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NMLE Stomatology study materials
NMLE Stomatology study resources

NMLE Stomatology practice questions

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Question 1Caries activity, mineral balance and restorative material mechanisms

What is the micromechanical bonding purpose of enamel acid conditioning in an appropriate resin adhesive system, without specifying one concentration or exposure time for every product?

  1. Selectively dissolving hydroxyapatite crystals to create micro-porosities for resin tag micromechanical retention Correct answer.
  2. Completely dissolving the collagen network within the dentin matrix
  3. Sterilizing the cavity floor to eliminate anaerobic pulp bacteria
  4. Forming a covalent chemical bond between calcium phosphate and composite monomers

Explanation

Acid etching of enamel with 35-37% phosphoric acid selectively dissolves prism cores or prism peripheries, creating high-energy micro-porosities (depth of 10-30 micrometers). Fluid resin bonding agents penetrate these micro-irregularities by capillary action, polymerizing to form micromechanical resin tags.

Question 2Caries activity, mineral balance and restorative material mechanisms

In contemporary adhesive systems, what defines the 'hybrid layer' originally described by Nakabayashi?

  1. The micromechanical interdiffusion zone formed by resin monomers polymerizing within demineralized dentin collagen fibrils Correct answer.
  2. The chemical bond between glass ionomer polyacrylic acid and hydroxyapatite
  3. The layer of residual cutting debris compacted into dentinal tubules (smear plug)
  4. The interface formed between the glass filler particles and silane coupling agent

Explanation

The hybrid layer (zone d'hybridation) is formed when adhesive hydrophilic monomers (e.g., HEMA, Bis-GMA) infiltrate the exposed collagen fibril meshwork produced by acid demineralization of dentin and polymerize in situ, creating a molecular-level mechanical interlocking between tooth structure and restorative resin.

Question 3Caries activity, mineral balance and restorative material mechanisms

During a routine clinical examination under clean, dry conditions with adequate lighting, a clinician observes an opaque, chalky white spot lesion (mancha blanca) on the cervical third of the facial surface of tooth 11. What is the fundamental histological characteristic of this non-cavitated early carious lesion?

  1. Total cavitary collapse of the outer enamel with exposed infected tubular dentin
  2. Subsurface demineralization with an intact, relatively hypermineralized external surface layer Correct answer.
  3. Complete pulp chamber obliteration by secondary reparative dentin
  4. Extensive bacterial colonization of the odontoblastic layer with micro-abscess formation

Explanation

Histologically, the incipient enamel carious lesion (white spot lesion) is characterized by subsurface demineralization (body of the lesion exhibiting 5% to 25% pore volume) beneath a relatively intact and well-mineralized outer surface zone (~30-50 micrometers thick), maintained by constant surface remineralization dynamics from saliva.

Question 4Endodontic diagnosis, disinfection, and structural prognosis

What does a conventional electric pulp test primarily assess?

  1. Neural response rather than direct pulpal blood flow Correct answer.
  2. The amount of calcium in root dentin
  3. The exact number of living pulp cells
  4. The diameter of the apical foramen

Explanation

Electric pulp testing elicits a sensory response and must be interpreted with other findings because it does not directly demonstrate pulpal circulation.

Question 5Endodontic diagnosis, disinfection, and structural prognosis

A recently traumatized immature permanent incisor does not respond to a sensibility test. What is the best interpretation?

  1. The tooth necessarily has a vertical root fracture
  2. Immediate extraction is required in every case
  3. The result proves that apical growth has stopped permanently
  4. One negative test alone does not establish pulp necrosis Correct answer.

Explanation

After trauma and in immature teeth, neural responsiveness may be unreliable; diagnosis should integrate history, serial testing, examination, and imaging.

Question 6Periodontal diagnosis, risk, and long-term stability

What finding most directly distinguishes periodontitis from plaque-induced gingivitis on an otherwise intact periodontium?

  1. Redness limited to the gingival margin
  2. Bleeding after gentle probing alone
  3. Loss of periodontal attachment attributable to periodontal disease Correct answer.
  4. Visible supragingival plaque alone

Explanation

Periodontitis involves destruction of the tooth-supporting attachment apparatus; bleeding and redness alone can occur with reversible gingival inflammation.

Question 7Periodontal diagnosis, risk, and long-term stability

A site has a probing depth of 4 mm and gingival recession of 2 mm from the cementoenamel junction. What is its clinical attachment level?

  1. 8 mm
  2. 6 mm Correct answer.
  3. 4 mm
  4. 2 mm

Explanation

With the gingival margin apical to the cementoenamel junction, clinical attachment loss is the probing depth plus recession.

