Nonsyndromic extremely premature eruption of teeth in preterm neonates – a report of three cases and a review of the literature

Introduction

The eruption of primary teeth typically begins at 6 months of age. The etiology of premature eruption (dentitio praecox) of primary teeth is still unknown. It is most likely caused by many general and local factors [1], [2]. The most frequent theory for premature eruption is based upon the result of a superficial position of the tooth germ, probably related to heredity. The premature eruption of primary teeth may be associated with an increased rate of eruption during or after febrile states, endocrine diseases, dietary deficiencies, hypovitaminosis and with the effect of congenital syphilis. Another theory explaining premature eruption is focused on environmental toxins, especially polychlorinated biphenyls and dibenzofurans [1]. Some authors [3], [4] have suggested that natal and neonatal teeth could be associated with certain syndromes and orofacial clefts.

Teeth that are present in the oral cavity at birth or erupt within the first 30 days of life are referred to as natal and neonatal teeth, respectively [2]. Teeth that erupt within 1–3 months after birth are called early infancy teeth or precociously erupted primary teeth (dentition praecox). Various terms have also been used to designate the presence of teeth in the oral cavity of neonates, such as congenital teeth, fetal teeth, predeciduous teeth and premature teeth [2], [5]. Approximately 90% of prematurely erupted teeth are primary teeth and 10% are supernumerary teeth [6], [7]. Natal teeth are more frequent than neonatal teeth, with a ratio of approximately 3:1 [8], [9].

Natal and neonatal teeth can be clinically classified according to their degree of maturity [10]. The first category is a mature natal or neonatal tooth, which is nearly or fully developed and has a relatively good prognosis for maintenance. The second type is an immature natal or neonatal tooth with incomplete or substandard structure and a poor prognosis for maintenance. The appearance of a natal or neonatal tooth varies and can be divided into four categories [11]: 1. Shell-shaped crown poorly fixed to the alveolus by gingival tissue and the absence of a root. 2. Solid crown poorly fixed to the alveolus by gingival tissue and a short or undeveloped root. 3. Eruption of the incisal edge of the crown through the gingival tissue. 4. Edema of gingival tissue with an unerupted but palpable tooth.

The treatment of infants with natal or neonatal teeth depends on several factors, such as degree of mobility, problems during breastfeeding and presence of sublingual frenum ulceration [5], [6], [8], [12].

Histologically, abnormalities of all dental tissues have been reported [3], [13], [14]. The enamel has been described as hypoplastic and hypomineralized. In the dentin, large interglobular spaces and irregular pattern of the dentinal tubules have been described. Concerning pulp tissue, absence of Weil’s basal layer and a cell rich zone were observed together with an increased rate of dilated blood vessels [9].

According to the definition of the World Health Organization [14], a preterm infant is one born before gestational week 37 or having a low birthweight (LBW). LBW is established as weighing less than 2500 g, regardless of the gestational age. LBW neonates are further subdivided into very low birthweights (VLBW) of <1500 g, and extremely low birthweights (ELBW) infants with birthweights <1000 g. Enamel hypomineralization and hypoplasia, notching of the alveolar ridge, palatal grooving, high arched palate, crossbite and palatal asymmetry are the most frequent conditions in preterm infants [15], [16]. For preterm VLBW infants, a significant delay in dental development and eruption of the primary teeth has been reported, when compared with full-term infants with normal birthweight (NBW) [17], [18]. The presence of teeth in newborns is a rare condition in full-term neonates and an extremely rare situation in prematurely delivered infants [6], [8].

The aim of the study was to describe clinical findings in three preterm infants with neonatal teeth and to find relevant articles in databases MEDLINE, Scopus and ScienceDirect.

Patients and methods

This study is a part of a long-term research project being conducted at the Department of Stomatology and Neonatology Faculty Hospital and Medical Faculty in Pilsen, Charles University in Prague, Czech Republic. There are approximately 3500 births annually at the Department of Obstetrics of the Faculty Hospital in Pilsen, Czech Republic. The three premature neonates with neonatal teeth who form the basis of the current study were born at this department and examined between January 1, 2015 and December 31, 2017. Personal data, including gender, gestational age, birthweight, mode of delivery, general health status and presence of genetic syndromes, were obtained from hospital records. The gestational age was estimated from the reported date of the mother’s last menstruation. Dental examination of neonates was performed at the Neonatological Department of the Faculty Hospital and Medical Faculty in Pilsen, Charles University in Prague, Czech Republic. The neonates were examined using a sterile dental mirror and artificial light. Dental examination included the type, location, clinical appearance according to Hebling et al. [11] and degree of mobility of the erupted teeth.

To find relevant articles in English, the databases MEDLINE, Scopus and ScienceDirect were searched from 1950 to 2016. The search was based upon the following key words: “natal teeth”, “neonatal teeth”, “preterm infant” in all fields. The inclusion criteria were the survey of at least 100 infants or case reports concerning clinical findings and treatment of nonsyndromic preterm infant with natal or neonatal teeth. The search was limited to articles in English. Supplementary searching by hand was also used. Irrelevant articles were excluded by title and, upon reading their summary, due to lack of relevance. Ultimately 12 articles remained: 10 case reports and two retrospective studies (Table 1).

