OBJECTIVE:To analyze the effect of a type II collagen mutation on craniofacial development in transgenic Del1 mice.DESIGN:Samples from homozygous (+/+) and heterozygous (+/-) transgenic Del1 mice harboring mutations in the type II collagen gene as well as non-transgenic (-/-) littermates were collected at days 12.5, 14.5, 16.5 and 18.5 of gestation. The cartilaginous and bony elements of the craniofacial skeleton were analyzed after staining with alcian blue, alizarin red S and von Kossa. The expression patterns of type II, IX and X collagens and aggrecan were analyzed by immunohistochemistry and in situ hybridization.RESULTS:Several abnormalities were observed in the craniofacial skeleton of transgenic Del1 mice. These include an overall retardation of chondrogenesis and osteogenesis in Del1 +/+ mice, and to a lesser extent also in Del1+/- mice. Characteristic findings in Del1 +/+ mice included a reduced anterioposterior length, a smaller size of the mandible, a palatal cleft and a downward bending snout. We also detected retarded ossification of calvarial bones in Del1 +/+ and +/- mice when compared with Del1 -/- mice. A surprising finding was the presence of both type II and X collagens and their mRNAs in the periosteum of the cranial base.CONCLUSION:The present study confirms the important role of type II collagen mutation in craniofacial development and growth. In addition to affecting endochondral ossification, the type II collagen mutation also disturbs intramembranous ossification in the developing craniofacial skeleton.

OBJECTIVESThe purpose of the present study was to investigate the possible effects of untreated terminal leukemia on craniofacial growth (Study I), and also the effects of the antineoplastic agent carmustine on craniofacial growth in both leukemic and healthy rats (Study II).MATERIALA total of 367 inbred Piebald variegated rats was used.METHODTransmission of leukemic cells was carried out intraperitoneally at 30 days of age, and without treatment (Study I), the rats reached the terminal phase within 17 +/- 1 days. Rats with induced leukemia was cured with 10 mg/kg carmustine (BCNU) given on days 6 and 13 following cell transmission (Study II), the rats remaining in remission until they were killed at 100 days of age. Final weight was recorded and 12 craniofacial dimensions and tibial length were measured with a digital sliding caliper.RESULTSThe results showed that the effect of untreated terminal rat leukemia (Study I) on craniofacial growth differed between the genders. Male rats showed clearly reduced dimensions of facial structures and also retarded general body growth, whereas females showed differences mainly in general body growth. The effect of cured leukemia (Study II) as such was minor, while BCNU had a strong and permanent reducing effect on both craniofacial and general body growth in both genders.CONCLUSIONWe suggest that the results in Study I came both from a direct effect of leukemia and an indirect effect of untreated terminal leukemia through malnutrition. The alkylating agent BCNU seemed to be the main cause of permanent craniofacial and general growth retardation in Study II.

OBJECTIVES:To elucidate the role of the fibroblast growth factors 1 and 3 (FGFR-1, -3) and the platelet derived growth factor (PDGFR) in the growth of the mandibular condylar cartilage in the rat.SETTING AND SAMPLE POPULATION:Institute of Dentistry and Department of Biostatistics, University of Turku, Turku, Finland. The material consisted of 1- to 21-day-old Long-Evans/Turku rats (total of 24 animals, three in each age group).DESIGN:An immunohistological in vivo study combined with histomorphometry and biostatistical analysis.EXPERIMENTAL VARIABLE:The animals were killed with an overdose of carbon dioxide and thereafter decapitated. Heads were fixed in 4% paraformaldehyde, decalcified in 12.5% ethylenediaminetetraacetic acid, cut sagittally into two halves and sectioned sagittally at 6 microns. In order to detect FGFR-1, -3 and PDGFR the sections were treated with H2O2/methanol (1:100), after which FGFR-1 and PDGFR monoclonal and FGFR-3 polyclonal antibodies were applied. The reaction products were visualized by using the Vectastain ABC Elite Kit using peroxidase substrate kit DAB as substrate. Negative and positive controls were also prepared. The sections were counterstained with hematoxylin.OUTCOME MEASURE:In order to measure the depth of the cell layer labeled with FGF-1, -3 and PDGF receptors, the condylar head was divided into four regions: anterior, superior, posterosuperior and posterior. The measurements were made perpendicular to the articular surface using a computerized image analysis system, the images being acquired by means of a microscope connected to a CCD camera. The mean of five equally distributed measurements of each region was used to indicate the depth of the cell layers secreting the receptors. Regression analysis was used to evaluate the association between the depth of the labeled cell layer in relation to total depth of the condylar head, as a function of age.RESULTS:Our results show that the depth of the cell layer labeled for FGFR-1, -3 and PDGFR increase significantly as a function of age in the mandibular condylar head of rats.CONCLUSION:Increase in the cell layer labeled for FGFR-1, -3 and PDGFR occurs during the stage when the articular function of the mandibular condyle intensifies. FGFR-1, -3 and PDGFR evidently have an important role in the growth regulation of the condylar cartilage during the most rapid growth period in the rat.

