MORPHOLOGY OF HUMAN PERMANENT DENTITION AND ERUPTION SEQUENCEPresented by:- Dr. Nitin GuptaPost graduate Student 1st year

OBJECTIVE Introduction of dental terminology and its application. Understanding dental anatomy. To study and facilitate communication about various aspects of teeth.

CONTENT INTRODUCTION CLASSIFICATION TOOTH STRUCTURE DENTAL ANATOMY

TERMINOLOGY GEOMETRIC

CONFIGURATION CONTACT AREAS AND

EMBRASURES SHAPE OF TOOTH &

CONTACT AREAS(Different Views)

ANATOMIC LANDMARKS ON TOOTH WITH INNERVATION

TOOTH IDENTIFICATION SYSTEM

TOOTH ERUPTION AND ITS MECHANISM

PERMANENT TOOTH MORPHOLOGY & VARIATION IN TOOTH MORPHOLOGY

ERUPTION SEQUENCE CONCLUSION REFERENCES

INTRODUCTIONTeeth are the calcified tissues present in oral cavity,Used in -chewing food, aids in speech, etc.

Dentition refers to set of all teeth in the upper jaw bone (maxilla)-maxillary teeth lower jaw bone (mandible)-mandibular teeth.

INTRODUCTIONHumans have 2 sets of teeth during a lifetime- Diphyodonty

(A)Primary/deciduous dentition- 1st set of teeth.

(B)Permanent/succedaneous dentition- 2nd set of teeth.

CLASSIFICATION BY MORPHOLOGY

HOMODONT DENTITION:- All teeth have same morphology

HETRODONT DENTITION:- Teeth have different morphology.

BY SETS OF TEETH

MONOPHYDONT DENTITION:-One set of teeth.DIPHYDONT DENTITION:- Two sets of teeth.POLYPHYDONT DENTITION:- Multiple sets of teeth.

DENTAL ANATOMY TERMINOLOGY

DENTAL ANATOMY TERMINOLOGY

Anterior teeth: Incisors and canines. 12 total (6 per arch).

Posterior teeth: Premolars and molars. 20 total (10 per arch).

CROWN TYPES

Anatomic crown: The portion of the tooth that extends from the cement enamel junction (CEJ) to the incisall edge or occlusal surface.

Clinical crown: The portion of the tooth that extends incisally or occlusally from the gingival margin (clinically visible portion of the tooth).

DENTAL ANATOMY TERMINOLOGY

CHEWING SURFACES Incisal edge: The chewing surface

of anterior teeth.

Occlusal surface: The chewing surface of posterior teeth consisting of cusps, ridges, and grooves.

Occlusal table: The occlusal surface within the cusp and marginal ridges.

TOOTH STRUCTURE

ENAMELImportant:- ORIGIN

Differentiated from ectodermal

cells of inner enamel epithelium

The most calcified and brittle substance in human body.

Color ranges from yellowish to grayish-white.

Semi translucent.

DENTIN An elastic vascular, mineralized tissue

that is harder than the bone but softer than the enamel.

Color is generally yellowish.

Important:- ORIGIN

Differentiated from

ectomesenchymal cells of dental

papilla.

PULP The soft connective tissue that supports

the dentin and is contained inside The pulp chamber of the tooth. Communicates to the periodontal

tissues via the apical foramen and accessory

Canals.

CLASSIFICATION OF PULPBy location Coronal: Found in the pulp horns. Radicular: Found in pulp canals.

FUNCTIONS OF PULP Formative: Has mesenchymal cells that

ultimately form dentin. Nutritive: Nourishes the avascular dentin. Sensory: Free nerve endings provide pain

sensation. Protective: Produces reparative dentin as

needed.

Important:- ORIGIN

Ectomesenchymal cells of the

dental papilla.

CEMENTUMAn avascular tissue about 10 μm thick that covers the radicular dentin.Composition most closely resembles bone.

FUNCTIONS OF CEMENTUM Support: Provides attachment for teeth

(Sharpey’s fibers). Protection: Helps prevent root

resorption during tooth movement. Formative: Continual apical cementum

deposition accounts for continual. Eruption: tooth eruption and

movement.

