Prosthetics III: Main Exam, 18 December 2018

Mount Kenya University · Department of Dental Sciences · BSCDT · BDS2106

Prosthetics III (BDS2106) Mount Kenya University 2018-2019 past exam with model answers.

Instructions: Answer ALL questions in section A and answer ANY TWO questions from

Section A ANSWER ALL THE QUESTIONS (5 marks)

1. Discuss denture preparation before reline procedure.

Model answer
  • Check the fit: ensure no gaps or pressure points.
  • Clean the denture: remove debris and plaque.
  • Assess the mucosa: look for ulcerations or sore spots.
  • Mark the reline area: identify the region needing adjustment.
  • Remove old base: if necessary, to expose the mucosa.
  • Prepare the tissue: apply a protective layer if needed.
  • Select the relining material: choose appropriate consistency.
  • Apply the material: evenly distribute over the marked area.
  • Seat the denture: allow the material to set.
  • Finish and polish: smooth the new base for comfort.

2. Describe simulation of melanin as a method of pigmentation. (5 marks)

Model answer
  • Simulation of melanin
  • Use a base colour of light tan or beige.
  • Add a thin layer of darker brown or black pigment to mimic melanin granules.
  • Apply the pigment in a stippled or stippling‑like pattern to represent uneven distribution.
  • Blend edges with a soft brush to avoid sharp borders.
  • Allow to dry before final glazing to lock in the pigmentation.

3. Outline desirable characteristics for a reline material. (5 marks)

Model answer
  • Desirable characteristics of a reline material
  • Good adhesion to denture base and mucosa.
  • Adequate compressive strength and wear resistance.
  • Low shrinkage during polymerisation.
  • Biocompatible and non‑irritating.
  • Easy to handle and mould.
  • Acceptable esthetics and colour match.

4. Explain the rationale for rebasing dentures. (5 marks)

Model answer
  • Rationale for rebasing dentures
  • To replace a worn or damaged base.
  • To improve fit and comfort.
  • To correct occlusal discrepancies.
  • To incorporate new teeth or adjust tooth position.
  • To restore structural integrity and longevity.

5. State contraindications for relining complete debentures. (5 marks)

Model answer
  • Contraindications for relining complete dentures
  • Severe mucosal disease or ulceration.
  • Active infection or inflammation.
  • Insufficient residual ridge height.
  • Uncontrolled systemic conditions affecting healing.
  • Patient’s inability to maintain oral hygiene.

6. Describe the closed mouth impression method during denture rebase. (5 marks)

Model answer
  • Closed mouth impression method during denture rebase
  • Seat the denture in the patient’s mouth.
  • Apply a light‑body impression material around the denture base.
  • Allow material to set with the patient maintaining a closed mouth.
  • Remove the denture and impression together.
  • Use the impression to fabricate a new base that fits the existing denture.

Section B ANSWER ALL THE QUESTIONS

1.

  1. a) Describe characterization of denture by teeth selection and setting. (10 marks)
    Model answer
    • Characterisation of denture by teeth selection and setting
    • Teeth selection
    • Choose tooth form (e.g., rounded, tapered) based on patient’s esthetic needs.
    • Select tooth colour matching adjacent natural teeth.
    • Arrange teeth in a balanced occlusion pattern.
    • Teeth setting
    • Position teeth on a wax rim to achieve proper vertical dimension.
    • Check centric and eccentric contacts.
    • Adjust tooth position to avoid interferences.
    • Finalise with a provisional try‑in for esthetic and functional assessment.
  2. b) Discuss methods used for denture base characterization. (10 marks)
    Model answer
    • Methods used for denture base characterization
    • Colour matching: use shade guides and layering techniques.
    • Texture simulation: apply surface coatings or micro‑fillings.
    • Gloss control: use polishing protocols to mimic natural enamel shine.
    • Translucency adjustment: incorporate translucent resins or opacifiers.
    • Surface detailing: add fine scratches or stains for realism.

2.

  1. a) Outline the set up for Angles class II dentures. (10 marks)
    Model answer
    • Setup for Angle’s Class II dentures
    • Teeth arrangement: place a canine in the canine region, premolars in the premolar region, and molars in the molar region.
    • Occlusal scheme: design a balanced occlusion with multiple contacts in centric and eccentric movements.
    • Vertical dimension: establish a proper vertical dimension of occlusion.
    • Centric relation: record centric relation before setting teeth.
    • Try‑in: perform a try‑in to check esthetics and function before final processing.
  2. b) Outline the flasking method for rebase of complete dentures. (10 marks)
    Model answer
    • Flasking method for rebase of complete dentures
    • Preparation: Clean the denture, remove old acrylic, and apply a thin layer of rebase material.
    • Flasking: Place the denture in a flask, fill with wax to create a mold.
    • Wax elimination: Burn out the wax using a heat source, leaving a cavity.
    • Rebase material: Pack the cavity with rebase acrylic resin.
    • Curing: Allow the resin to set under controlled temperature and pressure.
    • De-flasking: Remove the denture from the flask once cured.
    • Finishing: Trim excess material, polish, and check occlusion.
    • Adjustment: Make any necessary occlusal or fit adjustments.
    • Polishing: Final polish to restore surface finish.
    • Quality check: Verify fit, function, and aesthetics before delivery.

3.

  1. a) Outline set up of teeth for Angles class III denture. (10 marks)
    Model answer
    • Set up of teeth for Angle’s Class III denture
    • Upper arch: Position canines and premolars slightly forward to compensate for mandibular protrusion.
    • Lower arch: Align canines and premolars slightly posterior to achieve a balanced occlusion.
    • Incisal guidance: Reduce incisal overlap to prevent excessive protrusion during function.
    • Vertical dimension: Maintain normal VDO to avoid overclosure.
    • Centric relation: Establish a centric relation that allows the lower teeth to fit into the upper without interference.
    • Bite registration: Record the bite with a wax bite block to confirm centric and eccentric contacts.
    • Occlusal scheme: Use a balanced occlusion with simultaneous contacts on both sides.
    • Adjustment: Fine‑tune contacts to avoid premature contacts.
    • Polish and finish: Finish the denture for smooth function.
    • Trial fit: Verify esthetics and function before final processing.
  2. b) Outline the articulator method for relining dentures. (10 marks)
    Model answer
    • Articulator method for relining dentures
    • Mounting: Mount the existing denture on the articulator using a mounting jig.
    • Record base: Record the current occlusal contacts with a wax bite block.
    • Relining material: Select a suitable relining material (e.g., silicone or acrylic).
    • Application: Apply the relining material to the denture base and record new contacts.
    • Curing: Allow the material to set as per manufacturer’s instructions.
    • Adjustment: Remove excess material and adjust occlusion on the articulator.
    • Verification: Check centric and eccentric contacts on the articulator.
    • Transfer: Transfer the adjusted contacts back to the patient’s denture.
    • Trial fit: Have the patient wear the relined denture to confirm comfort and function.
    • Final adjustments: Make any final occlusal adjustments before final delivery.

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