INTRODUCTION:Osteochondral rib grafts are most commonly used for mandibular condylar replacements. However, when used in growing patients, unpredictable growth of the constructed condyle/ramus is a common complication. Clinically two types of overgrowth, linear or exuberant, have been described.PURPOSE:In order to investigate growth disorders associated with osteochondral rib grafts in children, overgrown grafts were examined histologically.PATIENTS AND METHODS:The material consisted of seven samples (six patients) of osteochondral rib grafts, that had been removed due to overgrowth.RESULTS:Examination revealed that the clinical type of overgrowth was not related to any specific microarchitecture, which in itself, showed considerable variation. In three of the samples, a typical endochondral ossification zone was seen and in two others, signs of metaplasia, i.e. a gradual transformation of the cartilage cells into osteocytes, were noted.CONCLUSIONS:The study reveals that the clinical type of overgrowth, linear or exuberant, cannot be related to any typical histological finding. Furthermore, the findings suggest that local factors, such as mandibular movements and loading of the reconstructed condyle may have an effect on the structure of the osteochondral rib graft, and eventually on its growth.

This study makes a molecular biological comparison of primary and secondary cartilage at an early phase of postnatal development. The distribution of insulin-like growth factor-I (IGF-I) mRNA expression in the mandibular condyle and rib cartilage of 1–28-day-old rats was examined after in situ hybridisation using an oligo probe cocktail for IGF-I mRNA. In the condyle, expression was localised to a narrow strip under the articular layer where the cells are undifferentiated. Essentially, no differences were found in IGF-I synthesis within three samples from the same age group or between different age groups. In rib cartilage, IGF-I mRNA was localised within the germinative, proliferative and early hypertrophic cell layers in 1–28-day-old rats. Again, there were no differences in expression among animals of the same age or as a function of age. This pattern of IGF-I mRNA expression indicates that IGF-I synthesis during growth of the mandibular condylar cartilage is different from that of costal cartilage. The findings shed light on the problem of overgrowth often associated with the use of costochondral grafts to replace defective mandibular condyles.

The purpose of this study was to examine craniofacial morphology, pharyngeal airway space and hyoid bone position in preschool children with sleep‐related breathing disorder associated with hypertrophy of tonsils (SBDT). Thirty‐eight preschool children, mean age 4.7 y, with SBDT and with an apnoea index (AI) of 0 < AI <5, were divided into two groups. One consisted of 15 children with sleep‐related breathing disorder (SBD) and more than 75% of the tonsils visible (GUI) and the other of 23 children with SBD and 25–75% of the tonsils visible (Gil). The control group consisted of 31 children without ear, nose and throat disease and with GI (barely visible) tonsils. Compared with the controls, GUI children had a retrognathic mandible, a large posterior facial height, a large interincisal angle with retroclined lower incisors, a narrow pharyngeal airway space, an anterior tongue base position and a long soft palate. Compared with the controls, Gil children had a large anterior lower facial height and a short nasal floor. However, like the controls, Gil children did not have a retrognathic mandible. Conclusion: The findings show that children with SBDT display a characteristic facial appearance at an early age. Since the condition has an effect on growth, it needs to be prevented by controlling morphology and function at the preschool age.

Objective: this study was aimed at characterizing the craniofacial structures, i.e. the facial skeleton, cranial base, dentition, pharyngeal airway space, and the hyoid bone position, in healthy preschool children without sleep-related breathing disorder. Materials and methods: from lateral cephalometric radiographs taken of 92 children for diagnostic purposes, 45 were selected for the present investigation on the basis of head position, and divided according to the classification of Siriwat and Jarabak (Angle Orthod. 55 (1985) 127) into groups representing counter-clockwise (CC), straight downward (SD), and clockwise (C) facial types. Results: the findings showed that, in comparison with the other groups, CC is associated with larger facial taper and posterior facial height, smaller mandibular line angle, ramus position, lower facial height and cranial base angle. By a similar comparison, C is associated with larger mandibular line, gonial angles and convexity, and with a smaller L–1 to mandibular line angle. There were no significant differences in hyoid bone position among the three groups. However, the distance of the lower pharynx was smaller in CC than in C, while the tongue base of CC was noted to be in a posterior position. Conclusions: thus, the results indicate that there are significant differences in the madibular position and form among the present three groups of children. It is proposed that the objective of vertical facial control ought to be included in the treatment of preschool children with malocclusion and respiratory disorder.

