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PubMed1988

Morphological and videofluorographic study of the hyoid apparatus and its function in the rabbit (Oryctolagus cuniculus).

The anatomy of the hyoid apparatus and positional changes of the hyoid bone during mastication and deglutition are described in the New Zealand White rabbit (Oryctolagus cuniculus). A testable model is constructed to predict the range of movement during function of the hyoid, a bone entirely suspended by soft tissue. Frame-by-frame analysis of a videofluorographic tape confirms the accuracy of the prediction through observation of hyoid bone excursion during oral behavior. During chewing, translation of the hyoid bone is diminutive and irregular, lacking a clearly discernible path of excursion. However, some movements of the hyoid occur with regularity. During fast opening, anterodorsal movement of the hyoid is interrupted with an abrupt posteroventral depression when the bolus is moved posteriorly toward the cheek teeth by the tongue. This clockwise rotation (when viewed from the right side) of the hyoid accompanies jaw opening and is reversed (posteroventral movement) for the jaw closing sequence. Lateral movements of the hyoid may be slightly coupled to mandibular rotation in the horizontal plane. The findings suggest that the hyoid bone maintains a relatively static position during the dynamics of chewing. The primary function would be to provide a stable base for the movements of the tongue. Another possible function would be to control the position of the larynx within the pharyngeal cavity. Some characteristic features of the rabbit hyoid apparatus may be consequential to relatively erect posture and a saltatory mode of locomotion.

Animals↗
PubMed1990

Videofluorographic analysis of tongue movement in the rabbit (Oryctolagus cuniculus).

The movement of the entire tongue and intermolar eminence during mastication is described in the domestic rabbit (Oryctolagus cuniculus). Tongue movement and jaw position were analyzed videofluorographically from separate lateral and dorso-ventral views in six rabbits. Metallic markers were inserted into the tongue so that its movement was visible on the fluorographic image. Frame-by-frame analysis of the videofluorographic tape recordings demonstrates that tongue movement in all animals was identical in direction during each part of the chewing cycle. In the lateral view the forepart of the tongue moves down and forward during the opening stroke, whereas the intermolar eminence moves up and forward to appose the palate. During the closing stroke, as the tip of the tongue moves up and back, the intermolar eminence lowers from the palate and retracts. During the power stroke the forepart of the tongue is at its most elevated and retruded position, while the intermolar eminence is its lowest and most retruded. The dorso-ventral view showed that lateral movement of the tongue and mandible are highly synchronous. The intermolar eminence decreases in width during the power stroke, possibly twisting to place or keep food on the teeth. An anterior to posterior undulating movement of the entire tongue occurs throughout the chewing cycle. As the intermolar eminence elevates to appose the palate during the opening stroke, it may replace the bolus on the teeth on the chewing side. The intermolar eminence also appears to be twisting during the closing and power strokes to place or maintain food on the teeth.

Animals↗
PubMed1995

Incisal biting in the mountain beaver (Aplodontia rufa) and woodchuck (Marmota monax).

Analysis of synchronously recorded cine-radiographs and electromyograms in two rodents (Aplodontia rufa and Marmota monax) demonstrates that jaw movements and muscle activities during incisal functions are distinctly different from those found during mastication. Movements during incisal biting are primarily along the midline, accompanied by symmetrical activity of the jaw adductor muscles. Most biting cycles do not end in contact between upper and lower incisors. When contact does occur, the lower incisors are dragged along the lingual surfaces of the upper incisors. Cropping, or tip-to-tip occlusion of upper and lower incisors, was not observed. Sharpening of the lower incisors, a behavior which may be unique to the Rodentia, was recorded in both A. rufa and M. monax. During sharpening, the lingual surface of the lower incisor is dragged across the tip of the upper incisor producing a lingual wear facet. Like incisal biting, sharpening movements are primarily confined to the midline, although there may be lateral movements in some sharpening cycles. Sharpening cycles are among the most rapid cyclic movements recorded in mammals, as the mean frequencies of sharpening are 11 cycles/s in A. rufa and 8 cycles/s in M. monax.

