Length of the occlusal glide at the lower incisal point during chewing

The purpose of this study was to estimate the length of the occlusal glide during gum chewing at the lower incisal point. Mandibular excursions with occlusal contacts in 25 females with permanent dentition were recorded using an optoelectronic system that can measure mandibular movement with 6 d.f. at a sampling frequency of 100 Hz. A curved mesh diagram of incisor coordinates during maximum mandibular excursions (CMDME) was plotted. Gum chewing movement was also measured using the same system and computer software which divided the chewing movement into cycles at each maximum opening position. Each cycle was standardized at 0.1 mm intervals from the most closed position. Finally, the distance between the CMDME and each position of the incisor during a chewing cycle was calculated. Whenever, this distance was less than 0.2 mm opposing teeth were considered to be in contact. The occlusal glide was defined as the distance travelled by the lower incisal point as the mandible moved along occlusal contacts of the CMDME. The vertical coordinates at the beginning of the occlusal glide (during closing) and at the end of occlusal glide (during opening) were also calculated. The lengths of the occlusal glide pathway averaged 1.29 mm during closing and 1.55 mm during opening, a total length of 2.84 mm. Mean vertical coordinates at the beginning and end of the glide were -0.95 and -1.12 mm from intercuspal position, respectively.     

A three-dimensional measuring system for the human face using three-directional photography.

This study was intended to develop a three-dimensional measuring system of the human face for clinical use, to ensure a high precision and a simple input operation by means of a personal computer and to measure the degree of its accuracy. With this system, it is possible to measure automatically two-dimensional coordinates of hundreds of grid points on photographs of the human face with an image scanner as a reading device and to calculate their three-dimensional coordinates with a computer. An orthognathic surgical case illustrates this technique in which the patient's face is displayed before and after the surgery on a cathode-ray tube (CRT), with the three-dimensional coordinates obtained with this system. A cubic plaster cast with a certain degree of irregularity has been constructed to measure the precision of this system. Comparison was then made between the three-dimensional coordinates obtained with this system and the coordinates obtained with the contact three-dimensional measuring system. The mean of errors and the standard deviation were 0.04 +/- 0.24 mm for the X coordinate, 0.03 +/- 0.16 mm for the Y coordinate, and 0.08 +/- 0.23 mm for the Z coordinate. Thus the accuracy of this system is high enough for the measurement of the human face.     

Length of the occlusal glide during chewing in children with primary dentition

summary   Chewing is one of the most important functions of the mandible, but, to date, there are very few studies of this function in children. The purpose of this study was to quantify the length of the occlusal glide at the lower incisal point during gum chewing in children with primary dentition. Eleven girls with primary dentition were selected for this study. Mandibular excursions with occlusal contacts and gum chewing movement were measured using an optoelectronic system that can measure mandibular movement with six degrees-of-freedom at a sampling frequency of 100 Hz. A curved mesh diagram of incisor coordinates during mandibular excursions was established to calculate the length of the occlusal glide for each subject. The occlusal glide lengths of children were compared with previously reported results for adults. The estimated length of the occlusal glide during closing was significantly shorter in children than in adults, contrary to that during opening. This result suggests that children have a characteristic chewing pattern that differs from adults.     

Development of a simulation system in mandibular orthognathic surgery based on integrated three-dimensional data

Purpose

Surgical simulation should reflect the 3D movement of dentition and the resultant movement of the osteotomized segments, which can influence surgical outcome. The present study was aimed at developing a new simulation system that enables virtual osteotomy of a given surgical situation and evaluation of the bony interference between the osteotomized segments of the mandible.

Subjects and methods

The data of 3D computer tomography (CT) for maxillomandibular dental casts were integrated into the standard coordinates of a 3D cephalogram. To evaluate the accuracy of the system, measurement errors of the 3D CT virtual model from a dry skull were compared with the computer simulation system and a contact-type 3D digitizer. To examine the clinical accessibility, 15 mandibular prognathism patients with mild to severe asymmetry were evaluated with the simulation program.

Results

The average error of measurement in all directions was 1.31?mm. It was possible to simulate various osteotomy procedures by conversion of the 3D coordinates of the dental cast and CT data into the standard coordinate system of a 3D cephalogram. Using this simulation system, it was possible to prevent condylar torque or segment malpositioning by removing the bony interference visualized by a 3D virtual model.

Conclusion

A new system, which enables the precise visualization of osteotomized segments and calculation of bony interference, was proposed in the present study. This new system provides an acceptable precision of treatment planning of orthognathic surgery, especially for facial asymmetry.     

