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EUC-ODON practice questions

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Question 1Clinical Periodontology and Implantology

According to the 2018 classification of periodontal and peri-implant diseases, a patient with interdental clinical attachment loss of 4 mm at two non-adjacent teeth, maximum probing depth of 5 mm, and no tooth loss from periodontitis would be classified as which stage?

  1. Stage III
  2. Stage IV
  3. Stage I
  4. Stage II Correct answer.

Explanation

Stage II periodontitis is defined by interdental CAL of 3–4 mm, maximum probing depth of 5 mm or less, and no tooth loss attributable to periodontitis. The described case fits these boundaries exactly. Stage III requires CAL of 5 mm or more or probing depths of 6 mm or more.

Question 2Clinical Periodontology and Implantology

In the 2018 classification, which descriptor distinguishes generalized from localized periodontitis?

  1. Percentage of teeth with bleeding on probing
  2. Proportion of teeth with interdental CAL of 1 mm or more Correct answer.
  3. Amount of radiographic bone loss at the worst site
  4. Number of teeth with probing depth of 4 mm or more

Explanation

Localized versus generalized extent is determined by the proportion of teeth showing interdental CAL of at least 1 mm. Localized means less than 30% of teeth are affected, while generalized means 30% or more. Bleeding on probing and probing depth are not the extent criteria.

Question 3Clinical Periodontology and Implantology

Which grading parameter is used as the primary determinant of periodontitis grade in the 2018 classification?

  1. Presence of supragingival calculus
  2. Gingival index score
  3. Percentage of radiographic bone loss divided by age Correct answer.
  4. Number of sites with bleeding on probing

Explanation

Grade reflects the rate of progression and is primarily estimated from the ratio of percentage radiographic bone loss to the patient's age. Grade modifiers such as smoking and diabetes are then applied. Bleeding, calculus, and gingival index are not primary grading parameters.

Question 4Clinical Periodontology and Implantology

A patient with periodontitis reports smoking 15 cigarettes per day and has a HbA1c of 8.2% with no known diabetes diagnosis. How do these findings affect the grade assignment?

  1. They have no effect on grade and only influence stage
  2. They act as grade modifiers that can shift the grade upward Correct answer.
  3. They exclude the patient from the 2018 classification
  4. They automatically assign Stage IV regardless of CAL

Explanation

Current smoking of 10 or more cigarettes per day and HbA1c of 7.0% or higher in diabetes are recognized grade modifiers that increase the risk of progression and can raise the grade. A HbA1c of 8.2% suggests undiagnosed diabetes and warrants medical referral. These factors modify grade rather than stage.

Question 5Clinical Periodontology and Implantology

Which clinical measurement is the reference point from which clinical attachment level is calculated?

  1. Gingival margin
  2. Cementoenamel junction Correct answer.
  3. Base of the sulcus
  4. Alveolar bone crest

Explanation

Clinical attachment level is measured from the cementoenamel junction to the base of the periodontal pocket. This reference remains stable even when the gingival margin recedes or becomes enlarged. Probing depth alone cannot distinguish recession from attachment loss.

Question 6Clinical Periodontology and Implantology

A patient has a probing depth of 6 mm with the gingival margin located 2 mm coronal to the cementoenamel junction. What is the clinical attachment level?

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

Explanation

When the gingival margin is coronal to the CEJ, the CAL equals the probing depth minus the amount of gingival enlargement. Here 6 mm minus 2 mm gives 4 mm of true attachment loss. Ignoring the margin position would overestimate attachment loss.

Question 7Clinical Periodontology and Implantology

Which probing error systematically leads to underestimation of true probing depth in inflamed tissues?

  1. Inadequate probe angulation
  2. Probe tip penetrating beyond the junctional epithelium Correct answer.
  3. Excessive probing force
  4. Probing immediately after scaling

Explanation

In inflamed connective tissue the probe tip can pass apically beyond the coronal extent of the junctional epithelium, giving a reading deeper than the true histologic attachment. This overestimates rather than underestimates depth in inflamed sites. Underestimation commonly results from inadequate force, poor angulation, or heavy calculus.

Question 8Clinical Periodontology and Implantology

Which radiographic finding is the earliest reliable sign of alveolar bone loss in periodontitis?

