Deciduous Teeth: Function, Types & Differences

• Deciduous teeth function during childhood
• Deciduous teeth are shed and replaced by permanent teeth

Eruption and Number

• Deciduous teeth emerge in children between 6 months and 2 years
• There are 20 deciduous teeth
• Of the 20 deciduous teeth, 10 are maxillary and 10 are mandibular

Types of Teeth

• Central incisor
• Lateral incisor
• Canine
• First molar
• Second molar
• There are no premolars in deciduous teeth

Role of Deciduous Teeth

• They play a very important role during childhood
• They maintain alignment, spacing, and occlusion of the permanent dentition
• Deciduous teeth lost prematurely can cause destructive results and should be avoided

Differences Between Primary and Permanent Teeth

• Deciduous teeth are smaller
• Deciduous teeth are whiter
• Deciduous teeth have more consistent shape
• Deciduous teeth number fewer (20)
• Cervical ridges are more prominent on deciduous teeth

Attrition, Enamel, and Dentin

• Enamel of deciduous teeth is less mineralized
• Enamel of deciduous teeth wears down easier
• Layers of enamel and dentin are thinner in deciduous teeth

Crown and Root

• Deciduous teeth have shorter crowns relative to their roots
• Crowns are rounded and have marked constriction at the neck
• Enamel bulges close to the cervical lines instead of gradually tapering
• Crowns of deciduous teeth appear bulbous
• Crowns of deciduous teeth are wider than they are long
• Buccal and lingual surfaces are flatter and have no grooves
• Enamel rods incline occlusally

Anterior Teeth

• The labial surface of the crowns of the incisors have no depressions
• There are no mamelones on the incisal edges
• The cervical ridge on the facial surface is prominent
• The cingulum is prominent
• Deciduous teeth are narrower mesiodistally than their permanent successors, creating leeway space

Posterior Teeth

• Molar crowns are narrow buccolingually and wide mesiodistally
• Molar crowns are short cervico occlusally
• There is a narrow occlusal table
• Molar occlusal surfaces are shallow
• Cusps are short
• Ridges are not pronounced
• Grooves are not deep
• Buccal cusps are not pointed, and their cusp slopes meet at a very wide obtuse angle
• A few grooves on deciduous teeth
• Contact areas are flatter, broader, and more cervically located

Roots

• Root furcation is near the crown, with little to no root trunk
• Roots are thin (slender), longer, and narrower
• Roots are widely spread to allow for the developing permanent successors
• Root completion occurs 1 year after eruption
• Primary teeth undergo physiologic resorption

Pulp Cavities and Horns

• Pulp cavities are proportionally larger compared to permanent teeth
• Pulp horns are high
• 80% of proximal caries occur in deciduous teeth
• This often results in pulp exposure

Root Canals and Pulp

• There are no clearly defined root canals entrance in deciduous teeth
• Pulp canals of deciduous molars follow a thin, tortuous, and branching path
• Primary pulp ages at a faster rate

Maxillary First Molar

• Maxillary first molar more closely resembles the maxillary first premolar
• It may have one of two types. They are : four-cusp type with two buccal and two lingual cusps
• OR three-cusp type having two buccal cusps and one lingual cusp

Maxillary First Molar Buccal Aspect

• Trapezoid shape, with the occlusal surface scalloped and no definite cusp ridge form
• There is a large mesiobuccal cusp and a small distobuccal cusp
• Cervical line is convex towards the root, and the crest of curvature is present mesially
• This outlines the most bulging part of the cervical ridge and has marked convergence of the crown cervically

Maxillary First Molar Roots

• There is no buccal groove on the buccal surface, but a notch exists
• A prominent cervical ridge is present with more prominence on the mesial half
• Three roots (MB, DB, & L) are thin and widely spread, with little root trunk
• Furcation is close to the cervical line and the distal root is considerably shorter than the mesial root

