Accepted Manuscript CBCT Comparison of Surgically-Assisted Rapid Palatal Expansion and Multi-piece Le Fort I Osteotomy William Yao, DMD, MS Sona Bekmezian, DDS Dan Hardy, DDS Harvey W. Kushner, PhD Arthur J. Miller, PhD John C. Huang, DMD, DMSc Janice S. Lee, DDS, MD PII:
S0278-2391(14)01373-1
DOI:
10.1016/j.joms.2014.08.024
Reference:
YJOMS 56473
To appear in:
Journal of Oral and Maxillofacial Surgery
Received Date: 16 February 2014 Revised Date:
12 August 2014
Accepted Date: 19 August 2014
Please cite this article as: Yao W, Bekmezian S, Hardy D, Kushner HW, Miller AJ, Huang JC, Lee JS, CBCT Comparison of Surgically-Assisted Rapid Palatal Expansion and Multi-piece Le Fort I Osteotomy, Journal of Oral and Maxillofacial Surgery (2014), doi: 10.1016/j.joms.2014.08.024. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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CBCT Comparison of Surgically-Assisted Rapid Palatal Expansion and Multi-piece Le Fort I Osteotomy
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William Yao, DMD, MSa Sona Bekmezian, DDSb Dan Hardy, DDSb Harvey W. Kushner, PhDc Arthur J. Miller, PhDd John C. Huang, DMD, DMSce Janice S. Lee, DDS, MDf* a
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Private practice, Saratoga, CA; former resident, Division of Orthodontics, Department of Orofacial Sciences, University of California, San Francisco, CA b Resident, Division of Orthodontics, Department of Orofacial Sciences, University of California, San Francisco, CA c Biomedical Computer Research Institute, Philadelphia, PA d Professor, Division of Orthodontics, Department of Orofacial Sciences, University of California, San Francisco, CA e Private practice, Moraga, CA; Associate Health Science Professor, Division of Orthodontics, Department of Orofacial Sciences, University of California, San Francisco, CA f Deputy Clinical Director, NIDCR/NIH, Bethesda, MA
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*This article was prepared while Janice S. Lee was employed at UCSF. The opinions expressed in this article are the author's own and do not reflect the view of the National Institutes of Health, the Department of Health and Human Services, or the United States government.
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Corresponding author: Janice S. Lee DDS, MD, FACS Deputy Clinical Director NIDCR/NIH 10 Center Drive Bldg 10/Rm 5-2531 (North East Atrium) Bethesda, MD 20892-1470
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Introduction Rapid palatal expansion with or without surgery is an important treatment tool to treat maxillary transverse deficiency, which can include a posterior crossbite, an omega-
suture may require the inclusion of surgery in the treatment.3,4
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shaped occlusion, and a high palatal vault.1,2 The age of the patient and a fused palatal
When the maxillary transverse deficiency exceeds 5-mm, surgical assistance may
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be necessary for skeletally mature patients.5,6 Surgical options include a multi-piece Le Fort osteotomy or surgically-assisted rapid palatal expansion (SARPE).7
Marchetti et
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al., examined the outcomes between patients receiving a SARPE (n=10) and segmental Le Fort I osteotomy (n=10) using plaster models to evaluate the adult patient before expansion, immediately after expansion, and two years after expansion.8 The intermolar distance increased 7-mm with SARPE and then decreased over two years by 3-mm (36%
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relapse), while the Le Fort I increased the molar distance 3.8-mm which then decreased by 0.8-mm (20% relapse) over two years. A two-dimensional study by Chamberland and Proffit9 provided long-term
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evaluation extending two years post-SARPE using posteroanterior cephalograms and dental casts. The mean maximum expansion at the first molar was 7.6-mm with a mean
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relapse of 1.8-mm (24%). They noted that approximately half of the expansion was skeletal (46%) Other studies have shown similar results.10-12 Three-dimensional imaging, particularly with cone-beam computed tomography
(CBCT), has provided a new method for assessing the amount of sutural separation and regions of greatest relapse following rapid maxillary expansion. Latravere et al., used CBCT three-dimensional images to compare transverse, vertical, and anteroposterior
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changes between a bone-anchored and a traditional tooth-anchored rapid maxillary expansion.13.14 Both approaches gave similar results with the greatest changes in the transverse plane, and minimal effects in the vertical and anteroposterior dimensions.
