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Introduction Recent studies have shown some contradictory results when evaluating the consequences of orthodontic-surgical treatments on the pharyngeal airway. Therefore, the purpose of this study was to correlate the amount of jaw displacement with the volume variation and the minimal cross-sectional area of the pharyngeal airway. A comparison was made between the correlations with the percentage and the absolute values of the measurement variations. Methods Forty-two patients were divided into 2 groups according to the kind of orthognathic surgery that they had undergone. Group 1 had 22 subjects who had undergone maxillary advancement associated with mandibular setback, and group 2 had 20 patients who had undergone maxillomandibular advancement. The pharyngeal airway was divided into the upper segment and the lower segment, and the sum of these volumetric measures resulted in the total volume. The maxillary and mandibular displacements were assessed using closest point iteration after a voxel-wise cone-beam computed tomography superimposition. Hence, jaw displacements were correlated, using Pearson's correlation and linear regression analysis, to the volume variations of the pharyngeal airway (first time separately and then both groups together) and to the minimal cross-sectional area variation. Results The strongest correlation found was between maxillary displacement and the upper segment in group 2 (r = 0.898, R2 = 0.888; P ≤0.001). With the groups' data combined, the variables mandibular displacement and the lower segment showed a linear correlation (r = 0.921, R2 = 0.914; P ≤0.001). Maxillary displacement showed a strong positive correlation with the minimal cross-sectional area variation in group 2 (r = 0.710, R2 = 0.604; P ≤0.01). Conclusions Correlations with the percentage values were substantially stronger than the correlations with the absolute values. Stronger positive correlations were found between the jaw's displacement and the volume variation of the volume segment that was closer to it in both kinds of surgeries. Only the maxillary displacement is a reliable predictor of the minimal cross-sectional area variation after maxillomandibular advancement.

AIM: To conduct an epidemiological study and find the prevalence of some transverse anomalies of occlusion in children aged 7-17 years from the region of Plovdiv; to determine the most appropriate time for early orthodontic treatment based on the results of the study. MATERIAL AND METHODS: The study included 883 children from Plovdiv (7-17 years old). The children were studied by means of extraoral examination, a clinical examination of dental arches and occlusion and by doing a clinical test to assess mandibular displacement. RESULTS: The prevalences of mandibular deviation, laterognathia and posterior crossbite (unilateral or bilateral of single teeth or a group of teeth) were 30.4%, 1.02%, 10.53%, respectively. CONCLUSION: Our results are consistent with the results reported by other authors which indicate that these malocclusions cannot self-regulate and for this reason they should be subject to strict prevention and early treatment.

Traditionally, superimposition of lateral cephalograms has been performed using the cranial base as a reference. However, the direction of mandibular displacement observed by using this technique often conflicts with the observations made by clinicians. This occurs because superimposition using the cranial base does not take into account changes in the maxilla resulting from growth and/or treatment that may affect the mandible. A technique of superimposing the maxilla and mandible together as a unit using the maxillary base as reference has been proposed. (The term maxillary base will be used throughout this article to mean the maxilla and mandible observed together as one unit.) It attempts to define true mandibular displacement as a result of orthodontic treatment mechanics and growth. Significant difference in mandibular displacements between the two superimposition methods have been reported on treated Class II samples. No reports have been made on treated and control Class III samples. The objective of this study was to compare the direction of mandibular displacements using the two methods of superimposition (cranial base versus maxillary base) in a control and treated sample of Class III subjects. The control sample received no treatment and the treated sample underwent orthopedic treatment with protraction headgear. Mandibular displacements were measured by plotting three mandibular landmarks pogonion (Pog), gnathion (Gn), and menton (Me). Superimpositions were made on the pretreatment (T1) and posttreatment (T2) films to determine the differences in vector angles, thus quantifying the direction of mandibular displacement. The results showed significant difference in mandibular displacements (alpha vector angles of Pog, Gn, and Me) in both the treatment group and the control group when comparing the cranial base and maxillary base superimposition methods ( P P

