Permanent IncisorsRevised 2006

The Permanent IncisorsFirst and second teeth from the midlineIncisors of the same arch resemble each otherMaxillary incisors larger than mandibular incisorsMaxillary central larger than maxillary lateral*Mandibular lateral larger than mandibular central

Functions of the IncisorsMastication - biting, cutting and shearingEsthetics - size, shape, color and manner of placement contribute to a person’s appearance. The incisorsalso provide facial support. Phonetics - they are necessary for the production of certain sounds.(to test if denture work right or not)Esthetics - beauty is in the eyes of the beholder.

Four Unique Features of the IncisorsIncisal edgeMamelonsPosition and angulation of the marginal ridges (on lingual surface)Lingual fossa and cingulum

Anterior Tooth Form - Mesial and Distal SurfacesIn a proximal view, the crowns of the anterior teeth exhibit a triangular or wedge shape. The base of the triangle is at the cervical.The apex of the triangle is at the incisal.In a labial view, the mesial surface of the crown is straighter; distal surface of the crown is more rounded or curved.In a labial view, the mesio-incisal line angle is squarer; disto-incisal line angle is more rounded.Don’t have to differentiate between 24 and 25 if not possible

Maxillary Central IncisorsShare mesial contactsCrown size - largest of the incisorsWidest mesiodistally of any anterior tooth

Maxillary Central Incisors - DevelopmentInitiation of calcification: 3 to 4 monthsCompletion of enamel: 4 to 5 yearsEruption: 7 to 8 yearsCompletion of root: 10 years2-3 years from eruption to complete

Maxillary Central IncisorLabial or lingual view - the crown is trapezoidal with the base or longest parallel side at the incisal.

Maxillary Central Incisors - Labial Incisal margin - generally straight and nearly perpendicular to long axisIncisocervical and mesiodistal crown dimensions more nearly equal than for other incisorsMesial outline - slightly convex (nearly straight). Height of contour - incisal thirdDistal outline - more rounded than mesial. Height of contour - incisal thirdMamelons - sometimes found on the incisal edge of newly erupted incisors and have been referred to as evidence of three labial lobes, the most common number of mamelons is three.Note - due to the rounding of the disto-incisal angle, the most common number of mamelons on a maxillary lateral incisor is two.Developmental depressions - straight, shallow depressions, which extend from the incisal edge toward the gingival, and fade out in the middle third.Imbrication lines - faint, curved lines which roughly parallel the CEJ in the cervical third of the crown. They are usually, but not always, present.

Maxillary Central Incisors - LingualLingual more narrow than labial - due to faciolingual taper.Lingual fossa - found in incisal half to two-thirds of the crown. The fossa covers the largest area of the crown’s lingual surface.Marginal ridges mark the mesial and distal borders of the crown’s lingual surface. Cingulum - bulky convexity located in the cervical portion of the crown’s lingual surface. The cingulum is generally smooth.A linguogingival groove and a lingual pit may also be found. These structures are not usual findings on the crown of any permanent incisor.

Maxillary Central Incisors - Proximal Labial height of contour - cervical thirdLingual height of contour - cervical thirdIncisal outline - on a newly, erupted incisor the projection of enamel at the incisal termination is the incisal ridge. The ridge is normally pointed or slightly rounded. As the incisal ridge wears, it flattens and becomes known as the incisal surface or incisal edge.

Incisal Wear On an older maxillary incisor, the incisal edge slants down from labial to lingual. The linguo-incisal line angle is lower than the labio-incisal line angle.On an older mandibular incisor, the incisal edge slants down from lingual to labial. The labio-incisal line angle is lower than the linguo-incisal line angle.

Maxillary Central Incisor - Mesial AspectWhen viewing a maxillary central incisor from the proximal, the incisal ridge of the crown is normally in line with the center of the root.

Maxillary Central Incisors - Incisal AspectCrown’s outline is roughly triangular in the incisal view.Incisal edge is relatively straight mesiodistally and is roughly centered over the root.Greatest contour of the cingulum is offset to the distal.

Maxillary Central Incisors - Root StructureThe root is single, conical, relatively straight and tapers to a rounded apex.A cervical cross section of the root shows a rounded triangular outline.In younger patients, the pulp chamber is triangular shaped, becoming more rounded with age.

Maxillary Central Incisors - Root StructureA mid-root cross section shows a somewhat ovoid outline.The root is approximately one and a half times the crown length.

