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Course Director

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

 

Access for Anterior Teeth

 

[Introduction] [Penetration] [Buccal Triangle] [Lingual Triangle] [Flaring] [Cleaning Pulp Chamber]

[Access Modification ] [Maxillary Incisors] [Mandibular Incisor] [Canines]


 

Access Preparations for Anterior Teeth

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The following description is an overview for all maxillary and mandibular anterior teeth. In every instance, the clinician must adapt principles of access preparation to the case being treated. This section also serves to introduce the fundamental concepts of access cavities for all teeth. Anatomical, morphological, and positional variation may alter the basic approach to any tooth.

 

Although the objective of access preparation is straight-line access to the apical foramen, this is not always practical in anterior teeth since the preservation of coronal tooth structure is a consideration. Straight line access would usually require destruction of enamel on the incisal and facial surfaces. This is not desirable unless a crown is to be used to restore the tooth. In such cases, the access preparation may extend to the incisal surface and possibly the facial surface as well.

Before actually proceeding with this section, please review the Endodontic Access lecture and the Section 7.5.2.1 in Pathways 10th edition.

Penetration

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Direct a long shank (surgical length), round carbide bur (#2 or #4) in a highspeed handpiece, perpendicular to the center of the lingual surface, just incisal to the cingulum (Figure 1) . Continue cutting until the bur has penetrated 2-3 mm or through the enamel and well into the dentin.

The bur used depends on the size of the tooth and the size of the pulp chamber.

Figure 1 Round bur at right angles to the lingual surface.

At this point, redirect the bur parallel to the long access of the tooth (Figure 2). While doing this, extend the cavity incisally so that enamel and dentin are beveled toward the incisal edge.

•  Cutting the incisal edge should be avoided unless the needs of the case dictate otherwise. Cutting the incisal edge is not permitted in the pre-clinical course or on state board board examinations.

Figure 2 Change direction to the long access of the tooth.

With the bur parallel to the long axis of the tooth, penetrate through the dentin into the pulp chamber (Figure 3).

•  During this procedure, the endodontic explorer (D.E. #16) is used to help locate canals and/or pulp horns.

 

 

NOTE: The sensation of "dropping" into the chamber may or may not be felt depending on the size of the chamber or the amount of pulpal calcification. If the pulp is receeded, then you will have to repeatedly check with an endodontic explorer when looking for a pulp chamber.

 

•  Confirm penetration of the pulp chamber by probing with an endodontic explorer (Figure 4).

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Figure 3 Penetrate into the pulp chamber.

Figure 4 Use the endodontic explorer to probe.

Removing the Buccal triangle

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With the same round bur used for penetration, re-enter the pulp chamber. Using light outward strokes, pull up, and cut away, the coronal overhanging ledge of dentin. This begins flaring and removes the buccal triangle (Figures 5 and 6).

•  This triangle is located incisal to the initial penetration and consists of enamel and dentin. Removal of this triangle simplifies placement of endodontic instruments into the canal.

 

•  Continue with the round bur mesio-distally to expose the pulp horns again using light outward strokes. DO NOT CUT THE CANAL ORIFICE.

 

•  This will create the triangular access cavity outline.

 

•  Exposing the pulp horns will allow complete removal of pulp tissue and prevent discoloration after treatment.

 

•  The degree of mesial distal flaring depends on the tooth being treated.

Figure 5 The bur is used to lift off the roof of the pulp chamber.

Figure 6 A slow or high speed round bur can be used to lift off the roof.

Removing the lingual triangle

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•  Place a slow speed round bur (#2 or #4) into the canal, past the orifice, just beyond the natural cervical constriction. This constriction is caused by an overhanging ledge of dentin.

•  With outward strokes, peel away the lingual triangle (Figure 7). DO NOT CUT APICALLY . This creates gouging.

•  Gouging can destroy canal anatomy, weaken the tooth structure, or result in a perforation that can lead to loss of the tooth.

Figure 7 Carefully peel away the lingual triangle.

Flaring (Funneling)

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When the cavity formed by penetration, and removal of the enamel and lingual triangles is roughly complete, smooth the internal walls with a high speed #31 safe end long tapered diamond bur. Use the orifice of the canal as a "pivot point" for the end of the diamond (Figure 8). Do not cut the canal orifice or the floor of the chamber

•  At this stage the access cavity should resemble a funnel with the larger opening at the occlusal end and the smaller opening at the canal orifice (Figure 9).

