Overseas Registration Exam (ORE) Clinical Dentistry and Operative Procedures Syllabus

State the average root canal numbers for the maxillary first molar and mandibular first molar.

Maxillary first molar: 3 roots, commonly 4 canals (MB1, MB2, DB, palatal) — the MB2 is frequently present (>$50\%$). Mandibular first molar: 2 roots, commonly 3-4 canals (mesiobuccal, mesiolingual, and one or two distal canals).

What are the objectives and ideal features of an endodontic access cavity?

Objectives: straight-line access to canal orifices, complete removal of the pulp chamber roof, conservation of sound tooth, and location of all canals. Ideal access removes all caries/old restoration, has divergent walls for visibility, smooth funnelled orifices, and an outline reflecting the pulp chamber floor anatomy.

What does Vertucci's classification describe, and give two examples.

Vertucci classified root canal configurations (number/branching from orifice to apex). Type I: single canal orifice to apex (1-1). Type II: two canals leaving the chamber that join into one (2-1). Type IV: two separate canals from orifice to apex (2-2). Eight types in total.

How is working length determined and what reference point is the target?

Working length is the distance from a coronal reference point to the apical constriction (the minor apical diameter), typically $0.5\text{-}1\,\mathrm{mm}$ short of the radiographic apex. Determined using an electronic apex locator confirmed by a radiograph; the apical constriction (cemento-dentinal junction) is the ideal apical limit of preparation and obturation.

What is the principal mechanism and concentration range of sodium hypochlorite as an endodontic irrigant?

$\ce{NaOCl}$ ($0.5\text{-}6\%$, commonly $1\text{-}3\%$) dissolves organic tissue (necrotic/vital pulp remnants) and is broadly antimicrobial via hypochlorous acid oxidation. It does not remove the inorganic smear layer, so it is paired with a chelator such as $17\%$ EDTA.

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

$17\%$ EDTA (ethylenediaminetetraacetic acid) is a chelating agent that removes the inorganic component of the smear layer and softens/decalcifies dentine, opening dentinal tubules. NaOCl removes the organic component; alternating/final-rinse use of both gives a cleaner canal wall for disinfection and obturation seal.

What design principles govern modern rotary NiTi canal preparation (e.g. crown-down/taper)?

Maintain the original canal curvature, keep the apical foramen small and positioned, produce a continuously tapering funnel (apex narrowest), avoid procedural errors (ledges, transportation, zips, perforation), and create enough taper/space for irrigant exchange while conserving radicular dentine; crown-down removes coronal interferences first.

Why is calcium hydroxide used as an inter-appointment intracanal medicament?

$\ce{Ca(OH)2}$ dissociates to release hydroxyl ions giving a high pH (~$12.5$) that is antibacterial (especially against most canal flora), inactivates LPS/endotoxin, dissolves remaining necrotic tissue, and creates a hostile environment between visits; limited efficacy against E. faecalis and Candida.

Describe lateral compaction obturation and its purpose.

A master gutta-percha cone is fitted to working length with sealer; a finger spreader creates space laterally for accessory cones, which are progressively compacted to fill the canal three-dimensionally. The aim is a dense, well-adapted gutta-percha/sealer fill that entombs residual bacteria and prevents coronal/apical leakage.

What is the role of root canal sealer, and name common sealer types.

Sealer fills the interface between gutta-percha and canal wall and the spaces between cones, providing a fluid-tight seal, lubrication during placement, and antibacterial action. Types: zinc-oxide eugenol, calcium hydroxide, glass-ionomer, epoxy-resin (e.g. AH Plus), and bioceramic/calcium silicate sealers.

Why does the coronal restoration matter for endodontic success, and what is the cuspal-coverage rule?

A well-sealed coronal restoration prevents bacterial recontamination (coronal leakage is a major cause of failure). Endodontically treated posterior teeth lose structural integrity, so cuspal coverage (onlay/crown) is generally recommended for molars and premolars to prevent catastrophic vertical fracture, whereas intact anterior teeth may need only a sealed access restoration.

When is a post-and-core indicated after root canal treatment, and what is the ferrule effect?

A post is indicated only when insufficient coronal tooth structure remains to retain a core; its purpose is core retention, not tooth reinforcement. The ferrule effect is a $1.5\text{-}2\,\mathrm{mm}$ circumferential band of sound dentine encircled by the crown above the margin, which markedly improves fracture resistance and reduces post-related failure.

