ANATOMY OF ROOT APEX AND ITS SIGNIFICANCE

DILU DAVISIIND YEAR POST GRADUATE

Contents • Introduction • Development Of Root Apex• Accessory Canal Formation• Root Length And Apical Closure• Anatomy Of Root Apex• Apical Constriction• CementoDentinal Junction• Apical Foramen• Variations In Morphology Of Apical Third Of The Root And It’s

Significance In Endodontics

• Accessory Canals• Areas Of Resorption• Pulp Stones• Varied Amounts Of Irregular Secondary Dentin• Radiographic Assessment Of Apical Third• Termination Point For Root Canal Procedures • Challenges Faced Due To Apical Third Anatomy During Endodontic

Procedures• Challenges Faced Due To Apical Third Anatomy During Endodontic

Surgery• Frequency Of Accessory Canals And Ramifications Found At Different

Levels Of Root Canals • Isthmus• Conclusion

INTRODUCTION

• Achievement of a perfect seal at the apex using an inert filling material is the ultimate goal for every endodontist

• The crux of endodontics revolves around the efficient and effective manipulation and obturation of the apical third of the root canal

• The importance of a thorough cleaning and hermetic filling of the apical part of the canal for successful healing of the periapex was highlighted analogically as early as 1939 itself, by KRONFELD 

• He has equated the microorganisms in the root canal to an army in the “mountains” which enters the ‘plains’ through the foramina or ‘the mountain pass’.

• As the bacteria enter in small numbers, they are destroyed by the ‘army’ of leucocytes which is maintained at the ‘front’ to counter the attack.

• A thorough cleaning and filling would make the maintenance of the army unnecessary allowing the environment to return to normality.

• Variations in external morphological features of crowns of teeth occur as variations in shape and size of head.

• External morphological features vary from person to person. In the same way internal morphology of crown and root also varies.

• Among these, the anatomy of the root apex, its morphological variations and treatment are technical challenges for the endodontist.

• Much of the knowledge of root apex is based on exhaustive work of HESS who studied 3000 permanent teeth and showed minute details like extensions, ramifications, branching as well as size, shape and number of root canals in different teeth

• Fracture of the apical third, resorption, weeping canals, immature foramina are some of the areas which continue to be under constant research work.

Development of root

• On completion of formation of crown,

i.e. once the enamel and dentin has been formed till the cemento-enamel junction, the inner and the outer enamel epithelium proliferates downwards to form Hertwig’s epithelial root sheath.

• This root sheath determines the size and shape of the root of the tooth

• Root sheath takes a bend horizontally towards the dental papilla to form epithelial diaphragm

• This process partially encloses the dental papilla and delineates the apical foramen.

• Soon the ectomesenchymal cells of dental papilla present above the epithelial diaphragm starts proliferating and root dentin deposition takes place.

• According to ORBAN, the epithelial diaphragm i.e. future root apex will remain in place while the tooth crown and supporting structures move occlusally.

• Once the dentin is deposited to the entire length of the root, the HERS split to get the cells of the dental sac in contact with the dentin.

• These cells of the dental sac get differentiated into cementoblasts and starts laying down cementum on radicular dentin.

• In single rooted teeth, the epithelial diaphragm has a single opening which guides the formation of root, root canal & apical foramen.

• In double rooted teeth, the diaphragm evaginates in two pre determined places that come together and form two openings.

• In three rooted teeth, the evagination occurs in three predetermined places to form three openings.

• In multi rooted the epithelial diaphragm guides the formation of the furcal roots, root canals and apical foramina .

Two kinds of cementum are laid down on the root:-• If the cementoblasts retracts as cementum is laid

down, it will be ACELLULAR CEMENTUM.• If cementoblasts do not retract and get surrounded by

new cementum the tissue formed will be CELLULAR CEMENTUM and the trapped cementoblasts will be called cementocytes.

• Acellular cementum will be formed around the coronal and middle third of root where as cellular cementum will be formed in the apical third of the root with alternating layers of acellular cementum. 

• This incremental deposition of the cementum continues throughout the life of the tooth and makes the layer of cementum on the apical third of the root thicker than cervical third.

• This continued deposition of the cementum on apical third maintains the length of the tooth constricts the apical foramen and also deviates the apical foramen from the center of the apex.

