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Lebanon Dental Colloquium practice questions

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Question 1Oral Medicine, Oral Pathology and Oral Diagnosis

A 12-year-old boy has a painless, fluctuant swelling of the lower lip that has recurred twice after minor trauma. Which lesion is most consistent with this history?

  1. Hemangioma of the lower lip
  2. Squamous cell carcinoma of the lower lip
  3. Mucocele of the lower lip Correct answer.
  4. Irritation fibroma of the lower lip

Explanation

Minor salivary gland duct rupture after lip biting causes mucus extravasation and a fluctuant, bluish, recurrent swelling, most often on the lower lip. The history of repeated trauma and recurrence is classic.

Question 2Oral Medicine, Oral Pathology and Oral Diagnosis

Which clinical presentation most strongly suggests oral lichen planus rather than lichenoid drug reaction?

  1. White plaque that resolves within weeks of stopping a drug
  2. Bilateral white striae on the buccal mucosa with a reticular pattern Correct answer.
  3. Unilateral white plaque at the site of a sharp cusp
  4. A solitary ulcer with a rolled border

Explanation

Reticular, bilateral Wickham striae on the buccal mucosa are the hallmark of oral lichen planus. Lichenoid drug reactions tend to be more unilateral, erosive, and resolve after withdrawal of the culprit drug.

Question 3Oral Medicine, Oral Pathology and Oral Diagnosis

A patient reports sudden onset of unilateral facial paralysis, inability to close the eye, and loss of taste on the anterior tongue. Which diagnosis is most likely?

  1. Cluster headache
  2. Trigeminal neuralgia
  3. Bell palsy Correct answer.
  4. Temporomandibular joint dislocation

Explanation

Lower motor neuron facial nerve palsy affecting the forehead plus loss of taste over the anterior two-thirds of the tongue is characteristic of Bell palsy. Trigeminal neuralgia causes paroxysmal lancinating pain, not motor weakness.

Question 4Oral Medicine, Oral Pathology and Oral Diagnosis

Which radiographic feature best distinguishes a radicular cyst from a periapical granuloma?

  1. A uniform widening of the periodontal ligament space only
  2. A mixed radiolucent-radiopaque lesion at the apex
  3. A well-defined radiolucency with a corticated border associated with a non-vital tooth Correct answer.
  4. A diffuse radiolucency at the apex of a vital tooth

Explanation

A radicular cyst typically shows a well-defined, corticated radiolucency at the apex of a non-vital tooth. Radiography alone cannot reliably separate a small cyst from a granuloma, so the corticated border and size help but histopathology is definitive.

Question 5Oral Medicine, Oral Pathology and Oral Diagnosis

Which condition is characterized by recurrent aphthous-like ulcers, genital ulcers, and uveitis?

  1. Pemphigus vulgaris
  2. Behcet disease Correct answer.
  3. Erythema multiforme
  4. Systemic lupus erythematosus

Explanation

The triad of recurrent oral ulcers, genital ulcers, and ocular inflammation is the classic presentation of Behcet disease. It is a systemic vasculitis with a relapsing course.

Question 6Oral Medicine, Oral Pathology and Oral Diagnosis

A patient has a painless, firm, slowly enlarging swelling at the angle of the mandible. Fine-needle aspiration yields fluid with a high amylase level. Which structure is most likely involved?

  1. Submandibular gland
  2. Thyroid gland
  3. Parotid gland Correct answer.
  4. Sublingual gland

Explanation

High-amylase fluid from a swelling at the angle of the mandible points to a parotid duct or gland lesion such as a mucocele or salivary fistula. The parotid is the major gland located at the mandibular angle.

Question 7Oral Medicine, Oral Pathology and Oral Diagnosis

Which organism is most commonly associated with acute necrotizing ulcerative gingivitis?

  1. Fusobacterium necrophorum with spirochetes Correct answer.
  2. Streptococcus mutans
  3. Actinomyces israelii
  4. Candida albicans

Explanation

Acute necrotizing ulcerative gingivitis is a polymicrobial infection in which fusiform bacteria and spirochetes, including Treponema species, predominate. The clinical picture includes punched-out papillae, pseudomembrane, and foul odor.

