CONTENTS

Introduction Learning objectives Normal tooth structure Components of pulp system Comparative study of deciduous and permanent tooth structure Techniques for vascularization of internal anatomy Detailed study of internal anatomy of permanent tooth Detailed study of internal anatomy of deciduous teeth Variation in normal pulpal structure and its significance

o Physiological o Pathological o Development o Others

Conclusion References

Introduction : The alliance between endodontics and pulp anatomy is inflexible and inseparable.

As a cause of treatment failure lack of know ledge of pulp anatomy ranks second only to error in diagnosis and treatment planning. This implies that an endodontist must be thoroughly cognizant of the anatomic shapes its variation and its relationship to other significant landmarks. Leading objectives :

- Recognize error that may cause difficulties or failures in root canal treatment owing to lack of knowledge or pulp anatomy.

- To know common shapes of root in cross section and common canal configurations.

- To know average tooth length, number of roots and most common root curvatures.

- Define pulp space and describe its major components. - State the tenet of pulp-root anatomy. - List and recognize the significance of iatrogenic or pathologic factors that may

alteration in pulp anatomy. - To know location, morphology frequency and importance or accessory canals. - To know the relationship between anatomic apex, radiographic apex and actual

location of apical foramen. NORMAL TOOTH STRUCTURE :

A tooth can be broadly divided into - Crown (coronal portion). - Root (Radicular portion).

The various components of tooth are _________ the outer most layer or crown is Enamel : It is the hardest calcified tissue in human body. It forms a protective covering over the entire surface of crown. The shape and contour of the cusps receive their final modeling in enamel. Dentin : The dentin provides the bulk and general form of the tooth and is characterized as a hard tissue with tubules throughout its thickness. Since it forms slightly before enamel it determines the shape of crown including the cusp and ridges and the number and size of roots. Pulp : The dental pulp occupies the center of each tooth and consists of soft connective tissue. Every person normally has a total or 52 pulp organs (32 permanent, 20 primary). Each or these organs has a shape that conform to that of respective tooth.

Total volume of all permanent teeth pulp organ = 0.38 cc. Mean volume of a single adult human pulp = 0.02 cc.

Cementum : Cementum is the mineralized dental tissue covering the anatomic roots of human teeth. It furnishes a medium for the attachment or collagen fibres that bend the tooth to the surrounding. Periodontal ligament : The periodontal ligament is the connective tissue that surrounds the root and connects it to the bone. It is continuous with the connective tissue or gingiva and communicates with marrow spaces through vascular channels in the bone.

COMPONENTS OF PULP SYSTEM : The pulp system can be classified into

- Coronal pulp - Radicular pulp

Coronal pulp : Each pulp organ is composed of a coronal pulp located centrally in the crowns of

teeth. The coronal pulp in young individuals resemble the shape of the outer surface of the crown dentin. The coronal pulp has six surfaces – occlusal (roof), mesial, distal, buccal, lingual and the floor.

The cervical region or pulp organ constricts as does the contour of the crown and at this zone the coronal pulp joins the radicular pulp. Because of continuous deposition of dentin the pulp becomes smaller with age. This is not uniform in all areas of coronal pulp but progresses faster on floor than on roof or side walls.

Dentinal maps as anatomical lines present on floor joining orifices. An important or coronal pulp is pulp horns. Pulp horns : These are prolongations / projections in the roof of pulp chamber that correspond to various major cusps or lobes.

A single pulp horn tends to correspond with each cusp in posterior teeth. Occlusal irtent correspond to height of contour in younger teeth whereas in order teeth it leis closer to cervical margin.

“Pulp horns represents what the dentist does not want to locate during restorative procedures but does want to locate during access preparation.”Clinical significance :

During access preparation the height and location of pulp horns may be more accurately determined by measuring from cusp tip to pulp horn or chamber roof using a bur and a handpiece. RADICULAR PULP :

Radicular pulp is that pulp extending from the cervical region of the crown to root apex. The radicular portion of the pulp are continuous with the periapical connective tissue through the apical foramen.

Significantly most canals are curved in faciolingual direction which may not be obvious on facial projection. CANAL CONFIGURATIONS : According to Weine : Type – I : Single canal from pulp chamber to apex. Type – II : Two separate canals leave the chamber to merge short of apex into one canal. Type – III : Two separate canals leaving the chamber to apex. Type – IV : One canal leaving the pulp chamber but dividing short of apex into two separate different foramina. According to verticle : Type I : A single canal extends from the pulp chamber to apex.

Type II : Two separate canals leave the pulp chamber and join short of the apex to form one canal. Type III : One canal leaves the pulp chamber and divides into two in the root; the two then merge to exit as one canal. Type IV : Two separate, distinct canals extend from the pulp chamber to apex. Type V : One canal leaves the pulp chamber and divides short of the apex into two separate distinct canals with separate apical foramen. Type VI : Two separate leave the pulp chamber merge in the body of the root and redivide short of the apex to exist as two distinct canals. Type VII : One canal leaves the pulp chamber divides and then rejoins in the body of the root and finally redivides into two distinct canals short of apex. Type VIII : Three separate distinct canal extend from pulp chamber to apex.. According to grossman : Type I : Single canal from pulp chamber to apex. Type II : Two separate canals leaving the chamber. Type III : One canal leaving the pulp chamber but dividing short of apex in two separate different canals with separate apical foramen. Type IV : Two separate canals leave the chamber to merge short of the apex into one canal. ACCESSORY CANALS :

Accessory canals are minute canals that extend in a hornontal vertical or lateral direction from pulp to peridontium.

73.5% - apical 1/3rd 11.4% - middle 1/3rd 15.1% - cervical 1/3rd

These canals contain connective tissue and vessels but do not supply pulp with collateral circulation. Formation :

They are formed by entrapment of periodontal vessels of periodontal vessels in Hertwigs epithelial root sheath during calcification.

Accessory canals have a mean diameter or 6 to 60 m. In anterior teeth Seltzer (1966) observed 34% incidence of accessory canals.

