were treated with surgical mandibular setbacks in conjunction with the mandibular narrowing. The angulation of the mandible did not appear to change during the evaluation period. Median angulation of the mandible before surgery (TO was 32.7 ~ (39.6 ~, 21.6~ at T, it was 33.4 ~ (39.3 ~ 23.0~ and at 8 weeks after surgery (T3) it was 31.7 ~ (41.0 ~ 25.4~ No statistically significant change in mandibular angulation was found in the sample between Tt and Tz (p > 0.05) or T2 and Tj (p > 0.05). Comparing periodontal changes graphically, no differences were found in the periodontal examinations. Pocket depth, gingival attachment level, gingival recession, gingival bleeding, and plaque index were comparable between the mandibular central incisors adjacent to the osteotomy site and the control tooth. Mandibular range of motion at T3 decreased sig-

Volume 103 Number l

Stability of mandibular constriction

19

11-

10" 9

i

-

Surgical Constriction

7-

(ram)

6-

I

9

Buccal Change T1-T2

~

[]

Lingual Change T1-T2

5 4 3

0 m

I

2

.3

4

5

6

7

8

9

10

11

12

13

14

15

Patient Number

Fig. 4. Individual surgical change T, to T2 (mm).

6

IR buccalChange T2[ ] Lingual Change T2-T3

5 4 Continued Constriction (ram)

3 2 1

0 Relapse of Surgical Constriction

(ram)

91 o

-2-3 1

2

3

4

5

6

7 8 9 10 Patient Number

11

12

13

14

15

Fig. 5. Individual postoperative response T2 to T3 (mm).

nificantly from the preoperative T, values (p < 0.05). At the: 5-month follow-up, examination (T4), opening movements returned to preoperative (Tl) values (p > 0.05), while lateral and protrusive movements showed little change from T3 measurements (p > 0.05). Pain associated with these movements did not vary between any time period (p > 0.5). The amount of joint noise associated with the mandibular movements remained consistent for the group. Detectable noise did not change significantly between each examination period (p > 0.5). Palpation of the TMJ at the three time intervals (Ti, T3, "I"4)showed no differ-

ence in sensitivity to force from loading or lateral and posterior pressure (p > 0.24). Muscle palpation revealed similar results (p > 0.5). DISCUSSION

The median amount of surgical mandibular constriction with a mandibular midline osteotomy was 4.64 mm buccally and 2.5 mm lingually. Postoperatively no median relapse was detected. Comparing buccal and lingual linear measurements taken from tomograms, clinically and statistically significant changes in width were demonstrated between the preoperative (Tt) and

20 Alexander, Bloomquist, and Wallen

Am. J. Orthod. Dentofac. Orthop. Janua~" 1993

Surgical Constriction

(turn)

Change T1-T2

Fig. 6

Change T2-T3

Median Surgical Change and

Postoperative Response(n=15) 'Significance at p,,:O.05

Fig. 6. Median surgical change and postoperative response (n = 15). "Significance at p < 0.05.

immediate postoperative (T,) periods. Comparison of these measurements at the same landmarks, at T,_ and Tj, did not result in any statistically significant change in the transverse dimensions (Fig. 6). Previous investigators demonstrated skeletal relapse in rigidly fixed maxillofacial surgery occurs by the sixth week after surgery, aS~'~Because no information exists on the skeletal stability of surgical mandibular constriction, the standards for stability in other skeletal components were applied to this study. For these reasons, T3 was chosen as a time interval acceptable for evaluating the stability of skeletal components after rigidly fixed maxillofacial surgery. Initially linear measurements were to include the inferior border of the mandible and the buccal surface of the molar crown, but because of the difficulty in consistently identifying these points, the measurements were excluded in the final analysis. Surgical alterations in the inferior border because of the genioplasties and the sagittal osteotomies resulted in the relocation of the inferior cortical border. Identifying the buccal surface of the molar was ~not consistent because some tomographic sections included interproximal areas between the first and second molars that produced a blurred buccal contour. The brackets on the bands also inhibited accurate identification. The median difference in the amount of surgical constriction (Tt to T ) between the buccal (4.6 ram) and lingual (2.5 mm) measurements were more than expected for the sample. The mandibular angulation data did not indicate that the long axis of the molar was

