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COMPLETE ANSWERS: ORAL MEDICINE & DENTAL RADIOLOGY

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PART 1: ORAL MEDICINE & ORAL PATHOLOGY

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1. Angular Chelitis (Angular Stomatitis)

• Local factors: Decreased vertical dimension (over-closure), drooling of saliva, ill-fitting dentures
• Microbial: Candida albicans (most common), Staphylococcus aureus, beta-hemolytic streptococci
• Nutritional deficiencies: Iron, riboflavin (B2), pyridoxine (B6), folic acid deficiency
• Systemic: Immunosuppression (HIV/AIDS), diabetes mellitus, xerostomia

• Erythema, fissuring, and cracking at oral commissures
• Crusting with occasional bleeding
• May be unilateral or bilateral

• Antifungal cream (clotrimazole, miconazole) if Candida involved
• Correct nutritional deficiencies
• Correct vertical dimension, replace ill-fitting dentures
• Topical antibacterial if bacterial origin

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2. Stomatitis Medicamentosa

• Antibiotics (penicillin, streptomycin, sulfonamides)
• Barbiturates, salicylates
• Phenytoin, gold salts, bismuth
• NSAIDs, antiepileptics

• Diffuse erythema of oral mucosa
• Vesicle and bullae formation
• Ulceration
• May be accompanied by skin lesions (erythema multiforme, Stevens-Johnson syndrome)
• Burning, pain

• Withdraw offending drug
• Systemic corticosteroids in severe cases
• Supportive therapy: antiseptic mouthwashes, analgesics
• Antihistamines

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3. Gardner's Syndrome

1. Multiple colonic polyps (adenomatous - high malignant potential)
2. Osteomas of the jaw and skull
3. Multiple skin cysts (epidermoid/sebaceous cysts) and fibromas

• Multiple osteomas of mandible and maxilla (most prominent at angle of mandible)
• Supernumerary teeth, odontomas
• Impacted permanent teeth
• Multiple compound odontomas

• Dense radiopaque masses (osteomas) in jaw
• Multiple impacted/supernumerary teeth

• Colectomy (mandatory due to malignant potential)
• Regular colonoscopy surveillance
• Dental management of osteomas/supernumerary teeth

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4. Corticosteroids (in Oral Medicine)

• Bind glucocorticoid receptors → inhibit phospholipase A2 → decrease arachidonic acid → reduce prostaglandin and leukotriene synthesis
• Reduce vascular permeability, inhibit leukocyte migration
• Immunosuppressive effects

• Recurrent aphthous stomatitis (RAS)
• Lichen planus
• Pemphigus vulgaris, mucous membrane pemphigoid
• Erythema multiforme
• Oral manifestations of systemic autoimmune diseases

• Prednisolone (most common): 0.5-1 mg/kg/day
• Dexamethasone, betamethasone (for severe cases)
• Triamcinolone acetonide injection (intralesional)

• Long-term: Cushing's syndrome, osteoporosis, adrenal suppression
• Increased susceptibility to infection (especially Candida)
• Hyperglycemia, hypertension, peptic ulcer
• Oral: Candidiasis, delayed healing

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5. Topical Corticosteroids (in Oral Medicine)

• First-line for recurrent aphthous ulcers, lichen planus, pemphigoid, erythema multiforme

• Creams, gels, ointments, mouthwashes, pellets, sprays

• Oral candidiasis (most common)
• Mucosal atrophy with prolonged use
• Delayed healing

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6. Immunofluorescence Test

• Detects immunoglobulins/complement deposits in tissue biopsy
• Tissue + fluorescent-labeled antibodies → examine under UV
• Used to diagnose: Pemphigus vulgaris, pemphigoid, lupus, lichen planus

• Detects circulating antibodies in serum
• Patient serum applied to substrate tissue → fluorescent anti-human antibody added

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7. Antibiotics in Oral Medicine

• Odontogenic infections (cellulitis, abscess)
• Acute necrotizing ulcerative gingivitis (ANUG)
• Pericoronitis
• Osteomyelitis
• Prevention of infective endocarditis

• Culture and sensitivity if possible
• Complete full course
• Reserve broad-spectrum for severe cases

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8. Topical Analgesics

• Benzocaine (2-20%): Ester local anesthetic; gels, creams, sprays
• Lidocaine (2-5%): Gel, spray, ointment
• Tetracaine (0.5-2%)

• Carboxymethylcellulose (CMC) - forms protective film
• Triamcinolone in Orabase - steroid + protective base

• Benzydamine hydrochloride (Difflam) 0.15% rinse - anti-inflammatory + analgesic
• Choline salicylate gel (Bonjela)

• Capsaicin (desensitizes substance P)

• Aphthous ulcers, herpetic ulcers, traumatic ulcers
• Post-extraction pain
• Mucosal pain from dentures, chemotherapy mucositis

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9. Peutz-Jeghers Syndrome

1. Multiple hamartomatous polyps in GI tract (small intestine most common)
2. Mucocutaneous melanotic pigmentation

• Melanotic macules (brown-black spots) on lips (especially lower lip), buccal mucosa, gingiva, hard palate
• Perioral skin (most characteristic)
• Also on fingers, toes, periorbital skin

• Multiple small (1-5 mm) flat, brown-black macules
• Present from birth/early childhood
• No treatment needed for pigmentation itself
• Fades at puberty (skin lesions fade; oral lesions persist)

• Intestinal obstruction/intussusception from polyps
• Increased risk of GI cancers, pancreatic, breast, ovarian cancers

• Regular endoscopic surveillance
• Genetic counseling
• Treatment of complications

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10. Trismus [2 Marks]

• Pericoronitis (3rd molar region)
• Dental abscess, cellulitis, Ludwig's angina
• Trauma (fractures of condyle, zygomatic arch, coronoid process)
• Post-injection trismus (inferior alveolar nerve block - pterygoid muscle injury/hematoma)
• TMJ ankylosis
• Post-radiation fibrosis
• Oral submucous fibrosis (OSMF)

• Tetanus (lockjaw - most severe)
• Tetany
• Hysteria
• Meningitis (neck stiffness + trismus)

• Treat underlying cause
• Physiotherapy (jaw exercises, Therabite appliance)
• Corticosteroids for inflammatory trismus
• Muscle relaxants (diazepam) for spasm
• Surgical: coronoidectomy in severe ankylosis

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11. Causes for Bleeding in the Oral Cavity

• Trauma (laceration, extraction socket)
• Periodontal disease (gingivitis, periodontitis)
• Dental procedures (extraction, surgery)
• Ulcers, erosions
• Neoplasms (benign - hemangioma; malignant - carcinoma)
• Vascular lesions (hemangioma, AVM)

• Thrombocytopenic purpura (ITP, TTP)
• Aplastic anemia, leukemia
• Aspirin/NSAID use

• Hemophilia A (Factor VIII deficiency), Hemophilia B (Factor IX deficiency)
• Von Willebrand disease
• Liver disease (decreased clotting factors)
• Anticoagulant therapy (warfarin, heparin, DOACs)
• Vitamin K deficiency

• Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu)
• Scurvy (Vitamin C deficiency)
• Ehlers-Danlos syndrome

• Anticoagulants (warfarin, heparin)
• Antiplatelets (aspirin, clopidogrel)
• NSAIDs

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12. Exfoliative Cytology

1. Clean the lesion with wet gauze
2. Scrape lesion firmly with wooden spatula or cytology brush
3. Spread on glass slide
4. Fix immediately (95% ethyl alcohol or spray fixative)
5. Stain: Papanicolaou stain (most common), Giemsa, H&E
6. Examine under microscope

• Class I: Normal cells
• Class II: Atypical but benign
• Class III: Intermediate (suspicious)
• Class IV: Strongly suspicious for malignancy
• Class V: Malignant cells

• Simple, non-invasive, painless
• Repeated sampling possible
• Screening tool

• Cannot determine invasion depth
• False negatives possible (20-30%)
• Cannot replace biopsy for definitive diagnosis
• Cannot detect submucosal lesions

• Screening for oral cancer, leukoplakia
• Diagnosing herpes simplex (multinucleated giant cells, Tzanck cells)
• Pemphigus (acantholytic cells/Tzanck cells)
• Candidiasis (fungal hyphae)
• Follow-up of treated lesions

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13. Halitosis

1. Genuine halitosis - True physiologic or pathologic bad breath
2. Pseudo-halitosis - Patient perceives it, others don't
3. Halitophobia - Persistent belief despite treatment

• Poor oral hygiene
• Periodontal disease (most important oral cause)
• Tongue coating (dorsal tongue - volatile sulfur compounds/VSCs)
• Dental caries, pericoronitis
• Xerostomia (reduced salivary flow)
• Impacted food
• Poor-fitting dentures
• Oral ulcerations/infections

• Respiratory: Sinusitis, tonsillitis, bronchiectasis, lung abscess
• GI: GERD, H. pylori gastritis
• Systemic: Diabetic ketoacidosis (fruity/acetone), renal failure (uremic/ammonia), liver failure (fetor hepaticus)
• Drugs: Metronidazole, alcohol

• Treat underlying cause
• Oral hygiene instruction, tongue scraping
• Chlorhexidine mouthwash (0.2%)
• Zinc-containing products (neutralize VSCs)
• Regular dental checkups

