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ORE Part 1 practice questions

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Question 1Applied biomedical and dental sciences

What is the approximate inorganic content of mature human enamel by weight?

  1. 96% Correct answer.
  2. 50%
  3. 70%
  4. 20%

Explanation

Mature enamel is approximately 96% inorganic by weight, composed mainly of hydroxyapatite. The small remaining fraction is water and organic material. This high mineral content underlies enamel's hardness and radiopacity.

Question 2Applied biomedical and dental sciences

How many roots does a typical maxillary first molar have?

  1. Three Correct answer.
  2. Four
  3. One
  4. Two

Explanation

The maxillary first molar usually has three roots: mesiobuccal, distobuccal and palatal. This root pattern helps anchor the tooth against masticatory forces. Variation can occur, but three is the typical number.

Question 3Applied biomedical and dental sciences

Which mandibular movement is produced by contraction of the masseter muscle?

  1. Lateral excursion
  2. Elevation Correct answer.
  3. Protrusion
  4. Depression

Explanation

The masseter is a primary elevator of the mandible and acts with the medial pterygoid and temporalis during closure. Its fibres run from the zygomatic arch to the ramus and angle of the mandible. Depression is produced mainly by the suprahyoid muscles.

Question 4Applied biomedical and dental sciences

Which microorganism is most strongly associated with the initiation of dental caries?

  1. Streptococcus mutans Correct answer.
  2. Lactobacillus species
  3. Candida albicans
  4. Actinomyces viscosus

Explanation

Streptococcus mutans is strongly associated with caries initiation because it adheres to enamel, produces acids and synthesises glucans from sucrose. Lactobacilli are more associated with progression of established lesions. Candida is primarily a fungal opportunist.

Question 5Applied biomedical and dental sciences

Which property is characteristic of glass ionomer cement?

  1. Complete insolubility in oral fluids
  2. High tensile strength
  3. Setting that requires no water
  4. Sustained fluoride release Correct answer.

Explanation

Glass ionomer cements release fluoride over time and can be recharged from topical fluoride. They bond chemically to tooth structure and are useful in high-caries-risk patients. Their mechanical strength is modest and they are not completely insoluble.

Question 6Applied biomedical and dental sciences

What is the principal risk of paracetamol overdose?

  1. Gastric ulceration
  2. Renal papillary necrosis
  3. Agranulocytosis
  4. Hepatotoxicity Correct answer.

Explanation

Paracetamol overdose saturates normal conjugation pathways, leading to accumulation of the toxic metabolite NAPQI. Once glutathione stores are depleted, hepatocellular necrosis can occur. Renal papillary necrosis and gastric ulceration are more associated with NSAIDs.

Question 7Applied biomedical and dental sciences

Which method is the most reliable for sterilising dental handpieces between patients?

  1. Steam autoclave at 134°C Correct answer.
  2. Storage in an ultraviolet cabinet
  3. Immersion in glutaraldehyde for 10 minutes
  4. Wiping with 70% alcohol

Explanation

Steam autoclaving under pressure at 134°C reliably kills bacteria, viruses and spores when the correct cycle is used. Alcohol wipes and ultraviolet cabinets are disinfectants at best and do not sterilise. Short glutaraldehyde immersion is high-level disinfection rather than sterilisation.

Question 8Applied biomedical and dental sciences

Which is a principal mechanism by which topically applied fluoride reduces caries?

  1. Promotes fluorapatite formation Correct answer.
  2. Reduces salivary buffer capacity
  3. Dissolves enamel crystals
  4. Increases enamel solubility

Explanation

Fluoride promotes remineralisation and the formation of fluorapatite, which is less acid-soluble than hydroxyapatite. It also inhibits demineralisation and interferes with bacterial metabolism. It does not increase enamel solubility or dissolve enamel crystals.

Question 9Applied biomedical and dental sciences

Which type of dentine lines the inner wall of dentinal tubules and is highly mineralised?

  1. Interglobular dentine
  2. Secondary dentine
  3. Peritubular dentine Correct answer.
  4. Circumpulpal dentine

Explanation

Peritubular dentine forms a highly mineralised cuff lining each dentinal tubule. It differs from intertubular dentine, which lies between tubules. Interglobular dentine is a hypomineralised area, while secondary dentine forms after root completion.

