Associated dental anomalies: The orthodontist decoding the genetics which regulates the dental development disturbances -------------------------------- orthotropics.co.uk -------------------------------- The transition from the deciduous to the permanent dentition is a complex biological process rich in details and represents one of the natures expressions of perfection. However, as all natural processes, the dental development can show imperfections and during the mixed dentition, the professional can face some irregularities: The dental anomalies. Dental anomalies may be expressed with different degrees of severity. From the mildest to the most severe manifestation, represented respectively by the developmental delay and by the tooth agenesis, there is a myriad of expressions, including microdontia, changes in dental morphology and ectopias. This article is related to the natures errors applied to dental development and discusses the etiology of the dental anomalies, the details for an accurate diagnosis, as well as some therapeutic approaches to intercept them appropriately. The influence of genetic and environmental factors in the etiology of malocclusions represents a subject of great importance in Orthodontics. The higher the genetic contribution in the etiology of a dentofacial irregularity, the lesser the possibility of prevention and, generally, worse is the prognosis for orthodontic/orthopedic treatment.22 And the new directions of dental research are toward the knowledge of the human genotype.30 Several studies have suggested a genetic and hereditary background in the etiology of dental anomalies of number, size, position, as well as timing of development.2,4,13,14,15,17,18,20,23,24,25,30 Such evidences come from studies in families,17,18,30 monozygotic twins20 and from the frequent observation of associations of certain dental anomalies.2,4,13,14,15,23,24,25 When a particular irregularity shows an increased prevalence in families of affected patients compared to the frequencies expected for the general population, genetics has an important influence in the etiology of the problem. The mandibular prognathism in the imperial Austro-Hungarian family of the Hapsburgs represents the most classic example of a genetic characteristic of orthodontic interest, transmitted by successive generations.22 Many of the dental anomalies that will be discussed in this article showed an increased prevalence in the family of affected patients (Figs 1 to 7).17,18,30 Currently, molecular biology studies can isolate mutant genes in families, since several members express the same irregularity.30 Monozygotic twins share almost identical genetic codes. Therefore, genetically defined features are similarly expressed in both twins. A high correlation for a particular irregularity in pairs of monozygotic twins is an evidence that genetics is an important etiology of such abnormality. Unlikely, dizygotic twins which have different genotypes would show a lower correlation for the same irregularity. Previous studies in twins constitutes important evidences of the genetic etiology of some dental anomalies.20,22 Certain dental anomalies appear often associated in the same patient, more than expected by chance. This occurs because a same genetic defect can determine different manifestations or phenotypes, including agenesis, microdontia, ectopias and delayed tooth development.2,4,13,14,15,23,24,25 A simplistic explanation is that a defective or mutant gene can express differently in distinct permanent teeth. The association between the unilateral agenesis of the maxillary lateral incisor and the microdontia of its antimere, often observed in clinical routine, well illustrates this condition. In this case, the same genetic defect which determined the agenesis has an incomplete expression in the opposite side of the dental arch, causing microdontia. However, the associations between the dental anomalies are not restricted to this classic example. There are many more interactions between different dental anomalies, which are exposed along this article. The clinical implications are important because the early diagnosis of a given dental anomaly can alert the professional to the possible development of other associated dental anomalies in the same patient or family, permitting early diagnosis and timely orthodontic intervention. The aim of this article is to help the clinicians in recognizing the main genetic dental anomalies, discussing important features of diagnosis and early orthodontic treatment of these abnormalities. Additionally, it aims to promote a comprehension of the pattern of associated dental anomalies. scielo.br/scielo.php?pid=S2176-94512010000200017&script=sci_arttext&tlng=en -------------------------------- orthotropics.co.uk --------------------------------
Posted on: Sun, 16 Mar 2014 16:30:01 +0000
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