Search

There is limited knowledge about masticatory function after the release of temporomandibular joint (TMJ) ankylosis. In this study, masticatory function was evaluated by measuring maximum voluntary bite force (MVBF) and chewing efficiency in 30 unilateral TMJ ankylosis patients who were treated with buccal fat pad (BFP) interpositional arthroplasty. Eighteen subjects over 12 years of age were included in study Group A and 12 subjects below 12 years of age in study Group B. Patients in the study groups had completed a minimum follow up of one year after surgery. Control groups C (over 12 years of age, n = 18) and D (under 12 years of age, n = 12) consisted of age, sex, and weight-matched normal subjects. The mean MVBF was measured between occluding molar teeth with a strain gauge transducer. Chewing efficiency was measured with two different coloured chewing gum strips. These were chewed for 5, 10, 20, 30, and 50 strokes. Compared with normal subjects, the study groups (A and B) could generate 64.7% (p = 0.004*) and 89.8% (p = 0.121) of MVBF, respectively. Overall chewing efficiency was 88.7% in Group A and 92.9% in Group B (p = 0.014* and p = 0.138, respectively) when compared with normal subjects. The study has shown that BFP interpositional arthroplasty effectively restores masticatory function.

Background/purpose While scan delay may affect the measurements of an occlusal pressure-sensitive film, Dental Prescale II (DPS2), the duration of scan delay was rarely reported in previous studies. This study aimed to clarify the effect of scan delay on DPS2 measurements. Materials and methods Two experiments were performed to clarify the effect of 0- to 10-min scan delay after DPS2 force registration. In both experiments, 11 loads were applied separately on a DPS2 film at 1-min interval between loads. Scanning was performed immediately after the 11th load in the 1-scan experiment and immediately after each load in the 11-scan experiment. A 300-N load was applied with a universal testing machine on 10 DPS2 films in each experiment and the DPS2 film was scanned with Bite Force Analyzer. Load measured, contact area, mean pressure, and maximum pressure were reported. ANOVA and Scheffe test were performed to compare the effect of number of scans and delay scan duration on these measurements with the critical value set at P ≤ 0.05. Results Number of scans had no significant effect on the four measurements studied. However, all measurements, except contact area, were significantly affected by scan delay; the longer the scan delay, the greater the increase in measurements. The load measured showed a rapid increase (13%) in the first 2 min, followed by a gradual increase from 2 min to 10 min (10%). Conclusion Scan delay does affect DPS2 measurements, and it is important to standardize and report scan delay duration in clinical studies.

The natural armors and weapons of the animal kingdom are serving as inspiration in the development of next-generation engineering materials. In this pursuit, seldom considered are the variations in properties across taxa that have evolved to meet their unique functional demands. Here, teeth from six different mammalian species were acquired and categorized according to their bite force quotient (BFQ), which accounts for the allometric scaling between bite force and body size. Selected chemical, microstructural, and mechanical properties of the enamel were quantified across the enamel thickness using spectroscopy and indentation techniques. Results showed that the chemical composition of enamel was significantly (P 0.05) different between the Low and High BFQ groups, whereas the apatite crystallinity was not. The enamel of all animals exhibited a spatial gradient in mechanical properties that was consistent when evaluated using a normalized framework. Although the elastic modulus, hardness and indentation brittleness were significantly lower in the High BFQ group, the fracture resistance of enamel was significantly higher in this group, potentially reflective of bite force requirements related to diet and predation. Enamel rod decussation was present in all teeth, but there were differences in specific microstructural features. Overall, these results highlight that the diversity of tooth enamel across species should be considered in the pursuit of nature-inspired structural materials. STATEMENT OF SIGNIFICANCE: Natural weapons are serving as inspiration in the development of next-generation engineering materials. Tooth enamel is a viable candidate, but variations in the structure and properties of enamel across taxa have not been explored. Here, teeth from six different mammalian species were categorized according to their bite force quotient (BFQ), and the enamel was compared in terms of selected chemical, microstructural, and mechanical properties. We show that specific aspects of the chemical composition and properties of the Low and High BFQ groups are unique, which appears reflective of bite forces associated with diet and predation. Overall, the results highlight that the diversity of tooth enamel across species should be considered in the pursuit of nature-inspired structural materials.

The relationship between diet, bite performance, and tooth structure is a topic of common interest for ecologists, biologists, materials scientists, and engineers. The highly specialized group of biters found in Serrasalmidae offers a unique opportunity to explore their functional diversity. Surprisingly, the piranha, whose teeth have a predominantly cutting function and whose main diet is soft flesh, is capable of exerting a greater bite force than a similarly sized pacu, who feeds on a hard durophagous diet. Herein, we expand our understanding of diet specialization in the Serrasalmidae family by investigating the influence of elemental composition and hierarchical structure on the local mechanical properties, stress distribution, and deformation mechanics of teeth from piranha (Pygocentrus nattereri) and pacu (Colossoma macropomum). Microscopic and spectroscopic analyses combined with nanoindentation and finite element simulations are used to probe the hierarchical features to uncover the structure-property relationships in piranha and pacu teeth. We show that the pacu teeth support a durophagous diet through its broad cusped-shaped teeth, thicker-irregular enameloid, interlocking interface of the dentin-enameloid junction, and increased hardness of the cuticle layer due to the larger concentrations of iron present. Comparatively, the piranha teeth are well suited for piercing due to their conical-shape which we report as having the greatest stiffness at the tip and evenly distributed enameloid. STATEMENT OF SIGNIFICANCE: The hierarchical structure and local mechanical properties of the piranha and pacu teeth are characterized and related to their feeding habits. Finite element models of the anterior teeth are generated to map local stress distribution under compressive loading. Bioinspired designs from the DEJ interface are developed and 3D printed. The pacu teeth are hierarchically structured and have local mechanical properties more suitable to a durophagous diet than the piranha. The findings here can provide insight into the design and fabrication of layered materials with suture interfaces for applications that require compressive loading conditions.

Effective interpretation of historical selective regimes requires comprehensive in vivo performance evaluations and well-constrained ecomorphological proxies. The feeding apparatus is a frequent target of such evolutionary studies due to a direct relationship between feeding and survivorship, and the durability of craniodental elements in the fossil record. Among vertebrates, behaviors such as bite force have been central to evaluation of clade dynamics; yet, in the absence of detailed performance studies, such evaluations can misidentify potential selective factors and their roles. Here, we combine the results of a total-clade performance study with fossil-inclusive, phylogenetically informed methods to assess bite-force proxies throughout mesoeucrocodylian evolution. Although bite-force shifts were previously thought to respond to changing rostrodental selective regimes, we find body-size dependent conservation of performance proxies throughout the history of the clade, indicating stabilizing selection for bite-force potential. Such stasis reveals that mesoeucrocodylians with dietary ecologies as disparate as herbivory and hypercarnivory maintain similar bite-force-to-body-size relationships, a pattern which contrasts the precept that vertebrate bite forces should vary most strongly by diet. Furthermore, it may signal that bite-force conservation supported mesoeucrocodylian craniodental disparity by providing a stable performance foundation for the exploration of novel ecomorphospace.

Background In children, stainless steel crowns (SSCs) have become an invaluable restorative option for grossly decayed primary teeth. The crowns are manufactured in different sizes with preformed anatomy which requires trimming or contouring as a necessary step to fit an individual tooth. Initially, this may produce variation in the occlusal contact points yet may not result in pain or discomfort. Little research exists regarding bite force equilibration measurements in children after placing SSC, and its influencing factors such as age and gender. Aim and objective To evaluate and compare the measurements of bite force pre- and post-cementation of SSC using the conventional technique at maximal intercuspal position (MIP) on primary molars at different time intervals and whether age and gender influence bite force measurements. Design Bite force and occlusal contacts during occlusion were made using T-Scan III. Twenty children scheduled for treatment who needed SSCs were included. T-Scan measurements of the bite force and occlusal contacts of the maxilla and mandibular teeth were recorded and analyzed before and immediately after cementation of SSC later 4 weeks during the follow-up period. These measurements were correlated with age and gender influence. Results There was no significant result in the percentage of bite force on the crowned tooth (placement of SSC) at different time intervals. Prematurities were present in all the groups but a significant reduction was seen on the crowned tooth from baseline to 1-month follow-up (p = 0.03). Also, a statistically significant increase in the bite force was seen in >7 years of age (p = 0.006) and no statistical significance among the gender. Conclusion Following the standard tooth preparation, the SSC will continue to appear clinically acceptable for many years. Our study children showed an adaptable masticatory system irrespective of age and gender during growth and development. How to cite this article Aishwarya N, Nagarathna C, Poovani S, et al. Comparison of Bite Force and the Influencing Factors Pre- and Post-cementation of Stainless Steel Crown in Children Using T-Scan. Int J Clin Pediatr Dent 2021;14(1):46-50.

