1.Tooth numbering systems2.Dental formula3.Chronology4.Individual tooth traits ( similarities and differences)

ORAL ANATOMY (REVIEW)

The dental formula for the primary/deciduous teeth in humans is as follows:

This formula should be read as: incisors, two maxillary and two mandibular; canines, one maxillary and one mandibular; molars, two maxillary and two mandibular—or 10 altogether on one side, right or left

A dental formula for the permanent human dentition is as follows:

Tooth Numbering Systems (primary)

The universal system of notation for the primary dentition uses uppercase letters for each of the primary teeth

The symbolic system for the permanent dentition was introduced by Adolph Zsigmondy of Vienna in 1861 and then modified for the primary dentition in 1874.

Tooth Numbering Systems (Primary)

Independently, Palmer published the symbolic system in 1870. The symbolic system is most often referred to as the Palmer notation system in the United States and less frequently as the Zsigmondy/Palmer notation system. In this system the arches are divided into quadrants with the entire dentition being notated as follows: (┘└ ┐┌)

Example: lower right central incisor

A two-digit system proposed by Fédération Dentaire Internationale (FDI) for both the primary and permanent dentitions has been adopted by the World Health Organization and accepted by other organizations such as the Inter- national Association for Dental Research. The FDI system of tooth notation is as follows. For the primary teeth:

Tooth Numbering Systems (Primary)

Primary teeth were numbered as follows:

upper right, 05+ to 01+; lower left, -01 to -05.

Tooth Numbering Systems (Primary)

Viktor Haderup of Denmark in 1891 devised a variant of the eight-tooth quadrant system

Tooth Numbering Systems (Permanent)

In the universal notation system for the permanent dentition, the maxillary teeth are numbered from 1 through 16, beginning with the right third molar. Beginning with the mandibular left third molar, the teeth are numbered 17 through 32. Thus, the right maxillary first molar is designated as 3, the maxillary left central incisor as 9, and the right mandibular first molar as 30. The following universal notation designates the entire permanent dentition.

The Zsigmondy/Palmer notation for the permanent dentition is a four-quadrant symbolic system in which, beginning with the central incisors, the teeth are numbered 1 through 8 (or more) in each arch. For example, the right maxillary first molar is designated as 6, and the left mandibular central incisor as Í1 .

The Palmer notation for the entire permanent dentition is as follows:

Tooth Numbering Systems (Permanent)

A two-digit system proposed by Fédération Dentaire Internationale (FDI)

Tooth Numbering Systems (Permanent)

Viktor Haderup of Denmark in 1891

devised a variant of the eight-tooth quadrant system in which plus (+) and minus (-) were used to differentiate between upper and lower quadrants and between right and left quadrants; in other words, +1 indicates the upper left central incisor and 1-indicates the lower right central incisor. Primary teeth were numbered as follows: upper right, 05+ to 01+; lower left, -01 to -05. This system is still taught in Denmark.5

Tooth Numbering Systems (Permanent)

cusp triangular ridge developmental groove

tubercle transverse ridge supplemental groove

cingulum oblique ridge pitridge fossa lobemarginal ridge sulcus

Tooth landmarks

A cusp is an elevation or mound on the crown portion of a tooth making up a divisional part of the occlusal surface

A tubercle is a smaller elevation on some portion of the crown produced by an extra formation of enamel. (These are deviations from the typical form.

A cingulum (Latin word for "girdle") is the lingual lobe of an anterior tooth. It makes up the bulk of the cervical third of the lingual surface. Its convexity mesiodistally resembles a girdle encircling the lingual surface at the cervical third

A ridge is any linear elevation on the surface of a tooth and is named according to its location (e.g., buccal ridge, incisal ridge, marginal ridge).

Marginal ridges are those rounded borders of the enamel that form the mesial and distal margins of the occlusal surfaces of premolars and molars and the mesial and distal margins of the lingual surfaces of the incisors and canines (Figures 1-10, A, and 1-11).

