The Permanent Mandibular Incisors PDF

# The permanent mandibular incisors ## Arch traits - Crown narrower MD - Central and lateral are Nearly equal in size & dimensions - Root - Smaller MD - Generally oblong in x-section ## The permanent mandibular central incisors ### Labial aspect - narrowest MD of all incisors - Bilaterall...

# The permanent mandibular incisors ## Arch traits - Crown narrower MD - Central and lateral are Nearly equal in size & dimensions - Root - Smaller MD - Generally oblong in x-section ## The permanent mandibular central incisors ### Labial aspect - narrowest MD of all incisors - Bilaterally symmetrical (type trait) - The surface is smooth, convex in the cervical third and flattened in the incisal third. - 3 mamelons - About 90° MI & DI angles and are at same level IC (type traits) - Both HOCs are within the incisal third - M & D outlines are almost straight lines - CEJ convex cervically - Root is narrow & conical ### Distal - Vertical root axis - Trapezoid facial form with shortest of uneven side towards cervix - Cervical line curved apically ### Mesial - Sharp distoincisal angles - Sharp mesioincisal angle - Crown bilaterally symmetrical - Mesial and distal outlines, tapers evenly towards cervix - Single conical root ## The permanent mandibular central incisors ### Lingual aspect - Shallow fossa & less prominent cingulum & marginal ridges - lingual convergence of the crown ### Mesial aspect - Labial HOC within cervical third - From HOC toward incisal edge labial outline is straight ### Distal aspect - CEJ is 1 mm less curved ### Lingual - Incisal ridge lingual to the long axis of root; crown shows lingual inclination over root - Concavoconvex lingual outline - Height of lingual contour at cervical 3rd on cingulum - Cervical line curves incisally *** ## The permanent mandibular lateral incisors ### Labial surface - Slightly wider than central - Lack of bilateral symmetry - MI angle is sharp while DI angle is rounded with the distal HOC being more cervically situated - Distoincisal angle rounded - Mesiodistal dimension greater than that of central incisor by 1 mm - Incisal ridge tends to slope downwards in a distal direction - Mesial outline longer than distal outline - Crown bilaterally asymmetrical (Distal slightly larger) - Conical root - Root apex ### Mesial - Well-developed marginal ridge ### Distal - Narrower lingual surface due to lingual convergence of crown - Shallow lingual fossa devoid of any grooves - Cingulum - Lingual convergence of root ### Lingual - Triangular proximal form - Incisal ridge lingual to the root axis line - Mesial contact area at incisal third nearer to incisal ridge - Concavoconvex lingual outline - Height of lingual contour at cervical 3rd on the cingulum - Labiolingually broad root - Distal contact area also within incisal 3rd but cervically placed than mesial contact area - Cervical line on distal is less curved ### Mesial and Distal aspects - Nearly identical to that of central *** ## Incisal aspect - Triangular or ovoid - Labial surface is flat compared to max. Incisors - Seldom labial lobe groove - Long axis of incisal edge is perpendicular to LL line (type trait) - Mesial outline = distal outline in length - More of labial surface seen due to lingual inclination of crown - Incisal ridge perpendicular to the labiolingual bisecting line - Crown shows lingual convergence - Oval incisal form - Crown bilaterally symmetrical - Lingual fossa - Cingulum - Labiolingual dimension greater than mesiodistal ## Root - straight from cervix to middle third then tapers apically - convex MD and flattened LL - Developmental grooves on both M and D surfaces,deeper on the D. - pointed apex - Apical third usually is straight, sometimes, exhibits distal curvature. ## Identification - Right and Left: The symmetry of this tooth makes a judgement on right and left unreliabe - CEJ, Root apex taper, grooves deeper on distal root. - Central vs Lateral: When viewed occlusally, incisal ridge is at the right angles to the line bisecting the crown labiolingually. ## Variation: - This tooth is consistent in development and is is rarely absent. - Small tooth - Short root - Bifurcation of root. rare ## Developmental anomalies - Talon's cusp - Missing - Fusion between mandibular, central and lateral incisors. - Gemination ## Pulp - Bifurcation of the canal because of the root proximal grroves ## Variation - Two canals in a single root - Long root - Small size of tooth - Bifurcation of root into labial and lingual divisions. ## Incisal aspect - The incisal edge is 'twisted' from the 90 degree angle with the LL line - DI angle is more toward lingual ## Pulp - Similar to that of central - Root: Similar to that of central but longer ## Identification - Right and Left and cent vs lateral: Two significant features assist in identification, even in a worn tooth. The incisal edge is 'twisted' relative to the labiolingual bisecting line anticipating the curvature of the dental arch. Also, the cingulum will be shifted toward the side from whence the tooth has come. ## Anomalies - Congenitally missing. - Fusion between mandibular central and lateral incisor. *** The image shows a diagram of several teeth. Each tooth is labeled with its name and its different parts are labeled as well. The teeth are shown in different views. There is also a diagram of a tooth showing the position of the root. There is also a diagram of a tooth showing the development of the root.