Differences Of The Condyle Relocation Range (CRR) Between Skeletal Class II And Skeletal Class III Patients: A Preliminary Study

Differences Of The Condyle Relocation Range (CRR) Between Skeletal Class II And Skeletal Class III Patients: A Preliminary Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Differences Of The Condyle Relocation Range (CRR) Between Skeletal Class II And Skeletal Class III Patients: A Preliminary Study Xinyu Cui, Hongyi Tang, Huazhi Li, Fu Zheng, Youchao Chen, Tong Wu, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4952515/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Introduction: The present study aimed to preliminarily compare the differences of the condyle relocation range (CRR) between skeletal class II and skeletal class III patients. Methods: Twenty skeletal class II and twenty skeletal class III young adult patients underwent wide-field cone beam computed tomography (CBCT) scans of the maximum intercuspation position (MIP) and most comfortable forward relocation (MCFR). We superimposed the CBCT images in two positions according to the bilateral zygomatic bone surface structure and then measured the dental and skeletal CRRs in three-dimensional space. Results: The median (interquartile range) dental and skeletal CRRs of skeletal class II malocclusion patients were 8.71 (3.55) mm and 8.47 (4.19) mm, respectively. The median (interquartile range) dental and skeletal CRRs for skeletal class III malocclusion patients were 1.37 (3.43) mm and 1.04 (1.44) mm, respectively. Both the dental and skeletal CRRs of skeletal class II patients were significantly greater than those of skeletal class III patients (p<0.01). Conclusions: The CRRs of the different skeletal types exhibit obvious differences. Therefore, the range of physiological mandible positions in patients should be given attention during orthodontic diagnosis and treatment. condyle relocation range (CRR) most comfortable forward relocation (MCFR) physiologically comfortable mandible position temporomandibular joint (TMJ) Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction The temporomandibular joint (TMJ) is one of the movable joints of the human body and the only movable joint in the maxillofacial region. General dentists and specialists are very familiar with the static anatomy of the TMJ. However, there are many different views on its functional anatomy. The prevailing view is that the TMJ is similar to the hip joint, and the relationship between the condyle and the glenoid fossa is similar to that of a delicate ball articulating in a socket. Some people believe that the optimal condyle‒fossa relationship is concentric relationship[ 1 – 3 ], and some orthodontists prefer to deprogram the mandible and reconstruct the maximum intercuspation position (MIP) in accordance with the centric relation position(CRP)[ 4 , 5 ]. However, others believe that the relationship between the condyle and the fossa is dynamic, for instance, the “long concentric” phenomenon in prosthodontics[ 6 , 7 ] and "the ball on the hill”, a new perspective on TMJ functional anatomy proposed by the orthodontist Charles S Greene [ 8 , 9 ]. In daily practice, we may find that skeletal class II patients can occlude in several different positions in the sagittal dimension without discomfort, while the mandibles of skeletal class III patients seem immovable in the sagittal dimension. To our knowledge, previous studies have not confirmed this phenomenon, and very few studies have shown similar effects. Turasi reported that the centric occlusion(CO)-maximum intercuspation (MI) discrepancy in patients with an increased overjet (OJ > 6mm) was greater than that in people with normal occlusion[ 10 ]. Rainer demonstrated that the free mandibular movement of skeletal class II patients is different from that of skeletal class I patients using an ultrasound measuring system[ 11 ]. The above studies suggested that the condyles of skeletal class II patients may exhibit a large range of movement related to glenoid fossae. TMJs undergo lifetime remodeling in response to biomechanical loading during either normal mandibular function or parafunction, which distinguishes them from other joints. Many studies have been conducted to determine the relationship between malocclusion and TMJ morphology[ 12 ]. Hasebe reported that the condyle size is the smallest in skeletal class II patients, followed by skeletal class I and class III patients[ 13 ]. Paknahad[ 14 ] and Katsavrias[ 15 ] both reported that the condyles of skeletal class II patients were located more anteriorly within the glenoid fossae than were those of other sagittal skeletal types. Vitral[ 16 ] and Li[ 17 ] reported that the condyles on the class I side of class II subdivision patients were located more anteriorly than those on the contralateral side. Furthermore, the effects of various dental therapies on TMJ remodeling have been widely studied. Li and her colleagues reported that an anterior repositioning splint (ARS) could induce osseous repair and regeneration of the condyle in early-phase degenerated temporomandibular disorder (TMD) lesions[ 18 , 19 ], and a “double contour” could be observed via radiography. Conventional orthodontic treatment can also modify TMJ morphology. Koide reported that the glenoid fossa exhibited remodeling after a four first premolar extraction therapy[ 20 ]. Alhammadi investigated a cohort of single jaw extraction cases and reported that the condyles had moved backward[ 21 ]. Bayirli and his colleagues demonstrated that the edgewise appliance could improve the pattern of mandibular forward growth displacement through the maintenance of vertical control[ 22 ]. The above studies illustrated that the condyle-fossa relationship is more complicated than previously believed. We speculate that the range of physiological condyle positions may vary among different skeletal types and the condyle-fossa relationship may undergo adaptive remodeling during orthodontic occlusal adjustment. Therefore, we developed a new concept, the condyle relocation range (CRR), to describe the physiological movement range of the condyle and mandible in the sagittal dimension. Specifically, the CRR refers to the range in which the mandible moves from the MIP to the most comfortable forward relocation (MCFR) position. The CRR is distinct from the range of mandibular border movement[ 23 – 25 ] and the centric occlusion (CO) -centric relation (CR) discrepancy[ 10 , 26 , 27 ]. MCFR, the anterior border of the CRR, refers to the position at which patients automatically protrude their mandibles as far as they can, while maintaining interocclusal contact between their anterior or posterior teeth and feeling no pain or stretching of their TMJs. The MCFRs of skeletal class II patients could be edge-to-edge positions or even more forward to the anterior crossbite positions. Specifically, the displacement of the condyle is called the skeletal CRR, and that of the lower central incisors is called the dental CRR. The difference of the CRR between skeletal class II and skeletal class III patients was investigated quantitatively in the present study. Materials and methods Based on the mandibular border movement (MBM) data from a previous study[24], a power calculation indicated that 14 patients were needed in each group to achieve a confidence level of 0.95 and a probability of 0.8, for a total of 28 patients all (t = (x1 - x2)/[s^2 * (1/n1 + 1/n2)]^0.5, set n1=n2). x1 and x2 represent the average of the two samples; s^2 represents the weighted average of the variances