Tooth Morphology Review Some general information Mixed dentition

Tooth Morphology Review

Some general information. . .

Mixed dentition: mix of deciduous and permanent, 6 - 12 yrs

Succedaneous teeth: permanent teeth that replace deciduous • Permanent molars are the only teeth not succedaneous • Premolars succeed primary molars – Only succedaneous teeth not having the same name as their primary counterparts

Normal eruption sequence (permanent teeth) • Mandibular teeth precede maxillary counterparts • Mandibular teeth erupt in anterior to posterior order • Maxillary arch: maxillary canine erupts after premolars (last succedaneous tooth to erupt)

Permanent Eruption Sequence • 1. Mandibular first molar: 6 - 7 yrs • 2. Maxillary first molar: 6 - 7 yrs • • 3. 4. 5. 6. Mandibular central incisor: 6 - 7 yrs Mandibular lateral incisor: 7 - 8 yrs Maxillary central incisor: 7 - 8 yrs Maxillary lateral incisor: 8 - 9 yrs

• • • 7. Mandibular canine: 9 - 10 yrs 8. Mandibular first premolar: 10 - 11 yrs 9. Maxillary first premolar: 10 - 11 yrs 10. Mandibular second premolar: 11 - 12 yrs 11. Maxillary second premolar: 11 - 12 yrs 12. Maxillary canine: 11 - 12 yrs • • 13. 14. 15. 16. Mandibular second molar: 11 - 13 yrs Maxillary second molar: 12 - 13 yrs Mandibular third molar: 17 - 21 yrs Maxillary third molar: 17 - 21 yrs

Notes: • Mandibular central is first succedaneous tooth to erupt • Maxillary canine is last succedaneous tooth to erupt • Premolars are the only succedaneous teeth having a different name than their deciduous counterpart • Root completion is generally 2 - 3 yrs after eruption

Know the following terms: • • Cusps Tubercles (mini cusps) Cingulum Ridges – – – Marginal ridges Triangular ridges Transverse ridges Oblique ridge Cusp ridges Incline planes

• • Mammelons Fossa Developmental groove Supplemental groove Pit Contact area Developmental lobe

Lobes: • All anterior teeth have 4 lobes – 3 labial – 1 lingual • Premolars: – 3 lobes for facial cusp – 1 or 2 lobes for lingual cusp(s) • Lobes of molar teeth correspond to the number of major cusps

Crown surface geometric outline forms: • Triangular • Trapezoidal • Rhomboidal

Facial and Lingual surfaces: • All have trapezoidal geometric form

Mesial and Distal surfaces: • Anteriors: triangular • Maxillary posteriors: trapezoidal • Mandibular posteriors: rhomboidal

Contact areas: • • • Central incisors: mesial contacts mesial Aids in stabilizing arch form Prevention of food impaction Aids food flow pattern Become larger over time

Notes: • Contacts become more cervical from anterior to posterior • Distal contact usually more cervical than mesial (exception: mandibular 1 st premolars & mandibular centrals) • Anterior contacts centered (F-L) • Posterior contacts are facial to center (F-L)

Embrasures: • Incisal (occlusal) embrasures increase in size from anterior to posterior • Cervical (gingival) embrasures decrease in size from anterior to posterior • Labial and lingual embrasures nearly equal in anteriors • Lingual embrasures larger than labials in posteriors

Facial and lingual heights of contour: • Facially: cervical third for ALL teeth • Lingually: – Anteriors: cervical third – Posteriors: middle third (exception: occlusal third for mand 2 nd premolar)

Curvature of CE line: • Curvature usually greater on mesial than distal • Curvatures become flatter from anterior to posterior

Important Characteristics of Tooth Types

Maxillary Central Incisor • Crown is almost as wide as it is long – Only incisor where MD = IC (almost) • Contact area – Mesial: incisal third – Distal: near junction of incisal and middle third

• Mesial CEJ has greatest depth of curvature of any tooth • Facial CEJ flatter curvature than other anteriors • Incisal view roughly triangular

Notes: (max central) • 1. M-D widest of all anteriors • 2. M-D nearly as wide as I-C • 3. M-D is wider than F-L (other anteriors are wider F-L than M-D, except maxillary lateral ) • 4. Cross-section at cervical is triangular

Maxillary Lateral Incisor: • Smaller, more rounded than central • Root length almost as long • Greater variation in form (except 3 rd molars) • Sometimes missing congenitally

