-
The Journal of Prosthetic Dentistry Dec 2021Monolithic zirconia restorations are directly exposed to cyclic loads and temperature changes in the oral cavity after cementation. These stresses may reduce the...
STATEMENT OF PROBLEM
Monolithic zirconia restorations are directly exposed to cyclic loads and temperature changes in the oral cavity after cementation. These stresses may reduce the long-term success of the material by causing uncontrolled phase transformations within the zirconia.
PURPOSE
The purpose of this in vitro study was to evaluate the effect of mastication simulation and different measurement points on the phase transformation of posterior 3-unit monolithic zirconia partial fixed dental prostheses (FDPs) in the posterior region.
MATERIAL AND METHODS
Posterior 3-unit FDPs of monolithic yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP), including BruxZir Shaded (group B), FireZr (group F), and Upcera (group U) (n=10), were machined from presintered blocks. All specimens were exposed to mastication simulation (240 000 cycles/1.7 Hz/50 N). The monoclinic phase content was evaluated by X-ray diffraction (XRD). Phase transformation was measured at the mesial connector (group M), distal connector (group D), and pontic regions (group P) before and after mastication simulation. The relative monoclinic phase amount (Xm) was calculated for all specimens. The data were analyzed by ANOVA and post hoc tests (α=.05).
RESULTS
According to XRD analysis, Xm for all groups and regions showed higher results after aging than before aging (P<.05). Group B has the lowest Xm among the groups. Group B showed a statistically significant difference compared with both group F and group U (P<.05). There was no significant difference between group F and group U (P>.05). When the regions were evaluated regardless of brand and the groups were evaluated in terms of regions, no statistically significant difference was observed between connectors and the pontic region (P>.05).
CONCLUSIONS
Mastication simulation causes an increase in the Xm. However, this increase was unlikely to be clinically significant. There may be differences in phase transformation depending on the contents of the brands and sintering procedures. Variations in the phase quantity were independent of the connector regions and pontic for FDPs.
Topics: Ceramics; Dental Materials; Denture, Partial, Fixed; Mastication; Materials Testing; Zirconium
PubMed: 34688478
DOI: 10.1016/j.prosdent.2021.09.022 -
Archives of Oral Biology Feb 2023The aims of this study were to develop a novel rodent model of masticatory muscle ischaemia via unilateral ligation of the external carotid artery (ECA), and to...
OBJECTIVE
The aims of this study were to develop a novel rodent model of masticatory muscle ischaemia via unilateral ligation of the external carotid artery (ECA), and to undertake a preliminary investigation to characterize its downstream effects on mechanosensitivity and cellular features of the masseter and temporalis muscles.
DESIGN
The right ECA of 18 male Sprague-Dawley rats was ligated under general anaesthesia. Mechanical detection thresholds (MDTs) at the masseter and temporalis bilaterally were measured immediately before ECA ligation and after euthanasia at 10-, 20-, and 35-days (n = 6 rats/timepoint). Tissue samples from both muscles and sides were harvested for histological analyses and for assessing changes in the expression of markers of hypoxia and muscle degeneration (Hif-1α, VegfA, and Fbxo32) via real time PCR. Data were analyzed using mixed effect models and non-parametric tests. Statistical significance was set at p < 0.05.
RESULTS
MDTs were higher in the right than left hemiface (p = 0.009) after 20 days. Histological changes indicative of muscle degeneration and fibrosis were observed in the right muscles. Hif-1α, VegfA, and Fbxo32 were more highly expressed in the masseter than temporalis muscles (all p < 0.05). Hif-1α and, VegfA did not change significantly with time in all muscles (all p > 0.05). Fbxo32 expression gradually increased in the right masseter (p = 0.024) and left temporalis (p = 0.05).
CONCLUSIONS
ECA ligation in rats induced hyposensitivity in the homolateral hemiface after 20 days accompanied by tissue degenerative changes. Our findings support the use of this model to study pathophysiologic mechanisms of masticatory muscle ischaemia in larger investigations.
Topics: Male; Rats; Animals; Rats, Sprague-Dawley; Mastication; Electromyography; Masticatory Muscles; Temporal Muscle; Masseter Muscle
PubMed: 36543038
DOI: 10.1016/j.archoralbio.2022.105602 -
The British Journal of Nutrition Feb 2020The bioaccessibility of fat has implications for satiety and postprandial lipidaemia. The prevailing view holds that the integrity of plant cell wall structure is the...