Orthodontic tooth movement is dependent upon the remodeling of the periodontal ligament and alveolar bone by mechanical means. Facial sutures are also fibrous articulations, and by remodeling these joints, one can alter the positional relationships of the bones of the facial skeleton. As might be expected from the structure and mobility of the temporomandibular joint (TMJ), this articulation is more resistant to mechanical deformation, and whether functional mandibular displacement can alter the growth of the condyle remains controversial. Clinical investigations of the effects of the Andresen activator and its variants on dentofacial growth suggest that the changes are essentially dento-alveolar. However, with the popularity of active functional appliances, such as the Herbst and twin-block based on ’jumping the bite’, attention has focused on how they achieve dentofacial change. Animal experimentation enables informed decisions to be made regarding the effects of orthodontic treatment on the facial skeleton at the tissue, cellular, and molecular levels. Both rat and monkey models have been widely used, and the following conclusions can be drawn from such experimentation: (1) Facial sutures readily respond to changes in their mechanical environment; (2) anterior mandibular displacement in rat models does not increase the mitotic activity of cells within the condyle to be of clinical significance, and (3) mandibular displacement in non-human primates initiates remodeling activity within the TMJ and can alter condylar growth direction. This last conclusion may have clinical utility, particularly in an actively growing child.

This paper describes the orthodontic treatment of two cases presented by the winner of the William Houston gold medal at the Membership in Orthodontics examination at the Royal College of Surgeons of Edinburgh and which also won the British Orthodontic Society (BOS) cases prize in 2013. The first case describes the management of a 20-year-old female patient with a Class II division 2 malocclusion complicated by moderate upper and severe lower arch crowding, increased overjet and overbite, a crossbite and centreline discrepancies. Treatment involved a combination of a transpalatal arch, temporary anchorage devices and fixed appliances. The second case describes the management of a 15-year-old male patient with a Class I malocclusion complicated by crossbites affecting the right buccal segment and UR2, an associated mandibular displacement forward and to the right, mild upper arch crowding and a centreline discrepancy. Treatment involved a combination of a quad-helix, headgear and fixed appliances.

目的: 本研究の目的は, 健常者および顎機能障害者の習慣性咬合位から咬頭嵌合位への下顎変位を三次元的に解析し, その変位量および変位方向の違いを明らかにすることである.方法: 被検者として, 健常有歯顎者6名と顎関節部の雑音を有する顎機能障害者6名を選択した. Light clenchingと30% MVC (Maximum voluntary clenching) の咬合力を発揮させて採得した, 2種類のシリコーンバイトを試料として, 非接触形状計測を行った. 頭部X線CTから, 頭蓋顔面骨の三次元構築データを抽出し, その解剖学的標点から, 基準座標を設定した. テフロン球をマーカーとして三次元構築データの位置合わせを行った後に, 上下顎歯列咬合面の位置合わせにより, 習慣性咬合位から咬頭嵌合位への下顎変位を算出した. 下顎変位を表現するパラメータとして, 下顎咬合平面を決定する三角形の重心の変位量および変位方向をMOD (Movement of dentition), 左右側下顎頭最上点の変位量および変位方向をMOC (Movement of condyle) とした.結果: 健常者に比べて顎機能障害者では, MOD, MOCともに下顎変位量が有意に大きかった. また変位方向については, すべての顎機能障害者において, 下顎歯列部では上方に, 下顎頭部では後方に変位する傾向が認められた.結論: 習慣性咬合位から咬頭嵌合位への下顎変位が, 顎関節雑音の発症に関連している可能性が示された.

