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At least 1,207 records · Page 67Linked to original sources
PubMed1988

Forage ingestion: effects of sward characteristics and body size.

A model of a grazing ruminant in a range environment integrates ingestive behaviors (bite size, chewing rate, movement rate) and processing behaviors (mastication and rumination requirements) with rumen function to predict the combination of behaviors that produces the highest rate of energy digestion per unit of time (DE/T). Ingestive and processing behaviors compensate to maintain DE/T as the environment changes. Compensation for a change in forage density is more complete than for a change in forage quality. Ingestive behaviors alone have limited ability to offset environment changes, and control of passage rate through processing behaviors is an important additional compensatory mechanism. Optimal solutions of the model maintain a high intake by sacrificing diet quality and maintain a high rate of passage by increasing mastication and rumination effort when eating low-quality diets. When the model is scaled to body size, decreases in body size lead to higher selectivity and more pronounced processing behaviors. In no case are optimal solutions characterized by less than maximum rumen fill. The model predicts that the small ruminant derives an increasing proportion of its energy from the cell contents. The model suggests that selection for production has produced plastic ingestive and processing behaviors and has increased body size.

Animal Feed↗
PubMed1989

Effects of time of day and monensin on the size distribution of particles in digestive tract sites of heifers fed corn silage.

Effects of time of day and dietary monensin in the distribution of size of digesta particles in different digestive tract sites and their intersite relationships were examined in six heifers (290 kg BW) with ruminal, duodenal and ileal cannulas given ad libitum access to corn silage, with or without 100 mg monensin.head-1.d-1, in a two-period crossover design. Ingestive masticate and digesta of corn silage were collected via esophageal, ruminal or intestinal cannulas. The distribution of particulate matter retained on sieves with apertures larger than 20 microm was determined by wet-sieving. The cumulative distribution of particulate matter on a series of sieves was regressed on retaining sieve aperture to estimate the sieve aperture that would retain 50% weight of the particulate matter (median retaining aperture, MRA). The MRA of masticate was 6,494 microm. The MRA of digesta particles decreased (P less than .05) from ventral rumen (1,847 microm) to dorsal rumen (1,797 microm) to duodenum (346 microm), but increased to the rectum (359 microm). The MRA was lower (P = .044) for the monensin treatment only in feces. The MRA of particulate matter in the dorsal and ventral rumen, duodenum and rectum all changed (P less than .05) over 24 h. An inverse pattern between the MRA of ruminal and duodenal digesta occurred, presumably the result of a nycterohemeral pattern of eating and ruminating activity. Across sampling times, an inverse relationship existed between MRA of ventral rumen and duodenal digesta. This relationship suggests that a ruminal digesta raft composed of larger particles (immediately following major meals) is more effective than a raft of smaller particles (prior to such meals) in preventing flux of large particles to the duodenum.

Animal Feed↗
PubMed1993

[Change in trigeminal mesencephalic neurons after teeth extraction in guinea pig].

Trigeminal mesencephalic (Mes V) neurons innervating the periodontal mechanoreceptor (PMR) are known to play an important role in controlling the bite force and jaw-movements during mastication. After teeth loss, the PMR disappears due to loss of the periodontal membrane. The present work is a study on whether cell death is induced in the Mes V neurons in association with teeth loss. The upper and lower incisors were extracted on the right side in 5 guinea pigs (extraction group) and the other 5 guinea pigs were kept intact (control group). In the extraction group, the animals were kept alive for 58-119 days after teeth extraction. Serial coronal sections (50 microns thick) were made of the midbrain and pons and stained with cresyl violet. The Mes V neurons were counted on every other section. In the caudal half of the Mes V nucleus, where the neurons innervating the PMR are reported to be located, the number of neurons was less on the right side than on the left side (P < 0.01) in the extraction group, while there was no difference between the right and left sides in the control group. We conclude that teeth extraction can induce cell death in the Mes V neurons innervating the PMR and produce a significant change in the brainstem mechanisms controlling mastication.

Animals↗
PubMed2003

[The effect of pontic occlusal form on abutment tooth displacement].