DETECTION OF ACCESSORY CANALS : Thickening of periodontal ligament or development of a frank lesion in the lateral wall of the root would reveal the presence of a lateral canal. So during examination complete stretch or lamina dura all around root should be studied. Many times in clinical practice the presence of these canals become noticeable only in post obturation x-ray.Clinical significance :

These act as avenues for interchange of / passage or irritants. Pulp may become inflamed or necrotic from the presence of deep periodontal pockets which cause deep periodontal pockets which cause exposure or the orifices of the canals thereby permitting the ingress or toxic products into the pulp. Conversely breakdown products

or inflammatory pulp lesions may have an effect on the periodontal tissues via these canals, causing inflammatory changes.

Furcation canals : Accessory canals may also occur in bifurcation or trifurcation of multirooted

teeth. Vertucei and Williams called these furcation canals. Formation :

These form as a result of entrapment of periodontal vessels during the fusion of the diaphragm which becomes the pulp chamber floor.

Diameter or furcation opening – 4 – 720 m. Mandibular teeth have a higher incidence of foramen on both pulpal chamber floor and furcation surface.

N mandibular molar these canals occurs in three distinct patterns. Clinical significance :

These canals may be the cause of primary endodontic lesions in the furcation of multirooted teeth. Isthumus :

Isthumus is a marrow ribbon shaped communication between two root canals that contain pulp or pulpally derived tissue.

It is also called as transverse anastomasis (Vertucei 1984), corridor (Green 1973) lateral connection (Pineda 1973).

Kim et al has identified five types or isthmi that can be found on believed root surface. Type I : It an incomplete isthmus, it is a faint communication between two canals.Type II : It is characterized by two canals with a definite connection between them (complete isthmus). Type III : It is a very short complete isthmus between two canals. Type VI : It, complete or incomplete isthmus between three or more canals. Type V : It is marked by two or three canal opening without visible connections.

Occurrence : Isthmi are found in 15% of anterior teeth in maxillary premolar they are found 16% at the 1mm resection level and in 52% at the 6mm resection level.

The prevalence isthmi increases in the misiobuccar root or maxillary first molar from 30% to 50% as root is resected from 2 to 4 mm level. Eighty presence of mesial root of mandibular first molar have isthmi at 3 to 4 mm resections level where as 15% or distal roots have isthmi – 3mm level. Clinical significance : Presence of isthmus must be suspected whenever multiple canals are seen on a resected root surface.

They must be prepared and failed during surgery as these isthmus acts as reservoir or bacteria. ANATOMY OF APICAL ROOT :

The classic concept of apical root anatomy is based on three anatomic and histologic landmarks in the apical region of a root.

- Apical constriction - Cementodentinal junction - Apical foramen.

Apical constriction : The apical constriction is considered the part of the root canal with the smallest

diameter. It is also the reference point clinicians most often as the apical termination for

shaping, cleaning and obturation. This is generally 0.5 – 1.5 mm inside the apical foramen. From the apical constriction or minor apical diameter the canal widens as it

approaches the apical foramen or major apical diameter. The space between the major and minor diameter has been described as funnel

shaped or hyperbolic or as having the shape or a morning glory. The mean distance between the major and minor apical diameter is 0.5 mm in a

young person and 0.67 mm in older individual. It is greater in older indivicial because of build up of cementum.

Apical foramen : The apical foramen is the circumference or rounded edge like funnel or crater that

differentiates the termination of cemental canal from the exterior surface of root. Diameter :

503 - (18-25 yrs) 681 - (over 55 yrs).The apical foramen does not normally exit at the anatomic apex but is offset 0.5 –

3 mm. This correction is more marked in older teeth through cementum apposition.Cementodentinal junction :

It is the point in the canal where cementum meets dentin. It is the point where the pulp tissue ends periodontal tissue begins. It is not in the same area as apical constriction but 1 mm from apical foramen.

Cementodentinal junction should be considered just a variable junction at which two histologic. Tissues meet in the root canal. The extent or cementum deposition on each wall of the root canal varies; one wall usually covered with a greater quality of cementum than the other wall. Apical delta :

The principal canal may or may not exit as a single apical foramen. In many instances it may slit near the apex and exit in two or more smaller foramina. This Y shaped branching of root canal near the apex is called apical delta.

Pulpal tissue :Pulpal tissue can be categorized into

- Apical pulp tissue - Coronal pulp tissue

Apical pulp tissue is mainly found in the apical end of root. Most probably continuing into surrounding periapical region. Apical tissue is more fibrous and contains fevers cells. Histochemical studies by Yamashi et al in 1986 demonstrated large concentrations or glycogen in apical pulp tissue, a condition compatible with the presence of anaerobic environment. In gross appearance the collagenous apical tissue is whitish in colour. The fibrous tissue acts as a barrier against apical progression of pulpal inflammation.

The coronal pulp tissue contains mainly cellular connector tissue and fever collagen fibers.

COMPARATIVE STUDY OF STRUCTURE OF DECIDUOUS AND PERMANENT TOOTHPrimary tooth Permanent tooth - Pulp chamber larger in relation to

crown sire- Pulp chamber smaller in relation to

crown sire. - Pulpal outline follows the DEJ

more closely - Pulpal outline follows DEJ less

closely. - Pulp horns are closer to outer

surface. Mesial pulp horn extends to a closer approximation of surface than does the distal pulp horns

- The pulp horn are comparatively aware from outer surface.

- Floor or pulp chamber is porous. Accessory canals in primary pulp chamber leads directly into inter radicular furcation

- Floor or pulp chamber does not have any accessory canal.

- The roots are larger and more slender in comparison to crown size

- The roots are shorter and bulbous in comparison to crown.

- Furcation is more towards cervical area so that root trunk is smaller

- Placement of furcation is apical these the root trunk is larger.

- The roots are narrower mesiodistaly

- The roots are broader mesiodistally

- At cervical region the roots of primary molar flare outward and continue to flare, as they approach the apices to accommodate the permanent.

- Marked flaring or root is absent.

- Root canals are ribbon like. The radicular pulp follows a thin tirtuous and branching pulp.

- Root canals are well defined with less branching.

- Roots have enlarged apical foramens. Thus abundant blood supply

- Foramens are restricted reduced blood supply favours calcific response and healing by calcific scar.