Question 8Oral Medicine, Oral Pathology and Oral Diagnosis

A patient with a history of recurrent herpes labialis develops a painful cluster of vesicles on the vermilion border after sun exposure. Which statement about this infection is correct?

  1. The virus remains active and is cleared within 48 hours
  2. The virus establishes latency in the trigeminal ganglion Correct answer.
  3. The lesions are caused by human papillomavirus
  4. The infection is transmitted only through blood products

Explanation

Herpes simplex virus type 1 establishes latency in the trigeminal ganglion and reactivates with triggers such as ultraviolet light, stress, or fever. Reactivation produces grouped vesicles at the vermilion border.

Question 9Oral Medicine, Oral Pathology and Oral Diagnosis

A 55-year-old smoker has a non-healing ulcer on the lateral border of the tongue with indurated margins and fixed submandibular lymph nodes. Which diagnostic step is most appropriate next?

  1. Incisional biopsy of the ulcer margin Correct answer.
  2. Topical corticosteroid therapy for two weeks
  3. Cytology of a saliva sample
  4. Reassurance and review in six months

Explanation

An indurated, non-healing tongue ulcer with fixed lymph nodes raises strong suspicion of squamous cell carcinoma. Incisional biopsy of the clinically active margin provides the definitive histologic diagnosis and grading.

Question 10Oral Medicine, Oral Pathology and Oral Diagnosis

Which finding on panoramic radiography is most characteristic of an odontogenic keratocyst?

  1. A ground-glass radiopacity of the maxilla
  2. A multilocular radiolucency with a scalloped anterior border in the posterior mandible Correct answer.
  3. A unilocular radiolucency with a radiopaque halo around the crown of an impacted tooth
  4. A sunburst periosteal reaction

Explanation

Odontogenic keratocysts often appear as well-defined radiolucencies that grow along the bone with scalloped margins, commonly in the posterior mandible. Multilocularity and anterior scalloping are typical but not exclusive.

Question 11Oral Medicine, Oral Pathology and Oral Diagnosis

A patient reports burning mouth symptoms that are worst in the morning and improve during meals, with a normal-appearing mucosa. Which condition should be considered first?

  1. Burning mouth syndrome Correct answer.
  2. Squamous cell carcinoma
  3. Oral candidiasis
  4. Geographic tongue

Explanation

Burning mouth syndrome presents with chronic oral burning and a clinically normal mucosa, often with symptoms that vary through the day and may ease during eating. Secondary causes such as anemia, diabetes, and xerostomia should be excluded.

Question 12Oral Medicine, Oral Pathology and Oral Diagnosis

Which autoantibody profile is most consistent with pemphigus vulgaris?

  1. IgG autoantibodies against desmoglein 3 Correct answer.
  2. IgG autoantibodies against BP180
  3. IgM autoantibodies against cardiolipin
  4. IgA autoantibodies against desmoglein 1

Explanation

Pemphigus vulgaris is caused by IgG autoantibodies directed against desmoglein 3, leading to intraepithelial acantholysis and suprabasal clefting. Direct immunofluorescence shows intercellular IgG deposition.

Question 13Oral Medicine, Oral Pathology and Oral Diagnosis

A 30-year-old woman has bilateral parotid enlargement, dry eyes, and dry mouth. Which test is most specific for the suspected diagnosis?

  1. Sialography showing ductal dilation
  2. Serum amylase measurement
  3. Salivary flow rate measurement
  4. Labial salivary gland biopsy showing focal lymphocytic sialadenitis Correct answer.

Explanation

Focal lymphocytic sialadenitis on labial gland biopsy is a specific criterion for Sjogren syndrome. Combined with dry eyes and dry mouth, it supports the diagnosis when serology is equivocal.

Question 14Oral Medicine, Oral Pathology and Oral Diagnosis

Which clinical feature best differentiates trigeminal neuralgia from temporomandibular disorder pain?

  1. Pain relieved by application of heat to the masseter
  2. Brief electric-shock pain triggered by light touch in a trigeminal division Correct answer.
  3. Pain accompanied by joint clicking and limited opening
  4. Dull ache worsened by chewing and jaw clenching

Explanation

Trigeminal neuralgia produces paroxysmal, lancinating pain in a trigeminal division, often triggered by innocuous stimuli such as touch or brushing. Temporomandibular disorder pain is typically a dull ache related to jaw function and joint loading.