Use of personal computers for Gothic arch tracing: analysis and evaluation of horizontal mandibular positions with edentulous prosthesis

STATEMENT OF PROBLEM: Determining mandibular position for an edentulous patient raises the question of whether to emphasize centric relation or muscular position. This challenge results from the lack of a convenient procedure for quantifying the horizontal mandibular position, which can be determined by a variety of methods. PURPOSE: This study analyzed and evaluated the horizontal mandibular positions produced by different guidance systems. MATERIAL AND METHODS: Twenty-six edentulous subjects with no clinical evidence of abnormality of temporomandibular disorder were selected. Horizontal position data for the mandible obtained by gothic arch tracing was loaded into a personal computer by setting the sensor portion of a digitizer into the oral cavity to serve as a miniature lightweight tracing board. By connecting this with a digitizer control circuit set in an extraoral location, each mandibular position was displayed in a distinguishable manner on a computer display in real time, then recorded and analyzed. RESULTS: The gothic arch apex and tapping point varied, depending on body position. In the supine position, the gothic arch apex and the tapping point were close to the mandibular position determined by bilateral manipulation. CONCLUSION: This system provides effective data concerning mandibular positions for fabrication of dentures.     

The accuracy with which the human condyle can be expressed in the coordinate system of JAWS3D using a unilateral fiducial marker

Previous studies have indicated that the selection of condylar referencing points can significantly influence condylar point trajectories, and the use of radiographically determined condylar points is essential for accurate representation of condylar movement. The aim of this investigation was to determine the accuracy with which the three-dimensional locations of condylar points could be determined in the coordinate system of the JAWS3D tracking device when an ipsilateral fiducial marker is used. A perspex mandible containing condylar radiographic markers was constructed. A JAWS3D target frame and a fiducial marker, supporting radiographic markers, were secured to the perspex mandible. The image data from computer tomography scans of the condyles and fiducial marker, together with photographs of the fiducial marker and the JAWS3D target frame were used to calculate condylar point coordinates in the JAWS3D coordinate system. These data were then compared with the data obtained by direct measurement of the condylar radiographic markers in the JAWS3D coordinates. The results suggest that a unilateral fiducial marker is sufficient to allow the registration of ipsilateral condylar point coordinates to an accuracy of approximately 1.0 mm.     

Fundamental study on the development of a measuring device using an accelerometer

It is important to clarify stomatognathic functions. To diagnose them, some measuring devices, such as MKG and the Gnatho-hexagraph, were developed. Such equipment, however, is not widely diffused, due to cost. The purpose of this fundamental study was to obtain information on position using an accelerometer. This system consists of a micro dual-axis accelerometer and a peripheral interface controller. Two-dimensional acceleration, velocity, and movement can be calculated by a computer. We examined the accuracy of this system using a laser measuring device. The result was as follows: The accuracy of the system was 0.03 (p-p values) using acceleration of gravity and a frequency of 72.5 Hz. In the present study, mandibular movements during chewing raisins were analyzed using this system. The new system demonstrated its value for analyzing mandibular movements.     

极坐标测量方法在Twin-Block矫治下颌后缩疗效分析中的应用

目的探讨极坐标测量分析方法用于Twin-Block矫治器矫治骨性Ⅱ类错疗效评价测量分析的临床应用价值。方法随机选取处于发育高峰期的骨性下颌后缩患者20例,男女各10例,采用Twin-Block矫治器矫治。对患者治疗前后的头颅侧位片采用极坐标测量分析方法,以S点为极坐标原点,前颅底平面（S-N）作极轴,建立极坐标测量体系,选取7个颌骨标志点A、Ptm、B、Po、Gn、Go、Ar,分别测量各标志点治疗前后极径和极角的大小,并作相应统计分析。结果 Ptm的极角和极径无明显改变,A点的极角和极径则均明显增大,说明Twin-Block矫治器对上颌骨生长无明显抑制作用;下颌标志点B、Po、Gn、Go点的极径在治疗后明显增大,但反映下颌骨改建方向的极角在治疗后则均无明显改变,说明Twin-Block矫治器对下颌骨的生长起到明显的促进作用,而对下颌骨生长方向没有明显影响。结论极坐标测量分析方法可以对颌骨标记点的生长量和生长方向作出准确的定量测量和定性分析,可弥补传统测量方法的不足;极坐标测量分析也表明,Twin-Block矫治器主要通过促进下颌骨的生长,而非通过抑制上颌骨的生长来调整上下颌骨矢状不调的位置关系,改善下颌后缩患者的侧貌美观。     

Experimental studies on adaptation of mandibular masticatory movements to given laterally shifted intercuspal position

