PEDIATRIC DENTISTRY/Copyright © 1988 by The American Academy of Pediatric Dentistry Volume 10, Number 1 Dental eruption in low birth-weight prema- turely born children: a controlled study W. Kim Seow, BDS, MDSc, FRACDS Carolyn Humphrys, BDS Rangsini Mahanonda, DDS, DipDH David I. Tudehope, MBBS, FRACP Abstract present study was designed to detect differences in the This study comparedthe dental eruption status of a group tooth eruption status of prematurely born, very low of prematurely born, very low birth-weight (VLBW,< 1500 birth-weight (VLBW,< 1500 g) children compared g) children with a group of low birth-weight (LBW, 1500- low birth-weight (LBW,1500-2500 g), and normal birth- 2500 g) as well as a group of normal birth-weight (NB W, weight (NBW,> 2500 g) children in order to determine 2500 g) children in order to determine if dental eruption is if dental eruption is affected by low birth weight and affected by low birth weight and prematurity of birth. Data prematurity of birth. were analyzed using chronological and corrected (true bio- logical) ages of the prematurelyborn group. The results show Patients and Methods that when chronological ages of the children were used, The VLBWchildren were those attending the VLBW children have significant retardation of dental erup- Growth and Development Clinic of the Mater tion compared with LBWand NBWchildren, particularly Children’s Hospital, South Brisbane. This clinic pro- before 24 months of age (P < 0.01). However,when corrected vides a multidisciplinary, longitudinal follow-up of all ages of the VLBW children wereused, there was no significant infants of very low birth weight managed at the Mater difference detected, indicating that the "delay" in dental Mother’s Hospital. Children in the LBWgroup and the eruption maybe simply due to their early birth. NBWgroup were born at the same time period as the VLBWgroup. They were selected at random from the Several studies on the growth and development of birth register of the hospital. Parent consent to partici- low birth-weight, prematurely born children have indi- pate in the study was given by > 97%of the patients we cated that although physical growth disturbances may were able to contact. There were 153 total subjects and be present for some time after birth, catch-up growth 97%were of Caucasian birth with three per cent part- usually occurs by early childhood (Fitzharding 1976). Caucasian. However, although the physical development of pre- Table 1 (next page)shows the characteristics of the maturely born children has been well investigated, patients in the study. In the VLBWgroup, 73 children there are relatively few studies on the dental develop- (30 males, 43 females) were available for study. Their ment of these children. Our previous investigations meangestational age was 29.4 _+ 2.5 weeks (range 24-33 supported others, showing a high prevalence of enamel weeks) and their mean birth weight was 1179 + 193 g defects~ of about 20-100%. (range 783-1499 g). It is not certain whetherdental eruption is affected by In the LBWgroup (1500-2499 g) there were 33 pa- prematurity of birth and low birth weight. Early studies tients (14 males, 19 females). Their meangestational age were in disagreement as to whether low birth-weight was 37.4_+ 3.1 weeks (range 32-41 weeks) and their mean children had delayed eruption (Tsubone 1962; Wedge- birth weight was 2176 g + 273 g (range 1577-2480g). wood and Holt 1968). Two later investigations sug- In the NBWgroup (> 2500 g), 47 children (22 males; gested that teething age of the first tooth was delayed in 25 females) were available for study. They were all born prematurely born children, but eruption of other teeth full term and their mean birth weight was 3360 + 450 g was not studied (Trupkin 1974; Golden et al. 1981). The (range 2510-4045 g). l Grahnenand Larsson1958; Mellander 1982; Johnsen 1984; Seow et The ages of the children at the time of dental exami- al. 1984a,1984b, 1987. nation varied from 24.3 + 1.2 months in the VLBWgroup PEDIATRIC DENTISTRY: MARCH 1988 ~ VOLUME 10, NUMBER 1 39 TABLE1. SomeCharacteristics of the Children in the Three Birth-weight Groups dren. As can be seen from the Ageat Examination* table, in the age groups 6-11 Chrono- months and 12-17 months, Birth Weight GestationalAge logicalAge Corrected Age the VLBW children had Group (g) (wk) (too) (too) fewer numbers of teeth com- VLBW(N = 73) 1179 + 193 29.4 + 2.5 24.3 + 1.2 21.8 + 1.2 pared to the LBWand the LBW(N = 33) 2176 273 38.4 3.1 25.5 1.8 25.2 1.8 NBWchildren. A two-way NBW(N = 47) 3360 + 450 40.0 + 2.0 30.3 + 1.5 30.3 + 1.5 ANOVAfor the number of *Chronologicalage indicatestrue age whereascorrected age indicates chronologicalage adjusted