Natural Chewing Research Articles

The Effectiveness of Salvadora persica (miswak) on Periodontal Health, Literature Review

Periodontal disease is a global prevalent burden on well-being and health-related quality of life. Adequate plaque control on a daily routine basis is the most critical thing to achieve periodontal health. Using toothbrushes in combination with dentifrices is one of the most common methods of oral hygiene maintenance. However, natural chewing sticks such as Salvadora persica are still used in many developing countries due to their low cost and religious background. Salvadora persica displays precious biotherapeutics capacity for antimicrobial, antiviral, antioxidant, and anti-inflammatory effects. Recently, a lot of Salvadora persica extract has been found in dentifrices, mouthwash, chewing Gum, and even local delivery drugs such as periodontal chips, which are still in the research stage. The present review aims to summarize the evidence of various pharmacological and therapeutic aspects of the effectiveness of Salvadora persica in promoting periodontal health and the treatment of periodontal disease.

Polylactic Acid/Saqqez Gum Blends for Chewing Gum Applications: Impact of Plasticizers on Thermo-Mechanical and Morphological Properties.

This study investigated a blend of poly (lactic acid) (PLA) and Saqqez gum, with a weight ratio of 70:30, respectively, along with two plasticizers, acetyl tributyl citrate (ATBC) and polyethylene glycol (PEG), at three different concentrations (14%, 16% and 18% by weight of the PLA). The blend was analyzed using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile tests, water-absorption behavior (coefficients of water absorption, sorption, diffusion and permeability of the samples during 240 h) and chemical resistance (exposure to 1 mol/L HCl and 1 mol/L NaOH for 240 h). The desired elastomer blend was then used to prepare natural chewing gum, which was subsequently subjected to texture profile analyzer (TPA) tests and sensory evaluation. The results showed that the addition of both plasticizers increased the tensile properties of the blend. Compared to neat PLA, all the blends exhibited an increase in elongation at break and a decrease in yield strength, with the maximum elongation at break (130.6%) and the minimum yield strength (12.2 MPa) observed in the blend containing 16% ATBC. Additionally, all the thermal attributes studied, including Tg, Tc and Tm, were lower than those of neat PLA, and the Tg values deviated from the values predicted via Fox's equation. SEM images of the blends confirmed that plasticization improved the homogeneity and distribution of the components in the blend structure. PEG 18% and ATBC 16% exhibit the highest and lowest water-absorption behavior, respectively. Regarding chemical resistance, all blends showed weight gain when exposed to HCl, while no weight loss was observed for resistance to NaOH. The chewing gum sample obtained similar values for the mentioned tests compared to the commercial control sample. Overall, the results indicate that plasticization enhances the structure and performance of the PLA/Saqqez gum blend and further investigation is warranted.

Natural rubber – Increasing diversity of an irreplaceable renewable resource

This paper discusses the importance of introducing domestic natural rubber production and presents the rediscovery of a rubber-producing species, Scorzonera tau-saghyz or “mountain gum”, originally discovered in 1929 on the Karatau mountains in Kazakhstan. This plant could potentially also be cultivated in the U.S. In this exploratory work, roots (2–5 years old) were harvested on June 16, 2021 from wild strands in the Karatau mountains, Kumantas ridge, and Saraba, Kazakhstan, and processed at the Ohio State University. The rubber extraction method was based on an indigenous method in Kazakhstan to make natural chewing gum. Water extraction followed by purification yielded 16.2 wt% rubber from the dry roots, in comparison with 4–8 wt% from most rubber dandelion (Taraxacum kok-saghyz) plants, also a potential domestic rubber producing plant. High-resolution size exclusion chromatography was used to analyze rubber samples. The molecular weights and gel and oligomer contents were very similar to the rubber from Hevea brasiliensis, the current commercial source of natural rubber. More detailed investigations of this very interesting rubber-producing plant are in progress.

