Morphology Of Deciduous Dentition

MORPHOLOGY OF DECIDUOUS TEETH

Dental Anatomy Dent 201 Summer semester 2005/2006

Deciduous dentition Set traits ● ● ●

Smaller in size Smaller crown height/tooth length ratio Greater crown width/height ratio

Set traits ●

More bulging B & L cervical ridges  Constricted cervix

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Buccal cervical ridges on deciduous molars  Occlusal aspect: constricted occlusal table

Deciduous dentition ❧ Set traits ●

Molar roots • More slender & relatively longer • More bowed & flared outward • Shorter root trunk

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Milk-white in color Enamel is thinner & pulp chamber is large Some class, arch & type traits in permanent dentition are applied to deciduous dentition Only new traits will be discussed

Deciduous incisors ❧ Eruption ● ●

Mandibular before maxillary incisors Central before lateral incisors

❧ No mamelons, labial grooves or lobes

Maxillary Central incisor ❧ The only incisor with MD breadth > crown height ❧ M & esp. D profiles overhang root profiles ❧ No labial grooves, depressions or lobes ❧ Cingulum ● ●

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Bulging & more incisally located May extend further toward the incisal edge – lingual ridge Unmarked by pits or grooves

❧ MRs are clearly evident

Maxillary Central incisor ❧ Constricted cervix from all aspects ❧ In proximal surfaces CL is more convex incisally ❧ Conical root with rounded apex ❧ Diamond-shaped from incisal aspect

Maxillary lateral incisor ❧ Much smaller than central ❧ M & D profiles are more in line with root profiles ❧ Distal incisal angle is more rounded ❧ Labial surface is more convex MD ❧ Lingual fossa is deeper ❧ MRs more prominent ❧ CL is similar to that of central ❧ Rounded from incisal aspect

Mandibular central incisor ❧ Bilaterally symmetrical ❧ 90 degree MI & DI angles ❧ Incisal margin is horizontal ❧ Prominent cingulum with lingual margin extending incisally ❧ MRs are less marked than those of max. incisors ❧ Lingual fossa is shallower

Mandibular central incisor ❧ Labial surface is flat MD ❧ CL is similar to that of Max. incisors ❧ Root ● ●

3 times the height of the crown Narrow & conical with pointed apex

Mandibular lateral incisor ❧ Incisal edge slopes distally ❧ DI angle is rounded ❧ D profile is more rounded ❧ Greater crown height/MD ratio than mand. central ❧ LL diameter > MD

Mandibular lateral incisor ❧ Cingulum, fossa & MRs are similar to those of mand. Central ❧ Root ● ● ●

Narrow & conical Apex has D inclination D surface has narrow vertical depression

Maxillary canine ❧ MD width > crown height ❧ Labial or lingual views: diamond in shape ❧ M & D profiles overhang root’s ❧ HOCs are much near the cervix than in permanent ❧ Labial & lingual cervical 1/3s are markedly convex ❧ MR prominence is related to race ● ●

Minimal in Caucasians Prominent in Mongoloid

❧ No labial ridge or depressions

Mandibular canine ❧ Crown height > MD width ❧ Less cervically converging M & D profiles ❧ Labial or lingual aspects: arrow in shape ❧ No labial ridge or grooves ❧ HOCs are much near the cervix than in permanent ❧ LL diameter < that of deciduous max. canine ❧ Less prominent cingulum or MRs & shallower fossae than in deciduous max. canine

Maxillary 1st molar ❧ Most atypical of all primary or permanent molars ❧ Intermediate between a premolar & a molar ❧ Smallest molar in all but BL diameter

Maxillary 1st molar ❧ Cusps ●

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Bicusped (only MB & ML cusp are present) A small DB cusp is frequently present on the D cusp ridge of the MB cusp Parastyle on the M ridge of MB cusp DL cusp rarely occurs In some cases, a nodular tubercle on the L portion of the D MR resembles a DL cusp

Maxillary 1st molar ❧ Buccal aspect ● ●

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MD diameter >> crown height M part is higher OC than D because it is more projected cervically onto the root area Marked cervical constriction Root • Very little root trunk • 3 roots strongly divergent • L root is midway between the 2 B roots

