Effects of masticatory muscle training on maximum bite force and muscular endurance.

OBJECTIVE: This study evaluates the effects of chewing training on strength and endurance of the masticatory muscles. MATERIALS AND METHODS: Of the 49 healthy young adults included in the study, nine served as controls for a baseline measurement of bite force. The 40 participants who actively trained their masticatory muscles were randomly divided into a 'continuous training group' (CTG) and an 'intermittent training group' (ITG). The participants performed oral motor training by clenching silicon tubes (Chewy Tubes(™)) according to a designed protocol. The muscular strength was studied in terms of maximum bite force. Muscular endurance was evaluated by measuring the duration for which the participants held 50% of their maximum bite force value. RESULTS: Both the maximum bite force and the muscular endurance capacity increased after intensive training for both groups. After 2 months, the ITG stopped training for 1 month. At this point, a significant difference was identified both in the mean bite force values and the mean muscular endurance duration: the ITG exhibited lower values. For both groups, the highest values were attained after 3 months of training. The maximum bite force values and the muscular endurance duration were observed to follow similar patterns. The effects attained decreased rapidly in both groups when the training stopped. CONCLUSIONS: For both the continuous and intermittent training groups, 4 months of chewing exercises strengthened masticatory muscles, but such effects diminished gradually for both groups when the exercises stopped.

Functional influence of masticatory muscles on the fibre characteristics and capillary distribution in growing ferrets (Mustela putonusfuro)--a histochemical analysis.

OBJECTIVE: Changes in the masticatory function of ferrets have been shown to cause alterations in their craniofacial morphology. The aim of the present study was to investigate how the functional changes influence the histochemical characteristics of fibres of the masticatory muscles of the animal. DESIGN: Forty five-week old male ferrets were divided into two groups: one group was fed a diet of hard pellets (HD group), and one group was fed the same diet but softened with water (SD group). After 6 months, specimens of temporalis, masseter and digastricus were taken from each ferret and prepared for enzyme histochemical analysis RESULTS: Type I muscle fibres constituted the majority of the temporalis and the masseter, while the digastricus mainly comprised type II muscle fibres. The fibre-type composition did not differ significantly between the two groups. The mean cross-sectional area of type I and type II fibres in the temporalis and the masseter, and type II fibres in the digastricus was significantly greater in the HD group than the SD group. Furthermore, the HD group had a significantly greater number of capillaries per fibre, but not per surface unit (mm2). CONCLUSIONS: The results suggest that the muscle fibre size and the number of capillaries per fibre of the masticatory muscles are readily adaptesd to the altered masticatory muscle functions.

Craniofacial growth in the ferret (Mustela putorius furo)--a cephalometric study.

OBJECTIVE: When suggesting the ferret as a valid laboratory model in craniofacial research, it is essential to know about its normal craniofacial growth. DESIGN: Sixteen ferret kits (eight male and eight female) were selected for the present investigation. Serial lateral and dorsoventral cephalograms were taken on each animal at a mean age of 25, 35, 55, 80 and 300 days. The cephalograms were then digitised and the coordinates of 33 landmarks were derived on each set of cephalograms. Thirty-four variables were then calculated on each set of cephalograms by computer image programs with the coordinate data. Results were analysed statistically, and the craniofacial growth pattern and related sexual dimorphism were described in three perspectives: lateral and dorsoventral viscero- and neurocranium, and lateral mandible. FINDINGS: In both sexes, the viscero- and neurocranium follow an orderly pattern of expansive growth in three dimensions. The growth of the mandible is mainly characterised by an anteroposterior elongation of the mandibular body, an enlargement of the coronoid process, and an increase in height of the alveolar process. The growth rate varies with site. Craniofacial growth in ferrets starts to slow down and finally ceases earlier in female than in male animals.

Craniofacial morphology and growth in the ferret: effects from alteration of masticatory function.

