Iran Dental Residency Entrance Exam cheat sheet

Ameloblastoma: benign but locally aggressive odontogenic epithelial tumor; most common in posterior mandible and ramus; radiographically multilocular "soap bubble" or honeycomb radiolucency; histologic patterns include follicular and plexiform; high recurrence after curettage, so resection with margin is preferred.

Odontogenic keratocyst (OKC): lined by parakeratinized stratified squamous epithelium with palisaded, hyperchromatic basal cells and corrugated surface keratin; high recurrence and association with PTCH1 and nevoid basal cell carcinoma syndrome; may grow anteroposteriorly without bony expansion.

Odontoma: hamartoma, most common odontogenic tumor; compound type shows multiple small tooth-like denticles, complex type an irregular radiopaque mass; treatment is conservative excision.

Squamous cell carcinoma of oral cavity: most common oral malignancy; risk factors tobacco, alcohol, areca nut, HPV16 (oropharynx); typical sites lateral tongue, floor of mouth, retromolar region; prognosis driven by TNM stage and nodal status.

Oral lichen planus: T-cell mediated interface mucositis; white Wickham striae, erosive gingival variant; histology shows band-like lymphocytic infiltrate and basal cell degeneration; malignant transformation risk is low (about 1% or less).

Pleomorphic adenoma: most common salivary gland tumor, mostly parotid; epithelial and myoepithelial cells in chondromyxoid stroma; capsule may be incomplete, so enucleation risks recurrence; risk of malignant transformation to carcinoma ex pleomorphic adenoma.

Mucoepidermoid carcinoma: most common malignant salivary tumor; mucous, intermediate, and epidermoid cells; MAML2 translocation t(11;19) is characteristic; low-grade tumors behave indolently while high-grade tumors metastasize.

Pemphigus vulgaris versus mucous membrane pemphigoid: pemphigus has suprabasal acantholysis with intraepithelial IgG and positive Nikolsky sign; pemphigoid has subepithelial split with linear basement membrane IgG and often negative Nikolsky sign; both require biopsy with direct immunofluorescence.

Periapical radiograph: use paralleling technique with beam perpendicular to receptor and tooth; bisecting-angle technique causes elongation when beam is too steep and foreshortening when too flat; ALARA principle governs all exposure decisions.

Radiographic density versus contrast: density is overall blackening of the image; contrast is the difference in density between adjacent areas; high-contrast images show fewer gray shades.

Radiolucent lesions of the jaws: inflammatory cysts (radicular, residual), OKC, ameloblastoma, central giant cell granuloma, and metastasis; radiopaque lesions include odontoma, cementoblastoma, osteoma, and idiopathic osteosclerosis.

Cone-beam computed tomography: gives isotropic sub-millimeter spatial resolution with lower dose than multidetector CT but poorer soft-tissue contrast; useful for impacted third molars, implant site assessment, and endodontic anatomy.

Caries detection: bitewing radiographs are best for proximal caries; early enamel lesions appear as radiolucent triangles in enamel; advanced lesions reach dentin and spread laterally along the dentinoenamel junction.

Panoramic radiograph: focal trough is a curved image layer; patient positioning errors produce ghost images, overlapping of anterior teeth, or distorted ramus; not suitable for fine caries or periodontal bone detail.

Cervical burnout versus caries: burnout is a radiolucency at the neck of the tooth caused by decreased X-ray attenuation between enamel and alveolar crest; it lacks the triangular shape and dentinal extension of caries.

Radiation doses: bitewing or periapical series delivers microsievert-level doses, panoramic about 10-20 microsieverts, and CBCT roughly 10 to 100 times a panoramic; lead apron and thyroid collar reduce dose.

Recurrent aphthous stomatitis: minor ulcers are under 1 cm, heal in 7-14 days without scarring; major ulcers exceed 1 cm and scar; herpetiform lesions are multiple 1-3 mm clusters; first-line therapy is topical corticosteroid.

