Adaptive condylar growth and mandibular remodelling changes with bionator therapy--an implant study

The purpose of this study was to describe condylar growth and mandibular remodelling changes associated with bionator therapy. Twenty-five patients (15 males and 10 females) between 6.9 and 11.2 years of age with Class II division 1 malocclusions were randomly allocated to either control (n = 11) or treatment (n = 14; bionator only) groups and followed longitudinally for approximately 1 year. Treatment consisted of a bionator only, constructed to clear the buccal dentition by 2 mm and to position the mandible into an edge-to-edge incisor relationship. Using metallic implants for superimposition, mandibular growth, displacement, and true rotation were evaluated cephalometrically. The results showed significant changes in the direction (more posterior) but not in the overall amount of condylar growth. The bionator appliance produced greater than expected posterior drift of landmarks in the condylar and gonial regions. Cranial base superimposition showed greater than expected anterior mandibular displacement, but little or no true mandibular forward rotation with bionator therapy. The bionator appliance alone produced changes in condylar growth direction and remodelling changes associated with mandibular rotation and displacement.     

Comparative cephalometric study of Class III malocclusion in Saudi and Japanese adult females

The cephalometric features of class III malocclusion in Saudi adult females were investigated and compared with reference data for Japanese females. The sample consisted of 30 standardized pre-treatment cephalometric radiographs of adult Saudi females diagnosed as having skeletal class III malocclusion. The radiographs were traced and digitized. Linear and angular variables were obtained for comparison of cranial base, maxilla, mandible, intermaxillary and dentoalveolar measurements. The method error in identifying and locating the anatomical landmarks was small and acceptable. Student's t-test was used for comparing the measurements. The results showed that Saudi females had a larger anterior cranial base, a smaller posterior cranial base, a smaller cranial base angle, smaller anterior and posterior facial heights, downward tipping of the maxilla, a retruded chin, a less steep mandibular plane, an increased joint angle, a smaller ramus, body and total mandibular length, and less retroclined mandibular incisors. The null hypothesis of no difference between the two groups was rejected. These results appear to suggest real differences in skeletal features between Saudi and Japanese adult females.     

Evaluation of Class II treatment by cephalometric regional superpositions versus conventional measurements.

INTRODUCTION: The aims of this study were (1) to evaluate cephalometric changes in subjects with Class II Division 1 malocclusion who were treated with headgear (HG) or Fr?nkel function regulator (FR) and (2) to compare findings from regional superpositions of cephalometric structures with those from conventional cephalometric measurements. METHODS: Cephalographs were taken at baseline, after 1 year, and after 2 years of 65 children enrolled in a prospective randomized clinical trial. The spatial location of the landmarks derived from regional superpositions was evaluated in a coordinate system oriented on natural head position. The superpositions included the best anatomic fit of the anterior cranial base, maxillary base, and mandibular structures. RESULTS: Both the HG and the FR were effective in correcting the distoclusion, and they generated enhanced differential growth between the jaws. Differences between cranial and maxillary superpositions regarding mandibular displacement (Point B, pogonion, gnathion, menton) were noted: the HG had a more horizontal vector on maxillary superposition that was also greater (.0001 < P < .05) than the horizontal displacement observed with the FR. This discrepancy appeared to be related to (1) the clockwise (backward) rotation of the palatal and mandibular planes observed with the HG; the palatal plane's rotation, which was transferred through the occlusion to the mandibular plane, was factored out on maxillary superposition; and (2) the interaction between the inclination of the maxillary incisors and the forward movement of the mandible during growth. CONCLUSIONS: Findings from superpositions agreed with conventional angular and linear measurements regarding the basic conclusions for the primary effects of HG and FR. However, the results suggest that inferences of mandibular displacement are more reliable from maxillary than cranial superposition when evaluating occlusal changes during treatment.     