Animals↗
PubMed2001

Biomechanical scaling of the hominoid mandibular symphysis.

Experimental investigation of mandibular bone strain in cercopithecine primates has established that the mandible is bent in the transverse plane during the power stroke of mastication. Additional comparative work also supports the assumption that the morphology of the mandibular symphysis is functionally linked to the biomechanics of lateral transverse bending, or "wishboning" of the mandibular corpus. There are currently no experimental data to verify that lateral transverse bending constitutes an important loading regime among hominoid primates. There are, however, allometric models from cercopithecoid primates that allow prediction of scaling patterns in hominoid mandibular dimensions that would be consistent with a mechanical environment that includes wishboning as a significant component. This study uses computed tomography (CT) scans to visualize cortical bone distribution in the anterior corpus of a sample of four genera of extant hominoids. From the cortical bone contours, area properties of the mandibular symphysis are calculated, and these variables are subjected to an allometric analysis to detect whether scaling of jaw dimensions are consistent with a wishboning loading regime. Scaling of the hominoid symphysis recalls patterns observed in cercopithecoid monkeys, which lends indirect support for the hypothesis that wishboning is an integral part of the masticatory loading environment in living apes. Inclination of the symphysis, rather than changes in cross-sectional shape or development of the superior transverse torus, represents a morphological solution for minimizing the potentially harmful effects of wishboning in the jaws of these primates.

Animals↗
PubMed2006

Complete rehabilitation of the mandible following segmental resection.

Segmental resection of the mandible leads to significant patient morbidity. Loss of mandibular support to the teeth, tongue and lip causes dysfunctional mastication, swallowing, speech, airway protection and oral competence. Patients also suffer disfigurement following segmental mandibulectomy because the mandible is an important aesthetic landmark. The degrees to which dysfunction and disfigurement occur depend both on the location of the mandibular segment removed and the amount of surrounding soft tissue excised. Between January 1985 and December 2004, 780 fibula osteoseptocutaneous flaps have been used for head and neck reconstruction at the Chang Gung Memorial Hospital, Taiwan. The fibula flap has proven to be the bony flap of choice because it has a lengthy bicortical segment of bone available, a reasonably long vascular pedicle, large diameter vessels, good bone quality, and is easily contoured with multiple osteotomies. The flap can be harvested while ablation is being performed. In addition, a reliable, mobile, thin skin component can always be included to address the soft tissue reconstructive requirements. A chimeric design employing a portion of the soleus muscle can provide further reconstructive options. Ideally complete rehabilitation of the mandible involves placement of titanium osseointegrated implants, which allow dental restoration. Primary placement of implants is preferred in patients without cancer. Selection of candidates to receive osseointegrated implants is paramount. The temporomandibular joint remains a challenge to reconstruct adequately.

Bone Transplantation↗
PubMed2005

Chewing pattern in patients with Meige's syndrome.

Meige's syndrome presents with a combination of upper and lower facial motor dysfunction, including eye closing spasms and oromandibular dystonia. While the pathophysiology of eye closing spasms has been extensively studied using the blink reflex and other trigeminofacial reflexes, very few studies have been carried out with regard to the abnormal perioral movements. We hypothesized that action-related dystonic features could be revealed by the analysis of the semiautomatic rhythmic movements required for chewing and swallowing. A total of 7 patients with Meige's syndrome that complained of chewing problems and 7 age-matched healthy volunteers were studied. Subjects were instructed to munch and swallow a small muffin while surface electromyographic (EMG) activity of masseter (MAS) and orbicularis oris (OOr) of the dominant side was recorded. In healthy subjects, MAS and OOr showed a rhythmic alternating phasic EMG pattern during chewing, which changed to a tonic cocontraction of both muscles during swallowing. Mean duration of MAS and OOr EMG bursts was, respectively, 297 +/- 28 msec and 328 +/- 29 msec. Patients exhibited the following alterations: excess duration of muscle activity, frequent cocontraction, loss of rhythmicity during chewing, and abnormalities in the chewing to swallowing transition phase. These abnormalities, similar in type to those encountered in other forms of focal dystonia, may be the expression of an abnormal motor control of basal ganglia over mastication-related movement pattern generators of the brainstem.