Oral candidiasis: pseudomembranous form wipes off leaving an erythematous base; chronic hyperplastic and erythematous variants do not wipe off; predisposing factors include inhaled steroids, xerostomia, diabetes, and immunosuppression.

Oral potentially malignant disorders: leukoplakia, erythroplakia, oral submucous fibrosis, and proliferative verrucous leukoplakia; erythroplakia carries the highest transformation risk; any non-healing ulcer over 2 weeks needs biopsy.

Trigeminal neuralgia: paroxysmal electric-shock pain in V2 or V3, triggered by touch, chewing, or cold; carbamazepine is first-line; atypical features, sensory loss, or young age warrant MRI to exclude secondary causes.

Dry mouth assessment: sialometry with unstimulated whole saliva below 0.1 mL/min indicates hyposalivation; management includes sugar-free chewing gum, topical fluoride, and pilocarpine or cevimeline when glands remain functional.

Odontogenic infection spread: infections of maxillary anterior teeth drain to upper lip and can cause cavernous sinus thrombosis; mandibular molar infections spread to submandibular and sublingual spaces; dysphagia, trismus, and floor elevation signal Ludwig angina.

Burning mouth syndrome: chronic intraoral burning with normal mucosa and normal lab values; often bilateral tongue involvement; consider anemia, diabetes, and vitamin B12 or iron deficiency before diagnosing primary BMS.

Drug-induced gingival overgrowth: associated with phenytoin, cyclosporine, and calcium channel blockers such as nifedipine and amlodipine; plaque control plus drug substitution when possible is the mainstay.

Working length: determine with apex locator and confirm radiographically; apical constriction lies about 0.5-1.0 mm short of the radiographic apex; instrumentation to the minor foramen limits extrusion and overinstrumentation.

Root canal irrigants: sodium hypochlorite 0.5-5.25% dissolves organic tissue and is antimicrobial but does not remove smear layer; EDTA 17% chelates inorganic debris; chlorhexidine is used as final rinse when NaOCl cannot be used.

Smear layer removal: 17% EDTA for 1 minute followed by NaOCl final rinse opens dentinal tubules; this improves sealer adaptation and disinfection of deeper dentin.

Canal configuration: Vertucci type I is a single canal from chamber to apex; type II two canals that merge into one; type III one canal that splits into two; type IV two separate canals throughout; type V one canal that splits and exits as two.

Endodontic flare-up: pain or swelling within days after treatment; associated with extrusion of debris, incomplete instrumentation, and occlusal trauma; management is drainage, occlusal relief, and analgesia.

Root resorption: external cervical resorption appears as a radiolucent defect at the cervical region with intact canal; internal resorption shows a ballooning radiolucency centered on the canal; both may need cone-beam CT for planning.

Nickel-titanium rotary instruments: superelastic alloy with shape memory; torque-controlled motors and crown-down sequence reduce fracture; cyclic fatigue increases in curved canals and reuse raises fracture risk.

Pulpal diagnosis: reversible pulpitis shows provoked pain that resolves; irreversible pulpitis shows spontaneous or lingering pain; necrotic pulp has no response to cold or EPT; symptomatic apical periodontitis is painful to percussion.

Periodontal staging: stage I and II reflect mild to moderate attachment loss; stage III severe with potential tooth loss; stage IV advanced with masticatory dysfunction; grading (A, B, C) reflects rate of progression based on bone loss to age ratio and risk factors.

Pocket depth versus clinical attachment level: pocket depth is measured from gingival margin to pocket base; CAL is measured from cementoenamel junction to pocket base; CAL is the more reliable measure of past destruction.

Gingival curettage and scaling: nonsurgical therapy includes supragingival and subgingival scaling with root planing; re-evaluation occurs 4-6 weeks later; residual pockets of 5 mm or more with bleeding need further therapy.

