A Studv of Primary Denal Enamel From Preterm and Full-term Children Uritg Light and Scanning Electron Microscopy

Purpose: The aim of this study was to examine the enamel thickness of the maxillary primary incisors of preterm children with very low birth weight (< 1,500 g) compared to full-term children with normal birth weight. Methods: A total of 90 exfoliated maxillary primary central incisors were investigated using light microscopy and scanning electron microscopy (SEM). Three serial buccolingual ground sections of each tooth were examined under light microscopy, and maximum di-"nsio.rs of the prenatally and postnatally formed enamel were measured. Results: The enamel of preterm teeth was approximately 20%o thinner than that for fullterm reeth. Most of the reduction was observed in the prenatally formed enamel. This was 5 to 1 3 times thinner than that for full-term children (P<.001). The "catch-up" thickness of postnatally formed enamel did not compensate fuliy for the de crease in prenatal enamel (R.001). Although none of the teeth used in this study had enamel defects visible to the naked eye, 52o/o of pretefm teeth showed enamei hypoplasia under sEM, compared with only 760/o found on full-term teeth (P<.001). These defects were Present as pits or irregular, shallow areas of missing enamel. Conclusions: Preterm primary dental enamel is abnormal in surface quality' and is significantly thinner compared to full-term enamel. The thinner enamel is due mainly to reduced prenatal growth and results in smaller dimensions of the primary dentition. (Pediat D ent 200 5 ;27 :37 4-37 9) KNYWONOS: DENTAL ENAMEL, PR3TERM CHILDREN, PRIMARY TEETH, NEONATAT LINE, ENAMEL THICKNESS -------fuiiid april 4, 2005 Reuision Accepted August 17' 2005 J t is now well known that prematurely born children I experience many oral complications associated with I their preterm births.l 6 Enamel hypoplasia has been reported tote present in over 70o/o of preterm children. This condition is likely the result of: 1. neonatal derangements in mineralization due to poor supply and absorption ofcalcium and phosphate; 2. localtrauma associated with laryngoscopy and endotracheal intubation. 1-7 In addition, short-term distortions of the palate may be caused by prolonged endotracheal intubation, which is frequently required for pulmonary ventilation of the preterm children.5'7As in other aspects of growth, Preterm children also show delayed dental develoPment and eruption in early childhood, but compensatory catch-up growth occurs in later childhood.2 Preterm children have reduced dental dimensions, compared to full-term children. In a controlled study using natural primary teeth, Seow and Wans showed that natural primary incisors from preterm children are significantly smaller in both mesiodistal and faciolingual dimensions compared to those from full-term children. From plaster casts of the primary dentition, Fearne and Brooke reported smaller sizes of the primary molars. The reduced dimensions are presumably the result of serious derangements of metabolic functions associated with their preterm births. It is unclear, however, whether the size reduction is due to a generalized reduction in crown dimension, or whether it is the result of a reduction in enamel thickness. 'Dr. Seota is associate professor, Pediatric Dentistry, ' Dr. Young is associate professor, Oral Biologt3Dr. Tsang h lecturer, Oral Health, andaMr. Daley is technical fficer, all at the School of Dentistry, (,lniuersitl of Queens land, Bris bane, Australia. Correspond with Dr. Seou, at [email protected] 374 Seou et al. Uhrastructure of preterm primary enamel Pediatric Dentistry 27:5, 2005 Preterm (N=45) Full-term (N=45) 2 value Boys (%) 25 (560/0) 25 (56Vo) NS* Girls (%) 20 (44o/o) 20 (44o/o) NS* Total (100o/o) 45 (r00%o) 45 (r00ok) NS* Birth weieht (stSD) 1,480=320 g 3370=300 g < . 0 1 1 Gestational age (wkstSD) l ) 1 + 1 5 39.2t2.7t0.32 wks < . 0 1 7 Rieht-side incisors 50 (100%) 23 6IVo) 27 (600/o) NS* Left-side incisors 40 ( I 00o/o) 22 (49Vo) 18 (40olo) NS* traumatic fracture, only those teeth without obvious enamel changes when examined with the naked eye were used for study. For the l ight microscopy study, 40 primary maxil lary incisor teeth (20 each from preterm and fullterm children) were selected. For the SEM study, another 50 teeth (25 each from preterm children and full-term children) were selected. There were approximately equal numbers of teeth from boys and girls in the preterm and full-term groups, respectively. The I *Chi-square test. tStudent's r test. The authors hypothesize that a reduction of enamel thickness in the teeth of preterm children contributes to their smaller dental dimensions. Thus, the present study aimed to compare the thickness of primary enamel in preterm and full-term children by examining the relarive amount ofenamel formed before and af ter b i r th in histological sections of primary cenual incisors. To further support the authors ' hypothesis that enamel is abnormal in the preterm chi ldren, scanning electron microscopy (SEM) studies were also carried out on other incisors ofPreterm Figure l. Photograp} ofsecrion ot a preterm looth snowlng I ne neonatal line (single-arrowhead )' prenaral enamel (iolid line). and posrnatal enamel (dotred l ine). and full-term control children to detect differences rn enamel surface qualiry.