Effect of occlusal vertical dimension changes on postsurgical skeletal changes in a surgery-first approach for skeletal Class III deformities

Early and 1-year postsurgical stability and its factors in patients with complicated skeletal Class Ⅲ malocclusion treated by conventional and surgery-first approach: A prospective cohort study

INTRODUCTION

This study aimed to compare postsurgical stability between conventional (CSA) and surgery-first (SFA) approaches and investigate its prognostic factors in patients with a skeletal Class Ⅲ extraction.

METHODS

Twenty and 19 patients treated with LeFort I osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) with premolar extraction were enrolled in SFA and CSA groups, respectively. Serial cone-beam computed tomography images obtained before surgery, immediately after surgery (T1), 3 months after surgery, and 12 months after surgery were used for 3-dimensional quantitative analysis. The condyle was segmented for analyzing volumetric changes. Repeated measures analysis of variance, independent t test, and chi-square test were used to compare time-course and intergroup differences. Pearson and Kendall correlation and multivariate linear regression analyses were used to explore prognostic factors affecting skeletal stability.

RESULTS

In both CSA and SFA, postsurgical relapse mainly occurred in the mandible sagittal and vertical dimensions and during the first 3 months after surgery. Stability in SFA was significantly less than that in CSA. Intraoperatively, inferolateral condylar displacement with proximal segment inwards, clockwise rotation, and return movements after surgery were observed regardless of the treatment approach. The condylar volume remained stable over time. Multivariate regression analysis showed that posterior vertical dimension (VD) at T1 (-1.63 mm), surgical amount of mandibular setback (-10.33 mm), surgical condylar downwards displacement (-1.28 mm), and anterior overjet at T1 (6.43 mm) were the most important predictors of early mandibular relapse (r2 = 0.593).

CONCLUSIONS

The risk of early relapse could be reduced by controlling the anterior, middle, and posterior constraints provided by the prediction model.

Three-dimensional evaluation of postoperative stability: a comparative study between surgery-first and surgery-late protocols

The main objective of this study was to compare the stability of the surgery-first and surgery-late approaches according to the standardized centre protocols, by three-dimensional evaluation after 1 year of follow-up. A retrospective study was designed that included a test group (surgery-first protocol) and a control group (surgery-late protocol), with a follow-up period of at least 1 year (average 14 months; range 12-24 months). Stability was evaluated using linear and angular measurements by superimposing cone beam computed tomography images obtained at specific points in time: preoperatively, 1 month after surgery, and at the end of the orthodontic treatment. A total of 56 patients with a mean age of 32.2 ± 11.1 years were included in the study. After surgery there were significant changes in all of the measurements in at least one dimension in both groups (except for the transverse maxillary dimension), which remained stable at the end of the treatment, with no statistically significant differences between the two groups. At the 1-year follow-up, both groups presented a SNA angle relapse; this relapse was more significant in the surgery-late group (P = 0.031) and was present only in Class III patients (P = 0.013). In conclusion, an equivalent three-dimensional stability between surgery-first and surgery-late protocols was demonstrated after 1 year of follow-up when eligibility criteria were strictly adhered to.

Comparison of 3-dimensional postoperative dental movement in Class III surgical correction with and without presurgical orthodontic treatment

Background

Surgery-first approach (SFA) is an emerging concept that surgically reposition the jaw bones without presurgical orthodontic treatment phase. The study investigated 3D dental movement in the postoperative orthodontic phase with orthodontic-first (OF) and SFA in orthognathic surgery (OGS).

Methods

This study included consecutive 40 patients (20, SF group; 20, OF group) skeletal Class III who underwent 2-jaw OGS correction. The data of cone-beam computed tomography were acquired at 3 stages with the scan of dental models to replace the dentition of the craniofacial images; at before OGS (T0), 1 week after OGS (T1) and at the completion of treatment (T2). The skeletal changes were obtained by overall superimposition. The post-operative dental movement was measured by 3D regional superimposition between T1 and T2.