  1. Furcation radiolucency
  2. Widening of the periodontal ligament space at the apex
  3. Reduction in crestal bone height relative to the CEJ Correct answer.
  4. Loss of lamina dura at the crest

Explanation

Early bone loss appears as reduced distance between the alveolar crest and the cementoenamel junction, normally about 1–2 mm. Crestal lamina dura loss can occur but is less specific. Furcation and apical changes reflect more advanced disease.

Question 9Clinical Periodontology and Implantology

Which factor most limits the diagnostic value of bitewing radiographs for assessing periodontal bone loss?

  1. They overestimate bone loss consistently
  2. They are contraindicated in periodontitis
  3. They do not display the CEJ clearly in all areas Correct answer.
  4. They cannot show the alveolar crest

Explanation

Accurate bone loss assessment requires a visible CEJ as a reference, and bitewings may not clearly show it, especially with restorations or overlapping. They do show the crest but with limited coverage. They do not systematically overestimate loss.

Question 10Clinical Periodontology and Implantology

Which instrument is most appropriate for subgingival calculus removal in a 6 mm pocket on the distal aspect of a mandibular molar?

  1. Periodontal probe
  2. Area-specific Gracey curette with an angled shank Correct answer.
  3. Explorer
  4. Universal curette with a straight shank

Explanation

Area-specific Gracey curettes have an angled shank and curved blade that adapt to root concavities and posterior pockets. A straight-shank universal curette has limited access to deep distal molar surfaces. Probes and explorers are diagnostic, not debridement, instruments.

Question 11Clinical Periodontology and Implantology

What is the primary rationale for using an ultrasonic scaler instead of hand instruments in supportive periodontal therapy?

  1. It sterilizes the pocket
  2. It eliminates the need for probing
  3. It guarantees complete calculus removal
  4. It reduces operator fatigue and improves access to deep pockets Correct answer.

Explanation

Ultrasonic scalers reduce operator fatigue, improve access to deep pockets and furcations, and provide lavage. They do not guarantee complete removal and must be complemented by careful assessment. Neither ultrasonic nor hand instrumentation sterilizes the pocket.

Question 12Clinical Periodontology and Implantology

Which host factor is most strongly associated with rapid progression of periodontitis?

  1. Mild gingivitis
  2. Occasional alcohol consumption
  3. Well-controlled type 2 diabetes with HbA1c of 6.5%
  4. Poorly controlled diabetes with HbA1c above 8% Correct answer.

Explanation

Poorly controlled diabetes, reflected by elevated HbA1c, impairs neutrophil function and healing and is strongly associated with rapid periodontal progression. Well-controlled diabetes carries much lower risk. Alcohol and mild gingivitis are not comparable risk factors.

Question 13Clinical Periodontology and Implantology

A 45-year-old patient has severe periodontitis with attachment loss far exceeding what would be expected for age, plus a sibling with similar early tooth loss. Which diagnosis should be considered?

  1. Grade C periodontitis with possible familial aggregation Correct answer.
  2. Peri-implant mucositis
  3. Grade A periodontitis
  4. Plaque-induced gingivitis

Explanation

Grade C denotes rapid progression, indicated by bone loss exceeding expected age-related levels or a familial pattern of early tooth loss. The described severity and family history support Grade C. Grade A indicates slow progression, and the other options do not match the presentation.

Question 14Clinical Periodontology and Implantology

Which clinical parameter is the most reliable predictor of future periodontal attachment loss at a site?

  1. Tooth mobility alone
  2. Persistent bleeding on probing combined with increasing probing depth Correct answer.
  3. Bleeding on probing alone
  4. Presence of supragingival plaque alone

Explanation

The absence of bleeding on probing has high negative predictive value for stability, while persistent bleeding together with increasing pocket depth strongly predicts future attachment loss. Bleeding alone is nonspecific because many sites bleed without progressing. Plaque and mobility alone are weaker predictors.

Question 15Clinical Periodontology and Implantology

Which procedure is the initial nonsurgical treatment of choice for chronic periodontitis?

