ANATOMICAL AND PHYSIOLOGICAL FEATURES OF PRIMARY TEETH
Humans are diphyodont as they have two dentitions: primary and permanent
- Humans are also heterodonts as they have different tooth groups
- Primary dentition consists of 20 teeth and permanent dentition consisting of 32 teeth
- Permanent teeth replacing the primary teeth are called successional teeth
- Permanent teeth with no predecessors are called accessional teeth
PRIMARY TOOTH ROOT:
- Shorter
- Roots of Molar are more diverging
- Curved roots with thinner walls
- Have flat ribbon shaped root canals. Canals are not narrowed with age
PRIMARY TOOTH STRUCTURE:
- Lower mineralization with thinner enamel and dentin
- Cervical enamel rods are directed occlusally and cervical area constricted significantly
- Have prism-less surface and reflects on the ability to etch the surface and provide an interface for attachment of sealants and other restorative procedures
- Pulp horns are closer to the outer surface
- Mesial pulp horn is much higher and relatively larger pulp
- More irregular pulp canals
- Root flare as they approach the apex
MANDIBULAR INCISORS
- Mandibular central incisor is almost symmetrically flat when viewed from buccal aspect
- No developmental grooves or mamelons
- Crown is one third the length of root with a cingulum on lingual surface
- Root is long and cylindrical
- Lateral incisor is distinguished from central incisor by their distal incisal angle which is more rounded
- Lateral incisor is longer and narrower than central incisor
- Pulp approximately 2.6mm from incisal edge in central incisor, 1.7mm from distal enamel surface and 1.0mm from mesial
- Pulp of lateral incisor has similar dimension but is somewhat smaller
MAXILLARY INCISORS
- Crown shape is a square with slightly rounded incisal edge in the distal incisal angle
- Crowns of maxillary lateral incisors are almost rectangular with an expressed distal incisal angle
- Primary central incisor is unique in that it is the only tooth in human dentition that has a greater mesiodistal dimension than crown height
- Contact points with adjacent teeth are broad, extending from incisal 1/3 to gingival 1/3
- Similar to mandibular incisors as it has a flat, labial surface and prominent lingual cingulum
- Root is conical and roughly 2.5x as long as crown height
PRIMARY CANINES
- Crowns of canines is characterised by abrasion of incisal edge
- Labial surface of crown is convex
- Palatal surface is characterised by a pronounced expansion cusp
- Enamel ends with expansion and with strong narrowing in neck of tooth
- Roots are rounded and slightly curved buccally