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14. Clindamycin

• Aerobic gram-positive cocci: Streptococci, Staphylococci (MSSA)
• Anaerobes: Bacteroides, Fusobacterium, Peptostreptococcus (excellent)
• NOT effective against gram-negative aerobes

• Penicillin allergy patients (alternative to amoxicillin)
• Odontogenic infections (excellent bone penetration)
• Osteomyelitis of jaw
• Endocarditis prophylaxis in penicillin allergy (600 mg single dose, 30-60 min before procedure)
• Periapical abscess, cellulitis

• Adults: 150-300 mg every 6 hours (oral); 600-900 mg IV every 8 hours
• Endocarditis prophylaxis: 600 mg single oral dose

• Antibiotic-associated pseudomembranous colitis (Clostridium difficile) - most serious
• Diarrhea, nausea, vomiting
• Metallic taste, glossitis

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15. Brachytherapy

• Interstitial brachytherapy: Radioactive seeds/needles implanted within tumor tissue
• Intracavitary: Source placed in body cavity
• Surface/Mold: Custom carrier placed on tumor surface

• Iridium-192 (Ir-192) - most common for oral cavity
• Cesium-137 (Cs-137)
• Iodine-125 (I-125) - seeds
• Palladium-103, Radium-226 (historical)

• Early oral cavity carcinomas (tongue, floor of mouth, lip)
• Adjuvant after surgery
• Recurrent tumors
• Small T1/T2 lesions

• High local dose
• Spare surrounding tissues
• Outpatient in some cases

• Radiation hazard to operator/family
• Risk of osteoradionecrosis
• Requires skilled implantation

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16. Antibiotics in Dentistry

1. Acute dentoalveolar abscess with systemic signs: Amoxicillin 500 mg TDS × 5 days
2. ANUG: Metronidazole 400 mg TDS × 5 days (drug of choice)
3. Pericoronitis: Amoxicillin + Metronidazole combination
4. Osteomyelitis: Clindamycin or Amoxicillin-Clavulanate (long course 4-6 weeks)
5. Infective endocarditis prophylaxis: Amoxicillin 2 g single dose (or Clindamycin 600 mg if penicillin allergy)
6. Implant placement: Amoxicillin 2 g pre-op + 500 mg TDS × 3 days (controversial)

• Patients with prosthetic heart valves
• Previous infective endocarditis
• Congenital heart disease (specific types)
• Immunocompromised patients

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17. Lip Prints (Cheiloscopy)

• Type I: Clear-cut grooves running vertically across the lip
• Type I': Vertical grooves not running full length
• Type II: Branched grooves (fork-shaped)
• Type III: Intersecting/crossed grooves
• Type IV: Reticular pattern
• Type V: Undetermined/other patterns

1. Apply lipstick/lip rouge
2. Press lips on paper/glass
3. Lift with cellophane tape or photograph
4. Preserve as evidence

• Identify individuals at crime scenes (glasses, cigarette butts, envelopes)
• Sex determination (Type I and I' more common in females)
• Identify deceased in mass disasters

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18. Functions of Maxillary Sinus

1. Humidification and warming of inspired air: Large air space + mucosa
2. Resonance/Voice quality: Acts as resonating chamber for speech
3. Lightening of skull weight: Air-filled space reduces skull mass
4. Immune defense: Mucociliary clearance of debris and microorganisms
5. Thermal insulation: Protects brain from extreme temperatures
6. Mucus production and drainage: Drains into middle meatus via ostium (superior-medial wall, a disadvantage as drainage is against gravity)
7. Olfactory role: Minor contribution
8. Cushioning/shock absorber: Absorbs impact forces to protect orbit and brain
9. Accommodation for dental roots: Floor provides space for maxillary posterior tooth roots (especially 2nd premolar, 1st and 2nd molars)

• Dental infections may spread to sinus (odontogenic sinusitis)
• Root tips may be displaced into sinus during extraction
• Sinus lift procedure for dental implants

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19. Four Names of Antibiotics with Dosage

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20. Bite Mark Analysis

• On victim's skin (assault, sexual crimes)
• On food items (cheese, chocolate, fruit)
• On inanimate objects (pens, steering wheel)

• Size, shape, and arrangement of individual teeth marks
• Distance between canines (arch width)
• Rotations, missing teeth, fractures, restorations
• Tooth size and shape

1. Photography: Scale photos (ABFO No. 2 scale) at right angles
2. Salivary swabs: DNA analysis from bite mark
3. Impressions: Silicone impressions of suspect's dentition
4. Overlay analysis: Computer-generated overlay of suspect's dental casts compared to bite mark
5. UV photography: Reveals healing bite marks
6. Scanning electron microscopy: Fine detail analysis

• American Board of Forensic Odontology (ABFO) guidelines
• Document before treatment
• Chain of custody maintained

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21. Biopsy

• Removal of representative portion of lesion
• Used for large lesions (>2 cm), suspicious malignancy, ulcerated/necrotic lesions
• Preferred for most oral lesions

• Complete removal of entire lesion with margin of normal tissue
• Used for small lesions (<1-1.5 cm), benign-appearing lesions (fibroma, small mucocele)

• Circular punch instrument used
• Skin or mucosal lesions

• Needle inserted into lesion, cells aspirated
• Salivary gland tumors, lymph nodes, neck masses

• Core of bone removed
• Intra-osseous lesions

• Core of tissue using cutting needle

• Any unexplained mucosal lesion persisting >2 weeks
• Leukoplakia, erythroplakia
• Suspicious lesions (ulcers, lumps)
• Before definitive treatment

• Necrotic/ulcerated center (take from edge)
• Avoid crossing anatomical boundaries
• Avoid critical structures (major vessels, nerves)

• Fix in 10% neutral buffered formalin
• Stain: H&E (routine), special stains as needed

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22. Wound Certificate

1. Name, age, sex, address of patient
2. Date and time of examination
3. Description of each injury:
   • Type (abrasion, contusion, laceration, incised wound, burn)
   • Site and dimensions (length × width × depth)
   • Shape, margins, floor, condition
   • Age estimation (fresh, old, healing)
4. Opinion on nature (simple/grievous) and cause (blunt/sharp)
5. Fitness for interrogation
6. Doctor's name, signature, designation, registration number, hospital stamp

• Abrasion: Superficial scraping of skin
• Contusion (bruise): Blunt trauma, hemorrhage under skin
• Laceration: Tearing of tissue (blunt trauma)
• Incised wound: Clean cut from sharp object
• Puncture/stab wound: Narrow deep wound

• Establishes nature of assault
• Evidence in court
• Documentation of injury severity
• Used in police investigation

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23. Role of Dentist in Mass Disasters

• Mass casualty incidents (air crashes, bombings)
• Natural disasters (earthquake, tsunami, fire)
• Wars, terror attacks

• Teeth are the hardest structures in the body
• Resistant to fire, decomposition, immersion
• Dental records are unique to each individual
• Dental work (restorations, crowns, implants, extractions) creates permanent records

1. Ante-mortem (AM) data collection:
   • Collect existing dental records, radiographs, study models from treating dentist
   • Dental charts, photographs
2. Post-mortem (PM) examination:
   • Examine jaws and teeth of deceased
   • Radiographs, photographs, charting
   • Fingerprints may be destroyed; dental ID possible
3. Comparison:
   • Match AM and PM records using Interpol DVI Forms
   • Use dental charting, bitewing radiographs, panoramic films, crown morphology
4. DNA Analysis:
   • Pulp tissue contains DNA, useful when dental records unavailable
5. Age Estimation:
   • Particularly useful for unidentified bodies
   • Eruption patterns in children, wear/root changes in adults
6. Other roles:
   • Bite mark analysis
   • Identification of torture victims
   • Documentation of child abuse

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PART 2: DENTAL RADIOLOGY

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1. Production of X-rays

• Cathode (negative electrode): Tungsten filament in focusing cup
• Anode (positive electrode): Tungsten target on copper block
• Glass envelope: High vacuum

1. Thermionic emission: Filament heated by low-voltage current → emits electrons (cloud = space charge)
2. Acceleration: High voltage (kVp) applied across tube → electrons accelerate from cathode to anode
3. X-ray production at anode by two mechanisms:

• Electrons decelerate when passing near tungsten nucleus
• Kinetic energy converted to X-ray photons
• Continuous spectrum of energies
• ("Brems" = braking in German)

• Electron ejects inner-shell electron from tungsten
• Outer electron falls into vacancy
• Energy difference released as X-ray photon of specific energy
• Only produced above certain kV threshold (~70 kV for tungsten K-shell)

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2. Hazards of Radiation

• Acute: Radiation sickness, erythema, epilation, GI disturbances (high doses)
• Chronic/Late: Radiation caries, xerostomia, osteoradionecrosis, cataracts
• Carcinogenesis: Leukemia, thyroid cancer, skin cancer, salivary gland tumors

• Mutation in germ cells → affect offspring
• Deletion/alteration of DNA in gonads

• Thyroid: Carcinoma
• Lens of eye: Cataracts
• Bone marrow: Leukemia
• Salivary glands: Tumors
• Skin: Dermatitis, carcinoma

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3. Radiation Effects on Oral Tissues

