A unique, multidisciplinary manual for the treatment of pediatric dental emergencies for general practitioners and non-pediatric specialists
Management of Dental Emergencies in Children and Adolescents presents the diagnostic skills, treatment options, and management strategies necessary to provide effective and appropriate dental care for children and adolescents.
This authoritative manual helps dental practitioners manage potentially stressful situations with children and adolescents while improving their competence in a wide range of urgent pediatric situations. An emphasis on managing the therapeutic demands of both younger patients and their parents enables readers to have greater confidence in handling demanding emergency situations in daily practice. An expert team of contributors explain how to manage tooth substance loss, endodontic problems in deciduous teeth, the long-term consequences of early tooth loss, the dental issues related to oral health, and more.
Guiding practitioners through the unique challenges of pediatric dental emergencies, this book:
* Explains the differences in treating and managing dental emergencies in children compared to adults
* Covers all types of pediatric dental emergencies including open pulp in permanent and deciduous teeth, missing teeth, and non-infective dental conditions
* Offers clinical vignettes and photographs to highlight clinical relevance
* Includes chapters by experts in multiple disciplines such as endodontics, restorative dentistry, pediatric dentistry, prosthodontics, and orthodontics
The first textbook to focus exclusively on young patients in need of acute dental care, Management of Dental Emergencies in Children and Adolescents is a much-needed resource for general and specialist dentists as well as trainee and specialist pediatric dentists.
Developmental and Histological Aspects of Deciduous and Young Permanent Teeth
Markus Schaffner and Adrian Lussi
Department of Preventive, Restorative and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland
Differences between Deciduous and Permanent Teeth
The most noticeable difference between deciduous and permanent teeth is related to their anatomy: deciduous teeth are generally smaller than their permanent counterparts and have a significantly thinner enamel layer (Grine, 2005; Mahoney, 2013) (Figure 1.1.1a,b). Additionally, histological differences may influence their susceptibility to dissolution.
Figure 1.1.1 (a) Deciduous teeth have a significantly thinner enamel layer than (b) permanent teeth. Note: The enamel - cementum border in the deciduous teeth is more coronal compared to permanent teeth.
Deciduous teeth have an outermost layer of aprismatic (prismless) enamel, with a thickness varying from 15 to 30?µm (Kodaka et al., 1989; Ripa, 1966; Ripa et al., 1966). The aprismatic layer is significantly thicker on the labial than the lingual surfaces of anterior deciduous teeth, but no significant differences have been found between the surfaces of deciduous molars (Shellis, 1984a).
A prismatic enamel layer has been observed in both deciduous and permanent teeth, with a variable thickness of between 10 and 30?µm (Horsted et al., 1976; Kodaka et al., 1991). In relation to the enamel crystals, the arrangement of enamel prisms is fairly similar in both deciduous and permanent teeth (Radlanski et al., 2001); they reach the surface at an almost perpendicular angle in both dentitions (Horsted et al., 1976). Shellis (1984a) was able to trace the prisms in permanent teeth all the way to the surface, but the prisms in deciduous teeth are distinctly different - more gently curved, with slightly more pronounced Hunter-Schreger bands (Shellis, 1984b) (Figure 1.1.2a,b). Furthermore, the prisms in deciduous teeth are smaller, with more complete boundaries, and are more widely spread out than those in permanent teeth (Shellis, 1984b), which is suggestive of more porous enamel in deciduous than in permanent teeth. The interprismatic fraction and prism-junction density are also greater in the enamel of deciduous teeth than in that of permanent teeth (Shellis, 1984a).
Figure 1.1.2 The prisms in deciduous teeth are more curved than those in permanent teeth. Therefore (a) deciduous teeth show more pronounced Hunter-Schreger bands than (b) permanent teeth.
The organic content of enamel also varies according to the kind of tooth. It has been shown to range between 0.7 and 12.0% in deciduous teeth, as compared to 0.4-0.8% in permanent ones (Stack, 1953). Studies of the inorganic content have found that a mineralisation gradient from the surface to the amelo-dentinal junction is clearly observable in both dentitions: a more mineralised layer of enamel is present nearer to the tooth surface and decreases towards the amelo-dentinal junction. In general, deciduous enamel is considerably less mineralised than permanent enamel (Wilson and Beynon, 1989). Moreover, Sønju Clasen and Ruyter (1997) observed that deciduous enamel has a greater total carbonate content than permanent enamel. The carbonate ion can occupy the position either of the hydroxyl (OH-) groups (type A carbonated hydroxyapatite) or of the phosphate (PO43-) groups (type B carbonated hydroxyapatite) in the hydroxyapatite crystal. The same authors noted that there is more type A carbonated hydroxyapatite in deciduous enamel than in permanent enamel.