Maxillary Lateral… • Incisally more rounded than other incisors • Lingual-gingival groove and lingual pit common • Contact area – Mesial: incisal 1/3 near junction of incisal and middle third – Distal: junction of incisal and middle third (most cervical of the incisors)

Notes: (max lateral) • 1. Incisal edge contour is more rounded than any other incisor • 2. Most likely to have lingual pit of all incisors • 3. Lingual fossa and marginal ridges more prominent than other incisors • 4. DI corner most rounded of all incisal corner • 5. MD close to FL dimension (MD>FL)

Mandibular Incisors: • Simplest, least variable teeth • Proximal view: Incisal edge is lingual to long axis of tooth • Lateral has distal twist to crown • Contact areas: – Mesial and distal: incisal third • Bifurcated root sometimes found

Notes: (mand incisors) • Mandibular Central Incisor – Bilaterally most symmetrical – M and D contact areas both at same level in incisal third – Root shortest of anterior teeth – One wear facet on incisal edge • Mandibular Lateral Incisor – DI corner visible from mesial view – Distal contact area more lingual than mesial contact area

Maxillary Canine: • • Crown + root length = longest tooth Last succedaneous tooth to erupt Facial/lingual view: pentagonal (5 -sided) Contact areas: – Mesial: junction of incisal and middle third – Distal: middle third (most cervical of the anteriors)

• Proximal view: cusp tip is just facial to mid-line of root • MI cusp ridge shorter than DI • Presence of labial and lingual ridges • Cingulum more pronounced than mandibular • Single root is longest of any tooth

Notes: (max canine) • 1. Crown length nearly as long as maxillary central’s • 2. Two lingual fossae - ML and DL separated by lingual ridge • 3. Root is longest of all teeth • 4. Largest F-L of anteriors

Mandibular Canine: • • Narrower MD than maxillary Mesial outline is straight line MI cusp ridge shorter than DI Cusp tip located lingual to proximal long axis • Bifurcated root sometimes found • Contact areas: – Mesial: incisal third – Distal: junction of incisal and middle third

Notes: (mand canine) • 1. Crown longer than maxillary canine (longest crown in the mouth) • 2. Longest root in mandibular arch • 3. Total length almost the same as maxillary canine • 4. M and D height of contours more incisal than maxillary canine • 5. Facial outline “moon-shape”

Maxillary Premolars: • Crowns are wider FL than MD • 2 cusps, nearly equal size • 1 st is little larger than 2 nd

Maxillary 1 st Premolar: • Occlusal outline is hexagonal • Facial outline is pentagonal • Contact areas: – Mesial: junction of occlusal and middle third; mesial marginal groove – Distal: more cervically and facially located than mesial • MF cusp ridge is longer than DF – Facial cusp tip offset to distal – Lingual cusp tip offset to mesial facial to

• Lingual cusp of 1 st is shortest of maxillary premolars • Pronounced mesial concavity • Pronounced mesial marginal groove • More angular than 2 nd • M and D pits further apart - longer central groove • Less secondary grooves than 2 nd

Root structure of max 1 st premolar: • Type I - single root with 2 pulp canals – Cross section is kidney shaped, mesial indented • Type II - bifurcated root with root trunk (most common) • Type III - laminated root – Cross section is hour-glass • Trifurcated roots sometimes found: 2 buccal, 1 lingual

Notes: (max 1 st premolar) • 1. MB cusp ridge longer than DB cusp ridge (similar to primary max canine) • 2. Buccal cusp tip located distal to tooth midline • 3. Lingual cusp shortest of maxillary premolar cusps, tipped mesially • 4. Strong mesial crown/root concavity

• 5. Mesial marginal ridge shorter than distal marginal ridge • 6. Cervical cross-section is kidney shape • 7. Two canals (F and L) – lingual has larger pulp canal – facial pulp canal is longer (facial cusp taller)

Maxillary 2 nd Premolar: • • • Smaller in all dimensions than 1 st More rounded crown form F and L cusps nearly equal in height Lingual cusp tip offset mesially No mesial concavity

• More rounded than 1 st • M and D pits closer - shorter central groove • More supplemental grooves • Normally single root, bifurcation possible

Notes: (max 2 nd premolar) • 1. F and L cusps more equal • 2. M and D halves more symmetrical than other premolars • 3. Distal root surface has deeper depression

