Condylar repositioning using centric relation bite in bimaxillary surgery

Effect of bimaxillary surgery on the stress distributions in patients with mandibular retrognathia under unilateral molar clenching

To investigate the effect of bimaxillary surgery on the stress distribution of the temporomandibular joint (TMJ) in patients with mandibular retrognathia under unilateral molar clenching (UMC). Five patients with mandibular retrognathia (preoperative group) and ten asymptomatic subjects (control group) were recruited. In addition, patients treated with bimaxillary surgery were considered as the postoperative group. The muscle forces corresponding to UMC were applied. The results showed that the discal stresses in the postoperative group were significantly greater than those in the preoperative and control groups. Bimaxillary surgery plus UMC had a detrimental effect on the TMJ.

Mandible-First Sequencing Increase Surgical Accuracy for Patients With Skeletal Class II Malocclusion Concomitant With Unstable Condyle-Fossa Relation

The aim of this study was to explore whether mandible-first sequencing increases the surgical accuracy in bimaxillary orthognathic surgery for patients with skeletal class II malocclusion concomitant with the unstable condyle-fossa relation. A retrospective evaluation of 19 patients who had undergone virtually planned double-splint orthognathic surgery with different operation sequences was performed: maxilla-first (n=9) or mandible-first (n=10) surgery. The centroid position, translational, and rotational differences in the maxilla were evaluated by comparing the virtual plans with actual results. The stability was assessed by comparing the actual results with the follow-up outcomes 6 months postoperatively. The accuracy of the maxilla centroid position was improved in mandible-first sequencing surgery: mandible-first 1.87±0.94 mm versus maxilla-first 2.70±0.75 mm (P<0.05). Moreover, no significant difference was detected in the translational and orientational discrepancies between the 2 groups. Neither sequencing procedure differed in the overall stability: maxilla-first (1.48±1.13 mm) versus mandible-first (1.57±0.90 mm). This study indicated that the mandible-first surgery leads to a more accurate maxilla position than the maxilla-first surgery for patients with skeletal class II malocclusion concomitant with the unstable condyle-fossa relation.

Centric relation-A biological perspective of a technical concept

BACKGROUND

Few terms and concepts have been so extensively debated in dentistry as the words 'centric relation' (CR). Debates involve its biological, diagnostic and therapeutic usefulness.

METHODS

A review of the literature on the current concepts on CR as a diagnostic or therapeutic aid in dentistry was provided. Clinical trials assessing the superiority of one CR recording method over the others to identify patients with temporomandibular disorders (diagnostic use) or to manage patients with prosthodontic or orthodontic needs (therapeutic use) were tentatively included.

RESULTS

Due to the absence of literature addressing either of the above targets, a comprehensive overview was provided. The diagnostic use of CR as a reference position to identify the correct position of the temporomandibular joint condyle within the glenoid fossa is not supported and lacks anatomical support. From a therapeutic standpoint, the use of CR can be pragmatically useful in prosthodontics as a maxillo-mandibular reference position when occlusal re-organization is warranted and/or when the position of maximum intercuspation is no longer available.

CONCLUSIONS

The derived occlusal goals from a diagnostic misuse of CR are generally the result of circular reasoning, that is a technique is based on the recording of a certain condylar position that is believed to be 'ideal' and the treatment is considered successful when such position is shown by the specific instrument that was manufactured for that purpose. The term 'Centric Relation' might be replaced with the term 'Maxillo-Mandibular Utility Position'.

Assessment of Surgical Accuracy in Maxillomandibular Advancement Surgery for Obstructive Sleep Apnea: A Preliminary Analysis