Question 8Restore function while respecting structure and supporting tissues

How do retention and resistance form differ for a conventional crown preparation?

  1. Retention opposes removal along the path of insertion; resistance opposes other dislodging forces Correct answer.
  2. Retention is the same as pulpal vitality
  3. Both refer only to the shade of ceramic
  4. Resistance means the tooth has no caries

Explanation

Preparation geometry should help resist both withdrawal and functional tipping; these related mechanical requirements are distinct from esthetics or the biological state of the tooth.

Question 9Restore function while respecting structure and supporting tissues

What is the purpose of a ferrule in restoring a structurally compromised endodontically treated tooth?

  1. It makes every root fracture repairable
  2. The ferrule sterilizes the root canal
  3. A band of remaining coronal tooth structure helps resist functional fracture stresses Correct answer.
  4. A post automatically replaces the need for sound tooth structure

Explanation

A ferrule uses remaining tooth structure encircled by the restoration to improve stress management; prognosis still depends on the overall tooth and restorative design.

Question 10Surgical assessment, anatomy, bleeding, and complications

Which sensory deficit most directly suggests inferior alveolar nerve involvement after mandibular surgery?

  1. Altered sensation of the lower lip and chin Correct answer.
  2. Loss of vision in one eye
  3. Loss of shoulder abduction
  4. Isolated numbness of the forehead

Explanation

The inferior alveolar nerve continues through the mental nerve to supply the lower lip and chin, making these areas useful for sensory assessment.

Question 11Surgical assessment, anatomy, bleeding, and complications

Which structure is particularly relevant to altered general sensation of the tongue after lower third-molar surgery?

  1. Phrenic nerve
  2. Greater occipital nerve
  3. Lingual nerve Correct answer.
  4. Optic nerve

Explanation

The lingual nerve supplies general sensation to the anterior tongue and lies near the mandibular third-molar region, creating a recognized surgical risk.

Question 12Describe lesions, construct differentials, and obtain a diagnosis

A persistent indurated ulcer on the lateral tongue has no clear traumatic explanation. What is the most appropriate next diagnostic priority?

  1. Observation indefinitely without documentation
  2. Prompt specialist assessment and biopsy planning Correct answer.
  3. Repeated polishing of adjacent intact teeth as definitive management
  4. Reassurance that all painless ulcers are harmless

Explanation

A persistent unexplained indurated ulcer is a concerning finding; a timely tissue diagnosis or appropriate referral takes priority over unsupported reassurance.

Question 13Describe lesions, construct differentials, and obtain a diagnosis

What does the clinical term leukoplakia describe?

  1. A predominantly white oral patch diagnosed after excluding other definable causes Correct answer.
  2. Any white material that wipes off the mucosa
  3. A guaranteed benign response to spicy food
  4. A histologic diagnosis of invasive carcinoma in every case

Explanation

Leukoplakia is a clinical exclusion diagnosis for a white lesion; histopathology is needed when indicated to evaluate dysplasia or another underlying process.

Question 14Care for the developing dentition with risk-based decisions

Why does the frequency of fermentable carbohydrate exposure matter in caries risk assessment?

  1. Repeated acid challenges can limit the time available for remineralization Correct answer.
  2. Only the color of the food affects caries
  3. Frequency has no effect if total daily intake is unchanged
  4. All carbohydrates permanently sterilize plaque

Explanation

Caries risk reflects the balance of repeated demineralizing challenges and protective factors, so exposure pattern is relevant alongside quantity, fluoride, and biofilm control.

Question 15Care for the developing dentition with risk-based decisions

What is the main anticaries purpose of topical fluoride varnish?

  1. Change primary teeth into permanent teeth
  2. Support remineralization and reduce susceptibility to demineralization Correct answer.
  3. Remove every established cavitated lesion
  4. Replace all need for plaque control

Explanation

Topical fluoride supports mineral balance at the tooth surface, but its use complements risk reduction and does not mechanically restore a cavitated defect.

Question 16Diagnose the cause before selecting mechanics or appliances

What biological process permits orthodontic tooth movement under controlled force?

  1. Remodeling of the periodontal ligament and adjacent alveolar bone Correct answer.
  2. Permanent dissolution of all root cementum
  3. Immediate stretching of enamel into a new shape
  4. Movement of the crown while the root remains fixed forever

Explanation

Orthodontic force produces tissue responses in the periodontal ligament and surrounding bone, allowing movement through coordinated remodeling rather than reshaping enamel.

Question 17Diagnose the cause before selecting mechanics or appliances

What does anchorage describe in orthodontic mechanics?