Bite force is an ecologically important biomechanical performance measure that is informative in inferring the ecology of extinct taxa. However, biomechanical modelling to estimate bite force is associated with some level of uncertainty. Here, I assess the accuracy of bite force estimates in extinct taxa using a Bayesian phylogenetic prediction model. I first fitted a phylogenetic regression model on a training set comprising extant data. The model predicts bite force from body mass and skull width while accounting for differences owing to biting position. The posterior predictive model has a 93% prediction accuracy as evaluated using leave-one-out cross-validation. I then predicted bite force in 37 species of extinct mammals and archosaurs from the posterior distribution of predictive models, generating posterior predictive distributions of null expectations given body mass, skull width and phylogenetic position. Biomechanically estimated bite forces from the literature fall within the posterior predictive distributions for all except four species of extinct taxa and are thus as accurate as predicted from body size and skull width, given the variation inherent in extant taxa and the amount of time available for variance to accrue. Biomechanical modelling remains a valuable means to estimate bite force in extinct taxa and should be reliably informative of functional performances and serve to provide insights into past ecologies.

Objective. To investigate the correlation of periodontal parameters and bite force in different stages of periodontitis after phase I periodontal therapy. Methods. Periodontal clinical parameters such as mobility, attachment loss, gingival recession, and percentage of bone remaining were recorded at the mandibular first molar region after phase I therapy in subjects categorized according to the stage of periodontitis. Corresponding bite force was recorded at the first mandibular molar region using a bite force device after phase I therapy. ANOVA test was used to assess the significant difference among different groups. Pearson correlation coefficient was used to assess the correlation between measured variables. Results. The ANOVA test represents that there is no statistical significant difference between the bite force in stage I, stage II, and stage III type of periodontitis. A strong positive correlation was found ( r = 0.537 ) between bite force and percentage of remaining alveolar bone support whereas negative correlation was observed in measured parameters such as mobility ( r = − 0.0181 ), attachment loss ( r = − 0.608 ), and gingival recession ( r = − 0.435 ). Conclusion. Among all periodontal clinical parameters, the percentage of remaining alveolar bone is the strong predictor of bite force and mobility; attachment loss and gingival recession cannot predict the bite force in the first molar region. Bite force is variable in different stages of periodontitis.

To prevent single-implant overdenture (SIO) fracture, the inclusion of a framework in the overdenture has been suggested. However, no investigations verified their benefits.To evaluate prosthetic maintenance events, patient satisfaction, and mastication of SIO reinforced by metallic framework users.Fifteen volunteers had a new set of complete dentures converted into an SIO containing a framework. Maintenance events were recorded, while patient satisfaction was assessed using a visual analog scale. Masticatory performance (MP) was evaluated using the sieving method, maximum bite force (MBF) by pressure sensors, and masseter thickness by ultrasound. Measurements were performed 2, 12, and 24 months after SIO use. Repeated-measures ANOVA and paired Student's t-tests (p 0.05) were applied.Matrix exchange was the most prevalent maintenance event (83.6%), and no SIO was fractured during the entire follow-up. Satisfaction with the SIO stability decreased (p 0.01) after 12 months. MP did not change between evaluations (p 0.05). Conversely, MBF and masseter thickness improved after 12 and 24 months of SIO use (p 0.05).Reinforced SIO did not fracture during 2 years but requires maintenance. It improves bite force and muscle thickness, maintaining MP values. Satisfaction with SIO stability decreased in the first year of use.

Decreases in masticatory function are believed to be related to the development of cardiovascular disease (CVD) through inappropriate nutritional intake. This study focused on maximum bite force (MBF), which is an objective, quantitative index of masticatory function, and its association with the development of CVD (stroke and coronary heart disease) was investigated. The subjects were 1547 participants of the Suita study with no history of CVD who underwent medical and dental health examinations between June 2008 and June 2013. In addition to undergoing a basic physical examination at baseline, their MBF was measured. They subsequently underwent follow-up surveys for the development of CVD (mean follow-up, 3.5 years). The association between baseline MBF and the development of CVD was investigated by multivariate adjustment using a Cox proportional hazards model. CVD developed in 32 subjects during follow-up. The trend test showed a significant association between baseline MBF and CVD in a model that combined men and women. When analysed by sex, the trend test found a significant association between baseline MBF and CVD in women. Low MBF, which is an objective and quantitative index of masticatory function, may be a risk factor for the development of CVD.

Purpose Total alloplastic temporomandibular joint replacement (TMJR) requires the detachment of the masseter muscle (MM) at its insertion to the lateral ramus and often the resection of the coronoid process (insertion of the temporalis muscle). There is little literature on how a detachment affects the muscles. The present study evaluates the long-term masticatory muscle activities and maximum voluntary bite force (MVC) in patients with unilateral TMJR. Patients and Methods Surface electromyography of the MM and anterior temporalis muscle during bite force testing and MVC were evaluated bilateral preoperatively (T0), 1 (T3), 2 (T4), 3 (T5), and 4 years (T6) postoperatively. The percentage overlapping coefficient (index of the symmetric distribution of muscular activity) was calculated. Differences between stock or custom devices were evaluated. Results Fourteen patients were enrolled, 4 males and 10 females, age 47.3 ± 14.3 years at TMJR placement. In 11 patients, the coronoid process was resected, 5 patients received stock, and 9 custom prostheses. After surgery, a trend in the improvement of bilateral surface electromyography activities and MVC was found without statistical significance for the side comparison or the time of the investigation. The percentage overlapping coefficient values showed postoperatively relative (>72%) symmetry in both muscles. Up to T5 on the TMJR side, MM showed higher activity when custom prostheses were used. There was no significant difference between stock and custom prostheses. Conclusions The vertical (anterior) fibers of the temporalis muscle are preserved despite the resection of the coronoid process. The anterior temporalis muscle, as a synergist of the MM on the TMJR side, postoperatively partially assumes its abduction function. The detached MM appears to reattach. Generally, the bilateral increase in muscle activity and MVC of both muscles suggests regeneration of the investigated muscles. Custom prostheses seem to have an initial advantage for the reattachment of the MM compared with stock prostheses.

