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NZDREX practice questions

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Question 1Diagnosis and Treatment Planning

Which radiographic view is the standard initial image for assessing a suspected mandibular fracture in an emergency setting?

  1. Panoramic radiograph Correct answer.
  2. Periapical of the upper incisors
  3. Lateral cephalometric radiograph
  4. Bitewing survey

Explanation

A panoramic radiograph shows the whole mandible, condyles and rami on one film and is the accepted first-line survey image in trauma. It guides whether additional views such as a reverse Towne or CT are needed. Bitewings and cephalometrics do not display the full mandibular outline.

Question 2Diagnosis and Treatment Planning

During a new-patient examination, a 45-year-old reports a 6 mm localized pocket on the mesial of the upper right first molar with bleeding on probing but no radiographic bone loss. What is the most appropriate provisional classification?

  1. Periodontal abscess
  2. Necrotizing periodontal disease
  3. Localized dental plaque-induced gingivitis Correct answer.
  4. Generalized periodontitis, stage III

Explanation

Pocketing with bleeding but no attachment loss or radiographic bone loss is consistent with plaque-induced gingivitis rather than periodontitis. Periodontitis staging requires demonstrable clinical attachment loss and bone loss. The localized nature and absence of necrosis or suppuration support the gingivitis diagnosis.

Question 3Diagnosis and Treatment Planning

Which clinical finding most strongly suggests a diagnosis of temporomandibular joint disc displacement with reduction?

  1. Limitation of opening to 20 mm with deviation to the affected side
  2. A reciprocal click on opening and closing that resolves with a protrusive opening Correct answer.
  3. Continuous pain over the masseter without any joint sound
  4. Crepitus on lateral excursion with no joint noise on opening

Explanation

Disc displacement with reduction classically produces an opening click as the disc reduces onto the condyle and a closing click as it displaces again. A protrusive opening path often eliminates the click because the condyle is repositioned. Crepitus and hard-end limitation point to degenerative or closed-lock presentations instead.

Question 4Diagnosis and Treatment Planning

A patient requests replacement of a missing upper first molar. Which finding would most strongly contraindicate a single implant-supported crown at that site?

  1. Insufficient mesiodistal space of 5 mm between adjacent roots Correct answer.
  2. Interocclusal space of 7 mm at the edentulous site
  3. A healed ridge with 8 mm of bone height above the sinus floor
  4. Adequate keratinized tissue band of 4 mm

Explanation

A 5 mm mesiodistal gap cannot accommodate a standard molar implant platform and its safety margins without encroaching on adjacent roots. Ridge height, keratinized tissue and interocclusal space in the stated values are generally favorable. Space analysis is therefore the decisive limiting factor here.

Question 5Diagnosis and Treatment Planning

Which record is essential before undertaking a full-mouth rehabilitation with a change in occlusal vertical dimension?

  1. Photographs of the smile only
  2. A screening panoramic radiograph alone
  3. A single bitewing radiograph
  4. Mounting of articulated study casts with a facebow and interocclusal record Correct answer.

Explanation

Changing vertical dimension requires articulated casts so the existing and proposed occlusal schemes can be compared and the new position transferred to the laboratory. A facebow and interocclusal record relate the maxilla to the hinge axis. Radiographs and smile photographs alone cannot define the occlusal relationship.

Question 6Diagnosis and Treatment Planning

A 12-year-old presents with a Class II division 1 malocclusion, increased overjet and a deep bite. Which initial diagnostic step best determines whether the overjet is skeletal or dental in origin?

  1. Recording the patient's preferred chewing side
  2. Cephalometric tracing to assess ANB angle and incisor inclination Correct answer.
  3. Measuring the overjet with a periodontal probe only
  4. Taking a single periapical radiograph of the upper incisors

Explanation

A lateral cephalometric tracing quantifies the anteroposterior jaw relationship (ANB) and the inclination of the upper and lower incisors. This distinguishes a skeletal Class II pattern from dental proclination or a combination. Clinical overjet measurement alone cannot make that distinction.

Question 7Diagnosis and Treatment Planning

Which of the following is the primary purpose of a diagnostic wax-up in treatment planning?