This retrospective study aimed to: (1) investigate the surgical accuracy of maxillomandibular advancement (MMA) in obstructive sleep apnea (OSA) patients, with a specific focus on maxillary and mandibular advancement and counter-clockwise rotation and (2) investigate the correlation between the amount of achieved advancement and the reduction in the relative apnea hypopnea index (AHI). Sixteen patients, for whom a three-dimensional virtual surgical plan was generated preoperatively and a computed tomography scan (CT) or cone-beam computer tomography (CBCT) was acquired postoperatively, were included. The postoperative CT or CBCT was compared to the virtual surgical plan, and differences in the mandibular and maxillary advancement and counter-clockwise rotation were assessed. Maxillary and mandibular advancement (median 3.1 mm, p = 0.002 and 2.3 mm, p = 0.03, respectively) and counter-clockwise rotation (median 3.7°, p = 0.006 and 4.7°, p = 0.001, respectively) were notably less than intended. A significant correlation was found between the planned maxillary advancement and the difference between the planned and actual maxillary advancement (p = 0.048; adjusted R2 = 0.1979) and also between the planned counter-clockwise rotation and the difference between the planned and actual counter-clockwise rotation for the mandible (p = 0.012; adjusted R2 = 0.3261). Neither the maxilla-first nor the mandible-first surgical sequence proved to be superior in terms of the ability to achieve the intended movements (p > 0.45). Despite a significant reduction (p = 0.001) in the apnea hypopnea index (AHI) from a median of 62.6 events/h to 19.4 events/h following MMA, no relationship was found between the extent of maxillary or mandibular advancement and AHI improvement in this small cohort (p = 0.389 and p = 0.387, respectively). This study underlines the necessity for surgeons and future research projects to be aware of surgical inaccuracies in MMA procedures for OSA patients. Additionally, further research is required to investigate if sufficient advancement is an important factor associated with MMA treatment outcome.

Static mandibular condyle positions studied by MRI and condylar position indicator

We compared mandibular condyle positions as determined by magnetic resonance imaging (MRI) and a mechanical device, the condylar position indicator (CPI). Both methods assessed 3 mandibular positions in 10 asymptomatic males and 10 asymptomatic females, aged 23 to 37 years, free from temporomandibular disorders: maximum intercuspation, bimanually manipulated centric relation, and the unguided neuromuscular position. Bite registrations were obtained for bimanual operator guidance and neuromuscular position. 3 T MRI scans of both temporomandibular joints produced 3D data of the most superior condylar points in all 3 mandibular positions. Using mounted plaster casts and the same bite registrations, an electronic CPI displayed 3D data of its condylar spheres in these positions. The results showed interclass correlation coefficients ranging from 0.03 to 0.66 (95% confidence intervals from 0 to 0.8) and significantly different condyle positions between both methods (p = 0.0012, p < 0.001). The implications of the study emphasize that condyle position is unpredictable and variable. Its exact knowledge requires radiological imaging and should not rely on CPI assessments.

Evaluation of the Mandibular Condyle Morphologic Relation before and after Orthognathic Surgery in Class II and III Malocclusion Patients Using Cone Beam Computed Tomography

Simple Summary

In individuals with severe malocclusions, orthognathic surgery seeks to rebalance the relationships between the jaws by providing a stable occlusion, a healthy muscle balance, and the functioning of the temporomandibular joint. Cone beam computed tomography may be used to determine the position of the mandibular condyle in the glenoid fossa. This study aimed to assess how the position of the mandibular condyle varies in class II and III malocclusions before and after bimaxillary orthognathic surgery. Before and after orthognathic surgery, 56 TMJs from 28 patients were studied. Following surgery, both class II and class III patients experienced changes in the anterior joint space, posterior joint space, condyle position, and condyle angle. The preliminary findings are promising for determining changes in condyle position and joint spaces that might guide oral and maxillofacial surgeons to address a debilitating clinical affliction.

Abstract

This study aimed at evaluating the mandibular condyle position changes before and after bimaxillary orthognathic surgery in class II and III malocclusion patients. CBCT scans from patients who underwent bimaxillary orthognathic surgery were analyzed: Le Fort I osteotomy and bilateral sagittal split osteotomy (BSSO). Both condyles were independently assessed for their largest anterior and posterior joint spaces, smallest medial joint spaces, and condyle angles concerning the transverse line. In the sagittal plane, the minimum size of the anterior and posterior joint spaces was measured. In the coronal plane, the smallest medial joint space was measured. The position of the condyle within the glenoid fossa was determined before and after surgery. A total of 56 TMJs from 28 patients were studied. Following orthognathic surgery, the anterior and posterior space in class II increased. Postoperatively, the anterior joint space in class III decreased. In 42.85% of malocclusion class II patients and 57.14% of malocclusion class III patients, the pre-and post-surgical position of the condyle changed, the condyle was anteriorly positioned (42.85%) in class II patients and centrically positioned (71.4%) in class III patients. Significant changes in the joint space, condylar position, and condyle angle were found in the class II and class III subjects.

