BDS Endodontics Syllabus

How can you differentiate referred pain from a true pulpal source in the suspect tooth?

Referred pain does not respond to local anaesthetic infiltration of the suspect tooth or to direct stimulation of it; true source pain is reproduced by testing the offending tooth and relieved by anaesthetising it.

Distinguish a periodontal abscess from a periapical (endodontic) abscess.

Periodontal abscess: vital pulp, deep periodontal pocket, swelling over the lateral root/gingiva. Periapical abscess: non-vital pulp, no deep pocket (unless perio-endo lesion), swelling near the apex.

What is the predominant microbial character of primary endodontic infections?

They are polymicrobial and predominantly anaerobic (obligate anaerobes such as Fusobacterium, Porphyromonas, Prevotella, Peptostreptococcus, and spirochaetes).

Which microorganism is most strongly associated with persistent/secondary endodontic infections and failed root canal treatment?

Enterococcus faecalis (a facultative anaerobe resistant to intracanal medicaments); Candida albicans is the fungus most often implicated.

Define a biofilm and explain its clinical importance in endodontics.

A biofilm is a structured community of microorganisms embedded in an extracellular polymeric matrix adherent to a surface (canal walls); its matrix makes bacteria far more resistant to antimicrobials and host defences, making mechanical/chemical disruption essential.

State Koch's-type evidence linking bacteria to pulp/periapical disease — the classic Kakehashi (1965) germ-free rat experiment showed what?

Exposed pulps in germ-free (gnotobiotic) rats healed with dentine bridge formation, whereas pulps in conventional rats with normal flora developed necrosis and periapical lesions — proving bacteria cause pulpal/periapical pathosis.

What is the gold-standard method of sterilisation for endodontic hand instruments and what parameters does it use?

Steam autoclaving (moist heat under pressure): typically 121°C at 15 psi for 15 minutes, or 134°C at ~30 psi for 3–4 minutes.

Differentiate sterilisation from disinfection.

Sterilisation destroys all microorganisms including bacterial spores; disinfection reduces the number of pathogenic microorganisms but does not necessarily kill all spores.

What is the most commonly used root canal irrigant and its key functions?

Sodium hypochlorite (NaOCl, usually 1–5.25%); it dissolves organic/necrotic tissue, is broadly antimicrobial, disrupts biofilm, and lubricates the canal.

Why is EDTA used as an endodontic irrigant, and how does it complement NaOCl?

EDTA (17%) is a chelating agent that removes the inorganic smear layer and softens dentine; NaOCl removes the organic component, so alternating them cleans canal walls and opens dentinal tubules.

What is the standard reference for the taper of conventional stainless-steel hand files, and what does an ISO size 25 file indicate?

ISO standard taper is 0.02 mm/mm (2% taper); an ISO size 25 file has a tip diameter (D0) of 0.25 mm.

Name the three basic types of stainless-steel endodontic hand instruments and their primary cutting motions.

K-files (twisting/reaming and filing), Hedström files (pull/filing stroke only), and reamers (rotational reaming); plus barbed broaches for pulp extirpation.

State the colour-coding sequence for ISO file sizes 15, 20, 25, 30, 35, 40.

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

What material advance made rotary endodontic instruments possible and why?

Nickel-titanium (NiTi) alloy; its superelasticity and shape memory allow files to flex around curved canals with less transportation and reduced risk of ledging compared with rigid stainless steel.

List two common failure modes of rotary NiTi instruments and a key preventive measure.

Cyclic (flexural) fatigue from repeated flexing in curves and torsional fatigue from tip binding; prevention includes single-use/limited-use files, a glide path, adequate irrigation, and avoiding excessive apical pressure.

What is the ideal (Grossman's) requirement list for a root canal obturating material — name four properties.

It should be easily introduced, seal laterally and apically, be non-irritating/biocompatible, dimensionally stable (non-shrinking), radiopaque, bacteriostatic, and easily removed if needed.

