Endo I Final - 1 - Endodontic Access Preparation

• Remove all the caries
• Conservation of tooth structure
• Completely un-roof the pulp chamber
• Remove all coronal pulp tissue, vital or necrotic
• Locate all root canal orifices
• Achieve straight line access
• Establish restorative margins

DG16

• Type I: 1->1
• Type II: 1->2->1
• Type III: 2->2 separate early
• Type IV: 1->2 separate late; most challenge

• single canal and single foramen Most of the times
• Canal form is usually type I
• The pulp in young patients has usually 3 pulp horns
• pulp chamber: MD > FL
• External access outline form: triangular, base toward incisal
• Lingual shoulder must be removed.

• single canal & single foramen
• type I canal form
• young patients usually have two pulp horns & MD > FL.
• canal is tapered
• apex is curved generally distally
• External access outline form: triangle or oval.
• Anomalies: Developmental groove, Dens invaginatus.

• central is shorter than lateral.
• root canal morphology: Type I more common than II or III.
• pulp chamber: smaller replica of upper incisors. MD < FL.
• When single canal, normally straight, but may curve distally.
• canal outline is oval @ CEJ
• External access outline form: triangle or oval.
• Lingual shoulder must be eliminated. A second canal (lingual) may be found underneath.

• The longest tooth (26.5mm)
• Pulp chamber: MD < FL.
• No pulp horn
• Rarely > 2 canals
• Oval Type I.
• Apex tapered and very thin, usually straight but may curve distally.
• External access outline form: OVAL.
• Lingual shoulder must be eliminated.
• Incisal extension of 2-3 mm to incisal edge to allow straight line access.

• Smaller than the max. canine
• Type I form; rarely 2 roots; very few times Type IV with 2 separate apical foraminas.
• MD < FL
• Access cavity OVAL.
• Lingual shoulder must be removed. Possible second canal underneath.
• Incisal extension toward incisal edge for straight line access

• Root canal: generally 2 roots w/ 2 canals, or 1 root w/ 2 canals w/ a common apical foramen.
• 2 pulp horns: B and P
• Pulp chamber: MD < BP

• Type I (48% ) w/ apical distal curvature.
• Pulp chamber: MD < BP
• Two pulpal horns.
• Canal orifice is in the center

• One canal 75%, 2 canals 25%
• - a single canal may bifurcate into two in the apical half
• Pulp chamber: MDTwo pulpal horns
• Access preparation in the center of the cusp tips
• Crown tilted to Lingual; access must start closer to the facial of the occlusal surface

• The most complex root canal anatomy.
• Three individual roots (MB,DB,P).
• Anatomical structures around the root apices makes radiographic interpretation of the roots difficult.
• Palatal root: the longest, larger diameter. One canal, curves buccally at apical third, flat, ribbon-like, and wider in MD direction.
• DB root: conical, 1/2 canals.
• MB root: Usually two canals (1-3). Concavity on the distal aspect, makes this wall thin.
• - 37% or more: two MB canals join into one foramen.
• - 25% or more: two MB canals exit through two separate foramina
• - MB2 canal always smaller in diameter than the other three.

• Always assume two MB canals exist until careful examination proves not.
• Rhomboid shape with the corners corresponding to the four orifices (MB1, MB2, DB, P);
• Mesial: not extend into the mesial marginal ridge.
• Distal: not penetrate through the ridge.
• Buccal: parallel to the line connecting MB1 and DB orifices, not to the buccal surface of the tooth.
• The initial point of penetration: over P, the major (largest) canal - Intrapulpal anesthetic injection can best be utilized in this area when anesthesia is a problem; the easiest to locate.

• Resemble the coronal anatomy of the maxillary first molars
• Differences:
• •The roots are closer and sometimes fused; when fused, may have only 2 canals, or one in rare cases.
• •The roots are shorted and not as curved as MxM1.
• •Usually each root only has one canal; 4 canals less likely.
• •The three orifices (MB, DB, P) usually form a flat triangle (sometimes a straight line):
• - MB is more buccal and mesial
• - DB is in the midpoint between MB and P.
• - P is at the most palatal aspect of the root.

