The impact of CBCT-head tilting on 3D condylar segmentation reproducibility

OBJECTIVES

To investigate whether variations in head positioning may influence the reproducibility of cone-beam CT (CBCT) three-dimensional (3D) segmented models of the mandibular condyle.

METHODS

Five fresh frozen cadaver heads were scanned in four different positions: reference position (RP) and a set of three tilted alternative head positions (AP) in anteroposterior direction (AP1: 2 cm anterior translation, AP2: 5° pitch rotation, AP3: 10° pitch rotation). Surface models of mandibular condyles were constructed and compared with the condylar reference position using voxel-based registration. Descriptive statistics and a linear mixed-effects model were performed to compare condylar volumetric differences and root mean square (RMS) distance between surfaces of AP vs RP.

RESULTS

The mean differences in condylar volumes of AP vs RP were 14.1 mm³ (95% CI [-79.3, 107.4]) for AP1, 1.0 mm³ (95% CI [-87.2, 89.2]) for AP2 and 0.1 mm³ (95% CI [-88.3, 88.4]) for AP3. Mean and absolute volumetric differences did not exceed earlier reported intraoperator differences of 30 mm³. The RMS distance values obtained per group were 0.12 mm (95% CI [0.05,0.20]) for AP1, 0.17 mm (95% CI [0.10, 0.22]) for AP2 and 0.17 mm for AP3 (95% CI [0.10,0.22]). The confidence intervals (CI) for RMS distance remained far below the threshold for clinical acceptability (0.5 mm).

CONCLUSIONS

Within the limits of the present study, it is suggested that tilted head positions may affect the reproducibility of 3D condylar segmentation, thereby influencing outcome in repeated CBCT scanning. Nevertheless, observed differences are unlikely to have a meaningful impact on clinical patient diagnosis and management.

Condylar positional changes and remodeling following bimaxillary anterior segment osteotomy with and without Le Fort I osteotomy: a three-dimensional comparative analysis

OBJECTIVE

To evaluate 3D condylar displacement and long-term remodeling following the correction of bimaxillary protrusion by anterior segment osteotomy (ASO) with and without Le Fort I surgery.

MATERIALS AND METHOD

This retrospective study included 32 adults with bimaxillary protrusion who underwent ASO alone (group 1) or with concomitant Le Fort I osteotomy (group 2). Subject's computed tomography scans at basic (T0), immediate postoperatively (T1), and at 1 year or more follow-up (T2) were collected. The condyle displacement was measured at superior-inferior, lateromedially, and anteroposterior surfaces, while condyle remodeling was measured at the superior, lateral, anterior, medial, and posterior surfaces. All 3D analyses were performed using 3D Slicer software (4.11.2).

RESULTS

At T1, 52.7%, 86.7%, and 94.4% of condyles in group 1 were displaced inferiorly, laterally, and posteriorly, respectively, as well as 75%, 89.2%, and 53.5% of condyles in group 2, which had not fully returned to the original preoperative positions at T2. Condylar remodeling was observed in both groups at T2, and no significant difference was found in the overall condylar volume between T1 and T2 in both groups. Patients in group 2 exhibited significant bone resorption at both lateral and anterior surfaces compared to group 1 (P = 0.000 and 0.01, respectively).

CONCLUSION

This study's results demonstrated that ASO is associated with a degree of condylar changes even if the posterior mandible is not osteomized. The positional changes vary between bimaxillary ASO alone and those with simultaneous Le Fort I osteotomy. However, both groups' condyle volume remained stable at the long-term follow-up.

A Nonsurgical Treatment Strategy for Longstanding, Nonreducible, Bilateral Temporomandibular Joint Dislocation: A Case Report

Temporomandibular joint (TMJ) dislocation is a condition in which the mandibular condyle is displaced from the glenoid fossa and must be manipulated to return it to its normal position. Among several diagnostic subtypes, long-standing or chronically protracted TMJ dislocation is rare and challenging to manage. Treatment options include various nonsurgical and surgical approaches. This case report describes the successful nonsurgical management of a longstanding bilateral TMJ dislocation using elastic traction with a removable appliance and posterior bite planes. This technique should be attempted before performing additional surgical interventions.

A Novel Imaging Technique for Analyzing Condylar Movement During Mastication in Patients With Jaw Deformities: Four-Dimensional Computed Tomography

OBJECTIVE

This study aimed to reveal characteristic condylar movements in patients with jaw deformities.

STUDY DESIGN

Thirty patients with jaw deformities before surgery were enrolled and instructed to chew a cookie during 4-dimensional computed tomography (4DCT). The distance between the most anterior and posterior positions of the bilateral condyles on 4DCT images was measured and compared among patients with different skeletal classes. Correlations between the condylar protrusion and cephalometric values were also determined.

RESULTS

The distances of condylar protrusion during mastication were significantly greater in the skeletal class II group than in the skeletal class III group ( P =0.0002). Significant correlations were found between the distances of condylar protrusion during mastication and the sella-nasion-B point angle ( r =-0.442, P =0.015), A point-nasion-B point angle ( r =0.516, P =0.004), sella-nasion plane to ramus plane angle ( r =0.464, P =0.01), sella-nasion plane to occlusal plane angle ( r =0.367, P =0.047), and condylion-gonion length ( r =-0.366, P =0.048).

CONCLUSION

Motion analysis with 4DCT images revealed that condylar movement in patients with retrognathism was larger than in patients with mandibular prognathism. Skeletal structure was therefore correlated with condylar movement during mastication.

A rare case of bilateral pseudoaneurysm secondary to mandibular condyle fracture-a case report with review of literature

This paper aims to present a rare case report of bilateral pseudoaneurysm secondary to condylar fracture and its management with a brief review of literature. A patient of age 19 years with alleged history of road traffic accident presented 6 weeks lately to our department with slow growing swelling in right preauricular area. History revealed bilateral condylar fracture with right parasymphysis fracture of mandible for which patient underwent maxillomandibular fixation for 4 weeks. The diffuse swelling in preauricular region showed positive signs of pulsation and audible bruit. Ultrasonography and contrast-enhanced computed tomography suggested the bilateral presence of vascular anamoly from the terminal branches of external carotid artery. Diagnostic angiography confirmed presence of pseudoaneurysm at the bifurcation of the internal maxillary artery and superficial temporal artery (STA) on right side whereas on the left side it was at proximal STA. Bilateral endovascular coil and gel foam embolization was done and thrombosis was confirmed with high frequency ultrasound on fourth postintervention day. The swelling completely resolved in a period of 1 month with no evidence of recurrence in the following 2-year follow-up period. Routine investigation revealed presence of pseudoaneurysm on left side which was completely without any clinical signs as repoterd by many cases of condylar fracture in the literature review. Pseudoaneurysm may remain silent and are exposed intraoperatively with massive bleeding which causes significant morbidity. Hence, prompt diagnosis and management is essential to avoid unexpected complication perioperatively.

Control of Mandibular Width With 3D Printed Occlusal Splint in Children With Multiple Mandibular Fractures

BACKGROUND

The fracture of mandibular symphysis combined with bilateral condylar fractures often leads to changes in the width of the mandible, which significantly widens the face of the child. Therefore, it is necessary to reposition the mandible through accurate adduction.

METHODS

To ensure that the mandible can be accurately repositioned, a 3D printed occlusal splint was used. Bilateral maxillomandibular fixation screws were implanted. The 3D printed occlusal splint was located on the maxillary dentition and fixed to the maxillomandibular fixation screws with wire loops. The reference basis for adduction is to make the mandibular dentition located in the occlusal splint. The absorbable plate was contoured according to the restored model and fixed at the fracture site. The 3D printed occlusal splint was retained in the maxillary dentition for two months.

RESULTS AND DISCUSSION

Postoperative computed tomography showed that the mandible had been adducted according to the preoperative design. Two months of follow-up showed that the child's facial development, mouth opening type, occlusion, and range of motion were good. It is especially suitable for children with mandibular symphyseal fractures accompanied by bilateral condylar fractures.

[Study of dental arch width in patients with idiopathic condylar resorption]

Objective:To investigate the relationship between idiopathic condylar resorption （ICR） and arch width disorder. Methods:Thirty-two patients with ICR and twenty patients without condylar resorption were enrolled according to the same inclusion criteria. They were divided into experimental group and control group. The experimental group was divided into unilateral ICR group and bilateral ICR group according to the affected side of condylar resorption, and then experimental group was divided into subgroups ICR Ⅰ, ICRⅡand ICR Ⅲ according to the degree of condylar resorption. Patients with no condylar resorption were used as a control group. The width of anterior, middle and posterior segments of dental arch on cone beam computed tomography（CBCT） was measured and the two groups of measured values were statistically analyzed. Results:Compared with the control group, the width of maxillary anterior, middle and posterior segments in ICR group was significantly reduced, and the difference was statistically significant（P<0.01）. But the width of mandibular segment was not significantly different from that in control group（P>0.05）. There was no significant difference in the width of anterior, middle and posterior dental arch between subgroups（P>0.05）. Conclusion:Almost all patients with ICR have malocclusion of maxillary and mandibular arch width, but there is no significant correlation between the malocclusion width and the severity of condylar resorption.