Maxillary 1st molar ❧Mesial aspect ● ●

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Mesial marginal groove B HOC is more cervically located than L Buccal cervical ridge is more prominent in 1st molars than in 2nd Roots • B roots are straight & buccally directed • L root is banana shaped with strong B curved apical 1/3

Maxillary 1st molar ❧ Occlusal aspect ● ● ● ● ● ● ● ● ●

Trapezoidal M & D profiles are straight & slightly L convergent B cusp > L B triangular ridge more prominent than L B groove separates DB cusp from MB Central pit Central groove Transverse ridge (oblique ridge?) between B groove & D MR H-shaped pit/groove pattern • Central groove • Triangular supplemental grooves

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M & D marginal grooves

Maxillary 2nd molar ❧ Morphologically considered a model for the permanent 1st maxillary molar ❧ Allows prediction of what the 1st maxillary molar will look like ❧ This concordance is called isomorphy ❧ Set traits ● ● ● ●

Cervical constriction Cervical 1/3 bulging Little root trunk Roots thinner & divergent

Mandibular 1st molar ❧ Molariform unlike max. 1st ❧ 4-cusped tooth ❧ Buccal aspect ● ● ●

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2 cusp: MB & DB M half > D half M half projects more occlusally & occupies 2/3s of crown area M profile is straight D profile is curved and overhanging CL inclines downward from D to M Roots • 2 divergent roots; M & D • M is longer

Mandibular 1st molar ❧ Lingual aspect ● ●

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2 cusps: ML & DL ML cusp is conical & larger than DL Outlines of B cusps are visible CL is more straight & horizontal than that of the B aspect

Mandibular 1st molar ❧ Mesial aspect ● ●

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Buccal cervical ridge (BCR) From MB cusp tip a straight incline to BCR Transverse ridge connecting MB & ML M MR is high & prominent Mesial marginal groove separates M MR from ML cusp ridge CL is convex occlusally & lower on the B end Root • Extremely broad BL (sometimes as broad as the crown) • Frequently bifid apex

Mandibular 1st molar ❧ Distal aspect ●

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All 4 cusps & M root profiles are visible B profile is less bulging than from mesial aspect D MR is lower and less prominent than M MR CL is more straight & horizontal than that of M aspect

Mandibular 1st molar ❧ Occlusal aspect ● ● ●

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Without the BCR, it is rectangular BL width is grater from M than D MB cusp is the largest, followed by ML, DB & DL M Transverse groove, interrupted by Central groove; extends from M pit to central pit M pit • 2 supplemental grooves; of which ML crosses M MR

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Central pit B& L grooves Often a D pit

Maxillary 2nd molar ❧ Morphologically considered a model for the permanent 1st mandibular molar ❧ Allows prediction of what the 1st mandibular molar will look like ❧ This concordance is called isomorphy ❧ Set traits ● ● ● ●

Cervical constriction Cervical 1/3 bulging Little root trunk Roots thinner & divergent

Deciduous teeth - size & eruption Tooth

Crown height

MD crown BL crown diameter diameter

Tooth length

Age at eruption

51 or 61

6.0 mm

6.5 mm

5.0 mm

16.0 mm

7.5 mths

52 or 62

5.6 mm

5.1 mm

4.0 mm

15.8 mm

8 mths

81 or 71

5.0 mm

4.2 mm

4.0 mm

14.0 mm

6.5 mths

82 or 72

5.2 mm

4.1 mm

4.0 mm

15.0 mm

7 mths

53 or 63

6.5 mm

7.0 mm

7.0 mm

19.0 mm

16-20 mths

83 or 73

6.0 mm

5.0 mm

4.8 mm

17.0 mm

16-20 mths

54 or 64

5.1 mm

7.3 mm

8.5 mm

15.2 mm

12-16 mths

55 or 65

5.7 mm

8.2 mm

10.0 mm

17.5 mm

20-30 mm

84 or 74

6.0 mm

7.7 mm

7.0 mm

15.8 mm

12-16 mm

85 or 75

5.5 mm

9.9 mm

8.7 mm

18.8 mm

20-30 mm