MORPHOLOGY OF INDIVIDUAL DECIDUOUS TEETH

objectives The morphology of the crown of each primary tooth The numbers and shape of the root of the primary teeth Differences in morphology between primary and permanent teeth

The deciduous maxillary central incisor is unique in that it is the only tooth in the human dentition that has a greater mesiodistal dimension than crown height.

The contact points with adjacent teeth are broad, extending from the incisal one-third to the gingival one-third.

Labial surface is flat. There is a prominent lingual cingulum. The root is conical and roughly 2.5 times as long as the crown height.

Maxillary lateral incisors The maxillary lateral incisor is smaller than the maxillary central incisor. The root is more conical.

Mandibular central Incisors • is almost flat when viewed from the labial aspect.

The crown is one-third the length of the root with a cingulum on the lingual surface.

The primary mandibular lateral incisor is distinguished from the mandibular central incisor by the distoincisal angle, which is more rounded. In overall dimensions, the primary lateral incisor is somewhat longer but narrower than the primary central incisor. M L C

2. The crown is constricted at the cemento-enamel junction (CEJ) Maxillary Canines 1. long and sharp. 2. The crown is constricted at the cemento-enamel junction (CEJ)

there is often a prominent cingulum. ROOT: long slender is more than twice the crown length.

• The mandibular canines • It is a long narrow tooth, much smaller than the primary maxillary canine. • The distal marginal ridge is much lower than the mesial marginal ridge. Mandibular Canines

The point of contact is very close to the cervical third of the tooth. The root is long and slender and is about twice the crown length.

Maxillary First Molars • The primary maxillary first molar resembles a molar and a premolar

The occlusal surface consists of four cusps, mesiobuccal and distobuccal cusps and mesiolingual and small distolingual on the lingual surface. This gives the tooth a square look. • There are three slender roots,

Mandibular First Molars It has four cusps, two buccal and two lingual. The occlusal surface is narrow due to the convergence of the mesiobuccal and mesiolingual cusps.

• Transverse ridge is very prominent and divides the occlusal surface • The enamel of this tooth is uniformly thick. • There are two broad but thin mesial and distal roots, one on the mesial aspect and one on the distal aspect.

Maxillary Second Molars The primary second molars are the last primary teeth to erupt. The primary maxillary second molar resembles the permanent maxillary first molar in appearance but is smaller.

A prominent transverse or oblique ridge connects the There are four cusps, two on the buccal and two on the lingual aspects. The largest one is the mesiopalatal. • Often there is a fifth cusp prominence, called as the tubercle of Carabelli on the palatal surface of the mesiopalatal cusp A prominent transverse or oblique ridge connects the Disto-buccal cusp with the mesiopalatal cusp. BDG, Buccal developmental groove; CDG, central developmental groove; CP, central pit; DBC, distobuccal cusp; DBDG, distobuccal developmental groove; DC, distal cusp; DDG, distal developmental groove; DLC, distolingual cusp; DP, distal pit; FC, fifth cusp; LDG, lingual developmental groove; MBC, mesio-buccal cusp; MBDG, mesiobuccal developmental groove; MLC, mesiolingual cusp; MP, mesial pit; MTF, mesial triangular fossa; OR, oblique ridge.

There are three roots The enamel is usually 1.2 mm thick uniformly on the tooth.

Mandibular Second Molars The primary mandibular second molar resembles a permanent mandibular first molar. • There are five cusps, three on the buccal surface and two on the lingual. • The enamel is uniformly 1.2 mm thick.

There are two roots which are narrow mesiodistally but very broad buccolingually.

A characteristic of all primary molars is that 1. the furcation of the roots begins at the CEJ. This is not apparent in permanent molars. 2. There is a very prominent buccal cervical ridge. 3. The roots are diverged and curved to accommodate the developing permanent tooth bud beneath

Morphological differences between permanent and Deciduous Teeth Dr. Bushra Rashid Noman

Features of a Deciduous Crown 1. The crown of the deciduous tooth is shorter than the permanent tooth.

2. The occlusal table of a deciduous tooth is narrower Labiolingually than is the permanent tooth.

3. The deciduous tooth is constricted in the cervical portion of the crown.

4. The enamel and dentin layers are thinner in the deciduous tooth.

5. The enamel rods in the gingival third extend in a slightly occlusal direction from the dentinoenamel junction in deciduous teeth but extend slightly apically in the permanent dentition.

6. The contact areas between the deciduous molars are very broad and flat.

7. The color of the deciduous tooth is lighter than permanent teeth.