uprighted in conjunction with the constriction, yet this was what the linear data suggest. A combination of several factors may provide an explanation for this finding. The mandibular angulation data was not consistent. Measurement error showed a much higher mean absolute difference as compared with the linear value. This was due to the difficulty in consistently identifying the molar root tip and the crown midpoint. Secondly, the error introduced by measuring the most buccal point and the most lingual point in the linear measurements promotes a positi~'e discrepancy between the two values. Lastly, the point of rotation of the mandibular constriction may also explain the difference. As illustrated in Fig. 1, the inferior.portion of the osteotomy was accomplished with an oscillating bone saw, which removed approximately 1 mm of bone. The interdental osteotomy was performed with an osteotome resulting in a fracture and no bone removal. The result was the point of rotation of the constriction being between the lingual interdental bone. This point of rotation would allow the inferior borders of the mandible to be constricted more than the interdental portion of the mandible because of the osteotomy space on the lingual that results from the bone saw. Translated to the actual linear measurements, the buccal was constricted more than the lingual because it was located closer to the inferior border, while the lingual was positioned at the level of the interdental fracture (Fig. 3). Skeletal relapse toward the original preoperative mandibular position was evident in 30% of the sample (patient nos. 6, 10, 12, 13, 15). In three patients from

Volume 103

Number 1

this subgroup, the amount of mandibular buccal constriction (change T~ to T2) was within the middle 50th percentile of the sample, yet changes between T_, and T3 showed mandibular widening. In subject no. 13 the relapse was over half the surgical narrowing, whereas the other two subjects relapsed less than 25%. The only concurrent variable in these patients was the inability to have maximum posterior interdigitation. Two of the patients, nos. 6 and 15, were missing posterior molars which prevented maximum intercuspation postoperatively. The remaining patient did not have orthodontic appliances on the second molars. Again, this might have prevented maximum intercuspation in the posterior segments if they were not in proper alignment. In the other two subjects from the skeletal relapse subgroup (nos. 10 and 12), the amount of surgical mandibular constriction appeared to have little affect on stability. Patient no. 12 had more buccal and lingual constriction than 93% of the sample, yet the subject who experienced the maximum anaoun!: 9 f buccal constriction showed no postoperative buccal relapse. Relapse was also evident with limited mandibular constriction as in patient no. 10. From these observations it appears that the amount of surgical relapse does not correlate directly with the amount of surgical constriction. Maximum intercuspation may play a role in stability, yet by no means can transverse surgical relapse be associated with lack of posterior interdigitation. Of the patients that continued to constrict in mandibular width postoperatively, the initial constriction in subject no. 11 was below the 25th percentile of the sample. Patient no. 1 showed postoperative constriction only in the buccal measurement, which indicates uprighting of the segments. In patient no. 8 the surgical narrowing was comparable with the sample median, but Tz to T~ changes were equal to the initial constriction (B = 4.0, L = 1.97). No angulation changes could be detected immediately after surgery, but the angulation of the mandible decreased by more than 10~ between the postoperative periods. This indicates continued c'onstriction of the buccal measurement between T, and T 3. This was the only subject to show this extreme amount of variability. ., The surgical stability of the two mandibular setback patients, nos. 5 and 14, were comparable with the ad"vancement group (Fig. 5). Because only two mandibular setback patients Were included in the study, a direct comparison with the advancement group could not be made. Variability in stability might be suspected in these patients because of the greater anteroposterior relapse with surgical mandibular setbacks as compared with surgical advancements:3~'49This would only effect

Stability of mandibular constriction

21

the transverse stability if the relapse occurred at the sagittal fixation site. The periodontium at the interdental osteotomy site responded favorably to the constriction when compared with the control site. This would be expected since the gingival attachment level was not interfered with during the surgical procedure. Alterations in the alveolar crest at the osteotomy site were not evaluated because the short-term nature of the study prevented natural bone remodeling to be completed at the surgical site. Investigators have shown, however, that the anaount of osseous loss at an osteotomy site is not clinically significant and that segmental osteotomies can be carried out without significantly modifying the height of interproximal bone. ~~ Temporomandibular joint examinations demonstrated no short-term (T4) changes in sensitivity or audible sounds. These findings are consistent with other studies that have found joint symptoms to decrease after surgical mandibular advancement. 37-3s Mandibular opening at "['4 was consistent with preoperative (Tt) movement, but excursive range of motion did not return to the original Tz mobilities. This decrease in excursive movement of the mandible might be related to condylar rotations caused by the surgical constriction and/or the rigid fixation of the sagittal split osteotomies. However, detecting joint dysfunction with the methods employed in this study have been shown to be unreliable. J-"Others believe the joint adapts morphologically to most physical changes and that minor torque changes in the condylar heads are within the range of adaptability, s3"s~No radiographs were taken to specifically determine condylar anatomic or positional changes induced by the mandibular constriction. In this short-term clinical evaluation, temporomandibular joint function appeared to adapt to the mandibular constriction. This examination may not be all that meaningful as the changes, if any, might be long-term and not detectable after 5 months. Because of the uniqueness of this Study, a few technical problems need to be addressed. The anatomy of the mandible is such that a Single tomographic section is oriented perpendicular to the two bodies of the mandible. The radiographic result is a blurred image of the two separate sides. This is because the tomographic plane does not go through the cortical plates of the "mandibular bodies at 90 ~ when both sides are included in the imaging. Tomograms including only one body of the mandible can be directed perpendicular to the mandible, producing sharp images used in many osseointegrated implant systems. Because of the desire to measure width between the two mandibular bodies, this compromise in clarity was accepted. Adding to this difficulty was the inability to place patients in the exact

