ENDODONTICS – QUICK EXAM NOTES

A. IRRIGATION

• Broad-spectrum, effective against E. faecalis and C. albicans
• Substantivity – binds to dentin, prolonged antimicrobial action (days)
• No tissue-dissolving/smear-layer removal action; used mainly as final rinse or intracanal medicament
• Mixing with NaOCl forms an orange-brown precipitate (para-chloroaniline, PCA) – potentially toxic, so canal must be rinsed with saline/dried between the two

B. DIAGNOSIS, WORKING LENGTH & INSTRUMENTS

• 1st gen – resistance/impedance-based, single frequency, needs dry canal, inaccurate with blood/electrolytes (e.g., Sono-Explorer)
• 2nd gen – impedance measured at 2 frequencies, frequency-dependent
• 3rd gen (current standard) – ratio method, multiple frequencies, accurate even with blood/pus/electrolytes (e.g., Root ZX)
• 4th/5th gen – multi-frequency + digital signal processing, often integrated into endo motors
• Principle: resistance between file and oral mucosa is constant (~6.5 kΩ) at the apical foramen regardless of canal diameter.

• Definition: distance from a coronal reference point to the point where canal prep/obturation should terminate (ideally at apical constriction, 0.5-1 mm short of radiographic apex)
• Methods: tactile sense, radiographic (Ingle's), electronic apex locator, paper-point method, digital radiography/CBCT
• Ingle's radiographic method: estimate length from pre-op film → subtract 1 mm for foreshortening → place file at estimated length → take radiograph with file in situ → measure discrepancy from apex → correct. Formula: Actual WL = (Known tooth length × length of file on film) / length of tooth on film

• Apical foramen – major diameter, actual exit point (often eccentric, 0.5-3 mm off the anatomic apex)
• Apical constriction – minor diameter, narrowest point = cementodentinal junction (CDJ); shifts apically with age (cementum deposition)
• Apical delta – accessory canal ramifications near apex – source of missed canals/persistent infection
• Clinical: instrumentation/obturation should stop at the constriction (minor diameter), NOT the foramen – preserves apical stop, avoids overfill, better prognosis. Important during apicoectomy/post-space prep since foramen location is variable.

• Composition ~55% Ni + 45% Ti (Nitinol); phases: austenite ↔ martensite → gives superelasticity/shape memory
• 2-3× more flexible than stainless steel, better maintains canal curvature, less transportation
• Cannot be pre-curved (returns to shape); fails suddenly without visible deformation, cannot be resharpened
• Advanced alloys: M-wire, R-phase, CM-wire (controlled memory), Gold/Blue heat-treated wires – improved cyclic-fatigue resistance
• Used in rotary/reciprocating systems (ProTaper, WaveOne, Reciproc)

• Uses modified flex-R files (non-cutting blunt tip)
• Sequence: insert to length → rotate clockwise 60-90° (engage dentin) → rotate counter-clockwise 120-180° with light apical pressure (shears dentin) → clockwise again to collect debris; repeat
• Keeps file centered, minimizes canal straightening/transportation in curved canals; used with hand SS files.

1. Continuously tapering conical shape, narrow apically–wide coronally
2. Cross-section smaller apically, larger at every point going coronally
3. Preserve original position of apical foramen
4. Keep apical opening as small as practically possible
5. Remove all pulp tissue/debris/microorganisms
6. No aberrations – no zips, elbows, ledges, perforations

• Classical hand techniques: standardized technique, step-back (telescopic), step-down/crown-down, balanced force, passive step-back
• Rotary/engine-driven: Gates-Glidden/Peeso for coronal flare; NiTi rotary systems (ProTaper Universal/Next/Gold, Mtwo, K3, Hero); reciprocating single-file systems (WaveOne, Reciproc) – reduce cyclic fatigue
• Newer alloys: M-wire, CM-wire, Gold/Blue wire – better flexibility/fatigue resistance
• Self-Adjusting File (SAF) – hollow, compressible lattice that adapts to any canal cross-section with continuous irrigation
• XP-endo Shaper/Finisher (MaxWire) – snake-like adaptive cleaning
• Irrigant activation: Passive Ultrasonic Irrigation (PUI), sonic activation (EndoActivator), Laser-Activated Irrigation/PIPS, GentleWave multisonic system
• CBCT-guided navigation for complex/calcified canals
• Conclusion: biomechanical preparation (mechanical + chemical) remains essential; recent advances focus on centered shaping, minimal transportation, better disinfection, minimally invasive access.