The three-dimensional displacements of abutment teeth in fixed partial dentures (FPDs) during mastication were measured while changing the pontic occlusal design, for comparison against those of natural teeth. The purpose of this study was to clarify the influence of pontic occlusal form on the displacements of the abutment teeth, and to decide the optimum pontic occlusal design. Three subjects, who each had a single missing tooth (upper first molar or second premolar), were chosen. After 3-unit FPDs were cemented, abutment tooth displacement during mastication was measured using a three-dimensional tooth displacement transducer Type M-3. The functional or non-functional cusp inclination of the pontic was changed gradually. The flatter the inclination of the functional cusp of pontic became, the more the abutment teeth displaced in the buccal direction. The flatter the inclination of pontic non-functional cusp became, the less the abutment teeth displaced in the buccal direction, and the more the abutment teeth mostly displaced in the palatal direction. If the inclination of the functional cusp of pontic becomes excessively flatter, or the inclination of pontic non-functional cusps becomes as steep as the natural teeth, non-physiological distortion may occur in periodontal tissues of the abutment teeth.

Adult↗
PubMed1998

Virtual jaw: a 3D simulation for computer assisted surgery and education.

The jaw is one of the most complex joints in the human body. Its sliding and gliding movements are difficult to understand. Therefore, up to now there exist only mechanical simulations. But there is a strong need for a computer model of the jaw--the virtual jaw--to support physicians and surgeons in diagnoses and preoperative planning. During the preoperative planning of craniofacial operations for example, individual patient data has to be examined and the operation has to be simulated. In the education of physicians such a simulation system gives a much better understanding of the anatomy and functionality of the jaw than static images in text books do. The paper presents a 3D simulation of the human mastication apparatus which can be used for the preoperative planning of craniofacial surgeries as well as the education of dentists and surgeons. It consists of three interacting components: A kinematic model which defines the constraints of the articulation, a model for the mastication muscles and a 3D graphical interface.

Computer Graphics↗
PubMedDate not supplied

Morphological change of the nasopremaxillary suture in growing "toothless" osteopetrotic (op/op) mice.

Osteopetrotic (op/op) mice are known to commonly show a failure of tooth eruption. It is also well understood that masticatory function is highly associated with the craniofacial morphology of the growing mouse; however, the effects on sutural growth have not been studied. The present study was conducted to examine, in detail, the morphological and histological changes of the nasopremaxillary suture in these mutant mice and to assess a role of mechanical stress from mastication in the sutural growth. The width of the nasopremaxillary suture was measured on the section for the superior (P1), middle (P2), and inferior (P3) levels. The width of the nasopremaxillary suture for the P1 level in the normal mice fed a solid diet was significantly smaller in 30-day-old mice than in 15-day-old mice, whereas the width for the level P3 was significantly greater in the 30-day-old mice than in the 15-day-old mice. These changes in the sutural space were more prominent in the normal mice fed a solid diet than in the normal mice fed a granular diet. The sutural widths for all the levels became smaller in the 30-day-old op/op mice than in the 10-day-old op/op mice. The endocranial area of the nasopremaxillary suture showed synostosis in 30-day-old op/op mice. In both the normal and op/op mice, the number of tartrate-resistant acid phosphatase (TRAP)-positive cells was greatest at the age of 15 days. Moreover, the TRAP-positive cell number was smaller in the op/op mice than in the normal mice for all the experimental stages. Since, in general, mastication begins in mice after tooth eruption, i.e. from 15 to 30 days after birth, the present findings suggest that failure of tooth eruption and the reduced masticatory function restrict sutural modification.

Animals↗
PubMed1999

[Oncologic post-resection reconstruction of mandibular defects].

