University Home

SDM Home Page

MyUB

Blackboard

Testing

 


Course Director

Carole T. Pantera, DDS, MS
240 Squire Hall
716-829-3847
pantera@buffalo.edu

 

Molars

[Mand Molar] [Mand Access] [Calcified Mand Molar] [Max Molars] [Calcified Max Molar]

 


 

Mandibular Molars

[top] [back] [next]

Access Preparation

[top] [back] [next]

Anatomy

•  The pulp chamber of each mandibular molar is located in the mesial 2/3 portion of the crown.

•  Root canal orifices

•  Mesio-buccal canal - located directly under the mesio-buccal cusp.

•  Mesio-lingual canal - located buccal to the mesio-lingual cusp almost under the central groove.

•  Distal canal - located just distal to the buccal groove.

•  At least 25% of the mandibular first molars have two canals in the distal root.

 

Penetration

•  Review the pre-operative radiograph to see

•  The size of the pulp chamber

•  The relative location of the pulp chamber

•  With a large and visible pulp chamber penetration is straight forward.

•  Use a #2 or #4 high speed round carbide bur.

•  Start in the central fossa at a right angle to the occlusal surface.

•  You should feel the bur penetrate (drop into) the pulp chamber after cutting 4-6 mm. NOTE: This "drop" may not be felt if there has been calcification in the pulp chamber.

•  Confirm the penetration by probing with an endodontic explorer.

•  Do not drill on floor of the pulp chamber, this can create a perforation which may result in tooth loss.

 

The access preparation is started in the central fossa. After penetration, the chamber roof is lifted off with the round bur.

Funneling

•  Completely unroof the pulp chamber and pulp horns using an outward uplifting or "peeling" motion.

•  This can be done with high speed or low speed using the same size round bur used for penetration.

•  The outward cutting is done in a mesial-occlusal direction and in a buccal-occlusal direction exposing the entire pulp chamber.

•  The walls can be made confluent with the canal orifices with the diamond bur.

•  Remove debris from the pulp chamber with irrigation and the endodontic excavator.

Youtube_icon Video demonstrating lifting up and unroofing the chamber.

Locating the root canal orifices.

•  Dry the pulp chamber with cotton pellets.

•  Examine the floor of the pulp chamber

•  The surface of the floor is smooth and light gray in color.

•  The floor is triangular (3 canals) or rhomboidal (4 canals) in shape.

•  The surface of the floor is smooth and gently curved sloping towards the canal orifice.

•  A common error is not penetrating and removing the chamber roof and mistaking the pulp horns as canal orifices.


Locate the distal orifice first.

•  Follow the dark, shallow groove on the pulpal floor to search for the mesial orifices.

•  The mesio-buccal canal extends in a mesio-buccal direction from the pulp chamber.

•  Often, direct access of this canal is difficult and is achieved by extending the mesio-buccal corner of the access cavity further mesially and/or buccally.

 

The mandibular molar can have 3 or 4 canals. The basic access outline is similar.

Length Determination

•  Use the endodontic explorer to locate the canal orifices.

•  Note the angle that the explorer enters the canal.

•  That angle must be reproduced with the file in order to enter each canal.

•  Do not confuse the endodontic explorer with the endodontic spreader.

•  Determine a reference point, Usually the corresponding cusp is used for molars (ie MB cusp for MB canal) Patency/pathfinding files are needed for each canal. Set a rubber stop at the estimated working length for each canal beginning with a #8 files.

•  After placing a pathfinding curve at the tip of each instrument, introduce the instrument into each canal with a gentle "slipping and sliding motion".

•  Don't force the instruments

Canal Patency

 

•  Canal patency should be established and maintained in the usual manner.

•  A file is placed in the mesiobuccal canal (MB) first. This is followed by the instrument in the distobuccal canal (DB) and lastly the lingual (L) or palatal (P) canal.

•  The tips of the files should be just barely seen at the apical foramen.

•  All files should have reference points. These need to be recorded on the Endodontic Treatment Record.

•  It is easiest to reference the same cusp as the canal being entered.

 

 

Working Length Radiograph

•  Expose and process the working length radiograph. Depending on the preclinical project, either clinical and proximal views or just the clinical view are exposed as before.

•  Adjust the files and retake the radiographic if the files are 2mm or more from the appropriate reference.

•  The WL radiograph must show each file at the end of each root canal (Figure 3). Shift shots may be necessary.

•  Record the lengths of each canal and the reference points on the tooth used for each file.

 

Figure 3 The working length radiograph should be taken with the largest files possible. Clinically, there is tissue mass that may obscure very small files.