• Mucositis (radiation stomatitis): Most acute complication; onset at 1-2 weeks; erythema → pseudomembrane → ulceration
• Heals 3-4 weeks after completion of RT

• Radiation sialadenitis
• Xerostomia (dry mouth): Most common permanent complication; begins 1st week; progressive
• Altered saliva: More viscous, acidic, reduced IgA, altered enzymes

• Radiation caries: Characteristic at cervical margins; brown discoloration; affects all surfaces; rapid progression
• Due to xerostomia + altered saliva + diet changes
• Enamel hypoplasia if radiation during tooth development

• Osteoradionecrosis (ORN): Most serious late complication
• Hypoxic, hypovascular, hypocellular tissue
• Mandible > maxilla (denser, less vascular)
• Risk highest >60 Gy

• Ageusia/dysgeusia: Loss/alteration of taste; begins ~2 weeks into RT; may recover partially

• Trismus: Fibrosis of masticatory muscles and TMJ; late complication

• Endarteritis obliterans: Narrowing of small vessels; contributes to ORN

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4. X-ray Machine/Tube - Functions of Each Component

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5. Tube Current and Tube Voltage

• Controls number of electrons produced (electron cloud density)
• Determines quantity of X-rays (number of photons)
• Increased mA → more electrons → more X-rays → increased film density/darkness
• Dental units: 7-15 mA
• Higher mA = shorter exposure time possible for same dose

• Controls the speed/energy of electrons
• Determines quality (penetrating power/energy) of X-rays
• Increased kVp → higher energy photons → greater penetration → reduced contrast (more gray scale)
• Dental units: 60-90 kVp (periapical: 60-70 kVp; OPG: 73-85 kVp)
• Higher kVp → shorter wavelength, higher frequency X-rays

• mA × time (seconds) = mAs (milliampere-seconds) = total radiation exposure
• kVp primarily affects beam quality/contrast

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6. Collimation

• Reduce patient radiation dose (most effective dose reduction method)
• Reduce scatter radiation (improves image quality)
• Limit beam to film/sensor size

• Round/circular collimator: Traditional; 2.75 inch (70 mm) diameter
• Rectangular collimator: Preferred; matches film size (periapical: 35×41 mm or 32×38 mm); reduces dose by ~60% compared to round
• Long/short cone (PID - Position Indicating Device): Determines source-to-skin distance; longer = less beam divergence, more parallel beam

• ~60% dose reduction compared to round
• Recommended by SEDENTEX and ICRP guidelines

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7. Filtration

• Removes soft/low-energy rays that cannot penetrate to reach film
• Reduces patient dose (skin dose especially)
• Hardens/increases average energy of beam

• From glass envelope, insulating oil, tube housing
• Equivalent to ~0.5-1.0 mm aluminum

• Aluminum discs placed in beam path
• Required minimum: 1.5 mm Al for <70 kVp; 2.5 mm Al for 70+ kVp (FDI/regulatory requirements)

• Increases mean photon energy
• Reduces intensity (fewer photons)
• Better patient protection

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8. Radiation Protection of the Operator

1. Distance: Most effective protection
   • Inverse square law: Stand ≥6 feet (1.8 m) from X-ray source
   • Stand at 90°-135° to the primary beam direction
   • Never hold film for patient
2. Shielding:
   • Lead-lined walls (≥1.6 mm lead equivalent)
   • Lead glass windows in control booth
   • Lead apron for operator if staying in room (not usually required at 6 feet distance)
3. Beam Direction:
   • Never stand in primary beam
   • Safe zone: ≥6 ft away, behind primary beam, 90°-135° to beam
4. Monitoring:
   • Radiation badge (dosimeter): Film badge, TLD (thermoluminescent dosimeter), OSL (optically stimulated luminescence)
   • Must be worn at chest level
   • Monitored monthly/quarterly
5. Equipment:
   • Rectangular collimator (reduces scatter)
   • Regular equipment quality assurance testing
   • Lead housing checks

• Occupational workers: 50 mSv/year (5 rem/year) whole body
• Pregnant radiation workers: 5 mSv (0.5 rem) during pregnancy
• Public: 1 mSv/year

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9. Radiolysis of Water

• X-rays interact with water (which constitutes 70-80% of body cells)
• Free radicals produced which damage DNA

1. X-ray photon → ejects electron from water molecule H₂O → H₂O⁺ + e⁻
2. H₂O⁺ → H⁺ + OH• (hydroxyl radical - most damaging)
3. e⁻ + H₂O → H₂O⁻ → OH⁻ + H• (hydrogen radical)
4. Also: H₂O → H• + OH•

• OH• (hydroxyl radical): Highly reactive, oxidizing
• H• (hydrogen radical)
• H₂O₂ (hydrogen peroxide): Cytotoxic
• HO₂• (hydroperoxyl radical)

• Indirect effect of radiation (vs. direct ionization of DNA)
• OH• attacks DNA strands → single-strand and double-strand breaks
• Indirect effect accounts for ~70% of radiation damage
• Presence of oxygen enhances damage (oxygen effect)

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10. Radiation Caries

• Radiation → xerostomia (reduced saliva)
• Saliva changes: Reduced flow, increased viscosity, decreased pH, reduced buffering capacity, reduced antimicrobial proteins (IgA, lysozyme, lactoferrin)
• Altered oral flora: Increase in S. mutans, Lactobacillus, C. albicans
• Reduced salivary flushing → increased plaque
• Direct radiation effect on tooth structure (altered protein matrix)

• Affects cervical margins of all teeth (including cusps, incisal edges)
• Brown-black discoloration
• Rapid, circumferential decay
• Hard to distinguish as "rampant caries" pattern
• Distinct from normal caries pattern

• Pre-radiation: Dental clearance (extract hopeless teeth)
• Daily fluoride applications (custom trays, 1% NaF gel)
• Regular dental review
• Saliva substitutes, pilocarpine for xerostomia
• Good oral hygiene

• Fluoride remineralization
• Avoid extractions post-radiation (risk of ORN)
• If extraction needed: Antibiotic prophylaxis + hyperbaric oxygen (HBO) therapy

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11. Factors Controlling X-ray Beam

1. Tube voltage (kVp): Determines beam quality (penetrating power); higher kVp = shorter wavelength, greater penetration
2. Tube current (mA): Determines quantity (number of photons)
3. Exposure time: Together with mA gives total exposure (mAs)
4. Filtration: Removes low-energy photons, hardens beam
5. Collimation: Limits beam size/shape
6. Focal spot size: Smaller focal spot = sharper image but more heat
7. Target-to-film distance (TFD): Greater TFD = less beam divergence (paralleling technique uses longer TFD)
8. Anode-cathode axis: Heel effect; intensity greater on cathode side
9. Rectification: Full-wave rectification gives more consistent beam

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12. Effects of Radiation on Teeth

• Enamel hypoplasia/hypomineralization
• Microdontia (stunted root development)
• Incomplete root formation
• Abnormal crown morphology
• Ankylosis

• Radiation caries (see above)
• Dentinal changes: Reduced dentin formation, pulp calcification
• Pulp changes: Reduced vascularity, fibrosis, necrosis possible

• Altered microstructure
• Increased porosity
• Reduced hardness with radiation doses >30 Gy

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13. Effects of Radiation on Salivary Glands

• Radiation sialadenitis
• Swelling, pain, tenderness of glands
• Initial parotid swelling within 24-48 hours

• Xerostomia: Most significant chronic effect
  • Major salivary glands (parotid most sensitive) atrophy → fibrosis
  • Parotid (serous, more radiosensitive) affected > submandibular/sublingual
  • Threshold: ~25-30 Gy
  • Severe reduction: >50-60 Gy → permanent xerostomia
• Sialorrhea: Occasionally, viscous secretion perceived as excessive
• Salivary composition: Reduced pH, reduced buffering, reduced IgA, lysozyme
• Increased risk of salivary gland tumors (long-term radiation carcinogen)

• Pilocarpine (muscarinic agonist): Stimulates residual gland function; 5 mg TID
• Saliva substitutes (methylcellulose-based)
• Good oral hygiene, fluoride therapy
• Intensity-modulated radiation therapy (IMRT): Spares parotid gland

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14. Inverse Square Law [2 Marks]

• Doubling the distance reduces intensity to one-quarter
• Operators should stand ≥6 feet (1.8 m) from tube to reduce exposure
• Explains why standing far from tube is effective protection
• Used to calculate exposure adjustments when changing TFD

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15. Scattered Radiation

• Compton scatter (incoherent): Most important in diagnostic radiology; electron ejected, photon deflected with reduced energy; responsible for most scatter
• Coherent (Classical/Thomson) scatter: Low energy; photon deflected without energy loss; wavelength unchanged; no ionization

• Reduces image contrast and definition (image fog/greyness)
• Increases patient dose
• Radiation hazard to operator

• Collimation (most effective): Limits primary beam size → less tissue irradiated
• Grids: Remove scatter before it reaches film
• Filtration: Hardens beam
• Fast films/sensors: Shorter exposure
• Lead aprons on patient

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16. Roentgen (R)

• Roentgen (R): Exposure (ionization in air)
• Rad: Absorbed dose (energy deposited per gram of tissue); SI = Gray (Gy); 1 Gy = 100 rad
• Rem: Equivalent dose (biological effect); SI = Sievert (Sv); 1 Sv = 100 rem
• Curie (Ci): Activity of radioactive source; SI = Becquerel (Bq)

