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KRISHNA VISHWA VIDYAPEETH - IV BDS EXAMINATION

Conservative Dentistry and Endodontics - JULY 2026

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SECTION - B

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Q.2 Answer any three out of four (3 × 2 = 6 Marks)

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(a) Indirect Pulp Capping (2 Marks)

• Deep caries close to pulp but no clinical signs of pulp pathology
• Vital tooth with no spontaneous pain, no swelling, normal responses to vitality tests

1. Administer local anesthesia and isolate with rubber dam.
2. Remove peripheral caries completely; leave the deepest layer of carious dentin over the pulp.
3. Apply a thin layer of calcium hydroxide (e.g., Dycal) or MTA directly over the remaining carious dentin.
4. Place a zinc oxide eugenol base followed by a permanent restoration.
5. Re-entry after 6-8 weeks (one-step technique skips re-entry): confirm arrested caries and secondary dentin bridge before final restoration.

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(b) Functions of Matrix and Wedge (2 Marks)

1. Provides the missing proximal wall so the restorative material can be condensed against it.
2. Helps restore proper proximal contour and contact point.
3. Prevents excess of material from flowing into the gingival sulcus.
4. Facilitates proper condensation of amalgam or packing of composite.
5. Allows carving of proper proximal anatomy.

1. Separates the teeth slightly to compensate for the thickness of the matrix band (prevents open contact).
2. Adapts the matrix band tightly against the cervical margin to prevent overhang.
3. Prevents sub-gingival flash of restorative material.
4. Provides cervical seal during condensation.
5. Helps in slight tooth separation for better matrix adaptation.

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(c) Air-Driven Handpiece - Speed Ranges and Uses (2 Marks)

• High-speed handpieces require continuous water coolant spray to prevent pulpal heat damage.
• Low-speed handpieces are used with straight or contra-angle attachments.
• Air-bearing turbines have minimal vibration and cutting efficiency declines under load.

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(d) Trituration (2 Marks)

• Hand trituration (mortar and pestle): Manual, time-consuming, inconsistent; rarely used today.
• Mechanical trituration (amalgamator): Capsule containing pre-measured alloy and mercury is placed in an amalgamator and triturated at controlled speed and time.

• Speed of amalgamator: 3200-4400 rpm
• Time: 8-15 seconds (varies with alloy)

• Grainy, crumbly, dull mix
• Reduced strength, increased marginal breakdown

• Hot, sticky, shiny mass
• Reduced working time, decreased compressive strength

• Homogeneous, shiny, smooth mass
• Slightly warm, forms a cohesive ball when squeezed
• Adequate working time (3-4 min) and setting time

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Q.3 Answer any three out of four (3 × 3 = 9 Marks)

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(a) Cast Inlays (3 Marks)

• Class I inlay: Involves only occlusal surface
• Class II inlay: Involves occlusal + one or both proximal surfaces (MOD)
• Class III inlay: Involves proximal surface of anterior teeth without incisal angle
• Class V inlay: Involves gingival one-third of facial or lingual surface

• Excellent marginal adaptation
• Superior strength and durability
• High accuracy; wear resistance similar to enamel
• Good contour and contact restoration

• Time-consuming - requires two appointments
• More tooth structure removal than amalgam
• Expensive; requires laboratory fabrication
• Unaesthetic (metal colour)

1. Retention form: Divergent walls (2-5° taper) from pulpal floor; no undercuts - inlay is seated from occlusal direction.
2. Resistance form: Flat pulpal floor, flat gingival floor.
3. Convenience form: Box form with flared proximal walls for wax pattern removal.
4. Dovetail on occlusal for retention in Class II.
5. All internal line angles rounded; external cavosurface angles at 90° (butt joint).
6. Finish line: Beveled cavosurface margin (cavosurface angle <90° to create acute metal margin).

1. Cavity preparation
2. Impression (usually elastomeric)
3. Wax pattern fabrication (direct or indirect)
4. Investing and casting (lost wax technique)
5. Finishing and polishing
6. Try-in and cementation (zinc phosphate or GIC cement)

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(b) Gingival Margin Trimmer (3 Marks)

• The cutting edge is curved and set at an angle to the blade
• It has a double-beveled cutting edge
• Available in paired instruments (mesial and distal) - they are mirror images of each other

• Formula: 8-7.5-14-80 (example for a GMT)
• The angle of the blade differentiates it from the hatchet

1. Primary function: To bevel the enamel at the gingival margin of Class II preparations, creating a proper cavosurface angle.
2. Planes and smoothes the gingival floor of the proximal box.
3. Removes unsupported enamel at the gingival margin.
4. Creates a defined gingival margin seat for inlay preparations.
5. Refines the gingival wall to be perpendicular to occlusal forces.

• Mesial GMT: Used on mesial box - chisel edge faces distally, used with a lateral scraping/planing motion.
• Distal GMT: Used on distal box - used on distal gingival margin.

