Mouth Preparation and Master Impressions Flashcards
4 phases of restorative treatment plan
immediate
hygienic (preparatory)
corrective (reconstructive)
maintenance
immediate phase in restorative treatment plan
Present with an issue and do something on the day to try and deal with complaint
e.g. Excavate pulp, ease denture, extract
hygienic (preparatory) phase in restorative treatment plan
Establish health (periodontal health, diet, alcohol, smoking
Establish good habits early on as less likely to fail later on
Can asses motivation and tailor treatment plan accordingly
corrective (restorative) phase in restorative treatment plan
Provision of RPDs, crown, bridge, implant
- Type of material and design thought of at beginning, may need prep
- Need to prep so retained well
maintenance phase in restorative treatment plan
Habits will wear out as time passes
Seen regularly to avoid disease progression
many clinical stages of RPD construction
Primary impressions
Primary jaw registration (if required)
Mounted, surveyed study casts
Design denture
Tooth preparation and master impressions
Jaw registration
Trial
Delivery
Review
primary impressions
Help assess teeth and how everything looks at beginning to help plan treatment
primary jaw registration
Record blocks on base plate (light cure or shellac)
Occlude casts without help (natural) no need for primary jaw registration
Adjust to occlude with upper natural teeth – shape and height
- Mount on articulator, allows to assess inter-occlusion space needed for denture so occlude the same (make contact with centric stops not CoCr)
- Do not cause or detriment to patient
survey primary casts
Determine where useful undercuts are for clasps, path of insertion
deign denture
Know where to do adjustments for seats
Minimal preparation with slow speed so not effect functioning without denture
Simple – few rests, consider gingival health to not cause iatrogenic damage
jaw registration
More accurate as know where denture will be seated
Choose size, colour and shape of teeth
trial
Trial CoCr framework
have teeth trial – in wax
Final check
6 different types of mouth preparation for RPD
Initial prosthetic treatment
Surgery
Periodontal treatment
Orthodontic treatment
Fixed prosthodontic treatment and endodontics
Tooth preparation
4 types of initial prosthetic treament
- repairs and additions (give a new temporary denture)
- lining
- occlusal adjustment
- treatment of denture stomatitis
why would repairs and additions (give a new temporary denture) be effective as a mouth preparation
To help reduce inflammation
Less microbial load
- Soak in milten if all acrylic or cholorhexidine
positives of lining be effective as a mouth preparation
Temporary
- For couple weeks
- Will become contaminated and loose elasticity
Need to sort issue
why do occlusal adjustment as a mouth preparation
Better fit to help reduce trauma issue
Establish occlusal contact at height – help patient correct occlusion so less trauma
how would you treat denture stomatitis if underlying haematinic problem
Antimicrobials
reasons for pre-prosthetic surgery in mouth preparation
Removed retained roots/unerupted teeth
- Don’t want to flare up once delivered as will mean no longer functioning
Remove pathology
Improve contours of edentulous areas – by reducing Bony tuberosities/prominences and hyperplastic soft tissue
- Not realistic to remove but sore and traumatise by RPDs
- Small tuberosities and fraenal attachments can be reduced slightly
- Try to catch early so that minimal tooth loss
Eliminate prominent fraenal attachments
reasons for periodontal treatment in mouth preparation for RPDs
Establish health in periodontal tissues
Assess dental motivation – plaque control
- Poor chose removable so can clean at night better
Detailed instruction in oral hygiene procedures
Scaling and tooth planing
- Scaling can be sore without local (uncomfortable can be hard for you too as they will not sit still)
Periodontal surgery
- Large deep pockets (6mm) scaling may not help – refer for periodontal surgery to try and gain some reattachment
reasons for orthodontic treatment for mouth preparation for RPDs
To optimise space
To optimise abutment alignment
Cleft patients, hypodontia patients and periodontal patients
- Can move teeth quickly when perio stabilise
why is fixed prosothodontic and endodontic work carried out as mouth preparation for RPD?
Should follow denture design ad precede denture construction
Establishes clinical integrity of teeth before master impressions recorded
Facilitates provision of crowns (and/or teeth) with guide planes, rest seats etc.
- Crowns with guide planes and rest seats more stable as load spread
Hyperaemic pulp – deal with at beginning of treatment plan
- Others can be done on non-urgent basis later but before placement
why is it important to know denture design before crown placement
to avoid removal of crown later
so that the denture will fit snuggly and well
3 types of tooth preparation
Provide rest seats
Establish guide surfaces
Modify unfavourable survey lines
rotary diamond instruments used to
shape enamel surfaces
Special burs, stones and abrasive-impregnated rubber wheels and points used to
smooth and polish the resultant roughened enamel surface.
