1. Introduction
Cleft lip and palate are the most common congenital craniofacial malformations, with an incidence ranging from 1.0/1000 to 2.2/1000 [1,2]. The prevalence is higher in the Asian population. Patients with cleft lip and palate could develop maxillary hypoplasia owing to intrinsic growth deficiency and extrinsic factors following surgical interventions. The maxillary deficiency causes dental malocclusion, skeletal discrepancy, maxillomandibular asymmetry, or facial disproportion requiring orthognathic surgery (OGS), with an incidence ranging between 9% and 60% [3,4,5,6,7,8].
Traditional design of OGS for the correction of maxillary retrusion in patients with cleft has been LeFort I osteotomy and advancement, aiming to correct the anteroposterior discrepancy. However, patients with cleft could likely have facial asymmetry and disproportion issues in addition to midface retrusion. Because of the improvement in surgical techniquea, safety in general anesthesia, 3-dimensional (3D) imaging simulation, and patient demand of aesthetic outcomes, there has been an increasing use of two-jaw surgery in the surgical plan. It is still controversial whether to plan one-jaw or two-jaw OGS, as each approach has its reasons and concerns [9,10,11,12]. Surgical design could be based on an individual patient’s maxillofacial condition, surgeon’s preference, or operating room facility. It would be ideal to have a prospective clinical study comparing the two approaches, but this is impractical, and the current data are deficient in this regard.
The trend has evolved over the past 40 years in our center, and two-jaw orthognathic surgery becomes the main approach for the correction of maxillofacial deformity in patients with cleft [13]. This study aimed to evaluate a series of consecutive patients with unilateral cleft lip and palate who had received orthognathic surgery and compare the two different designs (one-jaw versus two-jaw) using 3D imaging surgical simulation.
2. Materials and Methods
2.1. Patient Selection
This retrospective study recruited consecutive patients who received orthodontic treatment and orthognathic surgery in the senior authors’ Craniofacial Center from January 2017 through December 2020. Inclusion criteria were patients with complete unilateral cleft lip and palate, having cone-beam computed tomography (CBCT) with 3D surgical simulation, and surgery performed by the senior surgeon (LJL). Exclusion criteria were the presence of traumatic or syndromic craniofacial deformities, reoperated orthognathic surgery, segmental or subapical osteotomy, and incomplete data. In our practice, we did not perform maxillary expansion before the orthognathic surgery. We preferred to do minimal or minor presurgical orthodontic treatment, i.e., modified surgery (first approach). Maxillary expansion, if required, will be performed after the orthognathic surgery by orthodontic methods. Many times, the expansion was required in the cleft-side canine area, rather than the molar area. Fifty-two patients were recruited in the study. All were two-jaw OGS procedures. It must be mentioned that two-jaw surgery was routinely performed for patients with cleft in our center. Eleven patients were excluded because of incomplete data or poor quality of images (6 patients), combining segmental or subapical osteotomy (4 patients) and redo surgery (1 patient), leaving 41 patients eligible for final evaluation. All patients received preoperative and postoperative care in the same multidisciplinary team. The study was approved by the hospital ethical committee (IRB 202100523B0).
In this study, the original two-jaw surgical design was converted into a one-jaw procedure using the virtual surgical planning. LeFort I osteotomy with advancement was achieved keeping the same final occlusion. Comparisons of the maxillary and mandibular positions between the two-jaw and one-jaw surgical designs were performed.
2.2. Surgical Simulation
CBCT images were acquired using the same protocol and scanner (Imaging Sciences International, Hatfield, PA, USA). The data were processed and imported to Dolphin 3D software program (Dolphin Imaging and Management Solutions, Chatsworth, CA, USA) for virtual surgical planning. Digital dental images were integrated and registered with the CBCT model to replace the dentition [14]. The workflow of computer-assisted surgical planning was described in more detail in previous studies [15,16].
