Functional-rhythmical coupling of head and mandibular movements

It is known that small head movements accompany the movements of the jaw during mastication; however, it is unknown whether these movements occur rhythmically and synchronously. The objective of this study was to determine whether there exists a functional coupling between the head and mandibular movements. Four healthy male adults (mean age 25.5) with normal occlusion and without TMD history were selected as subjects. Using the Trimet system, we measured tridimensionally both the movement of the head and the mandible by tracking upper and lower incisal points, respectively, during tapping movements with different opening range and frequency, then analysed the vertical component of these movements. The upper incisal point moved in opposite direction to the mandible in all tapping strokes in all subjects, during opening the head moved in a cranial direction and during closing in a caudal direction; the incidence rate for this concomitant movement was 98%, implying that the head moves periodically and rhythmically, as the mandible does. The cycle time of these coincident movements showed a correlation coefficient of 0.94. Moreover, the vertical range of head movement was within 10% of the jaw's movement. From these results we concluded that, at least during teeth tapping, the head moves in rhythmical coordination with mandibular movement.     

Quantification of translational and gliding components in human temporomandibular joint during mouth opening

OBJECTIVE: In humans, the opening movement of the mouth requires a complex combination of rotation in the lower temporomandibular joint compartment and of translation in the upper compartment. The aim of the current study was to quantitatively assess the percentage contribution of rotation and translation movements of the mandible at maximum mouth opening in normal, healthy individuals. DESIGN: Free, habitual movements of mouth opening were recorded in 12 men and 15 women aged 19-30 years using an optoelectronic three-dimensional motion analyser. All subjects had a sound, complete, permanent dentitions with Angle Class I jaw relationships, without cast restorations or cuspal coverage, TMJ or craniocervical disorders. For each subject, the mandibular movements at the interincisor point (occlusal plane) were reconstructed, and, using suitable mathematical algorithms, divided into their rotation and gliding components. The relative contribution of the two components to the total movement was calculated for each frame of motion. In particular, the situation at maximum opening was assessed. RESULTS: At maximum mouth opening, on average, men had significantly larger displacement of the mandibular interincisor point (56 mm versus 46 mm) and angle of rotation (34 degrees versus 32 degrees), than women. The percentage of mandibular movement explained by rotation at maximum mouth opening (77%) was not influenced by sex. The degree of rotation was significantly related to the displacement of the interincisor point: in women r2 = 87%, in men, r2 = 45%. CONCLUSIONS: Overall, in normal subjects with a healthy stomatognathic apparatus, mouth opening was more determined by mandibular rotation than by translation.     

偏侧咀嚼对张闭口运动的影响

目的:分析偏侧咀嚼患者在最大张闭口运动中的下颌运动轨迹特征。方法:通过下颌运动轨迹描记检测技术,比较偏侧咀嚼和正常咀嚼人群在大张口运动中的运动轨迹,进行统计分析。结果:1)偏侧咀嚼组在大张口运动时开闭口轨迹多数分离,开口型与与双侧咀嚼组相比差异有统计学意义(P<0.05)。2)偏侧咀嚼组张闭口运动时垂直向和矢状向位移显著低于双侧咀嚼组(P<0.01)。结论:最大张闭口运动中偏侧咀嚼组开口型多数偏向工作侧,50%的人群开闭口轨迹分离,开口度减小,说明长期偏侧咀嚼会导致张闭口运动轨迹的异常。     

Correlation between facial morphology,mouth opening ability,and condylar movement during opening-closing jaw movements in female adults with normal occlusion

The aim of this study was to investigate the relationship between parameters of facial morphology, maximal voluntary mouth opening ability, and condylar movements in 21 adult females, aged between 20 and 24 years. The subjects had a normal occlusion without sign or symptoms of temporomandibular joint (TMJ) dysfunction. Mandibular movements were recorded using an opto-electric jaw movement recording system with six degrees of freedom under a series of maximal mouth opening-closing movements. Maximal jaw opening and coincident condylar movement were measured three-dimensionally. The mean values of the incisor and condylar path were 41.1 +/- 3.5 mm (range 35.6-50.9 mm) and 12.8 +/- 2.8 mm (range 8.1-19.2 mm), respectively. Although the positive correlation between maximal jaw opening and facial morphology was significant, none of the variables significantly differed between the value of the condylar path and facial morphology. The length of the path of maximum incisor movement and the condylar path during mandibular movement also did not correlate. Stepwise multiple regression analysis indicated a positive association between the maximal length of the incisor path and the cephalometric value of mandibular ramus inclination (R2 value was 0.369). The results of this study suggest that facial morphology size has a limited effect on maximal voluntary mandibular opening and condylar movements in normal adult female subjects.     