Important:- ORIGIN

Differentiated ectomesenchymal

cells of the dental follicle.

CEMENTUM MORPHOLOGY AT CEJ

ENAMEL SURFACE JUNCTION

LINE ANGLE:- Formed by 2 Surface.

POINT ANGLE:- formed by 3 surface.

Line angle

Point angle

Anterior 6 4Posterior 8 4

EMBRASURES Contact area:- The location

at which the proximal surfaces of two adjacent teeth make contact.

Embrasure:- A triangular-shaped space between the proximal surfaces of adjacent teeth which diverges in four directions from the contact area.

Buccal Lingual Occlusal/incisal Cervical/gingival :-

(interproximal space): In health, this space is completely filled within the gingival papilla.

IMPORTANT:-Largest occlusal

embrasure: between max

canine and PM1.

■ Largest incisal

embrasure: between max

lateral and canine.

■ Smallest incisal

embrasure: between

mandibular centrals.

■ In general, lingual

embrasures > buccal

embrasures, except Max

M1 (buccalembrasures > lingua

DIVISSION OF TEETH

CONTACT AREAS(Different views)

CONTACT AREAS MAXILLARY HEIGHT OF CO

NTOUR MANDIBULAR HEIGHT OF CON

TOUR

CONTACT AREAS PROXIMAL CONTACTS (FACIAL

VIEW)

Generally located increasingly more incisally (occlusally) from the posterior to the anterior.

The mesial contact is always located more incisally than the distal.

Proximal contacts prevent rotation, mesial drift, and food impaction.

PROXIMAL CONTACTS (OCCLUSAL VIEW)

All are located in the middle 1/3 of the crown. Posterior contacts are positioned slightly buccal  

GEOMATRIC CONFIGURATION

GEOMATRIC CONFIGUATION

PROXIMAL SURFACE SHAPES

Triangular: All anterior teeth.

Trapezoidal: All maxillary posterior teeth.

Rhomboidal: All mandibular posterior teeth

ANATOMIC LANDMARKS ON TEETH WITH INNERVATIONS

ENAMEL SURFACE ELEVATIONS

Lobe: The primary center of enamel formation in a tooth. In fully formed teeth, lobes are represented by cusps, mamelons, and cingula, and are separated by developmental depressions (anterior teeth) or developmental grooves (posterior teeth).

Mamelon: A round extension of enamel on the incisal edge of all incisors. There are usually three mamelons per incisor (one for each facial lobe). They are often translucent because of a lack of underlying dentin. Mamelons are typically worn down by attrition and mastication; thus, their presence in adults is an indication of malocclusion.

Cingulum: A bulbous convexity of enamel located on the cervical third of the lingual surface of all anterior teeth.

Cusp: A large elevation of enamel located on the occlusal surface of all posterior teeth and the incisal edge of canines.

Tubercle: An extra formation of enamel on the crown of a tooth. Often manifests as a supernumerary cusp, such as the cusp of Carabelli.

ENAMEL SURFACE ELEVATIONS

Ridge: A linear elevation on the enamel surface. Marginal ridge: A ridge on all teeth that forms the mesial and distal margins of posterior

occlusal surfaces and anterior lingual surfaces. Center of the facial crown surface. More prominent in maxillary canines.

Buccal (cusp) ridge: A ridge only on premolars that runs occlusocervically in the center of the buccal crown surface. More prominent in first premolars.

Cervical ridge: A ridge on all primary teeth and permanent molars that runs mesiodistally in the cervical third of the buccal surface of the crown.

Oblique ridge: A ridge on all maxillary molars that extends from the ML to DB cusps (it separates the MB and DL cusps).

Triangular ridge: A ridge on all posterior teeth that extends from the cusp tip to the central groove. The ML cusp of all maxillary molars has two triangular ridges.

Transverse ridge: A ridge on most posterior teeth that runs buccolingually and connects opposing buccal and lingual triangular ridges. Most common on maxillary premolars and mandibular molars.

ENAMEL SURFACE DEPRESSION

Sulcus: A V-shaped depression on the occlusal surface of posterior teeth between ridges and cusps.

Fossa: An irregularly shaped depression in the enamel surface.