Question 10Applied biomedical and dental sciences

Which principal periodontal ligament fibre group is most responsible for resisting intrusive forces on the tooth?

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

Explanation

Oblique fibres run from cementum to bone in an oblique direction and are the main group resisting axial intrusive forces. They convert vertical occlusal load into tension in the ligament. Apical and alveolar crest fibres resist other directions of force.

Question 11Applied biomedical and dental sciences

Which component of saliva provides most of its buffer capacity?

  1. Bicarbonate Correct answer.
  2. Mucin
  3. Lysozyme
  4. Amylase

Explanation

Bicarbonate is the principal buffer in stimulated saliva and neutralises plaque acids. Phosphate buffers contribute at low flow rates. Amylase and lysozyme have digestive and antibacterial roles rather than being the main buffers.

Question 12Applied biomedical and dental sciences

The acquired pellicle on a clean tooth surface is best described as:

  1. A layer of food debris
  2. A calcified bacterial deposit
  3. A salivary glycoprotein film Correct answer.
  4. An inflammatory exudate

Explanation

The acquired pellicle forms rapidly from selective adsorption of salivary glycoproteins onto the tooth surface. It is not a bacterial deposit and is not calcified. It modifies surface properties and provides a substrate for bacterial colonisation.

Question 13Applied biomedical and dental sciences

Local anaesthetics such as lidocaine block nerve conduction by acting on which target?

  1. Calcium release channels
  2. Voltage-gated potassium channels
  3. Voltage-gated sodium channels Correct answer.
  4. Acetylcholine receptors

Explanation

Local anaesthetics are weak bases that enter the nerve membrane and block voltage-gated sodium channels from the inside. This prevents sodium influx and the generation of an action potential. Potassium channels and acetylcholine receptors are not their primary target.

Question 14Applied biomedical and dental sciences

What is the main purpose of adding adrenaline to a local anaesthetic solution?

  1. To prolong anaesthesia Correct answer.
  2. To prevent allergy
  3. To buffer the solution
  4. To speed systemic absorption

Explanation

Adrenaline is a vasoconstrictor that reduces local blood flow, slowing systemic absorption of the anaesthetic. This prolongs the anaesthetic effect and improves haemostasis. It does not prevent true allergic reactions.

Question 15Applied biomedical and dental sciences

Which laboratory test is used to monitor warfarin therapy?

  1. Activated partial thromboplastin time
  2. Platelet count
  3. Bleeding time
  4. International normalised ratio Correct answer.

Explanation

Warfarin affects the extrinsic pathway by reducing vitamin K-dependent clotting factors, so it is monitored with the prothrombin time expressed as the INR. APTT is used mainly to monitor heparin. Platelet count and bleeding time assess different aspects of haemostasis.

Question 16Applied biomedical and dental sciences

What is the net effect of parathyroid hormone on serum calcium?

  1. Raises serum calcium Correct answer.
  2. Has no effect on serum calcium
  3. Lowers serum phosphate only
  4. Lowers serum calcium

Explanation

Parathyroid hormone raises serum calcium by increasing renal calcium reabsorption, stimulating bone resorption and activating vitamin D. It also increases renal phosphate excretion, so serum phosphate tends to fall. The net effect on calcium is an increase.

Question 17Applied biomedical and dental sciences

Which nerve is a branch of the mandibular division of the trigeminal nerve?

  1. Nasopalatine nerve
  2. Inferior alveolar nerve Correct answer.
  3. Infraorbital nerve
  4. Greater palatine nerve

Explanation

The mandibular division of the trigeminal nerve gives rise to the inferior alveolar, lingual, buccal and auriculotemporal nerves. The infraorbital, greater palatine and nasopalatine nerves are branches of the maxillary division. This distinction is important for regional anaesthesia.

Question 18Applied biomedical and dental sciences

Lymph from the central part of the lower lip drains primarily to which nodes?

  1. Submandibular nodes
  2. Submental nodes Correct answer.
  3. Parotid nodes
  4. Deep cervical nodes

Explanation

The central portion of the lower lip drains to the submental nodes, while the lateral portions drain to the submandibular nodes. This has implications for spread of lip carcinoma. Parotid nodes drain more posterior regions.

Question 19Applied biomedical and dental sciences

Which process describes the loss of water from a set alginate impression on standing?