The bioaccessibility of fat has implications for satiety and postprandial lipidaemia. The prevailing view holds that the integrity of plant cell wall structure is the primary determinant of energy and nutrient extraction from plant cells as they pass through the gastrointestinal (GI) tract. However, comparisons across nuts (walnuts, almonds and pistachios) with varying physical properties do not support this view. In the present study, masticated samples of three nuts from healthy adults were exposed to a static model of gastric digestion followed by simulated intestinal digestion. Primary outcomes were particle size and lipid release at each phase of digestion. Walnuts produced a significantly larger particle size post-mastication compared with almonds. Under gastric and intestinal conditions, the particle size was larger for walnuts compared with pistachios and almonds (P < 0·05). However, the masticated and digesta particle sizes were not related to the integrity of cell walls or lipid release. The total lipid release was comparable between nuts after the in vitro intestinal phase (P > 0·05). Microstructural examination showed ruptured and fissured cell walls that would allow digestion of cellular contents, and this may be governed by internal cellular properties such as oil body state. Furthermore, the cell walls of walnuts tend to rupture rather than separate and as walnut tissue passes through the GI tract, lipids tend to coalesce reducing digestion efficiency.
Topics: Adult; Biological Availability; Computer Simulation; Dietary Fats; Digestion; Energy Metabolism; Female; Gastrointestinal Tract; Humans; Hyperlipidemias; Juglans; Lipids; Male; Mastication; Particle Size; Pistacia; Postprandial Period; Prunus dulcis; Satiation
PubMed: 31619299
DOI: 10.1017/S0007114519002630 -
Physiology & Behavior Jun 2023This longitudinal study investigated developmental changes in jaw-closing muscle activities during ingestive behaviors in rats. On postnatal day (P) 10, electromyography...
This longitudinal study investigated developmental changes in jaw-closing muscle activities during ingestive behaviors in rats. On postnatal day (P) 10, electromyography (EMG) electrodes were inserted into the masseter and temporalis muscles of rat pups. EMG activities were recorded for the following ingestive behaviors between P14 and P49: for suckling, including nipple attachment and rhythmic sucking on P14 and for pasta biting, pellet chewing, and milk licking between P21 and P49. Burst rhythms and muscle coordination (i.e., the correlation and time lag) between masseter and temporalis activities were assessed for each behavior. The burst rhythms of nipple attachment and rhythmic sucking on P14 were significantly slower than those of pasta biting, pellet chewing, and milk licking on P21. Muscle coordination differed between suckling on P14 and mastication and licking on P21. Between P21 and P49, increases were observed in burst rhythms for pasta biting and pellet chewing. The rate of increases in burst rhythms was higher for pasta biting than for pellet chewing. Muscle coordination between the two muscle activities for pasta biting did not significantly change between P21 and P49, whereas that for pellet chewing significantly changed between P21 and P24 and stabilized after P24. Burst rhythms for milk licking did not significantly change over time, while muscle coordination between the two muscle activities changed from agonist to antagonist muscle-like activity on approximately P35. The present results demonstrate that distinct patterns of rhythmic jaw-closing muscle activities emerge before weaning, they continue to change over time, and they exhibit unique developmental dynamics for each behavior after weaning.
Topics: Animals; Rats; Masticatory Muscles; Weaning; Longitudinal Studies; Masseter Muscle; Temporal Muscle; Mastication; Electromyography
PubMed: 36965571
DOI: 10.1016/j.physbeh.2023.114173 -
Nutrients May 2020Bolus texture is a key factor for safe swallowing in patients with dysphagia since an improper texture may result in aspiration and/or pharyngeal residue. This article... (Review)
Review
Bolus texture is a key factor for safe swallowing in patients with dysphagia since an improper texture may result in aspiration and/or pharyngeal residue. This article discusses swallowing bolus texture from two key aspects: the textural change of solid food by mastication and the current standardized definition of food texture in Japan. When swallowing a liquid bolus, the texture is mostly maintained from ingestion to swallow onset. For solid food, however, the food is crushed by chewing and mixed with saliva before swallowing; the texture of the ingested food is modified to an easily swallowable form at swallow onset by mastication. Understanding the mechanism of mastication and its assessment are therefore important in deciding the proper diet for dysphagic patients. As standardized criteria for classifying the texture of food and liquid are essential as well, this report also describes the Japanese Dysphagia Diet 2013 that is commonly used as the standardized index for dysphagic diets in Japan.
