Early childhood caries in relation to mode of delivery, preterm birth, tooth brushing habits, and signs of the metabolic syndrome

Sammanfattning: Background: Early childhood caries (ECC) is defined as the presence of one or more decayed (non-cavitated or cavitated lesions), missing (due to caries), or filled surfaces in any primary tooth of a child under 6 years of age. ECC is highly prevalent in the world and largely untreated in children under the age of 3 years; it shares common risk factors with other non-communicable diseases such as cardiovascular disease, diabetes, and obesity. ECC can impair quality of life by causing difficulties in sleeping, eating, and attending school due to loss of tooth substance with consequent acute and chronic pain. Even though several risk factors associated with ECC are known, it is difficult to predict the condition. Variables that have been used when trying to predict ECC include oral habits, dietary habits, and socioeconomic status. It is known that children born vaginally have a gut microflora that differs from children delivered by cesarean section (C-section). Recently, the oral microbiota has also been explored in relation to mode of delivery. Aim: The aim of this thesis was to study whether mode of delivery affects selected oral bacteria during the first 6 months of life and to explore whether mode of delivery, early oral habits, family characteristics, perinatal factors, and nutritional and nursing habits during the first 2 years of life, are associated with ECC at 5 years of age. A further aim was to explore whether there is a correlation between ECC and metabolic risk factors according to IDEFICS monitoring levels for the metabolic syndrome. Methods: In paper I, 149 infants, delivered either vaginally or by C-section, were followed prospectively from birth to 6 months of age. Saliva samples were collected at 0, 1, 3, and 6 months of age. At 6 months a saliva sample was also taken from the mother of the child. The parents answered questionnaires on socioeconomic factors, feeding habits, prescribed antibiotics, and oral habits at baseline and at every sampling occasion. The samples were analyzed with 13 pre-determined bacterial probes using checkerboard DNA-DNA hybridization technique. In papers II–IV, 395 infants were invited to a prospective medical study at the pediatric clinic, Halland Hospital Halmstad, with a focus on growth and overweight prevention. This group was then merged with 156 infants delivered by C-section into a group that was followed for endocrine research purposes. Of the invited children, 336 were examined at the dental clinic at 2 years of age, 302 at three years of age, and 292 at 5 years of age. Two calibrated examiners at the dental clinic then assessed caries lesions (cavitated and non-cavitated) on tooth and surface levels. Background data on the mothers and perinatal data on the infants were extracted from hospital records. The parents of the child also answered sets of questionnaires about oral and feeding habits. Of the 292 children examined at the dental clinic at 5 years of age, 208 were than re-examined at the pediatric clinic at the age of 6.5 (paper IV). Results: In paper I, the children delivered vaginally had a greater diversity of the selected oral bacteria strains, compared to children delivered by C-section. In paper II, children delivered by C-section had a significantly elevated risk of having caries at 5 years of age. The risk of ECC at 5 years of age was also increased for children born preterm. The relative risk for ECC at 5 years of age (paper III) was significantly increased for tooth brushing less than twice daily at 2 as well as 3 years of age. In paper IV, the perinatal factors preterm birth or being born small for gestational age raised the risk of ECC at 5 years of age. Preschool children with ECC had higher fasting glucose levels, but no other signs of the metabolic syndrome. Conclusion: The findings of this thesis stress the need for a good cooperation between dental and pediatric professionals, even for infants. The health personnel should instruct and encourage parents to brush their child’s teeth twice daily, as well as give appropriate advice concerning food habits. The association between fasting blood glucose and caries, the relationship between perinatal factors and caries, and the influence and evolvement of the oral microbiome are all issues to be further explored in this cohort and in future studies.