Incidence and management of condylar resorption after orthognathic surgery: An overview

Three-Dimensional Mandibular Condyle Remodeling Post-Orthognathic Surgery: A Systematic Review

Background and Objectives: The most popular surgical procedures among orthognathic surgeries for Class II and III patients are Le Fort 1 osteotomy for the maxilla and bilateral sagittal split ramus osteotomy (BSSRO) for the mandible. Keeping the condyle in its proper place during fixation is one of the difficulties of orthognathic surgery. One of the worst post-orthognathic surgery consequences in the temporomandibular joint (TMJ) area may be condylar resorption. Condylar remodeling refers to a group of processes that occur in reaction to forces and stress placed on the temporomandibular joint in order to preserve morphological, functional, and occlusal balance. A systematic review of the literature was performed with the aim of identifying the mandibular condylar component of TMJ changes after orthognathic surgery in class II and III patients. Materials and Methods: An electronic search was carried out using the PubMed, Cochrane Library, and Google Scholar, databases. The inclusion criteria included trials in non-growing patients upon whom orthognathic surgery was performed due to Angle II or Angle III classes malocclusion; in addition, a CT or cone beam computed tomography (CBCT) scan was performed before and after surgery to track the mandibular condylar component of TMJ changes. The quality of the studies was evaluated by two independent authors. The risk of bias was assessed by using the Downs and Black checklist. Results: The electronic and manual literature search yielded 12 studies that fulfilled all necessary inclusion criteria. Observed studies were evaluated as good (3), fair (8), and poor (1) quality. Two studies evaluated class II patients, six studies observed class III patients, and four studies were comparative. Most of the studies evaluated condyle angle and space changes, and the condylar surface and volume changes were also observed. However, the methodology of evaluation in the publications differs. Conclusions: Reduction of bone density, especially in class II patients, and morphological condyle reshaping, with the apposition of the bone, is the main adaptive mechanism after orthognathic surgery. However, all of the studies we examined were conducted using different methods of evaluation, measurement, and reference points.

Three-Dimensional Evaluation of Changes in Condylar Position After Orthognathic Surgery With Different Types of Jaw Deformities

BACKGROUND

Assessing condyle position postorthognathic surgery is pivotal for optimizing surgical accuracy, sustaining postoperative stability, and ensuring predictable treatment outcomes.

PURPOSE

The aim of this study was to analyze the changes of condyle position after orthognathic surgery with different types of jaw deformity and to analyze whether the changes of condyle position are different.

STUDY DESIGN, SETTING, SAMPLE

A retrospective cohort study was designed and conducted, involving adults who underwent orthognathic surgery for jaw deformities at the affiliated Stomatological Hospital of Nanchang University between 2019 and 2022. Patients with incomplete computerized tomography data were excluded.

PREDICTOR/EXPOSURE/INDEPENDENT VARIABLE

The primary predictor variable was time (preoperative and postoperative) and types of jaw deformities (skeletal Class III, skeletal Class II, and mandibular deviation).

MAIN OUTCOME VARIABLE(S)

The main outcome variables were the three-dimensional linear and rotational positional changes of the condyle.

COVARIATES

Evaluated covariates included sex and age.

ANALYSES

MIMICS 20.0 software measured all data, and SPSS 22.0 software facilitated statistical analyses. Intragroup and intergroup correlation analyses employed paired t-tests and independent t-tests, with statistical significance set at P < .05.

RESULTS

The study sample was composed of 32 subjects with a mean age of 22.43 ± 1.6 and 9 were male. The analysis of changes of condylar position from virtual surgical planning to the immediate postoperative period showed that the maximum condylar displacement was 1.74 mm and the maximum angular change was 3.92°. The analysis of changes in condylar position from the immediate postoperative period to 1 year postoperatively showed no statistically significant changes for the same type of jaw deformity. But patients with Class II malocclusion exhibited distinct condylar displacement and rotation patterns compared to those with Class III malocclusion and mandibular deformity.

CONCLUSION AND RELEVANCE

The application of virtual surgical planning in orthognathic surgery ensures a high degree of consistency in achieving the desired condylar position. Moreover, no significant change in condylar position was observed after orthognathic surgery for the same type of jaw deformity. However, patients with Class II deformities exhibited a higher susceptibility to rotational displacement of the condyles compared to those with other types of jaw deformities.

