Major and Minor Connectors Flashcards
What is a major connector?
Rigid structure that joins the components on one side of the arch with those on the opposite side.
All other RPD components are either directly or indirectly attached to it.
What is the function of the major connected in an RPD?
Union of RPD components
Distribution of applied force throughout the arch to selected teeth and tissues
Minimization of torque to individual teeth
Control prosthesis movement (Cross-arch stability)
Assist indirect retention
Why should a major connector be rigid?
A flexible major connector would cause damage to hard and soft tissues.
It would allow forces to be concentrated on individual teeth and segments of residual ridges resulting in tooth mobility and loss, bone resorption leading to decreased support for associated denture bases.
Why should a major connector be in a favourable location?
To avoid impingement of gingival tissues (gingival margin)
Avoid tori and soft tissue prominences
Relief beneath major connector in areas of possible interferences
To be free of movable tissue
What are the important features of a major connector?
Rigidity
Favourable location
Rounded angles
Borders of major connector far from the gingival margin
Maintain the natural contour of subadjacent structures
How far should the major connector be from the gingival margin?
Mandible = 3 - 4 mm
Maxilla = 5 - 6 mm
What are the features of good major connectors?
Intimate contact of major connector and palatal mucosa improve retention and stability.
Lower the periodontal support the greater the palatal coverage.
The wider the major connector the thinner it can be the narrower it is the thicker it should be.
What are the types of majjor connectors?
Single palatal strap
Antierior-posterior strap or palatal plate
U-shaped palatal corridor
Broad palatal strap or palatal plate
Single palatal bar
Anterior-posterior palatal bar
When is a single palatal strap used?
Class III +/- mod (no anterior mod)
What are the design features of the single palatal strap?
Thin for tongue comfort but wide (>=8mm) enough for rigidity
Anterior border should follow the valleys but avoid cutting across the rugae
Anterior and posterior borders cross the suture line at right angles
When is an anterior-posterior palatal strap used?
Class II, III with anterior mod, IV
What are the design features of an anterior-posterior palatal strap?
Flat and at least 8mm wide
Posterior strap should be anterior to the hard/soft palate limit
When should the anterior-posterior palatal strap be avoided?
Inoperable torus extending to soft palate
When is a U-shaped palatal connector used?
Inoperable large palatal torus
Common with class IV
Significant gag reflex
What are the problems with the U-shaped palatal connector design?
Poorest design for rigidity
Bulk is often required where tongue space is needed (the most freedom is required in the rugae zone)
When is palatal plate or gull palatal coverage used?
Few remaining teeth such as only the anterior arrangement
Teeth with poor prognosis
Long, flat residual ridges
What are the design features of a single palatal bar?
Narrow
Cross-section is a half-oval shape
< 8mm in width
Class III with small edentulous area
What are the single palatal bar disadvantages?
Bulky - Discomfort, not to be placed anterior to the 2nd PM
Low vertical support
Where is the single palatal bar placed?
Anterior: located in the area of palatal rugae
Median: Behind palatal rugae (ideal)
Posterior: Placed in the limit hard-soft palate
What is an anterior-posterior palatal bar?
Combination of anterior and posterior bars. Anterior bar is more flat.
Has 2 longitudinal elements connecting the anterior bar to the posterior bar.
Replaces many teeth.
Why are anterior-posterior palatal bars used? What makes them not a good idea to use?
Used when torus is present. They are good at minimizing soft tissue coverage and to provide rigidity.
Not very comfortable so avoid using.
What maxillary major connector should be used for a mouth with weak periodontal support of remaining teeth?
More of the palate should be covered: Palatal strap/complete palate indicated.
If remaining teeth have adequate periodontal support which maxillary major connector should be used?
Palatal strap
Anteroposterior palatal bar
For long span distal extension where rigidity critical what should be used as a maxillary major connector?
Anteroposterior strap
Complete palate
Which maxillary major connector should be used for anterior teeth replacement?
Anteroposterior palatal strap
Horseshoe
Complete palate
Which maxillary major connector is used if the torus is present?
Anteroposterior palatal strap
Anteroposterior palatal bar
Horseshoe
Why are palatal bars and horseshoe MMCs not used often?
