Is skeletal stability after bimaxillary surgery for skeletal class III deformity related to surgical occlusal contact?

The surgery-first approach for orthognathic correction of maxillary deficiency-is it stable? Three-dimensional assessment of CBCT scans and digital dental models

The aim of this study was to determine the skeletal stability of Le Fort I maxillary advancement following the surgery-first approach, by three-dimensional (3D) assessment of cone beam computed tomography (CBCT) scans and digital dental models. CBCT scans of 25 class III patients obtained 1 week preoperatively (T0) and 1 week (T1) and 6 months (T2) postoperatively were superimposed to measure surgical movements (T0-T1) and skeletal relapse (T1-T2). The distorted dentition of the CBCT scans at T1 was replaced with 3D images of the dental models to assess the postoperative occlusion. Surgical movements of the maxilla (mean ± standard deviation values) were 6.79 ± 2.30 mm advancement, 1.28 ± 1.09 mm vertically, and 0.71 ± 0.79 mm mediolaterally. Horizontal rotation (yaw) was 1.56° ± 1.21°, vertical rotation (pitch) 1.86° ± 1.88°, and tilting (roll) 1.63° ± 1.54°. At T2, the posterior relapse was 0.72 ± 0.43 mm (P = 0.001) and relapse in pitch was 1.56° ± 1.42° (P = 0.007). There was no correlation between the size of the surgical movements and the amount of relapse. A weak correlation was noted between the number of teeth in occlusal contact immediately following surgery and relapse of maxillary roll (r = - 0.434, P = 0.030). The stability of maxillary advancement with the surgery-first approach was satisfactory and was not correlated with the quality of the immediate postoperative occlusion.

Three-dimensional evaluation of skeletal stability after surgery-first bimaxillary surgery for class III asymmetry in 70 consecutive patients

Background/purpose

Skeletal stability after orthognathic surgery is essential for positive treatment outcome. This study evaluated the stability of osteotomy segments after surgery-first bimaxillary surgery for class III asymmetry.

Materials and methods

Seventy adults with class III asymmetry consecutively corrected through surgery-first Le Fort I and bilateral sagittal split osteotomies were investigated. Cone-beam computed tomography before treatment (T0), 1-week after surgery (T1), and after all treatment (T2, ≥1-year after surgery) was used to assess surgical movement (T0 to T1) and skeletal stability (T1 to T2) regarding the translation and rotation of the maxillary, mandibular distal, and proximal segments.

Results

At T1, the maxillary segment had moved forward and upward, turned to the deviated side, and rotated downward (all P < 0.01). The distal segment of mandible had moved forward and upward and rotated upward (all P < 0.001). The deviated proximal segment had moved upward, tilted to the opposite side, and rotated upward (all P < 0.001). The opposite proximal segment had moved upward and tilted to the deviated side (both P < 0.01). At T2, significant relapse occurred in the mandible. The distal segment moved forward and upward and rotated upward (all P < 0.001). The deviated proximal segment moved upward, tilted to the opposite side, and rotated upward (all P < 0.001). The opposite proximal segment moved upward and tilted to the deviated side (both P < 0.01).

Conclusion

Clinically significant relapse of class III asymmetry was discovered on the mandibular distal and opposite proximal segments.

A New Approach to Virtual Occlusion in Orthognathic Surgery Planning Using Mixed Reality-A Technical Note and Review of the Literature

Orthognathic surgery plays a vital role in correcting various skeletal discrepancies of the maxillofacial region. Achieving optimal occlusion is a fundamental aspect of orthognathic surgery planning, as it directly influences postoperative outcomes and patient satisfaction. Traditional methods for setting final occlusion involve the use of dental casts which are time-consuming, prone to errors and cannot be easily shared among collaborating specialties. In recent years, advancements in digital technology have introduced innovative approaches, such as virtual occlusion, which may offer enhanced accuracy and efficiency in orthognathic surgery planning. Furthermore, the emergence of mixed reality devices and their 3D visualization capabilities have brought about novel benefits in the medical field, particularly in computer-assisted planning. This paper presents for the first time a prototype tool for setting virtual occlusion during orthognathic surgery planning using mixed reality technology. A complete walkthrough of the workflow is presented including an explanation of the implicit advantages of this novel tool. The new approach to defining virtual occlusion is set into context with other published methods of virtual occlusion setting, discussing advantages and limitations as well as concepts of surgical occlusion for orthognathic surgery.