Does mandibular advancement ortho-surgical procedure cause condyle changes? A case-series analysis

INTRODUCTION

Mandibular advancement surgery corrects bone bases while establishing patients' functional and aesthetic rehabilitation. However, little is known about the results of this procedure in the structures that make up the stomatognathic system, as the condyles.

OBJECTIVE

This study aimed to evaluate the structural and positional changes of mandibular condyles in ortho-surgical patients who underwent mandibular advancement surgery.

MATERIAL AND METHODS

A prospective investigation was conducted with cone-beam computed tomography images. Using Dolphin Imaging® software, seven ortho-surgical patients with Angle Class II malocclusion and mandibular deficiency were evaluated. The images assessed were obtained at pre-surgical phase and after, at least, 1 year of the procedure. To study the structural and positional changes of condyles, linear and angular measurements were obtained, and the right and left sides of patients were compared. Descriptive statistical analysis was performed and, in order to verify possible significant differences, normality tests (Kolmogorov-Smirnov) were applied, followed by a paired t-test to define significance.

RESULTS

For all measures evaluated in this study, no statistically significant differences were found.

CONCLUSION

The ortho-surgical procedure performed did not change the structure and position of the condyles of patients who underwent surgical mandibular advancement. Right and left mandibular condyles behaved similarly, suggesting stability and condylar adaptation after surgery.

An automated method for assessing condyle head changes in patients with skeletal class II malocclusion based on Cone-beam CT images

OBJECTIVES

Currently, there is no reliable automated measurement method to study the changes in the condylar process after orthognathic surgery. Therefore, this study proposes an automated method to measure condylar changes in patients with skeletal class II malocclusion following surgical-orthodontic treatment.

METHODS

Cone-beam CT (CBCT) scans from 48 patients were segmented using the nnU-Net network for automated maxillary and mandibular delineation. Regions unaffected by orthognathic surgery were selectively cropped. Automated registration yielded condylar displacement and volume calculations, each repeated three times for precision. Logistic regression and linear regression were used to analyse the correlation between condylar position changes at different time points.

RESULTS

The Dice score for the automated segmentation of the condyle was 0.971. The intraclass correlation coefficients (ICCs) for all repeated measurements ranged from 0.93 to 1.00. The results of the automated measurement showed that 83.33% of patients exhibited condylar resorption occurring six months or more after surgery. Logistic regression and linear regression indicated a positive correlation between counterclockwise rotation in the pitch plane and condylar resorption (P < .01). And a positive correlation between the rotational angles in both three planes and changes in the condylar volume at six months after surgery (P ≤ .04).

CONCLUSIONS

This study's automated method for measuring condylar changes shows excellent repeatability. Skeletal class II malocclusion patients may experience condylar resorption after bimaxillary orthognathic surgery, and this is correlated with counterclockwise rotation in the sagittal plane.

ADVANCES IN KNOWLEDGE

This study proposes an innovative multi-step registration method based on CBCT, and establishes an automated approach for quantitatively measuring condyle changes post-orthognathic surgery. This method opens up new possibilities for studying condylar morphology.

"Over-reviewing" of research? An analysis of orthodontic reviews

INTRODUCTION

Research overviews may be undertaken to identify gaps in the literature, evaluate existing systematic reviews (SRs), and summarize evidence. This paper aims to profile overviews that have been conducted in orthodontics and related interventions since 2012 and to evaluate the degree of overlap among these overviews.

METHODS

Overviews published between January 1, 2012 and June 20, 2023 were identified using an electronic search involving Google Scholar and PubMed. A descriptive summary was produced, and citation matrices were used to evaluate the percentage of overlap between overviews using corrected covered area and covered area. This was classified as slight, moderate, high, or very high.

RESULTS

A total of 35 overviews were identified across a wide range of topics. Eight overviews included <10 SRs; 21 had 10-20 SRs; and 6 included >20 SRs (median no. of SRs per overview, 15; range, 3-62). Meta-analysis was conducted in only 5 overviews. Overlap between overviews on the same topic ranged from slight (2.7%) to very high (53.8%).

