Chewing Side Research Articles

Comparative evaluation of hemispheric and masticatory laterality in complete dentures with two occlusal schemes - A prospective cohort study.

The lateralization can influence the choice of occlusion scheme, patient comfort and success of the prosthesis. The existence of favored masticatory side in complete denture patients and its influence with various occlusal schemes is less analyzed in the literature. The study objective was to compare the masticatory and hemispheric laterality in complete denture subjects rehabilitated with 2 different occlusal schemes at different time intervals. The cohort study recruited 26 patients in each group of balanced and non-balanced occlusion with definitive criteria. Conventional procedures were followed in denture fabrication. The hemispheric and masticatory laterality for all participants were established at 0,1,3- and 6-month intervals. The laterality was categorized as preferred chewing side (CPCS), predominant preferred chewing side (PPCS) and observed preferred chewing side (OPCS). The data on chewing side preference was analyzed by chi square test. (α=0.05). Right side preference was predominant in 86.1% of non-balanced and 60.1% of balanced occlusion participants. The side preference among the 2 laterality and across time interval decreased in masticatory laterality of balanced occlusion participants (P<.05) when compared to non-balanced occlusion. (P>.05). The balanced occlusion dentures had lesser masticatory side preference when compared to non-balanced occlusion complete denture.

Path pattern and movement during mastication on habitual and non-habitual chewing sides.

To clarify the presence or absence of differences in path pattern and movement during mastication between the habitual and non-habitual chewing sides. Participants were 225 healthy adults with natural dentition. Mandibular movement while chewing gummy jelly on each side was recorded, and masticatory path pattern was classified into five types (one normal and four abnormal). The frequency of each pattern was measured and compared between chewing sides. The amount, rhythm, velocity, and stability of movement and masticatory performance were measured and compared between chewing sides. A normal pattern was observed on the habitual chewing side in 84.4% of participants. There was a significant difference between chewing sides in masticatory path pattern (χ2 = 35.971, P < 0.001). Values of parameters regarding the amount and velocity of movement and masticatory performance were significantly higher on the habitual chewing side. Values of parameters regarding rhythm and stability of movement were significantly lower on the habitual chewing side. The present findings of functional differences between chewing sides in terms of path pattern and movement during mastication suggest that these factors should be analyzed on the habitual chewing side.

Does Orthodontic Treatment Change the Preferred Chewing Side of Patients with Malocclusion?

Whether orthodontic treatment can change the preferred chewing side (PCS) is unknown. This study examined (1) if the PCS changes after orthodontic treatment and (2) which factors contribute to this change. Two hundred fifty patients who visited the orthodontic clinic at Tokyo Medical and Dental University Hospital between 2017 and 2020 were included in the study. Mandibular kinesiograph (MKG) was taken at pre- and post-treatment, and PCS was determined. Patients who showed a change in PCS to the opposite side and those who showed no change in PCS at post-treatment were pooled into the PCS-changed and PCS-unchanged groups, respectively. The demographic, clinical, and cephalometric parameters were compared between the groups. Significant factors associated with changes in were of age &lt; 20 years at the beginning of orthodontic treatment (odds ratio (OR), 2.00), maximum lateral mandibular movement to PCS ≥ 10.0 mm at pre-treatment (OR, 6.51), and change in occlusal canting of ≥1.0° (OR, 2.72). The predicted probability of change in PCS was 13.2%, 36.0%, and 67.5% for no factor, one factor, and two factors associated with PCS change, respectively. Orthodontic treatment may change PCS due to patient age, maximum lateral mandibular movement to PCS, and change in occlusal canting.

Functional evaluation of jaw and suprahyoid muscle activities during chewing.

