RPD CLINICAL - MOUTH PREPARATION & MASTER IMPRESSION Flashcards
what are the 4 stages to a restorative treatment plan
immediate
hygienic (prepatory)
correct
maintenance
what is the immediate stage
the patient presents with an issue on the day and treatment is done to solve the problem on the day as well, after this is done we start the planning
what is the hygienic phase
this is where we establish periodontal health, diet, creating good habits, smoking cessation etc
it is when we assess motivation
which stage does RPD fit in
corrective
what are the stages in RPD construction
primary impressions primary jaw registration (if required) mounted, surveyed study casts design denture tooth prep and master impressions jaw reg trial delivery review
what does the primary impressions allow us to do
o This helps us in the diagnosis
o It allows us to see if there is a lack of space
o It allows us to look at the whole mouth using the cast from the primary impression to help plan the treatment plan and partial denture design
when is a primary jaw registration not required
o If enough teeth are present that the occlusion is obvious then a primary jaw registration is not required
when is a jaw registration required
when casts can’t be hand articulated
need to ask the lab to make primary record blocks which you can pop in the patient and record how the teeth meet and at what height in the patient and then you can mount it onto the articulator
what does surveying the study casts allow
allows us to determine undercuts/change the path of insertion
allows you to see where you can prep
what does the trial consist of
trial of the framework
trial of the teeth
what does mouth preparation consist of
- Initial prosthetic treatment
- Surgery
- Periodontal treatment
- Orthodontic treatment
- Fixed prosthodontic treatment and endodontics
- Tooth preparation
what does the initial prosthetic treatment involve
Initial prosthetic treatment may involve modification of an existing denture or provision of an interim prosthesis as a preparation for the definitive course of treatment.
what does the initial prosthetic treatment consist of
repairs and additions
temporary relines
occlusal adjustment
treatment of denture stomatitis
what does repairs and additions consist of
o Replacing clasps/rests
o Replacing detached teeth
o Connectors to hold together fractured dentures
o Addition/extension of flanges
what do temporary relines consist of
The acrylic base of an RPD may be relined temporarily where loss of fit has resulted in instability or mucosal injury
how is the temporary relining carried out
in the mouth using either soft or hard materials
what is done to the temporary relining when there is mucosal inflammation present
the cushioning effect of the short-term soft materials (tissue conditioners) is an advantage in that it distributes the load more evenly and thus promotes healing.
what should be taken into account when using hard reline materials for temporary relining
If a hard reline material is being used it is important to appreciate that it could flow into undercut areas around the teeth and that consequently the timing of removal of the denture from the mouth is critical. Failure to remove the denture before curing is complete will result in the denture being locked into place.
why should those with short term soft tissue materials for their temporary reline be given specific instructions
how to clean the lining as some of the things commonly used to clean it result in rapid deterioration of the lining will occur
why is occlusal adjustment carried out
occlusal deterioration
why does occlusal detororiation occurs
o The most common occlusal deterioration in dentures that have been worn for many years is loss of occlusal contact resulting from a combination of occlusal wear and sinking of the denture following alveolar resorption
why is correction of occlusion desirable before constructing the replacement dentures
as adaptive mandibular posture and mucosal inflammation resulting from this deterioration are likely to interfere with successful treatment
what is denture stomatitis
o Denture stomatitis is a diffuse inflammation of denture-bearing mucosa often of multiple aetiology
what are the most common causes of denture stomatitis
Overgrowth of the fungus candidia albicans encouraged by poor denture hygiene and mechanical trauma from the denture
Systemic conditions such as diabetes, deficiencies in iron, vitamin B12, folic acid and drug therapy, including broad-spectrum antibiotics, steroids and cytotoxic agents may predispose to denture stomatitis
when should treatment of denture stomatitis occur
should be carried out before working impressions are obtained because of associated mucosal swelling
what initiates the inflammation in denture stomatitis
o Toxins produced by the candida cells left on the denture surface by deficient hygiene measures, together with trauma from the denture, initiate an inflammatory reaction.
what does thinning of the mucosa result in in denture stomatitis
Thinning of the mucosa results in increased permeability and escape of inflammatory exudate. The exudate, together with desquamated mucosal cells, forms a favourable nutrient medium, which promotes the growth of candida albicans.
