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ADC Written Exam study materials
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ADC Written Exam practice questions

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Question 1Knowledge of the science and practice of dentistry

In the Universal numbering system, which tooth number designates the permanent maxillary right first molar?

  1. #30
  2. #2
  3. #14
  4. #3 Correct answer.

Explanation

Universal numbering starts at the maxillary right third molar as #1 and runs posterior-to-anterior, then across to the maxillary left, then down to the mandibular left and back to the right. Counting from #1 to #3 places the maxillary right first molar at #3.

Question 2Knowledge of the science and practice of dentistry

In the FDI two-digit system, tooth 36 refers to which tooth?

  1. Mandibular right first molar
  2. Maxillary left first molar
  3. Mandibular left first molar Correct answer.
  4. Mandibular left second molar

Explanation

The first digit gives the quadrant (1 maxillary right, 2 maxillary left, 3 mandibular left, 4 mandibular right) and the second digit the position from the midline (1 to 8). Thus 36 is the mandibular left first molar.

Question 3Knowledge of the science and practice of dentistry

Which dental hard tissue contains the highest proportion of inorganic mineral by weight?

  1. Alveolar bone
  2. Enamel Correct answer.
  3. Cementum
  4. Dentin

Explanation

Enamel is roughly 96% inorganic material by weight, chiefly hydroxyapatite, making it the most highly mineralized tissue in the body. The other dental hard tissues contain substantially more organic matrix and water.

Question 4Knowledge of the science and practice of dentistry

Which primary tooth is usually the first to erupt?

  1. Mandibular central incisor Correct answer.
  2. Maxillary first primary molar
  3. Mandibular first primary molar
  4. Maxillary central incisor

Explanation

The mandibular central incisors are normally the first primary teeth to appear, at about 6–10 months of age, followed by the maxillary central incisors. Eruption then proceeds posteriorly through the arch.

Question 5Knowledge of the science and practice of dentistry

Which principal fiber group of the periodontal ligament is the most numerous and resists axially directed intrusive forces?

  1. Oblique fibers Correct answer.
  2. Alveolar crest fibers
  3. Horizontal fibers
  4. Apical fibers

Explanation

Oblique fibers run from the alveolar bone obliquely upward to insert into cementum and form the largest fiber group. This orientation converts axially directed (intrusive) load into tension on the ligament, which the tissue tolerates best.

Question 6Knowledge of the science and practice of dentistry

Which of the following local anesthetics belongs to the ester class?

  1. Lidocaine
  2. Mepivacaine
  3. Benzocaine Correct answer.
  4. Articaine

Explanation

Esters are derivatives of para-aminobenzoic acid and are metabolized by plasma pseudocholinesterases; benzocaine is the ester in common dental use. The other agents listed share the amide linkage and are metabolized hepatically.

Question 7Knowledge of the science and practice of dentistry

Which microorganism is regarded as the principal initiator of coronal dental caries?

  1. Actinomyces viscosus
  2. Streptococcus mutans Correct answer.
  3. Lactobacillus acidophilus
  4. Streptococcus sanguinis

Explanation

Streptococcus mutans adheres to the pellicle via glucans synthesized from sucrose and produces acid rapidly at low pH, driving the initial demineralization of enamel. Lactobacilli are more closely tied to progression of established lesions.

Question 8Knowledge of the science and practice of dentistry

Which structure directs the formation of root dentin and determines the shape of the root?

  1. Hertwig's root sheath Correct answer.
  2. Reduced enamel epithelium
  3. Dental papilla
  4. Stellate reticulum

Explanation

Hertwig's epithelial root sheath is a collar of epithelial cells continuous with the enamel organ that induces adjacent papilla cells to differentiate into odontoblasts, laying down root dentin and setting root form. It later breaks up to leave the epithelial rests of Malassez.

Question 9Knowledge of the science and practice of dentistry

A patient has a Class II molar relationship with proclined maxillary central incisors and an increased overjet. Into which category does this fall?

  1. Class II division 2
  2. Class I with bimaxillary protrusion
  3. Class III
  4. Class II division 1 Correct answer.

Explanation

Class II division 1 is defined by a distal position of the mandibular first molar relative to the maxillary first molar together with proclined maxillary incisors and increased overjet. Division 2 shows the same molar relationship but with retroclined central incisors.