Although the carbonate ion can cause distortion of the apatite crystal lattice in both positions, when it is in the position of type A, it is assumed to be less tightly bound and to contribute to greater solubility of the enamel.
All of the preceding histological differences between deciduous and permanent enamel may be related to the fact that deciduous enamel has significantly lower surface microhardness (Lussi et al., 2000; Johansson et al., 2001; Magalhães et al., 2009) and elasticity (Lippert et al., 2004). This, in turn, could render deciduous teeth more susceptible to dissolution. In vitro studies of deciduous teeth have shown them to be more susceptible to caries-like acid dissolution than permanent teeth (Shellis, 1984a), and artificial caries lesions have been shown to progress 1.5 times faster in deciduous than in permanent enamel (Featherstone and Mellberg, 1981).
Tooth Development and Structural Characteristics of Dental Hard Tissue
Tooth development in the human embryo begins at between 28 and 40 days of gestation. Epithelial cells grow in the ectomesenchymal (mesectodermal) parts of the jaw. A protruberance of the oral epithelium is formed, derived from the inner and outer enamel epithelium of the enamel organ (bud stage; Figure 1.1.3a). The dental papilla is formed by the further penetration of the epithelial cells into the ectomesenchyme (cap and bell stage; Figures 1.1.3b, 1.1.4-1.1.6). At this time, cell differentiation for the formation of the dental hard tissue occurs. Ameloblasts arise from the ectodermal cells, whilst odontoblasts arise from the adjoining ectomesenchymal cells of the dental papilla, as part of a mutual induction chain. The formation of the dental hard tissue does not start simultaneously in the ectodermal parts and the dental papilla along the entire contact surface. In the case of front teeth, the first layers of enamel and dentin are formed in the middle of the later incisal edge; with lateral teeth, this occurs in the region of the later cusp tips (Figures 1.1.3b-d). With continued growth, the various areas of tooth formation fuse, forming the occlusal surface.
Figure 1.1.3 (a-d) Stages in the development of deciduous and permanent teeth: (1) development of deciduous tooth; (2) development of permanent teeth; (3) bud stage; (4) cap stage; (5) bell stage; (6) enamel epithelium; (7) dental papilla; (8) ameloblasts; (9) enamel; (10) odontoblasts; (11) dentin; (12) Hertwig epithelial root sheath.
Figure 1.1.4 Tooth germ at the cap stage.
Figure 1.1.5 Tooth germ at the early bell stage.
Figure 1.1.6 Tooth germ at the bell stage.
Through further penetration of the epithelial cells into the ectomesenchyme, the double-layered Hertwig's epithelial root sheath is produced (Figures 1.1.3d and 1.1.7). This determines the size, shape and number of the resulting tooth roots. In multirooted teeth, tongue-like extensions grow from the circular edge of the Hertwig's epithelial root sheath over the apical edge of the dental papilla. These projections fuse into the bi- or trifurcation. The resulting dentin layers will later form the base of the crown cavity. The Hertwig's epithelial sheaths proliferate apically and form the tooth roots (Figure 1.1.8a-d). The remnants of the Hertwig's epithelial sheaths are responsible for the formation of true enamel pearls or cementum-free root parts. These remnants are known as epithelial cell rests of Malassez, and play a role in the formation of odontogenic cysts.
Figure 1.1.7 Hertwig epithelial root sheath with outer and inner enamel epithelium.
Figure 1.1.8 Apical view (left) and view from the side (right) of the developing tooth roots. (a) The tongue-like projections meet in the region of the later bifurcation, fuse there and form new epithelial sheaths for the development of two tooth roots. (b-d) With increasing root development, there is a narrowing of the root canals until the apex is reached. The root growth accelerates the tooth eruption.
Structural Features of the Enamel
Light microscopy reveals brown lines in the enamel, which run obliquely to the occlusal direction from the enamel-dentin border. These are the cross-striations and striae of Retzius, which reflect the cyclical deposition of the enamel in the developing teeth (Figure 1.1.9). In a horizontal cross-section, these stripes resemble the annual rings of a tree. Where the striae of Retzius meet the surface of the enamel, imbrication lines are formed. Between the imbrication lines are the perikymata, which are easily recognisable in newly erupted teeth (Figure 1.1.10).
Figure 1.1.9 Vertical section through the crown of a permanent tooth. The cyclical pattern of enamel formation is reflected in the striae of Retzius.
Figure 1.1.10 Enlargement of the tooth surface, clearly showing the perikymata and the imbrication lines between them.
Structural Defects and Paraplasia of the Enamel
In most teeth, structural defects of the enamel are visible under the light microscope. A large proportion of these defects occur during enamel development. Examples include enamel spindles...