A radiographic interpretation of cranio-facial reference lines in relation to prosthodontic plane orientation

An analysis was made of prosthodontically related cranio-facial reference lines and angles of lateral skull radiographs taken for 60 edentulous Chinese adults wearing newly fabricated dentures.
The radiographic angle between the Frankfort horizontal line and Camper's line was compared across Chinese and Swedish male adults. This showed a significant increase in mean angle of 3.4° for Chinese subjects. The angular difference was explained on the basis of ethnic variation in 'orbitale' position which could probably account for the relative steepness of the Frankfort horizontal line in the Chinese.
The plane of orientation in the edentulous subject was made to conform to the ala-tragus line. The ala-tragus line in Chinese adults was observed radiographically to orient itself at a comparatively steep angle to the horizontal plane of the articulator.
The variation in 'orbitale' position and the influence of a steep occlusal plane in the edentulous Chinese could impose a limit to the smooth transfer of the facebow registration of the maxillary occlusal plane to the articulator.     

Changes in facial morphology in Macaca mulatta: a cephalometric study from 1.5 to 5 years of age

A cross-sectional and longitudinal (3.5 years) study on the craniofacial growth of 10 male rhesus monkeys, using metallic implants and a radiographic cephalometric technique based mainly on angular measurements, led to the following observations. (1) Maxilla and mandible were displaced in a forward and downward direction during growth, the sagittal changes being predominant over the vertical changes. (2) Maxillary and mandibular prognathism increased continuously during the whole time span. This increase was twice as great for the maxilla as for the mandible. (3) The inclination of the palatal plane and the mandibular plane changed very little over time. (4) Mandibular form remained constant, but the cranial base showed a significant flattening between approximately 1.5 and approximately 3 years of age. (5) Upper and lower occlusal plane angles changed little over time. (6) The interincisal angle decreased significantly until approximately 3 years of age in relation to the increase in proclination of the permanent incisors in the maxilla and mandible. The intermolar angle remained fairly constant. Changes in some of the variables reported (maxillary and mandibular prognathism, sagittal jaw relationship, mandibular length, interincisal angle, proclination of the upper and lower incisors, and opening of the cranial base angle) occurred as a function of age. The use of angular measurements allowed us to develop a series of templates that will provide a useful tool for a quick check of normal craniofacial morphology at three representative time points.     

Natural head position and inclination of craniofacial planes

PURPOSE: To assess the angles between craniofacial planes and the gravity horizontal plane (GHP). MATERIALS AND METHODS: The plumb line was hung from the ceiling, the Fox plane (FoxP) was placed in the mouth, and 56 Angle Class I subjects were photographed in a natural head position. FoxP represents the extraoral view of the occlusal plane. RESULTS: In frontal view, bipupilar plane (BP) and occlusal plane (FoxP) were almost parallel to GHP. In lateral view, FoxP was almost parallel to GHP, but Frankfort horizontal plane (FHP) and Camper's plane (CP) were not. FoxP and CP were not parallel. CONCLUSION: CP is not a reliable landmark for occlusal plane reconstruction. FHP does not represent GHP.     

Cephalometric and in vivo measurements of maxillomandibular anteroposterior discrepancies: a preliminary regression study

