Permanent Mandibular Incisors PDF

1/8/25 1. To identify the mandibular incisors and provide vital information. PERMANENT...

1/8/25 1. To identify the mandibular incisors and provide vital information. PERMANENT 2. Describe the location and contour of each mandibular incisor. MANDIBULAR INCISORS DR. KATRINA BIANCA B. CRUZ - NATIVIDAD DMD (NU), MDSc (Perio- CSMU) 1 2 OUTLINE CALCIFICATION & ERUPTION SCHEDULE § General information Calcification begins………… 3-4 months § Labial surface § Lingual surface Crown completed…………… 4.5 years § Proximal surface § Incisal surface Eruption (emergence) …….. 6.5 yrs/6-7 yrs Root completed…………….. 9 years 3 4 1  1/8/25 MANDIBULAR CENTRAL INCISOR § There are four mandibular incisors: § two central incisors and two lateral incisors. § Universal: 25 or 24 § FDI: 31 or 41 § The central and lateral incisors appear quite § Contact Area: Mesial: Incisal 3rd similar although the lateral incisor is larger. Distal: Incisal 3rd § No of roots: 1 § Viewed from the proximal surface, the § No. of pulp horn(s): 1 or 0 mandibular incisors have the same wedge § No. of pulp canal(s): usually 1; 2 possible shape as the maxillary incisors, and so are § Lobes: 4 suited, also, for incising food. § Crown Length: 10-11mm § Root Length: 12.5 mm § Mesiodistal measurement: 5 mm 5 6 PERMANENT IDENTIFYING FEATURES MANDIBULAR — Smallest permanent tooth. — Most symmetrical with its contralateral counterpart. — Smooth tooth; no developmental grooves or depression in crown CENTRAL INCISOR — Disto-incisal angle is as sharp as the mesioincisal angle. — Faciolingual dimension>mesiodistal dimension(from occlusal). — Marginal ridges are the same length. — Incisal edge is lingual to the long axis(same as mandibular lateral) — Cingulum (indistinct) is positioned centrally. — Occludes with maxillary central incisor. — Only one antagonist 7 8 2  1/8/25 § Asthe smallest tooth in the dentition, the mandibular central incisor has only one antagonist. This tooth and the maxillary third molar are the only teeth that have one antagonist; all others have two. 9 10 — Mesial — Mesial incisal angle — Distal LABIAL ASPECT — Distal incisal angle 11 12 3  1/8/25 § Crown outline trapezoidal with longer parallel side at incisal edge § Incisal edge straight and at right angle to (perpendicular to) the long axis line of the tooth § Mesial and distal incisal line angles are both said to be sharp almost 90 angles. However, the distal incisal line angle slightly more rounded than the mesial incisal line angle D M § The incisal 1/3 of the crown surface is relatively flat. The cervical two thirds of the surface is convex. 13 14 LABIAL SURFACE LINGUAL VIEW § The mesial outline may be slightly straighter than the distal outline § The anatomical features found on the § The crest of the curve of the lingual surfaces of all incisors (marginal cervical line may be ever so ridges and cinguli) are present but slightly to the distal of the relatively muted and not conspicuous on mesiodistal long axis bisector mandibular incisors § However when viewing the facial aspect of this crown, it is § The lingual fossa is trapezoidal in shape, considered to be bilaterally will be very shallow and limited to the symmetrical incisal 1/3 of the crown D M § The root converges evenly to a relatively pointed apex M D § The cingulum will be smoothly rounded § The apex may be slightly to the distal of the mesiodistal long axis and not as prominent as the cinguli of bisector but it will rarely if ever be the maxillary incisors curved to any great extent 15 16 4  1/8/25 LINGUAL SURFACE PROXIMAL SURFACE The outline of the lingual is — The width from labial to reverse of the labial view: lingual is broad. (The — Very smooth. width is necessary to — No grooves or pits. provide stability in the bone — Fossa and cingulum merge for such a small tooth). with gentle curve. — The root remains broad for — Marginal ridges are not two-thirds of its length, evident. tapering only at the apical — Cingulum covers the cervical third. third of the crown. — Both mesial and distal — The smooth shallow fossa surfaces have a deep occupies the remaining two depression extending most thirds. of the root length. 17 18 MESIAL SURFACE § The enamel on the lingual surface will MESIAL SURFACE extend apically about 0.5 mm farther than it does on the facial. This makes § The cervical line curves the measurement of the anatomical incisally more on the mesial crown 0.5 mm greater on the lingual surface than on the facial surface surface than on the distal § The crests of the cervical ridges surface (greatest curvatures) will not be at the same level facially and lingually (the § The root converges apically, crests of these ridges are about 1 mm evenly toward a relatively incisal to the cervical line) blunt (rounded) root end § Cervical ridges are not as well developed on mandibular anterior § A broad longitudinal root teeth. Their crests extend beyond the depression is usually found labiolingual diameter of the root at the cervix less than the 0.5 mm. When F L for most of the length of the F L compared to most other permanent root teeth, this is quite small 19 20 5  1/8/25 DISTAL SURFACE § The cervical line curves INCISAL SURFACE incisally for a relatively § The faciolingual