TECHNIQUES FOR STUDYING INTERNAL ANATOMY : - Diagnostic measures - Radiography - Dyes, lirafrony (India ink, Haematonyless, chenese). - Clearing (using xylene, berizone). - SEM (scanning electron microscope). - Dental operating microscope. - fiberoptic endoscopy.

Diagnostic measures : Diagnostic measures are important aid in localization or root canal orifices.

These include- Examining the pulp chamber with a sharp explorer. - Troughing grooves with ultrasonic tips. - Staining the chamber floor with methylene blue. - Performing the CHAMPAGNE BUBBLE TEST with sodium hypochlorite –

allowing the sodium hypochlorite to remain in the pulp chamber may aid in location or a calcified root canal orifice. The bubbles may appear in solution indicating the position of orifice.

Radiography : Inspite of the recent advances radiographs remain to be the primary and most commonly used method for visualization. Careful evaluation of two or more periapical radiographs exposed at different horizontal angulation helps in assessing the number and position or canals. Scanning election microscope :

It has been used to determine the number and size of main apical foramen and their distance from the anatomic apex and the size of accessory foramina. Dental operating microscope :

Introduction of dental operating microscope has lead to enhanced visibility and lighting to the internal architecture. Light is significantly improved because light or a microscope is parallel the line or sight. These have been found to be effective for locating MB-2 canals in maxillary molar DOM makes canal easier to locate by magnifying and illuminating the grooves in the pulpal floor and by distinguishing the color differences of the dentin of floor and wells.

Fiberoptic endoscopy : This helps immensely in a better visualization of root canal and periapical spaces.

This works in conjunction with a camera, light source and monitor currently there exists two diameter sizes of flexible fiberoptic probes used in endodontic.

- 1.8 mm (30,000 visual fiber). - 0.7 mm (10000 visual fiber).

A ring or much larger light transmitting fibre surrounds the visual fibres. The 0.7 mm fiberoptic probe is used for intra canal visualization and also to determine now well a canal is prepared.

STRUCTURE OF INDIVIDUAL TOOTH Maxillary central incisor

Average tooth length – 22.5 mm : (Root length is 1½ times or crown length). Pulp chamber : The pulp chamber of maxillary central incisor is equidistant from dentinal walls. Pulp chamber is wider mesiodistally than labio lingually with broadest pare incisally.

Three pulp horns corresponding to developmental Mamnelons are present. A lingual shoulder is present which must be removed to gain access to lingual wall.

Division between pulp chamber and canals are indistinct. Root canals :

The maxillary central incisor has one root with one root canal. It is broader labioparatally conical in shape and centrally located. Cross –section :

Cervical 1/3 - Triangular (young) Oval (old)

Middle 1/3 - OvoidApical - Round.

Lateral canals (24% or specimens) in apical third. Root curvatures - Straight – 75%

Labial – 9% Distal – 8% Mesial – 4%

The palatal and labial curvatures may not be seen in routine radiographs unless taken at different horizontal angles.

The apical foramen is centrally located in the anatomic apex in only 12% cases and apical delta is present in 1% cases.ANATOMIC RELATIONSHIP IN SITES L The labial surface of the root of the maxillary central incisor lies under the labial cortical plate of maxilla and may fuse with it. Because of proximity to the labial surface fenestration / dehiscence may be seen.

The relationship between apex of maxillary control incisor and nasal floor depends

- Height or face - Length of the root

Maxillary control incisor 20 mesioaxial. 250 palatoaxial.

Inclination in the alveolous. - Incisor canal parallel the long axis so its sever as guide for palatine injection.

Clinical significance : Lingual shoulder should be removed for straight line access. Outline of access cavity changes to more oval shape as tooth matures and pulp

horns recede.

MAXILLARY LATERAL INCISORAverage tooth length : 22 mm : Pulp chamber : The outline of pulp chamber is similar to central except it is smaller. It has two or no pulp horns. It is broader mesiodistally with its broadest past incisally. The division between root canal and pulp chamber is indistinct. ROOT CANALS : Maxillary lateral incisor has a single root and an single root canal but it has a finer diameter. CROSS SECTION : Cervical 1/3rd – Ovoid labiopalatally

Middle 1/3rd – Ovoid Apical 1.3rd – Round Lateral canals occur more frequently than central incisors.

Root curvature - Distal – 53% Straight – 30% Palatally – 4% Bayonet – 6%

The apical foramen is centrally located in the anatomic apex in 22% or cases and apical delta is present in only 3% of cases. Anatomic relationship in sites :

The labial surface of root of the maxillary lateral under the cortical plate of maxilla. Therefore fenestration dehiscence may be present. As this root curves distally it may be center or cancellous lower pointing palatally. Location in alveolus - 160 mesioaxial

290 palatoaxial Clinical significance :

- Two or three canals have been reported. - In cases of Dens invaginatez peg lateral, Talons cusp require modification in

access opening.

MAXILLARY CANINETooth length – 26.5 mm :Pulp chamber : The pulp chamber are largest of any single rooted teeth. no pulp horns smallest pointed incisal edge corresponds to single cusp. The pulp chamber is wider labiolingually than mesiodistally. Labiopalatally the pulp chamber is triangular shape apex towards the single cusp broad base towards the cervical third. Mesiodistally it is narrow resembling to flame. ROOT CANAL : The single root canal of maxillary canine larger than that of maxillary incisor. It is wider labiopalatally. Gradually it tapers to an apical constriction. CROSS SECTION :

Cervical 1/3 - Oval Middle - Oval

Apical - Constricted Lateral canals are present in 30% cases.

Root curvature - Straight – 39% Distally – 32%Palatally – 7% Labally – 13% Bayonet / s – 7% Dilacerations – 2%.

The apical foramen is centrally located in anatomic apex 14% of cases and an apical delta is present in only 3%.

ANATOMIC RELATIONSHIP IN SITES : An abscess originating in the maxillary cuspid usually perforates labial cortical plate.

- It below insertion of levatormuscle – Buccal vestibule. - It above the insertion – canine space cellulites.

Apical curettage may be difficult ding periradicular procedures because of length of the root. Location in alveolus - 60 Destoaxial

210 Palatoaxial Clinical significance :

- Buccal bone over canine immune disintegrates leading to fenestration. Slight permanent apical sensitivity occasionally occurs after root canal therapy. This can be corrected by apical root surgery.

