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Algeria Dental Residency Contest study materials
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Algeria Dental Residency Contest 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

In a simplified box-shaped Class I cavity model, five surfaces are bonded and one is unbonded. What configuration-factor value and associated shrinkage-stress concern fit this supplied model?

  1. C-factor = 5 (5 bonded walls to 1 unbonded wall), resulting in maximum polymerization stress at the adhesive interface Correct answer.
  2. C-factor = 1 (1 bonded wall to 5 unbonded walls), producing negligible contraction stress
  3. C-factor = 0.2, representing an ideal stress-free configuration
  4. C-factor = 2 (2 bonded walls to 4 unbonded walls)

Explanation

The supplied configuration factor is bonded area/surface count relative to unbonded area/surface count in this simplified equal-surface teaching model: five to one, giving five. Greater restraint can increase polymerization-stress concerns, but real stress also depends on actual areas, compliance, material, curing and technique. This is not a universal maximum or one required clinical layering method.

Question 25Caries activity, mineral balance and restorative material mechanisms

Which specific monomer incorporated into modern universal adhesive systems forms stable, insoluble nanolayered chemical bonds with calcium in hydroxyapatite (10-MDP-Ca salts)?

  1. 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP) Correct answer.
  2. 2-Hydroxyethyl methacrylate (HEMA)
  3. Bisphenol A-glycidyl methacrylate (Bis-GMA)
  4. Triethylene glycol dimethacrylate (TEGDMA)

Explanation

10-MDP (10-methacryloyloxydecyl dihydrogen phosphate) features a bifunctional structure: a polymerizable methacrylate group, a hydrophobic 10-carbon spacer, and a hydrophilic dihydrogen phosphate group that chemically coordinates with calcium in hydroxyapatite, forming regular self-assembled nanolayers (10-MDP-Ca salts) resistant to enzymatic biodegradation.

Question 26Caries activity, mineral balance and restorative material mechanisms

What is the primary purpose of applying a silane coupling agent (3-methacryloxypropyltrimethoxysilane) to the internal surface of a lithium disilicate ceramic restoration etched with hydrofluoric acid?

  1. Forming chemical covalent siloxane (Si-O-Si) bonds between the inorganic silica glass of the ceramic and the organic matrix of the resin cement Correct answer.
  2. Disinfecting the ceramic surface prior to cementation
  3. Etching the ceramic crystals to increase surface roughness
  4. Neutralizing the acidity of residual saliva

Explanation

Silane coupling agents are bifunctional molecules: the hydrolyzable alkoxy groups bond covalently to hydroxyl groups on the silica glass phase of ceramics (forming siloxane Si-O-Si bonds), while the organofunctional methacrylate group co-polymerizes with the resin cement matrix, creating true chemical adhesion.

Question 27Endodontic diagnosis, disinfection, and structural prognosis

Which clinical presentation is most consistent with symptomatic irreversible pulpitis (pulpite irréversible symptomatique)?

  1. Sharp, lingering, radiating pain induced by thermal stimuli that persists long after removal of the stimulus, often occurring spontaneously Correct answer.
  2. Brief, transient sharp pain provoked by cold or sweet food that ceases immediately within 1-2 seconds of stimulus removal
  3. Complete absence of response to cold, heat, and electric pulp testing with periapical bone radiolucency
  4. Severe dull throbbing pain elicited exclusively during mechanical mastication without thermal sensitivity

Explanation

Symptomatic irreversible pulpitis is characterized by persistent, lingering pain that outlasts the thermal stimulus by several seconds or minutes. Pain may be spontaneous, radiating, exacerbated when lying flat, and unprovoked by external stimuli, indicating advanced, unresolvable pulp inflammation requiring pulpectomy or root canal treatment.

Question 28Endodontic diagnosis, disinfection, and structural prognosis

Which endodontic irrigating solution is uniquely capable of simultaneously dissolving both vital and necrotic organic pulp tissue while providing potent broad-spectrum antimicrobial activity?

  1. Sodium hypochlorite (NaOCl) Correct answer.
  2. 17% Ethylenediaminetetraacetic acid (EDTA)
  3. 0.2% Chlorhexidine gluconate solution
  4. Physiological saline (0.9% NaCl)

Explanation

Sodium hypochlorite is the principal endodontic irrigant because it combines broad antimicrobial action with dissolution of vital and necrotic organic tissue. Clinically used concentrations vary; concentration, volume, contact time, activation, and safe delivery all affect efficacy and toxicity.