One of the aims of the present investigation was to assess three-dimensionally the anteroposterior discrepancy of dental bases using a noninvasive direct procedure. A second aim was to verify the relationship of three-dimensional soft-tissue measurement to the well-established two-dimensional cephalometric assessments of anteroposterior discrepancy. Dental and facial landmarks were directly digitized on 20 orthodontic and maxillofacial surgery patients aged 8 to 26 years using an electromagnetic three-dimensional computerized digitizer. The anteroposterior maxillomandibular discrepancy was measured by calculating the linear distances between the projections of subnasal and sublabial landmarks on the occlusal plane, subnasal and sublabial landmarks on Camper's plane, and insertion of maxillary and mandibular median labial frenula on the occlusal plane. From lateral cephalograms of the same patients, the following measurements were obtained: subspinale point-nasion-supramentale point (ANB) angle; corrected ANB angle that compensates for the position of the maxilla and rotation of the mandible relative to the cranial base; Wits appraisal; MM-Wits, linear distance between the projections of points A and B on the bisector of the palatal plane to mandibular plane angle; and soft-tissue Wits, linear distance between the projections of soft-tissue points A and B on the bisecting occlusal plane. The best two-dimensional vs three-dimensional linear regression (r = 0.91) was found between Wits appraisal and the linear distances between the projections of maxillary and mandibular median labial frenula on the occlusal plane (Wits = -1.05 x 3D measurement - 3.75). The three-dimensional evaluation of the sagittal discrepancy of the jaws directly performed in vivo may allow a more complete analysis of a patient's soft-tissue drape together with the underlying hard-tissue structure.     

The relationship of upper facial proportions and the plane of occlusion to anatomic reference planes

A study was made of 28 dentulous Chinese (Singaporean) adults by using lateral skull radiographs. The dimensions of the maxillae and various craniofacial reference lines related to prosthodontic use were analyzed. The craniofacial reference angles that reflect the vertical height and horizontal depth of the maxillae in Chinese adults differed significantly from the norms obtained in a white North American adult population. By comparison, Chinese adults have a vertically high and horizontally receded upper face that could cause planes such as the Frankfort horizontal plane or an arbitrary axis-orbitale plane to assume a steeper anterior inclination, thus modifying the mechanical inclination of the maxillary cast and occlusal plane on the articulator.     

Three-dimensional analysis of the occlusal plane related to the hamular-incisive-papilla occlusal plane in young adults

The planes which serve as references for cranium and face in dental clinical application included the occlusal plane, Frankfort plane, Camper's plane and hamular-incisive-papilla (HIP) plane. The HIP occlusal plane is a horizontal plane passing through the bilateral hamular notches and the incisive papilla (Dent Surv. 1975;51:60). The aim of this study was to estimate the relationship between the various occlusal planes and the HIP plane in Taiwanese young adults with approximately optimal occlusion. Study casts of 100 young adults (50 men and 50 women) were selected in this study. All market points on the maxillary casts were measured by a three-dimensional precise measuring device. The angular relationship between the four various occlusal planes and the HIP plane were investigated. The vertical distances between the cusp tips and incisal edges of maxillary teeth to the HIP plane were measured. Data were performed by the Statistic analysis software programme (JMP 4.02). The Student's t-test and Pearson's correlation test were used to test the statistical significance (P < 0.05). The results showed that the occlusal plane defined as the incisal edge of maxillary central incisor to mesiobuccal cusp tips of maxillary second molars had the smallest included angle with the HIP plane (2.61 +/- 0.81 degrees). The incisal edge of maxillary right central incisal to mesiopalatal cusp tips of maxillary first molars had the largest included angle with the HIP plane (7.72 +/- 1.60 degrees). The curve is drawn through the buccal cusp tips of maxillary teeth had better parallelism with the HIP plane.     

Biomechanical effects of maxillary protraction on the craniofacial complex

The deformational effects on the human skull resulting from maxillary protraction were examined by means of strain gauges and displacement transducers. A maxillary protraction appliance was used that included a reverse headgear attached to the maxillary first molars. The protraction forces that were applied to this appliance were parallel to the occlusal plane at the following locations: the height of the maxillary arch, 5 mm above the palatal plane, and 10 mm above the Frankfort horizontal plane. The results indicated that protraction forces at the level of the maxillary arch produced an anterior rotation and forward movement of the maxilla, protraction forces 10 mm above the Frankfort horizontal plane produced a posterior rotation of the maxilla with a forward movement of nasion, and protraction forces 5 mm above the palatal plane produced a combination of parallel forward movement and a very slight anterior rotation of the maxilla. Moreover, constriction of the anterior part of the palate occurred in all cases.     