Guided tissue regeneration: barrier membranes exclude epithelium and connective tissue to allow periodontal ligament and bone cells to repopulate; best outcomes in intrabony defects and mandibular Class II furcations.

Periodontal abscess: acute, painful, localized swelling with exudate and deep pocket; treatment is drainage through the sulcus or incision, irrigation, and systemic antibiotics if systemic signs are present.

Aggressive periodontitis features: rapid attachment loss and bone destruction in otherwise healthy patients; often first molars and incisors; familial aggregation; impaired neutrophil function is implicated.

Peri-implant mucositis versus peri-implantitis: mucositis is reversible inflammation with no bone loss; peri-implantitis adds progressive bone loss; risk factors include plaque, smoking, and history of periodontitis.

Antibiotic adjuncts: amoxicillin plus metronidazole is used with scaling and root planing in aggressive or necrotizing disease; antibiotics alone never substitute for mechanical debridement.

Finish line selection: chamfer is used for metal and metal-ceramic crowns; shoulder or deep chamfer is preferred for all-ceramic crowns to provide ceramic thickness; feather edge is contraindicated because it compromises margin adaptation.

Occlusal clearance: metal-ceramic needs about 1.5-2.0 mm occlusal reduction; all-ceramic zirconia needs 1.5-2.0 mm; metal alone needs 1.0-1.5 mm; inadequate reduction causes porcelain fracture or perforation.

Retention and resistance form: retention resists dislodgement along the path of insertion; resistance resists lateral and tipping forces; taper of 6-10 degrees per wall and a 4-5 mm axial wall height improve both.

Ante's rule: a fixed partial denture is indicated when the total periodontal surface area of the abutment roots equals or exceeds that of the missing teeth; this guides abutment selection.

Impression materials: addition silicone (polyvinyl siloxane) offers high dimensional stability and elastic recovery; polyether is rigid and hydrophilic but absorbs water; alginate is used only for study casts.

Provisional restorations: protect the pulp, maintain positional stability, and allow assessment of esthetics and occlusion; they should be cemented with non-eugenol temporary cement when final resin bonding is planned.

Cementation: resin cement is preferred for ceramic and zirconia restorations when retention is limited; glass ionomer and zinc phosphate are alternatives for metal-based restorations; moisture control is critical.

Margin fit: acceptable marginal discrepancy is generally under 100-120 micrometers; supragingival margins are easier to record and clean; subgingival margins are used for esthetics or short clinical crowns.

Complete denture support: primary support areas are the maxillary hard palate and the mandibular buccal shelf; relief areas include the incisive papilla, midpalatine raphe, and mental foramen region.

Border molding: uses modeling compound or polyvinyl siloxane to record functional border extensions; overextension causes soreness and dislodging forces; underextension causes loss of seal and retention.

Neutral zone: the space where forces from lips, cheeks, and tongue are balanced; arranging teeth within this zone improves stability of mandibular dentures.

Ridge resorption: mandible resorbs more and faster than maxilla; the mandibular arch resorbs downward and forward, the maxilla resorbs upward and inward, changing the occlusal plane relationship over time.

Kennedy classification: Class I bilateral edentulous posterior areas; Class II unilateral posterior edentulous area; Class III unilateral bounded posterior edentulous area; Class IV single anterior edentulous span crossing the midline.

Clasp design: circumferential (C-clasp) cast clasp provides good bracing and retention; wrought wire clasp is more flexible and kinder to abutments with reduced periodontal support; RPI design reduces torque on distal extension abutments.

Occlusal scheme for complete dentures: bilateral balanced occlusion is used in eccentric positions; monoplane or lingualized occlusion may suit severely resorbed ridges; balanced contacts reduce tipping of dentures.

Implant overdentures: two implants with ball or locator attachments in the anterior mandible improve retention and satisfaction; the McGill consensus supports two-implant overdentures as first choice for edentulous mandibles.

Amalgam: silver-tin-copper-mercury alloy; high-copper types are gamma-1 and eta phases with reduced creep; contraindicated in esthetic zones and in patients with allergy; no evidence linking it to systemic disease.