Triangular ridges descend from the tips of the cusps of molars and premolars toward the central part of the occlusal surfaces. They are so named because the slopes of each side of the ridge are inclined to resemble two sides of a triangle. They are named after the cusps to which they belong, for example, the triangular ridge of the buccal cusp of the maxillary first premolar.

When a buccal and a lingual triangular ridge join, they form a transverse ridge.

A transverse ridge is the union of two triangular ridges crossing transversely the surface of a posterior tooth

The oblique ridge is a ridge crossing obliquely the occlusal surfaces of maxillary molars and formed by the union of the triangular ridge of the distobuccal cusp and the distal cusp ridge of the mesiolingual cusp

Central fossae are on the occlusal surface of molars. They are formed by the convergence of ridges terminating at a central point in the bottom of the depression where there is a junction of grooves. Triangular fossae are found on molars and premolars on the occlusal surfaces mesial or distal to marginal ridges .They are sometimes found on the lingual surfaces of maxillary incisors at the edge of the lingual fossae where the marginal ridges and the cingulum meet.

A sulcus is a long depression or valley in the surface of a tooth between ridges and cusps, the inclines of which meet at an angle. A sulcus has a developmental groove at the junction of its inclines. (The term sulcus should not be confused with the term groove.)

A developmental groove is a shallow groove or line between the primary parts of the crown or root.

A supplemental groove, less distinct, is also a shallow linear depression on the surface of a tooth, but it is supplemental to a developmental groove and does not mark the junction of primary parts.

Buccal and lingual grooves are developmental grooves found on the

Pits are small pinpoint depressions located at the junction of developmental grooves or at terminals of those grooves. For instance, central pit is a term used to describe a landmark in the central fossa of molars where developmental grooves join .

A lobe is one of the primary sections of formation in the development of the crown. Cusps and mamelons are representative of lobes.

A mamelon is any one of the three rounded protuberances found on the incisal ridges of newly erupted incisor teeth.

Review of Tooth Morphology

Central Incisor Lateral Incisor

Facial/Labial Aspect

Proximal contacts Cervico-incisal location —

Mesial Incisal third Junction incisal/middle thirds

Distal Junction incisal/middle thirds Middle third

Mesioincisal angle Sharp right angle Slightly rounded

Distoincisal angle Slightly rounded Distinctly rounded

Mesial profile Straight Slightly rounded

Distal profile Nearly round Distinctly rounded

Mesiodistal width Comparatively wide Comparatively narrow

Pulp horn(s) 3 (facial view) Usually 2 (facial view)

Lobes 4 (Fig. 4-12, A) 4

Lingual Aspect Fig. 6-3 Fig. 6-14

Marginal ridges Moderate More prominent

Cingulum Moderately pronounced More prominent

Fossa Moderately deep Deep

Incisal Aspect Fig. 6-11 Fig. 6-18

Outline Triangular Ovoid

Labial Slightly convex More convex

Dimensions Table 6-1 Table 6-2

Crown length (cervico-incisal) 10.5 mm 9 mm

Crown diameter

Mesiodistal 8.5 mm 6.5 mm

Cervical 7.0 mm 5.0 mm

Labiolingual 7.0 mm 6.0 mm

Contour height 0.5 mm; Figs. 6-4, 6-5 0.5 mm; Fig. 6-13

Facial/lingual Both cervical third Both cervical third

Curvature at CEJ Table 6-1 Table 6-2

Mesial 3.5 mm 3.0 mm

Distal 2.5 mm 2.0 mmRoot Figs. 6-3, 6-5, 6-9, 6-10 Figs. 6-13, 6-19, 6-20Length 13.0 mm 13.0 mm

Pulp canal(s) 1Less frequent apical accessory canals

Chronology Tables 2-3, 6-1 Tables 2-3, 6-2Eruption 7-8 yr 8-9 yrRoot completed 10 yr 11 yrTooth Notations Topic 1 Topic 1Universal Right: 8; left: 9 Right: 7; left: 10International (FDI) Right: 11; left: 21 Right: 12; left: 22Palmer

