Permanent Mandibular Incisors Introduction Simplest least variable teeth

Permanent Mandibular Incisors

Introduction • Simplest, least variable teeth • Centrals slightly smaller than laterals • Crowns are narrower M-D relative to the I-C length

Permanent Mandibular Central Incisor • Arch position: adjacent to midline • Universal #24 and #25 • Narrowest M-D width and smallest crown size* • Very symmetrical crown

Development Timeline: • • Initial calcification: 3 - 4 months Enamel completed: 4 - 5 years Eruption: 6 - 7 years Root completion: 9 years

Labial View • Incisal 2/3 generally flat to slightly convex • Height of contour at cervical third • Geometric form: trapezoidal

Labial View - mesial outline: • Even straight taper towards cervical • MI angle angular • Mesial HOC at the incisal third

Labial View - distal outline: • Almost a mirror image of mesial outline • Difficult to distinguish M from D

Labial View - incisal outline: • Perpendicular to long axis • One wear facet only anterior tooth that opposes one tooth*

Lingual View • • Surface relatively smooth Marginal ridges indistinct Lingual fossa shallow No pits or grooves

Lingual view: • Diminished cingulum • Height of contour at cervical third

Mesial View • Labial outline fairly straight at incisal 2/3 • Facial and lingual heights of contour at cervical third

Mesial view: • Incisal edge lingual to long axis of tooth* • Incisal edge slopes facially • HOC at incisal third

Distal View • Similar to mesial • CE line curvature slightly less than mesial • HOC also at incisal third (unique)

Incisal View • • • Wider F-L than M-D Diamond-shaped outline See more of facial than lingual M and D halves symmetrical Incisal edge is perpendicular F-L bisector* to

Root • Normally single and straight, occasional bifurcated • Gradual taper to sharp apex

Root: • Wider F-L, narrower M-D • Slight root concavities M and D • Cross-section at cervical: rounded rectangle

Permanent Mandibular Lateral Incisor

General Characteristics • Arch position: 2 nd tooth from midline • Universal #23 and #26 • Very similar in form to mandibular central

Development Timeline: • • Initial calcification: 3 - 4 months Enamel completed: 4 - 5 years Eruption: 7 - 8 years Root completion: 10 years

Labial View • Very similar to mandibular central except DI angle slightly more rounded • M and D heights of contour at incisal third, D slightly more cervical

Lingual View • Similar to mandibular central • Cingulum slightly offset to distal

Mesial and Distal Views • Similar to mandibular central except: – Distal incisal corner visible from mesial*

M and D views: • Mesial CE line curvature slightly more than distal

Incisal View • Incisal edge curves towards lingual in distal portion* • Distal HOC more lingual than mesial • Cingulum appears offset to distal • Crown appears twisted on root • Two facets of wear

Root • Similar to mandibular central except slightly wider, thicker • Root concavities present with distal more pronounced • Occasional bifurcated root

How To Tell Mandibular Central from Lateral: • Distal corner of incisal edge twisted lingually on lateral* • One wear facet on central, two facets on lateral

Lateral vs central: • DI corner of lateral very slightly more rounded • Cingulum slightly offset to distal

How to tell right from left: • Very difficult with mandibular centrals

Right from left: • Laterals: – lingual twist of distal incisal edge* – DI slightly more rounded – Cingulum offset distally

Wax Quiz

Dimensions: • • • 10: 9: 8: 7: 6: 0 - 0. 1 mm off 0. 2 - 0. 4 mm off 0. 5 - 0. 9 mm off 1. 0 - 1. 5 mm off greater than 1. 5 mm off

Axial Contours: • Surface contours as compared to the original – Facial, lingual, mesial, distal, incisal, occlusal – Line angles, point angles

Occlusal surface: • Only posterior teeth! • Cusps, marginal ridges, cusp ridges, grooves, etc as compared with original

CE Line: • Position, contour, smoothness, transition from root to crown

Surface Texture: • Smoothness, without visible scratches or irregular surfaces • Wax additions should be seamless

Surface Polish: • Degree of surface shine • No foreign coating on the surface, e. g. Speedshine, die lube, etc.