Developmental groove: A well-defined, shallow, linear depression in enamel that separates the cusps, lobes, and marginal ridges of a tooth.

Fissure: A narrow crevice at the deepest portion of the developmental groove in enamel.

Pit: A small pinpoint concavity at the termination or junction of developmental grooves.

Supplemental groove: An irregularly defined, short groove auxiliary to a developmental groove that does not separate major tooth parts.

INNERVATION All dental and periodontal innervation arises from the

trigeminal nerve CN V). The maxillary nerve (V-2) supplies the maxillary

teeth. The mandibular nerve (V-3) supplies the mandibular

teeth.Blood Supply

ARTERIAL SUPPLY All dental and periodontal arterial supply arises from

the maxillary artery. The arterial supply generally parallels the

corresponding nerves. VENOUS RETURN All dental and periodontal venous return drains to the

pterygoid plexus of Veins, which eventually forms as the maxillary vein.

TOOTH IDENTIFICATION NUMBER

Tooth is represented by a number 1 – 8 (permanent) or a letter A – E (deciduous).

Two lines; indicates which quadrant the tooth belongs to A horizontal representing the

occlusal plane and A vertical representing the midline Examples: Maxillary right central incisor 1

Mandibular left second deciduous molar E

PALMER/ZSIGMONDY NOTATION SYSTEM

UNIVERSAL NUMBERING SYSTEM

Uppercase letters for deciduous teeth Consecutive from A to T Following a clockwise order from maxillary

right second molar to mandibular right second molar

Numbers for permanent teeth Consecutive from 1 to 32 Following a clockwise order from maxillary

right third molar to mandibular right third molar

FDI NUMBERING SYSTEMEach tooth is allocated a two-digit number; the left designates the quadrant and the right designates the tooth order Examples:-

Mandibular right permanent canine- 43Maxillary left deciduous lateral incisor- 62

TOOTH ERUPTION SEQUENCE AND MECHANISM

TOOTH ERUPTIONS 1. Primary dentition period - In this only deciduous teeth are present, and occurs

from approximately six months to six years of age. It ends with the eruption of the first permanent tooth, normally the mandibular first molar.

2. Mixed dentition period - That period during which both deciduous and permanent teeth are present, and lasts from approximately 6years to 12 years of age.

3. Permanent dentition period- That period when only permanent teeth are present, and which begins at approximately twelve years of age and continues through the rest of life.

ERUPTIONS

• 6months• Eruption of

deciduous mandibular central incisors

Primary

• 6 yrs• Eruption of

Permanent Mand. 1st molar

Mixed

• 12 yrs• Exfoliation

Of deciduous Maxillary 2nd molar

Permanent

THEORIES OF ERUPTIONThere are four most accepted theories of eruption, namely:

Root elongation theory

Alveolar bone remodelling theory

PDL (periodontal ligament) traction theory

Dental follicle theory

ROOT ELONGATION THEORY Root formation appears to be the

cause of tooth eruption since, it causes an overall increase in the length of the tooth along with the crown moving occlusally.

Some teeth erupt a greater distance than the total length of their roots, and teeth will still erupt after the completion of root formation or when the tissues forming the root--the apical papilla, Hertwig's epithelial root sheath, and periapical tissue are surgically removed.

ALVEOLAR BONE REMODELLING THEORY

Formation of bone apical to developing teeth has long been proposed as one mechanism for eruption.

It is observed that the alveolar process forms during tooth development and is locally deficient in sites where primary and permanent teeth fail to develop.

PDL(periodontal ligament) TRACTION THEORY Formation and renewal of PDL has

been considered a factor in tooth eruption because of the traction power that fibroblasts have.

This force is transmitted to the extracellular compartment to collagen fibres, which aligned in an appropriate inclination bring about root formation, bring about tooth movement.

Not accepted because-impacted teeth with well developed PDL do not erupt.

Rootless teeth also erupts

DENTAL FOLLICLE THEORY Reduced enamel epithelium(REE) &

follicle is associated with tooth eruption.

REE initiates a signalling mechanism that attracts osteoclasts, also secretes proteases which breaks connective tissue.

Dental follicle is necessary to permit bone remodelling while eruption.

CLINICAL CONSIDERATIONS• Local factors include –

Deciduous teeth with consequent drifting of opposing teeth to block the eruptive pathway.