22

Alexander, Bloomquist, and Wallen

position for the three tomographic series. Earrods, a frontal rod, and a light cross indicator were used in positioning. Exact positioning was rarely obtained. If patients were not positioned identically to previous tomograms, markings used to calculate location of previous tomographic sections were useless. Because of the aforementioned difficulties, matching the tomograms from the three time intervals was difficult. Teeth with distinct restorations or previous endodontic treatment served as excellent markers in identifying matched sections. Placing markers of some type on the mandibular second molars before tomography would be advisable in the future. In this study, markers were not placed because the tomographic image was thought to be exact enough to provide identifying landmarks. Other limiting factors in the matching of Tt, T-,, and T3 films were surgical structural changes of the mandibular borders and asymmetric mandibular positioning. With the sagittal split osteotomies including the lateral borders of the mandible adjacent to the second molar, bony contours were disrupted from the preoperative condition. Contour changes to the inferior border of the mandible were also present in the patients receiving horizontal advancement genioplasties. Asymmetric positioning of the mandible anteroposteriorly produced a situation where a tomogram taken at the preoperative period could be matched to only one side of the Tz tomogram. The result was a discrepancy in the exact amount of mandibular constriction measured either in a positive or negative manner depending on the asymmetry. A consideration not addressed was the facial impact of the procedure. Do we as clinicians want to constrict the lower third of the face? Is the narrowing esthetically noticeable? These questions were not answered in this study and need to be addressed in the future. With careful diagnosis, this procedure can be successfully adopted into the treatment of transverse discrepancies introduced by surgical mandibular repositioning. After the completion of all preoperative orthodontics, diagnostic models should be taken to simulate mandibular anteroposterior positioning and to determine the severity of the transverse discrepancy. If no surgical treatmetR is planned for the maxilla, special consideration should be made for mandibular narrowing. When surgery is planned for the maxilla, the decision has to be made as to the jaw in which the transverse disharmony is going to be corrected. If significant transverse correction is required, a combination of mandibular narrowing and maxillary expansion should be considered. ~5 The advantages o f this procedure are numerous when indicated. It prevents unnecessary maxillary expansion. Posterior teeth remain positioned over their

Am. J. Orthod. Dentofac. Orthop. January 1993

apical base postoperatively because dental compensations are not needed to correct transverse discrepancies. Compromises associated with posterior cross elastics are eliminated, such as the introduction of balancing interferences and the instability of the dental tipping. It also allows all surgical correction to be accomplished in one jaw. The short-term response of the procedure was found to be stable and biologically acceptable in this study. Reports are limited on this subject ms23'2932 and clinical research unexplored. More long-term investigations need to be conducted to evaluate skeletal stability of the mandibular constriction, as well as dental compensations associated with relapse. CONCLUSIONS

The following conclusions can be made from this study: 1. Mandibular constriction with a midline osteotomy provided stable correction of transverse discrepancies. 2. The short-term analysis showed the periodontium adjacent to the midline osteotomy to be unaffected by the surgical procedure. 3. Joint noise and sensitivity of the temporomandibular joint did not change postoperatively. Normal mandibular function returned in all mandibular movements except excursive movements. We thank Lars Hollender, DDS, Dr. Odont., and his staff for their radiographic expertise, Mr. Lloyd Manet for his statistical assistance and Jon/~rtun, DDS, Dr. Odont., David Crouch, DDS, MSD, and Don Joondeph, DDS, MS, for their support. Special thanks goes to Mrs. Keri Alexander for her clerical assistance. REFERENGES

