Dental Prosthesis Design: Key Considerations
1. Where May the Retainer Be Located?
Retainers are typically located on the buccal surface of teeth with little natural retention, usually on smaller teeth such as canines or incisors.
2. How Do You Choose the Different Types of Hooks?
The choice of hooks depends on the condition of the teeth where the hook will be located. Retention is always determined by studying the parallelism using a surveyor.
3. When Do You Use the RPI System?
The RPI (Rest, Proximal Plate, I-bar) system is used on posterior teeth, specifically premolars and molars.
4. What Is the Finish Line?
The finish line is the indicator that marks where the acrylic resin will end.
5. In Which Case Would You Use a Kennedy Bar?
A Kennedy bar is used when a hemi-arch lacks posterior teeth but has anterior teeth present.
6. Is It Possible to Weld a Hook on a Wrought Skeleton?
It is discouraged. If attempted, use a good coating and proceed carefully to avoid deforming the skeleton. Welding is generally possible if gold is used.
7. Advantages and Disadvantages of Steel Retainers
- Advantages
- Cheaper
- More rapid fabrication than milled retainers
- Can be adjusted without the danger of breakage
- Disadvantages
- Cannot always be added
- Soldering is not recommended
- Poor durability
8. List the Components of a Removable Partial Denture
- Major connector
- Minor connector
- Occlusal rests: direct and indirect
- Clasps
- Guide planes
- Retainers
9. What Is the Grid?
The grid is used to retain the acrylic resin during the finishing process.
10. What Do You Keep in Mind When Designing with a Y-Clasp?
The arm that goes through should be in contact with the tooth.
11. What Is a Combination Prosthesis?
A combination prosthesis combines fixed and removable prosthetic components.
12. What Is a Coronary Bar?
A coronary bar prevents the prosthesis from tilting and provides counterforce to the posterior teeth.
13. What Is the Palatal Thickness of a Skeleton?
Approximately 0.3 mm.
14. What Is the Lingual Bar Thickness?
Approximately 1.6 mm.
15. Different Types of Bars
- Simple palatal
- Simple lingual
- Double palatal
- Double lingual
- Coronary
- Cingulum
16. Explain Types of Occlusal Rests
- Direct: These are attached to a retainer.
- Indirect: These connect directly to the minor connector.
17. Is Hard or Soft Metal Preferable for a Skeleton?
Ideally, an alloy with a medium hardness, combining properties of both hard and soft metals, is preferred.
18. What Are Common Skeletal Materials?
- Cobalt-chromium
- Gold alloy
19. What Are Minor Connectors?
Minor connectors link the major connector to other components of the prosthesis.
20. Types of Major Connectors
- Palatal plate: U-shaped, ¾, full coverage
- Lingual bar
- Palatal bar
- Lingual plate
- Double palatal bar
- Double lingual bar
21. How Many Elements Can a Skeleton Have?
The number of elements depends on the specific design, the patient’s oral condition, and the number of remaining teeth.
22. Distance of Major Connector from Remaining Teeth
Maxillary: 5-6 mm from the gingival margin. Mandibular: 3-4 mm from the gingival margin.
23. Types of Support for a Removable Partial Denture
Tooth-supported: If there are teeth present, occlusal rests are used. Tissue-supported: If there are no teeth, the denture is supported by the underlying tissues.
24. What Is an Indirect Rest?
An indirect rest is a component that extends from the minor connector to provide additional support.
25. When Is an Anterior Finish Line Used?
An anterior finish line is used when the prosthesis does not extend to the posterior palate but starts on the anterior palate.
26. What Is Further?
In cases of a full denture or when the denture reaches the post-dam area, two finish lines may be used.
27. When Do You Use a U-Shaped Palatal Connector?
A U-shaped palatal connector is used when a palatal torus is present.
28. How Many Finish Lines Does a Cingulum Bar Have?
None.
29. Distance of Lingual Bar from the Gingival Margin
3-4 mm.
30. Why Use Boxes in a Mandibular Design?
Boxes are generally not placed in the mandibular arch for aesthetic reasons. However, they may be used in cases of bruxism or when there is limited space for the technician.