Postnatal development of the cat palate

Comparative histology of some craniofacial sutures and skull-base synchondroses in non-avian dinosaurs and their extant phylogenetic bracket

Sutures and synchondroses, the fibrous and cartilaginous articulations found in the skulls of vertebrates, have been studied for many biological applications at the morphological scale. However, little is known about these articulations at the microscopic scale in non-mammalian vertebrates, including extant archosaurs (birds and crocodilians). The major goals of this paper were to: (i) document the microstructure of some sutures and synchondroses through ontogeny in archosaurs; (ii) compare these microstructures with previously published sutural histology (i.e. that of mammals); and (iii) document how these articulations with different morphological degrees of closure (open or obliterated) appear histologically. This was performed with histological analyses of skulls of emus, American alligators, a fossil crocodilian and ornithischian dinosaurs (hadrosaurids, pachycephalosaurids and ceratopsids). Emus and mammals possess a sutural periosteum until sutural fusion, but it disappears rapidly during ontogeny in American alligators. This study identified seven types of sutural mineralized tissues in extant and extinct archosaurs and grouped them into four categories: periosteal tissues; acellular tissues; fibrous tissues; and intratendinous tissues. Due to the presence of a periosteum in their sutures, emus and mammals possess periosteal tissues at their sutural borders. The mineralized sutural tissues of crocodilians and ornithischian dinosaurs are more variable and can also develop via a form of necrosis for acellular tissues and metaplasia for fibrous and intratendinous tissues. It was hypothesized that non-avian dinosaurs, like the American alligator, lacked a sutural periosteum and that their primary mode of ossification involved the direct mineralization of craniofacial sutures (instead of intramembranous ossification found in mammals and birds). However, we keep in mind that a bird-like sutural microstructure might have arisen within non-avian saurichians. While synchondroseal histology is relatively similar in archosaurs and mammals, the microstructural differences between the sutures of these two clades are undeniable. Moreover, the current results suggest that the degree of sutural closure can only accurately be known via microstructural analyses. This study sheds light on the microstructure and growth of archosaurian sutures and synchondroses, and reveals a unique, undocumented histological diversity in non-avian dinosaur skulls.

Sutural Distraction Osteogenesis (SDO) Versus Osteotomy Distraction Osteogenesis (ODO) for Midfacial Advancement: A New Technique and Primary Clinical Report

A new technique of osteotomy distraction osteogenesis (ODO) and sutural distraction osteogenesis (SDO) by the use of bone-borne traction hooks is presented. The technique of osteotomy plus distraction osteogenesis is suitable for adult patients. The technique of sutural distraction osteogenesis is suitable for young patients, ages 6 through 12 years. The distraction system consists of a face-bow, orthodontic elastics, and bone-borne traction hooks. The bone-borne traction hooks are made of titanium, with two traction hooks running laterally or downwardly. When a Le Fort III osteotomy is needed, bone-borne traction hooks are inserted through the nostrils into a bone hole drilled at the lateral-inferior pyriform aperture. When no osteotomy is needed, only the bone-borne traction hooks are placed. Heavy elastics were used in the technique of osteotomy distraction osteogenesis for Le Fort III osteotomy adult patients, whereas light forces and thus light elastics were used for younger patients. Three adult patients and four children were treated by osteotomy distraction and sutural distraction, respectively. All seven patients with midfacial hypoplasia established a harmonious facial profile and normal occlusal relationships. Radiographic examination showed balanced advancement of the midfacial skeleton. It is suggested that the treatment of midfacial hypoplasia in children by the technique of sutural distraction osteogenesis is to be preferred because of its simplicity and relative noninvasiveness. Thus, the authors suggest that midfacial hypoplasia should be treated at a younger age by this technique, potentially eliminating the need for a Le Fort III osteotomy at an older age.