The craniofacial characteristics of osteogenesis imperfecta patients

The aim of this study was to identify the craniofacial characteristics of 16 osteogenesis imperfecta (OI) patients, 10 males and 6 females, aged 7-15 years. The control group comprised 863 Chinese children from 6 to 18 years of age. Eleven cephalometric reference points and 25 variables were measured on the lateral cephalometric radiographs. Cochrane's method of unequal variance t-test was used to differentiate the differences between two groups. A Class III occlusal relationship was found in 62.5 per cent of the OI patients. The maxilla was more retrusive than the mandible in relation to the cranial base. Face heights, the effective maxilla and mandibular lengths, and anterior and posterior cranial base lengths were significantly shorter than the control subjects. The facial divergence, the cranial base (N-S-Ar, P<0.001), and the gonial (Ar-Go-Gn, P<0.001) angles were significantly enlarged, while the articular angle (S-Ar-Go, P<0.001) was significantly reduced. The findings showed that the OI patient had a more prominent Class III occlusal relationship, prognathic mandible, larger facial divergence, shorter face heights, defective sagittal growth of the maxilla and mandible, a flattened cranial base angle, impaired cranial base growth, and more forward counterclockwise rotation in mandibular growth compared with the controls.     

Establishing the customized occlusal plane in systemized surgical treatment objectives of class III

The purpose of this study was to present a new approach for establishing the customized occlusal plane for an individual patient in systemized surgical treatment objective of class III cases. After the correction of incisor inclination to occlusal planes (U1-MxOP and L1-MnOP), the intermaxillary relationship can be established with normal overbite/overjet and maximum intercuspation. The anterior limits of the maxilla and the mandible can be positioned according to A to N perpendicular, Frankfort horizontal (FH) to AB plane angle, and upper incisor display. The vertical level of the upper first molar can then be determined in relation to the Y plane (an imaginary arch drawn using the distance between the lower incisor edge point and the rotation center point of the condylar head as a radius) and a triangle projected by the upper and lower limits of the FH to the occlusal plane (FH-OP triangle). Soft-tissue facial balance can be checked with the lip/chin projection in relation to the true vertical line at subnasale and the lower third facial height ratio. Appropriate superior impaction of the posterior part of the maxilla in relation to the Y plane and FH-OP triangle in case 1 produced significant improvement of the facial profile and occlusion. However, case 2 showed that the amount of superior impaction of the posterior part of the maxilla was not enough to produce a significant setback of the mandible and retraction of the lip and chin. The systemized surgical treatment objective flowchart that could set the customized occlusal plane for an individual patient might provide a useful guideline for obtaining optimal aesthetics and functional occlusion in class III cases.     

Orientation of the plane of occlusion

A study was made of 28 dentulous Chinese Singaporean adults, using lateral skull radiographs. Various craniofacial reference lines and their relations to the maxillary occlusal line were analyzed. The orientation of the natural occlusal line in Chinese adults differed significantly from Swedish white adults. The Frankfort horizontal line in particular was considered disadvantageous as a clinical reference plane largely because of the acknowledged variation of its inclination between Chinese Singaporean and Swedish white adults. The shallow anatomic cant of the maxillary occlusal line in the Chinese patient could be misrepresented by a steep mechanical inclination on the articulator.     

Statistical evaluation of possible factors affecting the sagittal position of the first permanent molar in the maxilla

A cephalometric analysis was designed to evaluate several factors that may affect the sagittal position of the maxillary first permanent molar. A total of 184 Class II and Class I malocclusion patients were randomly selected before orthodontic treatment. The mandibular and palatal planes were related to Frankfort Horizontal and used to create the interjaw or B angle. Age and cephalometric landmarks (Ba, N, point A, pterygomaxillary fissure, and maxillary molars) were projected at right angles to the Frankfort Horizontal for effective length. Actual maxillary length and actual molar location were determined by projecting landmarks at right angles to the palatal plane. Correlation coefficients and P values were used to evaluate the data with a minimal significance value of .05 to determine a 95% confidence level. A statistically significant linear and proportional positive correlation (P < .0001) existed between molar location, age, and maxillary size. There was a strong negative correlation (P < .0001), both linearly and as a proportion of the actual length of the maxilla, between the actual position of the maxillary molar and the interjaw and mandibular plane angles. A significant correlation also existed between the molar position and palatal plane angles. The results show that increased interjaw, mandibular, and palatal plane angles are accompanied by a more posterior position of the maxillary first molar in the maxilla, whereas the molar occupied a continuing more forward position in the maxilla with increasing age, cranial base length, and maxillary size.     