ACCESSORY CANAL FORMATION

• The accessory canals which are an inefficient source of collateral circulation for the pulp are formed during the development of the root.

• Defect in the epithelial root sheath • Failure in the induction of dentinogenesis• The presence of small blood vessels• Accessory canals are more prevalent in the apical third of the root.

produce a gap -accessory canal

ROOT LENGTH AND APICAL CLOSURE

• Knowledge about the dates of tooth eruption, the completion of the root length and apical closure is very important because the complex root formation and apical closure plays an important role in the repair of inflamed dental pulps following endodontic therapy.

MOORREES ET AL (1963) studied the root lengths and apical closure completion dates by using images on lateral jaw radiographs

• They found that root length completion and apical closure occurs early in females

• Maxillary teeth -not studied - images could not be identified clearly on lateral jaw radiographs

• But judging from the data of maxillary incisors and mandibular teeth, they summarize that the dates for completion of root lengths and apical closures for maxillary posterior teeth are slightly later than mandibular teeth

TOOTHINITIAL

MINERALISATION

ERUPTION ( IN YEARS )

ROOT COMPLETION ( IN YEARS )

MAXILLARY

1 3-4 months 7-8 102 10-12 months 8-9 113 4-5 months 11-12 13-154 11/2-13/4 years 10-11 12-135 2-21/4 years 10-12 12-146 At birth 6-7 9-107 21/2-3 years 12-13 14-168 7-9 years 17-21 18-25

MANDIBULAR

1 3-4 months 6-7 9-102 3-4 months 7-8 103 4-5 months 9-10 12-144 13/4-2 years 10-12 12-135 21/2-23/4 years 11-12 13-146 At birth 6-7 9-107 21/2-3years 12-13 14-158 8-10 years 17-21 18-25

TOOTH ROOT COMPLETION ( IN YEARS )

MAXILLARY

1 102 113 13-154 12-135 12-146 9-107 14-168 18-25

MANDIBULAR

1 9-102 103 12-144 12-135 13-146 9-107 14-158 18-25

Clinical Significance

• A funnel shaped opening exists at apex of young tooth that has incompletely formed root.

• This incompletely formed root apex contains connective tissue, blood vessels, nerves which enters and exit the root canals.

• Therefore successful repair of inflamed dental pulps occurs in teeth within complete apical closure when compared with the teeth with completed apical closure. This may be possibly due to the unobstructed metabolism.

Ouostarinen et al 1966

ANATOMY OF ROOT APEX

• The classic concept of apical root anatomy is that there exists 3 anatomic & histologic landmarks namely:-

1. Apical constriction 2. Cementodentinal junction3. Apical foramen

• KUTTLER’S description of anatomy of root apex –The narrowest diameter of the canal is definitely not at the

site of exiting of the canal from the tooth, but usually occurs within the dentin just prior to the initial layers of cementum.

He refers this position as the “minor diameter”Some call it “apical constriction”

Morphologically : most complex region

Therapeutically : challenging

Prognostically : important part

Radiographically : unfortunately most obscure and unclear area

However an endodontic treatment is almost always gauged by the way the root canal filling appears in apical 1/3 in the IOPA

Clinical Significance

Kuttler says that the canal preparations and obturations should be terminated at the minor diameter.

Major advantage is that during obturation procedures, minor diameter provides a bottle neck area. This allows the rapid development of a solid apical dentin matrix.

This will enhance the possibility of retaining the filling materials and sealers within the canal.

Pain free treatment can be done because of less or no impingement on periapical tissues. However techniques to locate exactly the minor diameter are lacking.

APICAL CONSTRICTION

• Generally considered to be the part of the root canal with a smallest diameter.

• Also called as Physiologic foramen.• It is also the reference point most often used by dentist as

the apical termination of shaping, cleaning & obturation procedures.

