Short-term and long-term effects of chewing training on occlusal perception of thickness

The aim of this study was to investigate the short-term and long-term effects of functional stimuli, induced by intense chewing and by prolonged systematic chewing training, on the response of occlusal perception of thickness. The material comprised 25 young adults divided into an experimental group (17) and a control group (8). The occlusal perception of thickness was tested by successively placing different thicknesses of aluminum foil between five pairs of occluding teeth, i.e. right and left second premolars and canines and one pair of the central incisors. The experimental group was tested 2 wk before the start of the experiment and at the start and the end of the experiment, i.e., after 4 wk systematic chewing training, and before and after 30 min intense chewing. The control group was tested on the same occasions but without performing any special chewing activity. The discrimination threshold increased in most of the subjects after 30 min of chewing, both before and after the 28-day training period. This threshold increase was found in all groups of teeth tested. No changes were found in the discrimination threshold of the teeth tested after 28 days of chewing training. In the controls no differences were found between the recording occasions. Since no statistically significant differences were observed between the groups of teeth tested, the changes in the threshold of occlusal perception after intense chewing may reflect the influence of receptors other than periodontal, for example those in TMJ and muscles, which are involved in the control of other neuromuscular mechanisms such as those that control the postural position of the mandible.     

Influence of occlusal vertical dimension on the masticatory performance during chewing with maxillary splints

Changing the occlusal vertical dimension is a common procedure in restorative dentistry, during treatment of patients with cranio-mandibular disorders, and during orthodontic and orthognathic treatment. The treatment may alter the length of the main jaw elevator muscles and the position of the mandibular head in the fossa temporalis. These changes may influence the bite forces that are generated during chewing and thus may affect the masticatory function. We measured the objective masticatory function, defined as masticatory performance, by determining an individual's capacity to pulverize a test food. The immediate influence of the increase in the occlusal vertical dimension on the masticatory performance was determined using three anatomical maxillary splints in a group of seven dentate subjects. The splints gave an increase in the occlusal vertical dimension of 2, 4 and 6 mm, respectively. Before we started the experiments the subjects practiced chewing with the splints during about 5 min. No significant differences were observed in masticatory performance among the conditions without and with the three splints. Thus, an increase in the occlusal vertical dimension up to 6 mm did not have a significant effect on the masticatory performance. Maxillary splints may be used to study the effect of occlusal factors on the chewing process by manipulating tooth shape and occlusal area of the splint.     

Influence of balancing‐side occlusal interference on smoothness of working‐side condylar movement and intra‐articular space in chewing efforts

Response of temporomandibular joint (TMJ) articulation adapting to occlusal alteration has been sparsely known. For 10 healthy adults with acceptably good occlusion, an artificial occlusal interference (OI) was introduced to the lower molar on the balancing side of unilateral chewing. Subjects were asked to chew a gum on their preferred side. The chewing jaw movements with/without the OI were recorded using a video‐based optoelectronic system. The mandibular movements were generated in each individual's TMJ model reconstructed by magnetic resonance images. The smoothness of local condylar point movements towards the normal direction of the condylar surface and interarticular space on the working side was measured. Overall, the smoothness of condylar point movements in the closing phase was impaired immediately after introduction of the OI. In the intercuspal phase, the OI increased the joint space. After about 60 chewing cycles, the movement smoothness and joint space began to recover. These findings suggest that OI on the balancing side induced irregular stress field translation on the working‐side condylar surface followed by acute recovery process.     

Complete denture wearers: electromyography of mastication and texture perception whilst eating meat

This study was undertaken to evaluate the sensitivity of denture wearers to different food textures and to follow masticatory pattern adaptation with variation in texture using electromyography (EMG) recordings. Nine patients with complete dentures and 9 dentate control patients without any oro-dental pathology were studied. Six different samples of beef were obtained from the same muscle by altering the state of the muscle fibres and by variation of the cooking temperature. The variations in texture were mechanically controlled. Electromyographic activity was recorded during chewing. The patients' subjective appreciation of texture was reported using a 10-cm non-structured analogue scale. The following parameters were analysed: muscle work, number of masticatory cycles, number of rejected samples, initial tenderness, overall tenderness, juiciness, and duration of chewing for each sample in the mouth. Muscle activity was less for the edentulous group, particularly that of the masseter muscles. The masticatory pattern of complete denture wearers was less adapted to each sample texture than was that of the control group. Both groups perceived differences in texture of the samples. It was concluded that although texture perception is little altered, muscular adaptation to the bolus is reduced in patients with complete dentures.     

