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1.
Myostatin (GDF8) and dystrophin are critical molecules for muscle organisation. Myostatin is involved in regulating muscle growth and development, whereas dystrophin is part of the dystrophin-glycoprotein complex (DGC), which anchors the cytoskeleton to the sarcolemma. We examined temporalis muscle morphology and function in myostatin deficient and dystrophin deficient (Mdx) mice in order to determine how myostatin and dystrophin affect bite force and muscle fibre composition. Bite forces from 4-month-old myostatin-/-, dystrophin deficient (Mdx) and normal control mice were measured by load cell and field stimulation of the temporalis muscle. Tissue sections were stained with haemotoxylin and eosin (H&E) and the periodic acid-Schiff reaction (PAS) to assess morphology and fibre type differences. A positive relationship between bite force and muscle mass for both genetic models was observed. Both Mstn-/- and Mdx mice showed significant elevation in bite force and muscle mass. Histological examination revealed greater muscle fibre cross-sectional area variability in Mdx mice (ANOVA, F=5.6, P<0.01). Surprisingly, the Mstn-/- mice demonstrated a disproportionate increase in bite force at higher stimulation frequencies with comparison of regression lines for force-frequency data (ANOVA, F=3.46, P<0.07). Muscle fibre typing using a PAS staining technique revealed significantly more type IIx/b glycolytic muscle fibres in the Mstn-/- mice. Our results suggest that histopathologies associated with Mdx mice did not diminish gross temporalis structure or function, whilst the force-frequency changes associated with Mstn-/- mice were reflected in an elevation of type IIx/b fibres.  相似文献   
2.
为观察总义齿咬合平面定位设计与患者咀嚼功能的关系,选择10名无牙颌患者,分别为每个患者各作4副总义齿,其中有一副义齿(标准义齿)的咬合平面以上中切牙近中切角为基准或向后上、或向后下、或向左右方向倾斜5°。测定患者戴各义齿用单侧尽最大力咬合时的力值,发现患者戴标准义齿时平均最大咬合力值显著高于其它义齿。该结果提示:总义齿的咬合平面平分颌间距离且与耳屏鼻翼线平行最有利于无牙颌患者咀嚼功能的发挥  相似文献   
3.

Purpose

The aim of this study was to determine the influences of oral motor function such as tongue function and bite force on masticatory performance in the elderly.

Methods

We randomly selected 245 subjects who has 28 natural teeth among community-dwelling elderly. We evaluated masticatory performance using a gummy jelly, and also measured bite force, tongue muscle force, and the speed of tongue movement.

Results

We found that reduced masticatory performance to be associated with decreased the speed of tongue movement and/or tongue muscle force, indicating that reduced oral motor function also influences masticatory performance.

Conclusions

These results suggest that keeping oral motor function, as well as maintenance of occlusal support, to be important for maintaining masticatory function in the elderly.  相似文献   
4.

Objectives

The aim of this in vivo study was to investigate how reproducible individuals find their habitual intercuspation.

Methods

A new type of highly accurate measuring procedure was involved using an intraoral optical scanning device (Cerec Bluecam). First, a pilot test investigated the accuracy of the procedure within a standardized setting. With regard to the in vivo study, fifteen participants with full dentition were selected. For each of these individuals, eight scans were taken both in the morning and in the afternoon. Furthermore, during each session, scans were taken both in horizontal and upright position. In order to compare this to ubiquitous used processes, plaster replicas of five individuals were investigated as well. The scans were analysed, and the differences in the position of the lower jaw were calculated by a specialized superimposition program (n = 570 comparisons/OraCheck).

Results

The results showed that there was no significant difference between the time of day and the position of the patient. The overall mean ± SD value for locating the habitual intercuspation was 42 ± 34 μm, however ranging from 22 ± 9 μm to 77 ± 58 μm for single individuals. On the other hand, the differences in positioning plaster replicas reached a mean of 135 ± 77 μm.

Conclusions

The reproducibility of the habitual intercuspation can be obtained under in vivo conditions by a newly developed and highly accurate measuring procedure. Individuals with full dentition show values in average of 42 μm.

Clinical significance

Determining the occlusal jaw relation is an important precondition in restorative dentistry and many methods are proposed for a proper occlusal registration. Although much is known about in vitro accuracy of these techniques, little is known how reproducible the habitual occlusal position itself is found between individuals.  相似文献   
5.