三维CT成像诊断髁突骨折的临床研究

目的：探讨获得高质量颞颌关节三维ＣＴ影像的方法,评价其对髁突骨折的诊断价值。方法;对１４例髁突骨折患者,采用３种扫描方式（横断,冠状,螺旋）,２种扫描范围（横断位：眶耳平面上方１ｃｍ至下颌升支中份或颏下点。冠状位：乳突至下颌升支前缘或颏前点）。和２种层厚（２．５ｎｍ,５．０ｍｍ）扫描,以勾画法删除层面影像中的颈椎,茎突,枕骨和部分乳突,表面阴影显示法（ＳＳＤ）完成三维重建。     

Frnkel矫治器对安氏Ⅱ类错患者髁突和下颌位置的影响

目的　了解Frankel矫治器治疗安氏Ⅱ类错过程中,髁突和下颌位置的变化情况。方法　选择经Frankel 矫治器治疗成功的安氏Ⅱ类错患者30例,男女各15例,对其治疗前后的头颅侧位定位片进行X线头影测量重叠分析。结果　①前颅底结构重叠显示治疗后患者的髁突点、下颌角点和颏前点发生明显的下移,同时男性患者颏前点发生明显的前移。②下颌结构重叠显示治疗后患者的髁突点发生明显的上移和后移(移位比约为2∶1),下颌角点相对颏部发生后移。结论　Frankel矫治器能刺激安氏Ⅱ类错患者髁突的生长,有利于下颌水平向的改建。     

3D evaluation of mandibular skeletal changes in juvenile arthritis patients treated with a distraction splint: A retrospective follow-up

Objective:To evaluate three-dimensional (3D) condylar and mandibular growth in patients with juvenile idiopathic arthritis (JIA) with unilateral temporomandibular joint involvement treated with a distraction splint.Materials and Methods:Cone-beam computed tomography (CBCT) scans were taken for 16 patients with JIA with unilateral TMJ involvement before treatment (T₀) and 2 years after treatment (T₁). All patients received orthopedic treatment with a distraction splint. Eleven patients without JIA who were undergoing orthodontic treatment without a functional appliance or Class II mechanics and who had taken CBCT scans before and after treatment, served as controls. Reconstructed 3D models of the mandibles at T₀ and T₁ were superimposed on stable structures. Intra- and intergroup growth differences in condylar and mandibular ramus modifications and growth vector direction of the mandibular ramus were evaluated.Results:In all patients with JIA there were asymmetric condylar volume, distal and vertical condylar displacement, and ramus length differences that were smaller on the affected side. Condylar displacement was more distal and less vertical in the JIA group than in the control group. A larger distal growth of the condylar head and a more medial rotation of the ramus on the affected side were found in the JIA group.Conclusion:The orthopedic functional treatment for patients with JIA allows for condylar adaptation and modeling, thereby hindering, although with a widely variable response, a further worsening of the asymmetry. Unilateral affection has a possible influence on the growth of the nonaffected side.     

A longitudinal study of condylar growth and mandibular rotation in untreated subjects with class II malocclusion

Condylar growth intensity, mandibular growth rotation, and the association between growth intensity and rotation were evaluated in 32 untreated subjects with Class II malocclusions. Condylar growth was measured on serial lateral head films annually from ages 8 to 13. The analysis showed that the growth intensity of the condyles varied only slightly between girls and boys, with boys growing more. Fluctuations in growth intensity were observed in all subjects from year to year. None of the individuals maintained a consistent growth velocity over two or more consecutive years. The average condylar growth intensity was two to three mm per year throughout the period from age 8 1/2 to 12 1/2 for both sexes, with boys growing slightly faster than girls at some ages. The greatest growth velocity observed was eight mm in one year, which was seen in one boy. Three girls had as much as six mm of condylar growth in one year. Average mandibular rotation was -0.8 (+/- 0.5 SD) per year in boys and -0.6 degrees (+/- 0.6 SD) in girls, with great individual variation for both sexes. Ninety percent of the subjects showed some degree of anterior or forward rotation; only one subject demonstrated posterior rotation and three demonstrated almost no rotation. No clear relationship was found between amount of condylar growth and mandibular rotation. This study shows that condylar growth intensity varies considerably between subjects and from year to year in each subject, and suggests that clinicians need to be conservative when estimating treatment length for a patient with a Class II malocclusion.     