  1. To record the patient's centric relation permanently
  2. To replace the need for articulated casts
  3. To preview the proposed tooth form and occlusion before irreversible preparation Correct answer.
  4. To provide the definitive restoration for cementation

Explanation

A diagnostic wax-up builds the planned contours and occlusion in wax so the clinician and patient can evaluate aesthetics and function before tooth reduction. It also allows fabrication of a stent or provisional matrix. It is a planning tool, not a definitive restoration.

Question 8Diagnosis and Treatment Planning

A patient with a history of infective endocarditis is scheduled for a simple extraction. Which planning consideration is most important?

  1. Arranging appropriate antibiotic prophylaxis according to current cardiology guidance Correct answer.
  2. Performing the extraction without any radiograph
  3. Deferring all local anaesthesia
  4. Scheduling the procedure without consulting the patient's physician

Explanation

Patients with a history of infective endocarditis are among the highest-risk groups for bacteraemia-related infection. Current cardiology guidance should be consulted and prophylaxis arranged where indicated. Local anaesthesia and preoperative imaging remain appropriate and necessary.

Question 9Diagnosis and Treatment Planning

A 55-year-old presents with a 10 mm firm, non-tender swelling in the upper neck that has been present for three months. What is the most appropriate initial management step?

  1. Prescription of antibiotics and review in three months
  2. Urgent referral for investigation of a possible malignancy Correct answer.
  3. Reassurance only, as the swelling is non-tender
  4. Incisional biopsy in the dental chair

Explanation

A persistent neck mass in an adult is a red flag for malignancy, including lymphoma and metastatic carcinoma. Prompt referral to an appropriate specialist for imaging, fine-needle aspiration and further workup is required. Antibiotics or reassurance delay diagnosis in a persistent, firm mass.

Question 10Diagnosis and Treatment Planning

A patient has generalized moderate chronic periodontitis. Which factor in the treatment plan most directly determines the prognosis of the remaining molars?

  1. The number of previous radiographs taken
  2. The patient's preferred toothpaste flavour
  3. The shade of the existing composite restorations
  4. The presence of furcation involvement and remaining attachment support Correct answer.

Explanation

Furcation involvement and residual attachment are the principal determinants of periodontal prognosis for multirooted teeth. They influence whether maintenance, regenerative surgery or extraction is planned. Restoration shade, toothpaste and radiographic history do not affect periodontal prognosis.

Question 11Diagnosis and Treatment Planning

A patient with a severely worn anterior dentition has lost 6 mm of clinical crown height. Which diagnostic finding best supports increasing the occlusal vertical dimension?

  1. A stable existing occlusion with no freeway space loss
  2. Generalized mild gingival recession
  3. A history of nocturnal bruxism alone
  4. A reproducible centric relation record and an interocclusal space of 4 mm at the retruded position Correct answer.

Explanation

Increasing vertical dimension is justified when the retruded position shows available interocclusal space, indicating the mandible can be repositioned without over-closing. A reproducible centric relation record allows this to be tested. Bruxism history alone does not indicate how much space is available.

Question 12Diagnosis and Treatment Planning

In planning a mandibular implant overdenture, which finding most strongly favours a two-implant rather than a single-implant design?

  1. A history of well-controlled hypertension
  2. Adequate bone volume across the symphysis
  3. A patient preference for a removable prosthesis
  4. A narrow anterior ridge with limited bone width in the midline Correct answer.

Explanation

A narrow midline ridge may not accommodate a single implant in the ideal position, so two implants placed lateral to the midline give better support and stability. Adequate symphyseal bone and patient preference for a removable prosthesis do not by themselves preclude a single implant. The anatomical limitation is the deciding factor.

Question 13Diagnosis and Treatment Planning

A patient reports a dull, poorly localized ache in the upper posterior region that worsens on bending forward. Which diagnosis should be considered first?

  1. Trigeminal neuralgia
  2. Myofascial pain of the masseter
  3. Irreversible pulpitis of a lower molar
  4. Maxillary sinusitis referred to the dentition Correct answer.

Explanation

A dull, poorly localized ache aggravated by postural change such as bending forward is characteristic of sinusitis referred to the upper teeth. Sinus pain often mimics odontogenic pain in the posterior maxilla. Pulpitis is typically well localized and provoked by thermal stimuli.

Question 14Diagnosis and Treatment Planning

Which radiographic finding on a panoramic film most suggests an odontogenic keratocyst rather than a radicular cyst?