2.3. Two-Jaw Surgical Simulation
Two-jaw surgery was the original surgical plan in this study cohort. LeFort I and bilateral sagittal split osteotomy (BSSO) were performed in the 3D images. The mandibular segment was moved to match the maxillary segment according to the setup final occlusion, forming the maxillomandibular complex (MMC). The MMC was moved and rotated to achieve an ideal facial profile, with adequate facial symmetry, midline, occlusal plane, and no bony collision in the ramus [15,16]. Genioplasty was performed as needed (Figure 1).
2.4. One-Jaw Surgical Simulation
The original two-jaw surgical simulation was converted to one-jaw. Using the same final occlusion, LeFort I osteotomy was performed and advanced to match the mandible. The mandible did not receive ramus osteotomy and remained in its original position without movement (Figure 1). In the other way, the MMC was repositioned so that the mandible returned to its original location by using the software.
2.5. The 3D Cephalometric Measurement
The preoperative (T0), one-jaw, and two-jaw simulation images were exported as STL files and imported to Simplant O&O software (Materialize, Leuven, Belgium) for landmark location and 3D cephalometric measurement (Table 1). All landmarks were identified by the same investigator. Three reference planes were defined. Frankfort horizontal plane (FHP) was the plane passing through bilateral orbitales and the midpoint between the right and left portions. The midsagittal plane (MSP) was the plane passing through nasion and basion and perpendicular to FHP. The coronal plane was the plane passing through nasion and perpendicular to FHP and MSP. After landmark identification, the 3D linear and angular measurements were calculated. Comparisons of cephalometric measurement were conducted among T0, one-jaw, two-jaw designs, as well as normative Taiwanese data [17]. For further investigation in the one-jaw surgical simulation, the samples were divided into large advancement design (more than 6 mm) and regular advancement design (6 mm or less) according to the amount of maxillary movement.
2.6. Asymmetry Index (ASI)
The distance from each landmark to the three reference planes was defined as dx, dy, and dz. To assess the degree of facial skeletal asymmetry, the difference between the bilateral landmarks relative to each reference plane was calculated using the asymmetry index [18,19,20] with the following equation:
For the midline landmarks, only dx was calculated with the following equation:
ASI indicated the degree of asymmetry between right and left paired landmarks. A higher ASI value showed more asymmetry. A zero ASI indicated perfect symmetry between the bilateral paired landmarks, or the midline landmarks located in the midsagittal plane.
2.7. Statistical Analysis
To assess intra-observer variability and reproducibility, 10 subjects were randomly selected for repeated tests. Landmark location and measurement were performed at a two-week interval. The intra-observer reproducibility was tested by Bland–Altman analysis. Measurement errors were calculated by the Euclidean distance using the following formula:
Δx, Δy, and Δz were the differences between the first and second landmarks in the X, Y, and Z coordinates.
The T0 was compared with normative Taiwanese data using an independent t-test. The Spearman correlation coefficient was first used to calculate the correlation between one-jaw and two-jaw designs. The p value less than 0.05 indicated that the correlation between two designs was high. Then, the paired or independent t-test was accordingly selected to examine the differences in 3D cephalometric measurements and ASI between the one-jaw and two-jaw designs. A p value of 0.05 was considered statistically significant. Statistical analyses were performed using SPSS software (SPSS Statistics for Windows, Version 17.0., SPSS Inc., Chicago, IL, USA).
3. Results
All subjects had complete unilateral cleft lip and palate (UCLP) (21 were males and 23 were left side) with a mean age of 18.5 years, ranging from 15.3 to 25.7 years. Average period of preoperative orthodontic treatment was 8.8 months. The intra-observer agreement showed excellent reliability and reproducibility in the repeated measurements (Figure 2). The mean and standard deviations of these intrarater differences were 0.0025 and 0.2360, respectively.
3.1. The 3D Cephalometric Measurements of T0 Stage
Table 2 presents the linear and angular 3D cephalometric measurements of T0 stage, and the comparisons with the Taiwanese norms in which data gender differences were not found. SNA, ANB, and A-N perpendicular were significantly smaller than norms (p < 0.01). There were no significant differences between the patients with UCLP and normal population on SNB and Pog-N perpendicular (p > 0.05). All five midline landmarks (ANS, A, Me, U1, and L1) presented a significant deviation in relation to MSP in T0 stage (p < 0.01).