- Apical curettage may be difficult. MAXILLARY FIRST PREMOLAR

Tooth length – 20.6 mm :Pulp chamber : The pulp chamber is wider bucco lingually and narrow mesiodistally. It has a pulp horn under each cusp but both may be missed in routine radiographic projections because of superimposition. Two pulp horns are present. Buccal is larger than the palatal one. Roof of the pulp chamber coronal to cervical line. Floor is convex. Usually below the cervical line. In cross section chamber is wide and ovoid in buccopalatal direction. ROOT CANALS :

- The maxillary first premolar has 2 roots in 54.6% cases. Out of this roots are separated (21.9%) partially fused (32.7).

- Irrespective or whether it has one root / two root it has 2 canals at the apex in 69% cases.

- When fused root occur a groove summing in occlusoapical direction dividing root into buccal and palatal portions.

- The palatal canal is larger of the two and is directly under palatal cusp and its orifice can be penetrated by following the palatal wall of pulp chamber.

- Twenty six percent of these teeth have only one canal at the apex. Of these only 1% have 1 canal exiting at the apex whereas 18% have 2 orifices in the pulp chamber that coalesce to form a single canal at apex. Transverse canals between canals are common.

- Lateral canals may be present in 49.5% cases with 11% found in furcation between buccal and palatal roots.

ROOT CURVATURES : In single rooted - Straight – (38.4%)

Distal – 36.8%)Buccally – (14.4%) Palatally – (2.4%) S or Bayonet (8%)

In double rooted Buccal root Palatal root Straight 27.8% Straight – 44% Buccal – 14% Buccal curve 27.8% Palatal – 36.2% Palatal – 8.3% Distal – 14% Distal – 14%

S / Bayonet – 5.5%

The apical foramen is centrally located in 12% cases and an apical delta only in 3.2% cases.

ANATOMIC RELATIONSHIP IN SITES : Relationship of first premolar socket to alveolar process varies with the number of roots. If one root then the socket is in close relationship to buccal cortical plate. If two roots are present then buccal is close to buccal cortical plate and palatal is centrally located. Clinical significance :

The outline form of cavity preparation varies with the number of canals. - When two canals are present access opening is oval / slot shaped wide

buccolignually. - But with three canals outline form becomes triangular base on buccal aspect.

Mesiobuccal and distobuccal corners directly on the orifice. - Prone to mesio distal fracture so full coverage restoration is required after root

canal treatment. MAXILLARY SECOND PREMOLAR

Tooth length – 21.5 mm :Pulp chamber : Like maxillary first premolar the pulp chamber is narrow mesiodistally but it is more wider buccopalatally than the first premolar. Two pulp horns are present. Buccal (larger) and palatal. Roof is similar to maxillary first but is deeper than the first if two canals are present.

If one root canal present then the canal orifice may be indistinct but if two canals are present the two orifices will be visible. ROOT CANALS :

Single root – 90.3% 2 well developed roots – 2%

Partially fused 2 roots – 7.7%. Lateral canals are present in 59.5% of cases 1.6% occur in furcation area if two

roots occur.

CROSS SECTION : Cervical – Ovoid and narrow Middle 1/3 – Ovoid (1 canal); round (2 canal)

Apical 1/3 – Round. Apical foramen is centrally located in 12% cases and an apical delta is present in

only 3.2% cases. Root curvature - Distal – 33.9%

Bayonet – 13%Buccal – 15.7% Straight – 37.4%

ANATOMICAL RELATIONSHIP IN SITES :There is a close relationship between the roots of premolar and maxillary sinus.

Clinical significance :Depending on the number of canals the external outline form varies.

One canal : Buccolingual width corresponds to width between buccal and palatal pulp horns. Two canals : Access preparation is nearly identical to first premolar. Three canals : The access outline form is same triangular shape.

MAXILLARY FIRST MOLARAverage tooth length – 20.8 mm :Pulp chamber : The pulp chamber of maxillary first molar is largest in the arch with four pulp horns - Mesiobuccal

Distobuccal Mesiopalatal Distopalatal

The four walls forming the roof converge towards the floor where the lingual wall almost disappear, the floor of the pulp chamber thus has a triangular form in cross-section. The orifices of the root canals are located in the three angles of the floor. Anatomic dark lines in the floor of the pulp chamber connect the orifices. Palatal orifice : It is the largest round or oval in shape and easily accessible for exploration. Mesiobuccal orifice : This orifice is under the mesiobuccal cusp, long buccopalatally and may have a depression at the palatal and in which fourth orifice may be present. The mesiobuccal orifice is located by insinuating the tip of a long shank explorer startite D-11 in a mesiobuccal –apical inclination into point angle at the juncture of buccal wall, mesial wall, and subpulpal floor of the pulp chamber. Distobuccal orifice : It is located slightly distal and palatal to mesiobuccal orifice and is accessible from mesial for exploration.

The floor chamber is in cervical third of root canal roof is in the cervical third of crown. Root canals :

It has 3 roots with usually 3 canals situated mesiobuccally distobuccally and palatally. Palatal root : Largest and longest of the three it offers the easiest access. It can contain 1-3 canals. It is flat ribbon like wider mesiodistally.

Lateral canals are present in 40% of these roots and apical deltas are only seen in 4%. Apical foramen is centrally located in only 18% cases. Distobuccal root : It is small and is more or less round in shape. If usually has a single root canal which is narrow tapering canal sometimes flattened in mesiodistal direction.

Lateral canals are present in 36% of cases. Apical deltas are present in only 2%. The apical foramen is centrally located in 19% or these teeth.

Mesiobuccal root : It has generated more research investigation than any other root in the mouth. It is narrowest of the three. Flattened in mesiodistal direction at orifice but round in apical third but round in apical third. In 64% of cases it has 1 canal and 1 foramen and oval and wider buccolingually. It two or more canals are present it becomes more circular.