Results

There were no significant difference in the postsurgical orthodontic movement in both groups except significant upper and lower molars extrusion by 2 mm in the SF group. Both groups exhibited no significant difference in mandibular stability in sagittal and vertical directions. The amount of extrusion in the molars was correlated with a postoperative sagittal mandibular forward movement. The total treatment duration was significantly shorter 230 days in the SF group.

Conclusion

The completion of the orthodontic treatment after OGS in the SFA was mainly accomplished through molar extrusive movement in both arches. The surgical setup of dental occlusion with 4 mm posterior open bite could be corrected during the postsurgical orthodontics in SFA through molar extrusion. The dental occlusion outcome was no different between OF and SFA.

Postsurgical changes of mandible based on vertical dimension increase in Skeletal Class III deformities

The aim of this study was to evaluate the postsurgical mandibular changes after surgery based on vertical dimension increase in skeletal Class III deformities. Patients who underwent mandibular setback surgery for skeletal Class III malocclusion correction with surgery-first orthognathic treatment were enrolled in the study. Lateral cephalograms were obtained at initial visit, immediately after surgery, 6 months after surgery, and at post-treatment. Postsurgical change of the mandible based on the vertical dimension increase was estimated using a diagrammatic method before surgery and this amount was compared with the actual amount of mandibular forward movement at 6 months after the surgery, using a paired t-test and Bland-Altman plot. Thirty patients (16 men and 14 women; mean age, 22.6 years) with skeletal Class III deformities had undergone mandibular setback surgery with the surgery-first orthognathic treatment. Immediately after surgery, the mandible setback was 9.4 ± 3.7 mm at pogonion. Six months after surgery, the mandible moved forward at an average of 2.3 ± 1.5 mm which corresponded to the estimated value of 2.2 ± 0.9 mm. The estimated amount of postsurgical movement did not show a statistically significant difference from the actual value on paired t-test (p = 0.349). The Bland-Altman analysis showed that the difference between the two values was within the limits of agreement. The postsurgical changes based on vertical dimension increase in surgery-first orthognathic treatment might be predicted by using a diagrammatic method.

Positional changes in the mandibular proximal segment after intraoral vertical ramus osteotomy: Surgery-first approach versus conventional approach

Objective

To compare postoperative positional changes in the mandibular proximal segment between the conventional orthognathic surgery (CS) and the surgery-first approach (SF) using intraoral vertical ramus osteotomy (IVRO) in patients with Class III malocclusion.

Methods

Thirty-eight patients with skeletal Class III malocclusion who underwent bimaxillary surgery were divided into two groups according to the use of preoperative orthodontic treatment CS group (n = 18) and SF group (n = 20). Skeletal changes in both groups were measured using computed tomography before (T0), 2 days after (T1), and 1 year after (T2) the surgery. Three-dimensional (3D) angular changes in the mandibular proximal segment, condylar position, and maxillomandibular landmarks were assessed.

Results

The mean amounts of mandibular setback and maxillary posterior impaction were similar in both groups. At T2, the posterior portion of the mandible moved upward in both groups. In the SF group, the anterior portion of the mandible moved upward by a mean distance of 0.9 ± 1.0 mm, which was statistically significant (p < 0.001). There were significant between-group differences in occlusal changes (p < 0.001) as well as in overjet and overbite. However, there were no significant between-group differences in proximal segment variables.

Conclusions

Despite postoperative occlusal changes, positional changes in the mandibular proximal segment and the position of the condyles were similar between CS and SF, which suggested that SF using IVRO achieved satisfactory postoperative stability. If active physiotherapy is conducted, the proximal segment can be adapted in the physiological position regardless of the occlusal changes.