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.     

Association between mouth opening and upper body movement with intake of different-size food pieces during eating

Head rotation is coordinated with mandibular movement during mouth opening, and the range of head rotation and mouth opening change with food size. However, past research did not include upper body movement, and no reports have related head and mandibular movement during realistic eating. The purpose of this study was to analyse head and mandibular movements with intake of different-sized food pieces during realistic eating. The test food consisted of apple cut into two different cube sizes (10mm and 20mm). Head and mandibular movements of 20 healthy young adults eating the apple pieces were simultaneously recorded in three dimensions by a wireless opto-electronic system. Reflective markers were attached to the upper lip and chin to measure the mouth opening range. Five markers were attached to eyeglasses frames to measure linear motion and rotation of the head. One marker was attached to the jugular notch of the sternum to measure linear motion of the upper body. Linear motion, and the inclination angle of the head and upper body, and mouth opening range were compared during intake of different-sized apple pieces. Mouth opening, head-neck rotation angle and the amount of upper body forward translation and inclination increased with larger apple pieces. However, isolated relative head motion was stabilized. We conclude that upper body forward motion and head-neck rotation assist mouth opening whilst stabilizing head orientation, and that the range of head-neck rotation angle, upper body translation and range of mouth opening change with food size during realistic eating.     

Size of variables in mandibular movements in autopsy material

Autopsy was performed on the right temporomandibular joint in eleven individuals with a mean age of 71 years. Standard positions indicative for protrusion, laterotrusive border movement and posterior opening movement were photographed in the sagittal plane. Size of movements of the disc and condylar head were recorded, as well as movements of a reference point in the mental region. The slope of the anterior discal movement was estimated and mandibular rotation during posterior opening was registered. Centre of rotation during the hinge movement was in all cases located to the craniodorsal part of the condylar head. Attempt to construct centres of rotation in the eminence and condylar head for the horizontal movements was in vain. The discussion deals with the influence of the specific kind of material on the results and the possible systematic differences to clinical material.     

Concomitant mandibular and head-neck movementsduring jaw opening–closing in man

To test the hypothesis of a functional relationship between the human mandibular and cranio-cervical motor systems, head-neck movements during voluntary mandibular movements were studied in 10 healthy young adults, using a wireless optoelectronic system for three-dimensional (3D) movement recording. The subjects, unaware of the underlying aim of the study, were instructed to perform maximal jaw opening–closing tasks at fast and slow speed. Movements were quantified as 3D movement amplitudes. A consistent finding in all subjects was parallel and coordinated head-neck movements during both fast and slow jaw opening–closing tasks. Jaw opening was always accompanied by head-neck extension and jaw closing by head-neck flexion. Combined movement and electromyographic recordings showed concomitant neck muscle activity during head-neck movements, indicative of an active repositioning of the head. No differences in 3D movement amplitudes could be seen with respect to speed. The head movement was 50% of the mandibular movement during jaw opening, but significantly smaller (30–40%), during the jaw closing phase. In repeated tests, the 3D movement amplitudes of the concomitant head movements were less variable during slow jaw movement and during the jaw opening phase, than during fast and jaw closing movements, suggesting speed- and phase-related differences in the mechanisms controlling the integrated mandibular and head-neck motor acts. The present results give further support to the concept of a functional trigemino-cervical coupling during jaw activities in man.     