Radicular Access (Straight-Line Access, Gates-Glidden Access)

•  Radicular access creates space in the coronal 1/3 of the canal and makes it easier to place and use instruments and irrigants while cleaning and shaping.

•  After the canal has been enlarged to a #25 to #35 file and the working length has been determined, flood the chamber with NaOCl.

•  Develop the radicular access with the #2 Gates-Glidden drill.

•  Activate and penetrate 1-2 mm, cutting on withdrawal while pulling away from the furcation.

 

Radicular access Left figure is before radicular access, right figure after. Radicular access facilitates striaght line access and reduces stress on files and rotary instruments.

•  This will have the effect of ellipticizing the canal orifice (Figure 4).

•  Irrigate, check patency, flood canal, penetrate deeper with the #2 Gates-Glidden

•  The Gates-glidden can only be used in the straight part of the canal.

•  Repeat with a #3 and #4 Gates-Glidden drill while incorporating the principles of step-back.

•  The more difficult the canal, the more irrigation and recapitulation is necessary to avoid preparation errors.

Figure 4 Radicular access is created by flaring the orifice away from the furcation.

Figure 4b Notice how the ML canal orifice has been eliptisized compared to the MB canal orifice.

 

Cleaning and Shaping

[top] [back] [next]

•  Use the technique described.

•  The MB and ML canals should be enlarged to at least a size #25 at the WL. The D canal should be enlarged to at least a #35 file ( these are just suggestions, file sizes are dictated by the needs of the case ).

•  Copious irrigation is necessary. It best to treat the tooth through a pool of NaOCl at all times.

•  Precurving of stainless steel files is necessary.

•  Anticurvature filing

•  Shaping away from the inside of the root curvature in the middle and coronal thirds

•  Pressure is applied to the outside wall away from the furcation.

Anitcurvature filing is up and away from the furcation.

Obturation of the Prepared Canals

•  Fit the master cone as described earlier.

•  Fine-medium is the optimum size cone to fit. In no instance should a cone smaller than a fine be used.

•  If there are problems fitting the cone, the canal should be reshaped

•  Prefit the pluggers, and obturate as described in previous exercises (Figure 5).

 

 

Figure 5 Well shaped and 3-dimensionally obturated mandibular molar.

Access Preparation for Calcified Molars

[top] [back] [next]

Reduced pulp chamber

•  Dentin formation secondary to caries, restorative procedures, and age can significantly alter and reduce the size of the pulp chamber. (Figure 6)

•  This occurs principally in the occlusal-apical dimension

•  There is more deposition on the FLOOR of the pulp chamber.

•  There is the danger of passing through the floor of the pulp chamber during access.

•  Evaluate the location of the pulp chamber on the pretreatment radiograph in reference to such external landmarks as the CEJ

Figure 6 The pulp chamber of #31 was obliterated by restorative procedures.

Penetration

•  With a high speed round carbide bur (#2 or #4), open into the central fossa.

•  Direct the bur at a right angle to the occlusal surface of the crown until the bur penetrates several millimeters into the dentin.

•  Use the same bur in an outward sweeping stroke, slightly flaring the access creating the appropriate outline shape.

Review the series of diagrams and text in "Methods of Locating Calcified Canals" in Pathways 8th edition, 7.6.

 

•  Use the endodontic explorer to look for pulp horns or canal orifices.

•  Penetrate a few more millimeters into the dentin and refine by flaring.

•  The flaring should develop into an idealized access outline.

•  Use the endodontic explorer to look for pulp horns or canal orifices.

•  This process of penetration and flaring is repeated until some portion of the root canal system is encountered.

•  Every effort should be made to avoid running high speed burs on the floor of the pulp chamber.

•  Using a lowspeed handpiece with help prevent perforation by being able to just "brush" away a small amount of dentin at a time.

 

Unroofing

•  Use a #2 long shank round bur in the slow speed handpiece to carefully remove the roof of the pulp chamber further developing the access outline.

•  The floor of the pulp chamber should not be cut.

 

Pulpstones

•  Occasionally pulp stones will be encountered in the chamber (Figure 7).

Youtube_icon

•  No attempt should be made to remove these calcifications until the entire roof of the pulp chamber has been removed.

•  Once the access is completed, the calcifications can be removed with a spoon excavators or slow speed round burs.

 

Figure 7 Clinical pulp stone.

Maxillary Molars

[top] [back] [next]

Access Preparation

Anatomy

•  The pulp chamber is usually located in the mesial two-thirds of the crown and centered beneath the central groove.

•  Occlusally, the pulp chamber is triangular in shape. Its base is toward the buccal and formed by the orifices of the two buccal root canals.

