Mongolia Dentist Licensing Exam cheat sheet

Enamel is 96% mineral by weight, avascular, and cannot regenerate; ameloblasts are lost after tooth eruption, so caries and wear defects are permanent.

Dentin is ~70% mineral, 20% organic (mostly type I collagen), 10% water; dentinal tubules run from the pulp to the DEJ with an S-shaped curve and are widest near the pulp.

Permanent tooth eruption chronology: first molar 6 yr, central incisor 6-7 yr, lateral 7-8 yr, canine 9-12 yr, premolars 9-12 yr, second molar 12 yr, third molar 17-21 yr.

Primary dentition erupts 6-30 months; the primary second molar and permanent first molar are the most caries-prone teeth because of their long intraoral exposure.

The periodontium comprises gingiva, periodontal ligament, cementum, and alveolar bone; the PDL is 0.15-0.38 mm wide and absorbs occlusal force.

The mandibular nerve exits the skull through the foramen ovale; the maxillary nerve exits through the foramen rotundum; the infraorbital nerve is a terminal branch of V2.

Lingual nerve lies medial to the mandibular third molar and is at risk during lingual flap retraction; the inferior alveolar nerve enters the mandible at the mandibular foramen.

Saliva flow is 0.5-1.5 L/day; resting pH ~6.7-7.4; bicarbonate is the main buffer, and the parotid contributes mostly serous amylase-rich secretion.

Recurrent aphthous stomatitis: minor (<1 cm, heals in 7-10 days), major (>1 cm, up to weeks, scarring), herpetiform (multiple small clustered ulcers).

Oral lichen planus shows bilateral white striae (Wickham striae) on buccal mucosa; erosive forms need biopsy to exclude dysplasia and periodic review for malignant transformation risk.

Leukoplakia is a clinical diagnosis of exclusion; any non-homogeneous or persistent lesion should be biopsied because of dysplasia and carcinoma risk.

Oral squamous cell carcinoma risk factors: tobacco, areca nut, alcohol, HPV-16 (oropharyngeal), chronic irritation, and immunosuppression; most common sites are tongue lateral border and floor of mouth.

Odontogenic cysts: radicular (periapical inflammatory, most common), dentigerous (around crown of impacted tooth), odontogenic keratocyst (high recurrence, PTCH1), and lateral periodontal cyst.

Ameloblastoma is a locally aggressive odontogenic tumor, most often in the mandibular posterior region, with a soap-bubble radiolucency; treatment is resection with margins.

Sjögren syndrome: dry eyes and mouth, parotid enlargement, anti-Ro/SSA and anti-La/SSB antibodies; increased risk of lymphoma, so persistent gland swelling warrants biopsy.

Oral candidiasis forms: pseudomembranous (thrush, wipeable white plaques), erythematous (denture stomatitis), and hyperplastic; treat with topical nystatin or systemic fluconazole when needed.

Caries is a biofilm-driven, pH-mediated process; the critical pH for enamel demineralization is ~5.5 and for dentin ~6.5.

Fluoride works mainly topically: it promotes remineralization, forms fluorapatite, and inhibits bacterial enolase; 1,000-1,500 ppm dentifrice is standard for adults.

G.V. Black cavity classification: Class I pits/fissures, II proximal posterior, III proximal anterior, IV proximal anterior including incisal angle, V cervical third.

Amalgam requires mechanical retention and is contraindicated in visible esthetic areas; resin composite bonds via acid etching and a dentin bonding agent.

Total-etch technique: 30-40% phosphoric acid 15 s on enamel, 10-15 s on dentin, rinse and keep dentin moist; over-drying causes collagen collapse and postoperative sensitivity.

Rubber dam isolation and a dry field are required for predictable bonding; moisture contamination reduces bond strength and increases microleakage.

Cusp coverage or cuspal replacement is indicated when remaining cuspal thickness is <2 mm or when the cavity undermines the cusp.

Minimum intervention dentistry: prioritize prevention, remineralization, and repair rather than replacement of restorations when margins are sound.

Working length is the apical constriction, typically 0.5-1.0 mm short of the radiographic apex; use an apex locator confirmed by radiograph.

Root canal irrigants: sodium hypochlorite 0.5-5.25% dissolves organic tissue and is antimicrobial; EDTA 17% removes the smear layer; chlorhexidine is an alternative when NaOCl is contraindicated.

NaOCl must never be extruded beyond the apex; extrusion causes severe pain, swelling, and possible airway compromise, so use side-vented needles and gentle irrigation.

Cleaning and shaping objectives: remove pulp tissue and infected dentin, maintain original canal curvature, and preserve the apical foramen while enlarging to the desired taper.