of the two samples (combined variances); and n1 and n2 represent the sample sizes of the two samples. Considering the difference between the MBM and the newly defined CRR, we expanded the sample size to 40 patients, 80 condyles, and each group contained 20 patients, 40 condyles. We recruited 20 skeletal class II and 20 skeletal class III young adult patients who visited the Department of Orthodontics or Orthognathic Surgery, *****, from March 1 to December 1, 2021. The inclusion criteria were as follows: 1) skeletal class II diagnosed by an ANB angle>5° or skeletal class III diagnosed by an ANB angle<0°; and 2) no symptoms of temporomandibular joint disorder. The exclusion criteria were as follows: 1) orthodontic treatment history; 2) anterior open bite; 3) unilateral posterior crossbite and scissors bite; 4) severe facial deviation; and 5) craniofacial development syndrome and cleft lip and palate. The study was approved by the biomedical ethics committee of *****(PKUSSIRB-202162020), and was conducted in accordance with the Helsinki Declaration of 1975, as revised in 2013. Participate consent was obtained from all the involved patients. The process of the experiment is described below, and all the subjects completed the experiment. Clinical trial number: not applicable. 1. Registration of MCFR: Patients were instructed to protrude their mandibles forward voluntarily as far as they could until the anterior teeth reached the edge-to-edge position and then even further forward to the anterior crossbite position, while maintaining interocclusal contact and feeling no pain or stretching in the TMJ region. After the patients had practiced three times, the MCFR was confirmed, and the researcher injected some silicone rubber bite recorder (O-Bite, Dmg, Hamburg, Germany) on the occlusal surface of their bilateral posterior teeth to register their MCFR. 2. Registration of MIP: Patients were instructed to occlude at the most stable and interdigitated position. 3. Wide-field CBCT ( Newtom Ag, Marburg, Germany) at the MCFR and MIP: The CBCT parameters were as follows: tube voltage, 110 kV; tube current, 2.03 mA; scan field, 15 × 15 cm; axial slice thickness, 0.3 mm; and exposure time, 3.6 s (Figure 1). 4. Synthesis and analysis of cephalograms: In Dolphin Imaging Software (Dolphin Imaging & Management Solutions, California, America), we adjusted the Frankfort plane to be parallel with the horizontal plane for head position adjustment and then synthesized a lateral cephalogram. Next, we measured the dental and skeletal craniofacial features of the MI and MCFR positions of each patient (Figure 2 Table1). 5. Measurement of the dental and skeletal CRRs: 1) Reconstruction of a 3D model of the full craniofacial bone: In Mimics Medical 20.0 Software (Materialise, Brussels, Belgium), the full craniofacial bone of MI and MCFR positions was extracted with the gray value of the condyle (approximately 400 HU), reconstructed into 3D models and subsequently saved in STL format (Figure 3) . 2) Superimposition of 3D models: After importing the reconstructed full craniofacial bone 3D model into Geomagic Studio 2013 Software (Geomagic, North Carolina, America). We sketched the contour of the bilateral zygomatic bones (inferior orbital border, zygomaticomaxillary suture, inferior border of the zygomatic arch, zygomatic temporal suture, superior border of the zygomatic arch); then, we superimposed the full craniofacial bone 3D models of the MCFR and MI positions according to the bilateral zygomatic bone surface (Figure 4,5). 3) Location of mark points (Figures6,7,8, Table1): Condylar innermost point (I): the most prominent point on the condylar inner surface Condylar outermost point (O): the most prominent point on the condylar outer surface Axis of condyle (Ax): a line connecting the condylar innermost point and outermost point Geometric center of condyle (CC): the midpoint of the axis of the condyle Lower incisor point (Li) 4) Measurement of CRR (Figure9): Skeletal CCR: the distance between the CC in the MIP and MCFR positions Dental CRR: the distance between Li in the MIP and MCFR positions Statistical analysis The statistical analysis was performed using SPSS 23.0 Software (IBM Corp., Armonk, Ny, America). The difference in the sex ratio between groups was compared by the chi-square test. Normality and homogeneity of variance were assessed by the Kolmogorov‒Smirnov test and Levene test, respectively. The age and cephalometric analysis results were normally distributed and were analyzed with an independent t test, while the CRR results were nonnormally distributed and were analyzed with the Wilcoxon rank sum test. Results 1. Baseline demographic characteristics (Table 2) : 1) The average age of skeletal class II patients was 22.04 (3.80) years, and the average age of skeletal class III patients was 22.13 (3.89) years. There was no significant difference between the two skeletal types (p=0.84 (P>0.05)). 2) The ratio of females to males in skeletal class II was 45%, whereas that in skeletal class III was 60%. There was no significant difference in the ratio of females to males between the two groups (p=0.34 (P>0.05)). 2. Craniofacial characteristic features of skeletal class II and skeletal class III patients in the MI and MCFR positions (Tables 3,4) : 1) For skeletal class II patients, the SNB(°), facial angle, L1-NB (mm), and L1-NB (°) values were greater in the MCFR position than in the MI position. The ANB and angle of convexity were smaller in the MCFR position than in the MI position (p=0.00 (p< 0.05)). 2) The SN-MP of skeletal class II patients in the MCFR position was smaller than that in the MI position (p=0.035 (p<0.05)), while the SN-MP of skeletal class III patients in the MCFR position was larger than that in the MI position (p=0.007 (p<0.05)). 3. CRRs of skeletal class II and skeletal class IIIpatients (Table 5) : 1) For skeletal class II patients, the median (interquartile range) dental CRR was 8.71 (3.55) mm, and the median (interquartile range) skeletal CRR was 8.47 (4.19) mm. The vertical component of the dental and skeletal CRRs was larger than the anteroposterior and horizontal components. 2) For skeletal class III patients, the median (interquartile range) dental CRR was 1.37 (3.43) mm, and the median (interquartile range) skeletal CRR was 1.04 (1.44) mm. The vertical component of the dental and skeletal CRR was greater than the anteroposterior and horizontal components. 