Tongue, palatal, hyoid and pharyngeal muscle activity during chewing, swallowing, and respiration

ObjectiveChewing, swallowing, and respiration are synchronized oropharyngeal functions. This study aimed to analyze the dynamics and coordination during natural chewing and swallowing in relation to respiratory phases. DesignEight oropharyngeal muscles in minipigs were recorded using electromyography, X-ray fluoroscopy, and nasopharyngeal dynamics. Chewing cycles and swallowing episodes were analyzed for timing and activity amplitude along respiratory cycles. Digastric and middle pharyngeal constrictor were used as zero-points for timing analysis in chewing cycles and swallowing episodes, respectively. The beginning of these cycles and episodes were used as the zero-point for timing analysis in respiration during feeding. ResultsThe timing of jaw closing (57.8%) was longer than opening (42.2%) during chewing. Muscle activity occurred 20% later than digastric onsets and 15% earlier than jaw closing phase. Duration of muscle activity was shorter in ipsilateral than contralateral sides except for palatal muscles. Pharyngeal, palatal, and hyoid muscles showed longer durations than tongue muscles in jaw opening (p < 0.05). Palatal and hyoid muscles showed 2-phased activity in chewing while hyoid muscles showed higher amplitude in chewing and swallowing than other muscles. About 80% of the chewing cycles and swallowing episodes occurred in expiration. Nasopharyngeal airflow velocity increased from jaw opening to swallowing while airflow pressure decreased. ConclusionThese findings indicate key activity of palatal and pharyngeal muscles mostly in chewing. The respiratory cycle changes in chewing and swallowing simultaneously with the activation of the tongue, palatal, and pharyngeal muscles. These findings will be useful for further understanding the mechanisms in swallowing and breathing disorders.

Effectiveness of plant-mediated synthesis of hydroxyapatite nano-particles impregnated in Pistachio oleogum resin on mineral contents of human teeth. An in-situ single-blind controlled study

ObjectivesThis study aimed to synthesize and characterize an environmentally friendly nanohydroxyapatite (n-HA) and evaluate its impact on enamel mineral content when incorporated into a Pistachio oleo gum resin (Saqqez) bio-chewing gum for in-situ models. We compared the effects of this green nano-hydroxyapatite (G n-HA) with those of a commercially available synthetic nano-hydroxyapatite (S n-HA). MethodsVarious analytical techniques were employed including XRD, FESEM, FT-IR, EDX/SEM and TGA/DTA to characterize the crystallinity, size and composition of the G n-HA powder. Three chewing gum groups were formulated: (1) Saqqez gum containing 10% wt G n-HA, (2) Saqqez gum containing 10% wt S n-HA, and (3) pure Saqqez gum. In order to evaluate the impact of these chewing gums on enamel, intraoral appliances were fabricated, each containing six enamel specimens. Participants were instructed to chew the gums while wearing these appliances. The calcium (Ca+2) and phosphorus (P) levels in enamel specimens, both with and without exposure to an acid challenge, were quantified using EDX/SEM. FE-SEM was employed to capture the microstructure of the enamel surface. In terms of the statistical analysis, one-way ANOVA and Tukey's post hoc tests were utilized to compare the data, where the significance level (α) was set at 0.05. ResultsThe characterization tests confirmed the successful synthesis of G n-HA. Furthermore, EDX/SEM analysis of the enamel specimens from the intraoral appliance revealed significant variations in calcium (Ca+2) content among the enamel specimens (P = 0.000). The S n-HA group, in particular, exhibited the highest Ca+2 content, while the pure Saqqez group displayed the lowest. Nonetheless, there was no statistically significant differences in phosphorus (P) content observed among the three groups (P = 0.27). ConclusionsSaqqez gum can be considered a wholesome natural chewing gum that serves, as a carrier for delivering remineralization agents to the tooth surfaces. This was evident in the groups containing n-HA, exhibiting elevated Ca+2 levels. It's noteworthy that G n-HA demonstrated less efficacy in enamel remineralization compared to S n-HA.