SUMMARY This study investigated mandibular displacement and masticatory muscle activity during clenching in lateral occlusal position in relation to the lateral occlusal pattern. Twenty healthy human subjects (mean = 26·5 years) volunteered for this study. Metallic occlusal overlays were fabricated for the lower working side canine to second molar and non-working side second molar in order to simulate a canine protected occlusion, group function occlusion and bilateral balanced occlusion (balancing contact). Three-dimensional displacements of the bilateral condyle and electromyography (EMG) activities in the bilateral masseter, anterior and posterior temporalis were recorded during maximal clenching. The experimental occlusal pattern was revealed to have statistically significant effects on both condylar displacement and EMG activity (P

Introduction Anterior cross bite is a common malocclusion and early treatment is indicated. Determining its prevalence is important to plan orthodontic services. Objective To assess the prevalence and associated features of anterior cross bite in pre-adolescent patients attending an orthodontic clinic. Methods A hospital based cross sectional study was conducted in patients attending the Division of Orthodontics, University Dental Hospital, Peradeniya. Seven hundred and twenty one consecutive patients were examined for anterior cross bite. All patients who consented were examined and anterior cross bite were recorded when maxillary incisor/s occluded lingually to mandibular incisor/s in centric occlusion. Mandibular displacement, gingival recession, tooth mobility, presence of posterior cross bite and skeletal pattern were also assessed. Results Sample consisted of 721 patients, of whom 193 (26.7%) had anterior cross bite. Twenty two (11.4%) had both anterior and posterior cross bite. Among patients with anterior cross bite 62% had unilateral involvement and 38% had bilateral involvement. One hundred (51.8%) had involvement of only one incisor while 64 (33.2%) had involvement of two incisors. Class 1 skeletal pattern was found in 103 (53.37%) patients with anterior cross bite, Class 2 skeletal pattern in 33 (17.1%) and Class 3 skeletal pattern in 57 (29.53%). Mandibular displacement was present in 93 (48.19%) patients and 5 (2.5%) showed tooth wear in anterior cross bite. Gingival recession was seen in 43 (22.3%) and tooth mobility of involved lower incisors in 12 (6.2%). Conclusion The prevalence of anterior cross bite is high in pre-adolescent patients attending an orthodontic clinic.

This study investigated mandibular displacements during clenching in the lateral mandibular position in relation to lateral occlusal relationships. Twelve healthy human subjects (mean=26.7 years) volunteered for this study. Acrylic occlusal devices were fabricated for the lower working-side canine, working-side second molar and balancing-side second molar in order to simulate a dominant canine guidance, working-side interference (WI), balancing-side interference (BI) and bilateral balanced occlusion (BO). Vertical displacements of the mandible were recorded by linear variable differential transformers during submaximal clenching in the right lateral position. The four experimental occlusal conditions were revealed to have a significant effect on mandibular displacement patterns (ANOVA, P < 0.001). A dominant canine raiser caused a mandibular elevation with the smallest displacement at the working-side premolar and the largest displacement at the balancing-side second molar. Clenching on a WI or BI caused a mandibular elevation with the smallest displacement at the working- or balancing-side second molar, respectively. A BO resulted in the smallest upward displacement among the four experimental conditions. These results suggest that the nature of reaction forces at the temporomandibular (TM) joints caused by the elevation of the mandible varies in a predictable manner depending upon lateral occlusal relationships.

To investigate the relationship between occlusal scheme and joint loading, mandibular displacement was measured during lateral clenching under experimentally altered occlusal conditions. Acrylic occlusal devices were fabricated for the lower working-side canine, working-side second molar, and balancingside second molar. With the aid of these devices, various occlusal states were simulated. Eight healthy subjects volunteered for this study and performed clenching tasks. Vertical displacements of the mandible were recorded by linear variable differential transformers, and the results were as follows:1. Clenching efforts in the lateral mandibular position caused elevation of the mandible.2. When a single occlusal device was placed unilaterally, the amount of the upward displacement near the supporting tooth tended to be smallest.3. Insertion of three occlusaldevices (bilateral tooth contacts) reduced the amplitude of mandibular displacement.These results suggested that the nature of reaction forces at the temporomandibular joints caused by the elevation of the mandible would be influenced by the occlusal status.

