Effect of salivary fluid characteristics on the physical features of in vitro bread bolus: From the absence of saliva to artificially simulated hypersalivation.

Saliva facilitates food oral processing, bolus formation, swallowing, and sensory perception, in addition to contributing to oral health and phonation. Ageing, health affections, and polymedication are among many causes altering salivary production, modifying the mastication process, the food impregnation ratio, and in turn altering the characteristics of the bolus, swallowing, and digestion. In this in vitro work, using the AM2 masticator apparatus, which replicates the mechanical actions taking place while chewing solid foods and produces realistic food bolus in various oral conditions, we investigated the effect of salivary fluid characteristics, i.e., composition, quantity (from absence to hypersalivation), temperature, and enzymatic action, on the physical characteristics (i.e., particle size distribution (PSD), bolus mass, salivary fluid content) of in vitro boluses of Traditional French baguette. A ready-to-swallow bolus of baguette displayed on average a d50 value (median particle size by mass) of 4.1 ± 0.4 mm, with saliva fluid constituting âˆ¼ 35 % of the final bolus mass. The absence of saliva in mouth led to a deficient oral processing, forming bread boluses constituted by extremely big particles (ca. 80 % of particles had a size > 7.1 mm) that likely cannot be swallowed safely. On the contrary, an excess of saliva favoured an excessive breaking down of bread, leading to bread boluses constituted by smaller particles than those formed under healthy salivary conditions (d50 decreased from 4.1 mm to 3.1 mm), having a higher salivary fluid content (+10 %). On the other hand, the salivary fluid temperature did not affect PSD, d50, bolus mass, or salivary fluid content of in vitro bread boluses, however, the addition of human salivary α-amylase did, favouring particle size reduction (d50 decreased to 2.6 mm). Therefore, beyond the correlation between bolus hydration by saliva and food properties such as hardness and moisture content, our findings indicate that the quantity of salivary fluid present in the oral cavity and the enzymatic activity of salivary α-amylase during bread mastication significantly influence both the particle size distribution and the fluid content of bread boluses, ultimately determining the physical properties of the bolus and, therefore, potentially impacting the subsequent swallowing process.

Contributory role of the tongue and mandible in modulating the in-mouth air cavity at rest.

OBJECTIVES: The tongue-to-palate distance influences the volume of the in-mouth air cavity (IMAC), thus conditioning the entry of aromatic compounds to the olfactory mucosa site. This study was set out to record the IMAC volume by measuring tongue-to-palate distance at rest. MATERIALS AND METHODS: Twelve young adults in good general health were tested--lips contacting, with at-rest posture of the tongue and jaw during a silent reading task. Observations in this study were limited to pre- and post-swallowing sequences. The tongue-to-palate distance was measured using three electromagnetic sensors placed on the tongue upper surface. IMAC volume was evaluated from a geometrical model, taking into account the tongue-to-palate distance, the IMAC transversal distance measured from dental casts and historic data giving the anterior-posterior distance of the oral cavity. RESULTS: (1) In the at-rest posture, the tongue-to-palate distance was significantly greater at the posterior sensor level. (2) A vertical shift in tongue posture at rest frequently appeared following deglutition. The upward shifts were of larger amplitude and more frequent than the downward shifts. (3) Evaluation of the IMAC volume gave an approximate value of 12 ml at rest. (4) The chin sensor at rest was 2.8 ± 0.8 mm below its position when in occlusion. CONCLUSION: The tongue and mandible contribute to shaping the IMAC volume. CLINICAL RELEVANCE: These and other results suggest that deglutition changes tongue-to-palate distance and influences aroma release during mastication/deglutition acts through modulation of the IMAC volume.

Comprehensive Dental Treatment under General Anesthesia Improves Mastication Capability in Children with Early Childhood Caries-A One-Year Follow-Up Study.