what is the impact of a high sucrose diet on the exudate in denture stomatitis
this exudate, and the sucrose rich diet, which may result from the dietary selection sometimes associated with the wearing of dentures, may contribute to the condition by increasing the adhesiveness of the candida cells, and thus encouraging the formation of denture plaque
what happens as candida proliferates
As candida proliferation occurs, the rate of production of these potent toxins by the micro-organisms increases. The passage of these toxins into the tissues is facilitated by the thinning and increased permeability of the mucosa.
why do anti candida antibodies not reach the candida cells
Anti candida antibody is secreted in parotid saliva but the denture base may restrict access of antibody to the candida cells
how should the patient be advised to clean their denture
use a small headed medium multi-tufted toothbrush which gives good access to all parts of the denture and good adaptability to the surface
what should the cleaning agent be for acrylic resin
low abrasiveness
if trauma appears to be a cause of the denture stomatitis what should be done
appropriate adjustments such as occlusal correction and temporary relinings should be made to the denture.
when is surgery necessary prior to RPD construction
to remove repainted roots or unerupted teeth
eliminate any pathology
improve contours of edentulous areas
how do you improve the contours of edentulous areas
by reducing bony prominences and hyperplastic soft tissue
what is a good screening tool to identify any retained roots
OPT
periodicals
what can prolonged wearing of an unsatisfactory denture cause
soft tissue hyperplasia
this tissue must be removed before a new denture is constructed
what should be done prior to RPD construction prior to prosthetic treatment
It is important to establish a condition of health in the periodontal tissues prior to prosthetic treatment and to ensure that patients receive detailed instruction in oral hygiene procedures so that accumulation of plaque around abutment teeth and RPD components is kept to a minimum
what needs to be done in periodontal treatment
- Establish health in periodontal tissues
- Assess patient motivation
- Detailed instruction in oral hygiene procedures
- Scaling and root planning
- Periodontal surgery
when is orthodontics of benefit
when RPDs are required and the space available for the prosthesis has become restricted due to movement of the adjacent teeth.
what is the use of orthodontic treatment for
- Optimize space
- Optimize abutment alignment
- Cleft patients, hypodontia patients, periodontal patients – you can move their teeth very quickly and it can tip teeth enough that it is good for aesthetics and the denture
what does fixed prosthodontics treatment/endodontics do
- Should follow denture design and precede denture construction
- Establishes clinical integrity of teeth before master impressions are recorded
- Facilitates provision of crowns (and/or teeth) with guide planes, rest seats etc
what is tooth preparation undertaken for
- Provide rest seats
- Establish guide surfaces
- Modify unfavorable survey lines
- Create retentive areas
what should tooth prep be planned on
articulated study casts after they have been surveyed and a denture design produced
what is shaping of enamel surfaces usually undertaken with
a rotary diamond instrument of appropriate size and shape
why is subsequent application of topical fluoridee varnish done for the modified enamel surfaces
to reduce the chance of carious attack
what are rest seats prepared for
- Produce favourable tooth surface for support
- Prevent interference with the occlusion
- Reduce the prominence of a rest
where is enamel thinner
inter proximally
what does having a well designed rest seat allow
positioning allows the forces to be transferred down the long axis of the tooth
why is there often a reduction in the height of the marginal ridge when preparing rest seats on the posterior teeth
in order to ensure an adequate bulk of material linking the occlusal rest to the minor connector
what is the shape of rest seats on posterior teeth
should normally be saucer-shaped so that a certain amount of horizontal movement of the rest seat within the seat is possible
why should rest seats be saucer shaped
so that a certain amount of horizontal movement of the rest seat within the seat is possible. Dissipation of some of the energy developed by the occlusal forces acting on the denture can then occur.
how thick should the rest seat be
rest seat should be 1mm thick for adequate strength.
if there is no space occlusally for a clasp toe extend buccally from an occlusal rest what is done
the preparation must be extended as a channel on to the buccal surface
why are rest seats easier on maxillary teeth
On maxillary anterior teeth, particularly canines the cingulum is often well enough developed so that modest preparation to accentuate its form creates a rest seat without penetration of enamel
what should be used to create the rest seat in the anterior tooth
A cylindrical diamond stone with a rounded tip should be used to prepare the rest seat. A spherical instrument tends to create unwanted undercuts
why is it difficult to make cingulum rest seats in mandibular anterior teeth
too vertical and the cingulum too poorly developed to allow preparation of a cingulum rest seat without penetration of the enamel.