Short-term effects of mechanical loading on the transdifferentiation of condylar chondrocytes

INTRODUCTION

Transdifferentiation of chondrocytes into bone cells explains most of the prenatal and early postnatal condylar growth, but its role during later postnatal growth and the mechanisms regulating transdifferentiation remain unknown. This study aimed to quantify the effects of mechanical loading on chondrocyte-derived osteogenesis during late postnatal condylar growth using a short-term mandibular laterotrusion model.

METHODS

Thirty 4-week-old Aggrecan-CreERT2, R26RtdTomato, and 2.3Col1a1-GFP compound mice received tamoxifen injections and were divided into control and experimental groups. Appliances were bonded to shift the mandibles of the experimental mice for 5 days, causing protrusion and retrusion of the right and left condyles, respectively. Radiographic, microcomputed tomographic, and histomorphometric analyses were performed.

RESULTS

The experimental and control groups showed substantial transdifferentiation of chondrocytes into bone cells. The experimental mice developed asymmetric mandibles, with the protrusive side significantly longer than the retrusive side. The protrusive condyles showed significantly increased chondrogenesis and greater numbers of chondrocyte-derived osteogenic cells, especially in the posterior third. The opposite effects were seen on the retrusive side.

CONCLUSIONS

Transdifferentiation of chondrocytes into bone cells occurs during late postnatal condylar growth. Laterotrusion regulates condylar chondrogenesis and chondrocyte transdifferentiation, which alters the amount and direction of condylar growth. Our study demonstrated that chondrocytes are key players in condylar bone formation and should be the focus of studies to control and further understand condylar growth.

Preliminary clinical study of the accuracy of a digital axiographic recording system for the assessment of sagittal condylar inclination

OBJECTIVES

The aim of this study was to clinically evaluate the accuracy of a digital axiographic recording system in tracing the sagittal condylar inclination.

METHODS

An axiographic examination that records the sagittal condylar path during protrusive/retrusive movement was performed on ten patients. Each subject was registered five different times by two different systems: 1) the Cadiax Gamma Diagnostic 4 computerized system as the control; 2) the Zebris Jaw Motion Analyser+  Optic System as the tested digital axiographic recording system. The records obtained allow to calculate the kinematic terminal transverse horizontal axis and the sagittal condylar inclination (SCI) at 3 and 5 mm along the pro-retrusive path. A linear mixed model was used to analyze if there was a statistically significant difference between the two systems.

RESULTS

The mean left SCI value recorded by Zebris system were 49.81 ± 10.64° at 3 mm, 48.10 ± 11.04° at 5 mm, while the values recorded by Gamma system were 55.16° at 3 mm, 52.18° at 5 mm. The mean right SCI value recorded by Zebris system were 54.53 ± 10.26° at 3 mm, 51.85 ± 8.55° at 5 mm, while the values recorded by Gamma system were 49.68° at 3 mm, 48.23° at 5 mm. Linear mixed model showed no significant statistical difference between the two systems.

CONCLUSIONS

Based on preliminary results, the Zebris Jaw Motion Analyzer+ Optic System demonstrates comparable accuracy to the Cadiax Gamma Diagnostic 4 when measuring sagittal condylar inclination.

CLINICAL SIGNIFICANCE

The digital axiographic recording system enables to evaluate sagittal condylar inclination and to adjust virtual articulators in a digital workflow.

Treatment of dentofacial deformities secondary to condylar hyperplasia

Dentofacial deformities secondary to condylar hyperplasiais a kind of disease presenting facial asymmetry, malocclusion, temporomandibular joint dysfunction, and other symptoms caused by non-neoplastic hyperplasia of the condyle. The etiology is still unknown, and currently, pre- and post-operative orthodontics accompanied by orthognathic surgery, temporomandibular joint surgery and jawbone contouring surgery are the main treatment methods. A personalized treatment plan was developed, considering the active degree of condyle hyperplasia, the severity of the jaw deformity, and the patient's will, to correct deformity, obtain ideal occlusal relationship, and regain good temporomandibular joint function. Combined with the author's clinical experience, the etiology, clinical and imageological features, treatment aims, and surgical methods of condylar hyperplasia and secondary dentofacial deformities were discussed in this paper.

Single photon emission computed tomography (SPECT) diagnostic accuracy in active unilateral condylar hyperplasia: Retrospective study

The aim of this study was to assess the diagnostic accuracy of single photon emission tomography (SPECT) in unilateral condylar hyperplasia (UCH). To this end, 3D morphometric changes of the mandibles in one year were assessed (T0 vs. T1) and compared over SPECT results in T1, in a sample of 40 patients. A contingency table was constructed based on these results for SPECT diagnostic accuracy evaluation, classifying patients as SPECT true-positive, true-negatives, false positives and false-negatives. Additionally, the morphometric analysis was used to describe the presentation of mandibular changes using principal component analysis (PCA) and non-parametric statistics. We obtained diagnostic accuracy results of sensitivity 81%, specificity 63%, positive predictor value (PPV) 59%, negative predictor value (NPV) 83% and accuracy 70%, showing that SPECT yields poor results regarding accuracy diagnostic performance. The morphometric analysis showed that individuals without progress of asymmetry and those with more progress differ particularly in a group of landmarks representing the mental region and the right mandibular body. Based on these landmarks, difference among the four SPECT-accuracy groups was statistically significant (p < 0.001), where the landmark showing the largest change within a year had a mean increase of 1.13 + 0.66 mm. Within the limitations of the study, it seems that SPECT alone is not suitable for making surgical decisions regarding condylectomy in active UCH. Follow up with morphological assessment methods are recommended for confirming an active UCH in combination with SPECT.

Comparison of accuracy of protrusive condylar guidance registration by two interocclusal recording materials in edentulous patients

Background and Purpose

During complete denture fabrication making Interocclusal records plays an integral role to obtain the condylar guidance value. The study was conducted to compare the protrusive condylar guidance registration by two interocclusal recording materials-Quick setting plaster and Luxabite®(bisacrylic composite) in semi adjustable articulator for completely edentulous patients.

Methodology

Maxillary and Mandibular casts of the completely edentulous patients were mounted in Hanau®Wide Vue articulator. The Quick setting plaster and Luxabite®(bisacrylic composite) was used as interocclusal recording materials to program the protrusive condylar guidance angles in the articulators.

Results

The protrusive condylar guidance values registered in the articulator for the different interocclusal records were tabulated and statistically analyzed.. The mean protrusive condylar guidance values registered in the articulator was compared with two parameters obtained from the radiographic tracings -- the protrusive condylar path angle obtained with Quick setting plaster and Luxabite with the inclination of articular eminence to the Frankfort horizontal plane.

Conclusion

From the study it was concluded that the Luxabite®(bisacrylic composite) material demonstrated better reproducibility of protrusive condylar guidance registration.than the Quick setting plaster.

Remodelling of mandibular condylar head after fixation of fractures with ultrasound activated resorbable pins: A retrospective case series

The aim of this study was to assess whether the resorption of poly-lactic acid pins, used for condylar head fracture fixation, adversely affect remodelling of the condylar head. A retrospective review of patients was performed that underwent ORIF of CHF with ultrasound activated resorbable poly-lactic acid pins and had CT/CBCT scans of the condyle at least 18 months after surgery, at which point the fixation material was expected to be resorbed. We reviewed the size, shape and position of the condylar head and compared this to the normal side and compared this to the results of conservative management and ORIF with titanium screws in the literature. Most patients had condylar heads normally positioned and shaped, with minimal bone changes. The position of the condyle in the fossa, its shape and bone changes compare favourably with previous studies on CHF managed conservatively or with titanium screw fixation. There was no radiographic evidence of the pins after 18 months. In conclusion, ultrasound activated resorbable pins can provide suitable fixation for ORIF of condylar head fractures, avoiding the need for screw removal, and there was no evidence that the resorption process adversely affected the remodelling of the condylar head.

retrospective evaluation of condylar morphology using panoramic radiography in a sample of Turkish population

BACKGROUND

The temporomandibular joint is one of the most complex anatomic structures. It takes a great role in masticatory system and helps to make possible some functions such as speaking, chewing and swallowing. Clinicians should have sufficient anatomical knowledge to assess relationships of the hard and soft tissues, including the mandibular condyle, glenoid fossa, articular eminence of the temporal bone, the articular disc and its attachments. The aim of this study was to evaluate the frequency of different types of mandibular condyles and its distribution according to the age and gender. It was also evaluated whether the condyle types were bilaterally symmetrical or not.