It has not yet been clarified how the type of the chewing task affects related muscle activity and how the suprahyoid muscles contribute to masticatory function in humans. This study aimed to investigate the difference in the suprahyoid muscle activity between the freely and unilaterally chewing tasks and between the working and non-working sides during chewing. Twenty healthy volunteers were instructed to chew peanuts and two different types of rice crackers in two ways: freely and unilaterally while surface electromyograms of the masseter and suprahyoid muscles were recorded. The chewing duration, number of chewing cycles and chewing rate were compared between the tasks. Furthermore, the masseter and suprahyoid muscle activities per chewing cycle were compared between the sides. The chewing duration was significantly longer, and the chewing rate was significantly higher during unilaterally chewing than freely chewing. The chewing duration differed significantly among the different foods; the harder the food, the longer the duration. Chewing rate and suprahyoid activity were significantly higher during soft rice cracker chewing. Masseter activity was higher on the chewing side than on the non-chewing side while there was no difference in suprahyoid activity between the sides. The current results demonstrate a difference in the masticatory efficacy between the chewing tasks and a functional role of the suprahyoid muscles during chewing, which does not differ between the chewing and non-chewing sides.

Relationship between age and occlusal force in adults with natural dentition.

This study aimed to clarify the relationship between age and occlusal force in adults with natural dentition. A total of 385 adults (180 males and 205 females) with natural dentition participated in this study. Subjects were asked to perform maximum clenching for approximately 3s, and the occlusal forces on both sides and habitual chewing side were calculated using a dental prescale. Regression analysis was performed by sex with occlusal forces on both sides and habitual chewing side as the dependent variable and age as the independent variable. In addition, all subjects were divided into three groups: young group (20-39years), middle group (40-59years), and old group (60years and over), and the occlusal forces on both sides and habitual chewing side were compared among the three groups. The occlusal forces did not differ from 20 to 60years old for both males and females, and the occlusal forces gradually decreased after 60years old. The curve of the polynomial equation was the most suitable. The occlusal forces on both sides and the habitual chewing side were similar in the young and middle groups, and the values of the old group were significantly smaller than those of the other two groups. From these results, it was suggested that the occlusal force of adults with natural dentition does not differ from 20 to 60years old and can be represented by a curve of a cubic polynomial, and it significantly decreases after 60years old.

Chewing side preference and laterality in patients treated with unilateral posterior implant-supported fixed partial prostheses.

It is not clear to what extent chewing is improved by unilateral oral rehabilitation with implant-supported fixed partial prostheses (ISFPPs). This study aimed to investigate whether patients treated with unilateral ISFPPs in the maxilla use their prostheses during mastication to the same extent as they used their contralateral natural teeth. A further aim was to investigate whether there is a correlation between preferred chewing side and laterality. Chewing side preference was assessed in 15 participants treated with unilateral ISFPPs in the maxilla. The first, second, third, fifth and tenth chewing cycles were assessed, and the test was repeated 10 times. All participants also answered a questionnaire about their chewing side preference. Most of the participants presented bilateral chewing, but two (13%) chewed only on the ISFPP. There was no statistically significant association between the objectively assessed chewing side and dental status (natural teeth or ISFPPs) during any of the recorded chewing cycles (p > .1). There were statistically significant correlations between both the subjectively reported usually preferred chewing side and the subjective chewing side preference during the test and the objectively assessed chewing side for the first three chewing cycles (p < .01). No correlation was found between handedness and the objectively assessed chewing side. In the present study, most participants chewed bilaterally, and chewing was performed both on the ISFPP and on the natural teeth. No correlation was found between the preferred chewing side, objectively or subjectively determined and laterality.

Mandibula processus coronoideus morfometrik parametrelerinin taraflar arası incelenmesi

Aim: In our study, the relationship between mandible coronoid process and other mandible morphometric parameters in dry bones and it is aimed to compare these data between the sides. Materials and Methods: In the anatomy laboratory, 22 mandible from the bone collection were photographed in three different ways, from right-left lateral and posterior, using a digital camera. Measurements were performed on digital images using Image J software. Morphometric parameters of coronoid process and morphometric parameters of mandible ramus and body were determined. Coronoid process types were hooked, triangular, round and square. The parameters were compared between the two sides and correlation analysis was performed. Results: There was no significant difference between the right and left sides in all parameters. There was no difference between the parties in the percent distribution of processus coronoideus types. There was a high correlation between processus coronoideus area and processus coronoideus height on both sides (p &amp;lt;0.001). Correlation values of the processus coronoideus parameters on the right side were higher than the left side. Conclusion: For the differences in the morphometric parameter values between the coronoid process between the sides, further studies should be conducted in the developmental process up to childhood, adolescence and adulthood. Furthermore, further studies are needed to evaluate the effects of chewing side preference on processus coronoideus and to assess the differences in side/gender.