  1. Creep
  2. Syneresis Correct answer.
  3. Gelation
  4. Imbibition

Explanation

Syneresis is the loss of water from the set alginate gel, causing shrinkage and dimensional change. Imbibition is the uptake of water, which can cause swelling. Impressions should therefore be cast promptly or stored correctly.

Question 20Applied biomedical and dental sciences

After a sugar challenge, the Stephan curve shows that plaque pH:

  1. Falls rapidly, then recovers within an hour Correct answer.
  2. Rises above neutral
  3. Remains unchanged throughout
  4. Falls and stays low for hours

Explanation

Fermentable carbohydrate is rapidly metabolised by plaque bacteria to acids, causing plaque pH to fall. Salivary buffering and clearance then restore the pH over roughly 30 to 60 minutes. Frequent sugar exposures prevent this recovery and increase caries risk.

Question 21Applied biomedical and dental sciences

Osteoclasts are derived from which cell lineage?

  1. Haematopoietic monocyte–macrophage lineage Correct answer.
  2. Fibroblast lineage
  3. Osteoprogenitor cells
  4. Neural crest mesenchymal cells

Explanation

Osteoclasts are multinucleated bone-resorbing cells derived from haematopoietic precursors of the monocyte–macrophage lineage. Osteoblasts, by contrast, arise from mesenchymal osteoprogenitor cells. This distinction is important in understanding bone remodelling and pathology.

Question 22Applied biomedical and dental sciences

Which agent is used to bond resin composite to silica-based ceramic or glass filler particles?

  1. Phosphoric acid
  2. Eugenol
  3. Calcium hydroxide
  4. Silane Correct answer.

Explanation

A silane coupling agent has hydrophilic and organophilic groups that bond silica-based surfaces to the resin matrix. It is used in composite fillers and ceramic bonding. Phosphoric acid etches enamel and eugenol is a sedative lining material.

Question 23Applied biomedical and dental sciences

Which artery is a direct branch of the maxillary artery?

  1. Lingual artery
  2. Middle meningeal artery Correct answer.
  3. Superficial temporal artery
  4. Facial artery

Explanation

The maxillary artery gives rise to branches including the middle meningeal, inferior alveolar and posterior superior alveolar arteries. The facial and lingual arteries arise from the external carotid artery. The superficial temporal artery is a terminal branch of the external carotid.

Question 24Applied biomedical and dental sciences

A radicular cyst arises from which structure?

  1. Dental lamina remnants
  2. Reduced enamel epithelium
  3. Follicular sac epithelium
  4. Rests of Malassez Correct answer.

Explanation

A radicular cyst is inflammatory and arises from epithelial cell rests of Malassez in the periodontal ligament after pulp necrosis. A dentigerous cyst arises from reduced enamel epithelium around an unerupted crown. Odontogenic keratocysts arise from dental lamina remnants.

Question 25Applied biomedical and dental sciences

Which statement about hepatitis B virus is correct?

  1. It is not spread by needle-stick injury
  2. It is an RNA virus
  3. It survives drying for at least 7 days Correct answer.
  4. It is spread only by transfusion

Explanation

Hepatitis B virus is a DNA virus that can remain infectious on dried environmental surfaces for at least seven days. It is transmitted by blood and body fluids, including through needle-stick injuries and transfusion. Standard precautions and vaccination are central to prevention.

Question 26Applied biomedical and dental sciences

In enamel hydroxyapatite, which ion substitutes for hydroxyl groups to form fluorapatite and thereby reduces crystal solubility in acid?

  1. Magnesium
  2. Carbonate
  3. Sodium
  4. Fluoride Correct answer.

Explanation

Fluoride replaces the hydroxyl ion in the apatite lattice, producing fluorapatite, which has a lower solubility product than hydroxyapatite and dissolves less readily during an acid challenge. Carbonate and magnesium substitutions have the opposite effect, making the crystal more acid-labile.

Question 27Applied biomedical and dental sciences

Which immunoglobulin is the predominant antibody present in whole saliva?

  1. IgG
  2. IgE
  3. IgA Correct answer.
  4. IgM

Explanation

Secretory IgA is produced by plasma cells in the major and minor salivary glands and is actively transported across the glandular epithelium with a secretory component. It is the dominant antibody class in saliva and contributes to mucosal immune defence.