Mandibular Premolars: • • • 1 st is smaller than 2 nd FL and MD dimensions about equal F cusp more prominent than L Crown profile tilts towards lingual Normally single rooted, bifurcation possible

Mandibular 1 st Premolar: • Looks and functions more like canine – Lingual cusp non-functional • M and D height of contour in middle third (distal possibly more occlusal*) • Lingual cusp tip offset to mesial • Presence of ML developmental groove

• Occlusal view: rounded diamond shape • Distal fossa circular, mesial fossa linear • Mesial marginal ridge slopes at 45 o, distal ridge is horizontal • Single root, bifurcation possible (F and L roots)

Notes: (mand 1 st premolar) • 1. Both M and D height of contours at middle third (with distal possibly even more occlusal) • 2. Only premolar with a ML groove • 3. Proximal view - buccal cusp tip centered over root midline (unique of all premolars) • 4. Pronounced transverse ridge separating M and D fossae

• 5. Mesial marginal ridge inclined more than other premolar marginal ridges, more cervical than distal marginal ridge • 6. Buccal cusp occupies more of the occlusal surface than other premolars

Mandibular 2 nd Premolar: • Larger than 1 st mand premolar • 2 forms: 2 cusps and 3 cusps – Y type groove (3 cusps) most common • 3 pits: M, D, and central • Lingual groove present • No transverse ridge – U and H type grooves (2 cusps) • 2 pits, M and D • Transverse ridge present

• Resembles small molar: marginal ridges horizontal • Lingual height of contour at occlusal third (unique) • Single root, bifurcation possible (F and L) • Sometimes congenitally missing

Notes: (mand 2 nd premolar) • 1. Buccal cusp ridges less steeply inclined than other premolars • 2. Lingual height of contour at occlusal third (unique) • 3. Three occlusal patterns: Y, U, H

• 4. Y-shape type: – – – 3 cusps 5 developmental lobes Possible lingual groove 3 pits, 3 fossae (M, C, D) No true transverse ridge Lingual M-D width possibly wider than facial width*

• 5. Two-cusp pattern: (U and H shape) – – – 4 developmental lobes Lingual cusp tipped mesially No lingual groove 2 pits, 2 fossae Transverse ridge present More lingual taper than 3 -cusp type

Permanent Molars: • 1 st molars are cornerstones in development of occlusion • Crowns are largest and most complex • 3 - 5 cusps • Multi-rooted

Maxillary Molars: • • Crowns wider FL than MD Oblique ridge and DL groove unique 3 roots: lingual, MB and DB 4 cusps: ML, MB, DL

Maxillary 1 st Molar: • Largest tooth in maxillary arch • Shorter O-C than premolars • Contact areas: – Mesial: junction of occlusal and middle third – Distal: middle third • Distal cervical crown/root concavity • MB root oftentimes has 2 canals; apex inline with MB cusp tip

• • ML cusp largest Cusp of Carabelli Distal view: all 4 Mesial view: only (ML>MB>DB>DL) on ML cusps visible 2 cusps visible

• Occlusal view: rhomboidal form – MB and DL corners acute angle – DB and ML corners obtuse • Wider MD on lingual than buccal • V-shape CE dip toward bifurcation on facial surface

Notes: (max 1 st molar) • 1. Largest tooth in maxillary arch • 2. Largest crown in mouth, largest F-L dimension of any tooth • 3. Least variable in anatomic form • 4. Presence of a facial bucco-gingival ridge running mesiodistally • 5. Lingual width possibly wider than facial width

• 6. Pronounced distal cervical concavity • 7. Oblique ridge about same height as marginal ridges • 8. Three pits and four fossae • 9. Palatal (lingual) root wider M-D than F-L • 10. MB root might have 2 pulp canals: MB and ML canals

Maxillary 2 nd Molar: • Smaller than 1 st, esp. M-D • 2 crown forms: – Rhomboidal (like 1 st) – Heart-shaped (smaller DL cusp)

Notes: (max 2 nd molar) • 1. Two crown forms: rhomboidal and heart-shape (diminished DL cusp) • 2. MB root apex is inline with buccal groove

Maxillary 3 rd Molar: • Smallest molar in mouth • Most variation in crown and root form of any maxillary tooth • Most often congenitally missing

Notes: (max 3 rd molar) • 1. Most variable anatomic form of all teeth • 2. Shortest O-C crown of any tooth • 3. Shortest roots of any tooth

Brain overload… …all the best tomorrow!