BACKGROUND AND AIM: If not reconstructed, mandibular defects resulting from oncological surgery can leave major functional and cosmetic sequelae which may impede these patients from returning to professional and family life. Reconstruction may be immediate or deferred, but the authors clearly recommend immediate reconstruction. METHODS: An analysis is made of the different techniques used for the reconstruction of mandibular defects, specifying those which are currently used and the situations in which they are applied. The advantages and disadvantages of microsurgical flaps and pedicled flaps are emphasised. The immediate use of endosseous implants is also discussed. RESULTS: The results of the various types of reconstruction are compared from a cosmetic and functional point of view. The latter includes a study of the quality of speech, deglutition, mastication and labial competence. Mastication is studied in two types of patients: those with osteointegrated implants with neomandibular reconstruction and those in whom osteointegrated implants were not used. All these patients survived 5 years after surgery. CONCLUSIONS: The authors recommend the immediate reconstruction of mandibular defects. Microsurgical flaps and pedicled flaps can be used for this purpose. Bone flaps may be used for endosseous titanium implants, whereas osseous flaps which do not provide a sufficient guarantee of rehabilitation should not be used. Implants should be inserted during oncological surgery, since postoperative radiotherapy may alter osteointegration of titanium implants are then used. The overall survival of these patients depends on the margins of local resection which are much wider using these techniques.

Dental Implantation, Endosseous↗
PubMed1975

[Bone statics of the face: the frontal-sphenoid-pterygoid bone pillars as biomechanic equivalents of the mandible].

In general biomechanics, trabecular osteo-architectonics is considered as a response to the mechanical strains present in the bone (compression or traction). The facial and cephalic skeleton is no exception to this law. The study of the bony architectionic provides the proof, since we have demonstrated in the fixed facial bone mass (at the limits of the facial skeleton and the skeleton of the base of the skull) the biomechanical equivalent of the mandible: the cranio-facial pterygo-spheno-frontal bony pillars. Paired, symmetrical and with a medio-frontal junction, they represent an embryological, anatomical and functional entity. Their ossification (mixed) may be compared to that of the mandible. They are made up of directional trabecular bone which may be analysed by stereology, electron microscope scanning and by strain gauges. Each pillar is made up of: - A part free of musculature corresponding to the supra-orbital frontal arch, which receives the four vertical pillars (naso-maxillary and maxillo-malo-frontal) of the superficial system of the face which transmit to the supra-orbital frontal arch the ascending mechanical strains of mastication registered in the spongy hard palate. The supra-orbital frontal arch is the biomechanical homologue in the fixed facial mass of the tooth bearing bony base of the mandible. - A spheno-pterygoid part, into which are inserted the alimentary muscles of the cephalic region (masticators, velar and superior pharyngeal). There is further functional homology between the ascending ramus of the mandible and the pterygoid greater wings and apophyses complex of the sphenoid. The 2 pterygo-spheno-frontal pillars also participate in the osseous statics of the orbit and the osseous statics of the temporo-mandibular joint. The basi-sphenoid plays a role of first importance in the general statics of the cephalic region. Thus the two pterygo-spheno-frontal pillars, biomechanical homologues of the mandible in the fixed facial mass, underline the functional interdependence of the osseous, dental and muscular systems of the cephalic region, a region which should be viewed as being in a stade of permanent dynamic equilibrium during growth and in the adult.

Biomechanical Phenomena↗
PubMed1999

A comparative study of various fixation methods for mandibular fracture.

BACKGROUND: Internal rigid fixation for mandibular fractures has been recognized as a reliable method for obtaining osteosynthesis. It may allow for early active physiotherapy and resumption of normal function. However, few studies have compared the various fixation methods. METHODS: From January 1993 through December 1997, 101 patients with mandibular fractures, who were selected for study, received treatment using various fixation methods at the Craniofacial Center, Chang Gung Memorial Hospital. The fixation methods included plate fixation in 44 patients, lag screw fixation in 30, combined plate and lag screw fixation in 15, and wire fixation in 12. Clinical data assessment was performed by reviewing hospital records. For assessment of the long-term surgical results, the patients were asked to complete a questionnaire including questions which specifically targeted history regarding occlusion, mastication, facial asymmetry, width of mouth opening, and general appearance. RESULTS: The outcome assessment showed statistically different results among the groups. The wire group required intermaxillary fixation more often and for a longer duration compared to the groups using plates and/or lag screws. The plate, lag screw, and combined plate and lag screw fixation groups had better total outcome scores, in particular for long-term dental occlusion and mastication function. CONCLUSION: This study shows that for mandible fractures, the more rigid types of fixation methods, i.e., plates and screws or lag screws, can offer better short and long-term outcomes.