Condylar repositioning according to digital bite registration method for virtual orthognathic surgery planning: A series of 49 consecutive patients

INTRODUCTION

The accurate mandibular condylar positioning for orthognathic surgical planning is fundamental in obtaining a planned occlusal result. The differences between the position of condyles seen on computed tomography or cone-beam computed tomography (CBCT) scans and during surgery reduce the accuracy of the result. This study aimed to assess the differences between the condylar position recorded on CBCT and a numerical 3-dimensional (3D) model created after mandibular repositioning for orthognathic surgery planning.

METHODS

This study retrospectively evaluated 49 patients who underwent virtual orthognathic surgery planning. The procedure involved recording a computed tomography or CBCT of the skull and dental surface using an intraoral digital scanner. The mandible was repositioned on the numerical 3D model according to the superimposed virtual bite registration in centric relation. Linear and angular measurements of the right and left condyles were recorded before and after mandibular repositioning.

RESULTS

The positions of 98 condyles were compared. Linear measurements of the posterior and superior joint spaces revealed a significant difference. Subgroup analyses displayed statistically significant differences for patients with skeletal Class II malocclusion.

CONCLUSION

According to the digital bite registration method, the difference between the mandibular position recorded on CBCT and on the numerical 3D model after repositioning may have clinical significance. Further studies are needed to validate this theory and test the accuracy of the clinical results.

Evaluation of the Predictability and Accuracy of Orthognathic Surgery in the Era of Virtual Surgical Planning

Virtual surgical planning allows orthognathic surgeons to design a surgical plan preoperatively and establish a personalized surgical protocol. This study aims to validate the predictability and accuracy of orthognathic surgery through a comparison of the three-dimensional (3D) models of the virtual planning and postoperative CBCT using free software (3D Slicer) on 40 patients who underwent bimaxillary orthognathic surgery. The distances of point A, point B, pogonion (Pog), and the first upper and lower molars, both in each axis (x, y, and z) and in the 3D space, were analyzed. The median of the distances in the mediolateral direction was the lowest, while the highest differences were found at point A and Pog in the anteroposterior direction (0.83 mm and 0.78 mm, respectively). Vertical differences were higher in the maxilla than in the mandible. In conclusion, we found that orthognathic bimaxillary surgery using virtual surgical planning was more accurate when positioning the bone segments in the mediolateral direction, using the information provided by the splint, as well as when positioning the mandible compared to the maxilla.

Three-dimensional analysis of condylar remodeling and skeletal relapse following LeFort-I osteotomy: A one-year follow-up bicenter study

The aim of the study was to quantify the postoperative condylar remodeling after Le Fort I surgery. Patients treated with a Le Fort I osteotomy were investigated. CBCT scans were acquired preoperatively, one week and one year postoperatively. A preoperative 3D cephalometric analysis was performed on the preoperative CBCT. Surgical movements were quantified using a voxel-registration based method (OrthoGnaticAnalyser). After rendering of the condyles from the CBCT, a volumetric analysis was performed. The correlation between the surgical movement of the maxilla and the postoperative condylar volume changes was determined with analysis of variance. RESULTS: A total of 45 subjects were included in this study. 47 of 90 condyles (52%) showed a mean volume reduction of 93 mm³ (4.9 volume-%) postoperatively. The maxilla was impacted in 12 patients (2.44 ± 2.49 mm) and extruded in 33 patients (1.78 ± 1.29 mm). The maxillary impaction group showed a volume reduction of 50 ± 122 mm³ and the extrusion group showed a mean volume gain of 21 ± 139 mm³ (p = 0.028). CONCLUSION: Clinicians should be aware of potential condylar remodeling following solitary Le Fort I osteotomies, particularly in female patients with maxillary impaction.

Accuracy of virtual planning in orthognathic surgery: a systematic review

BACKGROUND

The elaboration of a precise pre-surgical plan is essential during surgical treatment of dentofacial deformities. The aim of this study was to evaluate the accuracy of computer-aided simulation compared with the actual surgical outcome, following orthognathic surgery reported in clinical trials.

METHODS

Our search was performed in PubMed, EMBASE, Cochrane Library and SciELO for articles published in the last decade. A total of 392 articles identified were assessed independently and in a blinded manner using eligibility criteria, out of which only twelve articles were selected for inclusion in our research. Data were presented using intra-class correlation coefficient, and linear and angular differences in three planes.