Social and psychologic implications of missing teeth for chewing ability

The impact of loss of teeth on chewing ability was investigated in three groups of patients. One group already had missing teeth replaced by partial dentures, which were taken out during the tests. This group was taken as not being adapted to chew without a complete dentition. A second group had their missing teeth not replaced by partial dentures. During the test they were considered adapted to chew without a complete dentition. A third group had a complete natural dentition and they acted as control group. Tests were carried out regarding chewing ability and swallowing threshold. In addition, a clinical examination was carried out. It was found that the loss of molars significantly reduced chewing performance. Moreover the number of chewing-strokes before swallowing the food-bolus and the mean of the particle size at the point of swallowing were increased. Loss of molars resulted in less positive feelings concerning chewing. Both groups of persons with missing molars showed a similar chewing performance. The group of not adapted patients felt on average more negative about their chewing ability and they indicated more changes in daily activities because of missing teeth.     

Cinefluoroscopic study of long-term changes of bolus position and chewing cycle duration after fixed prosthetic treatment

Abstract— Some chewing parameters were studied in 12 patients with a complete maxillary denture and a 12-unit fixed mandibular denture anchored to the two canines. Registration by means of fluoroscopy were made before, 1 month after, and in four patients 13 yr after treatment. The mean velocity of the mandible during chewing increased after the prosthetic treatment and remained stable for meat during the observation period. At the first registration, before treatment, the bolus was most frequently located in the anterior region. After completion of the prosthetic rehabilitation, the bolus was mainly located to the lateral segments during chewing of the test foods, namely meat and bread. The recordings were almost identical 13 yr later. Despite a very reduced periodontal support, posterior cantilevered segments were satisfactorily used in comminution and the patients seemed to be unaware of the forces exerted on the remaining teeth.     

A study of the effects of chewing patterns on occlusal wear

The chewing cycle is a functional movement, closely related to occlusion, the neuromuscular system and the central nervous system. Although actual chewing paths are complicated and vary from individual to individual, there are two typical patterns. One is more vertical in nature and is similar to a chopping movement. The other is a more lateral type that is similar to a grinding movement. The purpose of this study was to evaluate the effects of chewing patterns on occlusal wear. Fifteen subjects exhibiting a chopping-chewing pattern and 15 subjects exhibiting a grinding-chewing pattern were selected using a jaw tracking device. The occlusal wear values, obtained by both ordinal and Woda's arbitrary scales, and frequencies of non-working facets were calculated for each group. The occlusal wear values in all teeth and in each segment, obtained by the use of the ordinal scale did not vary significantly between the chopping and the grinding type group. However, the occlusal wear values of the grinding type group in all teeth and in posterior teeth segments, obtained by the use of Woda's arbitrary scale, were significantly greater than those of the chopping type group. Frequencies of non-working facets in posterior teeth showed no significant differences between the groups.     

The influence of oral processing,food perception and social aspects on food consumption: a review

Eating is an essential activity to get energy and necessary nutrients for living. While chewing, the food is broken down by the teeth and dissolved by saliva. Taste, flavour and texture are perceived during chewing and will contribute to the appreciation of the food. The senses of taste and smell play an important role in selecting nutritive food instead of toxic substances. Also visual information of a food product is essential in the choice and the acceptance of food products, whereas auditory information obtained during the chewing of crispy products will provide information on whether a product is fresh or stale. Food perception does not just depend on one individual sense, but appears to be the result from multisensory integration of unimodal signals. Large differences in oral physiology parameters exist among individuals, which may lead to differences in food perception. Knowledge of the interplay between mastication and sensory experience for groups of individuals is important for the food industry to control quality and acceptability of their products. Environment factors during eating, like TV watching or electronic media use, may also play a role in food perception and the amount of food ingested. Distraction during eating a meal may lead to disregard about satiety and fullness feelings and thus to an increased risk of obesity. Genetic and social/cultural aspects seem to play an important role in taste sensitivity and food preference. Males generally show larger bite size, larger chewing power and a faster chewing rhythm than females. The size of swallowed particles seems to be larger for obese individuals, although there is no evidence until now of an ‘obese chewing style’. Elderly people tend to have fewer teeth and consequently a less good masticatory performance, which may lead to lower intakes of raw food and dietary fibre. The influence of impaired mastication on food selection is still controversial, but it is likely that it may at least cause adaptation in food choice. Systemic conditions, such as high blood pressure, diabetes and cancer, with or without medicine use, tend to be associated with taste and chewing alterations. However, definite conclusions seem hard to reach, as research protocols vary largely.     