What is the core (gold-standard) solid obturation material and its approximate composition?

Gutta-percha; approximately 20% gutta-percha (matrix), 65% zinc oxide (filler), plus waxes/resins and radiopacifiers/metal sulphates.

Why is gutta-percha used with a sealer rather than alone?

Gutta-percha does not bond to or adhere to dentine and cannot seal the interface by itself; the sealer fills the gap between the core material and canal wall and fills accessory canals/voids.

Name three categories of root canal sealers by base chemistry.

Zinc oxide–eugenol based, calcium hydroxide based, resin (epoxy, e.g. AH Plus) based, and bioceramic/calcium silicate based (e.g. MTA-based).

State the three classic phases of root canal treatment (the endodontic triad).

1) Access opening/diagnosis and biomechanical preparation (cleaning and shaping), 2) Disinfection/sterilisation of the canal, 3) Obturation (three-dimensional filling) — underpinned by asepsis (isolation).

What is 'working length' and how is it classically determined?

Working length is the distance from a coronal reference point to the point at which canal preparation and obturation terminate (usually the apical constriction, ~0.5–1 mm short of the radiographic apex); determined by radiograph and/or electronic apex locator.

Describe the objectives of biomechanical (cleaning and shaping) preparation.

To remove infected/necrotic pulp tissue and microorganisms, create a continuously tapering funnel shape, maintain the original canal anatomy, keep the apical foramen small and in position, and facilitate irrigation and obturation.

What is rubber dam isolation and why is it mandatory in endodontics?

A rubber sheet clamped over the tooth that isolates the operative field; it prevents salivary/bacterial contamination, protects the airway from aspiration/ingestion of instruments and irrigants, and improves visibility and moisture control.

Define endodontic retreatment and list two common indications.

Non-surgical re-entry of a previously root-filled tooth to remove existing filling material, re-clean/disinfect and re-obturate; indications include persistent periapical radiolucency, symptomatic failed RCT, inadequate/missed canals, or coronal leakage.

What is surgical endodontics (apicoectomy/periradicular surgery) and its principal steps?

Surgical removal of the root apex and periapical lesion when non-surgical treatment fails; steps include flap reflection, osteotomy, curettage of the lesion, root-end resection (apicoectomy), root-end cavity preparation, and root-end (retrograde) filling.

Which material is considered the gold standard for root-end (retrograde) fillings and why?

Mineral Trioxide Aggregate (MTA); it is biocompatible, sets in the presence of moisture/blood, seals well, is bacteriostatic and promotes hard-tissue (cementum) formation.

What is a 'ledge' and how does it occur during canal preparation?

An artificial irregularity/step created on the canal wall short of the working length that prevents instruments from reaching the apex; caused by forcing files, failing to pre-curve instruments in curved canals, or inadequate straight-line access.

List three common intraoperative complications of root canal treatment.

Instrument (file) separation/fracture, canal perforation (strip/furcation/apical), ledging/canal transportation, apical extrusion of irrigant (NaOCl accident), and overinstrumentation beyond the apex.

What is a sodium hypochlorite accident and its typical presentation?

Extrusion of NaOCl beyond the apex into periapical tissues, causing immediate severe pain, rapid diffuse swelling, bruising/ecchymosis, and possible tissue necrosis; managed by reassurance, analgesia, cold then warm compresses, and antibiotics if infection ensues.

Name two common postoperative complications after endodontic treatment and a management principle.

Post-obturation flare-up (pain/swelling) and persistent apical periodontitis; management includes occlusal reduction, analgesics/anti-inflammatories, drainage if abscess, and antibiotics only if systemic/spreading infection.

Why is pulp therapy in primary teeth different, and what is the material of choice for pulpotomy?

Primary teeth have larger pulp chambers, thinner dentine, and physiological root resorption, and treatment must not harm the succedaneous tooth; the historical material of choice for vital pulpotomy is formocresol, though MTA and ferric sulphate are now widely preferred alternatives.