RESUMEN
The purpose of this study was to evaluate the effect of a tricyclic antidepressant (amitriptyline) on nocturnal masseteric activity and duration of sleep in bruxists. Using a randomized, double blind, crossover design, ten females (mean age 39 yrs, +/- sd seven yrs) received active (amitriptyline 25 mg/night) and inactive (placebo 25 mg/night) medication, over a period of four weeks each. A portable EMG integrator recorded the nocturnal, unilateral, and cumulative myoelectrical activity (microV/min of sleep) of the masseter muscle during the fourth and eighth weeks of the study. The results showed that amitriptyline did not significantly decrease the mean EMG activity (df = 9, alpha = 0.05, paired-t = 0.892, p = 0.3964), nor did it significantly increase the duration of sleep (df = 9, alpha = 0.05, paired-t = 2.140, p = 0.061). The results of this study do not support the administration of 25 mg of amitriptyline per night over a period of four weeks for the management of sleep bruxism.
Asunto(s)
Amitriptilina/uso terapéutico , Antidepresivos Tricíclicos/uso terapéutico , Bruxismo del Sueño/tratamiento farmacológico , Adulto , Amitriptilina/administración & dosificación , Amitriptilina/efectos adversos , Análisis de Varianza , Antidepresivos Tricíclicos/administración & dosificación , Antidepresivos Tricíclicos/efectos adversos , Estudios Cruzados , Método Doble Ciego , Electromiografía/efectos de los fármacos , Femenino , Estudios de Seguimiento , Humanos , Modelos Lineales , Músculo Masetero/efectos de los fármacos , Distribución Normal , Placebos , Sueño/efectos de los fármacos , Estadística como Asunto , Resultado del TratamientoRESUMEN
To study mandibular motions with respect to time (kinematics) and the forces causing and resulting from these motions (kinetics), four subjects generated rapid depression and elevation of the mandible (displacement of 0.224 m; peak velocity of 0.237 m s(-1) during depression and 0.269 m s(-1) during elevation). The motion of depression (duration of 0.195 s; kinetic energy of 2.072 x 10(-3) J) could be divided into a phase of acceleration (2.742 m s(-2); +/- 0.28 gn) and a phase of deceleration (2.264 m s(-2); - 0.23 gn), and the terminal excess kinetic energy of depression was absorbed and dissipated by, primarily, the temporomandibular joint. Similarly, the ensuing motion of elevation (duration of 0.182 s; kinetic energy of 2.948 x 10(-3) J) could be divided into a phase of acceleration (3.498 m s(-2); + 0.36 gn) and a phase of deceleration (2.931 m s(-2); -0.30 gn), and the terminal excess kinetic energy of elevation was absorbed and dissipated by, primarily, the dentitions and, secondarily, by the temporomandibular joint. Rapid depression of the mandible appeared to be under the central control of a preprogrammed motor command, and ensuing rapid elevation of the mandible appeared to be under the peripheral control of a segmental and/or transcortical reflex. During rapid depression and elevation of the mandible, the anterior suprahyoid, anterior temporalis, and sternocleidomastoid muscles were myoelectrically active 56%, 73%, and 71% of the time, respectively, and myomechanically active 42%, 59%, and 57% of the time, respectively. Over a follow-up period of 12 months, the studied mandibular motions did not cause injury to the dentitions and temporomandibular joint.
Asunto(s)
Mandíbula/fisiología , Fenómenos Biomecánicos , Electromiografía/instrumentación , Electromiografía/métodos , Electromiografía/estadística & datos numéricos , Femenino , Humanos , Cinética , Masculino , Músculos Masticadores/fisiología , Persona de Mediana Edad , Movimiento/fisiología , Valores de Referencia , Articulación Temporomandibular/fisiología , Factores de TiempoRESUMEN
Following an introduction to the functional properties of a three-dimensional instantaneous helical axis pertaining to circular (rotatory) and linear (translatory) motions of the mandible, this feasibility study applied the concept of a mandibular average finite helical axis to the maneuver of cyclic opening and closing of the mouth in three healthy subjects. Through the accelerations and decelerations of a mandibular incisor point (instead of a mandibular condylar point) as well as the laws of physics, the kinetic reaction forces and reaction pressures in the upper and lower cavities of the temporomandibular joint (TMJ) were estimated over opening-closing distances of five and ten mm from centric occlusion. The translatory reaction pressures in the upper TMJ cavity (17-29 mm Hg) exceeded the rotatory reaction pressures in the lower TMJ cavity (5-12 mm Hg). The estimated reaction pressures were in close agreement with synovial fluid pressures measured in vivo in the TMJ of humans and pigs, and the biologic significance of frequent and/or prolonged increased TMJ hydrostatic pressures is discussed.