3.2. Comparisons between One-Jaw and Two-Jaw Designs
Table 3 presents the cephalometric measurements of one-jaw and two-jaw designs. SNA and SNB in the two-jaw design showed significantly smaller angles than those in norms and one-jaw designs. There was no significant difference in terms of ANB angle between one-jaw and two-jaw designs. The distance of A point to the N-perpendicular plane in one-jaw design was 2.66 mm larger than the two-jaw design (p < 0.01). In contrast, the Pog point in the two-jaw design is not significantly lower than the one-jaw design. Anterior and posterior occlusal plane cants in the two-jaw design were significantly improved by 1.54 and 1.58 degrees than the one-jaw design (p < 0.01). The posterior dental cant (between both first molars) was less than 1 degree in the two-jaw approach. The midline discrepancy was measured as the absolute value of the distance from the midsagittal plane. All four midline landmarks (A, Me, U1, and L1) in the one-jaw design were located significantly away from midsagittal plane compared to those in the two-jaw design. The ANS was constantly deviated from the midsagittal line in patients with a unilateral cleft lip and palate. The deviation is shown in Table 2. The ANS was also frequently burred during orthognathic surgery in our practice. Therefore, we did not use ANS as a midline landmark in the simulation as well as the assessment.
3.3. Larger versus Regular Maxillary Advancement in the One-Jaw Simulation
Advancement of 6 mm was set as the dividing distance in the one-jaw plan. Twenty-six patients (63%) needed larger maxillary advancement and 15 patients (37%) needed regular advancement in the one-jaw virtual surgical plan. In patients with larger maxillary advancement in the one-jaw plan, the two-jaw approach had significantly lower SNA, SNB, and A-N perpendicular data compared to the one-jaw plan (p < 0.01), but the ANB angle was not significantly different. However, in the regular maxillary advancement design, there was no significant difference in terms of SNA and A-N perpendicular between one-jaw and two-jaw surgery plans, but ANB angle in the two-jaw surgery was significantly larger than the one-jaw surgery by 3.28 degrees (p < 0.01) (Table 4).
3.4. Asymmetry Index
The ASI values of maxillary and mandibular landmarks in each design are shown in Table 5. The ASI of all maxillary landmarks was significantly larger in the one-jaw design compared to T0 and two-jaw designs (except for U1), indicating more asymmetry after surgery. ASI of all maxillary and mandibular landmarks in the two-jaw design were significantly improved compared to those in the one-jaw design.
4. Discussion
Cleft lip and palate are the most common congenital craniofacial anomaly. One of the common problems is midfacial retrusion owing to maxillary hypoplasia, which needs to be addressed after skeletal maturity. With the mandible in a relative prognathic position, patients have a class III facial profile. Orthognathic surgery serves as a definitive approach to rehabilitate function and esthetics [3,6]. Traditionally, a single-jaw LeFort I osteotomy with advancement was performed for the skeletal discrepancy, accepting that the mandible was generally in the correct anteroposterior position in order to avoid setting the mandible back [5]. However, orthognathic surgery for patients with cleft is more challenging due to scarring in orofacial tissues, less predictable vascular supply, inadequate tissue quality, and poor dental occlusion [21,22]. Compared to the cephalometric norms, SNA and A-N perpendicular of the subjects were significantly smaller, indicating prominent maxillary retrusion (Table 2). It is expected that the single movement of maxillary advancement could be more difficult.
For comparison of one-jaw and two-jaw designs, SNA, SNB, and A-N perpendicular were significantly smaller in the two-jaw design due to simultaneous mandible setback and clockwise pitch rotation of the maxillomandibular complex. The simulation after two-jaw surgery revealed a relatively bimaxillary retrusive facial profile as compared to the result with one-jaw surgery. However, Pog-N perpendicular was not significantly different because 31 out of 41 subjects received genioplasty in the two-jaw surgery (Table 3).
