ANATOMY OF PULP CANAL l Preclinical Endodontics MCQs

ANATOMY OF PULP CANAL l Preclinical Endodontics MCQs (multiple choice question) for dental students.

 

Pulp anatomy

1- Central region :

•  Cells [ odontoblasts + fibroblasts + undifferentiated mesenchymal cells + defense cells ]
•  Matrix [ collagen type 1 and 2]
•  ground substance [ gylcosaminoglycans and glycoproteins]
•  Blood vessels
•  Nerves [ subodontogenic plexus of rashkow + sensory afferent from trigeminal nerve ]

2- Peripheral region:

•  Odontoblastic layer
•  Cell free layer – zone of weil
•  Cell rich layer

 

Pulp develops from the ectomesencymal cells of the dental papilla, when the odontoblasts form dentine → the dental papilla changes into the pulp

 

Functions of the pulp:

1.  Formation of the dentine
2.  Maintain tooth fluid movement
3.  Sensation
4.  Proprioception
5.  Defense [ by blood supply forming reparative and secondary dentine ]

 

• Pulp has minimal collateral supply which reduces its capacity for repair

 

Innervation of pulp is both simple and complex

•  Simple – only free nerve endings and so lacks proprioception
•  Complex – innervation of odontoblastic process which produces high level of sensitivity to thermal and chemical change

 

Causes of pulpal disease: [ pathways bacteria can enter into the pulp]

1.  Caries - Most common cause of pulpal disease is bacterial contamination from caries , percolation around restorations
2.  Trauma [ fractures, luxation, avulsion or chronic trauma like bruxism]
3.  Marginal leakage around restorations or during cavity prep
4.  Periodontal pockets : through lateral canal and exposed DT
5.  Anachoresis: transportation of microbes through blood or lymph to a site of inflammation – does not occur in humans

 

Q: can radiation cause pulpal disease?

• Radiation affects the pulpal blood supply → pulpal necrosis , radiation also affects the salivary glands leading to hyposalivation → caries and pulpal disease

Q: how can caries cause pulpal inflammation?

• Carious lesions contain bacteria that get lesser as you get closer to the pulp but the pulp gets affected before the actual bacterial invasion by the noxious bacterial by- products. Once the pulp gets exposed to the bacteria → PMN infiltrate the pulp causing liquefactive necrosis that spreads throughout the pulp

 

• Pulpal infections are polymicrobial but anaerobes dominate

 

Complications of untreated Pulpitis:

• Upper teeth → sinusitis → meningitis / brain abscess / orbital cellulitis and cavernous sinus thrombosis
• Lower teeth → ludwig’s angina / parapharyngeal abscess / mediastinitis / pericarditis /emphysema

 Endodontic Coronal Cavity Preparation (Access Opening)

•  I. Outline Form
•  II. Convenience Form
•  III. Removal of the remaining carious dentin (and defective restorations)
•  IV. Toilet of the cavity

 

Endodontic Radicular Cavity Preparation (Instrumentation)

•  I and II. Outline Form and Convenience Form (continued)
•  IV. Toilet of the cavity (continued)
•  V. Retention Form
•  VI. Resistance Form

 

Access Cavity Preparation

 

Access opening rely, is the key of endodontics.

 

Rules for proper access preparation:

• to ensure that the most efficient access cavity is prepared, the following rules should be observed:
• Give direct access to the apical foramen, not only to the canal orifice.
• Access cavity preparations are different from typical operative occlusal preparations, in that they are not depend on the topography of occlusal grooves, pits, fissures and on the avoidance of underlying pulp. But the need to uncovering the roof of the pulp chamber and divergent walls.
• The likely interior anatomy of the tooth under treatment must be determined.
• Endodontic entries are prepared through the occlusal or lingual surface-never through the proximal or gingival surface.
• As part of the access preparation, the unsupported cusps of posterior teeth must be reduced.