Question 29Endodontic diagnosis, disinfection, and structural prognosis

Which permanent tooth most commonly has a second mesiobuccal canal (MB2) located palatal to the main mesiobuccal canal orifice?

  1. Maxillary first molar Correct answer.
  2. Mandibular first molar
  3. Maxillary first premolar
  4. Mandibular canine

Explanation

The permanent maxillary first molar commonly has a second canal in its mesiobuccal root. Reported prevalence varies with population and detection method, but clinicians should actively inspect the developmental groove palatal to MB1 because an untreated canal can contribute to persistent apical disease.

Question 30Endodontic diagnosis, disinfection, and structural prognosis

What is the primary histological mechanism responsible for internal inflammatory root resorption (résorption radiculaire interne)?

  1. Chronic pulpal inflammation activating clastic dentinoclasts within the pulp chamber and root canal space Correct answer.
  2. Pressure atrophy from an impacted adjacent canine root
  3. Microbial degradation of the external cementum by Gram-negative anaerobic periodontal bacteria
  4. Occlusal trauma causing avascular necrosis of the periodontal ligament

Explanation

Internal root resorption is initiated by persistent chronic bacterial pulpitis or trauma that destroys the unmineralized protective odontoblast/predentin layer lining the canal wall. Pulpal macrophage-derived multinucleated odontoclasts (dentinoclasts) directly resorb the inner canal dentin walls from within the canal lumen.

Question 31Endodontic diagnosis, disinfection, and structural prognosis

Which radiographic feature distinguishes internal root resorption from external cervical root resorption on intraoral periapical radiographs?

  1. On parallax tube-shift radiographs (Clark's rule), an internal resorption lesion moves along with the canal lumen, whereas an external resorption lesion shifts away from the root canal outline Correct answer.
  2. Internal root resorption is always accompanied by extensive periapical radiolucency
  3. External cervical resorption presents as a symmetrical ballooning of the root canal chamber
  4. Internal resorption always features a motheaten, ill-defined ragged border that invades alveolar bone

Explanation

An internal defect is centered on the canal, so its image generally remains centered relative to that canal on suitable changed-angle views. An external defect can shift relative to the canal outline, which may remain traceable. Projection findings have limitations and should be integrated with other evidence rather than treated as an infallible single-view diagnosis.

Question 32Endodontic diagnosis, disinfection, and structural prognosis

Which listed physical mechanism explains superelasticity in an appropriate conventional austenitic nickel-titanium endodontic instrument, rather than claiming identical phase behavior or fatigue life for every heat-treated file?

  1. Stress-induced martensitic-austenitic reversible pseudoelastic (superelastic) crystalline phase transformation Correct answer.
  2. Higher carbon content yielding a hard diamond-like coating
  3. Absence of nickel allowing completely rigid bending characteristics
  4. Continuous micro-melting of the file tip during rotational friction

Explanation

NiTi superelasticity arises chiefly from a reversible stress-induced transformation between the B2 cubic austenite phase and B19′ monoclinic martensite. Heat treatment and instrument design also influence flexibility and cyclic-fatigue behavior.

Question 33Endodontic diagnosis, disinfection, and structural prognosis

Which rotary file fracture mechanism occurs when an instrument's tip becomes mechanically bound in a constricted canal while the motor continues to rotate the coronal shank?

  1. Torsional failure (torsional fatigue) Correct answer.
  2. Cyclic fatigue (flexural fatigue)
  3. Corrosion stress cracking
  4. Abrasive cavitation failure

Explanation

Torsional fracture occurs when the tip or another part of the instrument binds in the canal walls while the shank continues to turn, exceeding the ultimate shear strength of the alloy. Examination shows unwinding or reverse winding of the cutting flutes near the fracture site.

Question 34Endodontic diagnosis, disinfection, and structural prognosis

What is the primary active chemical constituent in Mineral Trioxide Aggregate (MTA) responsible for its biocompatibility and hard-tissue inductive properties upon hydration?