RESULTS

The comparison of the accuracy analyses of the examined method has shown an average translation (< 2 mm) in the maxilla and also in the mandible (in three planes). The accuracy values for pitch, yaw, and roll (°) were (< 2.75, < 1.7 and < 1.1) for the maxilla, respectively, and (< 2.75, < 1.8, < 1.1) for the mandible. Cone-beam computed tomography (CBCT) with intra-oral scans of the dental casts is the most used imaging protocols for virtual orthognathic planning. Furthermore, calculation of the linear and angular differences between the virtual plan and postoperative outcomes was the most frequented method used for accuracy assessment (10 out of 12 studies) and a difference less than 2 mm/° was considered acceptable and accurate. When comparing this technique with the classical planning, virtual planning appears to be more accurate, especially in terms of frontal symmetry.

CONCLUSION

Virtual planning seems to be an accurate and reproducible method for orthognathic treatment planning. However, more clinical trials are needed to clearly determine the accuracy and validation of the virtual planning in orthognathic surgery.

Three-dimensional assessment of condylar position following orthognathic surgery using the centric relation bite and the ramal reference line: A retrospective clinical study

Orthognathic surgery (OGS) is a relatively common procedure for solving functional and aesthetic problems in facial and jaw areas in patients with dentofacial deformities. The positioning of the mandibular condylar segment during OGS has an impact on the surgical outcome. This study aimed to investigate the changes in the condyle-fossa relationship three dimensionally after OGS using the centric relation (CR) bite and the ramal reference line (RRL).Thirty-two patients with skeletal malocclusion underwent OGS. Condylar repositioning was performed using the CR bite, as previously reported. A RRL was added to the existing method and used during the surgery. Cone-beam computed tomography scans were acquired at 4 time points. Sixty-four condyles were evaluated in the coronal, sagittal, and axial views. Two groups were created according to the amount of mandible setback (SB1 vs SB2), and another 2 groups were created according to the maxillary operation (1-jaw vs 2-jaw). Each was then compared at the 4 time points. Differences between the values before (T0) and a year after surgery (T3) were also investigated. The positions of the pogonion and the menton were examined at T2 and T3 for the simple evaluation of relapse.The change in the condylar position was significant over a time-course (P < .001) but not between T0 and T3 (P > .05). Neither the setback amount nor the maxillary operation affected the positional change (P > .05). There were no significant changes between T2 and T3 in the relapse evaluation.This condylar repositioning method using the CR bite and a RRL showed stable results after OGS. This method is noninvasive and cost-effective and can be easily performed even by an inexperienced surgeon because it reduces errors in repositioning the condyle during OGS.

Computer assisted positioning of the proximal segment after sagittal split osteotomy of the mandible: Preclinical investigation of a novel electromagnetic navigation system

INTRODUCTION

Modifications of the temporomandibular joint position after mandible osteotomy are reluctantly accepted in orthognathic surgery. To tackle this problem, we developed a new navigation system using miniaturized electromagnetic sensors. Our imageless navigation approach is therefore optimized to avoid complications of previously proposed optical approaches such as the interference with established surgical procedures and the line of sight problem.

MATERIAL AND METHODS

High oblique sagittal split osteotomies were performed on 6 plastic skull mandibles in a laboratory under conditions comparable to the operating theatre. The subsequent condyle reposition was guided by an intuitive user interface and performed by electromagnetic navigation. To prove the suitability and accuracy of this novel approach for condyle navigation, the positions of 3 titanium marker screws placed on each of the proximal segments were compared using pre- and postoperative Cone Beam Computed Tomography (CBCT) imaging.

RESULTS

Guided by the electromagnetic navigation system, positioning of the condyles was highly accurate in all dimensions. Translational discrepancies up to 0,65 mm and rotations up to 0,38° in mean could be measured postoperatively. There were no statistically significant differences between navigation results and CBCT measurements.

CONCLUSION

The intuitive user interface provides a simple way to precisely restore the initial position and orientation of the proximal mandibular segments. Our electromagnetic navigation system therefore yields a promising approach for orthognathic surgery applications.

A New 3D Tool for Assessing the Accuracy of Bimaxillary Surgery: The OrthoGnathicAnalyser

AIM

The purpose of this study was to present and validate an innovative semi-automatic approach to quantify the accuracy of the surgical outcome in relation to 3D virtual orthognathic planning among patients who underwent bimaxillary surgery.