Made available in DSpace on 2022-04-29T08:32:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-09-01 Background: This study aimed to compare the masticatory efficiency, the maximum voluntary occlusal bite force (MVOBF) and the electrical activity (EMG) of masticatory muscles of practitioners of upper limb bodybuilding before and after physical activity. Methods: Twenty healthy individuals (10 men and 10 women, age from 18 to 30 (mean of 24.7 years old) without masticatory system disorders, that regularly practice hypertrophic physical activity were submitted to the analyses of masticatory efficiency, MVOBF, and surface EMG of the temporalis and masseter muscles. The masticatory efficiency was analyzed by comminution of the artificial material (Optocal®) and a sieving method. The MVOBF was measured by a dynamometer, and EMG was evaluated during resting mandibular position, maximum voluntary clenching (MVC), and MVC with a Parafilm M tape between teeth, and free mastication of chewing gum. The analyses were made before (T0) and immediately after the performance of upper limb bodybuilding exercises (T1). The data of masticatory efficiency and MVOBF were submitted to the Student T-test, and their correlations were analyzed by the Pearson correlation test, and the EMG data were submitted to the 2-way repeated measures ANOVA, all tests with a 5% significance. Results: There was a significant decrease of masticatory efficiency after the training. No statistical difference in the MVOBF and EMG was found, and there was a positive correlation between masticatory efficiency and MVOBF. Conclusions: Therefore, changes were found for masticatory efficiency only, which decreased after hypertrophic exercise. There was a positive correlation between masticatory efficiency and MVOBF Department of Dental Materials and Prosthodontics Araçatuba School of Dentistry São Paulo State University-UNESP, Road Jose Bonifacio 1193,Vila Mendonca KM Runner Incentivo Esporte Department of Dental Materials and Prosthodontics Araçatuba School of Dentistry São Paulo State University-UNESP, Road Jose Bonifacio 1193,Vila Mendonca

Aim and Objectives: This in vivo cross-sectional study aimed to measure and correlate the average and maximum bite forces between cleft and noncleft individuals. Materials and Methods: The study was conducted on thirty cleft and thirty noncleft lip and palate patients who were belonging to the age group of 14–30 years with unrepaired unilateral cleft lip and palate under treatment at the Craniofacial Center, Yenepoya Dental College, Mangalore, and G. S. R Craniofacial Center, Hyderabad, India. Dental Prescale® sheet was used to record the bite force of the patients and the test sheet was scanned with an Epson v330 color HD photo scanner, and the bite force was evaluated by an FDP 8010 analyzing system. The data were analyzed statistically by the Student's data t-test. Results: The control group had a statistically significantly higher mean pressed area on the left side (P = 0.034), maximum pressure on the left side (P < 0.001), mean maximum pressure on the right side (P = 0.024), and mean average pressure on the left side (P = 0.038). There was no statistically significant difference in the mean pressed area on the right side (P = 0.569) and average pressure on the right side of the control and study groups (P = 0.358). Conclusions: There was a statistically significant difference in the mean maximum pressure (P = 0.001) and average pressure (P = 0.039) among cleft lip and palate patients when compared with that of the control group. There was no significant difference between male and female subjects of both the groups.

Background: Muscle fatigue or the inability to maintain muscle strength is a protective mechanism to prevent muscle injury. Phototherapy or low-level laser therapy (LLLT) and therapeutic ultrasound are non-invasive and non-pharmacological forms of treatment modalities that have demonstrated effective and affirmative results when used to prevent muscle fatigue. Aim: The study evaluated the effect of phototherapy and therapeutic ultrasound in reducing muscle fatigue when administered before the induction of fatigue. Methodology: The study design was a blind, randomized, and sham-controlled clinical trial on laser and therapeutic ultrasound. The study sample consisted of 100 healthy young participants randomly allocated to four different groups of lasers, sham laser, therapeutic ultrasound, and sham ultrasound. All the individuals were subjected to clinical examination to record the bite force by the bite force dynamometer, maximum interincisal distance (MID) by using digital vernier calipers, and muscle fatigue by using EMG Retrainer's Device. The laser and therapeutic ultrasound were given on the masseter and anterior temporalis muscle on both sides and both sham groups were submitted to the same procedure but with the devices in the switch-off mode. All the individuals were instructed to chew two pieces of gum (one on each side) for 6 min to induce muscle fatigue and MID, the bite force and muscle fatigue were re-evaluated. Results: Statistically significant improvement was observed between the pre-and post-bite force, MID, and muscle fatigue in both the laser and Therapeutic ultrasound group as compared to the sham control groups with the P-value equal to 0.000. No, statistically significant difference was observed in the improvement of the muscle fatigue when both the treatment groups, i.e., laser and therapeutic ultrasound were compared with a P value >0.05. Conclusion: Muscle fatigue can be effectively reduced if any one of the physical modalities, either laser or therapeutic ultrasound is administered before the long-duration treatments; enabling administration of treatment comfortably and effectively in one appointment.

The mandible of vertebrates serves as insertion area for masticatory muscles that originate on the skull, and its functional properties are subject to selective forces related to trophic ecology. The efficiency of masticatory muscles can be measured as mechanical advantage on the mandible, which, in turn, has the property of correlating with bite force and shape. In the present work, we quantify the mechanical advantage of the mandible of akodontine rodents, which present a diverse radiation of insectivorous specialists, to assess their relationship to the estimated bite force and diet. We also tested the degree of morphofunctional convergence in response to insectivory on the group. We found the mechanical advantages to be convergent on insectivorous species, and associated with the estimated bite force, with higher mechanical advantages in species with a stronger bite and short, robust mandibles and lower mechanical advantages in insectivorous species with weaker bites and more elongated, dorso-ventrally compressed mandibles. Insectivorous species of Akodontini are functional specialists for the consumption of live prey and may exploit the resources that shrews, moles and hedgehogs consume elsewhere.

Background There is insufficient evidence for the efficacy of silicone soft reliner on the obturator prosthesis after maxillectomy for oral malignant tumors. Objective To verify the efficacy of silicone soft reliner on the obturator prosthesis after maxillectomy, by evaluating masticatory performance and quality of life (QoL). Methods This was a single‐arm prospective interventional study, verifying the efficacy of silicone soft reliner (GC RELINE II®) on the maxillary obturator prosthesis. Data were obtained from a comparison of the endpoints after 14 days of continuous use of acrylic and silicone soft‐lined prostheses. The primary endpoint was masticatory performance. The secondary endpoints were occlusal performance and oral health‐related QoL (OHRQoL). The masticatory performance, occlusal performance, and OHRQoL were assessed by glucose concentration, maximum bite force, and the Japanese version of Oral Health Impact Profile (OHIP‐J49), respectively. Results This study included five patients (two males, three females), aged between 71 and 88 years, with a median of 74 years. The median of glucose concentration indicated a statistically significant improvement between the acrylic resin (99.6 mg/dL) and silicone soft reliner (126.0 mg/dL) obturator prosthesis (p = .043). There was no significant difference in the median of maximum bite force between the acrylic resin (302.0 N) and silicone soft reliner (250.0 N) obturator prosthesis (p = .893). Functional limitations domain of the OHIP‐J49 indicated a statistically significant improvement between the acrylic resin and silicone soft reliner obturator prosthesis (p = .043). Conclusions This study indicated that an obturator relined with soft silicone improved masticatory performance and the OHRQoL post‐maxillectomy.

This cross-sectional observational study with 24 patients evaluated differences in bite force (BF) and masticatory performance (MP) between conventional complete denture (CCD) and implant mandibular overdenture (IMO) users and the correlation between these variables. The BF test was performed bilaterally with an occlusal force device. During the MP test, patients were asked to chew Optocal particles for 40 cycles. The Shapiro Wilk test was employed to verify the normality of the data, the student t test to identify differences between groups, and Pearson’s correlation to investigate interrelationships between variables. A multiple linear regression was subsequently performed via the stepwise method. P values ≤0.05 were considered statistically significant. Unlike IMO users, CCD users presented a significant difference (25.6%) in BF between the dominant and non-dominant chewing side (p=0.04). IMO users presented significantly higher BF (p=0.01) without presenting a dominant side (p=0.38), and also performed significantly better for the following MP parameters: MPX50 values decreased by 27.25% in IMO users (p=0.01), MPB decreased by 48.38% (p=0.01), and ME 5.6 decreased by 53.25% (p=0.02), while ME2.8 increased by 151.57% (p=0.01). The BF and MPX50 in the IMO wearers group were negatively correlated (-0.57; p=0.05); this correlation coefficient was the only parameter included in the multivariate regression model. IMO users have higher BF and better masticatory performance than CCD users, especially in terms of chewed particles size reduction. MP is correlated with a higher BF in IMO users through better particle trituration. Resumo Este estudo observacional transversal com 24 participantes teve como objetivo avaliar as diferenças na força de mordida (FM) e na PM (performance mastigatória) entre usuários de prótese total convencional (PTC) e de overdenture mandibular (OM) e a correlação entre essas variáveis. O teste de FM foi realizado bilateralmente com um dispositivo de força oclusal. Durante o teste de PM, os pacientes foram solicitados a mastigar uma porção padronizada de Optocal por 40 ciclos mastigatórios. O teste de Shapiro Wilk foi empregado para verificar a normalidade dos dados, o teste T de Student para identificar diferenças entre os grupos e os coeficientes de correlação de Pearson para investigar inter-relações entre variáveis. Uma regressão linear múltipla foi realizada pelo método stepwise. Valores de p≤0,05 foram considerados estatisticamente significantes. Diferentemente dos usuários de OM, os usuários de PTC apresentaram uma diferença significativa (34%) na FM entre o lado dominante e o não dominante (p=0,04). Os usuários de OM apresentaram FM significativamente maior (p=0,01) sem apresentar um lado dominante (p=0,38) e obtiveram PM significativamente melhor nos seguintes parâmetros: os valores de PMX50 diminuíram 27,25% (p=0,01), PMB diminuiu em 48,38% (p=0,01), e EM 5.6 diminuiu 53,25% (p=0,02), enquanto EM2.8 aumentou 151,57% (p=0,01). A FM e PMX50 no grupo de usuários da IMO foram negativamente correlacionados (-0,57;p=0,05); esse coeficiente de correlação foi o único parâmetro incluído no modelo de regressão multivariada. Os usuários da OM possuem maior FM e melhor performance mastigatória do que os usuários de PTC, observados principalmente na redução do tamanho das partículas mastigadas. A PM está correlacionada com um maior FM nos usuários da OM através de uma melhor trituração de partículas.