what is usually used instead of cingulum rest seats on mandibular anterior teeth
incisal rests
how are incisal rests prepared
Incisal rest seats can be prepared using a tapered cylindrical diamond. If incisal rests are made in gold they tend to show less
what are more aesthetic options instead of incisal rests
Alternative more aesthetic options are to produce a rest seat in composite applied to the cingulum area of the tooth, or to bond a cast metal cingulum rest seat to the tooth
what are guide planes
Guide planes are two or more parallel axial surfaces on abutment teeth which limit the path of insertion of a denture
what are the benefits of guide planes
increased stability
reciprocation
prevention of clasp deformation
improved appearance
how do guide planes provide increased stability
Achieved by the guide surfaces resisting displacement of the denture in directions other than along the planned path of displacement
how do guide planes provide reciprocation
o Allows a reciprocating component to maintain continuous contact with a tooth as the denture is displaced occlusally. The retentive arm of the clasp is thus forced to flex as it moves up the tooth. It is this elastic deformation of the clasp that creates the retentive force
how do guide planes prevent clasp deformation
o Guide surfaces ensure that the patient removes the denture along a planned path meaning the clasps are therefore flexed to the extent for which they were designed
o Without guide surfaces the patient may tilt or rotate the denture on removal, causing the clasps to flex beyond their proportional limit
how do guide planes improve appearance
o Guide surfaces on an anterior abutment tooth permits an intimate contact between saddle and tooth which allows one to blend with the other, creating a convincing natural appearance
what are the dimensions of the guide surface
surface should extend vertically 3mm but be kept as far from the gingival margin as possible
how much enamel should be removed when making guide planes
no more than 0.5mm of enamel should be removed
when is modification done
If there is unfavourable survey lines for example a high survey line can result in deformation of the clasp because, on insertion, the clasp is prevented from moving down the tooth by contact with the occlusal surface. Can also lead to occlusal interference and become annoying for the patient
how can retentive areas be created (modification)
by addition of acid etched composite
why do you need a broad area of attachment when adding acid etch composite
Need a broad area of attachment of the restoration to the enamel as this will reduce the chance of the restoration being displaced and will provide a contour more suitable for clasping.
which composites should be used for modification
ultrafine or hybrid composites as other ones can be abraded by the clasp arm resulting in weakening of the clasp and loss of retention.
what happens in the clinical part of the master impression stage
- Obtain an accurate impression of the denture bearing area
- Use individual trays
- Use an appropriate impression material
what happens in the lab part of the master impression stage
- Produce casts
- Produce casting (if cobalt chrome base) – cobalt chrome needs an improved cast so they have 2 casts, one being of 100% dental stone and one of improved stone so it does not chip or damage.
- Produce record blocks
- Produce trial denture
- Produce finished denture
what are individual trays made of
Individual trays are made on primary casts from heat cured or light cured acrylic.
how are individual trays made
The tray material is accurately moulded over a wax spacer 3mm in thickness. The borders are trimmed until they are smooth and located uniformly 2mm short of the depth of the sulci. This will provide sufficient support for the impression material while allowing unrestricted movement of the adjacent tissues during border moulding.
what do individual trays allow
They enable an accurate impression to be made of the functional depth and width of the sulci in those areas that will be related to the denture border and to components such as gingivally approaching clasps, connecting bars and plates
how should the individual tray be constructed
so that it is uniformly spaced from the teeth and adjacent tissues. This will provide for the layer of impression material of uniform and sufficient thickness necessary for optimum elastic recovery on removal from the mouth.
how are the individual trays often adjusted
by green stick tracing compound (thermal plastic material) which is heated on the bunson burner and made to flow and often used in the distal aspect in the upper and the lingual aspect on the lower so that material flows under the tongue.
what are the impression materials
- Alginate (alginate is not dimensionally stable for chrome – the master cast won’t be the same dimensions as the patients mouth so the chrome wont fit)
- Polyvinylsiloxane e.g extrude (medium body)
- Polyether e.g pentamix
what is the checklist for whether the impression is good enough or not
- Rounded borders that are correctly supported by the tray
- Minimum airblows and should be absent from any areas that are contacting the metal framework
- Ideally no portion of the tray (except for stops) should show through the tray
- You want to see the anatomy
what anatomy do you want to se
o Nice sulcus form
o Rugae on the palate
o All teeth there
o Frenal attachment