  1. The color of the brackets
  2. Resistance to unwanted movement of supporting teeth or structures Correct answer.
  3. A guarantee that no tooth will move
  4. The amount of fluoride in a mouth rinse

Explanation

Anchorage planning controls where reaction forces are expressed, helping achieve intended movement while limiting undesirable displacement of the supporting unit.

Question 18Imaging justification, geometry, and responsible interpretation

What is the principal justification for prescribing dental imaging?

  1. Replacement of history taking
  2. A clinical question for which the expected diagnostic benefit outweighs the imaging risk Correct answer.
  3. The patient's request for the largest image volume regardless of need
  4. A fixed need for every possible image at every visit

Explanation

Imaging selection follows clinical assessment and a defined diagnostic purpose, rather than indiscriminate exposure or a belief that more images always improve care.

Question 19Imaging justification, geometry, and responsible interpretation

When CBCT is indicated, what field of view should generally be chosen?

  1. The smallest field sufficient to answer the clinical question Correct answer.
  2. A field that intentionally excludes the lesion
  3. The largest available field for every patient
  4. A field selected only by the patient's height

Explanation

Field selection balances diagnostic coverage against unnecessary exposure, while still including the anatomy required to answer the specific clinical question.

Question 20Read evidence and design programs for the population

What does the prevalence of untreated caries describe in a defined survey population?

  1. Only new cases arising during future follow-up
  2. The probability that treatment will succeed
  3. The number of restorations placed per clinician
  4. The proportion with untreated caries at the specified assessment time Correct answer.

Explanation

Prevalence describes existing disease within a defined population and time frame, so its interpretation depends on the case definition and who was assessed.

Question 21Read evidence and design programs for the population

What does disease incidence measure in a longitudinal study?

  1. All cases ever diagnosed without a time reference
  2. Only the severity of disease at baseline
  3. The percentage of participants satisfied with the clinic
  4. New cases developing among the population at risk over a defined period Correct answer.

Explanation

Incidence concerns the occurrence of new disease over time among people initially at risk, distinguishing it from the burden of existing cases.

Question 22Prevent infection and prepare for physiological deterioration

Why can pulse oximetry alone be insufficient to detect early hypoventilation during sedation?

  1. Oxygen saturation may remain acceptable while ventilation deteriorates, especially with supplemental oxygen Correct answer.
  2. The monitor replaces continuous clinical observation
  3. Pulse oximetry directly measures exhaled carbon dioxide
  4. Normal saturation proves the airway cannot obstruct

Explanation

Oxygenation and ventilation are different physiological functions, so monitoring plans must not assume that a saturation reading provides a complete assessment of breathing.

Question 23Prevent infection and prepare for physiological deterioration

What information does capnography principally provide during procedural sedation?

  1. A direct measurement of pulpal blood flow
  2. The exact depth of dental caries
  3. The total number of viable oral bacteria
  4. Exhaled carbon dioxide patterns that help assess ventilation Correct answer.

Explanation

Capnography provides breath-related carbon dioxide information and waveform trends, supporting recognition of ventilatory problems alongside other monitoring and direct patient assessment.

Question 24Caries activity, mineral balance and restorative material mechanisms

Under polarized light microscopy of ground sections of non-cavitated smooth surface enamel caries (早期釉质龋), which zone represents the advancing front (deepest zone) of the carious lesion?

  1. Dark zone (暗层)
  2. Translucent zone (透明层) Correct answer.
  3. Body of the lesion (病损体部)
  4. Surface zone (表层)

Explanation

From the advancing front (deepest) toward the outer surface, the 4 classic zones of enamel caries are: (1) Translucent zone (pore volume ~1%, advancing front of demineralization), (2) Dark zone (pore volume 2–4%, remineralization area), (3) Body of the lesion (pore volume 5–25%, major demineralization area), and (4) Surface zone (pore volume <5%, relatively intact due to high fluoride/salivary remineralization).

Question 25Caries activity, mineral balance and restorative material mechanisms

According to G.V. Black's classic cavity classification, a cavity prepared on the proximal surface of an incisor or canine that DOES NOT involve the incisal angle is classified as:

  1. Class I cavity (Ⅰ类洞)
  2. Class II cavity (Ⅱ类洞)
  3. Class III cavity (Ⅲ类洞) Correct answer.
  4. Class IV cavity (Ⅳ类洞)

Explanation

G.V. Black classification: Class I = pits and fissures; Class II = proximal surfaces of premolars/molars; Class III = proximal surfaces of anterior teeth NOT involving the incisal edge/angle (前牙邻面未累及切角); Class IV = proximal surfaces of anterior teeth involving the incisal edge/angle; Class V = gingival third of facial/lingual surfaces.