Aged↗
PubMed1993

Inverse masticatory muscle activity due to syringobulbia.

The clinical, radiological, and electrophysiological data of a 25-year-old woman with "inverse masticatory muscle activity" due to syringobulbia is presented. This uncommon brain stem syndrome may be due to a disturbance in central programming of mastication.

Adult↗
PubMed2003

Biological activity of some naturally occurring resins, gums and pigments against in vitro LDL oxidation.

Naturally occurring gums and resins with beneficial pharmaceutical and nutraceutical properties were tested for their possible protective effect against copper-induced LDL oxidation in vitro. Chiosmastic gum (CMG) (Pistacia lentiscus var. Chia resin) was the most effective in protecting human LDL from oxidation. The minimum and maximum doses for the saturation phenomena of inhibition of LDL oxidation were 2.5 mg and 50 mg CMG (75.3% and 99.9%, respectively). The methanol/water extract of CMG was the most effective compared with other solvent combinations. CMG when fractionated in order to determine a structure-activity relationship showed that the total mastic essential oil, collofonium-like residue and acidic fractions of CMG exhibited a high protective activity ranging from 65.0% to 77.8%. The other natural gums and resins (CMG resin 'liquid collection', P. terebinthus var. Chia resin, dammar resin, acacia gum, tragacanth gum, storax gum) also tested as above, showed 27.0%-78.8% of the maximum LDL protection. The other naturally occurring substances, i.e. triterpenes (amyrin, oleanolic acid, ursolic acid, lupeol, 18-a-glycyrrhetinic acid) and hydroxynaphthoquinones (naphthazarin, shikonin and alkannin) showed 53.5%-78.8% and 27.0%-64.1% LDL protective activity, respectively. The combination effects (68.7%-76.2% LDL protection) of ursolic-, oleanolic- and ursodeoxycholic- acids were almost equal to the effect (75.3%) of the CMG extract in comparable doses.

Cholesterol, LDL↗
PubMed1997

Occlusal forces and mandibular bone strain: is the primate jaw "overdesigned"?

Finite element modelling of the function of the periodontium and surrounding alveolar bone suggests these tissues are subjected to unusually large strains in comparison with the bone of the basal mandibular corpus. These studies, in addition to certain experimental investigations, have led to the suggestion that the strains experienced in the basal mandibular corpus are not functionally important. Under this view, size and shape of the basal corpus are not functionally linked to masticatory forces. Since previous comparative investigations have been premised on the assumption that masticatory strains in the basal corpus are functionally important, the assertion that masticatory stresses are concentrated primarily in the alveolar process undermines the credibility of this body of work. The hypothesis that the biomechanical effects of masticatory forces are localized in the alveolar process can be evaluated by reference to a number of bone strain investigations, as well as through consideration of current understanding of bone biology and behavior. Experimental studies indicate that the effects of occlusal forces during mastication are quite apparent in alveolar bone, although relatively large strains are also observed in regions well-removed from a loaded alveolus. It is also apparent that both alveolar and basal mandibular bone are subject to bending and twisting strains associated not only with occlusal forces, but also with muscular and condylar reaction forces. The result is that strain levels in alveolar vs. basal bone may be roughly similar, in contradiction to some published theoretical models. Based on empirical evidence and theoretical considerations, it is premature to conclude that mandibular corpus size and shape are not functionally linked to the biomechanics of chewing and biting.

Animals↗
PubMed2001

Diets of fossil primates from the Fayum Depression of Egypt: a quantitative analysis of molar shearing.