MATERIALS AND METHODS

A total of 1315 digital panoramic images which obtained from the patients suffering from the dental problems were assessed. Demographic data, condylar morphology were noted. All obtained data were analysed by using descriptive statistics. Morphology of mandibular condyles were classified into four shapes as identified in other studies, namely: type I - oval shape, type II - diamond shape, type III - bird beak shape, type IV - crooked finger shape. Two independent examiners, who have 19 and 7 years of experience in oral and dentomaxillofacial radiology, made a consensus and evaluated all images.

RESULTS

A total of 1315 digital panoramic images were assessed. Seven hundred sixty-seven [58.3%] the patients were female and 548 [41.6%] were male. The age range of patients was from 18 to 84 years. Right-left condyle types were found to be symmetrical in the range of 67% of the subpopulation examined in the study. For the consensus, 'oval' condyle was common on both the right and left, while 'crooked finger' condyle was the rarest.

CONCLUSIONS

The temporomandibular joint is the most important structure for all jaw functions such as speech, swallowing. In order for all these functions to continue in a healthy way, the anatomical structure should be known very well down to the finest detail. Identification of anatomical structures and their variations can play an important role in implant dentistry. Clinicians commonly prefer conventional radiologic methods to evaluate dentomaxillofacial region. Although the most of the variations are asymptomatic and require no treatment,correct identification of these findings will reduce unnecessary further diagnostic assessments and will provide more appropriate treatment plans.

Degenerative changes of the mandibular condyle in relation to the temporomandibular joint space, gender and age: A multicenter CBCT study

BACKGROUND

Cone-beam computed tomography (CBCT) is used to provide multiplanar views of the temporomandibular joint (TMJ) bone components as well as TMJ pathologies without superposition, magnification or distortion.

OBJECTIVES

The study aimed to analyze degenerative changes in the condylar surface, and their relationship with patient age and gender, and the TMJ space measurements by using CBCT images.

MATERIAL AND METHODS

A total of 258 individuals were retrospectively analyzed. The degenerative bone changes of the condylar head were evaluated and classified on the right and left sides. The shortest distances from the anterior, superior and posterior parts of the condylar head to the glenoid fossa were measured to represent the TMJ space. Univariate and multivariate logistic regression analyses then evaluated the effect of age and gender on the presence of degenerative changes.

RESULTS

Condylar flattening was most frequently observed (413 TMJs, 53.5%). However, the presence or absence of the change types did not differ according to the sides. The mean values of the TMJ space measurements on the right and left sides were narrower in the group with changes than in the group without changes. Nonetheless, no statistically significant difference in the TMJ space was found between the groups (p > 0.05).

CONCLUSIONS

An increased risk of radiographically detectable degenerative alterations in left TMJs was detected for males and for increasing age. Degenerative changes in the condylar surface may affect the dimensions of the TMJ space.

Transoral Endoscopic-Assisted Reduction and Internal Fixation of Mandibular Condylar Fractures in Children

PURPOSE

Extraoral approaches for open reduction and fixation of condylar fractures in children are associated with serious risks of complications, including facial nerve injury, facial scarring, parotid fistula, and auriculotemporal nerve injury. The purpose of this study was to retrospectively evaluate the outcomes of transoral endoscopic-assisted open reduction and internal fixation of condylar fractures and hardware removal in pediatric patients.

MATERIAL AND METHODS

This study was designed as a retrospective case series. The study included pediatric patients admitted with condylar fractures that were indicated for treatment with open reduction and internal fixation. The patients were clinically and radiographically evaluated with regard to occlusion, mouth opening, lateral and protrusive movement of the mandible, pain, chewing and speech difficulties, and bone healing at the fracture site. Computed tomography images were used to assess the reduction of the fractured segment, the stability of fixation and progress of healing of the condylar fracture at follow-up visits. The same surgical treatment approach was applied to all patients. The data from the study were analyzed for a single group without any comparison to other groups.

RESULTS

The technique was used for the treatment of 14 condylar fractures in 12 patients between the ages of 3 to 11 years. A total of 28 transoral endoscopic-assisted approaches to the condylar region either for reduction and internal fixation or hardware removal were applied. The mean operating time was 53.1 (±11.3) minutes for the fracture repair and 20 (±2.6) minutes for hardware removal, respectively. The mean follow-up time of the patients was 17.8 (±2.7) months (median: 18) months. All patients regained stable occlusion, satisfactory mandibular motion, stable fixation, and complete bone healing at the fracture site at the end of their follow-up period. There was no transient of permanent facial nerve or trigeminal nerve injury in any of the patients.

CONCLUSIONS

Endoscopically assisted transoral approach is a reliable technique for reduction and internal fixation of condylar fracture and hardware removal in pediatric patients. The serious risks of extraoral approaches including facial nerve injury, facial scar, and parotid fistula can be eliminated by using this technique.

Effects of condyle on disc status of the reducing and nonreducing anterior disc displacement of the temporomandibular joint based on 3D reconstructive imaging: a pilot study

OBJECTIVES

Morphologic study is a common approach in the field of anterior disc displacement (ADD) pathology; however, analysis based on 3D reconstructive imaging has not been investigated. This study investigated the association between ADD and the status of the mandibular condyle and articular fossa.

METHOD AND MATERIALS

Thirty-four patients were divided into a normal articular disc position (NADP) group, an ADD with reduction (ADDwR) group, and an ADD without reduction (ADDwoR) group. Images reconstructed were used to determine multiple grouped comparisons of these three different types of disc position, and the diagnostic efficacy for the morphologic parameters with significant grouped difference was analyzed to assess.

RESULTS

The condylar volume and condylar superficial area of the NADP, ADDwR, and ADDwoR groups exhibited obvious changes (P < .05). A multivariate logistic ordinal regression model showed that the condylar volume (odds ratio [OR], 1.011; regression coefficient [RC] = .011, P = .018), superior joint space (OR, 8.817; RC = 2.177; P < .001), and medial joint space (OR, 1.492; RC = 0.400; P = .047) had a significantly positive impact on the groups.

CONCLUSION

The mandibular condyle and articular fossa in temporomandibular joint ADD exhibited altered dimensions. The condylar volume, condylar superficial area, superior joint space, and medial joint space could be considered as promising biometric markers for assessing ADD, and were investigated in this current pilot study. (Quintessence Int 2023;54:156-166; doi: 10.3290/j.qi.b3512027).

Effects of food hardness on temporomandibular joint osteoarthritis: Qualitative and quantitative micro-CT analysis of rats in vivo

BACKGROUND

Temporomandibular joint osteoarthritis (TMJ-OA) is a degenerative joint disease in which quantitative analysis based on magnetic resonance image (MRI) or cone-beam computed tomography (CBCT) remains limited. Moreover, the long-term effects of soft food on the adaptive condylar remodeling process in TMJ-OA remain unclear. This study aimed to assess the effects of food hardness on adaptive condylar remodeling in a healthy TMJ, TMJ-OA, and controlled TMJ-OA.

METHODS

Complete Freund's adjuvant (CFA) was used for TMJ-OA induction and Link-N (LN) for TMJ repair. Eighteen mature rats were randomly divided into six groups: (1) control/normal diet (Ctrl-N); (2) control/soft diet (Ctrl-S); (3) TMJ-OA/normal diet (CFA-N); (4) TMJ-OA/soft diet (CFA-S); (5) Link-N-controlled TMJ-OA/normal diet (LN-N); and (6) Link-N-controlled TMJ-OA/soft diet (LN-S). Micro-CT was performed 14, 21, and 28 days after CFA injection to analyze the bone volume, bone volume fraction (BVF), bone mineral density (BMD), and trabecular bone number and thickness (Tb.N, Tb.Th). MRI and histological imaging were performed to support the analysis.

RESULTS

Under CFA treatment, the BVF and BMD decreased significantly (p < 0.01) and later recovered to normal. However, more significant improvements occurred in normal-diet groups than soft-diet groups. Additionally, bone volume changes were more predictable in the normal-diet groups than in the soft-diet groups. The normal-diet groups presented a significant decrease and increase in the Tb.N and Tb.Th, respectively (p < 0.05), while the Tb.N and Tb.Th in the soft-diet groups remained largely unchanged. Furthermore, a significantly higher frequency of irregularities on the condylar articular surface was found in the soft-diet groups.

CONCLUSIONS

Compared with a soft diet, a normal diet may be beneficial for preserving condyle articular surface and directing bone remodeling in TMJ-OA rats.

Natural course of severe temporomandibular joint osteoarthrosis evaluated by a novel condylar remodelling scoring system and quantitative volumetric analysis

Temporomandibular joint osteoarthrosis (TMJ-OA) frequently causes mild, moderate, or severe condylar morphological changes. A novel condylar remodelling scoring system (CRSS) based on three-dimensional cone beam computed tomography images is proposed, which is used to grade condylar morphological changes. In the CRSS, the condyle is divided into 10 regions by 11 reference points. For each increase in the number of regions involved in TMJ-OA, one point is subtracted from the full score of 10. The intra-class correlation coefficients for intra- and inter-observer agreement (range 0.656-0.898 and 0.841-0.906, respectively) indicated that the CRSS had good reliability. Cephalometric analysis showed that the condyles with severe morphological changes were prone to present with a retrognathic and clockwise rotating mandible, shorter ramus height, reduced mandibular length, larger mandibular angle, and maxillary retrusion. Qualitative CRSS evaluation and quantitative volumetric analysis were performed to evaluate the stability of severe TMJ-OA in its natural course (343 condyles). The continuous cortex group showed no remarkable changes with an average follow-up of 2 years. In the discontinuous cortex group, most (74.4%) converted into a continuous cortex during follow-up (mean 2 years).