Facial asymmetry correction: From conventional orthognathic treatment to surgery-first approach

The surgery-first approach (SFA), which proceeds without presurgical orthodontic treatment, is assumed to shorten the treatment course because the direction of post-surgical orthodontic tooth movement conforms to the normal muscular forces. Moreover, the regional acceleratory phenomenon (RAP), evoked by surgery, helps in tooth alignment and compensation in a faster way. Although SFA has definite advantages, especially in class III individuals, there is a lack of data about its indications in patients with facial asymmetry. In this article, we reviewed recently published articles on the treatment of asymmetric patients using the SFA. Different aspects, including the three-dimensional assessment of stability in different planes, approaches for fabrication of a surgical splint, predictability of the results, skills needed for bimaxillary surgery, indications as the treatment of choice for condylar hyperplasia, and combination with distraction osteogenesis in candidates with severe asymmetries were found to be the main topics discussed for patients presenting with facial asymmetry

Surgery-first orthognathic approach: A “scoping review” for mapping outcomes and plausible recommendations to develop core outcome sets

Aims and Objectives

The aim of this scoping review was to identify the type of outcomes measured in surgery- first orthognathic approach (SFOA). The objectives were to classify the outcomes into predetermined domains and explore the degree of representation of each domain. Furthermore, to identify which domains are over- or under-represented and determine whether the findings of this scoping review could be employed to provide a template for core outcome sets (COS). Five outcomes were identified, and all the research pertinent to SFOA were assigned to these outcomes.

Materials and Methods

Electronic databases and additional records were searched from January 2009 to March 2019 to source the data, and 525 records were identified.

Results

The initial database and additional search resulted in 525 records, of which 54 potentially relevant articles were retrieved in full. 35 studies met the selection criteria following screening and were included in the scoping review with the results of the search depicted in the preferred reporting items for systematic reviews and meta-analyses. Domains such as morphological features or changes in maxillofacial skeleton and occlusion (n = 25, 71.42%) and psychosocial well-being including quality of life outcome (n = 8, 22.85%) were well represented while functional status (n = 1, 2.85%), health resource utilization (n = 0), and adverse effects (n = 1, 2.85 %) were under-represented.

Conclusions

Limited research on SFOA precludes development of COS. However, future SFOA clinical trials should consider underrepresented outcome domains to address the SFOA treatment modality comprehensively.

Current status of the surgery-first approach (part I): concepts and orthodontic protocols

The "surgery-first" approach, defined as a team approach between surgeons and orthodontists for orthognathic surgery without preoperative orthodontic treatment, is aimed at dental decompensation. A brief historical background and indications for the surgery-first approach are reviewed. Considering the complicated mechanism of postoperative orthodontic treatment, the proper selection of patients is a vital component of successful surgery-first approach.

Factors Related to Relapse After Mandibular Setback Surgery With Minimal Presurgical Orthodontics

PURPOSE

The aims of this study were to compare the presurgical conditions, surgical changes, and postsurgical changes in patients with skeletal Class III malocclusion with different degrees of horizontal relapse after mandibular setback surgery (MS) with minimal presurgical orthodontics (MPO) and to identify the factors contributing to this relapse.

MATERIALS AND METHODS

For this retrospective study, 33 consecutive patients who underwent MS-MPO were selected. Lateral cephalograms were taken preoperatively (T0), 1 month after surgery (T1), and at orthodontic debonding (T2). Patients were divided into low relapse (LR; n = 18; relapse, <1 mm) and high relapse (HR; n = 15; relapse, >2 mm) groups based on the cephalometric distance of mandibular horizontal relapse. Paired t test, independent t test, and Pearson correlation analysis were used to evaluate surgical (T0 to T1) and postsurgical (T1 to T2) changes in the skeletodental variables and to explore the relation between surgical changes and horizontal relapse.

RESULTS

Compared with the LR group, the HR group exhibited more upward movement with counterclockwise rotation of the mandible from T1 to T2. The HR group presented at T0 with a more prognathic mandible, greater vertical facial height, and a positive overbite. In addition, the HR group presented more posterior movement with clockwise rotation of the mandible, increased overjet, and decreased overbite from T0 to T1. Horizontal relapse of the mandible was positively correlated with the amount of setback and clockwise rotation of the mandible and the change in overjet and was negatively correlated with the change in overbite.

CONCLUSIONS

Mandibular instability was related to the extent of setback and clockwise rotation of the mandible, decreased overbite, and increased overjet during MS-MPO.

