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The influence of the tongue on craniofacial growth was studied in 96 Mini-Lewe miniature pigs. The animals were partially glossectomized at different ages and slaughtered at various intervals after operation. The skulls were macerated for biometric analysis. Mandibular growth was significantly reduced lengthwise in animals glossectomized at age 12 weeks. The role played by the tongue in orofacial growth was also indicated by the reduced width of the lower jaw. In pigs partially glossectomized at age 12 weeks, lateral growth of the entire lower jaw was reduced after eight weeks. In animals glossectomized at age six weeks, lateral growth of the lower jaw was reduced in the region of the 1st deciduous molars and the canines after glossectomy. Partial glossectomy had no significant effects on vertical growth of the lower jaw, growth of the upper jaw or overall skull growth. Shortening of the tongue in miniature pigs six weeks old resulted in no measurable jaw changes 23 weeks after surgery.

After unilateral ligature of the common carotid artery in young rats, the rostrum was observed to shift towards the ligated side. The scoliosis was combined with arthropathic changes in the temporomandibular joint. The deflection of the rostrum is situated in the region of the right premaxillar bone. It is assumed that the scoliosis is caused by reduction of the blood flow to the frontonasal sutures because the terminal branches of the infraorbital artery have no collaterals. Moreover, the reduction in the blood supply also leads to disturbance of the muscular function and thus to a reduction in growth stimuli to the frontonasal sutures.

In the miniature pig MINI-LEWE partial glossectomy had no significant effects on vertical growth of the lower jaw, growth of the upper jaw or overall skull growth. No relationship was found between age at glossectomy or post-surgical interval and the size of the gonion angle. The tongue, peri-oral muscles and the muscles of the floor of the mouth are in a state of functional equilibrium which changes in the course of development, the influence of either the tongue or the peri-oral muscles increasing as a result. Partial disruption of this state of equilibrium leads to dysgnathia.

The role played by the tongue in orofacial growth is also indicated by the reduced width of the lower jaw. In miniature pigs MINI-LEWE that were partially glossectomized at an age of 12 weeks lateral growth of the whole lower jaw was reduced after eight months. In animals that had been glossectomized at an age of six weeks lateral growth of the lower jaw was reduced in the region of the 1st deciduous molars and the canines right months after glossectomy.

The dimensions of the skull and the dry weight of the skull bones show definite sexual dimorphism. The dynamics of the growth in the skull dimensions and their vectorial presentation show that skull growth in Rattus norvegicus BERKENHOUT is most rapid between the 42nd d and the 4th month of life. This phase is followed by a phase of localized bone growth, which persists up to an age of 300 d. The faster growth of the viscerocranium leads to changes in the proportions of the skull. The relative positions of viscerocranium and mandible and the higher relative position of the dentures are similar to principle to those seen in man. Finally, the morphogenetic effect of the temporalis muscle together with that of the brain in the shaping of the skull are discussed.

All continuous teeth were unilaterally extracted on the right side of the upper and lower jaws of 57 male and female Vietnamese belly pig. The animals were slaughtered 6, 7, 8, 9, 10, 11 and 12 after the extraction. Our investigations into quantitative changes in the masticatory musculature after unilateral extraction showed the dry weight of the musculature on the extraction side was reduced. This reduction was greatest in the case of the M. temporalis. The findings relating to the muscles are consistent with the results of the skull evaluations reported in the first 2 publications, with indicated that tooth extraction leads to only local changes in the jaw during postnatal development. The findings published in the 3 publications of this series relating to the bones and muscles are discussed.

Ligature of the right common carotid artery induces compensatory dilatation of the arteries of the head and neck, and particularly of the left common carotid artery. Functional mechanisms also caused dilatation of the arterioles. The enlargement of previously formed anastomoses and collaterals was also observed. Angiophysical effects and histochemical phenomena are implicated in the modification of previously existing anastomoses. The transport capacity of the collaterals increases as the area of the summated lumena increases and as the length of the vascular pathways decreases. The time factor, finally, also plays an important in role the formation of anastomoses, which continues even after an observation period of 12 months in the rat.