I. Isaacson RJ, Ingrain All. Forces produced by rapid maxillary expansion, II. Forces presented during treatment. Angle Orthod 1964;34:261-9. 2. ltaas AJ. Rapid expansion of the maxillarydental arch and nasal cavity by opening of the midpalatal suture. Angle Orthod 1961;31:73-90. 3. Haas AJ. Palatal expansion: just the beginning of dentofacial orthopedics. AM J ORTItOD1970;57:219-55. 4. Cotton LA. Slow maxillary expansion: skeletal versus dental response to low magnitude force in Macaca mulatta. AM J OR"roOD 1978;73:1-23. 5. Storey E. Tissue response to the movement of bone. AM J ORTIIOD1973;64:229-47. 6. KennedyJW, Bell Wtt, KimbroughOL, James WB. Osteotomy as an adjunct to rapid maxillary expansion. AM J OgntoD 1976;70:123-37. 7. Alpern MC, YuroskoJJ. Rapid palatal expansion in adults with and without surgery. Angle Orthod 1987;57:245-63. 8. Bell RA. A review of maxillary expansion in relation to rate of expansion and patient's age. A.'q J ORTIIOD1982;81:32-7. 9. lsaacson RJ, Murphy TD. Some effects of rapid maxillary ex-

Volume 103 Number I pansion in cleft lip and palate patients. Angle Orthod 1964;34:143-54. 10. Epker BN, Wolford LW. Dento-facial defomlity, surgical-orthodontic correction. St. Louis: CV Mosby, 1980:305-31. I 1. Moss JP. Rapid expansion of the maxillary arch, part I. J Pract Orthod 1968a;2:165-71. 12. Moss JP. Rapid expansion of the maxillary arch, part II. J Pract Orthod 1968b;2:215-23. 13. Maguerza DE, Shapiro PA. Palatal mucoperiostomy: an attempt to reduce relapse after slow maxillary expansion. AM J ORTHOD 1980;78:540-58. 14. Timms DJ, Moss JP. An histological investigation into the effects of rapid maxillary expansion on the teeth and their supporting tissues. Trans Eur Orthod Soc 1971;34:263-71. 15. Lines PA. Adult rapid expansion with corticotomy. AM J ORT~IOD 1975;67:44-56. 16. Lehman JA, Hass AJ, Hass DG. Surgical orthodontic correction of transverse maxillary deficiency: a simplified approach. J Plast Reconst Surg 1984;73:62-8. 17. Bell WH, Proffitt WR, White RP. Surgical Correction of Dentofacial Deformities. Philadelphia: WB Saunders, 1980:883-8, 1024-5. 18. Soy,ray JH, Haskell R. Ostectomy of the mandibular symphysis. Br J Oral Surg 1967;5:97-102. 19. O'Driscoll PM. Ostectomy at the midline of the mandible. Br J Plast Surg 1971;24:71-7. . 20. Plumpton S. Surgical correction of unilateral mandibular prognathism by intra-oral ostectomy of the symphysis. Br J Plast Surg 1967;20:70-7. 21. MacDonald GB, Choukas NC, Skuble DF. Treatment of minimal pr~nathism by midline mandibular ostectomy. J Oral Surg 1975;33:386-9. 22. Dufetelle JD. Osteotomie mediane de la mandible. Rev Stomatol Chir Maxillofac 1983;84:50-3. 23. Trauner R, Obsegeser H. The surgical correction of mandibular pr~nathism and retr~nathia with consideration of genioplasty. Oral Surg Oral Med Oral Pathol 1957;10:677-89. 24. Dal Pont G. Retromolarosteotomy for the correction of prognathism. J Oral Surgery 1961;19:42-7. 25. ttunsuck E. A modified intraoral sagittal splitting technique for correction of mandibular prognathism. J Oral Surg 1968;26:24952. 26. Gallo W. Modification of the sagittal split ramus osteotomy for retrognathia. J Oral Surg 1976;34:178-9. 27. EpkerB. Modificationsinthesagittalosteotomyofthemandible. J Oral Surg 1977;35:157-9. 28. Jacobs JD. Control of the transverse dimension with surgery and orthodontics. AM J ORTIIOD 1980;77:284-306. 29. WolfordLM, Walter G, Schendel S, Fish LD, Epker BN. Man9 dibular deficiency syndrome I. Clinical delineation and therapeutic significance. Oral Surg Oral Med Oral Pathol

