There are twenty deciduous teeth in the primary dentition: ten in each arch, five in each quadrant. There is a central incisor, lateral incisor, canine, first molar, and second molar (there are no bicuspids in the deciduous dentition). The primary teeth may be referred to as the baby teeth, milk teeth, first teeth, or primary teeth, but the correct clinical term is deciduous teeth. They begin to erupt when the child is six months of age and finish erupting when the child is approximately two to three years of age.
It seems that less importance has been placed on the deciduous teeth because they are only temporary. Some patients prefer not to restore deciduous teeth and choose to have them removed; knowing that a permanent tooth will replace them. However, the deciduous teeth play a very important role in maintaining space for the permanent teeth, and they also aid the child in mastication and phonetics. Additionally, the appearances of the deciduous teeth play an important role in establishing a child’s good self-image. Even though the deciduous teeth begin exfoliation by age six, they are still an important part of facial development.
The deciduous teeth are normally smaller than the permanent teeth that replace them. The crown portion is quite short in comparison to the root, and the cervical ridge is much more pronounced. The crowns of the deciduous teeth appear whiter or light bluish in color, as compared to the yellow-gray color of the permanent teeth. This is because the enamel and dentin are much thinner and the pulp chamber is much larger. The deciduous molars have especially large mesial pulp horns. Knowing that the pulp is larger and closer to the surface of the deciduous tooth, a dental hygienist should take great care during the coronal polish not to overheat the tooth and cause injury to the pulp.
MaxillaryDeciduous Central Incisor
The maxillary deciduous central incisor resembles the permanent maxillary central in shape. It is much smaller in size than the permanent maxillary central and has a more pronounced cervical line. The crown is the only anterior tooth in either dentition to have a shorter inciso-cervical height than the mesio-distal width. This tooth erupts with no mamelons, and the labial surface is convex and smooth.
The maxillary deciduous lateral incisor is similar to the central incisor except it is smaller. Another difference is that it is longer than it is wide. The incisal edge of the deciduous maxillary lateral incisor is more rounded on the mesial and distal sides than the straight incisal edge of the central incisor.
Maxillary Deciduous Canine (Cuspid)
The maxillary deciduous canine appears to be wider than it is long; however, with the pointed incisal edge, it is slightly longer than it is wide. It is more convex than the permanent maxillary canine and constricts more at the cervix of the tooth. The mesio-incisal slope has a pronounced cingulum and mesial and distal marginal ridges. The root is similar to the incisors but is longer.
Maxillary Deciduous First Molar
The maxillary deciduous first molar resembles the permanent premolar (molar premolar combo) in many respects. It has four cusps; the mesio-buccal and the mesio-lingual are the most prominent. The mesio-lingual is the longest and the largest. The disto-lingual is the smallest or may even be absent. The tooth has transverse and oblique ridges like the permanent maxillary first molar, but they are not as prominent. The roots, like those of all deciduous molars, spread out rapidly from the crown of the tooth and are widely spaced. The maxillary deciduous first molar has three roots, like its permanent counterparts.
Maxillary Deciduous Second Molar
This tooth resembles the maxillary first permanent molar because it has four primary cusps and may even have a cusp that resembles the cusp of Carabelli. It has three roots.
Mandibular Deciduous Central Incisor
This tooth more closely resembles the permanent mandibular lateral incisor than its central incisor counterpart. The crown of the tooth is slightly wider than the permanent lateral incisor. The shape and form of the incisal edge is almost exactly the same as that of the permanent lateral. The root is slender and rather long. Mesial and distal surfaces of the root are flat, while lingual and labial surfaces are convex.
Mandibular Deciduous Lateral Incisor
The mandibular deciduous lateral resembles the mandibular deciduous central incisor except that it is slightly longer and wider. The cingulum and the mesial and distal marginal ridges are more pronounced and the fossa is not as shallow. The root curves toward the distal at the apex.
Mandibular Deciduous Canine (Cuspid)
The mandibular deciduous canine is much more delicate in form than that of the maxillary deciduous canine—even the root is not as large or long. The cingulum and the mesial and distal marginal ridges are less pronounced than those of the maxillary counterpart. The mesio-incisal slope is not as long as the disto-incisal slope; the maxillary incisal slopes are more nearly equal in length.
Mandibular Deciduous First Molar
This tooth resembles no other permanent or deciduous tooth. It has four cusps, with the mesio-buccal the largest and the mesio-lingual next in size. The distobuccal and the disto-lingual are much smaller. The tooth has two roots: a mesial root, which is much longer and wider, and a distal root. The apex of the mesial root is flattened or squared off.
Mandibular Deciduous Second Molar
The mandibular deciduous second molar closely resembles the permanent mandibular first molar. It is small in all dimensions and the mesio-buccal and the disto-buccal cusps are nearly equal in size, unlike in the permanent mandibular first molar. The distal root is smaller, while the mesial root is longer and wider. The permanent mandibular first molar has roots approximately the same length as this tooth.