The ancestor of recent vertebrate teeth was a tooth-like structure on the outer body surface of jawless fishes. Over the course of 500,000,000 years of evolution, many of those structures migrated into the mouth cavity. In addition, the total number of teeth per dentition generally decreased and teeth morphological complexity increased. Teeth form mainly on the jaws within the mouth cavity through mutual, delicate interactions between dental epithelium and oral ectomesenchyme. These interactions involve spatially restricted expression of several, teeth-related genes and the secretion of various transcription and signaling factors. Congenital disturbances in tooth formation, acquired dental diseases and odontogenic tumors affect millions of people and rank human oral pathology as the second most frequent clinical problem. On the basis of substantial experimental evidence and advances in bioengineering, many scientists strongly believe that a deep knowledge of the evolutionary relationships and the cellular and molecular mechanisms regulating the morphogenesis of a given tooth in its natural position, in vivo, will be useful in the near future to prevent and treat teeth pathologies and malformations and for in vitro and in vivo teeth tissue regeneration.
This review presents a brief account of the most significant biological effects and clinical applications of botulinum neurotoxins, in a way comprehensive even for casual readers who are not familiar with the subject. The most toxic known substances in botulinum neurotoxins are polypeptides naturally synthesized by bacteria of the genus Clostridium. These polypeptides inhibit acetylcholine release at neuromuscular junctions, thus causing muscle paralysis involving both somatic and autonomic innervation. There is substantial evidence that this muscle-paralyzing feature of botulinum neurotoxins is useful for their beneficial influence on more than 50 pathological conditions such as spastic paralysis, cerebral palsy, focal dystonia, essential tremor, headache, incontinence and a variety of cosmetic interventions. Injection of adequate quantities of botulinum toxins in spastic muscles is considered as a highly hopeful procedure for the treatment of people who suffer from dystonia, cerebral palsy or have experienced a stroke. So far, numerous and reliable studies have established the safety and efficacy of botulinum neurotoxins and advocate wider clinical therapeutic and cosmetic applications.
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