  1. A uniform widening of the periodontal ligament space
  2. A periapical radiolucency continuous with a non-vital tooth root
  3. A diffuse, ill-defined radiolucency with periosteal reaction
  4. A well-defined radiolucency with a scalloped border along the mandibular angle Correct answer.

Explanation

Odontogenic keratocysts often appear as well-defined, scalloped radiolucencies that grow along the bone rather than expanding it symmetrically. Radicular cysts are centred on the apex of a non-vital tooth. Diffuse ill-defined radiolucency with periosteal reaction suggests malignancy or osteomyelitis.

Question 15Diagnosis and Treatment Planning

A patient with a Class III incisor relationship and anterior crossbite requests orthodontic treatment. Which record is most useful in deciding whether orthodontics alone can correct the crossbite?

  1. A single periapical radiograph of the lower incisors
  2. Lateral cephalometric radiograph with skeletal tracing Correct answer.
  3. Photographs of the buccal corridor
  4. A panoramic radiograph alone

Explanation

A lateral cephalometric tracing shows whether the Class III pattern is skeletal or dental and how much dental compensation exists. This determines whether camouflage orthodontics is feasible or whether orthognathic surgery should be considered. A panoramic film or photographs alone cannot make this distinction.

Question 16Diagnosis and Treatment Planning

A patient is diagnosed with a cracked tooth on a mandibular molar with symptoms only on biting and no spontaneous pain. Which treatment plan is most appropriate initially?

  1. Root canal treatment without further assessment
  2. Full-coverage restoration with occlusal adjustment Correct answer.
  3. No treatment and review in six months
  4. Immediate extraction

Explanation

A cracked tooth with symptoms confined to biting and no spontaneous or lingering pain suggests the pulp is not irreversibly inflamed. Full-coverage restoration protects the cusp and prevents propagation. Extraction or root canal treatment is reserved for irreversible pulpal involvement or unrestorable fractures.

Question 17Diagnosis and Treatment Planning

A patient with type 2 diabetes and an HbA1c of 9.5% requires multiple extractions. Which planning decision is most appropriate?

  1. Avoid local anaesthesia entirely
  2. Proceed immediately without any medical liaison
  3. Extract all teeth in one visit regardless of control
  4. Coordinate with the physician to improve glycaemic control before elective surgery Correct answer.

Explanation

Poorly controlled diabetes impairs healing and increases infection risk, so elective surgery should be delayed until glycaemic control improves. Liaison with the physician allows this to be assessed and managed. Proceeding without coordination or avoiding anaesthesia are not appropriate responses.

Question 18Diagnosis and Treatment Planning

A patient presents with a localized gingival enlargement on the labial aspect of the upper incisors, and medication history includes a calcium channel blocker. What is the most appropriate initial management?

  1. No action, as drug-induced enlargement always resolves
  2. Consult the prescribing physician about an alternative medication and reinforce plaque control Correct answer.
  3. Immediate gingivectomy without further assessment
  4. Extraction of the affected teeth

Explanation

Drug-induced gingival enlargement is often improved when the causative medication is changed, in combination with meticulous plaque control. Consulting the prescriber is the appropriate first step. Surgery is considered only if enlargement persists after these measures.

Question 19Diagnosis and Treatment Planning

Which finding on a cone beam CT most influences the decision to place an implant in the posterior maxilla?

  1. Residual bone height and width relative to the sinus floor Correct answer.
  2. The patient's age alone
  3. The colour of the adjacent teeth
  4. The number of existing amalgam restorations

Explanation

Cone beam CT quantifies residual bone height and width and the position of the sinus floor, which determines whether a standard implant, sinus lift or short implant is planned. Restoration type, age alone and tooth colour do not define the surgical feasibility.

Question 20Diagnosis and Treatment Planning

A patient with a history of radiotherapy to the head and neck requires a lower molar extraction. Which planning consideration is most important?

  1. Extracting under general anaesthesia as the only safe option
  2. Assessing osteoradionecrosis risk and considering hyperbaric oxygen or a conservative approach Correct answer.
  3. Avoiding radiographs entirely
  4. Proceeding with a routine extraction with no additional precautions

Explanation

Radiotherapy to the head and neck increases the risk of osteoradionecrosis after extraction, especially in the mandible. The plan should assess dose and timing, consider atraumatic technique and, where appropriate, hyperbaric oxygen. Routine extraction without precautions is inappropriate.