Asunto(s)
Articulación Temporomandibular/fisiología , Fuerza de la Mordida , Fuerza Compresiva , Análisis del Estrés Dental , Elasticidad , Estudios de Factibilidad , Femenino , Humanos , Presión Hidrostática , Masculino , Persona de Mediana Edad , Rango del Movimiento Articular , Rotación , Estrés Mecánico , Líquido Sinovial/fisiología , Resistencia a la TracciónRESUMEN
Albeit never substantiated through experimental and clinical evidence, the theoretical linchpin of the mechanics of a so-called whiplash injury of the temporomandibular joint (TMJ) is the postulate that a pre-existing depressor force (continual anchoring force), generated by the anterior suprahyoid (SH) muscles, will always act on the mandible and cause traumatic mouth opening (anterior acceleration of the TMJ condyles) when the neck is extended (posterior acceleration of the head). To test aspects of this postulate, six subjects assumed the positions of neutral (0 degrees ), medium (32 degrees ) and maximum (58 degrees ) neck extension while the mandible was in its postural positions of rest and light centric occlusion. By means of surface electromyography, it was shown that the relative contractile activities of the anterior SH muscles never exceeded 7.3% of the contractile activity required to anchor the mandible in a position of maximum depression. By means of electrognathography, it was shown that the maxillary and mandibular incisors were never separated by more than 2.6 mm during neutral, medium, and maximum extension of the neck. In other words, during neck extensions there was no evidence of a continual or induced voluntary or involuntary depressor force that would and could anchor the mandible in a position of traumatic mouth opening. Accordingly, and in agreement with other biophysical and biomedical evidence, it was concluded that there is no foundation for the pseudoscientific speculations and unsubstantiated opinions offered in support of a concept and diagnosis of a so-called TMJ whiplash injury. Additionally, this study found co-activation of cervical flexor muscles and mandibular elevator as well as depressor muscles.
Asunto(s)
Electrodiagnóstico , Electromiografía , Mandíbula/fisiología , Cuello/fisiología , Aceleración , Fenómenos Biomecánicos , Oclusión Dental , Oclusión Dental Céntrica , Femenino , Humanos , Masculino , Mandíbula/anatomía & histología , Músculos Masticadores/fisiología , Maxilar/anatomía & histología , Persona de Mediana Edad , Movimiento , Contracción Muscular/fisiología , Cuello/anatomía & histología , Músculos del Cuello/fisiología , Postura , Articulación Temporomandibular/lesiones , Lesiones por Latigazo Cervical/fisiopatologíaRESUMEN
Referring to the temporomandibular joint (TMJ) of the human mandibular locomotor system, it has been asserted that displacement of the TMJ disc and inflammation of TMJ tissues are the results of acute and indirect trauma to the TMJ; on occasion this is allegedly experienced in motor vehicle accidents and commonly known as a TMJ whiplash injury. It is postulated that the TMJ whiplash injury is released in the occupant or occupants of a target vehicle when its rear end is impacted by the front end of a bullet vehicle. On the basis of detailed analyses of TMJ trauma/pain histories and TMJ magnetic resonance images, presented as circumstantial evidence in favour of the postulated TMJ whiplash injury, and detailed analyses of the mathematical biophysics of the mandibular locomotor system as well as direct experimental evidence, it is concluded that the postulated TMJ whiplash injury does not exist as a single and independent disease entity caused by motor vehicle accidents. If TMJ disc displacement and inflammation are present, they are expressions of an insidious and progressive pre-existing (pre-accident) disease entity that is comprised of TMJ synovitis/osteoarthritis (phase of inflammation with presence of immune system cells), TMJ internal derangement (phase of disc displacement and deformation with presence of proteinases), and TMJ osteoarthrosis (phase of degeneration with absence of immune system cells). For the asserted TMJ whiplash manoeuvre and ensuing injury to occur as postulated, the laws of physics and biology would have to be suspended.
