Is premature birth an orthodontic risk factor? A controlled epidemiological clinical study

Summary

Introduction

Although a “catch-up” growth occurs in early childhood, respiratory system immaturity and the use of oral and naso-gastric probes for prematurely born children are responsible for palatal and cranio-facial alterations.

Objective

To assess whether prematurity is a risk factor in orthodontics in terms of malocclusions, dysmorphoses and orthodontic treatment need compared to term-born children. To compare the differences of risk factors among these preterm birth subtypes according the severity.

Materials and methods

Distributed questionnaires within an orthodontic practice and in the Department of Odontology, Lyon Hospital, France. The evaluation criteria were calculated from the casts, photographs and radiographies carried out during the initial assessment. A statistical intergroup comparison was performed.

Results

Of the 537 questionnaires obtained, 47 preterm patients and 150 term-born patients were included in our study. Preterm infants had significantly more bilateral crossed-occlusions than patients in the term group (P = 0.003). In addition, very preterm and extremely preterm children had significantly more impacted tooth (P = 0.049) and a higher Index of Orthodontic Treatment Need (IOTN grade 5, P = 0.003) compared with term children.

Conclusion

Very preterm and extremely preterm births (occurring more than 8 weeks before the term) represent a risk factor in orthodontics and, therefore, a public health problem.

Résumé

Introduction

Bien qu’une croissance de « rattrapage » ait lieu dans la petite enfance, l’immaturité du système respiratoire et l’utilisation de sondes orales et nasogastriques chez les enfants nés prématurément seraient responsables d’altérations de la morphologie craniofaciale et palatine.

Objectifs

Évaluer si la prématurité constitue un facteur de risque en orthodontie en termes de malocclusions, dysmorphies et indications orthodontiques par rapport aux non-prématurés. Comparer les différences de facteurs de risque selon les différents stades de sévérité de la prématurité.

Matériels et méthodes

Des questionnaires ont été distribués dans un cabinet d’orthodontie et dans le service de consultations et traitements dentaires de Lyon, France. Les critères d’évaluation ont été calculés à partir des moulages, photographies et radiographies effectués lors du bilan initial. Une comparaison statistique intergroupe a été effectuée.

Résultats

Sur les 537 questionnaires obtenus, 47 patients nés prématurés et 150 patients nés à terme ont été inclus dans notre étude. Les prématurés présentent significativement plus d’occlusions croisées bilatérales que les patients du groupe non prématuré (p = 0,003). De plus, les grands et très grands prématurés ont significativement plus de dents incluses (p = 0,049) et donc plus d’indications orthodontiques (IOTN grade 5 : Index of Orthodontic Treatment Need, p = 0,003) par rapport aux non-prématurés.

Conclusion

La grande et très grande prématurité (caractérisée par une naissance survenant plus de 8 semaines avant le terme) représente un facteur de risque en orthodontie et, de ce fait, un problème de santé publique.

Introduction

According to the World Health Organization (WHO), prematurity is defined by a birth occurring before 37 completed weeks of gestation (i.e. more than 4 weeks before the term). Three subgroups can be distinguished [1]: moderately preterm birth (33 to 36^+6 days weeks); very preterm birth (28 to 32^+6 days weeks); extremely preterm birth (< 28 weeks). Prematurity affects around 15 million children a year (11% of live births), 60,000 of them in France, and its incidence has been increasing since the 1990s according to the WHO. More than 60% of premature births occur in Africa and South Asia, but this is a global problem. In Europe, the 2004 EuroPeristat data [2] shows a preterm birth rate between 5 and 11% of live births. France is rather in the low range with a prematurity rate of 6.3% (6.4 to 7.0% according to the AUDIPOG sentinel network [Association des Utilisateurs de Dossiers Informatisés en Périnatologie, Obstétrique et Gynécologie]), [3] in 2007. In the case of very preterm births (22 to 32 weeks^+6 days), the MOSAIC cohort [4] and EuroPeristat (European perinatal Heath report statistics) [2] reported an overall rate of 13.2/1000 births, representing 14.3% of total premature births. Less than 5% of preterm infants have a gestational age below 28 weeks (extremely preterm birth) [1]. The incidence of prematurity in France has been constantly increasing. Multiple factors are involved: increased number of premature triggered births, increased maternal age, increased use of medically assisted procreation and multiple pregnancies resulting from these techniques. Besides, the improvement of neonatal resuscitation techniques allows a greater survival of new-borns who are increasingly immature.

Characterized by a global immaturity, a preterm infant's body is not able to function and to defend itself. First, the immature lungs of the preterm infant sometimes require artificial oxygen supply (oxygen therapy) and assisted ventilation. Although it's vital, this oxygenation aid is not without risk, especially for infants born under 32 weeks. They are prone to develop chronic respiratory failure (bronchopulmonary dysplasia) when the oxygen requirement persists beyond 28 days of life. This respiratory pathology aggravates the eating disorders linked to difficulties in the coordination of sucking-swallowing-breathing and more generally to digestive immaturity. In addition, as the maturation of sucking occurs only at the end of the normal term of gestation, the baby born before 34 weeks of age is unable to feed on his own [5]. Feeding through an oral or nasogastric tube will then be necessary. This type of nutritional assistance leads to harmful consequences at several levels, irritation of the nose and/or the pharynx, or a disturbance of the sucking-swallowing reflex. It is also important to note the morphogenetic role of foetal sucking and swallowing on the development of the oral cavity [6].

Justification of the study: As other tissues and organs of the body, oral structures are affected by premature birth [7]. Premature birth and its adaptations have an effect on occlusal development, which may be associated with an increased orthodontic treatment need [8]. Moreover, palate morphology alterations, related to the use of probes, have been described [9], [10], [11]. While early catch-up growth periods seem to mitigate these defects [12], the head circumference is smaller at birth and remains lower with no catch-up growth until the age of 11 [13]. The craniofacial morphology of young patients (8–10 years) born extremely premature is characterized by a shorter anterior cranial base, a less convex profile and a shorter maxillary length [14].

The idea that prematurity is a risk factor in orthodontics is currently not yet proven. Indeed, the question of the impact of prematurity on orthodontic malocclusions and the orthodontic treatment need in these patients remains seldom studied. Only a few Scandinavian studies [7], [14], [15], [16], [17], [18], [19] have analysed the prevalence of malocclusions in premature subjects compared to term-born children, but the conclusions are variable and even contradictory as regards to the malocclusions most frequently observed. Because of contradictory results and a lack of longitudinal studies, scientific evidence is too weak to link prematurity with malocclusions [7]: low number of recent studies related to this topic, lack of sufficient scientific evidence, contradictions of the obtained results, the variability of the methodologies and old studies, can no longer be used as a reference because the care protocols evolve, without counting that they may vary from one country to another. Moreover, no French study has been carried out for now on this subject. The studies found are all Scandinavian (Swedish and Finnish), but there are significant differences between countries in terms of malocclusion prevalence and orthodontic treatment need [20]. The large variability according to the countries in the preterm infants care and the difference of preterm birth proportion in the populations prevents us from extrapolating these results on the French population.

The main objective of this study is to assess whether prematurity is a risk factor in orthodontics, in terms of malocclusions, dysmorphoses and treatment need.

The secondary objective is to compare, according to these same criteria, the different stages of prematurity (extremely/very preterm birth and moderately premature).