Question 21Diagnosis and Treatment Planning

A patient has a Class II division 2 malocclusion with a deep overbite and retroclined upper incisors. Which treatment-planning consideration is most relevant before aligning the upper arch?

  1. Using only a removable retainer as active treatment
  2. Ignoring the overbite until alignment is complete
  3. Extracting the lower first molars routinely
  4. Creating space and assessing the need to open the bite to allow incisor proclination Correct answer.

Explanation

Retroclined upper incisors in a deep bite have limited space to move forward without interference from the lower incisors. Space creation and bite opening are usually needed before alignment to avoid traumatic occlusion. Routine lower molar extraction or retainer-only therapy would not address the overbite.

Question 22Diagnosis and Treatment Planning

A patient reports a burning sensation of the oral mucosa with no visible lesions, and blood tests show low vitamin B12 and folate. What is the most appropriate next step?

  1. Investigate and correct the nutritional deficiencies and reassess symptoms Correct answer.
  2. Perform a biopsy of the tongue
  3. Reassure the patient without further investigation
  4. Diagnose burning mouth syndrome and prescribe a tricyclic immediately

Explanation

Burning mouth symptoms can be secondary to nutritional deficiencies, so identifying and correcting B12 and folate deficiency is the appropriate first step. Burning mouth syndrome is a diagnosis of exclusion after such causes are ruled out. Biopsy is not indicated in the absence of lesions.

Question 23Diagnosis and Treatment Planning

A patient has a 6 mm pocket on the distal of a lower second molar adjacent to a partially erupted third molar. Which diagnosis is most appropriate?

  1. Necrotizing ulcerative gingivitis
  2. Pericoronitis associated with the third molar Correct answer.
  3. Generalized chronic periodontitis
  4. Primary herpetic gingivostomatitis

Explanation

A localized deep pocket distal to the second molar adjacent to a partially erupted third molar is characteristic of pericoronitis. The inflammation is related to the operculum and plaque stagnation around the erupting tooth. Generalized periodontitis or viral conditions would present differently.

Question 24Diagnosis and Treatment Planning

A patient with a suspected medication-related osteonecrosis of the jaw has exposed bone for eight weeks after a dental extraction and is taking a bisphosphonate. Which management approach is most appropriate initially?

  1. No intervention and no follow-up
  2. Immediate radical resection of the mandible
  3. Conservative management with antimicrobial rinse, analgesia and infection control Correct answer.
  4. Extraction of all remaining teeth

Explanation

Early-stage medication-related osteonecrosis is managed conservatively with antimicrobial mouth rinse, analgesia and control of infection while avoiding further trauma. Radical resection is reserved for advanced, refractory disease. Removing all remaining teeth would create further bone exposure.

Question 25Diagnosis and Treatment Planning

A patient with a history of paroxysmal atrial fibrillation on a direct oral anticoagulant requires a single simple extraction. Which planning approach is most consistent with current guidance?

  1. Assess renal function and timing, and perform the extraction with local haemostatic measures without routinely stopping the drug Correct answer.
  2. Perform the extraction without any haemostatic precautions
  3. Stop the anticoagulant for one week before extraction without consulting the prescriber
  4. Refer for extraction only under general anaesthesia

Explanation

For simple extractions, direct oral anticoagulants are generally continued, with timing adjusted to the drug's peak effect and renal function considered. Local measures such as sutures and haemostatic agents control bleeding. Stopping the drug without prescriber involvement risks thromboembolism.

Question 26Diagnosis and Treatment Planning

When formulating a problem list for a new patient, which item belongs in the diagnosis section rather than the treatment plan section of the record?

  1. Review of occlusal contacts at three months after splinting
  2. Composite build-up of the upper right central incisor to restore guidance
  3. Reduced anterior overbite of 1 mm with fremitus on the upper right central incisor Correct answer.
  4. Splint therapy to redistribute occlusal load in the anterior segment

Explanation

A diagnosis records the identified condition and its clinical signs, such as reduced overbite with fremitus, because these describe what is wrong rather than what will be done. Treatment plan entries describe interventions and their review, so restorative build-up, splint therapy and follow-up reviews belong to the plan. Separating findings from interventions keeps the problem list auditable and links each planned step to a stated diagnosis.

Question 27Diagnosis and Treatment Planning

A patient attends for a full assessment before extensive crown and bridgework. Which record is essential for transferring the maxillary cast to the semi-adjustable articulator in the planned intercuspal position?