African American orthodontic patients often present with morphologic characteristics that prompt the extraction of premolars. Referring dentists, however, commonly see extraction as a cause of "dished in" profiles, collapsed arches, and temporomandibular dysfunction. If true, these claims imply that African American patients are disproportionately at risk of clinical misadventure. Unfortunately, a meaningful long-term comparison of alternative treatments--be it retrospective or prospective--requires samples of patients who were equally susceptible to the two alternatives. Thus, if a retrospective study is to be free of susceptibility bias, the samples must be matched with respect to the anatomic differences that prompted the clinicians' choice of treatments. The goals of this investigation, therefore, were the following: to gather a large sample of African American expatients and to identify by means of discriminant analysis the characteristics that seem to have been important to the extraction decision, to use this knowledge to assemble subsamples of extraction and nonextraction expatients (both Class I and II) who were similar before treatment, and, finally, to recall them so that the long-term impact of the two strategies could be compared. In the end, 60 expatients--30 extraction and 30 nonextraction--were recalled, on average, nearly 8 years after the completion of treatment. In general, both treatments reduced irregularity and neither seemed to produce posterior mandibular displacement. Premolar extraction led to a modest reduction in dental and soft tissue protrusion (half the incisor retraction minus one); nonextraction, by way of contrast, produced an increase. Long term, the difference between the two treatments was about 2 mm at the upper lip and 4 mm at the lower. Excessive profile flattening was not a common finding. Our findings thus imply that the various "functional orthodontic" arguments against premolar extraction do not apply to African Americans any more than they do to whites.

The purpose of this study was to investigate the postsurgical stability of the mandible in Japanese skeletal Class II patients who underwent sagittal split ramus osteotomy (SSRO). Twelve female patients who underwent surgical mandibular advancement with rigid osseous fixation using titanium miniplates were selected for this study. Seven patients underwent mandibular advancement only, and 5 patients underwent mandibular advancement in conjunction with genioplasty. The postsurgical stability of the mandible was evaluated by cephalometric analysis. As the result, the average mandibular position was stable after SSRO. No relationship was observed between the amount of mandibular displacement following surgery and that during postsurgical treatment, as well as between the amount of mandibular displacement and the mandibular plane angle immediately before surgery.

Intercuspal position (ICP) is the most important position in all functional mandibular positions for the stomatognathic system. While the clenching level was gradually increased, dynamic stability of the ICP in 10normal subjects and 10patients with temporomandibular disorders (TMD) was evaluated from occlusal contacts, deviation of the incisal point of the mandible and bilateral anterior temporalis and masseter muscle activity.The obtained results were as follows:1. Increases in the clenching level produced changes in the location of occlusal contacts of ICP in TMD patients.2. During clenching of ICP, displacement of the mandible in TMD patients was greater than in normal subjects.3. During clenching of ICP, activity of the masseter muscle had a greater effect on the occlusal contact stability than the anterior temporalis muscle.

Studies of the development of mastication in the normal growing individual have received little attention in the literature. The aim of this study was to determine whether changes in oral motor function occurred during growth. Ninety healthy individuals with normal occlusion were divided into six groups of males and females, 9-10, 13-15, and 20-22 years of age. Oral motor function, with respect to mandibular displacement and velocity, was monitored with an opto-electronic method. The results revealed that the total duration of the masticatory cycle was not influenced by age or gender. However, the time distribution between the different phases was found to be influenced by the age factor, causing a longer opening time and a shorter closing time in the adults. In mastication, both mandibular displacement and the mandibular velocity in closing were less in females. A reduction of the masticatory opening velocity and an increase in closing velocity were observed with increasing age. Physiological maturation of the masticatory system due to central and peripheral changes and functional adjustments due to changes in dentition and skeletal growth may be the underlying reasons for our findings.

