Natal and Neonatal Teeth: An Overview of the Literature

The occurrence of natal and neonatal teeth is an uncommon anomaly, which for centuries has been associated with diverse superstitions among different ethnic groups. Natal teeth are more frequent than neonatal teeth, with the ratio being approximately 3 : 1. It must be considered that natal and neonatal teeth are conditions of fundamental importance not only for a dental surgeon but also for a paediatrician since their presence may lead to numerous complications. Early detection and treatment of these teeth are recommended because they may induce deformity or mutilation of tongue, dehydration, inadequate nutrients intake by the infant, and growth retardation, the pattern and time of eruption of teeth and its morphology. This paper presents a concise review of the literature about neonatal teeth.


Introduction
Natal teeth are teeth present at birth, and "neonatal teeth" are teeth erupted within the first month of life. Premature eruption of a tooth at the time of birth or too early is combined with many misconceptions. They are further accompanied by various difficulties, such as pain on suckling and refusal to feed, faced by the mother and the child due to the natal tooth/teeth. Some families are so superstitious that the afflicted child may be deprived of parental love. The family hopes that the offending teeth be removed as soon as possible.
There was no difference in prevalence between males and females. However, a predilection for female was cited by some authors. Anegundi et al. reported a 66% proportion for females against a 31% proportion for males [47].

Multifactorial Etiology
Exact etiology for the premature eruption or for appearance of natal and neonatal teeth is not known. In the past, neonatal teeth were merely considered cysts of the dental lamina of the newborn [67]. Normally they appear corniform, white in colour, composed of compact keratin, and projected above the alveolar ridge [73].
It was also suggested that they occur due to inheritance as dominant autosomal trait. Endocrine disturbance resulting from pituitary, thyroid, and gonads also may be one of the key factors. Another hypothesis suggested is that excessive or increased resorption of overlying bone results in early eruption of the natal or neonatal teeth. Poor maternal health, endocrine disturbances, febrile episodes during pregnancy, and congenital syphilis are some of the contributing predisposing factors for the occurrence of natal and neonatal teeth suggested in the literature. However, according tǒ Stamfelj et al. the occurrence of natal teeth associated with agenesis of their primary successors appears to be related to an accelerated or premature pattern of dental development rather than to superficial positioning of the tooth germs [74].

Environmental Predisposing Factors
Environmental factors could play an important role in eruption of neonatal teeth. Polychlorinated biphenyls (PCBs), polychlorinated dibenzo--dioxins (PCDDs), and dibenzofurans (PCDFs) seem to cause the eruption of natal teeth [74]. The only environmental factor that may be regarded as a causative factor of natal teeth is the toxic polyhalogenated aromatic hydrocarbons: PCBs, PCDDs, and PCDFs. They are among the most widespread environmental pollutants. They cross the placenta, and concentrations of PCDD/Fs in the adipose tissue of a newborn are correlated with those in mother's milk. The children with natal or neonatal teeth usually show other associated symptoms [38].

Clinical Presentation
The natal teeth or neonatal teeth manifest usually with variable shape and size ranging from small, conical and may also resemble normal teeth. The appearance of these teeth is dependent on the degree of maturity, but most of the time they are loose, small, discoloured, and hypoplastic as in the cases presented here. They may show enamel           [79] and a small root formation suggestive of an immature nature. The majority of natal teeth may exhibit a brown-yellowish-/whitish-opaque colour [12].
They are attached to the oral mucosa in many instances as the root development is incomplete or defective. This leads to the mobility in teeth, with the risk of being swallowed or aspirated by the child. The mobility also may lead to degeneration of Hertwig's sheath which is responsible for the formation of root, thus resulting in further incomplete root development and stabilization.
Increase in mobility could also cause changes in the radicular part of teeth such as cervical dentin, pulp cavity, and cementum as well.

Histology
In a study of natal teeth, Hals [80] observed normal pulp tissue, except for the presence of inflammatory areas in some regions; moreover, Weil's basal layer and the cell-rich zone were absent [81]. Histologically, the thin layer of enamel or in extremely rare conditions absence of the enamel layer may be seen [77]. The enamel hypoplasia could be attributed to the disturbance/variation in amelogenesis process which was due to premature exposure of the tooth to the oral cavity. This may cause metaplastic alteration of the epithelium of the normally columnar enamel to a stratified squamous [80].
Dentino-enamal junction is not scalloped which similar to that found in deciduous teeth. Cervically dentin becomes atubular with spaces and enclosed cells [82]. Irregular dentinal tubules through the dentin along with calcospherites and predentin of various thicknesses could be present [33]. Atypical dentin was also observed in the natal/neonatal teeth which could have been the result due to the response to irritant stimulus from oral cavity.
Developing teeth often had no cementum, and in those cases where acellular cementum could be observed it was thinner than normal.
Pulp canal and pulp chamber become wider in most of the cases. Vascularised pulps along with few inflammatory cells were also reported [83].

Ultrastructure Findings
Jasmin and Clergeau-Guerithault [81] studied the surface topography of mandibular natal and neonatal incisors at the ultrastructural level using the scanning electron microscope (SEM). They observed that enamel of the teeth exhibited hypoplastic, depressed areas, and the incisal edge of natal tooth lacked enamel [81]. According to Uzamis et al., the thickness of enamel was around 280 microns compared to up to 1200 microns in normal teeth. This shows the retarded development of natal and neonatal teeth, because of incomplete mineralization at the time of birth [82].
In one of such extensive studies on natal and neonatal teeth, Masatomi et al. [55] reported that enamel has a normal prism structure and mineralization except in few cases where the prism structure was absent in the cervical part of the enamel. They also noticed that the cervical and apical dentin was tubular, and in developing teeth the dentin in these regions changed to an irregularly formed hard tissue of osteodentin character, in which enclosed cells could be observed.

Complications
A major complication from natal/neonatal teeth is ulceration on the ventral surface of the tongue caused by the tooth's sharp incisal edge. This condition is also known as Riga-Fede disease or syndrome [47]. Possibility of swallowing and aspiration which has already been described previously should also be one of the major concerns in complications. Other complications stated are injury to mother's breast and inconvenience during suckling. The consequences seen with the teeth include carious lesions, pulp polyp, or premature eruption of successor teeth.

Conclusion
Natal and neonatal teeth diagnosis requires detailed case history accompanied by thorough clinical and radiographic examination of the infant. It is important to rule out by radiographic examination whether they are components of normal dentition or supernumerary to decide the treatment plan. The clinician should also assess the risk of haemorrhage due to the hypoprothrombinemia commonly present in newborns.

Classification
(i) The appearance of each natal tooth in the oral cavity can be classified into four categories given as follows, as the teeth emerge in the oral cavity: (1) shell-shaped crown poorly fixed to the alveolus by the gingival tissue and absence of a root; (2) solid crown poorly fixed to the alveolus by the gingival tissue and little or no root; (3) eruption of the incisal margin of the crown through the gingival tissues; (4) edema of the gingival tissue with an unerupted but palpable tooth.
(ii) Spoug and Feasby have suggested that, clinically, natal and neonatal teeth are further classified according to their degree of maturity.
(1) A mature natal or neonatal tooth is the one which is nearly or fully developed and has relatively good prognosis for maintenance. (2) The term immature natal or neonatal teeth, on the other hand, implies a tooth with incomplete or substandard structure; it also implies a poor prognosis.
(iii) If the degree of mobility is more than 2 mm, the natal teeth of category (1) or (2) usually need extraction.