Development and Development and Morphology of Morphology of

the Primary the Primary TeethTeeth

LIFE CYCLE OF THE TOOTHInitiation (Bud Stage)Proliferation (Cap Stage)Histodifferentiation and Morphodifferentiation ( Bell Stage)AppositionCalcificationEARLY DEVELOPMENT AND CALCIFICATION OF THE ANTERIOR PRIMARY TEETHEARLY DEVELOPMENT AND CALCIFICATION OF THE POSTERIOR PRIMARY TEETH AND THE FIRST PERMANENT MOLARDEVELOPMENT OF THE PRIMARY DENTITIONDEVELOPMENT OF PERMANENT DENTITION

MORPHOLOGY OF INDIVIDUAL PRIMARY TEETHMaxillary Central IncisorMaxillary Lateral IncisorMaxillary CanineMandibular Central IncisorMandibular Lateral IncisorMandibular CanineMaxillary First MolarMaxillary Second MolarMandibular First MolarMandibular Second MolarMORPHOLOGIC DIFFERENCES BETWEEN PRIMARY AND PERMANENT TEETHSIZE AND MORPHOLOGY OF THE PRIMARY TOOTH PULP CHAMBER

review of development of teeth: An accurate chronology of primary tooth

calcification is of clinical significance to dentist.

Tetracycline pigmentation, developmental enamel defects, & generalized hereditary

anomalies can be explained if calcification schedule’s known.

Objective:

brief discussion of primary teeth morphology: is also appropriate before considering

restorative procedures for children.

LIFE CYCLE OF THE TOOTHLIFE CYCLE OF THE TOOTH

INITIATION INITIATION (BUD STAGE)(BUD STAGE)

Evidence of development of human tooth can be observed as early as sixth week of embryonic life.

Cells in basal layer of oral epithelium proliferate at a more rapid rate than do adjacent cells.

INITIATION (BUD STAGE)

This result in thickening which called primordium of the ectodermal portion of the teeth & what results is called dental lamina.

At the same time, 10 round or ovoid swellings occur in each jaw in position to be occupied by primary teeth.

Life cycle of the tooth. A, Initiation (bud stage)

Certain cells of basal layer begin to proliferate at a more rapid rate than do adjacent cells which contain entire growth potential of teeth.

PROLIFERATIOPROLIFERATION (CAP STAGE)N (CAP STAGE)

Proliferation of cells continues during cap stage.

As a result of unequal growth in different parts of bud, a cap is formed.

PROLIFERATION (CAP STAGE)

B, Proliferation (cap stage)

A shallow invagination appears on deep surface of bud.

peripheral cells of cap later form outer & inner enamel epithelium.

HISTODIFFERENTIATIONHISTODIFFERENTIATION&&

MORPHODIFFERENTIATIOMORPHODIFFERENTIATIONN

(BELL STAGE)(BELL STAGE)

• epithelium continues to invaginate & deepen until enamel organ takes on shape of a bell.

HISTODIFFERENTIATION AND MORPHODIFFERENTIATION

(BELL STAGE)

C, Histodifferentiation and morphodifferentiation (bell stage)

• It is during this stage that there is a differentiation of cells of dental papilla into odontoblasts & of cells of inner enamel epithelium into ameloblasts.

APPOSITIONAPPOSITION

is result of a layerlike deposition of a tissue matrix is deposited by formative cells, ameloblasts, & odontoblasts.

APPOSITION

formative cells begin their work at specific sites referred to as growth centers as soon as blueprint, dentinoenamel junction, is completed.

D, Apposition and calcification

CALCIFICATIONCALCIFICATION

Calcification (mineralization) takes place following matrix deposition & involves precipitation of inorganic calcium salts within deposited matrix.

CALCIFICATION

EARLY DEVELOPMENT & EARLY DEVELOPMENT & CALCIFICATION OF THECALCIFICATION OF THE

ANTERIOR PRIMARY TEETHANTERIOR PRIMARY TEETH

omorphologic development occurs at approximately 11 weeks in utero.

omaxillary & mandibular central incisor crowns appear identical at this early stage as tiny, hemispheric, moundlike.olateral incisors begin to develop

morphologic characteristics between 13 & 14 weeks.ocanines develop between 14 & 16 weeks.

oCalcification of central incisor begins at approximately 14 weeks in utero, with maxillary central incisor slightly preceding lower central.oinitial calcification of lateral incisor

occurs at 16 weeks & of canine at 17 weeks.