The carnivoran cranium undergoes tremendous growth in size and development of shape to process prey as adults and, importantly, these ontogenetic processes can also differ between the sexes. How these ontogenetic changes in morphology actually relate to the underlying jaw musculature and overall bite performance has rarely been investigated. In this study, I examined sex‐specific ontogenetic changes in cranial morphology, jaw adductor muscles, and theoretical bite force between subadults and adults in the fisher (Pekania pennanti) and American marten (Martes americana). I found evidence that cranial size alone does not completely explain ontogenetic increases in bite forces as found in other mammalian species. Instead, cranial shape development also drives ontogenetic increases in relative bite force by broadening the zygomatic arches and enlargement of the sagittal crest, both of which enable relatively larger jaw adductor muscles to attach. In contrast, examination of sexual dimorphism within each age‐class revealed that cranial shape dimorphism did not translate to dimorphism in either size‐corrected bite forces or size‐corrected physiological cross‐sectional area of the jaw adductor muscles. These results reveal that morphological size and shape variation can have different influences on bite performance depending on the level of intraspecific variation that is examined (i.e. ontogenetic versus sexual dimorphism).

Osteoarthrosis is a disorder of synovial joints, resulting from destruction of the cartilage and subchondral bone. The present study is aimed to investigate the molar bite force, thickness and efficiency of the masseter and temporalis muscles of subjects with osteoarthrosis. A total of forty-eight subjects participated in the study. They were distributed into two groups: with osteoarthrosis (n=24) and asymptomatic controls (n=24). Subjects were analyzed on the basis of maximal molar bite force (right and left side), thickness (mandibular rest and dental clenching in maximal voluntary contraction) and electromyographic activity of masticatory cycles through the linear envelope integral in habitual (raisins and peanuts) and non-habitual (Parafilm M) chewing of the masseter and temporalis muscles. All the data were analyzed statistically using t-test with a significance level of p≤0.05. There was no difference between groups in maximal molar bite force, muscle thickness and non-habitual chewing. Differences were found on the raisins (p=0.02) and peanuts (p=0.05) chewing for right temporal muscle, with reduced masticatory muscle efficiency in osteoarthrosis subjects. This study showed that osteoarthrosis induces negative changes in habitual chewing, highlighting the efficiency of the right temporalis muscles. The greater temporal muscle activity in subjects with osteoarthrosis may compromise chewing and consequently the nutritional status of adult subjects.

BACKGROUND Maximum bite force (MBF) is a common and useful index of masticatory function; it correlates with physical strength in elderly people. Palpation of stiffness in the masseter muscle during forceful biting has been considered to be associated with MBF. However, this assessment method relies on subjective judgments; no study has verified the relationship between MBF and quantitative measurements of masseter muscle stiffness (MMS). OBJECTIVE We aimed to verify the association between masseter muscle myotonometric assessment results and MBF. METHODS In total, 117 community-dwelling >65-year-old individuals from the Tokyo metropolitan area were assessed. MMS on the dominant side during forceful biting was measured with a MyotonPRO device. Masseter muscle thickness (MMT) during rest and forceful biting was measured with an ultrasonic diagnostic apparatus, and the difference in MMT (DMMT) between the rest and forceful biting conditions was determined. MBF data were obtained with a pressure-sensitive sheet and an associated device. To determine the independent variables affecting MBF and MMS, multivariate linear regression analyses with adjustments for age, sex and number of teeth were performed. RESULTS The multivariate analysis revealed that MBF correlated with the number of teeth (β = .489, P

Objectives This proof‐of‐principle, single‐center, randomized, examiner‐blind, crossover study compared two experimental polyvinyl acetate (PVA)‐based denture adhesives (Test Adhesives 1 and 2) with a marketed reference polymethyl vinyl ether/maleic anhydride (PMV/MA)‐based adhesive and no adhesive using incisal bite force area over baseline over 12 hr (AOB0–12) in participants with an at least moderately well‐fitting complete maxillary denture. Previous in vitro studies suggested the experimental denture adhesives provided superior performance. Materials and Methods Participants were randomized to a treatment sequence such that each received each treatment once. Prior to treatment application (baseline) and at 0.5, 1, 3, 6, 9, and 12 hr following the application, participants bit on a force transducer until their maxillary denture dislodged. Between‐treatment differences in AOB0–12 were analyzed using analysis of covariance. For study validity, the reference adhesive was compared with no adhesive. Participants were asked to rate sensory experiences and ease of denture removal. Results Twenty‐three participants were included in the modified intent‐to‐treat population. Although Test Adhesives 1 and 2 had a higher mean AOB0–12 than no adhesive, differences were not statistically significant. No statistically significant difference was also found between the reference adhesive and no adhesive; hence, study validity was not attained. Participants did not report any clear differences between the test or reference adhesives in terms of taste or feel; however, dentures were easier to remove with the test adhesives versus reference. No treatment‐related adverse events were reported. Conclusion Neither the experimental PVA‐based denture adhesives nor the PMV/MA‐based reference product demonstrated a statistically significant difference in incisal bite force AOB0‐12 compared with no adhesive. The reasons for these unexpected results is unclear; they suggest that findings of in vitro tests for denture adhesive performance are not always translated to in vivo performance (http://Clinicaltrials.gov: NCT02937870).

Purpose: The purpose of this study was to observe the impact of oral oncological treatment, including the recovery of several tongue functions (force, mobility, and sensory functions), and to determine the influence of these functions on masticatory performance. Materials and methods: Masticatory performance and tongue force, mobility, and sensory functions were determined in 123 patients with oral cavity cancer. The assessments were performed 4 weeks before treatment and 4 to 6 weeks, 6 months, 1 year, and 5 years after treatment. Generalized estimation equations and mixed model analyses were performed, correcting for previously identified factors in the same population. Results: A significant deterioration in tongue mobility and sensory function was observed in patients with mandible and tongue and/or floor-of-mouth tumors. Better tongue force and sensory function (thermal and tactile) positively influenced masticatory performance, and this effect was stronger where fewer occlusal units were present. The effect of both the tongue force and maximum bite force was weaker in dentate patients in comparison with patients with full dentures. A web-based application was developed to enable readers to explore our results and provide insight into the coherence between the found factors in the mixed model. Conclusions: Tongue function deteriorates after oral oncological treatment, without statistically significant recovery. Adequate bite and tongue forces are especially important for patients with a poor prosthetic state. Patients with sensory tongue function deficits especially benefit from the presence of more occluding pairs.