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17. Importance of Collimators

1. Primary function: Restrict X-ray beam to area of interest
2. Dose reduction: Rectangular collimation reduces patient dose by ~60% compared to round
3. Scatter reduction: Less tissue irradiated → less scatter → better image quality
4. Improved image contrast and definition
5. Protects surrounding tissues (thyroid, lens of eye)
6. Rectangular collimator recommended for periapical radiography (matches film size)
7. Part of equipment required by radiation protection guidelines

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18. Interaction of X-rays with Matter [4M/2M]

1. Coherent (Classical/Thomson) Scattering:
   • Low energy X-rays; no ionization
   • Photon deflected without energy loss
   • Minor importance in dental radiology
2. Photoelectric Effect:
   • Photon absorbed by inner-shell electron → electron ejected (photoelectron)
   • Photon completely absorbed
   • Characteristic X-rays may be emitted as outer electrons fill vacancy
   • Predominant at lower kV (<50 kVp)
   • Responsible for differential absorption (soft tissue vs bone contrast)
   • Greater in high-Z materials (bone, iodine contrast)
   • Most diagnostically important interaction
3. Compton Scattering (Incoherent):
   • Photon ejects outer-shell electron (recoil electron)
   • Photon deflected with reduced energy
   • Predominant in diagnostic radiology range (50-150 kVp)
   • Primary source of scatter radiation
   • Hazard to operator
4. Pair Production:
   • Occurs at high energies >1.02 MeV; not relevant in dental radiography
   • Photon → positron + electron
5. Photodisintegration:

   • 10 MeV; not relevant in dental radiology

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19. Coherent (Classical) Scattering

• Also called Rayleigh or Thomson scattering
• Photon of low energy (<20 keV) interacts with tightly bound atom
• Atom absorbs photon energy → excited state → re-emits photon in different direction
• No energy transfer to matter
• Wavelength unchanged
• No ionization (not biological significance)
• Contributes to scatter fog
• Primarily at lower photon energies

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20. Dosimetry

• Absorbed dose: Gray (Gy); 1 Gy = 1 J/kg tissue; older unit = rad (1 Gy = 100 rad)
• Equivalent dose: Sievert (Sv) = Gy × radiation weighting factor (WR); older = rem
• Effective dose: Sievert (Sv) = equivalent dose × tissue weighting factor; accounts for radiosensitivity of different tissues

• X-rays, gamma: WR = 1
• Protons: WR = 2
• Alpha particles: WR = 20
• Neutrons: WR = 5-20 depending on energy

• Film badge
• TLD (thermoluminescent dosimeter) - gold standard
• OSL (optically stimulated luminescence)
• Ionization chamber (in physics labs)
• Geiger-Müller counter

• Single periapical: ~0.01-0.03 mSv effective dose
• FMX (full mouth series): ~0.03-0.17 mSv
• OPG: ~0.01-0.02 mSv
• CBCT: ~0.005-0.65 mSv (varies widely by protocol)

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21. TLD - Thermoluminescent Dosimeter

• Lithium fluoride (LiF: Mg, Ti) - most common; tissue equivalent
• Lithium borate (Li₂B₄O₇): More tissue equivalent
• Calcium fluoride (CaF₂)
• Calcium sulfate

1. Irradiate TLD material → electrons trapped in crystal lattice defects
2. Store until ready to read
3. Heat TLD (to 200-300°C) → electrons released → emit light (thermoluminescence)
4. Light measured by photomultiplier tube → converted to dose reading
5. After reading, TLD is reset (re-annealed) and reusable

• Accurate, reproducible
• Reusable
• Wide dose range
• Tissue equivalent materials available
• Small size (can be placed intraorally)
• Stable - can be stored for months before reading

• Requires heating to read (destructive readout)
• Expensive reader
• Requires calibration

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22. Focal Trough and Focal Spot

• Small area on anode tungsten target where electrons strike
• The source of X-ray production
• Two sizes: actual focal spot (physical area) and effective focal spot (projected area toward patient; smaller due to anode angle = "line focus principle")
• Smaller effective focal spot = sharper image (less geometric unsharpness)
• But smaller focal spot = more heat per unit area = limited heat loading
• Dental units: ~0.4-0.8 mm focal spot

• Also called image layer, focal layer, or tomographic layer
• The three-dimensional curved zone in which structures are in focus on a panoramic radiograph
• Shaped to approximate the dental arches
• Structures within the focal trough appear sharp; outside appear blurred
• Defined by the rotation center and film movement system
• Width: ~25-30 mm
• Importance: Patient must be positioned correctly so teeth fall within focal trough

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23. Panoramic Radiograph (OPG - Advantages, Limitations, Principles)

• Tomographic technique - only focal trough layer is in focus
• X-ray tube and film/sensor rotate in opposite directions around patient
• Patient remains stationary
• Produces single image of both dental arches, TMJ, maxillary sinuses

1. Large area of anatomy in single image
2. Low radiation dose (~0.01-0.02 mSv effective dose)
3. Patient cooperation easier (no intraoral placement)
4. Good for edentulous patients, trismus, needle-phobic patients
5. Shows pathology: cysts, tumors, fractures, impacted teeth, bone conditions
6. Shows both TMJs and maxillary sinuses
7. Quick procedure

1. Magnification (average 1.2-1.3×; not uniform throughout image)
2. Superimposition of cervical spine in some areas
3. Ghost images (artifact from contralateral structures)
4. Focal trough positioning errors common
5. Not ideal for detecting caries, early periodontal disease
6. Less geometric accuracy than periapical films
7. Lower resolution than intraoral films
8. Cannot visualize multiple planes

• Based on tomographic layering using focal trough
• Movements: single center rotation (older) or multiple rotation centers (modern, better for arch shape)

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24. Faulty Radiographs and Their Rectification

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25. Intraoral Periapical (IOPA) Radiograph - Techniques

• Principle: X-ray beam directed perpendicular to bisector of angle formed between long axis of tooth and film plane
• Based on rule of isometry (Cieszynski's rule): two triangles sharing one side are equal if two angles are equal
• Advantages: Can use standard film holders; no special equipment; useful when palate is shallow
• Disadvantages: Image distortion (elongation or foreshortening more likely); variable horizontal angulation errors; less reproducible

• Principle: Film/sensor placed parallel to long axis of tooth; beam directed at right angles to tooth and film
• Film placed farther from tooth (in center of mouth); longer target-to-film distance (>16 inches) to compensate for magnification
• Advantages: Less distortion; more reproducible; better visualization of alveolar bone level; rectangular collimation possible
• Disadvantages: Requires film holder; patient cooperation; not possible in shallow palate/floor of mouth; initial discomfort

• Periapical pathology (abscess, granuloma, cyst)
• Root morphology assessment
• Endodontic therapy (working length, quality check)
• Periodontal bone levels
• Pre- and post-extraction assessment
• Assessment of unerupted/impacted teeth

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26. Intraoral Radiographic Techniques (Complete)

1. Periapical (IOPA) - as above
2. Bitewing (BW) - see below
3. Occlusal - see below

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27. Dental X-ray Film / Composition / Latent Image Formation

1. Protective overcoat (gelatin)
2. Emulsion (both sides for dental film = double emulsion): silver halide (AgBr mainly, ~95-99% AgBr + small AgI) crystals in gelatin
3. Adhesive layer
4. Film base (polyester/cellulose acetate - tinted blue or clear)
5. Adhesive layer (opposite side)
6. Emulsion (second side)
7. Protective overcoat

• Outer plastic wrapper (moisture-proof)
• Black paper (light-proof)
• Film
• Lead foil backing (absorbs scatter, prevents backscatter fog; causes herringbone pattern if reversed)

1. X-ray photons (or light photons) strike silver halide crystals in emulsion
2. Energy absorbed → electrons released (photoelectric effect)
3. Electrons migrate to sensitivity speck (silver sulfide impurities/crystal defects)
4. Sensitivity speck attracts Ag+ ions → reduced to metallic silver atoms
5. Accumulation of ~2-3 silver atoms at sensitivity speck = latent image center
6. Latent image is invisible until developed

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28. Factors Affecting Quality of Radiograph

1. Density (Optical density/film blackening):
   • Determined by mA, kVp, exposure time, film speed, source-to-film distance, development
   • Optimal: 0.3-2.0 OD
2. Contrast:
   • Difference in density between areas
   • Determined by kVp (lower kVp = higher contrast = short scale/black and white)
   • Also affected by: subject contrast (tissue differences), film contrast, development
3. Sharpness/Definition:
   • Affected by: focal spot size (smaller = sharper), patient movement, screen/film contact, film grain
   • Penumbra/geometric unsharpness depends on focal spot size, object-film distance, focal-object distance
4. Magnification:
   • Increases with longer object-to-film distance
   • Decreases with longer focal-to-film distance
5. Geometric Distortion:
   • Elongation/foreshortening from incorrect angulation
   • Overlapping from incorrect horizontal angulation
6. Film Speed (ISO/ASA):
   • D-speed, E-speed, F-speed (fastest, least dose)
   • Faster film = less exposure needed = reduced dose
7. Latitude:
   • Range of exposures that produce diagnostically acceptable densities
   • Wider latitude = more forgiving of exposure errors
   • Higher kVp = wider latitude (lower contrast)