Question 15Oral Medicine, Oral Pathology and Oral Diagnosis

A patient on long-term inhaled corticosteroids develops removable white plaques on the palate and buccal mucosa that wipe off to leave an erythematous base. Which management step is most appropriate?

  1. Systemic antibiotics
  2. Immediate biopsy of the plaque
  3. Topical corticosteroid application
  4. Topical antifungal therapy with nystatin or clotrimazole Correct answer.

Explanation

The presentation is pseudomembranous oral candidiasis, a common adverse effect of inhaled corticosteroids. Topical antifungals are first-line, along with rinsing the mouth after inhaler use.

Question 16Oral Medicine, Oral Pathology and Oral Diagnosis

Which radiographic appearance is typical of fibrous dysplasia of the jaws?

  1. A well-circumscribed radiolucency with a sclerotic rim
  2. A ground-glass radiopacity with blending into surrounding bone Correct answer.
  3. A diffuse periosteal sunburst pattern
  4. A multilocular soap-bubble radiolucency

Explanation

Fibrous dysplasia produces a ground-glass or orange-peel radiopacity that blends gradually with adjacent bone. Margins are ill-defined because the lesion merges with normal trabeculae.

Question 17Oral Medicine, Oral Pathology and Oral Diagnosis

A patient develops a painful, shallow ulcer with a yellow fibrin base and erythematous halo on the buccal mucosa that heals in ten days without scarring. What is the most likely diagnosis?

  1. Major recurrent aphthous ulcer
  2. Minor recurrent aphthous ulcer Correct answer.
  3. Oral lichen planus erosive type
  4. Herpes simplex primary infection

Explanation

Minor aphthous ulcers are small, shallow, heal within about two weeks, and leave no scar. Major aphthous ulcers are larger, persist longer, and often scar.

Question 18Oral Medicine, Oral Pathology and Oral Diagnosis

Which feature on a panoramic radiograph most suggests an ameloblastoma rather than a dentigerous cyst?

  1. A diffuse radiolucency crossing the midline of the maxilla
  2. A radiolucency with a sclerotic border at the apex of a carious tooth
  3. A unilocular radiolucency attached to the cementoenamel junction of an impacted tooth
  4. A multilocular radiolucency with cortical expansion and root resorption Correct answer.

Explanation

Ameloblastomas often appear multilocular with cortical expansion and root resorption, whereas dentigerous cysts are typically unilocular and attached at the cementoenamel junction. Root resorption favors a neoplastic process.

Question 19Oral Medicine, Oral Pathology and Oral Diagnosis

A patient with a history of radiotherapy to the head and neck develops exposed necrotic bone in the mandible that persists for three months without healing. Which diagnosis is most likely?

  1. Bisphosphonate-related osteonecrosis
  2. Osteomyelitis of the mandible
  3. Fibrous dysplasia
  4. Osteoradionecrosis Correct answer.

Explanation

Exposed bone persisting beyond eight weeks in a previously irradiated field, without infection or tumor recurrence, defines osteoradionecrosis. Radiation-induced hypovascularity impairs healing.

Question 20Oral Medicine, Oral Pathology and Oral Diagnosis

Which statement about oral hairy leukoplakia is correct?

  1. It is a premalignant lesion requiring excision
  2. It is caused by Candida albicans and resolves with antifungals alone
  3. It occurs mainly on the palate in healthy adults
  4. It appears as corrugated white plaques on the lateral tongue and is associated with Epstein-Barr virus Correct answer.

Explanation

Oral hairy leukoplakia presents as corrugated, non-removable white plaques on the lateral border of the tongue and is driven by Epstein-Barr virus, usually in immunocompromised patients. It is not considered premalignant.

Question 21Oral Medicine, Oral Pathology and Oral Diagnosis

A patient reports a dry mouth and a persistent salty taste. Examination shows a firm, lobulated mass in the floor of the mouth with intact mucosa. Which diagnosis should be considered first?