diameter is shorter distance on the greater than the mesiodistal distal than on the mesial width surface § The greatest curvature mesially § The broad root depression and distally (proximal contact may be deeper on the distal areas) are equidistant between the facial and lingual outlines surface of the root than on its mesial § The incisal ridge runs straight M D across the tooth mesiodistally § The apex of the root will be F parallel to but slightly lingual to even with the faciolingual L the faciolingual bisector of the long axis bisector crown 21 22 § Mesiofacial and distofacial line angles are more distinct (less § The incisal edge of the rounded) than those of a mandibular incisor is positioned maxillary lateral incisor because lingual to the midline. of the relative flatness of the incisal 1/3 of the facial surface § When the teeth occlude, the labial § The crest of the cingulum surface of the mandibular incisors lingually is usually slightly to the conforms to the lingual fossa of distal of the mesiodistal bisector the maxillary incisors. of the crown M D § In spite of this, the outline of the mandibular central incisor crown from the incisal view is said to be bilaterally symmetrical 23 24 6  1/8/25 § Root length: 12.5 mm § Root depressions/furrows: Deep vertical depressions on both mesial and distal surfaces § CEJ: Curves incisally 2–3 mm § Cervical area: May have shallow concavity on — Observing this tooth from the incisal aspect both mesial and distal surfaces assists in differentiating it from the mandibular lateral incisor. The central incisor has a straight incisal edge that is bilaterally symmetric. 25 26 Labial Surface. The characteristics of this surface are: Proximal Surfaces. The characteristics of these surfaces § A straight incisal edge with sharp incisal angles. are: § Mesial and distal sides that taper evenly to the cervix. § The tip of the incisal edge sitting lingual to the midline. § Mesial and distal contact areas located at the incisal § A cervical line that curves toward the incisal edge. angle. § A broad root, tapering at the apical third. § A smooth crown surface with no depressions. § A root furrow or depression on the mesial and distal § A straight root, tapering at the apical third. surfaces. Lingual Surface. The characteristics of this surface are: Incisal View. The characteristics of this surface are: § An outline that is the reverse of the labial view. § A straight incisal ridge. § A smooth fossa; a smooth cingulum. § A bilaterally symmetric form. § A convex cingulum that is one-third of the crown. 27 28 7  1/8/25 CALCIFICATION & ERUPTION SCHEDULE PERMANENT Calcification begins………… 3-4 months MANDIBULAR Crown completed…………… 4.5 years LATERAL INCISOR Eruption (emergence) …….. 7.5 yrs/7-8 yrs Root completed…………….. 10 years 29 30 MANDIBULAR LATERAL INCISOR — Mesial § Universal: 26 or 23 — Mesial incisal angle § FDI: 32 or 42 — Distal § Contact Area: Mesial: Incisal 3rd — Cervical to the incisal Distal: Incisal 3rd angle § No of roots: 1 § No. of pulp horn(s): variable; more prominent § No. of pulp canal(s): 1 § Lobes: 4 § Crown Length: 10-11mm § Root Length: 12.5 mm § Mesiodistal measurement: 5 mm 31 32 8  1/8/25 FACIAL SURFACE IDENTIFYING FEATURES The mandibular lateral incisor is larger than the mandibular central incisor in all dimensions. — Slightly larger in all dimensions than the mandibular central. The incisal edge is straight but it — Not as symmetrical as the central may appear slanted toward the — Crown is tilted distally on the root. distal. — Faciolingual dimension>mesiodistal dimension (from occlusal) — Mesial marginal ridge is longer than the distal. The mesial incisal line angle is said — Incisal edge is twisted distolingually. to be a sharp 90 degree angle; the — Incisal edge is lingual to the long axis (same as mandibular central) distal incisal line angle usually — Cingulum (indistinct) is positioned slightly distally. appears a little more rounded. — Root has mesial and distal concavities (hourglass-shaped) Proximal contacts are both within D — Occludes with maxillary central and lateral incisors. the incisal 1/3 of the crown and are M considered to be at essentially the same level. 33 34 There is often more curvature in — The lateral incisor looks like the the distal crown outline; central incisor in overall therefore, the crown is NOT appearance but is slightly larger considered symmetrical from and not bilaterally symmetric. the facial view. — In contrast with the CI which has The crest of the gingival a level incisal edge, the lateral curvature of the cervical line incisor declines towards the distal will be slightly distal to the and forms a rounded incisal mesiodistal long axis bisector. angle with the distal side. — Distal side is slightly convex The root tapers to a pointed D apex. It may curve slightly to M — The mesial incisal angle is sharp. the distal or remain straight. — The CL forms a narrow arch. 35 36 9  1/8/25 LINGUAL SURFACE — Except for size and length, Anatomical features are not as prominent as they the mandibular lateral are on maxillary incisors. incisor is similar to the CI The lingual fossa is trapezoidal in shape, shallow and has the same and limited to primarily the incisal 1/2 of the