Question 10Knowledge of the science and practice of dentistry

Which local anesthetic produces the longest duration of action when given with a vasoconstrictor?

  1. Lidocaine
  2. Bupivacaine Correct answer.
  3. Prilocaine
  4. Mepivacaine

Explanation

Bupivacaine is highly protein bound and has the longest duration of the amide anesthetics, giving roughly 90–180 minutes of pulpal anesthesia and up to 8–12 hours of soft tissue anesthesia. It is used when prolonged postoperative analgesia is desirable.

Question 11Knowledge of the science and practice of dentistry

The principal mechanism by which fluoride reduces dental caries is best described as:

  1. Stripping the acquired pellicle
  2. Killing cariogenic bacteria on contact
  3. Buffering salivary acid for hours
  4. Promoting remineralization as fluorapatite Correct answer.

Explanation

Fluoride delivered to the plaque-enamel interface enhances remineralization, forms less acid-soluble fluorapatite, and inhibits demineralization. Antibacterial and systemic pre-eruptive effects exist but are secondary to this physicochemical action.

Question 12Knowledge of the science and practice of dentistry

Enamel begins to demineralize when dental plaque fluid falls below a critical pH of approximately:

  1. 5.5 Correct answer.
  2. 4.0
  3. 6.5
  4. 7.0

Explanation

The critical pH for hydroxyapatite in enamel is about 5.5; below this value plaque fluid is unsaturated with respect to enamel mineral and net loss occurs. Values above the critical pH favour remineralization.

Question 13Knowledge of the science and practice of dentistry

A patient taking warfarin for atrial fibrillation (INR 3.0) needs a periodontally hopeless tooth extracted. What is the most appropriate management?

  1. Arrange admission for intravenous vitamin K
  2. Discontinue warfarin for five days before the procedure
  3. Refer every such patient to a maxillofacial unit
  4. Check INR and use local hemostatic measures Correct answer.

Explanation

Current guidance is to continue warfarin and confirm that the INR is within the therapeutic range (generally up to about 3.5) on the day of treatment. Local measures such as sutures, oxidized cellulose or tranexamic mouthwash control bleeding without interrupting anticoagulation.

Question 14Knowledge of the science and practice of dentistry

Which nerve carries sensation from the buccal gingiva of the mandibular molar teeth?

  1. Mental nerve
  2. Mylohyoid nerve
  3. Buccal nerve Correct answer.
  4. Lingual nerve

Explanation

The long buccal nerve, a branch of the mandibular division of the trigeminal nerve, supplies the buccal gingiva and mucosa of the mandibular molars. It is not anesthetized by a standard inferior alveolar nerve block, so a separate buccal infiltration is often needed.

Question 15Knowledge of the science and practice of dentistry

The red complex of periodontal pathogens comprises Porphyromonas gingivalis, Tannerella forsythia and which third organism?

  1. Fusobacterium nucleatum
  2. Treponema denticola Correct answer.
  3. Prevotella intermedia
  4. Aggregatibacter actinomycetemcomitans

Explanation

Socransky's microbial complexes place P. gingivalis, T. forsythia and T. denticola together as the red complex, whose members are strongly associated with established chronic periodontitis and deep pockets.

Question 16Knowledge of the science and practice of dentistry

Which is the most common odontogenic cyst of the jaws?

  1. Dentigerous cyst
  2. Odontogenic keratocyst
  3. Radicular cyst Correct answer.
  4. Lateral periodontal cyst

Explanation

The radicular (periapical) cyst arises from epithelial rests of Malassez stimulated within a periapical granuloma and accounts for the majority of odontogenic cysts. The dentigerous cyst is the second most common.

Question 17Knowledge of the science and practice of dentistry

In a conventional low-copper amalgam, which phase reacts with mercury to form the matrix during trituration?

  1. Ag2Hg3 (gamma-1)
  2. Sn8Hg (gamma-2)
  3. Ag3Sn (gamma) Correct answer.
  4. Cu6Sn5 (eta)

Explanation

Mercury attacks the gamma Ag3Sn phase of the alloy powder, dissolving it and precipitating gamma-1 (Ag2Hg3), which forms the matrix, together with gamma-2 (Sn8Hg). The gamma-2 phase is weak and corrosion-prone, which is why high-copper alloys were developed.