Question 26Caries activity, mineral balance and restorative material mechanisms

In adhesive dentistry, what microscopic structural layer is formed when resin monomers infiltrate and polymerize within the demineralized collagen fibril network of etched dentin?

  1. Smear layer (玷污层)
  2. Hybrid layer (混合层 / 杂化层) Correct answer.
  3. Oxygen-inhibited layer (阻氧层)
  4. Sclerotic layer (硬化层)

Explanation

The hybrid layer (混合层, Nakabayashi, 1982) is the interdiffusion zone created when adhesive resin monomers infiltrate the microporosities of acid-demineralized collagen meshwork in peritubular/intertubular dentin and polymerize in situ, providing micromechanical retention and hermetic seal.

Question 27Endodontic diagnosis, disinfection, and structural prognosis

A 16-year-old patient presents with a large carious cavity on tooth #36. Clinical examination shows a reddish-pink, fleshy, pedunculated tissue mass filling the entire cavity that bleeds slightly upon probing but has low pain sensitivity. The tooth tests vital. What is the clinical diagnosis?

  1. Chronic ulcerative pulpitis (慢性溃疡性牙髓炎)
  2. Chronic hyperplastic pulpitis / Pulp polyp (慢性增生性牙髓炎 / 牙髓息肉) Correct answer.
  3. Gingival fibroma (牙龈纤维瘤)
  4. Epulis (牙龈瘤)

Explanation

Chronic hyperplastic pulpitis (慢性增生性牙髓炎, pulp polyp) occurs primarily in children and young adults with high pulp vitality and wide open carious cavities. Chronic low-grade irritation stimulates extensive granulation tissue proliferation covered by stratified squamous epithelium from oral shedding.

Question 28Endodontic diagnosis, disinfection, and structural prognosis

What is the primary mechanical advantage of using the Crown-Down preparation technique (冠向下预备技术) with rotary nickel-titanium instruments in curved root canals?

  1. It completely eliminates the need for working length determination
  2. Early coronal flaring eliminates cervical constrictions, reduces torsional stress on apical files, and improves irrigant exchange (早期敞开冠部消除根管弯曲阻力，减少器械折断风险，增强冲洗效果) Correct answer.
  3. It automatically seals the apical foramen without requiring gutta-percha
  4. It allows shaping of the entire canal in a single rotation without irrigation

Explanation

Reducing relevant coronal interferences can improve access and reduce some mechanical demands on subsequent canal instruments. This does not eliminate fracture risk or specify one sequence, taper, preparation depth or irrigation delivery for every canal. Actual anatomy, instrument design and manufacturer instructions determine the professional technique.

Question 29Endodontic diagnosis, disinfection, and structural prognosis

Which listed alkaline chemical mechanism explains calcium hydroxide activity when it is appropriately used as an intracanal medicament, rather than claiming it is required for every interval between appointments?

  1. It permanently sets into an insoluble waterproof glass crystal
  2. It bonds chemically to composite resin restorations
  3. It acts as a local anesthetic inside the root canal
  4. High alkaline pH (~12.5) provides broad-spectrum bactericidal action, neutralizes acidic inflammatory products, and inactivates bacterial lipopolysaccharide/endotoxin (强碱性杀菌、中和酸性产物及灭活内毒素) Correct answer.

Explanation

Calcium hydroxide produces a strongly alkaline environment through hydroxide ions, which can damage susceptible microbial structures and modify relevant endotoxin components. The effect is conditional on contact, chemistry and the organisms involved. It does not reliably sterilize every canal or establish that every case needs an interappointment medicament.

Question 30Periodontal diagnosis, risk, and long-term stability

In periodontal probing, how is an infrabony (subcrestal / intrabony) pocket (骨下袋) differentiated from a suprabony (supracrestal) pocket (骨上袋)?

  1. The bottom of the pocket is coronal to the cementoenamel junction
  2. The bottom of the pocket (junctional epithelium) is located apical to the adjacent alveolar bone crest (牙周袋袋底位于牙槽嵴顶的根方) Correct answer.
  3. The pocket is accompanied by acute purulent exudate
  4. The tooth is always completely non-vital

Explanation

In an infrabony pocket (骨下袋), the base of the periodontal pocket (apical extent of the junctional epithelium) is apical to the crest of the surrounding alveolar bone, associated with vertical/angular bone resorption. In a suprabony pocket (骨上袋), the pocket base is coronal to the alveolar crest, associated with horizontal bone loss.

Question 31Periodontal diagnosis, risk, and long-term stability

In Guided Tissue Regeneration (GTR / 引导组织再生术) for vertical periodontal bone defects, what is the specific biological purpose of placing a barrier membrane (屏障膜)?