13名女性自9.5至15.5岁自然生长中下颌骨旋转的研究

目的通过对13名未经正畸治疗的女性个体自9.5至15.5岁拍摄头颅侧位片的重叠研究,探讨面部正常生长发育过程中下颌骨的旋转。方法选择美国密西根大学生长发育中心收集的Dr. Mathews长期追踪观察的13名未经正畸治疗的安氏Ⅰ类高加索人种女性9.5~15.5岁拍摄的头颅侧位片,以种植体作为标志点,重叠并描记所有头颅侧位片。通过Dentofacial Software完成头影测量分析, 采用SPSS 15.0软件对不同年龄段的面部生长变化进行配对t检验。结果高加索人种女性9.5～11.5岁时前下面高、后面高、下颌升支和下颌种植体平面角的变化有统计学差异;11.5～13.5岁时前下面高、后面高、下颌升支的变化有统计学差异;13.5～15.5岁时后面高、下颌平面角、下颌种植体平面角的变化有统计学差异。结论生长发育过程中下颌骨下缘的改建会引起下颌骨的整体旋转。     

Surgical control of mandibular growth: test of a recent biomechanical hypothesis

It has been suggested that, by changing the orientation (and hence the function) of the condyle/ascending ramus segment, surgical control of mandibular growth rotation is possible in growing children. To test one aspect of this hypothesis--the effect of changes in condylar orientation--one condyle in each of thirty-five young male rats was rotated surgically, either clockwise or counterclockwise, and then wired to the ramus to preserve the new orientation. Amalgam implants and lateral cephalograms were used to measure the subsequent pattern of mandibular growth. The findings revealed that surgical rotation of the condyle and the subsequent pattern of mandibular displacement are poorly correlated (r = 0.1-0.3). It was concluded, therefore, that changes in the pattern of mandibular rotation that may follow early mandibular advancement are the result of factors other than the orientation of the condyle following surgery.     

Three-dimensional condylar displacement and remodelling in patients with asymmetrical mandibular prognathism following bilateral sagittal split osteotomy

This study aims to assess the postoperative condylar displacement and the long-term condylar remodelling in patients with mandibular prognathism with transverse asymmetry after bilateral sagittal split ramus osteotomy (BSSRO). Forty-one consecutive patients (82 condyles) with a transverse mandibular asymmetry of more than 4 mm without occlusal canting treated by BSSRO were included. The preoperative (T1), immediate postoperative (T2) and long-term follow-up of an average of 16.2 months (T3) spiral computed tomography scans were gathered and processed to measure the condylar displacement and remodelling based on cranial base voxel-based and rigid regional registrations. The statistical analysis revealed that the majority of condyles (T1–T2) were transitionally displaced forwards, downwards and laterally, and were not fully returned to the preoperative position at T3. Condylar lateral displacement was significantly higher on the deviated side (DS) (P = 0.035). Non-deviated side (NDS) condyles were mainly subjected to upward pitch, medial yaw and medial roll compared with downward pitch, lateral yaw and lateral roll on DS. Condylar remodelling at T3 was observed, with the superior and posterior surfaces commonly subjected to bone resorption, whereas the anterior and medial surfaces were commonly subjected to bone apposition. Condylar volumetric changes were relatively comparable on NDS (3 ± 85.2 mm³) and DS (8.3 ± 111.7 mm³) condyles. Age, amount of preoperative asymmetry and follow-up period were not correlated with the condylar remodelling. Transitional and rotational displacements were to some extent significantly correlated with the condylar remodelling on both sides. Consequently, passive condylar seating without torque might prevent the long-term unfavourable condylar remodelling.     

Mandibular setback by sagittal split ramus osteotomy: a 12-year follow-up

Short- and long-term skeletal changes after mandibular setback were analyzed using bilateral sagittal split ramus osteotomy. Twelve patients who had undergone mandibular setback surgery between 1986 and 1990 were available for long-term cephalography on average 12 years after primary surgery. The mean amount of surgical setback had been 6.4 mm. After the first postoperative year, there was skeletal relapse of 1 mm at the B-point and pogonion (Pg), amounting to 14% of the initial skeletal setback. In contrast to condylar displacement and proximal segment rotation, osteotomy slippage was associated with positional changes at the B-point and Pg. From 1 to 12 years postoperatively, the B-point and Pg remained stable. Mandibular ramus and corpus length decreased 2.1 mm and 1.3 mm, respectively, indicating remodeling at the osteotomy sites and probably condylar resorption.     

