anatomy Flashcards
general laws that will help us find the pulp orifice
Krasner & Rankow 2004
1) law of centrality
- the floor of the pulp chamber is always located in the center of the tooth at the level of the CEJ
2) law of concentricity
- the walls of pulp chamber are always concentric to the external surface of the tooth at the level of the CEJ
- external root surface anatomy reflects internal pulp chamber anatomy
3) law of CEJ
- distance from the external surface of the clinical crown to the wall of the pulp chamber is the same throughout the circumference of the tooth at the level of the CEJ
- the CEJ is the most consistent, repeatable landmark for locating the position of the pulp chamber
4) law of symmetry 1
- except for maxillary molars, the orifices of the canal are equidistant from a line drawn in a MD directiong through the pulp chamber floor
5) law of symmetry 2
- except for maxillary molars, the orifices of the canals lie on a line perpendicular to a line drawn in a MD direction across the center of the pulp chamber floor
6) law of colour change
- colour of pulp chamber floor is always darker than pulp chamber walls
7) law of orifice location 1
- orifices are always located at the junction of the walls and the floor
8) law of orifice location 2
- orifice of root canals are located at the angles in the floor wall junction
9) law of orifice location 3
- orifices of root canals are located at terminus of root developmental fusion lines
root canal can be subdivided into which 2 components
1) main canal - mostly cleaned by mechanical means
2) lateral components
- isthmuses
- accessory canals: furcation, lateral & secondary canals
- recesses of flattened/ oval shaped canals
describe general cross sectional shape of canals
- longitudinal cross section: canals are usually broader FL than MD
- can classify cross sectional shape wrt mean aspect ratio, which is the major diameter divide by minor diameter. major diameter = distance between 2 most distal points FL, minor diameter = longest distance drawn at 90 degrees to major diameter
- MAR 1-2 = oval
- MAR 2-4 = long oval
- MAR >4 = flattened canal
challenge of isthmuses, how can the limitation be overcome?
- impossible (based on experimental studies) to obtain a complete mechanical debridement or chemical disinfection of isthmus due to presence of hard tissue debri packed into these areas durng mechanical prep of main root canal
- ovrecome limitation with chemical agents that can dissolve organic tissue at the fins and isthmus level, often associated with ultrasonic activations
isthmus configuration classification
Hsu & Kim, 1997
Type I: 2 canals with no notable communication
Type II: a hair thin connection between the 2 main canals
Type III: differs from type II bc of the presence of 3 canals instead of 2
Type IV: an isthmus with extended canals into the connection
Type V: a true connection or wide corridor of tissue between 2 main canals
defn of accessory and lateral canal
accessory is any branch of the root canal that communicates with the PDL
lateral is an accessory canal located at the coronal or middle third of the root
formation of accessory canals?
- localised fragmentation of Hertwigs epithelial root sheath develops, leaving a small gap
OR
- when blood vessels running from the dental sac through the dental papilla persist as collateral circulation
prevalence of accessory canals
De Deus 1975
- 27.4% of teeth have accessory canals
- apical third (17%) > middle (8.8%) > coronal (1.6%)
how do accessory canals present on radiographs
not usually visible on preop radiographs, but presence can be suspected when there is a localised thickening of PDL, or if there is a lesion on the lateral surface of the root
how to clean lateral canals
cannot be instrumented most of the time
- effective irrigation with suitable antimicrobial solution
- intracanal medication
what are furcation canals, how do they form and what is their prevalence
they are canals connecting the pulp chamber to the PDL in the furcation region
formation is by entrapment of periodotnal vessels during fusion of the diaphragm, which becomes the pulp chamber floor
prevalence (Vertucci & anthony 1986)
- 36% of max 1st molars, 12% of max 2nd molars
- 32% of mand 1st molars, 24% of mand 2nd molars
- most extend from center of the pulpal floor
where does the apical foramen open
where are multiple apical foramens seen
frequently opens laterally on the root surface at a mean distance of 0.2-3.8mm from the anatomic apex
multiple apical foramens are more common in
- mesial root of mand molars
- maxillary premolars
- MB root of maxillary molars
anatomy of the apical portion of the root canal
apical portion of the root canal with the narrowest diameter is the apical constriction (minor foramen)
- from the apical constriction, the canal widens as it approaches the apical foramen
- histologically, the apical constriction corresponds to the cementodentinal junction
- apical constriction is the natural stop where C&S should end, 1mm short of radiographic apex (Dummer 1984)
what is apical ramification of apical delta
what is its prevalance and implication
is a variation of the root canal at/near the apex
defined as a morpho in which the main canal divides into multiple accessory canals
prevalence:
- maxillary: 1% (in central incisors) to 15.1% (2nd PM)
- mandibular: 5% (central incisors) to 14% (distal root of 1M)
implication is that it causes a torturous and complex anatomic config which can be the cause of nonsurgical failure
why is knowledge on canal curvature important
