Structure of Supernumerary Teeth in a Scanning Microscope
Supernumerary or extra teeth also result from disturbances during the initiation and proliferation stages of dental development. The most common supernumerary tooth appears in the maxillary midline and is called a mesiodens. The maxillary midline is the most common location for a supernumerary tooth, which can be almost any shape.
Supernumerary or extra teeth constitute approximately 15 % of teething anomalies. Mesiodenses are the most common kind of supernumerary teeth . Extra teeth are the most frequent cause which hinders the eruption of permanent teeth.
The occurrence of supernumerary and extra teeth is characterised by an increased number of teeth. The anomaly arises as a result of disturbances in teeth development. It is caused by an increased activity of the dental lamina and most probably is genetically determined. Supernumerary teeth often co-occur with genetically determined disease syndromes such as Gardner syndrome, Leopard syndrome, Hallermann-Streiff syndrome, Nance-Horan syndrome for instance, and other rare syndromes. Supernumerary or extra teeth constitute approximately 15 % of teething anomalies.
Supernumerary teeth can most often be observed in permanent dentition, especially in the maxilla. They are often found in the area of incisor teeth in the maxilla, second premolar teeth in the mandible and maxilla, and molar teeth. They occur more frequently in males than females (2:1) . Mesiodens, i.e. a midline supernumerary tooth, is the most common kind of supernumerary teeth . Its incidence is estimated to be between 46 and 67 % of all supernumerary teeth .
The supernumerary may block the eruption of one or both of the central incisors, or may separate them widely and also displace the lateral incisors [3, 4].
They also cause occlusion defects. For these reasons they are an indication for surgical-orthodontic treatment.
The aim of the study was the analysis of mesiodens dentine and enamel surface in a scanning electron microscope.
The study was conducted on healthy extra teeth - mesiodenses extracted for aesthetic-orthodontic reasons. They were an impediment to permanent teeth eruption in children aged eight to 10.
Clinical examination revealed the presence of mesiodenses. An incision was made on the frontal plane of extracted teeth using a diamond separator. Enamel and dentine structures were evaluated by means of a scanning electron microscope LEO 1430 VP.
Microscope Image of Dentine and Enamel
The observations of dentine inner surface allowed to notice its abnormal structure. Dentine coronal surface was plicate and contained irregularly located tubules (fig. 1). The orifices of the tubules had different shapes and diameters. The diameter of tubule orifices ranged from 2-3 µm. There were observed individual tubules with closed lumina. Intertubular spaces had uneven surface and thickenings of various sizes.
In contrast to coronal dentine, radicular dentine had few tubules whose orifices considerably varied in shape and diameter (fig. 2). The diameter of tubule orifices was between 1 and 3 µm. The distribution of the tubules was irregular. The majority of them were undeveloped, their lumina were closed. The intertubular surface, however, was smooth.
In the enamel of the majority of the examined teeth areas of irregular arrangement of prisms were observed (fig. 3). The width of the prisms was varied. The interprismatic spaces were of different width in segments. Apart from enamel with changed structure there was observed enamel characteristic of a typical tooth where the arrangement of prisms is parallel.
The observations described above demonstrated anomalies in the structure of dentine and enamel of supernumerary teeth - mesiodenses. The highest incidence of changes was observed in radicular dentine, where tubules in a vestigial form were found. Such changes may indicate inhibited development of mesiodens radicular part. Further studies will allow to conduct more thorough analysis of the problem.
It should be emphasised that scanning microscopy is a perfect technique which enables to examine dental tissues without destroying of tooth structure. The use of scanning microscopy in our study contributed to the detailed analysis of dentine and enamel and simultaneously revealed the beauty of the analysed tissues, which occur in an anomaly though.
 Stellzig A., et al., J Orofac Orthop 58, 144-53 (1997)
 Van Buggenhout G and Bailleul-Forestier I., Eur J Med Genet 51, 178-81 (2008)
 Kurol J., Am J Orthod Dentofacial Orthop 129, S86-90 (2006)
 Proff P. et al., Ann Anat 188, 163-69 (2006)