Investigations of Bite Force in Northern Gulf of Mexico Shark Species, with Emphasis on Blacknose and Sharpnose Sharks

Bite force was investigated for nine shark species common to the waters of the Northern Gulf of Mexico using a bite force meter developed for this study. The two primary species examined in this study were blacknose, {Corcharhinus acronotus) and sharpnose (Rhizoprionodon terraenovae) sharks. Other species examined included blacktip (Corcharhinus limbatus), spinner (Corcharhinus brevipinna), finetooth (Corcharhinus isodon), sandbar (Corcharhinus plumbeus), bull (Corcharhinus leucus), tiger (Galeocerdo cuvieri), and bonnethead (Sphyrna tiburo) sharks. Absolute bite force values ranged from 0.9 to 11.79 kg for blacknose, 0.05 to 5.44 kg for sharpnose, 1.36 to 11.34 for blacktip, 1.36 to 5.90 kg for spinner, 1.81 to 3.63 for finetooth, 1.11 to 8.36 kg for bull, and 0.18 to 2.89 kg for tiger sharks. Only one bite force was obtained for bonnethead (0.45 kg) and sandbar (14.45 kg) sharks. Linear regression analysis revealed an increase in absolute bite force and a decrease in relative bite force as size increased for blacknose and sharpnose sharks. Jaw width was the best predictor of bite force in blacknose sharks explaining 8% of the variation. No significant difference in female and male absolute bite force was observed for sharpnose and blacknose sharks. Seventy-two percent of longline captured sharpnose had bite force measurements of 1.0 kg or less whereas only 37.5% of rod and reel captured sharpnose had bite force measurements in the same range. These data could be indications of stress rather than indications of physiological force generating capabilities. Electrically induced, involuntary bite force was consistently higher than voluntary bite force in sharpnose. Overall, it was concluded that sharks do not have a large bite force relative to body size in comparison to other vertebrates. Larger body mass simply allows for a bite force of high magnitude

Determinants Of Bite Force In Four Species Of Sharks From The Gulf Of Mexico With An Emphasis On The Atlantic Sharpnose Shark, Rhizoprionodon Terraenovae

Bite force can provide valuable information regarding the physiological ecology of an organism. However, there have been few studies wherein bite force in sharks has been considered. Herein I report on a study of the bite force of four species of sharks with particular emphasis on that of the atlantic sharpnose shark, rhizoprionodon terraenovae. Among the four species examined, blacktip shark, carcharhinus limbatus bite force was significantly higher than that of sharpnose, rhizoprionodon terraenovae. There was no significant difference between the bite force of those species compared with the same for finetooth shark, c. Isodon and spinner shark, c. Brevipinna. Within atlantic sharpnose sharks, I examined both voluntary and involuntary (obtained using jaw musculature stimulation) bite force measurements, and I investigated differences in bite force between size, sex, season, gape, and capture method. Additionally, I examined bite force differences between anterior and posterior positions in the jaw, and considered correlations between various head morphometrics and anterior bite force. Sharpnose sharks, ranging between 55.1 – 105.5 cm, had an anterior bite force between 4.4 – 60.2 n, and a posterior force of 20.9 – 102.8 n. There was no significant difference between the different methods used to determine bite force. Adult females had a greater anterior force than adult males, but there was no difference in posterior force. Anterior force was found to be weakest in the summer months and highest in the spring and fall. As gape increased the anterior bite force increased, with the greatest force found between 70 – 80% of maximum gape. Longlining captured sharks produced significantly lower bite force when compared to hook and line capture

Objective assessment of progressive increase in bite force post surgical correction of mandibular fractures using Nupai bite scan analyser

Background: Fracture of mandible is a common condition which is increasing in incidence in the trauma centers due to increasing motor vehicles and failure to abide by traffic regulations. Patients undergo surgical open reduction and internal fixation where post-operative occlusion and normal masticatory functions are targeted. Bite force can be taken as a guide of normal masticatory function of an individual which is dependent upon craniomandibular biomechanics. The aim of the study was to analyse bite force measurements post-operatively in patients who underwent open reduction and internal fixation for mandible fractures at different sites.Methods: Molar bite force was recorded in 31 post-operative patients who underwent open surgical procedure for fracture mandible in the department of plastic surgery from January 2018 to June 2019 by a pre-scale bite force recorder-Nupai bite force prescale system (FujiTM). Various parameters were recorded pre and post-operatively including age, gender, history, comorbidities, requirement of MMF, site and number of fractures and age of injury. Bite force were compared and improvement of bite force every 2 weeks was noted and analyzed upto 6 weeks postoperatively.Results: Bite force improvement was seen in all types of mandible fractures irrespective of the site and type of fractures over a period of 6 weeks post-operatively. This improvement was however not statistically significant. Decreased time interval form injury to surgery resulted in improved bite force measurements though not statistically significant.Conclusions: Although objective improvement in bite force could be demonstrated but extensive study involving more subjects and more patient variables would have statistical significance

Effects of body temperature on initial bite force in three species of rock- and crevice-dwelling lizards from Mexico

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

Lack of correlation between mouth-breathing and bite force

The correlation between mouth-breathing and bite force was studied in 81 children, 7 to 16 years old. Mouth-breathing was diagnosed on the basis of the subject history, the rhinomanometrically determined nasal airflow and the size of the airway measured on the profile cephalogram. The maximum bite force was measured at the first molars. In addition, the facial morphology was analysed on profile cephalograms. Both mouth-breathing and bite force were associated with the facial morphology but there was no association between mouth-breathing and bite force. It was concluded that the longface morphology characteristic of mouth-breathing children is not due to weak masticatory muscle

Can Masticatory Electromyography be Normalised to Submaximal Bite Force?