When, the intercuspal position is newly established during reconstruction of maxillomandibular relationship, understanding the process of adaptation for the laterally shifted eccentric intercuspal position is very significant for problems involving maxillo-mandibular registration and diagnosis of occlusion, which has very important meaning for clarifying the neuromuscular control system for mandibular movement. In this studies, changes in clinical symptoms and masticatory movements were observed longitudinally when the laterally shifted intercuspal positions were newly established. Conditions for selecting four subjects were that they wore suitable overlay maxillary dentures connected to abutment teeth and that their mandibular dentition were natural and included good fixed restoration. Experimentally prepared overlay dentures were identical to those worn by subjects except that they included a structure of lateral shift of artificial dentition positioning to given newly laterally shifted intercuspal position. The condition of lateral shift of the intercuspal positions are established by the protrusion of the condyle on one side, amounts of lateral shift of the intercuspal positions were 0, 0.5, 1 and 2mm. From immediately after until a week after insertion of the experimental denture, observations were made to determine clinical symptoms and alterations in the chewing strokes on the frontal plane and in the rhythm of chewing movements. At first, the experimental denture with no lateral shift was inserted into the subject's mouth. Next, this was replaced by the experimental denture with a lateral shift of 1mm, and then this was replaced with a denture with a lateral shift of 2mm. When clinical obstruction was encountered, during this process this was replaced by one with a lateral shift of 0.5mm. Analysis of data of mandibular movement obtained was performed by means of a personal computer system. Results 1. Individual difference was observed in the process of adapting to laterally shifted intercuspal positions. One subject adapted adequately to a shift of 2mm, another to a shift of 1mm; and still another to a shift of 0.5mm. One subject failed to adapt adequately to a shift of 0.5mm. 2. When the laterally shifted intercuspal position was newly established, subject complained of a slightly high feeling in occlusion on the direction opposite to the lateral shift, occlusal sounds, and glide from the initial contact positions to the intercuspal position. All subjects, however, found it difficult to indicate the amount or direction of lateral shift; and there was no obstruction to intentional mastication under these conditions.(ABSTRACT TRUNCATED AT 400 WORDS)     

An evaluation of horizontal jaw relations during standing and sitting with open or closed eyes

When determining the horizontal jaw relation and mandibular movements, a question arises as to the appropriate choice of registration positions. The current study was carried out using 22 adults with full dentition who did not have any discomfort in their skeletal and craniomandibular systems. Occlusion and mandibular movements were investigated with open and closed eyes in standing and sitting positions using an electronic, central-bearing tracing device. The coordinates of the measured parameters are presented using a two-dimensional computer vector diagram. The non-parametric Friedman test was used for statistical data analysis. The measured data obtained for the initial habitual centric relation record (HR), centric relation record (CR), final habitual centric relation record (HR), and protrusion (P) did not significantly differ in the sitting and standing positions or with opened and closed eyes (p = 1.00). With closed eyes, the differences in the average values between the two condylar positions (initial HR/final HR, initial HR/CR, and final HR/CR) decreased in a manner that was independent of the registration position. The CR that was measured in a sitting position with closed eyes was 2.26 mm more retrusive than that measured with open eyes. Before and after CR measurements, only laterotrusion showed significant differences (p=0.02) in patients who were standing with closed eyes. It was concluded that the registration position and visual system could individually influence the measurements of condylar position and mandibular movements. From a clinical perspective, these measurements exhibited the smallest differences when they were conducted with patients in a sitting position with closed eyes.     

Measuring system for lip movements using two video trackers

Movements of soft tissues surrounding the oral cavity, especially lips and cheeks, have a strong influence on mastication and phonetics. They also influence the relationship between a denture and its oral environment. The purpose of this study was to develop a three-dimensional measuring system for soft tissue movement. This system consisted of two video trackers placed stereographically and a computer. In addition, one video tracker was connected for measuring mandibular movements. The accuracy of this system was evaluated using computerized XYZ pulse stage. The resolution of this system was 0.10 x 0.10 x 0.10 mm, when the measurement was carried out in the area of the 24.0 (X) x 20.0 (Y) x 20.0 (Z) mm with a working distance of 500 mm and a frequency of 120 Hz. In the present study, the lip movements of a dentulous subject with mandibular movements during chewing peanuts were analysed using this system. The new system demonstrated its value for analysing soft tissue movement.     