Asunto(s)
Accidentes de Tránsito , Articulación Temporomandibular/lesiones , Lesiones por Latigazo Cervical/etiología , Artritis/diagnóstico , Artritis/etiología , Fenómenos Biofísicos , Biofisica , Progresión de la Enfermedad , Endopeptidasas/análisis , Dolor Facial/diagnóstico , Dolor Facial/etiología , Humanos , Luxaciones Articulares/diagnóstico , Luxaciones Articulares/enzimología , Luxaciones Articulares/etiología , Imagen por Resonancia Magnética , Modelos Biológicos , Osteoartritis/complicaciones , Sinovitis/complicaciones , Articulación Temporomandibular/patología , Disco de la Articulación Temporomandibular/enzimología , Disco de la Articulación Temporomandibular/lesiones , Disco de la Articulación Temporomandibular/patología , Trastornos de la Articulación Temporomandibular/diagnóstico , Trastornos de la Articulación Temporomandibular/enzimología , Trastornos de la Articulación Temporomandibular/etiología , Lesiones por Latigazo Cervical/diagnósticoRESUMEN
Because a so-called mandibular whiplash injury requires the absence of short-latency jaw-closing reflexes in order to explain the postulated mechanism of injury (excessive jaw opening); the authors studied the presence and absence and more importantly, the kinematics (duration, displacement, velocity, acceleration) of monosynaptic and possibly, polysynaptic myotatic (stretch) reflexes in the jaw elevator muscles. In six healthy adults jaw jerk maneuvers were elicited through a brisk tap on the chin, and surface electromyography identified elevator reflexes while translational electrognathography identified the kinematics of the reflexes. The maneuvers were done while maintaining the rest position (3% MVC) and moderate clenching of the teeth (30% MVC). Electromyography was also used to identify phasic elevator excitations during a passive brisk neck extension maneuver. A sudden and unexpected elongation of the jaw elevators released autogenic reflex responses that, in conjunction with augmented tissue elasticity (stiffness), elevated the mandible into centric occlusion within approximately 150 milliseconds. In 86% of trials, the responses occurred regardless of the prevailing resting and clenching contractile activities. There was no evidence of a depressor force that consistently would and could anchor the mandible in a position of extreme or moderate depression, the theoretical linchpin of the mandibular whiplash injury. It was concluded that the mandibular locomotor system is very efficient in maintaining the rest and intercuspal positions of the mandible. This study found no evidence corroborating the mechanism claimed to release a so-called mandibular whiplash injury.
Asunto(s)
Mandíbula/fisiología , Músculos Masticadores/fisiología , Reflejo de Estiramiento , Lesiones por Latigazo Cervical/fisiopatología , Aceleración , Adulto , Análisis de Varianza , Fuerza Compresiva , Elasticidad , Electromiografía , Femenino , Humanos , Contracción Isométrica , Registro de la Relación Maxilomandibular , Masculino , Mandíbula/fisiopatología , Músculos Masticadores/fisiopatología , Movimiento , Rigidez Muscular/etiología , Músculos del Cuello/fisiopatología , Reflejo Monosináptico , Procesamiento de Señales Asistido por Computador , TorqueRESUMEN
Using the mouth as an "in vivo articulator," the bilateral nonmasticatory ("empty") contact patterns of opposing cuspid and first molar teeth were determined in two healthy subjects with well-defined cuspid function and two healthy subjects with well-defined group function. The electronically recorded "empty" contact patterns pertained to the static intercuspal position and dynamic laterotrusion to the right and the left. On the basis of the "empty" tooth contact patterns and the number of electronically recorded masticatory cycles of one masticatory sequence, we postulated two simple models that attempted to predict the masticatory ("functional") tooth contacts of one sequence of unilateral mastication of apple and banana. Statistical comparisons between the predictions of the two models and the actual ("functional") contacts of in vivo mastication showed that the models predicted fairly well the observed tooth contacts on the nonchewing-side of the mouth, but not the observed tooth contacts on the chewing-side of the mouth. In consequence, "empty" (nonmasticatory) tooth contact patterns should not be equated with "functional" (masticatory) tooth contact patterns.
Asunto(s)
Oclusión Dental , Masticación , Adulto , Oclusión Dental Traumática/fisiopatología , Humanos , MasculinoRESUMEN
Using a double-blind and randomized experimental design, ten adult subjects with sleep bruxism were administered amitriptyline (25 mg/night) and placebo (25 mg/night), each compound over a period of one week. Neither the intensities and locations of pains nor the nocturnal masseteric electromyographic activities were significantly affected by the tricyclic antidepressant. In fact, intake of amitriptyline was unpredictably associated with either an increase or a decrease in masseteric electromyographic activity (microV.s/min of sleep). On the basis of this study, small doses of amitriptyline cannot be recommended for the control of sleep bruxism and associated discomforts.
