RPD - Connectors Flashcards
What is meant by the term ‘connector’?
- A term used to describe the rigid part of a partial denture that unites other components. There are minor connectors and major connectors
What are the 2 types of connectors?
- Minor and major connectors
What is the purpose of major connectors?
- Part of the denture that connects components on one side of the arch to components on the other side of the arch
What is the purpose of minor connectors?
- Join components such as rests to the major connector
- They transfer functional stresses to and from the abutment teeth
What are the requirements of a minor connector? (4 points)
- Be rigid
- Finish above (towards the occlusal surface) the survey line of the teeth
- Cross the gingival margin at right angles (to maintain gingival health)
- Cover as little gingival tissue as possible - trying to maintain the health of the gingiva
When using minor connectors what do you want to avoid?
- Avoid having multiple ‘windows’ (don’t want lots of thin bits connecting lots of bits together)
What are the requirements of a major connector? (4 points)
- Be rigid (no modifications to this rule)
- Avoid covering gingival margins
- Be comfortable, with as few edges as possible
- Cover al little tissue as is consistent with rigidity (apart from Craddock’s class 3)
What modifications may need to me made in major connectors? (6 points)
- Base distribution
- Need for tissue support
- Need for indirect retention
- Anatomical limitations
- Prognosis of the dentition
- Previous denture influence
In modifications for major connectors what is ‘prognosis of the dentition’?
- Situation where you’re planning on giving the patient a denture but there are a few teeth that are unlikely to last the full time of the denture - can factor this into the design so it is easy to add a tooth to the denture if it happens
In modifications for major connectors what is ‘previous denture influence’?
- If the previous denture is a denture they are happy with then don’t try to change this or try to change the design - just reproduce what they already have
Can a plate connector be made thinner in cross section but still maintain its rigidity?
- Yes
Which kind of connector design is the option for mucosa supported (Craddock’s class 2) designs?
- Plate designs
How thin can the cross sectional thickness of a plate be?
- As little as 0.5mm thin
Why are plate designs only recommended in the mandibular arch when no space is available for the bar?
- As it may cover gingival margins
To maintain rigidity of a plate what may it need to be in the cross section?
Thicker (this is depending on the coverage and shape of the mucosa areas)
As a general rule what do you need in a connector if you have less tooth support?
-Need greater mucosal coverage
What is the advantage of using a bar connector?
- There is less mucosal coverage
Why must a bar connector be made suitably thick in cross section?
- To maintain rigidity e.g. lingual bar should be at least 2mm thick
What type of connector is a common choice for a Craddock class 1?
- A bar connector
Why is a bar connector a default choice for the mandi bular arch?
- Because there is less space in the mandibular arch
What is the problem with a sublingual bar?
- Have to have recorded the functional floor of the mouth - if not recorded correctly it will be very uncomfortable for the patient
- Tends not to be regularly used as it is hard to get the impression accurate
What are the options for mandibular connectors? (5 points)
- Lingual bar
- Lingual plate
- Dental bar
- Sublingual bar
- Labial bar
When is the only time a labial bar would be used?
- When lower anterior teeth are lingually inclined therefore preventing the use of a lingual bar
Why are mucosa borne lower dentures not generally recommended?
- Due to the lack of mucosal support (coverage)
There is less space in the lower arch so the default choice of connector is a bar. Hoe far below the gingival margin on the lingual side does the bar need to be positioned?
- At least 3mm
What is the default type of connector for the mandibular denture?
- A lingual bar
The default type of mandibular connector is a lingual bar. Since the height of the bar is 4mm how much space is required?
- Approx. 8mm (3mm from gingival margin, 4mm height of bar and 1mm clearance to the functional floor)
What is another name for an anterior and posterior bar?
- A ‘ring’
IS the ring design connector a rigid design?
- Yes, exceptionally rigid
- Will withstand a drop very easily
What 3 theoretical principles does the anterior and posterior ‘ring’ bar adhere to for a connector?
- Little coverage of gingival tissue
- A rigid connector
- Wide relief of gingival margins to prevent food impaction
What are the downsides of using an anterior and posterior bar connector? (3 points)
- The posterior bar offers less support to the free end saddle across the hard palate (narrow coverage)
- There are a number of edges that some patients may find uncomfortable
- Greater cross-sectional thickness
What are the advantages of a plate design? (5 points)
- A rigid connector
- Wide relief of gingival margins to prevent food impaction
- Support across the palate for a free end saddle
- Less edges that the patient might find uncomfortable
- Thinner cross-section
What is a disadvantage of using a plate as a connector?
- The mucosal tissue is covered - no natural sensation
The extension of a major connector can assist stability. How can it do this?
- By resisting functional forces in a horizontal direction
- They can also provide indirect retention
How can major connectors provide indirect retention?
- By resisting movement about the axis of rotation
What is beading (food line)?
- To stop the ingress of food underneath the plate
- Also gives a degree of rigidity to the plate
Beading has to be placed all the way round the border of the cast. How far away should it stop from the gingival margin?
- 3mm
What is a ‘closed’ saddle design?
- More contact
- Greater retention
- Guide planes,
- Possible increased irritation to gingival tissues
What is an ‘open’ saddle design?
e.g. an every design has no gingival coverage, greater clearance and possible reduced irritation to gingival tissues
What is used to retain the acrylic flange and teeth to a metal denture with a saddle?
- Mechanical retention
What is required on an edentulous area of a denture with a saddle to check the fit and ensure the denture does not rotate?
- A stop
When vertical space is restricted the metal plate of a denture with a saddle area can contact the mucosa. However, this design cannot be relined precisely. Why is this?
- Due to the placement of internal finishing lines (particularly in the upper denture)
What are the general dimensions for rests?
- Thickness = 0.5mm minimum
- 1mm at junction with minor connector
What are the general dimensions for lingual bars?
- Height = 4mm
- Thickness = 2mm
- Oval or half pear shape
What are the general dimensions for Sub-lingual bars?
- Thickness = 4mm (‘kidney shaped’)
What are the general dimensions for maxillary connectors?
- 5mm clearance from the gingival margin
- Bead (pin dam/food line) 0.5mm deep to 1mm wide
- Bars: width 6mm, thickness 1.5mm
- Plates: thickness o.4mm minimum
What are the general dimensions for minor connectors?
- Width = 2mm
- Thickness = 1.5mm
What are the general dimensions for cast clasps?
- Length 15mm to engage 0.25mm