Topics: Deglutition; Deglutition Disorders; Diet; Food; Humans; Japan; Mastication; Saliva; Tongue; Viscosity
PubMed: 32486264
DOI: 10.3390/nu12061613 -
Journal of Dairy Science Jun 2023Historical research had shown that forage particle size influences chewing activity, ruminal pH, volatile fatty acid profiles, and milk fat percentage. With this in... (Review)
Review
Historical research had shown that forage particle size influences chewing activity, ruminal pH, volatile fatty acid profiles, and milk fat percentage. With this in mind, Mertens in 1997 published one of the most frequently cited papers in the Journal of Dairy Science that laid out a comprehensive system for integrating neutral detergent fiber (NDF) and particle size of feeds into one measure: physically effective NDF (peNDF). Based on total chewing time (i.e., eating plus ruminating), peNDF enabled ration formulation to meet the minimum fiber requirements of ruminants to maintain ruminal pH and milk fat. Total chewing time is related to feed NDF content and particle size, so Mertens proposed that peNDF could be determined simply from a chemical measure of NDF and particle size measured as the fraction of dry matter retained on a 1.18-mm sieve with vertical shaking of a dried sample. In the past 2 decades, the peNDF system has been incorporated into nutrition models and is routinely used in ration formulation. Early on, Mertens recognized that starch would affect the minimum peNDF requirements, and his work was the first to demonstrate that starch and fermentation pH affect ruminal fiber degradation kinetics. Subsequently, Mertens's insight into particle size analysis was extended from fibrous feeds to corn silage processing with the development of the commonly used corn silage fragmentation index for assessing starch availability. Participants at the 33rd Discover Conference on fiber in 2017 ranked improved physical description of feeds as a top priority for future research, undoubtedly recognizing the need to carry forward Mertens's pioneering work. Future research will likely focus on improving the physicochemical and biological evaluation of rumen fiber degradation and passage, thereby improving the prediction of animal response. The comprehensive system that David Mertens built for meeting the fiber requirements of ruminants has transformed ration formulation.
Topics: Female; Animals; Lactation; Diet; Digestion; Dietary Fiber; Silage; Mastication; Starch; Fermentation; Particle Size; Rumen
PubMed: 36400612
DOI: 10.3168/jds.2022-22419 -
Journal of Texture Studies Dec 2023Swallowing disorders, or dysphagia, affect a large part of the population due to factors such as degenerative diseases, medication side effects or simply age-related...
Swallowing disorders, or dysphagia, affect a large part of the population due to factors such as degenerative diseases, medication side effects or simply age-related impairment of physiological oropharyngeal function. The management of dysphagia is mainly handles through texture-modified foods of progressively softer, smoother, moister textures, depending on the severity of the disorder. Rheological and physiological-related properties of boluses were determined for a group of five older persons (average age, 74) for a set of texture-modified foods: bread, cheese and tomato and the combination into a sandwich. The softest class was gel food, after which came a smooth timbale; both were compared to boluses of regular food. The subjects chewed until ready to swallow, at which point the bolus was expectorated and measured regarding saliva content, linear viscoelasticity and shear viscosity. The results were compared to those of a previously studied younger group (average age, 38). The general physiological status of the subjects was determined by hand and tongue strength, diadochokinesis and one-legged standing and showed that all subjects were as healthy and fit as the younger group. Age-related properties such as one-legged standing with closed eyes and salivary flow plus bolus saliva content were lower for the older group, but the average chews-until-swallow was surprisingly also lower. Consequently, bolus modulus and viscosity were higher than for the younger group. Overall, the intended texture modification was reflected in bolus rheological and physiological-related properties. Bolus modulus, viscosity, saliva content and chews-until-swallowed all decreased from regular food to timbale food to gel food.