牙列缺损患者三维数字化牙颌模型数据库的建立

目的初步建立牙列缺损患者计算机三维数字化牙颌模型数据库。方法临床收集KennedyⅠ～Ⅳ类40例行可摘局部义齿修复的牙列缺损患者上下颌石膏模型,利用国产三维光栅投影测量系统将光栅投影至牙颌模型表面,数字相机采集反射的变形光栅条纹,通过系统的三维图像处理软件获取牙颌模型的三维点云数据,并进行一系列处理,得到牙尖交错位的上下颌咬合模型,以三角网格数据(*stl)格式存储。结果所建立的牙列缺损计算机三维数字化牙颌模型数据库中模型的精确度高、形态逼真、表面清晰。结论国产光栅投影测量可以作为实现临床牙列缺损患者牙颌模型三维数字化的一种较好方法,为可摘局部义齿计算机辅助设计和三维专家系统的临床进一步开发提供一基础平台。     

Dental and facial skeletal characteristics and growth of males and females with class II, division 1 malocclusion between the ages of 10 and 14 (revisited)-part I: characteristics of size, form, and position.

The purpose of this study was to describe and analyze the craniofacial and dentofacial skeletal characteristics associated with Angle's Class II, Division 1 malocclusion. The material examined included 613 lateral head radiographs comprising 2 series: (1) 278 films of children with "normal" occlusion and (2) 335 films of children with Class II, Division 1 malocclusion. Each series was subdivided into 6 samples (3 female and 3 male; skeletal ages 10, 12, 14, [+/-6 months]), representing children with chronological ages ranging from 8.5 to 15.5 years. The radiographs were converted to computer-readable X and Y coordinate data and 52 linear, angular, and coordinate axis measurements were taken. Findings were visually verified by superimposing the computer-drawn composite plots of the Class II, Division 1 series over those of the normal series. In all 6 intergroup comparisons, it was found that: (1) the mandible and its dentition is similar to the controls in size, form, and position except for the position of the lower incisors in males; (2) the forehead (Gl), anteriorcranial base (Nas), maxilla (A) and dentition (molars and incisors) are protrusive (mesial positioned), with an increased frontal bone thickness at the level of the sinus, and a larger A-P maxilla, the palate of which is inclined superiorly at its anterior half; (3) no vertical dysplasia was evident; (4) the cranial base angle is larger, as are the anterior and posterior sections that compose it, but it is not related to mandibular position; (5) angular indexes of maxillary and mandibular position that included point Nasion are highly misleading indicators of maxillary and mandibular size and position. Visualized diagnosis via a composite norm based on age and sex might offer a more reliable alternative or supplement to the numeric reference standards now in use. Enlarged sinuses may contribute to the cause of Class II, Division 1 malocclusion.     

Morphological studies on the cervical line of the deciduous teeth. Three-dimensional observation on mandibular second deciduous molars

Morphological observation of cervical line of deciduous teeth has been studied in many ways. But there are few reports of research observed from a three-dimensional view point. Using twenty seven mandibular right second deciduous molars, we studied morphological observation of cervical line of physiologically sound deciduous teeth by three-dimensional measuring system. Three-dimensional coordinate values were obtained from the center pit and the mesiolingual cusp of mandibular right second deciduous molar. We used the three-dimensional measuring system (Microcode BX 303: MITUTOYO), and then the three-dimensional coordinate values obtained were transferred to a microcomputer for analysis. As a result the figure of cervical line of the mandibular right second deciduous molar observed from the XY-axis can be grouped into two, and the Z-axis can be classified two types, and we found one new method related to the morphological observation of cervical line.     

Functional data analysis of mandibular movement using third-degree b-spline basis functions and self-modeling regression

The purposes of this study were (1) to establish a new method for analyzing the movement of an incisor point on the mandible as mandibular movement and for analyzing noisy mandibular finite helical axis (FHA) parameters, and (2) to apply this new method in a clinical situation. The subjects were patients with anterior crossbite who were scheduled to receive orthognathic surgery. Chewing movement was measured by an opto-electronic motion-analysis system that can detect mandibular movement in space. The population average curves (trajectories) of the incisor point and the position vector of the FHA during chewing were calculated using third-degree b-spline basis functions and self-modeling regression (SEMOR). Although this study focused on the use of a new statistical model for assessing mandibular movement, the results demonstrated the effectiveness of the combination of the FHA and an additional, supplementary scientific expression of movement, the trajectory of an incisor point. Furthermore, the effectiveness of this new method was demonstrated in a clinical situation. The results of this study demonstrated that the calculation of population average curves is effective for clarifying the characteristics of functional data, such as in mandibular movement.     