Question 18Knowledge of the science and practice of dentistry

Which elastomeric impression material is the most dimensionally stable after setting?

  1. Condensation silicone
  2. Polysulfide
  3. Alginate
  4. Addition silicone Correct answer.

Explanation

Addition silicones set by an addition reaction that liberates no by-product, so shrinkage is minimal and impressions can be poured after a delay or poured twice. The other materials either lose or absorb water or release by-products during setting.

Question 19Knowledge of the science and practice of dentistry

Which intraoral radiograph best demonstrates interproximal caries and alveolar crest bone levels?

  1. Occlusal
  2. Periapical
  3. Bitewing Correct answer.
  4. Lateral cephalometric

Explanation

The bitewing projection directs the beam through the crowns at right angles to the film, showing the proximal surfaces of both arches on one image together with the crestal bone. Periapical views overlap proximal contacts and are not the method of choice for this purpose.

Question 20Knowledge of the science and practice of dentistry

At what age does the permanent maxillary canine normally erupt?

  1. 9 to 10 years
  2. 8 to 9 years
  3. 13 to 14 years
  4. 11 to 12 years Correct answer.

Explanation

The permanent maxillary canine typically erupts between 11 and 12 years, later than the mandibular canine (around 9 to 10 years). Its late eruption and long path of eruption make it the most frequently impacted tooth after the third molar.

Question 21Knowledge of the science and practice of dentistry

Which medication is most strongly associated with medication-related osteonecrosis of the jaw?

  1. Zoledronic acid Correct answer.
  2. Levothyroxine
  3. Atorvastatin
  4. Metformin

Explanation

Zoledronic acid is a potent intravenous nitrogen-containing bisphosphonate that suppresses osteoclast function and is strongly implicated in medication-related osteonecrosis of the jaw, particularly after dentoalveolar surgery. Denosumab and antiangiogenic agents carry a similar risk.

Question 22Knowledge of the science and practice of dentistry

An otherwise healthy patient arrives within 20 minutes of avulsing a permanent maxillary central incisor that has been kept moist. Which storage medium is preferred while arrangements are made for replantation?

  1. Dry gauze
  2. Saline at room temperature
  3. Tap water
  4. Hanks' balanced salt solution Correct answer.

Explanation

Hanks' balanced salt solution is a cell-culture medium that preserves periodontal ligament cell viability better than any other readily available transport medium and is the first choice for an avulsed tooth. Milk is the best household alternative.

Question 23Knowledge of the science and practice of dentistry

Which bony landmark serves as the tactile guide for correct needle placement during an inferior alveolar nerve block?

  1. Lingula Correct answer.
  2. Genial tubercles
  3. Coronoid process
  4. Mylohyoid ridge

Explanation

The target is just superior to the lingula, which is palpated as a bony resistance on the medial surface of the ramus before the needle is withdrawn slightly and the solution deposited. Contact with bone deeper than this indicates the needle has passed the intended site.

Question 24Knowledge of the science and practice of dentistry

Which cephalometric measurement describes the anteroposterior relationship of the maxilla to the mandible?

  1. ANB angle Correct answer.
  2. SNB angle
  3. SNA angle
  4. Facial axis (FMA)

Explanation

The ANB angle is the difference between SNA and SNB and therefore expresses the sagittal relationship between the maxilla and the mandible; a positive value suggests a skeletal Class II pattern and a negative value a Class III pattern. SNA and SNB describe each jaw relative to the cranial base.

Question 25Knowledge of the science and practice of dentistry

Which graft material is considered osteoinductive because demineralization exposes bone morphogenetic proteins?

  1. Demineralized freeze-dried bone allograft Correct answer.
  2. Beta-tricalcium phosphate
  3. Deproteinized bovine bone mineral
  4. Mineralized freeze-dried bone allograft (FDBA)

Explanation

Acid demineralization of freeze-dried bone allograft exposes the collagen matrix and bone morphogenetic proteins, allowing the graft to induce host mesenchymal cells to differentiate into osteoblasts. Other graft types listed act predominantly by osteoconduction.

Question 26Knowledge of the science and practice of dentistry

At what age does the primary mandibular central incisor typically emerge into the oral cavity?