The purpose of this study was to investigate the long-term changes in the skeletal Class III profile subsequent to chincap therapy. The sample consisted of 63 Japanese girls who had skeletal Class III malocclusions before treatment. All underwent chincap therapy from the beginning of treatment. The duration of chincap therapy varied but averaged 4½ years. The samples were divided into the following three groups according to their ages when chincap therapy was started: A group that started at 7 years of age ( n = 23), a group that started at 9 years of age ( n = 20), and one that started at 11 years of age ( n = 20). The data were derived from lateral cephalometric head films, taken serially at the ages of 7, 9, 11, 14, and 17 years. Skeletal facial diagrams were constructed by X-Y coordinates of representative cephalometric landmarks. The data were analyzed statistically. The results of the present study were as follows: (1) The mandible showed no forward growth during the initial stages of chincap treatment in all three groups. (2) Patients who had entered treatment at 7 and 9 years of age appeared to show a catch-up manner of mandibular displacement in a forward and downward direction before growth was completed. (3) There was no statistical difference in the final skeletal profile between the group that had entered treatment at age 7 and the one that had entered at age 11. In conclusion, the skeletal profile was greatly improved during the initial stages of chincap therapy, but such changes were often not maintained thereafter. This finding indicated that chincap therapy did not necessarily guarantee positive correction of skeletal profile after complete growth.

Objective To record maxillary and mandibular displacement with articular growth and in response to bimaxillary surgical repositioning in patients with hemifacial microsomia (HFM) and to observe ipsilateral corpus/ramus growth in severely affected children. Design Prospective roentgen stereometric analysis (mean age 7 years 10 months to 18 years 0 months) and retrospective profile and panoramic roentgenograms. Mean total observation period was 9 years 1 month. Setting Department of Plastic and Reconstructive Surgery, Malmö University Hospital (Malmö, Sweden). Patients Twenty-one patients consecutively diagnosed from 1976 through 1988 with HMF, five of whom had bimaxillary surgery. Interventions Surgery was performed at the Department of Plastic and Reconstructive Surgery. Implants were inserted at the initial reconstructive surgical procedure under general anesthesia. Roentgen examinations were performed in connection with continued clinical evaluations and treatment. Main Outcome Measures Stereo roentgenograms were digitized at the Department of Orthopedic Surgery, Malmö University Hospital (Malmö, Sweden). Results Displacement of the jaws with articular growth and in response to bimaxillary surgical repositioning varied interindividually with no apparent common pattern. Relapse displacement occurred several years after bimaxillary surgery. Mandibular growth changes were found in the corpus/ramus area and alveolar process on the affected side. Conclusions A marked interindividual variability of maxillary and mandibular displacement indicates that the relevance of statistical analysis of HFM growth data may be questioned. We would suggest that precise and accurate longitudinal recordings of growth and response to surgery in individual HFM patients be more appropriate.

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 Fränkel function regulator (FR) and (2) to compare findings from regional superpositions of cephalometric structures with those from conventional cephalometric measurements.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.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 (.0001P.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.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.

The pattern of mandibular movement during chewing is influenced by several central and peripheral factors. The aim of the present study was to determine whether changes in masticatory function, characterized by mandibular velocity and displacement, occurred during individuals' normal growth. Forty-seven children, 9-15 years of age, were followed over a 6-year period. All had an Angle Class I occlusion with no obvious orthodontic problems. Oral motor function with respect to mandibular displacement, duration, and velocity was monitored 3-dimensionally with an opto-electronic method. The chewing cycle was divided into an opening, closing, and occlusal phase. Total body height was measured. During the follow-up period, all masticatory variables except the 3-dimensional opening distance showed significant changes. The total chewing cycle duration, the opening and occlusal time of the chewing cycle, and the 3-dimensional closing distance increased during the growth period, while the closing time of the chewing cycle, the 2-dimensional lateral and vertical distances and both the opening and closing velocity decreased. The children who grew proportionally most in height during the 6-year period, i.e. the youngest children in the group studied, showed a significantly larger decrease in the opening velocity. From this study it becomes evident that the variables of the chewing cycle undergo a continuous process of change during growth. This is possibly a reflection of anatomical changes, maturation of the central nervous system, and altered functional demands.