Question 28Applied biomedical and dental sciences

Deficiency of which vitamin impairs collagen hydroxylation and produces gingival swelling, bleeding and tooth mobility?

  1. Vitamin D
  2. Vitamin A
  3. Vitamin K
  4. Vitamin C Correct answer.

Explanation

Vitamin C is a cofactor for prolyl and lysyl hydroxylase, enzymes required for stable collagen triple-helix formation. In scurvy, defective collagen in the gingiva and periodontal ligament leads to bleeding, swelling and loosening of teeth.

Question 29Applied biomedical and dental sciences

Which primary tooth is normally the first to erupt in the mandible?

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

Explanation

Mandibular central incisors are the first primary teeth to emerge, usually between 6 and 10 months of age, followed by the lateral incisors and then the first molars. The canine is one of the later primary teeth to erupt.

Question 30Applied biomedical and dental sciences

Which collagen type predominates in the connective tissue of the gingival lamina propria?

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

Explanation

Type I collagen constitutes the majority of the collagen in gingival connective tissue and provides most of its tensile strength. Type III is present in smaller amounts as reticular fibres, while types II and IV occur in cartilage and basement membrane respectively.

Question 31Applied biomedical and dental sciences

The setting of a conventional glass ionomer cement depends primarily on which reaction?

  1. Hydration of calcium sulphate hemihydrate
  2. Free-radical addition polymerisation of methacrylate groups
  3. An acid-base reaction between polyalkenoic acid and fluoroaluminosilicate glass Correct answer.
  4. Chelation of zinc ions by eugenol

Explanation

In glass ionomer cement the polyalkenoic acid attacks the fluoroaluminosilicate glass particles, releasing metal cations that crosslink the polymer chains to form a hydrated polysalt gel. This acid-base reaction also allows sustained fluoride release from the glass phase.

Question 32Applied biomedical and dental sciences

After a dental amalgam has set, which phase forms the continuous matrix that binds the remaining alloy particles together?

  1. Gamma-1 phase (Ag2Hg3) Correct answer.
  2. Gamma phase (Ag3Sn)
  3. Epsilon phase (Cu3Sn)
  4. Gamma-2 phase (Sn7-8Hg)

Explanation

Mercury reacts with the silver in the alloy to form the gamma-1 (Ag2Hg3) phase, which constitutes the matrix surrounding the unreacted gamma particles and gives the restoration its strength. The gamma-2 phase is weak and corrosion-prone and is minimised in high-copper alloys.

Question 33Applied biomedical and dental sciences

Which microorganism is most strongly associated with progressive chronic periodontitis and belongs to the red complex of periodontal pathogens?

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

Explanation

Porphyromonas gingivalis is a Gram-negative anaerobic rod of the red complex, a group strongly linked with deep pocketing and attachment loss in chronic periodontitis. It possesses virulence factors such as gingipains and fimbriae that promote tissue destruction.

Question 34Applied biomedical and dental sciences

A 2% lidocaine solution is supplied in a 2.2 mL dental cartridge. How much lidocaine does one cartridge contain?

  1. 22 mg
  2. 11 mg
  3. 44 mg Correct answer.
  4. 88 mg

Explanation

A 2% solution contains 2 g per 100 mL, which is 20 mg per mL. Multiplying 20 mg/mL by the 2.2 mL cartridge volume gives 44 mg of lidocaine per cartridge.

Question 35Applied biomedical and dental sciences

On a periapical radiograph of an intact tooth, which tissue appears the most radiopaque?

  1. Cementum
  2. Pulp
  3. Enamel Correct answer.
  4. Dentine

Explanation

Radiopacity increases with mineral content and physical density, and enamel is the most highly mineralised dental tissue at roughly 90% by volume. It therefore attenuates the X-ray beam most strongly and appears the whitest structure on the image.

Question 36Applied biomedical and dental sciences

Which nerve fibre type is chiefly responsible for the sharp, well-localised pain elicited from a vital tooth by a cold stimulus?

  1. Sympathetic efferent fibres
  2. A-delta fibres Correct answer.
  3. C fibres
  4. A-beta fibres

Explanation

Cold stimuli cause rapid outward movement of dentinal fluid, which mechanically disturbs the nerve endings at the pulp-dentine border, where myelinated A-delta fibres predominate. Their fast conduction produces a sharp, brief, localised pain, in contrast with the slow dull pain carried by C fibres.