OBJECTIVE: The aim was to investigate relationships amongst interocclusal distances, masticatory muscle electromyographic (EMG) activity during isometric contraction of masticatory muscles, and craniofacial morphology.DESIGN: Twenty-eight women and 12 men (25.3 ± 3.8 years old) participated. After measuring maximal voluntary occlusal bite force (MVOBF) between the right-first premolars, the participants were asked to bite at submaximal levels of 0 (= holding the bite force transducer), 15, 22.5, and 30% MVOBF with the use of visual feedback. The thickness of a bite force transducer was set at 10, 12, 13, 14, 16, 17, 18, 19, 20, 22, and 24 mm (= interocclusal distance: IOD). Nine soft tissue craniofacial factors were assessed through digital photograph: face height, middle face height, lower face height, face width, inter-pupil distance and mandibular plane angle, lower face height / face height ratio, inter-pupil distance / facial width ratio and face width / face height ratio.RESULTS: In the masseter muscle, EMG activity decreased with increased IODs. The participants with higher mandibular plane angle had more negative slope coefficients of IOD-EMG graphs at 0% MVOBF especially in male temporalis and female masseter and temporalis muscles, suggesting that a greater mandibular plane angle is associated with lower EMG activity at longer IOD.CONCLUSIONS: Overall the findings support the notion that craniofacial morphology is associated with differences in neuromuscular activity of the masticatory muscles, and suggest that the neuromuscular effects of oral appliances may be dependent on patients' craniofacial morphology and the thickness of the device. (247/250 words).

BACKGROUND Although age-related changes in muscle quality influence muscle strength, the relationship between masseter muscle (MM) quality and maximum biting force (MBF) has never been studied. OBJECTIVE The aims of the study were to verify the relationship among MM quality, MBF, and the displacement of the MM while biting forcefully (MMD) and to clarify the age-related decline in MBF in healthy elderly persons. METHODS Seventy-four healthy community-dwelling individuals (mean age, >65 years) from Tokyo metropolis were recruited. The thickness (index of muscle quantity), echo intensity (index of muscle quality) and displacement of the MM while biting forcefully (MMT, MMEI and MMD, respectively) were measured by ultrasonography. MBF was measured using a pressure-sensitive sheet. Independent predictors of MBF and MMD were determined using multivariate linear regression analyses adjusted for age, sex and the number of present teeth. RESULTS MBF was significantly correlated with the number of teeth (β = 0.577, P

Aim: The narrowing of the mandible during opening and protrusion movements is defined as median mandibular flexure (MMF). MMF is caused by the attachment of mandibular muscles; therefore, it can be assumed that a greater amount of maximum occlusal force (MOF) may cause more flexion and could affect the survival of dental and implant restorations. The purpose of this study was to evaluate any relationship between MOF and MMF in a sample of adults. Settings and Design: In vivo – comparative study. Materials and Methods: In this descriptive, cross-sectional, nondirectional study, a sample of 90 volunteers were recruited (45 men and 45 women). MOF was measured by applying the strain gauge receptor to the first molar region, and MMF was measured by calculating the variation in the intermolar distance by a digital caliper with an accuracy of 0.01 mm using an impression and resulted in the stone cast during the maximum opening and closed-jaw positions. The body mass index (BMI) also was calculated. Statistical Analysis: Data were analyzed using the SPSS software (version 23) inferential and descriptive statistics, linear regression, and Pearson correlation coefficient. P < 0.05 was considered statistically significant. Results: There was no statistically significant relationship between MOF and MMF (P = 0.78), but there was a significant association between MOF and BMI (P < 0.001, r = 0.475) and gender. Conclusion: Although MOF and MMF are both important and effective factors in the success of prosthetic restorations, one cannot be expected by the other and both should be considered in the treatment plan separately.

Purpose: To determine the Maximum voluntary bite force among patients having different personality traits. Methods: In total, 323 patients were given the big-five inventory (BFI) questionnaire to fill and allotted to the various personality traits. The patients in the Agreeableness (n = 62) and Neuroticism traits (n = 62) were included in the study. They were categorized into groups as Group 1a – Neuroticism male (41 patients) and Group 1b – Neuroticism Female (21 patients) and Group 2a – Agreeableness male (26 patients) and Group 2b – Agreeableness female (36 patients). Highest value of the maximal voluntary bite force (MVBF) was recorded using FlexiForce sensor (B 201) (Tekscan, USA). The statistical data were analyzed by independent t-test (P < 0.05). Results: The mean bite force values for Neuroticism male was 778.66 N, Agreeableness male was 699 N, Neuroticism female was 686.24 N, and for Agreeableness female was 565.47 N. Statistically significant differences in the bite forces between the male and female groups of both the groups with the males showing significantly higher bite force values in both groups was seen. Also, the bite force in Neuroticism male was significantly higher than Agreeableness male and bite force in Neuroticism female was higher than Agreeableness female. Conclusion: In this study, the highest bite force was seen in Neuroticism males. Additionally, this study infers that personality has significant influence on the quantum of bite force. Thus, personality assessment of the patient can assist the clinician in planning the appropriate treatment.

Background Dysphagia is reported in patients with Duchenne or Becker muscular dystrophy. Our clinical experience suggests that, compared with Duchenne patients, impaired mastication and swallowing occur early in Becker patients relative to their skeletal muscle involvement. The aim of this study was to assess dysphagia in Duchenne and Becker patients in relation to ambulatory capacity. Methods In patients in the early ambulatory stage, clinical symptoms, quantitative muscle ultrasound of the orofacial muscles, and maximum bite force were assessed. The 6‐Minute Walk Test (6MWT) was used to measure ambulatory capacity. Results Eleven Duchenne and 11 Becker patients were included. Although Becker patients had a greater 6MWT distance than Duchenne patients, the occurrence of mastication and swallowing difficulties was similar. The temporalis muscle was significantly thicker in Becker patients. Conclusions Clinicians should be aware of dysphagia in both groups, even when ambulation is still well preserved.

Performance traits are energetically costly, and their expression and use can drive trade-offs with other energetically costly life-history traits. However, different performance traits incur distinct costs and may be sensitive to both resource limitation and to the types of resources that are accrued. Protein is likely to be especially important for supporting burst performance traits such as sprint speed, but the effect of varying diet composition on sprint training in lizards, an emerging model system for exercise training, is unknown. We tested the hypothesis that the response to sprint training is sensitive to both the type and amount of resources in Anolis carolinensis. We also measured bite force across all treatments as a control whole-organism performance trait that should be unaffected by locomotor training. Both mass and bite force are reduced by dietary restriction over the course of 9 weeks of sprint training, but sprint speed is unaffected by either training or dietary restriction relative to controls. Furthermore, protein supplementation does not rescue a decline in either mass or bite force in trained, diet-restricted males. These results contrast with those for endurance training, and suggest that sprint speed is more canalized than either endurance or bite force in green anoles.

The longitudinal change in mandibular volume and configuration was quantitatively evaluated in a patient with craniofacial fibrous dysplasia (FD). The influence of mechanical stress on the enlargement that is characteristic of FD was verified via finite element analysis (FEA). The patient was a 38-year-old man diagnosed with craniofacial FD in the mandible. He underwent surgical reduction of FD, but the lesion continued to grow and caused facial asymmetry and masticatory disturbance because of missing teeth. An occlusal overlay removable partial denture was constructed for his lower jaw. Computed tomography (CT) images were acquired 4 times in 10 years, and 3-dimensional (3-D) models were reconstructed from these data. The 3-D models were analyzed volumetrically and morphologically and used for FEA. The FD lesion in the mandible enlarged nonuniformly and had site specificity. From the results of FEA, it is suggested that compression stress induced by the occlusal force through the denture may have influenced the direction of enlargement in FD.

