Endodontics
Course Review
Enoch Ng, DDS 2014
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Laws of Symmetry
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Law of Centrality – floor of pulp chamber always at center of tooth at level of CEJ
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Law of Concentricity – external root surface anatomy reflects internal pulp chamber anatomy
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Law of the CEJ – distance of external surface of clinical crown vs wall of pulp chamber is the same
throughout the circumference of tooth at level of CEJ
o
CEJ – most consistent repeatable landmark for locating pulp chamber
o
1
st
Law of Symmetry – except for Mx molars, canal orifices are equidistant from line drawn mesio/disto
across center of pulp chamber floor
o
2
nd
Law of Symmetry – except for Mx molars, canal orifices lie on line perpendicular to above line
o
Law of Color Change – pulp chamber floor always DARKER than the walls
o
1
st
Law of the Orifice – orifices of the canals ALWAYS located at junction of walls and the floor
o
2
nd
Law of the Orifice – orifices of the canals ALWAYS located at the angles in the floor-wall junction
o
3
rd
Law of the Orifice – orifices of the canals ALWAYS located at terminus of roots developmental fusion
lines
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Access Preparation
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Use a #2, 4, or 6 friction grip round bur
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Endo Z bur (tapered safe ended bur)
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Sharp endo explorer
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Magnification
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Long shanked low speed burs
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Ultrasonics, transillumination, dye staining, irrigation and interim radiographs
Accessing Teeth
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Mx Incisors – always 1 root 1 canal
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Young patients = triangular, older patients = ovoid
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Mx canines – always 1 root 1 canal
o
Ovoid
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In middle 1/3 of lingual surface
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Mx Premolars
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Outline form ovoid facial/lingual
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Mesial concavity at CEJ
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When 2 canals are present, under B and L cusps
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Mx Molars
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Outline form triangular in mesial ½ of tooth
Base = facial, apex = lingual
o
Oblique ridge left intact (usually)
o
MB canal slightly distal to MB cusp tip, broad B/L, may have MB2 canal
MB2 canal 1-3mm lingual to MB1, slightly mesial to line drawn from MB1 to PC
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DB canal distal and slightly lingual to main MB canal, in line with buccal groove
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P canal slightly distal to ML cusp tip, largest canal
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Mn incisors – 25-40% have 2 canals
Facial easier to locate, generally more straight
Lingual often shielded by a lingual shelf
o
Outline form, shape, and access similar to Mx incisors