Maxillary Central Incisors - Variations and AnomaliesTalon cusp - large accessory cusp on the lingual surface of the crownSupernumerary teeth - extra teeth that may be found between the roots of the centrals Hutchinson’s incisors - screwdriver shaped crown caused by congenital syphilis

Maxillary Lateral IncisorsResembles the maxillary central incisor, but on a smaller scale.The lateral is generally a more rounded tooth.It is relatively longer incisocervically and narrower mesiodistally.Displays greatest variation in form of any permanent tooth, except for the third molars.

Maxillary Lateral Incisors - DevelopmentInitiation of calcification: 1 yearCompletion of enamel: 4 to 5 yearsIt erupts at 8 to 9 years of age.Completion of root: 11 yearsMaxillary lateral incisor - last permanent incisor to erupt.

Maxillary Lateral Incisors - LabialMesial outline - resembles maxillary central incisor, but mesio-incisal angle is more rounded. Height of contour - incisal thirdDistal outline - more rounded than the maxillary central incisor. The disto-incisal angle is noticeably more rounded. Height of contour - junction of the incisal and middle thirds

Maxillary Lateral Incisors - LabialIncisal margin - not as straight as the maxillary central incisor, due to the greater rounding of the two incisal angles. If mamelons present, the most common number is two.The labial surface is more convex.Labial developmental depressions and imbrication lines are normally present.The largest incisal embrasure exists between the maxillary lateral incisor and canine.

Maxillary Lateral Incisor - LingualThe marginal ridges are the most distinct of any of the incisors.The lingual fossa is the most distinct of any of the incisors.The crown’s lingual surface has been described as markedly concave.It is the anterior tooth most likely to have a lingual pit. The lingual pit is potential caries site. Linguogingival grooves and lingual pits more common than on the other incisors.

Maxillary Lateral Incisors - ProximalThe labial and lingual heights of contour are in the cervical third.Crown outline - triangular in shapeThe distal surface is smaller and more convex than the mesial surface.

Maxillary Lateral Incisors - IncisalThe crown resembles the maxillary central, but the cingulum is often more prominent.The crown exhibits relatively more convexity labially and lingually.The crown outline may appear somewhat rhomboidal.

Maxillary Lateral Incisors -Root StructureThe root is wider labiolingually than mesiodistally.The actual root length is the same length or slightly shorter than that of the central. The cervical and mid-root cross sections are ovoid.

Variations and Anomalies The maxillary lateral incisor has more variation in form than any other tooth except for the third molars.These include: congenitally missing (agenesis)

peg lateralpalatogingival groovelingual pitdens in dente.

Congenitally missing - agenesis (tooth bud does not form)Peg lateral - due to lack of development of the mesial and distal portions of the crown.Linguogingival fissure - a groove which extends from the lingual pit down onto the cingulum and sometimes the root. Syn.- palatogingival groove.Caries is often associated with the lingual pit and dens in dente.Dens in dente - an invagination of enamel and dentin into the tooth’s pulp cavity. The entrance site of the invagination is the lingual pit. Dens in dente literally means “tooth within a tooth.”The tooth frequently has an abnormal relationship and contact with adjacent teeth in the same arch.Distorted crowns and unusual root curvaturesTubercle - elevated structure found on the incisal portion of the cingulum.

Mandibular IncisorsSimplest and least variable teeth in the mouthSmallest of the permanent teethMandibular incisors resemble each other more than the maxillary incisors.The crowns are relatively longer incisocervically and markedly narrower mesiodistally.

Mandibular Central IncisorsNarrowest mesiodistally of any permanent toothThe crown is very symmetrical, with the mesial and distal halves being nearly identical.Difficult to distinguish between the mesial and distal portions

Mandibular Central Incisors - DevelopmentInitiation of calcification: 3 to 4 monthsCompletion of enamel: 4 to 5 yearsThe first permanent anterior teeth to erupt: 6 to 7 yearsCompletion of root: 9 yearsThe first succedaneous teeth to eruptNote - the first permanent teeth to erupt are the mandibular first molars.

Mandibular Central Incisors - LabialMesial and distal outlines - both outlines taper evenly towards the gingival in nearly straight lines.The labial surface has less convexity mesiodistally and incisocervically than the maxillary incisors. Developmental depressions and imbrication lines are not normally present. The mesial and distal heights of contour are in the incisal third.Incisal outline - straight and at a right angle to the long axis of the tooth.Mamelons - if present, the most common number is three.

Mandibular Central Incisors - LingualLingual surface is relatively smooth.Marginal ridges and lingual fossa are indistinct.There are normally no grooves, fissures or pits on the lingual surface.Cingulum is not as prominent as on the maxillary incisors.

Mandibular Central Incisors - ProximalLabial and lingual heights of contour are in the cervical third.Crown outline - triangular in shapeThe profile of the incisal edge develops an inclination down towards the labial. This is opposite to the slope of the incisal edges of the maxillary incisors.