  1. A set of intraoral photographs in maximum opening
  2. A facebow record plus an interocclusal registration Correct answer.
  3. A panoramic radiograph taken with a bite block
  4. A diagnostic wax-up of the mandibular arch only

Explanation

A facebow record relates the maxillary cast to the hinge axis and reference plane, while an interocclusal registration records the planned jaw relationship, so both are needed to mount casts accurately. A semi-adjustable articulator cannot be set from photographs or a panoramic film alone. Accurate mounting underpins occlusal analysis and the design of the planned restorations.

Question 28Diagnosis and Treatment Planning

A 45-year-old presents with pain on chewing in the upper left first molar. The tooth is heavily restored, responds normally to cold, and is tender to percussion, and the patient reports pain on release after clenching. Which diagnosis best fits this presentation?

  1. Reversible pulpitis
  2. Cracked tooth syndrome Correct answer.
  3. Symptomatic apical periodontitis
  4. Acute periapical abscess

Explanation

Pain on release after clenching, alongside normal cold response and tenderness to percussion in a heavily restored molar, is characteristic of a cracked tooth where the crack opens on loading and pain occurs when force is released. Symptomatic apical periodontitis would typically show a prolonged response to cold or a non-vital pulp and pain on biting rather than specifically on release. Reversible pulpitis would be provoked by thermal stimuli, not by clenching. An acute abscess would usually show swelling and severe spontaneous pain.

Question 29Diagnosis and Treatment Planning

A 30-year-old requests replacement of a missing upper central incisor. The adjacent teeth are sound and unrestored, the ridge is intact, bone width is adequate on CBCT, and the patient is a non-smoker with good plaque control. Which planning decision is most appropriate?

  1. A single implant-supported crown with a provisional restoration Correct answer.
  2. Extraction of the adjacent incisors to allow a wider prosthetic space
  3. A three-unit fixed bridge using the adjacent sound incisors as abutments
  4. A removable partial denture retained by clasps on the adjacent incisors

Explanation

When adjacent teeth are sound and bone volume is adequate, a single implant crown avoids preparing healthy teeth and preserves the interdental papillae and bone. A bridge would sacrifice intact enamel on two abutment teeth, which is hard to justify in a young patient. A removable prosthesis is a reasonable interim or fallback option but is not the preferred definitive plan here.

Question 30Diagnosis and Treatment Planning

A 60-year-old with a long history of stable angina is planned for multiple extractions under local anaesthesia. Which planning measure most reduces the risk of an intraoperative cardiac event?

  1. Arranging treatment in the supine position for the whole appointment
  2. Using a local anaesthetic containing adrenaline to ensure profound anaesthesia
  3. Withholding all anti-anginal medication on the morning of treatment
  4. Booking a short morning appointment with effective analgesia and anxiety control Correct answer.

Explanation

Pain, anxiety and catecholamine release are the main triggers of intraoperative ischaemia, so a short appointment with good anaesthesia, analgesia and anxiety control reduces cardiac demand. Adrenaline-containing local anaesthetic is generally acceptable in controlled doses, and avoiding pain is more important than avoiding vasoconstrictor entirely. Anti-anginal medication should be continued, and a fully supine position can worsen symptoms in some cardiac patients.

Question 31Operative Dentistry and Direct Restorations

Which bur is the standard choice for gaining access to the pulp chamber through the occlusal surface of a posterior tooth during root canal treatment?

  1. Fissure carbide bur Correct answer.
  2. Tapered fissure bur
  3. End-cutting carbide bur
  4. Round diamond bur

Explanation

A fissure carbide bur efficiently cuts through enamel and dentine with a controlled, non-selective action and creates a clean access outline without excessive removal of sound tissue. Diamonds are slower and clog, while end-cutting designs are used for axial wall preparation rather than initial penetration.

Question 32Operative Dentistry and Direct Restorations

In a Class II cavity, what is the main purpose of the proximal box?

  1. To gain access to the adjacent tooth
  2. To remove carious dentine from the proximal surface Correct answer.
  3. To provide a path for insertion of the restorative material
  4. To improve retention of the restoration

Explanation

The proximal box removes the carious lesion and unsupported enamel on the proximal surface, extending the outline to sound tissue. Retention and access are secondary considerations achieved through other features such as the dovetail and occlusal outline.