Occlusal analysis of patients with chewing side preference and symptoms of temporomandibular disorders.

In this study, TeeTester digital occlusal analysis system was used to analyse the occlusal characteristics of chewing side preference (CSP) and non-CSP patients with TMD symptoms. According to the questionnaire and oral examination, 80 subjects were screened and divided into four groups: 20 CSP patients with TMD symptoms, 20 CSP patients without TMD symptoms, 20 non-CSP patients with TMD symptoms, 20 non-CSP patients without TMD symptoms. TeeTester digital occlusal system was applied to measure the occlusal characteristics in all four groups, including total contect area (TCA), total occlution force (TOF), distribution of occlusal force (DOF), asymmetric index of occlusal force (AOF), occlusal time (OT), disclusion time (DT) and center of occlusal force(COF). SPSS 25.0 was used to analyze the statistical data. At intercuspal position, the data reveals significant differences in the maximum TOF and TCA among the four groups (P<0.05). There was significant difference in the distribution of occlusal force between the preferred side and the other side of CSP patients with or without TMD symptoms (P<0.05). Among the four groups, there were statistically significant difference in the position of the center point of occlusal force, the direction of the center point of occlusal force, and the vertical distance between the center point of occlusal force and the center line (P<0.05). The COF, maximum TOF and TCA of the preferred side of dentition were significantly positive correla⁃ted with CSP (P<0.05), according to Spearman correlation analysis. However, the maximum TOF and TCA of the both side of dentition were significantly negative correlated with TMD symptoms (P<0.05). 1) The occlusal characteristics of CSP patients and non-CSP patients with TMD symptoms are different. TeeTester digital occlusal analysis system provides objective parameters for the dynamic evaluation of occlusion. 2) Among all the occlusal cha⁃racteristics, maximum TOF, TCA and COF of the preferred side of dentition were positively correlated with CSP. The abnormal occlusal characteristics (maximum TOF and TCA of the whole dentition) caused by CSP are related to TMD symptoms.

Analysis of the characteristic of clinical symptoms and cone-beam CT imaging changes in temporomandibular joint osteoarthritis patients with chewing side preference

Objective: To investigate the clinical symptoms and cone-beam CT (CBCT) imaging characteristics of temporomandibular joint osteoarthritis (TMJOA) with chewing side preference (CSP). Methods: One hundred patients with TMJOA diagnosed in the Department of Stomatology, General Hospital of the Chinese PLA from January 2018 to December 2020 were enrolled, including 32 males and 68 females, with an median age of 27.5 years (16-71 years). According to the habit of CSP, 100 cases were divided into 71 cases of TMJOA with CSP group and 29 cases of TMJOA without CSP group. The clinical symptoms were observed, including pain, TMJ sounds, limited mouth opening as well as the radiograph imaging changes of condylar bone. When analyzing the radiograph imaging changes of condylar, the cases with bilateral TMJ symptoms were excluded and the remaining cases were divided into symptomatic sides and asymptomatic sides with CSP or without CSP according to the symptoms of the chief complaint. SPSS 25.0 was used to analyze the statistical data. Age data did not conform to normal distribution so that median and quartile spacing were used for description, and Mann-Whitney U test was used for nonparametric test. Qualitative data such as gender, clinical symptoms and condylar lesion types were described by composition ratio and Chi-Square test was performed. Results: There was no statistical significance in age and gender of TMJOA patients in the group with or without CSP (P>0.05). There incidence of pain in CSP group [83.1% (59/71)] was margina uy higher than that in non-CSP group but without statistical difference[65.5% (19/29)] (χ²=3.71, P=0.054). There was also no significant difference in TMJ sounds and limitation of mandibular movement between the two groups(χ²=0.11, P=0.742; χ²=0.48, P=0.489). Among all of joints, the most common types of TMJOA were articular flattening and shortening and erosion. CBCT showed that erosion [65.0% (130/200)], flattening and shortening [73.0% (146/200)], subcortical sclerosis [42.0% (84/200)], osteophyte [30.5% (61/200)] and subcortical cystic [15.5% (31/200)]. According to the different groups of chief complaint sides, intra-group comparisons show that the proportion of erosion in symptomatic sides of CSP group [80.0% (40/50)] was significantly higher than that in asymptomatic sides of CSP group [50.0% (25/50)] (χ²=9.89, P=0.002). Inter-group comparisons show that the proportion of condyle flattening and shortening in symptomatic sides of CSP group [84.0% (42/50)] was significantly higher than that in bilateral joint of non-CSP group (8/15) (χ²=8.81, P=0.032). There was no significant difference in the proportion of subcortical sclerosis, osteophyte and subcortical cystic between the group with or without CSP (P>0.05). Conclusions: TMJOA patients with CSP may be more prone to clinical symptoms of pain and CBCT imaging changes of condyle erosion as well as flattening and shortening. CSP may be a promoting factor for the development of TMJOA.