Central Incisor Lateral Incisor

Facial/Labial Aspect

Symmetry Symmetrical bilaterally AsymmetricalProximal contacts

Mesial Incisal third Incisal third

Distal Incisal third Incisal third

Mesioincisal angles Sharp right angles Some rounding

Distoincisal angles Sharp right angles More rounded than mesioincisal angle

Curvature at CEJ Fig. 5-27, Table 7-1 Table 7-2

Mesial 3.0 mm 3.0 mm

Distal 2.0 mm 2.0 mm

Incisal Aspect

Incisal edge (ridge) Right angle to line bisecting cingulum

Distolingual twist to line bisecting cingulum

Central Incisor Lateral Incisor

Pulp horn(s) 1 or 0 Variable; more prominent

Lobes 4 4

Dimensions Table 7-1 Table 7-2Crown length (cervico-incisal) 9.0 mm 9.5 mm

Crown diameter

Mesiodistal 5 mm 5.5 mm

Cervical 3.5 mm 4.0 mm

Labiolingual 6.0 mm 6.5 mm

Contour height Less than 0.5 mm; Fig. 7-7 Less than 0.5 mm

Facial/lingual Both cervical third Both cervical third

Dimensions Table 7-1 Table 7-2

Length 12.5 mm 14.0 mm

Pulp (root) canal(s) Usually 1; 2 possible 1

Maxillary Incisors Mandibular Incisors

Central incisor wider than lateral incisor Lateral incisor wider than central incisor

Wider than mandibular central incisor Narrowest of incisor class

Marginal ridges and cingulum more prominent Marginal ridges and cingulum not prominent

Lingual fossa pronounced, often with a lingual pit Lingual fossa shallow without grooves or pits

Crown width greater mesiodistally than labiolingually

Crown width greater labiolingually than mesiodistally

Roots rounded in cross section Roots thin mesiodistally

Incisal edge labial to root axis Incisal edge lingual to root axis

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Maxillary Canine Mandibular Canine

Facial/Labial Aspect

Proximal contacts

Mesial Junction incisal/middle thirds Incisal third

Distal Middle third Middle third

Mesial Aspect Wider faciolingually Narrower, longer

Lingual Aspect Deeper lingual fossae Flat lingual surface

Marginal ridges Pronounced; 2 fossae Parallel or slightly converging

Cingulum Large, centered mesiodistally

Smaller, may be off center distally

Lingual pits, grooves Common None

Incisal Aspect Marked asymmetry of mesial/distal halves

Less symmetry; distal cusp ridge rotated

Incisal/Proximal Aspects Cusp tip may be at or labial to root axis line

Cusp tip lingual to root axis line

Maxillary Canine Mandibular CanineDimensionsMesiodistal 7.5 mm 7.0 mmLabiolingual 8.0 mm 7.5 mmCurvature at CEJ 2.5 mm (mesial) 1.0 mm (distal)Incisal-cervical 10.0 mm 11.0 mmContour height 0.5 mm Less than 0.5 mmFacial/lingual Both cervical third Both cervical thirdPulp horn(s) 1 1Lobes 4 4RootTerminal (number) 1 Maybe 2 Length 17 mm 16 mm

Chronology Maxillary Canine

Mandibular Canine

Eruption 11-12 yr 9-10 yrRoot completed 13-15 yr 12-14 yr

Tooth Notations

Universal Right: 6; left: 11

Right: 27; left: 22

International (FDI)

Right: 13; left: 23

Right: 43; left: 33

Palmer

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Max First Premolar Second Premolar