Regulation of Energy Metabolism and Anti-Inflammatory Activities of Mastiha Fractions from Pistacia lentiscus L. var. chia

Pistacia lentiscus L. var. chia resin (Chios Mastiha), the first natural chewing gum, is widely used in Mediterranean cuisine and has been used in traditional medicine from ancient times. Regarding its chemical composition, Chios Mastiha is known to be rich in triterpenes. Triterpenes have a similar structure to glucocorticoids (GCs), the steroid hormones that exert strong anti-inflammatory activities and play crucial roles in the regulation of cellular metabolism. To simplify the characterization of the bioactive compounds of Mastiha resin, three different polarity fractions were isolated and were further analyzed regarding their main chemical composition and an assessment of their biological activities. The biological assessment focused on the evaluation of the potential anti-proliferative, anti-inflammatory, and apoptotic activities as well as the possible interference of the three different polarity Mastiha fractions with the glucocorticoid receptor signaling, with the aim of characterizing the biochemical mechanisms of the actions of the Mastiha fraction. Applying MTT cell viability assay, luciferase/β-galactosidase assay, and Western blot analysis showed that Chios Mastiha apolar, medium-polar, and polar fractions reduced the HEK293 cell viability in a dose-dependent manner, possibly by mitochondrial-mediated induction of apoptosis. Medium-polar and polar Mastiha fractions also suppressed the GR and NF-κΒ transcriptional activation and the p65 protein levels. These activities were accompanied by the modulation of protein levels of regulatory molecules playing a crucial role in cellular energy homeostasis, such as GR, phosphoenolpyruvate carboxykinase (PEPCK), and/or peroxisome proliferator-activated receptor alpha (PPARα), and by the induction of phosphorylation and the activation of the AMP-activated protein kinase (AMPK). The medium-polar fraction was found to be enriched in triterpenes, such as lupeol, 24Z-masticadienonic acid methyl ester, and 24Z-isomasticadienonic acid methyl ester, and it was the most active one, so we propose that triterpenes in medium-polar fraction are possibly the bioactive compounds responsible for Mastiha's regulatory actions on energy metabolism and anti-inflammatory activities via interference with GR, NF-κΒ, and AMPK signaling. This highlights its potential applications in many fields of pharmaceutical, cosmetic, and nutraceutical interest.

Consuming almonds with chocolate or lettuce influences oral processing behaviour, bolus properties and consequently predicted lipid release from almonds.

Lipids in almonds are naturally encapsulated by cell walls which may reduce the actual metabolizable energy content of almonds. Oral processing increases the accessibility of lipids to digestive enzymes by grinding the almond matrix. This study aimed to investigate the effect of adding accompanying foods (chocolate and iceberg lettuce) to almonds on oral processing behaviour, bolus properties and predicted lipid release. Natural chewing times of four almond model foods including one almond (1.3 g), four almonds (4.6 g), one almond with chocolate (4.3 g) and one almond with iceberg lettuce (4.3 g) were collected from n = 59 participants in duplicate. Expectorated boli at the moment of swallowing were characterized for number and mean area of almond bolus particles. Predicted lipid bioaccessibility was estimated using a previously validated model. At similar bite size (4.3-4.6 g), the addition of chocolate and iceberg lettuce to almonds significantly decreased (p < 0.05) chewing time and significantly increased (p < 0.05) eating rate compared to consumption of almonds alone. Almond bolus particle sizes were similar for almonds consumed alone (one and four almonds) and with chocolate, while consuming almonds with lettuce generated significantly fewer and larger almond bolus particles (p < 0.05). Predicted lipid bioaccessibility of almonds consumed with iceberg lettuce was significantly lower (p < 0.05) than for almonds consumed alone (one and four almonds) and almonds consumed with chocolate. Eating rate correlated significantly and positively with the mean area of bolus particles and significantly and negatively with predicted lipid release. In conclusion, combining almonds with other foods such as chocolate and lettuce influences oral processing behaviour and bolus properties and consequently predicted lipid bioaccessibility of almonds, highlighting the impact of food matrix and consumption context on these aspects.

A Prospective Study on Autotransplantation of Mandibular Third Molars With Complete Root Formation.

