essay 36 - endodontic access - opening the pulp cavity in the different teeth groups: stages, instruments

what is endodontic access?

• refers to the creation of an opening in the crown of a tooth to allow the dentist to locate, clean, shape, disinfect and obturate (fill) the root canal system. It is a critical first step in endodontic treatment

stages and instruments used in endodontic access

1. Penetration phase

• penetrate the pulp chamber by removing the roof. Round diamond bur on a high speed handpiece. If the pulp chamber is wide there is a ‘‘falling into a vacuum’’ sensation. Move the bur in circular motion to give the cavity a funnel shaped entrance. Phase ends once the roof of the pulp chamber is penetrated.

2. Enlargement phase

• enlarge and refine the shape of the cavity, remove undercuts and clean the dentinal walls. Round metal bur on a low speed handpiece. Work on the way out using a brushing motion.. This way dentin overhangs and soft tissue remnants are removed from the chamber

3. Finishing and flaring phase

• smooth cavity walls and flare the coronal entrance for unobstructed instrumentation and irrigation. Must preserve the floor anatomy without cutting it. Non end cutting diamond bur eg. self guiding bur/ Batts bur on a high speed handpiece. The non-cutting head allows one to touch the chamber floor with the bur and at the same time precludes modification of its very important anatomy. The use of a diamond bur on a high-speed handpiece is recommended, as fissure burs at low speed cause intolerable vibrations when they contact enamel. In this phase, one works simultaneously on dentin and enamel.

opening the pulp cavity in maxillary central incisors

1. entrance location: centre of the palatal surface

2. Bur direction and movement: perpendicular to the palatal surface. A mesiodistal movement is used to reach and include the pulp horn

3. Cavity shape: triangular

4. Notes: one straight canal. Prominent pulp horns must be included during access

opening the pulp cavity in maxillary lateral incisors

1. entrance location: slightly distal to the centre of the palatal surface

2. bur direction and movement: perpendicular to the palatal surface, adjusting to root curvature if present

3. cavity shape: oval or slightly triangular

4. Notes: usually one canal, but second canal (rare) may occur. Root often curves distally and palatally

opening the pulp cavity in maxillary canines

1. entrance location: middle third of the palatal surface; incisal extension may be needed if worn

2. bur direction and movement: perpendicular to palatal surface, then aligned with the long axis of the root

3. cavity shape: ovoid, long in apico coronal direction

4. Notes: one long, straight canal

opening the pulp cavity in maxillary first premolar

1. entrance location: centre of the occlusal surface and extend to lowest point of buccal and palatal cusps

2. bur direction and movement: perpendicular to occlusal surface, oval, brushing movement buccolingually

3. cavity shape: ovoid, wider buccolingually

4. Notes: typically 2 canals (buccal and palatal); root canal bifurcation is common, even if one root

opening the pulp cavity in maxillary secondary premolar

1. entrance location: centre of the occlusal surface and extend to lowest point of buccal and palatal cusps

2. bur direction and movement: perpendicular with a slight buccal inclination to follow the root axis

3. cavity shape: ovoid

4. Notes: usually one canal, but can have two. Sometimes appears fissure-like; prepare as two unless confirmed

opening the pulp cavity in maxillary first molar (2nd and 3rd follow same principle but may be fused or have less RC)

1. entrance location: in the mesial pit, slightly toward the oblique ridge (near mesiobuccal cusp). remove majority of mesiobuccal surface

2. bur direction and movement: perpendicular to occlusal, then guided toward the palatal root long axis

3. cavity shape: triangular trapezoidal

4. Notes: typically 3 roots and 4 canals. The second mesiobuccal (MB2) canal is very common and must be located

opening the pulp cavity in mandibular central incisors

1. entrance location: centre of the lingual surface, near the cingulum

2. bur direction and movement: perpendicular to the lingual surface; slight inclination along the root axis

3. cavity shape: ovoid (labio-lingual)

4. Notes: usually one canal, but -40% may have two (labial and lingual)

opening the pulp cavity in mandibular lateral incisors

1. entrance location: centre of the lingual surface

2. bur direction and movement: same as central - perpendicular, with inclination along the root

3. cavity shape: ovoid

4. Notes: more likely than central to have two canals. Apical bifurcation possible

opening the pulp cavity in mandibular canine

1. entrance location: centre of the lingual surface

2. bur direction and movement: perpendicular to lingual, then adjusting to long root axis

3. cavity shape: ovoid (long apico coronal)

4. Notes: usually one canal, but 2 canals in 10-15% of cases. Longest root

opening the pulp cavity in mandibular first premolar

1. entrance location: centre of occlusal surface on the occlusal grove and extend slightly lingually and buccally to create and ovoid shape

2. bur direction and movement: perpendicular to occlusal surface

3. cavity shape: ovoid

4. Notes: one canal in most cases, but up to 25% have two. Often challenging to locate a second canal

opening the pulp cavity in mandibular second premolar

1. entrance location: centre of occlusal surface on the occlusal grove and extend slightly lingually and buccally to create an ovoid shape

2. bur direction and movement: perpendicular, then aligned to long axis of root

3. cavity shape: ovoid

4. Notes: usually one large canal. Bifurcation is rare

opening the pulp cavity in mandibular first molar

1. entrance location: mesial to the central fossa between mesiobuccal and mesiolingual cusps. Remove majority of mesiobuccal surface

2. bur direction and movement: perpendicular to occlusal surface

3. cavity shape: trapezoidal, triangular, rectangular

4. Notes: typically 2 roots (mesial and distal); 3 canals common (2 mesial, 1 distal), but distal roots may have two canals

opening the pulp cavity in mandibular second molar

1. entrance location: mesial to the central fossa between mesiobuccal and mesiolingual cusps. Remove majority of mesiobuccal surface

2. bur direction and movement: perpendicular to occlusal

3. cavity shape: rectangular or C-shaped

4. Notes: may have fused roots with C-shaped canal system, especially in Asian populations. Number of canals variable