Facial/Buccal Aspect

Proximal contacts Mesial/distal: middle third Mesial/distal: middle third

Shoulders Prominent Narrow

Buccal cusp Tipped more to distal Not tipped

Cusp ridges Longer mesial ridge Similar

Cusp size, height Slightly wider, longer Shorter

Lingual Aspect Buccal profile visible Profile not visible

Mesial Aspect

Mesiomarginal groove Crosses marginal ridge Does not cross ridge

Mesial concavity Present Not present

Mesial root depression Present Present

Occlusal Aspect

Profile Hexagonal Ovoid

Central groove Long Short

Supplemental groves Usually not present Many; often present

Lobes 4 4

Pulp horn(s) 2 2

DimensionsCervico-occlusal 8.5 mm 8.5 mmCrown diameterMesiodistal 7.0 mm 7.0 mmCervical 5.0 mm 5.0 mmBuccolingual 9.0 mm 9.0 mmContour height Fig. 9-5 Fig. 9-19Facial/buccal crest Cervical third Cervical thirdLingual Middle third Middle thirdCurvature at CEJ Figs. 9-4, 9-5Mesial 1.0 mm 1.0 mmDistal 0.0 mm 0.0 mmLength of root 14.0 mm 14.0 mmGrooves Distinct, longitudinal No distinct groovesNumber of roots Usually 2 1 rootPulp canal(s) Often 2 Usually 1

Chronology Table 9-1 Table 9-2Eruption 10-11 yr 10-12 yrRoot completed 12-13 yr 12-14 yrTooth Notations Topic 1 Topic 1Universal Right, 5; left, 12 Right, 4; left, 13International (FDI) Right, 14; left, 24 Right, 15: left, 25Palmer

Mand First Premolar Mand Second Premolar

Facial/Buccal Aspect Figs. 10-2, 10-9 Figs. 10-13, 10-18

Proximal contacts Fig. 5-7 Fig. 5-7

Cervico-occlusal Mesial/distal: middle third Mesial/distal: middle third

Form Asymmetrical Bilaterally symmetrical

Lingual Aspect Fig. 10-3 Fig. 10-14

Buccal profile All buccal profile seen None seen

Cusp height Lingual less than buccal Buccal/lingual cusps nearly equal

Mesial Aspect Fig. 10-1 Fig. 10-15

Occlusal plane Tilted lingually Essentially horizontalTransverse ridge or buccal triangular ridge

Transverse ridge present (Fig. 10-1)

No transverse ridge present (Fig. 10-17)

Occlusal Aspect Figs. 10-6, 10-11 Fig. 10-17

Outline form Diamond-shaped Square

Cusps 2 (Fig. 10-1) 2 or 3 (Fig. 10-20)

Lobes 4 4 or 5

Mand First Premolar Mand Second PM

Dimensions Table 10-1 Table 10-2Crown length (cervico-occlusal) 8.5 mm 8.0 mm

Crown diameter

Mesiodistal 7.0 mm 7.0 mm

Cervical 5.0 mm 5.0 mm

Buccolingual 7.5 mm 8.0 mm

Contour height Figs. 5-27, 10-4 Fig. 10-16

Facial Cervical third Middle third

Lingual Middle third Middle third

Curvature at CEJ Table 10-1 (cervical line) Table 10-2

Mesial 1.0 mm 1.0 mm

Distal 0.0 mm 0.0 mm

Root Table 10-1 Table 10-2

Length 14.0 mm 14.5 mm

Pulp canal(s) 1 1

Pulp horn(s) 1 2

Chronology Table 2-3; Table 10-1 Table 2-3; Table 10-2

Eruption 10-12 yr 11-12 yr

Root completed 12-13 yr 13-14 yr

Tooth Notations Topic 1 Topic 1

Universal Right: 28; left: 21 Right: 29; left: 20

International (FDI) Right: 44; left: 34 Right: 45; left: 35

Palmer

Maxillary Premolars Mandibular PremolarsFacial/Buccal AspectCrowns are trapezoidal* Crowns are trapezoidalMesial Aspect: Fig. 4-16Crowns are trapezoidal Crowns are rhomboidal

Buccal and lingual cusps are almost equal in height

Lingual cusps comparatively much shorter than maxillary lingual cusps Lingual cusp tips may be lingual to the root