BACKGROUND: Using the granulometry of ready-to-swallow food boluses, this study investigated the evolution of masticatory capability of children with Early Childhood Caries (ECC) after comprehensive dental treatment under general anesthesia (GA). METHODS: Sixteen children with ECC were assessed before and over one year after dental treatment under GA, in comparison with 12 children with a Healthy Oral State (HOS). Oral health criteria, quality of life, body mass index, and frequency of orofacial dysfunctions were recorded. Masticatory kinematic parameters and median food bolus particle size (D50) at swallowing were assessed while masticating raw carrot (CAR), cheese (CHS), and breakfast cereals (CER). The impact of posterior teeth extractions was analyzed. RESULTS: Quality of life and orofacial functions improved after dental treatment. Chewing frequency for all three foods increased without reaching the values of children with HOS, while D50 values for CAR and CHS decreased. After one year, children with posterior teeth extractions exhibited higher D50 values for CAR and CHS than children with only conservative treatment. One third of children with ECC were overweight or obese. CONCLUSIONS: Comprehensive dental treatment improved children's mastication, and their BMI subsequently increased. Links between mastication and nutrition should be investigated further in children.

Do implant-supported prostheses affect bioavailability of nutrients of complete and partially edentulous patients? A systematic review with meta-analysis.

BACKGROUND & AIMS: Debate still exists about the impact of dental implant-supported prostheses on nutritional status of partially and complete edentulous patients. This review aims to answer the focused question: "Do complete and partial edentulous patients, using implant-supported prostheses, present better nutritional and masticatory functions when compared to those using conventional rehabilitations?". A possible cause-effect relationship between masticatory improvements and nutritional gain was also evaluated. METHODS: Literature search included 6 databases (PubMed/Medline, Embase, LILACS, Scopus, Web of Science, and The Cochrane Library - CENTRAL), grey literature (Google Scholar, Proquest Dissertations and Thesis and Open Grey databases) and manual search (last update June 2020), without language, publication time and follow-up restrictions. We included only studies evaluating both masticatory and nutritional outcomes. The PICO question comprised complete and partial edentulous patients (Population), submitted to implant-supported prostheses (Intervention), in comparison to conventional dental prosthetic rehabilitation, evaluating masticatory function and nutrition parameters (outcomes). Risk of bias was assessed by using Cochrane Collaboration's tool (randomized clinical trials), Joanna Briggs Institute critical appraisal checklist (paired clinical trials), and Meta-Analysis of Statistics Assessment and Review Instrument" (JBI - MAStARI) critical appraisal tools (cohort studies). All meta-analyses were conducted at 5% level of significance. This report followed the PRISMA guidelines. (Review registration PROSPERO - CRD42019135744). RESULTS: We identified 1199 articles while searching databases. Fourteen articles met eligibility criteria, including 817 prostheses installed in 660 patients (mean age = 66.8 years-old). Patients wearing implant overdentures (IOD) presented better masticatory function in comparison to conventional complete denture (CD) wearers (p < 0.05). However, bioavailability of several nutrients remained within the same range, except for serum folate that was lower in IOD patients after 6 (mean difference 3.51 nmol/L; p = 0.01) and 12 months of rehabilitation (mean difference 3.69 nmol/L; p = 0.003). When comparing the effects of CD and IOD rehabilitations along time (for the same patient), serum albumin and vitamin B12 levels also decreased for both groups after 12 months-follow-up, but still within the reference range. The additional retention of the implants did not interfere in body weight, but reduced the risk of malnutrition (using the Mini Nutritional Assessment). Implant-supported partial prostheses also improved mastication in comparison to the conventional ones, increasing short-term daily intake of carbohydrates, protein, calcium, fiber, and iron, whereas decreasing the consumption of cholesterol. However, no long-term changes on bioavailability of most nutrients were observed, expect for a slight increase in ferritin and cholinesterase, and a small reduction in folate and Vitamin A. CONCLUSION: Current evidence indicates significant masticatory improvements for dental fixed implant-supported prostheses in comparison to conventional removable prostheses. However, bioavailability remained stable for most of the nutrients, especially for complete edentulous patients. These results indicate the importance of a multidisciplinary approach during oral rehabilitation (nutrient specialist), in order to enhance food choices and promote health benefits to the patients.

Masticatory Adaptation to Occlusal Changes.

This review deals with the frequent wide variability of masticatory capacity/incapacity. Neither researchers nor clinicians have taken sufficient account of this variability despite its implications for nutrition. Mastication in normal healthy oral conditions is first described, followed by a short presentation of the mechanisms of masticatory adaptation in the nervous system. Capacity, incapacity, and successful compensatory adaptation of mastication are then defined, along with the different methods used for their evaluation. Examples of adaptation needs are given, such as those concomitant with dental wear or occlusal changes. Finally, given its vital importance for deeply impaired mastication/deglutition function, the impact of masticatory adaptation processes on nutrition is examined.

