The position of the occlusal plane in dentulous subjects with various skeletal jaw-relationships

This study was conducted to examine the level and inclination of the occlusal plane in dentulous subjects with various skeletal jaw-relationships with the purpose of finding more reliable guides for locating the occlusal plane in edentulous patients. The investigation was carried out on 140 lateral cephalometric radiographs of young people with natural teeth in the intercuspal position. The sample was divided into three groups according to the skeletal relation of the jaws. The occlusal plane in this study and the two reference planes (maxillary and mandibular plane) were established according to the cephalometric criteria of Schwarz. On each radiograph both the angulation and the perpendicular distance of the occlusal plane to the reference planes were recorded and the values of the obtained data were subject to statistical analysis. The selected mean values of the angles and linear distances between the occlusal plane and reference planes calculated on the probability level of 95% could be used as cephalometric indicators for the locating or correcting the position of the occlusal plane in the prosthetic treatment of edentulous patients.     

Critical assessment of a device to measure incisor crown inclination.

The aims of this study were to critically assess the use of a disposable device--the tooth inclination protractor (TIP)--to record incisor crown inclination and to compare its reliability and validity with that of traditional cephalometric radiographic analysis. The sample comprised 30 dental students with lateral cephalometric radiographs and dental casts. Four examiners were trained and calibrated to digitize radiographs and to use intraoral (on patients and dental casts) and extraoral (on dental casts) TIPs. The following angles were measured on the radiographs: maxillary incisor to maxillary plane, mandibular incisor to mandibular plane, maxillary incisor to occlusal plane, and mandibular incisor to occlusal plane. Measurements were also made with the TIP: maxillary incisor to occlusal plane and mandibular incisor to occlusal plane. All techniques were reliable between examiners. There were statistically significant systematic differences between the TIP and the radiographic assessments. The following differences were found. The TIP tended to record maxillary incisor crown inclination an average of 14 degrees less than maxillary incisor to maxillary plane. The TIP tended to record mandibular incisor crown inclination as similar to mandibular incisor to mandibular plane. The TIP recorded mandibular crown inclination 19 degrees less than mandibular incisor to occlusal plane. The disposable TIP was shown to be a simple, inexpensive, reliable, and valid method of assessing incisor inclination.     

Reproducibility of cephalometric measurements made by three radiology clinics

The purpose of this study was to assess reproducibility of cephalometric measurements in cephalograms obtained by three dentomaxillofacial radiology clinics. Forty lateral cephalometric radiographs were selected and sent at different times to three different clinics for cephalometric analyses. Each clinic digitized the radiographs with the same resolution, and landmarks were located with the mouse pointer directly on the digitized radiographic image on the screen. Three cephalograms were obtained from each radiograph, totaling 120 analyses. Data were analyzed with analysis of variance. Of the 32 factors studied, reproducibility of results was satisfactory for only four factors: position of maxilla relative to anterior cranial base, inclination of occlusal plane relative to anterior cranial base, position of lower incisor relative to nasion-pogonion line, and soft-tissue profile of face (P < .05). Differences in cephalometric measurements were present and such differences were significant for most factors analyzed. The different cephalometric measurements obtained by the three dental radiology clinics were not reproducible.     

Comparison of cast positions by using four face-bows

The positions that the maxillary right and left first molars occupy when a maxillary cast is mounted in the three-dimensional space of a semiadjustable articulator (Hanau H2) were studied. Mountings were made by using four face-bows, the Hanau Kinematic Face-bow, the Hanau Facia-bow, the Hanau 159 Earpiece Face-bow, and the Hanau Twirl Earpiece Face-bow. A kinematically determined hinge-axis was used arbitrarily as the baseline for comparisons among the three other bows. Deviations from the baseline were measured along the X, Y, and Z axes by using a contour meter (Fig. 1). The deviations showed great variability (Table I), and because maxillary casts are mounted in relation to anatomic landmarks that differ from subject to subject, it was not possible to establish clinical superiority of one face-bow over another.     

A study of the occlusal plane orientation in complete denture construction

A cephalometric study was conducted on eighteen dentulous subjects and fifty-six complete denture wearers to determine the location of the natural and artificial occlusal planes as related to Camper's plane. The results indicated that both the natural and artificial occlusal planes were not parallel to Camper's plane. However, the final anteroposterior inclination of the artificial occlusal plane in complete dentures was almost the same as the inclination of the natural occlusal plane.     