  1. Tricalcium silicate and dicalcium silicate (producing calcium silicate hydrate gel and releasing calcium hydroxide) Correct answer.
  2. Zinc oxide and eugenol
  3. Polyacrylic acid and fluoroaluminosilicate glass
  4. Bis-GMA and triethylene glycol dimethacrylate

Explanation

MTA is primarily a refined hydraulic cement composed of tricalcium silicate, dicalcium silicate, and tricalcium aluminate, with bismuth oxide added for radiopacity. Upon hydration, it forms a colloidal calcium silicate hydrate gel and releases calcium hydroxide (Ca(OH)2), creating a high-pH alkaline environment that induces hard-tissue bridge formation (dentinogenic and cementogenic).

Question 35Periodontal diagnosis, risk, and long-term stability

Which bacteria comprise Socransky's 'red complex', strongly associated with severe forms of chronic periodontitis and progressive clinical attachment loss?

  1. Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia Correct answer.
  2. Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces viscosus
  3. Aggregatibacter actinomycetemcomitans, Prevotella intermedia, and Fusobacterium nucleatum
  4. Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli

Explanation

Socransky's red complex represents the late colonizers in subgingival biofilm most strongly correlated with deep periodontal pockets, bleeding on probing, and severe active attachment loss: Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia.

Question 36Periodontal diagnosis, risk, and long-term stability

According to the 2018 World Workshop Classification of Periodontal and Peri-Implant Diseases, what distinguishes a diagnosis of Clinical Gingival Health on an intact periodontium from Gingivitis?

  1. Gingival health has < 10% bleeding sites on probing (BOP) with no attachment loss; Gingivitis is diagnosed when BOP is >= 10% Correct answer.
  2. Gingival health allows up to 25% bleeding on probing with pocket depths <= 5 mm
  3. Gingivitis is defined exclusively by the presence of radiographic alveolar bone loss
  4. Gingival health requires complete absence of all oral bacteria in plaque samples

Explanation

Under the 2018 global consensus classification, clinical gingival health on an intact periodontium is defined as < 10% bleeding on probing (BOP) and no clinical attachment loss (CAL). Gingivitis is defined as >= 10% BOP without clinical attachment loss or radiographic bone loss.

Question 37Periodontal diagnosis, risk, and long-term stability

In the 2018 Periodontitis Classification, how is 'Periodontitis Staging' (Stages I through IV) determined?

  1. Severity based on interdental clinical attachment loss (CAL), radiographic bone loss, tooth loss due to periodontitis, and local complexity factors Correct answer.
  2. Rate of progression estimated from bone loss/age ratio and systemic risk factors (smoking and diabetes)
  3. Exclusively by the total bacterial count of Porphyromonas gingivalis in subgingival plaque
  4. The duration of time since the patient's last professional scaling appointment

Explanation

Staging (Stages I-IV) defines the severity of disease at presentation: Stage I (initial, CAL 1-2 mm), Stage II (moderate, CAL 3-4 mm), Stage III (severe, CAL >= 5 mm with <= 4 teeth lost), and Stage IV (advanced, potential dentition loss with >= 5 teeth lost and masticatory dysfunction). Grading (Grades A-C) evaluates rate of progression.

Question 38Periodontal diagnosis, risk, and long-term stability

What is the primary biological objective of non-surgical periodontal therapy (scaling and root planing / surfaçage radiculaire)?

  1. Disrupting and removing subgingival biofilm and calculus while preserving sound root structure Correct answer.
  2. Surgically excising the entire attached gingiva to eliminate periodontal pockets
  3. Decalcifying the root dentin to promote dentinal bridge formation
  4. Sterilizing the gingival sulcus permanently through chemical cauterization

Explanation

The objective is to disrupt subgingival biofilm and remove retentive calculus while conserving sound root structure. Intentional indiscriminate cementum removal is not the objective. Healing, self-care, local anatomy and risk factors determine the response, which must be reassessed rather than assumed from the completion of instrumentation alone.

Question 39Periodontal diagnosis, risk, and long-term stability

According to the EFP S3 clinical practice guideline for stage I–III periodontitis, which statement best describes adjunctive systemic antibiotics?

  1. They should not be used routinely, but a specific regimen may be considered for selected high-risk categories after individual assessment Correct answer.
  2. They should be prescribed after instrumentation to every patient with periodontitis
  3. They replace subgingival instrumentation when deep pockets are present
  4. They are indicated solely because a pocket depth is at least 4 mm

Explanation

The EFP guideline does not recommend routine systemic antibiotics as an adjunct to subgingival instrumentation. Selected patients-for example, some young adults with generalized stage III periodontitis-may be considered after individualized benefit-risk and antimicrobial-stewardship assessment.

