ENDO 311 PDF - Endodontics for Third Year Students

‫‪:‬الرؤية‬ ‫تتطلع كلية طب الفم واالسنان ‪ -‬الجامعة الحديثة للتكنولوجيا والمعلومات إلى أن تكون من أكثر الكليات تميزا‬ ‫على المستوى المحلي و اإلقليمي في مجال طب االسنان‬ ‫‪:‬الرسالة‬ ‫تلتزم الكلية بإعداد أطباء أسنان يتميزون بالجدارة المهنية قادرين على...

‫‪:‬الرؤية‬ ‫تتطلع كلية طب الفم واالسنان ‪ -‬الجامعة الحديثة للتكنولوجيا والمعلومات إلى أن تكون من أكثر الكليات تميزا‬ ‫على المستوى المحلي و اإلقليمي في مجال طب االسنان‬ ‫‪:‬الرسالة‬ ‫تلتزم الكلية بإعداد أطباء أسنان يتميزون بالجدارة المهنية قادرين على التوافق مع متطلبات سوق العمل و‬ ‫مواكبة التطور العلمي و اإلسهام فيه باألنشطة البحثية مع تلبية إحتياجات المجتمع المحيط في اطار قيم اخالقية‬ ‫‪Vision:‬‬ ‫‪The College of Oral and Dental Medicine - Modern University for Technology and‬‬ ‫‪Information aspires to be one of the most distinguished colleges at the local and‬‬ ‫‪regional levels in the field of dentistry.‬‬ ‫‪Mission:‬‬ ‫‪The college is committed to preparing dentists who are distinguished by professional‬‬ ‫‪merit and are able to comply with the requirements of the labor market and keep‬‬ ‫‪pace with scientific development and contribute to it through research activities‬‬ ‫‪while meeting the needs of the surrounding community within the framework of‬‬ ‫‪ethical values.‬‬ ‫الغايات و األهداف‬ ‫الغاية األولى‪ :‬تحقيق قدرة تنافسية متميزة فى تعليم طب األسنان‬ ‫األهداف األستراتيجية‬ ‫الهدف األول‪:‬تطوير إستراتيجيات التدريس و التعلم بما يتفق مع اتجاه الدولة المصرية لتطوير التعليم‬ ‫الجامعي‬ ‫الهدف الثاني‪ :‬تطويرالمحتوى العلمي للبرنامج و نظم التقويم و الكتاب الجامعي‬ ‫الهدف الثالث‪ :‬دعم برامج التواصل مع الخريجين‬ ‫الهدف الرابع‪ :‬إ ستخدام تكنولوجيا المعلومات و أساليب التعلم الحديثة‬ ‫الهدف الخامس‪ :‬تنمية مهارات طالب الكلية بما يتفق مع متغيرات سوق العمل‪.‬‬  ‫الغاية الثانية ‪ :‬التميز و اإلبداع في مجال البحث العلمي‬ ‫األهداف األستراتيجية‬ ‫الهدف األول‪ :‬تحفيز منظومة البحث العلمي بما يدعم تقديم خدمات بحثية و عالجية للمجتمع المحلي و‬ ‫الدولي‪.‬‬ ‫الهدف الثاني‪ :‬المشاركة في المؤتمرات العلمية و تنظيم مؤتمر خاص بالكلية‬ ‫الهدف الثالث‪ :‬إصدار مجلة علمية دورية للكلية‬ ‫الهدف الرابع‪ :‬توسيع مجاالت التعاون و الشراكة البحثية محليا و اقليميا و عالميا‬ ‫الهدف الخامس‪ :‬وضع آلية لضمان اإللتزام بأخالقيات البحث العلمي و ضمان حقوق الملكية الفكرية‬ ‫الهدف السادس‪ :‬إنشاء برامج تعليمية لمرحلة الدراسات العليا تلبي احتياجات الخريجين فى سوق العمل‪.‬‬ ‫الغاية الثالثة ‪ :‬التكامل مع المجتمع المدنى لتقديم خدمات عالجية فى طب األسنان‬ ‫األهداف األستراتيجية‬ ‫الهدف األول‪ :‬التوعية التثقيفية المستمرة داخليا وخارجيا لتلبية احتياجات المجتمع المحيط بالرعاية‬ ‫الصحية لألسنان‪.‬‬ ‫الهدف الثانى‪ :‬التوسع فى التعاون مع مؤسسات المجتمع المدنى المحيط لتلبية احتياجات المجتمع‬ ‫الهدف الثالث‪ :‬وضع خطة إستباقية الدارة األزمات‬ ‫الغايــة الــرابعة‪ :‬التــ ُميز واإلبــداع الـمؤســسي‬ ‫األهداف األستراتيجية‬ ‫الهدف األول‪ :‬تطوير البنية التحتية و التكنولوجية للكلية‪.‬‬ ‫الهدف الثاني‪ :‬إستيفاء أعداد أعضاء هيئة التدريس و الهيئة المعاونة بما يتناسب مع أعداد الطالب‬ ‫الهدف الثالث‪ :‬تنمية قدرات القيادات االكاديمية و االدارية الحالية و المستقبلية‪.‬‬ ‫الهدف الرابع‪ :‬تنمية قدرات اعضاء هيئة التدريس و الهيئة المعاونة‬  ‫الغاية الخامسة‪ :‬الحصول على اإلعتماد المؤسسي‬ ‫األهداف اإلستراتيجية‬ ‫الهدف األول‪ :‬تطوير مركز ضمان الجودة بالكلية‬ ‫الهدف الثاني‪ :‬تنمية القدر ات المادية و البشرية للكلية للوصول للمعايير القومية المرجعية‬  endodontics for third year students 1 2  Contributors Assoc. Prof. Hajer Mohammed Abd ElHamed Associate Professor of Endodontics Endodontic Department Modern University for Technology and Information Dr. Zyad Alsayed Mohammad Lecturer of Endodontics Endodontic Department Modern University for Technology and Information 3 4 6  Contents Chapter Pulp Space Morphology 9 1 And Access Cavity Preparation Chapter Endodontic Instruments 43 2 Chapter Cleaning And Shaping 83 3 7 8 Pulp Space Morphology and Coronal Access Cavity Preparation 9  The dental pulp presents with a variety of configurations and shapes throughout the dentition. Therefore, a thorough knowledge of tooth morphology, careful interpretation of radiographic documentation, and adequate access to and exploration of the pulpal space are prerequisites for all root canal procedures, whether nonsurgical or surgical. The complexity of the root canal system is best understood by the integration of formative knowledge of tooth anatomy and the interpretation of radiographic documentation. The main objectives of root canal procedures are adequate enlargement, shaping, cleaning, and disinfection of all pulpal spaces, along with obturation of these spaces with an acceptable filling material. At times a root canal or its complex system may go undetected, which results in failure to achieve the stated objectives. Components of the root canal system Pulp Cavity “Space”: This is the central cavity within a tooth, which is entirely enclosed by dentin except at the apical foramen. The root canal system is divided into two portions: the pulp chamber, located in the anatomic crown of the tooth, and the pulp or root canal (or canals), found in the anatomic root. Pulp chamber: This is the pulp space that lies in the crown of the tooth. The shape of the pulp chamber usually reflects the external form of the crown. By aging and deposition of secondary dentin the size of the pulp chamber may be reduced. 10 Pulp Horn: Accentuation of the roof of the pulp chamber that is directly under a cusp or a developmental lobe. Pulp horns are important because the pulp in them is often exposed by caries, trauma, or mechanical invasion, which usually necessitates root canal procedures. Root Canal: This is the pulp space in the root of the tooth starting by the root canal orifice and ending by the apical foramen. The root canal begins as a funnel-shaped canal orifice, generally at or just apical to the cervical line, and ends at the apical foramen. Nearly all root canals are curved, particularly in a facio-lingual direction. These curves may pose problems during enlargement and shaping procedures. Major anatomic components of the root canal system 11 Apical Foramen: An aperture at or near the apex of the root through which the blood vessels and nerves of the pulp enters or leaves the pulp cavity. The root canal tapers from the canal orifice to the apical constriction (AC), which generally is 0.5 to 1.5 mm coronal to the apical foramen (AF). The AC generally is considered the part of the root canal with the smallest diameter; it also is the reference point clinicians use as the apical termination for enlarging, shaping, cleaning, disinfecting, and filling. Violation of this area with instruments or filling materials is not recommended for long-term, successful outcomes. The AF does not normally exit at the anatomic apex, but rather is offset 0.5 to 3 mm. This variation is more marked in older teeth through cementum apposition. Morphology of the root apex 12 Accessory or Lateral Canals: These are minute canals that extend in a horizontal, vertical, or lateral direction from the pulp space to the periodontium. Accessory canals may be found at any level but the majority is found in the apical half of the root or in the furcation area of multirooted teeth. Accessory canals contain connective tissue and vessels but do not supply the pulp with sufficient circulation to form a collateral source of blood flow. They may play a significant role in the communication of disease processes, serving as a passage of irritants from the pulp to the periodontium. They can occur due to: 1. The periodontal vessels curve around the root apex of a developing tooth and often become entrapped in Hertwig’s epithelial root sheath, frequently occurs in the apical third of the root. 2. Disintegration of an area of the Hertwig’s epithelial root sheath before induction of dentin formation so neither dentin nor cementum is formed. 3. Failure of fusion of the tongue like projections of the diaphragm in multi- rooted teeth resulting in accessory canals in the furcation areas. Accessory canals 13  Isthmus In teeth with multiple canals, isthmus is often found. It is defined as narrow passage or anatomic part connecting two larger structures. An isthmus is a narrow, ribbon shaped communication between two root canals which can be complete or incomplete. It contains pulp or pulpally derived tissue and acts as store house for bacteria so the isthmus should be well prepared and filled if seen on resected root surface. Basically an isthmus is a part of the root canal system and it is not a separate entity, so it should be cleaned, shaped and obturated as other root canals. Schematic representation of isthmus classifications 14  Root Canal Configurations Root canals take variable pathways throughout their course from the orifice to the apex. The pulp canal system is complex, and canals may branch, divide, and rejoin. Vertucci identified eight pulp space configurations, which can be briefly described as follows: Type I: A single canal extends from the pulp chamber to the apex (1). Type II: Two separate canals leave the pulp chamber and join short of the apex to form one canal (2-1). Type III: One canal leaves the pulp chamber and divides into two in the root; the two then merge to exit as one canal (1-2-1). Type IV: Two separate, distinct canals extend from the pulp chamber to the apex (2). Type V: One canal leaves the pulp chamber and divides short of the apex into two separate, distinct canals with separate apical foramina (1-2). Type VI: Two separate canals leave the pulp chamber, merge in the body of the root, and separate short of the apex to exit as two distinct canals (2-1-2). Type VII: One canal leaves the pulp chamber, divides and then rejoins in the body of the root, and finally separates into two distinct canals short of the apex (1-2-1- 2). Type VIII: Three separate, distinct canals extend from the pulp chamber to the apex (3). 