Traditional face-bow transfer versus three-dimensional virtual reconstruction in orthognathic surgery

Face-bow transfer is an essential step in articulator-based orthognathic surgery planning. However, it can be a source of inaccuracy. Virtual computer-based planning avoids this error through the use of direct patient-related three-dimensional imaging data. The aim of this prospective observational study was to determine the error of face-bow transfer three-dimensionally and correlate it to the different types of malocclusion. Orthognathic surgery performed on 38 patients (10 male, 28 female; mean (standard deviation) age 24.7 (6.9) years) was planned twice: first articulator-based with plaster models and second computer-based with surgery planning software. Both models were digitized and compared regarding the angle between the Frankfort horizontal plane and the occlusal plane. In most cases, the angle in the sagittal dimension was higher in the articulator-based model than in the computer-based model. The angle in the transverse dimension was as often under- as over-represented. The type of malocclusion, i.e. skeletal class, vertical relationship, and degree of asymmetry, had no significant impact on the amount of error. In conclusion, this study indicates that computer-based planning should be considered as an advantageous alternative in orthognathic surgery planning.     

Dentoalveolar compensation related to variations in sagittal jaw relationships

The purpose of this study was to investigate dentoalveolar compensation for variations in sagittal jaw relationships in 44 adult females with normal incisor relationships and either skeletal Class I or skeletal Class III jaw relationships. Cephalometric analysis was performed to evaluate sagittal jaw relationship, maxillary and mandibular incisor inclination, and the cant of the occlusal plane. Molar relationships were evaluated from study models. Correlation analysis was performed between skeletal and dental measurements. The most appropriate cephalometric parameters describing dental compensation quantitatively were SN-AB as a skeletal measurement and SN-U1, SN-L1, and SN-OP as dental measurements. Among the compensatory dentoalveolar changes, lower incisor inclination was strongly related to the sagittal jaw relationship and played an important role in obtaining a normal incisor relationship. Compensatory changes in the occlusal plane angulation were slight when compared with changes in the incisor regions. A Class I molar relationship was rare when SN-AB exceeded 84 degrees, even when incisor relationships were normal.     

Accuracy of face-bow transfer: effect on surgical prediction and postsurgical result.

One of the most common errors in model surgery for orthognathic surgery is in the mounting of the models on the articulator. This study assessed the ability of one type of face-bow to transfer the maxillary model to the articulator. Twenty-five consecutive mountings were evaluated by calculating the angle made between the maxillary occlusal plane on the cephalogram and comparing it with the maxillary occlusal plane angle on the articulator. An accurate face-bow transfer should transfer this angle, making the two similar. It was found that a significant difference between the maxillary occlusal plane angle on the cephalogram and the articulator was found in the average case. The implications of such errors and a technique to avoid them are presented.     

A study on a method to identify the border between mandibular corpus and ramus on lateral cephalometric radiograph.

The mandible has two major parts, the corpus and the ramus. These two parts must be considered separately because each has its own functional counterpart with the maxilla and the posterior cranial base. Since the mandible is a single bone, the border of the corpus and the ramus can not be visualized on the conventional two-dimensional lateral cephalometric radiograph. The purpose of this study is to propose a reliable method to distinguish the border between the mandibular corpus and the ramus on the lateral cephalometric radiograph. In this study, 64 dried skulls in different developmental stages were examined. Metallic markers were placed at the diverging point (point T) on both sides of the dried skulls. From the occlusal view of the mandible, point T was considered to be the lingual border of the corpus and the ramus. Then, the lateral cephalometric radiographs of the dried skulls were taken. On each lateral cephalometric radiograph, a vertical line L was drawn from point Ra (the intersection of the occlusal plane and the anterior border of the ramus) to the mandibular plane. Thus, the distance from the midpoint of point T on each side to the vertical line L was measured. As a result, over 80% of the midpoints T were found on the vertical line L. Therefore, the vertical line L from point Ra to the mandibular plane can be considered to play the role of a reasonable reference line for distinguishing between the corpus and the ramus on the lateral cephalometric radiograph.     