Autotransplantation, if possible, is a viable option for replacing a missing tooth when a donor tooth is available. The most typical tooth transplant is the transfer of a third molar to a first molar site. No immune reaction results from transplants of this nature. It restores the proprioceptive function and normal periodontal healing; thus, the patient can have a natural chewing feeling and natural biological response. This study aims to evaluate the prognosis of autotransplanted mandibular third molar and also to evaluate the cost effectiveness of the treatment performed when compared to the other treatment modalities for prosthetic rehabilitation. A prospective study was done in the Department of Oral & Maxillofacial Surgery, Sardar Patel Post Graduate Institute of Dental & Medical Sciences, Lucknow, UP, India, with over 20 patients to evaluate the prognosis of autotransplanted mandibular third molars with complete root formation after atraumatic extraction of first or second mandibular molar, which were randomly selected irrespective of race, sex, caste, and socio-economic status. Regular clinical and radiographical examinations were performed over a period of 1 year and the patients were assessed for pain, swelling, infection, dry socket, periodontal pocket depth, ankylosis, root resorption, tooth mobility, and level of buccal bone in relation to cementoenamel junction (CEJ). Eighteen out of 20 transplants were successful; only 2 mandibular transplants were extracted because of abnormal horizontal and axial mobility and the reason of failure was attributed to fact that the roots of transplant were short and conical and there was lack of alveolar bone height at the recipient site in one patient, while root resorption was the reason for failure of transplant in the other patient. This study assessed the efficacy of autotransplantation of molars and the viability of the procedure to replace unrestorable molar teeth; it also supports the hypothesis that transplantation of a mandibular third molar for replacement of a lost or seriously damaged molar tooth could be a reasonable alternative.

Overview of Chios Mastic Gum (Pistacia lentiscus) Effects on Human Health

Despite the remarkable development of the medical industry in the current era, herbal products with therapeutic potentials arise as attractive alternative treatments. Consequently, Chios mastiha, a natural, aromatic resin obtained from the trunk and brunches of the mastic tree, has recently gained increasing scientific interest due to its multiple beneficial actions. Chios mastiha is being exclusively produced on the southern part of Chios, a Greek island situated in the northern Aegean Sea, and its therapeutic properties have been known since Greek antiquity. There is now substantial evidence to suggest that mastiha demonstrates a plethora of favorable effects, mainly attributed to the anti-inflammatory and anti-oxidative properties of its components. The main use of mastiha nowadays, however, is for the production of natural chewing gum, although an approval by the European Medicines Agency for mild dyspeptic disorders and for inflammations of the skin has been given. The aim of this article is to summarize the most important data about the therapeutic actions of Chios mastiha and discuss future fields for its medical application.

Chew on it: influence of oral processing behaviour on in vitro protein digestion of chicken and soya-based vegetarian chicken.

Oral processing behaviour can affect the bioavailability of macronutrients. The aim of the present study was to determine the influence of oral processing behaviour on bolus properties and in vitro protein digestion of chicken and soya-based vegetarian chicken. Natural chewing time and chewing frequency of both foods were determined in healthy adults (n 96). While natural chewing time differed considerably between consumers (chicken: 7·7-39·4 s; soya-based vegetarian chicken: 7·8-46·2 s), chewing frequency (1·4 chews/s) did not differ considerably between consumers and was independent of product type. Natural chewing times of 11 and 24 s were found for clusters of consumers showing shortest and longest chewing time for both products. Chicken and soya-based vegetarian chicken were chewed for 11 and 24 s and boli expectorated by n 16 consumers to determine in vitro gastric digestion and by n 7 to determine in vitro intestinal digestion. For both foods, longer chewing time resulted in the formation of significantly (P<0·05) more and smaller bolus fragments and higher in vitro degree of protein hydrolysis (DH%) than shorter chewing time (chicken: DH%11s = 7±23 % and DH%24s = 89±26 %; soya-based vegetarian chicken: DH%11s = 57±18 % and DH%24s = 70±21 %, P<0·001). In vitro degree of protein hydrolysis was higher for chicken than that for soya-based vegetarian chicken regardless of chewing time. We conclude that naturally occurring longer chewing time leads to more and smaller bolus particles of chicken and soya-based vegetarian chicken and thereby increases in vitro protein hydrolysis compared with shorter chewing time.