List common procedural complications of root canal treatment.

Ledge formation, canal transportation/zipping, apical perforation, strip perforation (furcation), instrument (file) separation/fracture, NaOCl extrusion accident, blockage with debris, vertical root fracture, and missed canals — the last being a frequent cause of persistent disease.

What factors guide the decision between non-surgical re-treatment and periapical surgery for a failing root-filled tooth?

Re-treatment is favoured when the cause is correctable through the canal (missed canal, inadequate fill, coronal leakage) and access is feasible. Surgery (apicectomy/retrograde fill) is favoured when orthograde access is blocked (post/crown that should not be removed, separated instrument, calcified canal) or to biopsy/manage persistent extraradicular disease.

What is the role of MTA (mineral trioxide aggregate) in endodontic complication management?

MTA is a calcium-silicate cement that sets in moisture, is biocompatible and bacteriostatic, and seals against tissue fluids. Uses: perforation repair, root-end (retrograde) filling, apexification/apical barrier in open-apex teeth, pulp capping, and pulpotomy.

What is the Kennedy classification of partial edentulism?

Class I: bilateral free-end saddles (edentulous areas posterior to remaining teeth on both sides). Class II: unilateral free-end saddle. Class III: unilateral bounded saddle (teeth anterior and posterior). Class IV: single bounded edentulous area crossing the midline anterior to remaining teeth. Modification spaces describe additional saddles (Class IV has none).

What patient and site factors must be assessed when treatment planning for tooth replacement (denture vs bridge vs implant)?

Number/position of missing teeth, condition and prognosis of abutment/remaining teeth, periodontal status, occlusion and space, ridge form and bone volume, soft-tissue and aesthetic demands, oral hygiene/caries risk, medical history (e.g. bisphosphonates, smoking, diabetes), patient wishes, cost and maintenance.

Define the terms 'retention', 'support' and 'stability' for complete dentures.

Retention: resistance to vertical displacement away from the tissues (from adhesion, cohesion, border seal, atmospheric pressure). Support: resistance to displacement towards the tissues (from the denture-bearing area/ridge). Stability: resistance to horizontal/rotational displacement during function.

What anatomical landmark provides the posterior border seal of a maxillary complete denture, and why is it important?

The posterior palatal seal is placed along the vibrating line region (junction of hard and soft palate, between the hamular notches). Slight compression of the displaceable soft-palate tissue here creates a border seal that maintains retention by preventing air ingress beneath the denture.

How is the occlusal vertical dimension (OVD) determined in complete denture construction, and what is freeway space?

OVD is established from rest vertical dimension (RVD) minus the interocclusal freeway space. Freeway space is the gap between teeth at rest, normally $2\text{-}4\,\mathrm{mm}$, i.e. $\text{OVD} = \text{RVD} - \text{freeway space}$. Determined using facial measurements, speech, swallowing and aesthetics.

What are the components of a removable partial denture framework?

Major connector (joins components across the arch), minor connectors (link components to the major connector), rests (transmit occlusal load, provide support), direct retainers/clasps (retention), indirect retainers (resist rotation of free-end saddles about the fulcrum line), and the denture base supporting the artificial teeth.

State the requirements of a clasp for an RPD and the difference between a suprabulge and infrabulge clasp.

A clasp needs an encircling arm engaging the survey-line undercut, a reciprocating (bracing) arm, and a rest for support; it must engage more than $180^\circ$ of the tooth. Suprabulge (circumferential, e.g. Akers) approaches the undercut from the occlusal/above the survey line; infrabulge (bar/I-bar) approaches from the gingival/below, giving better aesthetics and reduced tooth coverage.

Compare a fixed-fixed conventional bridge with a cantilever bridge.

Fixed-fixed: a pontic rigidly connected to retainers on abutments at both ends; strong and well-distributed load but requires preparation of two (or more) abutments and a common path of insertion. Cantilever: pontic supported by a retainer at one end only; conserves the contralateral abutment and avoids path-of-insertion problems but loads the abutment unfavourably, so used for short spans (often replacing a single small tooth).

What is a resin-bonded (Maryland) bridge and its main indications and failure mode?