Over the last 90 years, Eocene and Oligocene aged sediments in the Fayum Depression of Egypt have yielded at least 17 genera of fossil primates. However, of this diverse sample the diets of only four early Oligocene anthropoid genera have been previously studied using quantitative methods. Here we present dietary assessments for 11 additional Fayum primate genera based on the analysis of body mass and molar shearing crest development. These studies reveal that all late Eocene Fayum anthropoids were probably frugivorous despite marked subfamilial differences in dental morphology. By contrast, late Eocene Fayum prosimians demonstrated remarkable dietary diversity, including specialized insectivory (Anchomomys), generalized frugivory (Plesiopithecus), frugivory+insectivory (Wadilemur), and strict folivory (Aframonius). This evidence that sympatric prosimians and early anthropoids jointly occupied frugivorous niches during the late Eocene reinforces the hypothesis that changes in diet did not form the primary ecological impetus for the origin of the Anthropoidea. Early Oligocene Fayum localities differ from late Eocene Fayum localities in lacking large-bodied frugivorous and folivorous prosimians, and may document the first appearance of primate communities with trophic structures like those of extant primate communities in continental Africa. A similar change in primate community structure during the Eocene-Oligocene transition is not evident in the Asian fossil record. Putative large anthropoids from the Eocene of Asia, such as Amphipithecus mogaungensis, Pondaungia cotteri, and Siamopithecus eocaenus, share with early Oligocene Fayum anthropoids derived features of molar anatomy related to an emphasis on crushing and grinding during mastication. However, these dental specializations are not seen in late Eocene Fayum anthropoids that are broadly ancestral to the later-occurring anthropoids of the Fayum's upper sequence. This lack of resemblance to undisputed Eocene African anthropoids suggests that the "progressive" anthropoid-like dental features of some large-bodied Eocene Asian primates may be the result of dietary convergence rather than close phyletic affinity with the Anthropoidea.

Animals↗
PubMed1990

A new model for calculating muscle forces from electromyograms.

A muscle model is described that uses electromyogram (EMG), muscle length and speed of contraction to predict muscle force. Physiological parameters are the Hill constants and the shape of the twitch response to a single stimulus. The model was incorporated in a jaw model of the rabbit and tested by predicting the bite force produced by the jaw muscles during mastication. The time course of the calculated force appeared to match the bite force, measured in vivo by a strain gauge, applied to the bone below the teeth. The variation in peak strain amplitude from cycle to cycle correlated with the variation predicted by the model. The peak amplitude of the integrated EMGs of individual jaw muscles showed an average correlation with peak strain of 0.41. Use of the sum of the available peak amplitudes, weighted according to their effect upon the bite force increased the correlation to 0.46; the model predicted bite forces showed a correlation of 0.57 with the strain. The increase in correlation was statistically significant. The muscle forces were calculated using a minimum number of easily obtainable constants.

Animals↗
PubMed1996

Prepharyngeal dysphagia in Parkinson's disease.

Dysphagia in patients with Parkinson's disease (PD) is most often attributed to pharyngeoesophageal motor abnormalities. In our study of patients with idiopathic PD, attention was focused on prepharyngeal symptoms and motor functions. Using the Hoehn and Yahr disease severity scale, patients were grouped into those with mild/moderate disease [subgroup I (n = 38)] and those with advanced disease [subgroup II (n = 34)]. Dysphagia symptoms were present in 82% of all patients, but subgroup I patients voiced significantly more complaints. Conversely, many prepharyngeal abnormalities of ingestion, including jaw rigidity, impaired head and neck posture during meals, upper extremity dysmotility, impulsive feeding behavior, impaired amount regulation, and lingual transfer movements were statistically more frequent in subgroup II patients. Impaired mastication and oral preparatory lingual movements were the most common aberrations observed during dynamic videofluoroscopy (48/71), with most patients being concordant for both. The motor disturbances of ingestion reported herein reflect the disintegration of volitional and automatic movements caused by PD-related akinesia, bradykinesia, and rigidity.

Aged↗
PubMed1996

Flavour release from rehydrated french beans (Phaseolus vulgaris) influenced by composition and volume of artificial saliva.