crown. characteristics. The cingulum is smoothly rounded and not well delineated. — However, the cingulum is The root has less toot structure on the lingual distally displaced as it starts aspect, than on the facial aspect to curve towards the D No root surface depression is present on the M lingual surface 37 38 — Root depressions on the mesial The incisal ridge will be lingual to the and distal surfaces. faciolingual long axis bisector of the tooth. — The distal depression is deeper. When measured, the anatomical crown is longer from the incisal ridge to the cervical line on the lingual surface. Enamel extends apically 0.5 mm more on the lingual than on the facial surface. The crest of the facial cervical ridge will be at a higher level incisally than the crest of the lingual cervical ridge. The height of contour of the crown beyond the root facially and lingually will be less than 0.5 mm on either surface. F L 39 40 10  1/8/25 The cervical line curves incisally to a higher level on the mesial surface DISTAL SURFACE than on the distal. Since the crown of this tooth is The distal outline of this tooth slightly “twisted” on its root and the resembles the distal of the distal end of the incisal ridge is mandibular central incisor. It is NOT more inclined to the lingual, a part of the distal marginal ridge can be a reverse image of the mesial view of seen beyond the lingual outline of the mandibular lateral incisor. From the mesial marginal ridge. This is a distinctive characteristic of this tooth the distal aspect, the mesial marginal from the mesial view. ridge CANNOT be seen protruding to The mesial surface of the root will the lingual as it is hidden by the be similar in outline to that of the mandibular central incisor. A broad outline of the distal marginal ridge. root depression will exist for most of The cervical line curves less incisally F L the root length. than on the mesial. F L 41 42 The faciolingual measurement The root outline and root depression are is greater than the mesiodistal. similar to that of the distal surface of the The mesial contact area is root of a mandibular central incisor. centered faciolingually but the The apex of the root will be in line with distal proximal contact will be the faciolingual long axis bisector. slightly to the lingual of the faciolingual bisector. The incisal ridge will be M D lingual to the faciolingual bisector of the crown outline in F its entirety; however, the distal L end of the ridge will be more toward the lingual than the mesial end. 43 44 11  1/8/25 The incisal ridge will be relatively straight but it is not — The incisal edge of the lateral straight across the tooth incisor curves toward the distal mesiodistally. It slants to the following the contour of the lingual at its distal end and is not parallel to the faciolingual mandibular arch, whereas the bisector. edge of the central incisor is The crest of the cingulum straight. lingually will be slightly distal to M D the mesiodistal bisector. — The curvature on the lateral The crown of the mandibular incisor creates a distally lateral incisor from the incisal displaced cingulum as view is said to look “twisted” or “rotated” on its axis, not at all compared to the centrally symmetrical. situated cingulum of the central incisor. 45 46 § Root length: 14 mm § Root depressions/furrows: Both mesial and Labial Surface. The characteristics of this surface are: distal with deeper distal depression § An incisal edge that declines toward the distal. § CEJ: Curves incisally 2–3 mm § A mesial surface that tapers gradually toward the cervix. § Cervical area: May have shallow concavity § A distal side that is slightly convex, tapering toward the cervix. § A sharp mesial incisal angle; a rounded distal incisal angle. § Mesial and distal contact areas at the junction of the incisal edge and the mesial or distal side. § A smooth surface. § A straight root that tapers evenly. 47 48 12  1/8/25 Lingual Surface. The characteristics of this surface are: Incisal View. The characteristics of this view are: § An outline that is the reverse of the labial side. § An incisal edge that curves toward the distal and inward § Cingulum, fossa, and ridges that appear the same as toward the lingual. those on the central incisor. § A cingulum that is distally displaced. Proximal Surfaces. The characteristics of these surfaces are: § Root depressions on the mesial and distal surfaces; the distal depression is deeper. § All other characteristics that are the same as those pertaining to the central incisor. 49 50 CENTRAL LATERAL SUMMARY OF THE MANDIBULAR SIZE SMALLER BIGGER INCISORS DEVELOPMENTAL LESS PROMINENT DEEPER,MORE (MAND CI & MAND LATERAL) DEPRESSION PROMINENT BILATERAL PRESENT ABSENT § Mandibular incisors assist the maxillary SYMMETRY incisors in biting and cutting food. INCISAL RIDGE REGULAR STRAIGHT SLOPING TOWARDS MD DIRECTION DISTAL, ROUNDED DI WITH SHARP ANGLE ANGLE § From the labial view, both mandibular incisors are small, narrow teeth with a straight incisal edge and tapering mesial and distal sides. LABIAL SURFACE LESS CONVEX MORE CONVEX § The mandibular central incisor is the smallest LINGUAL SURFACE LESS CONCAVE MORE CONCAVE tooth in the dentition. ROOT STRAIGHT TWISTED 51 52 13  1/8/25 53 54 55 14