  1. Subgingival scaling and root planing with oral hygiene instruction Correct answer.
  2. Extraction of all involved teeth
  3. Immediate flap surgery
  4. Systemic antibiotics alone

Explanation

Subgingival scaling and root planing combined with oral hygiene instruction is the first-line treatment for periodontitis. Surgery is considered only after re-evaluation if residual pockets persist. Antibiotics are adjunctive and never replace mechanical debridement.

Question 16Clinical Periodontology and Implantology

When is systemic antibiotic therapy most appropriately added to nonsurgical periodontal treatment?

  1. Routinely for all patients with gingivitis
  2. Instead of mechanical debridement
  3. As an adjunct in Grade C or Stage III–IV periodontitis after full-mouth debridement Correct answer.
  4. Only when the patient refuses oral hygiene instruction

Explanation

Systemic antibiotics are considered adjunctive for severe or rapidly progressing periodontitis, typically after mechanical debridement has disrupted the biofilm. They are not indicated for gingivitis and never substitute for debridement. Overuse promotes resistance.

Question 17Clinical Periodontology and Implantology

What is the main limitation of systemic antibiotics as an adjunct in periodontitis treatment?

  1. They cause immediate periodontal regeneration
  2. They are ineffective against any periodontal pathogen
  3. They cannot reach the gingival crevicular fluid
  4. They do not penetrate the biofilm effectively and raise resistance concerns Correct answer.

Explanation

Systemic antibiotics reach gingival crevicular fluid but penetrate biofilm poorly, and widespread use raises antimicrobial resistance concerns. They are therefore adjunctive after mechanical disruption of the biofilm. They do not produce periodontal regeneration.

Question 18Clinical Periodontology and Implantology

Which flap design is most appropriate for access to deep intrabony defects on the facial aspect of anterior teeth while preserving aesthetics?

  1. Modified Widman flap Correct answer.
  2. Apically positioned flap
  3. Free gingival graft
  4. Laterally positioned flap

Explanation

The modified Widman flap provides access for debridement and defect management with minimal recession, which is desirable in the aesthetic zone. Apically and laterally positioned flaps intentionally move tissue and cause recession. A free gingival graft is used to increase keratinized tissue, not for defect access.

Question 19Clinical Periodontology and Implantology

Which graft material provides both osteoconductive and osteoinductive properties?

  1. Deproteinized bovine bone mineral
  2. Calcium sulfate
  3. Autogenous bone Correct answer.
  4. Collagen membrane

Explanation

Autogenous bone contains viable osteogenic cells and growth factors, providing osteoconductive, osteoinductive, and osteogenic potential. Deproteinized bovine bone is primarily osteoconductive. Calcium sulfate is a barrier/space filler, and collagen membranes are barriers, not graft materials.

Question 20Clinical Periodontology and Implantology

Which factor most strongly determines the success of guided tissue regeneration in an intrabony defect?

  1. Use of a suture material
  2. Presence of supragingival calculus
  3. Defect morphology with a narrow, deep, well-contained defect Correct answer.
  4. Patient's age alone

Explanation

Guided tissue regeneration succeeds best in narrow, deep, well-contained intrabony defects with adequate space maintenance. Defect morphology is a stronger determinant than age alone. Calculus and suture choice influence healing but are not primary determinants of regeneration.

Question 21Clinical Periodontology and Implantology

Which definition best describes peri-implant mucositis?

  1. Infection of the implant body
  2. Reversible inflammation of peri-implant soft tissue without bone loss Correct answer.
  3. Progressive bone loss around an implant
  4. Irreversible loss of the implant

Explanation

Peri-implant mucositis is reversible inflammation of the soft tissues around an implant without progressive bone loss. Peri-implantitis, by contrast, involves progressive bone loss. The distinction guides management and prognosis.

Question 22Clinical Periodontology and Implantology

A patient presents with bleeding on probing and suppuration around an implant, probing depth of 7 mm, and radiographic bone loss of 3 mm compared with the baseline radiograph. Which diagnosis is most likely?

  1. Peri-implant mucositis
  2. Healthy peri-implant tissue
  3. Implant fracture
  4. Peri-implantitis Correct answer.

Explanation

Peri-implantitis is characterized by inflammation, bleeding and suppuration, increasing probing depth, and progressive radiographic bone loss beyond initial remodeling. Bone loss of 3 mm with bleeding and suppuration exceeds the mucositis picture. Healthy tissue and fracture do not match these findings.