Development of an experimental optoelectronic device to study the amplitude of mandibular movements

This study aimed to present a wireless mandibular motion tracking device and optoelectronic data acquisition system developed to analyze the real-time spatial motion of the entire mandible during mouth opening and closing with no restriction of any movement. The procedures were divided into three phases: confection of a kinematic arch, dynamic digital video image acquisition, and image processing and analysis by using graphic computation. Four sequences of jaw opening/closing movements were recorded in lateral view: two from the maximum intercuspation (MIC) and the other two from a forced mandibular retruded position. Jaw motion was recorded by a digital video camera and processed as spatial coordinates corresponding to the position variation of the markers in the kinematic arch. The results showed that the method was capable of recording and processing the dynamics of the mandibular movements during jaw opening/closing using pixel-magnitude points. The mandible showed points with less displacement located near the temporomandibular joint during the opening/closing movements from the mandibular retruded position. When the jaw movements were recorded from MIC, these points were located near the mandibular foramen.     

牙列磨耗对口颌系统影响的研究进展

磨耗在人类牙列中非常普遍。随着人口老龄化进程的加剧,磨耗问题日益突出。牙列磨耗与口颌系统结构及功能的健康协调密切相关,本文就牙列磨耗对牙合、咀嚼肌、颞下颌关节、下颌运动、面形等的影响及其咬合重建治疗等方面作一综述。     

Nonsurgical Treatment of Anterior Disk Displacement Without Reduction of the Temporomandibular Joint: A Case Report on the Relationship between Condylar Rotation and Translation

Farrar reported that in chronic anterior disk displacement without reduction (ADD w/o R) of the temporomandibular joint (TMJ), the range of mandibular movement gradually increases and the condylar movement normal-disk is still displaced anteriorly. The relationship between condylar rotation and translation was studied in opening/closing jaw movements before and after joint stabilization splint therapy in a patient with ADD w/o R. Movements were recorded by means of an optoelectronic jaw tracking system (Metropoly, Jaws-3D) consisting of three cameras that register the position of six light-emitting diodes (LEDs) mounted on two target frames separately attached to the upper and lower jaw. A computer produced plots of the condylar paths in the sagittal, frontal, and horizontal plane, as well as the opening angle against the anterior condylar translation. Results indicated some variations in the relationship between condylar rotation and translation during jaw opening movement. In the joint with ADD w/o R an increase in anterior condylar translation was found and the relationship between rotation and translation became more linear after joint stabilization therapy. This study supported a hypothesis of Farrar's that condylar movement in chronic ADD w/o R is similar to that expected in asymptomatic TMJs.     

Using the Kinesiograph to measure mandibular movements during speech: a pilot study

This study was a pilot investigation to determine a method of measuring mandibular movement during speech using the Kinesiograph. Some observations and trends were evident. 1. The Kinesiograph is an excellent instrument for measuring mandibular movement in three dimensions. 2. Production of the /s/ sound can occur anywhere within a three-dimensional range rather than at one position. 3. The distance between the upper and lower incisors during speech was much less than 1 mm and was consistent throughout the range used by each subject. 4. The functional angle of mandibular movement during speech to the maxillary occlusal plane was essentially the same as the angle of rest position to centric occlusion and appeared to be related to the cephalometric occlusal plane angle. It seems likely that rest position is the key to functional mandibular movement. 5. Three-dimensional clinical studies of mandibular movement during speech using the Kinesiograph could lead to more precise answers to questions concerning mandibular function and occlusal dysfunction.     

新型3DSS-STD-Ⅱ结构光三维测量系统重建牙颌模型的可靠性对比研究

目的应用一种新型的三维测量系统3DSS- STD- Ⅱ对牙颌模型进行三维重建,评价该三维测量重建结果的可靠性,为口腔修复体计算机辅助设计奠定基础。方法利用新型结构光测量系统3DSS- STD- Ⅱ对标准下牙列模型从咬合面、右后侧牙列、前牙列区、左后侧牙列和正后方5个角度进行扫描,扫描后的结果经过数据合并、数据精简,利用反求软件Geomagic 6.0重建下颌牙列数字化模型。然后,用此软件自带测量工具测量切牙牙冠宽度、牙弓前段宽度、牙弓后段宽度、牙弓前段长度和牙弓后段长度相关指标,游标卡尺在石膏模型上测量各个相关指标,分析系统的可靠性、可重复性以及扫描精度。结果3DSS- STD- Ⅱ系统的可靠性与可重复性好,扫描精度结果显示与游标卡尺测量结果差异无统计学意义。结论新型结构光三维测量系统3DSS- STD- Ⅱ可靠性高、测量速度快,可以满足口腔模型三维数据快速采集和计算机辅助设计建模的需要。