teeth for the three birth- for the prematurityof birth, i.e., correctedage = chronologicalage - (weeksof prematurity). weight groups and the four to 30.3 + 1.5 months in the NBWgroup. This variability age groups showed a significant interaction between in the age at examination is due to the fact that the chronological age and birth weight (Table 3), indicating examinations were extended over a period of time. The that the lower the birth weight, the fewer the teeth corrected age of each child was computed from the present (P < 0.01). However, by 18 months, the differ- chronological (true biological) age using the following ences in the number of teeth in the three birth-weight formula: corrected age equals chronological age minus groups were not evident (P > 0.1). weeks of prematurity. The dental examinations were performed at the Corrected Age University of Queensland Dental School. All erupted As prematurely born children are not fully mature at teeth were recorded in a comprehensive chart. A tooth the time of birth, their chronological ages do not corre- was considered erupted if any part of its crown had spond to their true biological ages. Hence, a meaningful penetrated the mucous membrane. Other abnormalities comparison with full-term, normal children can only be of the dentition also were noted. Intraoral l~hotographs made if the ages of prematurely born children are cor- were taken in some children. Postnatal medical and rected for the early births. dental histories were obtained from the parents. Mater- Table 4 shows the mean number of teeth present in nal and neonatal medical histories were obtained from each age group of children within each individual birth- hospital records. weight group using the corrected ages of the children. In It was noted from the histories that no child in the contrast to the results using chronological ages of chil- study had had dental extractions or tooth loss from dren, a two-way ANOVAfor the number of teeth for the trauma prior to the time of examination. three birth-weight groups and the four age groups As the study was cross-sectional and not relating to showed a nonsignificant interaction between corrected sequence, timing of eruption was not studied. Instead, age and birth weight (Table 5). the number of teeth present in each subject was noted with reference to age at the time of dental examination. Disussion Data were coded, computerized, and analyzed using analysis of variance (ANOVA)tests to detect statistical Various general factors have been suggested to influ- differences between groups. ence dental eruption in the healthy child. These include race, sex, and physical development (Falkner 1957; Friedlaender and Bailit 1969). Because prematurity of Results birth and low birth weight may influence general physi- In this cross-sectional study, it was necessary to cal development, it is likely that dental development divide the children into various age groups of 6-11 may be similarly affected, but few studies have ad- months, 12-17 months, 18-23 months, and 24+ months. dressed this issue. Most of these previous studies were This division was necessary because the children were uncontrolled and usually only the eruption time of a examined at different times and it was pertinent to determine whether at any particular age group, a low TABLE2. Mean Number of Teeth Present in Each Age birth-weight child had significantly fewer numbers of Group (Chronological Age) Within Each Birth-Weight Group teeth compared to the child with normal birth weight. MeanNo. of Teeth (+_SE) These age groups of five-monthly intervals were chosen Age Group to include approximately the mean eruption times of the (mo) VLBW LBW NBW primary incisors, first molars, canines, and second 6-11 1.0 + 1.3 3.7 + 1.4 3.0 + 1.8 12-17 6.6 0.6 8.0 1.3 11.8 1.0 molars, respectively. 18-23 14.0 0.6 15.5 0.8 14.8 0.8 Chronological Age 24+ 18.7 + 0.4 19.0 _+ 0.6 18.4 _+ 0.5 Table 2 shows the mean number of teeth present in A two-way analysis of variance for the number of teeth for the three birth-weight and four age groups showed a significant in- each age group of children within each individual birth- teraction between chronological age and birth weight (Table 3). weight group, using the chronological ages of the chil- 40 DENTAL ERUPTION IN LowBIRTH-WEIGHT CHILDREN: SEOW ET AL. TABLE3. Analysis of Variance for Number of Teeth Present in the Three Birth-weight eruption. These conditions Groups of Children Using Chronological Ages include supernumerary Degreesof Sum of Mean Variance teeth, impacted teeth, cysts, Sourceof Variation Freedom Squares Square Ratio P Value and tumors which may cause Age group 3 3637.9 1212.6 404.2 0.001 local delayed eruption.