Question 40Periodontal diagnosis, risk, and long-term stability

What is the primary biological principle governing Guided Tissue Regeneration (GTR) in periodontal surgery?

  1. Using a barrier membrane to mechanically exclude rapidly proliferating gingival epithelial and connective tissue cells, allowing slower pluripotential cells from the periodontal ligament and alveolar bone to repopulate the root surface Correct answer.
  2. Applying topical antibiotics directly into the defect to kill all bacteria
  3. Grinding away all interdental bone crests to create flat architectural contours
  4. Stimulating rapid epithelial migration to form a long junctional epithelium

Explanation

GTR is based on cell kinetics principles (Melcher hypothesis): gingival epithelium migrates fastest, forming a long junctional epithelium that prevents true regeneration. Placing a physical barrier membrane over the osseous defect excludes epithelial and gingival connective tissue cells, granting periodontal ligament cells and perivascular osteoprogenitors the time required to regenerate new cementum, functional Sharpey fibers, and alveolar bone.

Question 41Periodontal diagnosis, risk, and long-term stability

According to the Cairo classification of gingival recessions (2011), how is a Recession Type 1 (RT1) defined?

  1. Gingival recession with no loss of interproximal attachment; interproximal CEJ is clinically not detectable at either mesial or distal aspects Correct answer.
  2. Gingival recession associated with interproximal clinical attachment loss that is less than or equal to buccal attachment loss
  3. Gingival recession associated with interproximal attachment loss greater than the buccal attachment loss
  4. Gingival recession extending into mobile alveolar mucosa with complete loss of interdental bone

Explanation

In the Cairo classification, RT1 is recession without interproximal attachment loss; the interproximal CEJ is not clinically detectable. RT1 has the greatest potential for complete root coverage, but an individual outcome is not guaranteed.

Question 42Periodontal diagnosis, risk, and long-term stability

With other relevant factors held comparable, which listed intrabony defect provides the most surrounding bony containment for a regenerative wound?

  1. Three-wall intra-bony defect (entouré de 3 parois osseuses) Correct answer.
  2. One-wall intra-bony defect (hemiseptal defect)
  3. Two-wall intra-bony defect (crater defect)
  4. Suprabony horizontal bone loss

Explanation

A three-wall intra-bony defect (surrounded by three intact vascularized osseous walls and the root surface) provides maximum vascular supply, optimal clot stability, and ideal spatial mechanical containment for bone replacement grafts and regenerative barrier membranes.

Question 43Restore function while respecting structure and supporting tissues

Which dental elastomeric impression material undergoes polymerisation via an addition reaction with zero volatile by-products, exhibiting exceptional dimensional stability that permits delayed or multiple pourings?

  1. Addition silicone (Polyvinyl siloxane / PVS) Correct answer.
  2. Condensation silicone (Polysiloxane releasing ethanol)
  3. Polysulfide rubber base (releasing water)
  4. Reversible hydrocolloid (agar-agar)

Explanation

The addition reaction of the relevant polyvinyl siloxane system avoids the volatile alcohol or water by-products characteristic of the listed condensation materials. This contributes to useful dimensional stability. Actual handling, residual gas behavior and permitted pouring intervals depend on the product instructions; no material is perfectly dimensionally unchanged or universally suitable for unlimited delayed pours.

Question 44Restore function while respecting structure and supporting tissues

What chemical interaction can completely inhibit the surface polymerization of addition silicone (PVS) impression materials, resulting in uncured, tacky margins?

  1. Sulfur compounds present in latex clinical gloves and rubber dam sheets Correct answer.
  2. Traces of water or physiological saliva on tooth margins
  3. Exposure to ambient room light and dental unit operating lamps
  4. Contact with dried calcium hydroxide powder

Explanation

Sulfur-containing contaminants associated with some latex products can interfere with the platinum-catalyzed setting reaction of susceptible addition silicones. The interaction depends on the actual materials and contamination. It is not proof that every latex contact completely prevents every PVS from setting; use compatible materials and manufacturer instructions.

Question 45Restore function while respecting structure and supporting tissues

A patient has lost every molar on both sides of a mandibular arch, while the anterior teeth and premolars remain. How is this bilateral distal-extension pattern classified by Kennedy?

