Teeth as pearls of wisdom.

The role of teeth as lifestyle indicators of the past and present, and as key elements of evolutionary and forensic studies is explored. The wisdom of entrenched information in the structure of enamel, dentine and the DNA of dental pulp cells is being extracted by new technologies.

Mirror-image dental fusion and discordance in monozygotic twins.

A pair of monozygotic twins had similar but not identical dental anomalies. One twin had fusion of deciduous mandibular lateral incisor and canine on the left, with normal dentition on the right; the co-twin had right mandibular incisor/canine fusion, with aplasia of the lateral incisor on the left. These findings are discussed in the context of the related phenomena of situs inversus, mirror-imaging in twins, and gradients of severity of anomalies in the four copies of the mandibular developmental dental field.

Microscopic study of holoprosencephalic facial anomalies in trisomy 13 fetuses.

The cerebral and facial anatomy of four trisomy 13 fetuses was studied in order to delineate the varying degrees of expression of severity of holoprosencephaly. Fetal heads were serially sectioned and analyzed microscopically in the horizontal plane. Examples of cyclopia, cebocephaly, and a proposed new category, premaxillary dysgenesis, were studied. The last category represents the least severe end of the facial spectrum of holoprosencephaly in this series. In this condition, there are deficiencies or clefts within the premaxilla, in contrast to the usual site of clefting between the maxilla and the premaxilla. There is asymmetry of the defects in the anterior midface of all four cases.

Computer graphic three-dimensional reconstruction of normal human embryo morphogenesis.

Three-dimensional computer graphic reconstructions of four human embryos at Carnegie stages 11 to 23 portray the relationships and dimensions of individual organ systems. This paper illustrates the cranial, neural, pharyngeal, gut, vascular and nephric architecture in these developing embryos. This technology can be applied to in situ hybridization and immunohistochemistry to map zones and times of developmental gene activity.

3D-reconstruction of craniofacial structures of a human anencephalic fetus. Case report.

It was the purpose of this study to investigate the craniofacial bones, cartilages and major blood vessels of a human anencephalic fetus and to describe the malformations of these structures accompanying this developmental disruption. The head of a 16 week old human fetus with anencephaly was serially sectioned and the craniofacial bones, cartilages and major blood vessels were traced and reconstructed by 3D-computer technology. The sphenoidal, temporal and occipital bones showed severe malformations, whereas the bones of the facial cranium were normally developed. Both internal carotid arteries ended within the cerebro-vascular area with no further branches. The vertebral arteries also ended within the cerebro-vascular area. No arterial circle of Willis was developed. The notochord terminated normally in the sphenoid body. The observations indicate that the possible reason for this malformation was non-closure of the anterior neuropore of the neural tube. The normal termination of the notochord suggests that it had no influence on the pathogenesis of this malformation. The malformations of the temporal and occipital bones are contradictory to the hypothesis of Marin-Padilla (1991) that anencephaly is caused by a maldevelopment of the sphenoidal bone.

Anatomy of the circle of Willis in three cases of human fetal synophthalmic holoprosencephaly.

In three human fetuses with synophthalmic holoprosencephaly (8, 14, 23 weeks post conceptionem) the circle of Willis was studied using serial histological sections and computer aided three dimensional reconstruction methods. This structure was abnormal in all cases. In two cases the anterior communicating arteries were absent. In all cases the anterior cerebral arteries could not be found. One case showed an incomplete circle with no posterior communicating artery. The results indicate that the malformation of the circle of Willis reflects the malformation of the brain.

Cranio-facial skeletal development in three human synophthalmic holoprosencephalic fetuses.

In three human fetuses with synophthalmic holoprosencephaly (8, 14, 23 wks. p.c.) and two normal human fetuses (9 and 13 wks. p.c.) the anatomy of the cranial base, facial cranium and their relation to the notochord was studied using serial histological sections and computer aided three-dimensional reconstruction methods. Mesethmoidal cartilage differentiation was variably deficient in all three holoprosencephalic cases. The premaxillary bones were rudimentary with missing tooth buds. The development of the sphenoid bone was defective in two of the holoprosencephalic cases (8, 14 wks. p.c.). The notochord terminated normally within the sphenoid body in all investigated cases. Our results indicate that in holoprosencephaly there is a general defect in the midline cranial cartilage differentiation rostral to the notochord.