BRISENO MARROQUIN ET AL did a study on Egyptian population & concluded that the shape of the physiologic foramen or apical constriction shape was oval (70%)

The study of the same group repeated high % of two physiologic foramina in • mesial roots of mandibular (87%) • mesiobuccal roots of mandibular (71%)• maxillary first molars Morphology of the Physiological Foramen:I. Maxillary and Mandibular Molars VOL. 30, NO.5,MAY2004

ACCESSORY FORAMINA

• High frequency of accessory foramina in maxillary mesiobuccal roots (33%) & mandibular mesial roots (26%)

CEMENTODENTINAL JUNCTION ( CDJ )

• Point where the pulp tissue ends & the periodontal tissues begin (meeting point of two histologic tissues)

• Its location in the root canal is highly variable.

• Generally, it is not the same area as the Apical Constriction & is not a fixed point in the population of different countries.SMULSON ET AL estimated that the CDJ is located approximately 1.0 mm from the Apical Foramen.

It is the point in the canal where cementum meets dentin

LOCATION & DIAMETER OF CDJ

PONCE & VILAR FERNANDEZ ET AL evaluated histologic sections of maxillary anteriors to determine the location & diameter of CDJ :• They observed that the CDJ extension from the Apical

Foramen into the root canal differed considerably on the opposite canal walls.

• Cementum reached the same level on all the cavity walls only 5% of the time.

• The greatest extension generally occurred on the concave side of the canal curvature.

• This variability confirmed that CDJ & apical constriction are generally not coinciding with the same area.

THE DIAMETER OF THE CANAL at CDJ was highly irregular

• Maxillary central incisors - 353µm• Lateral incisors - 292µm• Canines - 298µm

APICAL FORAMEN

• From the Apical Constriction or minor diameter, the canal widens as it approaches the Apical Foramen or the major diameter.

• The shape of the space between the major & the minor diameter has been described as:-

Funnel shapedHyperbolicMorning glory

• Apical foramen is the circumference or the rounded edge like a funnel or crater, that differentiates the termination of the cemental canal from the exterior surface of the root.

• MEAN DISTANCE between major & minor diameter 0.5 mm – young person

0.67 mm – older individualThe increased length in the older individual is due to increased buildup of cementum.

• DIAMETER OF AF was determined by KUTLER demonstrated that the diameter of AF grows with age.

502 µm – 18 to 25 yrs 681 µm – over 55 yrs

EXIT OF AF

The AF does not normally exit at the anatomic apex but is offset 0.5 – 3.0 mm

Variation more marked in older teeth because of cementum apposition

MIZUTANI ET AL - Both the root apex & apical foramen of central incisors & canines showed distolabial displacement while the lateral incisors showed distolingual displacement.

Number of apical foramen - MORFIS ET AL studied apices of 213 permanent teeth with SEM & determined :

1. More than 1 main apical foramen was observed in all the teeth except for distal root of mandibular molars & palatal root of maxillary molars.

2. Highest % of multiple apical foramen was seen in :•MESIAL ROOT – mandibular molars (50%) •MAXILLARY PREMOLARS – 48.3%•MESIAL ROOT OF MAXILLARY MOLARS – 41.7%

This finding is consistent with observations that blunted roots usually have more than 1 root canal.

• Size of apical foramen – mean values of the size of apical foramen varied from 210µm for maxillary premolars to 392µm in the distal root mandibular molars.

• All groups of teeth exhibited atleast one accessory foramina.

• Maxillary premolars have the largest number & size of accessory foramen (53.4µm) with the most complicated apical makeup.

• This is followed next by mandibular premolars strikingly similar characteristics, probably the reason why pulp space therapy may fail in this group.

Variations in morphology of apical third of the root & its significance in endodontics

MJOR ET AL found tremendous variations in morphology of the apical region of root :• ACCESSORY CANALS• AREAS OF RESORPTION • REPAIRED RESORPTION • PULP STONES – ATTACHED, EMBEDED & FREE• VARIED AMOUNTS OF IRREGULAR SECONDARY DENTIN • PRIMARY DENTINAL TUBULES • AREAS DEVOID OF TUBULES• FREQUENT PRESENCE OF FINE TUBULAR BRANCHES &

MICRO BRANCHES

• These variable structures in the apical region presents with challenges in the pulp space therapy.

• Obturation techniques that rely on the penetration of the adhesives into dentinal tubules may not provide successful sealing in the apical region.

• Therefore the formation of a hybrid layer may become an important part of adhesive systems used in the apical root canal

ACCESSORY CANAL

• A canal that branches off from the main root canal, usually somewhere in the apical region of two root.