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(c) Recent Advances in Composites (3 Marks)

• Filler size: 5-75 nm (nanomers) and 0.6-1.4 μm (nanoclusters)
• Examples: Filtek Supreme (3M ESPE)
• Advantages: Excellent polishability, good strength, reduced polymerization shrinkage, superior aesthetics
• Application: Anterior and posterior restorations

• Combination of nano-sized fillers with conventional hybrid fillers
• High filler loading: 70-80% by weight
• Better mechanical properties + good polish
• Examples: Tetric EvoCeram, Grandio

• Allow placement in increments up to 4-5 mm depth (conventional = 2 mm)
• Low polymerization stress due to stress-relieving monomers
• Examples: SureFil SDR (Dentsply), Tetric EvoCeram Bulk Fill, X-tra fil
• Used mainly in posterior teeth

• Incorporate adhesive monomers (e.g., MDP) within composite
• No separate bonding step required
• Example: Vertise Flow (Kerr)

• Inorganic-organic copolymer network
• Reduced residual monomer; reduced allergic potential
• Example: Admira (Voco)

• Contain PRG (pre-reacted glass ionomer) fillers
• Fluoride release + recharge capacity + composite aesthetics
• Example: Beautifil (Shofu)

• Lower viscosity; better adaptation to cavity walls
• Used as base/liner, pit and fissure sealant, small Class I and V restorations
• Higher shrinkage than packable composites

• High filler loading; stiffer consistency similar to amalgam
• Better proximal contact restoration
• Example: SureFil, P60 (3M)

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(d) Matrices Used for Class II Amalgam and Composite Restorations (3 Marks)

• Most commonly used for amalgam
• Components: Retainer (holder) + stainless steel matrix band (0.05 mm thick)
• Band available in various widths; contoured bands available
• Placement: Gingival edge apical to gingival margin of preparation
• Retainer can be placed buccally, lingually, or distally

• Self-supporting; no retainer needed
• Tightened by a coil mechanism
• Used in areas of limited access

• Plain sheet of stainless steel
• Custom formed and held by finger pressure or copper band
• For complex cavities

• Examples: Palodent, Composi-Tight, BiTine
• Components: Thin contoured sectional matrix band + ring (separation ring with tension wings) + wedge
• Advantages:
  • Creates tight proximal contact
  • Provides excellent proximal contour
  • Separates teeth adequately
  • Better cervical adaptation
  • Allows incremental composite placement

• Mylar (cellulose acetate) strips
• Allows light curing through the matrix
• Used mainly for anterior composite Class III/IV; limited use for Class II

• Advanced sectional matrix with 3D ring design
• Provides better tooth separation and tighter contacts

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Q.4 Answer any one out of two (1 × 10 = 10 Marks)

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(a) Define and Classify Dental Caries. Explain in Detail Diagnosis and Management of Dental Caries (10 Marks)

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• Class I: Pit and fissure caries - occlusal surfaces of premolars and molars, buccal pits of mandibular molars, lingual pits of maxillary incisors
• Class II: Proximal surface caries of posterior teeth (premolars and molars)
• Class III: Proximal surface caries of anterior teeth without involving incisal angle
• Class IV: Proximal surface caries of anterior teeth involving incisal angle
• Class V: Cervical one-third of facial/lingual surface (smooth surface caries)
• Class VI (Simon's addition): Cusp tips and incisal edges

• Enamel caries (initial/incipient)
• Dentinal caries
• Cemental caries (root caries)

• Acute (rampant) caries: Rapidly progressing, light yellow/whitish, wet, soft
• Chronic caries: Slow progressing, dark brown/black, dry, leathery
• Arrested caries: Caries process has stopped

• Primary caries: Occurring in a sound tooth surface
• Secondary (recurrent) caries: Occurring at margins of existing restoration
• Residual caries: Caries remaining after incomplete removal during cavity preparation

• Code 0: Sound
• Code 1: Initial changes (white spot after air drying)
• Code 2: Distinct white/brown spot change visible on wet surface
• Code 3: Localised enamel breakdown
• Code 4: Underlying dark shadow from dentin
• Code 5: Distinct cavity with visible dentin
• Code 6: Extensive cavity with visible dentin (>50% surface)

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• Clean and dry teeth thoroughly
• Look for: White spot lesions (early enamel caries), cavitation, discolouration (brown/black), loss of translucency
• Light source: Good illumination, fibre optic transillumination

• Sharp explorer passed over surface
• Positive sign: "Catch" or "stick" in pit/fissure
• Note: Excessive pressure may cause iatrogenic cavitation - use of explorer is controversial for early caries

• Bright light passed through tooth
• Carious lesion appears as dark shadow due to disrupted light transmission
• Useful for proximal and incisal caries

• Digital version of FOTI
• Images stored and compared over time

• Shows interproximal caries of premolars and molars
• Can detect caries before clinical cavitation
• Radiolucency seen within enamel or dentin

• R0: No radiographic evidence
• R1: Radiolucency in outer half of enamel
• R2: Radiolucency in inner half of enamel
• R3: Radiolucency in outer third of dentin
• R4: Radiolucency in middle/inner third of dentin