Aim

To compare characteristics of gender, age, body part and breed in dog bites.

Methods

We reviewed 14 956 dog bites (4195 paediatric) reported to the Allegheny County Health Department, USA, between 2007 and 2015. Using predefined age groups, we performed linear regression to assess for subject age and bite frequency and used binary logistic regression to evaluate for differences in gender and body part. We used chi‐squared test with Bonferroni correction to evaluate for differences in reported breeds with age.

Results

There was a negative correlation (?0.80, r2 = 0.64) between age and bite frequency. Children 0–3 years had a higher odds ratio (OR) of bites to the face [21.12, 95% confidence interval (CI): 17.61–25.33] and a lower OR of bites to the upper (OR: 0.14, 95% CI: 0.12–0.18) and lower (OR: 0.19, 95% CI: 0.14–0.27) extremities. ‘Pit bulls’ accounted for 27.2% of dog bites and were more common in children 13–18 years (p < 0.01). Shih‐Tzu bites were more common in children three years of age and younger (p < 0.01).

Conclusion

Dog bites occur with higher frequency at younger ages, and head and neck injuries are more common in younger children. Pit bull bites are more common in adolescents and Shih‐Tzu bites more common in younger children.  相似文献   
6.
The ability to perform key behaviors, particularly those associated with reproduction, has been linked to reproductive success. However, it remains unclear as to which underlying mechanisms govern variation in the performance capacities of these behaviors. Due to its ability to mediate physiological and morphological changes, the steroid hormone testosterone has been hypothesized to influence performance. This hypothesis, however, has not been tested in a broad range of taxa or mating systems. In this study, seasonal patterns of bite force and locomotor performance were quantified concurrently with circulating testosterone levels in males of a non-territorial polygynous lizard species (Aspidoscelis sexlineata). Bite force and one measure of locomotor performance were significantly greater in the breeding season than in the post-breeding season, and this seasonal variation in performance was correlated with seasonal changes in testosterone levels. These results suggest that the performance capacities of behaviors important for acquiring mating opportunities in this species are maximized during the breeding season by elevated testosterone levels.  相似文献   
7.
8.

Purpose

The aim of this study was to investigate how the physical variables of fibular reconstructed mandibles with dental implants affects the relative bite force in oral cancer patients.

Materials and methods

Over 7 years of follow-up, 13 oral cancer patients were enrolled who included 51 successful implants in the fibular flap. The tactile sensor analyzer evaluated the bite force. The crown-implant ratio, fibular, and rehabilitated dental length were measured using radiographic images. Linear regression was used to analyze the bite force related to the variables of the implants in the fibular reconstructed mandible.

Results

Even when the results showed no statistical significance (P > 0.05), increasing the crown-implant ratio, length of the fibular flap, and implant prosthetic reconstructed dentition had a tendency to decrease the bite force (estimate from ?0.08% to ?4.27%); there was a positive trend of occlusal force and the length of rehabilitative dentition compared with the dental antagonist (estimate = 6.95).

Conclusion

In this study, the crown-implant ratio, implant dentition, and fibular flap length revealed no significant impact on the bite force or implant success in oral cancer patients; however, a trend to weaken the bite force was suggested once the numerical values of these variables increased.  相似文献   
9.
10.
We designed this study to determine the efficiency and stability of anterior segmental osteotomies (ASO) without orthodontics for various dentofacial deformities. Records of patients treated with maxillary or mandibular ASO, or both, without orthodontics in the past 15 years were analysed. The assessment included postoperative analysis of patients’ aesthetics and functional satisfaction using a questionnaire and grading (score 0 - 4) system, and the amount of relapse calculated from 12-month postoperative cephalograms. A total of 26 ASO subjects (age range 13- 31 years) were studied (14 maxillary, two mandibular, and 10 bimaxillary). Long-term stability was acceptable in all cases with no significant relapse (p>0.05). No major complications were encountered. All patients reported good to excellent (score = 3 to 4) satisfaction following surgery. Using meticulous planning and a careful surgical technique, ASO without orthodontics is a simple, quick, safe, and stable option for the correction of dentofacial deformities.  相似文献   
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