Vibration perception thresholds of human maxillary and mandibular central incisors

Tactile information from dental mechanoreceptors contributes to the perception of food bolus textures and the control of mastication. While numerous studies have measured the light-touch sensory thresholds of teeth, little information is available about the vibrotactile perception thresholds of teeth. This study uses an adaptive psychophysical procedure to determine thresholds of vibratory stimulation of maxillary and mandibular central incisors in 16 healthy human subjects. An electromechanical vibrator delivered labiolingual forces perpendicular to the long axis of the maxillary and mandibular incisors at 10 stimulation frequencies between 40 and 315 Hz. The median thresholds ranged between 44 and 104 mN. A linear regression analysis revealed a significant increase in the vibrotactile thresholds with increasing frequencies for stimulation of the maxillary and mandibular incisors. No significant differences were found between regression slopes of the thresholds of the maxillary and mandibular incisors. These results indicated that maxillary and mandibular incisors should be able to discriminate effectively among a variety of textures based on their ability to encode a wide range of vibration frequencies.     

Occlusal perception of thickness in patients with bridges on osseointegrated oral implants

Abstract – Perception of thickness was estimated in subjects with osseointegrated oral implant bridges (OIB), complete denture wearers and subjects with complete natural dentitions. The test was performed with factory-produced aluminum foil, 9, 20, 50, 100 and 150 μm thick, in the regions of the right second premolars, the canines and the central incisors. Occlusal perception did not differ between the three regions in any of the groups. Certain perceptiveness (>80% of tests correct) was found at the 20 μm level in subjects with natural dentitions, at the 50 μm level in OIB subjects and at the 100 μm level in subjects with a complete denture in one or both jaws. It is concluded that partial or complete lack of periodontal receptors is compensated for by other perceptive organs and that implant bridge therapy ad modum Brånemark partly restores occlusal sensibility.     

义齿附着剂增强总义齿咀嚼功能的研究

目的:本文对使用义齿附着剂后总义齿4小时内咀嚼效率的变化进行研究。方法:选择临床复诊的总义齿病例,在使用Biotene义齿附着剂前和使用后即刻,及使用4小时后用称重法测定总义齿的咀嚼效率。结果:使用义齿附着剂后即刻,总义齿咀嚼效率较使用前明显增加(P<0.05);使用后4小时内总义齿咀嚼效率较使用后即刻无明显变化。结论:义齿附着剂可显著增加总义齿咀嚼效率,4小时内无明显改变。     

Effect of chewing speed on energy expenditure in healthy subjects

Objective. The aim of the study was to investigate the effect of rate of chewing on energy expenditure in human subjects. Materials and methods. Fourteen healthy subjects (aged 18–24 years) within the normal range of BMI participated in a cross-over experiment consisting of two 6-min sessions of gum chewing, slow (～60 cycles/min) and fast (～120 cycles/min) chewing. The resting energy expenditure (REE) and during gum chewing was measured using a ventilated hood connected to a gas analyzer system. The normality of data was explored using the Shapiro-Wilk test. The energy expenditure rate during chewing and the energy expenditure per chewing cycle were compared between the two chewing speeds using Wilcoxon signed ranks tests. Results. The energy expenditure per chewing cycle during slow chewing (median 1.4, range 5.2 cal; mean 2.1±1.6 cal) was significantly higher than that during fast chewing (median 0.9, range 2.2 cal; mean 1.0±0.7 cal) (p < 0.005). However, the energy expenditure rate was not significantly different between the two chewing speeds (p > 0.05). Conclusions. The results of this study suggest that chewing at a slower speed could increase the energy expenditure per cycle and might affect the total daily energy expenditure.     