Study of mandibular movements in mandibulectomy patients--border movements and functional movements during mastication, deglutition and speech

In mandibulectomy patients who have not undergone surgical reconstruction, the remaining mandibular segment is unstable and often deviated. Its movements have low reproducibility during mastication, deglutition and speech. The purpose of this study was to clarify three-dimensionally the differences in mandibular movements for each of these oral functions in mandibulectomy patients with and without mandibular continuity. Four mandibulectomy subjects (Group I) without mandibular continuity and three subjects (Group II) with mandibular continuity were selected. Their mandibular movements were recorded using a jaw movement tracking device with six degrees of freedom. Each movement was assessed graphically at the virtual incisor point and the rotational angles of the mandible in the frontal, sagittal and horizontal plane were analyzed. The findings were as follows; 1. In Group I, the border movements at the virtual incisor point exhibited an irregular and asymmetric envelope deviated to the resected side in the frontal plane, whereas Group II exhibited a smooth and symmetric envelope. 2. In Group I, the rotational angles in the frontal plane during border movements and mastication, in all planes during speech, and in the frontal and horizontal plane during deglutition were significantly larger than in Group II. A comparison among border and all functional movements in mandibulectomy patients revealed characteristic movements in the rotation of the mandible in the frontal plane. It is suggested that the rotational angle of the mandible is a useful parameter for assessment of mandibular movements in mandibulectomy patients.     

Is the postretention relapse of maxillary and mandibular incisor alignment related?

Previous studies suggest a poor association between initial and postretention pattern of incisor irregularity. One explanation may be that the incisor movements are limited by the boundaries provided by the incisors in the opposite arch. If so, postretention malalignment of the maxillary and mandibular incisors may be related. To test this hypothesis, long-term postretention study models of 96 patients with acceptable occlusion at the time of appliance removal were examined. The occlusal surfaces of the postretention study models were photocopied, and tooth anatomical contact points were digitized. An algorithm was used to fit the dental arch to the digitized points. The amount of incisor rotation and anatomical contact point displacement of maxillary and mandibular anterior teeth, relative to their respective dental arches, were computer generated. Overbite, the number of occlusal contact points in the anterior segment, and concavity of the lingual surfaces of the maxillary incisors were recorded manually. Statistical analyses demonstrated a significant association (P <.05) between the overall irregularity of the maxillary and mandibular incisors. The association did not differ among subgroups that were stratified according to overbite or number of occlusal contacts. No associations were found for the overall amount of incisor rotation in the 2 arches (P >.05). The amount and direction of displacement of antagonistic pairs of maxillary and mandibular central incisors were also associated (P <.05), but not the amount and direction of rotation (P >.05). The lingual configuration of the maxillary incisors did not affect the pattern of mandibular incisor malalignment.     

Relationship between condylar and incisor point displacement during habitual maximum open-close movements

SUMMARY The relationship between condylar movements and incisor point movements during habitual maximum open-close movements were studied in 10 healthy male and 10 healthy female subjects. Jaw movements were recorded by means of an opto-electronic jaw movement recording system, OKAS-3D, capable of recording the six degrees of freedom at a sample frequency of 300 Hz. The lower jaw position of the lateral pole of the condyles was found by means of palpation. In order to analyse the movements, the opening and closing path of the incisor point were divided into ten equal intervals and the corresponding condylar displacement in each interval was calculated. A displacement index was obtained by normalizing the condylar displacement with respect to the maximum condylar displacement. Due to the normalization, the displacement index is not sensitive to possible errors in the location of the lateral condylar point. A clear condylar displacement was already recorded in the first movement interval, right at the start of opening (average displacement index in the first opening interval was significantly greater than zero, P < 0.0005). The condylar displacements in the start and the end interval of opening and closing were smaller than in the intermediate movement intervals ( P < 0.00005).     