Question 23Clinical Periodontology and Implantology

Which risk indicator is most consistently associated with peri-implantitis?

  1. Use of titanium implants
  2. Female sex
  3. Use of a surgical guide
  4. History of periodontitis Correct answer.

Explanation

A history of periodontitis is among the strongest risk indicators for peri-implantitis, along with smoking and poor plaque control. Implant material, sex, and guided surgery are not established risk indicators of comparable strength.

Question 24Clinical Periodontology and Implantology

Which surgical approach is used to treat a peri-implant lesion with a suprabony defect and no implant mobility?

  1. Apicoectomy of the implant
  2. Flap elevation with debridement and decontamination of the implant surface Correct answer.
  3. Immediate implant removal
  4. Crown lengthening around the implant

Explanation

For peri-implantitis with a suprabony defect and a stable implant, a surgical flap with debridement and surface decontamination is appropriate. Implant removal is reserved for mobile or hopeless implants. Apicoectomy and crown lengthening do not apply to implants.

Question 25Clinical Periodontology and Implantology

Which maintenance interval is generally recommended for a patient with a history of treated periodontitis and multiple residual pockets?

  1. Only when symptoms arise
  2. Every 3 to 4 months Correct answer.
  3. Every 12 months
  4. Every 6 months

Explanation

Patients with treated periodontitis and residual pockets benefit from supportive periodontal therapy at 3- to 4-month intervals, which reduces the risk of recurrence. Longer intervals are appropriate only for stable, low-risk patients. Symptom-driven care allows silent progression.

Question 26Clinical Periodontology and Implantology

In the 2018 EFP/AAP classification, a patient with interdental clinical attachment loss of 4 mm, maximum probing depth of 5 mm, no tooth loss from periodontitis, and fewer than 10 teeth with probing depth ≥5 mm is assigned which stage?

  1. Stage I
  2. Stage IV
  3. Stage II Correct answer.
  4. Stage III

Explanation

Staging is set by the most severe dimension: interdental CAL 3–4 mm defines Stage II, and complexity factors such as probing depth ≤5 mm, horizontal bone loss confined to the coronal third, and no periodontitis-related tooth loss keep the case at that stage. Stage III requires CAL ≥5 mm, and Stage IV requires CAL ≥5 mm plus advanced complexity such as masticatory dysfunction or bite collapse.

Question 27Clinical Periodontology and Implantology

Which grade descriptor corresponds to a patient whose radiographic bone loss is 60% at age 50, giving a bone-loss-to-age ratio of approximately 1.2?

  1. Grade A
  2. Grade C Correct answer.
  3. Grade D
  4. Grade B

Explanation

Grade is estimated from the ratio of percentage radiographic bone loss to age in years: below 0.25 is Grade A, 0.25–1.0 is Grade B, and above 1.0 is Grade C. A ratio of about 1.2 therefore places the patient in Grade C, indicating rapid progression.

Question 28Clinical Periodontology and Implantology

Which clinical measurement is used to calculate clinical attachment level at a site?

  1. Probing depth plus the distance from the cementoenamel junction to the gingival margin Correct answer.
  2. The distance from the cementoenamel junction to the mucogingival junction
  3. Probing depth minus the distance from the gingival margin to the mucogingival junction
  4. Probing depth alone, recorded to the nearest millimetre

Explanation

Clinical attachment level expresses the position of the junctional epithelium relative to a fixed landmark, the cementoenamel junction. It is obtained by combining probing depth with the position of the gingival margin, adding the margin-to-CEJ distance when recession is present and subtracting it when the margin is coronal to the CEJ.

Question 29Clinical Periodontology and Implantology

A patient has generalized gingival inflammation with bleeding on probing at nearly every site, but no sites show attachment loss beyond the expected age-related change. Which diagnosis fits best?