While there are numerous investigations on hormonal control of long bone epiphyseal growth, corresponding knowledge is sparse concerning the condylar cartilage. We investigated the distribution of growth hormone (GH) and insulin-like growth factor I (IGF-I) receptors in the temporomandibular joint (TMJ), especially the condyle, and compared the findings with information of long bone epiphyseal plates. The localization of the receptors was examined in vivo by immunohistochemical methods in one- to 21-day-old rats. GH receptors were detected in various components of the TMJ, but not in the fibrous articular surface or in the cartilage layers of the condyle. IGF-I receptors were found in the fibrous articular surface of the condyle and particularly in the superior and posterosuperior regions of the condylar cartilage, the depth of the labeled cell layer increasing significantly with age. It is evident that the expression of GH and IGF-I receptors is area-specific in the TMJ. Early post-natal growth and development of the mandibular condylar cartilage seem to be IGF-I-dependent but not directly dependent on GH.

Because of increased survival rates in childhood cancer, special interest has been focused on the side-effects of the therapy and the quality of life in long-term survivors. Our aim was to investigate craniofacial growth in children who had received different kinds of antineoplastic therapies for solid tumors. A total of 40 children treated in the Turku University Central Hospital were examined and divided into three different groups. Group 1 comprised 18 children treated for intracranial tumors with cranial irradiation (CRI) and chemotherapy (CT) including alkylating agents. Seven children out of 18 in this group received growth hormone (GH) therapy. In Group 2, 11 children with extracranial solid tumors also received multiagent CT including alkylating agents, but no CRI. Group 3 consisted of 11 children treated for Wilm's tumor with CT, which did not include alkylating agents or CRI. A total of 19 linear and four angular variables from the lateral cephalograms of the subjects were measured. Most deviations in craniofacial structures were found in children treated with combined CRI and multiagent CT. All disturbances were seen in the vertical measurements which were reduced when compared to the matched controls. It seems reasonable to assume that impaired growth following combined radio- and chemotherapy, as well as GH treatment, particularly affects cartilage-mediated growth. However, the deviations seen in the present study were fairly minor and did not usually require clinical consideration.

The subjects of the investigation comprised 95 girls and 73 boys with juvenile rheumatoid arthritis (JRA), and 102 girls and 66 boys representing healthy controls, all with a chronological age from 6.3 to 14.4 yr. The dental development was assessed from panoramic radiographs using a seven-tooth model. The radiographs were evaluated on three separate occasions with a minimum interval of one month in a randomized order, and blind with respect to absence or presence of JRA. In both JRA patients and healthy controls, dental maturity was ahead of chronological age. In addition, dental maturity was significantly advanced in JRA patients with 0.26 yr in girls and 0.28 yr in boys. It is tentatively suggested that the advanced dental development in JRA patients compared with healthy children was partly an effect of treatment with cortisone, while the influence of the disorder per se remains to be elucidated.

The distribution of type I and II collagen synthesis in the temporomandibular joint (TMJ) area of 1- to 28-day-old rats was studied after hybridization with probes to pro alpha1(I) and pro alpha1(II) collagen mRNA, and stain intensity through the various cartilaginous zones of the mandibular condyle and other areas of TMJ was assessed. The pro alpha(I) collagen mRNA was detected in the perichondrium/periosteum, in the fibrous and undifferentiated cell layers of the mandibular condyle, in the articular disc, and in all bone structures and muscles. The pro alpha1(II) collagen mRNA was found in the condylar cartilage and the articular fossa. Intensity in the condyle was highest in the chondroblastic layer and decreased towards the lower hypertrophic layer. In the condylar cartilage of the 21- to 28-day-old rats the chondroblastic cell zone was relatively narrow compared with the younger animals, whereas the reverse seems to be the case in the cartilage of the articular fossa. Changes in the pro alpha1(II) collagen mRNA were observed in the osseochondral junction area of the primary spongiosa, in that at the age of 5 days intense staining was found, whereas no staining was observed by 14 days. In the mineralizing zone, however, the majority of osteoblastic cells gave a positive signal with the pro alpha1(I) collagen probe. In conclusion, type II collagen synthesis of the mandibular condyle is restricted to its upper area. This differs from the long bone epiphyseal plate, where this type of collagen is produced virtually throughout the cartilage. Type II collagen synthesis of the fossal cartilage seems to increase as a function of age.

Skull morphology and histology in the heterozygous offspring of a transgenic founder mouse Del1, harbouring 6 copies of deletion mutation in Col2a1 gene, were compared with those in normal siblings. On visual observation and roentgenocephalometric examination the heads of heterozygous Del1 mice were smaller than normal. Histologically the sizes of cartilaginous structures of the cranial base were reduced. Severe defects were seen in the temporomandibular joint as progressive osteoarthritic lesions. These observations elucidate the relationship between the genotype and phenotype and demonstrate that heterozygous Del1 mice are a useful model for studies on a genetic disturbance where ‘clinical’ manifestations are not evident until adult age.