Effect of natural mediotrusive contact on electromyographic activity of jaw and cervical muscles during chewing

Abstract

Objective. This study evaluated the effect of a natural mediotrusive contact on the electromyographic (EMG) activity of the anterior temporalis and sternocleidomastoid muscles during chewing in healthy subjects. Materials and methods. The study sample included two groups of 15 subjects each (Group 1: with natural mediotrusive contact; Group 2: without natural mediotrusive contact). Bilateral surface EMG activity was recorded on anterior temporalis and sternocleidomastoid muscles during unilateral chewing of a half cookie and unilateral chewing of a piece of apple. Anterior temporalis and sternocleidomastoid muscle activity was normalized against activity recorded during maximal voluntary clenching in intercuspal position and maximal intentional isometric head–neck rotation to each side, respectively. The partial and total asymmetry indexes were also calculated. Data were analyzed using Mann-Whitney, Wilcoxon and unpaired t-test. Results. EMG activity of anterior temporalis and sternocleidomastoid muscles showed no significant difference between the groups. EMG activity of anterior temporalis was similar between working and non-working sides during chewing in both groups. EMG activity of sternocleidomastoid muscle was higher in the working side than in the non-working side in Group 2 subjects. Asymmetry indexes were not significantly different between groups. Conclusions. The similar EMG pattern and asymmetry indexes observed suggest the predominance of central nervous control over peripheral inputs on anterior temporalis and sternocleidomastoid motor neuron pools.     

Effect of complete and partial removable dentures on chewing movements

Partial or complete edentulism impairs mastication. However, it is unclear how the chewing cycle is affected by prosthetics. We evaluated the chewing movements of patients fitted with complete (CD) or removable partial denture (RPD). A total of 29 subjects were kinesiographically evaluated during chewing of peanuts and Optocal portions in a random sequence. The subjects were divided into two groups according to prosthesis type. Group RPD was composed of 14 partially edentulous patients using a lower distal extension RPD (mean age 61 ± 8 years), and group CD contained 15 completely edentulous patients using CD (mean age 65·9 ± 7·9 years) in both jaws. Opening, closing, occlusal and masticatory cycle times, movement angle (opening and closing), maximum velocity (opening and closing), total area and chewing cycle amplitudes were evaluated. The results were subjected to anova and Tukey's HSD test at a significance level of 5%. The RPD group exhibited shorter opening and closing phases and masticatory cycle time (P < 0·05). Maximum velocities were also higher in the RPD group, irrespective of the test material (P < 0·05). The area and amplitude of the chewing envelope was smaller in the CD group (P < 0·0001). The test material did not influence chewing cycles in any of the parameters evaluated (P > 0·05). RPD wearers use a faster chewing sequence with greater vertical and lateral jaw excursions compared with CD wearers.     

Influence of static and dynamic occlusal characteristics and muscle force on masticatory performance in dentate adults

Masticatory performance is the outcome of a complex interplay of several factors. This study was carried out to determine the relationship between masticatory performance and several muscular-related and occlusion-related factors in a population with a full or near-full complement of natural teeth. One-hundred dentate young adults participated in this cross-sectional study. Maximum muscular force with jaw, hand, tongue, and cheek were measured by means of a gnatodynamometer. Occlusal contact area and number of teeth in contact were determined in the maximal intercuspal position and in a 1.5-mm right and left lateral excursion by means of interocclusal registrations that were scanned and analysed using image software. Masticatory performance was determined by sieving the Optosil particles resulting from 20 chewing cycles. Stepwise multiple linear regression analysis showed that the maximum bite force in the region of the first molar had the best correlation with masticatory performance and explained 36% of its variation. Static occlusion characteristics such as occlusal contact area, the lack of lateral crossbite and the number of anterior teeth in contact explained an additional 9% of the variation in masticatory performance. These findings suggest that variables related to dynamic occlusion or tongue or cheek force do not enhance the prediction of masticatory performance.     