The combination of bite force and jaw muscle electromyography (EMG) provides an insight into the performance of the stomatognathic system, especially in relation to dynamic movement tasks. Literature has extensively investigated possible methods for normalising EMG data encapsulating many different approaches. However, bite force literature trends towards normalising EMG to a maximal voluntary contraction (MVC), which could be difficult for ageing populations or those with poor dental health or limiting conditions such as temporomandibular disorder. The objectives of this study were to (i) determine whether jaw-closing muscle activity is linearly correlated with incremental submaximal and maximal bite force levels and (ii) assess whether normalising maximal and submaximal muscle activity to that produced when performing a low submaximal bite force (20 N) improves repeatability of EMG values. Thirty healthy adults (15 men, 15 women; mean age 21 ± 1·2 years) had bite force measurements obtained using a custom-made button strain gauge load cell. Masseter and anterior temporalis muscle activities were collected bilaterally using surface EMG sensors whilst participants performed maximal biting and three levels of submaximal biting. Furthermore, a small group (n = 4 females) were retested for reliability purposes. Coefficients of variation and intra-class correlation coefficients showed markedly improved reliability when EMG data were normalised compared to non-normalised. This study shows that jaw muscle EMG may be successfully normalised to a very low bite force. This may open possibilities for comparisons between at-risk sample groups that may otherwise find it difficult to produce maximal bite force values

Chiropractic manipulation increases maximal bite force in healthy individuals

Recent research has shown that chiropractic spinal manipulation can alter central sensorimotor integration and motor cortical drive to human voluntary muscles of the upper and lower limb. The aim of this paper was to explore whether spinal manipulation could also influence maximal bite force. Twenty-eight people were divided into two groups of 14, one that received chiropractic care and one that received sham chiropractic care. All subjects were naive to chiropractic. Maximum bite force was assessed pre- and post-intervention and at 1-week follow up. Bite force in the chiropractic group increased compared to the control group (p = 0.02) post-intervention and this between-group difference was also present at the 1-week follow-up (p < 0.01). Bite force in the chiropractic group increased significantly by 11.0% (±18.6%) post-intervention (p = 0.04) and remained increased by 13.0% (±12.9%, p = 0.04) at the 1 week follow up. Bite force did not change significantly in the control group immediately after the intervention (−2.3 ± 9.0%, p = 0.20), and decreased by 6.3% (±3.4%, p = 0.01) at the 1-week follow-up. These results indicate that chiropractic spinal manipulation can increase maximal bite force

Bite force and its correlation with long face in children and youth

Background: Bite force is one of the indicators of proper functioning of the stomatognathic system, and its value may have diagnostic significance in disorders of the musculoskeletal system of facial bones. The aim of the study was to evaluate the relationship between gender and age, and bite force in patients with high­-angle vertical relationship of jaws and cranial bases. Materials and methods: The study group comprised 66 subjects aged 7–17 years, in whom the mandibular jaw base line and maxillary jaw-base line (ML-NL) angles were greater than 27° and the mandibular jaw-baseline and the anterior cranial base line (ML-NSL) above 33°, and a control group (n = 54) aged 7–16 years, in which the ML-NL angles were 20.0 ± 7.0° and ML-NSL 28.0 ± 5.0°. For measuring the bite force, a Japanese digital dynamometer Imada type ZPS-LM­-2000N was used. Results: In the study group no statistically significant correlation between the bite force and gender was shown, and in the control group the average bite force on the right side was significantly different for boys and girls, whereas for boys it was higher. In the study group the relationship between the age and average and maximum bite force on the right and left side was significant. In the group of people with a high-angle relationship of bases of jaws and skull no statistically significant correlation between the bite force and gender was shown. Conclusions: The was no effect of gender on the bite force in all subjects up to 18 years of age, both in patients with a high-angle and normal relationship of bases of jaws and skull. In people with a high-angle relationship of bases of jaws and cranium masticatory forces increase with age

Predictive value of molar bite force on Class II functional appliance treatment outcomes

Sagittal intermaxillary changes brought about by functional appliances show large inter-individual variation. One factor that may in part explain these differences is the masticatory musculature and its functional capacity. The aims of this study were to investigate changes in maximal molar bite force during functional appliance treatment and to assess the influence of pre-treatment maximal molar bite force on treatment outcomes with functional appliances used in Class II malocclusion children. Twenty-five children (17 males and 8 females), aged 9-13 years, with a Class II malocclusion and increased overjet were treated with functional appliances for 1-2 years. Dental casts, lateral cephalograms, maximal molar bite force, and finger force measurements were performed before (T1) and after (T2) treatment. These same measurements were also performed 1-2 years before treatment (T0); the intermediate period before starting treatment served as the control. Multiple regression analyses were used to determine possible correlations between initial maximal molar bite force and dental or cephalometric changes during treatment. Maximal molar bite force, which increased pre-treatment (T0-T1), decreased during functional appliance treatment (T1-T2). Children with a weaker T1 maximal molar bite force showed a larger overjet reduction, greater improvement in molar relationship, greater reduction in ANB angle, and greater augmentation in SNB angle from T1 to T2. Treatment of children with Class II malocclusions with functional appliances seems to lead to more favourable treatment outcomes in those with a weaker maximal molar bite force. This was observed both as regards improvements in dental sagittal relationships, namely overjet and molar Class, as well as skeletal changes due to a decrease in ANB and an increase in SNB angle