Asunto(s)
Amitriptilina/uso terapéutico , Antidepresivos Tricíclicos/uso terapéutico , Bruxismo/tratamiento farmacológico , Músculo Masetero/efectos de los fármacos , Trastornos del Sueño-Vigilia/tratamiento farmacológico , Adulto , Amitriptilina/efectos adversos , Antidepresivos Tricíclicos/efectos adversos , Bruxismo/fisiopatología , Método Doble Ciego , Electromiografía/efectos de los fármacos , Electromiografía/estadística & datos numéricos , Femenino , Humanos , Masculino , Músculo Masetero/fisiopatología , Persona de Mediana Edad , Trastornos del Sueño-Vigilia/fisiopatología , Resultado del TratamientoRESUMEN
In 46 non-patients and 46 patients, the authors examined the presence (+) and absence (-) of canine tooth guidance (CG), i.e. dynamic dental articulation events in contrast to static dental occlusion events. During a right and a left laterotrusion of the mandible, the number of simple, mutually exclusive and exhaustive tooth guidance events (possibilities) was four. In addition, the authors examined the associations between temporomandibular joint (TMJ) sounds and canine guidance events. In non-patients, CG+ was relatively infrequent (30%), and CG- was relatively frequent (70%). In patients, CG+ was relatively infrequent (22%), and CG- was relatively frequent (78%). In both non-patients and patients, bilateral CG+ was rather infrequent (15%). In both non-patients and patients with the presence of TMJ sounds, CG+ was relatively infrequent (38%) while CG- was relatively frequent (61%). In non-patients as well as patients, no evidence was found that distal CG+ (putative lateral retrusive guidance) was associated with ipsilateral TMJ sounds (relative risk = 0%), nor that the association between mesial CG+ (putative lateral protrusive guidance) and ipsilateral TMJ sounds was beyond that of mere chance (relative risk = 50%).
Asunto(s)
Diente Canino/fisiología , Oclusión Dental , Trastornos de la Articulación Temporomandibular/fisiopatología , Articulación Temporomandibular/fisiología , Articuladores Dentales , Femenino , Humanos , Registro de la Relación Maxilomandibular/instrumentación , Masculino , Mandíbula/fisiología , Prevalencia , Probabilidad , Factores de Riesgo , Sonido , Síndrome de la Disfunción de Articulación Temporomandibular/fisiopatologíaRESUMEN
In ten healthy subjects, bilateral contacts between opposing cuspid and first molar teeth were recorded during one sequence of unilateral chewing of apple, peanuts, and banana. Unknown magnitudes of mechanophysical (masticatory) forces were inferred to act directly on the chewing-side cuspid teeth in 71% of all masticatory cycles and on the nonchewing-side cuspid teeth in 68% of all masticatory cycles. In addition, unknown magnitudes of mechanophysical forces were inferred to act directly on the chewing-side first molar teeth in 74% of all masticatory cycles and on the nonchewing-side first molar teeth in 86% of all masticatory cycles. During the chewing of peanuts, the total number of chewing-side cuspid contacts exceeded significantly the total number of nonchewing-side cuspid contacts, suggesting more repetitive direct mechanophysical loading of the chewing-side cuspid teeth. During the chewing of apple, the total number of nonchewing-side first molar contacts exceeded significantly the total number of chewing-side first molar contacts, suggesting more repetitive direct mechanophysical loading of the nonchewing-side first molar teeth. The variable contact patterns were, to a large extent, explained by rotational movements of the entire mandible resulting in translational movements of the hemimandible.
Asunto(s)
Oclusión Dental , Masticación/fisiología , Adulto , Diente Canino , Electromiografía , Alimentos , Humanos , Masculino , Músculos Masticadores/fisiología , Modelos Biológicos , Diente Molar , Estadística como AsuntoRESUMEN
As it specifically pertains to temporomandibular disorders (TMD), this article is an educational analysis and discussion of some recently proposed diagnostic criteria, diagnostic methods, and diagnostic decision processes. On the basis of a discussion of classic probability theory, classic measurement theory, and examples using nonparametric inferential statistical tests, it is suggested that certain TMD diagnostic criteria and methods, and their associated decision matrix, favor subjective clinical opinions (largely pseudoscientific observations) and arbitrary clinical indices rather than objective scientific facts.