Impact of the lateral skeletal stability following bilateral sagittal split ramus osteotomy for mandibular asymmetry

This study evaluated the stability of bilateral sagittal split ramus osteotomy (BSSRO) associated with positional plagiocephaly and temporal and masseter muscles using posteroanterior cephalogram analysis and three-dimensional computed tomography (3D-CT). This retrospective cohort study included 31 patients who underwent BSSRO for mandibular asymmetry. The cranial vault asymmetry index (CVAI) and the cephalic index were used as indicators of positional plagiocephaly. The distance from the vertical reference line to the menton (Me) was measured on posteroanterior cephalograms immediately and 1 year after surgery, and postoperative stability was assessed. Temporal and masseter muscles were constructed from 3D-CT data and their volumes were measured. Simple regression analysis showed a significant correlation between postoperative changes in the vertical reference line to the Me and the CVAI (R = 0.56, p = 0.001), the amount of surgical movement in the vertical reference line to the Me (R = 0.41, p = 0.023), and the variable temporal muscle volume (R = 0.27, p = 0.028). There was no significant correlation between postoperative changes in the vertical reference line to the Me and the cephalic index (R = 0.093, p = 0.62) and variable masseter muscle volume (R = 0.16, p = 0.38). According to multivariate analysis, CVAI (p = 0.003) and amount of surgical movement in the vertical reference line to the Me (p = 0.014) were significant predictors of postoperative change in the vertical reference line to the Me. Positional plagiocephaly and amount of surgical movement influence lateral skeletal stability following BSSRO for mandibular asymmetry.

Comparison of regional soft tissue changes after bimaxillary rotational surgery between class III deformity with overbite and open bite: A 3D imaging analysis

BACKGROUND

This prospective study aimed to compare regional soft tissue changes between patients with class III overbite and open bite deformities treated with bimaxillary surgery involving clockwise and counter-clockwise mandibular setback, respectively.

MATERIAL AND METHODS

Class III deformity adults receiving Le Fort I and bilateral sagittal split osteotomies were grouped according to the incisal occlusion: overbite (n = 30) and open bite (n = 30). Combined cone-beam CT scans and 3D facial photographs preoperative and at least 1-year postoperative were taken to assess the soft tissue changes.

RESULTS

Postoperative changes for the overbite and open bite groups included anterior repositioning of nose (-0.8 ± 1.2 mm and -1.1 ± 1.1 mm, respectively) and cheek (-1.9 ± 1.3 mm and -1.7 ± 2.6 mm, respectively), posterior repositioning of chin (5.2 ± 4.0 mm and 4.9 ± 3.2 mm, respectively), and medial (-1.7 ± 2.0 mm and -1.9 ± 2.1 mm, respectively) and posterior (2.7 ± 1.4 mm and 2.8 ± 2.3 mm, respectively) repositioning of bilateral angles. Posterior (1.2 ± 2.0 mm and 5.1 ± 3.3 mm) and inferior (-1.4 ± 2.2 mm and -2.4 ± 2.7 mm) repositioning of upper lip and lower lip occurred in overbite group. Inferior (-2.3 ± 2.4 mm) and superior (3.7 ± 3.4 mm) repositioning of chin occurred in the overbite and open bite groups, respectively.

CONCLUSIONS

Treatment of class III overbite and open bite deformities with bimaxillary rotational surgery resulted in comparable regional soft tissue changes, except for upper lip, lower lip and chin.

The effect of lateral bone cut end on the patterns of the lingual split during BSSO in patients with skeletal class III malocclusion

This study examines the effect of the lateral bone cut end (LBCE) on the pattern of lingual split during bilateral sagittal split osteotomy (BSSO) in patients with skeletal class III malocclusion. A case-control study according to the pattern of the sagittal split osteotomy (SSO) lingual split line was conducted in patients who underwent BSSO. The primary predictor variable was the ratio of the LBCE. The primary outcome variable was the type of lingual fracture line classified according to the lingual split scale (LSS). Other variables included patients' weight, sex, age, left and right sides of the mandible, and experience of the surgeon. Logistic regression analysis or the chi-squared test was performed to determine the effect of these variables on various types of lingual fracture line. The significance level was 95% (p < 0.05). There were 271 patients enrolled in this study. The SSO lingual split lines were divided into LSS1 (329/542), LSS2 (82/542), LSS3 (93/542), and LSS4 (38/542) splits. Logistic regression analysis showed that the LSS3 split was more likely to appear when the LBCE was closer to the lingual side (p = 0.0017). The age of patients significantly affected the possibilities of LSS2 (p = 0.0008) and LSS3 (p = 0.0023) splits. A LBCE close to the lingual side was an inducer for the formation of a LSS3 split in patients with skeletal class III malocclusion during BSSO. The age of the patient also affected the possibility of LSS2 and LSS3 splits.