Natural food mastication capability in preschool children according to their oral condition: A preliminary study.

This study investigated, for the first time, the masticatory capability of preschool children using natural foods, and the impact of an early oral health alteration (early childhood caries: ECC) on the granulometry of ready-to-swallow food boluses. Thirteen children with ECC were compared to 13 preschool children with a healthy oral condition. Oral health criteria and NOT-S scores (Nordic Orofacial dysfunction Test-Screening) were recorded. For each child, number of masticatory cycles (Nc), chewing time (Ti), and frequency (Fq = Nc/Ti) were recorded during mastication of raw carrot (CAR), cheese (CHS) and breakfast cereals (CER) samples. Food boluses were collected by stopping children at their food-dependent individual swallowing threshold (Nc), and the median food bolus particle size value (D50) was calculated. Correlations were sought between oral health and masticatory criteria. In the ECC group, mean Fq values were significantly decreased for all three foods (p ≤ .001) and mean D50 values were significantly increased (p ≤ .001) compared to the control group (i.e., D50 CAR = 4,384 µm ± 929 vs. 2,960 µm ± 627). These alterations were related to the extent of ECC. The NOT-S mean global score was significantly increased in children with ECC (2.62 ± 1.37 vs. 1 ± 0.91 in the control group, p ≤ .01), due to "Mastication and swallowing" domain impairment. This study gives granulometric normative values for three foods in preschool children and shows the impact of ECC on D50 values. The progression of children's masticatory capability after dental treatment, and the impact of such modifications of sensory input on future eating habits should be explored.

Which variables should be controlled when measuring the granulometry of a chewed bolus? A systematic review.

The distribution of food particles in a chewed bolus characterizes the food destruction after food oral processing (FOP). Previous reviews report that it could be affected by a lot of parameters as the number of chewing strokes, the dental status, but the conditions for producing reproducible data allowing inter-studies comparison have not been clearly described yet. This systematic review aims to identify the variables that can affect bolus granulometry determination, and to calculate their relative weights in the median particle size (D50 ) variations. The systematic review focuses on granulometry expressed as D50 of the most used foods (peanuts, carrots, and almonds) and materials (Optosil and Optocal). Based on 58 studies, 5 variables among 60 being extracted could explain the D50 variations. Conceptual differences between the conditions for FOP should be considered. After Chewing-test, the bolus is collected after a predefined number of strokes and its granulometry characterizes the effects of the dental and muscular apparatus on food destruction, while after Mastication-test the bolus is collected at the swallowing threshold, and its granulometry reflects the outcome of the abilities of the subject to adapt his/her mastication behavior to food texture. Experimental conditions related either to physical sieving or image analysis used to analyze the collected boluses impact the D50 values. Finally, when type of test, sieving conditions, type of food or material, number of chewing strokes, and the oral status of the subjects are controlled, mean D50 values are reproducible and could be used for inter-studies comparisons. PRACTICAL APPLICATIONS: This review provides tables that could be useful to control mean D50 variations in further research.

Effect of occlusal appliance wear on chewing in persons with Down syndrome.

The effects of Down syndrome (DS) include orofacial dysmorphology with neuro-motor difficulties and inter-maxillary discrepancy. It is unclear whether improving the inter-arch relationship would suffice to overcome feeding difficulties in persons with DS. This randomized, double-blind, placebo-controlled crossover study is a first step in evaluating the impact of wearing an orthetic intra-oral appliance on chewing variables in 8 subjects with DS (4 males and 4 females; mean age: 27.6+/-6.1 years). The primary chewing variables were measured through video and electromyographic (EMG) recordings. Secondary variables were (i) modifications in oral health status using the oral assessment for Down syndrome (OADS) questionnaire, (ii) number of inter-arch contacting units (ICUs), (iii) subjects' compliance in wearing the appliance and (iv) subjects' preference between placebo and occlusal appliances. The simultaneous use of EMG and video recordings revealed the presence of lower jaw movements not corresponding to EMG activities in the masticatory muscles. Compared with the pre-treatment situation, wearing an occlusal appliance decreased chewing frequency and increased masticatory time. It is not known whether these changes were indicative of an improvement or a worsening of masticatory function. Persons with DS did not fully adapt to changes in food hardness. A large inter-subject variability was noted, but pre-treatment individual values were not predictive of appliance effect. The maintenance of the number of ICUs obtained at the first installation of appliance and the responses to OADS and satisfaction questionnaires suggested that patients felt more comfortable and that jaw and tongue protrusion were reduced with the appliance.