The aetiopathogenesis of craniofacial anomalies.

Craniofacial embryogenesis with emphasis on the mechanisms of morphogenesis as a basis for understanding developmental anomalies is reviewed. A classification of maldevelopment into malformation, deformation and disruption is illustrated by examples. A brief review of the clinical consequences of craniofacial anomalies and possible therapeutic modalities is undertaken.

Pathogenesis and morphogenesis of craniofacial developmental anomalies.

A condensed review of the morphogenetic mechanisms of facial fabrication, providing insights into developmental anomalies of clinical concern. Genetics, epigenetics and regulation of molecular, cellular, tissue and organ formation are being elucidated in normal and dysmorphological patterns. The pathogenesis of craniosynostosis is related to fibroblast growth factor expression. Analysis of a 28-month-old-child's dysmorphic synostotic skull explores possible mechanisms of malformation and deformation.

Fabricating a face: the essence of embryology in the dental curriculum.

The current explosive growth in developmental biology, fuelled by the almost completed sequencing of the human genome, is bound to have a profound impact upon the practice of medicine and dentistry in the twenty-first century. No other discipline more accurately reflects this impact than embryology, which combines the basic and clinical sciences of genetics, ontogeny, phylogeny, teratology, and syndromology into the essence of modern medical and dental practice. The advent of in vitro fertilization, chorionic villus sampling, amniocentesis, prenatal ultrasonography, intrauterine surgery, and stem cell therapy has vaulted the previously esoteric subject of embryology into clinical consciousness. All these aforementioned procedures require an intimate knowledge of the different stages of development. The alphabet soup of acronyms that now peppers papers proclaiming the genetics and characteristics of various growth factors and cytokines (e.g., FGF, TGFalpha) are all based upon an understanding of the developmental mechanisms occurring in the embryo and subsequently in wound healing and oncology. Congenital abnormalities ranging from lethal syndromes to dental malocclusions cannot be diagnosed, treated, cured, or prognosticated upon without a sound conceptualization of embryology. Computer technology has revolutionized the understanding and teaching of embryology by portraying developmental phenomena as three-dimensional model images in sequential depictions of changes proceeding in the fourth dimension of time. Embryology must now form the essential core of the basic sciences in medical and dental curricula. Future dental practice will become rooted in the genetics and morphogenesis of facial fabrication.

The genesis of craniofacial biology as a health science discipline.

The craniofacial complex encapsulates the brain and contains the organs for key functions of the body, including sight, hearing and balance, smell, taste, respiration and mastication. All these systems are intimately integrated within the head. The combination of these diverse systems into a new field was dictated by the dental profession's desire for a research branch of basic science devoted and attuned to its specific needs. The traditional subjects of genetics, embryology, anatomy, physiology, biochemistry, dental materials, odontology, molecular biology and palaeoanthropology pertaining to dentistry have been drawn together by many newly emerging technologies. These new technologies include gene sequencing, CAT scanning, MRI imaging, laser scanning, image analysis, ultrasonography, spectroscopy and visualosonics. A vibrant unitary discipline of investigation, craniofacial biology, has emerged that builds on the original concept of 'oral biology' that began in the 1960s. This paper reviews some of the developments that have led to the genesis of craniofacial biology as a fully-fledged health science discipline of significance in the advancement of clinical dental practice. Some of the key figures and milestones in craniofacial biology are identified.

The role of teeth in human evolution.

A review of recent insights into palaeodiets provided by new dating techniques, spectroscopy and attritional wear of enamel in ancient and recent human fossils. Fossilised dental plaque reveals changing dietary content and varying oral microbiota between Neolithic and Industrial era populations. DNA analysis of ancient dental pulpal tissue provides evidence of contemporary hereditary relationships and gene flow of human populations.