• 655 nm diode laser probe; measures fluorescence of bacterial metabolites
• Scale: 0-99; values >20 suggest caries; >35 dentin caries
• Useful for occlusal caries detection

• Measures loss of fluorescence from demineralized enamel
• Can detect very early lesions

• Measures electrical conductance through tooth
• Carious lesion has higher conductance than sound enamel

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1. Dietary counselling: Reduce frequency of fermentable carbohydrate intake; limit sugary snacks between meals
2. Fluoride therapy:
   • Topical fluoride (fluoride varnish, gels) - promotes remineralization
   • Fluoridated toothpaste (1000-1500 ppm)
   • Professional fluoride application
3. Fissure Sealants: Seal occlusal pits and fissures; prevent bacterial colonization
4. Antimicrobials: Chlorhexidine varnish to reduce Streptococcus mutans
5. Remineralizing agents: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) - GC Tooth Mousse; recaldent technology
6. Oral hygiene instructions: Proper brushing technique, flossing, use of interdental aids
7. Pit and fissure sealants
8. Silver Diamine Fluoride (SDF): Arrests caries; used in primary dentition and high-risk patients

• Remove caries with hand instruments only (spoon excavator)
• Restore with GIC (Glass Ionomer Cement)
• Used in developing countries, field settings, children
• GIC releases fluoride, chemically bonds to tooth

• Local anaesthesia and rubber dam isolation
• Cavity preparation: Outline form → Resistance form → Retention form → Convenience form → Removal of remaining caries → Toilet of cavity
• Liner/base placement (calcium hydroxide for deep cavities, GIC base)
• Restorative material selection:
  • Amalgam: Class I, II, V posterior; durable, strong
  • Composite resin: Class I-V; tooth-coloured; bonded restoration
  • GIC: Class III, V; primary teeth; fluoride-releasing
  • Cast gold/inlay: Large posterior cavities requiring strength
  • Resin-modified GIC: Combines properties of both

1. Diagnose caries using all available tools
2. Assess risk factors (diet, saliva, fluoride exposure, oral hygiene)
3. Classify caries by severity (ICDAS)
4. Non-operative for incipient; operative for cavitated lesions
5. Treat all active caries, stabilise dentition
6. Preventive programme to prevent recurrence
7. Regular recall examinations (3-6 monthly for high-risk patients)

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(b) Define Adhesion. Classify Dentine Bonding Agents. Describe the Mechanism of Dentine Bonding Agents (10 Marks)

• Adhesive (primer/bond): The material that facilitates adhesion between two dissimilar surfaces.
• Adherend: The substrate to which adhesion occurs (enamel or dentin).
• Adhesion to enamel is primarily micromechanical (acid etching creates resin tags).
• Adhesion to dentin is complex due to the wet, organic, heterogeneous nature of dentin and the presence of smear layer.

1. Mechanical adhesion: Interlocking between adhesive and irregularities on surface
2. Chemical adhesion: Formation of chemical bonds (ionic, covalent) at interface
3. Physical adhesion: Van der Waals forces; weak
4. Diffusion adhesion: Interpenetration of materials at interface

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• 37% phosphoric acid applied to enamel AND dentin, rinsed off
• Completely removes smear layer and opens dentinal tubules
• Three-step: Etch + Primer + Bond (e.g., Optibond FL, All-Bond 3)
• Two-step: Etch + Primer/Bond combined (e.g., Single Bond 2, Prime & Bond NT)

• Acidic primers that simultaneously condition and prime dentin; no separate rinse step
• Smear layer is modified/incorporated rather than removed
• Two-step self-etch: Primer + Bond separately (e.g., Clearfil SE Bond, AdheSE)
• One-step self-etch: All-in-one bottle (e.g., Adper Prompt L-Pop, iBond, G-Bond)

• Can be used in etch-and-rinse, selective etch, or self-etch mode
• Contain MDP monomer; bond to enamel, dentin, metal, zirconia
• Examples: Scotchbond Universal (3M), All-Bond Universal, Adhese Universal

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• When dentin is cut with instruments, a 1-2 μm thick amorphous layer forms on the surface = smear layer
• Composed of: Hydroxyapatite crystals + denatured collagen + bacteria + cutting debris
• Smear plugs occlude dentinal tubules reducing dentinal fluid flow
• Smear layer must be either removed (etch-and-rinse) or modified/infiltrated (self-etch)

• 37% phosphoric acid for 15 sec (dentin), 30 sec (enamel)
• Dissolves smear layer + hydroxyapatite crystals
• Exposes collagen fibrils to a depth of 5-8 μm
• Opens dentinal tubules
• Creates microporosities in enamel (prism cores dissolved preferentially = honeycomb pattern)

• Acidic monomers (e.g., 10-MDP, 4-META, phenyl-P)
• Simultaneously demineralize and infiltrate dentin
• Shallower demineralization (1-2 μm)
• Smear layer is incorporated into hybrid layer
• Less post-operative sensitivity (smear plugs partially maintained)