Two major cusps of almost equal size and prominence

Buccal and lingual cusps of uneven height and prominence

*A trapezoid is a four-sided plane figure having two sides parallel. A rhomboid is an oblique-angled parallelogram with only the opposite sides equal

Maxillary Molars: Type Traits and Other Characteristics General Characteristics of All Molars

Height of Contour: Buccal crest is at cervical third; lingual crest is at middle third of crown

Proximal Contacts: Cervical-occlusal location of mesial contact is at middle third (toward occlusal third); distal contact is at middle third, slightly toward cervical third Crown Dimensions: Crowns are wider mesiodistally than cervico-occlusal height

Characteristic First Molar Second Molar Third MolarFacial/Buccal Aspect Figs. 11-4, 11-15 Figs. 11-19, 11-24 Figs. 11-28, 11-33

Dimensions Widest of three Middle in width Smallest of three

Distobuccal cusp height

Equals mesiobuccal cusp height

Slightly less than mesiobuccal

Much less than mesiobuccal

Lingual Aspect Fig. 11-6 Fig. 11-20 Fig. 11-29

Distolingual cusp Largest distolingual cusp

Smaller width/height Usually missing

Lingual root Widest mesiodistally Narrower Narrowest

Occlusal Aspect Fig. 11-12 Fig. 11-23 Fig. 11-32

Crown form Trapezoid to rhomboid More rhomboidal Heart-shaped

Lobes 5 4 3 or 4

Characteristic First Molar Second Molar Third Molar

Dimensions Table 11-1 Table 11-2 Table 11-3Crown length (cervico-occlusal) 7.5 mm 7.0 mm 6.5 mm

Crown diameter

Mesiodistal 10.0 mm 9.0 mm 8.5 mm

Cervical 8.0 mm 7.0 mm 6.5 mm

Buccolingual 11.0 mm 11.0 mm 10.0 mm

Contour height 0.5 mm; Fig. 11-13

0.5 mm; Fig. 11-21

0.5 mm; Fig. 11-30

Buccal crest Cervical third Cervical third Cervical third

Lingual crest Middle third Middle third Middle third

Curvature at CEJ Table 11-1 Table 11-2 Table 11-3

Mesial 1.0 mm 1.0 mm 1.0 mm

Distal 0.0 mm 0.0 mm 0.0 mm

Characteristic First Molar Second Molar Third Molar

Root Table 11-1 Table 11-2 Table 11-3

Length, buccal 12.0 mm 11.0 mm 11.0 mm

Length, lingual 13.0 mm 12.0 mm

Chronology Table 11-1 Table 11-2 Table 11-3

Eruption 6 yr 12-13 yr 17-21 yr

Root completed 9-10 yr 14-16 yr 18-25 yr

Tooth Notations Topic 1 Topic 1 Topic 1

Universal Right: 3; left: 14 Right: 2; left: 15 Right: 1; left: 16International (FDI)

Right: 16; left: 26

Right: 17; left: 27

Right: 18; left: 28

Palmer

Characteristic Mand First Molar Second Molar Third Molar

Facial/Buccal Aspect Figs. 12-4, 12-14 Figs. 12-18, 12-23 Figs. 12-29, 12-34

Crown size Largest; widest mesiodistally Smaller Smallest

Cusps5 Cusps: mesiobuccal, distobuccal, mesiolingual, distolingual, distal

4 Cusps: mesiobuccal, distobuccal, mesiolingual, distolingual

4 Cusps: mesiobuccal, distobuccal, mesiolingual, distolingual

Groove(s)/pit(s) 1 Mesiobuccal ± pit, 1 distobuccal 1 Buccal ± pit 1 Buccal ± pit