3D Hyolingual Kinematics Reveal New Insights Into the Biomechanical and Neural Control of Chewing and Swallowing in Macaque Primates

Hyolingual kinematics are difficult to measure, but are central to hypotheses regarding musculoskeletal mechanisms and motor control. Recent application of biplanar videoradiography to the study of hyolingual kinematics in nonhuman primates provides new insight into tongue movements during chewing and swallowing, and into the role of hyoid movement in tongue base retraction and the oral phase of swallowing. During grape chewing, complex shape changes in the tongue were dominated by a combination of flexion in the tongue’s sagittal planes and roll about its long axis. As hypothesized for humans, in macaques during tongue retraction the molar region of the tongue rolls to the chewing side simultaneous with sagittal flexion, while the tongue tip flexes to the balancing side. Twisting and flexion reach their maxima early in the fast close phase of chewing cycles, positioning the food bolus between the approaching teeth prior to the power stroke. The muscular drivers of these movements are likely to include a combination of intrinsic and extrinsic tongue muscles. Nerve block of tactile sensation from trigeminal innervated oral structures decreased feeding performance, and the fast open phase of the gape cycle became significantly longer, relative to the other phases. The tongue made similar shapes in both the control and nerve block conditions, but the pattern of tongue‐jaw coordination became significantly more variable after the block. Disruption of oral somatosensation impacts feeding performance by introducing variability into the typically tight pattern of tongue‐jaw coordination. During primate swallowing, tongue base retraction (TBR) drives the food bolus across the oropharynx towards the esophagus but the mechanics of TBR are poorly understood. XROMM of four macaque monkeys falsifies both the hypothesis that extrinsic tongue muscle shortening pulls the tongue base posteriorly, and the muscular hydrostat hypothesis that intrinsic muscle shortening displaces the tongue base posteriorly by increasing tongue length. Our data suggest a novel hydraulic mechanism of TBR: shortening and rotation of suprahyoid muscles compresses the tongue between the hard palate, hyoid and mouth floor, squeezing the midline tongue base and food bolus back into the oropharynx. Hyoid elevation and protraction are powered by concentric activation and rotation of mylohyoid and digastric, followed by concentric activation of geniohyoid. This research suggests that structure, function, and coordination of mylohyoid and geniohyoid muscles are especially important determinants of swallowing performance in macaques, and probably humans.

Biomechanical properties of masticatory balance in cases with RPDs-The influence of preferred and nonpreferred chewing side: A pilot study.

ObjectivesRemovable partial dentures (RPDs) are inserted with the aim to restore masticatory function. There is however inconsistent evidence supporting the alleged improvements, posterior occlusal contacts being one of the decisive factors. We hypothesized that the distribution of abutment teeth in RPDs influences masticatory performance and functional parameters. To evaluate the masticatory performance and functional parameters in patients with a RPD using a single mathematical parameter (tilting index [TI]) for both jaws that predicts biomechanical behavior on the basis of the distribution of abutment teeth.Materials and MethodsMasticatory performance was measured in patients wearing long‐time adapted RPDs using the standardized test food optocal, yielding the mean particle size (X 50). Mastication on the preferred and nonpreferred chewing sides was analyzed. Total muscle work (TMW) was calculated using bipolar electromyographic recordings of the masseter and anterior temporalis muscle. Functional parameters were subjected to multiple linear regression analysis including X 50 as a dependent variable and functional units (FU), the number of teeth, bite forces, and sagittal and frontal components of TI (TI α and TI β) as independent variables.ResultsWhen the preferred chewing side was tested, none of the investigated parameters correlated significantly with X 50. In contrast, chewing on the nonpreferred side was correlated significantly with performance for most variables (p < .05). This means that increased dental support improved chewing performance with RPDs under these conditions.ConclusionsIn well‐adapted RPDs, the distribution of abutment teeth as expressed by the tilting index seems to be of subordinate importance for masticatory performance.