•  The preparation is almost always entirely within the mesial half of the tooth and rarely crosses the oblique ridge.

Penetration

•  Examine the pre-operative radiograph to see

•  The size of the pulp chamber

•  The relative location of the pulp chamber

•  With a large and visible pulp chamber

•  Penetration is direct (Figure 8)

•  Use a #2 or #4 high speed round carbide bur.

•  Start in the central fossa at a right angle to the occlusal surface.

•  You should feel the bur penetrate (drop into) the pulp chamber after cutting 4-6 mm.

•  Confirm the penetration by probing with an endodontic explorer.

•  Do not drill on floor of the pulp chamber.

 

Figure 8 The access preparation is started in the central fossa. After penetration, the chamber roof is lifted off with the round bur.

Funneling

•  Completely remove the roof and pulp horns using an outward uplifting or "peeling" motion (Figure 8).

•  This can be done with high speed or low speed using the same size round bur used for penetration.

•  Remove debris from the pulp chamber with irrigation and the endodontic excavator.

•  Dry the pulp chamber with cotton pellets.

•  Examine the floor of the pulp chamber.

•  The surface of the floor is smooth and light gray in color.

•  The floor is triangular in shape with the canal orifices located at the corners of the triangle (Figure 9).

Figure 9 Over 50% of Maxillary 1st molars have 4 canals.

Locating the root canal orifices

 

•  Usual locations (Figure 10)

•  Palatal canal

•  Located midway between palatal cusp tip and central fossa.

•  Mesio-buccal canals

•  Located under the mesio-buccal cusps tip.

•  Over 50% of the maxillary first molars have two mesio-buccal canals.

•  They occur but are less frequent in older teeth

 

Figure 10 Maxillary molar with access cavity and orifices visible.

•  It is sometimes difficult to locate the lingual of the two mesio-buccal canals.

•  The orifice of this canal (#2) lies in the groove linking the orifice of the palatal canal (#3) with the buccal of the mesio-buccal canal (#1).

•  Less frequently, the orifice may lie inside the orifice of the mesio-buccal canal

•  Disto-buccal canal

•  The DB canal orifice is located approximately 2-3 mm to the distal and slightly to the lingual aspect of the MB orifice.

•  located beneath the buccal groove.

 

•  Technique

•  Use the endodontic explorer

•  Locate the palatal orifice first and follow the grooves to search for the buccal orifices.

Direct, straight line access

•  The goal is to have direct access with the walls of the access cavity confluent with the orifice of the canals

•  Judiciously modify the access opening to facilitate direct access to the canal orifices.

•  Occasionally, the mesio-buccal cusp needs to be compromised in order to gain access to the mesio-buccal canal orifices.

•  The external outline form of the access cavity should be larger but similar in form to the internal floor of the pulp chamber.

•  Modification of the access cavity

•  Frequently, the access cavity must be modified or developed as cleaning the shaping of the root canals progress.

 

Access Preparation for Calcified Molars

[top] [back]

Reduced pulp chamber

•  Dentin formation can significantly reduce the size of the pulp chamber.

•  This occurs principally in the occlusal-apical dimension

•  There is more deposition on the FLOOR of the pulp chamber.

•  There is the danger of passing through the floor of the pulp chamber during access.

•  Evaluate the location of the pulp chamber in reference to such external landmarks as the CEJ

 

Penetration

•  With a high speed round carbide bur (#2 or #4), open into the central fossa (Figure 11).

•  Direct the bur at a right angle to the occlusal surface of the crown until the bur penetrates several millimeters into the dentin.

•  Use the same bur in an outward sweeping stroke, slightly flaring the access creating the appropriate outline shape.

•  Use the endodontic explorer to look for pulp horns or canal orifices.

•  Penetrate a few more millimeters into the dentin and refine by flaring.

•  The flaring should develop into an idealized access outline.

•  Use the endodontic explorer to look for pulp horns or canal orifices.

•  This process of penetration and flaring is repeated until some portion of the root canal system is encountered, frequently a palatal pulp horn.

•  Every effort should be made to avoid running high speed burs on the floor of the pulp chamber.

 

Figure 11 Penetration and flaring are done together. It is important to use the endo explorer and to take time with a difficult access.

Unroofing

•  Use a #2 long shank round bur in the slow speed handpiece to carefully remove the roof of the pulp chamber further developing the access outline.

•  The floor of the pulp chamber should not be cut.

Pulpstones

•  Occasionally pulp stones will be encountered in the chamber.

•  No attempt should be made to remove these calcifications until the entire roof of the pulp chamber has been removed.

•  Once the access is completed, the calcifications can be removed with a spoon excavators or slow speed round burs.