Differential growth among components of the palate in rhesus monkeys (Macaca mulatta)

To understand the etiology of maxillary hypoplasia better, which is common in individuals with cleft palate and other craniofacial anomalies, the relative growth and contribution of the maxillary and palatine segments to enlargement of the hard palate was examined in rhesus monkeys. The purpose of the study was to identify and evaluate sites of differential growth of the palatine and maxillary segments as they contribute to the development of the midface and facial prognathism. One hundred and eight male and 107 female skulls ranging from 1.0 to 7.0 years of age were examined. Measurements of the maxillary and palatine lengths, palatal width, midface depth, canine length, and molar surface areas in the ontogenetic sample were collected. Univariate and bivariate statistics were used to describe dimensional changes and evaluate region-specific sex differences. The relative growth of palatal dimensions was evaluated using allometric analysis methods. Significant sex differences were observed (t-test, p < or = .05) for all palatal dimensions by 4 years of age. However, proportions of the maxillary and palatine segments to overall palate length appeared to be similar throughout growth for both sexes. The results suggest that sutures of the midface, in particular the transverse palatine suture, may be important in the bony development of the palate during growth. These sutures may contribute to the overall modulation of palatal development.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of the intermaxillary suture cartilage to alterations in masticatory function

Like the condylar cartilage of the mandible, the cartilage at the intermaxillary suture in the rat is secondary in origin and persists well into adulthood. While the condylar cartilage is generally considered to be responsive to changes in its local biomechanical environment, little is known of the response of the intermaxillary suture cartilage to similar stimuli. In order to study the effect of changes in occlusal loads on intermaxillary suture cartilage metabolism, male weanling Sprague-Dawley rats were divided into four groups: soft diet (to discourage molar mastication), incisor clipped (to discourage incision), incisor clipped/soft diet (both treatments), and control (untreated). At 39 days of age, the intermaxillary suture opposite the first molars was removed and compared to control tissue by using histological, histochemical, and biochemical analyses. Alcian blue-stained coronal sections demonstrated moderate decreases in staining intensity and decreased chondrocyte hypertrophy in the soft diet and incisor-clipped groups. However, sutures in the incisor-clipped/soft diet group showed a considerably reduced extent of cartilage and greatly diminished cartilage hypertrophy. [35S]-sulfate incorporation (dpm/micrograms DNA) into acid-insoluble proteoglycans was significantly reduced (P less than or equal to .01) in all three experimental groups compared to controls. [35S] incorporation was further reduced in the incisor-clipped/soft diet group relative to both of the other experimental groups. Staining for alkaline phosphatase activity showed decreased intensity in the experimental groups and was almost absent in the incisor-clipped/soft diet group. These data demonstrate the plasticity of the intermaxillary suture cartilage and provide circumstantial evidence that the observed changes in cartilage morphology and metabolism may be attributable to alterations in the local biomechanical environment of the suture.

Concomitant transverse growth of the maxillary base and dental arch in experimental submucous mid-palatal clefts. A biometrical study in the domestic cat

To obtain information on correlated growth of the maxillary base and dental arch in submucous mid-palatal clefts, such clefts were surgically created in 18 domestic cats. The growth ratios of the dento-maxillary complex were then compared with corresponding parameters in 18 unoperated controls. When fully grown, the operated cats had developed a significant hypoplasia of the maxillary base. Also the upper dental arch in these cats showed a slight reduction in width, but significantly so only in the posterior region. The results obtained seemed to demonstrate a mutual dependence in growth of these two parts of the dento-maxillary complex, but to a limited degree. Whereas the maxillary base was significantly influenced by the altered morphology in the mid-palatal area, the dental arch growth and its final dimension seemed to be more responsive to compensatory mechanisms.

The postnatal development of the palatomaxillary region studied on human autopsy material

Greater understanding of the postnatal region of the maxilla is necessary if the normal growth of the maxillary complex, as well as its reaction to orthopedic forces, is to be comprehended. The area in question was studied at various stages of development, both on dry skulls and on autopsy material. The skull material demonstrated an increasing approximation between the palatal bone and the adjacent bones, the maxilla and pterygoid process. Disarticulation of the bones studied was possible only on skulls representing the infantile and earliest adolescent periods. Attempted disarticulation in the later juvenile and early adolescent periods was always accompanied by fracture of the heavily interdigitated osseous surfaces. The complexity of the articulating surfaces was studied further and, by means of quantitation of the bony surfaces, an "index of complexity" was calculated. The findings of the present study that the palatal bone acts as a "buffer" between two areas of differing intrinsic growth pattern and that the remodeling processes in the area seem to reflect different functional demands to the bony pharynx and the maxillary complex. The rigidity of the area as a result of the observed sutural complexity indicates that the center of rotation for the observed spatial changes in the maxillary complex as a result of orthopedic forces could be localized in the palatomaxillary region.