  1. Plaque-induced gingivitis Correct answer.
  2. Peri-implant mucositis
  3. Periodontitis, Stage I
  4. Necrotizing gingivitis

Explanation

Gingivitis is defined by reversible inflammation of the gingiva with bleeding and erythema but without clinical attachment loss. Because no attachment loss is present, a periodontitis diagnosis cannot be made regardless of how widespread the bleeding is.

Question 30Clinical Periodontology and Implantology

Which local anatomic factor most directly predisposes a mandibular molar to localized periodontitis by favouring plaque retention?

  1. A shallow vestibular depth
  2. A wide zone of attached gingiva
  3. A cervical enamel projection extending into the furcation Correct answer.
  4. Presence of a mandibular tori

Explanation

Cervical enamel projections create a physical discontinuity where the junctional epithelium cannot form a normal seal, and the enamel surface favours biofilm retention in the furcation. This makes the site more vulnerable to localized attachment loss.

Question 31Clinical Periodontology and Implantology

Which smoking-related parameter is most useful to record because it modifies both periodontal grading and implant risk assessment?

  1. Type of tobacco brand only
  2. Whether the patient smokes indoors or outdoors
  3. Age at which smoking started only
  4. Number of cigarettes per day and years of smoking Correct answer.

Explanation

Cumulative exposure, expressed as cigarettes per day and years smoked, is what drives the dose-dependent effect of smoking on attachment loss and implant failure. Current versus former status and pack-years are the values used in grading and in implant risk discussion.

Question 32Clinical Periodontology and Implantology

Which systemic condition is most characteristically associated with a 'furry' gingival enlargement that is often resistant to plaque control alone?

  1. Phenytoin therapy Correct answer.
  2. Iron-deficiency anaemia
  3. Type 2 diabetes mellitus
  4. Hyperthyroidism

Explanation

Phenytoin is a classic drug cause of fibrous gingival overgrowth, which may require surgical reduction in addition to plaque control. Drug-influenced enlargement often persists despite excellent hygiene because the fibrous component is not purely inflammatory.

Question 33Clinical Periodontology and Implantology

Which finding on a periodontal chart best supports a diagnosis of a true furcation involvement rather than a deep proximal pocket?

  1. Horizontal probing into the furcation from the buccal aspect with a Nabers probe Correct answer.
  2. A probing depth of 7 mm on the mesial aspect of the tooth
  3. Radiographic widening of the periodontal ligament space at the apex
  4. Bleeding on probing at the distobuccal line angle

Explanation

Furcation involvement is confirmed by horizontal probing into the furcation entrance, which demonstrates access between the roots. Deep proximal probing depths and bleeding alone reflect interproximal attachment loss and do not establish furcation entry.

Question 34Clinical Periodontology and Implantology

Which outcome measure is the most sensitive indicator of disease progression when monitoring a patient in supportive periodontal care over several years?

  1. Change in clinical attachment level at individual sites over time Correct answer.
  2. Probing depth at a single visit
  3. Plaque score at a single visit
  4. Bleeding on probing at a single visit

Explanation

Attachment level is measured against the fixed cementoenamel junction, so serial changes reflect true loss or gain of supporting tissue. Single-visit bleeding, plaque and probing depth values fluctuate with inflammation and do not by themselves demonstrate progression.

Question 35Clinical Periodontology and Implantology

A patient with generalized Stage III periodontitis has a 7 mm pocket on a maxillary central incisor with 2 mm of recession and no bleeding after subgingival debridement. Which interpretation of the residual pocket is most appropriate?

  1. Systemic antibiotics are indicated solely because the pocket is 7 mm
  2. The site may be maintained without surgery because bleeding on probing is absent and the patient can clean it Correct answer.
  3. The site should be re-instrumented every two weeks indefinitely
  4. Immediate extraction is indicated because the pocket exceeds 6 mm

Explanation

Residual pocket depth alone is a weak predictor of progression; absence of bleeding on probing after therapy indicates a low risk of further breakdown, and a site that the patient can maintain may be kept under close monitoring. Surgical access is considered when inflammation persists or the site cannot be kept clean.

Question 36Clinical Periodontology and Implantology

Which principle best explains why subgingival debridement with hand instruments is difficult to complete in pockets deeper than 5 mm?