• Hydrophilic monomers penetrate into the water-wet demineralized collagen network
• Primer contains HEMA (hydroxyethyl methacrylate) in water/alcohol/acetone solvent
• Replaces water around collagen fibrils with resin monomers
• Keeps collagen fibrils from collapsing

• Key concept introduced by Nakabayashi (1982)
• Resin monomers infiltrate the demineralized collagen network and polymerize
• Creates a 1-5 μm thick hybrid layer (resin-reinforced dentin, zone of co-polymerization)
• Hybrid layer = demineralized dentin interpenetrated by resin = neither dentin nor resin alone
• Resistance to acid/enzyme degradation; provides micro-mechanical interlocking
• Resin tags extend into dentinal tubules (0.5-3 mm depth)

• Less hydrophilic bonding resin applied over primed surface
• Acts as a bridge between hydrophilic primer/dentin and hydrophobic composite
• Light-cured to polymerize

1. Micromechanical retention: Resin tags in tubules + hybrid layer entanglement
2. Chemical bonding: MDP monomer chemically bonds to calcium in hydroxyapatite (Ca-O-P bond)
3. Hydrogen bonding and van der Waals forces: Between resin monomers and collagen
4. Ionic bonds: With calcium ions of hydroxyapatite

• Water/ions can still permeate through the hybrid layer through nano-sized porosities even without bulk microleakage
• Leads to degradation of bond over time (hydrolytic degradation of collagen + monomer leaching)

• Maintain moist dentin (wet bonding technique) during bonding with etch-and-rinse systems
• Avoid over-drying (collagen collapse) or over-wetting (dilutes adhesive)
• Self-etch systems are more technique-friendly - less sensitive to moisture
• MDP-containing adhesives show best chemical adhesion; low degradation over time

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SECTION - C

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Q.5 Answer any three out of four (3 × 2 = 6 Marks)

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(a) Define Obturation (2 Marks)

1. To seal the canal completely - prevent reinfection and recontamination from oral fluids
2. To entomb any remaining microorganisms so they cannot proliferate
3. To eliminate dead space where bacteria could grow
4. To prevent periapical pathogens from re-entering the canal
5. To seal the apical foramen at the CDJ level

1. Should seal the canal laterally and apically
2. Dimensionally stable (not shrink/expand)
3. Bacteriostatic or not support bacterial growth
4. Biocompatible - non-toxic, non-irritating to periapical tissues
5. Radio-opaque (to allow radiographic verification)
6. Not stain tooth structure
7. Easy to manipulate; adequate working time
8. Insoluble in tissue fluids
9. Easily removable if retreatment needed

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(b) Apexification and Apexogenesis (2 Marks)

• Definition: A vital pulp therapy procedure aimed at preserving the vitality of the radicular (root) pulp to allow continued physiological root development (root elongation and apical closure) in an immature permanent tooth.
• Indication: Vital immature permanent tooth with irreversible pulpitis limited to coronal pulp (or pulp exposure in young permanent tooth)
• Procedure: Pulpotomy - remove coronal pulp, apply calcium hydroxide or MTA over radicular pulp stump, restore coronally
• Goal: Allow continued root development - apical closure achieved naturally by Hertwig's epithelial root sheath
• Outcome: Completed root length, converging apex, physiological root development

• Definition: A procedure to induce the formation of a calcified barrier (hard tissue) at the open apex of a non-vital, immature permanent tooth with incomplete root development, WITHOUT continued root development.
• Indication: Non-vital immature permanent tooth with open apex and necrotic pulp
• Methods:
  1. Calcium Hydroxide Apexification (conventional): Calcium hydroxide paste placed in canal and changed every 3-6 months; hard tissue barrier forms in 6-24 months; then obturated with gutta-percha
  2. MTA Apical Plug (one-step apexification/apical barrier technique): 4 mm MTA plug placed at apex in single visit; no need to wait months; immediate obturation with thermoplasticized gutta-percha
• Goal: Create a hard tissue stop/barrier against which obturation material can be condensed
• Root development does NOT continue in apexification

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(c) Zones of Pulp (2 Marks)

• Outermost layer adjacent to predentin/dentin
• Contains the cell bodies of odontoblasts - tall columnar cells
• Odontoblastic processes extend into dentinal tubules (Tomes fibers)
• Function: Dentinogenesis throughout life (secondary and tertiary dentin formation)

• Just internal to the odontoblastic layer
• Contains blood capillaries, nerve fibers, lymphatics
• Relatively acellular; contains subodontoblastic nerve plexus (plexus of Raschkow)

• Central to cell-free zone
• Contains many fibroblasts, undifferentiated mesenchymal cells
• Also contains macrophages, lymphocytes, plasma cells (defense cells)
• These cells can differentiate into odontoblasts when needed (repair)