  1. 15 to 19 months
  2. 1 to 4 months
  3. 6 to 10 months Correct answer.
  4. 11 to 14 months

Explanation

The primary mandibular central incisors are usually the first teeth to erupt, appearing between about 6 and 10 months of age, followed by the mandibular laterals and then the maxillary incisors. Eruption timing varies with sex, ethnicity and individual growth, but this range is the accepted norm.

Question 27Knowledge of the science and practice of dentistry

On which permanent tooth is the cusp of Carabelli most frequently found?

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

Explanation

The cusp of Carabelli is an accessory cusp on the mesiolingual surface of the maxillary permanent first molar, present in a majority of individuals to some degree. It is far less common on maxillary second molars and does not occur on mandibular teeth.

Question 28Knowledge of the science and practice of dentistry

Which buffer system provides the greatest buffering capacity in stimulated whole saliva?

  1. Ammonia system
  2. Bicarbonate system Correct answer.
  3. Phosphate system
  4. Protein and albumin system

Explanation

Bicarbonate concentration rises steeply with salivary flow rate, so it dominates buffering in stimulated saliva. The phosphate system is relatively more important in resting saliva, where bicarbonate is low.

Question 29Knowledge of the science and practice of dentistry

Which direct restorative material is capable of releasing fluoride over time?

  1. Admixed high-copper amalgam
  2. Autopolymerizing acrylic resin
  3. Microfilled composite resin
  4. Conventional glass ionomer Correct answer.

Explanation

Glass ionomer cements contain a fluoroaluminosilicate glass phase that releases fluoride and can be recharged from topical sources. This property is absent from resin composites and metallic restorations.

Question 30Knowledge of the science and practice of dentistry

Which masticatory muscle is chiefly responsible for depressing and protruding the mandible?

  1. Temporalis
  2. Lateral pterygoid Correct answer.
  3. Medial pterygoid
  4. Masseter

Explanation

The lateral pterygoid is the only masticatory muscle that depresses the mandible; its inferior head protrudes the condyle and helps open the jaw. The other three muscles of mastication are elevators.

Question 31Knowledge of the science and practice of dentistry

Which method provides the most reliable verification of sterilizer efficacy?

  1. Routine physical parameter log
  2. Weekly chemical indicator strip
  3. Biological spore test Correct answer.
  4. Daily Bowie-Dick test

Explanation

Biological indicators contain highly resistant bacterial spores, such as Geobacillus stearothermophilus for steam sterilization, and directly demonstrate that the cycle killed microorganisms. Chemical and physical monitoring only confirm that cycle parameters were reached.

Question 32Knowledge of the science and practice of dentistry

Which injection technique is preferred to anesthetize a maxillary central incisor for a simple restorative procedure?

  1. Long buccal nerve block
  2. Supraperiosteal infiltration Correct answer.
  3. Inferior alveolar nerve block
  4. Greater palatine nerve block

Explanation

Maxillary alveolar bone is thin and porous, so a supraperiosteal infiltration near the apex reliably achieves pulpal anesthesia of anterior teeth. Regional blocks are rarely needed in the maxilla and are required for completely different territories.

Question 33Knowledge of the science and practice of dentistry

After the third molars, which tooth is most frequently impacted?

  1. Mandibular lateral incisor
  2. Maxillary central incisor
  3. Mandibular first premolar
  4. Maxillary canine Correct answer.

Explanation

The maxillary canine has the longest path of eruption and a limited arch space, making it the second most commonly impacted tooth after the third molars. Palatal impaction is most frequent, followed by labial displacement.

Question 34Knowledge of the science and practice of dentistry

Which principal fiber group of the periodontal ligament primarily resists intrusive forces on the tooth?

  1. Oblique fibers Correct answer.
  2. Transseptal fibers
  3. Horizontal fibers
  4. Apical fibers

Explanation

Oblique fibers run from the cementum apically and insert into bone coronally, so axial loading puts them under tension and converts intrusive force into tension on the alveolus. The other groups resist different directions of displacement.

Question 35Knowledge of the science and practice of dentistry

Which irrigant is used during root canal treatment specifically to remove the smear layer by chelating calcium ions?

