Iran Dental Basic Sciences Exam cheat sheet

Mandibular nerve exits skull via foramen ovale; maxillary nerve via foramen rotundum; ophthalmic via superior orbital fissure.

Facial nerve branches (temporal, zygomatic, buccal, marginal mandibular, cervical) run within the parotid gland; marginal mandibular injury causes lower-lip depressor loss.

Lingual nerve carries general sensation to anterior two-thirds of tongue; chorda tympani supplies taste and parasympathetic fibers to submandibular/sublingual glands.

Internal carotid enters carotid canal; external carotid gives superior thyroid, lingual, facial, maxillary, superficial temporal branches.

Tooth development: bud (8th week) → cap (10th) → bell (12th); enamel organ derived from ectoderm, dental papilla from neural-crest ectomesenchyme.

Enamel is formed by ameloblasts (apoptose after secretion); dentin by odontoblasts, which persist; cementum by cementoblasts.

Maxillary sinus drains via middle meatus; ostium located high on medial wall, predisposing to retention and oroantral communication after molar extraction.

TMJ is a synovial, bilateral joint with articular disc; lateral pterygoid initiates opening and translates the condyle.

Bell stage: inner enamel epithelium → ameloblasts; dental papilla → odontoblasts; Hertwig epithelial root sheath maps root shape.

Resting membrane potential ≈ −70 mV, set mainly by K+ permeability (Nernst for K+ ≈ −90 mV) and Na+/K+-ATPase (3 Na+ out, 2 K+ in).

Salivary secretion is predominantly parasympathetic (CN VII, IX); primary saliva is isotonic, ductal Na+ reabsorption and K+/HCO3− secretion make final saliva hypotonic.

GFR = Kf × net filtration pressure; autoregulation via afferent arteriole myogenic tone and tubuloglomerular feedback (macula densa).

Oxygen–hemoglobin curve shifts right (↓affinity) with ↑CO2, ↑H+, ↑temperature, ↑2,3-BPG.

Cardiac output = heart rate × stroke volume; mean arterial pressure ≈ diastolic + 1/3(systolic − diastolic).

Skeletal muscle contraction: Ca2+ binds troponin C, moves tropomyosin, exposes actin; smooth muscle uses calmodulin and myosin light-chain kinase.

Pain from pulp travels via A-delta (sharp, dentinal) and C fibers (dull, slow); gate control theory: Aβ touch input inhibits pain transmission in dorsal horn.

Gustation: sweet/umami/bitter via GPCR (T1R/T2R), salty/sour via ion channels; CN VII, IX, X carry taste.

Glycolysis net: glucose → 2 pyruvate + 2 ATP + 2 NADH; committed step is phosphofructokinase-1, inhibited by ATP and citrate.

TCA cycle per acetyl-CoA: 3 NADH, 1 FADH2, 1 GTP; oxidative phosphorylation yields ~2.5 ATP/NADH and ~1.5 ATP/FADH2.

Rate-limiting enzymes: hexokinase/glucokinase, PFK-1, pyruvate dehydrogenase (glycolysis); acetyl-CoA carboxylase (fatty acid synthesis); HMG-CoA reductase (cholesterol).

Collagen synthesis: hydroxylation of proline/lysine requires vitamin C and Fe2+; cross-linking via lysyl oxidase (copper-dependent).

Urea cycle occurs in liver mitochondria/cytosol; rate-limiting carbamoyl phosphate synthetase I; fumarate links to TCA.

Vitamin C deficiency (scurvy) causes impaired collagen cross-linking: bleeding gums, poor wound healing, tooth mobility.

Fluoride inhibits enolase in glycolysis of oral bacteria, reducing acid production; systemic F− forms fluorapatite in enamel.

Osteocalcin and dentin phosphoprotein are non-collagenous matrix proteins; alkaline phosphatase marker of bone formation.

Streptococcus mutans: cariogenic via glucosyltransferases producing glucans and lactic acid; grows at low pH.

Periodontal pathogens: Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola (red complex); Aggregatibacter actinomycetemcomitans associated with localized aggressive periodontitis.

Candida albicans: pseudohyphae, germ tube positive; opportunistic in denture stomatitis, xerostomia, immunosuppression.

Herpes simplex virus: latent in trigeminal ganglion; reactivation causes cold sores (HSV-1) and herpetic whitlow in dental staff.

Hepatitis B transmission via blood/saliva; post-exposure prophylaxis includes vaccine and HBIG; HBV is more infectious than HIV.

Innate immunity: neutrophils, macrophages, complement; adaptive: B cells (antibody) and T cells (CD4 helper, CD8 cytotoxic).

IgA is predominant in saliva and mucosal secretions; IgE mediates type I hypersensitivity (anaphylaxis to latex or drugs).

Sterilization: autoclave 121°C at 15 psi for 15–20 min; spore test with Geobacillus stearothermophilus verifies effectiveness.

Inflammation: acute phase has vasodilation, increased permeability, neutrophil emigration; chronic phase has lymphocytes, plasma cells, macrophages.

Granuloma: collection of epithelioid macrophages, Langhans giant cells, lymphocytes; seen in tuberculosis, sarcoidosis, foreign body reaction.