CONCLUSIONS

Almost all overview topics address treatments and their effects, with a wide variation in the number and quality of SRs included. There is considerable overlap in some orthodontic overviews, suggesting unnecessary duplication and research waste. Researchers should be encouraged to focus on primary data collection to add more high-quality data to SRs, which will ultimately enhance the yield from secondary and tertiary orthodontic research.

Impact of clear aligner therapy on masticatory musculature and stomatognathic system: a systematic review conducted according to PRISMA guidelines and the Cochrane handbook for systematic reviews of interventions

BACKGROUND

Clear aligner therapy has gained popularity as a minimally invasive orthodontic treatment option. However, its impact on the masticatory musculature and the stomatognathic system is an area of growing interest, as it involves the adjustment of occlusion and tooth movement. This systematic review aims to comprehensively assess and synthesise existing evidence regarding the influence of clear aligner therapy on the masticatory musculature and the stomatognathic system.

METHODS

An exhaustive search was performed on electronic databases that adhered to PRISMA guidelines. Clinical studies that evaluated the impact of patients receiving aligner orthodontic treatment on the muscles of the mastication and stomatognathic systems were included. A standardised data extraction form was devised for relevant variables. Two reviewers extracted the data variables. ROB-2 was used for bias evaluation in the selected studies.

RESULTS

A total of six studies met the inclusion criteria. The wearing of clear aligners significantly impacted the muscles of mastication. Muscle activity and discomfort showed a significant alteration in the initial days of appliance placement. but this observation was temporary, with no significant changes thereafter in subsequent follow-up. Bite force reduction was also noted. All the studies evaluated showed good methodological quality.

CONCLUSION

The review found that aligned orthodontic treatment may have a variable impact on muscles of mastication, with a potential for initial exacerbation of symptoms followed by possible improvement. However, due to the limited number of studies and their heterogeneous nature, further robust research is recommended to fully understand the relationship between aligned orthodontic treatment and masticatory muscles.

Enhancing skeletal stability and Class III correction through active orthodontist engagement in virtual surgical planning: A voxel-based 3-dimensional analysis

INTRODUCTION

Skeletal stability after bimaxillary surgical correction of Class III malocclusion was investigated through a qualitative and quantitative analysis of the maxilla and the distal and proximal mandibular segments using a 3-dimensional voxel-based superimposition among virtual surgical predictions performed by the orthodontist in close communication with the maxillofacial surgeon and 12-18 months postoperative outcomes.

METHODS

A comprehensive secondary data analysis was conducted on deidentified preoperative (1 month before surgery [T1]) and 12-18 months postoperative (midterm [T2]) cone-beam computed tomography scans, along with virtual surgical planning (VSP) data obtained by Dolphin Imaging software. The sample for the study consisted of 17 patients (mean age, 24.8 ± 3.5 years). Using 3D Slicer software, automated tools based on deep-learning approaches were used for cone-beam computed tomography orientation, registration, bone segmentation, and landmark identification. Colormaps were generated for qualitative analysis, whereas linear and angular differences between the planned (T1-VSP) and observed (T1-T2) outcomes were calculated for quantitative assessments. Statistical analysis was conducted with a significance level of α = 0.05.

RESULTS

The midterm surgical outcomes revealed a slight but significantly less maxillary advancement compared with the planned position (mean difference, 1.84 ± 1.50 mm; P = 0.004). The repositioning of the mandibular distal segment was stable, with insignificant differences in linear (T1-VSP, 1.01 ± 3.66 mm; T1-T2, 0.32 ± 4.17 mm) and angular (T1-VSP, 1.53° ± 1.60°; T1-T2, 1.54° ± 1.50°) displacements (P >0.05). The proximal segments exhibited lateral displacement within 1.5° for both the mandibular right and left ramus at T1-VSP and T1-T2 (P >0.05).

CONCLUSIONS

The analysis of fully digital planned and surgically repositioned maxilla and mandible revealed excellent precision. In the midterm surgical outcomes of maxillary advancement, a minor deviation from the planned anterior movement was observed.

Exploring the relationship between the number of systematic reviews and quality of evidence: an orthognathic surgery-based study

OBJECTIVE

We analyzed the quality and quantity of systematic reviews (SRs) of orthognathic surgery, the most frequently published topic in maxillofacial surgery.