MATERIAL AND METHOD

For the validation of this new semi-automatic approach, CBCT scans of ten patients who underwent bimaxillary surgery were acquired pre-operatively. Individualized 3D virtual operation plans were made for all patients prior to surgery. During surgery, the maxillary and mandibular segments were positioned as planned by using 3D milled interocclusal wafers. Consequently, post-operative CBCT scan were acquired. The 3D rendered pre- and postoperative virtual head models were aligned by voxel-based registration upon the anterior cranial base. To calculate the discrepancies between the 3D planning and the actual surgical outcome, the 3D planned maxillary and mandibular segments were segmented and superimposed upon the postoperative maxillary and mandibular segments. The translation matrices obtained from this registration process were translated into translational and rotational discrepancies between the 3D planning and the surgical outcome, by using the newly developed tool, the OrthoGnathicAnalyser. To evaluate the reproducibility of this method, the process was performed by two independent observers multiple times.

RESULTS

Low intra-observer and inter-observer variations in measurement error (mean error < 0.25 mm) and high intraclass correlation coefficients (> 0.97) were found, supportive of the observer independent character of the OrthoGnathicAnalyser. The pitch of the maxilla and mandible showed the highest discrepancy between the 3D planning and the postoperative results, 2.72° and 2.75° respectively.

CONCLUSION

This novel method provides a reproducible tool for the evaluation of bimaxillary surgery, making it possible to compare larger patient groups in an objective and time-efficient manner in order to optimize the current workflow in orthognathic surgery.

Intraoperative condyle positioning by sonographic monitoring in orthognathic surgery verified by MRI

OBJECTIVE

Repositioning of the jaw in orthognathic surgery must produce precise and stable long-term results; an effective and practical method of intraoperative condyle positioning is required to achieve this. Most traditional methods, such as manual positioning or positioning plates do not permit intraoperative monitoring of the temporomandibular joint (TMJ) position. This study evaluates the results of intraoperative, sonographically-monitored joint positioning, comparing preoperative and postoperative MRI scans.

PATIENTS AND METHODS

Of the 97 patients who were originally assessed (53 female, average age 29 ± 10.93; and 44 male, average age 28 ± 9.25), 21 had incomplete data sets and were excluded, leaving 76 evaluable patients. MRIs were performed preoperatively between 2 days and 100 weeks (median 30.5 days), and postoperatively between 12 and 96 weeks (median 150 days). Condyle positioning, intercondylar distance, and disc degeneration and dislocation were compared in preoperative and postoperative MRIs, and differentiated by Angle class on horizontal, axial and sagittal scans. Condyle to fossa distances were measured on parasagittal images from 0° (the vertical sagittal plane), 45° anteriorly and 45° posteriorly. The intercondylar distances between the condylar head midpoints were measured on axial sections. Two-sided t-tests (α < 0.05) were used for comparisons within classes; the interclass correlation was performed using univariate ANOVA and linear correlation for paired sample correlation settings.

RESULTS

In 27 Angle class II cases, the anterior distance of both condyles increased on average 0.3 ± 1.0 mm, the posterior position decreased 0.1 ± 1.2 mm, and the vertical position decreased 0.2 ± 1.1 mm postoperatively. In 47 Angle class III cases the anterior distance of both condyles increased on average 0.3 ± 0.8 mm, the posterior 0.1 ± 0.8 mm and the vertical distance 0.1 ± 0.8 mm postoperatively. All alterations of the condyle-fossa relation were non-significant except for the anterior distance in Angle class ІІІ (p = 0.02). Alterations of the disc position and disc degeneration were non-significant in class II. In class ІІІ, the disc degeneration deteriorated slightly on the left side (p = 0.02). Intercondylar distance increased 1 ± 5.5 mm in class ІІ and decreased by 1 ± 5.5 mm in class ІІІ postoperatively, alterations were non-significant.

CONCLUSION

Sonography is a non-invasive, comfortable, fast, economical and effective intraoperative method of condyle positioning. The results of the present study support this statement because the degree of disc degeneration and luxation remained unaltered and the condyle position did not change significantly. Prospective randomized comparison to manual positioning is in preparation and will be conducted in the near future.