Influence of vertical growth pattern on faciolingual inclinations and treatment mechanics

Control of faciolingual tooth inclinations is obtained by using rectangular wire with third-order bends and standard edgewise brackets or by using a straight wire in a preadjusted appliance system. Ideal faciolingual inclinations have been determined previously by measuring facial surface contours relative to coronal long axes. This study evaluates faciolingual inclinations based on occlusal table inclinations relative to occlusal planes. The samples compared include untreated ideal occlusions and malocclusions in three different vertical skeletal growth patterns. Faciolingual inclinations of first molars and central incisors were measured relative to the occlusal plane and to selected cephalometric angular measurements. Statistical comparisons between groups revealed significant differences in the inclinations of the upper incisor relative to the occlusal plane (U1-OP) and the inclination of the occlusal plane relative to sella nasion (OP-SN). No statistically significant intergroup differences were found in the inclination of the lower incisor relative to the occlusal plane (L1-OP) or in the faciolingual inclinations of the maxillary and mandibular first molars. On the basis of the large intergroup differences in the mean angle between the occlusal plane and sella nasion (OP-SN), the use of straight-wire appliance therapy is discussed in terms of the potential for creating differential moments. Because differential moments may facilitate or hinder treatment goals, the practitioner must know the biomechanical sequelae resulting from occlusal plane-sella nasion variations, which differ from normative values when preadjusted brackets are used.     

Picture archiving and communications systems: a study of reliability of orthodontic cephalometric analysis

The objectives of this study were to investigate the possibility of using a picture archiving and communications system (PACS) for basic chairside cephalometric analysis and to compare PACS with hand-tracing and on-screen digitization using a commercial program (Dolphin Imaging Plus Version 10.0). One hundred digital lateral cephalometric radiographs were selected and analysed using the Eastman analysis. Angular and linear measurements were recorded and a single operator traced each radiograph twice, using each of the following methods: PACS, hand-tracing, and Dolphin Imaging. The British Standards Institution Coefficient of Repeatability was used to investigate repeatability within each method and the Bland and Altman method to investigate systematic and random errors between methods. The PACS was more repeatable than Dolphin for measuring the angle between the upper incisors and the maxillary plane but was less repeatable than hand-tracing for measuring percentage lower anterior face height (LAFH). There were statistically significant systematic differences between PACS, hand-tracing, and Dolphin for measurement of lower incisor inclination. However, all three methods agreed, on average, and differences between methods were all within clinically acceptable limits. PACS was found to be clinically acceptable to be used chairside, without the need for hand-tracing or involvement of any orthodontic software. This offers the freedom to analyse digital cephalograms within a clinical area at the same appointment as when the digital radiograph is taken.     

Comparative study of condylar settings of three semiadjustable articulators

The reproducibility of arcon semiadjustable Whip Mix, Denar Mark II, and Hanau 158 articulators was tested using multiple protrusive and lateral edge-to-edge wax interarch registrations made with an interocclusal device. Photographic and cephalometric tracings verified an identical angulation between the axis-orbital craniofacial reference plane and the maxillary occlusal plane for the subject and both the Denar Mark II and Hanau 158 articulators. This angle was 2.5 degrees less in the Whip Mix instrument. Three operators made three settings for each of 12 protrusive and 24 lateral interarch registrations for each articulator. Results showed significant differences between instruments. Whip Mix consistently gave the highest.angulations and Hanau 158 the lowest. For protrusive records there was no significant difference between examiners, but for lateral records a significant difference in examiner registration was found. For both protrusive and nonworking registrations, interaction was seen between instrument and operator and between instrument and registration, and a significant difference was seen between records. This study supports previous studies showing that semiadjustable articulators using interarch records have a low level of reproducibility and are subject to variables of instrument, operator, and occlusal records.     