C. OBTURATION

• Cold lateral condensation – master cone + accessory cones + sealer, spreader compacts laterally (most widely taught/used)
• Warm vertical condensation (Schilder's technique) – heat pluggers, downpack + backfill
• Continuous wave of condensation (Buchanan) – electric heat carrier modification
• Thermoplasticized injection (Obtura/Ultrafil)
• Carrier-based obturation (Thermafil, GuttaCore)
• Single-cone technique (matched-taper rotary + bioceramic sealer)
• McSpadden mechanical compaction
• Solvent (chloropercha) technique – largely obsolete due to shrinkage/toxicity

• GP softened to flowable state for 3-D fill of canal irregularities/lateral canals
• Injection type (Obtura II/III) – heated GP injected in increments
• Carrier-based (Thermafil/GuttaCore) – GP-coated carrier heated in oven, placed to WL
• Pros: better adaptation to fins/isthmuses; Cons: overextension risk, shrinkage on cooling, retreatment difficulty (carrier type)

D. PULP & PERIRADICULAR PATHOLOGY

• Structured microbial community encased in self-produced extracellular polymeric substance (EPS), adherent to canal wall/apex
• Stages: adhesion → microcolony → maturation → dispersal
• Up to 1000× more resistant to antimicrobials than planktonic bacteria; quorum sensing coordinates behavior
• Endodontic relevance: intracanal + extraradicular biofilms cause persistent/chronic apical periodontitis; require mechanical disruption plus irrigation (NaOCl/CHX), cannot be eliminated by irrigant alone.

• Primary infection (untreated) – polymicrobial, mainly obligate anaerobes: Porphyromonas, Prevotella, Fusobacterium (Gram-negative rods), Peptostreptococcus (Gram-positive anaerobic cocci)
• Secondary/persistent infection (post-treatment failure) – fewer species, resistant: Enterococcus faecalis, Candida albicans, Actinomyces (extraradicular), Propionibacterium
• Routes of entry: caries, dentinal tubules, trauma, cracks, periodontal pocket (retrograde), anachoresis (rare, hematogenous)

• Most common odontogenic cyst; inflammatory, arises from epithelial rests of Malassez stimulated by pulp necrosis → periapical granuloma → cystic degeneration
• Radiograph: well-defined, unilocular, corticated periapical radiolucency, associated with a non-vital tooth
• Histopathology: non-keratinized stratified squamous epithelium lining (arcading pattern), chronic inflammatory infiltrate, cholesterol clefts, Rushton bodies
• Treatment: RCT/apicoectomy with enucleation, or marsupialization for large lesions; residual cyst = persists after extraction of causative tooth.

1. Acute (symptomatic) apical periodontitis
2. Chronic (asymptomatic) apical periodontitis / periapical granuloma
3. Acute apical (alveolar) abscess
4. Chronic apical abscess (with sinus tract)
5. Radicular cyst
6. Condensing (sclerosing) osteitis
7. External/internal root resorption 2° to periradicular disease

• Definition: acute inflammation of the periodontal ligament at the apex, usually sequela of pulpitis/pulp necrosis, occlusal trauma, or iatrogenic irritation (over-instrumentation/extruded irrigant/high filling)
• Etiology: bacterial toxins from necrotic pulp; chemical irritants; mechanical trauma
• Symptoms: spontaneous, moderate-severe pain; tooth tender to percussion/palpation; sensation of premature contact/extrusion; slight mobility
• Pulp test: may be vital (traumatic cause) or non-vital (necrotic pulp cause)
• Radiograph: usually normal, or slight PDL widening (bone resorption hasn't had time to appear)
• Histology: vascular congestion, edema, PMN infiltration confined to apical PDL
• Treatment: remove the cause (occlusal adjustment if vital/traumatic; RCT/pulpectomy if pulp necrotic; correct overextended filling), establish drainage if abscess forming, analgesics (NSAIDs), keep tooth out of occlusion during healing
• Prognosis: good if the cause is removed early.