  1. Ranula of the sublingual gland
  2. Sialolith of the submandibular duct
  3. Mucoepidermoid carcinoma of the parotid
  4. Pleomorphic adenoma of the sublingual gland Correct answer.

Explanation

A firm, lobulated, painless mass in the sublingual region with intact mucosa suggests a benign salivary neoplasm, most often pleomorphic adenoma. Ranulas are fluctuant and bluish, and stones cause intermittent obstructive pain.

Question 22Oral Medicine, Oral Pathology and Oral Diagnosis

A patient with chronic kidney disease has a diffuse, painless enlargement of the maxilla with a ground-glass radiographic appearance and elevated serum parathyroid hormone. Which diagnosis is most likely?

  1. Brown tumor of hyperparathyroidism Correct answer.
  2. Cherubism
  3. Paget disease of bone
  4. Osteosarcoma

Explanation

Renal osteodystrophy with secondary hyperparathyroidism can produce brown tumors, which appear as well-defined radiolucencies or diffuse enlargement and ground-glass change. Elevated parathyroid hormone is the key clue.

Question 23Oral Medicine, Oral Pathology and Oral Diagnosis

Which histopathologic finding is most characteristic of pemphigoid rather than pemphigus?

  1. Subepithelial separation with linear IgG and C3 along the basement membrane Correct answer.
  2. Perivascular infiltration by atypical lymphocytes
  3. Intraepithelial abscesses containing eosinophils
  4. Suprabasal acantholysis with intercellular IgG deposition

Explanation

Bullous pemphigoid and mucous membrane pemphigoid show subepithelial blistering with linear deposition of IgG and C3 along the basement membrane zone. Pemphigus, by contrast, shows intraepithelial acantholysis with intercellular deposits.

Question 24Oral Medicine, Oral Pathology and Oral Diagnosis

A 60-year-old with a 40-pack-year smoking history has a painless, non-healing ulcer on the floor of the mouth. Which combination of features most increases the likelihood of malignancy?

  1. Recurrence after a course of topical antifungal treatment
  2. Bilateral white striae and a burning sensation
  3. Superficial ulceration with a history of trauma from a denture
  4. Induration at the margins with ipsilateral lymphadenopathy Correct answer.

Explanation

Induration and regional lymphadenopathy in a smoker strongly raise the probability of oral squamous cell carcinoma. The floor of the mouth is a high-risk site for malignant transformation.

Question 25Oral Medicine, Oral Pathology and Oral Diagnosis

A patient develops sudden unilateral swelling of the submandibular region during meals, with pain that subsides between meals. Which imaging modality is most appropriate to confirm the suspected cause?

  1. Positron emission tomography of the neck
  2. Occlusal or panoramic radiography to detect a radiopaque sialolith Correct answer.
  3. Cone-beam computed tomography of the temporomandibular joint
  4. Magnetic resonance imaging of the brain

Explanation

Mealtime-related submandibular swelling suggests obstructive sialadenitis, most often due to a duct stone. Occlusal or panoramic radiography can detect radiopaque calculi, and ultrasound may be added for radiolucent stones.

Question 26Oral Medicine, Oral Pathology and Oral Diagnosis

A 24-year-old woman reports recurrent episodes of unilateral facial paralysis, fissured tongue, and painless swelling of the upper lip that has been present for two years. She also notes occasional episodes of facial edema. Which diagnosis best explains this combination of findings?

  1. Bell palsy
  2. Systemic lupus erythematosus
  3. Sarcoidosis
  4. Melkersson-Rosenthal syndrome Correct answer.

Explanation

The triad of recurrent facial palsy, fissured tongue (lingua plicata), and orofacial edema (often of the lip) defines Melkersson-Rosenthal syndrome. The episodic nature and absence of systemic symptoms make other causes less likely. Bell palsy is isolated and non-recurrent, while sarcoidosis and lupus would show additional systemic features.

Question 27Oral Medicine, Oral Pathology and Oral Diagnosis

A 35-year-old man presents with a painless, freely movable, yellowish nodule on the buccal mucosa. He reports a habit of repeatedly biting the area. Excisional biopsy shows a circumscribed mass of mature adipocytes. Which diagnosis is most consistent with these findings?