  1. Local anaesthetic cannot be used in deep pockets
  2. Curettes cannot reach the cementoenamel junction
  3. Blind instrumentation limits tactile detection and access to the full pocket base Correct answer.
  4. Ultrasonic tips are contraindicated beyond 5 mm

Explanation

Without surgical access the operator works by tactile feedback, and deeper pockets, furcations and root concavities reduce the completeness of calculus removal. This is why residual deposits are more frequent in deep sites and why re-evaluation is needed.

Question 37Clinical Periodontology and Implantology

Which regenerative material is described as osteoconductive, osteoinductive and osteogenic because it retains viable cells and matrix proteins?

  1. Autogenous bone graft Correct answer.
  2. Freeze-dried bone allograft
  3. Deproteinized bovine bone mineral
  4. Calcium sulphate

Explanation

Only fresh autogenous bone carries living osteogenic cells together with osteoinductive matrix proteins and an osteoconductive scaffold. All other graft classes supply at most two of these three properties.

Question 38Clinical Periodontology and Implantology

Which suture technique is most appropriate for achieving primary closure over a barrier membrane in a mandibular posterior site with limited keratinized tissue?

  1. A continuous blanket suture left in place for four weeks
  2. Sutures placed only through the lingual mucosa
  3. Interrupted sutures placed without tension after periosteal release Correct answer.
  4. Interrupted sutures placed under maximum tension to advance the flap

Explanation

Membrane exposure is the main cause of regenerative failure, so closure must be tension-free. Periosteal release allows the flap to advance passively, and interrupted sutures provide secure apposition without strangulating the tissue.

Question 39Clinical Periodontology and Implantology

Which finding is the most reliable clinical sign that a peri-implant site is healthy rather than inflamed?

  1. A probing depth of 3 mm at a single visit
  2. A radiograph taken at implant placement
  3. Presence of keratinized mucosa alone
  4. Absence of bleeding on probing with a shallow probing depth and stable bone level Correct answer.

Explanation

Implant health is defined by absence of bleeding and suppuration on gentle probing, shallow probing depths and stable marginal bone over time. A single depth measurement or a baseline radiograph cannot demonstrate current stability.

Question 40Clinical Periodontology and Implantology

Which management is most appropriate for a single implant with peri-implant mucositis and no bone loss on radiographs?

  1. Resective surgery with implantoplasty
  2. Mechanical debridement of the implant surface with reinforcement of oral hygiene Correct answer.
  3. Systemic antibiotics without debridement
  4. Immediate explantation of the implant

Explanation

Peri-implant mucositis is reversible inflammation confined to soft tissue, so treatment is non-surgical: mechanical removal of biofilm with appropriate instruments plus hygiene instruction and supportive maintenance. Surgery and antibiotics are not indicated without bone loss.

Question 41Endodontics

Which pulp diagnosis is defined by provoked pain that lingers after the stimulus is removed and is poorly localized?

  1. Symptomatic irreversible pulpitis Correct answer.
  2. Normal pulp
  3. Asymptomatic irreversible pulpitis
  4. Reversible pulpitis

Explanation

Symptomatic irreversible pulpitis is characterized by spontaneous or provoked pain that persists well beyond removal of the stimulus, often poorly localized because of pulpal inflammation. The lingering quality reflects a pulp that cannot heal and requires root canal treatment or extraction.

Question 42Endodontics

A tooth is unresponsive to cold and EPT testing, tender to percussion, and shows a widened periodontal ligament space with a periapical radiolucency. Which pulpal and apical diagnosis fits best?

  1. Necrotic pulp with asymptomatic apical periodontitis
  2. Necrotic pulp with symptomatic apical periodontitis Correct answer.
  3. Reversible pulpitis with normal apical tissues
  4. Irreversible pulpitis with acute apical abscess

Explanation

A nonresponsive pulp indicates necrosis, and percussion tenderness plus a widened PDL space indicate symptomatic apical periodontitis. The presence of a periapical radiolucency confirms established apical disease, but pain on percussion is what makes it symptomatic.

Question 43Endodontics

Which sensibility test is most reliable for distinguishing a vital from a necrotic pulp in a tooth with a mature apex?