In this computer-assisted surgical simulation study, the occlusal set-up of one-jaw and two-jaw was identical. The final occlusion of all cases was set up by the same orthodontist in this study cohort. Overjet and overbite were set up at 2 mm with upper and lower dental midline coincidence. To achieve stable postoperative occlusion, the movement of maxilla was restricted by mandible and dental occlusion in the one-jaw surgery. Therefore, the occlusal plane cannot be adjusted without a mandibular osteotomy. Both anterior and posterior occlusal plane cants of the two-jaw design were superior to the one-jaw design. However, in clinical practice, we try to level the posterior dental cant but do not intend to make it 0 degrees, but rather coordinate with other parameters for symmetric and harmonious positioning of the maxillomandibular complex. The posterior dental cant was revealed in the range of −0.88–2.68, matching our clinical purpose (Table 3). For the same reason, the midline was easier to align by moving and rotating the maxillomandibular complex. Hence, the anatomic landmarks were more significantly centered and symmetric when undertaking the two-jaw surgery (Table 3).
A large amount of maxillary advancement could cause problems such as postoperative instability, a high relapse rate, velopharyngeal insufficiency, or inadequate blood supply. The limitation of LeFort I maxillary advancement was suggested as 10 mm for non-cleft patients, but the amount was advised to be conservative and no more than 6 mm in patients with cleft [23,24,25,26,27,28]. It was suggested that if the maxillomandibular discrepancy was more than 6 mm, bone graft, a combined mandibular setback osteotomy or distraction osteogenesis should be considered. In the present study, the maxilla was advanced by an average of 7.46 mm in the one-jaw design and 4.80 mm in the two-jaw design, respectively (Table 2 and Table 3, A-N perpendicular). Two-jaw surgery with mandibular setback compensated for the amount of maxillary advancement by an average of 2.66 mm. When completing one-jaw surgery, 26 patients (63%) needed maxillary advancement of more than 6 mm which was an unfavorable condition causing possible relapse (Table 4). Only 15 patients (37%) with moderate maxillary advancement were suitable and qualified for one-jaw surgery design for the correction of anteroposterior discrepancy in this study cohort. Although the regular amount of maxillary advancement was adequate to achieve positive overjet and acceptable occlusion, the skeletal relationship was still a prognathic profile with a mean ANB angle 0.25° (Table 4). Patients would complain of inadequate correction of facial appearance in our practice. By completing the two-jaw surgery, the maxillomandibular complex was allowed to rotate clockwise in the pitch direction in order to increase the ANB angle with A point forward and B point backward in order to achieve skeletal class I appearance with a better facial profile. An average gain of 3.28° (0.25°–3.53°) in ANB angle by the clockwise rotation was achieved in the present study (Table 4). Therefore, the mandibular setback osteotomy was not only able to compensate for the amount of maxillary advancement, but also to improve the jaw relationship by the clockwise rotation in cases of minor sagittal discrepancy (Figure 3).
Patients with a unilateral cleft lip and palate tend to have a more asymmetrical face compared to the normal population, not only showing in the nasomaxillary region, but also in the lower facial skeleton [20,29,30,31]. It is consistent with the results of this study that both maxillary and mandibular midline landmarks were significantly deviated from the midsagittal plane compared to norms (Table 2). The deviation and asymmetry could only be improved by the two-jaw approach but not the one-jaw surgery (Table 3). The asymmetry index (ASI) was first proposed for assessing right and left ramal height symmetry in 2-dimensional orthopantomograms [18]. ASI was then used to evaluate the extent of 3-dimensional asymmetry of facial skeletons [19,32], and applied in cleft orthognathic surgery planning [20]. The present study showed that in comparison with ASI, the two-jaw design obtained more symmetry in both the maxilla and mandible (Figure 1). By undertaking a two-jaw surgery, the U1 in the maxilla and all midline landmarks in the mandible were significantly improved (Table 5). In the one-jaw OGS simulation, the maxillary symmetry could get worse, and the mandibular asymmetry remained the same (Table 5). The results indicated that the two-jaw surgery could more likely achieve facial symmetry and balance, particularly in the lower part of the face [20].