Asunto(s)
Interpretación Estadística de Datos , Técnicas de Apoyo para la Decisión , Teoría de la Probabilidad , Trastornos de la Articulación Temporomandibular/diagnóstico , Humanos , Oportunidad Relativa , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Estadísticas no ParamétricasRESUMEN
In 46 non-patients and 46 patients, the authors examined the presence (+) and the absence (-) of laterotrusive (LG) and mediotrusive (MG) tooth guidance, i.e. dynamic dental articulation events in contrast to static dental occlusion events. During a right and left laterotrusion/mediotrusion of the mandible, the number of compound, mutually exclusive and exhaustive tooth guidance events (possibilities) was six. In addition, the presence and the absence of temporomandibular joint (TMJ) sounds, provoked TMJ pains, and the associations between TMJ sounds and tooth guidance events were examined. In non-patients, LG+ and MG+ was relatively infrequent (30%) while LG+ and MG- was relatively frequent (70%). In patients, LG+ and MG+ was relatively frequent (58%) while LG+ and MG- was relatively infrequent (42%). LG- and MG+ was absent in non-patients and rare in patients (3%). Either unilateral or bilateral MG+ was relatively infrequent in non-patients (30%) and relatively frequent in patients (59%). Bilateral MG+ was relatively infrequent in non-patients (20%) and relatively frequent in patients (52%). Either unilateral or bilateral TMJ sounds were relatively infrequent in non-patients (39%) and relatively frequent in patients (74%). Either unilateral or bilateral provoked TMJ pains were absent in non-patients and relatively frequent in patients (72%). The authors found no evidence that TMJ sounds were associated with the ipsilateral absence of so-called balancing contacts (MG-) in non-patients and patients. Finally, no evidence supporting the use of a so-called positive predictive value, and "extension concept' of probability theory was found.
Asunto(s)
Oclusión Dental , Análisis del Estrés Dental , Trastornos de la Articulación Temporomandibular/fisiopatología , Articulación Temporomandibular/fisiología , Adulto , Estudios de Casos y Controles , Intervalos de Confianza , Oclusión Dental Traumática/complicaciones , Oclusión Dental Traumática/fisiopatología , Femenino , Humanos , Registro de la Relación Maxilomandibular , Masculino , Oportunidad Relativa , Valor Predictivo de las Pruebas , Probabilidad , Sonido , Trastornos de la Articulación Temporomandibular/etiologíaRESUMEN
Twelve healthy subjects performed 10 s, 15 s, 20 s, and 25 s of right-sided and, subsequently, left-sided gum chewing. The contractile activities of the ipsilateral (chewing side) and contralateral (non-chewing side) masseter muscles, mainly the concentric contractions of the phase of jaw closing and the isometric contractions of the phase of dental occlusion, were recorded through cumulative surface electromyography (EMG). A linear function (y = ax + b) described the association between an increase in the duration (x) of unilateral gum chewing and the cumulative EMG (y) of both the ipsilateral and the contralateral masseter muscle, and because of different slopes (a) of the two straight lines a geometric function (y = aqx) described the progressively larger differences between the paired and straight lines. When differential calculus was applied to the exponential functions, it became evident that the chewing forces generated by the ipsilateral masseter muscle continually exceeded those generated by the contralateral masseter muscle, and that the positive work (force x distance) produced by the concentric contractions of the ipsilateral masseter muscle continually exceeded that produced by the concentric contractions of the contralateral masseter muscle. It was inferred that mechano-physical work plays a major role if clinical muscle fatigue develops during prolonged unilateral gum chewing.
Asunto(s)
Goma de Mascar , Músculo Masetero/fisiología , Masticación/fisiología , Fatiga Muscular/fisiología , Adulto , Electromiografía , Femenino , Humanos , Modelos Lineales , Masculino , Modelos BiológicosRESUMEN
This article is an educational analysis and discussion of some recently proposed diagnostic criteria, diagnostic methods, and diagnostic decision processes, pertaining specifically to temporomandibular disorders (TMD). On the basis of a discussion of classic probability theory, classic measurement theory, and examples using nonparametric inferential statistical tests, it is suggested that certain TMD diagnostic criteria and methods, and their associated decision matrix, favor subjective clinical opinions (largely pseudoscientific observations) and arbitrary clinical indices rather than objective scientific facts.