Correction of condylar displacement following intraoral vertical ramus osteotomy

Fifteen patients who demonstrated condylar sag after intraoral vertical ramus osteotomy for the correction of mandibular prognathism were treated nonsurgically to establish the desired postoperative occlusion. A mean inferior displacement of 3.33 mm and anterior displacement of 2.18 mm were observed tomographically after surgery. Postoperatively, a geometric splint was constructed to compensate for the magnitude of condylar displacement and was used to replace the original splint to hold the distal segment in an overcorrected position. Skeletal fixation was maintained for 5 to 6 weeks. Tomographic evaluation of the temporomandibular joint (TMJ) during maxillomandibular fixation showed a slight superior (1.03 mm) and posterior (0.51 mm) movement of the condyle in the fossa. After release of fixation and removal of splint, a further superior (2.05 mm) and posterior (1.01 mm) repositioning of the condyle was observed. This later movement correlated with the placement of light class III elastic traction to seat the condyles into the glenoid fossae and establish a class I occlusion. Temporomandibular joint tomograms confirmed complete seating of the condyles in the fossa and lateral cephalograms demonstrated a corresponding change in the position of the mandible to the desired postoperative position. This technique has been effective in preventing postoperative malocclusion resulting from condylar sag.     

Evaluation of effects of activator treatment on mandibular growth by analyzing components of condylar growth and mandibular rotation

PurposeThe objective of this study is to clarify the effects of activator treatment on mandibular growth in relation to condylar growth and total rotation of the mandible, and to investigate the relationships between the treatment responses and pretreatment facial morphology.Materials and methodsThirty Japanese girls with Class II division 1 malocclusion treated with activator were examined. Mean age at the start of treatment was 9.6 ± 1.6 years. Mean treatment duration was 19 ± 4 months. Lateral cephalograms obtained before and after treatment were used to analyze skeletal changes during treatment. Regional superimposition analysis was performed to evaluate activator effects by decomposing the mandibular growth into condylar growth and mandibular total rotation.ResultsThe changes in intermaxillary relationships were significantly correlated with vertical condylar growth and mandibular total rotation (P < 0.05 and P < 0.01). The changes in the forward displacement of the mandible were significantly correlated with sagittal condylar growth and mandibular total rotation (P < 0.05 and P < 0.01). Vertical condylar growth and mandibular total rotation were significantly correlated with pretreatment mandibular morphology (P < 0.05 and P < 0.01).ConclusionBoth the sagittal condylar growth and counterclockwise mandibular total rotation attributed to activator treatment contribute to forward displacement of the mandible. The activator effects are expected greater in patients with flat mandibular plane, small gonial angle, backwardly inclined mandibular ramus and long posterior facial height.     

Anthropometric analysis of mandibular asymmetry in infants with deformational posterior plagiocephaly.