3) The dental and skeletal CRRs of skeletal class II patients were significantly greater than those of skeletal class III patients (p<0.05). Discussion For the first time, we developed the concept of the CRR to describe the potential range of mandible positions under physiological conditions. The CRR is distinct from the range of MBM. The anterior border of the MBM is the most protrusive position (MPP), the most forward mandibular position that is used for chewing or speaking, which is temporary, rather than interdigitating and persistently maintaining the mandible position. The mandible is protruded to the greatest extent in the MPP. However, the anterior border of the CRR is the MCFR, which has two connotations. The first is comfort, which guarantees that the mandibular position within the CRR has no impact on TMJ health and can be stably maintained; that is, the MCFR is a physiological mandibular position. The second is maintaining occlusal contact, which ensures the anteroposterior range of mandibular relocation under the precondition of a specific vertical dimension. The present study clearly demonstrated that the CRR of skeletal class II patients was greater than that of class III patients, which is consistent with our clinical observations and confirms our hypothesis. These findings deepen our understanding of functional TMJ anatomy and broaden our understanding of human maxillofacial morphology. Orthodontic treatment involves not only intra-arch tooth movement within the dental alveolar bone but also interarch occlusal adjustment, which changes the mandibular position and remodels the TMJ. For example, Herbst devoted himself to using the Herbst appliance to treat the retrusive mandible of nongrowing patients[28, 29]. In our clinical practice, we have successfully treated numerous skeletal class II patients with retrusive mandibles who refused orthognathic surgery intervention by exploiting their considerably large CRRs. The following description is a representative case. A 41-year-old male patient diagnosed as skeletal class II with a retrusive mandible (ANB=8.1°, SNB=68.4°), a full cusp class II molar relationship, a deep overjet (9 mm) and a deep overbite (7 mm). TMJ CBCT indicated that he had degenerative temporomandibular joint disease that was in a quiescent stage. He underwent four first premolar extraction therapy and used an edgewise appliance. After four years of orthodontic treatment, his mandible was relocated forward within his CRR, his facial profile greatly improved, and the final occlusion was stable (Figures 10, Table 6 ). The use of the condylar position indicator (CPI) is the most common approach for measuring condylar shift. The condyle center is located by an empirically chosen skin surface marker, which is definitely not accurate[10, 26, 27]. As the condyle and glenoid fossa have irregular geometries, a 3D reconstructed condyle model from CBCT images could comprehensively and accurately reveal the actual stereoscopic structure and unique position of the TMJ[30]. In this study, we developed a condylar displacement measurement method. After reconstructing a 3D model of the full craniofacial bone in the MIP and the MCFR position, we superimposed the two models according to the bizygomatic surfaces and then measured the condylar shift in three-dimensional space. Giuntini concluded that the posteriorly displaced glenoid fossa is a characteristic of class II malocclusion with mandibular retrusion[31]. Several studies have verified that more anteriorly positioned condyles are present in skeletal class II patients than in skeletal class I and skeletal class III patients[14, 15]. We speculate that the condyles of skeletal class II patients are located more anteriorly to compensate for the retrusive mandibles, which are restrained by the posteriorly located glenoid fossa. In addition, the small size of the condyles of skeletal class II patients[13, 32-34] may facilitate the ability of the mandibles to freely relocate anteriorly, which may constitute the morphological basis of the large CRR in skeletal class II patients. The CRR is a functional craniofacial characteristic and should be included in pre-orthodontic examinations to facilitate comprehensive assessment of the patients. Exploiting the relatively large CRR, an alternative treatment paradigm for skeletal class II patients was introduced, in which the condyle was relocated forward to compensate for the retrusive mandible rather than causing proclination of the lower incisors. This paradigm is especially applicable for adult patients who refuse orthognathic surgery intervention but have relatively large CRRs. Adolescent skeletal class II patients with large CRRs could also incorporate the CRR into their treatment plan to achieve a better facial profile outcome. Nevertheless, combined orthodontic and surgical treatment is still the best option for skeletal class III patients because of their small CRR. Although the present study yielded several noteworthy findings, it is not without limitations. Vertical skeletal patterns should be considered in subsequent studies with larger sample sizes, and it is better to examine disc position by MRI first because of its possible impact on condylar position[35]. In addition, clinical studies are needed to explore the outcome and long-term stability of the new treatment paradigm. Conclusion The CRR is a functional craniofacial characteristic that varies among different skeletal types. The CRR in skeletal class II patients is significantly greater than that in skeletal class III patients. CRR measurement should be included in pre-orthodontic examinations, and orthodontists should pay attention to the range of physiological mandible positions. Abbreviations Condyle Relocation Range, CRR cone beam computed tomography, CBCT maximum intercuspation position, MIP most comfortable forward relocation, MCFR temporomandibular joint, TMJ centric relation position, CRP centric occlusion, CO maximum intercuspation, MI anterior repositioning splint, ARS temporomandibular disorder, TMD centric relation, CR mandibular border movement, MBM most protrusive position, MPP condylar position indicator, CPI Declarations Acknowledgement: Not applicable Funding: National Natural Science Foundation of China (Grant/Award Numbers: U233010010). Availability of data and materials: All data generated or analyzed during this study are included in this published article. Human ethics and consent to participate declaration: The study was approved by the biomedical ethics committee of Peking University School of Stomatology (PKUSSIRB-202162020), and was conducted in accordance with the Helsinki Declaration of 1975, as revised in 2013. Participate consents were signed by all the patients involved in the study. All the forty photocopies of the Consent to participate declaration in Chinese have been uploaded as related files. Clinical trial number: Not applicable. Competing interests The authors declare that they have no competing interests. Consent for publication Informed consent for publication of images has been obtained from the participants. Authors’ contributions X.Y.C. contributed to conceptualization, methodology, software and writing - original draft. H.Y.T. contributed to writing - review & editing. H.Z.L., F.Z., Y.C.C. and T.W. participated in case collection. J.J.H. and C.Y.L. contributed to conceptualization, writing- review& editing and supervision. References Pullinger, A.G., et al., Relationship of mandibular condylar position to dental occlusion factors in an asymptomatic population. Am J Orthod Dentofacial Orthop, 1987. 91 (3): p. 200-6. Rodrigues, A.F., M.R. Fraga, and R.W. Vitral, Computed tomography evaluation of the temporomandibular joint in Class I malocclusion patients: condylar symmetry and condyle-fossa relationship. Am J Orthod Dentofacial Orthop, 2009. 136 (2): p. 192-8. Kandasamy, S., C.S. Greene, and A. Obrez, An evidence-based evaluation of the concept of centric relation in the 21st century. Quintessence Int, 2018. 49 (9): p. 755-760. Fornai, C., et al., Centric relation: A matter of form and substance. J Oral Rehabil, 2022. 49 (7): p. 687-690. Fornai, C., et al., Robert M. Ricketts and Rudolf Slavicek: dentistry by the rules of nature. Angle Orthod, 2023. 93 (5): p. 497-500. He, H., S. Zhang, and J. Xu, Impact of occlusal reconstruction positions on airway dimensions in patients with edentulism and long centric occlusion. BMC Oral Health, 2023. 23 (1): p. 215. Martinović, Z., et al., [Concept of "long centric"]. Srp Arh Celok Lek, 2004. 132 (11-12): p. 441-7. 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Am J Orthod Dentofacial Orthop, 1999. 