MB – 2 (Meseobuccal – 2) is generally present mescal to or directly on a line joining MB – 1 and palates orifice (3.6 mm palatally and 2 mm mescal to MR – 1 orifice). Not all MB–2 orifices read to canals (only 84%). Root curvatures :

Meseobuccal Distobuccal PalatalDistal – 78% Straight – 54% Straight – 48%

Straight – 21% Distal – 17% Buccally – 55%s/tayonet – 1% s/ Bayonet – 10% Distally – 1%

Anatomic relationship insitu : There is close relationship of maxi. first molar with maxillary sinus. This close

relationship may produce more ness in maxillary teeth due to maxillary sinusitis conversely infection of the sinus may result from pulpal disease. Clinical significance : Pulp stones may be present in the pulp chamber which must be identified and

removed during access preparation. Generally a concavity exists on the distal aspect or mesiobuccal root which

makes this wall thin. The clinician must take care not instrument excessively elase a strip perforation may occur.

Negotiation or MB-2 is often difficult is a redge or dentin covers its orifice. The orifice has a mesiobuccal inclination on the pulpal floor and canal’s pathway often takes one or two abrupt curves in coronal past or root. These can be eliminated by throughing and countersinking by ultrasonic tips.

Maxillary second molar : Tooth length – 20 mm Pulp chamber – Similar to maxillary first molar except it is narrower

mesiodistally. Because of this narrower dimension the roof of the pulp chamber is rhomboidal in cross section and the floor is an obtuse triangle in cross section and mesiobuccal and distobuccal canals are closer together and may appear to have a common opening but they are readily distinguishable from each other. Sometimes all three are in a straight time. Root canals :

The maxillary second molar has 3 roots which are closely grouped. Because of this close grouping buccal roots may fuse and occasionally all three may fuse. Studies have reported this characteristic in 46% cases. It 3 roots are present one usually sees 3 canal with a fourth canal is less

frequently than in the maxillary first molar. It the buccal roots fuse to form 1 buccal root the tooth may have 2 canals (1

buccal, 1 palatal). A tooth with only 1 root usually has only 1 conical root canal.

Fever lateral canals are present in the roots or furcation. In only16% foramena are centrally located and only apical deltas are seen in 3% roots. Anatomic Relationship Insitu :

The maxillary second molar is usually more closely related to maxillary sinus than the maxillary first molar. Clinical significance : Access cavity varies number of canals

Four – Rhomboidal Three – Triangular Two – Ovoid widest in buccopalatal direction

Mesial marginal ridge should not be involved. To enhance radiographic risibility especially when interferences arises from

molar process a more perpendicular and distoangular radiograph may be exposed. Maxillary third molar :

Tooth length – 17 mm Pulp chamber : The maxillary third molar anatomically resembles the second molar. The pulp chamber can be similar to that of second molar but it may vary greatly. This may have odd shaped chamber with four or five root canal orifices or a conical chamber with only on root canal. Root canals :

It may have three well developed roots that are closely grouped. It may also have fused roots, one conical roots or four or more independent roots. The roots may be straight curved or dilacerated and they may fully or partially developed.

Root canals vary from 1 to 4 or even five depending on the number of roots. One may find a C-shaped pulp chamber with a C-shaped root canal. Anatomic Relationship Insitue :

The maxillary third molar is closely related to maxillary sinus and maxillary tuberosity. Mandibular central incisor :

Tooth length – 20.7 mm Pulp chamber : Smallest tooth in the arch. The pulp chamber is small and flat mesiodistally. The three distinct pulp horns present in recently erupted tooth become calcified and disappear early in life because of constant masticatory stimulus.

Labiolingually the pulp chamber is wide ovoid in cross section in cervical third of the crown and tapers incisally.

Root canals : The mandibular central incisor has 1 root flat and narrow mesiodistaly but wide

labiolingually. The canal configuration varies

1 canal exiting in 1 Apical foramen – 70% 2 canal existing in 1 Apical foramen – 5% 1 canal bifurcating, into 2 coming together and exiting into 1 apical foramen –

22% 2 canals may exit in 2 foramen – 3% Cross section :

Cervical 1/3 – ovoidMiddle 1/3 – ribbon shaped in labiolingual direction due to flatness or root in this

region (clinical significance) Apical 1/3 – round

Root curvature : Straight – 60% Distal – 23% Labial – 13% Lateral canals are present in 20% cases apical deltas in 5%. The apical foramen is

situated centrally in the root 25% or cases. Anatomic relationship in situ :

The roots of the anterior teeth are broad labiolingually occupy most of the alveolar process and the labial and lingual surfaces f the roots therefore fuse with labial and lingual cortical plates. Location alveolus – 20 mesioaxial

200 linguoaxial Clinical significance :

Because of small six and internal anatomy may be most difficult tooth for access opening. Complete removal of lingual shoulder critical often the second canal is present. For this one should extend preparation into lingulum gingivally. Mandiublar lateral incisor :

Average toothy length – 20.7 mm. Pulp chamber : The configuration of pulp chamber of mandibular lateral incisor is similar to mandibular central but the lateral tooth has larger dimension. Root canals :

Although the root of mandibular lateral incisor is larger than that of mandibular central it has basically same configuration. The incidence of double root canals at the apex is about the same as in central incisor and their anatomy in cross section also similar. Lateral canals are present in 18% cases; only 6% have apical diction. The apical foramen is in the center of radiographic apex in 200 % cases.

Location in alveolus – 170 mesioaxial 200 linguoaxial

Root curvature – Straight (Majority)

Distal sharper) Clinical significance : Germination and fusion are common in mandibular anterior teeth. Mandibular canine :

Tooth length – 25.7 mmPulp chamber : The mandibular canine resembles maxillary canine but it is smaller in dimensions. The pulp chamber is narrow mesiodistally. When viewed labiolungually chamber narrows to a point in the incisal third of crown but it is wide in the cervical third.

Only one pulp horn is present in the adult tooth. In cross section pulp chamber is ovoid in cervical third.

Root canals : Although the tooth usually has a single root it may have two (2.3%) cases and

two canals (‘labially; lingually). These canals are narrow mesiodistally wider labiolingually.

Variable canal configuration present are 1 canal exiting in 1 apical foramen - 78% 2 canal come together and exit in 1 foramen – 5% 1 canal bifurcates and coalesces to exit in 1 apical foramen – 18% 2 canals exit in 2 apical foramen – 2%.