Severe trauma – Eruption cyst.Crowding of teeth in small jaws –Third molars and canines are

teeth mostly impacted.

Systemic Factors

Nutrition Genetic Endocrine

MORPHOLOGY OF PERMANENT DENTITION

TO BE DISCUSS MAXILLAY TEETH

1. CENTRAL INCISOR2. LATERAL INCISOR3. CANINE4. FIRST PRE MOLAR5. SECOND PRE MOLAR6. FIRST MOLAR7. SECOND MOLAR

MANDIBULAR TEETH1. CENTRAL INCISOR2. LATERAL INCISOR3. CANINE4. FIRST PRE MOLAR5. SECOND PRE MOLAR6. FIRST MOLAR7. SECOND MOLAR

MAXILLARY THIRD MOLAR

Maxillary 3rd Molar

DIMENSIONS

FACIAL VIEW Crown Dimensions

The mesiodistal crown dimension is greater than the occlusocervical crown dimension Crown-Root Dimensions

The maxillary third molar has a uniquely small apical-occlusal (crown and root combined) dimension Crown Outline Form

The outline form of the crown has been described as trapezoidal Facial Cusp Height/Form

The distofacial (distobuccal) cusp is very short and flattened Facial Groove Location

The facial groove is closer to the distal surface of the crown, making the mesiofacial cusp larger than the distofacial cusp

Mesial Proximal ContactThe area of greatest mesial convexity (mesial proximal contact) has been located in the middle third of the crown

Root LengthIn the maxillary arch, the third molar has uniquely short roots

Root CurvatureMost of the roots curve distally in the apical third

 

LINGUAL VIEW Mesiolingual Cusp Size

The mesiolingual cusp is usually the largest cusp Distolingual Cusp Size/Pressure

The distolingual cusp is very poorly developed or may be entirely missing Lingual Root Curvature

The lingual root often has a marked distal inclination

MESIAL VIEW Crown Dimensions

The faciolingual (buccolingual) crown dimension is greater than the occlusocervical crown dimension

Crown Outline FormThe outline form of the crown has been described as trapezoidal

Facial Height of ContourThe facial height of contour is in the cervical third of the crown

Lingual Height of ContourThe lingual height of contour is in the middle third of the crown

DISTAL VIEW Occlusal Surface Visibility

Much of the occlusal surface is visible because of the angulation of the occlusal surface relative to the long axis of the root

Facial Surface VisibilityThe markedly smaller distofacial cusp permits much of the facial surface to be visible

Marginal Ridge LocationThe distal marginal ridge is located farther apically than the mesial marginal ridge

OCCLUSAL VIEW Mesial Crown Dimension

The faciolingual dimension of the mesial half of the crown is considerably larger than the distal half

Crown Outline FormThe predominant occlusal outline form is “heart-shaped”

Mesial Proximal ContactThe mesial proximal contact has been located facial to the faciolingual center of the crown

Lingual Surface FormThe form of the lingual aspect of the crown is semicircular

CuspsThere are 3 functioning cusps on the typical third molar: two facial and one lingual cusp

Oblique RidgeThe oblique ridge is poorly developed and often absent

Supplemental Grooves There are numerous supplemental grooves present, giving it a “wrinkled”

appearance 

MANDIBULAR THIRD MOLAR

DIMENSIONS

Facial View

Crown DimensionsThe mesiodistal crown dimension is greater than the occlusocervical crown dimension

Occlusocervical Crown DimensionFrom a facial view, the distal half of the crown has a noticeably shorter than the mesial half

Mesiofacial CuspThe mesiofacial cusp is often the widest and tallest of the facial cusps

Mesial Proximal ContactThe mesial proximal contact has been located at the junction of the occlusal and middle thirds

Root LengthThe root length is only about half again as long as the occlusocervical crown dimension

Root TrunkThe root trunk is long

Root ProximityThe roots are often fused together and if separate, the root trunk is long and the root apices are usually pointed

 

LINGUAL VIEW

Cusp SizeThe mesiolingual cusp is the largest of all the cusps

Cusp FormThe lingual cusps are rounded

MESIAL VIEW

Crown DimensionsThe faciolingual (buccolingual) crown dimension is greater than the occlusocervical crown dimension