Composite resin: Bis-GMA and UDMA monomers with silane-treated filler; polymerization shrinkage of 2-3% causes cuspal deflection and microleakage; incremental layering and adhesive bonding reduce stress.

Dentin bonding: total-etch uses phosphoric acid to remove smear layer; self-etch uses acidic monomers that modify the smear layer; moisture control and adequate solvent evaporation determine bond durability.

Glass ionomer cement: releases fluoride, bonds chemically to tooth structure, and has a coefficient of thermal expansion close to dentin; low fracture toughness limits use in high-stress areas.

Zirconia: transformation toughening from tetragonal to monoclinic phase resists crack propagation; high flexural strength but requires proper sintering and surface treatment; hydrofluoric acid etching is ineffective, so airborne-particle abrasion with a primer is used.

Ceramic etching: hydrofluoric acid 5-9.5% etches glass-based ceramics such as lithium disilicate and feldspathic porcelain; silane coupling agent then bonds resin cement to the etched surface.

C-factor: ratio of bonded to unbonded surface area; high C-factor in Class I cavities increases shrinkage stress; flowable liners, soft-start curing, and indirect techniques help.

Post and core: a post does not strengthen the tooth; it retains the core; at least 4-5 mm of apical gutta-percha should remain; ferrule of 1.5-2.0 mm of sound tooth structure improves fracture resistance.

Eruption timing: first primary tooth at 6-10 months; primary dentition complete by about 30 months; first permanent molar erupts at 6 years; mixed dentition spans roughly 6 to 12 years.

Nolla staging: stages 1-10 describe crown and root formation from initial crypt to closed apex; stage 6 marks completed crown formation; useful for timing of extraction or trauma management.

Pulpotomy in primary molars: indicated for vital pulp with coronal inflammation; formocresol, ferric sulfate, or MTA are used; radicular pulp must be vital and hemorrhage controllable.

Stainless steel crown: indicated for extensive caries, after pulpotomy, and in hypoplastic primary molars; requires 1-2 mm occlusal reduction and adequate proximal clearance; cemented with glass ionomer.

Space maintenance: a band-and-loop or crown-and-loop maintains space after premature loss of a primary molar; a transpalatal arch or Nance appliance preserves arch length after bilateral loss; timing depends on dental age.

Early childhood caries: affects children under 6; maxillary anterior teeth are affected first; associated with frequent sugar exposure and bottle use; prevention includes fluoride varnish and caregiver counseling.

Dental trauma in children: avulsed permanent tooth is replanted after gentle handling of the root; avoid drying; splint flexibly for 2 weeks; primary avulsed teeth are not replanted to protect the permanent germ.

Fluoride varnish: 5% sodium fluoride (22,600 ppm) applied 2-4 times yearly; safe from eruption of first tooth; reduces caries incidence; avoid in ulcerative gingivitis or asthma with sulfite sensitivity.

Angle classification: Class I has normal mesiodistal relationship of first molars; Class II has the mandibular first molar distal to the maxillary; Class III has it mesial; division 1 has protrusive upper incisors, division 2 has retroclined centrals.

Cephalometric landmarks: SNA averages about 82 degrees, SNB about 80 degrees, ANB about 2 degrees; increased ANB suggests skeletal Class II; decreased or negative ANB suggests Class III.

Growth assessment: cervical vertebral maturation stages CS1-CS6 estimate skeletal maturity; peak mandibular growth occurs around CS3-CS4; timing affects functional appliance and orthopedic treatment planning.

Anchorage: maximum anchorage requires minimal mesial movement of molars; achieved with headgear, palatal implants, or miniscrews; reciprocal movement is planned when anchorage demand is low.

Arch wire sequence: start with light nickel-titanium for alignment, progress to stainless steel for space closure and torque; wire stiffness rises with diameter to the fourth power.