• The innermost zone
• Contains large blood vessels (arterioles, venules), nerves (large myelinated A-beta and A-delta fibers and unmyelinated C-fibers), lymphatics
• Ground substance: Glycosaminoglycans
• Fibroblasts are most numerous cell type in pulp overall

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(d) Schilder's Objectives of Shaping and Cleaning of the Root Canal System (2 Marks)

1. The prepared canal should develop a continuously tapering cone from the apex to the access cavity opening - wider coronally and narrower apically; no abrupt changes in shape
2. The cross-sectional diameter of the canal should be narrower at every point apically - the preparation should be progressively wider from the apex to the occlusal; apical portion always smaller than the coronal portion
3. The canal preparation should maintain the original shape of the canal - the natural curvatures of the root should be followed; no ledging or straightening
4. The apical foramen should remain in its original position - no apical transportation; the apex should not be moved buccally/lingually
5. The apical opening should be kept as small as practical - maintain the apical constriction (CDJ); prevents extrusion of irrigants and filling material

1. Remove all organic debris - vital, necrotic tissue, microorganisms from the entire root canal system
2. Entomb all non-removable debris - debris packed deeply and sealed in lateral canals that cannot be reached
3. Do not force debris through the apical foramen - prevent periapical contamination
4. Create a clean root canal system - complete debridement
5. Avoid damage to the periapical tissues - instruments and irrigants should not be forced through the apex

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Q.6 Answer any three out of four (3 × 3 = 9 Marks)

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(a) Standardization of Root Canal Instruments (3 Marks)

• Before standardization, instruments from different manufacturers varied widely in tip diameter, taper, length, and material, making predictable canal preparation impossible.

• Instruments are numbered from 08 to 140 (ISO sizes)
• The number corresponds to the diameter at the tip (D1) in hundredths of a millimeter
• Example: Size 15 = D1 diameter of 0.15 mm; Size 25 = D1 = 0.25 mm
• Standard sizes: 06, 08, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100, 110, 120, 130, 140

• Each instrument has a uniform taper of 0.02 mm per mm of working length (2% taper)
• D16 (16 mm from tip) is always 0.32 mm larger than D1
• This gives a consistent increase in diameter along the blade

• Standard blade length = 16 mm (fluted working portion)

• Available in: 21 mm, 25 mm, 28 mm, 31 mm

• Color-coded handles for easy identification (standardized colour code)

• Standardized cutting tip: angle between 75° and 90° (for K-files and reamers)
• Non-cutting pilot tip: Hedstrom files have different tip design

• Ensures interchangeability between brands
• Allows sequential, predictable canal enlargement
• Facilitates standardized gutta-percha selection matching instrument size
• Enables reproducible results and research comparison

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(b) Ellis's Classification (3 Marks)

• Class I: Smoothen sharp edges; composite resin bonding for aesthetics
• Class II: Protect dentin (zinc oxide eugenol or calcium hydroxide liner + composite); vital pulp therapy if close to pulp
• Class III: Pulp capping (direct) if small exposure, vital tooth, seen within 24 hours; otherwise pulpotomy or root canal treatment
• Class IV: Root canal treatment followed by post-core and crown
• Class V (Avulsion): Reimplant immediately (within 30 min = best prognosis); store in milk/Hank's balanced salt solution/saline/saliva if delay; root canal treatment after reimplantation
• Class VI (Root fracture): Depends on level - cervical third = extract; middle third = splinting + monitor; apical third = monitor only
• Class VII: Repositioning and splinting; root canal if non-vital

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(c) Cold Lateral Compaction Technique (3 Marks)

• Master gutta-percha cone (standardized to match master apical file)
• Accessory/auxiliary gutta-percha cones (smaller sized: fine-fine, fine, medium)
• Root canal sealer (e.g., AH Plus, Tubliseal, Sealapex)
• Finger spreaders or D-11T spreader
• Dental dam and rubber dam clamp
• Endodontic ruler, radiograph

• Select gutta-percha cone same size as master apical file (MAF)
• Trim if necessary; should have "tug-back" (slight resistance) when placed at working length
• Confirm with radiograph (master cone trial/cone fit radiograph)

• Mix root canal sealer per manufacturer's instructions
• Coat the master cone with sealer or spin a lentulo spiral to coat canal walls
• Place master cone to working length with sealer coat

• Insert a D-11T spreader or finger spreader alongside the master cone
• Penetrate to 1-2 mm short of working length with firm apical pressure
• Use gentle clockwise-anticlockwise rotation (watch-winding motion)
• Hold spreader in place for 15-30 seconds to create space
• Remove spreader with slight rotation

• Insert first accessory cone (same size as spreader or one size smaller) into space created by spreader
• Apply sealer on accessory cone
• Repeat spreading + accessory cone insertion cycle until spreader can only penetrate 3-4 mm into canal

• Once canal is filled, sear off excess gutta-percha at canal orifice with a heated instrument (e.g., heated plugger or touch-n-heat)
• Compact coronally with a cold plugger