STUDY DESIGN

We searched the PubMed database for SRs of orthognathic surgery with no restriction on the language of publication date. We assessed the certainty of evidence presented according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol and the Leiden Manifesto using the Grading of Recommendations Assessment, Development, and Evaluation approach. We analyzed the data using descriptive statistics, Pearson´s correlation test, and linear regression.

RESULTS

Of the 171 SRs evaluated, approximately one fifth presented evidence with a high level of certainty. The number of orthognathic surgery SRs has been increasing, and many SRs were published after very similar topics had already been published. There is no relationship between the impact factor and the certainty of evidence.

CONCLUSIONS

An excessive number of SRs of orthognathic surgery are published, and many SRs are superfluous, simply reporting previous findings. Clinicians should not base treatment decisions solely on the evidence presented in SRs, and journal editors and reviewers should evaluate these SRs more critically, particularly when they address topics that have already been covered in the literature.

3D analysis of condylar and mandibular remodeling one year after intra-oral ramus vertical lengthening osteotomy

OBJECTIVES

Among the existing techniques for the correction of mandibular posterior vertical insufficiency (PVI), the intra-oral ramus vertical lengthening osteotomy (IORVLO) can be proposed as it allows simultaneous correction of mandibular height and retrusion. This study assessed the 3D morpho-anatomical changes of the ramus-condyle unit and occlusal stability after IORVLO.

MATERIALS AND METHODS

This retrospective analysis compared immediate and 1-year post-operative 3D CBCT reconstructions. The analysis focused on the condylar height (primary endpoint) and on the changes in condylar (condylar diameter, condylar axis angle) and mandibular (ramus height, Frankfort-mandibular plane angle, gonion position, intergonial distance, angular remodeling) parameters. Additionally, this analysis investigated the maxillary markers and occlusal stability.

RESULTS

On the 38 condyles studied in 21 included patients (mean age 23.7 ± 3.9 years), a condylar height (CH) loss of 0.66 mm (p < 0,03) was observed, with no correlation with the degree of ramus lengthening (mean 13.3 ± 0.76 mm). Only one patient presented an occlusal relapse of Class II, but a 3.4 mm (28%) condylar diameter loss and a 33% condylar volume reduction with loss of 1 mm and 3.4 mm in CH and condyle diameter, respectively. A mean 3.56 mm (p < 0.001) decrease in ramus height was noted, mainly due to bone resorption in the mandibular angles.

CONCLUSION

This study confirms the overall stability obtained with IORVLO for the correction of PVI.

CLINICAL RELEVANCE

This study aims to precise indication of IORVLO, and to validate the clinical and anatomical stability of results.

Short- and Long-Term Effects of Maxillary Expander with Tongue Crib in Growing Open-Bite and Skeletal Class II Patients: A Retrospective Study

The purpose of this study was to evaluate short- and long-term changes in growing patients with Class II malocclusion and open bite after rapid maxillary expansion (RME). A retrospective cohort study was conducted with 16 growing patients with open-bite malocclusion enrolled in a group treated with a rapid maxillary expander (RME) with a crib (TG), and 16 untreated patients with similar malocclusion in the control group (CG). Cephalograms were recorded before starting the treatment (T0), at the end of the latency phase (T1), and before the fixed therapy (T2) in order to analyze skeletal and dental changes in vertical, transversal, and sagittal relationships. Statistical analysis was performed with α = 0.05 as level of significance. At the end of the active expansion (T1), all subjects in the TG showed a corrected overbite with a statistically significant difference compared to the CG (p > 0.05). A significant decrease in jaw divergence was found in the TG compared to the CG (p < 0.05). At T2, all treated patients maintained a correct overbite. Statistical analysis revealed a significant decrease in maxillary, mandibular, and intermaxillary divergence in the TG compared to the CG (p < 0.05). This protocol could be effective in growing open-bite patients, showing a long-term decrease in facial divergence. The fixed crib allowed to normalize myofunctional activity.