Three-Dimensional Assessment of Temporomandibular Joint Morphology and Facial Asymmetry in Individuals with Different Vertical Skeletal Growth Patterns

The aim of the current study was to investigate, by means of Cone-Beam Computed Tomography (CBCT), condyle−fossa relationship, temporomandibular joint (TMJ) morphology and facial asymmetry in subjects with different vertical skeletal growth patterns. CBCT of 56 patients (112 TMJs) were categorized into three groups according to the mandibular plane angle (MP): Hypodivergent (MP ≤ 23°), Normodivergent (23° < MP < 30°), and Hyperdivergent (MP ≥ 30°). TMJ spaces, width and depth of the condyle and thickness of the fossa were measured. Horizontal and vertical measurements were used to assess facial asymmetry. One-way Analysis of Variance (ANOVA) and post-hoc Turkey tests were computed for the between-groups comparison. Statistical significance was set at p < 0.05. Larger anterior joint space and smaller condylar dimensions (medio-lateral diameter and medio-lateral thickness) were observed in the hyperdivergent group compared to the normodivergent and hypodivergent groups. Right condylar distances to midsagittal plane were significantly larger than left distances in all the three groups. A vertical pattern of growth in healthy individuals seems to be associated with condylar position and dimension, while facial asymmetry values do not differ among different vertical groups.

[The effects of a total TMJ endoprosthesis on the contralateral condyle]

OBJECTIVE

To correlate the magnitude of the amount of translation of prosthesis and the native joint, and the postoperative change in the volume of the contralateral condylar process after unilateral total joint replacement.

MATERIAL AND METHODS

The study examined 16 patients with post-traumatic jaw deformation treated with unilateral TMJ replacement using total endoprosthesis. The mandible kinematics was recorded using the Cadiax Diagnostic system and correlated with the remodeling of the native joint.

RESULT

On average, the group showed an 8.5% decrease in the volume of the native condylar process. In 13 patients, the amplitude of the native joint movement in the mouth opening and the mandible pro- and laterotrusion markedly deviated quantitatively that combined with the translational movement of the TMJ endoprosthesis in all types of mandibular abduction in all the patients. Correlation analysis showed a moderate negative relationship (r= -0.43) in opening the mouth between the amplitude of movement of the native joint and of the endoprosthesis, as well as a noticeable negative strength of relationship. Also, the correlation analysis showed a moderate positive relationship between the change in the native condylar process volume and movement amplitude when opening the mouth, and an inverse correlation of the high strength of relationship between the change in the native condylar process volume and movement amplitude of the TMJ endoprosthesis.

CONCLUSION

Electronic axiography found that patients in the postoperative period could restore some of the translational movements even with the attachment of the lateral pterygoid muscle cut off. The main factor influencing the magnitude of the endoprosthesis translational movement is the design of the fossa component: the ratio of the circumferential surface of the fossa to the diameter of the head of the endoprosthesis, as well as the presence of lateral stoppers. The study showed that unilateral TMJ reconstruction provides changes in the volume of the native joint directly related to the amplitude of the movement of the joint itself and inversely correlated with the amplitude of the movement of the endoprosthesis.

In vivo study of cone beam computed tomography texture analysis of mandibular condyle and its correlation with gender and age

OBJECTIVE

Texture analysis is an image processing method that aims to assess the distribution of gray-level intensity and spatial organization of the pixels in the image. The purpose of this study was to investigate whether the texture analysis applied to cone beam computed tomography (CBCT) images could detect variation in the condyle trabecular bone of individuals from different age groups and genders.

METHODS

The sample consisted of imaging exams from 63 individuals divided into three groups according to age groups of 03-13, 14-24 and 25-34. For texture analysis, the MaZda^® software was used to extract the following parameters: second angular momentum, contrast, correlation, sum of squares, inverse difference moment, sum entropy and entropy. Statistical analysis was performed using Mann-Whitney test for gender and Kruskal-Wallis test for age (P = 5%).

RESULTS

No statistically significant differences were found between age groups for any of the parameters. Males had lower values for the parameter correlation than those of females (P < 0.05).

CONCLUSION

Texture analysis proved to be useful to discriminate mandibular condyle trabecular bone between genders.

Long-term masticatory performance and ability following closed treatment for unilateral mandibular condylar neck or base fractures: a cross-sectional study

PURPOSE

The aim of this study was to find explanatory variables for objective and patient-reported long-term masticatory functioning in patients treated with maxillomandibular fixation for unilateral condylar neck or base fractures. These outcomes were compared to healthy control subjects.

METHODS

Patients treated between 1996 and 2013 were enrolled in the study. Objective measurements included the mixing ability test (MAT) for masticatory performance, and range of motion of the mandible. Patient-reported measurements included the mandibular function impairment questionnaire (MFIQ) for masticatory ability, and the visual analogue scale for pain. Healthy subjects were recruited between October 2018 and January 2019, and performed the MAT and MFIQ.

RESULTS

Twenty-one patients and 30 healthy subjects were included. The average follow-up period was 11.67 years. In adjusted regression analysis, the amount of occlusal units (OU) was associated with the MAT (P = 0.020; R² = 0.253) and MFIQ (P = 0.001, R² = 0.454). The MAT outcome was similar in both groups when correcting for OU (P = 0.001; R² = 0.201). The MFIQ was inferior in the patient group (P = 0.001).

CONCLUSION

Long-term masticatory performance was similar in patients with a history of condylar neck or base fracture and healthy subjects; however, masticatory ability was inferior in patients compared to healthy subjects.

Comparison of two different therapeutic approaches for skeletal Class II patients with temporomandibular degenerative joint disease

OBJECTIVES

To compare two different therapeutic approaches for skeletal Class II patients with temporomandibular degenerative joint disease.

MATERIALS AND METHODS

A total of 47 patients were included in this study. Group anterior repositioning splint (ARS) was treated with temporomandibular joint (TMJ) disc surgery followed by an ARS and camouflage orthodontic treatment. Group stabilization splint (SS) was treated with an SS followed by orthodontic treatment combined with orthognathic surgery. Cephalometric analysis of lateral radiographs and measurements of condylar height were evaluated before and after splints.

RESULTS

In group ARS, mandibular advancement was observed after treatment in 21 of 24 patients (87.5%). The SNB angle increased by an average of 1.40 ± 1.01°. The ANB angle, overjet, Wits, and convexity decreased. Facial angle and soft tissue N Vert to pogonion increased. Vertically, MP-FH, MP-SN, y-axis, and vertical ratio decreased and ANS-Me/N-Me and S-Go/N-Me increased, suggesting a counterclockwise rotation of the mandible. In group SS, 18 of 23 patients (78.3%) showed a backward change tendency. The SNB angle reduced by 0.90 ± 0.93°. The ANB angle, overjet, Wits, convexity, and y-axis increased. The facial angle and soft tissue N Vert to soft tissue pogonion (ST N Vert to ST pogonion) decreased. Magnetic resonance imaging showed condylar height increased by 1.45 ± 3.05 mm (P = .002) in group ARS. In group SS, condylar height change was not consistent.

CONCLUSIONS

TMJ disc surgery followed by ARS promoted condylar bone remodeling and regeneration. The SNB angle increased, and the severity of skeletal Class II was improved. The SS enabled the mandible to withdraw backward and revealed a retrognathic but true mandible position.

