RPD design - connectors Flashcards
what is a connector
- a term used to describe the rigid part of a partial denture that unites other components
- there are minor and major
what is a minor connector
- joins points of other components
what is a major connector
- provides rigidity and stableness
what does a minor connector do
- join components such as rests to a major connector
- transfer functional stresses to an abutment tooth
what should a minor connector be
- rigid
- finish above the survey line on teeth
- cross gingival margin at right angles
- keep area self cleaning
- cover as little gingival tissue as possible
why must the minor connector cross the gingival margin at right angles
- maintain gingival health
- if it had acute angles these would create little spaces called windows that can irritate the gingiva
what should you avoid in minor connectors
- mupltiple ‘Windows’
- these are food ad plaque traps
what should a major connector do
- connects components on one side of the arch to components on the other side
what should major connectors be
- rigid
- avoid covering the gingival margins
- be comfortable, as few edges as possible
- cover as little tissue as is consistent with rigidity
what modifications can be made for major connectors
- base distribution
- need for tissue support
- need for indirect retention
- anatomical limitations
- prognosis of dentition = planning on giving a denture but some of the teeth you know will not last long so design denture so that it can easily add on more teeth
- previous denture influence = patient is valuable resource on denture design = if they’re happy reproduce what they already had
what can a major connector be
either a plate or a bar
what is a plate connector like
- thinner
- covers wider area as not as thick
- option for Craddock class 2 designs
- cross sectional thickness can be as little as 0.5mm
- plate designs may cover gingival margin so are only recommended in mandibular is there is no space for a bar
- to maintain rigidity, depending on coverage and shape of mucosa areas, plate may require to be thicker in cross section
- general rule = less tooth support= more mucosa support
what are bar connectors like
- advantage of less mucosal coverage
- must be made suitably thick in cross section to maintain rigidity = bulky
- common choice for Craddock class 1
- as there is less space in mandibular arch a bar connector is default choice
what maxillary connectors can you get
- anterior palatal strap
- mid palatal strap
- anterior/posterior strap (ring)
- horseshoe
- posterior palatal strap
what different about acrylic designs compared to cobalt chrome
- design are pretty much the same
- but acrylic don’t tend to have bars = not good in cross sectional dimension, don’t have lower lingual bar in acrylic
what other type of maxillary connectors can you get in acrylic
- ‘spoon’
- modified ‘spoon’
- every
what does the ‘every’ design do
- maintains space between teeth
- doesn’t allow distal drift as has metal connector at back of last standing teeth
what mandibular connectors can you get
- lingual bar
- lingual plate
- dental bar
- sublingual bar
- labial bar
when is a lingual bar used
is the go-to design for lower dentures
what are the advantages and disadvantages of lingual plate
- advantage = thinner and gives indirect retention
- disadvantage = covers all gingival margins
what are the advantages and disadvantages of a dental bar
- lots of indirect retention
- but covers all cingulum of teeth
- dental bar is actually a continuous clasp
what are the advantages and disadvantages of a sublingual bar
- advantage = its below the tongue to patient is not as aware of it
- disadvantage = need to record function of the flow of the mouth well, as if not it will be very uncomfortable for the patient
when is a labial bar used
- used only when the lower anterior teeth are lingually inclined preventing lingual bar
- very rare
why are mucosal borne lower dentures generally not recommended
- due to lack of mucosal support
what is the default bar choice for lower arch
- lingual bar
- bar that is positioned at least 3mm below the gingival margin
- since the height of the bar is 4mm, the space required is approximately 8mm (3mm from gingival margin, 4mm height of bar, 1mm clearance to functional floor of mouth)
- need to sure you have the correct spacing the whole way around the lingual bar
what bars can you get
- anterior, mid palatal, posterior and anterior and posterior
what is good about bar designs
- contain all the theoretical principles advocated for a connect regarding
= little covering of gingival tissue
= wide relied of gingival margin to prevent food impaction
= patient uniquely to be able to distort this denture
what is not good about bar designs
- posterior bar offers less support to free-end saddle across the hard palate
- there are a number of edges that some patients may find uncomfortable = can be problematic
- greater cross sectional thickness
what kinds of plate designs can you get
- full palatal coverage, anterior, mid palatal, posterior and plates can be extended onto tooth surface to provide bracing and reciprocation
what is good about plate designs
- rigid connector = but not as rigid as bar
- wide relief for gingival margins to prevent food impaction
- support across hard palate for free end saddle
- less edges for patient to find uncomfortable
- thinner cross section = more comfortable and smoother for patient
what is not good about plate designs
- mucosal tissue is covered = no natural sensation
- need to be careful of windows = these can cause food impaction, but the alternative would cover gingival margins
what are some other functions of a major connectors
- extension of major connector can assist stability by resisting functional forces in a horizontal direction
- help with bracing and stability = especially in deep palatal vault
- can also provide indirect retention = given support by connectors to resist movement about the axis of the rotation
what is beading
- the ‘food line’
- improves strength and rigidity
- beading all the way around the border but stops 3mm from the gingival margin
- it is suggested that a bead on the impression surface of maxillary dentures is useful to facilitate an intimate contact between denture and tissue that will prevent food ingression
- offers greater degree of rigidity around plate
what does and open or closed design depend on
- are we facilitating the passing of saliva from lingual to buccal or labial to palatal
what is a closed design
- more contact
- greeter retention, guide planes
- possible increased irritation to gingival tissues
what is an open design
- an every design has no gingival coverage, greater clearance
- possible reduced irritation to gingival tissues
- if can do an open design then that is what you want to improve patients oral health
what are saddles for
- mechanical retention is used to retain acrylic flange and teeth to metal base
- a stop is required on edentulous areas to check fit and ensure denture does not rotate
- when vertical space is restricted the metal plate can contact the mucosa = however this design can not be retained precisely due to placement of internal finishing lines (particularly in upper dentures)
why must tooth position be considered
- can really affect shape of denture
- should do a tooth trial of replacement teeth before you prescribe a final denture = tooth position is established with putty register on a cast base then established on trial denture
- tooth position may affect natural occlusion
what can be done to maintain natural occlusion
- if lower incisor occludes with the cingulum of the upper anterior teeth then may be damaged in occlusion
- when occlusion is such that there is limited space between incisor teeth a metal backing can be incorporated to provide an occlusal contact, therefore preventing pressure on upper artificial teeth from debunking from denture base
- might want to protect artificial tooth from occluding against real tooth
what are the dimensions of different denture components
- rests = thickness 0.5mm, 1mm at junction with minor connector
- lingual bar = height 4mm, thickness 2mm, oval or half pear shape
- sublingual bar = thickness 4mm, kidney shaped
- maxillary connectors = 5mm clearance from gingival margin, bead 0.5mm deep to 1mm wide, bars 6mm width and 1.5mm thickness, plate 0.4 thickness
- minor connectors = width 2mm, thickness 1.5mm
- cast clasp = length 15mm to engage 0.25mm
