Effect of setback Le Fort I osteotomy on midfacial soft-tissue changes as evaluated by cone-beam computed tomography superimposition for cases of skeletal Class III malocclusion

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.

Effectiveness of subspinal Le Fort I osteotomy in preventing postoperative nasal deformation

PURPOSE

This study sought to determine the effectiveness of subspinal Le Fort I osteotomy (SLFIO) in preventing nasal deformation, by analyzing changes in the nasal profile on three-dimensional computed tomography (3D-CT) images.

PATIENTS AND METHODS

The participants were 39 Japanese patients with mandibular prognathism (6 men and 33 women) who underwent bilateral sagittal split ramus osteotomy and Le Fort I osteotomy with maxillary advancement: SLFIO was performed in 20 patients and conventional Le Fort I osteotomy (CLFIO) in 19 patients. All patients underwent modified alar base cinch suture, V-Y closure, and reduction of the piriform aperture. CT data acquired before and 1 year after the surgery were evaluated three-dimensionally with software to determine changes in the nasal profile.

RESULTS

Changes in alar width, alar base width, nasal length, and nasofrontal angle were significantly smaller following SLFIO than following CLFIO, although there were no significant differences in nasal projection, nasal tip angle, or nasolabial angle between two procedures.

CONCLUSION

SLFIO for anterior repositioning of the maxilla can prevent undesirable transverse soft tissue changes of the nose.

The effect of hard tissue surgical changes on soft tissue displacement: a pilot CBCT study

INTRODUCTION

This pilot study had as main objective to test the reliability of a new method to evaluate orthognathic surgery outcomes and also, to understand the effect of hard tissue changes on soft tissue displacement.

METHODS

The sample consisted of eight patients that underwent bimaxillary advancement and had CBCT at two time points (before surgery and 6-8 months follow-up). Voxel-based cranial base superimposition was used to register the scans. A different technique of iterative closest point (ICP) was used to measure and correlate the changes. The average displacement of 15 areas (4 hard tissue and 11 soft tissue) were measured twice.

RESULTS

ICC was > 0.99 for all areas. Changes in the tip of the nose did not correlate with changes in any maxillary area, whereas soft tissue A point, A point and upper lips had correlation with several areas. The highest correlation for the maxilla was between the upper lip and the left/right supra cheilion (p< 0.001, r= 0.91 and p< 0.001, r= 0.93, respectively). In the mandible, the majority of the correlations involved soft tissue pogonion, pogonion and lower incisors, with the strongest one between pogonion and lower incisors (p< 0.001, r= 0.98).

CONCLUSION

With the proper case selection, ICP is a reliable method that can be used to assess three-dimensional changes.

Displacement Patterns of the Maxilla During Parallel and Rotational Setback Movements: A Finite Element Analysis

BACKGROUND The purpose of this analysis was to evaluate the displacement patterns of the maxilla under parallel and rotational setbacks using the finite element method (FEM). MATERIAL AND METHODS A three-dimensional (3D) finite element model of a hemimaxilla was constructed. Through a conventional Le Fort I osteotomy, 2 and 3 mm of posterior movement in a parallel and rotational manner were simulated and the displacement pattern of the maxilla in each movement type was evaluated. RESULTS Both parallel and rotational setbacks resulted in lateral and inferior displacement of the maxillary segment. The largest inferior displacement was 3.0 mm and the largest lateral displacement was 1.84 mm. All lateral displacements in the anterior region were found to be more than 1 mm. CONCLUSIONS The results of this study may provide insight into how the maxilla tends to move during total maxillary setback surgery.

Soft tissue changes after posterior impaction and setback of the maxilla with Le Fort I osteotomy in skeletal class III patients

The purpose of this retrospective study was to evaluate the changes in the upper lip (UL) by posterior impaction and setback (PI-SB) of the maxilla. The samples consisted of 29 skeletal Class III patients (10 men and 19 women) who received bimaxillary surgery including PI-SB of the maxilla after Le Fort I osteotomy. Lateral cephalograms were taken at 1 week before surgery (T0) and 6 months after surgery (T1). After linear and angular changes of the hard and soft tissue variables were measured, the paired t test, Pearson correlation test, and univariate linear regression analysis were performed for statistical analyses. The changes in the hard tissue landmarks were as follows: ANS, U1E, and U6MBC moved backward (P < 0.001, P < 0.001, and P < 0.05, respectively) and upward (P < 0.001, P < 0.01, and P < 0.001, respectively), whereas A point, U1A, and PNS moved upward only (P < 0.01, P < 0.01, and P < 0.001, respectively). In terms of the soft tissue change, although subnasale (Sn) did not show significant change, pronasale (Pn) moved upward (P < 0.05); UL, backward and downward (all P < 0.001); and Stms (stomodium-superius), backward (P < 0.001). There were significant correlations between the horizontal change of the UL and that of A point and U1E (P < 0.01, P < 0.05). The regression equation of the horizontal change of UL and U1E was [INCREMENT]UL-vertical reference line (VRL) = (0.476 × [INCREMENT]U1E-VRL) - 0.581 (P < 0.05). If U1E moves backward by 3 mm and 5 mm, the UL is predicted to move backward by 0.9 mm and 1.8 mm, respectively. These results might provide a guideline in diagnosis and treatment planning for maxillary surgery with PI-SB.