E. ENDO-PERIO & SURGICAL ENDODONTICS

• Classification: primary endodontic; primary endo + secondary perio; primary periodontic; primary perio + secondary endo; true combined lesion
• Management:
  • Primary endo → RCT alone (best prognosis, perio defect resolves)
  • Primary endo + secondary perio → RCT first, reassess, then perio therapy if needed
  • Primary perio → periodontal therapy alone
  • Primary perio + secondary endo → both treatments
  • True combined → both, guarded prognosis
• Differentiate using vitality tests, sinus tract tracing, probing pattern (isolated narrow vs generalized), radiographic pattern (J-shaped/halo vs generalized bone loss)

• Full mucoperiosteal (triangular) – one vertical + horizontal sulcular incision
• Rectangular/trapezoidal – two vertical releases + horizontal
• Semilunar – curved incision in unattached mucosa (largely abandoned – poor visibility/scarring)
• Submarginal (Luebke-Ochsenbein) – scalloped incision 2-3 mm from gingival margin, preserves papillae, good with crowns
• Papilla-base flap – preserves interdental papilla for esthetics
• Choice depends on esthetic zone, existing restorations, lesion extent, access needed.

• Cavity prepared in the resected root end (after apicoectomy) for a root-end filling
• Older method: round bur – shallow, off-axis, misses isthmus
• Current: ultrasonic retrotips – coaxial with canal, ~3 mm depth, better isthmus cleaning, less perforation risk
• Followed by retrofill: MTA, Super-EBA, IRM, Biodentine (amalgam historically).

• Causes: cyclic/torsional fatigue, canal curvature, forcing/over-use, inadequate lubrication, manufacturing flaw
• Management: bypass with a smaller file; ultrasonic removal (Masserann kit, trepan/tube techniques, IRS kit) under magnification; if unable to remove and canal is otherwise clean apically, may incorporate into obturation; surgical removal (apicoectomy + retrofill) as last resort
• Prognosis depends on stage of instrumentation at fracture, infection status, fragment position (coronal > apical)
• Prevention: single-use NiTi files, adequate glide path, crown-down technique, avoid excess apical force.

F. TRAUMA

• Management brief: I – smoothing/composite; II – dentin seal + restore, monitor pulp; III – pulp cap/pulpotomy/RCT + restore depending on exposure size & time elapsed; IV – RCT ± apexification + restore; V – reimplantation protocol (store in milk/saline, splint 2 weeks, RCT at 7-10 days); VI – depends on fracture level (coronal-third worse prognosis, apical-third may heal with splinting); VII – reposition + splint, monitor vitality.

• Enamel + dentin + cementum fracture WITH pulp exposure; mobile fragment attached by soft tissue
• Management: remove coronal fragment + RCT + post-core-crown (± surgical/orthodontic extrusion if subgingival), or fragment reattachment if minimal subgingival extension, or extraction if unrestorable.

• Incomplete fracture of a vital posterior tooth (may extend into dentin/pulp)
• Symptoms: sharp pain on biting/release (rebound pain), cold sensitivity, hard to localize
• Diagnosis: bite test (Tooth Slooth), transillumination, dye staining, magnification; radiograph often normal
• Treatment: cuspal coverage restoration if pulp uninvolved; RCT + crown if pulp involved; extraction if crack extends subgingivally/into root (vertical root fracture).