Adolescent↗
PubMed2000

[Comparative study of three feeding methods for draught horses of the Swiss army].

Three feeding methods were compared in 36 4- to 6-year-old Franche-Montagne horses during the military school of St-Luzisteig (GR) of Spring 1992. The horses were separated into 3 groups: a group with the traditional oats-hay ration (OH), a group with a pelleted feed and hay ration (PFH), and a group with the complete diet (CD). Feed analyses were performed and food consumption, eating behavior and digestibility were studied. The horses received their daily amount of feed in 3 portions covering the requirements for a medium work: OH = 8 kg hay and 3 kg oats, PFH = 8 kg hay and 3 kg pelleted feed and CD = 10 kg of the complete diet. For the 3 rations, the amount of digestible crude protein for horses was higher than the reference value for the requirement of a 600 kg horse with a medium work. In the 3 diets, the calcium content was higher than the required 32 g per day (g/d). Not enough sodium (OH: 1.2 g/d; PFH: 7.3 g/d; CD: 9.6 g/d) and too much potassium (OH: 140.3 g/d; PFH 153.0 g/d; CD: 167.5 g/d) were present in the diets, both without consequences for the blood parameters. In 3 meals of 60 minutes, the horses of the group OH, PFH and CD ingested 82%, 89% and 92%, respectively, of the daily ration. The complete diet was ingested more quickly than the hay. The number of mastications per minute was smaller for the complete diet than for the hay. Ingestion times were similar for oats and pelleted feed. However, the number of mastications per minute was smaller for the pelleted feed. The digestibility of nutrients was not influenced by the method of feeding. In conclusion, these results demonstrate that the 3 types of ration studied here are adequate for the swiss army horses if sodium is added to the diet. However, despite the fact that both PFH and CD correct excessive supply or deficiencies of nutrients and despite the fact that these two feeding methods offer nutrients in amounts that are closer to the requirements of the horse, the method PFH was introduced in 1994.

Animal Feed↗
PubMed2001

Double-coping technique in prosthesis fabrication for osseointegrated teeth implantation: case report.

Reconstruction of segmental mandibular defects resulting from trauma, infection, or tumor resection still remains difficult. Although cosmetic improvement was seen in patients who had immediate reconstruction of the mandibular continuity, normal mastication and deglutition could not be achieved by conventional removable dentures. Since 1988, the treatment protocol has been modified to use endosseous root-form implants to support dental prostheses instead of the conventional removable prostheses in these patients. There are 2 types of prostheses that can be constructed over dental implants: (1) a removable implant overdenture and (2) a fixed detachable prosthesis. Although the latter better meets in patients' psychological needs, it may present problems such as phonetic discrepancies, food impaction, difficult home care, and poor esthetics if the patient has a high lip line. In addition, it is not easy to fabricate accurately in the laboratory. To overcome these problems, a case is presented to illustrate the use of another fixed-type prosthesis, a double-coping technique, for fabricating dentures so that any discrepancy between the inner and outer copings can be filled by cement. The technique not only improves the shortcomings of fixed detachable prostheses but also satisfactorily meets patients' desire for normal mastication and deglutition. Follow-up after 4 years showed no significant changes around the implants by clinical and radiographic examinations.

Dental Implantation↗
PubMed2000

[Correction of dento-maxillofacial deformities by using both of orthodontics and orthognathic surgery].

OBJECTIVE: To study the clinical results and stability after correction of dento-maxillofacial deformities by using both of orthodontics and orthognathic surgery. METHODS: A group of 45 patients with dento-maxillofacial deformities were corrected by preoperative orthodontics-orthognathic surgery-postoperative orthodontics procedure. As a control, another group of 64 patients with the deformities were corrected by orthognathic surgery only. The facial appearance, occlusion and stability of two groups after correction were investigated and compared. RESULTS: In orthodontics and orthognathic surgery group, 62.2% of patients declared that their mastication were improved. Relapse rate of deformities was 4.4%. In orthognathic surgery group, 42.2% of patients declared that their mastication were improved. Relapse rate of deformities was 9.4%. CONCLUSIONS: Using both of orthodontics and orthognathic surgery to correct dento-maxillofacial deformities is a good approach to improve results of correction, keep balance of occlusion and reduce the relapse of the deformities.