正常(牙合)青年(牙合)平面与咀嚼运动轨迹的相关性分析

目的 分析个别正常(牙合)青年(牙合)平面与咀嚼运动轨迹特征的相关性,以期为临床定位(牙合)平面提供参考.方法 收集43名个别正常(牙合)青年志愿者,拍摄头颅侧位X线片,测量耠平面倾斜度(OP-CP);记录下颌中切牙切点的左右侧咀嚼运动轨迹,测量矢状面垂直向最大位移(V)、矢状面水平向前后最大位移之和(P+A)、冠状面水平向左右侧方位移之和(L+R)以及(牙合)平面与咀嚼运动轨迹的夹角,对(牙合)平面倾斜度(OP-CP)与V、(P+A)、(L+R)以及(牙合)平面与咀嚼运动轨迹的夹角进行Pearson线性相关分析.结果 OP-CP为(2.1±3.8)°.V为(20.22±4.28)mm,(P+A)为(11.42±2.45)mm,(L+R)为(8.62±1.52)mm.OP-CP与(L+R)呈负相关,相关系数r为-0.39(P<0.05).矢状面(牙合)平面与牙尖交错位及其附近的咀嚼运动开闭口轨迹近似垂直;OP-CP与咀嚼运动轨迹(牙合)期阶段2.0 mm、(牙合)外期上段的(牙合)平面-闭口轨迹角呈正相关(P<0.05);咀嚼轴角平均为(66.50±7.98)°,与OP-CP不相关(P>0.05).结论 矢状面(牙合)平面倾斜度与咀嚼运动轨迹有一定相关性.(牙合)平面对咀嚼运动(牙合)期闭合轨迹的影响较明显.     

Panoramic radiographs: determination of mandibular steepness

The aim of this study was to evaluate the potential of panoramic radiographs to measure mandibular inclination and steepness. Standardized panoramic and lateral cephalometric radiographs were taken for 95 subjects (46 females, mean age 12.4 +/- 1.2 years; 49 males, mean age 12.1 +/- 1.3 years). Mandibular inclination from panoramic radiograph was measured using gonial angle formed by the tangents of the lower border of the mandible and the distal border of the ascending ramus and the condyle. A correlation test was performed to check for similarity between the measurements. The mean values for the gonial angle were 127.3 +/- 6.2 and 125.7 +/- 6.5 degrees measured from the panoramic and cephalometric radiographs respectively. A high correlation between the measurements taken from both radiographs was found (r = 0.83, P < 0.001). Panoramic radiographs are a useful tool for the measurement of gonial angle, which is an indicator of manibular steepness and subsequently mandibular growth direction. The ability to determine growth direction from the orthopantomogram will be useful because majority of dentists request an OPG for patients during routine dental examination. This will enable the dental professional to spot vertical growth problems using a readily available tool.     

Lower incisor position in different?malocclusions?and?facial patterns

Introduction: The position of lower incisor has been of considerable concern when planning an orthodontic treatment, having been recognized as one of diagnostic keys, Very important in the development of malocclusion and facial pattern. Objectives: In this study we claim to determine the importance of the position and inclination of lower incisor in the different malocclusions and facial patterns, and to base which of the cephalometric measurement parameters are the mostreliable. Material and Methods: Ninety lateral radiographies were taken, and they were classified by skeletal malocclusion and facial pattern.These teleradiographies have been performed cephalometric analysis, which includelower incisor position belong the following analysis: Ricketts, Riolo, Tweed, McHorris, Jarabak-MSE and Holdaway. Study Design: Cross-sectional study where we perform statistical analysis Anova test, Pearson correlations and Bonferroni analysis. Results: The analyzed measurements present a statistically significant differentiation in lower incisor inclination respect to the anterior cranial base, McHorris angle, angulation of lower incisor respect to occlusal plane and mandibular plane. Conclusions: There are statistically significant differentiation in lower incisor position and inclination respect the malocclusion and individual facial pattern. Key words:Lower incisor, cephalometric analysis, facial patterns, facial biotype, skeletal malocclusions.     

Importance of occlusal plane reproduction on the semi-adjustable articulator in planning maxillary impactions for orthognathic surgery

Introduction

The aim of this study was to evaluate whether a 6° counterclockwise change in occlusal plane inclination would produce significant modifications on the final result of a maxillary impaction and mandible advancement model surgery.

Materials and methods

Four groups were used in this study, with ten identical maxillary casts and one mandibular cast mounted on the same semi-adjustable articulator, with the same malocclusion. The occlusal plane of the two control and study groups had an inclination of 13° and 7°, respectively. Preoperative and postoperative measures were performed using the Erickson platform and impactions of 6 and 10 mm were tested. To control these movements during model surgery, two splints were fabricated using another two maxillary and mandibular casts mounted with occlusal plane of 13°, simulating the proposed movement.