Asunto(s)
Interpretación Estadística de Datos , Técnicas de Apoyo para la Decisión , Teoría de la Probabilidad , Trastornos de la Articulación Temporomandibular/diagnóstico , Distribución Binomial , Estudios de Casos y Controles , Distribución de Chi-Cuadrado , Humanos , Reproducibilidad de los Resultados , Estadísticas no ParamétricasRESUMEN
To study possible associations between gum chewing and fatigue and pains in the jaw muscles, eight healthy adults performed prolonged idling, prolonged unilateral chewing of gum, and brief vigorous clenching of the teeth (MVC). Through surface electromyography (EMG), the authors monitored the cumulative (microV.s) as well as the average rates (microV.s-1) of contractile activities in the right and left masseter muscles. During 10 min of idling there was an absence of muscle fatigue and muscle pains when the EMG rates of the right and left masseter muscles were 2% and 3%, respectively, of those required to elicit isometric muscle pains through MVC. During 10 min of right-sided gum chewing at a rate of 1.2 Hz, the majority of subjects (75%) experienced weak jaw muscle fatigue-not jaw muscle pains-when the EMG rates of the right and left masseter muscles were 38% and 19%, respectively, of those required to elicit isometric pains through MVC. In comparison with 10 min of idling, the weak muscle fatigue of 10 min of unilateral gum chewing appeared when the total contractile activities of the right and left masseter muscles were increased by 1664% and 519%, respectively. It seemed as if prolonged unilateral gum chewing and previous pain-releasing MVC caused some sensitization of muscle nociceptors which, in turn, aggravated subsequent isometric jaw muscle pains elicited through MVC. Even though the right masseter muscle was the most frequent site of clinical fatigue and pains, the authors found no evidence supporting the theoretical foundation of the myofascial pain/dysfunction syndrome.
Asunto(s)
Goma de Mascar , Dolor Facial/fisiopatología , Músculo Masetero/fisiopatología , Masticación , Fatiga Muscular/fisiología , Adulto , Fuerza de la Mordida , Electromiografía , Femenino , Humanos , Contracción Isométrica , Masculino , Contracción Muscular , Nociceptores/fisiología , Tiempo de Reacción , Músculo Temporal/fisiopatología , Articulación Temporomandibular/fisiopatología , Síndrome de la Disfunción de Articulación Temporomandibular/fisiopatología , Factores de TiempoRESUMEN
In seven (88%) of eight healthy subjects, weak to moderate pains were elicited in the masseter muscles through the isometric contractions of maximum voluntary teeth clenching. Integrated surface electromyograms of the right and left masseter muscles were used to quantify the absolute and relative contractile activities of the two muscles. The risk (relative probability) of inducing pain onset in the single masseter muscle generating the larger amount of isometric activity was 2.5 times the risk of eliciting pain onset in the single masseter muscle generating the lesser amount of isometric activity. However, as an aid in the diagnosis of pain onset, the method of masseteric surface electromyography had a false diagnostic ratio of 0.67.
Asunto(s)
Electromiografía , Dolor Facial/diagnóstico , Músculo Masetero/fisiopatología , Adulto , Dolor Facial/fisiopatología , Reacciones Falso Positivas , Femenino , Predicción , Humanos , Contracción Isométrica , Masculino , Riesgo , Sensibilidad y Especificidad , Músculo Temporal/fisiopatologíaRESUMEN
Frontal plane mandibular rotations and corresponding hemimandibular translations were studied in vitro by using direct observations of a human cadaver mandible and in vivo by using the indirect observations of rotational electrognathography. A comparison between the two methods showed that rotational electrognathography erred in measuring the clinically relevant hemimandibular translations resulting from mandibular rotations having a unilateral molar point (simulated occlusal interference) as the pivot of frontal plane torque. In vitro frontal plane rotations about a unilateral mandibular molar tooth (simulated occlusal interference) suggested that the resulting hemimandibular upward translations of the lateral portion of the mandibular condyle, contralateral to the molar tooth, would cause considerable compressive loading of the temporomandibular joint disc.