[Cone-beam CT analysis of vertical control of mandible and changes of temporomandibular joint in adult patients with skeletal class Ⅱ malocclusion with high angle]

Objective: To investigate the shape and position changes of temporomandibular joint (TMJ) in adult skeletal class Ⅱ malocclusion with high angle patients after vertical mandibular control, and the correlation between vertical mandibular changes and condylar position changes. Methods: Twenty adult skeletal class Ⅱ malocclusion with high angle patients [6 males and 14 females, aged (21.4±2.4) years] who underwent extraction treatment and active vertical control in the Department of Orthodontics, Lanzhou University Stomatological Hospital from October 2017 to November 2020 were selected. Cone-beam CT data of the patient before and after treatment were imported into Invivo Dental 5.0 software for three-dimensional reconstruction and correction, and the vertical index of mandible in reconstructed lateral cephalogram (mandibular plane angle, posterior anterior height ratio, mandibular true rotation angle) were measured. Incisal angle and variables of condyle shape, position and articular fossa shape were measured. Paired t test was performed on the results before and after treatment, and the correlation between mandibular vertical changes and condylar position changes was determined by Pearson correlation coefficient calculation. Results: After treatment, the overbite and overjet were within normal range, and the vertical height of the molars was controlled. Compared with the measurement before treatment, mandibular plane angle and mandibular true rotation angle were decreased by 2.05°±1.22° (t=7.60, P<0.001) and 1.42°±1.92° (t=3.54, P=0.002), respectively. The posterior anterior height ratio was increased by (1.89±3.32)% (t=2.56, P=0.019). After treatment, the mediolateral diameter of condyle, the anteroposterior diameter of condyle, the maximum cross-sectional area of condyle, the height of condyle head, the width of articular fossa, the depth of articular fossa and the articular nodular angle were increased by (0.55±0.76) mm (t=-2.73, P=0.015), (0.27±3.51) mm (t=-3.23, P=0.006), (6.01±7.36) mm² (t=-2.80, P=0.013), (0.33±0.72) mm (t=-2.14, P=0.046), (0.56±0.93) mm (t=-2.37, P=0.032), 0.33 (0.14, 0.51) mm (Z=-2.76, P=0.006) and 1.50°±2.40° (t=-2.44, P=0.028), respectively. The internal condylar space and the external condylar space were decreased by (0.33±0.49) mm (t=2.31, P=0.035) and (0.20±0.23) mm (t=3.58, P=0.003), respectively. Before orthodontic treatment, 6 patients were with anterior displacement of the condyle, 7 patients with central position of the condyle, and 7 patients with posterior displacement of the condyle. After correction, patients who were with central position of the condyle have not changed much. The posterior displaced condyle in 2 patients and anterior displaced condyle in 3 patients became in central position after treatment. The joint space index was closer to the central position in 3 patients with anterior displacement and 3 patients with posterior displacement. The position of condyle in 1 patient with posterior displacement and 1 patient with anterior displacement remained basically unchanged. There was a significant negative correlation between the change of the posterior-anterior height ratio and the change of the internal condylar space in patients (r=-0.52, P=0.019), and a low correlation with the contral condylar space and the external condylar space(r=-0.48, P=0.031; r=-0.47, P=0.035). Conclusions: Skeletal class Ⅱ malocclusion with high angle adult patients achieved normal overbite and overjet and remodeling of condyle and articular fossa occurred after orthodontic treatmnet and vertical control. There was a certain negative correlation between the change of posterior-anterior height ratio and the change of condylar position.

Descriptions of the dynamic joint space of the temporomandibular joint

BACKGROUND

Clinical diagnosis and treatment depended heavily on the motion analysis of the human joints. Although the dynamic joint space (DJS) of other organs was widely used in academic investigations, they were not universally used in the temporomandibular joint (TMJ) field, which was also important for the motion evaluation of the TMJ. The objectives of this study are to introduce the DJS of the TMJ and characterize the DJS regulars of mandibular movements.

METHODS

Ten asymptomatic subjects were selected to instruct this application. The mouth opening and closing, mandibular protrusion, and left and right protrusions, were tracked by the optical motion tracking system. According to trajectories of markers and reconstructed models from computed tomography, the motions of the mandibles could be obtained. The DJSes, which were described as the minimum Euclidian distances, were subsequently calculated based on the geometrical surfaces between the condyle and fossa during the motions. Then, the DJS map could be drawn based on the calculated values.

RESULTS

The DJS map manifested a decreasing trend when the condyle crossed the glenoid fossa, while it generally increased after the condyle crossed the fossa during the mouth opening. The results showed that the average maximum and minimum anterior joint spaces were 5.39 mm and 2.07 mm during mouth opening respectively with a great discrepancy existing among the subjects. The average maximum and minimum anterior joint spaces were 4.74 mm and 2.19 mm during mandibular protrusion. As for left and right protrusions, the DJS of the contralateral side was greater than that of the ipsilateral side.

CONCLUSION

In comparison to morphological analyses or only mandibular motions, the DJS provides more dynamic and interactive information about the TMJ. The research and methodology may help us comprehend TMJ motions and temporomandibular disorders.

Three-dimensional evaluation of condylar position after mandibular reconstruction with a fibula free flap—comparison of different surgical techniques

Three-dimensional positional changes of the temporomandibular joint after mandible reconstruction using microvascular fibula flaps were investigated in 58 patients. The results of preoperative virtually planned surgery, intraoperative resection- and cutting-guided surgery, and non-guided surgery were compared. Pre- and postoperative computed tomography data of each patient were processed and superimposed digitally. The condyle deviations and rotations along the axes and planes of the skull, as well as Euclidean distances, were determined. Reliability analyses, descriptive statistics, and non-parametric tests were performed with the alpha level set at P = 0.05. Reliability proved to be excellent for all variables. The median Euclidean distance was 2.07 mm for the left condyle and 2.11 mm for the right condyle. Deviations of ≥ 10 mm occurred in nine (16%) cases. The maximum deviation occurred in the horizontal plane and the least deviation in the sagittal plane. Median rotation was ≤ 1.4° around all axes. The condylar displacements did not differ significantly between the different surgical techniques investigated. The three-dimensional measurement method applied is highly reliable for evaluating the three-dimensional condylar position after mandibular reconstruction.

Evaluating the effects of orthodontic treatment with clear aligners and conventional brackets on mandibular condyle bone quality using fractal dimension analysis of panoramic radiographs

OBJECTIVE

Orthodontic treatment carried out with clear aligners has become a method that is preferred by patients. In this study, the effect following orthodontic treatment with clear aligners and with conventional brackets, on the mandibular condyle trabecular bone formation is aimed to be examined.

MATERIALS AND METHODS

Thirty two individuals (16 females and 16 males) with a mean age of 16.80 ± 3,10 years who received orthodontic treatment with clear aligners and conventional brackets were included in the study. Individuals included in the study from the archive data were divided into two groups according to treatment types. The mandibular condyle bone quality in the panoramic images taken from the patients before orthodontic treatment (T0) and after orthodontic treatment (T1) has been compared retrospectively. This examination is carried out via the fractal analysis method.

RESULT

The mandibular condyle bone density in individuals that have undergone orthodontic treatment with clear aligners, has been reduced following orthodontic treatment. In individuals that have undergone orthodontic treatment with conventional brackets however the mandibular condyle bone density has increased following treatment (T0) in comparison to before being treated (T1). The mandibular condyle bone density change according to different treatment groups has been found to be statistically different.

CONCLUSION

Orthodontic treatment with clear aligners provides several advantages to patients. However, besides determining the effectiveness of the treatment, complications must also be examined. Application of clear aligners in orthodontic treatment may cause a decrease in bone density in the mandibular condyle. When evaluating orthodontic treatments carried out with clear aligners, the change of the mandibular condyle head bone should be taken into consideration.

Comparative Study of Temporomandibular Articular Fossa Bone Surface and the Envelope Surface of the Condyle Movement

OBJECTIVE

To investigate the differences between temporomandibular articular fossa bone surface and the envelope surface of the mandibular condyle movement.

METHODS

Thirty-four healthy adults underwent skull base and mandible scans using CBCT and performed mandibular border movement using the mandibular movement recording system. Landmarks of the fossa and tubercle were indicated and distance and angle parameters were measured on the 3D models reconstructed from the CBCT. The condyle movement envelope surfaces were formed according to models reconstructed from CBCT and the mandibular movement trajectory using computer simulation. The highest and lowest points of the envelope surface were indicated to create parameters. The data were analysed using a paired t test in SPSS (version 24.0, IBM, Armonk, NY, USA).

RESULTS

The mandibular fossa bone surface was statistically different to the envelope surface for the height of the first peak of the envelope surface (3.280 ± 1.319 mm) and depth of the mandibular fossa (6.338 ± 2.389 mm) (the ratio was 51.75%), the height of the second peak of the envelope surface (1.463 ± 0.745 mm) and the height of the tubercle (2.000 ± 0.968 mm) (the ratio was 73.15%), and the downwards angle of the envelope surface (25.933 ± 7.539 degrees) and the posterior slope angle of the articular tubercle (35.059 ± 5.224 degrees) (the ratio was 73.97%).

CONCLUSION

The downwards angle of the envelope surface was statistically significantly smaller than the posterior slope angle of the articular tubercle, suggesting that the condyle movement is flatter than the mandibular fossa bone surface.

Dynamic 3D images fusion of the temporomandibular joints: A novel technique

OBJECTIVES

To demonstrate a procedure for fusing images from cone-beam computed tomography (CBCT), magnetic resonance imaging (MRI) and optical positioning tracking system to dynamically evaluate the relative motion of the temporomandibular joint (TMJ) for the diagnosis of temporomandibular disorders (TMD).

METHODS

CBCT data was collected from a patient wearing a fixation device with markers in the intercuspal position. The patient's mandibular movements were recorded using an optical positioning tracking system. The CBCT data were imported into a virtual simulation system to reproduce the mandibular movement. Five jaw positions were selected for 3D printing of the occlusal plate that the patient wore to undergo MRI. MRI scans were registered with the CBCT image for fusion and reconstruction.