• In anterior teeth, SELTZER IN 1966 observed 34% incidence of accessory canals and dichotomy were evident ( histology )

• According to Green, 10% in maxillary central incisor & mandibular cuspid and 47 % in mandibular 2nd premolar

• Accessory canals are seen frequently in apical third of roots.

• According to HESS • Accessory foramina have a mean diameter of 6 to 60 µm in many

teeth• The width of the accessory canals & sometimes the lateral canals

is exceedingly small permitting only presence of small caliber blood vessels & their supporting stroma.

• Usually these small canals cannot be observed in radiographs.

Accessory canals occur in three distinct patterns in the mandibular first molars. A, In 13% a single furcation canal extends from the pulp chamber to the intraradicular region. B, In 23% a lateral canal extends from the coronal third of a major root canal to the furcation region (80% extend from the distal root canal).C, About 10% have both lateral and furcation canals.

Clinical Significance• No of accessory canal in the root does not appear to be significant factor in success or failure of endodontics thrapy in teeth with vital pulp. If they were, most endodontic therapy would fail.

• In teeth with totally inflamed or necrotic pulps, granulation tissue is found in the accessory canal prior to endodontic therapy

• The significance of the involved tissue remaining in accessory foramina as a factor in failure or repair after endodontics therapy has not yet been definitely determined

• Interestingly although the incidence of occurrence of lateral and accessory canal in human teeth is high and canals are believed to have potential to harbour irritant and perpetuate pathological problem, the percentage of failures due to unfilled lateral canals is small in clinical practice

• It has been pointed out the this is probably because of biological hard closure of lateral canal foramina subsequent to elimination of chronic inflammation of the pulp or irritants from the main root canal

Areas of resorption• Shallow resorption of dentin in the apical portion of the root

canal are normal occurrences.• Resorption of cementum & dentin occurs on the body of the

root also at the periapical region.• Apical root resorption is mainly due to

Orthodontic tooth movementInflammation of the apical pulp & periapical periodontal tissues

• Orthodontically induced root resorption is mediated by prostaglandins elaborated by localized cells which stimulate osteoclastic activity.

• The resorption widens the apical foramen leaving a funnel shaped structure

• As inflammation subsides, repair of resorbed region occurs by deposition of secondary cementum.

• As a result of resorption & repair, change in the anatomy of the root apex occurs, as a result, the principal apical foramen which is in the center of the root originally shift towards one side

PULP STONES / DENTICLES

• Denticles are formed around foci of mineralizing pulp tissue components such as collagen & nerve fibers, blood vessels, ground substance & necrotic cells.

• These can be attached or embedded being partially or completely surrounded by dentin.

• In the apical third of the root approximately 15% of the teeth show pulp stone & more than one pulp stone is usually found.

Apical Calcification• In case of chronic inflammation and aging, the

calcification of the root canal occurs. • In some root canals the apical 1/3 are calcified,

complete obturation of such cases would be difficult. • Effort should be made to negotiate the canal with the

help of EDTA and thin files.

VARIED AMOUNTS OF IRREGULAR SECONDARY DENTIN

• Secondary dentin is deposited continuously by the radicular pulp tissues.

• Secondary dentin is seen on the root canal walls of some teeth & in great quantities in periodontally involved teeth.

• Towards the apex of the tooth the dentinal tubules appear to blend with cementum canaliculi.

• Continuous dentin & cementum deposition will reduce the size of apical foramen but complete closure does not occur as long as vital pulp tissue remain.

RADIOGRAPHIC ASSESSMENT OF APICAL THIRD

• The lateral, accessory canals & other anatomic aberrations cannot be easily identified in a radiograph.

• The clinician should have a sound knowledge about these anatomic variations.

• Clinically also we should also examine carefully for extra canals by probing the potential areas using sharp pointed or an endodontic explorer.

• When the radiograph shows root canal that descends from the pulpal floor & suddenly stops in the apical region can be expected.

• To confirm this, a 2nd radiograph is exposed from a mesial or distal angulation of 10 – 30o- show more roots / vertical line indicating peripheries of additional root surfaces.