15  Diagrammatic representation of canal configurations OBJECTIVES OF ACCESS CAVITY PREPARATION (1) Removal of all caries and defective restorations when present: Caries and defective restorations must be removed for three reasons: (1) to eliminate mechanically as many bacteria as possible, (2) to eliminate the discolored tooth structure, and (3) to eliminate the possibility of any bacteria laden saliva leaking into the prepared cavity. (2) Conservation of sound tooth structure (3) De-roofing the pulp chamber completely (4) Removal of all coronal pulp tissue (vital or necrotic) (5) Locating all root canal orifices (6) Achieving straight- or direct-line access to the apical foramen or to the initial curvature of the canal: 16  ❖ Allow instruments to be placed easily into orifices of each canal without interference from overhanging walls. Unobstructed access to the canal orifice ❖ Allow the endodontic instruments freedom within the coronal cavity. So, they can extend down the canal in an unstrained position. Endodontic instruments should have enough freedom to reach apical area without strain. ❖ Allow Complete authority over the enlarging instruments: If the instrument is impinged at the canal orifice by tooth structure, the dentist will lose control of the direction of the tip of the instrument. On the other hand, if the tooth structure around the orifice is removed, the instrument will then be controlled by two factors only: the clinician’s fingers holding the instrument and the walls of the canal touching tip of the instrument. 17  Pulp space morphology of anterior teeth Maxillary Central Incisor: Average Length: 23 mm. Root Number and Form: One and Bulky Canal Type: Type I Labiolingual Section: Narrow near the incisal edge then widen as it approaches the cervical line and then narrow to the apex. The apical foramen frequently exits short of the apex to the labial. Lingual shoulder is present cervically. Mesiodistal Section: Wide incisally with pulp horns and gradually taper to the apex. Cross Sections: Cervical: nearly triangular in shape with apex lingually and base labially. Mid root: oval Mesiodistally. Apical: Round. Outline Form: Triangular in the middle middle third of lingual surface. A B C D Maxillary Central Incisor; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 18  Maxillary Lateral Incisor: Average Length: 22.5 mm. Root Number and Form: one “slender” frequently with distal or lingual curvature or dilaceration Canal Type: Type I Labiolingual Section: Like maxillary central Incisor. Lingual shoulder is present at a point where chamber and canal join. Mesiodistal Section: Like maxillary central incisor. Cross Sections: Cervical: oval in labiolingual direction. Mid Root: ovoid Apical: round Outline Form: Triangular in the middle middle third of lingual surface. Maxillary Lateral Incisor; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 19  Maxillary Canine: Average Length: 26 mm. Root Number and Form: One, slender labially but bulkyproximally. Distal apical curvature may be found. Canal Type: Type I Labiolingual Section: Begins as a point incisally and widens at the cervical and midroot regions then narrows in the apical one third to the apical foramen. Mesiodistal Section: Much narrow than in labiolingual section with nearly uniform taper to the apex. Cross Sections: Cervical: oval in labiolingualdirection. Mid Root: oval Apical: Round Outline Form: oval in the middle middle third of lingual surface. Maxillary Canine; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 20  Mandibular Central and Lateral Incisors: Average Length: 21 mm. Root Number and Form: One narrow mesiodistally but relatively broad labiolingually. It has distal and/or lingual curvature. Sometimes, two roots have been reported. Canal Type: Type I. 60%. Type II. 30%. Type III. 10%. Labiolingual Section: Wide broad canal can be found or two canals either join near the apex (type II) or remain separate (type III) lingual shoulder is present. Mesiodistal Section: Quite narrow canal following curve of the root “distal and/or lingual”. Cross Sections: Cervical: long oval in L.L direction and narrow in M.D direction. Mid root: ribbon shaped due to flatness of the root. Apical: round Outline Form: Triangular in the middle middle third of lingual surface. Maxillary Central Incisor; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 21  Mandibular Canine: Average Length: 25 mm. Root Number and Form: One narrow mesiodistally but broad labiolingually. Rarely, two roots can be found, buccal and lingual. Canal Type: Type I. 94%. Type II or type III. 6% Labiolingual Section: Broad like mandibular Incisors. Mesiodistal Section: Much narrow than in labiolingual section with nearly uniform taper to the apex. Cross Sections: Cervical: oval in Labiolingual direction. Mid root: ovoid. Apical: round Outline Form: Oval in the middle middle third of lingual surface. Maxillary Central Incisor; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 22 Endodontic coronal cavity preparation of maxillary and mandibular anterior teeth: a) The access preparation is always on the lingual surface. For incisors the outline form is triangular in shape with the apex toward the cingulum and base toward the incisal edge. For canines the outline form is oval in shape in the B-L plane. b) The lingual surface is divided into thirds and the initial penetration is made in the middle third. c) Remove all the caries and any defective restorations so as to prevent contamination of pulp space as well as to have a straight line access into the canals. d) Access opening is started at center of the lingual surface. If it is made too small and too close to the cingulum the instrument tends to bind the canal walls and thus may not work optimally. e) Direct a round bur perpendicular to the lingual surface at its center to penetrate the enamel. Once enamel is penetrated, bur is directed parallel to the long axis of the tooth, until ‘a drop’ in effect is felt. f) Now when pulp chamber has been penetrated, the remainder of chamber roof is removed by working a round bur from inside to outside. This is done to remove all the obstructions of enamel and dentin overhangs that would entrap debris, tissues and other materials. g) Now locate the canal orifices using endodontic explorer. Sharp explorer tip is used to locate the canal orifices, to penetrate the calcific deposits if present, and also to evaluate the straight line access. h) Once the canal orifices are located, the lingual shoulder is removed using fine tapered stone. Lingual shoulder is basically a prominence of dentin which extends from the cingulum to approximately 2 mm apical to the orifice. By this a straight line access to the apical foramen is attained, i.e. an endodontic file can reach up to apical foramen without bending or binding to the root canal wall. Any deflection of file occurring should be corrected because it can lead to instrumental errors. The deflected instruments work under more stress, more chance of instrument separation is there. Deflected instruments also result in procedural accidents like canal transportations, perforations, ledging and zipping. 23  i) Irrigate the pulp chamber with sodium hypochlorite 2.5% to remove surface debris and the outline form is probed for any binding. If the probe binds against any wall of the access preparation this area should be enlarged until probe can be freely placed into the canal. j) Final smoothness of the dentin walls is best achieved using the tapered fissure diamond stone. Steps of coronal cavity preparation 24  Errors during Endodontic Cavity Preparation: 1. Gouging the labial wall caused by failure to notice the lingual axial inclination of anterior teeth. 2. Gouging of the distal wall caused by failure to notice the mesial axial inclination of anterior teeth. 3. Labiocervical perforation caused by failure to complete convenience extension toward the incisal prior to the entrance of the shaft of the bur. 4. Discoloration of the crown caused by failure to remove pulp debris due to incisally under extended cavity. 5. Errors in intraradicular cavity preparation (e.g. ledge and perforation) caused by incomplete authority over enlarging instruments due to failure to complete the convenience extension. (1) (2) (3) (4) (5) Errors during Endodontic coronal cavity preparation 25  Pulp space morphology of premolars Maxillary First Premolar: Average Length: 21 mm. Root Number and Form: Two roots in about 60% of the cases ( buccal and palatal ). One root in 38% of the cases. Three roots in less than 2% of cases (Two buccal and one palatal) Canal Type: Three roots: Each has type I. Two roots: Each has type I One root:Type III 70%. Type II 20%. Type I 10%. Buccolingual Section: Wide, two pulp horns under each cusp. Buccal is more prominent in young teeth. Roof of pulp chamber is coronal to the cervical line. The floor is convex, with two orifices buccal and palatal. The floor lies deep in the coronal one third of the root below cervical line. Mesiodistal Section: Narrow resembling upper canine. Cross Sections: Cervical: One canal : oval Two roots: ribbon shaped or figure “8”. Mid root: One canal: ovoid Two canals: round Apical: round. Outline Form: Oval buccolingual in the center of occlusal surface. In case of three root canals triangular outline (base buccal and apex palatal) Maxillary first premolar; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 26  Maxillary Second Premolar Average Length: 22 mm. Root Number and Form: One root in 85% of cases. Two roots in 15% of cases. Canal Type: One root: Type I =70%. Type II =20%. Type III= 10%. Two roots: Each root type I Buccolingual Section: It is similar to the maxillary first premolar except that the floor is deeper if two canals are present. Single canal is large and centered inside the root. Mesiodistal Section: Narrow resembling maxillary first premolar. Cross Sections: Cervical: one canal: oval. Two canals: ribbon or figure 8 Mid root: one canal: ovoid Two canals: round Apical: round Outline Form: Ovoid Buccolingual in the center of occlusal surface. Maxillary second premolar; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 27  Mandibular First Premolar: Average Length: 22 