RESULTS

The anatomical structures of the articular fossa, articular disc, and condyle were clearly displayed in the CBCT-MRI fused images. The spatial posture and relative position of the fossa-disc-condyle during mandibular movement could be reproduced dynamically using the 3D reconstruction model.

CONCLUSIONS

This method can visually display mandibular motion trajectories and the relative TMJ positions. Virtual reproduction provides a comprehensive understanding of the articular disc's morphology and position in different states from a 3D perspective.

CLINICAL SIGNIFICANCE

This method can be used in clinical studies of TMJ as an adjunct to the 3D dynamic diagnosis and assessment for complex patients with TMD and provide relevant data for doctors.

CAD/CAM and conventional reconstruction of the mandibular condyle by fibula free flap: a clinical and radiological evaluation

The aim of this study was to analyse the radiological and clinical outcomes of condylar reconstruction by fibula free flap (FFF), comparing conventional freehand and CAD/CAM techniques. Fifteen patients (nine CAD/CAM, six freehand) who underwent condylar reconstruction with a FFF were reviewed retrospectively regarding pre- and postoperative computed tomography/cone beam computed tomography scans and clinical function. After surgery, all patients were free of temporomandibular joint pain. Mean postoperative mouth opening was 30.80 mm, with no significant difference between the freehand and CAD/CAM groups. In all patients, laterotrusion was decreased to the contralateral side (P = 0.002), with no difference between freehand and CAD/CAM, while the axis of mouth opening deviated to the side of surgery (P < 0.001). All patients showed significant radiological deviation of the fibular neocondyle in the laterocaudal direction (lateral: P = 0.015; caudal: P = 0.001), independent of the technique. In conclusion, reconstruction of the mandibular condyle by FFF provided favourable functional results in terms of mouth opening, reduction of pain, and mandibular excursions. Radiological deviation of the neocondyle and deviation of laterotrusion and mouth opening did not impair clinical function. CAD/CAM planning facilitated surgery, decreased the surgery time, and improved the fit of the neocondyle in the fossa.

Observer agreement of imaging measurements used for evaluation of dentofacial deformity in juvenile idiopathic arthritis

OBJECTIVES

To examine the precision of imaging measures commonly used to assess mandibular morphology in children and adolescents with juvenile idiopathic arthritis (JIA). Secondly, to compare cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI) in the measurement of condylar height.

METHODS

Those included were children diagnosed with JIA during 2015-18 who had had an MRI, a CBCT of the temporomandibular joints (TMJs) and a lateral cephalogram (ceph) of the head within one month of each other. Agreement within and between observers and methods was examined using Bland-Altman mean-difference plots and 95% limits of agreement (LOA). A 95% LOA within 15% of the sample mean was considered acceptable. Minimal detectable change (MDC) within and between observers was estimated.

RESULTS

90 patients (33 males) were included, with a mean age of 12.8 years. For MRI, intra- and interobserver 95% LOA were relatively narrow for total mandibular length: 9.6% of the sample mean. For CBCT, condylar height, both intra- and interobserver 95% LOA were wide: 16.0 and 28.4% of the sample mean, respectively. For ceph, both intra- and interobserver 95% LOA were narrow for the SNA-angle and gonion angle: 5.9 and 8% of the sample mean, and 6.2 and 6.8%, respectively.

CONCLUSIONS

We have identified a set of precise measurements for facial morphology assessments in JIA, including one MRI-based (total mandibular length), one CBCT-based (condylar height), and three ceph-based. Condylar height was higher for MRI than for CBCT; however, the measurement was too imprecise for clinical use. MDC was also determined for a series of measurements.

Study on the reconstruction of a four-dimensional movement model and the envelope surface of the condyle in normal adults

The objective of this study was to reconstruct the envelope surface of the condyle and the four-dimensional trajectory model in mandibular border movement in normal adults. Eleven healthy subjects were selected as volunteers. Cone-beam computed tomographic (CBCT) scanning was performed on the volunteers. The three-dimensional (3D) movement path of the mandible was recorded using a virtual articulator (PN-300), which was based on a 3D model of the mandible. We used Proplan CMF 3.0 (Materialise) software to perform this from the DICOM data generated by CBCT scans. The distance of condylar movement was measured in this model during volunteers' mouth opening, protrusion, and lateral excursions. The envelope surface of the condyle was reconstructed by merging a functional condylar surface at each recording moment during the movement of the whole border. In the mandibular digital models, the condyle moved downward firstly, and moved upward to the position of maximum mouth opening. The condyle moved forward and downward during protrusion. The working condyle rotated slightly and the non-working condyle moved forward, downward, and inward during lateral excursions. The mean (SD) movement distance of 11 subjects was 19.04 (4.37) mm during mouth opening (including downward and upward) and 9.75 (2.38) mm during protrusion. During lateral excursions the mean (SD) movement distance of the working condyle was 2.87 (1.13) mm, the mean (SD) movement distance of the non-working condyle was 10.85 (3.25) mm. The envelope surface of healthy volunteers showed a double-peak pattern. The envelope surface of the condyle and four-dimensional movement model can be reconstructed by merging the trajectory of the mandible recorded from the novel virtual articulator PN300 and a 3D image of the mandible.

Three-dimensional radiological anatomy of condyle trabecular bone based on a Volume-of-Interest analysis

OBJECTIVES

Three-dimensional radiological anatomic characteristics of condyle trabeculae was obtained quantitatively based on a volume-of-interest (VOI) analysis.

METHODS

Nine human mandibular condyle specimens were scanned by micro-computed tomography (micro-CT). A total of 34 VOIs were selected from each condyle specimen, which were divided into six layers and four parts to analyze the morphological characteristics of trabeculae based on cylindrical VOIs with a diameter and height of 2 mm. One-way analysis of variance was used to compare the regional differences of morphological parameters among each layer and part.

RESULTS

Values for bone mineral density, bone volume/total volume, trabecular thickness, and trabecular bone number were greater in the anterior part compared with the posterior part; and the lateral part was larger than the medial part in the first, second, and third layers, while the medial part was larger in the fourth and fifth layers; these values in the first and sixth layers were much larger, while those in the third and fourth layers were smaller. Bone surface area/bone volume, trabecular spacing, and trabecular bone pattern factor were larger in the posterior part than in the anterior part; and the lateral part was larger than the medial part in the fourth and fifth layers, while the medial part was larger in the first and second layers.

CONCLUSIONS

The morphological distribution of VOIs was anisotropic within trabecular bone of human mandibular condyles. The upper and lower ends of trabecular bone were much more compact, with higher bone density, trabecular thickness, and trabecular number than in the middle layers.

Correlation between the position of the glenoid fossa and condylar translational movement in skeletal Class III mandibular asymmetry patients

OBJECTIVES

Understanding the mechanism of mandibular asymmetry (MA) is important to provide suggestions for occlusal treatment and to know the developmental process of masticatory dysfunction. To investigate the morphological and functional effects on MA, we evaluated the three-dimensional position of the glenoid fossa and its relationship to asymmetrical condylar translational movement.

METHODS

In this retrospective study, 50 subjects who previously underwent computed tomography for surgical purposes were divided into MA and control groups according to a menton deviation of at least 4 mm from the mid-sagittal plane. The glenoid fossae positions were evaluated using a three-dimensional analysis program. Condylar translational movements were recorded and measured by computerized axiography on protrusion. Side-to-side asymmetry was measured for each parameter. Asymmetry index value was calculated to assess the correlation between glenoid fossa position and condylar movement. Wilcoxon's signed-ranked test, Mann-Whitney U-test, and Spearman's rank correlation were used for the statistical analysis.

RESULTS

In the MA group, glenoid fossa position on the shifted side was significantly inferior and posterior as compared to that on the non-shifted side and of the control group. Condylar path length and sagittal condylar inclination were significantly greater on the shifted side versus non-shifted side, while no significant difference was found in transverse condylar inclination. The asymmetry index of the anterior-posterior glenoid fossa position was significantly correlated with that of condylar path length and bilateral transverse condylar inclination. In the control group, there were no significant correlations among the morphological and functional parameters.

LIMITATIONS

This study did not consider muscle activity and disc position, which may affect condylar movement.

CONCLUSIONS

Functional asymmetry of condylar translational movements is closely related to asymmetry of glenoid fossa position in MA patients.

Virtual surgical planning is a useful tool in the surgical management of mandibular condylar fractures

PURPOSE

The aim of this study is to evaluate the application value of virtual surgical planning in the management of mandibular condylar fractures and to provide a reliable reference.