Short‐term changes in chewing efficiency and subjective evaluation in normal dentate subjects after insertion of oral appliances with an occlusal flat table

Oral appliances with an occlusal flat table are used as treatment dentures. However, the short‐term effect of insertion of such oral appliances on chewing has not been reported. This study aimed to determine whether experimental and continuous insertion of oral appliances with an occlusal flat table has an effect on chewing efficiency and Oral Health Impact Profile (OHIP) in healthy participants. Ten participants each in the oral‐appliance and control (no oral‐appliance insertion) groups attended six data collection sessions for 5 consecutive days. Participants answered the OHIP questionnaire and underwent the chewing efficiency test. For each parameter, intergroup differences were investigated in terms of change from baseline to immediately after oral‐appliance insertion (0 hour; P < .05) and from 0 hour to 24, 48, 72 and 96 hours after oral‐appliance insertion (P < .05). There were significant differences between groups in the degree of change in chewing efficiency and OHIP scores for functional limitation, physical pain, physical disability and handicap from baseline to 0 hour (all, P < .001); among these, only OHIP scores for functional limitation and physical pain demonstrated significant differences in degree of change between the two groups at 96 hours after appliance insertion (P = .477 and .275, respectively). Differences between the two groups in the degree of change in other parameters were not significant. Insertion of oral appliances caused a decrease in chewing efficiency and an increase in OHIP scores. Continuous insertion improved functional limitation and physical pain within 96 hours.     

Influence of intra‐oral sensory impairment by anaesthesia on food comminution and mixing in dentate subjects

Sensory input from sensory receptors regarding food morsels can affect jaw motor behaviours during mastication. The aim was to clarify the effects of intra‐oral sensory input on the food‐comminuting and food‐mixing capacities of dentate subjects. Eleven dentate subjects without sensory dysfunction in their oro‐facial region participated in this study. Local anaesthesia was achieved on the periodontal structures and on the oral mucosa of the subjects' preferred chewing side by injecting a lidocaine solution with adrenalin. At baseline (control) and after anaesthesia, data on the subjects' food‐comminuting and food‐mixing capacities were gathered. The food‐comminuting capacity was quantified by measuring the degree of pulverisation of peanuts (objective hardness; 45·3 [Newton, N]) after a prescribed 20 chewing strokes. The food‐mixing capacity was measured as the degree of immixture of a two‐coloured paraffin wax cube after 10 chewing strokes. Wax cubes of three different hardness levels were used (soft, medium and hard: 20·3, 32·6 and 75·5 [N], respectively) and were chewed in random order. After anaesthesia, the subjects' food‐comminuting capacity significantly decreased (P < 0·001), as did the food‐mixing capacity for each hardness level of the wax cubes (P < 0·01). A significant correlation was observed between the objective hardness values and the anaesthesia effects for the food‐mixing capacity (P < 0·05), indicating that after anaesthesia, deterioration of the mixing capacity increased as the hardness increased. In conclusion, intra‐oral sensory input can affect both food‐comminuting and food‐mixing capacities.     

Effect of body posture on chewing behaviours in healthy volunteers

Mastication is essential to the eating process and forms an important part of feeding behaviour. Many factors related to the food bolus, such as bolus texture and size, are known to influence mastication. The aim of this study was to determine the effects of body posture on (i) chewing duration prior to the first swallow and (ii) patterns of mastication‐related EMG activity. We asked 10 healthy adults to chew 8 g of steamed rice with barium sulphate while we recorded masseter, suprahyoid and infrahyoid muscle activity and simultaneously collected videofluorographic images. Participants chewed in either an upright or reclining position. Chewing duration, which was defined as the time from the start of mastication to the first swallow, was not different between the positions. However, the variability of chewing duration was larger in the upright versus reclining position, and the chewing duration in the reclining position was distributed around 15 s. Masseter activity gradually decreased in a time‐dependent manner and was significantly larger at the early versus late stage of mastication. Suprahyoid activity was significantly larger at the early versus middle stage of mastication in the upright position only. Finally, masseter activity per second was negatively correlated with changes in chewing duration, that is, the larger the increase in chewing duration in the reclining position, the more the decrease in masseter activity per second. These results suggest that position‐dependent changes in chewing behaviours, as described by chewing duration and EMG activity, may vary among participants.