mm. Root Number and Form: One root. Relatively bulky crown in relation to the more slender root. Rarely, two roots can exist, Buccal and lingual. Canal Type: One root : Type I : 85%. Type II or III 15% Two roots, one canal in every root is present (type I). Buccolingual Section: Wide, with prominent buccal pulp horn. In young teeth, a small lingual pulp horn is present which may disappear by age giving the pulp the o appearance of mandibular canine. The crown has a lingual inclination of 30 to the long axis of the root. Mesiodistal Section: Narrow and simulate mandibular canine. Cross Sections: Cervical: slightly oval Midroot: ovoid Apical: round Outline Form: Ovoid Buccolingual. The access cavity is Located toward Buccal cusp. Mandibular first premolar; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 28  Mandibular Second Premolar: Average Length: 21.5 mm. Root Number and Form: One root. Two roots can occur very rare (Buccal and lingual). Three roots can occur extremely rare (two buccal and one lingual) Canal Type: Type I. 85%. Type II, III. 15%. In case of more than one root, each has type I Buccolingual Section: Similar to the Mandibular first premolar except the Lingual pulp horn which is more prominent under well developed lingual cusp. Mesiodistal Section: Similar to Mandibular first premolar. Cross Sections: Cervical: oval Mid root: ovoid Apical: round Outline Form: Ovoid Buccolingual in the center of the occlusal surface. Mandibular second premolar; A: Mesiodistal section, B: labiolingual section, C: cross sections (cervical, mid-root, apical), D: outline form. 29  Endodontic coronal cavity preparation of maxillary and mandibular premolar teeth: a) The basic step of access cavity preparation is removal of the caries and any other permanent restoration material if present. b) Determine the site of access opening on the tooth. In premolars, it is in the center of occlusal surface between buccal and the lingual cusp tips except in the lower first premolar the access opening must be at the center of the buccal slope due to lingual inclination of the crown. c) Slight variations exist between mandibular and maxillary premolars because of the lingual tilt of mandibular premolars. The outline form is oval except in the lower first premolar the outline form is ovoid with the largest diameter buccolingually. d) Penetrate the enamel with No. 2 round bur. The bur should be directed parallel to the long axis of tooth and perpendicular to the occlusal table. Generally, the external outline form for premolars is oval in shape with greater dimensions of buccolingual side. e) Once the clinician feels “drop” into the pulp chamber, penetrate deep enough to remove the roof of pulp chamber without cutting the floor of pulp chamber. To remove the roof of pulp chamber and pulp horns, place the bur alongside the walls of pulp chamber and work from inside to outside. For removal of pulp chamber roof, round bur, a fine tapered stone can be used. f) After removal of roof of pulp chamber, locate the canal orifices with the help of sharp endodontic explorer. Ideally the canal orifices should be located at the corners of final preparation. Extension of orifices to the axial walls results in Mouse Hole Effect. Mouse hole effect is caused because of under extension of the access cavity. This may result in preventing straight line access which may further cause procedural errors. g) Irrigation and removal of any remaining cervical bulges or obstructions using safety tip burs or Gates-Glidden drills and obtain a straight line access to the canals. It can be confirmed by passing a file passively into the canal which should reach the apex or the first point of curvature without any deflection. 30  Steps of Endodontic coronal cavity preparation of maxillary and mandibular premolar teeth. The mouse hole effect 31  Errors during premolar´s Endodontic Cavity Preparation: 1. Under extended preparation exposing only pulp horns due to lack of knowledge about position of the floor of pulp chamber in premolars. The lighter color of dentin is a clue to a shallow cavity. 2. Over extended preparation occurred during searching for root canal orifices. This is caused by failure to notice the recessed pulp in pre-operative radiograph. 3. Perforation at the mesiocervical area due to failure to recognize the distal axial inclination of the tooth. 4. Failure to explore, debride and obturate a second canal due to under extended cavity. (1) (2) (3) (4) Errors during Endodontic Coronal Cavity Preparation of Premolars 32  Pulp space morphology of Molars Maxillary first molar: Average Length: 20.5 mm Root Number and Form: Three roots, two buccal and one palatal. Mesiobuccal (MB): first curves to Mesial and nearly at the mid root region curves to distal. Distobuccal (DB) curvature is less than MB and usually to mesial "cow horn appearance" Palatal (P): most broad one. Diverge palataly but it might have a buccal curvature at the apex. Canal Type: MB root: Type I 60%. Type II 30%. Type III 10%. DB root: Type I “narrow” P root: Type I “wide and broad” on rare occasions DB and P roots may have 2 root canals each. Buccolingual Section: The floor of the pulp chamber is in the cervical one third of the root and the roof is in the cervical one third of the crown. Pulp horn extends under each cusp. Palatal canal is wider and may have a buccal curvature. Mesiodistal Section: Buccal canals are thin and well centered in their respective roots but with both orifices on the mesial 3/5 of the crown. Cross Section: Cervical: floor of pulp chamber appears quadrilateral with canal orifices at each corner. MB is ribbon shaped or 2 separate canals. DB is small and round. P. is wide and oval in M-D direction. 33  Outline Form: Triangular outline form, with the base toward the buccal and the apex toward the palatal, reflects the anatomy of the pulp chamber, with the orifices positioned at each angle of the triangle. Both buccal and lingual walls slope buccally. Mesial and distal walls funnel slightly outward. The cavity is entirely within the mesial 2/3 of the tooth and should be extensive enough to allow positioning of instruments and filling materials needed to enlarge and fill canals. The orifice to the second mesiobuccal canal (MB2) may be found in the groove near the mesiobuccal canal (MB1). Maxillary First Molar; a: Mesiodistal section, B: Buccolingual section, C: Cross section (cervical), D: Outline form. Outline of access cavity of maxillary molars is determined by mesial and distal boundary. Mesial boundary is a line joining the mesial cusps and the distal boundary is the oblique ridge. The starting point of bur penetration is on the central groove midway between mesial and distal boundaries 34  Maxillary second Molar: Average Length: 20 mm Root Number and Form: Three roots, two buccal and one palatal (90%) Two roots, one buccal and one palatal (10%). Buccal root may have type II or III infrequently. Canal type: Three roots: same as maxillary first molar. Two roots: Each root has type I most freq. Buccolingual Section: Same as maxillary first molar. Mesiodistal Section: Same as maxillary first molar. Cross Section: Cervical: like maxillary first molar but in crowns compressed M.D, DB orifice may be located toward center. Outline Form: Triangular like maxillary first molar, but flattened due to the position of the DB canal (near center of cavity floor). Maxillary Second Molar; A: Mesiodistal section, B: Buccolingual section, C: cross section (cervical), D: Outline form (three canals), E: Outline form (two canals). 35  Endodontic coronal cavity preparation of maxillary molar teeth: The access preparation is always on the occlusal surface. The outline form is triangular in shape with the base toward the buccal surface and the apex toward the palatal. The entire preparation is located within the mesial half of the tooth without or slightly crossing the oblique ridge. The access preparation is made using round bur # 3. The initial penetration is made in the exact center of the mesial pit (midway between the mesial ridge and the oblique ridge). The bur is slightly directed toward the palatal where the greatest space in the pulp chamber exists. Once the pulp chamber is penetrated, the operator will have the sensation of dropping into an empty space. The roof of the pulp chamber is completely removed on withdrawal. Irrigate the pulp chamber, dry it and start locating the orifices. The orifice of the MB canal should be present beneath the MB cusp tip. The DB canal orifice is located 2-3 mm to the distal and slightly palatal to the MB orifice. The orifice of the palatal canal is located beneath the MP cusp. The access preparation is to be enlarged where necessary so that the explorer can be freely inserted into each canal orifice. Planning, flaring and smoothening of the cavity walls should be achieved using tapered fissure bur. Steps of Endodontic coronal cavity preparation of maxillary molar teeth 36  Mandibular first molar: Average Length: 21 mm Root Number and Form: Two roots, one mesial and one distal. Mesial root usually curves distally, broad B-L narrow M-D. Distal root either straight or have mesial curvature. It is narrower than the mesial root B-L but wider M-D. Canal Type: Mesial root: Type III (90%) Type II (10%) N.B: Middle Mesial canal ( MM) may be present with incidence (1-15%). It is present in the developmental groove between MB, ML. Distal root :Type I (60%), Type II or III (40%) Buccolingual Section: Pulp chamber is in the center of the crown. Distal canal is wide and ribbon shaped whereas the mesial canals are thin. Mesiodistal Section: Orifices of both mesial and distal canals lie in the mesial 2/3 of the crown. The canals are will centered in their roots. Cross Section: Cervical: trapezoidal with canal orifices at each corner. Distal canal is wide ribbon shaped or kidney shaped. Outline Form: Triangular outline form reflects the anatomy of the pulp chamber. Both mesial and distal walls slope mesially. The cavity is primarily within the mesial 2/3 of the tooth but is extensive enough to allow positioning of instruments and filling materials. Further exploration should determine whether a fourth canal could be found in the distal. 