Evaluation of differential growth and orthodontic treatment outcome by regional cephalometric superpositions.

Cephalometric superimposition on cranial base is the accepted method for evaluating mandibular displacement during orthodontic treatment and/or growth. However, assessing mandibular position relative to the maxillary base may yield different information. The aim of this study was to evaluate the effects of regional superpositions (cranial versus maxillary) on interpreting mandibular displacement. Both methods were applied to pre- and posttreatment cephalograms of 22 growing children (12 female, 10 male) treated for Class II Division 1 malocclusion. Differences in linear and angular measurements of three mandibular landmarks (pogonion, gnathion, menton) between cranial and maxillary superpositions were statistically significant (p = 0.0001). Vertical displacement of these landmarks contributed significantly to the differences (p = 0.0001). The contribution of horizontal displacement was not statistically significant. The results support the proposition that, in growing children, posttreatment displacement of mandibular skeletal and dental components should be assessed by both maxillary and cranial base superimpositions. The maxilla is subject to rotational and translational changes during growth that may affect the position of the mandible relative to the maxilla in a way inconsistent with the mandibular displacement perceived upon cranial superposition. Since occlusion is directly associated with the positions of the maxillary and mandibular basal bones, the positions of these bones relative to each other is critical in assessing occlusal changes in individual patients.     

Transition of molar relationships in different skeletal growth patterns.

This study investigated maxillary and mandibular growth differences and their effect on the changes in molar relationships from early transitional dentition to adult permanent dentition. Various landmarks were identified and measurements made on the longitudinal cephalometric radiographs of 40 people. The subjects were classified into 3 groups based on the amount of sagittal skeletal growth difference between the jaws. In group A, the mandible grew more than did the maxilla; in Group B, growth was about the same; and in group C, the maxilla grew more than did the mandible. The results revealed that skeletal growth differences between the jaws significantly influenced the changes in molar relationship during the transitional dentition, not only by translating basal bones but also by altering the amount of physiologic mesial shift in the dentition. However, the skeletal growth difference during the permanent dentition did not influence the changes in molar relationship. The sagittal growth difference between the jaws was largely absorbed by a dentoalveolar compensation. Tooth movement showed different characteristic features depending on the amount of the skeletal growth difference: (1) If the mandible grew more than did the maxilla, the growth difference was mostly absorbed by mesial displacement of the maxillary first molars and counterclockwise rotation of the occlusal plane. Anterior occlusion was adjusted by mesial displacement and labial inclination of the maxillary incisors and lingual inclination of the mandibular incisors. (2) If the maxilla grew more than did the mandible, the growth difference was mainly absorbed by mesial displacement of the mandibular molars. Then the maxillary molars showed minimal mesial displacement. The occlusal plane also showed minimal rotational change. Anterior occlusion was adjusted by lingual tipping of the maxillary incisors and mesial displacement and labial tipping of the mandibular incisors.     

Application of dentition and facial morphology integration system for occlusal correction

A system to provide quantitative information on the angle between dentition and face was developed using a three-dimensional (3D) integrated configuration measured by a non-contact 3D digitizer. The integrated configuration angles between the Camper's plane and occlusal plane on the sagittal and the horizontal projected planes were obtained. Clinical application for a patient to improve the tegmenta of the anterior tooth by setting a temporary bridge on her lower dentition was attempted. Her dentition and face were measured on her first visit and after treatment, and 3D data of them were integrated. The quantitative change of the angle between the Camper's plane and lower occlusal plane were successfully analyzed by the present system, and after treatment, rotation of the lower occlusal plane for 1 degrees in a clockwise direction on the sagittal plane projection, and that for 1 degrees in a counterclockwise direction on the horizontal plane projection relative to the Camper's plane were detected.     