Results

The results were compared using the t test. Only the antero-posterior movement of the upper incisor was statistically significant for both study groups (p?<?0.05), with a mean of 0.48 and 0.94 mm in the 10 and 6 mm impaction groups, respectively.

Discussion

This information means that if an error in the occlusal plane transference occur, it will not be clinically significant, because differences smaller than 1 mm does not have influence on soft and hard tissue final result.     

Dentoalveolar compensation in negative overjet cases

The purpose of this study was to investigate dentoalveolar compensation in negative overjet cases. Eighty-eight adult females with either skeletal Class I or skeletal Class III jaw relationships were examined. Of the total, 44 cases showed anterior crossbite and the remaining 44 cases had normal incisor relationships. Four cephalometric parameters were measured: the sagittal jaw relationship, maxillary and mandibular incisor inclination, and the occlusal plane angulation. In the negative overjet cases, correlation analysis was performed between the skeletal and dental measurements. Stepwise discriminate analysis was carried out to separate the negative and normal overjet cases. Compensatory changes for sagittal jaw discrepancies in the negative overjet cases were statistically confirmed for both incisor inclination and occlusal plane angulation. However, the compensatory effects were weaker than in the normal overjet cases. The discriminate analysis successfully separated the normal and negative overjet cases, suggesting that negative overjet results from insufficient dentoalveolar compensation for variations in the sagittal jaw relationships.     

Lateral cephalometric analysis of the pharyngeal airway space affected by head posture

To clarify the relationship between head posture and pharyngeal airway space (PAS), the cephalometric parameters at different head postures were examined. Twelve normal Japanese adults (6 males and 6 females) were examined. Lateral cephalometric radiographs were taken at five different head postures in each person. All radiographs were traced, and the measurements were analyzed statistically. PAS was significantly increased by forward inclination of the cervical spine. The most significant correlation was found between the change in CVT/NSL (cranio-cervical inclination in the second and fourth vertebrae) and the change in PAS-TP (the minimal pharyngeal airway space) (r(2)=0.79 in males, r(2)=0.67 in females). The mean CVT/NSL when the head was in the natural (neutral) position was 100.9 degrees in males and 103.5 degrees in females. Linear regression analysis revealed DeltaPAS (mm)=0.37DeltaCVT/NSL (degree) (r(2)=0.79, p<0.0001) in males, and DeltaPAS (mm)=0.33DeltaCVT/NSL (degree) (r(2)=0.51, p<0.0001) in females. The correlation equations were obtained as follows: the corrected PAS (mm)=the actual PAS (mm)+0.37[100.9-the actual NSL/CVT (degree)] in males, and the corrected PAS (mm)=the actual PAS (mm)+0.33[103.5-the actual NSL/CVT (degree)] in females. These results will contribute to obtaining an accurate assessment of the PAS that should be corrected by the cranio-cervical inclination.     

Soft tissue profile in Anatolian Turkish adults: Part II. Comparison of different soft tissue analyses in the evaluation of beauty.

This study examined the soft tissue analyses of Steiner, Ricketts, Burstone, Sushner, Holdaway, and Merrifield to evaluate orthodontists' perceptions of Anatolian Turkish adults' beauty. Forty-four subjects (21 females, mean age, 21.35 years; 23 males, mean age, 21.41 years) with Angle Class I occlusal relationship, and normal anteroposterior (ANB angle, 2 degrees +/- 2 degrees ) and vertical (SN-MP angle, 32 degrees +/- 5 degrees ) skeletal relationships were selected from the dental students at the University of Istanbul. The material consisted of lateral cephalometric radiographs and facial-profile slides of these subjects. Ten linear and 6 angular measurements were analyzed on each radiograph, and the facial profiles were judged as poor, fair, good, or excellent by 6 raters. After the scoring, 34 subjects (16 females and 18 males) were placed in the unattractive group, and 10 subjects (5 females and 5 males) were placed in the attractive group. The significance of the differences between the groups was studied by means of the Mann-Whitney U test. The results demonstrated that persons having a high mandibular plane angle, a small nose, protrusive lips, and a retrusive profile were selected as attractive. Among the 7 esthetic lines used to evaluate the soft tissue profile, only Ricketts' norms for upper and lower lips corresponded to the values we found for attractive profiles.