115 (6): p. 607-18. Hans Ulrik Paulsen and A. Karle, Computer tomographic and radiographic changes in the temporomandibular joints of two young adults with occlusal asymmetry, treated with the Herbst appliance. European Journal of Orthodontics, 2000. 22 (2000) 649–656 . Zhang, Y., X. Xu, and Z. Liu, Comparison of Morphologic Parameters of Temporomandibular Joint for Asymptomatic Subjects Using the Two-Dimensional and Three-Dimensional Measuring Methods. J Healthc Eng, 2017. 2017 : p. 5680708. Giuntini, V., et al., Glenoid fossa position in Class II malocclusion associated with mandibular retrusion. Angle Orthod, 2008. 78 (5): p. 808-12. Alhammadi, M.S., M.S. Fayed, and A. Labib, Three-dimensional assessment of temporomandibular joints in skeletal Class I, Class II, and Class III malocclusions: Cone beam computed tomography analysis. Journal of the World Federation of Orthodontists, 2016. 5 (3): p. 80-86. Zhang, Y., et al., Three-dimensional condylar positions and forms associated with different anteroposterior skeletal patterns and facial asymmetry in Chinese adolescents. Acta Odontol Scand, 2013. 71 (5): p. 1174-80. Ma, Q., et al., Temporomandibular condylar morphology in diverse maxillary-mandibular skeletal patterns: A 3-dimensional cone-beam computed tomography study. J Am Dent Assoc, 2018. 149 (7): p. 589-598. Ikeda, K. and A. Kawamura, Disc displacement and changes in condylar position. Dentomaxillofac Radiol, 2013. 42 (3): p. 84227642. Tables Tables 1 to 6 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Tables.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Stomatology","correspondingAuthor":false,"prefix":"","firstName":"Hongyi","middleName":"","lastName":"Tang","suffix":""},{"id":375157097,"identity":"e717bc01-f0eb-4dc9-b60a-0e5a15411faa","order_by":2,"name":"Huazhi Li","email":"","orcid":"","institution":"Peking University School and Hospital of Stomatology","correspondingAuthor":false,"prefix":"","firstName":"Huazhi","middleName":"","lastName":"Li","suffix":""},{"id":375157098,"identity":"2d438583-ba50-49f7-a12f-db71a7d302f5","order_by":3,"name":"Fu Zheng","email":"","orcid":"","institution":"Peking University School and Hospital of Stomatology","correspondingAuthor":false,"prefix":"","firstName":"Fu","middleName":"","lastName":"Zheng","suffix":""},{"id":375157099,"identity":"2477bb3a-521c-4d4b-82b6-dd127b4c04ea","order_by":4,"name":"Youchao Chen","email":"","orcid":"","institution":"Peking University School and Hospital of Stomatology","correspondingAuthor":false,"prefix":"","firstName":"Youchao","middleName":"","lastName":"Chen","suffix":""},{"id":375157102,"identity":"76f512c3-b054-4b68-93bc-f6c6eb74cbc8","order_by":5,"name":"Tong Wu","email":"","orcid":"","institution":"Peking University School and Hospital of Stomatology","correspondingAuthor":false,"prefix":"","firstName":"Tong","middleName":"","lastName":"Wu","suffix":""},{"id":375157103,"identity":"d1a3a188-5731-4219-b8f4-a1cf131b339d","order_by":6,"name":"Cuiying Li","email":"","orcid":"","institution":"Peking University School and Hospital of Stomatology","correspondingAuthor":false,"prefix":"","firstName":"Cuiying","middleName":"","lastName":"Li","suffix":""},{"id":375157104,"identity":"f7eb49d5-e0f9-4481-aa06-2526c429f998","order_by":7,"name":"Jiuhui Jiang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwklEQVRIiWNgGAWjYDCCAwwJB0A0PzPz4QekaZFsZ0szIFYLBBic51GQIEoH3+0DDw/83FGbuPkwD4MBQ41NNEEtkucSEg72njmeuO0w74EHDMfSchsIaTE4A/QLb9ux3G2H+RIMGBsOE6fl4F+gls3NPAYSRGs5zNtWk7uBmVgtkiAtsm0H6mccBgZyAjF+4TvDk/zxbVudMX//4cMPPtTYENbCwMCTACQOQ9gJhJWDAPsBIFFHnNpRMApGwSgYmQAAn9NILvQiJn0AAAAASUVORK5CYII=","orcid":"","institution":"Peking University School and Hospital of Stomatology","correspondingAuthor":true,"prefix":"","firstName":"Jiuhui","middleName":"","lastName":"Jiang","suffix":""}],"badges":[],"createdAt":"2024-08-21 15:01:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4952515/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4952515/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":70371250,"identity":"3a236465-7357-44b4-95bc-d3afb38af2c3","added_by":"auto","created_at":"2024-12-02 14:48:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":338959,"visible":true,"origin":"","legend":"\u003cp\u003eafter registration of MIP and MCFR, patients underwent wide-field CBCT\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/0cc3405f973edee535d2603d.png"},{"id":70368339,"identity":"c2f94778-06f7-4b7e-be74-87d229ae30cd","added_by":"auto","created_at":"2024-12-02 14:24:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":127481,"visible":true,"origin":"","legend":"\u003cp\u003eSynthesis and analysis cephalograms using dolphin imaging software\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/c2fc42406c09095bcc0f87e4.png"},{"id":70369018,"identity":"33c6be73-aac5-411f-82bd-a3638f42ffa2","added_by":"auto","created_at":"2024-12-02 14:32:49","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":119354,"visible":true,"origin":"","legend":"\u003cp\u003e3D reconstruction of CBCT using mimics software\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/d2d0105c882ec3ff167067e5.png"},{"id":70368347,"identity":"9a12acb9-1cc5-4c22-bd1e-613baa8b055b","added_by":"auto","created_at":"2024-12-02 14:24:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":322472,"visible":true,"origin":"","legend":"\u003cp\u003esuperimposition of reconstructed 3D models by bilateral zygomatic bones\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/c4ab98512b8a1bf2d70c5180.png"},{"id":70370449,"identity":"e32c5b31-7b55-479a-9826-de48d8c54e05","added_by":"auto","created_at":"2024-12-02 14:40:49","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":218816,"visible":true,"origin":"","legend":"\u003cp\u003ereconstructed mandibles in MIP( colored blue) and MCFR( colored grey)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/825ba6c166de3cb0ff667ec8.png"},{"id":70368337,"identity":"09d5e120-f4ec-4b63-beb7-5fb272fd6955","added_by":"auto","created_at":"2024-12-02 14:24:49","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":39453,"visible":true,"origin":"","legend":"\u003cp\u003ea reconstructed right condyle with mark points. Condylar innermost point-right condyle(I-R); condylar outmost point-right condyle(O-R); axial of condyle-right condyle( Ax-R) ; geometric center of condyle- right condyle(CC-R)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/2db4e21885534b6b6465086c.png"},{"id":70368343,"identity":"52e83513-f1e7-430b-88b8-2f8ff88a794d","added_by":"auto","created_at":"2024-12-02 14:24:50","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":69128,"visible":true,"origin":"","legend":"\u003cp\u003ea reconstructed mandible with a mark point\u003cstrong\u003e \u003c/strong\u003elower incisor point (Li)\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/fea739721d8cd40cfeb5a41c.png"},{"id":70369023,"identity":"42a5a1ea-4b9b-459f-a595-1d9739e0154f","added_by":"auto","created_at":"2024-12-02 14:32:50","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":258599,"visible":true,"origin":"","legend":"\u003cp\u003ereconstructed mandibles in MIP and MCFR with mark points. Geometric center of condyle- right condyle in MI (CC-R-MI)；condylar outmost point-left condyle in MCFR（O-L-MCFR）etc.