Pulpal diagnoses: reversible pulpitis, symptomatic/asymptomatic irreversible pulpitis, necrosis, previously treated, previously initiated therapy.

Periapical diagnoses: normal, symptomatic apical periodontitis, asymptomatic apical periodontitis, acute apical abscess, chronic apical abscess, condensing osteitis.

Single-visit versus multiple-visit endodontics: both acceptable; multiple visits are favored when infection is uncontrolled, there is persistent exudate, or retreatment is complex.

Obturation aims for a fluid-tight seal to the apical constriction using gutta-percha with sealer; extrusion beyond the apex is associated with poorer outcomes.

Gingivitis is reversible inflammation limited to the gingiva; periodontitis involves attachment loss, clinical attachment level, and radiographic bone loss.

Probing depth >3 mm suggests pocketing, but attachment loss must be confirmed by measuring the cementoenamel junction to the sulcus base.

2018 classification uses staging (I-IV severity and complexity) and grading (A-C rate of progression) based on bone loss, probing depth, and risk factors such as smoking and diabetes.

Scaling and root planing is the initial therapy for periodontitis; re-evaluate at 6-8 weeks and consider surgery for residual pockets ≥5-6 mm.

Risk factors: smoking (dose-dependent), poorly controlled diabetes, plaque, calculus, and genetic factors; smoking reduces bleeding, masking inflammation.

Aggressive periodontitis (now stage/grade) often shows molar-incisor pattern and rapid bone loss in younger patients; check for systemic conditions such as diabetes.

Peri-implant mucositis is reversible inflammation without bone loss; peri-implantitis includes bone loss and requires decontamination and possible surgical treatment.

Antibiotic adjuncts (e.g., amoxicillin plus metronidazole) are reserved for specific cases such as aggressive periodontitis or necrotizing disease, not routine scaling.

Complete denture retention depends on adhesion, cohesion, surface tension, atmospheric pressure, and border seal; the neutral zone is where forces from tongue and cheek balance.

Occlusal vertical dimension is the distance between two selected points when the teeth are in occlusion; excessive loss causes angular cheilitis and reduced facial support.

Balanced occlusion in complete dentures: bilateral simultaneous contacts in centric relation and working/nonworking excursions to stabilize the bases.

Fixed partial denture (bridge) abutment selection requires adequate crown-root ratio, periodontal support, and a common path of insertion.

Abutment preparation principles: 6-10 degrees taper, 1.5-2 mm occlusal reduction, and a defined finish line (chamfer or shoulder) for ceramic crowns.

Implant-supported prostheses require osseointegration; avoid loading before healing (3-6 months in the mandible, 4-6 months in the maxilla) unless immediate loading is planned.

Removable partial denture design: use rests, clasps, and major connectors to distribute forces; the Kennedy classification describes the edentulous span pattern.

Centric relation is a maxillomandibular relationship with the condyles in their most anterior-superior position against the articular eminence; record it for complete dentures.

Third molar extraction indications: recurrent pericoronitis, caries, cyst, orthodontic need, and pathology; contraindications include uncontrolled systemic disease and high risk of nerve injury.

Inferior alveolar nerve injury risk is highest with deeply impacted mandibular third molars; obtain informed consent and consider CBCT when roots are close to the canal.

Postoperative bleeding is managed by pressure, sutures, and hemostatic agents; persistent bleeding requires reassessment for coagulation disorders.

Dry socket (alveolar osteitis) presents 2-4 days after extraction with severe pain and an empty socket; treat with irrigation and a medicated dressing, not antibiotics routinely.

Mandibular fractures: most common site is the angle, then condyle; assess occlusion, sensation, and step deformities; treat with closed or open reduction.

Odontogenic infection spreads along fascial planes; Ludwig angina is a bilateral submandibular-sublingual infection with floor-of-mouth elevation and airway risk, requiring urgent drainage and airway management.

Biopsy principles: incisional for large or suspicious lesions, excisional for small lesions; avoid sampling necrotic tissue and always send for histopathology.

Orthognathic surgery planning uses cephalometric analysis and model surgery; Le Fort I osteotomy addresses maxillary hypoplasia, and BSSO addresses mandibular position.

Angle classification: Class I normal molar relationship, Class II distal mandibular position, Class III mesial mandibular position; assess canine relationship and overjet/overbite.

Normal overjet is 2-3 mm and overbite 2-3 mm; increased overjet raises trauma risk to incisors.

Growth modification works best during the pubertal growth spurt; assess skeletal maturity by cervical vertebral maturation or hand-wrist radiograph.

Ectopic eruption and crowding require early assessment; space maintenance is needed after premature primary tooth loss to prevent space loss.