G. RESTORATIVE MATERIALS & ADJUNCTS

• Ready-made posts for core retention in endo-treated teeth with major coronal loss
• Types: metallic (SS, titanium) vs non-metallic (zirconia, carbon/glass/quartz fiber); parallel vs tapered shape; active (threaded) vs passive (cemented) surface
• Fiber posts – modulus similar to dentin, reduce root fracture risk, esthetic under all-ceramic crowns
• Advantages over cast post-core: chairside, single visit, conservative (parallel design).

• Auxiliary retention for core buildup when coronal structure is deficient; screwed directly into dentin (self-tapping)
• Types: self-threading (most retentive, risk of dentin crazing), self-shearing/friction-locked, cemented
• Placement: pinhole 2 mm from DEJ, in bulkiest dentin, parallel to external root surface, avoiding pulp/perforation
• Complications: crazing, perforation, stress concentration/crack propagation.

• Purpose: aid proximal contact/contour/marginal seal with matrix band in Class II restorations
• Types: wooden (absorbs moisture, expands, most common), plastic/light-transmitting (for composite), anatomic wedges
• Function: compensates matrix thickness, seats band against gingival margin (prevents overhang), protects gingiva, aids contour; inserted from wider embrasure (usually lingual for posteriors).

• Patient-applied custom tray + carbamide peroxide (10-16%) or low-conc. hydrogen peroxide gel, worn hours/day or overnight, 2-6 weeks
• Mechanism: peroxide diffuses through enamel/dentin, oxidizes pigment molecules into smaller/less colored ones
• Pros: cheap, low technique sensitivity; Cons: compliance-dependent, slow, sensitivity/gingival irritation
• Contraindications: pregnancy, peroxide allergy, extensive anterior restorations.

• Hand-cutting bladed instrument (like an angled hatchet) used to sharpen internal line/point angles, plane cavity walls, and place retention grooves in Class II/III preparations.

• Angled cavosurface margin created to: increase marginal strength, remove unsupported enamel rods, improve seal/adaptation, compensate for casting shrinkage, improve esthetics, reduce microleakage
• Contraindicated in amalgam; indicated in cast restorations and selectively in composite/ceramic.

• Since amalgam has no adhesion, retention comes from cavity shape:
  • Occlusal convergence of walls (narrower occlusally than at pulpal floor)
  • Retention grooves/coves in proximal boxes
  • Slots/pins for extensive restorations
  • Adequate depth (1.5-2 mm into dentin) and wall height for friction.

• Thin coating on cavity walls (dentin) providing a chemical barrier + mild therapeutic action (not mechanical/thermal protection – that's a base's job)
• Examples: Ca(OH)₂ liners (Dycal), resin-modified GIC liners
• Applications: over deep/near-exposed dentin – antibacterial action, stimulates reparative dentin, protects pulp from restorative-material irritants; placed under amalgam, composite, or cast restorations.

• Composition: fluoroaluminosilicate glass powder + polyacrylic/polymaleic acid liquid
• Stages:
  1. Dissolution – acid attacks glass surface, releases Ca²⁺, Al³⁺, F⁻, Na⁺, Si ions
  2. Gelation (initial set) – fast Ca²⁺ cross-linking of polyacid chains → calcium polyacrylate gel
  3. Hardening (maturation, ~24 hr) – slower Al³⁺ cross-linking replaces Ca links → final strength; silica gel forms around unreacted glass cores
• Final structure: unreacted glass core + silica gel coat + polysalt matrix; continuous F⁻ release (anticariogenic); moisture-sensitive early on – needs protection.

H. RECENT ADVANCES / DIAGNOSTIC AIDS

• Thermal: cold (Endo-Ice, CO₂ snow), heat (warm GP/water)
• Electric pulp test (EPT) – tests neural response only, false results with immature apex/recent trauma/reparative dentin
• Laser Doppler flowmetry / pulse oximetry – measure actual blood flow (gold standard, not routinely used)
• Others: cavity test (last resort), transillumination, percussion/palpation (periradicular status), selective anesthesia.