  1. Transillumination
  2. Electric pulp testing
  3. Percussion testing
  4. Cold thermal testing Correct answer.

Explanation

Cold thermal testing has better support as the first-line sensibility test for distinguishing a vital from a necrotic pulp in mature teeth. Comparative clinical evidence favors its accuracy and reproducibility. It assesses neural responsiveness, not blood flow, so clinical findings and complementary tests remain relevant.

Question 44Endodontics

During access preparation in a mandibular first molar, the clinician finds four canals. Which configuration is most consistent with the typical anatomy?

  1. Four canals all located in the distal root
  2. Two mesial canals and two distal canals Correct answer.
  3. One mesial canal and three distal canals
  4. Three mesial canals and one distal canal

Explanation

The mandibular first molar most commonly has two mesial canals (mesiobuccal and mesiolingual) and one or two distal canals, so a four-canal pattern usually represents two mesial and two distal canals. A separate second distal canal occurs in a minority of teeth and must be sought actively.

Question 45Endodontics

A maxillary first molar typically has which canal configuration that clinicians must anticipate during negotiation?

  1. A second mesiobuccal canal in a substantial proportion of cases Correct answer.
  2. One mesiobuccal canal in nearly all cases
  3. Two distobuccal canals in most cases
  4. A single palatal canal that is always the narrowest

Explanation

The maxillary first molar frequently has a second mesiobuccal canal (MB2), found in a majority of teeth in anatomic studies, so clinicians should carefully search the mesiobuccal pulp chamber floor. The palatal canal is typically the largest and most readily negotiated.

Question 46Endodontics

Which working length determination method is considered the most accurate during root canal treatment?

  1. Tactile sensation alone
  2. Average canal length tables
  3. Apex locator combined with a confirmatory radiograph Correct answer.
  4. Radiograph alone without an apex locator

Explanation

Electronic apex locators locate the apical constriction with high accuracy, and combining this with a confirmatory radiograph improves reliability, especially in the presence of blood or irrigant. Relying on a single method alone increases the risk of over- or under-instrumentation.

Question 47Endodontics

Which irrigant is the primary choice for dissolving necrotic tissue and providing antimicrobial action during chemomechanical preparation?

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

Explanation

Sodium hypochlorite is the main irrigant because it dissolves organic tissue and has broad antimicrobial activity against bacteria and biofilm in the canal. Its concentration varies by protocol, but its tissue-dissolving property is unique among the common irrigants.

Question 48Endodontics

What is the principal role of EDTA irrigation during root canal treatment?

  1. Removing the inorganic smear layer and facilitating dentinal tubule penetration Correct answer.
  2. Providing sustained antimicrobial effect between visits
  3. Dissolving organic pulp remnants
  4. Neutralizing sodium hypochlorite to prevent extrusion

Explanation

EDTA is a chelating agent that removes the inorganic component of the smear layer, opening dentinal tubules and allowing irrigants and sealers to penetrate. It is typically used as a final rinse after sodium hypochlorite, not as the primary tissue solvent.

Question 49Endodontics

Which sequence best describes the rationale for alternating sodium hypochlorite and EDTA during canal irrigation?

  1. EDTA is used first to soften dentin, then hypochlorite is used as a final rinse
  2. Hypochlorite dissolves organic debris, then EDTA removes the smear layer, then hypochlorite is reapplied Correct answer.
  3. EDTA is used only in the coronal third while hypochlorite is used only apically
  4. Hypochlorite and EDTA are mixed in the same syringe to save time

Explanation

Sodium hypochlorite dissolves organic tissue and kills microorganisms, while EDTA chelates the inorganic smear layer; alternating them with a final hypochlorite rinse maximizes cleaning of the canal system. Mixing them directly reduces the effectiveness of both agents.

Question 50Endodontics

Which motion is characteristic of a reciprocating single-file nickel-titanium system?

  1. Vertical hand filing without rotation
  2. Alternating clockwise and counterclockwise rotation of unequal angles Correct answer.
  3. Continuous 360-degree rotation in one direction
  4. Ultrasonic oscillation of the file

Explanation

Reciprocating systems rotate the file clockwise and counterclockwise through unequal angles, which reduces torsional stress and the risk of cyclic fatigue. This balanced motion allows a single file to prepare many canals efficiently.