37 Mandibular First Molar; A: Mesiodistal section, B: Buccolingual section (Mesial view), C: cross sections (cervical), D: Buccolingual section (Distal view), E: outline form. Access cavities for the mandibular first molar. A, Three mesial canal orifices and one distal canal orifice. B, Two mesial and two distal canal orifices. B, Buccal; D, distal, distal orifice; DB, distobuccal orifice; DL, distolingual orifice; L, labial; M, mesial; MB, mesiobuccal orifice; ML, mesiolingual orifice; MM, middle mesial orifice. Outline of access preparation of mandibular molars. The enamel is penetrated with No. 4 round bur on the central fossa midway between the mesial and distal boundaries. The mesial boundary is a line joining the mesial cusp tips and the distal boundary is the line joining buccal and the lingual grooves 38  Mandibular Second Molar: Average Length: 20 mm Root Number and Form:It may have: Two roots, mesial and distal. Three roots two mesial and one distal. One root. Canal Type: Two roots : Mesial root: Two canals type II or III most freq. Type I least freq. Distal root: almost always type I One root: Two canals “mesial and distal” type III or II One canal “large”"rare" C-shaped Buccolingual Section: Same as Mandibular first molar. Mesiolingual Section: Same as Mandibular first molar Cross Sections: Same as Mandibular first molar. Outline Form: Triangular like Mandibular first molar. However, mesial canals can be closer to each other. Sometimes having the same orifice. Mandibular Second Molar; A: Mesiodistal section, B: Buccolingual section (Mesial view), C: cross sections (cervical), D: Buccolingual section (Distal view), E: outline form. 39  Access cavity for a mandibular second molar as viewed through the dental operating microscope. A, Two canal orifices (M and D). B, Three canal orifices (MB, ML, and D). C, Four canal orifices identified (MB, ML, DB, and DL) Endodontic coronal cavity preparation of mandibular molar teeth: The access preparation is always on the occlusal surface. The outline form is triangular or rectangular in shape with the base toward the mesial surface and the apex toward the distal. The entire preparation is located within the mesial two-thirds of the tooth. The access preparation is made using round bur # 3. The initial penetration is made in the central pit. The bur is slightly directed toward the distal where the greatest space in the pulp chamber exists. Once the pulp chamber is penetrated, the operator will have the sensation of dropping into an empty space. The roof of the pulp chamber is completely removed on withdrawal. Irrigate the pulp chamber, dry it and start to locate the orifices. The orifice of the MB canal should be present beneath the MB cusp tip. The ML canal orifice is located 2-3 mm to the lingual to the MB orifice. The orifice of the distal canal is located slightly distal to the central pit. The access preparation is to be enlarged where necessary so that the explorer can be freely inserted into each canal orifice. Planning, flaring and smoothening of the cavity walls should be achieved using tapered fissure bur. 40 Steps of Endodontic coronal cavity preparation of mandibular molar teeth. 41 Errors during endodontic cavity preparation: 1. under extended preparation. Only pulp horns have been exposed. The entire roof of pulp chamber remains. This is due to luck of knowledge of the position of the floor of pulp chamber. The lighter color of dentin is a clue to shallow cavity. 2. Overextended preparation and badly gauging the crown due to failure to observe pulp recession in pre-operative radiograph. 3. Perforation into the furcation area resulting from failure to notice that the narrow pulp chamber had been passed. A preventive measure is to mark length of bur needed to reach pulpal floor on preoperative radiograph. 4. Perforation at the mesial-cervical in lower molars caused by failure to orient the bur with the long axis of the molar severely tipped to mesial. 5. Failure to find all canals due to under extended endodontic cavity preparation leaving part of pulpal roof un-removed. 6. Disoriented occlusal outline form exposing only one canal. A faulty cavity has been prepared in full crown, which was placed to straighten up a lingually tipped molar. 1 2 333 B 4 5 6 Errors occurring during endodontic coronal cavity preparation of maxillary and mandibular molars. 42 Endodontic Instruments 43 44  Successful Endodontic treatment procedures need a large number of endodontic instruments. Careful selection of instruments depends on understanding the advantages and limitations of all instruments. The armamentarium of endodontics has grown in complexity over the past 30 years; yet, the basic instruments used today are not much different from those used at the turn of the century. Classification of endodontic instruments:- Endodontic instruments could be classified according to their sequence of usage during performing root canal procedure into: I. Diagnostic instruments II. Access cavity preparation instruments III. Tooth isolating instruments IV. Tooth length determination instruments V. Extirpating instruments VI. Enlarging instruments VII. Obturating instruments VIII. Miscellaneous 45  I- Diagnostic instruments I. Basic diagnostic kit Dental mirror, endodontic explorer, tweezer, excavator and periodontal probe. II. Pulp vitality testers These are used to give an idea about the health status of the dental pulp. They are divided to two types of tests: a) Tests for the pulpal nerve supply Involve the application of a thermal agent (cold & / or hot) or an electric current on the tooth to stimulate pulpal A-delta sensory nerve fibers to elicit a response. This response is compared to the response of a normal tooth for judgment. A similar response suggests a normal pulp, an early response suggests an inflamed pulp, and a delayed response suggests a degenerated pulp while a negative responsesuggests a non vital pulp. b) Tests for pulpal blood supply. These tests measure pulpal blood flow and the degree of oxygen saturation. These tests are more accurate than neural tests, because pulp vitality dependsprimarily on its vascularity. III. Visual aids Recently, magnifying elements have been incorporated in the endodontic practice to enhance vision in the operative site. These could be as simple as magnifying loops being attached to ordinary eye glasses giving a magnification of 2.5X. Surgical microscopes have recently been adopted in the dental operatories. They offer a wide range of magnification from 2.5-20X together 46 with fiber optic illumination. Operator can work through the eyepiece or a monitor. IV. Radiographs The radiographic interpretation of a potential endodontic pathosis is an integral part of endodontic diagnosis and prognosis assessment. However, the image should be used only as one sign, providing important clues in the diagnostic investigation. When not coupled with a proper history and clinical examination and testing, the radiograph alone can lead to a misinterpretation of normality and pathosis. For standard two-dimensional radiography, clinicians basically project x- radiation through an object and capture the image on a recording medium, either x-ray film or a digital sensor. Much like “casting a shadow” from a light source, the image appearance may vary greatly depending on how the radiographic source is directed. The anatomic features that are closest to the film (or sensor) will move the least when there is a change in the horizontal or vertical angulation of the radiation source. This may be helpful in determining the existence of additional roots, the location of pathosis, and the unmasking of anatomic structures. 47  In general, when endodontic pathosis appears radiographically, it appears as a widening or a break in the lamina dura, or it may present as a radiolucent area at the apex of the root or in the alveolar bone adjacent to the exit of a lateral or furcation accessory canal. On occasion there may be no radiographic change at all, even in the presence of a disease process in the alveolar bone. 48  Two-dimensional dental radiography has two basic shortcomings: (1) the lack of early detection of pathosis in the cancellous bone, because of the density of the cortical plates, and (2) the influence of the superimposition of anatomic structures. Radiographic changes from bone loss will not be detected if the loss is only in cancellous bone. However, the radiographic evidence of pathosis will be observed once this bone loss extends to the junction of the cortical and cancellous bone. Several factors in uence the quality of radiographic interpretation: 1. Skill of the person exposing the radiograph. 2. Quality of the radiographic lm. 3. Quality of the exposure source. 4. Quality of the lm processing. 5. Skill in viewing the lm. Many factors can influence the quality of the radiographic interpretation, including (1) the ability of the person exposing the radiograph, (2) the quality of the radiographic film, (3) the quality of the exposure source, (4) the quality of the film processing, and (5) the skill with which the film is viewed. Digital radiography: uses no x-ray film and requires no chemical processing. Instead, a sensor is used to capture the image created by the radiation source. This sensor is attached to a local computer, which interprets this signal and, using specialized software, translates the signal into a two-dimensional digital image that can be displayed, enhanced, and analyzed. The image is stored in the patient’s file, typically in a dedicated network server, and can be recalled as needed. 