INTRODUCTION: Our hypothesis is that any effects on craniofacial growth and morphology induced by altering the masticatory function will vary according to the species involved. The general aim of this thesis was to test the possible effects of altering the masticatory function on craniofacial growth and morphology, as well as features of masticatory muscles in ferrets. To better elucidate these mechanisms involved, the anatomy of the skull, craniofacial growth pattern and development of occlusion in the ferret were investigated to serve as baseline data. MATERIALS AND METHODS: The description of the anatomy and the radiographic features of the skull was based on observations of 100 skulls of adult ferrets of both sexes. The craniofacial growth pattern was studied in 16 young ferrets of both sexes using serial cephalograms taken on 5 occasions according to age: 25 days, 35 days, 55 days, 80 days and 300 days. To follow the development of occlusion, these animals underwent dental examinations every other day. Forty male ferrets were divided into two groups from the age of 5 weeks. One group was fed hard pellets (hard-diet group), and the other the same diet but softened with water (soft-diet group). After six months, specimens of masticatory muscles were dissected and analysed histochemically, and cephalograms were analysed cephalometrically. RESULTS: The ferret skull is relatively elongated with a short facial region, being longer and broader in males than in females. The viscero- and neurocranium follow an orderly pattern of expansive growth. The growth of the mandible is mainly characterized by an anteroposterior body elongation, and enlargement of the coronoid process. Craniofacial growth in ferrets ceases earlier in female than in male animals. The deciduous teeth erupted between the 19th and 31st postnatal day, and exfoliated approximately between days 51 and 76. The time of eruption of the permanent teeth ranged from 42 to 77 days. The female ferrets were generally ahead of the males regarding the eruption age of permanent teeth. The alteration of the masticatory function by feeding the animals a soft diet caused a hard palate plane more distant from the cranial base plane, smaller inter-frontal and inter-parietal widths, and a slenderer zygomatic arch, as well as a generally shorter and narrower coronoid process. Variations of most variables are greater in animals fed on soft diet. The mean cross-sectional area of type I and type II fibres in the temporalis and the masseter, and type II fibres in the digastricus, as well as the number of capillaries per fibre were significantly smaller in the soft-diet animals. CONCLUSION: Altered masticatory function has induced changes in masticatory muscles and certain effects on craniofacial growth in ferrets. These changes are not the same as those reported in other species (e.g. rats). It appears that reduced masticatory function leads to smaller fibres in the elevators and transverse skull dimensions. The different effects are presumably related to the differences in craniofacial anatomy and growth pattern, as well as the masticatory system, in the various species studied previously.

Effects of masticatory muscle function on craniofacial morphology in growing ferrets (Mustela putorius furo).

Studying the effects of masticatory muscle function on craniofacial morphology in animal models with different masticatory systems is important for further understanding of related issues in humans. Forty 5-wk-old male ferrets were equally divided into two groups. One group was fed a diet of hard pellets (HDG) and the other group was fed the same diet but softened with water (SDG). Lateral and dorsoventral cephalograms were taken on each group after 6 months. Cephalometric measurements were performed by digital procedures. For SDG ferrets, the hard palate plane was more distant from the cranial base plane, and canines were more proclined compared with HDG ferrets. The SDG ferrets were also found to have smaller interfrontal and interparietal widths, and a slenderer zygomatic arch than the HDG ferrets. In the mandible, the coronoid process was generally shorter and narrower for the SDG ferrets. The effects of the altered masticatory muscle function on craniofacial morphology in growing ferrets seemed to differ from those previously reported in other animal models studied under similar experimental conditions. Such differences in the effects are presumably related to the differences in the mode of mastication, craniofacial anatomy and growth pattern in different animal models.

Dental eruption and exfoliation chronology in the ferret (Mustela putorius furo).

Substituting ferrets for rats and dogs as animal models for craniofacial research is favourable because of the similarity of many of the ferret's anatomical, metabolic and physiological features to those of man. Other advantages are cost-effectiveness and possibly less ethical controversy. However, information on the dental chronology of ferrets needs to be supplemented if this animal is to be promoted as an alternative model. Dental development was here examined in 16 ferrets (eight males, eight females) from three litters at between 12 and 90 days of age. Dental eruption and exfoliation were assessed and recorded every second day. The sequence of eruption of deciduous and permanent teeth was determined and data were analysed statistically. Also, any sex-related differences in eruption and exfoliation ages were defined. No deciduous incisors were observed to erupt in this group of animals. Other deciduous teeth erupted between the 19th and 31st postnatal days, and exfoliated between days 51 and 76. The time of eruption of the permanent teeth ranged from 42 to 77 days, in accordance with the stage of the mixed dentition. The female ferrets were generally ahead of the males in the exfoliation age of their deciduous teeth and the eruption age of their permanent teeth, but this, a sex difference did not apply to the eruption age of the deciduous teeth. These extended basic data might facilitate the introduction of this alternative experimental animal into craniofacial research.