  1. Provide a permanent rigid replacement for the lost alveolar bone
  2. Physically block gingival epithelial cells and fibroblasts from migrating apically along the root surface, allowing slower-migrating PDL cells and osteoblasts to regenerate new cementum, PDL, and bone (阻止牙龈上皮和结缔组织细胞向根面迁移，选择性引导牙周膜干细胞和成骨细胞生长) Correct answer.
  3. Release systemic antibiotics continuously for 5 years
  4. Accelerate the downward proliferation of junctional epithelium

Explanation

Melcher's biological principle: Gingival epithelial cells migrate fastest down the root surface, resulting in a long junctional epithelium without regeneration. GTR places a resorbable (collagen) or non-resorbable (ePTFE) barrier membrane to exclude epithelial and gingival connective tissue, giving progenitor cells from the periodontal ligament and bone time to form new attachment apparatus (cementum, Sharpey's fibers, and bone).

Question 32Periodontal diagnosis, risk, and long-term stability

According to Glickman's classification of furcation involvement (根分叉病变分度), a Class III furcation lesion is defined as:

  1. Incipient suprabony pocketing into the furcation fluting without horizontal penetration
  2. Horizontal bone loss into the furcation exceeding 1/3 of tooth width but not through-and-through
  3. Through-and-through bone destruction between the roots, but the furcation is covered by gingival soft tissue and not clinically visible (贯通性骨吸收，但分叉区被软组织覆盖) Correct answer.
  4. Through-and-through bone destruction where the furcation is clinically exposed and completely visible (贯通性骨缺损且分叉区完全暴露直视)

Explanation

Glickman classification: Class I = incipient/early involvement into the fluting; Class II = cul-de-sac defect (probe penetrates >1/3 width but not through); Class III = complete through-and-through bone loss under the dome, but soft tissue covers the entrance; Class IV = through-and-through bone loss with gingival recession making the furcation tunnel clinically visible.

Question 33Describe lesions, construct differentials, and obtain a diagnosis

A 28-year-old male presents with a radiolucent lesion in the mandibular ramus. Histopathology reveals a 6–8 cell thick uniform stratified squamous epithelial lining with a wavy (corrugated) parakeratinized surface, a prominent palisaded basal cell layer with 'tombstone' hyperchromatic nuclei, and satellite/daughter cysts in the fibrous wall. What is the diagnosis?

  1. Periapical cyst (根尖周囊肿)
  2. Dentigerous cyst (含牙囊肿)
  3. Odontogenic keratocyst / OKC (牙源性角化囊肿) Correct answer.
  4. Calcifying odontogenic cyst (钙化牙源性囊肿)

Explanation

These classic histological features-uniform thin parakeratinized epithelium, wavy/corrugated surface, hyperchromatic palisaded basal layer (tombstone appearance), absence of rete pegs, and satellite/daughter microcysts in the capsule-are diagnostic of Odontogenic Keratocyst (OKC / 牙源性角化囊肿), explaining its high recurrence rate.

Question 34Describe lesions, construct differentials, and obtain a diagnosis

Which odontogenic cyst originates from the accumulation of fluid between the reduced enamel epithelium and the crown of an unerupted or impacted tooth, attaching specifically at the cementoenamel junction (CEJ)?

  1. Dentigerous cyst / Follicular cyst (含牙囊肿 / 滤泡囊肿) Correct answer.
  2. Radicular cyst (根尖周囊肿)
  3. Lateral periodontal cyst (侧方牙周囊肿)
  4. Gingival cyst of the adult (成人牙龈囊肿)

Explanation

A dentigerous cyst (含牙囊肿) encloses the crown of an unerupted tooth (most commonly mandibular third molars or maxillary canines) and attaches precisely at the cementoenamel junction (CEJ). It arises from proliferation of the reduced enamel epithelium.

Question 35Describe lesions, construct differentials, and obtain a diagnosis

Histopathologic examination of a multicystic ameloblastoma (成釉细胞瘤, follicular type) typically reveals epithelial islands consisting of:

  1. Sheets of uniform small round cells with abundant glycogen
  2. Concentric lamellated calcifications (calcospherites) within squamous whorls
  3. Glandular duct-like structures lined by double-layered cuboidal cells
  4. Central star-shaped cells resembling the stellate reticulum surrounded by a peripheral layer of columnar cells with reversed nuclear polarity (中心呈星网状细胞，周围呈反极性柱状细胞) Correct answer.

