23 research outputs found
Variation in the masseteric silent period in older dentate humans and in denture wearers
The masseteric silent period was elicited by chin taps at 40% clenching
in the masseter muscle of the preferred chewing side in 22 younger
dentate individuals, in 22 older dentate individuals, in 22 older
experienced denture wearers and in 7 older inexperienced denture
wearers. One simple and three combined types of silent period
(combination of early and late phases of depression) were recorded in
all groups. An early silent period was always elicited, the only
exception being in some inexperienced denture wearers. Both the age and
the extent of rehabilitation with dentures in the trained denture
wearers affected reflex latencies (p < 0.05), while the variation in
duration was not significant (p > 0.05). The duration of the silent
period was, however, affected by the type of silent period, thus by the
measuring technique (p < 0.05). Increased variation was observed in the
inexperienced denture wearers, who were in a period of adaptation
Jaw reflexes in healthy old people
Objective: to investigate variations in the masseteric myotatic reflex
(jaw-jerk) and the silent period from the 5th to the 9th decades of
life.
Subjects and methods: electromyographic data were recorded from the
masseter muscle of the preferred chewing side by surface electrodes,
using a computerized recording and analysis system. Chin taps were
applied with a neurologist’s hammer during mandibular rest and at 40%
intercuspal clenching in 30 healthy people aged from 49 to 87 years. The
influence of age, gender and silent period type were analysed by
multiple regression analysis (P less than or equal to 0.05).
Results: even in the very old subjects all reflexes were elicited, at
least once. However, with increasing age the overall occurrence of the
jaw-jerk reflex at rest (%) and its amplitude, at rest and at clench,
were reduced, while its latency at rest was significantly increased (P
less than or equal to 0.05). No age effects were recorded in most
parameters of the jaw-jerk reflex at clench and in the silent period.
Women showed a tendency for reduced latencies of the jaw-jerk and the
early silent period and increased silent period duration (P less than or
equal to 0.05). They also had a steeper decline in myotatic reflex
activity, particularly at rest.
Conclusion: simple masseteric reflex activity is maintained until very
old age, particularly when elicited during contraction of the jaw
elevators
DIGASTRIC MUSCLE RESPONSE AS A FUNCTION OF KNOWLEDGE OF THE TASK TO BE PERFORMED
Whether the motor programme executed by the digastric muscles during a forceful bite is modified according to a subject's expectation that the resistance between the teeth will change was investigated. There were two experimental conditions: (1) tracking a ramp (drawn on an oscilloscope screen) by biting (isometrically) on a force transducer and holding it at 120 N, and (2) tracking the same ramp with a sudden unloading at 100 N. There were two groups of experiments: (1) control experiments in which subjects underwent a sudden and unexpected unloading of the jaw, and (2) experiments in which subjects were previously informed whether or not there was to be an unloading. In all experiments the subjects co-contracted their digastric muscles during the bite as compared to the state at rest. The subjects' responses fell into the three different types: (i) those who varied the level of tonic digastric activity only as a function of the experimental condition, (ii) those who co-contracted the digastric muscles at the same time as the masseter muscles, and (iii) those who changed the contraction pattern of the digastric muscles as a function of the experimental condition. If modulation of the digastric muscles occurred this is a 'feedforward' strategy mainly based on immediate past performance
Three-dimensional analysis of the occlusal plane related to the hamular?incisive?papilla occlusal plane in young adults
The Ala-Tragus Line as a Guide for Orientation of the Occlusal Plane in Complete Dentures
Electromyographic evaluation of mastication and swallowing in elderly individuals with mandibular fixed implant-supported prostheses
This study evaluated the effect of implant-supported oral rehabilitation in the mandible on the electromyographic activity during mastication and swallowing in edentulous elderly individuals. Fifteen patients aged more than 60 years were evaluated, being 10 females and 5 males. All patients were edentulous, wore removable complete dentures on both dental arches, and had the mandibular dentures replaced by implant-supported prostheses. All patients were submitted to electromyographic evaluation of the masseter, superior orbicularis oris muscles, and the submental muscles, before surgery and 3, 6 and 18 months postoperatively, using foods of different textures. The results obtained at the different periods were analyzed statistically by Kruskal-Wallis non-parametric test. Statistical analysis showed that only the masseter muscle had a significant loss in electromyographic activity (p<0.001), with a tendency of similar response for the submental muscles. Moreover, there was an increase in the activity of the orbicularis oris muscle during rubber chewing after treatment, yet without statistically significant difference. Mandibular fixed implant-supported prostheses in elderly individuals revealed a decrease in electromyographic amplitude for the masseter muscles during swallowing, which may indicate adaptation to new conditions of stability provided by fixation of the complete denture in the mandibular arch