The surgical design of cleft OGS is based on the patient’s deformity, surgeon’s preference and training background. In the literature review, Table 6 shows that the rate of one-jaw or two-jaw surgery varied among different institutions, ranging from 12% to 100% for two-jaw surgery. From 2017 to 2020, all patients with a unilateral cleft lip and palate received two-jaw orthognathic surgery in our center. An important reason for such a high rate of two-jaw cleft OGS was the application of 3D imaging and virtual surgery planning, which accurately detected bony abnormalities to achieve symmetry in the simulation [33]. Mandibular yaw rotation to avoid ramus bony collision and attain cheek symmetry was conveniently achieved in the two-jaw surgery planning (Figure 4). More than 98% of patients with cleft received two-jaw orthognathic surgery when it was indicated. This paradigm shift was mentioned in our previous publications, with the more reasons than facial symmetry, but also including other facial aesthetic purposes, such as smile arc. It is the center’s treatment preference and could be a bias. However, for the discrepancies that remain after the one-jaw surgery, there is the possibility of orthodontic correction with temporary anchorage devices which can correct the occlusal cantus and midline discrepancies for the unoperated maxilla. It is believed that with the right collaboration, some of the cases which were two-jaw surgery at the first glance can be resolved with only one-jaw surgery if temporary anchorage devices are placed. The occlusal plane can also be adjusted by maxillary molar intrusion.
Ethnic differences should be considered in designing the cleft OGS. It is noted that Asians have a higher incidence of Angle class III malocclusion and a relatively large mandible compared to maxilla and cranial base [34,35]. It is, therefore, favorable and popular to include mandibular setback and rotation in the cleft OGS [36,37,38]. Possible drawbacks from the addition of mandibular osteotomy should also be concerned. These included longer operative time, infection, blood loss, and chin numbness. With preoperative imaging of the inferior alveolar nerves and careful performance of the ramus split osteotomy, the neurosensory disturbance should be kept to a minimum [39,40]. Airway decrease by mandibular setback was reported and should be cautioned in patients with breathing problems [41,42]. However, the improvement in sleep apnea and snoring without airway-related problems was also described [43,44]. This is consistent with our clinical experience.
Table 6The incidence of one-jaw and two-jaw cleft orthognathic surgery in different institutions.
| Author Year | Country | Patient Number | One-Jaw Surgery (LeFort I) | Two-Jaw Surgery |
|---|---|---|---|---|
| Posnick et al., 1996 [45] | USA | 116 | 72.4% | 27.6% |
| Iannetti et al., 2004 [46] | Italy | 93 | 40.0% | 60.0% |
| Chong et al., 2009 [47] | USA | 103 | 50.5% | 49.5% |
| Broome et al., 2010 [48] | Switzerland | 58 | 84.5% | 15.5% |
| Watts et al., 2014 [49] | Canada | 30 | 46.7% | 53.3% |
| Fahradyan et al., 2018 [50] | USA | 136 | 46.3% | 53.7% |
| Impieri et al., 2018 [51] | Norway | 47 | 63.8% | 36.2% |
| Marion et al., 2019 [52] | France | 54 | 68.5% | 31.5% |
| Yatabe-Ioshida et al., 2019 [44] | Brazil | 9 | 22.2% | 77.8% |
| Chung et al., 2019 [53] | Korea | 44 | 0% | 100% |
| Hwang et al., 2019 [22] | Korea | 17 | 0% | 100% |
| Harjunpää et al., 2019 [54] | Finland | 93 | 74.2% | 25.8% |
| Wang et al., 2020 [55] | China | 90 | 52.2% | 47.8% |
| Wangsrimongkol et al., 2021 [56] | USA | 73 | 88.0% | 12.0% |
The limitations in this study were the retrospective nature and the virtual surgical planning without looking at the actual postoperative outcome between the two designs. As satisfactory translation of the 3D plan to the operating theater has been confirmed in the previous reports, the extended outcome assessment between one-jaw and two-jaw cleft OGS appeared to be unimportant in this report. The final dental occlusion was set and applied in both study designs of one-jaw and two-jaw surgery. In actual clinical practice, the final occlusion could be modified in order to obtain a better maxillomandibular relationship for the movement in virtual planning, as the patients with cleft might have dental deficiency and irregularity. One should carefully interpret the data in this study. A routine two-jaw OGS planning for patients with cleft is not advocated. The patient’s deformity, expectation, and surgeon’s preference should be considered. The planning is best undertaken by the multidisciplinary team.