• Obtain post-obturation radiograph
• Ideal fill: Radiopaque, homogeneous, 0.5-1 mm short of radiographic apex, no voids

• Seal access cavity immediately with zinc oxide eugenol or IRM temporarily, then permanent restoration

• Predictable, standardized, well-researched technique
• Good apical seal when done properly
• Relatively inexpensive; no special equipment needed

• Lateral condensation may not fill fins, deltas, oval canals, lateral canals
• Risk of root fracture from excessive spreader pressure
• Multiple void spaces between cones (though sealer fills them)
• Gaps at apical third in curved canals

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(d) Define Working Length. Explain in Detail Ingle's Radiographic Technique (3 Marks)

• Under-preparation and under-obturation: Leaves infected tissue; treatment failure
• Over-instrumentation: Damage to periapical tissues; spreads infection; post-operative pain

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• Radiograph of the tooth with millimeter ruler
• Diagnostic file (any size; usually 10 or 15)
• Endodontic file with rubber stop (silicone stop)
• Radiograph holder (Ingle's holder) with film, aiming device

• Measure the length of the tooth on a pre-operative periapical radiograph with a millimeter ruler (from cusp tip/incisal edge to apex)
• Subtract 1 mm from this measurement = Estimated Working Length (EWL)
• This accounts for radiographic elongation

• Insert a file (size 10 or 15) to the EWL with a rubber stop set at the coronal reference point
• The rubber stop must be horizontal and perpendicular to the file

• Use a paralleling technique (long cone technique) with the film parallel to the long axis of the tooth and the beam perpendicular to both
• Place film in Ingle's film holder
• Expose radiograph

• On the radiograph, measure:
  • Distance from rubber stop to file tip = Length of file in canal (A)
  • Distance from rubber stop to radiographic apex = B
  • The difference between the two (if file tip is short of apex: B - A; if file extends beyond apex: A - B)

AWL = EWL + (Difference between file tip and apex)

• Reset rubber stop on file to AWL
• Reinsert to final working length
• Expose a second confirmatory radiograph
• File tip should appear 0.5-1 mm from radiographic apex

1. Radiograph is a 2D image of 3D structure - cannot show buccal/lingual deviations
2. Root apex may not correspond to radiographic apex (anatomical apex vs radiographic apex)
3. Radiation exposure
4. Multiple radiographs needed
5. CDJ not directly visible radiographically
6. Superimposition of anatomical structures (e.g., maxillary sinus, zygomatic arch)
7. Patient cooperation required

• Measures electrical impedance to locate CDJ
• Reduces radiation exposure
• More accurate than radiographic technique alone
• Combined use of EAL + radiograph is the gold standard

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Q.7 Answer any one out of two (1 × 10 = 10 Marks)

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(a) Armamentarium for Access Cavity Preparation. Explain in Detail Access Opening of Maxillary Central Incisor along with Suitable Diagrams (10 Marks)

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• Round bur (no. 2, 4): Initial entry into enamel; remove roof of pulp chamber
• Tapered fissure bur (no. 556, 557, 701): Extend outline form; refine walls
• Safe-ended/end-cutting bur: Remove remaining pulp chamber roof without gouging floor
• Endo-Z bur (non-cutting tip): Safeguard instrument; used to flare and clean access cavity walls without risk to pulpal floor

• Spoon excavator: Remove soft caries and pulp tissue remnants
• DG-16 endodontic explorer (double-ended): Locate canal orifices, feel for calcified canals
• Endodontic probe/pathfinder: Explore canal orifices

• Sodium hypochlorite (NaOCl) 2.5-5.25%: Irrigating syringe; 27-gauge needle; dissolves organic tissue
• Sterile water/saline: For final rinse
• EDTA 17%: Chelating agent to remove smear layer; lubricant during instrumentation

• Rubber dam (dam + clamp + frame): Mandatory for isolation; prevents contamination and aspiration of instruments
• Mirror and explorer: Examination
• Radiographs and viewer
• Electric pulp tester / cold vitality test
• Local anaesthetic (2% lignocaine with 1:80,000 adrenaline)
• Cavity cleaning instruments
• Cotton pellets, paper points
• Mouth mirror, probe

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• The maxillary central incisor has a single root with a single root canal (in most cases)
• Pulp chamber: Located in the crown, wider incisally, narrows toward root
• Pulp horns: Three pulp horns (mesial, middle, distal) in young teeth, prominent in young patients
• Canal: Single, wide in young teeth; may show calcification in older patients
• Apical foramen: Usually at or near radiographic apex; may deviate slightly

• Shape: Triangular (rounded triangle) with the base toward the incisal edge and apex toward the cervical area
• Location: On the lingual (palatal) surface
• Centered on the lingual surface, in the middle third
• Incisally: Extends to within 2 mm of the incisal edge (to access incisal pulp horns)
• Gingivally: Extends to cingulum area
• Mesiodistally: 2-2.5 mm wide
• Outline form mirrors the cross-sectional shape of the pulp chamber