• Root canal shadow abruptly stops in the middle third of the root or if the diameter of the root canal suddenly narrows down - root canal may be dividing into two

• This is very common occurrence in mandibular premolars.•  Lateral radiolucency - apical one third of the root - possibility

of lateral canal accessory canals or presence of periodontal lesions

• If there is a radiolucent line running along the diagnostic instrument whose long axis is not in relation to the instrument then there is high chance of additional canal. 

• The recent advancements like xeroradiography, radiovisiography, digitalsubstraction radiography, computed tomography also will be helpful for identifying these minute anatomical variations.

OTHER FEATURES OF APEX ON RADIOGRAPHS:

THIN “PINCHED” APEX Care should be taken during instrumentation to avoid perforation.

BULBOUS APEX Bulbous appearance of apex is due to hypercementosis.

In cases of bulbous apex apical constriction may be significantly shorter from the radiographic apex compared to normal teeth.

RESORBED APEX• Advanced inflammation at the periapex usually causes resorption

of cementum, either widening of apical foramen.

• Such changes will make working length determination difficult with proper apical preparation and condensation of gutta-percha.

• So apical stop should be created in such teeth.

BLUNDERBUSS APEX• A newly formed tooth would normally show an incompletely

formed root having a wide root canal and an open apex.

• Such a canal is termed immature or blunderbuss canal.

Treatment of open apex with no vital pulp • Apexification – induce closure of immature apex by formation of

osteocementum or other bone like tissue• Most commonly used : Ca(OH)2 mixed with CMCP, metacresyl acetate,

cresanol, physiologic saline, ringer solution or distilled water• Tricalcium phosphate, collagen Ca Phosphate, osteogenic protein 1, bone

growth factor or MTA

Treatment of open apex with vital pulp

Pulpotomy is indicated to allow completion of apical closure as long as pulp remains vital – apexogenesis

• Usual time required for apexification – 6-24 months ( avg – 1 yr ± 7months

• Patient is recalled at 3 months interval for monitoring of the tooth• After clinical verification of apexification made by failure of small

instrument to penetrate through apex, canal obturation is don’t with GP in usual manner

TERMINATION POINT FOR ROOT CANAL PROCEDURES

• Considerable controversy exists over the exact termination point for root canal therapy.

• Clinical determination of apical canal morphology is difficult.• The existence of apical constriction may be more conceptual

than real.• DUMMER ET AL has reported that traditional single apical

constriction was present less than half the time when apical root resorption & periradicular pathosis were factors.

• Apical root canal often is tapered or walls are parallel to each other or the canals has multiple constrictions.

• Some authors have therefore recommended the following termination points

WEINES RECOMMENDATIONS

FROM THE APEX CONDITION

1mm No bone/root resorption

1.5mm Only bone resorption

2mm Bone & root resorption

WU ET AL stated that to locate the apical constriction & apical foramen clinically is difficult, so radiographic apex is more reliable

reference point. So it is recommended that root canal procedures to terminate at

0 – 3mm from radiographic apex depending upon pulpal diagnosis.

For vital cases, clinical & biological evidence indicates that a favorable point to terminate 2 – 3mm short of radiographic apex. This leads an apical pulp stem which prevents extrusion of irritating filling materials into the periradicular tissues.

• For necrotic pulp, bacteria & their byproducts may be present in the apical root canal which could jeopardize healing.

• Better success rate was achieved when therapy ends at or within 2mm of the radiographic apex.

• When the therapy ended shorter than 2mm or extended past the radiographic apex, success rate declined by 20%.

• In retreatment cases, therapy should extend to or preferably 1 – 2mm short of the radiographic apex to prevent over extension of instruments & filling materials into the periradicular tissues.

LANGELAND & RICUCCI stated that after evaluating apical periradicular tissues following pulp space therapy concluded that :

• Most favorable prognosis were obtained when procedures were terminated at the apical constriction and the worst prognosis was produced by treatment that extended beyond the apical constriction.

• Sealer or guttapercha in the periradicular tissues, lateral canals & apical ramification always caused a severe inflammatory reaction.

• The apical limit of instrumentation & obturation continues to be the subject of major controversy in root canal therapy.