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/e833d1648fd57bcd85e282e0.png"},{"id":70369020,"identity":"3e429c8d-e6e2-4bcc-abfa-2ffca8a49f5f","added_by":"auto","created_at":"2024-12-02 14:32:49","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":47200,"visible":true,"origin":"","legend":"\u003cp\u003emeasurement of skeletal CRR\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/3915a6975220b2c0955c912e.png"},{"id":70370450,"identity":"c30a301e-8114-4b6a-a596-80f7ab4fe35a","added_by":"auto","created_at":"2024-12-02 14:40:50","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":534294,"visible":true,"origin":"","legend":"\u003cp\u003ea skeletal class II patient with retrusive mandible who refused orthognathic surgery intervention by exploiting his considerably large CRR.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/9a67255973ddcafb7e6cf890.png"},{"id":92413714,"identity":"2ac58a15-d9da-4417-8a0e-0e9d2717835e","added_by":"auto","created_at":"2025-09-29 13:02:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3228633,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/7db1ab1b-3088-4513-9db1-4b0ee8874c22.pdf"},{"id":70370448,"identity":"fd9e5283-54fb-4874-a984-ebc26b3002bd","added_by":"auto","created_at":"2024-12-02 14:40:49","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":59350,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-4952515/v1/f3f7bc65d620c2146b3e91fa.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Differences Of The Condyle Relocation Range (CRR) Between Skeletal Class II And Skeletal Class III Patients: A Preliminary Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe temporomandibular joint (TMJ) is one of the movable joints of the human body and the only movable joint in the maxillofacial region. General dentists and specialists are very familiar with the static anatomy of the TMJ. However, there are many different views on its functional anatomy. The prevailing view is that the TMJ is similar to the hip joint, and the relationship between the condyle and the glenoid fossa is similar to that of a delicate ball articulating in a socket. Some people believe that the optimal condyle‒fossa relationship is concentric relationship[\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], and some orthodontists prefer to deprogram the mandible and reconstruct the maximum intercuspation position (MIP) in accordance with the centric relation position(CRP)[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, others believe that the relationship between the condyle and the fossa is dynamic, for instance, the \u0026ldquo;long concentric\u0026rdquo; phenomenon in prosthodontics[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and \"the ball on the hill\u0026rdquo;, a new perspective on TMJ functional anatomy proposed by the orthodontist Charles S Greene [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn daily practice, we may find that skeletal class II patients can occlude in several different positions in the sagittal dimension without discomfort, while the mandibles of skeletal class III patients seem immovable in the sagittal dimension. To our knowledge, previous studies have not confirmed this phenomenon, and very few studies have shown similar effects. Turasi reported that the centric occlusion(CO)-maximum intercuspation (MI) discrepancy in patients with an increased overjet (OJ\u0026thinsp;\u0026gt;\u0026thinsp;6mm) was greater than that in people with normal occlusion[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Rainer demonstrated that the free mandibular movement of skeletal class II patients is different from that of skeletal class I patients using an ultrasound measuring system[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The above studies suggested that the condyles of skeletal class II patients may exhibit a large range of movement related to glenoid fossae.\u003c/p\u003e \u003cp\u003eTMJs undergo lifetime remodeling in response to biomechanical loading during either normal mandibular function or parafunction, which distinguishes them from other joints. Many studies have been conducted to determine the relationship between malocclusion and TMJ morphology[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Hasebe reported that the condyle size is the smallest in skeletal class II patients, followed by skeletal class I and class III patients[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Paknahad[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and Katsavrias[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] both reported that the condyles of skeletal class II patients were located more anteriorly within the glenoid fossae than were those of other sagittal skeletal types. Vitral[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] and Li[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] reported that the condyles on the class I side of class II subdivision patients were located more anteriorly than those on the contralateral side. Furthermore, the effects of various dental therapies on TMJ remodeling have been widely studied. Li and her colleagues reported that an anterior repositioning splint (ARS) could induce osseous repair and regeneration of the condyle in early-phase degenerated temporomandibular disorder (TMD) lesions[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], and a \u0026ldquo;double contour\u0026rdquo; could be observed via radiography. Conventional orthodontic treatment can also modify TMJ morphology. Koide reported that the glenoid fossa exhibited remodeling after a four first premolar extraction therapy[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Alhammadi investigated a cohort of single jaw extraction cases and reported that the condyles had moved backward[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Bayirli and his colleagues demonstrated that the edgewise appliance could improve the pattern of mandibular forward growth displacement through the maintenance of vertical control[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe above studies illustrated that the condyle-fossa relationship is more complicated than previously believed. We speculate that the range of physiological condyle positions may vary among different skeletal types and the condyle-fossa relationship may undergo adaptive remodeling during orthodontic occlusal adjustment. Therefore, we developed a new concept, the condyle relocation range (CRR), to describe the physiological movement range of the condyle and mandible in the sagittal dimension. Specifically, the CRR refers to the range in which the mandible moves from the MIP to the most comfortable forward relocation (MCFR) position. The CRR is distinct from the range of mandibular border movement[\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] and the centric occlusion (CO) -centric relation (CR) discrepancy[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. MCFR, the anterior border of the CRR, refers to the position at which patients automatically protrude their mandibles as far as they can, while maintaining interocclusal contact between their anterior or posterior teeth and feeling no pain or stretching of their TMJs. The MCFRs of skeletal class II patients could be edge-to-edge positions or even more forward to the anterior crossbite positions. Specifically, the displacement of the condyle is called the skeletal CRR, and that of the lower central incisors is called the dental CRR.\u003c/p\u003e \u003cp\u003eThe difference of the CRR between skeletal class II and skeletal class III patients was investigated quantitatively in the present study.