Extraction decisions: premolar extraction is considered for severe crowding, bimaxillary protrusion, and Class II division 1 with increased overjet; arch length discrepancy guides the number and site of extractions.

Retention: relapse occurs from periodontal fiber memory and growth; fixed lingual retainers plus removable retainers are common; lower incisor relapse is common without long-term retention.

Impacted canines: cone-beam CT localizes position; interceptive extraction of the primary canine may allow eruption; surgical exposure with orthodontic traction is used when eruption will not occur spontaneously.

Third molar assessment: indications include recurrent pericoronitis, caries, periodontal defect on the adjacent tooth, pathology, and orthodontic need; risks include inferior alveolar nerve injury, especially with roots near the canal on CBCT.

Ludwig angina: bilateral infection of submandibular, sublingual, and submental spaces; board-like floor of mouth, tongue elevation, airway compromise; treatment is airway protection, incision and drainage, and intravenous antibiotics.

Orthognathic surgery: Le Fort I osteotomy moves the maxilla; bilateral sagittal split osteotomy moves the mandible; genioplasty adjusts the chin; presurgical orthodontics and model surgery guide the plan.

TMJ internal derangement: anterior disc displacement with reduction produces a click; without reduction produces limited opening and deviation; imaging includes MRI; conservative therapy precedes surgery.

Implant osseointegration: direct bone-to-implant contact without fibrous interposition; depends on primary stability, surface topography, and healing time; mandibular implants load earlier than maxillary ones.

Fracture treatment: mandibular angle fractures are commonly treated with a single miniplate on the superior border via an intraoral approach; maxillary fractures are classified by Le Fort I, II, and III patterns.

Local anesthesia: inferior alveolar nerve block anesthetizes mandibular teeth, buccal gingiva anterior to the mental foramen, and lower lip; the lingual nerve requires a separate lingual block for lingual soft tissue.

Bisphosphonate-related osteonecrosis: occurs with intravenous and high-dose oral bisphosphonates; presents as exposed bone persisting over 8 weeks in the maxillofacial region; conservative management and avoidance of elective surgery are preferred.

Cranial nerves: trigeminal (V) provides general sensation to the face and motor supply to muscles of mastication; facial (VII) supplies muscles of facial expression and taste to the anterior two-thirds of the tongue; hypoglossal (XII) innervates tongue muscles.

Tooth histology: enamel is 96% mineral by weight with hydroxyapatite rods and no cells; dentin is about 70% mineral with dentinal tubules and odontoblast processes; cementum is about 50% mineral and provides attachment via Sharpey fibers.

Salivary secretion: parotid is serous, submandibular mixed with serous predominance, sublingual mostly mucous; parasympathetic stimulation increases watery secretion; sympathetic stimulation increases protein-rich viscous secretion.

Bone remodeling: osteoblasts form bone and express alkaline phosphatase; osteoclasts resorb bone and are activated by RANKL; osteoprotegerin is a decoy receptor that inhibits RANKL; PTH increases RANKL and bone resorption.

Pharmacology of local anesthetics: lidocaine is an amide with onset 2-3 minutes and duration 1-2 hours with epinephrine; articaine contains a thiophene ring and is metabolized by plasma esterases; maximum dose of lidocaine with epinephrine is 7 mg/kg.

Antibiotic mechanisms: penicillins inhibit cell wall synthesis; macrolides and tetracyclines inhibit protein synthesis at the 50S and 30S subunits; metronidazole targets anaerobic DNA; aminoglycosides bind the 30S subunit.

Immunology: IgA is the dominant secretory immunoglobulin in saliva; IgG crosses the placenta; IgE mediates type I hypersensitivity; complement activation follows classical, alternative, and lectin pathways.

Biochemistry: glycolysis yields 2 ATP per glucose; the Krebs cycle and oxidative phosphorylation yield about 30-32 ATP; fluoride inhibits enolase in glycolysis, reducing acid production by cariogenic bacteria.