Surgical Stability After Proximal Segment Angle Alteration in Patients with Class III Facial Asymmetry

PURPOSE

Patients with facial asymmetry often seek improved symmetry in lower face contour resulting in transverse movement of the proximal segments. The study aimed to investigate the association between transverse change in the proximal segments and postoperative relapse after the surgical correction of skeletal Class III facial asymmetry.

METHODS

The retrospective cohort study included consecutive patients with skeletal Class III asymmetry who underwent 2-jaw orthognathic surgery. The primary predictor variable was ramus plane angle (RPA). The patients were grouped as small (S group, <4°) and large (L group, ≥4°) changes in RPA. The primary outcome was the positional change of B point, menton, and the intergonial width. Cone-beam computed tomography images were obtained before surgery (T0), 1 week after surgery (T1), and debond (T2). Intergroup comparison was conducted with independent t test. Correlations between the variables were estimated by Pearson correlation.

RESULTS

The study sample was composed of 60 subjects with 30 subjects in each study group. In the S group, the mean surgical changes of RPA were inward rotated 0.91° bilaterally. In the L group, the mean surgical changes of RPA were inward rotated 4.80° and 0.32° on the deviated and non-deviated side. After surgery, further minor inward adaptation of both sides was noted (<1 mm), and intergonial distance reduced with these changes in the proximal segments. By comparing the postsurgical stability between S and L group, the overall sagittal and vertical stability had no significant difference between 2 groups. However, the postsurgical transverse menton relapse (ΔMe in T2-T1) was significantly larger in L group (0.81 ± 1.40 mm) than S group (0.04 ± 1.32 mm) by 0.77 mm (P = .014).

CONCLUSION

Greater surgical changes in the proximal segments had minor clinical effect on transverse stability. Minor transvers overcorrection of 1 mm is recommended in cases with severe facial symmetry with extensive changes in the proximal segments.

Relapse patterns of two-jaw surgical correction in patients with skeletal Class III malocclusion and different vertical facial types

The aim of this study was to evaluate postoperative relapse after the surgical correction of skeletal Class III deformities of various facial patterns as a guide to surgical planning. A retrospective cohort study of 90 consecutive patients with skeletal Class III malocclusion who underwent bimaxillary surgery was performed. The surgical outcomes and postoperative stability were compared. The primary predictor variable was vertical facial type, which was classified into three groups according to the Frankfort mandibular plane angle (FMA). The primary outcome of angular and linear measurements was obtained using serial cone beam computed tomography scans obtained at time points of preoperative, 1 week after surgery, and orthodontic debonding. No significant difference in skeletal relapse was observed in patients with the different vertical facial types. The mandible displayed a forward and upward relapse in all three groups postoperatively. The patients with a low FMA exhibited a more consistent mandibular relapse pattern than those with a normal or high FMA. These findings suggest that bimaxillary surgery is clinically stable for mandibular prognathism regardless of the vertical facial pattern. However, 1-1.5 mm of overcorrection in the mandible setback should be considered in patients with a low FMA, because of the greater facial depth and consistent forward and upward mandibular relapse pattern.

Skeletal stability after bimaxillary surgery with surgery-first approach for class III asymmetry is not related to virtual surgical occlusal contact

OBJECTIVES

Surgery-first orthognathic surgery is rarely used in class III asymmetry due to concerns of reduced skeletal stability from unstable surgical occlusion. This study aimed to evaluate if skeletal stability after surgery-first orthognathic surgery is related to virtual surgical occlusal contact or surgical change.

MATERIALS AND METHODS

We studied 58 adults with class III asymmetry, consecutively corrected by Le Fort I osteotomy and bilateral sagittal split osteotomy using a surgery-first approach. Dental casts were manually set to measure virtual surgical occlusal contact including contact distribution, contact number, and contact area. Cone-beam computed tomography taken before treatment, 1-week post-surgery, and after treatment was used to measure surgical change and post-surgical stability of the maxilla and mandible in translation (left/right, posterior/anterior, superior/inferior) and rotation (pitch, roll, yaw). The relationship between skeletal stability and surgical occlusal contact or surgical change was evaluated with correlation analysis.

RESULTS

Significant instability was found in the mandible but not in the maxilla. No correlation was found between the maxillary or mandibular stability and surgical occlusal contact (all p > 0.01). However, a significant correlation was found between the maxillary (roll and yaw) or mandibular (shift, roll and pitch) stability and its surgical change (all p < 0.001).