Aim To illustrate a simple effective method for early treatment of pseudo Class III in the mixed dentition and to highlight the advantages of early treatment by showing a 4-year follow-up of the treatment effects. Subjects Twenty-one consecutive southern Chinese patients with a mean age of 9.6 years were included in the early treated group with pseudo Class III malocclusion. Methods Lateral cephalometric films taken at the beginning and at the end of treatment were analysed. The arithmetic mean and standard deviation (SD) were calculated for each cephalometric variable and paired t-tests were performed to assess the statistical significance of the treatment effects. Results Anterior crossbites and mandibular displacements were eliminated after the treatment. The angulation of the upper incisors to the maxillary plane showed an increase by a mean of 9.5° (P < 0.001), while the angulation of the lower incisors to the mandibular plane showed a decrease by a mean of 4.9° (P < 0.001). Conclusion In pseudo Class III malocclusion, proclination of upper incisors and/or retroclination of lower incisors with simple fixed appliances contribute to the correction of anterior crossbite and the elimination of mandibular displacement. Proclination of upper incisors, use of Leeway space and arch width increase provide space required for the eruption of the premolars and canines.

Food texture is known to influence several mastication parameters such as forces, muscular activities or mandibular displacement. This preliminary study was conducted to examine whether jaw movement recordings could be a reliable method to investigate food texture properties. Masticatory movements were recorded with an electromagnetic system. The subjects sat with their head in a magnetic field. Two coils were attached on the central upper and lower incisors. These receiver coils recorded a current when in the magnetic field. Five foods were chosen to display various rheological behaviours (meat, coconut, 2 cheeses and chocolate). All samples were prepared in standardised dominoe shape. Six replicates of each food were randomly presented and 8 subjects, free of any dental pathology, were asked to perform free style mastication. Durations, amplitudes and velocities of opening and closing phases of the masticatory cycles were measured. These movement parameters allowed discrimination between the foods. For all parameters there was significant variation between subjects. The main finding was the demonstration that mastication differed with the type of food chewed and thus this method of recording mandibular movements during mastication could be of a great interest for objective studies of food texture and to determine the basis of food texture perception.

The effect of the treatment of Angle Class II, Division 2 malocclusion was studied in 22 children by x-ray cephalometry and by recording the relation between the retruded and the intercuspal mandibular positions. The treatment was performed in three phases. In the first phase the upper incisors were proclined, and the deep bite was corrected with an upper removable plate. In the second phase the distal occlusion was corrected with an activator. The result was retained in the third phase with a second activator designed for retention. The relation between the retruded (RCP) and the intercuspal (ICP) mandibular positions was recorded with wax bites and dental casts mounted in a modified gnathothesiometer. The anteroposterior distance between RCP and ICP was large before the start of the treatment. The distance was unchanged after proclination of the upper incisors and correction of the deep bite but decreased after correction of the distal occlusion and increased again somewhat during the retention phase. The proclination of the upper incisors and the correction of the deep bite (phase one of the treatment) did not result in mandibular anterior positioning. This fact and the results of the recordings of the relation between RCP and ICP were interpreted as evidence that the mandible is not posteriorly displaced in Class II, Division 2 malocclusion.

Summary Experiments were carried out to study changes in masticatory movements in the chewing sequence of young dentate persons and complete denture wearers rehabilitated with bridges on osseo-integrated implants (OIB) in the lower jaw. Two test foods were used in the dentate group (apple, bread) and bread in the OIB group. A computer-based opto-electronic system (Selspot) was employed to record and analyse all single chewing cycles, regarding parameters reflecting, chewing rhythm, mandibular velocity and displacement. The different parameters were tested both intra- and inter-individually versus the series of the single and overall chewing cycles in the masticatory sequences respectively. The results indicated that different subjects performed different patterns of mastication within the chewing period when chewing the same type of food. Different test foods (texture, size) also seemed to affect the chewing pattern in a different way, e.g. mandibular displacement showed an obvious reduction when chewing apple, probably due to the bigger size of the bolus. The inter- and intra-individual analysis showed in some parameters discrepancies implying problems in analysing the chewing pattern within the chewing sequence without using both methods.