The craniofacial complex in 47, XXX females

A study of the craniofacial complex in four 47, XXX Finnish females, or females with an extra X chromosome, was carried out using cephalometric analysis comprising linear and angular measurements. The lengths of the anterior and posterior cranial bases, the calvarium, mandibular ramus and posterior and upper anterior face heights were found to be significantly shorter than in female controls, while the angles between the foraminal and clival planes, the mandibular plane and cranial base, the maxillary and occlusal planes, the maxillary and mandibular planes and the foraminal and mandibular planes, and also the gonial angle, were significantly enlarged.The present findings of reduced linear measurements, together with the results of studies on the craniofacial complex of 47, XXY and 47, XYY males, suggest dimensional variation between these groups from the promoting effect of an extra Y chromosome and the retarding effect of an extra X chromosome on craniofacial growth.     

以前颅底长度评价前牙反的骨性机制

目的　探讨前颅底长度的稳定性及其评价上下颌骨骨性结构发育状况的价值。方法　采用 83例安氏Ⅲ类前牙反牙合者的头颅侧位定位片 ,对相关角度、前颅底长度、上下颌骨长度及前颅底长度与上下颌骨长度的比例进行测量 ,根据正常标准分析前牙反牙合者在替牙期组和恒牙期组的颌骨发育改变。结果　前牙反牙合组前颅底长度与正常对照组比较无显著性差异 ,而其前颅底长度、上下颌骨间的比率与正常组比较有显著性差异。根据前颅底长度评价上下颌骨发育状况 ,前牙反牙合可分为上颌正常、下颌过长 ,上颌不足、下颌正常 ,以及上颌不足、下颌过长 3种骨性结构 ,其中下颌过长为主要因素。结论　前颅底长度稳定 ,用其参考评价上、下颌骨的发育状况 ,分析反牙合的骨性结构机理 ,具有更个体化、更准确的优点     

Components of adult Class II open-bite malocclusion

In an effort to identify the frequency and distribution of the dental and skeletal components of adult Class II malocclusion with and without open-bite, 124 adults, half of whom had an anterior open-bite, were evaluated. Significant differences (P less than 0.05) between the open-bite and non-open-bite groups were found for the following measurements: the posterior maxilla exhibited vertical excess in the open-bite group; the maxillary occlusal plane was less steep in the open-bite group; the mandibular occlusal plane was more steep in the open-bite group; the gonial angle was higher in the open-bite group; the mandibular plane angle was higher in the open-bite group; the mandibular ramus was positioned in a more downward and backward (clockwise) location in the open-bite group; the total and lower anterior facial height were increased in the open-bite group; and the mandible was less protrusive in the open-bite group. No significant intergroup differences were noted in the cranial base, the anteroposterior position of the maxilla or of the upper and lower incisors, the palatal plane, posterior facial height, mandibular ramus height, or mandibular body length. The results of this analysis indicate that the average Class II open-bite malocclusion is characterized by aberrations in both the maxilla and the mandible. Therapy, therefore, may frequently require surgical intervention in both jaws to successfully correct this deformity.     

The evaluation of horizontal reference planes of adult Chinese in natural head position.