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29. Composition of Developer and Fixer

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30. Normal Radiographic Anatomy of Maxilla

• Alveolar bone (cortical + cancellous)
• Anterior nasal spine
• Nasal fossa (radiolucent)
• Nasal septum (radiopaque midline)
• Inferior turbinate (radiopaque shadow in nasal floor)
• Maxillary sinus (large radiolucent space; floor, walls)
• Incisive foramen (midline oval radiolucency between central incisors)
• Incisive/nasopalatine canal
• Median palatine suture (midline radiolucent line)
• Zygomatic process of maxilla (inverted J/U shape superimposed over molar region)
• Zygomatic bone/arch

• Tooth crowns, roots, pulp chamber, root canals
• Lamina dura (dense white line around root)
• Periodontal ligament space (PDL) - thin radiolucent line around root

• Soft tissue of nose
• Lip (in anterior periapicals)

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31. Water's View (Occipitomental Projection)

• PA projection
• Head tilted back so orbitomeatal line makes 45° with horizontal
• Midsagittal plane perpendicular to film
• Chin touching cassette; nose raised from cassette

• Directed horizontally (perpendicular to midsagittal plane)
• From posterior to anterior

• Maxillary sinuses (best view)
• Orbital floors (blow-out fractures)
• Nasal cavity and septum
• Zygomatic arches
• Middle cranial fossa (partially)

• Petrous ridges below maxillary sinuses (confirm correct angulation)

• Sinusitis (fluid level in maxillary sinus)
• Orbital floor fractures
• Zygomatic fractures
• Midfacial fractures (Le Fort)

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32. PNS (Paranasal Sinus) View

• Forehead and nose touching cassette
• Orbitomeatal line perpendicular to cassette
• Beam directed 15° caudally from posterior to anterior
• Shows: Frontal sinuses, ethmoid sinuses, upper maxillary sinuses, orbits

• Best for maxillary sinuses (see above)

• All four pairs of sinuses: Maxillary (largest), frontal, ethmoid (multiple small cells), sphenoid
• Nasal septum deviation
• Turbinates
• Fluid levels, mucosal thickening

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33. Intensifying Screens and Grids

• Used in extraoral radiography (not intraoral)
• Cassette contains screen on both sides of film
• Screen contains phosphor crystals (calcium tungstate - old; rare earth - gadolinium, lanthanum - modern)
• X-ray photons → phosphor crystals → emit light → expose film
• ~95% of film exposure from screen light; only ~5% from direct X-ray

• Greatly reduces exposure time (by factor of 50-100× compared to direct exposure)
• Reduces patient dose significantly
• Rare earth screens: More efficient than calcium tungstate

• Reduces image sharpness (increased unsharpness)
• Film must be matched to screen emission spectrum

• Thin strips of radiopaque (lead) material alternating with radiolucent strips (aluminum or fiber)
• Placed between patient and film
• Purpose: Absorb scatter radiation before it reaches film → improves contrast
• Ratio: Grid ratio = height of lead strips / width of space between them (typical: 5:1 to 16:1)
• Higher ratio = more efficient scatter removal but more critical alignment needed

• Linear (parallel), crossed, focused, pseudo-focused
• Stationary (Potter-Bucky diaphragm in oscillating form; Burns and Bucky in non-oscillating)
• Moving (Potter-Bucky): Eliminates grid lines from image by moving during exposure

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34. Radiographic Artifacts

• Ghost images (OPG): Metallic objects outside focal trough appear magnified on opposite side
• Amalgam fragments, earrings, glasses, hairpins, dentures
• Soft tissue calcifications

• Herringbone/tire track pattern: Film placed backwards
• Reticulation: Temperature differences between solutions
• Static electricity marks: Low humidity, rapid packet opening
• Darkroom light leaks: Fog, reduced contrast
• Chemical contamination marks
• Finger marks/abrasion marks
• Scratches on emulsion

• Cone cut: Part of image missing
• Double exposure: Two images superimposed
• Bent/crumpled film
• Chin/spine superimposition on OPG

• Defective film
• Screen artifacts (scratches)

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35. Occlusal Radiography

• Maxillary Standard Occlusal: Beam at 65° to occlusal plane; shows anterior maxilla, nasopalatine area
• Maxillary True (Vertex) Occlusal: Beam perpendicular to occlusal plane (from top of head); shows transverse view of maxillary arch, palate, nasal structures
• Mandibular (True) Occlusal: Beam perpendicular from below chin; shows mandibular arch, floor of mouth, mylohyoid ridge
• Mandibular Cross-sectional: Beam at 90° to occlusal plane from chin; shows lingual and buccal cortical plates

• Cleft palate
• Unerupted/supernumerary teeth
• Cysts and tumors of palate/floor of mouth
• Sialolith in Wharton's duct
• Fractures of anterior teeth/alveolar bone
• Root apex of teeth too long for periapical
• Large lesions not fitting in periapical
• Localization of foreign bodies

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36. Normal Radiographic Anatomy of Teeth and Supporting Structures

• Enamel: Most radiopaque; covers crown
• Dentin: Less radiopaque than enamel; forms bulk of tooth
• Pulp chamber and root canals: Radiolucent; enclosed by dentin
• Cementum: Same radiopacity as dentin (indistinguishable radiographically)

• Periodontal ligament (PDL) space: Thin radiolucent line surrounding root (0.2-0.4 mm); uniform width
• Lamina dura: Dense radiopaque line around root (represents cortical bone of alveolar socket); loss = indicates periapical pathology, early signs of pathological changes
• Alveolar bone proper (cribriform plate): = lamina dura
• Trabecular (cancellous) bone: Radiolucent spaces (marrow) between radiopaque trabeculae
• Cortical bone: Dense radiopaque borders (buccal and lingual plates, inferior cortex of mandible)
• Alveolar crest: Most coronal bone between teeth (1.5-2 mm below CEJ normally)

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37. Bitewing Radiography

• Standard bitewing: Shows premolar-molar area; most common
• Vertical bitewing: Film oriented vertically; shows more root and bone level (for periodontitis monitoring)

• Film placed parallel to crowns of both arches
• Beam directed at +8-10° vertical angulation, horizontal beam through contacts
• Patient bites on wing

1. Interproximal caries (most sensitive technique)
2. Recurrent caries under restorations
3. Overhanging margins of restorations
4. Monitoring alveolar bone levels (vertical bitewing)
5. Evaluating crown height and pulp chambers
6. Secondary dentin formation
7. Calculus detection

• #2 standard; #3 long bitewing (more teeth)

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38. Film Processing (Manual)

1. Developing (20°C, 4-5 minutes): Developer converts exposed AgBr to metallic Ag; forms visible image
2. Rinsing (30 seconds, running water): Stops development, removes developer
3. Fixing (2× development time, minimum 10 min): Removes unexposed AgBr; hardens emulsion; clears film
4. Washing (20 minutes, running water): Removes fixer chemicals
5. Drying: Hang to dry or dry cabinet

• 68°F (20°C): 4-5 min
• Lower temp: Longer time needed
• Time-temperature method preferred for consistency

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39. Processing Errors

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40. Bisecting Angle Technique with Diagram

• X-ray beam directed perpendicular to the imaginary line that bisects the angle formed by:
  • The long axis of the tooth
  • The plane of the film

• If beam is perpendicular to bisector, image length = actual tooth length
• If directed along tooth axis → foreshortened image
• If directed along film → elongated image

• Excessive angulation → foreshortening
• Insufficient angulation → elongation
• Incorrect horizontal angulation → overlapping contacts

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41. Digital Radiography - Advantages and Disadvantages [4M/2M]

1. Significantly reduced radiation dose (50-90% less than conventional film)
2. Immediate image display (no processing time)
3. No darkroom, chemicals, or processing required
4. Image enhancement (brightness, contrast, zoom, invert, color coding)
5. Easy digital storage and retrieval
6. Easy transmission (email, PACS, teledentistry)
7. No film disposal/environmental concerns
8. Image can be shown to patient on screen (patient education)
9. Eliminates film processing errors
10. PSP (phosphor plates) can be reused

1. High initial cost (equipment, software, computer)
2. Sensor rigidity and size (less comfortable than film)
3. Risk of cross-contamination of sensors
4. Image quality can be manipulated (legal/forensic issues)
5. Computer system failures can lose data
6. Learning curve for staff
7. PSP plates more fragile; can be scratched
8. Sensor cable can interfere with patient placement

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42. SLOB Rule (Same Lingual, Opposite Buccal)

• Take two radiographs changing the horizontal (or vertical) tube angulation
• If the object moves in the SAME direction as the tube shift → object is on the LINGUAL side
• If the object moves in the OPPOSITE direction to the tube shift → object is on the BUCCAL side

• Localization of unerupted/impacted canines (buccal vs palatal)
• Localization of extra roots
• Localization of foreign bodies, root canal posts, calcifications
• Determining position of supernumerary teeth

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43. ALARA Principle

1. Time: Minimize exposure time
2. Distance: Maximize distance from source (inverse square law)
3. Shielding: Use appropriate shielding materials