METHODS

This was a prospective randomized controlled study and recruited 50 patients requiring surgical treatment for their mandibular condylar fractures. The inclusion criteria were patients (1) diagnosed with a condylar fracture by two clinically experienced doctors and required surgical treatment; (2) have given consent for the surgical treatment; and (3) had no contraindications to the surgery. Patients were excluded from this study if: (1) they were diagnosed with a non-dislocated or only slightly dislocated condylar fracture; (2) the comminuted condylar fracture was too severe to be treated with internal reduction and fixation; or (3) patients could not complete follow-up for 3 months. There were 33 male and 17 female patients with 33 unilateral condylar fractures and 17 bilateral condylar fractures included. The 50 patients were randomly (random number) divided into control group (25 patients with 35 sides of condylar fractures) and experimental group (25 patients with 32 sides of condylar fractures). Virtual surgical planning was used in the experimental group, but only clinical experience was used in the control group. The patients were followed up for 1, 3, 6 and 12 months after operation. Variables including the rate of perfect reduction by radiological analysis, the average distance of deviation between preoperative and postoperative CT measurements using Geomagic software and postoperative clinical examinations (e.g., mouth opening, occlusion) were investigated for outcome measurement. SPSS 19 was adopted for data analysis.

RESULTS

The average operation time was 180.60 min in the experimental group and 223.2 min in the control group. One week postoperatively, CT images showed that the anatomic reduction rate was 90.63% (29/32) in the experimental group and 68.57% (24/35) in the control group, revealing significant difference (X² = 4.919, p = 0.027). Geomagic comparative analysis revealed that the average distance of deviation was also much smaller in the experimental group than that in the control group (0.639 mm vs. 0.995 mm; t = 3.824, p < 0.001).

CONCLUSION

These findings suggest that virtual surgical planning can assist surgeons in surgical procedures, reduce operative time, and improve the anatomic reduction rate & accuracy, and thus of value in the diagnosis and treatment of condylar fractures.

Morphologic and histologic characterization of sheep and porcine TMJ as large animal models for tissue engineering applications

Objective

The aim of this study was to compare and characterize the structural and ultrastructural organization of the temporomandibular joint (TMJ) between two large animal models for use in the development of tissue engineering strategies.

Materials and methods

Whole TMJs from sheep and pigs were evaluated with micro-computed tomography (μCT) for morphology and quantitative analyses of bone parameters. Histological examination was performed on the TMJ disc and its attachments to investigate regional distribution of collagen, elastin, and glycosaminoglycans (GAGs).

Results

μCT analyses demonstrate higher bone mineral density (BMD) in the temporal fossa compared to the mandibular condyle in both species, with this variable being significantly higher in sheep than pig. Quantitative morphometry of the trabecular condyle reveals no statistical differences between the species. Histology demonstrates similar structural organization of collagen and elastin between species. Elastin staining was nearly twofold greater in sheep than in the pig disc. Finally, Safranin-O staining for GAGs in the TMJ disc was localized to the intermediate zone in the sheep but was absent from the porcine disc.

Conclusions

Our findings show some important differences in the pig and sheep TMJ μCT variables and histology and composition of the disc and discal attachment. These disparities likely reflect differences in masticatory and TMJ functional loading patterns between the two species and provide insights into large animal models towards human applications.

Clinical relevance

As with the established pig model, the sheep is a suitable large animal model for TMJ research such as regenerative strategies, with specific considerations for design parameters appropriate for human-analog applications.

Association between Condylar Bone Density and Disk Displacement in the Temporomandibular Joint

Measuring bone density (BD) is a common method of determining bone quality; however, the relationship between condylar BD and the occurrence of temporomandibular joint (TMJ) disorders has not been investigated. To address this knowledge gap, we aimed to investigate condylar BD in terms of TMJ disk displacement (TMJ DD) using computed tomography (CT) and magnetic resonance imaging (MRI). We classified TMJ MRI results according to the position of the disk: normal disk position (Normal), anterior disk displacement with reduction (ADDR), and anterior disk displacement without reduction (ADDNR). After retrospectively evaluating 86 female condyles, we determined the total, cortical, and trabecular BD in the upper-joint portion of the condyle and the whole condyle using CT data. To standardize condylar BD, we calculated the BD ratios by dividing the condylar BD by the cervical axis BD. The Kruskal-Wallis test analyzed the differences in BD measurements in the TMJ DD patient groups and showed significant between-group differences in condylar BD. The total and trabecular BD was significantly higher in ADDNR condyles than in Normal or ADDR condyles (Normal = ADDR < ADDNR). However, there was no significant difference in the cortical BD among the three TMJ DD groups. The BD ratios showed a similar tendency with condylar BD. These results suggest that increased condylar BD - specifically total and trabecular BD - may be significantly associated with ADDNR condyles. Our findings will help clinicians determine the course of treatment for patients with disk-related TMJ disorders.

A comparative study of audiology and cone beam computed tomography in TMD patients with otological symptoms through occlusal splint therapy

INTRODUCTION

To investigate the changes of audiological tests and the cone beam computed tomography (CBCT) measurements of temporomandibular joint (TMJ) and middle-inner ear structure after occlusal splint therapy in temporomandibular disorders (TMD) patients with otological symptoms, and explore the etiological mechanism between TMD and otological symptoms.

METHODS

The 25 subjects aged 18 to 40 years who diagnosed with TMD combined the otological symptoms enrolled in the study.They all had received orthodontic treatment in the outpatient clinic of the orthodontic department in Beijing Stomatological Hospital. All the subjects underwent the audiological tests of pure tone audiometry (PTA) and CBCT before and after the occlusal splint therapy.

RESULTS

After the stabilization occlusal splint therapy, subjects with improvement or complete remission in TMD and otological symptoms accounted for 84% and 80% in all subjects respectively. There were statistically differences in the distances between condylar center (CoC) and sella (S) in sagittal and vertical directions before and after treatment, and statistically difference between ATM and S in sagittal direction. The threshold of PTA at 8000Hz were negatively correlated with the sagittal displacement of condyle and positively correlated with the coronal displacement of condyle. The thickness of top 1/3 of anterior wall of tympanum in sagittal were positively correlated with the threshold of PTA at 4000Hz.

CONCLUSION

The changes in the TMJ position through occlusal splint therapy might cause the changes in structure of middle-inner ear, which might be one of the reasons for the improvement in otological symptoms.

KEY WORDS

Audiology, CBCT, Otological symptoms, TMD.

[3D analysis of anatomical and functional parameters of TMJ and their correlation]

THE AIM OF THE STUDY

Was determination of TMJ anatomical and functional parameters in patients without clinical manifestations of TMJ dysfunction and analysis of possible relationships between them.

MATERIAL AND METHODS

TMJ anatomical parameters of 25 volunteers (22-27 years old) without TMJ dysfunction, malocclusion and more than one tooth adentia were determined on CT scans and lab teeth scans: inclination of the distal slopes of the articular eminence (DS AE), height and width of the condyles, height of AE, inclination of the longitudinal axes of the condyles; as well as functional parameters of LJ movements: horizontal condylar inclination (HCI) during protrusion and laterotrusion, lateral condylar inclination during protrusion and laterotrusion, immediate side shift, incisor and canine guidance, and correlations between them were evaluated.

RESULTS

The majority of the TMJ anatomical parameters are almost equal by mean values on the right and left sides. The main TMJ functional parameters on the right and left sides also have similar values but much higher variability, asymmetry and unpredictability. The existing anatomical asymmetry of the DS AE is compensated by articular discs, which makes HCI more symmetrical.

CONCLUSION

Protrusion movements have a higher probability of reproduction by mechanical articulators while laterotrusion movements have a very low probability. The existence of relationship between the inclination of DS AE and HCI, between HCI and the incisor guidance, between the inclination of DS AE and the incisor guidance is questionable. The conducted research proves the weakness or complete absence of correlation between them.

[Validation of the technique of TMJ 3D analysis based on computer tomography]

OBJECTIVE

The main aim of the study is devoted to optimization of the technique of 3D analysis of TMJ parameters, analysis of the causes of possible errors.

MATERIALS AND METHODS

The technique of 3D analysis of the width of the articular gap, the size of the condyle, the height and slope of the distal slope of the articular tubercle in the Avantis3D software (Russia) according to computed tomography is presented. The influence of repeated manual corrections of the condyles and articular fossa contours, shifting of the sectors measuring center, the position of starting point of the measurement sectors, and different algorithms for determining the longitudinal axis of the condyles on the accuracy of TMJ parameters detection.

RESULTS

The study showed that any artificial displacement of the center of measurement sectors, which coincides with the longitudinal axis of the condyle, leads to significant value changes of the parameters. In this regard, the exact determination of the longitudinal axis of the condyles, independent of the human factor, is of particular importance. The greatest inaccuracy and variability of the results of measuring the parameters of the TMJ, as shown by the study, is associated with the possible manual correction of the contours of the surfaces of the condyles and articular fossa. The study did not find a noticeable difference in measurements if the sectors starts from the top of the articular tubercle or from the line parallel to the Frankfurt horizontal. As the optimal settings of the developed method was determined, it was used to determine the average values of the TMJ parameters for patients with a conventional «norm», as well as for patients with TMJ dysfunction. A noticeable and statistically significant difference was found between the groups only for upper and posterior width of the joint space.

CONCLUSION

The average values of the intra-articular spaces width were justified, and can be used as the basis for the virtual assignment of the lower jaw reconstructive position for prosthetic or orthodontic treatment.