Explanation

Follicular ameloblastoma is characterized by epithelial islands embedded in fibrous stroma. The peripheral cells are columnar pre-ameloblast-like cells showing reverse nuclear polarity (nuclei polarized away from the basement membrane), while the central core is composed of loosely cohesive stellate reticulum-like cells (Vickers-Gorlin criteria).

Question 36Describe lesions, construct differentials, and obtain a diagnosis

A 45-year-old female presents with a painless, slow-growing, movable mass in the right parotid gland for 3 years. Biopsy demonstrates a 'mixed tumor' with epithelial and myoepithelial elements arranged in cords and ducts embedded in a chondromyxoid and hyaline stroma. What is the diagnosis?

  1. Warthin tumor / Adenolymphoma (沃辛瘤 / 腺淋巴瘤)
  2. Adenoid cystic carcinoma (腺样囊性癌)
  3. Pleomorphic adenoma (多形性腺瘤 / 混合瘤) Correct answer.
  4. Mucoepidermoid carcinoma (黏液表皮样癌)

Explanation

Pleomorphic adenoma (多形性腺瘤, formerly mixed tumor) is the most common benign salivary gland tumor. Its hallmark is tissue pleomorphism featuring ductal epithelial cells, myoepithelial cells, and mesenchymal-like chondroid, myxoid, and hyaline matrix.

Question 37Describe lesions, construct differentials, and obtain a diagnosis

In the histological grading of Mucoepidermoid Carcinoma (黏液表皮样癌) of the salivary glands, what distinguishes low-grade from high-grade tumors?

  1. Low-grade tumors display frequent perineural invasion and vascular thrombosis
  2. Low-grade tumors are dominated by mature mucus-secreting cells and cystic spaces, whereas high-grade tumors consist primarily of solid sheets of squamous and intermediate cells with marked cytological atypia (低分化以实性表皮样/中间细胞为主，高分化以黏液细胞和囊腔为主) Correct answer.
  3. High-grade tumors are entirely composed of chondroid metaplasia
  4. Low-grade tumors are encapsulated by thick mature lamellar bone

Explanation

Mucoepidermoid carcinoma (MEC) is graded based on the proportion of cell types: Low-grade MEC has prominent cystic spaces lined by well-differentiated mucous cells (>50%) with minimal atypia. High-grade MEC is predominantly solid sheets of atypical squamous and intermediate cells (<10% mucous cells), high mitotic activity, and aggressive invasive behavior.

Question 38Describe lesions, construct differentials, and obtain a diagnosis

Which of the following architectural and cellular changes is considered a definitive histological criterion of oral epithelial dysplasia (口腔上皮异常增生)?

  1. Uniform hyperkeratosis without cellular atypia
  2. Subepithelial dense band-like lymphocytic infiltration with intact basement membrane
  3. Formation of microabscesses within the stratum corneum (Munro microabscesses)
  4. Loss of basal cell polarity, bulbous drop-shaped rete pegs, nuclear pleomorphism, and abnormal mitotic figures above the basal layer (基底细胞极性丧失、滴状上皮钉突、核多形性及异常核分裂象) Correct answer.

Explanation

WHO criteria for oral epithelial dysplasia include architectural disturbances (loss of polarity, bulbous/drop-shaped rete pegs, premature keratinization) and cytological atypia (nuclear/cellular pleomorphism, hyperchromatism, increased N:C ratio, and mitoses in upper epithelial layers).

Question 39Describe lesions, construct differentials, and obtain a diagnosis

A 50-year-old female presents with bilateral, symmetric, lace-like white lines and papules on the buccal mucosa. The lesions are asymptomatic and do not rub off. Histopathology shows hyperkeratosis, liquefaction degeneration of the basal cell layer, and a dense band-like subepithelial lymphocytic infiltrate. What is the diagnosis?

  1. Oral leukoplakia (口腔白斑病)
  2. Oral Lichen Planus (口腔扁平苔藓 / OLP) Correct answer.
  3. Pseudomembranous candidiasis (假膜型念珠菌病)
  4. Pemphigus vulgaris (寻常型天疱疮)

Explanation

Oral lichen planus (OLP / 口腔扁平苔藓) is a chronic T-cell-mediated autoimmune mucosal disease. Clinically, it features bilateral symmetric white lace-like keratotic networks (Wickham striae). Histologically, the classic triad is hyperkeratosis, basal cell liquefaction degeneration (基底细胞液化变性), and a band-like subepithelial T-lymphocytic infiltrate.

Question 40Describe lesions, construct differentials, and obtain a diagnosis

A 3-year-old child presents with high fever (39.5°C), irritability, submandibular lymphadenopathy, and swollen, fiery-red marginal and attached gingiva studded with clusters of small vesicles that rupture into painful round ulcers. What is the primary etiology?