• Use fast film/sensors (E, F speed, digital)
• Rectangular collimation
• Use appropriate kVp (higher kVp = less dose)
• Take only clinically justified radiographs (selection criteria)
• Lead apron + thyroid collar
• Paralleling technique (less dose than bisecting for same diagnostic quality)

• Stand ≥6 feet away
• Do not hold film for patient
• Wear dosimetry badge
• Stand at 90°-135° to primary beam
• Lead-lined walls and barriers

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44. Tyre (Tire) Track Effect

• Film is underexposed (lead foil attenuates the beam before it reaches film)
• Image appears pale/light
• Patterned artifact from foil embossing

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45. Digital Imaging in Dentistry

1. Direct Digital Radiography (DDR/CCD):
   • Charge-Coupled Device (CCD) or CMOS sensor
   • Wired sensor connected directly to computer
   • Immediate image (real-time)
   • Advantages: Best image quality, immediate; Disadvantages: stiff sensor, cable
2. Semi-direct (PSP - Photostimulable Phosphor):
   • Flexible phosphor plates (barium fluorohalide)
   • Exposed plates scanned by laser reader → image digitized
   • Advantages: Flexible, thin, no cable; Disadvantages: ~5 min delay for scanning
   • Plates can be erased and reused
3. Indirect Digital:
   • Conventional film developed → scanned/digitized
   • Least common; highest dose

• Periapical, bitewing, panoramic, CBCT, cephalometric

• Brightness/contrast adjustment
• Pseudo-color enhancement
• Subtraction radiography (shows change between two radiographs)
• Edge enhancement

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46. Density, Contrast, Latitude of Film

• Degree of film darkening after processing
• OD = log₁₀(I₀/It) where I₀ = incident light, It = transmitted light
• Optimal diagnostic range: 0.3-2.0 OD
• Affected by: kVp, mA, time, film speed, processing

• Difference in density between adjacent areas
• Types: Subject contrast (differences in tissue), film contrast (film's inherent property), radiographic contrast (combined result)
• Short scale contrast (high contrast): Few shades, black/white; produced by low kVp; good for detecting caries
• Long scale contrast (low contrast): Many grey shades; produced by high kVp; wider latitude; better for bone detail

• Range of exposures that produce diagnostically acceptable density
• Wider latitude = more forgiving of exposure errors
• Affected by kVp: Higher kVp = longer scale contrast = wider latitude
• Affected by film speed: Faster film = narrower latitude in some systems

• High kVp → low contrast + wide latitude
• Low kVp → high contrast + narrow latitude

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47. Sensors in Digital Radiography

1. CCD (Charge-Coupled Device):
   • Silicon-based semiconductor
   • Direct conversion of X-rays → electrical signal → digital image
   • Most sensors have scintillating layer (cesium iodide) that converts X-rays to light → CCD
   • High resolution, immediate readout
   • Connected via fiber optic cable or wire
2. CMOS (Complementary Metal Oxide Semiconductor):
   • Similar to CCD but different amplification architecture
   • Lower power consumption
   • Can be manufactured with active pixel sensors (APS)
   • Increasingly popular; approaching CCD quality
3. PSP (Photostimulable Phosphor - "Imaging Plates"):
   • Barium fluorohalide with europium dopant
   • Stores latent image as trapped electrons in F-centers
   • Released and read by laser scanner (photostimulated luminescence)
   • Flexible, thin (like conventional film), no cable
   • ~50% dose reduction vs F-speed film

• CCD/CMOS: 10-20 lp/mm (line pairs/mm)
• PSP: 7-10 lp/mm
• Conventional F-speed film: ~20 lp/mm

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48. Object Localization Techniques

1. SLOB Rule (Clark's rule): (see above - most common)
2. Right-angle/Cross-sectional method:
   • Two radiographs taken at 90° to each other
   • Triangulation used to pinpoint 3D position
   • E.g., periapical + occlusal
3. Parallax method (tube shift):
   • Same as SLOB; shift tube and observe object movement
   • Vertical shift or horizontal shift
4. CBCT:
   • Most accurate; true 3D localization
   • Gold standard when precise localization needed (impacted canine, complex root morphology)
5. CT scan: 3D localization; higher dose

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49. Four Uses of Bitewing Radiography

1. Detection of interproximal (proximal) caries - most sensitive technique; detects early carious lesions in contact areas
2. Detection of recurrent/secondary caries under existing restorations
3. Evaluation of marginal integrity of restorations (overhangs, open margins)
4. Assessment of alveolar bone levels (especially vertical bitewing); monitoring periodontal disease

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50. Uses of Computed Tomography (CT) / Drawbacks of CT

1. Implant site assessment (bone height, width, density)
2. Pre-surgical planning (impacted teeth, complex extractions)
3. TMJ assessment
4. Tumor extent and invasion
5. Salivary gland pathology
6. Jaw fractures (complex, condylar)
7. Cysts and lesions - 3D extent
8. Nerve and vessel mapping (IANC, mental foramen)
9. Sinus evaluation before surgery
10. Orthognathic surgery planning

1. High radiation dose (much higher than CBCT or conventional films)
2. Metal artifact (streak artifact from amalgam, implants)
3. Expensive and not widely available in dental offices
4. Large equipment (hospital/radiology center)
5. Longer scan time than CBCT
6. Limited soft tissue resolution compared to MRI
7. Contraindicated in pregnancy (radiation)
8. Medical CT not optimized for dental anatomy (CBCT preferred)

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51. MRI - Indications and Contraindications

1. TMJ soft tissue evaluation (disc position, disc morphology, disc displacement)
2. Salivary gland tumors (extent, capsule, nerve involvement)
3. Oral/oropharyngeal carcinoma (invasion, nodal involvement)
4. Vascular lesions (hemangioma, AVM)
5. Osteomyelitis (marrow changes)
6. Sjogren's syndrome assessment
7. Nerve pathology
8. Perineural spread of tumors
9. Osteoradionecrosis assessment
10. Bone marrow disorders

• No ionizing radiation
• Excellent soft tissue contrast
• Multiplanar imaging
• No metal artifact (generally)

• Absolute: Cardiac pacemaker, cochlear implants, older ferromagnetic aneurysm clips, metallic foreign bodies in eyes, certain implantable devices
• Relative: Pregnancy (1st trimester - caution), claustrophobia, some dental implants (MRI-compatible implants now available), orthodontic brackets (local artifact)

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52. Principles of Projection Geometry

1. Focal spot size: Smaller = less geometric unsharpness (penumbra); sharper image
2. Object-to-film distance (OFD): Shorter = less magnification and less unsharpness; film close to tooth
3. Focal-to-film distance (FFD)/Source-to-image distance: Greater = less magnification; less beam divergence
4. Object-film parallelism: Film parallel to object = less distortion
5. Beam direction: Beam perpendicular to both tooth and film (paralleling technique) = minimal distortion

• Magnification factor = FFD / (FFD - OFD)
• Ideally: magnification = 1 (no magnification)

• Penumbra = (focal spot size × OFD) / (FFD - OFD)
• Minimize: Small focal spot, short OFD, long FFD

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53. Inverted Y Line of Ennis [2 Marks]

• Appears as an inverted "Y" shape
• The lateral nasal wall forms one arm
• The anterior sinus wall forms the other arm
• They join at a common point (apex of the Y points superiorly when inverted)

• Normal anatomical landmark; should not be mistaken for pathology
• Useful in identifying the maxillary sinus boundary
• Helps distinguish normal anatomy from periapical pathology

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54. Types of Grids

• Linear grid (Parallel): Strips run parallel; simple; limited to centered beam
• Crossed grid: Two linear grids at 90°; more effective scatter removal; very sensitive to alignment
• Focused grid: Lead strips angled to converge at focal spot distance; for use at specific FFD; reduces cutoff

• Stationary grid: Fixed in position; grid lines visible on film
• Moving grid (Potter-Bucky diaphragm): Moves during exposure, blurs grid lines from image

• Linear: Parallel strips in one direction
• Crossed: Strips in two perpendicular directions

• Grid ratio: Height/Width of lead strips; higher ratio = better scatter removal; typical 5:1, 8:1, 10:1, 12:1
• Grid frequency: Lines per cm (80-60/cm); higher = less visible lines

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55. Ghost Images in OPG

• Dense objects (high radiopacity) outside focal trough absorb X-rays
• As the tube rotates to the opposite side, the shadow of the previously irradiated object appears on the opposite side
• The ghost is:
  • Magnified (compared to original)
  • Blurred
  • Located HIGHER (superior to) the original object
  • On the contralateral side

• Earrings, hearing aids, metallic hair ornaments
• Hard cervical collar, necklaces
• Spinal column (ghost appears in maxillary antrum region)
• Tongue ring

• Remove all metallic objects before OPG
• Use lead-lined apron to cover neck and chest

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56. Principles of Bisecting Angle Technique (with Diagram)

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57. Advantages and Disadvantages of Digital Radiography [4M/2M]

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58. Advantages and Disadvantages of OPG

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59. Indications and Technique of Panoramic Radiography