Caries progression: enamel demineralization (white spot) precedes dentin involvement; pulpitis caused by bacterial toxins, not direct invasion initially.

Periapical granuloma is most common periapical lesion; radicular cyst is the most common inflammatory odontogenic cyst, lined by non-keratinized epithelium.

Ameloblastoma: benign but locally aggressive odontogenic tumor; soap-bubble radiolucency, posterior mandible; common in adults.

Odontoma is the most common odontogenic tumor; compound type has tooth-like structures, complex type is amorphous mass.

Squamous cell carcinoma of oral cavity: most common oral malignancy; risk factors tobacco, alcohol, HPV (oropharyngeal); lateral tongue and floor of mouth common sites.

Aphthous ulcer: recurrent, painful, yellow-white with erythematous halo; not infectious.

Leukoplakia is a clinical diagnosis (white patch not otherwise classifiable); dysplasia grading predicts malignant transformation.

Local anesthetics block voltage-gated Na+ channels from inside; efficacy requires uncharged form to cross membrane then charged form to bind.

Lidocaine has pKa 7.9, onset fast; pKa > physiologic pH means more charged form at tissue pH; inflammation (acidic) reduces efficacy.

Epinephrine in local anesthetic causes vasoconstriction, prolongs duration, reduces systemic absorption and bleeding; avoid in uncontrolled hypertension or with nonselective β-blockers (risk of hypertension).

Maximum doses: lidocaine 4.4 mg/kg (7 mg/kg with epinephrine); articaine 7 mg/kg; avoid prilocaine >8 mg/kg due to methemoglobinemia.

Benzodiazepines (midazolam) for sedation: enhance GABA-A; flumazenil reverses; respiratory depression risk with opioids.

NSAIDs inhibit COX; aspirin irreversibly acetylates COX-1; avoid aspirin in children (Reye syndrome) and near surgery.

Antibiotics: amoxicillin first-line for odontogenic infection; penicillin allergy → clindamycin or azithromycin; metronidazole for anaerobes.

Antifungals: nystatin (topical) and fluconazole (systemic) for oral candidiasis; chlorhexidine 0.12–0.2% as antiseptic rinse.

Amalgam: setting expansion from γ2 (Sn-Hg) phase; high copper reduces γ2, improves strength and corrosion resistance.

Composite: Bis-GMA/UDMA matrix, silane-treated filler; polymerization shrinkage causes marginal gap; incremental layering reduces stress.

Dentin bonding: etch-and-rinse uses phosphoric acid; self-etch uses acidic primer; hybrid layer formed by resin infiltration of demineralized dentin.

Glass ionomer: fluoride release, chemical adhesion to tooth, low strength; resin-modified GI adds light-cure resin.

Zinc oxide-eugenol: obtundent effect on pulp, used as base; eugenol inhibits polymerization of composite resins.

Elastomeric impression: addition silicone (polyvinyl siloxane) is most accurate and dimensionally stable; condensation silicone shrinks.

Ceramics: leucite-reinforced (low strength), lithium disilicate (moderate, etchable), zirconia (high strength, needs primer with MDP).

Gypsum: beta-hemihydrate (plaster) needs more water, lower strength; alpha-hemihydrate (stone) higher strength; setting expansion relevant to dies.

X-ray production: electrons accelerated from cathode to anode; bremsstrahlung and characteristic radiation; tungsten target.

Attenuation follows I = I0·e^(−μx); denser tissue (enamel, bone, metal) attenuates more and appears radiopaque.

Aluminum equivalent (mm Al) quantifies beam filtration; total filtration ≥1.5 mm Al for machines ≤70 kVp, ≥2.5 mm Al above 70 kVp.

ALARA: minimize dose; use rectangular collimation, thyroid collar, lead apron, fast film (E/F) or digital sensors.

Digital radiography reduces dose; bitewing shows crowns and crestal bone; panoramic shows entire dentition and jaws but lower resolution.

Radiolucent lesions: cyst, granuloma, tumor, osteomyelitis; radiopaque: odontoma, osteoma, amalgam tattoo (may be mixed).

Cone beam CT gives 3D images with lower dose than medical CT; useful for implant planning and impacted teeth.

Film processing: developer reduces silver halide to silver; fixer removes unexposed silver; dark image = overexposure or overdevelopment.

Informed consent requires capacity, disclosure of risks/benefits/alternatives, understanding, and voluntary decision; document it.

Autonomy, beneficence, nonmaleficence, and justice are core bioethical principles; confidentiality may be breached only when legally required or to prevent serious harm.

Dental anxiety management: tell–show–do for children; systematic desensitization; pharmacological sedation only when indicated and monitored.

Health belief model: perceived susceptibility, severity, benefits, barriers, cues to action, self-efficacy predict preventive behavior.

Motivational interviewing uses open questions, reflective listening, and affirmations to build intrinsic motivation for oral hygiene.

Mandatory reporting: suspected child abuse, certain communicable diseases, and impaired colleagues; follow local law.

Record keeping: complete, contemporaneous, legible notes are legal documents; alterations must be dated and signed.

Professional boundaries: avoid dual relationships; advertising must not be false or misleading; maintain patient privacy (HIPAA-like rules).