Associations between incisor and mandibular condylar movements during maximum mouth opening in humans

This study evaluated the common clinical assumption that condylar translation and mouth opening at the incisor are closely related. The sample studied comprised 27 adult females (23-35 years), selected for normal temporomandibular function, occlusion, and skeletal patterns. Condylar and mandibular central incisor movements (straight-line distances and curvilinear pathways) were recorded in three dimensions (3D) for 20 s with an optoelectric (Optotrak(R)) jaw-tracking system while each participant performed multiple maximum opening cycles. Masticatory analysis and multilevel statistical programs computed the 3D movements of the incisors and condylar hinge axis during opening and closing. The incisor point moved an average straight-line distance of 46.6 mm during opening and 45.9 mm during closing; the lengths of the opening and closing curvilinear pathways were 48.6 and 47.7 mm, respectively. The condyles moved average straight-line distances of 11.9 and 12.2 mm during opening and closing, respectively. The condyles' curvilinear pathways during opening and closing were 14 and 14.6 mm, respectively. Ranges of condylar movement varied widely between individuals. The straight-line distances and curvilinear pathways were highly correlated for the incisors (R=0.98) and the condyles (R=0.98). Neither the straight-line distances nor curvilinear pathways of the incisors were correlated with those of the condyles. Incisor straight-line distances and curvilinear pathways were moderately correlated with mandibular rotation (R(between subjects)=0.82 and R(between repeats)=0.88). During repeated openings, both condylar and incisor excursions increased, but during repeated closings only incisor excursions increased. It is concluded that (1) maximum incisor opening does not provide reliable information about condylar translation and its use as a diagnostic indicator of condylar movement should be limited, (2) healthy individuals may perform normal opening with highly variable amounts of condylar translation, (3) the straight-line distances of the incisor and condyles provide adequate information about the length of the curvilinear pathway, and (4) variation in maximum incisor opening is largely explained by variation in the amount of mandibular rotation.     

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.     

Translation and rotation of the mandible during habitual mouth opening movement in children with anterior reverse bite in the primary dentition

Translation and rotation of the mandible during habitual mouth opening movements were studied in 13 children with skeletal-based anterior reverse bite (reverse bite group) and in 13 children with normal occlusion (normal occlusion group) whose dental stage was the primary dentition. Movements were recorded by an opto-electronic movement-analyzing system that could measure mandibular movements with six degrees of freedom. Inferior translation of the mandible was analyzed at the left primary central incisor, both of the primary canines, and both of the primary second molars. Anterior translation of the mandible was analyzed at both of the condyles. Rotation of the mandible was measured in the sagittal plane. The results showed that the associations between the translation and rotation of the mandible during habitual mouth opening in the reverse bite group differed from those in the normal occlusion group. The reverse bite group had greater anterior translation of both of the condylar points than did the normal occlusion group. No significant differences were found in the inferior translation or rotation of the mandible between the two groups.     

Kinematics of the human mandible for different head postures

The influence of head posture on movement paths of the incisal point (IP) and of the mandibular condyles during free open-close movements was studied. Ten persons, without craniomandibular or cervical spine disorders, participated in the study. Open close mandibular movements were recorded with the head in five postures, viz., natural head posture, forward head posture, military posture, and lateroflexion to the right and to the left side, using the Oral Kinesiologic Analysis System (OKAS-3D). This study showed that in a military head posture, the opening movement path of the incisal point is shifted anteriorly relative to the path in a natural head posture. In a forward head posture, the movement path is shifted posteriorly whereas during lateroflexion, it deviates to the side the head has moved to. Moreover, the intra-articular distance in the temporomandibular joint during closing is smaller with the head in military posture and greater in forward head posture, as compared to the natural head posture. During lateroflexion, the intra-articular distance on the ipsilateral side is smaller. The influence of head posture upon the kinematics of the mandible is probably a manifestation of differences in mandibular loading in the different head postures.     

Biomechanics of the mandible part I: measurement of mandibular functional deformation using custom-fabricated displacement transducers.