NeckSense: A Multi-Sensor Necklace for Detecting Eating Activities in Free-Living Conditions.

We present the design, implementation, and evaluation of a multi-sensor, low-power necklace, NeckSense, for automatically and unobtrusively capturing fine-grained information about an individual's eating activity and eating episodes, across an entire waking day in a naturalistic setting. NeckSense fuses and classifies the proximity of the necklace from the chin, the ambient light, the Lean Forward Angle, and the energy signals to determine chewing sequences, a building block of the eating activity. It then clusters the identified chewing sequences to determine eating episodes. We tested NeckSense on 11 participants with and 9 participants without obesity, across two studies, where we collected more than 470 hours of data in a naturalistic setting. Our results demonstrate that NeckSense enables reliable eating detection for individuals with diverse body mass index (BMI) profiles, across an entire waking day, even in free-living environments. Overall, our system achieves an F1-score of 81.6% in detecting eating episodes in an exploratory study. Moreover, our system can achieve an F1-score of 77.1% for episodes even in an all-day-long free-living setting. With more than 15.8 hours of battery life, NeckSense will allow researchers and dietitians to better understand natural chewing and eating behaviors. In the future, researchers and dietitians can use NeckSense to provide appropriate real-time interventions when an eating episode is detected or when problematic eating is identified.

Miswak and oral health: An evidence-based review.

Poor oral health has been associated with several chronic and systemic disease. Currently, the most common method of teeth cleaning is the use of a toothbrush together with dentifrices. However, natural chewing stick such as S. persica miswak is still used in many developing countries due to their low cost and availability. The present review aims to summarize the evidences on effectiveness of miswak in promoting oral health. The search was performed using Medline via Ebscohost, Scopus and Google Scholar database to obtain relevant articles published between 2010 to May 2020 using the following set of keywords 1) Miswak OR Salvadora OR persica AND 2) dental OR caries OR plaque OR oral OR orthodontics. Isolated microbial inhibition studies were excluded from the review due to its well-established wealth of literature. Miswak was administered as ten different forms, namely mouthwash, toothpaste, chewing stick, essential oil, aqueous extract, ethanol extract, probiotic spray, dental varnish, dental cement or chewing gum. All studies reported a positive effect of miswak as an anti-plaque, anti-gingivitis, anti-cariogenic, promotion of gingival wound healing, whitening properties, orthodontic chain preservation, and biocompatibility with oral cells. Miswak in its different forms demonstrated positive effect towards oral health maintenance and management.

Sensitive imprinted optical sensor based on mesoporous structure and green nanoparticles for the detection of methamphetamine in plasma and urine.

Methamphetamine (MA), a psychoactive substance with many medicinal applications in different countries, has destructive impacts on the nervous system and brain and can lead to addiction. The optimal system for MA determination must be able to measure the tiny amount of MA in complex matrixes accurately. In the current work, a simple and biocompatible sensitive optical probe was developed based on molecularly imprinted polymers (MIPs) technique and by using green CQDs and mesoporous structured imprinting microspheres (SiO2@CQDs@ms-MIPs). CQDs (ФF=33%) were synthesized via the hydrothermal method using natural chewing gum as carbon source. SiO2 nanoparticles were used as the backup substrate for the placement of CQDs. In spite of biocompatibility, porosity and having high specific area are the unique features of SiO2 nanoparticles. When MA is present, the fluorescence response of MIPs enhances. This is caused by the passivation and adjustment of active clusters that are present on the surface of CQDs. By this optical sensor, the favorable linear dynamic range (5.0-250μM) and the detection limit (1.6μM) were obtained. The applicability of the advanced sensor was studied in real samples such as human urine and human blood plasma. Acceptable results were obtained and recovery amounts were in the 92-110% interval.