3 reasons for rest seat preparation
Produce favourable tooth surface for support
Prevent interference with occlusion
- Avoid interference of denture components with occlusal balance that was present before started treatment
Reduce prominence of the rest
- Prepare teeth minimally for master impression features needed for denture can be seen for master cast (denture made on)
- Shallow, saucer shape depression
- Want rest to flush to existing tooth surface so patient not aware
how to engage clasp with tooth if no undercut present
add material to the tooth
- create a guide plane
where should the RPD load be directed
down the long axis of the tooth
rest seats of maxillary anteriors
well-developed cingulum allows prep to stay within enamel.
- Use a cylindrical diamond stone with a rounded tip or green stone for anterior maxillary teeth
rest seats on mandibular anteriors
Lower is vertical/flat and cingulum is too poorly developed so harder to prepare to avoid penetrating the enamel
- can do incisal rests but not popular as metal seen
- Can get incisal rests gold plated in lab less obvious than chrome ones
More wear – rest on incisal tip, lip of labial enamel means not seen potentially
rest seats in posterior teeth
Reduce marginal ridge
Saucer shaped depression
- Allows some horizontal movement and dissipation of occlusal forces
- Use cast to visualise amount of preparation needed for rest
Need 1mm depth to have integrity and not too flexible
Clasp arm to come interproximal (if no space occlusally to extend buccally from occlusal rest) need grove/channel on buccal surface to not prop open occlusion
Need to be flush to occlusal surface
how far do you need the minor connector from gingival margin
3mm
in order to be cleansable
- maintain gingival health and food less likely to get stuck
guide planes
Two or more parallel axial surfaces on abutment teeth which limit path of insertion of a denture
- May occur naturally but often need to be prepared
- One path of insertion (easier insertion/removal)
Acrylic can get locked on undercut s if don’t prepare guide plane
Minimal preparation
4 things guide planes provide
Increased stability
Reciprocation
Prevention of clasp deformation
Improved appearance
guide surface should extend….
3mm vertically but be kept as far from the gingival margin as possible
Small amount removed – thinner enamel at side of tooth (not more than 0.5mm enamel should be removed)
what happens if the clasp is placed to close to occlusal surface
Occlusal interference
- Patient annoyance
Deformation of clasp
due to unfavourable survey lines
how to create retentive areas
Can be created by addition of acid-etch composite
Try to use anatomy to guide adding and removal
- Blend in a broad area to avoid sticking out
Use ultrafine or hybrid composites
clinical requirements for taking master impression
Obtain an accurate impression of the denture-bearing area
Use individual special trays
Use an appropriate impression material
laboratory requirements of taking master impressions
Produce casts
Produce casting (if cobalt chrome base, 2 needed, one 100% and one imporved)
Produce record blocks
Produce trial denture
Produce finished denture
special/individual trays
Made on primary casts from heat-cured or light cured acrylic
- Try in
- Adjust periphery if required with green stick
what type of material if green stick
thermo plastic
how to use green stick
Heat in Bunsen burner, flow (hold above as can spark if too low)
Temper in hot water to not be runny and burn patient but still molten so can be flowing onto tray
where do you use green stick in individual/special trays
Use in distal aspect of upper tray
- Stop incisally
May have in edge of lower lingual to capture surface form
3 types of impression material
alginate
Polyvinylsiloxane e.g. Extrude (medium body)
Polyether e.g. Pentamix
Plus correct adhesive (different for each material)
properties of alginate
not dimensionally stable
- if not poured in 1 hour master cast may not be same dimensions as patient so not ideal for chrome
Better to use more dimensionally stable material so more likely to be like patient
what may you do if long time (e.g. summer) between taking master impressions and jaw registration?
delay stages as master may not fit and take when back as patients teeth may drift/move
what should you put around mouth/on beard to stop impression material sticking?
vaseline
how to take upper impressions
behind patient
- Use handle in centre of mouth to align
how to take lower impressions
in front of patient
- Use hand on chin to support
3 things to check impression for after taking it
No large air bubbles as inaccuracy on cast
Good surface detail and sulcus form which is accurate
See rugae
then write laboratory card
(next stage is record blocks for jaw registration)