PURPOSE: The incidence of deformational posterior plagiocephaly has increased dramatically since 1992. We tested the hypothesis that mandibular asymmetry, associated with this condition, is secondary to anterior displacement of the ipsilateral temporomandibular joint. The response to molding helmet therapy was also evaluated. PATIENTS AND METHODS: A caliper was used to measure mandibular dimensions in 27 infants (16 boys and 11 girls) with deformational posterior plagiocephaly; the mean age was 6.2 months (range, 3 to 12 months). Anthropometric measures included ramal height (condylion-gonion), body length (gonion-gnathion), and condylion-gnathion. Gonial angle was calculated from the law of cosines: C(2) = A(2) + B(2) - 2AB cos c. The position of the temporomandibular joint was accepted as corresponding to auricular position and measured from tragion to subnasal. Cranial asymmetry was measured, in the horizontal plane, from orbitale superius to the contralateral parieto-occipital point at the level of inion. Ten of 27 patients were remeasured 5 months after beginning helmet therapy to evaluate change in mandibular dimensions. RESULTS: Two thirds of infants (67%) had right-sided and one third (33%) had left-sided deformational posterior plagiocephaly. The mean auricular anterior displacement was 79.7 mm on the affected side and 83.4 mm on the unaffected side. The mean difference of 3.8 mm between the sides was statistically significant (P <.001). Transverse cranial dimension averaged 136.0 mm on the affected side and 146.8 mm on the unaffected side; this was also significant (P <.001). There was a significant positive correlation between auricular displacement and cranial asymmetry [R(23) =.59, P <.01). Auricular (temporomandibular joint) displacement also resulted in an apparent mandibular asymmetry with rotation of the jaw to the affected side. Mean mandibular measurements on the affected and unaffected sides were ramus height of 35.2 and 36.4 mm, body length of 59.0 and 60.3 mm, and gonial angle of 127.1 degrees and 126.8 degrees, respectively. Comparison of the affected with the unaffected sides, using a paired-samples t test, was not statistically significant. Improvement in cranial asymmetry occurred with helmet therapy, but there was no correction of auricular and temporomandibular joint position. CONCLUSIONS: This study supports the clinical observation that the mandibular asymmetry in deformational posterior plagiocephaly is secondary to rotation of the cranial base and anterior displacement of the temporomandibular joint (quantified by anterior auricular position) and not the result of primary mandibular deformity.     

Three-dimensional computed tomography evaluation of postsurgical condylar displacement after mandibular osteotomy

Objective. The purpose of this study was to examine both condylar displacement of the temporomandibular joint after sagittal split ramus osteotomy with rigid osteosynthesis and intraoral vertical ramus osteotomy without osteosynthesis in patients with mandibular prognathism by means of three-dimensional computed tomography.Study design. In this pilot study, five patients treated with sagittal split ramus osteotomy and 5 patients treated with intraoral vertical ramus osteotomy were evaluated. A technique to superimpose a postoperative three-dimensional computed tomography image on its corresponding preoperative image was designed. Postoperative condylar displacement, rotation, and tilting were measured in three-dimensional computed tomography images.Results. Within 3 to 6 months after surgery, changes in the inclination of the condylar axes were distinctly seen, although changes in the position of the condyles within the joints were minimal. In particular, outward rotation of the condylar long axes after intraoral vertical ramus osteotomy was a frequent finding.Conclusions. The three-dimensional computed tomography superimposition technique was a practical method of evaluating post-surgical condylar displacement after mandibular osteotomy.     

双颌手术升支截骨后退术后下颌稳定性及与关节关系的研究

目的　探讨升支矢状劈开截骨术(BSSRO)小钛板坚固内固定与口内入路升支垂直截骨术(BIVRO)下颌后退术后颌稳定性的不同规律,了解导致复发的有关因素特别是髁状突移位在不同手术后复发过程中的意义。方法　升支截骨手术后退下颌的患者共38例,皆为双颌手术,其中下颌BSSRO19例,BIVRO后退术19例。于手术前1周(T1),手术后1周(T2),3个月(T3)及1年(T4)分别拍摄定位头颅侧位片及定位颞下颌关节薛氏位片用于测量下颌移动幅度及关节髁状突的手术后移位。结果　双颌手术下颌升支截骨后退术后,BSSRO坚固内固定组1年时的复发率为25%,而BIVRO组大部分患者1年时下颌发生了与手术目的相同的移动,两组的不稳定主要发生在术后3个月内。结论　手术使髁状突移位术后位置的调整可导致BIVRO术后的下颌继续后移而不稳定,而髁状突近心骨段术中向后旋转术后位置的调整可导致BSSRO术后的下颌骨继续向前而不稳定     

The inter-relationship between mandibular autorotation and maxillary LeFort I impaction osteotomies