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Garrett et al.,15 used CBCT to evaluate the effect of rapid maxillary expansion using a Hyrax appliance in children (mean age 13.8y) and found that transverse expansion can occur via separation of the palatal suture (38%), bending or tipping of the palate (13%),
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and buccal tipping of the dentition (49%). The CBCT studies with surface rendered volumetric images have also shown that palatal expansion is greatest anteriorly and
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decreases posteriorly.16
The purpose of this study was to examine and compare the dental and skeletal changes between the SARPE versus multi-piece Le Fort I osteotomy to correct maxillary transverse deficiencies using 3D imaging. The specific aim was to determine if dental We
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and skeletal movements correlate at the time of surgery and during relapse.
hypothesize that the multi-piece Le Fort procedure would produce more expansion skeletally than dentally as compared to the SARPE approach and that both groups would
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have more dental relapse than skeletal relapse.
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Materials and Methods STUDY DESIGN and SUBJECTS The investigators designed and implemented a prospective longitudinal study.
The study population was composed of patients presenting for evaluation and management of skeletal maxillary transverse deficiency (MTD) between August 2008 to August 2010.
Patients were included if they were diagnosed with skeletal maxillary
transverse deficiency through clinical exam, cephalograms or CBCT, and diagnostic 2
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casts, and required surgical expansion of the maxilla. Patients were excluded if they were missing the required set of CBCT scans, had a craniofacial anomaly that could alter the
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effects of expansion, or had previous surgery.
This study was approved by the UCSF Committee on Human Research (IRB#1000564). The authors of this study obtained informed consent for all subjects. Subjects
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underwent a 2-piece or 3-piece Le Fort I osteotomy or a SARPE by faculty of the Department of Oral and Maxillofacial Surgery to correct the MTD.
Subjects obtained
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CBCT scans at 3 timepoints: T0=preoperative, T1=within 1 month post-operative, T2=6+months postoperative for patients undergoing a multi-piece Le Fort I, and T0=preoperative, T1=post-expansion in retention, and T2=6+months post-expansion for
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patients undergoing a SARPE.
SURGICAL PROTOCOLS
At our institution, for skeletally mature patients, the algorithm of treatment
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includes using non-surgical orthopedic maxillary expansion (OME) for transverse discrepancies up to 3-mm, and surgical assistance for those greater than 3-mm,
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particularly when a maxillary osteotomy is already part of the overall treatment plan (for other planar discrepancies, i.e., vertical or sagittal). For transverse discrepancies between 3-6-mm, a 2- or 3-piece Le Fort I osteotomy is considered, while a SARPE is considered when the transverse discrepancy is greater than 6-mm due to the anatomical limitations of expanding the maxilla during a Le Fort I osteotomy and the concern for greater relapse with a Le Fort I for larger transverse discrepancies.
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Le Fort I Osteotomy All patients received pre-surgical orthodontic treatment consisting of full-fixed orthodontic appliances. Prior to surgery, a pre-surgical CBCT scan was taken (T0). The
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surgical technique consisted of lateral maxillary osteotomies from the piriform aperture to the zygomatic buttress with separation along the septum, lateral nasal walls, pterygomaxillary fissure, and complete downfracture of the maxilla. The multi-piece
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osteotomy was performed either between the central incisors for a 2-piece, or between the canines and first premolars for a 3-piece Le Fort I. A para-sagittal osteotomy was made
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along the palate behind the nasopalatine foramen to complete the multi-piece Le Fort I. The segments were confirmed to be mobile and separated. Patients obtained maxillary transverse expansion guided by an intra-operative surgical splint. Stabilization of the segments was achieved via rigid fixation using four titanium plates. The patients were
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kept in intermaxillary fixation (IMF) with elastics for 2-3 weeks after surgery. Postoperative stabilization of the maxilla included continuous use of an acrylic surgical splint for 6-8 weeks. The surgical splints were made using the model surgery technique on a
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fully adjustable dental articulator. After the surgery, the patient returned for a postoperative CBCT scan within 1 month of surgery (T1). A third CBCT scan was taken at
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least 6 months after surgery (T2). The patient continued with full-fixed orthodontic treatment during this period and was monitored by the Department of Oral and Maxillofacial Surgery at follow-up visits.