EARLY DEVELOPMENT & EARLY DEVELOPMENT & CALCIFICATION OF THE CALCIFICATION OF THE

POSTERIOR PRIMARY TEETH POSTERIOR PRIMARY TEETH & THE FIRST PERMANENT & THE FIRST PERMANENT

MOLARMOLAR

maxillary first primary molar appears macroscopically at 12'/2 weeks in utero. as early as 151/2 weeks apex of mesiobuccal cusp may undergo calcification. At approximately 34 weeks entire occlusal surface is covered by calcified tissue. At the time of birth, calcification includes roughly three fourths of occlusal gingival height of crown.

maxillary second primary molar also appears macroscopically at about 121/2 weeks in utero. calcification of mesiobuccal cusp as early as 19 weeks. At birth, calcification extends occlusogingivally to include approximately one fourth of height of crown.

mandibular first primary molar initially becomes evident macroscopically at about 12 weeks in utero. Calcification may be observed as early as 151/2 weeks at apex of mesiobuccal cusp. At birth, a completely calcified cap covers occlusal surface.

mandibular second primary molar also becomes evident macroscopically at 121/2 weeks in utero. calcification may begin at 18 weeks. At the time of birth, five centers have coalesced & only a small area of uncalcified tissue remains in middle of occlusal surface.

There are sharp conical cusps, angular ridges, & a smooth occlusal surface, all of which indicate that calcification is incomplete at birth. Thus there is a calcification sequence of central incisor, first molar, lateral incisor, canine, and second molar.

adjacent second primary and first permanent molars undergo identical patterns of morphodifferentiation but at different times & that initial development of first permanent molar occurs slightly later. first permanent molars are uncalcified before 28 weeks of age; at any time thereafter calcification may begin. Some degree of calcification is always present at birth.

DEVELOPMENT OF THE PRIMARY DENTITION

o Deciduous dentition is completed at the age of 2- 2 ½ years

MIXED DENTITION STAGEIt is the stage wherein you can see both primary

and permanent teeth “clinically” inside the mouth of a child.

At age of 12, All should be permanent.

STAGES OF MIXED DENTITION Early Mixed Dentition - 6 to 8 years oldFirst molarsCentral incisorsLateral incisorsMiddle mixed dentition - 8 to 10 years oldLower caninesUpper and lower first premolarsLate mixed dentition - 10 to 12 years oldUpper caninesUpper and lower second premolarsSecond molars

DEVELOPMENT OF PERMANENT DENTITION

Processes that would occur simultaneously:As the permanent tooth would erupt, it will go to the occlusal surface. Its root would

continue to develop and elongate while the roots of the deciduous predecessors would

resorb. As the permanent teeth would erupt, it will cause an increase in height of

the alveolar bone.

SEQUENCE OF ERUPTION OF THE PERMANENT DENTITION

Maxillary teeth6 – 1 – 2 – 4 – 5 – 3 – 7  Mandibular teeth6 – 1 – 2 – 3 – 4 – 5 – 7

MORPHOLOGY OF MORPHOLOGY OF INDIVIDUAL PRIMARY TEETHINDIVIDUAL PRIMARY TEETH

MAXILLARY CENTRAL INCISOR

• mesiodistal width crown mx CI > cervicoincisal length.

• labial surface is smooth.• root of incisor is cone shaped with tapered

sides.

Primary right anterior teeth, labial aspect. A, Maxillary central incisor. B, Maxillary lateral incisor. C, Maxillary canine. D, Mandibular central incisor. E, Mandibular lateral incisor. F, Mandibular canine.

Primary right anterior teeth, lingual aspect. A, Maxillary central incisor. B, Maxillary lateral incisor. C, Maxillary canine. D, Mandibular central incisor. E, Mandibular lateral incisor. F, Mandibular canine.

MAXILLARY LATERAL INCISOR

o outline of mx LI is similar to that of CI, but crown is smaller in all dimensions.

o length of crown from cervical to incisal edge > mesiodistal width.

o root outline is similar to that of CI but is longer in proportion to crown.

MAXILLARY CANINE

crown of mx C is more constricted at cervical region than are incisors, & incisal & distal surfaces are more convex.

C has a long, slender, tapering root that is more than twice length of crown. root is usually inclined distally, apical to middle third.

MANDIBULAR CENTRAL INCISOR

md CI is smaller than mx CI, but its labiolingual measurement is usually only 1 mm less.

labial aspect presents a flat surface without developmental grooves.

root is approximately twice length of crown.

MANDIBULAR LATERAL INCISOR

outline of md LI is similar to that of CI but is somewhat larger in a dimensions except labiolingually.

lingual surfa may have greater concavity between margin ridges.

incisal edge slopes toward distal aspe of tooth.