1978;45:329-48. 30. Bell WH, Jacobs JD. Com'~iued orthodontic-surgical correction of moderate mandibular deficiency. AM J ORT~IOD 1979;75:481506. 3 I. Poulton DR, Ware WH. Surgical-orthodontic treatment of severe mandibular retrusion. AM J ORTHOD 1974;3:237-55. 32. Brusati R, Sesenna E, Mannucci N, Gamoletti R. The midline mandibular osteotomy-ostectomy in the correction of dentofacial deformities, lnt J Adult Orthod Orthognath Surg 1987;2:37-50. 33. Caskey RT, Trupin D, Bloomquist D. Stability of mandibular lengthening using bicortical screw fixation. AM J ORTHOD

1989;96:320-6. 34. Zachnison BU, Alnaes L. Periodontal condition in orthodontically treated and untreated individuals. 1. Loss of attachment,

Stability o f mandibular constriction

35.

36.

37.

38.

39.

40. 41. 42. 43. 44. 45.

46. 47.

48.

49. 50.

51.

52. 53.

54.

55.

23

gingival pocket depth and clinical crown height. Angle Orthod 1973 ;43:402- I I. Hamp S-E, Lundstrom F, Nymans S. Periodontal condition in adolescents subjected to multiband orthodontic treatment with controlled oral hygiene. Eur J Orthod 1982;4:77-86. Ericsson I, Thilander B. Orthodontic forces and recurrence of periodontal disease. An experimental study in dogs. AM J OR"nXOD 1978;74:41-50. Karabouta I, Martis C. TMJ Dysfunction Syndrome before and after Sagittal Split Osteotomy of the Ramus. J Maxillofac Surg 1985;13:185-8. Kerstens H, Tuinzing D, van der Kwast W. Temporomandibular Joint Symptoms in Orthognathic Surgery. J Craniomaxillofac SurE. 1989;17:215-8. Amett GW, Tamborello JA, Rathbone JA. Orthognathic surgery and temporomandibular joint function, modem practice in orthognathic and reconstructive surgery. Philadelphia: WB Saundcrs, 1990. Badersten A, Nilveus R, Egelberg J. Effects of non-surgical periodontal therapy. J Clin Periodontal 1985;12:190-200. Ainamo J, Bay I. Problems and proposals for recording gingivitis and plaque, lnt Dent J 1975;25:229-35. Silness P0Loe tt. Periodontal disease in pregnancy. Acta Odontol Scand 1964;22:121-35. Loe tt. The gingival index, the plaque index and the retention index systems. J Periodontol 1967;38:610-6. Howard J. Diagnosis of internal derangements of the temporomandibular joint. Seattle: Benjamin Moffett, 1984:13-20. Mayo KH, Ellis E. Stability of the mandible after advancement and use of dental plus skeletal maxillomandibular fixation: an experimental investigation in Macaca nzulatta. J Oral Maxillofac Surg 1987;45:243-50. Epker BN. Superior surgical repositioning of the maxilla: long term results. J Maxillofac Surg 1981;9:237-46. Skoczylas LJ, Ellis E, Fonseca RJ, Gallo WJ. Stability of simultaneous maxillary intrusion and mandibular advancement: a comparison of rigid and nonrigid fixation techniques. J Oral Maxillofac Surg 1988;46:1056-64. Grassmann CJ, Van Sickds JE, Thrash WJ. Causes, location, and timing of relapse following rigid fixation after mandibular advancement. J Oral Maxillofac Surg 1990;48:450-4. Franco JE. Factors contributing to relapse in rigidly fixed mandibular setbacks. J Oral Maxillofae Surg 1989;47:451-6. Dorfman HS, Turvey TA. Alterations in osseous crestal height following interdental osteotomies. Oral Surg Oral Med Oral Pathol 1979;48;120-5. Kwon H, Dihlstrom B, Waite DE. Effects of the peridontium of vertical bone cutting for segmental osteotomy. J Oral Maxillofacial Surg 1985;43:952-5. Dworkin SF, LeResche L. Reliability of clinical measures on the TMJ. Clin J Pain 1988;4:89-99. Moffett BC, Johnson LC, McCabe JB, Askew HC. Articular remodeling in the adult human TMJ. Am J Anat 1964;115:11942. Nickerson JW, Boering G. Natural course of osteoarthrosis as it relates to internal derangement of the temporornandibular joint. Oral Maxillofac Surg Clin North Am 1989;1:27-45. Lanigan DT, Hey J|l, West RA. Aseptic necrosis following maxillary osteotomies. J Oral Maxillofac Surg 1990;48:142-56.

Reprint requests to: Dr. Charles D. Alexander 840 W. Mitchell Arlington, TX 76013