Condylar Positional Changes in Skeletal Class II and Class III Malocclusions after Bimaxillary Orthognathic Surgery

Orthognathic surgery is indicated to modify the position of the maxillomandibular structure; changes in the mandibular position after osteotomy can be related to changes in the position of the mandibular condyle in the articular fossa. The aim of this study was to determine changes produced in the mandibular condyle 6 months after orthognathic surgery. A cross-sectional study was conducted that included subjects who had undergone bimaxillary orthognathic surgery to treat dentofacial deformity of Angle class II (group CII) or Angle class III (group CIII). Standardized images were taken using cone-beam computed tomography 21 days before surgery and 6 months after surgery; measurement scales were used to identify the condylar position and its relations with the anterior, superior, and posterior joint spaces. The results were analyzed using the Shapiro-Wilk and Student's t-tests, while considering a value of p < 0.05 as indicating a significant difference. Fifty-two joints from 26 patients, with an average age of 27.9 years (±10.81), were analyzed. All subjects in both group CII and group CIII showed a significant change in the anterior, superior, and posterior joint spaces. However, postoperative changes in the position of the condyle in the articular fossa were not significant in the anteroposterior analysis. We conclude that orthognathic surgery causes changes in the sagittal position of the mandibular condyle in subjects with mandibular retrognathism and prognathism.

Condylar remodelling in a severe class II deep bite dento-skeletal malocclusion treated with an ortho-surgical approach: A five-year follow-up case report

Condylar displacement and remodelling are phenomena closely related to orthognathic surgery and critically involved in occlusal and skeletal stability. The aim of the present case report is to describe over time condylar displacement and surface remodelling after bilateral split sagittal osteotomy (BSSO) in an adult patient with severe class II skeletal malocclusion treated with ortho-surgical approach. A male of 21years comes to our observation. The extraoral examination shows a symmetrical square-shaped face, a convex profile, an acute nasolabial angle and a deep labiomental fold. Intraoral examination reveals a class II division 2 with a 2mm deviation of the mandibular midline to the left and the presence of a scissor bite of the bicuspids between quadrants II and III. The Spee curve and overbite are extremely accentuated (OV 14.3mm) as the overjet (11.1mm). Axiographic reconstructions of CBCT show a normal shape and position of both condyles. The cephalometric analysis shows a reduced lower facial height, a normal upper jaw position, a mandibular underdevelopment masked by a very developed symphysis and an extremely low divergence (FMA 11.2°). BSSO for mandibular setback was performed in the 13th month of orthodontic therapy. Original CBCT data before surgery (T0), at the end of treatment (T1), 2years postoperatively (T2) and 5years postoperatively (T3) were collected and reconstructed for 3-dimensional (3D) qualitative analyse. At the end of the surgical-orthodontic treatment (26months), good function and good aesthetics were achieved. The qualitative and comparative analysis of the superimpositions and the cuts made on the CBCT at T0, T1, T2, T3 showed a physiological remodelling and adaptation of the condyles.

Changes in Preexisting Temporomandibular Joint Clicking after Orthognathic Surgery in Patients with Mandibular Prognathism

This study aimed to investigate the changes in preexisting temporomandibular joint (TMJ) clicking and the new incidence of TMJ clicking after orthognathic surgery. A total of 60 patients (30 men and 30 women) with mandibular prognathism underwent intraoral vertical ramus osteotomy (IVRO) for a mandibular setback. The setback amount and TMJ clicking symptoms (preoperative and one year postoperative) were recorded. To assess the risk of new incidence of TMJ clicking in asymptomatic patients, the cutoff value for postoperative mandibular setback was set at 8 mm. The left and right mandibular setbacks were 11.1 and 10.9 mm in men, respectively, and 10.7 and 10.0 mm in women, respectively. Thus, no difference in setback amount on either side was observed between the sexes. The improvement rate in patients with preexisting TMJ clicking was 69.2% (18 of 26 sides); the postoperative improvement rates were 71.4% (setback amount > 8 mm) and 60% (setback amount ≤ 8 mm). IVRO may reduce the severity of preexisting TMJ clicking. A high setback amount (>8 mm) may not be associated with a considerable increase in the risk of postoperative TMJ clicking.

Mandibular stability and condylar changes following orthognathic surgery in mandibular hypoplasia patients associated with preoperative condylar resorption

OBJECTIVES

To evaluate postoperative mandibular stability and condylar changes in patients with mandibular hypoplasia and preoperative condylar resorption (CR) undergoing orthognathic surgery.