The purposes of the present investigation were to: 1)locate the instantaneous rotation center of mandible autorotation during maxillary surgical impaction; 2) identify the discrepancies between the resultant mandibular position following by maxillary surgical impaction and presurgical predictions, which use the radiographic condylar center as the rotation center for mandibular autorotation; and 3)find the interrelation between the magnitude of maxillary surgical impaction and the sagittal change of mandible. Ten patients underwent maxillary LeFort I impaction without concomitant major mandibular ramus split osteotomies were included. The preoperative (T0) and postoperative (T1) lateral cephalograms were used to evaluate the surgical changes and locate the center of rotation of mandibular autorotation with Reuleaux method. Prediction errors were measured by comparing the predicted (Tp) and postoperative (T1) cephalometric tracings. The magnitude of the maxillary surgical impaction was compared to the positional changes of mandible after mandibular autorotation with correlation and regression analysis. The results demonstrated that the centers of mandibular autorotation located 2.5 mm behind and 19.6 mm below the radiographic condylar center of the mandible in average with large individual variations. By using the radiographic condylar center of the mandible to predict the mandibular autorotation would overestimate the horizontal position of chin by 2 mm and underestimate the vertical position of chin by 1.3 mm following an average of 5 mm surgical maxillary impaction. The magnitude of maxillary impaction was highly and positively correlated to the horizontal displacement of chin position. The rotation centers of mandibular autorotation following by maxillary LeFort I impaction osteotomies might not usually locate at the radiographic condylar center of the mandible also with large individual variations in their positions. Surgeons and orthodontists should be aware of the horizontal and vertical discrepancies of chin positions while planning a two-jaw surgery by using the radiographic center of mandibular condyle as the rotation center in mandibular autorotation.     

颅底结构螺旋CT影像的三维定量测量

目的　分析健康成人当下颌骨处在正常牙尖交错位时 ,髁突与颅底颈内动脉管外口、颈静脉窝、卵圆孔、棘孔、破裂孔等之间的空间位置关系 ,为术中对其他重要结构的位置评估提供依据。方法　选择健康成人 10 0名 ,在正常牙尖交错位时 ,用螺旋CT扫描、颅底三维影像重建 ,测量各结构间的最短距离和空间角度。 12个定点 ,测量 2 8项距离和空间角度以极坐标表示 ,髁突内缘点为中心点 ,髁突长轴为 0°轴作为参照系。结果　颌下入路能顺利显露髁突内缘点和髁突长轴的方向 ,以此为参照系 ,确定颈内动脉管外口外缘点为 12 0 1± 2 71mm ,5 14± 1 2 2° ,颈静脉窝外缘点为 15 11±2 72mm ,- 5 6 2 7± 14 0 5°。结论　以髁突内缘点为中心点 ,髁突长轴为 0°轴参照系有助于为颌下入路颅底手术的术中定位及颅底解剖教学提供参考。     

Mechanics, growth, and class II corrections.

Growth of the orofacial region is quantitatively described by locating the center of mandibular rotation relative to the cranial base. The center of mandibular rotation is positioned by the ratio of vertical facial growth (AFH/PFH) and the direction of condylar growth. Appliance therapy is associated with changes in the means of both of these parameters. These changes reduce or stop favorable anterior mandibular rotation and redirect the mean condylar growth vector more posteriorly. When appliance therapy is stopped, these parameters return toward their resting values. The mean direction of the condylar growth vector became even more anteriorly directed after treatment than the pretreatment mean value. These data support the hypothesis that orthodontic appliances significantly alter the facial growth pattern and when they are stopped, the growth pattern tends to rebound to or beyond the pretreatment values.     

Incremental growth charts for condylar growth between 6 and 16 years of age.

This study provides sex specific reference data for the incremental growth of the mandibular condyle. The results pertain to a mixed-longitudinal sample of 113 males and 108 females followed annually between 6 and 16 years of age (total of 1647 observations). Growth of condylion was evaluated using naturally stable mandibular reference structures. The mean growth curves were estimated by multilevel models using iterative least squares procedures; between subject variation was estimated based on the sample's percentile distributions. Mean yearly velocities of condylar growth for males ranged between 2.1 and 3.1 mm/year. Growth rates decreased during childhood, increased during adolescence, and attained a maximum of 3.1 mm/year at approximately 14.3 years of age. Females showed a more constant rate of condylar growth during childhood (2.0-2.7 mm/year), a smaller adolescent peak (2.3 mm/year) at approximately 12.2 years and rapid deceleration after the peak. These reference data offer orthodontists an objective means of evaluating growth potential and treatment outcome in individual patients. Charts are provided for evaluating condylar growth of individual patients.