Question 37Applied biomedical and dental sciences

Which best describes the principal mechanism by which chlorhexidine reduces supragingival plaque?

  1. Selective inhibition of collagenase produced by anaerobic rods
  2. Binding to bacterial cell walls and disrupting the cytoplasmic membrane Correct answer.
  3. Blocking of bacterial adhesion through a calcium phosphate precipitate
  4. Inhibition of bacterial enolase in the glycolytic pathway

Explanation

Chlorhexidine is a cationic bisbiguanide that binds to the negatively charged bacterial surface, causing leakage of cytoplasmic contents and precipitation of intracellular material. It also adsorbs onto oral surfaces, giving prolonged substantivity and continued bacterial suppression.

Question 38Applied biomedical and dental sciences

In an early approximal enamel lesion, which histological zone shows the greatest mineral loss?

  1. The body of the lesion Correct answer.
  2. The surface zone
  3. The translucent zone
  4. The dark zone

Explanation

Early enamel caries develops four zones from the surface inwards: a relatively intact surface zone, the body of the lesion, the dark zone and the advancing translucent zone. The body of the lesion is the most porous region and represents the greatest net mineral loss.

Question 39Applied biomedical and dental sciences

An older patient has reduced hepatic drug metabolism and low serum albumin. Which change best explains an increased risk of toxicity from a standard intravenous dose of a highly protein-bound drug?

  1. A greater fraction of unbound drug in the plasma Correct answer.
  2. Increased renal tubular secretion of the drug
  3. An increased volume of distribution of unbound drug
  4. Reduced first-pass metabolism in the gut wall

Explanation

Only the unbound fraction of a drug is pharmacologically active and available for distribution and elimination. Hypoalbuminaemia increases the free fraction in plasma, so a standard dose produces a greater pharmacological effect and a higher risk of toxicity.

Question 40Applied biomedical and dental sciences

Lidocaine has a pKa of 7.9. In an inflamed tissue bed at pH 6.5, which consequence for access of the drug to the nerve membrane is expected?

  1. A smaller proportion of drug is in the uncharged base form, so less crosses the membrane Correct answer.
  2. A larger proportion of drug is uncharged and crosses the membrane more readily
  3. The drug becomes irreversibly bound to tissue protein and is inactivated
  4. The ratio of charged to uncharged drug is unchanged because the pKa is fixed

Explanation

By the Henderson-Hasselbalch relationship, when the tissue pH falls below the pKa of the drug, a greater proportion of the molecules exist in the protonated, cationic form. Since only the uncharged base crosses the lipid axonal membrane, an acidic inflamed site reduces drug penetration and renders the block less effective.

Question 41Restorative dentistry, endodontics and prosthodontics

Moisture contamination of a zinc-containing dental amalgam during condensation most characteristically produces which effect?

  1. An immediate rise in compressive strength
  2. Delayed expansion of the restoration Correct answer.
  3. Excessive setting contraction of the alloy
  4. Accelerated corrosion at the restoration margins

Explanation

Zinc in the alloy reacts with water to liberate hydrogen gas, which accumulates within the set material and produces expansion that may appear days later. Zinc-free alloys are much less prone to this phenomenon, which is why moisture control matters most with zinc-containing products.

Question 42Restorative dentistry, endodontics and prosthodontics

Which irrigant is used during root canal treatment primarily for its capacity to dissolve organic tissue and kill micro-organisms?

  1. Chlorhexidine gluconate
  2. 0.9% sodium chloride
  3. Sodium hypochlorite Correct answer.
  4. 17% EDTA solution

Explanation

Sodium hypochlorite is the only commonly used irrigant that both dissolves necrotic and vital pulp tissue and has a broad antibacterial effect. It is normally used alongside a chelating agent because it does not remove the inorganic smear layer.

Question 43Restorative dentistry, endodontics and prosthodontics

Where is the apical constriction usually located in relation to the radiographic apex?