Adolescent↗
PubMed2003

[Do temporomandibular disorders really exist?].

Temporomandibular Disorders (TMD) is a collective term embracing a number of clinical problems that involve the muscles of mastication, the temporomandibular joint (TMJ) and associated structures or both. This group of disorders has been identified as the chief cause of pain, which is not of dental origin, in the orofacial area, and is defined as a subgroup in the category of musculoskeletal disorders. These disorders impair the quality of life of those suffering from them due to the extent of the pain and the chronic nature of its symptoms. It is known that chronic pain causes the development of psychological disturbances (anxiety, depression, etc.). The most common symptoms of TMD are the pain that usually appears as the result of mandibular activity (speaking or chewing), and is usually located in the masticulatory muscles, in the preauricular area and the temporomandibular joint (TMJ). Additional common symptoms are: a. restriction in jaw movement; b. asymmetry in jaw movement; c. noises from the joint. Patients suffering from TMD are likely to exhibit additional symptoms: hypertrophy of the muscles of mastication (an adaptive and asymptomatic phenomenon), abnormal occlusar erosion due to nighttime or daytime bruxism, or teeth grinding. Most functional temporomandibular disorders have similar signs and symptoms. As a result, diagnosis of the various disorders presents a serious problem. Functional temporomandibular disorders are often accompanied by mental symptoms such as depression, anxiety and/or somatization on various levels. One of today's accepted methods of classification also refers to the mental aspect and thus enables, for the first time, a suitable scientific comparison of the epidemiological, diagnostic and treatment data in the various studies. This method, initiated by Dworkin and LeResche (1992) is known as Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). The purpose of this method is to classify every subgroup of TMD according to agreed upon, clear and measurable diagnostic criteria, both from the physical (AXIS I) and the mental (AXIS II) aspect. The method includes a scale which grades the extent of severity, damage and limitations caused by the illness, in a manner which now can make scientific comparisons between the various studies and between the population of patients and the general population. Temporomandibular disorders are very common and affect between 30%-50% of the population, and appear to be more prevalent among women than among men. Studies conducted on youth revealed significant relationships between oral parafunctions (especially chewing gum and "jaw playing"), and functional temporomandibular disorders. The significance of this finding is in the need to warn young people of the possible risks of engaging in intensive oral practices. The high prevalence of signs and symptoms among the Israeli population obligates us, in our opinion, to change the physical examination for identification of these disorders, to a routine procedure in all dental clinics in Israel.

Anxiety↗
PubMed2003

[Clinical evaluation on effects of functional muscular equal pressure zone on complete denture].

OBJECTIVE: To study the clinical effect of the functional muscular equal pressure zone on complete denture. METHODS: Artificial teeth were arranged within the functional muscular equal pressure zone. With this technique 35 complete dentures were made to rehabilitate 35 edentulous patients whose alveolar bones were moderately or seriously absorbed. After three months' following up, the satisfaction of these patients were investigate. RESULTS: After prosthesis treatment, 35 patients enunciated well and the aesthetic effect was favorable. 89 percent of these patients satisfied the retention and the stability of the maxillary denture, and 78 percent satisfied the retention and the stability of the mandibular denture. 79.5 percent of these patients satisfied the mastication efficiency. CONCLUSION: With the technique, the complete denture is fairly stable in patient's mouth. The technique can enhance the denture's retention and improve the patient's mastication efficiency, especially to these whose alveolar bones are moderately or seriously absorbed. Clinically the technique is of high practical value to these edentulous patients who are difficult to be rehabilitated.

Aged↗
PubMed1992

[Evaluation of temporo-mandibular myoarthropathies, the status of the masticatory system and patients' personality based on the tests and clinical studies].

