Morphology of Deciduous Dentition

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MORPHOLOGY OF DECIDUOUS TEETH

Dental Anatomy & Occlusion Dent 202

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

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

Milk-white in color Enamel is thinner & pulp chamber is largeSome 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

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 incisorBilaterally 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 roots 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 Cusps

st 1

molar

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 Buccal aspect

st 1

molar

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

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

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

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

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 Mesial aspect

st 1

molar

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

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

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

Central pit B& L grooves Often a D pit

Mandibular 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 & eruptionTooth51 or 61 52 or 62 81 or 71 82 or 72 53 or 63 83 or 73 54 or 64 55 or 65 84 or 74 85 or 75

Crown height6.0 mm 5.6 mm 5.0 mm 5.2 mm 6.5 mm 6.0 mm 5.1 mm 5.7 mm 6.0 mm 5.5 mm

MD crown BL crown diameter diameter6.5 mm 5.1 mm 4.2 mm 4.1 mm 7.0 mm 5.0 mm 7.3 mm 8.2 mm 7.7 mm 9.9 mm 5.0 mm 4.0 mm 4.0 mm 4.0 mm 7.0 mm 4.8 mm 8.5 mm 10.0 mm 7.0 mm 8.7 mm

Tooth length16.0 mm 15.8 mm 14.0 mm 15.0 mm 19.0 mm 17.0 mm 15.2 mm 17.5 mm 15.8 mm 18.8 mm

Age at eruption7.5 mths 8 mths 6.5 mths 7 mths 16-20 mths 16-20 mths 12-16 mths 20-30 mm 12-16 mm 20-30 mm

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