Root Canal Anatomy Flashcards
Q84 : What is the incidence of two canals in a mandibular incisor?
Benjamin & Dawson (Oral surg -1974) investigated the incidence of 2 canals in human mandibular incisors.
- 58.6 % had one main root canal (Type 1).
- 41.4 % had 2 clinically separate canals (Type II).
- 1.3% had 2 separate canals with 2 separate apical foramina (Type III).
Q85 : What is the second most predominant canal type (Weine classification) in mandibular 1st premolars?
Type IV
Explanation:
Baisden et al (JOE-1992) described the internal anatomy of the MAN 1st premolar in 106 extracted teeth. 76% demonstrated Type I canals and 24% demonstrated Type IV canals.
Q86 : What are the anatomical boundaries of the pterygomandibular space?
Explanation:
The lateral border is the medial surface of the mandible.
The medial border is the medial pterygoid muscle. The superior border (roof) is the lateral pterygoid muscle.
The posterior border is the fascia of the parotid gland.
The anterior portion is bordered by the attachment of the temporal muscle (deep tendon), buccinator muscle and medial pterygoid muscle.
Q87 : What is “Dens Invaginatus”?
Dens Invaginatus also known as “Dens in Dent” or tooth within a tooth. They are most common in maxillary lateral incisors.
Oehlers (000-1957) classified dens invaginatus in to:
Type 1: confined within crown (image A),
Type II: Extends past the CEJ but does not involve
the periapical tissue (Image B).
Type III: Extends past the CEJ and may result in the
formation of a 2nd apical foramen laterally (Image C)
or apically (Image D).
Q88 : What is the average size of apical constrictions in molar teeth prior to root canal instrumentation?
El Ayouti et al. (JOE - 2014) showed in a micro-CT study that the size of the constriction in molars corresponded to instrument size #30 and young patients had a significantly larger constriction than older patients. They also showed no significant differences between MAX and MAN molars or between different canal types.
The mean size of constriction was
a) in roots with 1 canal size #35
b) In roots with 2 canals, -size #30
The reason why a clinician may feel that canals are smaller during root canal instrumentation is that the canals may be smaller in a mesio-distal dimension but wider in the bucco-lingual dimension.
Q89 : What is “Dens Evaginatus”?
Common developmental condition with a tubercle cusp or talon cusp located on the occlusal surface of teeth. It is affecting predominantly premolar teeth of Asian population. It is usually bilateral.
Q90 : What is the incidence of two canals in the distal root of mandibular first molars?
Von Arx, (IEJ 2005) showed that 36% of the distal root had 2 canals with an isthmus. Pineda & Kuttler, (Oral Surg -1972) showed that 27% of the distal roots have 2 canals.
Q92 : What is the incidence of MB2 in maxillary molars?
Kulild & Peters (JOE-1990) reported the highest incidence of 96% in MAX 1st molar and 93.7% in MAX 2nd molar. The sample size of this study, however, was only 83 extracted teeth.
In a clinical study with large sample size (1732 teeth), Stropko (JOE-1999) showed that MB2 is present in 73.2% of MAX 1st molar and 50.7% in MAX 2nd molar. When surgical operating microscope was used in part of the study, the incidence of finding MB2 increased to 93% in Max 1st molar and 60.4% in maxillary 2nd molar.
Wolcott et al. (JOE-2005) reported the largest study on locating MB2 in maxillary molars over a 5-yr. period (5616 teeth) :
For 1st molars, MB2 was located in:
57.9% Initially treated cases
66.0% RET cases
For 2nd molars, MB2 was located in:
34.4% initially treated cases
39.9% RET cases
Q93 : What is the difference between Radix Entomolaris and Radix Paramolaris?
Radix, is an additional root located in mandibular molars. The difference between Entomolaris or Paramolaris depends on the location of the addition root. Mandibular molars can have an additional root located lingually (Radix Entomolaris) or buccally (Radix Paramolaris) (Calberson et al. JOE - 2007)
Q94 : Would missing an MB2 affect the treatment outcome of maxillary molars?
Yes
Wolcott et al. (JOE-2005) reported the largest study on locating MB2 in maxillary molars over a 5-yr. period (5616 teeth).
For 1st molars, MB2 was located in:
57.9% initially treated cases
66.0% RET cases
For 2nd molars, MB2 was located in:
34.4% initially treated cases
39.9% RET case
The significant difference in the incidence of a MB2 canal between initial treatments and retreatments suggests that failure to find and treat existing MB2 canals will decrease the long-term prognosis.
Q95 : How frequent is a root canal isthmus present in molar teeth?
Teixeira et al. (IEJ - 2003) showed that the incidence of isthmus in the MB root of the MAX 1st molars and in the mesial root of the MAN 1st molars were high particularly in sections 3-5 mm from the apex. 70% of MB roots of maxillary 1st molars, 59% of the mesial roots of mandibular 1st molars had an isthmus using light microscope.
Von Arx (IEJ-2005) resected the apical 3-4 mm of the MB root of MAX molars and Mesial roots of MAN molars. Roots were then inspected using an endoscope.
- MB root of maxillary 1st molar: 76% of the MB roots had 2 canals and an isthmus.
- Mesial root of mandibular 1st molar: 83% had 2 canals with an isthmus
- Distal root of mandibular 1st molar: 36% had 2 canals with an isthmus
Q96 : What is the incidence of furcation canals in molar teeth?
Burch & Hulen (000-1974) examined the furcation of MAX & MAN 1st and 2nd molar All using 30x magnification. Around 77% of all molars presented openings in the furcation area.
Vertucci & Anthony (Oral Surg - 1986) examined 100 MAX & MAN molars of foramina than did the MAX teeth (48%). In SEM. MAN teeth had a higher incidence (56%).
Q97 : Describe the anatomy of the pulp chamber?
Krasner & Rankow (JOE-2004) observed the anatomy of the pulp chamber and the pulp chamber floor to see if there is any specific consistent landmarks or configurations. Accordingly, they came up with some laws:
1- Law of Centricity: pulpal floor is located in the tooth center at the CEJ level
2- Law of Concentricity walls of the pulp chamber are concentric to external surface
3- Law of CEJ: the CEJ landmarks the pulp chamber location
4- Law of Symmetry. Except Max molars, orifices are equidistant & perpendicular from M-D line drawn through center of pulpal floor.
5- Law of Color Change: pulpal floor is darker than walls
6- Law of Orifice Location : orifices are located at the junction of the floor and walls.
Q98 : What is “Taurodontism” ?
According to Jafarzadeh et al. (IEJ-2008) it’s a change in tooth shape caused by the failure of Hertwig’s epithelial sheath diaphragm to invaginate at the proper horizontal level resulting in an enlarged pulp chamber, apical displacement of the pulpal floor, and no constriction at the level of the cementoenamel junction
Q99 : What is the prevalence of a middle mesial canal in mandibular molars?
Clinical studies
Pomeranz et al. (JOE-1981) showed that the prevalence was 12%.
Nosrat et al. (JOE-2015) reported 20% of mandibular molars have MM canals with higher prevalence in younger patients.
Azim et al. (JOE-2015) reported 46% of mandibular molars have accessible MM canals, where age, magnification and proper troughing between the MB and ML canal appeared to significantly affect the prevalence.
Ex-Vivo studies
A micro CT study by Wolf et al. (JOE-2016) on 118 MAN molars showed a connecting canal between the MB and ML canals in 30.5% of the teeth.
It should be noted that all these studies were based on either very small patient sample size or limited number of extracted teeth.