CONCLUSIONS

In correction of class III asymmetry with surgery-first bimaxillary surgery, the skeletal stability is not related to the virtual surgical occlusal contact, but surgical skeletal change.

CLINICAL RELEVANCE

Planned over-correction is a reasonable option for correction of severe shift or roll mandibular asymmetry in bimaxillary surgery for class III deformity.

Skeletal and upper airway stability following modified maxillomandibular advancement for treatment of obstructive sleep apnea in skeletal class I or II deformity

OBJECTIVES

Maxillomandibular advancement (MMA) is an effective short-term treatment for obstructive sleep apnea (OSA). This study aimed to evaluate the long-term stability of the facial skeleton, upper airway, and its surrounding structures, as well as improvement in OSA following MMA.

MATERIALS AND METHODS

Thirty-one adults with moderate-to-severe OSA underwent surgery-first modified MMA as primary surgery. Polysomnography and cone-beam computed tomography were obtained pre-surgery, early post-surgery, and at follow-up (i.e., ≥ 2 years post-surgery). Image analysis software assessed the facial skeleton, upper airway, and its surrounding structures.

RESULTS

Early post-surgery, apnea-hypopnea index (AHI) had decreased significantly (p < 0.001) and the minimum oxygen saturation (MSAT) increased (p = 0.001), indicating significant improvement in OSA. At follow-up, the AHI and MSAT remained stable. However, the anterior maxilla, soft palate, and tongue moved backward while the hyoid moved downward. There was also a significant decrease in the minimal cross-sectional area of the oropharynx. The reduction in AHI was significantly related to the anterior movement of the anterior maxilla and tongue, inferior movement of the posterior maxilla, and superior movement of the soft palate tip.

CONCLUSIONS

The improvement of OSA after modified MMA remained stable for at least 2 years following treatment, despite the relapse of the facial skeleton, upper airway, and its surrounding structures. The reduction of AHI was not related to changes in the caliber of the upper airway but to the movement of the maxilla, soft palate, and tongue. Clinical relevance Modified MMA is clinically effective for long-term treatment of patients with moderate-to-severe OSA.

Comparative stability and outcomes of two surgical approaches for correction of class III asymmetry with lip or occlusal cant

OBJECTIVES

To assess and compare the stability and outcomes of the two surgical approaches for patients with roll asymmetry.

MATERIALS AND METHODS

A total of 50 adult patients were consecutively recruited for this prospective study. Patients with class III asymmetry and lip or occlusal cant who underwent bimaxillary surgery were grouped according to surgical approach: asymmetric posterior impaction on both sides (API, n = 31) and posterior impaction on one side and posterior extrusion on the other side (PIE, n = 19). Postsurgical stability and outcomes between groups were determined with cone-beam computed tomography for facial midline, lip, and occlusal cant at 1 week (T1), and at least 12-month postsurgery (T2, completion of orthodontic treatment).

RESULTS

Presurgery, the upper anterior occlusal cant and lip cant were significantly greater for the PIE group (p < 0.05). Postsurgery (T2), the mandible moved upward and rotated upward in both groups. However, the upward rotation was significantly greater in the PIE group compared with the API group. Although the two approaches resulted in significant improvements in facial symmetry, the deviation in the facial midline remained under-corrected for most API patients.

CONCLUSIONS

Patient outcomes for mandibular stability and facial symmetry differed between the two surgical approaches for correction of class III asymmetry with lip or occlusal cant.

CLINICAL RELEVANCE

The findings of this study suggest that planned over-correction is a reasonable option for the approach of asymmetric posterior impaction on both sides.

Type of maxillary segment mobilization affects three-dimensional nasal morphology

BACKGROUND

Surgical mobilization of the maxillary segment affects nasal morphology. This study assessed the impact of the type of maxillary mobilization on the three-dimensional (3D) nasal morphometry.

METHODS

Pre- and postsurgery cone beam computed tomography-derived facial image datasets of consecutive patients who underwent two-jaw orthognathic surgery were reviewed. Using preoperative 3D facial models as the positional reference of the skeletal framework, 12-month postoperative 3D facial models were classified into four types of maxillary mobilizations (advancement [n = 83], setback [n = 24], intrusion [n = 55], and extrusion [n = 52]) and four types of final maxillary positions (anterosuperior [n = 44], anteroinferior [n = 39], posterosuperior [n = 11], and posteroinferior [n = 13]). Six 3D soft tissue nasal morphometric parameters were measured, with excellent intra- and interexaminer reliability scores (ICC>0.897) for all the measurements. The 3D nasal change for each nasal parameter was computed as the difference between postoperative and preoperative measurement values.