49  Significant advantages of digital radiographs over conventional radiographs include (1) lower radiation doses, (2) instant viewing, (3) convenient manipulation, duplication, archiving and transmission of an image (e.g. via the Internet). Cone-Beam Computerized Tomography: Limitations in conventional two- dimensional radiography created a need for three-dimensional imaging, known as cone-beam computerized tomography (CBCT). CBCT machines are similar to dental panoramic radiographic machines. However, the radiation source of CBCT is different from that of conventional two- dimensional dental imaging in that the radiation beam is conical in shape. This cone-shaped radiographic beam is directed to the target area with a reciprocating capturing sensor on the opposite side. The resulting information is digitally reconstructed and interpreted to create series of images whereby the clinician can three dimensionally interpret “slices” of the patient’s tissues in a multitude of planes. The radiation source of CBCT is different from that of conventional two- dimensional dental imaging in that the radiation beam created is conical in shape. 50  Compared with two-dimensional radiographs, CBCT can clearly visualize the interior of the cancellous bone without the superimposition of the cortical bone. 51  II. Access cavity preparation instruments  Access opening burs: Round carbide burs (sizes #2, #4, and #6) are used extensively in the preparation of access cavities. They are used to excavate caries and to create the initial external outline shape. They also are useful for penetrating through the roof of the pulp chamber and for removing the roof.  Access refining burs: Fissure carbide and diamond burs with safety tips (i.e. non-cutting ends) are safer choices for axial wall extensions. Because they have no cutting end, the burs can be allowed to extend to the pulp floor, and the entire axial wall can be moved and oriented all in one plane from the enamel surface to the pulp floor. Such a technique produces axial walls free of gouges as the final access extensions are created. 52  Trans-metal burs: Many teeth requiring access cavity preparations have metal restorations that must be penetrated. These restorations may be amalgams, all-metal cast restorations, or metal copings of porcelain fused to metal crowns. A trans- metal bur is excellent for cutting through metal because of its exceptional cutting efficiency. To penetrate a metallic restoration, a new trans-metal bur is recommended for each restoration, together with copious water spray for maximal cutting effect.  Extended shank (surgical length) burs: When a receded pulp chamber and calcified orifice are identified, or to locate and identify the canal orifice, cutting into the root is often indicated. Extended-shank round burs, such as the Mueller bur or Extendo Bur, also known as the LN bur can be used. The extra-long shank of these burs moves the head of the handpiece away from the tooth, improving the clinician’s visibility during this delicate procedure. (As an alternative, ultrasonic tips offer good visibility with precision cutting) 53  Endodontic explorer: Various hand instruments are useful for preparing access cavities. The endodontic explorer (e.g. DG-16 endodontic explorer) is used to identify canal orifices and to determine canal angulation. A #17 operative explorer, which can also be found as a doubled-ended instrument with the DG-16, is useful for detecting any remaining overhang from the pulp chamber roof, particularly in the area of a pulp horn of anterior teeth. DG 16/17 endo explorer 54  III. Tooth isolating instruments Rubber dam equipment 1. Rubber dam sheet 2. Rubber dam clamps 3. Rubber dam forceps 4. Rubber dam frame 5. Rubber dam punch Tooth isolation using rubber dam 55  IV. Tooth length determination instruments I. Radiographic method: by introducing a file set at a specified length into the root canal (based on tooth’s average length, pre-operative radiograph and tactile sense of operator), then taking a radiograph and adjusting the working length to be within 0.5-1 mm from the end of the root. Files inserted and radiographed II. Electronic apex locator Depend on the resistance of different tissues to electricity. All apex locators have 2 electrodes: one touches the patient’s oral mucosa (lip clip) & the second is connected to a file introduced inside the canal (file clip). The electrical resistance decrease as the file is advanced apically until the file reaches the periapical tissues. This is displayed by a digital reading, light & / or sound. Recent generations of electronic apex locators have comparable accuracy to radiographs 56  II- Extirpating instruments Barbed (nerve) Broaches This instrument is manufactured from soft steel by placement of a series of extrusive incisions along the shaft (parallel to the shaft). These incisions are then elevated forming sharp projections. Barbed broaches are used for the removal of intact pulp tissue being slowly introduced into the canal, rotated fullturn to entangle the pulp tissue then withdrawn. Because of its weak design (sharp projections), this instrument is limited for usage in large size canals to avoid fracture. In small sized canals any of the enlarging instruments (H-file) can be used for pulp extirpation. The barbed broach and its cross section 57  III- Enlarging instruments Cleaning and shaping of the pulpal space can be achieved by either Hand- driven instruments or a combination of Hand-driven and Engine-driven instruments. *Design Elements: Root canal preparation instruments follow certain design principles: A- Tip Design: In root canal preparation, an instrument tip has two main functions: to guide the file through the canal and to aid the file in penetrating deeper into the canal. 58 B- Longitudinal and Cross-Sectional Design: * Cutting edge: forms and deflects chips along the wall of the canal and severs or snags soft tissue. * Helical angle: The angle the cutting edge forms with the long axis of the file * Rake angle: the angle formed by the cutting edge and the radius of the file through the point of contact with the radicular wall (may be negative “scraping” or positive “cutting”). A positive rake angle reduces the cutting forces. However, nearly all root canal instruments requiring a rotary reaming working motion have a negative rake angle, such as reamers, K-file, and rotary NiTi instruments. Although a negative rake angle makes these instruments less effective, they can be better controlled inside the root canal as their tendency to penetrate deeper into the root canal dentin is reduced (aka screw-in effect) compared to instruments having positive rake angles. Moreover, a negative rake angle increases the strength and the wear resistance (longevity) of the cutting edges. * Rake angle: the angle formed by the leading edge and the radius of the file through the point of contact with the radicular wall. If the angle formed by the leading edge and the surface to be cut is 90 degrees, the rake angle is said to be neutral. The rake angle may be negative or scraping or positive or cutting. 59 * Cutting angle: the angle formed by the cutting edge of the file and a tangent to the radicular wall in the point of contact. * Pitch: the distance between a point on the cutting edge and the corresponding point on the adjacent cutting edge (the distance from one “spiral twist” to the next). The smaller the pitch or the shorter the distance between corresponding points, the more spirals the file has and the greater the helix angle. 60 * Chip space: This is the difference between the area of the canal lumen and the area of the cross-section of the particular instrument used. The chip space is directly related to the cutting efficiency of any root canal instrument and its cleaning effectiveness. Simply stated, the greater the chip space the more efficient is the instrument in transporting dentin and debris out of the canal. Design elements of the cutting part of root canal instruments * Radial land: a surface that projects axially from the central axis, between flutes, as far as the cutting edge. It is the combination of a non-cutting tip and radial land that keeps a file centered in the canal. Another way of evaluating radial lands is blade support. Files derive their strength from the mass of material in the core. Peripheral strength can also be added to a file by extending the width of the radial land. 61 * Core: The core diameter of any root canal instrument affects its flexibility as well as its resistance to fracture. A greater core diameter is associated with an increased resistance to fracture but at the same time with a decreased flexibility. The core diameter depends on the cross-sectional shape of the instrument. For hand instruments, the core diameter decreases from square, to triangular and further to S-shaped cross-sections. C- Taper: The amount the file diameter increases each millimeter along its working surface from the tip toward the file handle. For example, a size #25 file with a.02 taper would have a 0.27-mm diameter 1 mm from the tip, a 0.29-mm diameter 2 mm from the tip, a 0.31 mm diameter 3 mm from the tip, and so forth. 62 *Standardization of endodontic basic instruments: Before 1958, endodontic enlarging instruments were manufactured without any established criteria where an instrument of one company rarely coincided with a comparable instrument of another company. The standardization included the following items: 1- Numbering and color coding: The sizing system goes as follows: 6,8,10…..15,20,25,30,35,40…..45,50,55,60,70,80…...90,100,110,120,130,140. This sizing system is not arbitrary but is based on the diameter of the instrument in hundredths of a millimeter at the tip of the instrument (Do). As an example, an instrument size 60 means that the diameter of the instrument at Do = 60/100 = 0.6 mm. 2- Standardization of length The first standard in length is the full extent of the shaft up to the instrument handle and this comes in three lengths: 25 mm (standard), 31 mm (long) and 21 mm (short). The second standard in length is the length of the instrument blade (working or cutting area). This length is standard to be 16mm starting at Do and ending at D16. 