The cross sectional areas of arteries were calculated from their measured thicknesses. The monthly increase in size of the cross sectional area of the aorta is higher in both the controls and the operated animals between the 6th week and 4th month of life than during the subsequent period. The rate at which the cross sectional area of the aorta increased in operated animals was about twice that observed in the controls. The left common carotid artery increased its cross section in the operated animals most rapidly up to the fourth month. The cross sectional areas of all anastomoses increased five-fold by the 12th month of life. The quantities of blood flowing correlated closely with the angiometric values.

Following up on the 1st part of this cycle of publications, the 2nd Bulletin deals with investigations on upper and lower jaw growth in the Vietnamese belly pig after extracting all teeth as they appeared in the right half of the jaw. The results showed characteristic changes on the side of the extraction compared with the skull on the other side. They also show clearly that the effects of unilateral loss of teeth on the development of the bony part of the chewing apparatus are very local. This is made evident by analysis distances measured for the 3rd and 4th upper jaw widths and the 2nd vertical height of the bottom jaw. In contrast to other authors, we found no changes in the longitudinal and lateral development of the bottom jaw. Due to the slight degree of development of the alveolar process of the bottom jaw in the region of the 1st permanent molar, a significant reduction in surface area was found when removing the 2nd molars, which was performed usually at an early point, only in the group slaughtered after 12 months.

Post-natal craniofacial growth in the miniature pig MIN-LEWE is influenced by the tongue in various ways. Periodic and locally differentiated intensive craniofacial growth explains why the tongue has a measurable effect on jaw growth only at certain times. This is the situation in animals glossectomized at an age of 12 weeks. Shortening of the tongue in miniature pigs aged six weeks resulted in no measurable changes in the jaw after a prolonged post-surgical interval (23 weeks), which indicates that the capacity of the orofacial system during post-natal development is considerable.

The areas obtained by planimetry of parafrontal sections showed distinct asymmetry in the region of the cavitas nasi in the Beagles that had been operated. Although differences between the sides were also observed in the skulls of the control Beagles, they were very slight. There were no differences between the left and right sides in regard of the areas of the cavitas cerebri in either the operated or the control Beagles. In the operated skulls they are slightly larger than normal, but in the control animals they are within the physiological range of variation.

The influence of the blood supply on craniofacial growth was investigated in 396 albino rats (Rattus norvegicus Berkenhout). This was done by blocking the right common carotid artery of animals aged 42 d. The rats were slaughtered at previously specified intervals after the operation. The ligature led to dilation of the other major arteries of the neck. Numerous collaterals and anastomoses were also formed. These occurred on the ligature side in the flow region between the proximal and distal stumps of the right common carotid artery, between the flow regions of the right external carotid artery and the right vertebral artery and between the flow regions of the right subclavian artery and the right external carotid artery. Further anastomoses arose between the arteries of the other side, i.e. the rostral thyroid artery, lingual artery, submental artery and labial mandibular artery.

Biophysical studies of the orofacial system require a profound knowledge of the development and morphology of the skull. The skull is the result of phylogenetic and ontogenetic evolution. A great number of multifarious factors have effects on the growth of the skull. In animal experiments the effects of some of these factors on pre- and postnatal craniofacial growth as well as the resulting maintenance of the functional balance have been analyzed. These basic research findings will be a contribution to our understanding of the factors influencing and controlling maxillocranial growth and will aid us in evaluating their inherent laws.

The dry weight of the skull and jaw bone increases faster in operated rats than in the controls during the fourth and 12 months, but their rates of growth do not differ in the 8th month. The distances measured on the mandible reveal definite sexual dimorphism in the development of the different lengths and heights, these distance being greater in the male rats. Growth in the length of the processes predominated over the growth of the body of the mandible. Local changes in the bone were observed at the points of origin and attachment of muscles.