Cusp ProximityThe faciolingual distance between the cusp tips is reduced

Facial Crown FormThe facial surface is very convex and the tooth has a bulbous form

Mesial Proximal ContactThe mesial proximal contact has been located one third of the distance between the cusp tip and the cervical line

Mesial RootThe mesial root is broad faciolingually but short

DISTAL VIEW

Cervical Crown FormThe contour of the cervical crown surface has been described as flat or slightly convex

Distal RootThe distal root is narrower faciolingually and shorter than the mesial root

 

    OCCLUSAL VIEW

Crown DimensionsThe mesiodistal crown dimension is greater than the faciolingual crown dimension

Faciolingual DimensionThe mesial aspect of the crown is much wider faciolingually than the distal half

Crown Outline FormThe occlusal outline form is often ovoid

Crown ConvergenceThe crown tapers from mesial to distal but only slightly from facial to lingual

Number of CuspsThird molars often have 4 cusps (mesiofacial, distofacial, mesiolingual, and distolingual)

Marginal Ridge FormThe mesial and distal marginal ridges are highly convex arcs

Pit-Groove FormThe pit-groove pattern is highly irregular

The occlusal surface is quite “wrinkled” due to numerous supplemental grooves and ridges

DIFFERENCE BETWEEN PERMANENT AND DECIDOUS TEETH Lighter in color. Pulp cavities are large Crown is more bulbous and constricted. Crown is smoother. Anterior teeth are wider M-D & shorter Insicocervically. Primary molars are shorter & narrower M-D at cervical 3rd. Root tapers more rapidly. Root are long 7 slender Root trunk is shorter. Enamel stops abruptly at CEJ. Enamel is thinner

DENTAL ANATOMY FACTS  The primary second molar generally exhibits cusp of Carabelli Mandibular central incisors and Maxillary third molars generally occlude with only one

opposing tooth.. The tooth with the longest root is the maxillary canine. Maxillary incisors are the only anterior teeth that are wider mesio-distally than facio-lingually Mandibular Molars are the only posterior teeth that are wider mesio-distally than facio-

lingually The MAX canine is the only tooth that has potentional of contacting both anterior and

posterior teeth There are a total of 12 teeth in the permanent dentition that normally have cingulums Maxillary lateral incisors have the most distinct and deepest lingual fossa’s of all anterior

teeth. The DL groove of a MAX lateral incisor is an anatomical feature that complicates root

planning

The softest dental tissue is cementum. The hardest dental tissue is enamel

The maxillary 1st premolar has a mesial concavity that makes it difficult to adapt a matrix band

The largest root of the maxillary molar is the palatal. The smallest root of the maxillary molar is the distofacial

The Mandibular 1st molar has the greatest m-d diameter of all molars A key feature that differentiates a mandibular1st & 2nd molar is the number

of developmental grooves Another feature is the number of cusps The facial cusp of the maxillary 1st premolar is offset to the distal The distolingual cusp of maxillary molar is the only one that is not part of

the molar cusp triangle Mesiolingual groove is an identifying characteristic for the mandibular 1st

premolar

CONCLUSION Exact tooth contours can only be reproduced in a restoration when we are clear

with the anatomy of that particular tooth. Studying the morphology of the teeth helps us to understand the relationship of

teeth to one another, to differentiate each type of tooth, define restoration contours and visualize the crown contours in order to adapt the instruments properly and replicate the morphology.

Thus if we are able to reproduce the exact contours of the tooth in our restoration , we provide the patient with a harmonious occlusion and in turn healthy and physiologic stomatognathic system.

REFERENCE Ash MM, Nelson S. Wheeler’s Dental Anatomy, Physiology and

Occlusion.8th ed. Saunders; 2003. Woelfel JB, Scheid RC. Dental anatomy : its relevance to dentistry. 7th ed.

Lippincott Williams and Wilkins; 2007. Neville B, Damm DD, Allen CM, Bouquot J. Oral and maxillofacial pathology.

3rd ed. Elsevier; 2009. Ten Cate AR, Copeland E. Oral Histology.7th ed. Mosby; 2008.