63  3- Standardization of taper The file diameter increases at a standard rate of 0.02mm/mm starting at Do ending at D16. This means that the difference in diameter between Do and D16 regardless the instrument size is always 0.32mm (0.02x16=0.32). 4-Standardization of tip angle The angle formed between the instrument tip and the long axis of the instrument shaft is standardized to be 75o + 15o. Standardization of basic enlarging instruments 6-Incremental increase in size There must be a gradual incremental increase in size among subsequent instruments - Sizes 6-10 : 0.02 mm or 2% - Sizes 10-60 : 0.05 mm or 5% - Sizes 60-150 : 0.1 mm or 10% 64 - Essay compare between different alloys used in manufactiring of endodontic instruments according to - Composition - advantages -Disadvantages  *Alloys used for manufacturing of Endodontic Instruments: - Essay compare between different alloys used in manufactiring of endodontic instruments according to - Composition - advantages -Disadvantages 1- Carbon steel: These alloys contain less-than 2.1% of carbon. Advantage: They have high hardness than stainless steel instruments. Disadvantages: Prone to corrosion, so cannot be re-sterilized. 2- Stainless steel: These are corrosion resistant instruments. They contain 18 % chromium, 8-10 % nickel and 0.12 % carbon. Advantage: Corrosion resistant Disadvantages Stiff in nature Prone to distortion and fracture 3- Nickel titanium: NiTi alloy used in endodontic instruments contain approximately 56 wt% nickel and 44 wt% titanium. This alloy can exist in two different temperature-dependent crystal structures named austenite (high-temperature, with a cubic B2 crystal structure) and martensite phase (low-temperature phase, with a monoclinic B190 crystal structure). 65  These alloys show stress induced martensitic transformation from parent austenitic structure. On releasing stresses, the material returns to austenitic and its original shape. Advantages: Super elasticity : Complete recoverable elastic deformation up to 8% strain due to phase transformation between stable austenite and stress-induced martensitic phase Shape memory: Ability of deformed NiTi to recover its original shape when heated due to phase transformation of stable deformed martensite to stable austenite phase Low modulus of elasticity Corrosion resistant Disadvantages: Poor cutting efficiency. NiTi files do not show signs of fatigue before they fracture. 66  Classification of instruments used for shaping of the root canal space Group I: Hand-driven enlarging instruments, such as K-type and H-type files and their modifications. Group II: low speed instruments with a latch type attachment, such as Gates Glidden drills and Peeso reamers. Group III: Engine-driven (rotary or reciprocating) nickel-titanium instruments. Group IV: sonic and ultrasonic vibratory instruments. Group1: Hand-driven enlarging instruments: a. Basic enlarging instruments: These instruments were introduced by the beginning of the last century (1904) and are considered by far the most commonly used intracanal instruments. These include four basic instruments, which are: (I) K-file Fabrication of a K-file starts as a round St.St. wire that is cut to form a tapered instrument ending by a pointed tip with square cross-section. This wire is then twisted in a counter clock wise direction to form spirals (flutes), which are 1.5 – 2.5 flute/mm. The cross section is symmetrical with negative rake angles, allowing dentin to be adequately cut in both clockwise and counter- clockwise direction. 67  Number of flutes is higher than K-reamer. Clearance space is smaller than K-reamer with increased tendency for clogging. Helical angle of this file is 25°-40°. It is a universal file can be used in filing motion for preparing middle third or watch winding motion in preparing apical third due to intermediate helical angle. K-files are produced to give a smooth tactile sense inside the canal during instrumentation. (II) K-reamer Similar to K-file, the K-reamer starts as a round St.St wire cut to form a tapered instrument ending by a pointed tip with triangular cross section. This wire is then twisted in counter clock wise direction to form flutes, which are not as tight as the K-file. The number of flutes on the shaft of the reamer are 0.5 – 1 flute/mm. Reamers can be used in reaming action only. Tip design is sharp for better initial scouting of root canals but unfortunately, sharp tip increase tendency for ledge creation, zipping, and apical transportation. Number of flutes is less than K-file. Clearance space is wider than K-file with superior debris removal quality. Helical angle is of this file is 10°-20°. 68  Although the square cross-section of the K-file have a cutting angle of 90o which is considered to be less efficient than the cutting angle of K-reamer (60o), yet, this is compensated by the greater number of flutes the K-file have. K-file K-reamer 69  During use, if k-type instruments are locked in the canal, continuous clockwise rotation will result in unwinding and elongation of the flutes with ultimate ductile fracture. While if rotated in a counter clockwise direction, this will result in increased work hardening of the alloy and sudden breakage termed brittle fracture. (III) H-file (Hedstrom file) This file is constructed from round St. St. wire by machine grinding forming a series of intersecting cones. This design produces sharp edges at the base of each cone, which cuts tooth structure on pulling only. The cross-section of this instrument shows that it is coma shaped (tear drop) with one cutting edge. Because of a positive rake angle and a blade with a cutting rather than a scraping angle, H-files are by far more efficient than reamers or K-files as they cut away more root canal dentin per time unit than K-files. At the junction between each two cones, the shaft of the instrument is weak facilitating its breakage if used in any form of rotation (reaming action).Therefore, H-files are to be used in filing action only. 70  Due to the manufacturing milling process, grinding cracks may result on the surface of the instrument. This fact, together with the relatively low core diameter of Hedstrom files, explains why these instruments show an increased risk of fracture compared to reamers or K-files. In general, milled instruments like Hedstrom files are not recommended for use in narrow or curved canals due to their higher risk to fracture. b. Flexible Instruments In order to avoid undesirable shaping effects in curved root canals, such as straightening, ledging, zip and elbow formation, several manufacturers have developed new stainless steel alloys characterized by higher flexibility in bending compared with conventional stainless steel. Flex-R-file: Modification from K-file (with triangular cross section) Non-cutting tip Manufactured by machine grinding Cross section : triangle Advantages : 1. Better cutting ability 2. More clearance space 3. Better flexibility 4. Non-cutting tip 71  Flex O Files These are similar to the K-Flex files except that they have triangular cross section. This feature provides them more flexibility and thus ability to resist fracture. The tip of file is modified to non-cutting type. They are made up to NiTi. They have more flexibility but less of cutting efficiency. K-flex file: This instrument has a rhomboid cross-section. The cutting edge of the K- flex file is formed of two acute angles (high flutes), which present increased sharpness while the two obtuse angles (low flutes) provide more space for debris removal. In addition, this change in design increased instrument flexibility. Flex-R file K-file K-flex file K-reamer 72 Group II: low speed instruments with a latch type attachment: Gates Glidden Drills - Made from stainless steel (thus rigid), flame shaped with non cutting tip. - Used for coronal flaring (in the straight part of the canal). - Available in 6 sizes (1-6) equivalent to ISO sizes (50,70,90,110,130 & 150). - Size of instrument demarcated by thenumber of rings on the shaft. - Designed to break near the shaft tofacilitate its retrieval. Peeso Reamers - Also made from stainless steel and has a longer working part with a non cutting tip. - Available in sizes (1-6) equivalent to ISO sizes (70,90,110,130,150 &170). - Size of instrument demarcated by the number of rings on the shaft. - Used for coronal flaring or to remove root canal filling material for post crown 73 Group III: Engine-driven (rotary or reciprocating) nickel-titanium instruments In 1960 a novel nickel-titanium alloy was developed by William Bueller in Silver Springs, Maryland at the United States Naval Ordinance Laboratory (that is why it is often refered to NITINOL where NOL stands for Naval Ordnance Laboratory). In 1988, Harmeet Walia and his colleagues proposed Nitinol for shaping canals, as it is 2 to 3 times more flexible, in the same file sizes, compared to stainless steel. Files manufactured from Ni-Ti can mechanically prepare curved canals utilizing a continuous rotary motion which has been proven as a trend changing outcome. By the mid- 1990s, the first commercially available Ni-Ti rotary files had come to market. First generation rotary instruments:- Dr. Johnson in 1994 introduced the PROFILE line with 0.04 and 0.06 tapered instrument system. In general, first generation Ni-Ti files have fixed tapers of 4% and 6% over the length of their active blades. The single most important design feature of first generation Ni-Ti rotary file was passive radial lands. This encouraged a file to stay centered in canal curvatures during work but these systems required a considerable number of files to achieve preparation objectives. Examples include Profile, Quantec and Great taper (GT) file systems. 