Prosthetics II: Main Exam, 17 December 2018
Mount Kenya University · Department of Dental Sciences · Diploma in Dental Technology · BDS1204
Prosthetics II past exam from Mount Kenya University 2018-2019 with model answers for BDS1204.
Instructions: ANSWER ALL QUESTIONS IN SECTION A (COMPULSORY) AND ANY OTHER TWO QUESTIONS IN SECTION B
Section A 30 MARKS
1. What are the factors that determine the shade selection in artificial teeth. (4 marks)
- Shade selection factors
- Natural tooth color and translucency
- Incisal edge translucency vs. cervical opacity
- Presence of stains or discoloration
- Lighting conditions and patient’s visual perception
- Adjacent tooth color and harmony
- Material translucency and opacity of the artificial tooth
- Desired esthetic outcome and patient expectations
2. Define festooning of a denture. (2 marks)
- Festooning is the excessive, irregular, or uneven margin of a denture where the tissue surface is not smooth, leading to a “festooned” appearance.
3. Give the importance of working up of a denture. (4 marks)
- Accurate fit of the denture
- Identification of functional and esthetic requirements
- Detection of missing or damaged teeth
- Assessment of occlusion and jaw relationships
- Planning of tooth arrangement and shade
- Basis for fabrication of a well‑contoured, comfortable denture
4. State two contra indications of relining. (2 marks)
- Severe mucosal disease (e.g., uncontrolled ulceration)
- Active infection or inflammation in the oral tissues
5. Explain what resilient on soft timing materials of a denture are. (2 marks)
- Resilient or soft‑timing materials are elastic, rubber‑like bases used in dentures to provide a cushioning effect and improve comfort.
6. Define rebasing as applied in prosthetics. (2 marks)
- Rebasing is the remaking of the denture base by adding new material over the existing base to correct fit or occlusion issues.
7. Write down four indications of rebasing. (4 marks)
- Poor fit or leakage
- Occlusal discrepancies
- Wear or fracture of the base
- Changes in the oral tissues or tooth position
- More answers:
- Residual denture base material degradation
- Patient discomfort due to improper seating
8. State two errors that could arise by setting lower anserior teeth more lingual in a class II Jew relationship. (2 marks)
- Increased overbite leading to excessive incisal contact
- Misoriented occlusion causing premature contacts on the lingual side
9. What is the importance of denture identification? (4 marks)
- Legal and safety: ensures correct patient identification in emergencies.
- Clinical management: aids in tracking wear, maintenance and adjustments.
- Insurance and billing: provides proof of ownership for claims.
- Professional accountability: records dentist’s responsibility and traceability.
10. Give four requirements of a denture identification. (4 marks)
- Patient name
- Dentist name
- Date of fabrication
- Unique serial number
- More answers: additional identifiers such as patient ID, laboratory code, or implant locator.
Section B
1. Discuss aesthetical considerations in teeth selection during complete denture fabrication. (20 marks)
- Smile line: align with natural smile arc.
- Proportion: tooth size relative to face and each other.
- Shape: mimic natural tooth morphology.
- Color: match adjacent teeth and gingival tone.
- Transparency: use of opalescence for realism.
- Surface texture: enamel-like polish.
- Occlusal scheme: functional contacts and centric relation.
- Cusp height: appropriate for esthetics and function.
- Gingival margin: smooth, natural-looking finish.
- Labial contour: avoid excessive bulk.
- Shade selection: consider ethnic background.
- Symmetry: balanced arrangement of anterior teeth.
2.
- a) Describe the laboratory procedure of rebasing using flasking method. (10 marks)Model answer
- Prepare the master cast: clean and mount in articulator.
- Place the denture: seat in the cast, record centric relation.
- Mark the base: note the existing base for reference.
- Create a new mold: use a silicone or polyvinyl siloxane impression material.
- Pour the new base: with autopolymerising acrylic resin.
- Flask the assembly: embed in plaster, remove the old base.
- Burn out the old base: heat to vaporise resin.
- Pack new base: pack fresh acrylic into the flask.
- Polymerise: in a water bath at 90–100 °C for 1–2 h.
- Deflask and finish: remove, trim, polish, and fit.
- b) What are the problems, causes and the solutions associated with the flasking method of rebasing. (10 marks)Model answer
- Problems: distortion, voids, incomplete removal of old base.
- Causes: inadequate flasking technique, over‑pressure, poor venting.
- Solutions: use proper venting, controlled pressure, correct flasking angle, and thorough cleaning before rebasing.
3.
- a) What are soft linens? Write down the uses of tissue conditioners. (8 marks)Model answer
- Soft linens: temporary denture bases made of tissue‑conditioning material.
- Uses: 1) to relieve sore spots, 2) to allow tissue healing, 3) to provide a smooth interim base, 4) to assess fit before final relining.
- b) Explain the composition of tissue conditioners and the properties that make them effective. (12 marks)Model answer
- Composition: acrylic resin, plasticisers, water‑absorbing agents, and sometimes antibiotics.
- Effective properties: 1) softness for comfort, 2) moisture retention, 3) antibacterial action, 4) easy removal, 5) biocompatibility.