Pediatric behavior management: tell-show-do, positive reinforcement, and parental involvement; avoid restraint unless clearly indicated and documented.

First dental visit by age 1 or within 6 months of first tooth eruption; fluoride varnish application every 3-6 months for high-risk children.

Nursing bottle caries affects maxillary incisors first and spares mandibular incisors because of tongue shielding and saliva; advise no bottles at bedtime.

Pulpotomy in primary teeth uses formocresol or MTA; pulpectomy is indicated when radicular pulp is infected; stainless steel crowns restore badly broken primary molars.

Bitewing radiographs show crowns and alveolar crests and are best for interproximal caries; periapicals show the full tooth and periapical region.

Panoramic radiograph gives a broad overview but has lower resolution; it is not a substitute for periapical images when fine detail is needed.

CBCT provides 3D imaging for implant planning, impacted teeth, and endodontic anatomy; use the ALARA principle and limit field of view.

Radiographic caries: interproximal radiolucency in enamel is seen when demineralization reaches ~40-50% mineral loss; bitewings detect early lesions.

Radiolucent periapical lesion indicates bone loss; a well-defined radiolucency with a sclerotic border suggests a cyst, while ill-defined borders suggest malignancy or infection.

Radiation protection: lead apron and thyroid collar, fastest film/sensor, collimation, and avoid repeat exposures; pregnant patients should be assessed individually, not automatically excluded.

Digital sensors require less exposure than film; image processing can enhance contrast but must not be used to mask diagnostic errors.

Anatomical landmarks on panoramic images: maxillary sinus, mandibular canal, mental foramen, and nasal cavity; recognize ghost images and superimposition artifacts.

Lidocaine 2% with 1:100,000 epinephrine: maximum dose 4.4 mg/kg (7 mg/kg with epinephrine), and 1:100,000 epinephrine is contraindicated in uncontrolled hyperthyroidism and pheochromocytoma.

Articaine 4% has greater lipid solubility and bone diffusion; use caution in patients with sulfite allergy because of the epinephrine preservative.

Local anesthetic systemic toxicity presents with perioral numbness, tinnitus, seizures, and cardiovascular collapse; treat with airway support and lipid emulsion in severe cases.

Epinephrine in local anesthetics causes vasoconstriction, prolongs anesthesia, and reduces bleeding; avoid in patients with unstable cardiovascular disease.

Analgesic ladder: paracetamol and NSAIDs for mild-moderate pain; avoid NSAIDs in peptic ulcer, renal impairment, and third-trimester pregnancy; opioids only when indicated.

Antibiotic prophylaxis is indicated for infective endocarditis in high-risk patients (prosthetic valve, prior endocarditis, certain congenital heart disease) before invasive dental procedures.

Syncope is the most common dental emergency; place the patient supine with legs elevated, ensure airway, and monitor vital signs.

Anaphylaxis: give intramuscular epinephrine 0.3-0.5 mg (1:1,000) into the thigh, call emergency services, and provide oxygen and IV fluids.

Hand hygiene is the single most effective infection control measure; use alcohol-based rub for routine decontamination and soap and water when hands are visibly soiled.

Personal protective equipment: gloves, mask, eye protection, and gown; change gloves between patients and never wash gloves for reuse.

Sterilization of critical and semi-critical instruments requires autoclaving at 121°C for 15 minutes or 134°C for 3-4 minutes; monitor with biological indicators (spore tests) weekly.

High-level disinfection is acceptable for semi-critical items that cannot be heat-sterilized; critical items must be sterile.

Sharps must be disposed of in puncture-resistant containers immediately after use; never recap needles with two hands.

Vaccination of dental staff against hepatitis B is recommended; needlestick injuries require immediate washing and post-exposure assessment.

Surface disinfection uses hospital-grade disinfectants; barriers are preferred for frequently touched surfaces.

Dental unit waterlines must be flushed and treated to keep microbial counts within accepted limits; use sterile water or saline for surgical procedures.

DMFT and dmft indices measure decayed, missing, and filled teeth; DMFS counts surfaces and is more sensitive for caries experience.

Community water fluoridation is the most cost-effective population caries prevention; optimal level depends on climate and is typically 0.7-1.0 ppm.

Informed consent requires capacity, disclosure of material risks and alternatives, and voluntary agreement; document the discussion.

Confidentiality is a core ethical duty; disclose patient information only with consent or when required by law.

Professional regulation in Mongolia: dentists must hold a valid license from the relevant health authority and comply with continuing education requirements.

Scope of practice: perform only procedures within your competence and training; refer when a case exceeds your ability.

Mandatory reporting includes suspected child abuse and certain communicable diseases, depending on national law.

Public health screening: school-based programs and high-risk group targeting improve early caries detection and prevention.