Mathematical modelling on the fracture of a laminar prosthesis basis under natural chewing loads

The modern orthopaedic dentistry offers different constructions for restoration of masticatory efficiency. The choice of construction depends on medical indications with individual patient’s features. Because of that during the dental prosthesis implantation, a doctor faced to the problem of the shape and position parameters choose. Generally, this problem is solved based on empirical guidelines for doctors and personal experience. However, even in the practice of the doctor with a large clinique experience, the prosthesis lifetime does not always reach the guaranteed durability. This paper is focused on the problem of prosthesis base fracture under the natural chewing loads. The mathematical model of prosthesis base interaction with oral tissues is proposed together with 3D finite element simulation of chewing loads. The results of the simulation show a principle distribution of stress in the basis of prosthesis under chewing loads depending on its application. It is outlined an important role of prosthesis base interaction with an anatomic features (torus) of oral cavity. The relation between prosthesis base shape and critical stress state under natural chewing loads is studied.

Characterization of Saqez as a natural chewing gum

In this study, oleo-gum resin obtained from wild pistachio trees (Pistacia atlantica Desf. Subsp. kurdica), known as Saqez, was used as a biodegradable, biocompatible, natural, and edible chewing gum. Saqez was characterized by ash content, texture profile analysis, and differential scanning calorimetry (DSC). Furthermore, Saqez was also compared to commercial chewing gum samples. The total ash content was found highest in chewing gums followed by Saqez. Moreover, all texture parameter values of Saqez were lower than conventional chewing gums. The analysis of DSC in Saqez confirmed that the glass transition temperature was comparable to commercial chewing gums. Saqez gum was seen to be an ideal replacement for a synthetic gum base in the manufacturing of a commercial chewing gum. The present study offers new information on Saqez gum, which will be precious and useful for explaining its unique textural properties and thermal behavior in the area of food science and technology.

Excitatory drive of masseter muscle during mastication with dental implants

Previously we have reported a biphasic increase in excitatory drive of the masseter muscle during natural chewing in young adults. We now hypothesize that sensory inputs from the periodontal mechanoreceptors (PMRs) are responsible for the late increase in excitatory drive during this biphasic movement. 13 participants with implant-supported bridges in both jaws, and thus lacking PMRs, and 13 participants with natural dentition chewed and swallowed model food of different hardness. Electromyographic (EMG) activity of the masseter muscle was recorded, along with the position of the mandible, and the muscle activity and jaw kinematics during the different phases of the chewing cycle were analyzed. Throughout the entire masticatory sequence, the excitatory drive of the masseter muscle during the jaw closing increased in a biphasic manner for the dentate participants; whereas biphasic elevation was observed only during the middle and last segments in the implant participants. Dentate participants exhibited significantly greater boosting of the EMG activity during late jaw closing than the implant participants, irrespective of food hardness and segment of the masticatory sequence. Sensory information from PMRs are required for boosting the enhancement of masseter muscle activity during the late jaw closing, during tooth-food contact.

Two-colour chewing gum mixing ability test for evaluating masticatory performance in children with mixed dentition: validity and reliability study.

The unappealing taste of the chewing material and the time-consuming repetitive task in masticatory performance tests using artificial foodstuff may discourage children from performing natural chewing movements. Therefore, the aim was to determine the validity and reliability of a two-colour chewing gum mixing ability test for masticatory performance (MP) assessment in mixed dentition children. Masticatory performance was tested in two groups: systemically healthy fully dentate young adults and children in mixed dentition. Median particle size was assessed using a comminution test, and a two-colour chewing gum mixing ability test was applied for MP analysis. Validity was tested with Pearson correlation, and reliability was tested with intra-class correlation coefficient, Pearson correlation and Bland-Altman plots. Both comminution and two-colour chewing gum mixing ability tests revealed statistically significant MP differences between children (n = 25) and adults (n = 27, both P < 0·01). Pearson correlation between comminution and two-colour chewing gum mixing ability tests was positive and significant (r = 0·418, P = 0·002). Correlations for interobserver reliability and test-retest values were significant (r = 0·990, P = 0·0001 and r = 0·995, P = 0·0001). Although both methods could discriminate MP differences, the comminution test detected these differences generally in a wider range compared to two-colour chewing gum mixing ability test. However, considering the high reliability of the results, the two-colour chewing gum mixing ability test can be used to assess masticatory performance in children, especially at non-clinical settings.