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003eBased on the mandibular border movement (MBM) data from a previous study[24], a power calculation indicated that 14 patients were needed in each group to achieve a confidence level of 0.95 and a probability of 0.8, for a total of 28 patients all (t = (x1 - x2)/[s^2 * (1/n1 + 1/n2)]^0.5, set n1=n2). x1 and x2 represent the average of the two samples; s^2 represents the weighted average of the variances of the two samples (combined variances); and n1 and n2 represent the sample sizes of the two samples. Considering the difference between the MBM and the newly defined CRR, we expanded the sample size to 40 patients, 80 condyles, and each group contained 20 patients, 40 condyles.\u003c/p\u003e\n\u003cp\u003eWe recruited 20 skeletal class II and 20 skeletal class III young adult patients who visited the Department of Orthodontics or Orthognathic Surgery, *****, from March 1 to December 1, 2021. The inclusion criteria were as follows: 1) skeletal class II diagnosed by an ANB angle\u0026gt;5° or skeletal class III diagnosed by an ANB angle\u0026lt;0°; and 2) no symptoms of temporomandibular joint disorder. The exclusion criteria were as follows: 1) orthodontic treatment history; 2) anterior open bite; 3) unilateral posterior crossbite and scissors bite; 4) severe facial deviation; and 5) craniofacial development syndrome and cleft lip and palate. The study was approved by the biomedical ethics committee of *****(PKUSSIRB-202162020), and was conducted in accordance with the Helsinki Declaration of 1975, as revised in 2013. Participate consent was obtained from all the involved patients. The process of the experiment is described below, and all the subjects completed the experiment. Clinical trial number: not applicable.\u003c/p\u003e\n\u003cp\u003e1. \u003cstrong\u003eRegistration of MCFR: \u003c/strong\u003ePatients were instructed to protrude their mandibles forward voluntarily as far as they could until the anterior teeth reached the edge-to-edge position and then even further forward to the anterior crossbite position, while maintaining interocclusal contact and feeling no pain or stretching in the TMJ region. After the patients had practiced three times, the MCFR was confirmed, and the researcher injected some silicone rubber bite recorder (O-Bite, Dmg, Hamburg, Germany) on the occlusal surface of their bilateral posterior teeth to register their MCFR.\u003c/p\u003e\n\u003cp\u003e2. \u003cstrong\u003eRegistration of MIP:\u003c/strong\u003e Patients were instructed to occlude at the most stable and interdigitated position.\u003c/p\u003e\n\u003cp\u003e3. \u003cstrong\u003eWide-field CBCT ( Newtom Ag, Marburg, Germany) at the MCFR and MIP: \u003c/strong\u003eThe CBCT parameters were as follows: tube voltage, 110 kV; tube current, 2.03 mA; scan field, 15 × 15 cm; axial slice thickness, 0.3 mm; and exposure time, 3.6 s \u003cstrong\u003e\u003cem\u003e(Figure 1).\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e4. \u003cstrong\u003eSynthesis and analysis of cephalograms: \u003c/strong\u003eIn Dolphin Imaging Software (Dolphin Imaging \u0026amp; Management Solutions, California, America), we adjusted the Frankfort plane to be parallel with the horizontal plane for head position adjustment and then synthesized a lateral cephalogram. Next, we measured the dental and skeletal craniofacial features of the MI and MCFR positions of each patient\u003cstrong\u003e\u003cem\u003e (Figure 2 Table1).\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5. Measurement of the dental and skeletal CRRs:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e1) \u003cstrong\u003eReconstruction of a 3D model of the full craniofacial bone:\u003c/strong\u003e In Mimics Medical 20.0 Software (Materialise, Brussels, Belgium), the full craniofacial bone of MI and MCFR positions was extracted with the gray value of the condyle (approximately 400 HU), reconstructed into 3D models and subsequently saved in STL format \u003cstrong\u003e\u003cem\u003e(Figure 3)\u003c/em\u003e\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e2) \u003cstrong\u003eSuperimposition of 3D models:\u003c/strong\u003e After importing the reconstructed full craniofacial bone 3D model into Geomagic Studio 2013 Software (Geomagic, North Carolina, America). We sketched the contour of the bilateral zygomatic bones (inferior orbital border, zygomaticomaxillary suture, inferior border of the zygomatic arch, zygomatic temporal suture, superior border of the zygomatic arch); then, we superimposed the full craniofacial bone 3D models of the MCFR and MI positions according to the bilateral zygomatic bone surface \u003cstrong\u003e\u003cem\u003e(Figure 4,5).\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3) Location of mark points\u003cem\u003e (Figures6,7,8, Table1):\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCondylar innermost point (I): the most prominent point on the condylar inner surface\u003c/p\u003e\n\u003cp\u003eCondylar outermost point (O): the most prominent point on the condylar outer surface\u003c/p\u003e\n\u003cp\u003eAxis of condyle (Ax): a line connecting the condylar innermost point and outermost point\u003c/p\u003e\n\u003cp\u003eGeometric center of condyle (CC): the midpoint of the axis of the condyle\u003c/p\u003e\n\u003cp\u003eLower incisor point (Li)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4) Measurement of CRR\u003cem\u003e (Figure9):\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSkeletal CCR: the distance between the CC in the MIP and MCFR positions\u003c/p\u003e\n\u003cp\u003eDental CRR: the distance between Li in the MIP and MCFR positions\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe statistical analysis was performed using SPSS 23.0 Software (IBM Corp., Armonk, Ny, America). The difference in the sex ratio between groups was compared by the chi-square test. Normality and homogeneity of variance were assessed by the Kolmogorov‒Smirnov test and Levene test, respectively. The age and cephalometric analysis results were normally distributed and were analyzed with an independent t test, while the CRR results were nonnormally distributed and were analyzed with the Wilcoxon rank sum test.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003e1.\u0026nbsp; \u0026nbsp;\u0026nbsp;Baseline demographic \u003cem\u003echaracteristics (Table 2)\u003c/em\u003e:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e1)\u0026nbsp; \u0026nbsp;\u0026nbsp;The average age of skeletal class II patients was 22.04 (3.80) years, and the average age of skeletal class III patients was 22.13 (3.89) years. There was no significant difference between the two skeletal types (p=0.84 (P\u0026gt;0.05)).\u003c/p\u003e\n\u003cp\u003e2)\u0026nbsp; \u0026nbsp;\u0026nbsp;The ratio of females to males in skeletal class II was 45%, whereas that in skeletal class III was 60%. There was no significant difference in the ratio of females to males between the two groups (p=0.34 (P\u0026gt;0.05)).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.\u0026nbsp; \u0026nbsp;\u0026nbsp;Craniofacial characteristic features of skeletal class II and skeletal class III patients in the MI and MCFR positions\u003cem\u003e\u0026nbsp;(Tables 3,4)\u003c/em\u003e:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e1)\u0026nbsp; \u0026nbsp;For skeletal class II patients, the SNB(°), facial angle, L1-NB (mm), and L1-NB (°) values were greater in the MCFR position than in the MI position. The ANB and angle of convexity were smaller in the MCFR position than in the MI position (p=0.00 (p\u0026lt; 0.05)).\u003c/p\u003e\n\u003cp\u003e2)\u0026nbsp; \u0026nbsp;The SN-MP of skeletal class II patients in the MCFR position was smaller than that in the MI position (p=0.035 (p\u0026lt;0.05)), while the SN-MP of skeletal class III patients in the MCFR position was larger than that in the MI position (p=0.007 (p\u0026lt;0.05)).