NEET MDS Endodontics Syllabus

What features distinguish odontogenic pain from non-odontogenic pain mimics?

Odontogenic pain usually responds to thermal/percussion testing and localizes to a tooth; non-odontogenic mimics (sinusitis, trigeminal neuralgia, atypical odontalgia, cardiac referred pain) lack a reproducible dental stimulus and do not resolve with dental therapy.

What is the predominant microbial character of primary endodontic infections?

Primary infections are polymicrobial and dominated by anaerobic (mostly Gram-negative) bacteria, such as Fusobacterium, Porphyromonas, Prevotella, Tannerella, Treponema, and Dialister species.

Which organism is most associated with persistent/secondary endodontic infections and failed root canals?

Enterococcus faecalis, a facultative Gram-positive coccus resistant to high pH and able to survive in nutrient-poor canals. The fungus Candida albicans is also implicated.

Why are biofilms significant in endodontic infection?

Bacteria organize into biofilms on canal and apical surfaces that resist host defenses and antimicrobials, requiring mechanical disruption plus chemical irrigation for effective elimination.

Define sterilization versus disinfection in the dental setting.

Sterilization destroys all microbial life including spores; disinfection eliminates most pathogenic microorganisms but not necessarily all spores.

What is the standard autoclave (steam sterilization) cycle for endodontic instruments?

Saturated steam at 121 C (15 psi) for 15-20 minutes, or 134 C (about 30 psi) for 3-4 minutes.

What is the most commonly used root canal irrigant and its primary actions?

Sodium hypochlorite (NaOCl, typically 1-6%): it dissolves organic tissue and is broadly antibacterial, including against biofilm."},

Why is EDTA used during root canal irrigation, and how does it complement NaOCl?

EDTA (usually 17%) is a chelating agent that removes the inorganic smear layer and lubricates canals; NaOCl removes the organic component, so alternating them cleans both parts of the smear layer.

What is chlorhexidine's role as an endodontic irrigant and its key limitation?

Chlorhexidine (2%) is antibacterial with substantivity (residual action) and is useful against E. faecalis, but it does not dissolve organic tissue and forms a toxic precipitate (parachloroaniline) when mixed with NaOCl.

Name the standard ISO color code sequence for hand files sizes 15 to 40.

15 = white, 20 = yellow, 25 = red, 30 = blue, 35 = green, 40 = black (the white-yellow-red-blue-green-black sequence repeats for higher sizes).

Differentiate K-files, Hedstrom files, and reamers by manufacture/action.

K-files: twisted square/triangular blanks, used in reaming (rotation) and filing. Reamers: twisted with fewer flutes, primarily cutting on rotation. Hedstrom files: machined from a round blank with a snail-shell cross-section, cut aggressively only on a pull (filing) stroke.

What does the taper of an endodontic instrument mean, and what is standard ISO taper?

Taper is the increase in diameter per millimeter along the working blade. Standard ISO hand files have a 0.02 (2%) taper, i.e., diameter increases 0.02 mm per mm of length.

How is the D0 (tip) diameter calculated from an ISO file size number?

D0 diameter in mm = ISO size number divided by 100 (e.g., a size 25 file has a 0.25 mm tip diameter).

What is the principal advantage of NiTi rotary instruments over stainless steel hand files?

Nickel-titanium's superelasticity (shape memory) lets files flex around curvatures while maintaining the original canal shape, reducing transportation, ledging, and procedural errors in curved canals.

What is the difference between continuous rotation and reciprocating NiTi motion?

Continuous rotation turns 360 degrees in one direction; reciprocation alternates a larger cutting counterclockwise angle with a smaller clockwise release angle, reducing cyclic fatigue and file separation and often allowing single-file use.

What property change does heat treatment (e.g., CM-wire, M-wire) give to NiTi rotary files?

Heat treatment alters the transformation temperature, increasing flexibility and resistance to cyclic fatigue, and allows files to be pre-bent, improving safety in curved canals.

What is the gold-standard core obturation material and why?

Gutta-percha: it is biocompatible, dimensionally stable, radiopaque, easily compacted, and removable for retreatment, though it does not bond to dentin and requires a sealer.

What is the composition of gutta-percha points?

Approximately 20% gutta-percha (matrix), 60-75% zinc oxide (filler), plus radiopacifiers (heavy metal salts/barium sulfate) and waxes/resins as plasticizers."},

Why is a root canal sealer required even with a well-fitted gutta-percha cone?

Sealer fills the interface between gutta-percha and canal wall, fills voids/lateral canals, entombs residual bacteria, and provides a fluid-tight seal since gutta-percha does not adhere to dentin.

Name the main categories of root canal sealers.

Zinc oxide-eugenol based, calcium hydroxide based, glass ionomer based, resin based (e.g., epoxy resin like AH Plus), silicone based, and bioceramic/calcium silicate based sealers.

What are the advantages of bioceramic (calcium silicate) sealers?

High biocompatibility, dimensional stability, alkaline antibacterial pH, hydrophilicity (sets in moisture), bond/sealing ability, and bioactivity (apatite formation promoting healing).

List the basic sequential steps of conventional root canal treatment.

Diagnosis and anesthesia, isolation (rubber dam), access cavity preparation, working length determination, cleaning and shaping (biomechanical preparation with irrigation), drying, obturation, and coronal restoration.