Development of a Natural Chewing Gum from Plant Based Polymer

In this study, Kenger gum obtained from Kenger plant (Gundelia tournefortii) was used in the production of biodegradable and edible chewing gum. Kenger gum was able to be softened by thermal process to improve its textural properties. 80% methanolic extract of gum showed 195.6 gallic acid equivalents (GAE) mg/100 g gum antioxidant activity and 17.9 mm inhibition zone for Escherichia coli O157:H7 as an antimicrobial activity. Softened Kenger gum was also characterized by texture properties, scanning electron microscope (SEM) images and chemical compositions. Hardness value of gum decreased from 864 to 238 g which was comparable to commercial chewing gums. Softened Kenger gum was observed to be a perfect substitute for a synthetic gum base in the production of a conventional chewing gum. Moreover, resilience value was remarkably found to be the best standard parameter to select chewing gums with desired textural properties.

Relationships between chewing rate, occlusion, cephalometric anatomy, muscle activity, and masticatory performance

ObjectiveMastication consists of rhythmic jaw openings and closings. Recent studies suggest that muscle mechanical properties determine the rhythmic rate; however, speed-accuracy tradeoffs may also play a role. This study evaluated how variation in chewing rate affected chewing performance, how masticatory muscle activity varied with chewing rate, and whether morphology and demographics contributed to performance. DesignChewing performance and muscle activity were sampled in 23 healthy, fully-dentate adults, who chewed a standardized test food to a metronome set at 0.5, 0.75, 1, 2 and 3 times their ‘natural’ chewing rates. Subjects produced ten chews per trial, and five trials for each of the five rates. Surface electromyographic (EMG) activity was sampled from masseter and temporalis muscles bilaterally. Demographic, occlusal, and cephalometric data were also obtained. ResultsChewing performance, defined by median particle size, was inversely related to chewing rate; however, performance was not remarkably improved at rates slower than the natural chewing rate. Above the natural chewing rate, variability in EMG bursts diminished, suggesting a reduction in muscle activity modulation at fast rates. Occlusal contacts and most morphological features appeared to play a limited or no role in performance. ConclusionsResults support the hypothesis that the ‘natural’ chewing rate is selected to be as fast as possible while providing sufficient time to allow EMG modulation for improved performance. The interplay between EMG modulation and individual variation in skeletal morphology is likely critical for optimal chewing performance.

Differences between the chewing and non-chewing sides of the mandibular first molars and condyles in the closing phase during chewing in normal subjects

ObjectiveThis study aimed to assess differences between the closing paths of the chewing and non-chewing sides of mandibular first molars and condyles during natural mastication, using standardized model food in healthy subjects. DesignThirty-two healthy young adults (age: 19–25 years; 22 men, 10 women) with normal occlusion and function chewed on standardized gummy jelly. Using an optoelectric jaw-tracking system with six degrees of freedom, we recorded the path of the mandibular first molars and condyles on both sides for 10 strokes during unilateral chewing. Variables were compared between the chewing side and the non-chewing side of first molars and condyles on frontal, sagittal, and horizontal views during the early-, middle- and late-closing phases. ResultsOn superior/inferior displacements, the chewing side first molar and condyle were positioned superior to those on the non-chewing side during the early- and middle-closing phases. Conversely, the first molar and condyle on the non-chewing side were positioned significantly superior to those on the chewing side during the late-closing phase. On anterior/posterior displacements, the chewing side mandibular first molar and condyle were positioned significantly posterior to those on the non-chewing side throughout all closing phases. ConclusionOur results showed the differences between the mandibular first molars and condyles on both sides with respect to masticatory path during natural chewing of a model food. These differences can be useful for informing initial diagnostic tests for impaired masticatory function in the clinical environment.