Surgically-assisted rapid maxillary expansion Patients were fitted with a tooth-borne Hyrax expander prior to surgery. The expander consisted of an expansion screw with four 0.05-inch stainless steel arms 4
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soldered to four stainless steel bands fitted to the maxillary first premolars and first molars. The expander was cemented in place using common light-cured glass ionomerresin cement. A 0.036-inch stainless steel wire was placed lingual to the dentition to add
when present. A CBCT was taken prior to surgery (T0).
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rigidity and to extend the expansion to include the maxillary canines and second molars
The surgical technique consisted of lateral maxillary osteotomies from the
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piriform aperture and posterior to the zygomatic buttress with separation of the lateral nasal walls to the descending palatal neurovascular bundle.
A midline osteotomy
osteotomes,
was
performed
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between the central incisors to the posterior nasal spine, using 6-mm or spatula blindly
without
downfracture
of
the
maxilla.
Intraoperatively, the expansion appliance was activated to achieve a 1-2 mm separation at the maxillary central incisors. A latency period of typically 5 days was observed, after
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which patients were instructed to activate the expansion screw four times a day (two turns in the morning and two turns in the evening, 0.25 mm per turn). Patients were monitored weekly until the desired expansion was achieved. The expansion device was kept in
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place for approximately three times the duration of the activation period, and until fullfixed orthodontic brackets were bonded and orthodontic treatment was initiated on the
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maxillary teeth. When expansion was complete, a CBCT scan was taken during the retention period (T1). retention period (T2).
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The patient returned for a third scan 6 months beyond the
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CONE BEAM COMPUTED TOMOGRAPHY A Hitachi CB MercuRay (Hitachi Medical Corporation, Tokyo, Japan) was used for all patient scans. The machine was set to capture images at the manufacturer’s All patients were positioned in an
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recommended settings of 15-mA and 120-kVp.
upright, seated position, with their head stabilized against a headrest. The technician ensured that the scan was generated in a natural head position by having the patient look
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into his or her own eyes in a mirror directly in front of the machine. Patients were asked
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to close their teeth into occlusion and hold their breath with their tongue to the palate.
EVALUATING SKELETAL AND DENTAL EXPANSION AND RELAPSE From a pilot study, two skeletal measurements and two dental measurements were selected to be used in this study to represent transverse skeletal changes and transverse
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intra-arch dental changes due to their ease of identification and reproducibility (Table 1). The skeletal measurements chosen were the greater palatine superior intercanal width in the axial view to represent the posterior width of the maxilla (posterior skeletal, Figure
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1), and the piriform base width to represent the anterior width (anterior skeletal). The dental measurements selected were the intermolar width of the first molar to represent
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posterior dental change (Figure 2) and the intercanine width to represent anterior dental change. Although these dental landmarks have been used extensively in previous studies to represent maxillary width changes, their use in a CBCT 3D analysis was confirmed statistically for use in our study.
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STATISTICAL ANALYSIS
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In this study, the predictor variable was the operation to manage the transverse discrepancy and is a binary variable grouped as SARPE vs. multi-piece Le Fort I. The primary outcome variables were changes in two skeletal and dental measurements over
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time. Age and gender were not evaluated as separate variables. A Wilcoxon signed-rank test was used to evaluate statistical significance of the reported outcomes values. A
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Wilcoxon two-sample rank-sum test was used to compare the ratio of dentoalveolar to skeletal change in the Le Fort and SARPE groups. All statistical analysis was performed by one investigator (HK) using the SAS system (SAS systems, Cary, NC). P-value