  1. Hemangioma
  2. Fibroma
  3. Lipoma Correct answer.
  4. Mucocele

Explanation

Lipomas are benign neoplasms of mature adipocytes that present as soft, movable, yellowish nodules, often in the buccal mucosa. The histologic finding of circumscribed mature fat cells is diagnostic. Fibromas consist of fibrous connective tissue, mucoceles are cystic lesions of salivary glands, and hemangiomas are vascular malformations.

Question 28Oral Medicine, Oral Pathology and Oral Diagnosis

A 50-year-old woman has a 1-cm painless ulcer on the ventral tongue that has persisted for 6 weeks. She has no history of smoking or alcohol use. Examination reveals induration at the ulcer base. Which is the most appropriate next step in management?

  1. Perform a cytologic smear and observe
  2. Prescribe a topical corticosteroid and review in 2 weeks
  3. Refer for incisional biopsy and histopathologic examination Correct answer.
  4. Reassure the patient and review in 6 months

Explanation

Any oral ulcer persisting beyond 2 weeks, especially with induration, warrants biopsy to exclude malignancy. Incisional biopsy provides tissue for definitive histopathologic diagnosis. Topical steroids or observation would delay diagnosis, and cytology is not reliable for oral mucosal lesions.

Question 29Oral Medicine, Oral Pathology and Oral Diagnosis

A 45-year-old man with a history of treated pulmonary tuberculosis presents with a chronic, non-healing ulcer on the dorsum of the tongue. The ulcer has a granular, vegetating base and undermined edges. He also has a chronic cough and low-grade fever. Which condition should be considered in the differential diagnosis?

  1. Squamous cell carcinoma
  2. Primary syphilis
  3. Oral tuberculosis Correct answer.
  4. Traumatic ulcer

Explanation

Oral tuberculosis can present as a chronic, painful ulcer with undermined edges and a granular base, often on the tongue, in patients with a history of tuberculosis. Systemic symptoms such as chronic cough and low-grade fever support this diagnosis. Although squamous cell carcinoma is a key differential, the specific history and ulcer characteristics point toward tuberculosis, which requires confirmation by biopsy and microbiologic studies.

Question 30Oral Medicine, Oral Pathology and Oral Diagnosis

A 60-year-old woman with type 2 diabetes mellitus complains of a burning sensation and dryness of the mouth. Examination reveals generalized erythema of the oral mucosa, depapillation of the dorsal tongue, and angular cheilitis. She is not taking any medications. Which underlying condition is most likely responsible for these findings?

  1. Vitamin B12 deficiency Correct answer.
  2. Iron deficiency anemia
  3. Oral candidiasis
  4. Xerostomia due to diabetes

Explanation

Vitamin B12 deficiency can cause glossitis with depapillation, oral erythema, angular cheilitis, and burning mouth symptoms. These features are also seen in other deficiencies, but the combination of glossitis, angular cheilitis, and burning in a patient with diabetes (which may predispose to B12 deficiency due to metformin use, though not stated) makes B12 deficiency a strong consideration. Iron deficiency anemia can cause similar findings, but B12 deficiency is particularly associated with neurological symptoms and glossitis.

Question 31Restorative Dentistry and Endodontics

According to the classic G.V. Black classification, a carious lesion involving the proximal surface of an incisor that includes the incisal angle is classified as which cavity class?

  1. Class III
  2. Class II
  3. Class V
  4. Class IV Correct answer.

Explanation

Black's Class IV designation is reserved for proximal lesions of anterior teeth that also involve the incisal angle, which changes the restorative approach because the angle must be rebuilt. A proximal anterior lesion that leaves the incisal angle intact is Class III, and cervical lesions are Class V. Because the incisal angle is lost here, Class IV is the accurate classification.

Question 32Restorative Dentistry and Endodontics

Which bur is most appropriate for initial access and bulk removal of enamel and dentine during cavity preparation while preserving a smooth cavosurface margin?