Topics: Humans; Aged; Aged, 80 and over; Adult; Deglutition Disorders; Deglutition; Cheese; Mastication; Rheology
PubMed: 37463674
DOI: 10.1111/jtxs.12789 -
International Journal of Obesity (2005) Dec 2020Early attempts at the objective measurement of food intake in humans followed many heuristic pioneer studies in laboratory animals, which revealed how homeostatic and... (Review)
Review
Early attempts at the objective measurement of food intake in humans followed many heuristic pioneer studies in laboratory animals, which revealed how homeostatic and hedonic factors interact to shape the daily eating patterns. Early studies in humans examined the characteristics of intake responses at discrete ingestive events. Described for the first time in 1969, the edogram consisted of a parallel recording of chewing and swallowing responses during standardized lunches, allowing parameters of the "microstructure of meals" to be quantified under varying conditions of deprivation or sensory stimulation, in parallel with overall meal size, meal duration, and eating rate. Edographic studies showed consistent changes in the microstructure of meals in response to palatability level (increased eating rate, decreased chewing time and number of chews per food unit, shorter intrameal pauses, and increased prandial drinking under improved palatability). Longer premeal deprivation affected the eating responses at the beginning of meals (decreased chewing time and number of chews per food unit) but not at the end. Eating rate decelerated during the course of meals in normal-weight participants but not in participants with obesity. These observations largely agreed with contemporary works using other objective measurement methods. They were confirmed and expanded in later studies, notably in the investigation of satiation mechanisms affecting weight control. Importantly, research has demonstrated that the parameters of the microstructure of meals not only reflect the influence of stimulatory/inhibitory factors but can, per se, exert a causal role in satiation and satiety. The early edographic recording instruments were improved over the years and taken out of laboratory settings in order to address the measurement of spontaneous intake responses in free-living individuals. Much remains to be done to make these instruments entirely reliable under the immense variety of situations where food consumption occurs.
Topics: Appetite; Deglutition; Eating; Energy Intake; Humans; Mastication; Meals; Satiation
PubMed: 32843712
DOI: 10.1038/s41366-020-00653-w -
CoDAS 2021To characterize the masticatory function of the elderly and to compare total amount of time, masticatory strokes and total mastication score among the elderly and young... (Observational Study)
Observational Study
PURPOSE
To characterize the masticatory function of the elderly and to compare total amount of time, masticatory strokes and total mastication score among the elderly and young adults.
METHODS
It is an observational, cross-sectional and analytical study. A total of 50 individuals participated, 25 elderly (mean age 66 years) and 25 young adults (mean age 22 years). The evaluation of mastication was performed by standardized filming of the usual mastication of a wheat flour biscuit. The masticatory type (alternated bilateral, simultaneous bilateral, preferential unilateral, chronic and anterior), masticatory score, total masticatory time and the total number of masticatory strokes were verified and compared between the elderly and young adults.
RESULTS
The predominant masticatory pattern in the young adults was the alternated bilateral mastication (52%), while, in the elderly, the simultaneous bilateral mastication predominated (48%). The use of dental prostheses had a significant influence on the total mastication score; elderly presented greater masticatory time and greater amount of masticatory strokes; however, the total masticatory score was lower for this group.
CONCLUSION
The use of dental prosthesis has a significant influence on masticatory function. When compared to young adults, the elderly had a greater amount of time and masticatory strokes and a lower total mastication score.
Topics: Adult; Aged; Cross-Sectional Studies; Flour; Humans; Mastication; Triticum; Young Adult
PubMed: 34705926
DOI: 10.1590/2317-1782/20212020364 -
International Journal of Environmental... Mar 2022We investigated how jelly is crushed and examined the relationship between tongue pressure and tongue food crushing ability among older adults requiring nursing home...
We investigated how jelly is crushed and examined the relationship between tongue pressure and tongue food crushing ability among older adults requiring nursing home care. Seventy-two participants were instructed to freely crush the test foods soft jelly (SJ) and hard jelly (HJ). We visually evaluated the crushability of the test food and identified the intraoral tissues (active sites) used to crush the test food. The active sites were consistent for all participants for both SJ and HJ, and they included the maxillary and mandibular teeth in 41 participants, teeth and residual ridges in 15 participants, maxillary and mandibular residual ridges in 10 participants, and tongue and palate in six participants. Two participants failed to crush the SJ; the active sites in both participants were the tongue and palate. No participant using the tongue and palate as active sites could crush the HJ. Furthermore, 64 participants could crush the SJ and 23 could crush the HJ using the tongue and palate. The cutoff value of the tongue pressure for crushability of the HJ was 22.0 kPa. Assessing tongue pressure and intraoral active sites involved in food crushing could help determine an appropriate diet for older adults requiring nursing home care.
Topics: Aged; Food; Humans; Mastication; Nursing Homes; Pilot Projects; Pressure; Tongue
PubMed: 35329105
DOI: 10.3390/ijerph19063419