Mandibular Central Incisors - IncisalMost notable features are

(1) the symmetry of the mesial and distal portions (2) the straight incisal edge.

Crown outline is roughly four sided or diamond-shaped.The tooth is normally wider labiolingually than mesiodistally.Cingulum is centered.

Mandibular Central Incisors - Root StructureThe root is normally single and straight.The root is wider labiolingually than mesiodistally.In cross section the root is roughly rectangular with rounded corners.Root concavities or longitudinal grooves may be present on the mesial and distal surfaces of the roots.

Clinical Significance - Root Concavities Increase the surface area of the rootProvide a mechanical lock for the alveolar bone. This not only increases retention, but it also helps the tooth resist forces which are not on the long axis of the tooth.With recession of the supporting structures, the root concavities are exposed and are difficult to clean.

Mandibular Central Incisors - Variations and AnomaliesVariations and anomalies are rare . Most common variation is a bifurcated root. Branches are on the labial and lingual.Fusion between the mandibular centrals or the centrals and laterals can occur.

Mandibular Lateral IncisorsThe mandibular lateral incisors closely resemble the mandibular central incisors.The mandibular lateral incisor is slightly larger.It complements the central in function.

Mandibular Lateral Incisors - LabialIncisal outline - the incisal surface may slope slightly gingivally toward the distal. The disto-incisal angle is more rounded than that of the central incisor.The mesial and distal heights of contour are both in the incisal third.

Mandibular Lateral Incisors - LingualThe cingulum is offset to the distal.The curvature of the cervical line is also offset distally.

Mandibular Lateral Incisors - IncisalIncisal edge is not straight mesiodistally; it angles towards the lingual as it progresses distally.It is easy to visualize the bulking of the cingulum to distal.These factors give the crown the appearance of being slightly twisted on its root. This positions the distal marginal ridge more lingual than the mesial marginal ridge.

Mandibular Lateral Incisors - MesialIn a mesial view, you can see the distal marginal ridge peeking out on the lingual surface. (Favorite national board question.)*This is due to incisal surface angling lingually as it goes distally.The distal surface is slightly shorter than the mesial surface.

Mandibular Lateral Incisors - Root StructureThe root is slightly longer, thicker and wider than that of the central.If root concavities are present, the concavity on the distal is usually more pronounced.

Mandibular Movements and Positions - CentricCentric Occlusion/ Maximum Intercuspation – a tooth to tooth relationship of the jaws determined by the relation of the occlusal surfaces of the teeth where the maxillary and mandibular teeth interdigitate maximally.

Mandibular Movements and Positions - ProtrusiveProtrusive Movement - the straight forward movement of the mandible Incisal Edge Position - the relationship that the maxillary and mandibular teeth assume as they move forward to the edge-to edge position.

Mandibular Movements and Positions – Lateral ExcursionsRight and Left Lateral Movements - the side the mandible moves toward is the working side. The side it moves away from is the non- working side.

Canine Protected OcclusionCanine Protected Occlusion (syn. Cuspid Rise) - the canine protects the posterior teeth as the jaw moves to the working side. The canines are the only teeth that contact in this movement. In the picture cuspid rise is illustrated on the left side.

Group Function

Group function - all the teeth on the working side function together as the jaw moves to that side.

OverbiteOverbite - the vertical overlapping of the anterior teeth. The normal amount of overbite is 1.5-2.0 mm.

OverjetOverjet - the horizontal overlapping of the anterior teeth

Anterior GuidanceAnterior guidance - the functional relationships of the anterior teeth during mandibular movements.Anterior guidance is largely determined by the overbite and overjet.

Dentinogenic Theory of Tooth FormThe dentinogenic theory relates the incisal point angles and incisal embrasures of anterior teeth to female and male characteristics.Female form - open incisal embrasures and rounded point angles.Male form - closed incisal embrasures and square point angles.This theory is no longer considered valid.

Square, Tapering, Ovoid TheoryThe square, tapering, ovoid theory relates anterior tooth form to the inverse of the patient’s face form. Three measurements are taken across the patient’s face (temple, malar process and angle of the jaw) and one the length of the face (hair line to the border of the chin).Tooth form is taken as 1/16 to 1/17 of these measurements.

Smile LineSmile line - a relationship formed by the line through the maxillary incisal edges and the line formed by the lower lip when smiling.A more curved smile line is characteristic of a feminine form.A straighter smile line is characteristic of a masculine form.

Oral HabitsBruxism - clenching, grindingMouth habit - opening bobby pins, holding objects in mouth Thumb sucking - causes anterior open biteTongue thrusting - causes anterior open bite