  1. A round tungsten carbide bur in a high-speed handpiece
  2. A tapered fissure tungsten carbide bur in a high-speed handpiece Correct answer.
  3. A fine-grit diamond finishing bur
  4. A fissurotomy bur with a pointed tip

Explanation

A tapered fissure carbide bur cuts efficiently through enamel and dentine and produces straight walls with well-defined cavosurface margins, which suits outline form and bulk excavation. Round burs create rounded, less defined walls, and fine-grit diamonds are for finishing rather than bulk removal. Fissurotomy burs are narrow and designed for sealing shallow pits, not for cavity outline.

Question 33Restorative Dentistry and Endodontics

Which material property best explains why amalgam restorations require a minimum thickness and adequate unsupported enamel removal at the cavosurface?

  1. Low compressive strength
  2. High thermal conductivity
  3. High tensile strength
  4. Low edge strength and brittleness in thin sections Correct answer.

Explanation

Amalgam is strong in compression but weak in tension and has poor edge strength, so thin unsupported enamel or overhanging unsupported amalgam fractures under occlusal load. This is why preparations need butt-joint margins and adequate bulk. Thermal conductivity affects pulpal response and is managed with liners, not with thickness rules.

Question 34Restorative Dentistry and Endodontics

During root canal treatment, the working length is best defined as which reference point?

  1. The level of the cementoenamel junction
  2. The most coronal point of the canal orifice
  3. The radiographic apex of the root
  4. The apical constriction, typically 0.5 to 1.0 mm short of the radiographic apex Correct answer.

Explanation

Working length is the distance from a coronal reference point to the apical constriction, which usually lies 0.5 to 1.0 mm short of the radiographic apex. Instrumenting to this point avoids overextension into periapical tissues while allowing cleaning of the apical portion. The CEJ and canal orifice are coronal landmarks used for reference, not the apical limit.

Question 35Restorative Dentistry and Endodontics

Which irrigant is the standard choice for dissolving necrotic pulp tissue and lubricating canals during instrumentation?

  1. Chlorhexidine gluconate
  2. 0.9% sterile saline
  3. Sodium hypochlorite Correct answer.
  4. EDTA

Explanation

Sodium hypochlorite is the primary endodontic irrigant because it dissolves organic tissue, has antimicrobial action, and lubricates the canal. Chlorhexidine is antimicrobial but does not dissolve tissue, and EDTA is used to remove the smear layer and chelate inorganic debris. Saline provides only mechanical flushing.

Question 36Restorative Dentistry and Endodontics

Which feature distinguishes a reversible pulpitis from an irreversible pulpitis on clinical testing?

  1. Reversible pulpitis produces lingering pain after the stimulus is removed
  2. Irreversible pulpitis always shows a negative response to cold testing
  3. Reversible pulpitis is accompanied by a periapical radiolucency
  4. Reversible pulpitis produces sharp pain that subsides promptly once the stimulus is removed Correct answer.

Explanation

In reversible pulpitis the provoked pain is sharp and resolves quickly after the stimulus is withdrawn, and the pulp remains vital. Irreversible pulpitis characteristically produces lingering or spontaneous pain, and periapical radiolucency indicates pulpal necrosis with apical periodontitis rather than reversible disease.

Question 37Restorative Dentistry and Endodontics

Which instrument is used to remove the smear layer from the root canal wall before obturation?

  1. A Gates-Glidden drill
  2. Paper points
  3. 17% EDTA solution Correct answer.
  4. 5.25% sodium hypochlorite

Explanation

EDTA is a chelating agent that removes the inorganic component of the smear layer, and it is typically combined with sodium hypochlorite to remove the organic component. Sodium hypochlorite alone dissolves organic tissue but leaves the smear layer largely intact. Gates-Glidden drills shape the coronal canal, and paper points dry it.

Question 38Restorative Dentistry and Endodontics

Which adhesive strategy involves etching enamel and dentine with phosphoric acid, rinsing, and then applying a primer and bonding resin?

  1. Glass ionomer conditioning
  2. Self-etch approach
  3. Etch-and-rinse (total-etch) approach Correct answer.
  4. Selective enamel etch

Explanation

The etch-and-rinse, or total-etch, approach uses phosphoric acid on enamel and dentine followed by rinsing, priming, and bonding. Self-etch systems use acidic primers that are not rinsed, and selective enamel etch applies acid to enamel only before a self-etch adhesive. The defining feature is acid etching of both substrates with a rinse step.

