Dental Anatomy, Morphology and Occlusion Max & Mandibular Incisors RSD 811

Dental Anatomy and Morphology

MAXILLARY AND MANDIBULAR INCISORS

MAXILLARY CENTRAL INCISOR General Characteristics Development Views Axial Inclination & Occlusion Root Pulp Spaces

General Characteristics Widest Incisor Crown; 2nd Largest tooth Shape and position affect facial esthetics Geometrical shapes: Labial or lingual view: trapezoid Proximal: triangle Adjacent to midline; mesials contact

DEVELOPMENT Calcification begins: 3-4 months Enamel completed: 4-5 years Eruption: 7-8 years Root completed 10 years Develops from 4 lobes 3 labial lobes(mammelons) 4th lobe yields Cingulum

LABIAL VIEW Tooth length is 22-24 mm Coronal length is 10-16 mm(2nd largest tooth in mouth Coronal width at interproximal contacts: 8 to 9 mm Widest of all the incisors At CEJ: 6-7 mm

LABIAL VIEW(CON’T) Basic coronal shape is trapezoid Mammelons may be on newly erupted teeth Incisal edge shows a slight convexity, but is basically straight Mesioincisal angle approaches 90 degrees

LABIAL VIEW(CON’T) Mesio incisal angle is located more incisally than the more rounded disto-incisal angle. Therefore the incisal edge goes slightly more gingivally from the mesio labial to disto-labial line angles.

LABIAL VIEW(CON’T) Mesial outline is relatively straight Distal outline is more convex Mesio labial line angle longer and straighter than distolabial line angle Interproxinal contacts occur at the greatest convexity of the proximal surfaces

LABIAL VIEW(CON’T) Mesial contact is in the incisal 1/3rd near the incisal edge; very small incisal embrasure Distal contact near the junction of the incisal and middle 1/3rd’s Buccal cervical line(CEJ) is convex in an apical direction; centered distal to midline Flat mesial and distal emergence angles

LABIAL VIEW(CON’T) Generally smooth with small irregularities Two labial grooves Root is cone-shaped, regular, and blunt Length of the root is 12-14 mm which is 2-3 mm longer than the crown Root has a small distal inclination

LINGUAL VIEW Similar to labial, but slightly smaller Has convexities and concavities(unlike the labial), resulting in “scoop” form Prominent mesial and distal marginal ridges extend cervically and flow into cingulum

LINGUAL VIEW(CON’T) Incisal ridge is raised and continuous with mesial and distal marginal ridges Lingual fossa is concave in mesio distal and inciso cervical dimensions Prominent marginal ridges and well developed lingual fossa are arch traits for maxillary incisors

LINGUAL VIEW(CON’T) Large cingulum in cervical 1/3rd of the lingual surface Incisal to the cingulum, the lingual surface is concave forming the lingual fossa A lingual pit may be found at the cervical end of the lingual fossa(more commonly found in max lateral incisors)

LINGUAL VIEW(CON’T) CEJ is convex apically; centered distal to midline Lingual CEJ more convex than labial CEJ Root tapers lingually(arch trait)

PROXIMAL VIEWS Shape is a triangle with the base at CEJ and apex at incisal ridge Incisal ridge is centered labiolingually Labial surface is convex inciso-cervically Lingual surface has both convex and concave areas

PROXIMAL VIEWS(CON’T) Greatest labiolingual dimension is about 7 mm At CEJ, the labiolingual dimension is approximately 6 mm Labial and Lingual heights of contour are in the cervical 1/3rd of the crown

PROXIMAL VIEWS (CON’T) Interproximal contact area is more incisal on the mesial than the distal CEJ shows greater convexity on mesial than distal Crown may appear thicker labiolingually from a distal view point Facial of root is more convex than lingual

INCISAL VIEW Shape is a triangle with base on the labial Mesial outline is longer, resulting in distal positioning of the apex of the triangle Root is completely obscured from view Labial surface is convex mesiodistally with a slight distolingual shape

INCISAL VIEW(CON’T) Labial developmental grooves can be viewed, if present Mesiolabial and distolabial line angles are clearly seen Lingual line angles are less evident Lingual embrasures are wider than those of the labial

ROOT Conical, but converges lingually to give a triangular form Much variability in apical 1/3rd of this and all other teeth Horizontal view Labial, lingual, distal surfaces: convex Mesial: convex and concave

OCCLUSION The lingual surface of the maxillary central incisors occludes normally with the labio-incisal surface of the mandibular central and lateral incisors

AXIAL INCLINATION Proximal view: 28 degrees(apex tilted lingually) Labial view: 2 degrees(Apex tilted mesially)

PULP SPACES Horizontal sections: circular in the apical; elliptical at CEJ, and wider elliptically (mesiodistally) in the coronal portion of the pulp chamber Large, single, widest mesiodistally at roof Sections: Longitudinal section: Mesiodistal-3 horns Labiolingual-smooth apical taper; slight labiolingual constriction at CEJ

MAXILLARY LATERAL INCISOR General characteristics Development Views Axial Inclinations & Occlusion Root and Pulp Spaces

GENERAL CHARACTERISTICS Closely resembles central but smaller in all dimensions

DEVELOPMENT First evidence of calcification: 1 yr Enamel completed 4-5 yrs Eruption 8-9 yrs Root completed 11 yrs

DEVELOPMENT(CON’T) Development may not be normal Most variation of any tooth except 3rd molars Peg-shaped laterals Congenitally-missing laterals