  1. Coxsackie A16 virus (柯萨奇病毒A16型)
  2. Herpes Simplex Virus Type 1 (原发性单纯疱疹病毒1型 / HSV-1) Correct answer.
  3. Epstein-Barr virus (EB病毒)
  4. Human Immunodeficiency Virus (人类免疫缺陷病毒)

Explanation

Primary herpetic gingivostomatitis (原发性疱疹性龈口炎) is the classic initial infection of HSV-1 in young children (ages 1–5). Symptoms include high fever, acute diffuse marginal gingivitis ('fiery red gingiva'), and clusters of pinhead vesicles that rupture into painful coalescing ulcers across keratinized and non-keratinized mucosa.

Question 41Describe lesions, construct differentials, and obtain a diagnosis

A 55-year-old patient presents with widespread, extremely painful, flaccid oral bullae and erosions. On clinical examination, sliding finger pressure on normal-appearing perilesional mucosa causes epithelial peeling and blister formation (positive Nikolsky's sign / 尼氏征阳性). Histopathology demonstrates suprabasilar intraepithelial clefting and acantholytic Tzanck cells. What is the diagnosis?

  1. Mucous membrane pemphigoid (良性黏膜类天疱疮)
  2. Bullous erythema multiforme (大疱性多形红斑)
  3. Oral lichen planus (口腔扁平苔藓)
  4. Pemphigus vulgaris (寻常型天疱疮) Correct answer.

Explanation

Pemphigus vulgaris (寻常型天疱疮) is an autoimmune blistering disease caused by IgG autoantibodies targeting desmoglein 3 in desmosomes. Hallmarks include: (1) Suprabasilar intraepithelial blisters (棘层内疱), (2) Acantholytic Tzanck cells, and (3) Positive Nikolsky sign (尼氏征阳性 / detachment of epidermis with light tangential pressure).

Question 42Describe lesions, construct differentials, and obtain a diagnosis

A 40-year-old male presents with recurrent swelling and pain in the right submandibular region that characteristically worsens immediately before and during meals ('salivary colic' / 进食性胀痛). Bimanual palpation along the floor of the mouth reveals a hard, tender nodule in Wharton's duct. What is the most likely diagnosis?

  1. Submandibular gland sialolithiasis and sialadenitis (下颌下腺导管结石伴下颌下腺炎) Correct answer.
  2. Submandibular lymphadenitis (下颌下淋巴结炎)
  3. Ranula (舌下腺囊肿)
  4. Pleomorphic adenoma of the submandibular gland (下颌下腺多形性腺瘤)

Explanation

Sialolithiasis (涎石病) occurs most commonly in the submandibular gland (~85%) due to its long upward duct, thick mucinous secretions, and high calcium/phosphate content. The classic presentation is 'mealtime salivary syndrome' (进食时腺体胀痛) due to ductal obstruction, and stones are palpable on bimanual examination (双合诊).

Question 43Surgical assessment, anatomy, bleeding, and complications

On the permanent maxillary first molar (上颌第一磨牙), on which anatomical surface and cusp is the fifth cusp (Cusp of Carabelli / 卡氏尖) typically located?

  1. Lingual surface of the mesiolingual cusp (近中舌尖的舌侧面) Correct answer.
  2. Buccal surface of the mesiobuccal cusp (近中颊尖的颊侧面)
  3. Lingual surface of the distolingual cusp (远中舌尖的舌侧面)
  4. Occlusal surface of the distobuccal cusp (远中颊尖的牙合面)

Explanation

The cusp of Carabelli (卡氏尖) is an accessory tubercle found predominantly on the lingual surface of the mesiolingual cusp of the permanent maxillary first molar (and primary maxillary second molar). It is a key morphological landmark in dental anatomy and anthropological identification.

Question 44Surgical assessment, anatomy, bleeding, and complications

Which pulp horn (髓角) in the crown of the permanent mandibular first molar is the highest and most susceptible to accidental exposure during cavity preparation?

  1. Mesiobuccal pulp horn (近中颊侧髓角) Correct answer.
  2. Distobuccal pulp horn (远中颊侧髓角)
  3. Distal pulp horn (远中髓角)
  4. Mesiolingual pulp horn (近中舌侧髓角)

Explanation

In the mandibular first molar, the mesiobuccal pulp horn (近中颊侧髓角) is anatomically the highest and largest, projecting furthest toward the occlusal surface. Clinicians must be particularly cautious during occlusal cavity preparation to prevent accidental mechanical exposure.

Question 45Surgical assessment, anatomy, bleeding, and complications

In the temporomandibular joint (颞下颌关节, TMJ), which zone of the articular disc (关节盘) is avascular and aneural, and serves as the primary load-bearing area during mandibular function?