• Direct – medicament placed directly on a small vital pulp exposure (mechanical/traumatic, minimal, recent) to promote dentin bridge formation. Materials: Ca(OH)₂ (traditional, tunnel defects), MTA/Biodentine (superior seal & biocompatibility)
• Indirect – medicament placed over a thin remaining layer of sound/affected dentin (no exposure) to protect pulp and encourage reparative dentin
• Success needs: hemorrhage control, no bacterial contamination, small exposure, good coronal seal.

• Types: Nd:YAG, Er:YAG, Er,Cr:YSGG, diode, CO₂
• Uses: canal disinfection, smear layer removal (Er:YAG), PIPS (photon-induced photoacoustic streaming) for 3-D irrigant activation, pulpotomy/hemostasis, laser-assisted apicoectomy, bleaching activation
• Pros: deeper tubule penetration, reduced microbial load; Cons: thermal damage risk, cost, cannot replace mechanical instrumentation.

• 3-D imaging, lower radiation than medical CT
• Uses: detecting extra canals (e.g., MB2)/C-shaped canals, diagnosing vertical root fractures, assessing periapical lesion extent and relation to IAN canal/sinus, surgical planning, distinguishing internal vs external resorption, evaluating trauma
• Limitation: higher radiation than periapical film, metal artifacts, reserved for cases where 2D imaging is inconclusive (AAE/AAOMR position).

• Loupes (2.5-6×) and dental operating microscope (up to 20-30×)
• Uses: locating MB2/extra canals, removing separated instruments, managing perforations/cracks, precision in retro-prep, ergonomics, documentation
• Improves diagnostic accuracy and treatment outcomes across access, cleaning/shaping, obturation, retreatment, and surgery.

• Method to induce an apical hard-tissue barrier in a non-vital, immature permanent tooth (open apex) so it can be conventionally obturated
• Traditional: Ca(OH)₂ dressing changed every ~3 months until barrier forms (6-24 months) – risk of cervical root fracture with prolonged use, unpredictable timeline
• Newer: MTA apical plug (single-visit apexification) – 3-5 mm MTA plug placed against a resorbable matrix, backfilled with GP; faster, comparable success. Biodentine also used.
• Different from regenerative endodontic procedures (revascularization), which aim for continued root maturation.

• Outline form: trapezoidal, mesial side wider, oriented toward mesiobuccal cusp
• Canals: MB1, MB2 (present 60-95%), DB, P (widest/most divergent) → usually 4 canals
• Orifice landmarks: MB1-DB-P form a triangle; MB2 lies mesial and slightly palatal to MB1 (law of orifice location/symmetry)
• Clinical significance: a missed MB2 is a leading cause of endodontic treatment failure.

I. LONG ESSAYS – FULL OUTLINES

• Retention form (resists pulling/tensile dislodgement along path of insertion): near-parallel opposing walls (2-5° taper/wall, ~6° total convergence), grooves, boxes, occlusal dovetail, proximal grooves in inlays, pins, cement as secondary retention
• Resistance form (resists tipping/rotation/shear): flat pulpal/gingival floors perpendicular to occlusal load, box-shaped preparation, walls near right angle to floor, adequate bulk, minimal excessive taper, grooves/proximal locks against rotation, adequate isthmus width
• Factors: total occlusal convergence angle (ideal 6-10°), surface area, wall height, W:H ratio, surface roughness
• Auxiliary retention: grooves, boxes, pins (threaded/cemented), slots, skirts

• Overall defect categories: distortion, surface roughness/irregularities, porosity (shrinkage, gas/pinhole, back-pressure), cracks, incomplete casting (misruns), nodules
• Back-hole porosity: caused when gases generated during casting cannot escape (single/inadequate sprue, dense/impermeable investment, blocked venting); occurs at the point in the mold farthest from the sprue (last area filled) – molten metal cannot fully displace trapped gas → void
• Prevention: proper sprue design/attachment at bulkiest point, adequately porous investment, correct casting/mold temperature, additional vent sprues for large patterns, vacuum investing/vibration to avoid trapped air
• Clinical significance: weakens casting, may be internal/invisible until finishing, can compromise fit/margins.