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.\u0026nbsp; \u0026nbsp;\u0026nbsp;CRRs of skeletal class II and skeletal class IIIpatients\u003cem\u003e\u0026nbsp;(Table 5)\u003c/em\u003e:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e1)\u0026nbsp; \u0026nbsp;For skeletal class II patients, the median (interquartile range) dental CRR was 8.71 (3.55) mm, and the median (interquartile range) skeletal CRR was 8.47 (4.19) mm. The vertical component of the dental and skeletal CRRs was larger than the anteroposterior and horizontal components.\u003c/p\u003e\n\u003cp\u003e2)\u0026nbsp; \u0026nbsp;For skeletal class III patients, the median (interquartile range) dental CRR was 1.37 (3.43) mm, and the median (interquartile range) skeletal CRR was 1.04 (1.44) mm. The vertical component of the dental and skeletal CRR was greater than the anteroposterior and horizontal components.\u003c/p\u003e\n\u003cp\u003e3) \u0026nbsp; The dental and skeletal CRRs of skeletal class II patients were significantly greater than those of skeletal class III patients (p\u0026lt;0.05).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eFor the first time, we developed the concept of the CRR to describe the potential range of mandible\u0026nbsp;positions under physiological conditions. The CRR is distinct from the range of MBM. The anterior border of the MBM is the most protrusive position (MPP), the most forward mandibular position that is used for chewing or speaking, which is temporary, rather than interdigitating and persistently maintaining the mandible position. The mandible is protruded to the greatest extent in the MPP. However, the anterior border of the CRR is the MCFR, which has two connotations. The first is comfort, which guarantees that the mandibular position within the CRR has no impact on TMJ health and can be stably maintained; that is, the MCFR is a physiological mandibular position. The second is maintaining occlusal contact, which ensures the anteroposterior range of mandibular relocation under the precondition of a specific vertical dimension.\u003c/p\u003e\n\u003cp\u003eThe present study clearly demonstrated that the CRR of skeletal class II patients was greater than that of class III patients, which is consistent with our clinical observations and confirms our hypothesis. These\u0026nbsp;findings deepen our understanding of functional TMJ anatomy and broaden our\u0026nbsp;understanding\u0026nbsp;of human maxillofacial morphology.\u0026nbsp;Orthodontic treatment involves not only intra-arch tooth movement within the dental alveolar bone but also interarch occlusal adjustment, which changes the mandibular position and remodels the TMJ. For example, Herbst devoted himself\u0026nbsp;to\u0026nbsp;using\u0026nbsp;the Herbst appliance to treat\u0026nbsp;the retrusive mandible of\u0026nbsp;nongrowing\u0026nbsp;patients[28, 29].\u003c/p\u003e\n\u003cp\u003eIn our clinical practice, we have successfully treated numerous\u0026nbsp;skeletal class II patients with retrusive\u0026nbsp;mandibles\u0026nbsp;who refused orthognathic surgery intervention by exploiting their\u0026nbsp;considerably\u0026nbsp;large\u0026nbsp;CRRs.\u0026nbsp;The following description is a representative case. A 41-year-old male patient diagnosed\u0026nbsp;as\u0026nbsp;skeletal class II with\u0026nbsp;a retrusive\u0026nbsp;mandible (ANB=8.1°, SNB=68.4°),\u0026nbsp;a full cusp class II molar relationship,\u0026nbsp;a deep overjet (9\u0026nbsp;mm) and\u0026nbsp;a deep overbite (7 mm).\u0026nbsp;TMJ CBCT\u0026nbsp;indicated that\u0026nbsp;he had degenerative temporomandibular joint disease that\u0026nbsp;was in\u0026nbsp;a quiescent stage. He underwent four first\u0026nbsp;premolar\u0026nbsp;extraction therapy\u0026nbsp;and used an\u0026nbsp;edgewise appliance. After\u0026nbsp;four years of\u0026nbsp;orthodontic treatment, his mandible was relocated forward within his CRR, his facial profile greatly improved, and the final occlusion was stable\u003cstrong\u003e\u003cem\u003e\u0026nbsp;(Figures 10, Table 6\u003c/em\u003e\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003eThe use of the condylar position indicator (CPI) is the most common approach for measuring condylar shift. The condyle center is located by an empirically chosen skin surface marker, which is definitely not accurate[10, 26, 27]. As the condyle and glenoid fossa have irregular geometries, a 3D reconstructed condyle model from CBCT images could comprehensively and accurately reveal the actual stereoscopic structure and unique position of the TMJ[30]. In this study, we developed a\u0026nbsp;condylar displacement measurement method. After reconstructing a 3D model of the full craniofacial bone in the MIP and the MCFR position, we superimposed the two models according to the bizygomatic surfaces and then measured the condylar shift in three-dimensional space.\u003c/p\u003e\n\u003cp\u003eGiuntini concluded that the posteriorly displaced glenoid fossa is a characteristic of class II malocclusion with mandibular retrusion[31]. Several studies have verified that more anteriorly positioned condyles are present in skeletal class II patients than in skeletal class I and skeletal class III patients[14, 15]. We speculate that the condyles of skeletal class II patients are located more anteriorly to compensate for the retrusive mandibles, which are restrained by the posteriorly located glenoid fossa. In addition, the small size of the condyles of skeletal class II patients[13, 32-34]\u0026nbsp;may facilitate the ability of the mandibles to freely relocate anteriorly, which\u0026nbsp;may constitute\u0026nbsp;the morphological basis of\u0026nbsp;the large CRR\u0026nbsp;in\u0026nbsp;skeletal class II patients.\u003c/p\u003e\n\u003cp\u003eThe CRR is a functional craniofacial characteristic and should be included in pre-orthodontic examinations to facilitate comprehensive assessment of the patients. Exploiting the relatively large CRR, an alternative treatment paradigm for skeletal class II patients was introduced, in which the condyle was relocated forward to compensate for the retrusive mandible rather than causing proclination of the lower incisors. This paradigm is especially applicable for adult patients who refuse orthognathic surgery intervention but have relatively large CRRs. Adolescent skeletal class II patients with large CRRs could also incorporate the CRR into their treatment plan to achieve a better facial profile outcome. Nevertheless, combined orthodontic and surgical treatment is still the best option for skeletal class III patients because of their small CRR.\u003c/p\u003e\n\u003cp\u003eAlthough the present study yielded several noteworthy findings, it is not without limitations. Vertical skeletal patterns should be considered in subsequent studies with larger sample sizes, and it is better to examine disc position by MRI first because of its possible impact on condylar position[35]. In addition, clinical studies are needed to explore the outcome and long-term stability of the new treatment paradigm.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe CRR is a functional craniofacial characteristic that varies among different skeletal types. The CRR in skeletal class II patients is significantly greater than that in skeletal class III patients. CRR measurement should be included in pre-orthodontic examinations, and orthodontists should pay attention to the range of physiological mandible positions.