Influence of saliva composition and volume on flavour release from rehydrated French beans (Phaseolus vulgaris) was studied in three types of mouth model systems; dynamic headspace (DH), dynamic headspace and mastication (DHM) and a purge-and-trap (PT) model system. Volatile compounds were analysed by gas chromatography, using flame ionization detection (FID), mass spectrometry and sniffing port detection. Areas of FID peaks were largest in the PT system, followed by those of the DHM and DH systems, respectively. Saliva composition as well as volume influenced the release of volatile compounds from rehydrated French beans. Generally, FID data showed a decrease in release by the saliva component mucin, because of interactions between volatile compounds and protein, and in increase in release by its alpha-amylase, probably due to degradation of inclusion complexes of starch. The decrease in flavour release by the enlarged saliva volume was evaluated by a model study. Sniffing patterns of odour active compounds were barely influenced by either saliva composition or volume.

Chromatography, Gas↗
PubMed1989

[The effect on chewing of treating distal bite with an activator].

The aim of this study was to analyse the influence of activator treatment on chewing efficiency. The subject material consisted of 60 children, adolescents and adults: Twelve children (ten years of age) with a Class II, Division 1 malocclusion were treated successfully with activators to a normal occlusion (16 years of age). Three normal occlusion samples, ten years (n = 12), 16 years (n = 12) and 29 years (n = 12) of age as well as an untreated Class II sample (n = 12), 16 years of age, served as control groups to the activator patients. The chewing ability was evaluated with the aid of a chewing efficiency test. The dental occlusion was appraised on dental casts. Recordings were made of number of erupted teeth, number of intermaxillary occlusal tooth contacts, overjet and overbite. The results revealed that chewing efficiency in activator patients was doubled from ten to 16 years of age. When comparing untreated subjects 16 years and ten years of age a greater chewing efficiency was seen in the older subjects. This was true for both Class II malocclusion and normal occlusion cases. Furthermore, in 16 year old subjects the chewing efficiency was comparable in treated and untreated normal occlusions as well as untreated Class II malocclusions. Thus, the investigation did not ascertain whether activator treatment per se resulted in an improved chewing efficiency. Furthermore, in the activator group no direct association existed between improvement in chewing efficiency and increased number of erupted teeth on one hand and increased number of intermaxillary occlusal tooth contacts, reduced overjet and overbite on the other. It is suggested that chewing efficiency is partly age related. The sagittal intermaxillary dental arch relationship doesn't seem to play an important role in determining chewing ability. However, harmonious interplay between the occluding teeth and the muscles influencing them (the muscles of mastication, the tongue-, lip- and cheek-musculature) is certainly of importance.

Activator Appliances↗
PubMed1998

Functional oral-motor skills: Do they change with age?

Dysphagia, a difficulty eating or drinking, appears to increase with age and is a concern for our growing elderly population. Mastication, tongue mobility, and lip closure are skills of the oral phase of ingestion, and have been shown to deteriorate with age. However, it is not clear whether these changes affect functional feeding. It is also unclear whether dysphagia is the result of the aging process itself, or whether it is secondary to disease. Therefore, the purpose of this study was to identify changes during the oral phase of ingestion in a group of healthy seniors. Functional feeding skills and oral praxis abilities were measured in 79 healthy adults aged 60-97 years. The Modified Functional Feeding Assessment (FFAm) subscale of the Multidisciplinary Feeding Profile (MFP) and the Oral Praxis Subtest (OPS) of the Southern California Sensory Integration Test were administered respectively. An interview followed to obtain information on denture wear, use of hearing aids and glasses, and types of foods avoided. Seniors maintained functional feeding skills throughout the four decades studied. These skills were not age-dependent, but depended on whether or not subjects wore full dentures. Even though all of the seniors maintained functional feeding skills, more seniors in the younger group (7th decade 60%, 8th decade 67%) had difficulty with a variety of food textures such as soft, hard, fibrous, and some with tough skins, than the older group (9th decade 40%, 10th decade 44%). Oral praxis abilities were correlated significantly with age, but not with hearing aid use. Overall, healthy seniors maintained their functional feeding and oral praxis skills. Good health and natural dentition appear to be excellent indicators for functional feeding ability.

Aged↗
PubMed2003

Oral comfort, function and hygiene in patients with lingual brackets. A prospective longitudinal study.