Results

Clinical observation

Intraoral examinations of the three premature infants revealed the presence of partially erupted teeth in the anterior mandibular region. Every neonate had one erupted lower central incisor. According to the gestational age of neonates (<40 weeks) the eruption of teeth was extremely premature. All teeth erupted between 4 and 6 weeks after preterm birth and findings of protuberancies in the top of the anterior alveolar ridge preceded the eruption. All neonatal teeth had a partially visible clinical crown, hypermobility and inflammation of the surrounding gingiva without any symptoms of bleeding. The teeth had hypoplastic and hypomineralized enamel, the crown size and form resembled primary lower incisors (Figure 1). Clinically the teeth were classified as immature with solid crowns poorly fitted to the alveolus by gingival tissue. There were no ulcerations on the sublingual frenum and no other intraoral pathology. The neonates were fed by means of a nasogastric tube and therefore the presence of mobile neonatal teeth was not connected with feeding difficulties. Dental radiographs could not be obtained to confirm the diagnosis and distinguish the supernumerary teeth, as difficulties with using intraoral radiographs are common in the case of neonates and X-ray examination in preterm infants would be non-ethical. The teeth were extracted due to their hypermobility. The extractions were performed with extreme precautions under mucous anesthesia with sterile forceps and hemorrhage was stopped by digital compression with the help of sterile gauze. All extracted neonatal teeth were rootless. The healing after extraction was without complications. Regular recall was recommended for monitoring of development and eruption of primary teeth.

Figure 1:

ELBW preterm neonate with lower incisor.

Discussion

The occurrence of natal or neonatal teeth represents a rare anomaly of chronology of primary teeth eruption or the presence of supernumerary teeth. The finding of natal or neonatal teeth in preterm infants is a highly specific clinical problem as the primary teeth eruption in preterm infants is delayed in comparison with full-term infants.

The prevalence of natal and neonatal teeth in the population has varied from 1:1000 to 1:30,000 live births. Although the condition has always been very rare, there seems to be a slight tendency toward higher prevalence during the last 40 years [1]. The prevalence of natal or neonatal teeth in preterm infants is unknown. Three preterm infants with three neonatal teeth were identified in the Neonatology Department of the Faculty Hospital in Pilsen, Czech Republic. The incidence of premature neonates with natal or neonatal teeth in this hospital over a 3-year period was 1:3500. 85% of natal or neonatal teeth are mandibular incisors, 11% are maxillary incisors, 3% mandibular canines or molars and only 1% are maxillary canines and molars [7], [8]. In the present cases, all erupted teeth were lower central incisors. The same situation occurred in all the cases of preterm infants with natal or neonatal teeth described in the literature [19], [20], [21], [22], [23], [25], [26], [27], [29].

Natal teeth are more frequent than neonatal teeth [8], [9]. The findings in preterm infants may differ. The erupted teeth in nine cases of preterm infants were classified as natal [6], [21], [22], [24], [25], [26], [27] and four teeth as neonatal [20], [23], [29]. In the current cases, all described teeth in preterm infants were not present in the oral cavity at birth and according to prematurity were classified as neonatal.

The presence of teeth in the oral cavity of neonates can indicate some systemic disturbances or may be associated with some syndromes and developmental anomalies. It has been suggested that presence of natal or neonatal teeth can give warning signs in a syndrome diagnosis [30]. Natal and neonatal teeth may cause a local problem during breastfeeding or bottle feeding, may result in trauma of the sublingual frenum and due to hypermobility can represent a danger of aspiration or swallowing of these teeth [6], [7]. The presence of natal and neonatal teeth can be associated with inflammation and edema of the surrounding gingival tissue [24]. In the current cases, all neonatal teeth in preterm infants were hypermobile with inflammation of surrounding gingiva. All preterm infants were fed with nasogastric tubes and therefore discomfort during suckling was not observed.

The decision on a treatment plan is based on the degree of tooth mobility, inconvenience during suckling, interference with breastfeeding, and whether the tooth is supernumerary or part of primary dentition [12], [25]. Distinguishing prematurely erupted primary teeth from supernumerary teeth is possible only after radiographic examination or long-term observation. In the literature [7], [8], [12] radiographic examination is recommended for the reason described; however, the authors also mention the difficulties connected with this type of examination in newborns and infants. Treatment of natal or neonatal teeth should be planned carefully, due to complications connected with premature loss of primary teeth [31]. The clinical approach adopted in the current cases was based on extraction of prematurely erupted teeth due to their mobility, immature appearance and inflammation of surrounding tissue.

Long-term periodic recalls and follow-up care of preterm infants with natal or neonatal teeth is mandatory for monitoring of orofacial development and early diagnosis of all abnormalities.

The presence of natal or neonatal teeth in preterm infants is a rare situation requiring a multi-professional approach to the treatment decision and elimination of a possible association with various syndromes. In addition, a knowledge of problems concerning natal and neonatal teeth is essential for diagnosis and management, as well as parental counseling.