Question 39Restorative Dentistry and Endodontics

A patient reports sharp pain on biting that resolves immediately when pressure is released, and the tooth has a deep occlusal amalgam with a marginal ridge that appears unsupported. Which is the most likely diagnosis?

  1. Cracked tooth syndrome Correct answer.
  2. Acute apical abscess
  3. Irreversible pulpitis
  4. Reversible pulpitis

Explanation

Pain on biting that resolves immediately on release, especially in a heavily restored tooth with an unsupported cusp or marginal ridge, points to cracked tooth syndrome. The pulp may still be vital, and the classic sign is provocation by biting on a specific cusp. Irreversible pulpitis and abscess produce spontaneous or lingering pain and periapical signs.

Question 40Restorative Dentistry and Endodontics

When placing a Class II composite restoration, which technique best reduces polymerization shrinkage stress at the gingival margin?

  1. Curing from the occlusal surface only after the full restoration is placed
  2. Placing the composite without any bonding agent
  3. Bulk filling the entire cavity in one increment
  4. Using an incremental oblique layering technique with a flowable liner Correct answer.

Explanation

Incremental oblique layering reduces the C-factor and shrinkage stress by keeping each increment small, and a flowable liner improves adaptation at the gingival margin. Bulk filling increases shrinkage stress and the risk of marginal gap formation. Curing after full placement and omitting bonding both compromise the seal.

Question 41Restorative Dentistry and Endodontics

A maxillary first molar has three canals instrumented, but a fourth canal is suspected. Which canal is most commonly missed in this tooth?

  1. The distolingual canal
  2. The distobuccal canal
  3. The mesiobuccal second canal (MB2) Correct answer.
  4. The palatal canal

Explanation

The maxillary first molar most often has a second mesiobuccal canal (MB2), located lingual to the main MB canal, and failure to locate it is a common cause of persistent symptoms. The distobuccal and palatal canals are consistently present and easier to find. A distolingual canal is not a normal feature of this tooth.

Question 42Restorative Dentistry and Endodontics

Which factor most directly explains the reduced bond strength of a resin composite to dentine compared with enamel?

  1. Dentine is more highly mineralized and drier than enamel
  2. Dentine contains more organic material and tubular fluid that interfere with hybridization Correct answer.
  3. Dentine has a higher inorganic content than enamel
  4. Dentine has no collagen matrix

Explanation

Dentine is roughly 50% mineral by volume with substantial organic content and fluid-filled tubules, so bonding depends on hybridizing the collagen network, which is technique-sensitive. Enamel is about 96% mineral and provides a more reliable etch pattern. The presence of water and organic matrix, not higher mineralization, explains the weaker dentine bond.

Question 43Restorative Dentistry and Endodontics

During access preparation for a mandibular first molar, the operator notes the canal orifices form a roughly rectangular pattern. Which configuration is most consistent with this finding?

  1. Three canals with two mesial and one distal
  2. A single C-shaped canal
  3. Four canals with two mesial and two distal Correct answer.
  4. Two canals, one mesial and one distal

Explanation

The mandibular first molar commonly has two mesial and two distal canals, producing a rectangular orifice pattern; the second distal canal is the one most often overlooked. Two-canal and three-canal patterns also occur but give a different orifice outline. A C-shaped canal is characteristic of mandibular second molars and produces a continuous curved slit.

Question 44Restorative Dentistry and Endodontics

Which protocol best minimizes the risk of a sodium hypochlorite accident during irrigation?

  1. Wedging a narrow needle deep into the canal and applying firm pressure
  2. Using a side-vented needle positioned short of the working length with gentle, slow delivery Correct answer.
  3. Using a high-concentration solution with rapid, forceful irrigation
  4. Irrigating without a rubber dam to observe soft tissue responses

Explanation

A side-vented needle placed 1 to 2 mm short of working length with slow, gentle delivery limits extrusion of irrigant into periapical tissues. Needle wedging and forceful delivery raise apical pressure and cause accidents. A rubber dam is mandatory, and observing soft tissue is not a substitute for controlled delivery.