The aim of the current systematic review was to summarize and to evaluate the available information on the effectiveness of oral exercise in improving the masticatory function of people ≥18 y. Electronic databases (Medline, Embase, CENTRAL) and gray literatures were searched (up to December 2020) for relevant randomized and nonrandomized controlled clinical trials. Two reviewers independently conducted the study selection, data extraction, and quality assessments. Meta-analysis was conducted for the comparison of bite force and masticatory performance using mean difference (MD) and standardized mean difference (SMD), respectively. GRADE (Grading of Recommendations Assessment, Development, and Evaluation) assessment was adopted for collective grading of the overall body of evidence. Of the 1,576 records identified, 18 studies (21 articles) were included in the analysis. Results of meta-analysis indicated that oral exercise could significantly improve the mean bite force of the participants (parallel comparison: MD, 41.2; 95% CI, 11.6–70.7, P = 0.006; longitudinal comparison: MD, 126.5; 95% CI, 105.2–144.9, P < 0.001). However, the improvement in masticatory performance was not significant (parallel comparison: SMD, 0.11; 95% CI, –0.20 to 0.42, P = 0.48; longitudinal comparison: SMD, 0.4; 95% CI, –0.11 to 0.91, P = 0.13). Results of meta-regression showed that greater improvements in bite force can be achieved among younger adults and with more intensive exercise. Chewing exercise is the most effective oral exercise, followed by clenching exercise, while simple oral exercise may not have a significant effect. Based on the results of the meta-analysis and GRADE assessment, a weak recommendation for people with declined masticatory function to practice oral exercise is made.

Purpose: to assess the bite force in people with Parkinson’s disease and correlate it with age, sex, stage and time of the disease, dentures use, presence of temporomandibular disorder, side of symptom onset, and masticatory preference. Methods: the Research Diagnostic Criteria for Temporomandibular Disorders and the Hoehn & Yahr Parkinson’s disease scale were used, and the participants’ oral cavity was clinically examined. Then, the bite force was measured with an analog dynamometer, whose bar was adapted for mouth grip. The bite force results and their correlation with the variables were analyzed with the independent t-test (p

Background: Removable partial dentures are a frequently used prosthetic treatment in the elderly population, but different types or RPDs might guarantee different chewing capabilities. In many studies, the relationship between chewing and aging has been reported and it has been shown that efficient chewing can improve the overall quality of life. Objectives: In the present study, the relationship between maximum bite force (MBF) and RPDs was studied. A relationship between the body mass index (BMI) and the type of prosthesis was also analyzed. Methods: 240 elderly patients, 120 males and 120 females, with bilateral posterior edentulism (class 1 of Kennedy classification) who had been wearing an RPD for at least a year, were recruited. Patients were divided into two groups: Group 1: male (n = 60) and female (n = 60) patients with bilateral edentulous areas located posterior to the remaining natural teeth and natural teeth in the opposite dental arch. Group 2: male (n = 60) and female (n = 60) patients with maxillary and mandibular bilateral edentulous areas located posterior to the remaining natural teeth. Their Body Mass Index (BMI) and Maximum bite force (MBF) were measured and compared according to the material and design of their RPD. Results: In both Groups, patients wearing cobalt-chrome alloy RPDs (Co-Cr-RPD) (Group 1: 20.25 ± 6.7 MBF, p &lt, 0.001, Group 2: 16.0 ± 5.7 MBF, p &lt, 0.001) had an increased MBF when compared to polymethylmethacrylate RPD (PMMA-RPD) (Group 1: 12.9 ± 3.36 MBF, Group 2: 10.4 + 2.8 MBF), and Valplast RPD (V-RPD) (Group 1: 14.3 ± 4.7 MBF, Group 2: 11.3 ± 3.4 MBF) users. There were no significant differences in bite force between patients wearing PMMA-RPD and V- RPD in both Groups. Patients in Group 2 showed a lower MBF than those in Group 1 (Group 1: 16.05 ± 6.13 MBF, Group 2: 12.6 ± 4.84 MBF, p &lt, 0.001). Conclusions: A reduction in chewing force can lead to choosing softer foods for nutrition, which can lead to an increase in BMI. Our results show that only CoCr-RPD wearers were able to chew consistent food, whereas PMMA- RPD and V-RPD, due to the properties of the materials, their instability, and the possibility of causing pain during mastication, determined a limitation in the choice of food for many of the participants.

OBJECTIVES The aims of this study were to compare oral diadochokinesis and to test associations with oro-facial functional parameters in healthy young and old German speakers. BACKGROUND Oral diadochokinesis is a key component in the concept of oro-facial hypofunction and relates to tongue and lip motor function but may depend on the linguistic background. MATERIALS AND METHODS Healthy German speakers with a minimum of 20 teeth were recruited to form a young (

The extraordinary success of social insects is partially based on division of labour, i.e. individuals exclusively or preferentially perform specific tasks. Task preference may correlate with morphological adaptations so implying task specialization, but the extent of such specialization can be difficult to determine. Here, we demonstrate how the physical foundation of some tasks can be leveraged to quantitatively link morphology and performance. We study the allometry of bite force capacity in Atta vollenweideri leaf-cutter ants, polymorphic insects in which the mechanical processing of plant material is a key aspect of the behavioural portfolio. Through a morphometric analysis of tomographic scans, we show that the bite force capacity of the heaviest colony workers is twice as large as predicted by isometry. This disproportionate ‘boost’ is predominantly achieved through increased investment in muscle volume; geometrical parameters such as mechanical advantage, fibre length or pennation angle are likely constrained by the need to maintain a constant mandibular opening range. We analyse this preference for an increase in size-specific muscle volume and the adaptations in internal and external head anatomy required to accommodate it with simple geometric and physical models, so providing a quantitative understanding of the functional anatomy of the musculoskeletal bite apparatus in insects.

Bite force can be an important aspect of a lizard’s organismal performance, and is likely to be subject to influence by ambient conditions including an individual’s thermal environment. We examined the effects of body temperature (Tb) on initial bite force of rock- and crevice-dwelling individuals of three species of lizards: Abronia graminea (Anguidae), Barisia imbricata (Anguidae), and Xenosaurus fractus (Xenosauridae) from Mexico. In B. imbricata and X. fractus from one site (Xochititan, Puebla) initial bite force was greatest at intermediate Tb. In contrast, X. fractus from a second site (Tlatlauquitepec, Puebla) showed a weak tendency for initial bite force to increase with Tb. Initial bite force in A. graminea was not affected by Tb. Taking our results together, we infer that initial bite force in rock- or crevice-dwelling lizards is often, but not always, related to Tb.

Background Measuring mammals’ bite force in laboratory conditions is not a simple task, let alone on wild medium-sized mammals in the field. Thus, morphometric-proxies are usually used to infer morphofunctional properties of musculoskeletal features. For instance, the study of bite force-indexes suggests that different capacities to crack food items reduce the competition between coexistent collared and white-lipped peccaries (Pecari tajacu and Tayassu pecari). The presence of exotic feral hogs (Sus scrofa) in peccaries’ endemic areas gives rise to new ecological interactions between them. An example is the Brazilian Pantanal wetland, where ecomorphological mechanisms may play a role in their ecological relations. Taking this scenario as a case of study, we aimed to verify if the morphometric-proxies are de facto reliable tools, by comparing bite forces-indexes with the in vivo bite forces of these species. Methods We captured 21 collared and white-lipped peccaries and feral hogs in the Brazilian Pantanal to assess their bite force at first molar. The Bite Force Measuring Tube (BiTu) is a robust and simple mechanical device designed to be used in field conditions. Only 11 individuals successfully bit the BiTu before being released. Their body measurements were compared and correlated with their bite force. The in vivo bite forces were compared with bite force-indexes of two papers based on independent morphometric methods and datasets: Sicuro & Oliveira (2002) used classic morphometrics to infer the bite forces of these three species in the Brazilian Pantanal, and Hendges et al. (2019) used geometric morphometrics to compare bite forces-indexes and feeding habits of the extant peccary species. The results of all species were standardized (Z-curves) according to each method. Doing so, we obtained comparable dimensionless comparable values but maintaining the differences between them. Results The morphometric-proxies-based studies presented similar results: collared peccaries present weaker bites than white-lipped peccaries and feral hogs, while these two species presented no significant differences in their bite force-indexes. The in vivo bite force results suggest the same relations predicted by the morphometric models, including the high variation among the feral hogs. We found a significant correlation between the individuals’ weight (kg) and their actual bite force (N) but no significant correlations with the head length. Conclusions The BiTu proved to be a functional and low-cost tool to measure bite force in field conditions. The in vivo results presented a good correspondence with the predictions based on morphometric-proxies by Sicuro & Oliveira (2002) and Hendges et al. (2019). The results denote that these studies succeed in capturing the biomechanical signal of the three species’ skull-jaw systems. This empirical validation confirms that these morphometric-proxies analyses are reliable methods to ecomorphological and evolutionary inferences.