Influence of maxillary advancement surgery on skeletal and soft-tissue changes in the nose - a retrospective cone-beam computed tomography study

Objectives

Surgical correction of skeletal maxillary retroposition is often associated with changes in the morphology of the nose. Unwanted alar flaring of the nose is observed in many cases. The aim of the present study was therefore to investigate the influence of surgical advancement of the maxilla on changes in the soft-tissue morphology of the nose. Having a coefficient that allows prediction of change in the nasal width in Caucasian patients after surgery would be helpful for treatment planning.

Materials and methods

All 33 patients included in this retrospective study were of Caucasian descent and had skeletal Class III with maxillary retrognathia. They were all treated with maxillary advancement using a combination of orthodontic and maxillofacial surgery methods. Two cone-beam computed tomography (CBCT) datasets were available for all of the study's participants (16 female, 17 male; age 24.3 ± 10.4 years): the first CBCT imaging was obtained before the planned procedure (T0) and the second 14.1 ± 6.4 months postoperatively (T1). Morphological changes were recorded three-dimensionally using computer-aided methods (Mimics (Materialise NV, Leuven/Belgium), Geomagic (Geomagics, Morrisville/USA)). Statistical analysis was carried out using SPSS 21 for Mac.

Results

The mean sagittal advancement of the maxilla was 5.58 mm. The width of the nose at the alar base (Alb) changed by a mean of + 2.59 mm (±1.26 mm) and at the ala (Al) by a mean of + 3.17 mm (±1.32 mm). Both of these changes were statistically highly significant (P = 0.000). The increase in the width of the nose corresponded to approximately half of the maxillary advancement distance in over 80 % of the patients. The nasolabial angle declined by an average of −6.65° (±7.71°).

Conclusions

Maxillary advancement correlates with a distinct morphological change in nasal width. This should be taken into account in the treatment approach and in the information provided to patients.

Three-dimensional cephalometric superimposition of the nasomaxillary complex

INTRODUCTION

Two-dimensional maxillary superimposition techniques have been routinely used in clinical practice, but a 3-dimensional plane has yet to be introduced and validated. The purposes of this study were to propose a new plane for regional superimposition of the maxillary complex and then to validate it through clinical data.

METHODS

Pretreatment and posttreatment palatal expansion records were used. The magnitudes of the transverse expansion at the levels of the first premolars and the first molars were assessed using the proposed superimposition plane and then were compared with the gold standard plaster model measurements. Descriptive statistics and agreement testing were performed to compare the methods.

RESULTS

When comparing the superimposition and plaster measurement methods, the mean errors for intermolar and interpremolar distances were 0.57 and 0.59 mm, respectively. Both the intraclass correlation coefficient and the Bland-Altman plot demonstrated high agreement between the 2 methods (intraclass correlation coefficient greater than 0.9).

CONCLUSIONS

The proposed maxillary superimposition plane yields clinically suitable results when compared with the gold standard technique, with a mean error of less than 0.6 mm for typical intra-arch measurements. This new landmark-derived maxillary plane for superimposition is a promising tool for evaluating maxillary dentoalveolar changes after treatment.

Differences in three-dimensional soft tissue changes after upper, lower, or both jaw orthognathic surgery in skeletal class III patients

The decision is not always straightforward as to which orthognathic procedure is best for a good aesthetic result; three-dimensional imaging has brought new insight into this topic. The aim of this prospective study was to verify objectively whether postoperative changes occur within those regions not directly affected by surgical movements of the underlying jaw bones. The study included 83 young adults with skeletal class III deformities. They were classified into three groups according to the type of surgery: bilateral sagittal split osteotomy set-back of the mandible (BSSO), Le Fort I advancement of the maxilla, or a combination of both. Pre- and postoperative optical scans were registered as regional best-fits on the areas of the foreheads and both orbits. The shell to shell differences were measured and the average distances between the observed regions were calculated. As expected, changes were greatest in the regions where the underlying bones had been moved, but regardless of the operation performed, changes were found over the whole face. Changes in the nose, cheek, and upper lip regions in the BSSO group and in the lower lip and chin region in the Le Fort I group confirmed the concept of the facial soft tissue mask acting as one unit.