Variation in human gape cycle kinematics and occlusal topography

Prolonged use of a soft diet during early growth and development alters feeding behavior and chewing kinematics in a young animal model

In infants and children with feeding and swallowing issues, modifying solid foods to form a liquid or puree is used to ensure adequate growth and nutrition. However, the behavioral and neurophysiological effects of prolonged use of this intervention during critical periods of postnatal oral skill development have not been systematically examined, although substantial anecdotal evidence suggests that it negatively impacts downstream feeding motor and coordination skills, possibly due to immature sensorimotor development. Using an established animal model for infant and juvenile feeding physiology, we leverage X-ray reconstruction of moving morphology to compare feeding behavior and kinematics between 12-week-old pigs reared on solid chow (control) and an age- and sex-matched cohort raised on the same chow softened to a liquid. When feeding on two novel foods, almond and apple, maintenance on a soft diet decreases gape cycle duration, resulting in a higher chewing frequency. When feeding on almonds, pigs in this group spent less time ingesting foods compared to controls, and chewing cycles were characterized by less jaw rotation about a dorsoventral axis (yaw) necessary for food reduction. There was also a reduced tendency to alternate chewing side with every chew during almond chewing, a behavioral pattern typical of pigs. These more pronounced impacts on behavior and kinematics during feeding on almonds, a tougher and stiffer food than apples, suggest that food properties mediate the behavioral and physiological impacts of early texture modification and that the ability to adapt to different food properties may be underdeveloped. In contrast, the limited effects of food texture modification on apple chewing indicate that such intervention/treatment does not alter feeding behavior of less challenging foods. Observed differences cannot be attributed to morphology because texture modification over the treatment period had limited impact on craniodental growth. Short-term impacts of soft-texture modification during postweaning development on feeding dynamics should be considered as potential negative outcomes of this treatment strategy.

Energetic costs of feeding in 12 species of small-bodied primates

There are no comparative, empirical studies of the energetic costs of feeding in mammals. As a result, we lack physiological data to better understand the selection pressures on the mammalian feeding apparatus and the influence of variables such as food geometric and material properties. This study investigates interspecific scaling of the net energetic costs of feeding in relation to body size, jaw-adductor muscle mass and food properties in a sample of 12 non-human primate species ranging in size from 0.08 to 4.2 kg. Net energetic costs during feeding were measured by indirect calorimetry for a variety of pre-cut and whole raw foods varying in geometric and material properties. Net feeding costs were determined in two ways: by subtracting either the initial metabolic rate prior to feeding or subtracting the postprandial metabolic rate. Interspecific scaling relationships were evaluated using pGLS and OLS regression. Net feeding costs scale negatively relative to both body mass and jaw-adductor mass. Large animals incur relatively lower feeding costs indicating that small and large animals experience and solve mechanical challenges in relation to energetics in different ways. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

Review on Mandibular Muscle Kinematics

The complexity of mandibular dynamics encourages constant research as a vehicle to improve oral health. The gold standard motion capture system might help us to understand its functioning and its relation to body position, aiming to perform an exhaustive bibliographic review in the Dentistry field. Six different electronic databases were used (Dentistry & Oral Sciences Source, Scopus, Web of Science, PubMed, CINAHL and SPORTDiscus) in April 2022. The selection criteria includes a biography, critical analysis, and the full text from 1984 to April 2022, based on the odontological gold standard, whether or not in combination with additional devices. Clinical cases, bibliographic reviews or meta-analysis and grey literature were excluded. The checklist of the critical assessment methodology by Joanna Brigs was used (JBI). After choosing scientific articles published in peer-reviewed journals, 23 out of 186 investigations were classified as eligible with a total of 384 participants. The issue being addressed is related to the speech properties, posture and body movement in relation to dento-oro-facial muscle and facial analysis, mandibular kinematics and mandibular dynamics during the mastication process. The markers arrangement depends on the dynamic to be analysed. From a physiologic and pathologic perspective, the applications of the optic system are relevant in Dentistry. The scarcity of literature obtained implies the need for future research.

Feeding postural behaviors and food geometric and material properties in bearded capuchin monkeys ( Sapajus libidinosus )

Objectives

Foods that are geometrically and mechanically challenging to eat have been associated with specializations in feeding behavior and craniodental morphology across primates, and many of these foods are embedded, requiring a variety of positional behaviors during feeding. However, variation in positional behaviors in response to food properties is not well understood. Here, we examine differences in feeding postural behaviors across feeding events in relation to substrate and food geometric and material properties in a species of extractive foragers, bearded capuchins (Sapajus libidinosus).

Methods and materials

We coded over 1400 co‐occurring postural and feeding behaviors, their durations, and relative sizes of substrate and food from videos recorded at Fazenda Boa Vista in Gilbués, Piauí, Brazil. Food material properties were measured from foods collected at the time of the video recordings.

Results

Our results suggest that bearded capuchin feeding postures significantly differ across the feeding sequence, with substrate size, and between foods of high and low toughness and elastic modulus. Feeding postures were less variable for highly mechanically challenging foods. Food size also had a significant effect on postural behaviors. Large foods were more likely to be associated with suspended postures and small foods with sitting and squatting. Feeding postural behaviors were best explained by a combination of substrate and food variables.