Root(s) Figs. 12-4, 12-14 Fig. 12-18 Fig. 12-29

Widely separated; nearly vertical

Close together, parallel; distally inclined

Most short, fused, less inclination

Lingual Aspect Fig. 12-6 Fig. 12-19 Fig. 12-30

Cervix Crown narrower Less narrow Less narrow

Occlusal Aspect Fig. 12-2 Fig. 12-25 Fig. 12-33

Crown form Quadrilateral or hexagonal, pentagonal Quadrilateral or rectangular Quadrilateral or ovoid

Lobes 5 (Fig. 4-12, C) 4 4

Pulp horn(s) 5 4 4

Dimensions Table 12-1 Table 12-2 Table 12-3Crown length (cervico-occlusal) 7.5 mm 7.0 mm 7.0 mm

Crown diameter

Mesiodistal 11.0 mm 10.5 mm 10.0 mm

Cervical 9.0 mm 8.0 mm 7.5 mm

Buccolingual 10.5 mm 10.0 mm 9.5 mm

Contour height Figs. 12-7, 12-12 Figs. 12-20, 12-21 Figs. 12-31, 12-32

Buccal crest Cervical third, 0.5 mm

Cervical third, 0.5 mm

Cervical third, 0.5 mm

Lingual crest Middle third, 1.0 mm

Middle third, 1.0 mm

Middle third, 1.0 mm

Curvature at CEJ Figs. 5-27, 12-12 Fig. 12-12 Fig. 12-32

Mesial 1.0 mm 1.0 mm 1.0 mmDistal 0.0 mm 0.0 mm 0.0 mmRoot Fig. 12-7 Fig. 12-21 Fig. 12-31

Length 14.0 mm; Table 1-1 13.0 mm; Table 1-1 11.0 mm; Table 1-1

ChronologyEruption 6-7 yr 11-13 yr 17-21 yr

Root complete 9-10 yr 14-15 yr 18-25 yr

Tooth Notations Topic 1 Topic 1 Topic 1

Universal Right: 30; left: 19 Right: 31; left: 18 Right: 32; left : 17

International (FDI) Right: 46; left: 36 Right: 47; left: 37 Right: 48; left: 38

Palmer

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largest, longest, and strongest root?Palatal root-3rd largest on maxilla behind canine and 2nd PM-most palatal roots have a lingual depression

Sharpest cusp? Distobuccal cuspShortest root? distobuccal rootLargest and tallest cusp? mesiolingual cusp

Cusps from largest to smallest mesiolingual, mesiobuccal, distobuccal, distolingual, and cusp of Carabelli-[distobuccal and distolingual may be switched]

trigon triangular arrangement of mesiobuccal, distobuccal, and mesiolingual cusps

fossae size from largest to smallest central, distal, mesial triangular, and distal triangular [it is the same on max 2nd molar]

2 major fossae central and distal2 minor fossae mesial triangular and distal triangularlargest and deepest fossae? central

developmental grooves5 of them-central, buccal, distal oblique, lingual, and transverse groove of the oblique ridge-distal oblique and lingual sometimes combined as distolingual groove

What cusp tips are visible from the buccal?Mesiobuccal, distobuccal, & mesiolingual

-distolingual is NOT visible

What does t he buccal groove parallel? the long axis of the distobuccal rootDoes the buccal groove usually have a pit? no

root cross section roughly ovoid-buccodistal will be more rounded than mesial

Is the cusp of carabelli every present unilaterally [just on one side]? no

Occlusally, where is the distal proximal contact located? At the center of the crownexception to the rule

Which is located closer to the cervical line: the mesial bifurcation or the buccal bifurcation?

mesial bifurcation[shorter furcation = longer root, which increases anchorage]

mesial furcation < buccal furcation < distal furcationMost apically located bifurcation? distal bifurcationHow many canals in the mesial root? 2Which cusps are visible from the distal? all 4

Terms DefinitionsEvidence of calcification 3 yrsenamel completed 7yrseruption 12 yrsroot completed 15yrs

Which tooth is the oblique ridge less prominent? max 2nd molar

which cusp is less developed on the 2nd max molar than the 1st. DLi

How many roots on a max 2nd molar? 3; MB,DB, lingual

Which root is the longest? LingualWhich root is the shortest? DBuWhich root is usually straighter? DBu# roots 3# pulp horns 4#cusps 4# of developmental lobe 4

What is the occlusal outline shape? rhomboidal to heart shaped

THE DECIDUOUS DENTITION

-It is also known as the primary, baby, milk or lacteal dentition.