  1. 2.5% sodium hypochlorite
  2. Sterile distilled water
  3. 17% EDTA Correct answer.
  4. 0.2% chlorhexidine gluconate

Explanation

EDTA is a chelator that binds calcium and removes the inorganic component of the smear layer, opening dentinal tubules. Sodium hypochlorite then dissolves the remaining organic debris and pulp tissue.

Question 36Knowledge of the science and practice of dentistry

Which phosphoric acid concentration is most commonly used to etch enamel before placing a resin composite?

  1. 5% buffered solution
  2. 37% gelled solution Correct answer.
  3. 60% gelled solution
  4. 15% gelled solution

Explanation

Etching enamel with 30 to 40 percent phosphoric acid for about 15 to 30 seconds produces the classic type I and type II etch patterns that allow resin tags to form. Higher concentrations do not improve bonding and may be more injurious to dentin.

Question 37Knowledge of the science and practice of dentistry

What is the recommended single prophylactic dose of amoxicillin for an adult with a prosthetic heart valve who is not allergic to penicillin?

  1. 250 mg orally the night before
  2. 1 g orally 2 hours after
  3. 2 g orally 30 to 60 minutes before Correct answer.
  4. 500 mg orally 1 hour before

Explanation

Current guidelines recommend a single 2 g oral dose of amoxicillin taken 30 to 60 minutes before the procedure for adults who can take oral medication. Clindamycin is no longer recommended because of adverse-effect concerns, and the dose is not given after the procedure.

Question 38Knowledge of the science and practice of dentistry

Which extraction site is most frequently followed by alveolar osteitis (dry socket)?

  1. Maxillary first molar
  2. Maxillary central incisor
  3. Mandibular third molar Correct answer.
  4. Mandibular first premolar

Explanation

Alveolar osteitis most often follows surgical removal of mandibular third molars, particularly with traumatic technique, smoking, or use of oral contraceptives. The condition results from loss of the protective blood clot and exposure of bare bone.

Question 39Knowledge of the science and practice of dentistry

Which intraoral site is the most common location for squamous cell carcinoma?

  1. Lateral border of the tongue Correct answer.
  2. Buccal mucosa
  3. Hard palate
  4. Attached gingiva

Explanation

The lateral border and ventral surface of the tongue, together with the floor of the mouth, account for the majority of oral squamous cell carcinomas. These sites are bathed in saliva and expose tissue to pooled carcinogens.

Question 40Knowledge of the science and practice of dentistry

What is the first-line treatment to reduce pain and shorten the duration of a recurrent aphthous ulcer?

  1. Oral fluconazole
  2. Oral acyclovir 400 mg
  3. Systemic prednisolone taper
  4. Topical corticosteroid Correct answer.

Explanation

Topical corticosteroids applied at the prodromal or early ulcer stage reduce inflammation and promote faster healing. Systemic steroids are reserved for severe or refractory disease, and antimicrobials directed at viruses or fungi have no effect on aphthae.

Question 41Knowledge of the science and practice of dentistry

Which radiographic technique places the central ray perpendicular to an imaginary plane that bisects the long axis of the tooth and the receptor?

  1. Occlusal projection technique
  2. Paralleling long-cone technique
  3. Bisecting angle technique Correct answer.
  4. SLOB localization technique

Explanation

The bisecting angle principle assumes the central ray should be perpendicular to the bisector of the angle formed by the tooth axis and the film, producing an image of true length. The paralleling technique instead places the receptor parallel to the tooth and directs the beam perpendicular to both.

Question 42Knowledge of the science and practice of dentistry

Clinical attachment level is measured from which reference point to the base of the pocket?

  1. Cementoenamel junction Correct answer.
  2. Mucogingival junction
  3. Gingival margin
  4. Alveolar crest

Explanation

Clinical attachment level is referenced to the cementoenamel junction, so it reflects true loss of attachment and is unaffected by gingival swelling or recession. Probing depth, by contrast, is measured from the gingival margin.

Question 43Knowledge of the science and practice of dentistry

Which occlusal scheme is usually prescribed for complete dentures so that contacts are maintained on both the working and balancing sides during lateral excursion?