Y.-H.T. was responsible for data collection, analysis, and writing manuscript. B.C.J.P. was responsible for setting up final occlusion in the study patients. H.-H.L. was in charge of the image measurement and data analysis. C.-T.H. supervised the measurement and data analysis. L.-J.L. was responsible for analysis and editing of the manuscript. All authors have read and agreed to the published version of the manuscript.
The Institutional Review Board of Chang Gung Foundation (IRB 202100523B0) approved this study.
Informed consent was obtained from all subjects involved in the study.
We would like to thank Ping-Hsuan Huang, Center for Big Data Analytics and Statistics, Chang Gung Memorial Hospital, for statistical consultation. This study was supported by grants from Chang Gung Memorial Hospital (CMRPG3K0981 and CMRPG3L0351).
The authors declare no conflict of interest.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Enlarge this image.Figure 1. A case with left cleft lip and palate showing the frontal, lateral, and basal views of 3D surgical simulation using Dolphin 3D software. (Left) Preoperative 3D cephalometric images showing skeletal class III (SNA:80.51°, SNB: 84.78°, ANB: −4.26°), occlusal plane cant (U6R-FH plane: 48.47 mm, U6L-FH plane: 44.72 mm), and chin deviation (Pog deviation of 4.75 mm toward the left side). (Middle) One-jaw surgical plan with maxillary advancement alone. A point of maxilla was advanced 7.24 mm. Skeletal class I was achieved (ANB: 3.11°) without correction of the occlusal plane cant and chin deviation. (Right) Two-jaw surgical plan with a combination of maxillary advancement and mandibular setback osteotomy and rotation. Skeletal class I was achieved by A point advancement of 2.43 mm, B point setback of 8.99 mm, and clockwise (pitch) rotation of 7.69°. Roll rotation (−3°) and yaw rotation (5°) were applied to avoid bony collision and to correct the occlusal plane cant and chin deviation.
Enlarge this image.Figure 2. The Bland–Altman plot showing adequate intra-observer reproducibility (n = 540).
Enlarge this image.Figure 3. A case in the regular advancement design showed that the jaw relationship was improved by the clockwise rotation of the maxillomandibular complex. (Left) Preoperative image showing that ANB was −5.26°. (Middle) In one-jaw surgical simulation, the maxilla was advanced 4.63 mm following Le Fort I osteotomy. The skeletal class III jaw relationship was not fully corrected with the ANB angle of 0.11°. (Right) A skeletal class I jaw relationship with an ANB angle of 3.57° was achieved following two-jaw surgery with the clockwise rotation of the maxillomandibular complex.
Enlarge this image.Figure 4. The same case as in Figure 1 demonstrated roll and yaw rotations of the maxillomandibular complex for asymmetry correction in two-jaw surgical planning. (A) Occlusal plane and chin deviation were improved after clockwise rotation in the roll direction. (B) Elimination of residual asymmetry of contour and interference between the osteotomized bony segments by counterclockwise rotation of the maxillomandibular complex in the yaw direction. As a result, the advancement in the LeFort I level was 1.50 mm in the right piriform and 5.07 mm in the left piriform.
