Unique Characteristics

Anterior Teeth

Maxillary Central Incisor 1. Mesiodistal-incisocervical crown dimension The primary maxillary central incisor is the only primary or secondary incisor where the mesiodistal crown dimension is greater than the incisocervical crown dimension (Fuller/Denehy/Schulein; Jordan/Abrams/Kraus; Woelfel/Scheid). 2. Cingulum size-form The cingula of maxillary incisor “extends much farther incisally” than the cingula of secondary incisors (Jordan/Abrams/Kraus). The cingula of maxillary anterior teeth are large and “seem to bulge”, encompassing about one-third of the incisocervical crown dimension (Woelfel/Scheid).

Mandibular Central Incisor 1. Crown form The primary mandibular central incisor crown is symmetrical “just like” the secondary mandibular central incisor crown when it is viewed facially, lingually, or incisally (Fuller/Denehy/Schulein). The primary mandibular central incisor is bilaterally symmetrical when viewed facially or lingually (Jordan/Abrams/Kraus). 2. Incisal edge form The incisal edge of the primary mandibular central incisor is horizontally straight (Jordan/Abrams/Kraus), the only primary incisor to display this trait.

Primary incisor crowns 1. Crown surface form The facial surfaces of incisor crowns are usually smooth and there are no depressions (Woelfel/Scheid).

Anterior tooth roots 1. Root curvature The apical aspect of primary anterior tooth roots curves facially (Woelfel/Scheid).

Maxillary Canines 1. Mesial contact location The primary maxillary canine has a mesial proximal contact that is located cervical to the distal proximal contact, the only primary tooth with this characteristic (Woelfel/Scheid). This unique primary dentition feature is shared with the secondary mandibular first premolar (Woelfel/Scheid). 2. Root length The primary maxillary canine has the longest root of any primary tooth (Black; Linek; Woelfel/Scheid).

Posterior Teeth

Maxillary first molars 1. Unique Crown Form: The primary maxillary first molar has the second most

variable crown form relative to other primary and secondary teeth (Ash/Wheeler) although one author (Fuller/Denehy/Schulein) indicates it bears a resemblance to secondary premolars.

2. Distofacial Cusp Form: A distofacial cusp is frequently present on primary maxillary first molars and it is the most underdeveloped facial cusp present on any primary or secondary molar.

3. Facial Convexity: The maxillary primary first molar has a “pronounced convexity” on the facial surface in the cervical third and this area appears overdeveloped compared to any other tooth, primary or secondary, with the primary mandibular first molar being a “close contender” (Ash/Wheeler).

4. Facial Bifurcation: The facial bifurcation on the maxillary first molar is closer to the cervical line (average of 1.5 millimeters) than any other molar furcation (Kramer/Ireland).

Maxillary Second molars 1. Root Divergence: The maxillary second molar has the greatest root divergence of

any primary molar with an average separation of 12.6 millimeters between the lingual surface of the lingual root and the facial surface of the mesiofacial root (Kramer/Ireland).

2. Distal Bifurcation: The distal bifurcation on the maxillary second molar is located farther apical to the cervical line (average of 2.9 millimeters) than any other molar furcation (Kramer/Ireland).

Mandibular First Molars 1. Crown Form: The mandibular primary first molar has a crown form that does not

resemble any other primary or secondary tooth (Ash/Wheeler; Dewey; Fuller/Denehy/Schulein; Woelfel/Scheid) and because it is so different “it appears strange and primitive” (Ash/Wheeler).

2. Mesiolingual Cusp: The mesiolingual cusp of the mandibular primary first molar is the “most conical” of the primary and secondary molar cusps (Jordan/Abrams/Kraus).

3. Distolingual Cusp: The distolingual cusp on the primary mandibular first molar is “a bulging protuberance” on the distal aspect of the tooth (Jordan/Abrams/Kraus) that is a unique cusp form.

4. Occlusal Table: The primary mandibular first molar has an occlusal table which is the narrowest found on any primary or secondary molar (Kramer/Ireland).

5. Facial Outline Form: From a facial view, the outline form of the mesial surface of the mandibular first molar crown is “uniquely straight” in an occlusocervical dimension (Fuller/Denehy/Schulein).

6. Mesial Marginal Ridge: The mesial marginal ridge of the primary mandibular first molar is so well developed that it looks like a cusp (Ash/Wheeler; Woelfel/Scheid) and it could be considered as “another small cusp” located lingually (Ash/Wheeler).

7. Mesial Root Form: From a mesial view, the outline form of the mesial root of the primary mandibular first molar does not resemble any other primary tooth root since the facial and lingual surfaces are straight (do not converge apically) for more than half the root length. (Ash/Wheeler; McDonald/Avery).

8. Mesial Root Form: From a mesial view, the mandibular first molar has a mesial root with an apical portion that is “normally flat” and almost square (Fuller/Denehy/Schulein).

Mandibular Second Molars 1. Dentin Thickness: The dentin thickness is particularly limited in some areas of the

primary mandibular second molar (Ash/Wheeler).