6. RPD Design - Connectors

Question 1

Definition of major connector

Answer 1

The part of the denture that connects components on one side of the arch to components on the other side of the arch

Question 2

Guidelines of a connector (4)

Answer 2

Be rigid (no modifications)
Avoid covering gingival margins
Be comfortable, with as few edges as possible
Cover as little tissue as is consistent with rigidity

Question 3

Connector modifications (6)

Answer 3

Base distribution
Need for tissue support
Need for indirect retention
Anatomical limitations
Prognosis of the dentition
Previous denture influence

Question 4

Features of plate connectors (5)

Answer 4

A plate connector can be made thinner in cross-section and still maintain rigidity (the corrugated shape of the rugae or interproximal areas)
Plate designs are the option for mucosal supported designs
Plate designs cover gingival margins and therefore are only recommended in the maxillary arch (when no space is available for a bar)
To maintain rigidity depending on coverage and shape of the mucosa areas, the plate may require being thicker in cross-section
As a general rule, the less tooth support available will require utilising more mucosal coverage, therefore plate connectors (large area coverage) are preferred

Question 5

Cross-sectional thickness of plate connectors

Answer 5

Can be as thin as 0.5mm

Question 6

Features of bar connectors (5)

Answer 6

A bar connector has the advantage of less mucosal coverage including coverage of gingival margins
A bar must be made suitably thick on cross-section to maintain rigidity
Bar connectors are a more likely choice for tooth supported designs
The cross-sectional thickness of a lingual bar is 2mm to maintain rigidity
As less space is available in the mandibular arch, a bar connector is the default connector

Question 7

Types of maxillary connectors (9)

Answer 7

Anterior
Mid-palatal strap
Anterior/posterior bar (ring)
Horseshoe
Posterior palatal
Full coverage
Spoon
Modified spoon
Every

Question 8

Types of mandibular connectors (6)

Answer 8

Lingual bar (default connector)
Lingual plate
Dental bar
Sublingual bar
Labial bar
Lingual bar with dental bar (continuous clasp)

Question 9

Minimum space required for a lingual bar

Answer 9

8mm
4mm space for height of bar
3mm from the gingival amrgin
1mm above the raised functional depth of the floor of the mouth

Question 10

Indications for sublingual bar

Answer 10

When lack of space precludes using a lingual bar
Due to mechanical forces on the bar this requires being thicker in cross-section than the lingual bar
In addition, a functional impression to record the functional movement of the floor of the mouth is required

Question 11

Function of minor connectors

Answer 11

Join components such as rests to the major connector

Transfer functional stresses to and from abutment teeth

Question 12

Features of minor connectors (4)

Answer 12

Be rigid
Finish above the survey line
Cross the gingival margin at right angles (creates a large angle that can be easily cleaned)
Cover as little gingival marginal tissue as possible

Question 13

Minor connector modifications

Answer 13

Cover gingival margins rather than have lots of small “windows” (consider the oral health and hygiene of the patient)

Question 14

Advantages of bar connectors (4)

Answer 14

Little coverage of gingival tissue
Rigid connector
Wide relief of gingival margins to prevent food impaction

Question 15

Disadvantages of bar connectors (3)

Answer 15

Posterior bar offers less support to the free-end saddle across the hard palate (narrow coverage)
Number of edges that some patients may find uncomfortable
Greater cross-sectional thickness

Question 16

Advantages of plate connectors (5)

Answer 16

Rigid connector
Wide relief of gingival margins to prevent food impaction
Support across the hard palate for the free-end saddle
Less edges that may be uncomfortable
Thinner cross-sectional area

Question 17

Disadvantages of plate connectors

Answer 17

Mucosa tissue is covered (no natural sensation)

Question 18

How do major connectors provide indirect retention

Answer 18

By resisting movement about the axis of rotation

Question 19

Major connector design is influenced by the amount of gingival coverage; whether the design is (2)

Answer 19

Open

Closed

Question 20

Features of closed design (2)

Answer 20

More contact –> greater retention (guide planes)

Possible increased irritation to gingival tissues

Question 21

Features of open design (2)

Answer 21

Every design has no gingival coverage and greater clearance

Possible reduced irritation to gingival tissues

Question 22

Functions of mechanical retention

Answer 22

Retain the acrylic flange and teeth to the metal base
A stop is required on edentulous areas to check the fit and ensure the denture does not rotate
When vertical space is restricted, the metal plate can contact the mucosa. However, this design cannot be relined precisely due to placement of internal finishing lines (particularly in the upper denture)

Question 23

Three alternative designs for a connector for the same case (3)

Answer 23

Larger palatal coverage
Less palatal coverage
Open design with gingival margins not covered

Question 24

Distance between an upper connector from the gingival margins

Answer 24

5mm

Angle of the connector to the tooth should be 90 degrees

Question 25

Distance between a lower connector from the gingival margins

Answer 25

3mm

As there is less space available for the major connector in the mandible