Is the goal of mastication reached in young dentates, aged dentates and aged denture wearers?

The objective of the present study was to assess the impact of age and dentition status on masticatory function. A three-arm case-control study was performed. Group 1 (n 14) was composed of young fully dentate subjects (age 35.6 +/- 10.6 years), group 2 (n 14) of aged fully dentate subjects (age 68.8 +/- 7.0 years) and group 3 (n 14) of aged full denture wearers (age 68.1 +/- 7.2 years). Mastication adaptation was assessed in the course of chewing groundnuts and carrots to swallowing threshold. Particle size distribution of the chewed food, electromyographic (EMG) activity of the masseter and temporalis muscles during chewing, and resting and stimulated whole saliva rates were measured. Aged dentate subjects used significantly more chewing strokes to reach swallowing threshold than younger dentate subjects (P < 0.05), with increased particle size reduction, longer chewing sequence duration (P < 0.05) and greater total EMG activity (P < 0.05) for both groundnuts and carrots. In addition, aged denture wearers made significantly more chewing strokes than aged dentate subjects (P < 0.001) to reach swallowing threshold for groundnuts. Particle size reduction at time of swallowing was significantly poorer for denture wearers than for their aged dentate counterparts, despite an increase in chewing strokes, sequence duration and EMG activity per sequence. Masticatory function was thus adapted to ageing, but was impaired in denture wearers, who failed to adapt fully to their deficient masticatory apparatus.

The challenge of mastication: preparing a bolus suitable for deglutition.

The main function of mastication is to transform a solid food into a bolus that can be swallowed safely. The bolus characteristics such as particles size or cohesiveness, are continuously sensed during mastication and they are important in initiating deglutition. This study examined the following question: What is the condition of the bolus just before swallowing? Ten subjects with normal dentition aged 37.5 +/- 3.7 years were asked to chew without swallowing six different foods (three nuts and three vegetables) while the number of cycles and the duration of the sequence were recorded. The particle size distribution shown by the expectorated food bolus just before swallowing was examined by image analysis. The results showed that, for a given food, the sizes of the bolus particles just before swallowing were comparable in all subjects. However, the number of cycles and duration of the sequence varied between subjects. Taken together these data strongly suggest that the granularity of the bolus before swallowing has to reach a predetermined state which is obtained by using an individual chewing strategy. This suggests that the bolus structure reflects a key factor for homeostasis and explains the large interindividual variability of the mastication physiologic parameters.

Influence of age on adaptability of human mastication.

The objective of this work was to study the influence of age on the ability of subjects to adapt mastication to changes in the hardness of foods. The study was carried out on 67 volunteers aged from 25 to 75 yr (29 males, 38 females) who had complete healthy dentitions. Surface electromyograms of the left and right masseter and temporalis muscles were recorded simultaneously with jaw movements using an electromagnetic transducer. Each volunteer was asked to chew and swallow four visco-elastic model foods of different hardness, each presented three times in random order. The number of masticatory cycles, their frequency, and the sum of all electromyographic (EMG) activity in all four muscles were calculated for each masticatory sequence. Multiple linear regression analyses were used to assess the effects of hardness, age, and gender. Hardness was associated to an increase in the mean number of cycles and mean summed EMG activity per sequence. It also increased mean vertical amplitude. Mean vertical amplitude and mean summed EMG activity per sequence were higher in males. These adaptations were present at all ages. Age was associated with an increase of 0.3 cycles per sequence per year of life and with a progressive increase in mean summed EMG activity per sequence. Cycle and opening duration early in the sequence also fell with age. We concluded that although the number of cycles needed to chew a standard piece of food increases progressively with age, the capacity to adapt to changes in the hardness of food is maintained.