Id rote ures and materials involved in the articulation of the maxillomandibular relationship are subject to numerous sources of error. The importance of analyzing this relationship is reflected by the literature devoted to mandibular positional analysis. Various formats of three-dimensional mandibular descriptions have been used in static and dynamic studies. Several investigations have studied single-point displacements and their envelopes of motion.le5 Other studies have relied on mechanical recording and playback mechanisms for describing mandibular displacement and have used three-dimensional traces engraved in plastic blocks to record mandibular position.‘,‘j*’ However, there is no consistent format in the literature for a comprehensive description of mandibular displacement. Lack of data compatibility prevents the comparison of results among different studies analyzing interocclusal regis.ration materials and hinge axis location. The major purpose of this investigation was to establish a method of evaluating materials, techniques, and procedures that relate the mandibular to the maxillary arch. Prior to mounting casts, the two halves of an articulator are mechanically related to one another by means of the two simulated condylar areas and the incisal pin and table assembly. The clinical recording of maxillomandibular relationships is desired without the influence of the dentition. In these instances the maxillary and mandibular members of the articulator are related by means of the two condylar mechanisms

A comparison was made in this study of the prevalence of mandibular displacement in varying degrees of complexity with the incidence of parafunctional occlusal habits and some sequelae. The prevalence of occlusal habits in all patients was high but became greater with the increased complexity of the mandibular displacement, especially an asymmetrical slide from RCP to IP. The multifactorial etiology of parafunctional occlusal habits and their sequelae tends to make the relationships more complex than a simple "cause and effect" and therefore must be considered.

A review of the recent literature indicates that, contrary to Wolff's law and Roux's principle, epiphyseal cartilage plates remain highly unresponsive to mechanical stimuli. A controlled experiment in three rhesus monkeys, aged 44 to 50 months, was designed to assess condylar response to orthopedic stimulation. Roentgenographic, vital-staining, and histologic analyses of the temporomandibular articulations after treatment periods of two and one-half and four and one-half months, respectively, yielded the following results: 1. 1. The condylar cartilage with its endochondral growth apparatus responded most actively to functional therapy. Upon treatment, the condylar head assumed a prolonged, bilobed shape as part of a growth response that tended to compensate for the induced mandibular displacement. 2. 2. Transformations of the joint structures of the temporal bone remained at a microscopic level. Comparison with experimental results so far published (Table II) suggests that this was due to the advanced age of the animals and the shortness of the experiment. The unique properties of condylar cartilage among the endochondral growth apparatus were evaluated both from the biologic aspect and from the standpoint of its impact on orthodontic therapy.

The prevalence and magnitude of mandibular displacement from RCP to IP in a principally adult sample was evaluated. The findings and their possible clinical significance were discussed.

Longitudinal records, in the form of study casts, of 35 Class I cases were examined for factors associated with changes of sagittal molar relationship during childhood. These were studied at two phases: between the deciduous and mixed dentitions, and between the mixed and permanent dentitions. During the first of these periods, there was a small, but general move to a less post-normal occlusion, although some cases were found to show a slight reverse trend. In the second period, the permanent molar relationship became less post-normal, but this was reflected only weakly in that of the canines. Throughout development, asymmetry of occlusal relation became more marked with age, an unexplained bias towards less post-normal occlusion on the left side developing in the second phase. The amount of change in this period was related to variations of deciduous molar size, especially that of the upper second molar.

Mandibular displacement during /s/ production was monitored via a mercury strain gauge which was taped to the face of two normally articulating and six /s/-misarticulating children. Simultaneous audio and jaw displacement visicorder traces were produced from an FM-tape recording of each experimental session, and were subsequently analyzed. Results indicated that various /s/-misarticulating subgroups exhibit different mandibular positions during /s/- production, and phonetic contextual effects upon mandibular position also vary by articulatory type.

