RPD DESIGN 3: Connectors Flashcards
Define a connector
Rigid part of an RPD that unites other components
State the guidelines for minor connectors (4)
- Be rigid
- Finish above the survey line of teeth
- Cross gingival margin at right angles (to maintain gingival health)
- Cover as little gingival tissue as possible
Modifications for minor connectors
Avoid multiple windows
- So cover gingival margins rather than having lots of windows (consider oral hygiene of patient)
Define a minor connector
> Joins components like rests to the major connector
> Transfer functional stresses to and from the abutment teeth
Define a major connector
> Connects components of 1 side of the arch to components on the other side of the arch
State the guidelines for major connectors (4)
- Be rigid
- Avoid covering gingival margins
- Be comfortable with as few edges as possible
- Cover as little tissue as is consistent with rigidity
Give some reasons why there may need to be modifications applied to the major connector guidelines (4)
- Base distribution
- Need for tissue support
- Need for indirect retention
- Previous denture influence
What are the main forms of major connector (2)
- Plate/strap
2. Bar
What type of major connector is most likely used for mucosal supported designs (Craddock class 2) ?
Plate design
Properties of a plate connector
Can be made thinner in cross-section (minimum 0.5mm) and still maintain rigidity
Why are plate designs not normally recommended for mandibular designs?
They may cover gingival margins
When would a plate need to be used in the mandibular arch?
When there is no space available for a bar
Compare the size difference between plates/bars
PLATE
- Thinner and covers more tissue
BARS
- Thicker to maintain rigidity and covers less tissue
State the advantage of a bar connector
Less mucosal coverage + coverage of gingival margins
What type of major connector is most likely used for tooth supported designs? (Craddock class 1)?
Bars
State the cross-sectional thickness of a lingual bar
2mm to maintain rigidity
State the default connector for the mandibular arch
Bar - as less space is available
Why are there no acrylic bars?
Not strong enough
List the maxillary connectors (6)
- Anterior palatal strap
- Mid-palatal strap
- Posterior palatal strap
- Anterior and posterior strap (ring)
- Horseshoe
- Full palatal coverage
List the additional acrylic maxillary connectors (3)
- Spoon
- Modified spoon
- Every
List the mandibular connectors
- Lingual bar
- Lingual plate
- Dental bar
- Sublingual bar
- Labial bar
What is a lingual bar combined with a dental bar referred to as?
Continuous clasp
What’s the default connector for the mandibular arch?
Lingual bar
What connector is used if there isn’t 8mm clearance from gingival margin to functional floor of mouth for a lingual bar
Lingual plate
What mandibular connectors are usually avoided?
- Dental bar
2. Sub-lingual
State an advantage and a disadvantage of continuous clasps
- Give lots of indirect retention
- Cover all cingulum of the teeth
Moveable and uncomfortable for patients
Disadvantage of a lingual plate
Covers all the gingival margins as it goes up to cingulum of teeth
Advantage of a lingual plate
Thinner and provides with indirect retention
Advantage of a continuous clasp
Lots of indirect retention
Disadvantages of a continuous clasp (2)
> Covers all the cingulum of the teeth
> Moveable and uncomfortable for the patients
Advantage of a dental bar
Doesn’t go over soft tissue, stops roughly 1mm short of the gingival margin so doesn’t make a plaque trap
Disadvantage of a dental bar
Quite bulky to achieve rigidity so patients don’t like it much due to irritation
When is a dental bar used?
- If crowns are very large
2. Insufficient room between the gingival margin and the floor of the mouth for sublingual /lingual bar
Why is a sublingual bar usually avoided
Must record the functional floor of the mouth - if not reordered correctly it will be very uncomfortable for the patient
Advantage of a sublingual bar
Below patients tongue so not as noticeable for patient
When is the labial bar used (very rare)
Only when lower anterior teeth are lingually inclined, preventing a lingual bar
Describe how the 8mm height of a lingual bar is achieved
- 3mm from gingival margin
- 4mm height of the bar
- 1mm clearance to functional floor of the mouth
How can major connectors also act as indirect retention
By resisting movement about the axis of rotation
Disadvantages of a Anterior posterior ring design (3)
- Offers less support to the free end saddle across the hard palate (narrow coverage)
- There are a number of edges that the patient may find uncomfortable
- Greater cross sectional thickness
Advantages of an anterior posterior ring design (3)
- Little coverage of gingival tissue
- Rigid connector
- Wide relief of gingival margins to prevent food impaction
Advantages of beading
Intimate contact between the denture + the tissue will prevent food ingression
Where is beading done?
All the way around the border but stops 3mm from the gingival margin
Advantage of a closed denture design
More contact- so gives greater retention and guide planes
Disadvantages of a closed denture design
Possible increased irritation to gingival tissues
Advantages of an open denture design (2)
Greater clearance
Reduced irritation to gingival tissues
What design is normally preferred, open or closed?
Closed - especially at the top
What is required on edentulous areas of an acrylic denture?
A STOP:
Needed to check the fit and ensure the denture does not rotate
What can happen when vertical space is restricted in a denture?
The metal plate can contact the mucosa
Purpose of posts in a denture
Retain the teeth- prevent them ‘pinging off’
This is common in anterior teeth
What may be needed when occlusion is limited, or a deep overlap is encountered?
A metal backing
A metal base can provide this backing
What is the preferred material for connectors?
Metal (cobalt chrome)
- High strength, less bulk, less tissue coverage (gingival margin
When may acrylic be used as a connector?
In the maxilla if the area being covered is large
State the dimensions of a rest
0.5-1mm at junction with minor connector
Give the dimensions of a lingual bar.
Height- 4mm
Thickness- 2mm, oval or half pear shape
Give the dimensions of a sub-lingual bar.
Thickness- 4mm
Kidney shaped
Give the dimensions of maxillary connectors.
5mm clearance from the gingival margin
Bead- 0.5mm deep to 1mm wide
Give the dimensions of bar maxillary connectors
Width- 6mm
Thickness- 1.5mm
Give the dimensions of plate/strap maxillary connectors
Thickness 0.4mm minimum
Give the dimensions of minor connectors
Width- 2mm
Thickness- 1.5mm
Give the dimensions of cast clasps
Length 15mm to engage 0.25mm