Comparison of different treatment techniques in the mandibular condyle fracture

BACKGROUND

Mandibular condyle fractures can be treated conservatively by intermaxillary fixation (IMF) or by open reposition and internal fixation. Although many studies have discussed for the optimal treatment method, the issue remains controversial. In this study, we aimed to compare conservative techniques in the mandibular condyle fractures.

METHODS

Twenty four unilateral condyle fracture patients aged between 18 and 48 years were treated according to one of three different modalities. Bracketing, arch bar or mini screw was applied to all non-surgery patients to obtain IMF. Eight patients were treated with only IMF meanwhile eleven patients were treated with one or double-sided amplifier occlusal splint according to the status of fractured segments, in addition to IMF. Remaining five patients have undergone open reduction and fractured segments immobilized with mini plates. Pre- and post-operative images were recorded with a computerized tomography device. Clinical and radiological examinations were performed by orthodontists and surgeons at baseline and at 6 months of treatment.

RESULTS

The condyle lengths of the patients with unilateral fracture after recovery were compared with the unaffected side. The length between the most protruding point of the condyle and the mandible was measured and the length difference was only 5.94 mm in patients who were treated by IMF. The length difference of patients who used brackets and splints was 3.36 mm (p<0.05). The length difference of patients who were repaired by plate screws was 1.80 mm (p>0.05). However, there was no statistically significant difference (p>0.05) between the groups in the IMF, occlusal splint and IMF and mini plate groups, between the trauma side and the opposite side. None of the patients developed ankylosis, open mouth, limitation of mouth opening, facial asymmetry, laterognathia, and retrognathia. The occlusion of the patients who were not known to have pre-trauma occlusions were directed, repositioned and provided an appropriate occlusion.

CONCLUSION

The use of IMF with an occlusal splint is a more conservative and acceptable treatment modality than open reduction in selected cases.

Growth trends analysis of unilateral condylar hyperplasia followed up with planar scintigraphy: Retrospective overview of 249 cases

The current research aimed to retrospectively investigate the trends of the growth of condylar hyperplasia with serial planar scintigraphs.Patients of unilateral condylar hyperplasia with at least one follow-up planar scintigraph were retrospectively included in the study. Patients' age, gender at the initial scan, durations of following scans, and ratios between condylar activities were recorded.The study retrospectively included 111 patients of unilateral condylar hyperplasia. Patients were divided into 3 groups (progressive, relatively stable, regressive) according to ratio variation between initial and last scans. There were 23 (21%) patients fell into the progressive group, 40 (36%) patients into the relatively stable group, and 48 (43%) patients into the regressive group. More female patients were in the progressive group than those in the other groups (P < .01). There were no significant differences among the 3 groups in terms of age or durations of follow-up (P > .05). There were no strong relations between ratio differences and ages. However, a weak relation seems to exist in the regressive group with r = -0.240, (P = .10).Our investigation showed that more than a half of patients with condylar hyperplasia remain constantly or progressively active growth in patients in the follow-up scans. Roughly less than a half of patients showed regressive trends toward normal growth. Patients' age seemly does not play a role in the growth trend pattern, although there are no optimum follow-up periods, regularly follow-up scans are needed to determine the growth status of condylar hyperplasia.

Evaluation of the effect of vitamin D3 on mandibular condyles in an ovariectomized mouse model: a micro-CT study

BACKGROUND

This study aimed to investigate the effect of ovariectomy and vitamin D3 on bone microstructure; this effect was examined in three regions of interest at one femoral and two mandibular sampling sites bone in an ovariectomized mouse model.

METHODS

Thirty-six week-old female mice were randomly divided into three groups: 10 subjects were given oral cholecalciferol (vitamin D3) daily for 6 weeks after undergoing bilateral ovariectomy (D3 group), while 10 ovariectomized subjects (OVX) and 10 subjects who underwent a sham operation (SHAM) received peanut oil daily during the investigation. After extermination, the left hemimandible and femur were removed and scanned by micro-CT. The bone micromorphology parameters were analyzed and the BMD was calculated.

RESULTS

The bone volume fraction (BV/TV) was significantly lower in the trabecular bone of the mandibular condyle in the OVX group than in the SHAM and D3 groups. Also there was a significant difference between the SHAM and D3 groups. The specific bone surface (BS/BV) was significantly higher in the OVX and D3 groups than in the SHAM group. Trabecular thickness (Tb.Th) was significantly higher in the SHAM group, and the trabecular bone pattern factor (Tb.Pf) was significantly higher in the OVX group than in the other two groups. Bone mineral density (BMD) of the femur and the mandible was significantly lower in the OVX group than in the SHAM and D3 groups.

CONCLUSIONS

Our results show that ovariectomy causes a significantly weaker bone microstructure in the mandibular condyle, where the protective effect of vitamin D3 resulted in a partial resorption.

Evaluation of horizontal condylar angle in malocclusions with mandibular lateral displacement using cone-beam computed tomography

OBJECTIVES

To evaluate the horizontal condylar angle (HCA) in mandibular lateral displacement (MLD).

MATERIALS AND METHODS

HCA in MLD malocclusions were examined using cone-beam computed tomography data in subjects with MLD and control subjects.

RESULTS

HCA in joints of control patients and contralateral side joints of MLD patients were not significantly different. The mean HCA on the shifted side was larger than on the contralateral side (P < .001) in the different HCA groups. HCA was significantly larger on the shifted side than on the contralateral side in skeletal Class I, Class II, and Class III groups (P < .001).

CONCLUSIONS

(1) There was no statistically significant difference between HCA in control patients and on the contralateral side in MLD patients. (2) HCA was significantly larger on the shifted side than on the contralateral side. (3) HCA on the shifted side and the contralateral side in MLD Class I, Class II, and Class III are significantly different.

[Three-dimensional finite element analysis of traumatic mechanism of mandibular symphyseal fracture combined with bilateral intracapsular condylar fractures]

OBJECTIVE

To analyze the biomechanical mechanism of mandibular symphyseal fracture combined with bilateral intracapsular condylar fractures using finite element analysis (FEA).

METHODS

Maxillofacial CT scans and temporomandibular joint (TMJ) MRI were performed on a young male with normal mandible, no wisdom teeth and no history of TMJ diseases. The three-dimensional finite element model of mandible was established by Mimics and ANSYS based on the CT and MRI data. The stress distributions of mandible with different angles of traumatic loads applied on the symphyseal region were analyzed. Besides, two models with or without disc, two working conditions in occlusal or non-occlusal status were established, respectively, and the differences of stress distribution between them were compared.

RESULTS

A three-dimensional finite element model of mandible including TMJ was established successfully with the geometry and mechanical properties to reproduce a normal mandibular structure. Following a blow to the mandibular symphysis with different angles, stress concentration areas were mainly located at condyle, anterior border of ramus and symphyseal region under all conditions. The maximum equivalent stress always appeared on condylar articular surface. As the angle between the external force and the horizontal plane gradually increased from 0° to 60°, the stress on the mandible gradually concentrated to symphysis and bilateral condyle. However, when the angle between the external force and the horizontal plane exceeded 60°, the stress tended to disperse to other parts of the mandible. Compared with the condition without simulating the disc, the stress distribution of articular surface and condylar neck decreased significantly when the disc was present. Compared with non-occlusal status, the stress on the mandible in occlusal status mainly distributed on the occlusal surface, and no stress concentration was found in other parts of the mandible.

CONCLUSION

When the direction of external force is 60° from the horizontal plane, the stress distribution mainly concentrates on symphyseal region and bilateral condylar surface, which explains the occurrence of symphyseal fracture and intracapsular condylar fracture. The stress distribution of condyle (including articular surface and condylar neck) decreases significantly in the presence of arti-cular disc and in stable occlusal status when mandibular symphysis is under traumatic force.

Automated cortical thickness measurement of the mandibular condyle head on CBCT images using a deep learning method

This study proposes a deep learning model for cortical bone segmentation in the mandibular condyle head using cone-beam computed tomography (CBCT) and an automated method for measuring cortical thickness with a color display based on the segmentation results. In total, 12,800 CBCT images from 25 normal subjects, manually labeled by an oral radiologist, served as the gold-standard. The segmentation model combined a modified U-Net and a convolutional neural network for target region classification. Model performance was evaluated using intersection over union (IoU) and the Hausdorff distance in comparison with the gold standard. The second automated model measured the cortical thickness based on a three-dimensional (3D) model rendered from the segmentation results and presented a color visualization of the measurements. The IoU and Hausdorff distance showed high accuracy (0.870 and 0.928 for marrow bone and 0.734 and 1.247 for cortical bone, respectively). A visual comparison of the 3D color maps showed a similar trend to the gold standard. This algorithm for automatic segmentation of the mandibular condyle head and visualization of the measured cortical thickness as a 3D-rendered model with a color map may contribute to the automated quantification of bone thickness changes of the temporomandibular joint complex on CBCT.