What is the objective of access cavity preparation?

To achieve straight-line access to all canal orifices, completely remove the pulp chamber roof, and conserve sound tooth structure for an unobstructed instrument path.

Where is the ideal apical termination (working length endpoint) of canal preparation and obturation?

At the apical constriction (the cementodentinal junction), generally about 0.5-1 mm short of the radiographic apex, where the canal is narrowest.

What is the gold-standard obturation technique for adaptation to canal walls?

Warm vertical compaction (Schilder technique) of thermoplasticized gutta-percha, which adapts well to irregularities and lateral canals; lateral cold compaction is a common alternative.

What are the main indications for endodontic retreatment?

Persistent or recurrent periapical disease, inadequate previous obturation, missed canals, coronal leakage/recontamination, or new caries/fracture compromising a previously treated tooth that is restorable.

What materials/obstructions complicate nonsurgical retreatment, and how are they managed?

Gutta-percha (removed with solvents like chloroform plus files/rotary), pastes, separated instruments, posts, and ledges; carrier-based or hard pastes and separated files often require ultrasonics or specialized removal kits."},

What is an apicoectomy and when is it indicated?

Surgical removal of the apical portion of the root (root-end resection) with retrograde filling, indicated when nonsurgical treatment/retreatment is not feasible or has failed, e.g., persistent apical pathology, blocked canals, or large cysts requiring biopsy.

What is the preferred root-end filling (retrofill) material in modern surgical endodontics and why?

MTA (mineral trioxide aggregate) or other calcium silicate cements, due to excellent sealing, biocompatibility, hydrophilic setting, and promotion of periapical healing/hard tissue formation.

Differentiate hemisection from root amputation (radisectomy).

Hemisection: a multirooted (usually mandibular molar) tooth is split and one half (root plus its crown portion) is removed. Root amputation: only a root is removed while the entire crown is retained, typically on maxillary molars.

How is a sodium hypochlorite accident managed intraoperatively?

NaOCl extruded beyond the apex causes sudden severe pain, swelling, bleeding, and possible bruising; manage with copious saline irrigation, analgesics, cold then warm compresses, antibiotics if indicated, and reassurance with follow-up.

What is a separated (fractured) instrument and what factors influence the prognosis?

A file fragment retained in the canal; prognosis depends on the stage of cleaning when it broke, the canal already prepared apically, the position relative to curvature, and whether infection control was achieved before separation.

What is canal transportation and how is it avoided?

Deviation of the prepared canal away from its original axis (e.g., zipping at curves, strip perforation), caused by stiff instruments; avoided by using flexible NiTi files, pre-curving, maintaining patency, and crown-down sequencing.

What is a common postoperative complication after obturation and how is it managed?

Post-obturation flare-up (interappointment or post-treatment pain/swelling from periapical inflammation or extrusion); managed with occlusal reduction, analgesics/NSAIDs, drainage if needed, and antibiotics only with systemic involvement.

What is the material of choice for pulpotomy in primary teeth and a traditional alternative?

MTA (and increasingly Biodentine) is the preferred medicament; formocresol was the long-standing traditional agent, now declining due to toxicity/carcinogenicity concerns. Ferric sulfate is another alternative.

Why is obturation of primary teeth done with resorbable materials?

Because primary roots physiologically resorb before exfoliation, fillers such as zinc oxide-eugenol, calcium hydroxide/iodoform pastes (e.g., Vitapex), or Metapex are used so they resorb with the root and do not deflect the succedaneous tooth.

What is apexogenesis and when is it indicated?

A vital pulp therapy in an immature permanent tooth that preserves the vital radicular pulp (e.g., via pulpotomy) to allow continued normal root development and physiologic apical closure.

What is apexification and the materials used?

Inducing a calcific apical barrier in a non-vital immature permanent tooth: traditionally multi-visit calcium hydroxide, now commonly a single-visit MTA (or Biodentine) apical plug to allow obturation of the open apex.

What is regenerative endodontics (revascularization)?

A biologically based procedure to replace damaged pulp-dentin tissue, including the root structures, in immature necrotic teeth, aiming to restore vitality and continued root development rather than placing an artificial barrier.

What is the triad of tissue engineering applied in regenerative endodontics?

Stem cells (e.g., from the apical papilla, induced via periapical bleeding), scaffolds (blood clot, PRP/PRF), and signaling molecules/growth factors, supported by disinfection and a coronal seal.

Why is a triple antibiotic paste (or calcium hydroxide) used in regenerative protocols, and what is a caution?

It disinfects the canal without aggressive instrumentation that would weaken thin immature walls. Caution: minocycline in triple antibiotic paste causes tooth discoloration, so it may be omitted or substituted (double antibiotic paste).

How do operating microscopes and ultrasonics improve endodontic outcomes?

Magnification and coaxial illumination allow location of calcified/extra canals (e.g., MB2), detection of fractures and perforations, and conservative refined preparation; ultrasonics aid access refinement, irrigant activation, and removal of obstructions.

What is laser-activated (or sonic/ultrasonic) irrigation and its benefit?

Energizing the irrigant to create acoustic streaming/cavitation that enhances penetration into isthmuses, lateral canals, and dentinal tubules, improving smear layer and biofilm removal beyond passive irrigation.