When one root canal is present, a labiolingual view shows a canal that is broad in the middle third and tapers to a constriction in to apical third. CROSS SECTION :

Cervical 1/3 – ovoid Middle 1/3 – ovoid Apical – round

Root curvature : Straight – 68% Distal – 20% Mesial – 1% Labial – 7% S/Bayonet – 2% Lateral canals are present in 30% cases apical deltas in 8Z%. Apical foramen is

centrally located in 30% of these teeth. Anatomic Relationship Insitu :

Location in alveolus – 130 mesioaxial 150 linguoaxial

Clinical significance : Lingual shoulder must be removed to gain access to second canal / lingual wall. Incisal extension can approach incisal edge for straighten access. Mandibular first premolar :

Tooth length – 21.6 mm

Pulp chamber : It is a transitional tooth between anterior and posterior tooth. The mesiodistal width of the pulp chamber is narrow. Buccolingually the pulp chamber is wide with a prominent buccal pulp horn that extends under a well developed buccal cusp. In young tooth one sees a small lingual pulp horn that disappears with age and may give pulp chamber an appearance of a cuspid. The prominent buccal cusp and the smaller lingual cusp give the crown of about a tilt or 300.Root canals :

The mandibular first premolar has a short conical root. This root may divide in apical third into 2 or 3 roots. Narrow mesiodistally broader labiolingually. Canal configuration : 1 canal exiting in 1 foramen - 70% 1 canal bifurcurating into two then uniting to exist in 1 foramen – 4% 1 canal bifurcates into two and exists into two foramen 24%. 2 canals exit in 2 foramen – 1.5% 3 canals exit in 2 foramen – 2%. CROSS SECTION :

Cervical 1/3 – ovoid Middle 1/3 – ovoid Apical 1/3 – round

Lateral root curvature : Straight – 48% Distally – 35% Buccally – 2% Lingually – 7% Bayonet/S – 7% Lateral canals are present in 44.3% and apical deltas are found in 5.7%. Apical

foramen is centrally located in only 15%, or teeth. Anatomic relationship in situ :

The mental canal and foramen are sometimes close to root apex of mandibular first premolar. The radiographic appearance may suggest periapical pathoses. Location in alveolus : 140 distoaxial

100 linguoaxial Clinical significance : Befurcation / Trefurcation are the most common anomalies. Mandibular second premolarTooth length – 22.3 mm Pulp chamber : The pulp chamber is similar to 1st premolar except the lingual horn is more prominent under a well developed lingual cusp. Root canals :

The mandibular second premolar usually has a single root but on rare occasions 2 to 3 are present. The root has a greater girth and is wider buccolingually usually 1 canal exists in 1apical foramen in 97.5% In 2.5% cases a single canal may bifurcate exiting in 2 foramina.

Root curvature : Distally – 40% Straight – 39% Buccal – 10% Lingual – 3% Bayonet – 7%

Anatomical relationship in situ : Mandibular second premolar is in close relationship to mental foramen. Location in alveolus – 100 distoaxial

340 buccoaxial Clinical significance : Because the crown typically has less lingual inclination less extension up to

buccal cusp incline is required to gain straight line access. As the lingual half is more well developed so access extension typically is

halfway up the lingual cusp incline. In case two lingual cusps are present the access is centred mesiodistally on a line

connecting buccal cusp and the lingual groove between the lingual cusp tips.Mandibular first molar :

Average tooth length – 21 mm. Pulp chamber : The roof of the pulp chamber is often rectangular in shape. The mesial wall is straight, the distal wall I round and buccal and lingual walls converge to meet the mesial and distal walls and to form a shomboidal floor. The roof of the pulp chamber has four pulp horns; mesiobuccal mesiolingual, distobuccal and distolingual. The roof is located in the cervical third of crown just above the cervix of tooth and the floor is located in the cervical third of root. Three distinct orificesMesiobuccal : It is present under the mesiobuccal orifice is under the mesiobuccal cusp and is usually difficult to find if not enough tooth structure is removed. A long shank starlite D-11 explorer is inserted in mesiobucco apical inclination into the point angle created at the juncture of mesial wall, buccal wall and ssubpulpal floor of pulp chamber. Mesiolingual : It is located in a depression formed by mesial and lingual wall. The orifice can be explored in a distobuccal direction. A groove generally connects the mesiobuccal and mesiolingual canals. Distal : The distal orifice which is oval in shape with the widest diameter buccolingually. The opening is generally located distal to the buccal groove. The orifice usually can be explosed from the mesial with either an endodontic explorer or small K file. If the file takes a sharp turn in a distobuccal or distolingual direction the clinician should search for yet another orifice. ROOT CANALS

Usually 2 well differentiated rots are present in mandibular first molar 1 mesial and 1 distal. Both the roots are wide and flat buccolingually with a depression in the middle of the root buccolingually

This anatomic characteristic may accentuated in the mesial root. A third root is found in some cases either distally or medially. Although two roots are present 3 canals are usually these. Canal configuration for mesial root : 2 canals that exit in 2 foramen – 41% 2 canals that coalesce to exit in 1 foramen -28%. 2 canal that coalesce to form 1 again bifurcate and exit in 2 foramina – 10% 1 canal hat exits in 1 foramen – 12% 1 canal that bifurcates and exists in two foramen – 8%. Canal configuration for Distal root 1 canal exiting in 1 foramen – 70% 1 anal bifurcation existing in 2 foramina 8% 2 canals coalescing and exiting in 1 foramen – 15%. 2 canals 2 foramina 5%

When 2 canals are present in either root they may converge toward and exit in 1 foramen or they may have inter connecting lateral canals between them that form a single ribbon canal ending in 1 foramen. CROSS SECTION Cervical 1/3 – Ovoid Middle 1/3 – Ovoid Apical 1/3 – Round Root curvature :

Measure DistalDistally – 84% Straight – 74% Straight – 16% Distal – 21%

Mesial – 5%

Lateral canals are present in furcation in 23% cases, in mesial root 45% and distal root 30%. Apical deltas are present in mesial root 10% and distal root in 14%. Anatomic relationship in sites :

The mesial root of the mandibular terse molar is in close prormity to buccal cortical plate where as distal root is centrally located. 580 buccoacial in alcohols.Chemical significance : Pulp stones may be present.