A. Overview. You will recall that we are diphyodont, that is, with two sets of teeth.

The term deciduous means literally 'to fall off.'

http://www.uic.edu/classes/orla/orla312/DeciduousDent.htm

-There are twenty deciduous teeth that are classified into three classes.

Do you recall the term heterodont?

There are ten maxillary teeth and ten mandibular teeth. The dentition consists of incisors, canines and molars.

-The dental formula is as follows.

-The notation for deciduous teeth is A though J, K through T. It is 'clockwise'just like it is for permanent teeth as you look at the patient from in front.

B. Role in development

A person 70 years old will have spent 91% of his/her life chewing on permanent teeth, but only 6% of his/her chewing career with the deciduous dentition.

-Although the deciduous teeth are in time replaced by the succedaneous teeth, the deciduous teeth play a very important role in the proper alignment, spacing, and occlusion of the permanent teeth.

-The deciduous incisor teeth are functional in the mouth for approximately five years, while the deciduous molars are functional for approximately nine years. They therefore have considerable functional significance. When second deciduous molars are lost prematurely, this can be very detrimental to the alignment of the permanent teeth.

Development of the Deciduous Dentitionhttp://what-when-how.com/dental-anatomy-physiology-and-occlusion/development-and-eruption-of-the-

teeth-dental-anatomy-physiology-and-occlusion-part-1/

II. Formation and Eruption of Deciduous Teeth.

-Calcification begins during the fourth month of fetal life. By the end of the sixth month, all of the deciduous teeth have begun calcification. -Clinical hint: good nutrition is essential. -By the time the deciduous teeth have fully erupted (two to two and one half years of age), calcification of the crowns of permanent teeth is under way. First permanent molars have begun calcification at the time of birth. Clinical hint: with deciduous molars, extract with caution. -Here are some things to know about eruption patterns: (1) Teeth tend to erupt in pairs. (2) Clinical hint: look for asymmetry. Take an X-ray film as required.

(2) Usually, lower deciduous teeth erupt first. Congenitally missing deciduous teeth is infrequent. Usually, the lower deciduous central incisors are the first to erupt thus initiating the deciduous dentition. The appearance of the deciduous second molars completes the deciduous dentition by 2 to 2 1/2 years of age.

-Note :Eruption dates are variable. Some infants get them early, others do so late. If the teeth are unduly early or late, you should inquire about siblings, or the parents themselves. Timing of eruption 'runs in families.'

Note : Deciduous teeth shed earlier and permanent teeth erupt earlier in girls. : The orderly pattern of eruption and their orderly replacement by permanent teeth is important.

The textbook order for eruption of the deciduous teeth is as follows:

(1) Central incisor.........Lower 6 ½ months, Upper 7 ½ months (2) Lateral incisor.........Lower 7 months, Upper 8 months (3) First deciduous molar...Lower 12-16 months, Upper 12-16 months (4) Deciduous canine........Lower 16-20 months, Upper 16-20 months (5) Second deciduous molar..Lower 20-30 months, Upper 20-30 months

III. Root Formation and ObliterationA. In general, the root of a deciduous tooth is completely

formed in just about one year after eruption of that tooth into the mouth.

B. The intact root of the deciduous tooth is short lived. The roots remain fully formed only for about three years.

C. The intact root then begins to resorb at the apex or to the side of the apex, depending on the position of the developing permanent tooth bud.

D. Anterior permanent teeth tend to form toward the lingual of the deciduous teeth, although the canines can be the exception. Premolar teeth form between the roots of the deciduous molar teeth.