LABIAL VIEW More curvature than the central Rounded incisal edge Rounded incisal angles(mesial and distal) Disto incisal angle is more rounded than the mesial

LABIAL VIEW(CON’T) Proximal contacts Emergence Angle Mesial: junction of incisal and middle 1/3rd Distal: middle 1/3rd (incisal portion) Emergence Angle Flat interproximally; allows room for interdental papilla

LINGUAL VIEW The marginal ridges, cingulum, and incisal ridge are more pronounced than the central incisors resulting in a more accentuated lingual fossa The tooth tapers lingually-similar to the central incisor Pit more likely

PROXIMAL VIEW Smaller crown/root ratio than central Smaller labiolingual measurement Curvature of CEJ is less than central Longitudinal curves may be seen on root, resulting in flat or concave mesial and distal root surfaces Width of crown looks thicker from distal view

Incisal The labial surface is more convex than the central incisors Resembles a small canine

AXIAL INCLINATION Proximal View: 26 degrees (apex to lingual) Labial View: 7 degrees (apex to mesial)

Occlusion Occlusion is with mandibular lateral incisor and canine

ROOTS AND PULP CHAMBER Apex is more pointed than central Frequent distal bend of the apex Smaller than central More likely to exhibit constrictions and accessory canals

MANDIBULAR CENTRAL INCISOR General Characteristics Development Views Axial Inclination and Occlusion

GENERAL CHARACTERISTICS Smallest tooth in the dental arch Narrower mesiodistally, but almost as wide labiolingually as maxillary central Masticating forces are in a labiolingual direction Long root relative to the maxillary central

DEVELOPMENT(4 LOBES) First calcification seen 3-4 months Enamel completed 4-5 years Eruption 6-7 years Root completed 9 years Normal path of eruption from the lingual

LABIAL VIEW Length of crown 9mm Mesial-distal width of crown 5mm Labio-lingual width of crown 6mm Length of tooth 21.5mm General outline Form Trapezoid

LABIAL VIEW(CON’T) Labial surfaces of #24, #25 are relatively straight and smooth Disto incisal angle is only slightly more rounded than mesial Convexity is greater cervically than incisally Proximal contacts are in the incisal 1/3rd

LINGUAL VIEW The lingual surface incisal to the cingulum and within the small marginal ridges is slightly concave mesio distally and inciso cervically. This results in a small, shallow lingual fossa and the absence of a lingual pit

PROXIMAL VIEWS General shape is triangular Facial surface-convex Lingual surface-concave and convex Height of contours: ½(or less) mm from CEJ-Curvature of CEJ greater on mesial The incisal edge is slightly lingual of a perpendicular line that bisects the tooth labiolingually

Incisal View Very symmetrical Incisal edge is almost centered labiolingually Tapers lingually Lingual development is slight

AXIAL INCLINATION 22 degrees (apex to lingual) 2 degrees (apex to mesial)

OCCLUSION The normal occlusion of the mandibular central incisor is with the incisolingual surfaces of the maxillary central incisor

MANDIBULAR LATERAL INCISOR General Characteristics Development Views Axial Inclination and Occlusion Root and Pulp Spaces

GENERAL CHARACTERISTICS Slightly wider mesiodistally than central (maxillary incisors are just the opposite) Similar in form and function to central Mesial and distal contacts are in incisal 1/3rd with small incisal embrasures Few traces of development; mammelons are normally lost soon after birth

DEVELOPMENT 4 lobes First calcification: 3-4 months Enamel completed: 4-5 years Eruption: 7-8 years Root Completed 10 years

LABIAL VIEW Slightly wider mesiodistally than central (arch trait) Mesial line angle often longer than distal Incisal edge is often more cervical as one proceeds distally Disto incisal angle is more rounded and more cervical than the mesio incisal angle

LINGUAL VIEW Similarity to central very close except for: Asymmetry mesiodistally, distal 1/3rd more convex Tooth is slightly wider than central Lingual fossa of the mandibular lateral incisor is slightly more evident

PROXIMAL VIEWS Mesial and distal views are very similar to central except for the CEJ Slightly higher on mesial than distal

INCISAL VIEW Incisal ridge is not perpendicular to a line bisecting the tooth labiolingually Allows for curvature of the arch Crown appears twisted distolingually on the root

AXIAL INCLINATION Proximal view: 23 degrees (apex lingual) Labial view: 0 degrees (midline)

OCCLUSION The mandibular lateral incisor occludes with the incisolingual surfaces of the maxillary central incisor and maxillary lateral incisor

ROOTS Roots of mandibular incisors are flattened on the mesial and distal surfaces with the possibility of longitudinal grooves Roots are symmetrical and straight(lateral incisors may be dilacerated in apical 1/3rd of root) Lateral’s root is larger than centrals

PULP SPACES Pulp chamber follows external form; wider in the labiolingual direction Horizontal cross-section of the pulp chamber shows an elliptical shape that is widest mesiodistally in the crown, widest facio-lingually in mid-root and circular in apex Two canals may be present

SUMMARY: MANDIBULAR INCISORS Narrowest teeth of incisors Lateral wider than central Shallow lingual fossa Flat labial surfaces Roots oval in cross-section, much wider labio- lingually than mesio distally Crown wider labiolingually

Today in D-611 Continue all projects you have started Begin: 1.2 Waxing proximal contours of #10(UL29) and #12 MO (UL49A) 1.3 #7 MFL(UR24) and MFLI #9(UL14A)