Mandibular second molarAverage tooth length – 19.8mmPulp chamber : The pulp chamber is smaller than that or mandibular first molar and the root canal orifices are smaller and closer together. Root canals : Majority or mandibular second molars have

2 roots (71%)1 root (27%)3 roots (2%)

Three root canals are usually present in mandibular second molars. Most frequent vacation is presence or only 2 canals. When the mescal root or the mandibular second molar has two canals they often join near the apex to root as single foramen. Cross section :

Cervical - ovoid Middle - ovoid Apical - round

Root curvatures :In single rooted It 2 rooted

Straight – 53% Mesial Distal Distally – 2.6% Distally – 61% Straight – 58%Lingually - 2% Straight – 27% Distally – 18%Bayonet – 19% Buccaly – 4% Messally – 10%

Bayonet – 7% Bucally – 4%Bayonet – 6%

Lateral canals are present – [Meseal root (45%) Distal root (34%)].

Apical delta [Meseal (6%) Distal (7%)]

Lateral canals are present in furcation area in 11% cases. Anatomic relation slup in siter :

The meseal root is more untrally located and the distal root is closer to lingual cortical plate. Clinical significance :

The appear of this tooth very close to mandibular canal the clinician must take care not to allow instruments or felling material to invade this space because paresthesia may result.

Mandibular Third MolarTooth length – 18.5 mm Pulp chamber : The pulp chamber resembles the pulp chamber or mandibular first and second molars. It is large and possess many anomalous configuration such c-shaped root canal orifices may occur. Root canals :

The mandibular third molar usually has two roots and two canals but occasionally one root and one canal or three roots and three canals may be present. The root canals are generally large and short. Anatomic Relationship in Setir :

The alveolar socket may project onto the lingual plate or the mandible. The apex or the root may be in close proximity to mandibular canal. Clinical significance :

The anatomy of mandibular third molar is very unpredictable therefore access cavity can take any or the several shapes.

DETAILED TOOTH STRUCTURE OF DECIDUOUS TEETHMaxillary first molar

Pulp cavity : The pulp cavity of maxillary first molar consists of 3-4 pulp horns. These pulp horns are more sharply pointed then the corresponding cusps.

Mescobuccal pulp norms largest pulp horn with its apex slightly mesial to the body of the pulp chamber. Distobuccal occupies the distobuccal angle. Occlusally it appears a roughly triangular with rounded corners. SixMB > ML > DB

The mesiolingual part is obtual whereas the mesiobuccal and distobuccal are acute.

Roots : Usually Maxillary first molar consorts of three roots. Mesiobuccal Distobuccal – shortest Lingual – longest averages in lingual direction.

Maxillary second molarPulp cavity : The pulp cavity consists of a pulp chamber and three pulp canals. The pulp chamber conforms to the general outline or the tooth and has four pulpal horns a fifth horn projecting from the lingual aspect of the mescolingual horn may be present and when present is small. Mesiobuccal pulp horn and largest. It extends occlusally above other cusps and is pointed. Meseolngual is second in sine but slightly longer than the distobuccal. When combined with fifth pulp horn it appears quite bukky. Projections on the incisal border. The chamber tapers cervicaly in mesiodistal diameter but is widest at cervical ridge labiolingually. There is no distinct demarcation between pulp chamber and canal.

Maxillary lateral incisors are quite similar in contour to maxillary central incisors except that they are not as wide mesiodistally. Their cervioincisal length is almost same. The labial surface is little more flattened the ungulum is not so pronounced and blends with the lingual marginal ridges. In lateral incisor there is slight demarcation between the pulp chamber and the canal especially on the labial and lingual aspects. Root :

The root is single and conical in shape. It is fairly regular in form ending in a well rounded apex.

The distobuccal is third in size. Its general contour is such that it joins the mesiolingual pulp horn as slight elevation and separates a central pit and a distal pit corresponding to occlusal outline of the tooth in this area.

Destolingual pulp horn is smallest and shortest and extends only slightly above the occlusal level. Root canals :

There are three pulp canals corresponding to the three roots. These leave the floor of the chamber at the mesiobuccal and distobuccal corners and from the lingual area. The root canals follow the general contour of the roots.

MAXILLARY PRIMARY INCISORPulp cavity : The pulp cavity confirms to the general outside surface of the tooth. The pulp chamber has three slight projection

MANDIBULAR FIRST PRIMARY MOLAR Pulp chamber : The pulp chamber viewed from the occlusal is rhomboidal shape and closely follows the contour of the surface of crown. It has four pulpal horns.

Mesiobuccal pulpal horn is the largest and occupies a considerable part of the pulp chamber. It is rounded and connects with the mesiolingual pulpal horn in a high ridge making the mesial area especially vulnerable to mechanical exposure.

Distobuccal pulp horn is second in area but lacks the height of the mesial horn. Mesiolingual pulp horn because of the contour of the pulp chamber lies slightly

mesial to corresponding cusp. Although it is third in size it is second in height. MAXILLARY PRIMARY CUSPID

Pulp cavity : The pulp cavity conforms to the general surface contour of the tooth. There is a central pulpal horn projecting incisally considerably further that the remainder of the pulp. Because of the greater length of the distal surface this horn is larger than the mesial projection. There is very little demaseation between the pulp chamber and the canal. Roots :

The root of maxillary cuspid is long thick in diameter and slightly flattened on its mesial and distal surfaces. The root is tapering however there is a slight increase in diameter as it progresses from the cervical margin. The apex of the tooth is rounded.

The distolingual pulp horn is smallest. It is more pointed than the buccal horns and small compared to other three pulp horns. Roots / canals :

There are three pulp canals. A mesiobuccal and mesiolingual are confluent and leave the chamber widened buccolingually in the form of a ribbon. The two pulp canals soon separate to form a buccal and lingual which gradually taper to apical foramen.

Distal pulp canal projects in ribbon fashion from the floor of the chamber in the distal aspect. This canal is wide buccolingaully and may be constricted in center reflecting the outside contour of the root.

MANDIBULAR SECOND MOLARPulp cavity : The pulp cavity is made up of a chamber and three canals. The pulp chamber has five pulp horns.