Question 33Operative Dentistry and Direct Restorations

Which factor most strongly determines the choice of a glass ionomer restoration over a composite in a primary tooth?

  1. The patient's age at the time of treatment
  2. The need for fluoride release and moisture tolerance Correct answer.
  3. The shade match with the adjacent tooth
  4. The occlusal load on the restored surface

Explanation

Glass ionomer cements release fluoride and tolerate moisture better than composites, making them useful in primary teeth where isolation is difficult. Shade and occlusal load favour composite, while patient age alone does not dictate material selection.

Question 34Operative Dentistry and Direct Restorations

What is the recommended occlusal clearance for a direct composite restoration in a posterior tooth?

  1. 0.5 mm
  2. 2.0 mm Correct answer.
  3. 3.0 mm
  4. 1.0 mm

Explanation

A minimum of about 2 mm of composite is required over the occlusal contact area to provide adequate strength and wear resistance. Thinner layers risk fracture and wear-through under masticatory load.

Question 35Operative Dentistry and Direct Restorations

Which instrument is most appropriate for carving the occlusal anatomy of a freshly placed amalgam restoration?

  1. Hollenback carver Correct answer.
  2. Amalgam plugger
  3. Condenser
  4. Burnisher

Explanation

A Hollenback carver has a sharp, curved blade designed to carve occlusal anatomy and remove excess amalgam. Pluggers and condensers compact material, while burnishers smooth the surface without carving anatomy.

Question 36Operative Dentistry and Direct Restorations

What is the primary function of a matrix band during placement of a Class II restoration?

  1. To protect the adjacent tooth from iatrogenic damage
  2. To retain the restorative material in the cavity
  3. To restore the proximal contour and contact Correct answer.
  4. To isolate the operating field from saliva

Explanation

A matrix band recreates the missing proximal wall so the restorative material can be condensed to the correct contour and contact. Protection of the adjacent tooth is a secondary benefit, and isolation is achieved with other aids.

Question 37Operative Dentistry and Direct Restorations

Which etchant concentration and application time is standard for total-etch enamel bonding?

  1. 37% phosphoric acid for 15 seconds
  2. 5% phosphoric acid for 90 seconds
  3. 10% phosphoric acid for 60 seconds
  4. 37% phosphoric acid for 30 seconds Correct answer.

Explanation

A 37% phosphoric acid gel applied for about 30 seconds adequately etches enamel, creating microporosity for micromechanical retention. Shorter or weaker applications may produce inadequate etch patterns.

Question 38Operative Dentistry and Direct Restorations

Which of the following best describes the purpose of a bevel on the cavosurface margin of a Class III preparation?

  1. To increase retention of the composite
  2. To prevent marginal staining
  3. To expose enamel prisms for improved bonding Correct answer.
  4. To reduce the amount of tooth structure removed

Explanation

A bevel exposes the ends of enamel prisms, which improves the bond strength of composite at the cavosurface margin. Retention is achieved through other means, and the bevel actually removes additional tooth structure.

Question 39Operative Dentistry and Direct Restorations

During a Class V preparation on a mandibular premolar, which factor most influences the decision to place a gingival bevel?

  1. The colour of the adjacent tooth
  2. The presence of enamel at the gingival margin Correct answer.
  3. The type of matrix used
  4. The depth of the lesion

Explanation

A gingival bevel is placed when enamel remains at the gingival margin, allowing the composite to blend and bond at the cavosurface. Where the margin lies in root dentine, the bevel is not appropriate.

Question 40Operative Dentistry and Direct Restorations

A patient reports sensitivity after a direct composite restoration. Which cause is most likely related to the bonding procedure?

  1. Incomplete polymerisation of the composite
  2. Overfilling of the cavity
  3. Use of a matrix band
  4. Excessive etching of dentine Correct answer.

Explanation

Over-etching dentine can leave the collagen network inadequately infiltrated by adhesive, causing postoperative sensitivity from fluid movement. Incomplete polymerisation and overfilling produce other symptoms, and a matrix band does not cause sensitivity.

Question 41Operative Dentistry and Direct Restorations

Which layer of the tooth does the hybrid layer form between when using an etch-and-rinse adhesive?

  1. Dentine and pulp
  2. Enamel and dentine
  3. Enamel and composite
  4. Dentine and composite Correct answer.

Explanation

The hybrid layer is the interdiffusion zone formed between the demineralised dentine collagen network and the infiltrating adhesive resin. It does not form at the enamel-composite interface in the same way.