The regulatory effect of the periosteum on the growth of the mandibular condylar process has previously been investigated by relieving the periosteal tension, e.g. by dividing the periosteum, but no unanimous conclusion has been reached. In the present investigation, a different experimental design was applied in that the growth of the condylar process was observed following a provoked periosteal damage. Using 15-day-old rats, the mandibular ramus on the right side was exposed, and the periosteum subjacent to the condylar cartilage was frozen by a cryotechnique. Controls were treated similarly, with the exception of the freezing. The height of the ramus and the length of the mandibular corpus were measured on separated dry mandibular halves 15 or 30 days postoperatively. The measurements showed that the mandibular halves on which the periosteum had been frozen were significantly smaller than the contralateral ones. A tendency in the same direction was also found in the sham-operated animals. It can be concluded that the presumably increased restriction following damage to the periosteum, and evidently also scarring resulting from the operation, has an inhibitory effect on the growth of the condylar process. However, it is still open to discussion whether the reduced growth is transmitted by mechanical means according to the periosteal-tension hypothesis and/or by here unspecified mitogenic factors.

The tissue-separating capacity of chondral structures has been debated for more than 30 years, and one aspect that has particularly been questioned is whether the secondary cartilage of the mandibular condyle is comparable to primary growth cartilage, e.g. the epiphyseal growth plate. The present report summarizes information gained by using a specific interosseal transplantation method. These findings lead to the conclusion that all the structures examined, i.e. the proximal epiphyseal cartilage of the tibia, the cartilage of the costochondral junction of the ribs, the basicranial synchondroses, the medial cartilage of the clavicle and the mandibular condyle, have the capacity to separate adjoining skeletal structures. The changes induced by the transplanted structures in the recipient area vary, however, suggesting a hierarchial arrangement of cartilages with regard to their tissue-separating capacity. It is suggested that the tissue-separating capacity is a basic phenomenon in the function of growth, not only of primary growth cartilages, but of secondary cartilages as well.

A histological analysis was performed on two secondary cartilages, the mandibular condyle and the medial end of clavicle, in transgenic mice harboring two different types of mutations in the cartilage-specific type II collagen gene. Considerable differences were observed in the maturation zone of the chondrocytes and the hypertrophic cells of the growth regions of the two secondary cartilages examined between the transgenic mice and their transgene-negative littermates, which served as controls. Looseness of the perichondrium/periosteum was a distinct feature seen in both mutations. However, phenotypic consequences of the mutations in secondary cartilages were less severe than those in primary cartilages. We propose that the differences between primary and secondary cartilages are due to differences in their origin, mode of growth, architecture and behavior under extrinsic factors.

Basicranial synchondroses are remnants of the fetal chondrocranium and thus represent primary cartilage, whereas the chondral part of the mandibular condyle, for example, develops unattached to the chondrocranium, as secondary cartilage. The two cartilage groups show differences in structure and cell proliferation pattern, and yet both are endowed with tissue-separating qualities.

The purpose of this investigation was to examine the interrelation in growth and morphogenesis between the maxilla and the mandible. Asymmetrical growth was induced in the maxilla of 10-day-old LE/T rats by means of unilateral artificial synostosis of the frontonasal and frontopremaxillary sutures. Untreated rats were used as controls. Biometric and microscopic observations were made at the ages of 30, 50, and 100 days. The arrest of sutural growth was followed by reduced sagittal growth of the maxilla, significantly more so on the treated side. Its anterior part became bent towards the treated side and rotated around the sagittal axis. In response to the primary alteration in maxillary shape, the mandible adapted by developing a secondary asymmetry in that it was shorter on the treated side than on the contralateral side throughout the experiment and shorter on the untreated side than in the untreated controls at 30 days. When the distances were adjusted for body weight, the mandibular length on the untreated side appeared to be virtually unaffected by the experimental procedure or even exceeded the control value at 50 days. The mandibular ramus was higher on the treated side than on the contralateral side at 30 days, and became bilaterally higher than in the untreated controls with increasing age. The results imply that the growth in length of the mandible follows that of the maxilla to some extent and are indicative of a restraining effect of the shortened maxilla on mandibular growth. The existence of a mechanism responsible for keeping the height of the ramus the same on both sides is suggested.

The cranial vault is composed of several flat membranous bones whose growth is mainly a result of the activity in the interposing sutures. The reactions of the calvarium and cranial base to provoke stimuli of the sutures differ depending on their developmental stage. In this report the effects of pressure, exerted extracranially by means of mechanical forces or intracranially by means of hydrodynamic fluctuations, are described.