Question 45Restorative Dentistry and Endodontics

A patient requests replacement of a failing amalgam in a premolar with a direct composite. Which consideration most strongly favors placing a cuspal coverage restoration instead?

  1. The remaining marginal ridge and cusp are thin and unsupported Correct answer.
  2. The tooth has a small occlusal caries lesion
  3. The opposing tooth is restored with amalgam
  4. The patient prefers a tooth-colored material

Explanation

When remaining cusps or marginal ridges are thin and unsupported, direct composite may be unable to withstand occlusal load, and cuspal coverage protects against cusp fracture. Material preference alone does not dictate coverage. Small lesions and the opposing restoration do not by themselves indicate cuspal coverage.

Question 46Restorative Dentistry and Endodontics

Which radiographic finding most supports a diagnosis of asymptomatic apical periodontitis in a previously treated tooth?

  1. A widened periodontal ligament space confined to the coronal third
  2. A periapical radiolucency in a tooth with a nonvital pulp and no symptoms Correct answer.
  3. A periapical radiolucency with a vital, responsive pulp
  4. A diffuse radiopacity at the apex

Explanation

Asymptomatic apical periodontitis presents as a periapical radiolucency in a nonvital or previously treated tooth without spontaneous symptoms. A vital, responsive pulp argues against an endodontic periapical lesion. A widened coronal PDL space alone is nonspecific, and apical radiopacity suggests sclerosis or other pathology rather than a lucent lesion.

Question 47Restorative Dentistry and Endodontics

Which step in the root canal obturation sequence is performed immediately before the sealer and gutta-percha are placed?

  1. Application of a temporary restoration
  2. Final irrigation and drying of the canal with paper points Correct answer.
  3. Canal enlargement with a Gates-Glidden drill
  4. Placement of a cotton pellet in the pulp chamber

Explanation

After shaping and final irrigation, the canal must be dried with paper points before sealer and gutta-percha are introduced, since residual moisture and irrigant impair sealer adaptation. Cotton pellets and temporary restorations follow obturation. Gates-Glidden enlargement is a shaping step performed earlier, not immediately before obturation.

Question 48Restorative Dentistry and Endodontics

A patient presents with a fractured cusp on a mandibular molar with a large MOD amalgam. The pulp tests normal and there is no percussion tenderness. Which management is most appropriate?

  1. Replacement of the restoration with cuspal coverage Correct answer.
  2. Immediate extraction and implant planning
  3. Endodontic treatment followed by a post and core
  4. Application of a desensitizing agent only

Explanation

A fractured cusp in a vital, asymptomatic tooth with no periapical signs is managed by removing the fractured portion and restoring the tooth with cuspal coverage to protect the remaining structure. Extraction, endodontics, and desensitizing alone are inappropriate when the pulp is healthy. The key is that the pulp status is normal and the tooth is restorable.

Question 49Restorative Dentistry and Endodontics

Which factor is most likely to cause a post-endodontic restoration to fail despite an adequate root canal filling?

  1. A post placed in the canal with a passive fit
  2. A minimal ferrule and inadequate coronal seal Correct answer.
  3. A well-adapted coronal seal with cuspal coverage
  4. Adequate remaining dentine thickness

Explanation

A minimal ferrule and inadequate coronal seal are major predictors of failure in post-endodontic restorations because they permit leakage and root fracture. A well-adapted seal with cuspal coverage and adequate dentine thickness are protective factors. A passively fitting post is desirable and reduces the risk of root fracture.

Question 50Restorative Dentistry and Endodontics

Which property of glass ionomer cement makes it useful as a liner or base under restorations?

  1. Chemical bonding to tooth structure and fluoride release Correct answer.
  2. High compressive strength comparable to amalgam
  3. Complete insolubility in oral fluids
  4. Ability to polymerize without any water contamination

Explanation

Glass ionomer bonds chemically to enamel and dentine and releases fluoride, which makes it useful as a liner or base and in some pediatric applications. Its compressive strength is lower than amalgam, it is susceptible to moisture during early setting, and it is not completely insoluble. These properties explain its specific role rather than use as a definitive load-bearing restoration.