Question 42Operative Dentistry and Direct Restorations

Which of the following is the most appropriate management for a small proximal carious lesion in a primary molar with an intact marginal ridge?

  1. Extraction of the tooth
  2. Stainless steel crown
  3. Direct composite restoration Correct answer.
  4. Fluoride varnish and monitoring

Explanation

A small proximal lesion with an intact marginal ridge can be managed with a direct composite restoration that conserves tooth structure. Extraction and stainless steel crowns are excessive, and monitoring alone risks progression.

Question 43Operative Dentistry and Direct Restorations

What is the main advantage of a sectional matrix system over a circumferential band for a Class II composite?

  1. It provides better proximal contour and contact Correct answer.
  2. It requires less operator skill
  3. It eliminates the need for wedges
  4. It is quicker to apply

Explanation

A sectional matrix with a separating ring produces a tighter proximal contact and more anatomically accurate contour than a circumferential band. Speed and operator skill are not the primary advantages.

Question 44Operative Dentistry and Direct Restorations

During placement of a large amalgam restoration, why is condensation pressure important?

  1. To reduce voids and adapt amalgam to cavity walls Correct answer.
  2. To polish the surface
  3. To improve the colour match
  4. To speed up setting

Explanation

Firm condensation pressure reduces voids and adapts the amalgam closely to the cavity walls, improving strength and marginal seal. It does not polish, accelerate setting, or affect colour.

Question 45Operative Dentistry and Direct Restorations

Which cavity preparation feature is used to retain a Class I amalgam restoration?

  1. A bevel
  2. A dovetail
  3. A proximal box
  4. A retentive groove Correct answer.

Explanation

Retentive grooves placed in the proximal walls or undercuts provide mechanical retention for amalgam. A dovetail is used in Class II preparations, and a bevel is not appropriate for amalgam margins.

Question 46Operative Dentistry and Direct Restorations

A dentist is choosing between a flowable and a packable composite for an occlusal restoration. Which property best justifies using a packable composite?

  1. Higher filler content for better wear resistance Correct answer.
  2. Lower shrinkage for better seal
  3. Lower viscosity for better adaptation
  4. Greater flow for easier placement

Explanation

Packable composites have higher filler loading, giving better wear resistance and strength for occlusal load-bearing surfaces. Flowable composites have lower viscosity and are used in low-stress areas.

Question 47Operative Dentistry and Direct Restorations

Which factor most increases the risk of marginal leakage in a direct composite restoration?

  1. Use of a sectional matrix
  2. Use of a rubber dam
  3. Placement of a bevel
  4. Inadequate adhesive application Correct answer.

Explanation

Inadequate adhesive application leaves gaps at the interface, allowing bacterial and fluid leakage. Rubber dam, bevels, and sectional matrices all generally reduce leakage risk.

Question 48Operative Dentistry and Direct Restorations

What is the recommended curing time for a 2 mm increment of composite using a standard curing light?

  1. 20 seconds
  2. 60 seconds
  3. The time specified in the manufacturer's instructions for the composite, shade, increment thickness and curing-light irradiance Correct answer.
  4. 10 seconds

Explanation

The curing time for a 2 mm increment depends on the composite, shade and light output. Follow the manufacturer's instructions for the specified increment and irradiance; calling a light 'standard' does not establish a universal 40-second exposure.

Question 49Operative Dentistry and Direct Restorations

Which of the following best explains why a glass ionomer restoration may be preferred in a patient with a high caries risk?

  1. It has superior aesthetic properties
  2. It bonds chemically to enamel only
  3. It has higher compressive strength
  4. It releases fluoride over time Correct answer.

Explanation

Glass ionomer releases fluoride over time, which can help inhibit secondary caries in high-risk patients. Its aesthetics and strength are inferior to composite.

Question 50Operative Dentistry and Direct Restorations

A Class II composite restoration shows a poor proximal contact post-operatively. Which factor is the most likely cause?

  1. Excessive curing time
  2. Inadequate matrix adaptation Correct answer.
  3. Insufficient etching time
  4. Use of a wedge

Explanation

Poor matrix adaptation allows composite to spread beyond the intended contour, producing an open or weak contact. Etching time and curing time affect bond strength, not contact.