On Muscular Factor Question in the Correction of Transversal Incisor Occlusion

The aim of our study was to evaluate the role of the muscle factor and the effectiveness of manual treatment of masticatory muscle dysfunction in patients with transversal incisor occlusion (TIO). Methods and Results: We examined and treated 35 patients aged 18-25 years with clinical signs of TIO in the clinic of orthopedic dentistry. Diagnostic methods for TIO included an interview, face and oral cavity examination, and clinical functional tests. Occlusion was assessed using anthropometric measurements and examination of plaster jaw models in an articulator for additional diagnostics of the dental factor; a radiological method (jaw orthopantomography with the inclusion of articular joints) was also used for the articular factor diagnostics and examination of masticatory muscles and neck muscles. The treatment methods included manual treatment of masticatory muscle dysfunction: "myofascial trigger point release technique," "stretching-push," and "post-isometric relaxation." All patients' complaints were mainly confined to improper occlusion of the front teeth, namely, a misalignment of the centerline between the upper and lower anterior teeth. Moreover, 71.4% of patients noted intermittent clicking in one or both articular joints of the temporomandibular joint, 42.8% of patients reported pain in the region of one temporomandibular joint, 28.6% of patients noted noise in the ear of the same joint, as well as discomfort while chewing. On external examination, all patients had a slight asymmetry of the lips and cheeks on the habitual chewing side. The apex of the chin was positioned slightly to the side relative to the facial midline. All patients had a disturbed movement trajectory of the lower jaw. During mouth opening, the lower jaw trajectory changed relative to the facial midline: at first, it was straight, for a very short period, and then it deviated sideways, after which it returned to the center. There was a misalignment of the central line of the lower dentition relative to the midline of the face in the anterior region. The radiological picture showed signs of articular joint dysfunction: difference in the size of the articular gaps on the right and left sides. After a single session of manual treatment of masticatory muscles, all patients noted that the improper occlusion of the front teeth was corrected, pain and clicking sensations in the TMJ disappeared in 42.8% of patients, and pain disappeared in the area of one joint, along with noise in the ears and chewing discomfort. Headache in the parietal and temporal areas disappeared. The trajectory of lower jaw movements during mouth opening normalized in all patients after the performed manual treatment. Conclusion: We can conclude that when diagnosing and treating occlusal disorders, it is necessary to pay attention not only to the position of the teeth and the TMJ elements, but also to the muscular factor – the condition of the masticatory muscles. Special attention should be paid to the condition of the lateral wing muscles.