Large-Scale Study of Long-Term Vertical Skeletal Stability in a Surgery-First Orthognathic Approach Without Presurgical Orthodontic Treatment: Part II

The surgery-first approach (SFA) is a new paradigm in orthognathic surgery. In our experience over the last 10 years, SFA, particularly for the correction of the class III dentofacial deformity and facial asymmetry, has demonstrated high success rates without any major complications. However, many craniofacial surgeons remain concerned about the skeletal stability of SFA. In the present study, the authors aimed to compare the traditional and SFA with regard to the long-term outcomes of vertical skeletal stability using large-scale data. The authors enrolled patients with skeletal class III dentofacial deformities who had undergone and completed orthognathic surgery between December 2007 and December 2015. The inclusion criteria were based on the presurgical simulation of the dental model, and the authors predicted the potential of the SFA based on this preoperative simulation model. Patients with cleft-related syndromes, and those who had undergone orthognathic surgeries for facial asymmetry or class II deformity were excluded. A total of 104 and 51 class III patients were enrolled in the surgery-first and traditional orthodontics-first groups, respectively. Satisfactory results were achieved in all 155 patients with dentofacial deformity. The initial preoperative measurements of cephalometric analysis, particularly vertical skeletal stability, were similar and well maintained after the procedure in both groups. In conclusion, the SFA without any presurgical orthodontic treatment for correcting dentofacial deformities can achieve similar long-term vertical stability results to the orthodontic treatment-first approach.

Evaluation of Postoperative Mandibular Positional Changes After Mandibular Setback Surgery in a Surgery-First Approach: Isolated Mandibular Surgery Versus Bimaxillary Surgery

PURPOSE

The aim of this study was to compare postoperative positional changes in the mandible after isolated mandibular surgery (IMS) or bimaxillary surgery (BMS) in a surgery-first approach (SFA).

MATERIALS AND METHODS

The authors designed and implemented a retrospective cohort study composed of patients who underwent mandibular setback surgery using the SFA. Surgical and postoperative changes were evaluated using lateral cephalograms taken 1 month before surgery (T0), 1 week after surgery (T1), and immediately after debonding of orthodontic appliances (T2; 16.6 ± 8.7 months after surgery). To predict postoperative mandibular positional changes from the increase in vertical dimension (VD) in surgical occlusion, the mandible was rotated counterclockwise to the preoperative VD on the lateral cephalogram at T1, and resultant mandibular positional changes were measured. To evaluate actual postoperative mandibular positional changes between each time point and compare them between the 2 groups, independent t test, paired t test, and repeated-measures analysis of variance were performed.

RESULTS

Thirty patients were evaluated (16 in IMS group and 14 in BMS group). The 2 groups showed significant time-course mandibular positional changes from T0 to T1 and from T1 to T2 within each group (point B, P < .001), although no statistically significant differences were observed between groups. There was no statistically relevant difference between groups in the predicted and actual postoperative rotational movements. In addition to the mandibular forward movement that resulted from postoperative mandibular counterclockwise rotation, additional horizontal relapse occurred.

CONCLUSION

The present findings suggest that the mandible exhibits notable postoperative forward movement during postoperative orthodontic treatment, regardless of the extent of the orthognathic surgery in the SFA, and it is necessary to consider mandibular forward movement from the VD increase in surgical occlusion and additional relapse during the treatment planning stage.

Qualitative correlation between postoperatively increased vertical dimension and mandibular position in skeletal class III using partial-least-square path modeling

Background

This study constructed a partial-least-square path-modeling (PLS-PM) model and found the pathway by which the postsurgical vertical dimension (VD) affects the extent of the final mandibular setback on the B point at the posttreatment stage for the skeletal class III surgery-first approach (SFA).

Methods

This study re-analyzed the data from the retrospective study by Lee et al. on 40 patients with skeletal class III bimaxillary SFA. Variables were obtained from cone beam computed tomography (CBCT)-generated cephalograms. Authors investigated all variables at each time point to build a PLS-PM model to verify the effect of the VD on the final setback of the mandible.