  1. Bilateral balanced occlusion Correct answer.
  2. Canine-protected occlusion
  3. Mutually protected occlusion
  4. Group function occlusion

Explanation

Complete dentures rely on bilateral balanced occlusion to stabilize the bases and distribute load during excursive movements. The natural-dentition schemes depend on proprioception and periodontal support that denture wearers lack.

Question 44Knowledge of the science and practice of dentistry

What is the maximum recommended dose of lidocaine administered with 1:100,000 epinephrine in a healthy adult?

  1. 7.0 mg/kg Correct answer.
  2. 4.4 mg/kg
  3. 10.0 mg/kg
  4. 2.0 mg/kg

Explanation

The maximum recommended dose for lidocaine with a vasoconstrictor is about 7 mg/kg, with an absolute cap of roughly 500 mg in adults. Without a vasoconstrictor the limit falls to approximately 4.4 mg/kg because systemic absorption is faster.

Question 45Knowledge of the science and practice of dentistry

Which property of calcium hydroxide underlies its use as a direct pulp-capping agent?

  1. It neutralizes plaque-derived acids
  2. It dissolves the dentinal smear layer
  3. It provides a durable hermetic seal
  4. It stimulates reparative dentin formation Correct answer.

Explanation

Calcium hydroxide induces a zone of necrosis at the interface that provokes an inflammatory response and subsequent formation of a dentin bridge. Its high solubility limits its sealing ability, but its reparative effect is well established.

Question 46Knowledge of the science and practice of dentistry

Hunter-Schreger bands observed in ground sections of enamel arise from which structural arrangement?

  1. Alternating directions of enamel prisms Correct answer.
  2. Cross-striations within individual prisms
  3. Variation in the mineral content of rods
  4. Incremental deposition of perikymata

Explanation

Hunter-Schreger bands are an optical phenomenon produced by groups of prisms that decussate, alternating in direction between adjacent bands. This arrangement increases the resistance of enamel to crack propagation under occlusal load.

Question 47Knowledge of the science and practice of dentistry

Two amide local anesthetics have identical lipid solubility and protein binding, but drug A has a pKa of 7.7 and drug B a pKa of 8.1. At a tissue pH of 7.4, which outcome is expected?

  1. Drug A will act faster because more of it is uncharged Correct answer.
  2. Drug B will act faster because more of it is ionized
  3. Drug A will last longer because more of it is ionized
  4. Both will act at the same speed because potency is equal

Explanation

The pKa determines the fraction of drug existing as uncharged base at tissue pH; the closer the pKa is to 7.4, the greater that fraction and the faster the drug crosses the nerve membrane. Once inside the axon, the molecule re-ionizes and blocks the sodium channel.

Question 48Knowledge of the science and practice of dentistry

Which method allows skeletal maturity to be judged from the lateral cephalogram already taken for orthodontic treatment planning?

  1. Hand-wrist radiograph staging
  2. Midpalatal suture maturation
  3. Cervical vertebral maturation Correct answer.
  4. Dental age from panoramic films

Explanation

Cervical vertebral maturation stages can be read from the cervical vertebrae visible on a routine lateral cephalogram, so no extra exposure is required. This allows the timing of growth modification to be matched to the pubertal growth spurt.

Question 49Knowledge of the science and practice of dentistry

Epinephrine prolongs the clinical effect of a local anesthetic mainly through which action?

  1. Raising the pH of the tissue fluid
  2. Reducing local blood flow Correct answer.
  3. Slowing hepatic biotransformation of the drug
  4. Increasing drug binding to sodium channels

Explanation

Vasoconstriction decreases perfusion at the injection site, slowing systemic absorption and keeping a higher concentration of anesthetic at the nerve for longer. The same mechanism lowers peak plasma levels and reduces the risk of systemic toxicity.

Question 50Knowledge of the science and practice of dentistry

In total-etch dentin bonding, incomplete infiltration of resin into the demineralized collagen network leaves nanometer-scale voids that allow fluid movement within the hybrid layer. This phenomenon is called:

  1. Nanoleakage Correct answer.
  2. Resin tag formation
  3. Smear layer formation
  4. Hybrid layer collapse

Explanation

Nanoleakage refers to fluid-filled spaces within the hybrid layer where resin fails to encapsulate all exposed collagen fibrils, even when the restoration margin appears sealed. It can lead to hydrolytic degradation of the bond over time.