Maxillary First Molar Lingual Aspect

• Crown is narrower due to lingual convergence with a very convex surface
• In the four-cusp type, the distolingual cusp is poorly defined
• The lingual root is the largest

Maxillary First Molar Mesial Aspect

• Outline form is trapezoid, the shortest of the uneven sides present occlusally
• The buccal outline is very convex cervically
• This represents the prominent mesiobuccal cervical ridge
• Then it becomes straight from the ridge to the occlusal margin
• Lingual outline is more convex in the cervical and middle thirds, straight in the occlusal third

Maxillary First Molar Occlusal and Roots

• The mesiolingual cusp is sharper than the mesiobuccal cusp
• A mesial marginal ridge is wide buccolingually
• Cervical line shows some curvature occlusally
• There is a short root trunk and the mesiobuccal root is sufficiently wide to hide the distobuccal root

Maxillary First Molar Distal Aspect

• The crown is narrower and shorter than the mesial side
• Distal marginal ridge is more cervically oriented
• In the four cusp tooth, the distolingual cusp is poorly developed and shorter than the distobuccal cusp
• All three roots can be seen from this angle, but the distobuccal root is superimposed on the mesiobuccal root

Maxillary First Molar Occlusal Aspect

• It's rectangular with B side and M sides are broader than the L and D sides
• In the four-cusp type, there are two large cusps (MB & ML) and two very small cusps (DB & DL)
• In the three-cusp type there is a large MB cusp, an indistinct DB cusp, and a large L cusp
• Sometimes an oblique ridge connects the ML and DB cusps of the four-cusp type molar
• Central, M∆, and D∆ fossae exist, each has developmental pits
• Central, Buccal, and lingual D. grooves + some supplemental grooves are on the tooth

Mandibular First Molar

• This tooth does not resemble any other teeth, deciduous or permanent
• This it appears strange and primitive and varies so much

Mandibular First Molar Buccal Aspect

• Outline form is trapezoid Mesial outline is nearly straight
• Distal side is convex and converges markedly toward the cervix
• The mesiobuccal cusp is much wider than the distobuccal cusp+ has no groove between them
• Cervical line is convex towards the root and slopes occlusally from mesial to distal
• Mesial portion of the crown is longer than the distal

Mandibular First Molar Root

• The buccal surface has a prominent cervical ridge, and it is present in the mesially
• The mesial root is wider and longer than the distal root and the roots roots are slender
• Furcation is close to the cervical line

Mandibular First Molar Lingual Aspect

• Mesiolingual cusp is larger, longer, and sharper than DL cusp
• The mesial marginal ridge is so well-developed that it resembles a cusp
• Cervical line is almost straight and the lingual surface is narrower than the buccal+ lingual convergence
• Roots are narrower lingually

Mandibular First Molar Mesial Aspect

• Outline form is rhomboidal
• The buccal outline is extremely convex at the cervical third representing the most prominent mesiobuccal cervical ridge
• Buccal outline of the crown is longer than the lingual+straight till the tip of the mesiobuccal cusp.
• Has lingual outline is convex with + maximum convexity present in the middle third and it extend lingually beyond the confines of the root base

Mandibular First Molar Table

• Occlusal table is small buccolingually and both Mesiolingually and Mesially are seen from
• Has mesial are convex toward occlusal Slants from buccal to lingual

Mandibular First Molar Apex

• Mesial root outlines are straight from the neck till the apical third, then it tapers to end in a flat and broad apex
• Root has a depression on most of its length

Mandibular First Molar Distal Aspect

• Has almost equal length and are nearly the same
• L and that distal is smaller in Marginal and is located cervically

Mnadibular First Molar Other Points

• The cervical line is almost straight
• The distal root is more rounded, less broad, thinner, and shorter than the mesial root

Anterior teeth points to note

• Crown is wider + the angle is acute
• Because because of angle because prominent and it has the other angle
• Has point to it and of M is distal and also, a line
• Has has a great area anatomy is shallow, there is anatomy shallow,
• There also not.there pit