A group of 112 adult females (average age 25.66) and 104 adult males (average age 25.62) were subjected to cephalometric evaluation in their natural head position. No significant differences were found in the nasionsella (SN) plane, Frankfort horizontal (FH) plane or palatal planes between male and female subjects. The SN plane was found to be located at 7.26 degrees above the true horizontal on the average, and the FH plane differed on the average 1.92 degrees from the true horizontal with the line diverging forward and upward. The palatal plane was found to be located in a downward and forward direction at 1.17 degrees from the true horizontal plane on the average. The orbitale (Or) was found to be located at 2.34 mm on the average above the true horizontal plane depicted from the porion (Po) in this study, which implies that the racial characteristic of a high zygomatic bone in Chinese may have some influence upon the position of Or, and this should be taken into consideration when the FH plane is used as the true horizontal during face bow transfer. The mandibular plane (MP) angle, occlusal plane (OP) angle and the gonial angle (GA) of males were found to be smaller than those of females, with a significant difference at the level of P less than 0.001, P less than 0.01 and P less than 0.01, respectively. The upper facial divergent angles of males and females were quite similar, as reflected by the similarity in the SN-FH angles and SN-PP angles between the sexes A significant difference was found to exist in the lower facial divergent angles between males and females. The SN-MP angle, PP-OP angle and PP-MP angle were all significantly smaller in males, with a P less than 0.001. The OP-MP angle was also smaller in males with P less than 0.05.     

虚拟手术设计在双颌正颌手术中的精准性研究

目的评估虚拟手术设计在双颌正颌手术中的精准性,以期为临床提供参考。方法纳入需行双颌正颌手术的患者30例,利用CT数据和牙弓平面扫描数据建立复合颅骨模型,在Dolphin Imaging 11.7 Premium软件上模拟上颌骨LeFort I型骨切开术和双侧下颌支矢状骨劈开术,必要时行颏成形术,利用3D打印的手术导板将虚拟手术设计转移到术中。选择3个平面:眶耳平面(FHP)、面中平面(垂直于FHP且通过鼻根点)和冠状面(垂直于FHP且通过蝶鞍点)。选择6个标志点:上、下颌中切牙的近中接触点(UI、LI)以及上下颌第一磨牙的近中颊尖(U6-R、U6-L、L6-R、L6-L)。在虚拟手术模型和真实术后模型上测量选定标志点和对称平面之间的距离,并计算两模型之间的线性差异和总体平均线性差异(UI、LI、U6-R、U6-L、L6-R、L6-L分别与眶耳平面、面中平面和冠状面之间距离的平均差异)。确定由咬合平面、腭平面和下颌平面分别与眶耳平面和面中平面构成的角度值,并计算虚拟手术模型和真实术后模型之间的角度差异和总体平均角度差异。结果借助3D打印手术导板,虚拟手术设计被成功转移至实际手术中,所有患者术后对面型和咬合都很满意。虚拟与真实模型间的总体平均线性差异为0.81 mm(上颌骨0.71 mm,下颌骨0.91 mm);总体平均角度差异为0.95°(相对于眶耳平面的平均角度差异为1.10°,相对于面中平面的平均角度差异为0.83°)。结论虚拟手术设计有助于牙颌面畸形的诊断和治疗计划的制定,可以增加双颌正颌手术中骨块定位的精准性。     

Orthognathic surgical norms for a sample of Saudi adults: Hard tissue measurements

Objective

The aim of the study is to establish hard tissue cephalometric norms for orthognathic surgery for a sample of Saudi adults.

Materials and methods

Sixty-two lateral cephalometric radiographs for 31 females and 31 males, age range of 22–24 years, were analysed. The mean values of the hard and dental measurements were compared with those of European-American adults using Burstone analysis, as well as comparison between Saudi males and females.

Results

Saudi males had an increased cranial base length, the mandible lied more posterior to maxilla, increased mandibular plane angle and backward rotation of the mandible with less prominent chin, shorter maxillary length, and also less proclination of lower incisors compared to those of European Americans. Saudi females had similar cranial base length and shorter maxillary length than European Americans. In both gender; lower anterior and posterior dental heights were smaller when compared with the European-Americans’ values. A significant difference between Saudi males and females was found. Saudi males showed longer cranial base length, larger vertical skeletal proportion, increased dental values, longer maxillary and mandibular length than the female group.

Conclusion

This study may be useful in providing racially specific cephalometric norms for diagnosis and treatment planning for orthognathic surgery for a sample of Saudi adults.