CHALLENGES FACED DUE TO APICAL THIRD ANATOMY DURING ENDODONTIC PROCEDURES

• Hallmarks of apical region are its variability & unpredictability.• The tremendous variation in canal shapes & diameter

complicates the clinicians to shape & clean canals in all dimensions.

• The initial file chosen for exploring the canal anatomy & for binding in the canal is used as a measure of the diameter of the apical root canal.

• However, this technique does not accurately gauge the size of the oval shaped apical root canals.

Mandibular first premolar with three separate roots trifurcating at midroot. B, Radiograph of three views. Small canals diverging from the main canal create a configuration that is very difficult to prepare and obturate biomechanically

Root section of a premolar showing a ribbon-shaped canal system

Diagrammatic representation of Kartal and Yanikoglu’s canal configurations

Mesial view of a mandibular premolar with a Vertucci type V canal configuration. The lingual canal separates from the main canal at nearly a right angle. B, This anatomy requires widening of access in a lingual direction to achieve straight-line access to the lingual canal.

WU ET AL – attempted to gauge the size of the oval shaped root canal & demonstrated that 75% of the cases, the initial file contacted only on one side of the apical canal wall.

• Remaining 25%, instrument failed to contact any wall.• In 90% of canals, the diameter of initial instruments was

smaller than the short diameter of the canal. • Hence, using the initial binding file to gauge the diameter of

apical canal & as a guidance for apical enlargement is not reliable.

• In order to counter this problem, CONTRERAS ET AL suggested radicular flaring before canal exploration - removes interferences & increases the initial file size that is snug at the apex.

• Early flaring gives the clinician a better size of the canal allowing better decisions about the final diameter needed for apical shaping & cleaning.

• This is one of the other advantage of crown down instrumentation.

GANI & VISVISIAN ET AL evaluated the root canal diameters of the apical root canal of maxillary first molars with D0 diameter of the endodontic instrument & found that:-

• Circular shape predominated in the palatal & MB2 canals.• Flat shaped occured most often in MB1 canal.• Circular & flat were found in distobuccal canal.• Flat ribbon shape most often in MB1.

Concluded that maxillary first molar shows a very complicated canal shape at the apical limit which makes cleaning & shaping

followed by obturation difficult, particularly in MB1 & distobuccal canals.

• Because of this variability, guidelines for instrument calibers that would guarantee adequate canal preparation are virtually impossible to establish.

WU ET AL studied apical canal diameters & tapers of each tooth group & demonstrated that root canals are frequently long oval or ribbon shape in apical 5mm.

• Long oval canal was found to occur in 25% of all cross sections except, palatal canal of maxillary first molar.

• Lack of technology to measure the above mentioned diameter makes it very difficult to adequately debride all canals by instrumentation alone.

RODIG ET AL stated that NI-TI rotary instruments created a round bulge in the canal leaving unprepared extensions filled with smear layer & debris.

• Attempting to find a better way to clean & disinfect root canals, one group of investigators determined that enlarging canals above the traditional recommended apical sizes was the only way to remove culturable bacteria from the canal effectively.

• A potential adverse effect of enlarging the apical canal diameter may be an increased risk of procedural errors or root fractures.

As a supplement to these procedures acoustic streaming by sonic & ultrasonic irrigation appears to enhance the cleanliness of oval canals

JURECKO ET AL & LUMLEY ET AL

ABOU RASS ET AL – anticurvature file reduced risk of perforation when preparing curved canals

Controlled & directed canal preparation into the bulky portions / safety zones, away from the thinner portions of the curved canals – which risk of stripping or perforation – danger zone.

LIM & STOCK stated that 0.3 mm of dentin approx. is the minimal canal wall thickness that should remain after preparation in order to provide sufficient resistance to obturation forces.

PETERS ET AL studied effect of 5 NI - TI rotary instrumentation systems on canal debridement & concluded that all of them do good in shaping the canal but a poor job in accomplishing total canal debridement.

CHALLENGES FACED DUE TO APICAL THIRD ANATOMY IN ENDODONTIC SURGERY

KIM ET AL stated bevel should be perpendicular to the long axis of the root & apical ramification of accessory canals because it exposes the small amounts of microtubules compared to 45° bevel

• Because of this, chances of leakage into & out of the root canal is reduced.

VERTUCCI & BEATTY recommended retro preparations to extend coronally to height of the bevel.