Results

From PLS-PM, an increase in VD₁₀ was found to decrease the absolute value of the final setback amount of the mandible, which reflects the postsurgical physiological responses to both surgery and orthodontic treatment, which, in turn, can be interpreted as an increase in postoperative mandibular changes.

Conclusions

To resolve the issue of collinear cephalometric data, the present study adopted PLS-PM to assess the orthodontic treatment. From PLS-PM, it was able to summarize the effect of increased postsurgery occlusal vertical dimension on the increased changeability of the B point position at the posttreatment stage.

Postoperative changes in mandibular position after mandibular setback surgery via the surgery-first approach in relation to the increase of vertical dimension and the amount of mandibular setback

OBJECTIVES

This study aimed to compare preoperatively predicted rotational relapse with actual post-treatment mandibular position after mandibular setback surgery via the surgery-first approach and to evaluate the effect of the increase of vertical dimension (VD) on surgical occlusion and the amount of mandibular setback on postoperative mandibular positional changes.

STUDY DESIGN

Twenty-nine patients who underwent bilateral sagittal split ramus osteotomy for mandibular prognathism were evaluated by using lateral cephalograms, which had been obtained preoperatively, immediately postoperatively, and immediately after debonding. Increase of VD on surgical occlusion was measured preoperatively. We estimated the mandibular forward movement resulting from the postoperative mandibular anticlockwise rotation during postoperative orthodontic treatment and compared it with the actual post-treatment mandibular position.

RESULTS

The actual postoperative mandibular forward movement (2.1 mm) was significantly greater compared with the forward movement (1 mm) predicted preoperatively (P < .01). The postoperative mandibular forward movement was greater in the groups with greater VD increase (>1.5 mm) or greater mandibular setback (>10 mm), even though there was no statistically significant difference.

CONCLUSIONS

These results suggest that additional postoperative relapse may occur with mandibular rotational relapse, and VD increase and the amount of mandibular setback may affect post-treatment mandibular position in surgery-first orthodontic treatment.

Comparison of the Stability After Mandibular Setback With Minimal Orthodontics of Class III Patients With Different Facial Types

PURPOSE

Most studies on the surgery-first approach focused on skeletal relapse compared with conventional surgery. The objective of this study was to compare the stability of skeletal Class III patients with 2 different vertical facial types after mandibular setback surgery (MS) with minimal orthodontic preparation (MO).

MATERIALS AND METHODS

In this retrospective study, the patients were recruited from a population that had undergone MS. Consecutive patients were selected based on the following inclusion criteria: skeletal Class III malocclusion with mandibular prognathism, MO without extraction for less than 6 months, and sagittal split ramus osteotomy. The vertical facial types of the patients were classified based on the Frankfort mandibular-plane angle (FMA). Lateral cephalograms were taken at the presurgical stage, at 1 month after surgery (T1), and at the debonding stage (T2). To evaluate surgical changes (T1 - presurgical stage) and relapse (T2 - T1), the linear, angular, and dental measurements were analyzed using a paired t test and an independent t test.

RESULTS

The 26 patients were divided into 2 groups: normal-angle group (n = 14; mean FMA, 23.58°) and high-angle (HA) group (n = 12; mean FMA, 30.26°). From T1 to T2, the normal-angle and HA groups showed significant forward and counterclockwise rotation of the mandible (distance between pogonion and perpendicular line to Frankfort horizontal plane from sella, 1.71 mm and 1.51 mm, respectively; distance between menton and perpendicular line to Frankfort horizontal plane from sella, 1.91 mm and 1.60 mm, respectively; angle between articulare-menton line and Frankfort horizontal plane, -0.55° and -0.89°, respectively). The HA group showed a significant upward movement of the mandible (distance from Frankfort horizontal plane to pogonion, -1.13 mm; distance from Frankfort horizontal plane to menton, -0.78 mm). However, there was no significant difference in the skeletal-dental changes between the 2 groups from T1 to T2.

CONCLUSIONS

The vertical facial types of Class III patients with similar prognathic mandible and dental patterns may not cause any differences in the relapse pattern after MS-MO.