Mandibular Molars: • MD wider than FL • Rectangular occlusal outline • 4 - 5 cusps – 2 lingual cusps same size

Mandibular 1 st Molar: • • 1 st permanent tooth to erupt Largest tooth of mandibular arch 5 cusps: MB>ML>DL>DB>D Contact areas: – Mesial: junction of occlusal and middle third – Distal: junction of occlusal and middle third

• CE sometimes dips towards bifurcation on facial • No transverse ridges(? ) • 3 fossae: central, mesial, distal • 2 roots: mesial larger than distal – Mesial has 2 root canals (MB & ML) • 3 roots sometimes: MB, ML, D

Notes: (mand 1 st molar) • 1. Facial surface is largest surface of any tooth • 2. CE line more occlusal on lingual than buccal i. e. root length is longer on lingual than buccal • 3. Mesial root has 2 pulp canals: MB & ML

• 4. Distal surface of M root and mesial surface of D root have deeper root depressions (inner surfaces of both roots) • 5. May exhibit 3 roots: – 2 mesial (MB, ML) roots – 1 distal root

Mandibular 2 nd Molar: • • • 4 cusps: MB largest Occlusal anatomy simplest of any molar Most symmetrical of molars 2 transverse ridges Root form similar to 1 st

Mandibular 3 rd Molar: • Variable in size and shape: • Type I: crown similar to 2 nd molar • Type II: crown similar to 1 st molar (5 cusps) • Often congenitally missing

Pulp morphology: • Functions of pulp: – – Formation of dentin Nutrition Sensation Defense and protection (reparative dentin)

Some things to remember: • Outline of pulp cavity follows external contour of tooth • Roots with round cross section possess one canal • Roots with oval or elongated cross section often more than one canal

• Lateral (accessory) canals: lateral canals found in the apical third • Supplementary canal: canal in excess of normal number of canals • Anastomosis: canal branch that connects horizontally between canals

• Know anatomical root forms of each tooth type, esp. in cross-section – Comparative widths (M-D vs F-L) – Shapes (e. g. oval, round, triangular, etc) – Number of pulp canals

Maxillary Central Incisor: • Newly erupted central has 3 pulp horns • Pulp chamber wider MD than FL • Cervical cross section, pulp outline triangular

Maxillary Canine: • Pulp cavity wider FL than MD (oval) • Root canal longest in mouth

Maxillary 1 st Premolar: • • • Wider FL than MD 2 roots (F and L), 2 canals Buccal pulp horn larger (larger F cusp) Lingual pulp canal larger diameter Cervical cross section is kidney shape

Maxillary 1 st Premolar

Maxillary 1 st Molar: • 3 roots, 3 - 4 canals • MB often has 2 canals (70%) • Lingual root/canal largest wider ML than FL

Mandibular Canine: • Sometimes has two roots and two canals (F and L)

Mandibular 1 st Premolar: • 1 -2 pulp horns, larger buccal, smaller/diminished lingual • 2 roots and 2 canals possible (F and L)

Mandibular 1 st Molar: • 2 roots, mesial (larger) and distal • 3 canals (70%) MB, ML, and D

Deciduous Dentition Some unique features. . .

Maxillary Central (primary) • 1. No mamelons • 2. M-D crown width greater than I-C width (only anterior tooth, primary or permanent, with this characteristic)

Maxillary Canine (primary) • 1. M & D contacts at same level • 2. M-D and I-C dimensions similar • 3. Mesial cusp ridge longer than D cusp ridge (similar to max 1 st premolar)

Maxillary 1 st Molar (primary) • 1. Crown does not resemble any other molar - appears more like a premolar • 2. Facial CE line dips prominently towards mesial • 3. No root trunk

Maxillary 2 nd Molar (primary) • 1. Larger than primary 1 st max molar • 2. Most closely resembles permanent 1 st maxillary molar • 3. Presence of Carabelli cusp • 4. No root trunk

Mandibular 1 st Molar (primary) • 1. Crown unlike any other tooth, primary or permanent • 2. Facial CE line dips prominently towards mesial • 3. Facial cervical ridge has strong mesial bulge

• 4. Pronounced mesial transverse ridge • 5. Mesial and central pits, no distal pit • 6. No root trunk

Mandibular 2 nd Molar (primary) • 1. Closely resembles permanent 1 st mandibular molar • 2. No root trunk

That’s Enough for Today!!!