RESULTS

The intrusion maxillary mobilization resulted in a significantly (all p<0.05) larger 3D nasal change in terms of alar width, alar base width, and nostril angle parameters, and a smaller change in terms of the nasal tip height parameter than the extrusion maxillary mobilization; however, no significant (all p>0.05) difference was observed between advancement and setback maxillary mobilizations. The anterosuperior and posterosuperior maxillary positions had a significantly (all p<0.05) larger 3D nasal change in terms of the alar base width and nostril angle than the anteroinferior and posteroinferior maxillary positions.

CONCLUSION

The type of maxillary mobilization affects the 3D nasal morphometry.

Surgery-first orthognathic approach vs conventional orthognathic approach: A systematic review of systematic reviews

Surgery-first approach (SFA) has been introduced as an alternative for conventional orthognathic approach (COA) in the treatment of patients with dentoskeletal deformities. This review aimed to evaluate skeletal stability, treatment time, surgical complications, and quality of life in SFA and COA. Six databases were accessed up to May 2020 to obtain all systematic reviews (SRs). After title and abstract reading, data extraction was performed from eligible SRs. The methodological quality was calculated for the included SRs using the last version of A Measurement Tool to Assess Systematic Review (AMSTAR-2). Ten SRs were included in this review. A good stability of the jaws was assessed both with SFA and COA by most of low- or critically low-quality SRs. Less treatment time was reported for SFA than COA with a moderate quality level. Slightly higher complications rate was recorded with SFA than COA by SRs with low or moderate quality. A better quality of life with SFA than COA was reported by moderate- or low-quality SRs. SFA may represent a reasonable alternative to COA. However, for the heterogeneity of the included SRs, well-designed studies with a long term follow-up are needed to clarify the findings of this analysis.

Stability of the surgery-only orthognathic approach in class III patients with maxillary retrognathia

Introduction: The aim was to compare the stability of the surgery-only approach (SOA, indicating surgery without orthodontics) to the orthodontics-first approach (OFA; orthodontics followed by surgery) in patients with dentofacial deformities. Methods: All ten patients who underwent SOA and 10 OFA were included. Cephalometric radiographs were taken before surgery (T0), and six months after SOA or OFA(T2). The actual maxillary movement was measured intraoperatively (T1). The difference between T2-T0 and T1 is accepted as relapse. Each cephalometric film was analyzed using specialized software and the stability of actual advancement was analyzed. Results: Difference of relapse amount between SOA and OFA groups was statistically significant (p = 0.016). Conclusion: Although the stability of SOA was less than OFA, the amount of advancement was higher in SOA

Modern Surgery-First Approach Concept in Cleft-Orthognathic Surgery: A Comparative Cohort Study with 3D Quantitative Analysis of Surgical-Occlusion Setup

Despite the evident benefits of the modern surgery-first orthognathic surgery approach (reduced treatment time, efficient tooth decompensation, and early improvement in facial esthetics), the challenge of the surgical-occlusion setup acts as a hindering factor for the widespread and global adoption of this therapeutic modality, especially for the management of cleft-skeletofacial deformity. This is the first study to assess three-dimensional (3D) quantitative data of the surgical-occlusion setup in surgery-first cleft-orthognathic surgery. This comparative retrospective study was performed on 3D image datasets from consecutive patients with skeletal Class III deformity who had a unilateral cleft lip/palate (cleft cohort, n = 44) or a noncleft dentofacial deformity (noncleft cohort, n = 22) and underwent 3D computer-assisted single-splint two-jaw surgery by a single multidisciplinary team between 2014 and 2018. They received conventional orthodontics-first or surgery-first approaches. 3D quantitative characterization (linear, angular, and positional measurements) of the final surgical-occlusion setup was performed and adopted for comparative analyses. In the cleft cohort, the occlusion setup in the surgery-first approach had a significantly (all p < 0.05) smaller number of anterior teeth contacts and larger incisor overjet compared to the conventional approach. Considering the surgery-first approach, the cleft cohort presented significantly (all p < 0.05) larger (canine lateral overjet parameter) and smaller (incisor overjet, maxillary intercanine distance, maxillary intermolar distance, ratio of intercanine distance, and ratio of intermolar distance parameters) values than the noncleft cohort. This study contributes to the literature by providing 3D quantitative data of the surgical-occlusion setup in surgery-first cleft-orthognathic surgery, and delivers information that may assist multidisciplinary teams to adopt the surgery-first concept to optimize cleft care.