  1. Kennedy Class I Correct answer.
  2. Kennedy Class II
  3. Kennedy Class III
  4. Kennedy Class IV

Explanation

Kennedy Class I describes an edentulous condition characterized by bilateral edentulous areas situated posterior to the remaining natural teeth (bilateral distal-extension arches, or édentement distal bilatéral).

Question 46Restore function while respecting structure and supporting tissues

In a Kennedy Class I or Class II removable partial denture, what is the functional purpose of placing an indirect retainer (retenue indirecte) anterior to the fulcrum line?

  1. To resist rotational dislodgement of the distal extension base away from the residual ridge tissues during sticky food mastication Correct answer.
  2. To bear primary vertical occlusal chewing forces and transmit them to the anterior teeth
  3. To provide aesthetic replacement for missing anterior incisors
  4. To act as a primary clasp retentive arm engaging an infrabulge undercut

Explanation

An indirect retainer is a rest placed anterior to the retentive fulcrum line (axe de rotation). When sticky foods pull the distal extension base occlusally away from the edentulous ridge, the indirect retainer seats into its rest seat, resisting this tipping rotation around the fulcrum axis.

Question 47Restore function while respecting structure and supporting tissues

Which mandibular movement constitutes 'Bennett angle' (angle de Bennett) measured during lateral excursion on an adjustable articulator?

  1. The angle, viewed horizontally, between the sagittal plane and the forward-medial path of the non-working condyle Correct answer.
  2. The horizontal angle of the incisal guidance table
  3. The vertical angle of the working condyle's rotation
  4. The angle between the Frankfort horizontal plane and the occlusal plane

Explanation

The Bennett angle is measured in the horizontal plane between the sagittal plane and the forward-medial path of the non-working (orbiting) condyle during lateral excursion. Bennett movement instead refers to the lateral bodily shift of the working side.

Question 48Restore function while respecting structure and supporting tissues

What is the primary aesthetic and structural advantage of high-translucency Zirconia (monolithic 4Y-PSZ / 5Y-PSZ) over traditional 3Y-TZP core zirconia in restorative dentistry?

  1. Increased cubic crystalline phase content improving optical translucency, though with lower flexural strength and fracture toughness Correct answer.
  2. Complete elimination of all crystalline phases resulting in an amorphous glass network
  3. Higher flexural strength exceeding 1,500 MPa permitting ultra-thin margins
  4. Ability to be etched with 37% phosphoric acid for predictable resin bonding

Explanation

Higher-yttria zirconia formulations can contain more optically favorable cubic phase and offer greater translucency than conventional 3Y-TZP, with a trade-off in transformation toughening and fracture properties. Actual composition, processing and product design matter. The comparison does not assign one strength or phase percentage to every commercial material or authorize a universal preparation design.

Question 49Restore function while respecting structure and supporting tissues

What is the purpose of the facebow transfer (arc facial) in complex fixed prosthodontics and oral rehabilitation?

  1. To record the spatial relationship of the maxillary dental arch to the transverse horizontal hinge axis of the TMJs and transfer it to a semi-adjustable articulator Correct answer.
  2. To register the patient's maximal voluntary biting force
  3. To determine the horizontal canine guidance angle on the incisal table
  4. To measure the vertical dimension of occlusion

Explanation

A facebow records the spatial three-dimensional orientation of the maxillary arch relative to the terminal hinge axis of the condyles and an anterior cranial reference plane (e.g., Frankfort horizontal or orbitale). This allows accurate mounting of the maxillary cast onto a semi-adjustable articulator, replicating the true arc of closure.

Question 50Restore function while respecting structure and supporting tissues

Which clasp assembly design is specifically engineered for distal-extension removable partial dentures (Kennedy Class I and II) to release stress from the terminal abutment tooth during masticatory loading, avoiding harmful distal tipping forces?

  1. RPI system (Rest, Proximal plate, I-bar) Correct answer.
  2. Circumferential Akers clasp with a distal occlusal rest
  3. Ring clasp with auxiliary bracing strut
  4. Embrasure (double Akers) clasp

Explanation

The RPI clasp assembly (Mesial Rest, Distal Proximal Plate, and Infrabulge I-bar) is specifically designed for tooth-mucosa-supported distal extension bases (Krol design). Under occlusal load, the denture base sinks into the soft tissue, causing the I-bar and proximal plate to disengage and move forward and gingivally into the tooth undercut, eliminating torquing forces on the abutment.