Timing of the first deciduous tooth eruption (incisors) and its related factors in infants: a longitudinal study using Cox’s proportional hazards model

The present study was performed to investigate the timing of the first deciduous tooth eruption in infants and its relationship with environmental and nutritional factors such as weight, height, and head circumstance at birth, type of childbirth, duration of breastfeeding, and initiation time of semi-solid food.

This study is a prospective study conducted on newborn infants during 2008-2009 years. For these infants, variables such as parental education level, parental ages, type of childbirth, infant's breastfeeding duration, initiation time of semi-solid food, weight, height, and head circumstance at birth, and then the researchers entered the data into the statistical software STATA 12 and analyzed the data by COX regression model.

The mean age of the infants receiving semi-solid food was 0.033 ± 5.99 months, and the mean height of the infants at birth was 0.078 ± 50.26 cm. The mean weight of the newborns at birth was 0.016 ± 3.37 kg. Finally, the mean head circumference of the newborns at birth was 0.062 ± 35.02 cm. By increasing the maternal childbearing age, the eruption time of the first primary tooth increases in the newborns. Furthermore, increasing the age of receiving semi-solid food in infants causes an increase in the eruption time of primary tooth in newborns.

The study uncovered that higher maternal childbearing age, increased duration of breastfeeding, increased age of infants in initiation time of receiving semi-solid food were significantly associated with delayed eruption of the first primary tooth in infants. However, infant's high birth weight had a significant relationship with the earlier eruption of the first primary tooth.