Macaques get their tongues in a twist

Primates chew their food on one side of their mouth. Try it with a sandwich: take a bite, and immediately the piece of food will be ushered to the left or right cheek teeth. This action occurs when the jaws open up and happens because of one mysterious and versatile structure – the tongue. Whilst it is easy to see the action of the upper and lower jaw when we eat, it is far harder to know how the motion of the tongue simultaneously pushes food around, as it's encased by the flesh and bone of our heads. So far, some have theorised what might be happening, but no one has yet been able to see the motion of the tongue in three dimensions.Kara Feilich and Callum Ross from the University of Chicago, USA, wanted to know how primates use their tongue during eating. Together with their colleagues Jeffrey Laurence-Chasen (University of Chicago, USA), Courteny Orsbon (University of Vermont Medical Center, USA) and Nicholas Gidmark (Knox College, USA), Feilich and Ross set out to shed light on how the tongue moves during the ingestion of food. They trained four rhesus macaques to sit and eat grapes whilst being filmed using a three-dimensional x-ray system. This allowed the researchers to see inside the mouth whilst the macaques ate their grapes, to figure out how the tongue makes its twists and turns.Feilich found that the bending of the tongue was in synchrony with the opening–closing motion of the jaws. After biting down on the grapes, the jaws opened whilst the body of the tongue pushed the food sideways by rolling to one side, feeding it between the upper and lower cheek teeth – all ready to be chewed. You'll be aware of doing the same thing, perhaps even more so when it goes wrong. If you've ever bitten your tongue during eating, chances are you've over-enthusiastically squashed your own tongue into your gnashing teeth.Analysing the tongue's manoeuvres, Feilich and colleagues realised that the tongue bending came about by asymmetrical changes along its length. Whilst the tongue rolled towards the chewing side, it simultaneously bent itself away, so that the tip pointed to the opposite side – perhaps to avoid the pain of being chewed on. Feilich pondered how the tongue contorts itself into these complex shapes. Assuming that the tongue keeps a constant volume, asymmetrical muscle contractions could produce the tongue-twisting shapes demonstrated by the macaques.Primates’ lingual dexterity assists in other functions too, such as vocalisation and grooming. But despite this varied repertoire, Feilich and colleagues found that tongue motion during eating was remarkably consistent, which hints that this pattern is important for primates in general, you and I included. Irrespective of the occasional masticatory mistake, Feilich and colleagues revealed the tongue's twisting role in shifting food, which can be further studied by medical colleagues to help patients recovering from tongue damage and neuromuscular disorders.

Correlation Between Unilateral Free End Edentulous and Morphological Variations of Condyle Using Panoramic Radiographs

Background: Unilateral free end edentulous can cause a habit of one side chewing which will affect the condition of the temporomandibular joint (TMJ) mechanism. The TMJ is a complex joint consisting of the glenoid fossa, mandibular condyle and disc articular. No previous studies have examined the correlation between free end edentulous and morphological variations in the mandibular condyles. Purpose: to determine the correlation between unilateral free end edentulous and morphological variations of condyle using panoramic radiographs at South Sumatera RSKGM. Methods: This analytic observational study was using 68 samples of panoramic radiographs at RSKGM South Sumatra in September 2019 - March 2020. The sample was divided into 34 unilateral free end edentulous and 34 complete teeth. The condyle morphology of each sample was traced, and the data obtained were analyzed using the Chi-square method in the SPSS application. Results: Morphological abnormalities of the condyles were more frequently seen in patients with unilateral free end edentulous conditions, that is 41.18%. While in patients with complete teeth, the visible abnormalities of the condyles was only 5.88%. There was a significant correlation between unilateral free end edentulous and morphological variations of mandibular condyles (p&lt;0.005). Conclusion: There is a correlation between unilateral free end edentulous and morphological variations of condyle using panoramic radiographs in Dental Hospital of South Sumatera Province.

Facial asymmetry tracks genetic diversity among Gorilla subspecies.

Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from three Gorilla subspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes.

A comparative study of condyle position in temporomandibular disorder patients with chewing side preference using cone-beam computed tomography.

Chewing side preference (CSP) could cause structural and morphological changes of temporomandibular joint (TMJ) and has been suggested as one aetiology of temporomandibular disorders (TMDs), but the condylar position in TMD patients with CSP is unknown. To compare the condylar position in the TMD patients with and without CSP. Ninety TMD patients with unilateral symptom (69 with CSP and 21 without CSP) and 20 asymptomatic participants received cone-beam computed tomography. The condylar position was determined based on the measurements of sagittal joint spaces. Intergroup and intra-group comparisons of the condylar position were performed. The condyles in asymptomatic participants located nearly randomly in anterior, centric and posterior positions. Patients without CSP had significantly more posterior condyles than asymptomatic participants (57.1% vs 30.0%, p<0.05). In patients with CSP, 50.7% of the condyles on the preferred chewing side and 42.0% on the unpreferred side located posteriorly, reaching no significant level compared with the asymptomatic participants and patients without CSP (p>0.05). The symptomatic joints and asymptomatic joints in patients with CSP and without CSP showed no significant differences in condylar position. While patients without CSP had significantly more posterior condyles in symptomatic joints than asymptomatic participants (p<0.05), patients with CSP showed a trend towards more posterior condyles in symptomatic joints compared with the asymptomatic participants (53.6% vs 30.0%, p=0.054). Condylar position is not a strong indicator to differentiate CSP-related TMDs from non-CSP-related TMDs. Posterior condyle could not be viewed as one indicator of TMD.