IV. The Transition from the Deciduous to the Permanent Dentition.

A. The transition begins with the eruption of the four first permanent molars, and replacement of the lower deciduous central incisors by the permanent lower central incisors.

B. Complete resorption of the deciduous tooth roots permits exfoliation of that tooth and replacement by the permanent (successional) teeth.

C. The mixed dentition exists from approximately age 6 years to approximately age 12 years. In contrast, the intact deciduous dentition is functional from age 2 - 2 /2 years of age to 6 years of age. D. The enamel organ of each permanent anterior tooth is connected to the oral epithelium via a fibrous cord, the gubernaculum. The foramina through which it passes can be seen in youthful skulls.

V. Differences Between the Deciduous and Permanent TeethA. Deciduous teeth are fewer in number and smaller in size but the deciduous molars are wider mesiodistally than the premolars. The deciduous anteriors are narrower mesiodistally than their permanent successors. B. Their enamel is thinner and whiter in appearance. Side by side, this is obvious in most young patients. C. The crowns are rounded. The deciduous teeth are constricted at the neck (cervix). D. The roots of deciduous anterior teeth are longer and narrower than the roots of their permanent successors. E. The roots of deciduous molars are longer and more slender than the roots of the permanent molars. Also, they flare greatly.

F. The cervical ridges of enamel seen on deciduous teeth are more prominent than on the permanent teeth. This 'bulge' is very pronounced at the mesiobuccal of deciduous first molars. G. Deciduous cervical enamel rods incline incisally/occlusally.

MORPHOLOGY OF THE DECIDUOUS TEETH

The primary anteriors are morphologically similar to the permanent anteriors. -The incisors are relatively simple in their morphology. -The roots are long and narrow. -When compared to the permanent incisors, the mesiodistal dimension is relatively larger when compared to axial crown length. In other words, they look 'squatty,' especially when worn. -At the time of eruption, mamelons are not present in deciduous incisors. -They are narrower mesiodistally than their permanent successors.

VI. Deciduous Anterior Teeth.

VII. Maxillary First Deciduous Molar.

-The notation is B or I. -It looks a bit like an upper 1st premolar. -There are three roots. -It has a strong bulbous enamel bulge that protrudes buccally at the mesial. -It is the smallest of the deciduous molars in crown height and in the mesiodistal dimension.

VIII. Maxillary Second Deciduous Molar.

The notation is A or J. -It looks like a first permanent molar -There are three roots. -Usually it has four well developed cusps. -It is somewhat rhomboidal in outline. -They often have the Carabelli trait. -Studies have shown that the shape the maxillary first permanent molar strongly resembles that of the adjacent deciduous second molar.

Upper Row: Lower First Molar Lower Row: Lower First Molar

-The notation is L or S. -This tooth doesn't resemble any other tooth. It is unique unto itself. -There are two roots. -There is a strong bulbous enamel bulge buccally at the mesial. -A favorite National Board question asks that you know about the cusps. The thing to remember is that the mesiolingual cusps on this tooth is the highest and largest of the cusps.

IX. Mandibular First Deciduous Molar.

X. Mandibular Second Deciduous Molar

The notation is K or T. -This tooth resembles the lower first permanent molar that is distal to it in the dental arch. -There are two roots and five cusps. The three buccal cusps are all about the same size. This is in contrast to the lower first molar where the 'distal' cusp is smaller that the mesiobuccal and distobuccal cusps. -The distal of the three buccal cusps may be shifted of onto the distal marginal ridge.

Summary

-Upper molars have three roots, lowers have two roots. -Upper and lower second deciduous molars resemble first permanent molars in the same quadrant. -Upper first deciduous molars vaguely resemble upper premolars. -Lower first deciduous molars are odd and unique unto themselves. -First deciduous molars (upper and lower) have a prominent bulge of enamel on the buccal at the mesial. These help in determining right and left. (Incidentally, there is a somewhat similar bulge of enamel seen on the permanent lower second molar. It is helpful in determining right and left.)