The Effect of Premature Birth on The Primary Dentition 1217 – 1812 : NISS

Aims: The aims of the present study were to determine if primary teeth eruption and the presence of enamel defect are affected by low birth weight and prematurely of birth. Materials and Methods: The total subjects of (420) child aged 4 – 24 months were included in this study, consisted of (210) prematurely born (<37 gestational weeks and birth weight < 2.500 Kg) children and 210 control children (≥40 gestational weeks and birth weight ≥ 2.500 Kg). Those children selected randomly the children who came to the primary health care centers with their mother for vaccination and the mothers asked to participate in this study. For each child, clinical exanimation was performed in dental chair. The criterion used for enamel defect to include various enamel hypoplasias, deficiency of enamel in the form of pits, grooves or other quantitative surface loss and enamel hypocalcifications and opacities. Data were analyzed using numbers, percentages, means and standard deviations. T – test, Z – test Chi – square (X) test were used for determining the differences concerning different variables. The differences were considered significant at p≤ 0.05. Results: There was no significant difference (p>0.05) between different genders numbers among in each age group for the preterm and control children. The results showed significantly (p<0.05) delayed eruption of the primary teeth in the prematurely born children as compared with the control children in all age groups except in 4 – 6 months age group, also there was significantly higher percentages of enamel defect present in preterm children, than in control children in all age groups except in 4 – 6 months age group. Conclusions: The findings indicated that the eruption of deciduous teeth was delayed and the percentage of enamel defect was significantly increased in prematurely born children.


INTRODUCTION
Prematurely born infants have a short prenatal development period and predisposed to various neonatal complications and developmental problems.According to the World Health Organization definition, a delivery is preterm when it occurs before the 37 th completed week of pregnancy and the prematurity had been defined by birth weight under 2500 grams (1) .
Many aetiological factors for premature birth exist, many of which are associated with the maternal and foetal diseases, but often the cause remains obscure.There are several systemic derangements that can interfere with the developing teeth, especially teeth that are at a critical stage of development at the time of the insult and not calcified or dimensionally complete at the time of birth (2) .
Various theories have been put forward to explain the tooth eruption process, which is still largely unknown.Root growth, dentine formation, proliferation of the dental pulp, the periodontal ligament, the connection between the enamel organ and the oral epithelium and the role of the dental follicle, including its innervation and blood supply, are considered to be essential (3,4) .

Studies of preterm children have
shown that the developing dentition may be affected at a time of an exceptionally early delivery.The prevalence of enamel defects in the deciduous (5,6) and permanent dentition (7) has been reported to be higher in premature infants.
Different studies found that hypomineralization of the teeth has been thought to be associated with the systemic derangements of preterm birth such as nutritional problems (8) , neonatal infections (9) and metabolic disorders (10) .While dental defects arising from local causes tend to affect only single teeth or groups of teeth.Local traumatic factors associated with endotracheal intubation and laryngoscopy during a critical period of tooth amelogenesis may also contribute to dental defects in the deciduous dentition.A close correlation exists between birth weight, dental defects and the intubation period, the prevalence of dental defects generally increasing with a longer period of orotracheal intubation (7,11,12) .
The purposes of the present study were to determine if the primary teeth eruption and the presence of enamel defect are affected by low birth weight and prematurely of birth.

MATERIALS AND METHODS
The total subjects of (420) child aged 4 -24 months were included in this study, consisted of (210) prematurely born (< 37 gestational weeks and birth weight < 2.500 Kg) children and (210) control children (≥ 40 gestational weeks and birth weight ≥ 2.500 Kg), those children selected randomly from children who came to the primary health care centers with their mothers for vaccination and the mothers were asked to participate in this study.None of the mothers refused to answer the questionnaire form which was applied by face -to -face interview technique.The questions clarify to the gestation period and birth weight of the child.
For each child, clinical exanimation was performed on dental chair.In each clinical examination, gauze pads were used to clean and dry the tooth surface.The examination was conducted with a visual and non tactile technique; this me-thod is known as "lift the lip" technique.No dental probing was performed on these children and the mouth mirror was used for indirect vision in lingual areas of the teeth (13) .All cases of enamel defects with family history were excluded from this study.
The criterion used for the enamel defect include various enamel hypoplasias, deficiency of enamel in the form of pits, grooves or other quantitative surface loss and enamel hypocalcifications and opacities, i.e. qualitative changes in the translucency of the enamel without loss of the enamel surface in the form of stained or white opaque flecks (14) .
Data were analyzed using numbers, percentages, means and standard deviations.T -test was used to determine the differences in the means of teeth present per child in preterm and control groups.Z -test between two proportions was used for determining the differences in the enamel defect present in preterm and control groups for each group.Chi -square (X2) test was used for determining the gender differences for each group.The differences were considered significant at p ≤ 0.05.

RESULTS
The total subjects of (420) child aged 4 -24 months were included in this study, consisted of (210) prematurely born children (103 males and 107 females) and (210) control children (102 males and 108 females).The number of children (males, females and total sample), were distributed according to the age groups are shown in Table (1).There was no significant difference (p>0.05) between different genders numbers among in each age group for the preterm and control children.
The number of teeth present in addition to the means and standard deviations of teeth present per child in each age group of preterm and control children were illustrated in Table (2).The results showed significantly (p<0.05)delayed eruption of the primary teeth in the prematurely born children as compared with the control children in all age groups except in 4 -6 months age group.

DISCUSSION
Both genetic and environmental factors acting during odontogenesis are associated with the tooth eruption process.The environment, prenatal and maternal factors, social factors, nutrition, socioeconomic status, climate may influence the timing of tooth eruption (15 -17) , although the eruption of teeth includes local controlling factors such as crowding and premature or delayed loss of deciduous teeth.The chronology of the eruption of the deciduous teeth is thought to be more extensively genetically determined than in the case of the permanent teeth (18) .
In the present study significantly delayed eruption of the primary teeth in the prematurely born children as compared with the control children in most age groups, these results were in agreement with other studies (18 -20) , who found an association between birthweight and tooth eruption and has been suggested by children who are heavier at birth experiencing to have teeth eruption significantly earlier.Meanwhile, other found that the degree of prematurity significantly affects timing of primary tooth eruption (21) .
The results of the present study showed significantly higher percentages of enamel defect (hypoplasia and hypocalcification) present in pretmature children than in control children in most age groups.These results were in agreement with the findings of other studies which some of them hypothesized that metabolic derangements in the prenatal and postnatal periods affect the mineralization of teeth (11 -13) , while other studies discussed the possible pathogenesis of the dental defects associated with the premature birth may be related to the direct damage to the ameloblasts as in maternal infections (rubella, cytomegalovirus) (22) , or complications of the pregnancy that reduce the maternal serum calcium concentrations like diabetes, hyperparathyroidism and maternal calcium and vitamin D deficiencies, while various complications associated with prematurity predispose these infants to severe metabolic derangements, and these conditions may result in disturbed enamel formation.The problem of deranged calcium metabolism occurs to varying degrees in most premature infants, because two-thirds of the individual's stores of calcium and phosphorus accumulate during the last trimester of pregnancy and preterm infants miss much of this mineral accretion (23) .

CONCLUSIONS
The findings indicate that the eruption of deciduous teeth was significantly delayed and the percentage of enamel defect was also significantly increased in prematurely born children.

Table ( 1
): Numbers of children in each age group distributed according to the birth weight and gender of preterm and control groups.