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCondyle Relocation Range, CRR\u003c/p\u003e\n\u003cp\u003econe beam computed tomography, CBCT\u003c/p\u003e\n\u003cp\u003emaximum intercuspation position, MIP\u0026nbsp;\u003c/p\u003e\n\u003cp\u003emost comfortable forward relocation, MCFR\u003c/p\u003e\n\u003cp\u003etemporomandibular joint, TMJ\u003c/p\u003e\n\u003cp\u003ecentric relation position, CRP\u003c/p\u003e\n\u003cp\u003ecentric occlusion, CO\u003c/p\u003e\n\u003cp\u003emaximum intercuspation, MI\u003c/p\u003e\n\u003cp\u003eanterior repositioning splint, ARS\u003c/p\u003e\n\u003cp\u003etemporomandibular disorder,\u0026nbsp;TMD\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ecentric relation, CR\u003c/p\u003e\n\u003cp\u003emandibular border movement, MBM\u003c/p\u003e\n\u003cp\u003emost protrusive position, MPP\u003c/p\u003e\n\u003cp\u003econdylar position indicator, CPI\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNational Natural Science Foundation of China (Grant/Award Numbers: U233010010).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHuman ethics and consent to participate declaration:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was approved by the biomedical ethics committee of Peking University School of Stomatology (PKUSSIRB-202162020), and was conducted in accordance with the Helsinki Declaration of 1975, as revised in 2013.\u0026nbsp;Participate consents were signed by all the patients involved in the study. All the forty photocopies of the Consent to participate declaration in Chinese have been uploaded as related files.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent for publication of images has been obtained from the participants.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eX.Y.C. contributed to conceptualization, methodology, software and writing - original draft.\u003c/p\u003e\n\u003cp\u003eH.Y.T. contributed to writing - review \u0026amp; editing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eH.Z.L., F.Z., Y.C.C. and T.W. participated in case collection.\u003c/p\u003e\n\u003cp\u003eJ.J.H. and C.Y.L. contributed to conceptualization, writing- review\u0026amp; editing and supervision.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003ePullinger, A.G., et al., \u003cem\u003eRelationship of mandibular condylar position to dental occlusion factors in an asymptomatic population.\u003c/em\u003e Am J Orthod Dentofacial Orthop, 1987. \u003cstrong\u003e91\u003c/strong\u003e(3): p. 200-6.\u003c/li\u003e\n\u003cli\u003eRodrigues, A.F., M.R. 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Pancherz, \u003cem\u003eTemporomandibular joint remodeling in adolescents and young adults during Herbst treatment: A prospective longitudinal magnetic resonance imaging and cephalometric radiographic investigation.\u003c/em\u003e Am J Orthod Dentofacial Orthop, 1999. \u003cstrong\u003e115\u003c/strong\u003e(6): p. 607-18.\u003c/li\u003e\n\u003cli\u003eHans Ulrik Paulsen and A. Karle, \u003cem\u003eComputer tomographic and radiographic changes in the temporomandibular joints of two young adults with occlusal asymmetry, treated with the Herbst appliance.\u003c/em\u003e European Journal of Orthodontics, 2000. \u003cstrong\u003e22 (2000) 649\u0026ndash;656\u003c/strong\u003e.\u003c/li\u003e\n\u003cli\u003eZhang, Y., X. Xu, and Z. Liu, \u003cem\u003eComparison of Morphologic Parameters of Temporomandibular Joint for Asymptomatic Subjects Using the Two-Dimensional and Three-Dimensional Measuring Methods.\u003c/em\u003e J Healthc Eng, 2017. \u003cstrong\u003e2017\u003c/strong\u003e: p. 5680708.\u003c/li\u003e\n\u003cli\u003eGiuntini, V., et al., \u003cem\u003eGlenoid fossa position in Class II malocclusion associated with mandibular retrusion.\u003c/em\u003e Angle Orthod, 2008. \u003cstrong\u003e78\u003c/strong\u003e(5): p. 808-12.\u003c/li\u003e\n\u003cli\u003eAlhammadi, M.S., M.S. Fayed, and A. Labib, \u003cem\u003eThree-dimensional assessment of temporomandibular joints in skeletal Class I, Class II, and Class III malocclusions: Cone beam computed tomography analysis.\u003c/em\u003e Journal of the World Federation of Orthodontists, 2016. \u003cstrong\u003e5\u003c/strong\u003e(3): p. 80-86.\u003c/li\u003e\n\u003cli\u003eZhang, Y., et al., \u003cem\u003eThree-dimensional condylar positions and forms associated with different anteroposterior skeletal patterns and facial asymmetry in Chinese adolescents.\u003c/em\u003e Acta Odontol Scand, 2013. \u003cstrong\u003e71\u003c/strong\u003e(5): p. 1174-80.\u003c/li\u003e\n\u003cli\u003eMa, Q., et al., \u003cem\u003eTemporomandibular condylar morphology in diverse maxillary-mandibular skeletal patterns: A 3-dimensional cone-beam computed tomography study.\u003c/em\u003e J Am Dent Assoc, 2018. \u003cstrong\u003e149\u003c/strong\u003e(7): p. 589-598.\u003c/li\u003e\n\u003cli\u003eIkeda, K. and A. Kawamura, \u003cem\u003eDisc displacement and changes in condylar position.\u003c/em\u003e Dentomaxillofac Radiol, 2013. \u003cstrong\u003e42\u003c/strong\u003e(3): p. 84227642.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 6 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"condyle relocation range (CRR), most comfortable forward relocation (MCFR), physiologically comfortable mandible position, temporomandibular joint (TMJ)","lastPublishedDoi":"10.21203/rs.3.rs-4952515/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4952515/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction: \u003c/strong\u003eThe present study aimed to preliminarily compare the differences of the condyle relocation range (CRR) between skeletal class II and skeletal class III patients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e Twenty skeletal class II and twenty skeletal class III young adult patients underwent wide-field cone beam computed tomography (CBCT) scans of the maximum intercuspation position (MIP) and most comfortable forward relocation (MCFR). We superimposed the CBCT images in two positions according to the bilateral zygomatic bone surface structure and then measured the dental and skeletal CRRs in three-dimensional space.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eThe median (interquartile range) dental and skeletal CRRs of skeletal class II malocclusion patients were 8.71 (3.55) mm and 8.47 (4.19) mm, respectively. The median (interquartile range) dental and skeletal CRRs for skeletal class III malocclusion patients were 1.37 (3.43) mm and 1.04 (1.44) mm, respectively. Both the dental and skeletal CRRs of skeletal class II patients were significantly greater than those of skeletal class III patients (p\u0026lt;0.01).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions:\u003c/strong\u003e The CRRs of the different skeletal types exhibit obvious differences. Therefore, the range of physiological mandible positions in patients should be given attention during orthodontic diagnosis and treatment.\u003c/p\u003e","manuscriptTitle":"Differences Of The Condyle Relocation Range (CRR) Between Skeletal Class II And Skeletal Class III Patients: A Preliminary Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-02 14:24:44","doi":"10.21203/rs.3.rs-4952515/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5b54c780-26a6-4049-86e3-72be3bae069a","owner":[],"postedDate":"December 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-12T16:09:04+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-02 14:24:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4952515","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4952515","identity":"rs-4952515","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}