• Apply rubber dam; clamp on tooth (212 clamp or W8A)
• Disinfect the field

• With a round bur (no. 2) in high-speed handpiece, penetrate the lingual surface at the cingulum at approximately 45° to the long axis of the tooth
• Initial penetration: Through enamel, then dentin to enter pulp chamber

• Switch to a tapered fissure bur (no. 556) or Endo-Z bur
• Extend the cavity in a coronal direction toward the incisal edge to access the mesial and distal pulp horns
• The cavity is extended to include all three pulp horns

• Use a no. 4 round bur or end-cutting bur to remove the complete roof of the pulp chamber
• Straight-line access: The instrument should slide freely into the canal without any obstruction from the access walls

• The access cavity walls should taper and guide instruments directly into the canal without deflection
• Use Endo-Z bur to flare and smooth the walls
• The lingual wall may need to be extended slightly incisally to allow straight-line access
• Remove any overhanging enamel

• With DG-16 explorer, locate the single canal orifice at the center of the floor
• In calcified canals, use EDTA + ultrasonic tips

• Irrigate with NaOCl
• Remove all pulp tissue from access cavity

• External outline: Triangular on lingual surface, with rounded corners
• Base of triangle: Toward the incisal edge
• Apex of triangle: Toward the cingulum/gingival area
• Walls: Flared, smooth, converging toward the canal orifice
• Straight-line access: File or reamer inserted into canal should be in line with the long axis of the root

     Incisal edge
          ___
         /   \
        | *** |  <- Pulp horns (3)
        |     |
        |  O  |  <- Canal orifice (single)
        |     |
         \   /
          ---
         Root

     Incisal edge
        _____
       / /_\ \
      | / A \ |   <- Triangular access outline (shaded area)
      |/     \|   Apex of triangle toward cingulum
      |   O   |   <- Canal orifice
      |_______|
      Cingulum

Labial    Lingual
  |       /\  |
  |      /  \ |   <- Access cavity (triangular, on lingual)
  |     / O  \|   O = canal
  |    /______\

1. Perforation: Instrument exits through root surface (most common at cervical area)
2. Ledge formation: Instrument deviates from canal path
3. Inadequate access (missed canal): Insufficient extension, pulp horns not removed
4. Over-extension: Weakens tooth structure
5. Loss of straight-line access: Instrument deflected by cavity wall
6. Gouging of pulpal floor: Use of round bur on floor

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(b) Define and Classify Procedures of Bleaching. Factors Affecting Bleaching. Explain in Detail Walking Bleach Technique (10 Marks)

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• The active agent generates free radicals (reactive oxygen species) through oxidation-reduction reactions.
• These free radicals break down large, complex organic chromophore molecules into smaller, colourless/lighter molecules.
• The process is reversible to some degree and does not remove tooth structure.

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1. In-office (Chair-side) Bleaching:
   • High concentration bleaching agent (30-40% hydrogen peroxide)
   • Activated by light (LED, halogen, plasma arc lamp) or heat
   • Applied by dentist; rubber dam/gingival barrier used
   • Results seen in single visit (1-2 hours)
   • Examples: Zoom! (Philips), Opalescence Boost, BriteSmile
2. Home Bleaching (Dentist-prescribed):
   • Custom-made bleaching tray + 10-22% carbamide peroxide gel (CP) or 3-7% hydrogen peroxide
   • Worn 2-8 hours/day (or overnight for 10% CP)
   • Duration: 2-6 weeks
   • Supervised by dentist
   • Example: Opalescence Take-Home, Nite White
3. Over-the-Counter (OTC) Bleaching:
   • Low concentration products (3-6% HP or <10% CP)
   • Whitening strips (e.g., Crest Whitestrips), whitening toothpastes, paint-on gels, whitening trays
   • Minimal/no professional involvement
   • Less dramatic results
4. In-office followed by home bleaching (Combined technique):
   • Best results; rapid initial improvement + sustained maintenance

1. Walking Bleach Technique (most common; detailed below)
2. In-office (Thermocatalytic) Technique / Heated Bleach:
   • 30-35% hydrogen peroxide placed in access cavity
   • Activated with heat (hot plugger, heated instrument)
   • Risk: External cervical resorption
3. Combined Technique:
   • In-office bleach + walking bleach
4. Inside-Outside Bleaching:
   • Bleaching agent in access cavity AND whitening tray worn simultaneously

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• Extrinsic stains (tea, coffee, tobacco): Respond best - easily removed
• Intrinsic stains (tetracycline, fluorosis, traumatic, endodontic): Variable response
• Mild tetracycline staining: Responds to prolonged bleaching
• Severe tetracycline staining (grey/dark): Poor response; may need veneers/crowns
• Fluorosis: Variable; white spots may become more prominent initially
• Pulpal haemorrhage: Responds well to walking bleach

• Higher concentration = faster but more side effects
• H2O2 penetrates enamel more rapidly than CP
• 10% CP releases ~3.35% H2O2 over 8-10 hours