74 Second generation rotary instruments:- The next generation of NiTi rotary files came to market in 2001. The critical distinction of this generation of instruments is they have active (positive) cutting edges and require fewer instruments to fully prepare a canal. To this generation belongs EndoSequence and BioRace file systems, which provide file lines with alternating contact point. This helps to prevent taper lock and the resultant screw effect associated with other fixed tapered Ni-Ti instruments (Although this file system still has a fixed tapered design). To increase the resistance to file separation, the manufacturers electropolished these files to remove surface irregularities caused from the traditional grinding process. However, electropolishing dulls the sharp cutting edges which has been clinically observed and scientifically reported. The critical breakthrough occurred when ProTaper file system came to market. They have multiple increasing or decreasing percentage tapers on a single file. This revolutionary, progressively tapered design limits each file’s cutting action to a specific region of the canal and affords a shorter sequence of files to safely produce the required preparation shapes. 75 Third generation rotary instruments:- Improvements in Ni-Ti metallurgy gave rise to the third generation of rotary shaping files. In 2007, manufacturers began to focus on utilizing heating and cooling methods to reduce cyclic fatigue and improve safety when rotary Ni-Ti instruments work in more curved canals. Special heat treatment provides files with more resistance to stress and fatigue. Examples include Hyflex CM, K3XF, Profile GTX, Profile Vortex and Vortex blue, Twisted files (TF) and WaveOne. 76 Fourth generation rotary instruments:- This generation is characterized by utilizing reciprocation, which is defined as repetitive up-and-down or back-and-forth motion. In comparison to full rotation, a reciprocating file that utilizes an equal bidirectional movement requires more inward pressure to progress and will not cut as efficiently as a same-size rotary file. Also it is more limited in getting debris out of the canal. Single file concept: a single file coupled with a reciprocating motor that drives this file in unequal bidirectional angles. The counterclockwise (CCW) engaging angle is 5 times the clockwise (CW) disengaging angle which is designed to be less than the elastic limit of the file. After 3 CCW and CW cutting cycles, the file will have rotated to 360°, or one circle. This novel reciprocating movement allows a file to more readily progress, efficiently cut, and effectively gets the debris out of the canal. Examples include: WaveOne and Reciproc file systems 77 Fifth generation rotary instruments:- The fifth generation of shaping files has a wave motion along the active part of the files. They have been designed such that the center of mass and/or the center of rotation are offset that conveys mechanical rotation into wave motion. This offset design serves to further minimize the engagement between the file and dentin. It also enhances getting debris out of a canal and improves flexibility along the active portion of the file. Examples include REVO-S, ONE SHAPE, and Protaper Next. Group IV: (sonic & ultrasonic instruments) Sonic systems * Vibration frequency: less than 20 KHz * Power: compressed air Ultrasonic systems * Vibration frequency: 20-50 KHz * Power: electric current 78 Debriding action of Sonic and Ultrasonic instruments The main debriding action of Sonics/ultrasonics was initially thought to be by “Cavitation”, a process by which bubbles formed from the action of the file become unstable and collapse causing vacuum-like action. The mechanism involved in ultrasonic cleaning is “Acoustic micro- streaming”; which is the rapid agitation of the irrigating solution in the prepared enlarged canal by a small sizedultrasonic instrument. 79 Uses of Ultrasonics  Access refinement, finding calcified canals, and removal of attached pulp stones: One of the challenges in endodontics is to locate canals, particularly in cases in which the orifice has become occluded by secondary dentin or calcified dentin after the placement of restorative materials or pulpotomies. One of the important advantages of ultrasonic tips is that they do not rotate, thus enhancing safety and control, while maintaining a high cutting efficiency. This is especially important when the risk of perforation is high. 80  The visual access and superior control that ultrasonic cutting tips provide during access procedures make them a most convenient tool, especially when treating difficult molars. When searching for hidden canals, one should remember that secondary dentin is generally whitish or opaque, whereas the floor of the pulp chamber is darker and gray in appearance.  Increased action of irrigating solutions: The effectiveness of irrigation relies on both the mechanical flushing action and the chemical ability of irrigants to dissolve tissue. The flushing action from syringe irrigation is relatively weak and depends on the depth of placement and the diameter of the needle. It has been shown that irrigants can only progress 1 mm beyond the tip of the needle. The only effective way to clean webs and fins is through movement of the irrigation solution, as they cannot be mechanically cleaned. Ultrasonics is useful adjunct in cleaning these difficult anatomical features. Acoustic streaming has been shown to produce sufficient shear forces to dislodge debris in instrumented canals. When files were activated with ultrasonic energy in a passive manner, acoustic streaming was sufficient to produce significantly cleaner canals compared with hand filing alone. 81  Sealer placement and condensation of Gutta Percha: In a warm lateral condensation technique, ultrasonic activated spreaders that vibrate linearly and produce heat (thus thermoplasticizing the gutta-percha), achieve a more homogeneous mass with a decrease in number and size of voids and produce a more complete three- dimensional obturation of the root canal system. In addition, it has been demonstrated that placement of sealers with an ultrasonically energized file promoted a better covering of canal walls with better filled accessory canals than placement of sealers with hand instruments.  Removal Of Intracanal Obstructions 1- Intraradicular post-removal: Ultrasonic instrumentation for post-removal typically involves removing coronal cement and buildup material from around the post, then activating the tip of the ultrasonic instrument against the metal post. i.e ultrasound energy transfers to the post and breaks down the surrounding cement until the post loosens and is easily removed. 2-Gutta-percha removal: Studies have shown that ultrasonic instrumentation alone or with a solvent is as effective as hand instrumentation in removing gutta-percha from root canals. 3-Silver point removal: A conservative approach for removing defective silver points. In this canal alongside the silver point. 4- Removal of broken instruments: it is used by making vibration action around the broken file to remove it from the canal. 82 Cleaning & Shaping 83 84  Root canal preparation is considered the most important and challenging step during root canal treatment. It involves using mechanical and chemical means to remove pulpal tissue, reduce microbial load, and enable appropriate obturation of the radicular spaces. Although the terms cleaning and shaping are often used to describe root canal treatment procedures, reversing the order to shaping and cleaning more correctly reflects the fact that enlarged canals direct and facilitate the cleaning action of irrigants and the removal of infected dentin. Principles of cleaning and shaping The general objectives in cleaning and shaping the root canal system are to do the following: ◆ Remove infected soft and hard tissue ◆ Give disinfecting irrigants access to the apical canal space ◆ Create space for the delivery of medicaments and subsequent obturation ◆ Retain the integrity of radicular structures The aims of root canal preparation, also termed as enlargement, shaping, or instrumentation of the root canal, have been outlined by Herbert Schilder in 1974. He suggested five mechanical and five biological objectives for root canal preparation. The mechanical objectives are: 1- Continuously tapering funnel from the apex to the access cavity. 2- Cross-sectional diameter should be narrower at every point apically. 3- The root canal preparation should flow with the shape of the original canal. 4- The apical foramen should remain in its original position. 5- The apical foramen should be kept as small as practical 85  The biologic objectives are: 1- Confinement of instrumentation to the roots themselves. 2- Not forcing necrotic debris beyond the apical foramen. 3- Removal of all tissue and debris from the root canal space. 4- Creation of sufficient space for intracanal medicaments. 5- Completion of preparation in one appointment. Steps of Mechanical preparation of Root canals Mechanical preparation can be divided into six main parts: A) Preparation of the coronal access cavity B) Preparation of the pulp chamber C) Identification of root canal orifices D) Preparation of a secondary access to the root canals (coronal flaring) E) Preparation of a glide path to the apical foramen F) Preparation of the middle and apical parts of the root canal. 86  B) Preparation of the pulp chamber: Following the coronal access cavity preparation, the pulp chamber itself should be cleaned meticulously from all necrotic or vital tissue. It should be noted that in a tooth with a necrotic infected pulp, the majority of microorganisms are located in the pulp chamber. Instrumenting a root canal through a contaminated pulp chamber will force microorganisms further into the root canal and transport them apically. Mechanical cleaning can be done using rose burs, and ultrasonic or sonic instruments. The pulp chamber is repeatedly flooded with copious amounts of sodium hypochlorite thus initiating disinfection of the endodontic cavity immediately upon starting treatment. Calcifications and pulp stones may present a challenge since they can cause difficulties to locate and prepare all root canal orifices. Coronal calcifications and constant narrowing of the pulp chamber are a result of deposition of secondary and sometimes also tertiary dentin. Calcification can be accelerated in the presence of active caries, stimulating dentin secretion by odontoblasts, and has been detected in more than 90% of patients older than 40 years. Complete canal calcification is the exception and can be detected following dental trauma. Otherwise, calcification is usually incomplete and limited to the coronal part(s) of the root canal. Calcification is incomplete if: A canal space can be detected on the radiograph. The tip of a file is engaging inside the canal. Electronic determination of root canal length reveals a signal. An apical lesion is present. Bubbles can be observed evading from an irrigated root canal. Pain upon instrumentation occurs. 