Asunto(s)
Oclusión Dental Traumática/fisiopatología , Análisis del Estrés Dental/instrumentación , Análisis del Estrés Dental/métodos , Registro de la Relación Maxilomandibular/instrumentación , Mandíbula/fisiopatología , Adulto , Análisis de Varianza , Fenómenos Biomecánicos , Fuerza de la Mordida , Fuerza Compresiva , Electrodiagnóstico/instrumentación , Femenino , Humanos , Registro de la Relación Maxilomandibular/métodos , Modelos Lineales , Magnetismo , Masculino , Cóndilo Mandibular/fisiopatología , Valores de Referencia , Reproducibilidad de los Resultados , Rotación , Procesamiento de Señales Asistido por Computador , Programas Informáticos , Disco de la Articulación Temporomandibular/fisiopatología , Torque , Dimensión VerticalRESUMEN
In 12 subjects, a pliable, yet unbreakable, intercuspal interference (aluminum shim onlay splint; uniform height of 0.25 mm) was placed between either the right or left maxillary and mandibular second premolars and first molars. During brief and forceful biting (dynamic chewing stroke of about 20 kg force) the interference emulated a semisoft food bolus, and at the end of biting (subsequent static clenching stroke of about 20 kg force) it emulated a rigid metal interference. During dynamic/static biting, rotational electrognathography measured maximum frontal and horizontal plane torque of the right and left mandibular condyles. Eleven subjects (92%) showed frontal plane upward rotation (mean of 1.0 degree) of the condyle contralateral to the interference, and one subject (8%) showed frontal plane upward rotation (0.4 degree) of the condyle ipsilateral to the interference. Two subjects (17%) showed no horizontal plane rotation; seven subjects (58%) showed backward rotation (mean of 0.4 degree) of the condyle contralateral to the interference; and three subjects (25%) showed backward rotation (mean of 0.3 degree) of the condyle ipsilateral to the interference. It is suggested that, in the presence of an occlusal interference, mastication may have both short- and long-term detrimental effects.
Asunto(s)
Oclusión Dental Traumática/fisiopatología , Cóndilo Mandibular/fisiopatología , Articulación Temporomandibular/fisiopatología , Adulto , Humanos , Modelos Lineales , Masculino , Reproducibilidad de los Resultados , Rotación , Estrés MecánicoRESUMEN
A rigid intercuspal interference (minimum mean height of 0.24 mm) was placed on either the right or left mandibular second premolar and first molar of 12 subjects. During brisk and forceful biting on the interference, rotational electrognathography measured maximum torque of the right and left mandibular condyles in the frontal and horizontal planes of orientation. All subjects showed frontal plan upward rotation (mean of 0.7 degrees) of the mandibular condyle contralateral to the interference. In 33% of the subjects there was no horizontal plane backward rotation. In 58% of the subjects there was horizontal plane backward rotation (mean of 0.5 degrees) of the mandibular condyle ipsilateral to the interference, and in one subject (8%) there was backward horizontal plane rotation (0.1 degree) of the mandibular condyle contralateral to the interference. It was inferred that the masseter muscle, ipsilateral to the interference, generated negative work in order to decelerate frontal plane 'unseating' of the mandibular condyle ipsilateral to the interference. It was inferred that the masseter muscle, contralateral to the interference, produced positive work in order to accelerate frontal plane 'seating' of the mandibular condyle contralateral to the interference. Finally, it was speculated that the impact forces of frontal plane 'seating' of the mandibular condyle, contralateral to the interference, might lead to 'vacuum sticking' of the temporomandibular joint disc because of the formation of negative hydrostatic pressures.
Asunto(s)
Oclusión Dental Traumática/fisiopatología , Mandíbula/fisiopatología , Articulación Temporomandibular/fisiopatología , Adulto , Fuerza de la Mordida , Análisis del Estrés Dental , Electromiografía , Femenino , Humanos , Registro de la Relación Maxilomandibular/métodos , Modelos Lineales , Magnetismo , Masculino , Cóndilo Mandibular/fisiopatología , Músculo Masetero/fisiopatología , Masticación , Movimiento , Distribución Normal , Reclutamiento Neurofisiológico , Rotación , Estrés MecánicoRESUMEN
This review shows that experimental occlusal interferences (prematurities) may cause changes in the myoelectric contraction patterns of the human jaw muscles, and changes in the translatory motion patterns of the human mandible. However, it has not been unequivocally established that the observed changes have specific long-term detrimental effects. On the other hand, it is apparent that experimental occlusal interferences are associated with short-term clinical symptoms and signs, such as jaw muscle fatigue and pains, headaches, pains and clickings in the temporomandibular joints. This review suggests that new paradigms involving experimental occlusal interferences should be introduced.