Resorting to commonly applied methods and clinical indices, the masticatory organ state was evaluated in 64 patients with symptoms of myoarthropathy (studied group)) and in 61 patients without the symptoms of the disease (control group). The assumption laid down in the work was that the studied group and the control one do differ with regard to the incidence rate and the intensity of the investigated local parameters and the level of neuroticism as well as extraversion. The aim of the paper was to show the mutual correlation between the parameters studied, and to determine their effect on the inception of the temporal jaw dysfunction. It has been revealed that the advancement of age is accompanied by statistically significant increase in the incidence rate and intensity of local diseases as well as by malfunctions, a rise in the level of neuroticism and a drop of the extraversion level. In consequence of the former findings, severe forms of dysfunction of the mandibular articulation arose in 89% of patients within the highest age group. Comparing the parameters between the studied group and the controls provided the possibility to isolate the features that make the both groups differ, thus facilitating the determination of the influence the individual factors exert on the origination of dysfunction of the mandibular articulation. The most essential differences affected five factors: unilateral mode of mastication, parafunction, teeth deficit, abnormal occlusion and high neuroticism. The lack of statistically significant differences between the studied and control groups with respect to periodontal diseases, looseness of teeth, dental abrasion do not authorize us to exclude their influence on the formation of temporal jaw myoarthropathy, since these factors are responsible for the loss of teeth, occlusal articulation disorders, and in an indirect way they, undoubtedly, exert destructive influence on the organ of mastication.

Adolescent↗
PubMed1992

Scanning electron microscopic studies of the oral mucosa and its microvasculature: a review of the palatine mucosa and its microvascular architecture in mammals.

The present paper deals with the microvascular architecture of the palatine mucosa in primates, carnivorae, and rodentia utilizing microvascular corrosion castings and epithelium-separated specimens. The submucous vascular network is under-developed since the hard palatine mucosa was designated the mucoperiosteum, except some areas. The palatine venous plexus appears to show regional differences with animal species differences. The well-developed plexus is observed to be two-layered and may contribute to the process of regurgitation of rough food and assist in mastication with the palatine plicae. Formation and patterns of the arterial network in the lamina propria are in a close relation with connective tissue elements. The subepithelial capillary network constitutes an advanced base for the ascending crus of the capillary loop and its pattern is affected by the properties of the connective tissue papillae and the diverging fashion of the capillary loops. Capillary loops of the transverse palatine plica are arranged parallel to the sagittal axis and at right angles to the top line of each plica. Features of the capillary loops are characteristics in the top, the anterior and posterior slopes of the plica, respectively. High connective tissue papillae in both the anterior slope and plical top may be of a resistant form for mollifying exhaustion, affected by the periodicity and mastication function. Although it is difficult to elucidate the lamination of the palatine mucosa in histological slides, it was resolved by examination on its vascular architectures.

Animals↗
PubMed1992

Malocclusion and masticatory muscle activity: a comparison of four types of malocclusion.

Electromyographic activities of the temporalis and masseter muscles during mastication were measured in patients who visited this clinic for orthodontic treatment of progenia. The results obtained were compared with those previously obtained in patients with other types of malocclusion and relationships between types of malocclusion and activities of the masticatory muscles were examined. Several interesting results were obtained, including: 1) the muscle activities were significantly higher in patients with deep bite than in patients with any other types of malocclusion and 2) inefficient mastication patterns, evidenced by higher temporalis muscle activities on the balancing side than on the working side, were most frequently observed in patients with edge bite. These results indicate that the clinical evaluation of masticatory muscle activities may be useful in improving orthodontic treatment and in determining a proper retention period after the treatment. The results also suggest that orthodontic treatment should include some type of dynamic myofunctional therapy in addition to the correction of static structural abnormalities.

Child↗
PubMed2005

[Ontogeny of the jaw].

Four pairs of branchial arch appear apparently in the neck region of human embryo about 32 days after fertilization. Maxillary prominence of the first branchial arch gives rise to the maxilla and zygomatic bone etc., and mandibular prominence forms the mandible and so on. Muscles for mastication are also derived from 1st branchial arch, into which fifth cranial nerves grow from the brain. Thus, human embryo improves the 1st branchial arches into the upper and lower jaws, and forms digestive organs needed for intake, mastication, and swallowing of foods. Finally they develop the brain for integral treatment of sensory information from eyes, tongue, nose, and ears.

Brain↗