87  C) Identification of Root Canal Orifices: 1- Anatomic Rules Krasner and Rankow described some patterns in orifice location, pulp chamber size and shape, and hard tissue color and shape: *Law of Centrality: The floor of the pulp chamber is always located in the center of the tooth at the level of the Cemento-Enamel Junction (CEJ). *Law of Concentricity: The walls of the pulp chamber are always concentric to the external surface of the tooth at the level of the CEJ, that is, the external root surface anatomy reflects the internal pulp chamber anatomy. *Law of the CEJ: The distance from the external surface of the clinical crown to the wall of the pulp chamber is the same throughout the circumference of the tooth at the level of the CEJ. The CEJ is the most consistent repeatable landmark for locating the position of the pulp chamber. *Laws of Symmetry: 1. Except for the maxillary molars, the orifices of the canals are equidistant from a line drawn in a mesial–distal direction, through the pulp chamber floor. 2. Except for the maxillary molars, the orifices of the canals lie on a line perpendicular to a line drawn in a mesial–distal direction across the center of the floor of the pulp chamber. *Law of Color Change: The color of the pulp chamber floor is always darker than the walls. *Laws of Orifice Location: 1. The orifices of the root canals are always located at the junction of the walls and the floor. 2. The orifices of the root canals are located at the angles in the floor–wall junction. 88  3. The orifices of the root canals are located at the terminus of the root developmental fusion lines. Diagrammatic representation of centrality and concentricity of symmetry and location of canal orifices. 2- Techniques and devices: *Dental Explorer: Debris can be accumulated on the pulp chamber floor clogging canal orifices. Chipping away the dentinal shavings using a small and sharp endodontic explorer can disclose the orifice. 89  *Dyes: Dyes such as Methylene blue can be used. After application of the dye, the cavity is washed out and searched for traces of remaining dye that may indicate the location of a previously undetected orifice. *Sodium Hypochlorite: A drop of sodium hypochlorite is applied to the access cavity floor and observed under magnification and illumination for bubbles evading from a hidden root canal (champagne test). The bubbles are a result of disintegration of remaining pulpal tissue induced by the sodium hypochlorite. Bubble test of Sod. Hypochlorite 90 D) Preparation of a secondary access to the root canals (coronal flaring): Coronal flaring has the following objectives: Facilitates insertion of instrument without coronal interferences. Reduces friction of the instruments and thereby allows better control of the instrument and reduces the risk of instrument fracture. Flaring outside of the curvature can reduce the degree of the curvature and facilitate further preparation of the middle and apical thirds of the canal. Allows early application of large amounts of irrigant into the canal. *Instruments for Coronal Flaring: Gates-Glidden - Peeso Drills - Orifice Openers 91 E) Preparation of a glide path to the apical foramen: *Objectives: Exploration of the root canal system to be prepared. (Assessment of canal width, and curvatures) Reduction of friction of small NiTi instruments thereby lowering the risk of instrument separation. *Pathfinding Instruments: Conventional ISO size instruments possess a low resistance to buckling. When these instruments are used to penetrate narrow canals they are submitted to a load parallel to their long axis, and they deform easily and their progression towards the apex is hindered. On the basis of these considerations, special stainless steel Pathfinding instruments were introduced to improve negotiation of narrow and calcified canals. These instruments are characterized by design features that improve their buckling resistance.  K-files (ISO-sizes 06, 08, 10 regarded as the classical instruments for glide path preparation. They are used in a watchwinding motion with slight apical pressure.  C+-Files: These instruments are manufactured by grinding stainless steel wires of a square cross-section. The apical 4 mm show a 4% taper to increase the stiffness of the tip; the coronal part shows a 2% taper to maintain flexibility. C+ files 92   PathFiles: Rotary glide path file system that consists of three instruments with the following characteristics: 1- Tip diameters respectively, 0.13, 0.16 and 0.19 mm. The gradual increase in tip diameter (similar to that of Profiles Series 29) facilitates their progression, without the need to apply strong axial pressure. 2- Tip design is non-cutting rounded rather than cutting, to avoid ledges and zips. 3- Square cross section to: increase their resistance to torsional stress + the four cutting edges increase their cutting efficacy. 4- Flexibility as a property of nickel titanium alloy and due to their low taper, which is only 0.02. Pathfile tip design Pathfile sequence 93 F) Preparation of the middle and apical parts of the root canal: *Basic instrumentation motions: Cleaning and shaping of the root canal is performed by endodontic instruments (files) being moved against the dentin walls either in a linear motion (up and down) or rotation motion. These motions are being referred to as "BASIC INSTRUMENTATION MOTIONS. 1. Linear motion: Filing motion: This is a linear motion in the form of push and pulls action. It is the most efficient motion in cutting dentin. All types of files can be used with this motion; however, the H-file is considered the best. This motion is recommended for enlarging the coronal 2/3 of the canal (circumferential filling). Filing motion showing push and pull action of instrument 2. Rotation motions: a. Reaming motion: This is a rotation motion. The term ream indicates clockwise or right-hand rotation of the instrument. It is assumed that this motion produces round cross-section of the root canal, however, chances of the instrument to fracture is increased. Reaming motion involving clockwise rotation of instrument 94 b. Turn and pull: This is a combination of reaming and filing where the instrument is inserted with a quarter turn clockwise (reaming) then the file is subsequently withdrawn (filing) Reaming motion involving clockwise rotation of instrument c. Watch winding motion: This is a rotation motion. The instrument is being inserted in the canal with a gentle clockwise/counterclockwise motion (right and left). Rotation of file in watch-winding motion 95 d. Balanced force: It is a rotation motion. It is identical to the watch winding in which the instrument is rotated right and left inside the canal until reaching the desired length. Now the instrument is rotated to the left (counter clockwise). This left rotation attempts to drive it out of the canal so, the clinician must apply apical pressure to prevent outward movement to obtain cutting. Simultaneous apical pressure and counter clockwise rotation of the file strikes a balance between the tooth structure and instrument. This balance keeps the instrument centralized inside the canal thus, minimizing the chances for canal transportation. balanced force technique 96  *Techniques of instrumentation: (I) Step-Back Technique: (Telescopic Canal Preparation/Serial Root Canal Preparation) Phase one (apical preparation): - Tooth length determination - Initial file should reach the full working length with slight resistance at the apical third - Initial file inserted with (watch winding motion) when reaches the full working length (turn & pull motion) - Last file used to the working length called (MAF) 97  Phase two (Flaring): - Inserting a bigger file sizes and shorting the working length 1mm with a filling action - Irrigate the canal and go back again to the MAF to full working length to carry the collected debris outside the canal (Recapitulation). - The master apical file is used in rotation motion - Use Gates Glidden drills to gain the funnel canal shape - Final refining of the root canal is done using master apical file with push–pull strokes to achieve a smooth taper form of the root canal Final refining of the root canal * Disadvantages of step back technique: - Difficult to insert instruments in canal - Difficult to irrigate apical region - More chances of pushing debris periapically - More tendency to straighten the curved canal - Increased chances of iatrogenic errors (e.g. ledge formation, - instrument separation, zipping of the apical area, apical blockage) 98 (II) Crow-Down Technique: - Tooth length determination - The canal is negotiated using K file # 15. - H file # 40 – 50 are passively inserted inside the root canal using watch winding motion then the coronal 1/3 is enlarged using circumferential filing. - Sequential usage of smaller sizes permits deeper penetration of the files until reaching the apical 1/3 of the root canal. - Apical terminus of the root canal is prepared using smaller K files in rotation motion. - GG can be used in initial coronal enlargement to achieve fast cutting Schematic representation of crown down technique 99 * Advantages of Crown-Down technique: - Permits straighter access to the apical region - Removes bulk of the tissue and microorganisms