•  Probe the canal orifice with the endodontic explorer (DG #16). The explorer should not bind against any wall of the access preparation. The explorer should flow into the canal orifice from any wall of the access preparation.

•  If binding occurs, modify the area with the appropriate bur so that the explorer instrument goes freely into the canal.

•  Review access evaluation .

Figure 8 Carefully use a safe end tapered diamond bur to flare and make the access cavity confluent with the orifice of the canal.

Figure 9 Ideal, tapered access form.

Cleaning and irrigatiing the pulp chamber

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•  Irrigate while developing the access cavity. This is done with a 50% sodium hypochlorite solution (NaOCl) using syringes. IMPORTANT: The irrigating syringe is never fixed or locked into the tooth at any time. It should always be kept free and moving.

•  If suction is not available or for some other reason not used, a cotton roll can be used to absorb fluids.

•  Remove chamber pulp tissue with a sharp endodontic spoon excavator (#31L).

 

Access Modification

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•  As treatment continues, the original outline form of the access cavity may have to be modified. It may need to be enlarged or extended in a lingual or incisal direction (Figure 10). This is to allow instruments to have optimum access to as much of the canal as possible. It facilitated cleaning and shaping and eventually obturation.

•  Access modification is especially helpful in lower anterior incisors and essential in posterior access design.

•  Although preservation of coronal tooth structure is an important consideration, complete cleaning and shaping of an ovoid canal shape other morphologic variations cannot be compromised by inadequate access cavity preparation.

 

Figure 10 Restricted access will not allow adequate cleaning of the palatal wall of the canal.


Access Preparations for Specific Anterior Teeth

In addition to the generic access preparation for anterior teeth, following are additional notes for specific teeth.

 

•  Maxillary Incisors

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•  The access preparation is always on the lingual surface. The outline form is basically triangular in shape with the apex toward the cingulum area and the base toward the incisal edge (Figure 11).

•  The lingual surface of the crown is divided into thirds, and the initial penetration is made in the middle third.

•  Please note that in clinical situations the crown and not the whole tooth is used in determining angle of initial penetration. If the angle of entry is incorrect, the possibility of gouging the facial or proximal walls and/or perforation is greatly increased.

Figure 11 Create a grid on the lingual surface, begin penetration in the middle third.

Mandibular incisor

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•  The access preparation is always on the lingual surface. The outline form is basically triangular with the apex toward the cingulum area and the base toward the incisal edge (Figure 12).

•  The lingual surface of the crown is divided into thirds, and the initial penetration is made in the middle third (Figure 12).

Figure 12 The access cavity for mandibular incisors is much smaller than maxillary incisors.

•  Penetration is made with the bur parallel to the long axis of the tooth. Note that this will be in a lingual direction relative to the facial surface of the crown.

•  Caution must be exercised so the facial tooth structure is not cut, gouged or perforated. The tooth is relatively thin and as much tooth structure as possible should be preserved.

•  The M-D dimension is kept narrow since it is easy to perforate the proximal walls on these teeth.

•  The incisal-gingival dimension of the preparation is much larger with the incisal extent of the preparation closely approaching the incisal edge.

•  This is necessary to locate and treat the lingual canal in teeth with 2 canals or to completely clean and shape the lingual wall of teeth with a single canal.

Maxillary and Mandibular Canines

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•  The access preparation is always on the lingual surface. The outline form is ovoid shaped with the largest dimension from incisal to gingival (Figure 13).

 

•  The lingual surface is divided into thirds, and the initial penetration is made in the middle third (Figure 13).

Figure 13 The Access cavity is ovoid in canines.

•  The bur is aligned parallel to the long axis of the tooth.

•  Note this angle of entry will be slightly lingual to a line parallel to the facial surface of the tooth.

•  The M-D width of the access cavity is kept relatively narrow.

For the preclinical course only . If your canine or any project tooth is longer than 25 mm (the length of your files) tell your laboratory instructor. In this situation, prepare the access cavity as describe, have it evaluated and signed off by your instructor. Your instructor will then have you cut off a portion of the crown so that the final length of the tooth is 25 mm or less.