• •Four canals: rhomboid shape.
• •Three canals: rounded triangle with the base to the buccal.
• •The oblique ridge usually is not invaded.
• •The mesial marginal ridge is not invade.
• •Two canals: oval, widest in the FL dimension.

• Most frequent for RCT.
• Four pulp horns: MB, ML, DB, DL.
• Two or three roots.
• Distal surface of M root and mesial surface of D root have root concavities, very thin walls - danger zones.
• Three or four canals: two in M root (MB and ML canal) and one (Distal canal) or two (DB, DL canal) in D root
• All Orifices: usually in the mesial two thirds of the crown .
• Pulp chamber floor: trapezoid or rhomboid shape.

• Flattened MD morphology with complex root canal configuration.
• Conical distal roots: frequently single canal.
• Diameter larger than mesial root.
• Occasionally, orifice extends wide bucco-lingually.
• Wide BL anatomy: indicates a second canal or ribbon-like complex webbing.
• When two separate canals: much thinner than a single distal canal, and located towards buccal and lingual. When a distal canal can not accommodate size #15 file at the initial entrance and is not centrally located, be suspicious of two distal canals.

• Wider than Distal.
• Curves mesially from the cervical line to the middle third and then angles distally to the apex.
• Often two independent foramina.
• MB canal always curved, ML canal usually straight and shorter.

• Mesial: not to invade the marginal ridge.
• Distal: allow straight line access to the distal canal(s).
• MB orifice: commonly under MB cusp.
• ML orifice: lingual to the central groove.
• Middle mesial canals may be present between MB and ML orifices (1% to 15% of the time).
• If only one distal canal: oval buccolingually and located distal to the buccal groove.
• Initial point of penetration: over the major (largest, distal) canal: Effective Intrapulpal anesthetic injection; the easiest to locate.

Extra distolingual root (common in Asian population). Radix entomolaris (RE): supernumerary root located distolingually in mandibular molars. Each root usually contains a single root canal.

• Smaller coronally than M1 and more symmetrical.
• Two roots, close to each other, sometimes fused.
• Pulp chamber and canal orifices are not as large as MdM1.
• One, two, three or four canals.
• Mesial canals: are located closer together.
• Mesial root: less curvature than MdM1; somewhat shorter.
• Easier to treat mechanically.
• Slight mesial inclination -> angle of approach is somewhat easier.
• Anatomy variations: some single or fused roots have C-shaped canal; the two canals are connected by a semicircular slit.

• Similar to MdM1, a little more triangular and less rhomboid.
• Sometimes only two canals, one M & one D, orifices nearly equal in size and line up in the center of the occlusal surface.

• Occasionally, the loss of M1 & M2 makes M3 a strategic abutment for fixed/removable appliances.
• Can present problems for RCT, mostly related to accessibility and anatomy.
• Reaching the most posterior tooth with a handpiece and hand instrument can be difficult because of poor visibility and the restricted jaw opening.
• Often tipped mesially - to the advantage of the clinician.
• Keeping in mind the long axis of the tooth and pulp chamber is centrally located will assist in the initial cavity preparation.

• Unroofed preparation: The pulpal horns have merely been exposed and the entire roof of the pulp chamber remains.
• Over extended preparation: undermining the enamel walls; The crown is badly gouged due to the failure to observe recession in the radiograph.
• Perforation into the furcation: using a surgical length bur and failing to realize the narrow pulp chamber had been passed.
• Inadequate vertical preparation: failure to recognize severe buccal inclination of an unopposed molar.
• Perforation at the mesial cervical: failure to orient the bur with the long axis severely tipped to the mesial (mandibular molars)
• Disoriented occlusal outline form exposing only the palatal canal: The faulty cavity has been prepared in a full crown which was placed to “straighten” a rotated molar.
• Disoriented occlusal outline form exposing only the mesiobuccalcanal: The faulty cavity has been prepared in a full crown which was placed to “straighten-up” a lingually-tipped molar.
• Failure to find the second distal canal: lack of exploration for the fourth canal.