Definition of the three-dimensional skeletal landmarks, angle and reference planes.
| Landmark | Definition |
|---|---|
| Basion (Ba) | The most anterior point of the great foramen (foramen magnum). |
| Nasion (N) | The midpoint of the frontonasal sutures. |
| Sella (S) | The center of the hypophyseal fossa (sella turcica). |
| Porion (Po) | The most superior point of each external acoustic meatus. |
| Orbitale (Or) | The most inferior point of each infra-orbital rim. |
| Anterior nasal spine (ANS) | The most anterior midpoint of the anterior nasal spine of the maxilla. |
| A point (A) | The point of maximum concavity in the mid-line of the alveolar process of the maxilla. |
| B point (B) | The point of maximum concavity in the mid-line of the alveolar process of the mandible. |
| Pogonion (Pog) | The most anterior midpoint of the chin on the outline of the mandibular symphysis. |
| Menton (Me) | The most inferior midpoint of the chin on the outline of the mandibular symphysis. |
| Gonion (Go) | Dropping a perpendicular from the intersection point of the tangent lines to the posterior margin of the mandibular vertical ramus and inferior margin of the mandibular body or horizontal ramus. |
| Upper incisors (U1) | The midpoint between the crowns of the maxillary central incisors. |
| Lower incisors (L1) | The midpoint between the crowns of the mandibular central incisors. |
| Upper canine (U3R/L) | The cusp tip of the maxillary canine on the right/left side. |
| Lower canine (L3R/L) | The cusp tip of the mandibular canine on the right/left side. |
| Upper first molar (U6R/L) | The mesio-buccal cusp of the maxillary first molar on the right/left side. |
| Lower first molar (L6R/L) | The mesio-buccal cusp of the mandibular first molar on the right/left side. |
| Anterior occlusal cant | Angle between the line of canines and Frankfort horizontal plane. |
| Posterior occlusal cant |
Angle between the line of first molars and Frankfort horizontal plane. |
The 3D cephalometric measurements of the preoperative image (T0 stage) and the comparisons with normative data.
| Parameters | T0 Stage | Norms | p Value | ||
|---|---|---|---|---|---|
| Mean | SD | Mean | SD | ||
| SNA | 75.90 | 4.32 | 83.22 | 2.95 | 0.000 ** |
| SNB | 80.44 | 4.70 | 80.02 | 3.24 | 0.768 |
| ANB | −4.72 | 4.10 | 3.34 | 1.56 | 0.000 ** |
| A-N perpendicular | −4.98 | 3.47 | 1.10 | 2.66 | 0.000 ** |
| Pog-N perpendicular | −0.11 | 7.36 | −3.10 | 6.50 | 0.462 |
| SN/MP | 35.30 | 7.42 | 33.63 | 5.11 | 0.639 |
| The midline discrepancy | |||||
| ANS | 2.87 | 2.09 | 0.73 | 0.50 | 0.000 ** |
| A | 1.57 | 1.99 | 0.67 | 0.43 | 0.000 ** |
| Me | 2.58 | 2.99 | 0.92 | 0.42 | 0.000 ** |
| U1 | 3.01 | 2.97 | 0.59 | 0.26 | 0.000 ** |
| L1 | 2.16 | 2.76 | 0.47 | 0.24 | 0.000 ** |
** p < 0.01.
The 3D cephalometric measurements of one-jaw and two-jaw designs.
| Parameters | One-Jaw | Two-Jaw | One-Jaw vs. Two-Jaw | ||
|---|---|---|---|---|---|
| Mean | SD | Mean | SD | p Value | |
| SNA | 83.48 | 5.25 | 80.79 | 3.61 | 0.000 ** |
| SNB | 80.44 | 4.70 | 77.57 | 3.45 | 0.000 ** |
| ANB | 3.12 | 4.22 | 3.37 | 3.44 | 0.706 |
| A-N perpendicular | 2.48 | 4.32 | −0.18 | 3.04 | 0.000 ** |
| Pog-N perpendicular | −0.11 | 7.36 | −1.76 | 4.28 | 0.099 |
| Anterior cant | 4.64 | 3.80 | 3.10 | 2.67 | 0.000 ** |
| Posterior cant | 2.48 | 1.81 | 0.90 | 0.89 | 0.000 ** |
| The midline discrepancy | |||||
| A | 2.27 | 1.60 | 1.75 | 1.19 | 0.039 * |
| Me | 2.52 | 2.20 | 1.51 | 1.01 | 0.012 * |
| U1 | 2.77 | 2.20 | 1.37 | 1.41 | 0.001 ** |
| L1 | 2.16 | 1.88 | 1.45 | 1.06 | 0.038 * |
* p < 0.05. ** p < 0.01.