BACKGROUND: Oral comfort, speech, mastication and swallowing, as well as oral hygiene were to be evaluated in a prospective longitudinal study before and after insertion of lingual brackets. PATIENTS AND METHOD: 22 patients (five male, 17 female, mean age 34.7 years, SD 10.4) were enrolled in the study and filled in a standardized questionnaire directly before placement of lingual brackets (T0), within 24 hours thereafter (T1), and 3 months (+/- 1 week) later (T2). At both T1 and T2, treatment was confined to the upper arch. RESULTS: In comparison with T0, significantly poorer results were recorded at T2 for the parameters "restriction of the tongue space", "lesions to the tongue", "tongue position", "subjective and semiobjective rating of articulation", "chewing", "biting" and "oral hygiene", although significant improvements, i.e. adaptations, had been recorded from T1 to T2 with the exception of the parameters "tongue space", "tongue position", "chewing", "biting" and "oral hygiene". At none of the registration timepoints was fluid intake impaired by the lingual brackets. CONCLUSION: The results of the present study suggest that detailed briefing on the extent and duration of potential impairments in oral comfort, functions and hygiene is advisable prior to the insertion of lingual brackets.

Adult↗
PubMed2003

Decelerating and sex-dependent tooth wear in Norwegian red deer.

In ungulates, tooth wear is often suggested as a proximate cause of senescence. Tooth wear is expected to be sex-dependent since energetic requirements and food selection varies largely between sexes in sexually dimorphic ungulates. Furthermore, tooth wear may lower mastication efficiency, and we predict a negative correlation between tooth wear and body weight or condition. We tested these predictions on data on tooth wear (estimated as height of first molar) of 1,311 male and 1,348 female red deer ( Cervus elaphus) aged 3-25 years and harvested along the west coast of Norway. The rate of tooth wear decreased with age. Males wear teeth at a higher rate (from 0.61 mm/year in 4-year olds to 0.45 mm/year in 11-year olds) than females (from 0.52 mm/year in 4-year olds to 0.39 mm/year in 11-year olds). Molar height correlated positively with body weight in both sexes, but not after adjusting for body size. Molar height was strongly dependent on body size in 3-year-old individuals (when tooth wear is minimal). Earlier reports in the literature of a positive correlation between tooth height and body weight may therefore be due to initial size differences rather than differences in condition due to tooth wear.

Aging↗
PubMed2003

Masticatory and nutritional aspects on fixed and removable partial dentures.

The aim of the present study was to evaluate mastication, food selection and nutritional aspects in two groups of persons restored with fixed (FPD, N=44) and removable (RPD, N=40) partial dentures respectively. The subjects were part of a cohort study of 67-68-year-old men living in Malmö, Sweden. The two groups were very similar regarding social factors and the inclusion criteria were chosen so that the groups were very equal regarding oral factors, apart from the difference in fixed and removable partial dentures. The number of natural teeth, number of replaced teeth and occlusal contacts did not differ significantly between the two groups, nor did the distribution of maxillary and mandibular dentures. A comprehensive examination of several general health factors included a home interview of dietary habits. A clinical examination included a 20-minute oral examination with registration of number of teeth, FPDs, RPDs, and occlusal contacts. It also included masticatory tests: chewing gum colour mixing, chewing gum bolus shaping, and swallowing threshold (number of strokes to the first swallow of an almond). The consumption of hard and soft foods was revealed by the dietary interview as well as the intake of energy and some nutrients. There was a significant difference between the groups regarding the capacity to mix the two-coloured chewing gum, to shape the chewing gum bolus and in the consumption of hard foods. There was no difference in the swallowing threshold and the consumption of soft foods. The intake of energy and nutrients did not differ significantly between the groups. The differences in masticatory capacity found thus seem to have little, if any, effect on the factors of importance for general health. A reasonable explanation for the differences found is that artificial teeth that are well retained, such as FPDs, make more active chewing possible than do removable, and often somewhat loose-fitting partial dentures.

Aged↗