A minimally invasive bridge in which a metal/zirconia wing is adhesively bonded to enamel on the abutment, retaining a pontic with little or no tooth preparation. Indicated for replacing single anterior (or small posterior) teeth in patients with sound abutments and good occlusion. The commonest failure is debonding; cantilever single-wing designs now reduce this.

What is Ante's law in bridge design?

Ante's law states that the combined root surface area of the abutment teeth should be equal to or greater than the root surface area of the teeth being replaced by the pontics. It is a guideline for assessing whether abutments can withstand the additional functional load, though modern evidence treats it as a rough guide rather than an absolute rule.

Define centric relation and maximum intercuspation, and how they differ.

Centric relation (CR/RCP) is a reproducible jaw relationship with the condyles in their most superior-anterior position against the articular eminences, independent of tooth contact. Maximum intercuspation (ICP/MIP) is the position of maximum cusp interdigitation of the teeth. They coincide in only a minority of people; the difference is the 'slide in centric'.

Distinguish canine-guided occlusion from group function, and what is anterior guidance.

Canine guidance: during lateral excursion only the canines contact on the working side, disoccluding all other teeth. Group function: several teeth on the working side share lateral contact, distributing load. Anterior guidance is the influence of the contacting anterior teeth (incisors/canines) on mandibular movement, which should disclude the posterior teeth in protrusion (mutually protected occlusion).

What measurements and indices are recorded in a comprehensive periodontal examination (e.g. for a 6-point pocket chart)?

Probing pocket depth (6 sites per tooth), gingival recession, clinical attachment level (CAL = probing depth + recession), bleeding on probing, plaque score, suppuration, furcation involvement, tooth mobility, and full-mouth radiographic bone levels. The BPE/CPITN is used as an initial screening tool.

Summarise the 2017 (Chicago) classification staging and grading of periodontitis.

Staging (I-IV) reflects severity/complexity based on interdental CAL, radiographic bone loss, tooth loss and management complexity. Grading (A slow, B moderate, C rapid) reflects rate of progression, estimated from bone loss/age ratio and risk factors (smoking, diabetes). Extent is described as localised (<$30\%$ of teeth), generalised, or molar-incisor pattern.

What are the major modifiable and non-modifiable risk factors for periodontitis?

Modifiable: smoking, poorly controlled diabetes, plaque/poor oral hygiene, stress, obesity, certain drugs. Non-modifiable: genetic susceptibility, age, and host immune-inflammatory response. Smoking and diabetes are the two strongest modifiable factors and are central to grading and prognosis.

What are the aims and typical clinical end-points of non-surgical periodontal therapy (root surface debridement)?

Aims: disrupt and remove subgingival biofilm and calculus, reduce inflammation and bacterial load, and arrest attachment loss. End-points/targets at review: pocket depths $\leq 4\,\mathrm{mm}$, bleeding on probing reduced (full-mouth BoP <$10\text{-}30\%$), no residual deep bleeding pockets, and patient-performed plaque control established before any surgery is considered.

When is periodontal surgery indicated and what is the difference between resective and regenerative surgery?

Indicated for residual deep pockets/persistent BoP after non-surgical therapy in a compliant patient with good plaque control. Resective surgery (e.g. apically repositioned flap, osseous recontouring) reduces pockets by removing tissue/recontouring bone. Regenerative surgery (e.g. guided tissue regeneration with membranes, enamel matrix derivative, bone grafts) aims to rebuild lost periodontal attachment, especially in intrabony defects and Class II furcations.

Describe the management of peri-implant mucositis versus peri-implantitis.

Peri-implant mucositis: reversible inflammation of soft tissue without bone loss; managed by non-surgical biofilm removal, oral-hygiene reinforcement and removing plaque-retentive factors. Peri-implantitis: inflammation with progressive supporting bone loss; needs non-surgical decontamination and usually surgical access for implant-surface decontamination, with resective or regenerative procedures, and ongoing supportive care.

What is supportive periodontal therapy (maintenance) and how is the recall interval decided?

A structured programme of regular reassessment (updated charting/BoP), reinforcement of oral hygiene, professional biofilm and calculus removal, and risk-factor management to maintain stability and prevent recurrence. Recall interval is individualised by risk (often every 3 months for higher-risk/treated periodontitis patients, extending as stability is demonstrated).