Measures of attachment or accommodation area on the skeleton are a popular means of rapidly generating estimates of muscle proportions and functional performance for use in large-scale macroevolutionary studies. Herein, we provide the first evaluation of the accuracy of these muscle area assessment (MAA) techniques for estimating muscle proportions, force outputs and bone loading in a comparative macroevolutionary context using the rodent masticatory system as a case study. We find that MAA approaches perform poorly, yielding large absolute errors in muscle properties, bite force and particularly bone stress. Perhaps more fundamentally, these methods regularly fail to correctly capture many qualitative differences between rodent morphotypes, particularly in stress patterns in finite-element models. Our findings cast doubts on the validity of these approaches as means to provide input data for biomechanical models applied to understand functional transitions in the fossil record, and perhaps even in taxon-rich statistical models that examine broad-scale macroevolutionary patterns. We suggest that future work should go back to the bones to test if correlations between attachment area and muscle size within homologous muscles across a large number of species yield strong predictive relationships that could be used to deliver more accurate predictions for macroevolutionary and functional studies.

In carnivorans, bite force is a critical and ecologically informative variable that has been correlated with multiple morphological, behavioral, and environmental attributes. Whereas in vivo measures of biting performance are difficult to obtain in many taxa-and impossible in extinct species-numerous osteological proxies exist for estimating masticatory muscle size and force. These proxies include both volumetric approximations of muscle dimensions and direct measurements of muscular attachment sites. In this study, we compare three cranial osteological techniques for estimating muscle size (including 2D-photographic and 3D-surface data approaches) against dissection-derived muscle weights and physiological cross-sectional area (PCSA) within the jaw adductor musculature of 40 carnivoran taxa spanning eight families, four orders of magnitude in body size, and the full dietary spectrum of the order. Our results indicate that 3D-approaches provide more accurate estimates of muscle size than do surfaces measured from 2D-lateral photographs. However, estimates of a muscle's maximum cross-sectional area are more closely correlated with muscle mass and PCSA than any estimates derived from muscle attachment areas. These findings highlight the importance of accounting for muscle thickness in osteological estimations of the masticatory musculature; as muscles become volumetrically larger, their larger cross-sectional area does not appear to be associated with a proportional increase in the attachment site area. Though volumetric approaches approximate muscle dimensions well across the order as a whole, caution should be exercised when applying any single method as a predictor across diverse phylogenies.

OBJECTIVE Stroke is a neurological deficit of cerebrovascular origin, considered a 21st-century epidemic that causes functional changes in the human body. This study aimed to evaluate the stomatognathic system of patients after hemorrhagic stroke through the bite force, thickness, and skin temperature in the region of the masseter and temporalis muscles. MATERIAL AND METHODS Twenty-four subjects were divided into groups: post-hemorrhagic stroke; with right side of the affected body (n = 12) and without the neurological disorder (n = 12). Maximum molar bite force was verified using a digital dynamometer. Muscle thickness was measured using ultrasound images obtained at rest and during maximal voluntary contraction of the masseter and temporalis muscles. Thermographic camera was used to record the thermographic patterns of the masseter and temporalis muscles. Data were subjected to Student's t-test (P

BackgroundBite marks attributed to adultTyrannosaurus rexhave been subject to numerous studies. However, few bite marks attributed toT. rexhave been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous.MethodsHere we present bite force estimates for a juvenileTyrannosaurus rexbased on mechanical tests designed to replicate bite marks previously attributed to aT. rexof approximately 13 years old. A maxillary tooth of the juvenileTyrannosaurusspecimen BMR P2002.4.1 was digitized, replicated in dental grade cobalt chromium alloy, and mounted to an electromechanical testing system. The tooth was then pressed into bovine long bones in various locations with differing cortical bone thicknesses at varying speeds for a total of 17 trials. Forces required to replicate punctures were recorded and puncture dimensions were measured.ResultsOur experimentally derived linear models suggest bite forces up to 5,641.19 N from cortical bone thickness estimated from puncture marks on anEdmontosaurusand a juvenileTyrannosaurus. These findings are slightly higher than previously estimated bite forces for a juvenileTyrannosaurus rexof approximately the same size as BMR P2002.4.1 but fall within the expected range when compared to estimates of adultT. rex.DiscussionThe results of this study offer further insight into the role of juvenile tyrannosaurs in late Cretaceous ecosystems. Furthermore, we discuss the implications for feeding mechanisms, feeding behaviors, and ontogenetic niche partitioning.

This study was to assess the efficiency of using a combination of one microplate and one miniplate for management of patients with parasymphyseal mandibular fractures versus two miniplates through measurement of the biting force. The study sample consisted of sixteen patients with an isolated mandibular fracture and randomly divided into two groups; group I was managed using two miniplates, while group II was managed using a combination of one microplate at subapical region and one miniplate at the inferior border of the mandible. The biting force was measured at 1 week, 1 month, and 3 months follow-up visits. A control group consisted of 40 healthy adult volunteers was selected to measure the normal biting force. The mean of the normal biting force of the control group was 435 N ± 219, 103.2 N ± 4.8, and 390.6 N ± 195.4 at right molar, incisor, and left molar regions respectively. There was a statistically non-significant difference regarding the bite force of both study groups, with a progressive increase through the different follow-up visits and a period of 3 months is sufficient for recovery of patients to regain their normal biting force. Consequently a combination of one microplate and one miniplate is efficient for the management of isolated parasymphyseal mandibular fracture in the same way as two miniplates.

PURPOSE To compare maximum bite force, masseter thickness, and oral health-related quality of life (OHRQoL) in elderly patients rehabilitated with conventional complete dentures (CDs) and single-implant overdentures (SIOs). MATERIALS AND METHODS A paired design was conducted, and 12 elderly patients were selected. Initially, a set of new CDs was manufactured and placed. After a 2-month adaptation period, the mandibular CD was transformed into an SIO by inserting one osseointegrated implant into the symphysis region. All variables were evaluated 2 months after both treatments (CD and SIO). Maximum bite force was evaluated using pressure sensors, while masseter thickness was obtained via ultrasound during muscle contraction and relaxation. The Oral Health Impact Profile for edentulous people (OHIP-Edent) was used to measure OHRQoL. Data were analyzed using Student t test and Wilcoxon test. Pearson coefficient of correlation between bite force and masseter thickness was calculated. RESULTS Values for maximum bite force and masseter thickness during contraction increased significantly after SIO use (P < .001), indicating an improvement in muscle function. Considering OHRQoL, the general score and the domains functional limitation and physical pain were reduced (P < .05), indicating better perception of OHRQoL, with SIO use. Moreover, masseter thickness during contraction was moderately correlated with bite force (r = 0.480; P = .018). CONCLUSION Using SIO increased the maximum bite force and masseter thickness of elderly patients, leading to an improved OHRQoL.

Tumors, trauma and infections are the main reasons for subjecting a patient to a bone reconstruction made with the use of bone grafts or prosthetic elements, using for example components such as osteosynthesis plates, meshes and screws for their stabilization.This study focuses on the photoelastic analysis of a customized prosthesis of the jaw for a patient diagnosed with osteonecrosis. A resin model was manufactured as follows: DICOM files were processed in ScanIP software to obtain an STL file that was used to generate an antagonist model of the healthy section of the jaw using CATIA software, then, models were printed in Acrylonitrile Butadiene Styrene (ABS). Following the resin casting technique, the printed model of the jaw was used to construct a resin model, which is tested to determine its mechanical behavior.After carrying out the photoelastic analysis, it was found that the assembly process generates stress concentration zones. Here, the stress reaches a maximum value after the application of a bite force of 130.9 N in the premolars. In this study near the premolars, 3 stress concentration zones were identified and overlap of stress fields is reveled.The results show the importance of planning in the design and assembly process to obtain the best results in the reconstruction, reducing in this way the risk of a surgical reoperation due to problems of rupture or loosening of the prosthesis.