  1. Anterior band (前带)
  2. Intermediate zone (中间带) Correct answer.
  3. Posterior band (后带)
  4. Bilaminar retrodiscal zone (双板区 / 关节盘后区)

Explanation

The articular disc is divided into anterior band, intermediate zone, posterior band, and bilaminar zone. The intermediate zone (中间带) is the thinnest, contains no blood vessels or nerve fibers, and is positioned between the condyle and articular tubercle to bear functional masticatory loads.

Question 46Surgical assessment, anatomy, bleeding, and complications

Which muscle of mastication is primarily responsible for the protrusion (前伸运动) and initial depression of the mandible when contracting bilaterally?

  1. Masseter muscle (咬肌)
  2. Temporalis muscle (颞肌)
  3. Medial pterygoid muscle (翼内肌)
  4. Lateral pterygoid muscle (翼外肌) Correct answer.

Explanation

Bilateral contraction of the lateral pterygoid muscles (翼外肌, especially the inferior bellies) pulls the condyles and articular discs forward and downward along the articular eminences, resulting in mandibular protrusion and depression (mouth opening).

Question 47Surgical assessment, anatomy, bleeding, and complications

Which branch of the mandibular nerve (CN V3 / 下颌神经) passes between the two heads of the lateral pterygoid muscle to supply sensory innervation to the cheek skin and buccal gingiva of the mandibular molars?

  1. Inferior alveolar nerve (下牙槽神经)
  2. Lingual nerve (舌神经)
  3. Buccal nerve / Long buccal nerve (颊神经) Correct answer.
  4. Auriculotemporal nerve (耳颞神经)

Explanation

The buccal nerve (颊神经 / long buccal nerve) branches from the anterior trunk of CN V3, passes between the superior and inferior heads of the lateral pterygoid muscle, crosses the anterior border of the ramus, and provides sensory innervation to the cheek mucosa, skin, and buccal gingiva adjacent to the mandibular molars.

Question 48Surgical assessment, anatomy, bleeding, and complications

During surgery involving the parotid gland or submandibular incision, injury to the marginal mandibular branch of the facial nerve (面神经下颌边缘支) will result in which clinical manifestation?

  1. Inability to close the eyelid (眼睑闭合不全 / 兔眼)
  2. Drooping of the corner of the mouth and inability to pull the lower lip downward and outward (口角下垂及下唇不能向下外侧运动) Correct answer.
  3. Loss of forehead wrinkling on the affected side (额纹消失)
  4. Deviation of the tongue on protrusion (伸舌偏斜)

Explanation

The marginal mandibular branch of the facial nerve innervates the depressor anguli oris, depressor labii inferioris, and mentalis muscles. Injury causes paralysis of the lower lip depressors, producing an asymmetric smile with elevation of the affected corner and inability to evert/depress the lower lip.

Question 49Surgical assessment, anatomy, bleeding, and complications

Where does the main excretory duct of the submandibular gland (Wharton's duct / 下颌下腺导管) open into the oral cavity?

  1. Sublingual caruncle beside the lingual frenum (舌系带旁的舌下肉阜) Correct answer.
  2. Buccal mucosa opposite the maxillary second molar (上颌第二磨牙相对的颊黏膜)
  3. Sublingual fold (舌下襞上的多个小孔)
  4. Incisive papilla (切牙乳头)

Explanation

Wharton's duct travels forward in the sublingual space between the mylohyoid and hyoglossus muscles, loops over the lingual nerve, and opens at the sublingual caruncle (舌下肉阜) located on either side of the lingual frenulum.

Question 50Surgical assessment, anatomy, bleeding, and complications

Histologically, the dental pulp is arranged into four distinct concentric zones from the periphery to the center. What is the correct sequence?

  1. Odontoblast layer → Cell-free zone of Weil → Cell-rich zone → Pulp core (成牙本质细胞层 → 魏尔无细胞层 → 多细胞层 → 髓核固有牙髓) Correct answer.
  2. Cell-rich zone → Odontoblast layer → Cell-free zone → Pulp core
  3. Pulp core → Cell-free zone → Cell-rich zone → Odontoblast layer
  4. Cell-free zone → Odontoblast layer → Pulp core → Cell-rich zone

Explanation

The histological architecture of the coronal dental pulp from outermost to center is: (1) Odontoblast layer, (2) Cell-free zone of Weil (containing the subodontoblastic nerve plexus of Raschkow), (3) Cell-rich zone (fibroblasts and undifferentiated mesenchymal cells), and (4) Pulp core (vascular and nervous stromal tissue).