• Longer exposure = more bleaching effect
• Most active period: First 2-4 hours

• Heat accelerates bleaching reaction (10°C rise doubles reaction rate)
• Risk: Heat may damage pulp if excessive

• Enamel thickness: Thicker enamel reduces penetration
• Dentin permeability: Higher permeability allows better agent penetration
• Age: Older teeth with more secondary dentin = slower bleaching
• Young teeth with open dentinal tubules = faster/better response

• Acidic pH (3.5-5.0) for H2O2 is most effective
• Alkaline environment for sodium perborate-based bleach

• Accelerates breakdown of H2O2; faster results
• LED or plasma arc used for chairside

• In non-vital bleaching: Remove superficial smear layer with EDTA
• Zinc oxide eugenol-based sealers may interfere with bleaching

• Gutta-percha should be removed 2 mm below CEJ to allow bleach access to coronal dentinal tubules

• Inadequate cervical seal = bleaching agent reaches PDL through lateral and accessory canals = External Cervical Resorption (ECR)
• Glass ionomer cement barrier 2 mm coronal to CEJ is mandatory

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• Discoloured non-vital endodontically treated anterior tooth
• Discolouration due to: Pulpal haemorrhage, metallic coronal restorations, residual pulp tissue, incomplete removal of pulp horns

• Incomplete root canal treatment
• Inadequate apical seal
• Internal/external root resorption
• Very thin root walls

• Sodium perborate powder (anhydrous sodium perborate or monohydrate)
• 30% hydrogen peroxide solution (optional; can use distilled water instead)
• Glass ionomer cement (for cervical barrier)
• Cotton pellets
• Temporary filling material (IRM, Cavit, or ZOE)
• Plastic mixing spatula
• Excavator

• Confirm adequate root canal treatment radiographically (well-obturated, no periapical pathology)
• Photograph the tooth for shade comparison
• Record initial shade with shade guide (VITA)
• Inform patient: 2-4 visits over 2-3 weeks; temporary bleaching

• Rubber dam isolation to protect soft tissues from bleaching agent

• Remove the existing filling material from the access cavity using appropriate burs

• Remove gutta-percha from root canal to a level 2 mm below the cemento-enamel junction (CEJ)
• This is critical to allow bleach to access the coronal dentinal tubules
• Use a heated plugger, Gates Glidden drill, or appropriate bur
• Do NOT leave gutta-percha too coronal (ineffective bleaching) or too deep (risk of resorption)

• This is the most critical step to prevent external cervical resorption
• Place 2 mm thick layer of Glass Ionomer Cement (GIC) at the level of CEJ, over the exposed gutta-percha
• This seals the dentinal tubules at the cervical area (where they communicate with the PDL via cementum)
• Allow GIC to set
• Some clinicians use zinc phosphate cement, but GIC is preferred (bonds to dentin, fluoride-releasing)

• Mix sodium perborate powder with:
  • Distilled water/saline: Gentler; lower risk of resorption (Spasser's original)
  • 30% H2O2: More effective (Nutting and Poe) - though distilled water now preferred to reduce ECR risk

• Dry the access cavity with cotton pellets (not paper points - absorb bleach)
• Place the paste/mix of sodium perborate into the pulp chamber with a plastic instrument
• Pack firmly into all pulp horns and recesses
• Place a dry cotton pellet over the paste

• Seal the access cavity with a temporary restoration (IRM, Cavit, or ZOE) - at least 3-4 mm thick
• Do NOT use zinc oxide eugenol directly (eugenol may bleach more aggressively or interfere)
• Instruct patient: Return in 3-7 days

• Remove temporary restoration
• Remove old bleaching agent
• Assess colour change (compare with pre-operative shade)
• If satisfactory improvement: Proceed to final restoration
• If not enough: Repeat steps 6-9 for another cycle
• Usually 2-4 cycles are needed; maximum 4-5 visits

• Once desired shade achieved: Wait 2 weeks before placing final composite (residual H2O2 inhibits polymerization)
• Alternatively, place sodium ascorbate (10%) in cavity for 30 min to neutralize peroxide
• Restore access cavity with composite resin or appropriate material
• Match shade carefully (shade may slightly regress after ceasing bleaching)

• Most serious complication (described by Harrington & Natkin, 1979)
• Bleaching agent + low pH + dental tubules at CEJ → bleach diffuses through cementum → stimulates PDL inflammatory cells → resorption
• Prevention: Adequate cervical GIC barrier 2 mm below CEJ; prefer sodium perborate + water (low H2O2 concentration); don't remove gutta-percha too far
• Management: Stop bleaching; treat resorption defect if detected

• Transient post-operative sensitivity
• Managed with fluoride application

• Shade darkens over months/years
• Top-up bleaching as needed

• Chalky, opaque appearance
• Avoid by monitoring shade and not over-treating

• Bleaching agent in access cavity + home bleaching tray worn simultaneously
• Faster results in severe discolouration

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Quick Reference - What Was Answered

SECTION B

SECTION C