1. Assessment of developing dentition and mixed dentition
2. Third molar assessment (impaction, position, relation to IANC)
3. Pre-implant planning (gross assessment; CBCT preferred for measurements)
4. Fractures of mandible (especially body, angle, condyle)
5. Cysts and tumors of jaw (large lesions)
6. Periodontal bone assessment (overview)
7. Orthodontic treatment planning
8. Edentulous patients
9. TMJ assessment (preliminary)
10. Patients with trismus, gagging, physical disability

1. Remove all metallic objects (earrings, necklaces, glasses, hearing aids)
2. Position patient standing or seated upright
3. Patient bites on bite peg (or uses chin rest)
4. Frankfort plane horizontal
5. Midsagittal plane vertical
6. Patient positioned so dental arches align within focal trough
7. Instruct patient: lips closed, tongue on palate, remain still
8. Activate rotation

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60. Ultrasonography in Dentistry

• High-frequency sound waves (1-15 MHz) emitted by piezoelectric transducer
• Waves reflected differently from different tissue densities → image formed
• No ionizing radiation

• Salivary gland imaging: Sialolithiasis, tumors, Sjogren's syndrome
• Soft tissue masses: Neck masses, submandibular swelling
• TMJ: Joint effusion, disc assessment (limited by bone)
• Periodontal assessment: PDL width, bone levels
• Cyst aspiration guidance
• Nerve blocks (US-guided): Inferior alveolar, lingual nerve blocks
• Mucosal lesions: Thickness assessment

• No radiation
• Real-time imaging
• Portable
• Soft tissue excellent
• Cheap

• Cannot penetrate bone
• Operator-dependent
• Limited for intrabony lesions

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61. Cone Beam CT (CBCT)

• Cone-shaped X-ray beam rotates 360° (or 180°) around patient
• 2D flat panel detector captures multiple images
• Reconstruction produces 3D volumetric dataset
• Lower dose than medical CT; higher dose than 2D dental X-rays

1. Implant planning (accurate bone measurement)
2. Third molar and impacted tooth localization
3. Root canal morphology (complex root anatomy, missed canals)
4. Jaw pathology (cysts, tumors, bone lesions)
5. TMJ assessment
6. Orthognathic surgery planning
7. Orthodontic treatment planning (3D)
8. Dental trauma (root fractures, dentoalveolar injury)
9. Airway analysis
10. Obstructive sleep apnea evaluation

• True 3D data
• Multiplanar reconstruction (axial, coronal, sagittal, oblique, curved)
• Lower dose than medical CT
• Dental-specific systems available

• Higher dose than 2D films
• Metal artifacts (scatter from amalgam, crowns)
• Cannot assess soft tissue as well as MRI
• Cost; not all dental offices have it
• Training required for interpretation

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62. Sensors in Digital Radiography

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63. TMJ Imaging [9M]

• Condylar head (size, shape, morphology)
• Articular eminence
• Glenoid fossa
• Joint space (superior, anterior, posterior)
• Articular disc (soft tissue - requires MRI)

1. Plain Radiographs (Transcranial):
   • Basic, cheap
   • Lateral oblique view at 0° and 30° mouth open/closed
   • Shows condyle, eminence, glenoid fossa
   • Limitations: Superimposition, projection distortion
2. Transpharyngeal (Toller's) view:
   • Shows medial pole of condyle better
3. OPG:
   • Routine screening; shows condylar shape and size
   • Limited detail; magnification errors
4. Submentovertex view: Shows medial-lateral condylar axis
5. Tomography (Conventional TMJ tomography):
   • Single-layer imaging; reduces superimposition
   • Corrected tomography preferred for true lateral view
6. Arthrography:
   • Contrast injected into superior and/or inferior joint space
   • Outlines disc indirectly
   • Shows disc displacement, perforation
   • Invasive; largely replaced by MRI
7. CT (Computed Tomography):
   • Excellent for bony detail
   • Condylar fractures, ankylosis, bony erosion, tumors
   • CBCT: Lower dose, good bony detail
8. MRI (Gold standard for disc):
   • Best visualization of articular disc
   • Shows disc displacement (anterior with/without reduction), disc morphology
   • Joint effusion (bright T2 signal)
   • No ionizing radiation
   • Protocol: T1 and T2 sagittal and coronal, open/closed
9. Bone scan (Nuclear medicine):
   • Technetium-99m phosphate
   • Shows condylar hyperplasia, active arthritis, osteonecrosis
   • Functional/metabolic information

• Transcranial lateral oblique
• Transpharyngeal
• Submentovertex
• Reverse Towne's (shows condylar neck; condylar fractures)
• AP skull

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64. Paranasal Sinus Radiograph and Uses

• Odontogenic sinusitis
• Post-operative assessment (Caldwell-Luc, sinus grafts)
• Foreign body detection
• Mucocele, polyps
• Malignant tumors (opacification, bone destruction)

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65. Differences: Periapical Abscess vs Granuloma vs Cyst

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66. Age Estimation by Dental Radiographs

• Dental eruption stages: Most accurate up to ~14 years
• Demirjian's method: Assigns stages A-H to 7 permanent mandibular teeth; uses numerical scores → age estimate
• Nolla's stages: 10 stages of tooth development
• Moorrees, Fanning and Hunt method
• Tooth calcification stages on OPG/IOPA

• Gustafson's method (post-mortem): 6 regressive changes scored (attrition, secondary dentin, cementum apposition, root resorption, root transparency, periodontosis) → age estimation (±10 years)
• Kvaal's method: Radiographic measurement of pulp/tooth ratio; pulp size decreases with age due to secondary dentin deposition
• Root transparency: Increases with age; visible on extracted teeth
• Cemental annulations: Counted like tree rings (specialized microscopy)

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67. Radiographic Features of Dentigerous Cyst

• Well-defined, unilocular radiolucency
• Corticated/sclerotic border (thin radiopaque margin)
• Crown of unerupted tooth within the cyst (attached at CEJ)
• Most commonly associated with mandibular third molars, then maxillary canines, mandibular second premolars
• Size: Variable; can be large
• Displacement: Adjacent teeth displaced; roots of adjacent teeth may be resorbed
• Expansion of cortical plates possible
• May extend toward inferior border of mandible or displace inferior dental canal

• Central type: Cyst surrounds crown symmetrically
• Lateral type: Cyst extends to one side of crown
• Circumferential type: Entire tooth enclosed

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68. Radiographic Interpretation of Caries

• Appears as radiolucent notch or zone at proximal surface
• Bitewing best for detecting proximal caries
• Not visible until enamel decalcification is ~30-40%
• Pit/fissure caries: V-shaped radiolucency under fissure

• Radiolucency spreading within dentin
• "Halo" effect (semicircular spread along DEJ)
• Secondary dentin: Radiopaque deposit within pulp chamber

• Pulp horn approached/involved: Radiolucency reaches pulp chamber

• Zone of destruction (outermost, most radiolucent)
• Zone of bacterial invasion
• Zone of demineralization
• Zone of sclerosis (innermost, hypermineralized reactive dentin)

• Most sensitive for proximal caries
• Detects early lesions before clinical detection

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69. Antemortem Radiographs [2 Marks]

• Used for comparison with post-mortem radiographs for identification of deceased
• Key tool in Disaster Victim Identification (DVI)

• Root morphology (unique configuration of roots)
• Bone pattern (trabecular pattern)
• Restorations (shape, material, location)
• Missing teeth, extraction sockets
• Periodontal bone levels
• Endodontic treatment
• Implants, crowns, bridges
• Developmental anomalies
• Sinus shape (frontal sinuses are unique)

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70. Multilocular Radiolucencies of the Jaw

• "Honeycomb" pattern: Small, round compartments
• "Soap bubble" pattern: Larger, rounded compartments
• "Tennis racket" pattern: Linear septae

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71. Unilocular Radiolucency of the Jaw

• Radicular/periapical cyst
• Dentigerous cyst (pericoronal)
• Odontogenic keratocyst (OKC)
• Simple bone cyst (traumatic bone cyst) - scallops between roots
• Nasopalatine duct cyst (midline, heart-shaped)
• Lateral periodontal cyst
• Globulomaxillary cyst (inverted pear-shaped between 12 and 13 region)

• Periapical granuloma/abscess
• Early ameloblastoma

• Dentigerous cyst
• Ameloblastoma
• Adenomatoid odontogenic tumor

• Lateral periodontal cyst
• Lateral radicular cyst

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72. Periapical Radiolucencies of the Jaw

• Periapical abscess
• Periapical granuloma (most common)
• Radicular cyst

• Giant cell granuloma (non-odontogenic)
• Malignancy (metastasis, primary jaw malignancy)
• Multiple myeloma (punched-out lesions)
• Lymphoma

• Mental foramen (if apex of premolar is adjacent)
• Incisive foramen
• Maxillary sinus floor proximity

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73. Radiotherapy

• Units: Gray (Gy); 1 Gy = 1 J/kg absorbed dose
• Head and neck cancers typically receive 60-70 Gy over 6-7 weeks
• Fractionation: Divide total dose into multiple fractions (typically 2 Gy/day, 5 days/week)
• Rationale for fractionation: 4 Rs of Radiobiology - Repair, Reoxygenation, Redistribution, Repopulation
• Types: External beam RT; brachytherapy; IMRT (intensity-modulated)
• Pre-radiation dental clearance: Extract teeth with <5-year prognosis before RT begins (extractions post-RT risk ORN)