Palatal bar rarely indicated due to less rigidity
Horseshoe due to reduced rigidity
What are bead lines?
Lines at the borders of maxillary major connectors present to prevent collection of food particles under the major connector.
How do bead lines work?
They displace adjacent soft tissues to produce a mechanical seal.
Which forms of mandibular RPDs require Major connector relief and which don’t?
Kennedy class III - teeth supported RPD - No relief or small relief needed.
Kennedy class I, II, and IV - Moderate relief (around 1.5mm)
No bead lines required
What are the requirements of a mandibular major connector?
Not invade floor of the mouth, lingual frenulum, and mandibular tori area.
No bead lines required
What are the types of mandibular major connectors?
Lingual bar
Lingual plate
Sublingual bar
Cingulum bar
Double lingual bar
Sublingual bar
What are the design features of a lingual bar?
Half-pear shape cross section
Superior border tapered towards the gingival tissues superiorly
Inferior border is the broadest portion
Need at least 8mm from gingival margin to the floor of the mouth. (remember minimum height of 5mm and 3mm of gingival margin)
What are the design features of a lingual plate?
Thin metal sheet that adapts intimately to the cingulum
When is a lingual plate indicated?
Where the floor of the mouth is shallow or there is an inoperable torus (no space for lingual bar)
High frenum attachment.
What are the advantages and disadvantages of a lingual plate?
Advantages:
Good indirect retention
Stabilize teeth with guarded prognosis
Disadvantages:
May irritate underlying soft tissues
Caries when patient has poor oral hygiene
When is a cingulum bar used?
Only used if there is long enough clinical crowns and alternatives are not possible.
What are contraindications for a cingulum bar?
Retroclined anterior teeth
Wide diastemas
What are the features of a lingual bar?
Lingual bar with a secondary bar above the cingulum
Secondary bar acts as an indirect retainer
What are the advantages of a double lingual bar?
Expose most of the lingual surface of the teeth and the interproximal soft tissue
Natural stimulation of gingival margins
What are the disadvantages of a double lingual bar?
Tendency to trap food debris (marked crowding leads to inaccurate adaptation)
Irritation of the tongue (multiple borders)
What are the design features of a sublingual bar?
The sublingual bar is essentially a lingual bar by design but it is placed more posterior and inferior.
Lying over and parallel to the anterior floor of the mouth
Shallow floor of mouth or lingual undercuts
Low frenulum attachment
What are the fucntions of minor connectors?
Join remaining components of RPD to the major connector (Clasp assemblies, indirect retainers, etc)
Distribute applied forces to the supporting teeth and oral tissues, help reciprocation
Join denture base to major connector
What are the primary attributes of a minor connector?
Rigid
Form right angle with major connector
Preferably located in interdental space
Wider linguobuccal direction, narrow mesiodistal
What are the features of minor connectors that connect the denture bases to the major connector?
Gridwork
Rigid
No interference with artificial teeth
Provide adequate support and retention for resin base: Maxilla covers tuberosity, mandible 2/3rds of edentulous ridge.
What is the cast stop?
Used in Kennedy class I and II free end saddles.
Small area of minor connector contacting the master cast.
What is the function of the cast stop?
Prevents displacement or deformation of the metal framework during packing and processing of acrylic resin
What are internal and external finishing lines?
Resin-metal interfaces are referred to as finish lines.
They function to help lock the acrylic to the major connector.
Make the transition from the denture base and the framework
What is the function of the saddles?
Support artificial teeth and replace alveolar tissues
Receive and distribute occlusal forces to supporting structures (Kennedy class I and II)
Aid retention: Adhesion and cohesion.
Stimulate underlying tissues of the residual ridge to prevent alveolar ridge atrophy.
Prevent tooth migration
Add cosmetic effect
What are the types of denture bases?
Metallic (eg CoCr)
Acryllic
What are the advantages and disadvantages of metallic denture bases?
Adv:
Thermal stimulus
Resistance
Easy to clean
Less volume
Disadv:
Difficult to adjust
Not able to reline
Cost
Weight
What are the advantages and disadvantages of acryllic?
Adv:
Lighter
Aesthetic
Good adaptation
Potential for future relining
Disadv:
Distortion
No thermal stimulus
Hygiene