Evaluation of the correlation between unilateral chewing and postural deviations

The objective of this study is to describe the head posture and postural deviations in individuals with unilateral chewing. The sample was composed of 31 individuals of both sexes aged between 7 and 17 years old, who presented median line deviation and predominant unilateral mastication. The evaluation was made by three professionals (a speech therapist, a physiotherapist and a dentist) through a postural exam, where the patient is placed on a symmetrograph in an erect position: the head in position of repose, eyes fixed on the horizon, arms along the body, and feet physiologically positioned. Each patient was analyzed under frontal, sagittal, and lateral planes, in search for an eventual lateral deviation of the spine. Additionally, the posture was analyzed in photographs and videos, where body movement was recorded. After clinical analyses, a segmenting radiographic study of the spinal column was conducted. Results showed a high prevalence of head rotation towards the chewing side and lateral flexion towards the opposite side. Also, forward head posture (anteroposition) and scoliotic attitude were found. The X-rays confirmed a high prevalence of scoliosis with no association to the chewing side. The data suggest that children and adolescents with unilateral mastication present some postural deviation.

Twist and chew: three-dimensional tongue kinematics during chewing in macaque primates.

Three-dimensional (3D) tongue movements are central to performance of feeding functions by mammals and other tetrapods, but 3D tongue kinematics during feeding are poorly understood. Tongue kinematics were recorded during grape chewing by macaque primates using biplanar videoradiography. Complex shape changes in the tongue during chewing are dominated by a combination of flexion in the tongue's sagittal planes and roll about its long axis. As hypothesized for humans, in macaques during tongue retraction, the middle (molar region) of the tongue rolls to the chewing (working) side simultaneous with sagittal flexion, while the tongue tip flexes to the other (balancing) side. Twisting and flexion reach their maxima early in the fast close phase of chewing cycles, positioning the food bolus between the approaching teeth prior to the power stroke. Although 3D tongue kinematics undoubtedly vary with food type, the mechanical role of this movement—placing the food bolus on the post-canine teeth for breakdown—is likely to be a powerful constraint on tongue kinematics during this phase of the chewing cycle. The muscular drivers of these movements are likely to include a combination of intrinsic and extrinsic tongue muscles.

Fracture Fixation Technique and Chewing Side Impact Jaw Mechanics in Mandible Fracture Repair.

ABSTRACTLower jaw (mandible) fractures significantly impact patient health and well‐being due to pain and difficulty eating, but the best technique for repairing the most common subtype—angle fractures—and rehabilitating mastication is unknown. Our study is the first to use realistic in silico simulation of chewing to quantify the effects of Champy and biplanar techniques of angle fracture fixation. We show that more rigid, biplanar fixation results in lower strain magnitudes in the miniplates, the bone around the screws, and in the fracture zone, and that the mandibular strain regime approximates the unfractured condition. Importantly, the strain regime in the fracture zone is affected by chewing laterality, suggesting that both fixation type and the patient's post‐fixation masticatory pattern—ipsi‐ or contralateral to the fracture— impact the bone healing environment. Our study calls for further investigation of the impact of fixation technique on chewing behavior. Research that combines in vivo and in silico approaches can link jaw mechanics to bone healing and yield more definitive recommendations for fixation, hardware, and postoperative rehabilitation to improve outcomes. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Facial asymmetry and chewing sides in twins

Objective To resolve how the preferred chewing side (PCS) affects facial asymmetry in twins, whether there are differences between monozygotic (MZ) and dizygotic (DZ) twins, and whether the twins with PCS have more asymmetric faces compared to symmetrically chewing twins. Material and methods The study included 106 Lithuanian twin pairs of the same sex, 59 MZ and 47 DZ pairs. The data were analysed from facial 3D images and manually added landmarks. 3D images were analysed by Rapidform2006 software and statistical analyses were done by using the R software environment version 4.1.0. Results The contralateral effect of PCS and larger chin side was dominant among right and non-right side chewing twins. Being female increased the whole face symmetry. Conclusion The volume of the chin becomes larger on the side opposite to the twins’ habitual chewing side. As the results are quite similar in both twin types, functional factors are more prominent than heredity.