Leakage through dentinal tubules originating at the beveled root surface. A, Reverse filling does not extend coronally to the height of the bevel. Arrows indicate a possible pathway for fluid penetration.B, Reverse filling extends coronally to the height of the bevel, blocking fluid penetration (arrows) into the root canal space.

FREQUENCY OF ACCESSORY CANALS & RAMIFICATION FOUND AT DIFFERENT LEVELS OF

ROOT CANALS• The root apex contains a variety of anatomic structures & tissue

remnants.• Inter canal connections can become exposed & a single foramen can

become multiple foramina.• Treatment results are poor, if this altered anatomy is not recognized,

prepared & obturated.• One study evaluated the root apex of the teeth with refractory apical

periodontitis that did not respond to root canal therapy & found that 70% had significant apical ramifications.

• This incidence strongly suggest a close relationship between the anatomic complexity of the root canal system & persistence of periradicular pathosis.

ISTHMUS• An isthmus is a narrow, ribbon shaped communication

between two root canals that contains pulp or pulpally derived tissue.

• All isthmus must be found, prepared & filled - they can function as bacterial reservoirs.

• Any root with 2 or more canals may have an isthmus.• Suspected whenever a multiple canals are seen on a

resected root surface.

• In a study an isthmus in the mesiobuccal root of maxillary first molars were found most often 3-5mm from the root apex.

• A complete or partial isthmus was found at the 4 mm level (100%)

• In another study, partial isthmus was found more often than complete isthmi.

• Identification & treatment of isthmus are vital to in success of surgical procedures.

Evangelos et al 2010 Braz Dent J (2010) 21(5): 428-431

KIM ET AL- 5 types of isthmus that can be found on a root surface

Schematic representation of isthmus classifications described by Kim et al. Type I is an incomplete isthmus - faint communication between two canals. Type II is characterized by two canals with a definite connection between them (complete isthmus). Type III is a very short, complete isthmus between two canals. Type IV is a complete or incomplete isthmus between three or more canals. Type V is marked by two or three canal openings without visible connections.

• Isthmus are found in 15% of anterior teeth; in maxillary premolar teeth they are found in 16% at the 1mm resection level & in 52% at the 6mm resection level.

• The prevelance of isthmus increases in the mesiobuccal root of the maxillary first molar from 30% to 50% as root is resected from 2-4mm level.

• 80% of mesial roots of mandibular first molars have isthmus at the 3-4 mm resection level whereas 15% of distal root have isthmus at 3mm level.

Clinical Significance• Conventional mechanical cleaning and shaping methods

can not physically debride this vitally important area• Only way to clean such anatomic variations is thorough use

of chemical irrigants such as sodium hypochlorite• Can lead to failures in conventional orthograde treatment • Ultrasonics and their associated tips have aided in

thorough debridement of apical root canal system

• Since the introduction of micro surgical endodontic therapy, the clinicians are able to visualize the resected root surface & identify the isthmus, preparing it with ultrasonic tips & fill the root end preparation with acceptable materials.

• The recognition & micro endodontic treatment of canal isthmi have significantly reduced the failure rate of endodontic surgery.

• The morphological variations and the technical challenges involved in treatment of the apical third seems infinite. It has to be remembered while treating the apical third that the proximity of the apices of certain teeth are in close association with important structures like maxillary sinus an inferior alveolar nerve. Inadequate attention and improper handling of the apical third of these teeth may lead to serious clinical implications. The root apex is morphologically the most complex region therapeutically a challenging zone and prognostically an important and unfortunately most obscure and unclear area. So, endodontist should have detailed knowledge of the anatomic variations and mechanical challenges involved in the treatment of apical third for effective and efficient management during endodontic therapy.

Conclusion

• Careful interpretation of angled radiographs…• Proper access preparation…• Proper cleaning and shaping of the apical third… and

obturation• Detailed exploration of the the interior anatomy of the

tooth , ideally undermagnification….

These are essential prerequisites for successful treatment outcome

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• Endodontic Therapy – Weine

• Endodontics – Ingle

• DCNA – Microscope in Endodontics

• DCNA 1997 Oral Histology

• Oral Histology – Orbans

• Ten Cate’

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