The 3D cephalometric measurements in the larger (more than 6 mm) and regular (6 mm or less) advancement designs.
| Parameters | One-Jaw | Two-Jaw | One-Jaw vs. Two-Jaw | ||
|---|---|---|---|---|---|
| Mean | SD | Mean | SD | p Value | |
| Larger advancement (n = 26) | |||||
| SNA | 85.23 | 4.25 | 80.68 | 2.95 | 0.000 ** |
| SNB | 80.83 | 4.86 | 77.73 | 3.67 | 0.000 ** |
| ANB | 4.67 | 3.41 | 3.20 | 3.12 | 0.050 |
| A-N perpendicular | 3.88 | 3.94 | −0.66 | 2.85 | 0.000 ** |
| Pog-N perpendicular | −0.13 | 8.42 | −1.90 | 4.36 | 0.188 |
| Regular advancement (n = 15) | |||||
| SNA | 80.41 | 5.77 | 80.99 | 4.82 | 0.316 |
| SNB | 79.91 | 4.64 | 77.73 | 3.21 | 0.007 ** |
| ANB | 0.25 | 4.34 | 3.53 | 4.15 | 0.004 ** |
| A-N perpendicular | 0.05 | 4.13 | 0.67 | 3.38 | 0.236 |
| Pog-N perpendicular | 0.14 | 5.42 | −1.32 | 4.94 | 0.441 |
** p < 0.01.
Asymmetry index of T0 group, one-jaw design, and two-jaw design.
| Landmarks | T0 | One-Jaw | Two-Jaw | T0 vs. One-Jaw | T0 vs. Two-Jaw | One-Jaw vs. Two-Jaw | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SD | Mean | SD | Mean | SD | p Value | p Value | p Value | ||
| Maxilla | ||||||||||
| A | 1.58 | 1.19 | 2.27 | 1.60 | 1.75 | 1.19 | 0.010 * | 0.497 | 0.039 * | |
| U1 | 3.06 | 1.90 | 2.77 | 2.20 | 1.37 | 1.41 | 0.299 | 0.000 * | 0.001 * | |
| U3 | 6.28 | 3.87 | 7.68 | 3.73 | 6.53 | 3.87 | 0.013 * | 0.628 | 0.027 * | |
| U6 | 4.36 | 2.05 | 6.40 | 3.55 | 4.98 | 2.94 | 0.000 ** | 0.176 | 0.000 ** | |
| Mandible | ||||||||||
| B | 2.30 | 2.09 | 2.30 | 2.09 | 1.34 | 1.15 | NS | 0.004 ** | 0.012 * | |
| Pog | 2.50 | 2.14 | 2.50 | 2.14 | 1.57 | 1.10 | NS | 0.016 * | 0.017 * | |
| Me | 2.52 | 2.20 | 2.52 | 2.20 | 1.51 | 1.01 | NS | 0.011 * | 0.009 ** | |
| L1 | 2.16 | 1.88 | 2.16 | 1.88 | 1.45 | 1.06 | NS | 0.031 * | 0.038 * | |
| L3 | 5.13 | 3.42 | 5.13 | 3.42 | 3.92 | 2.22 | NS | 0.038 * | 0.038 * | |
| L6 | 4.92 | 3.28 | 4.92 | 3.28 | 3.29 | 1.83 | NS | 0.001 ** | 0.001 ** | |
* p < 0.05; ** p < 0.01; NS, no significant difference.
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1 Department of Dentistry, Fu-Jen Catholic University Hospital, New Taipei 242, Taiwan;
2 Craniofacial Orthodontics, Department of Dentistry, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan;
3 Craniofacial Research Center, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan 333, Taiwan
4 Plastic & Reconstructive Surgery, and Craniofacial Research Center, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan 333, Taiwan