PURPOSE: The purpose of this study was to measure corporal approximation, dorsoventral shear, and corporal rotation in edentulous subjects treated with dental implants, during normal mandibular movements. MATERIALS AND METHODS: Three patterns of jaw deformation (corporal approximation [CA], corporal rotation [CR], and dorsoventral [DV] shear) were measured using custom-fabricated displacement transducers in 12 edentulous subjects who had been treated with dental implants. Measurements were made in real time using a multichannel analogue/digital converter and a personal computer for data storage and analysis. Corporal approximation was measured as the linear change in the orientation of the 2 implants in the horizontal plane. Corporal rotation was recorded as a relative rotation of the right and left mandibular bodies projected into the frontal plane, and dorsoventral shear as the relative rotation of the 2 implants projected onto the median sagittal plane. RESULTS: All 3 patterns of mandibular deformation occurred concurrently and immediately on commencement of jaw movement. Different jaw movements produced different patterns of mandibular deformation. The highest values of jaw deformation were recorded during protrusion. CA ranged between 11.0 microm and 57.8 microm. Corporal rotation and DV shear ranged between 0.4 degrees and 2.8 degrees . CONCLUSION: This clinical study shows and measures 3 different and concurrent patterns of jaw deformation, during normal mandibular movements, using custom fabricated displacement transducers. The transducers may have a potential for routine clinical applications.     

A mathematical model of mandibular protrusion.

Mathematical expressions were derived to describe the sagittal plane movements of the mandible. It was shown that mandibular rotation during protrusion was a function of incisor and condylar guidances, initial mandibular angulation, mandibular size, and the extent of the excursion. Cusp tip displacement and center of rotation calculation algorithms were also developed for the protrusive path.     

Head motion may help mouth opening in children

Concomitant head and mandibular movement during jaw function is well known in adults; however, its importance in children has not been studied. The brain attains 85–90% of its adult weight at 5 years of age, though the maximum rate of condylar growth is attained at approximately 14 years of age. These findings suggest that the coordination of the head and mandible may differ between children and adults. This study investigated head and mandibular movements of 19 children with complete primary dentition (average age: 5 years 5 months) and compared their functional integration of jaw and head movements to those of 16 female adults (average age: 20 years 3 months) with permanent dentition. Although the mandibular opening distance was significantly greater in the adults, the magnitude of concomitant head motion was greater in children. The results suggest that head extension in children helps increase the magnitude of mouth opening more than in adult women.     

Head movement properties during voluntary rapid jaw movement in humans

The purpose of this study was to determine whether the start of the synchronized head movement during mandibular movement is evoked by the peripheral reflexes following mandibular movement (i.e. stretch or trigemino-neck reflexes), or, alternatively, is started by pre-programmed central command. Head movement accompanying voluntary rapid jaw opening movement was studied using accelerometers fixed to the upper and lower incisors, as well as electromyographs (EMGs) of the neck muscles. The direction of head acceleration at the upper incisor was towards head extension at the beginning of jaw opening movement in 89.2% of all trials, opposite to the direction of lower jaw acceleration. The onset of head acceleration was later than that of the lower jaw acceleration by averages of 6.2-10.7 ms, and the onset of electromyographic activities of the sternocleidomastoid (SCM) muscle preceded that of head acceleration by an average of 12.5-24.3 ms. These findings suggest that head movement during mandibular movement is not started by peripheral reflexes but by pre-programmed central commands. This may be relevant to muscular discomfort in the neck and shoulder regions of patients with stomatognathic disorders.     

下颌前突患者下颌支矢状劈开截骨术后髁突运动轨迹的改变

目的:研究双侧下颌支矢状劈开截骨术对下颌前突患者髁突运动轨迹的影响。方法:采用ARCUSdigma下颌三维运动轨迹描记仪,以髁突运动中心为参考点,研究30例正常受试者、14例下颌前突患者手术前后开口、前伸和左右侧向髁突运动的轨迹。用SPSSV11.0统计软件包进行配对t检验和成组t检验。结果:下颌前突患者术前、术后、正常组左侧髁突的运动轨迹与右侧基本相同,左侧髁突与右侧的开口、前伸和侧方运动范围无显著性差异(P>0.05)。术前组与正常组髁突运动轨迹差别较大,术前开口、前伸和侧方运动范围均小于正常组(P<0.05);术后与正常组髁突运动轨迹接近,术后开口、前伸和侧方运动范围与正常组无统计学差异;术前与术后组髁突运动轨迹差别较大,术前开口、前伸和侧方运动范围均显著小于术后组(P<0.05)。结论:下颌前突患者手术后,随着术后正畸治疗及咬合自我调整,建立了正常的咬合引导关系,使下颌功能运动趋向正常。