A new computer-based analysis of the single chewing cycle was described as a complement to the Selspot system used for recording mandibular movements. Fifteen adults took part in a clinical investigation of masticatory movements recorded in two sessions with an interval of about 4 weeks. The analysis of the single cycle was performed in regard to chewing rhythm, mandibular displacement, and velocity; the results showed agreement with earlier published results. Most parameters showed agreement between the two registrations, but there was an indication of a weak adaptation to the test situation that should not be disregarded in repeated test situations.

Disocclusion of the teeth has been postulated to have a deregulating or promoting influence on mandibular growth. The clinical effects of disocclusion were evaluated with a prospective pilot study of 16 children with mixed dentition who wore either a maxillary Hawley biteplane or the functional regulator of Frankel. The pilot study was used to assess individual variations to establish the feasibility of a larger, more statistically valid investigation. The biteplane was used to evaluate the effects of vertical mandibular displacement on craniofacial growth. The Frankel regulator was used to evaluate the effects of both vertical and horizontal mandibular displacement. The relationships between patient cooperation, personality characteristic, and treatment effects were also evaluated. After 9 months of treatment, the biteplane group had an increase in the mandibular plane angle with little or no horizontal mandibular growth and tendency toward an interior open bite. This was deemed to be clinically detrimental and the biteplane therapy was discontinued. The results of this study are presented to aid the clinician in his or her decision to use biteplane therapy. In the biteplane group, the bite opening was associated with molar, and not incisor, extrusion. Though the biteplane group had primarily a vertical increase in the length of the lower third of the face, the Frankel group had a combination of anterior and inferior mandibular growth. In both groups, the mandibular incisor usually moved anteriorly. The maxially incisor usually moved labially in the biteplane group and lingually in the Frankel group, although exceptions were in both groups. Correlation coefficients between self-esteem, compliance, and cognitive level were not statistically significant. These findings suggest that a constant protracting force on the mandible, rather than bite opening only, may be necessary for increasing mandibular length. Thus the biteplane should only be used to increase the vertical dentoalveolar and facial heights in patients with normal anteroposterior maxillary-mandibular relationships.

Summary In a small group of individuals the chewing behaviour was recorded through light-emitting diodes in the Selspot system repeatedly over a 7-month period. The test food was crispbread of a standard size. It was shown that a characteristic chewing pattern can be recognized in each test person, and that the pattern was stable during the test period with only insignificant variations in chewing rhythm and magnitude of mandibular displacement.

Part of the biting force is believed to be transmitted to the temporomandibular joint and cause interarticular pressure. This pressure's degree and function, however, are not clarified. In this paper, I shall examine this pressure from condylar movement measured by the face-bow. For the measurement of condylar movement caused by biting-pressure, I used an intraoral appliance which consisted of a pair of Co-Cr clutches and a pivot. While the patient exerted both maximum and medium biting force on the pivot located at the first molar, mandibular movements were measured. Both sides of the condyle tended to move anterosuperiorly. Condylar movement averaged 0.29 mm on the working side, and 0.46 mm on the balancing side during maximum bite force. Distance and direction of the condylar movements were equal to the results of previous investigations, excepting the direction of working side condyle. The difference was considered to be primarily due to experimental variables. The condylar movement during biting was smaller than that during pushing the jaw upward with manual forces. This suggests that interarticular pressure is only slight on both sides during first molar bite action.

A retrospective cephalometric study investigated the differences in the skeletal pattern of the Class III malocclusion. Thirty Caucasian adolescents with an anterior mandibular displacement on closure were compared to an equal number without such a displacement before treatment, at the end of treatment and at least 1 year out of retention.

Prosthodontic rehabilitation with complete maxillary dentures and mandibular bilateral distal-extension removable partial dentures did not change the general masticatory function to any great extent. However, the velocity of the mandible was increased, especially in the opening phase, and so was the mandibular displacement. The latter seems to be the cause for a long closing duration. The chewing cycle became more even and teardrop shaped, and the prosthodontic rehabilitation also resulted in a decrease of the number of chewing cycles. The Selspot system offers a possibility to study adaptation to prosthodontic treatment objectively by measurements of time and movement.