MANDIBULAR CANINE

form of md C is similar to that of mx C, with a few exceptions.

crown is slightly shorter, & root may be as much as 2 mm shorter than that of mx C.

md C is not as large labiolingually as its maxillary opponent.

MAXILLARY FIRST MOLAR

mesiolingual cusp is largest & sharpest. buccal surface is smooth, with little evidence

of developmental grooves. three roots are long, slender, & widely

spread.

Primary right molars, buccal aspect. A, Maxillary first molar. B, Maxillary second molar. C, Mandibular firs molar. D, Mandibular second molar.

Primary right molars, lingual aspect. A, Maxillary first molar. B, Maxillary second molar. C, Mandibular firs molar. D, Mandibular second molar.

Primary right molars, mesial aspect. A, Maxillary first molar. B, Maxillary second molar. C, Mandibular first molar. D, Mandibular second molar.

MAXILLARY SECOND MOLAR

• There is considerable resemblance between mx primary second molar & mx 1 PM.

• There are two well-defined buccal cusps, with a developmental groove between them.

• crown of 2M is larger than that of 1 M.• roots are longer & heavier than those of 1

primary molar, & lingual root is large & thick compared with other roots.

Primary right molars, buccal aspect. A, Maxillary first molar. B, Maxillary second molar. C, Mandibular firs molar. D, Mandibular second molar.

Primary right molars, lingual aspect. A, Maxillary first molar. B, Maxillary second molar. C, Mandibular firs molar. D, Mandibular second molar.

• lingual surface has three cusps:1- a mesiolingual cusp that is large & well

developed,2- a distolingual cusp, &3- a third & smaller supplemental cusp (cusp of

Carabelli).

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; DTF, distal triangular fossa; FC, fifth cusp; LDG, lingual developmental groove; MBC, mesiobuccal cusp; MBDG, mesiobuccal developmental groove; MLC, mesiolingual cusp; MP, mesial pit; MTF, mesial triangular fossa; OR, oblique ridge.

Primary right molars, occlusal aspect. A, Maxillary first molar. B, Maxillary second molar. C, Mandibular first molar. D, Mandibular second molar.

MANDIBULAR FIRST MOLAR

oUnlike other primary teeth, 1 primary molar does not resemble any of permanent teeth.

omesial outline of tooth, when viewed from buccal aspect, is almost straight from contact area to cervical region.

odistal area of tooth is Shorter than mesial area.

o When tooth is viewed from mesial aspect, there is an extreme curvature buccally at cervical third.

o mesial root, when viewed from mesial aspect, does not resemble any other primary root. end of root is flat & almost square.

MANDIBULAR SECOND MOLAR

md 2 M resembles md 1 permanent molar, except that primary tooth is smaller in all its dimensions.

primary second molar, when viewed from occlusal surface, appears rectangular

roots of primary second molar are long & slender, with a characteristic flare mesiodistally in middle & apical thirds.

MORPHOLOGIC MORPHOLOGIC DIFFERENCES BETWEEN DIFFERENCES BETWEEN

PRIMARY AND PERMANENT PRIMARY AND PERMANENT TEETHTEETH

1. crowns of primary teeth are wider 2. roots of primary anterior teeth are narrow &

long compared with crown width & length.

3. roots of primary molars are relatively longer & more slender than roots of permanent teeth.4. cervical ridge of enamel at cervical third of anterior crowns is much more prominent labially & lingually in primary.

5. crowns & roots of primary molars are more slender mesiodistally at cervical third.6. cervical ridge on buccal aspect of primary molars is much more definite, particularly on mx & md 1 M.

7. buccal & lingual surfaces of primary molars are flatter above cervical curvatures, which makes occlusal surface narrower.8. primary teeth are usually lighter in color.

SIZE AND MORPHOLOGY OF SIZE AND MORPHOLOGY OF THE PRIMARY TOOTH PULP THE PRIMARY TOOTH PULP

CHAMBERCHAMBER

Considerable individual variation exists in size of pulp chamber & pulp canal of primary teeth.

Immediately after eruption of teeth pulp chambers are large, & in general they follow outline of crown. pulp chamber decreases in size as age increases & under influence of function & of abrasion of occlusal & incisal surfaces of teeth.

it is suggested that dentist examine critically bite-wing radiographs of child. Just as there are individual differences in morphology of crowns & size of pulp chamber.

It should be remembered, however, that radiograph will not demonstrate completely extent of pulp horn into cuspal area.

Thank you

Rostamkhani Simin