MATERIALS AND METHODS

Fifty-four patients were included in this retrospective study. Computed tomography (CT) scans were acquired preoperatively (T0), 2-7 days immediate postoperatively (T1), and at least 1 year postoperatively (T2). Three-dimensional (3D) cephalometric analysis and measurements of condylar angle, volume, and position (joint spaces) were performed. A 2-mm mandibular relapse was deemed clinically acceptable. We also analyzed the correlations between relapse and postoperative CR and susceptible factors using a multivariate logistic regression model.

RESULTS

The results showed one year after the surgery, the average mandibular relapse was 1.0 mm (p < 0.05), and the average reduction of condylar volume was 152.4 mm³ (12.7%). Condyle-fossa relationships were improved immediately after the surgery, with a tendency of returning to their original state in the follow-up (p < 0.05). Anteroposterior advancement at point B (B-CP advancement) at T1 and superior joint space (SJS) at T0 were significantly correlated with mandibular relapse, and postoperative CR was mainly associated with vertical increasement at point B (B-AP increasement) at T1. The optimal cut-off values were as follows: 1.6 mm for SJS, 4.2 mm for B-CP advancement, and 1.8 mm for B-AP increasement. Concomitant advancement Genioplasty showed no significant correlation with relapse and postoperative CR.

CONCLUSIONS

While patients with mandibular hypoplasia and preoperative CR were vulnerable to further condylar resorption after mandibular advancement, the treatment outcomes were generally clinically acceptable. Postoperative relapse was associated with a larger than 4.2 mm of mandibular advancement measured at B-CP and a larger than 1.6 mm of superior joint space measured at SJS, and postoperative CR was associated with a larger than 1.8 mm of mandibular vertical increasement measured at B-AP.

CLINICAL RELEVANCE

The findings of this study suggested that the mandibular advancement might be limited to 5 mm for patients with preoperative CR. A concomitant advancement genioplasty might also be considered to achieve a better facial profile in these patients.

Osseous Union after Mandible Reconstruction with Fibula Free Flap Using Manually Bent Plates vs. Patient-Specific Implants: A Retrospective Analysis of 89 Patients

The aim of this monocentric, retrospective clinical study was to evaluate the status of osseous union in uni- and poly-segmental mandible reconstructions regarding conventional angle-stable manually bent osteosynthesis plates (Unilock 2.0 mm) versus titan laser-melted PSI patient-specific implant’s (PSI). The clinical impact of PSI’s high stiffness fixation methods on bone healing and regeneration is still not well addressed. The special interest was in evaluating the ossification of junctions between mandible and fibula and between osteotomized fibula free flap (FFF) segments. Panoramic radiograph (OPT), computed tomography (CT) scans, or cone-beam CTs (CBCT) of patients who underwent successful FFF for mandible reconstruction from January 2005 to December 2020 were analyzed. A total number of 89 cases (28 females (31.5%), 61 males (68.5%), mean age 58.2 ± 11.3 years, range: 22.8–82.7 years) fulfilled the chosen inclusion criteria for analysis (conventional: n = 44 vs. PSI: n = 45). The present study found an overall incomplete ossification (IOU) rate of 24.7% (conventional: 13.6% vs. PSI: 35.6%; p = 0.017) for mandible to fibula and intersegmental junctions. Between osteotomized FFF segments, an IOU rate of 16% was found in the PSI-group, while no IOU was recorded in the conventional group (p = 0.015). Significant differences were registered for IOU rates in poly-segmental (p = 0.041), and lateral (p = 0.016) mandibular reconstructions when PSI was used. Multivariate logistic regression analysis identified plate exposure and type of plate used as independent risk factors for IOU. Previous or adjuvant radiotherapy did not impact incomplete osseous union in the evaluated study sample. PSI is more rigid than bent mini-plates and shields functional mechanical stimuli, and is the main reason for increasing the rate of incomplete ossification. To enhance the functional stimulus for ossification it has to be discussed if patient-specific implants can be designed to be thinner, and should be divided into segmental plates. This directs chewing forces through the bone and improves physiological bone remodeling.