knowledge of root curvature is an important factor in choosing the appropriate chemomechanical protocol for C&S
- nearly all canals are curved in the apical third, particularly faciolingually (which is not evident on 2D radiographs)
- highest degree of curvatures was observed in MB canal of max molars and M canal of mandibular molars
- secondary curvatues (S shaped canals) are observed in 12.3% of max canals and 23.3% of mand canals
what is a way of determining root canal curvature
Shneider’s method of determining root canal curvature (1971)
- draw a line parallel to the long axis of the canal
- draw second line connecting the apical foramen to the point in the first line whre the canal beigns to leave the long axis
5 degrees or less - straight
10-20 degrees - moderate
25-70 degrees - severe
what is the root canal configuration classification system
Weine classification system ( Weine 1969)
developed based on a sectioning study of the MB root of permanent maxillary 1M
- 1st number is the no of canals found at the pulp chamber floor
- 2nd number is the canal configuration at the apex
Type I; 1-1
Type II: 2-1
TYpe III: 2-2
typee IV: 1-2
OR
Vertucci classification system (1974)
developed based on dye injection into canals of 200 max 2PM
- 8 canal types
- type I: 1-1
- type II: 2-1
- type III: 1-2-1
- type IV: 2-2
- type V: 1-2
- type VI: 2-1-2
- type VII: 1-2-1-2
- type VIII: 3-3
what is dens invaginatus, clinical presentation, radiographic presentation, prevalence, etiology and classification
is a developmental defect resulting from invagination in the surface of the tooth crown before calcifcation has occurred
clinically:
- appears as an accentuation of the lingual pit in anterior teeth
radiographically:
- shows infolding of enamel and dentine, that may extend deep into pulp cavity, root and even reach the root apex
etiology:
- controversial & unclear
prevalence:
- 0.25-10%
- most common in permanent maxillary lateral incisors
classification (Oehlers 1957)
- type 1 - invagination confined to crown and does not extend beyond CEJ
- Type 2 - invagination extends past CEJ and does not involve periradicular tissues, but may communicate with the dental pulp
- type 3 - invagination extends beyond the CEJ and may present a second apical foramen, with no immediate communication with the pulp
clinical implication of dens inv
- early pulpal involvement as invagination is separated from pulpal tissue by only a thin layer of enamel and dentine
- condition must be recognised early and tooth prophylactically restored
what is dens e, prevalence, clinical implications
dens e is an anomalous outgrowth of tooth structure with the projection of structure exhibiting enamel, dentine and pulp tissue
- results from the folding of IEE into the stellate reticulum
- affects mostly occlusal surface of posterior teeth
prevalence:
- predom in Asians - Leong’s premolar
- lingual surface of anterior teeth - Talon cusps
clinical implications:
- tubercle may extend above the occlusal surface - malocclusion/ attrition may cause abnormal wear/ fracture of tubercle, leading to pulp exposure in tubercle
- should treat prophylactically soon after eruption
what is radix and clinical implications
refers to additional roots of teeth, mostly molars
associated with certain ethnic groups: Sino americans (chinese, inuit, american indians)
clinical implications:
- orifice inclination and root canal curvature present challenges to RCT
- pre op PAs at different horizontal angles or CBCT required to identify additional root
- modified access cav required
main anatomic feature of c shaped canals, which teeth are these usually found in, ethnic variation?
classification of c shaped canals
anatomic feature
- presence of one or more isthmuses connecting individual canals, which can change the cross sectional and 3D canal shape along the root
- found in teeth with root fusion on the B or L aspect
- when there is failure of hertwigs epithelial root sheath to develop or fuse in the furcation area
- most common in mand 2M (2.7-44.5%)
- other common areas: max molar, mand 1PM
significant ethnic variation in
- more in asians than caucasians
- chinese 31.5%
- koreans 44.5%
classification: Fan et al 2004 (imagine like a fan shape bc C shape)
cat I - shape is an uninterrupted C with no separation or division
cat II - canal shape resembled a semicolon resulting from a discontinuation of the C outline
cat III - 2 or 3 separate canals
cat IV - only 1 round or oval canal in the cross section (normally found near the apex)
cat V - no canal lumen (usually seen near apex only)
clinical implications of c shaped canals
- pre op dx of c shaped canals is complex and not easily recognised by 2D PAs and so might need CBCT
- floor of pulp chamber is often situated deeply and may have an unusual anatomic appearance
- root structure below the orifice level can have a wide range of anatomic variations, irregular areas can house infected debri/ soft tissue remnants causing pain and bleeding
- isthmus area is difficult to C&S
- use of microscope + US can make tx more predictable
- frequent occurrence of endo failure
defn of fusion
the union of 2 distinct dental sprouts that occurs in any stage of the dental organ
- joined by dentine, but pulp chambers and canals may/may not be linked
- depends on dev stage when union occurs
- more frequent in anterior teeth
defn of gemination
disturbance during odontogenesis in which partial cleavage of the tooth germ occurs, resulting in a tooth that has a double/ twin crown
- usually not completely separated, and share a common root and pulp space
- root and pulp are also irregular in morpho