  1. 3.5 to 4.0 mm short of the radiographic apex
  2. 0.5 to 1.0 mm short of the radiographic apex Correct answer.
  3. 2.5 to 3.0 mm short of the radiographic apex
  4. Exactly at the radiographic apex

Explanation

The cemento-dentinal junction, where the apical constriction lies, is typically 0.5 to 1.0 mm coronal to the radiographic apex. Preparing to this level supports healing while reducing the risk of over-instrumentation and extrusion of debris.

Question 44Restorative dentistry, endodontics and prosthodontics

Which impression material is the most dimensionally stable, allowing a cast to be poured several days after the impression is recorded?

  1. Zinc oxide-eugenol impression paste
  2. Reversible hydrocolloid
  3. Alginate
  4. Addition-cured silicone Correct answer.

Explanation

Addition-cured silicones set by a non-byproduct polymerisation reaction, so they undergo negligible dimensional change after removal from the mouth. This allows a delay before pouring without loss of accuracy.

Question 45Restorative dentistry, endodontics and prosthodontics

In a metal-ceramic crown, the principal bond between the cast metal substructure and the veneering porcelain is:

  1. Van der Waals attraction between the porcelain and the polished metal
  2. chemical bonding via an oxide layer formed on the metal surface Correct answer.
  3. adhesion provided by the resin luting cement at the margins
  4. mechanical retention achieved by macroscopic undercuts cut into the metal framework

Explanation

A controlled oxide layer on the metal surface reacts chemically with the porcelain to form a genuine chemical bond, supplemented by micromechanical and compressive components. Excess or insufficient oxide both compromise the union.

Question 46Restorative dentistry, endodontics and prosthodontics

During a lateral excursion, contact between maxillary and mandibular posterior teeth on the side to which the mandible has moved, shared by several teeth, is described as:

  1. Group function Correct answer.
  2. Canine guidance
  3. Mutually protected occlusion
  4. A balancing-side interference

Explanation

Group function describes the distribution of lateral excursive contacts across several teeth on the working side. It contrasts with canine guidance, where the canine alone discludes the remaining teeth.

Question 47Restorative dentistry, endodontics and prosthodontics

The principal function of a post placed in an endodontically treated tooth is to:

  1. retain the core and the coronal restoration Correct answer.
  2. strengthen the root against vertical fracture
  3. prevent recolonisation of the canal by micro-organisms
  4. seal the apical portion of the root canal system

Explanation

A post provides retention for a core when insufficient coronal dentine remains; it does not reinforce the root. Preparation of a post space removes dentine and can therefore reduce resistance to fracture, so a post is used only when needed.

Question 48Restorative dentistry, endodontics and prosthodontics

Shade selection for a ceramic restoration is most reliably performed under which conditions?

  1. In natural daylight, with bright colours removed from the patient's field of view Correct answer.
  2. Under ultraviolet illumination to reveal fluorescence
  3. With the patient supine beneath conventional fluorescent room lighting
  4. Directly under the dental operating light with the unit switched on

Explanation

Neutral daylight approximates the colour temperature for which shade guides are designed, and removing coloured clothing, lipstick and bibs prevents simultaneous contrast effects. Operating lights are far too bright and have a blue bias.

Question 49Restorative dentistry, endodontics and prosthodontics

A Class I cavity prepared in a molar has a configuration factor (C-factor) of approximately 5. What is the most likely consequence during polymerisation of a light-cured composite placed in it?

  1. High shrinkage stress, because few surfaces are free to deform Correct answer.
  2. Negligible stress, because the free occlusal surface allows unrestricted flow
  3. Complete relief of stress by plastic deformation of the composite
  4. Separation of the restoration from the cavity floor with no marginal effect

Explanation

C-factor is the ratio of bonded to unbonded surface area; a high value means most of the shrinking material is constrained, so stress is transmitted to the bond and the cusps. Incremental placement and lower-shrinkage materials reduce this effect.

Question 50Restorative dentistry, endodontics and prosthodontics

Conventional glass ionomer cement bonds to dentine mainly by:

  1. micromechanical tags formed after phosphoric acid etching of the dentine
  2. polymerisation of resin into the dentinal tubules
  3. ionic interaction with calcium in the surface hydroxyapatite Correct answer.
  4. covalent bonding to exposed collagen fibrils

Explanation

The polyalkenoic acid chains of glass ionomer displace phosphate and combine with calcium ions in the apatite of enamel and dentine, producing a true chemical adhesion. This does not depend on a separate etch step.