The masticatory apparatus has been the focus of many studies in comparative anatomy-especially analyses of skulls and teeth, but also of the mandibular adductor muscles which are responsible for the production of bite force and the movements of the mandible during food processing and transport. The fiber architecture of these muscles has been correlated to specific diets (e.g., prey size in felids) and modes of foraging (e.g., tree gouging in marmosets). Despite the well-elucidated functional implications of this architecture, little is known about its ontogeny. To characterize age-related myological changes, we studied the masticatory muscles in a large (n = 33) intraspecific sample of a small, Malagasy primate, Microcebus murinus including neonatal through geriatric individuals. We removed each of the mandibular adductors and recorded its mass as well as other linear measurements. We then chemically dissected each muscle to study its architecture-fascicle length and physiological cross-sectional area (PCSA) which relate to stretch (gape) and force capabilities, respectively. We observed PCSA and muscle mass to increase rapidly and plateau in adulthood through senescence. Fascicle lengths remained relatively constant once maximal length was reached, which occurred early in life, suggesting that subsequent changes in PCSA are driven by changes in muscle mass. Quadratic curvilinear models of each of the architectural variables of all adductors combined as well as individual muscles regressed against age were all significant. Anat Rec, 303:1364-1373, 2020. © 2019 American Association for Anatomy.

Made available in DSpace on 2019-10-06T16:27:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Purpose: The present cross-over study evaluated the masticatory function and maximum occlusal force of edentulous patients with complete dentures with bilateral balanced occlusion (BBO) and canine guidance (CG), with normal (NR) and resorbed mandibular ridges (RR). Methods: Participants received new complete dentures and both occlusal concepts (BBO and CG) were applied for a period of 30 days each. The masticatory performance was evaluated with the sieving method; masticatory ability with a visual analog scale (VAS) and maximum occlusal force was assessed by means of a gnatodynamometer. Data were analyzed using repeated-measure ANOVA or Generalized Estimating Equations (GEEs), α = 0.05. Results: Thirty women completed the trial. The height of mandibular ridge was significant for the masticatory performance (ANOVA, p < 0.001, NR = 46.35 ± 12.18%, RR = 30.39 ± 9.94%), regardless of the occlusion guidance. A significant effect of the occlusion guidance was observed for the maximum occlusal force (ANOVA, p = 0.021, CG = 31.99 ± 12.74 N, BBO = 28.37 ± 9.83 N). The occlusion guidance was not significant for the masticatory performance (ANOVA, p = 0.156) and the height of the mandibular ridge did not influence on the occlusal force (ANOVA, p = 0.060). The interaction of the factors (guidance × ridge) was not significant for masticatory performance (ANOVA, p = 0.184) and occlusal force (ANOVA, p = 0.236). The VAS scores showed a significant effect of the ridge on chewing of lettuce, resulting in greater ease (GEEs, p = 0.016) and chewing quality (GEE, p = 0.028) of this food for participants with resorbed ridges. Participants with CG reported greater ease of chewing fresh bread and beef, and expressed higher quality of chew raw carrot. Participants with CG and normal ridges exhibited the highest overall chewing ability, in comparison to BBO (Bonferroni, p < 0.05, CG = 91.9, BBO = 72.7). Conclusions: CG represents a viable alternative to the BBO in complete dentures with satisfactory clinical results related to the self-perception of chewing and occlusal force. Department of Dental Materials and Prosthodontics Araraquara Dental School São Paulo State University (UNESP) Department of Dental Materials and Prosthodontics Araraquara Dental School São Paulo State University (UNESP) FAPESP: 2015/09873-2 FAPESP: 2015/10663-2

Bite force is a measure of feeding performance used to elucidate links between animal morphology, ecology, and fitness. Obtaining live individuals for in vivo bite-force measurements or freshly deceased specimens for bite force modeling is challenging for many species. Thomason's dry skull method for mammals relies solely on osteological specimens and, therefore, presents an advantageous approach that enables researchers to estimate and compare bite forces across extant and even extinct species. However, how accurately the dry skull method estimates physiological cross-sectional area (PCSA) of the jaw adductor muscles and theoretical bite force has rarely been tested. Here, we use an ontogenetic series of southern sea otters (Enhydra lutris nereis) to test the hypothesis that skeletomuscular traits estimated from the dry skull method accurately predicts test traits derived from dissection-based biomechanical modeling. Although variables from these two methods exhibited strong positive relationships across ontogeny, we found that the dry skull method overestimates PCSA of the masseter and underestimates PCSA of the temporalis. Jaw adductor in-levers for both jaw muscles and overall bite force are overestimated. Surprisingly, we reveal that sexual dimorphism in craniomandibular shape affects temporalis PCSA estimations; the dry skull method predicted female temporalis PCSA well but underestimates male temporalis PCSA across ontogeny. These results highlight the importance of accounting for sexual dimorphism and other intraspecific variation when using the dry skull method. Together, we found the dry skull method provides an underestimation of bite force over ontogeny and that the underlying anatomical components driving bite force may be misrepresented.

Dietary ecology and its relationship with both muscle architecture and bite force potential has been studied in many mammalian (and non-mammalian) taxa. However, despite the diversity of dietary niches that characterizes the superfamily Musteloidea, the masticatory muscle fiber architecture of its members has yet to be investigated anatomically. In this study, we present myological data from the jaw adductors in combination with biomechanical data derived from craniomandibular measurements for 17 species representing all four families (Ailuridae, Mephitidae, Mustelidae, and Procyonidae) of Musteloid. These data are combined to calculate bite force potential at each of three bite points along the dental row. Across our sample as a whole, masticatory muscle mass scaled with isometry or slight positive allometry against both body mass and skull size (measured via a cranial geometric mean). Total jaw adductor physiological cross-sectional area scaled with positive allometry against both body mass and skull size, while weighted fiber length scaled with negative allometry. From a dietary perspective, fiber length is strongly correlated with dietary size such that taxa that exploit larger foods demonstrated myological adaptations toward gape maximization. However, no consistent relationship between bite force potential and dietary mechanical resistance was observed. These trends confirm previous findings observed within the carnivoran family Felidae (as well as within primates), suggesting that the mechanisms by which masticatory anatomy adapts to dietary ecology may be more universally consistent than previously recognized. Anat Rec, 302:2287-2299, 2019. © 2019 American Association for Anatomy.

This study aimed to determine the electrical activity of masseter and anterior temporal muscles in patients with unilateral cleft lip and palate (CLP) and compare it with healthy volunteers. The study involved 20 female patients (mean age 20 ± 4 years) with unilateral cleft lip and palate who had undergone lip and palate surgery in childhood and finished the first-phase orthodontic therapy with level and align teeth. Twenty age- and sex-matched volunteers with no cleft lip and palate were involved as controls. Electromyographic (EMG) signals of masseter and anterior temporal muscles were recorded at rest position, during swallowing and during maximum bite force (MBF). EMG signals at different test conditions were compared between the cleft and noncleft sides of CLP patients and between CLP patients and healthy individuals. The EMG potentials of masseter (rest, swallowing, MBF) and temporal (rest, MBF) muscles were significantly higher in the cleft than the noncleft side of CLP patients (P value 0.001). Generally, patients with unilateral cleft lip and palate experienced a significant increase in the electrical activity of the masseter and temporal muscles in both sides compared to the control group (P 0.05). In conclusion, patients with unilateral cleft lip and palate exhibit overall greater masticatory muscle activity compared to healthy individuals. The asymmetric masticatory function in subjects with unilateral cleft lip and palate may be associated with severe consequences such as asymmetric facial growth, implying the importance of early diagnosis and orthodontic treatment to achieve a favorable environment for balanced facial growth in CLP affected patients.