Conclusions

Our results indicate that food geometric and mechanical properties have a significant influence on feeding postural behaviors in bearded capuchins. We posit that feeding postural behaviors reflect a combination of substrate variables and food properties, and large, mechanically challenging foods have a limiting effect on postural variation.

Grit your teeth and chew your food: Implications of food material properties and abrasives for rates of dental microwear formation in laboratory Sapajus apella (Primates)

Dental microwear analysis has been employed in studies of a wide range of modern and fossil animals, yielding insights into the biology/ecology of those taxa. Some researchers have suggested that dental microwear patterns ultimately relate back to the material properties of the foods being consumed, whereas others have suggested that, because exogenous grit is harder than organic materials in food, grit should have an overwhelming impact on dental microwear patterns. To shed light on this issue, laboratory-based feeding experiments were conducted on tufted capuchin monkeys [Sapajus apella] with dental impressions taken before and after consumption of different artificial foods. The foods were (1) brittle custom-made biscuits laced with either of two differently-sized aluminum silicate abrasives, and (2) ductile custom-made "gummies" laced with either of the two same abrasives. In both cases, animals were allowed to feed on the foods for 36 hours before follow-up dental impressions were taken. Resultant casts were analyzed using a scanning electron microscope. We asked five questions: (1) would the animals consume different amounts of each food item, (2) what types of dental microwear would be formed, (3) would rates of dental microwear differ between the consumption of biscuits (i.e., brittle) versus gummies (i.e., ductile), (4) would rates of dental microwear differ between foods including larger- versus smaller-grained abrasives, and (5) would rates of dental microwear differ between molar shearing and crushing facets in the animals in these experiments? Results indicated that (1) fewer biscuits were consumed when laced with larger-grained abrasives (as opposed to smaller-grained abrasives), but no such difference was observed in the consumption of gummies, (2) in all cases, a variety of dental microwear features was formed, (3) rates of dental microwear were higher when biscuits versus gummies were consumed, (4) biscuits laced with larger-grained abrasives caused a higher percentage of new features per item consumed, and (5) the only difference between facets occurred with the processing of biscuits, where crushing facets showed a faster rate of wear than shearing facets. These findings suggest that the impact of exogenous grit on dental microwear is the result of a dynamic, complex interaction between (at the very least) grit size, food material properties, and time spent feeding - which is further evidence of the multifactorial nature of dental microwear formation.

Understanding the oral processing of solid foods: Insights from food structure

Understanding the relationship between the structure of solid foods and their oral processing is paramount for enhancing features such as texture and taste and for improving health-related factors such as management of body weight or dysphagia. This paper discusses the main aspects of the oral processing of solid foods across different categories: (1) oral physiology related to chewing, (2) in-mouth food transformation, (3) texture perception, and (4) taste perception, and emphasis is placed on unveiling the underlying mechanisms of how food structure influences the oral processing of solid foods; this is exemplified by comparing the chewing behaviors for a number of representative solid foods. It highlights that modification of the texture/taste of food based on food structure design opens up the possibility for the development of food products that can be applied in the management of health.

Muscle architecture dynamics modulate performance of the superficial anterior temporalis muscle during chewing in capuchins

Jaw-muscle architecture is a key determinant of jaw movements and bite force. While static length-force and force-velocity relationships are well documented in mammals, architecture dynamics of the chewing muscles and their impact on muscle performance are largely unknown. We provide novel data on how fiber architecture of the superficial anterior temporalis (SAT) varies dynamically during naturalistic feeding in tufted capuchins (Sapajus apella). We collected data on architecture dynamics (changes in muscle shape or the architectural gear ratio) during the gape cycle while subjects fed on foods of different mechanical properties. Architecture of the SAT varied with phases of the gape cycle, but gape distance accounted for the majority of dynamic changes in architecture. In addition, lower gear ratios (low muscle velocity relative to fascicle velocity) were observed when animals chewed on more mechanically resistant foods. At lower gear ratios, fibers rotated less during shortening resulting in smaller pinnation angles, a configuration that favors increased force production. Our results suggest that architectural dynamics may influence jaw-muscle performance by enabling the production of higher bite forces during the occlusal phase of the gape cycle and while processing mechanically challenging foods.

On the relationship between maxillary molar root shape and jaw kinematics in Australopithecus africanus and Paranthropus robustus

Plio-Pleistocene hominins from South Africa remain poorly understood. Here, we focus on how Australopithecus africanus and Paranthropus robustus exploited and-in part-partitioned their environment. Specifically, we explore the extent to which first maxillary molar roots (M1) are oriented and thus, by proxy, estimate the direction of loads habitually exerted on the chewing surface. Landmark-based shape analysis of M1 root reconstructions of 26 South African hominins and three East African Paranthropus boisei suggest that A. africanus may have been able to dissipate the widest range of laterally directed loads. Paranthropus robustus and P. boisei, despite having overlapping morphologies, differ in aspects of root shape/size, dento-cranial morphologies, microwear textures and C4 food consumption. Hence, while Paranthropus monophyly cannot be excluded, equivalence of dietary niche can. The South African hominins occupied distinct ecological niches, whereby P. robustus appears uniquely adapted to dissipate antero-posteriorly directed loads.