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74. Duplicate Radiographs

• Medicolegal record
• Copy for referral
• Antemortem record for forensics
• Research/teaching

1. Direct duplicating film: Special film exposed to ultraviolet light through original; produces direct positive (not negative like copying process would); requires special duplicating film and UV light box
2. Digital copying: Scan original → digital file → print or store
3. Digital radiographs: Copy digital file; send via PACS or email

• Direct positive: Exposed areas appear lighter (opposite of regular film reversal during developing)
• Requires minimal exposure to UV light

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75. Mixed Radiolucent and Radiopaque Lesions of the Jaw

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76. Specialized Views of the TMJ

1. Transcranial lateral oblique
2. Transpharyngeal (Toller's)
3. Submentovertex
4. Reverse Towne's projection (for condylar neck and head)
5. AP skull view
6. Conventional tomography (corrected TMJ tomograms)
7. Arthrography (contrast)
8. CT/CBCT
9. MRI (gold standard for disc)
10. Bone scan (99mTc)

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77. Radiographic Investigations for Condylar Fracture

• OPG: First-line; shows condylar head/neck; bilateral fractures visible
• PA (postero-anterior) mandible: Shows medial/lateral displacement

• Reverse Towne's projection: Best conventional view for condylar head/neck fractures; shows medial and lateral condylar poles
• Transcranial lateral oblique: Condylar head in lateral view
• Submentovertex: Shows medial displacement

• CT/CBCT: Gold standard; 3D reconstruction; shows exact displacement/comminution; surgical planning
• MRI: If soft tissue (TMJ disc) injury suspected

• Type I: Condylar head fracture without displacement
• Type II: Low condylar neck with displacement, no dislocation
• Type III: Low condylar neck with dislocation
• Type IV: High condylar neck with displacement
• Type V: High condylar neck with dislocation
• Type VI: Intra-articular (condylar head) fracture

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78. Differential Diagnosis of Periapical Radiopacities

1. Condensing osteitis (focal sclerosing osteomyelitis): Radiopaque periapical area; associated with low-grade infection; increased trabecular density
2. Periapical cemental dysplasia (mature stage): Calcified mass at root apex; non-vital pulp NOT required (vital teeth)
3. Hypercementosis: Root enlargement due to excess cementum; fusiform thickening of root
4. Cementoblastoma: Dense opaque mass fused to molar/premolar root; surrounded by thin radiolucent zone
5. Idiopathic osteosclerosis (bone scar, enostosis): Dense bone island; no associated pathology; no PDL space widening
6. Chronic periapical abscess with calcification
7. Retained root fragments
8. Foreign bodies (gutta percha, amalgam)
9. Impacted tooth/dens invaginatus nearby

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79. Radiographic Appearance of Osteosarcoma and Ewing's Sarcoma

• Most common primary malignant bone tumor
• Most common jaw site: Mandible (body/symphysis); also maxilla
• Peak: 3rd decade (jaw) vs 2nd decade (long bones)

• "Sunray" or "sunburst" pattern: Spicules of new bone radiating from lesion center (characteristic but not pathognomonic)
• Mixed radiolucent and radiopaque pattern
• Widened PDL space (thickening of PDL space around root) - early sign; important!
• Ill-defined, destructive margins
• Moth-eaten bone pattern
• Cortical destruction
• Periosteal reaction (Codman's triangle sometimes)
• Tooth displacement and root resorption

• Malignant round cell tumor
• Rare in jaw (mandible more common than maxilla)
• Younger patients (2nd decade)
• Derived from primitive neuroectodermal cells

• "Onion peel" or "onion skin" periosteal reaction (multiple layers of new bone, parallel to cortex) - characteristic
• Diffuse, moth-eaten bone destruction
• Ill-defined margins
• Large soft tissue mass
• May mimic osteomyelitis (similar in jaw - harder to see onion skin pattern)
• Widening of PDL space possible

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80. Functional Imaging Techniques

1. Nuclear Medicine (Scintigraphy):
   • Technetium-99m bone scan: Condylar hyperplasia, osteomyelitis, bone tumors; shows metabolic activity
   • SPECT (Single-Photon Emission CT): 3D scintigraphy; better localization
   • PET (Positron Emission Tomography): FDG-PET; shows glucose metabolism; detects occult metastases, recurrence; used in oral cancer staging
2. MRI Spectroscopy: Metabolic information from soft tissue tumors (research stage)
3. Functional MRI (fMRI): Brain activity assessment; TMD pain research
4. SPECT-CT / PET-CT: Hybrid imaging combining metabolic + anatomical data; most useful for oral cancer staging and follow-up

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81. Differences Between Periapical and Periodontal Abscess

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INDEX OF ALL TOPICS COVERED

ORAL MEDICINE (Image 1)

1. Angular Chelitis
2. Stomatitis Medicamentosa
3. Gardner's Syndrome
4. Corticosteroids
5. Topical Corticosteroids
6. Immunofluorescence Test (DIF/IIF patterns in pemphigus, pemphigoid, lupus, LP)
7. Antibiotics in Oral Medicine
8. Topical Analgesics
9. Peutz-Jeghers Syndrome
10. Trismus [2M]
11. Causes for Bleeding in Oral Cavity
12. Exfoliative Cytology
13. Halitosis
14. Clindamycin
15. Brachytherapy
16. Antibiotics in Dentistry
17. Lip Prints (Cheiloscopy)
18. Functions of Maxillary Sinus
19. Four Antibiotics with Dosage
20. Bite Mark Analysis
21. Biopsy (all types)
22. Wound Certificate
23. Role of Dentist in Mass Disasters

DENTAL RADIOLOGY (Images 2-4)

1. Production of X-rays (bremsstrahlung + characteristic)
2. Hazards of Radiation (deterministic vs stochastic)
3. Radiation Effects on Oral Tissues
4. X-ray Tube Components and Functions
5. Tube Current and Tube Voltage
6. Collimation
7. Filtration
8. Radiation Protection of Operator
9. Radiolysis of Water
10. Radiation Caries
11. Factors Controlling X-ray Beam
12. Effects of Radiation on Teeth
13. Effects of Radiation on Salivary Glands
14. Inverse Square Law [2M]
15. Scattered Radiation
16. Roentgen (unit)
17. Importance of Collimators
18. Interaction of X-rays with Matter [4M/2M]
19. Coherent Scattering
20. Dosimetry
21. TLD (Thermoluminescent Dosimeter)
22. Focal Trough and Focal Spot
23. Panoramic Radiograph (OPG) - Advantages/Limitations/Principles
24. Faulty Radiographs and Rectification
25. IOPA - Bisecting Angle and Paralleling Techniques
26. Dental X-ray Film / Latent Image Formation
27. Factors Affecting Quality of Radiograph (Density, Contrast, Sharpness)
28. Composition of Developer and Fixer
29. Normal Radiographic Anatomy of Maxilla
30. Water's View
31. PNS View (Caldwell/Water's projections)
32. Intensifying Screens and Grids
33. Radiographic Artifacts
34. Occlusal Radiography
35. Bitewing Radiography
36. Film Processing (manual)
37. Processing Errors
38. Bisecting Angle Technique (with angles)
39. Digital Radiography - Advantages and Disadvantages [4M/2M]
40. SLOB Rule
41. ALARA Principle
42. Tire Track Effect / Herringbone Pattern
43. Digital Imaging (CCD, CMOS, PSP)
44. Density, Contrast, Latitude of Film
45. Sensors in Digital Radiography
46. Object Localization Techniques
47. Four Uses of Bitewing Radiography
48. Uses of CT / Drawbacks of CT
49. MRI - Indications and Contraindications
50. Principles of Projection Geometry
51. Inverted Y Line of Ennis [2M]
52. Types of Grids
53. Ghost Images in OPG
54. Cone Beam CT (CBCT)
55. Ultrasonography in Dentistry
56. TMJ Imaging [9M] - All modalities
57. Paranasal Sinus Radiograph
58. Periapical Abscess vs Granuloma vs Cyst (table)
59. Age Estimation by Dental Radiographs
60. Radiographic Features of Dentigerous Cyst
61. Radiographic Interpretation of Caries
62. Antemortem Radiographs [2M]
63. Multilocular Radiolucencies of the Jaw
64. Unilocular Radiolucency of the Jaw
65. Periapical Radiolucencies
66. Radiotherapy (fractionation, dose, complications)
67. Duplicate Radiographs
68. Mixed Radiolucent and Radiopaque Lesions
69. Specialized Views of the TMJ
70. Radiographic Investigations for Condylar Fracture
71. Differential Diagnosis of Periapical Radiopacities
72. Radiographic Appearance of Osteosarcoma and Ewing's Sarcoma
73. Functional Imaging Techniques (bone scan, PET-CT, SPECT)
74. Periapical vs Periodontal Abscess (comparison table)

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• Osteoradionecrosis (within radiation effects)
• Automatic film processing (within film processing)
• Submentovertex projection (within TMJ imaging)
• Xeroradiography (electrostatic imaging - historical; uses selenium-coated plates, no wet processing; replaced by digital)
• Film holders (Rinn XCP, Snap-a-ray, Eez-ee grips - hold film parallel to tooth; recommended with paralleling technique)
• New processing methods: Rapid processing, automatic processing, digital