|SECTION IV||CLASS AND TYPE TRAITS OF PRIMARY ANTERIOR TEETH|
Now, consider the traits that apply to most crowns of all types of primary anterior teeth. Refer to Appendix page 9 while studying these traits.
- Prominent cervical ridges on facial surfaces run mesiodistally in the cervical third (Appendix 9a, facial surfaces).
- The prominent lingual cingula seem to bulge and occupy about one third of the cervicoincisal length (Appendix 9a, lingual surfaces, and Fig. 6-16).
- Similar to their successors, incisal ridges of primary anterior maxillary teeth are located labial to the root axis line (considerably so on maxillary primary canines), whereas incisal ridges of mandibular incisors are located on the root axis line or slightly lingual to the root axis line (seen on some anterior teeth in Fig. 6-17).
- Usually, there are no depressions, mamelons, or perikymata on the labial or incisal surfaces of the crowns of the primary incisors. These surfaces are smoother than on their successors.
- Cervical lines of all primary anterior teeth curve incisally more on the mesial side than on the distal side, just like on permanent anterior teeth. Also, the cervical lines are positioned more apical on the lingual than on the labial.
- From the incisal view, primary anterior tooth crowns taper narrower toward the lingual and have a relatively thick incisal edge that curves mesiodistally.
The following traits apply to the roots of all types of primary anterior teeth.
- The roots of primary anterior teeth are long in proportion to crown length (Appendix 9f and Fig. 6-15) and are relatively narrow mesiodistally (Appendix 9b).
- The roots of most primary anterior teeth bend labially in their apical one third to one half by as much as 10° (Appendix 9c and Fig. 6-17). This apical bend provides space for the developing succedaneous incisors, which form just lingual and apical to the primary root.
1. Primary Incisors from the Labial View
a. Outline Shape of Primary Incisor Crowns from the Labial View
The crown of the primary maxillary central incisor is somewhat symmetrical, and the incisal edge is relatively straight, but as on permanent maxillary central incisor crowns, the distoincisal angle of the incisal edge of the primary, before wear, is more rounded than the mesioincisal angle. However, the primary maxillary central incisor is the ONLY anterior tooth (primary or secondary) whose crown is wider mesiodistally than incisocervically (Appendix 9e and Fig. 6-18). The crown of the primary maxillary lateral incisor is similar in shape to the central incisor but is smaller, less symmetrical with distoincisal angles even more rounded, and longer incisocervically than wide mesiodistally. Note this difference between these teeth in Figures 6-19 and 6-20.