Corresponding to five cusps. The roof of the chamber being extremely concave towards the apices.

Mesiobuccal and mesiolingual pulpal horns are largest. Mesiolingual pulpal horns slightly less pointed but of same height. These horns are connected by a higher ridge of pulpal tissue that is found connecting the distal horns of the pulp.

Distobuccal pulp horn is not as large as the mesiobuccal pulpal horn but somewhat larger than either distolingual or distal horn.

Distal pulpal horn is the shortest and smallest occupies a position distal to distobuccal horn and its distal inclination carries the apex distal to distolingual horn. Roots :

The two mesial pulp canals are confluent as they leave the floor of the pulp chamber through a common orifice that is wide buccolingually but narrow mesiodistally. The root of the lateral incisor is longer and also tapers towards the apex.

MANDIBULAR PRIMARY CUSPID :Pulp cavity : The pulp chamber follows the external contour of the tooth being approximately as wide mesiodistally as labiolingually there is no differentiation between chamber and canal. Roots / canals : The root is single with a broader labial than lingual diameter. The mesial and distal surfaces are slightly flattened. The root tapers Aa a rather pointed apex.

The canal soon divides into a larger mesiobuccal and a smaller mesiolingual canal.

The distal canal is somewhat constricted in the center. All three canals taper as they approach the apical foramen.

MANDIBULAR PRIMARY INCISOR Pulp cavity : The pulp cavity conforms to the general surface contour of the tooth. The pulp chamber is widest mesiodistally at the roof of the chamber. Labiolingually the chamber is widest at the ungulum.

There is a definite demarcation between the pulp chamber and canal in central incisor which is not present in lateral incisor. Roots / canals :

The root of the central incisor is only slightly flattened on its mesial and distal aspects and tapers towards the apex.

VARIATIONS TO NORMAL PULPAL STRUCTURE AND ITS SIGNIFICANCE

Factors 1) Physiological 2) Developmental 3) Pathological

Physiological : Age : Although dentin formation occurs with age on all surfaces it occurs predominantly in certain areas. As in case of molars the roof and floor of the chamber show more dentin formation eventually making the chamber almost disc like in configuration. Clinical significance : With gradual deposition of dentin there is a change in internal anatomy which leads to difficulty in locating chamber and canals.

PATHOLOGICAL FACTORSIrritants :

Anything that exposes dentin to oral cavity can potentially stimulate increased dentin formation at the base of tubules in the underlying pulp. Causes of such dentin exposure include caries periodontal disease, abrasion, erosion, attraction cavity preparation, root planning and cusp fractures. Vital pulp therapy such as pulpotomy pulp capping or placement of irritating material in a deep cavity may cause increase dentin formation occlusion. Calcific metamorphosis resorption or other unusual configuration in chamber a canal. These tertiary dentin formation tend to occurs directly under involved tubules. Clinical significance : It is imperative clinician study radiograph and usually examine the tooth. Failure to do so may result in serious error lost time and inadequate treatment.

Calcifications : Calcification can take two basic forms within the pulp – pulp stones true false,

diffuse calcification. Pulp stones are usually found in pulp chamber whereas diffuse calcification

within the radicular pulp. These calcifications may form either normally or in response to irritation. Pulp stones are often seen on radiograph diffuse calcification are visible only

histologically. Clinical significance : Pulp stones may reach considerable size and alter the internal anatomy. They may often make the process of orifice locating challenging. These large pulp stones may be free or attached and are removed during access preparation.INTERNAL RESORPTION :

Internal resorption is an unusual form of tooth resorption that begins centrally within the tooth apparently initiated in most cases by a percussion inflammatory hyperplasia of the pulp.

Most resorption ar small and not detectable on radiograph or during canal preparation. When visible radiographically they are usually extensive and often perforate. Clinical significance : Internal resorption usually create operative difficulties.

DEVELOPMENTAL FACTORSDens in dente / dens invaginaties : The dens in dente is a developmental variation which is thought to arise as a result of an invagination in the surface of tooth crown before calcification has occlusal causes may include localized external pressure, focal growth retardation and focal growth stimulation.

Permanent lateral incisors are the teeth more frequently involved. Such teeth are predisposed to decay because of anatomic malformation and pulp disease before the root apex is fully developed. DENS EVAGINATUS :

It is a developmental condition that appears clinically as an accessory cusp or a globule or enamel on the occlusal surface between buccal and lingual cusps of premolar.

The pathogenesis is thought to be proliferation and evagination of an area of inner enamel epithelium and subjacent odontogenic mesenchyme into the dental organ during early tooth development.

These malformation often contain an extension of pulp which may get exposed when the fragile tubercle fractures. HIGH PULP HORNS :

Occasionally a pulp horn extends for into the cusp resulting in premature exposure by caries or accidental exposure during cavity preparation. Lingual groove :

Usually found in maxillary lateral incisor a lingual groove appears as a surface infolding of dentin oriented from cervical toward the apical direction.

This results in a deep narrow periodontal defect that occasionally communicates with pulp causing an endodontic / periodontal problem. Dilacerations :

The term dilacerations refers to an angulation or sharp bend or curve in the root or crown or a formed tooth. Many or these curvatures are found in a faccolingual plane and are not obvious on standard radiographic projections.

Other variations : A not uncommon variation is the C-shaped canal. This usually occurs in

mandibular molars. The C-shaped canal was first reported in 1979 most C shaped canals occurs in

mandibular second molar. C – shaped canals are so named because of cross sectional morphology of their

roots and root canals instead of having discrete orifices the pulp chamber of a molar with a C-shaped canal system is a single ribbon orifice with an are of 1800 or more.

It starts at the mesiolingual line angle and sweeps around either to the buccal or lingual to end at distal aspect of pulp chamber.

Below the orifice the root structure can show a wide range of anatomic variations. These can be classified into two basic types.

1. Those with a single ribbon like C-shaped canal from orifice to apex. 2. Those with three or more distinct canals below the usual C shaped orifice.

Most common is the second type. Significant Ethmic variation can be seen the anatomy is much more common in

Asians and Caucasians. Teeth with C-shaped anatomy pose a considerable technical challenge however

use of DOM, sonic and ultrasonic instrumentation and plasticized techniques have made treatment successful.