Mouth Preparation and Master Impressions

Question 1

4 phases of restorative treatment plan

Answer 1

immediate

hygienic (preparatory)

corrective (reconstructive)

maintenance

Question 2

immediate phase in restorative treatment plan

Answer 2

Present with an issue and do something on the day to try and deal with complaint

e.g. Excavate pulp, ease denture, extract

Question 3

hygienic (preparatory) phase in restorative treatment plan

Answer 3

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

Question 4

corrective (restorative) phase in restorative treatment plan

Answer 4

Provision of RPDs, crown, bridge, implant

• Type of material and design thought of at beginning, may need prep
• Need to prep so retained well

Question 5

maintenance phase in restorative treatment plan

Answer 5

Habits will wear out as time passes

Seen regularly to avoid disease progression

Question 6

many clinical stages of RPD construction

Answer 6

Primary impressions

Primary jaw registration (if required)

Mounted, surveyed study casts

Design denture

Tooth preparation and master impressions

Jaw registration

Trial

Delivery

Review

Question 7

primary impressions

Answer 7

Help assess teeth and how everything looks at beginning to help plan treatment

Question 8

primary jaw registration

Answer 8

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

Question 9

survey primary casts

Answer 9

Determine where useful undercuts are for clasps, path of insertion

Question 10

deign denture

Answer 10

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

Question 11

jaw registration

Answer 11

More accurate as know where denture will be seated

Choose size, colour and shape of teeth

Question 12

trial

Answer 12

Trial CoCr framework
have teeth trial – in wax
Final check

Question 13

6 different types of mouth preparation for RPD

Answer 13

Initial prosthetic treatment

Surgery

Periodontal treatment

Orthodontic treatment

Fixed prosthodontic treatment and endodontics

Tooth preparation

Question 14

4 types of initial prosthetic treament

Answer 14

• repairs and additions (give a new temporary denture)
• lining
• occlusal adjustment
• treatment of denture stomatitis

Question 15

why would repairs and additions (give a new temporary denture) be effective as a mouth preparation

Answer 15

To help reduce inflammation

Less microbial load
- Soak in milten if all acrylic or cholorhexidine

Question 16

positives of lining be effective as a mouth preparation

Answer 16

Temporary
- For couple weeks
- Will become contaminated and loose elasticity
Need to sort issue

Question 17

why do occlusal adjustment as a mouth preparation

Answer 17

Better fit to help reduce trauma issue

Establish occlusal contact at height – help patient correct occlusion so less trauma

Question 18

how would you treat denture stomatitis if underlying haematinic problem

Answer 18

Antimicrobials

Question 19

reasons for pre-prosthetic surgery in mouth preparation

Answer 19

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

Question 20

reasons for periodontal treatment in mouth preparation for RPDs

Answer 20

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

Question 21

reasons for orthodontic treatment for mouth preparation for RPDs

Answer 21

To optimise space

To optimise abutment alignment

Cleft patients, hypodontia patients and periodontal patients
- Can move teeth quickly when perio stabilise

Question 22

why is fixed prosothodontic and endodontic work carried out as mouth preparation for RPD?

Answer 22

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

Question 23

why is it important to know denture design before crown placement

Answer 23

to avoid removal of crown later

so that the denture will fit snuggly and well

Question 24

3 types of tooth preparation

Answer 24

Provide rest seats

Establish guide surfaces

Modify unfavourable survey lines

Question 25

rotary diamond instruments used to

Answer 25

shape enamel surfaces

Question 26

Special burs, stones and abrasive-impregnated rubber wheels and points used to

Answer 26

smooth and polish the resultant roughened enamel surface.

Question 27

3 reasons for rest seat preparation

Answer 27

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

Question 28

how to engage clasp with tooth if no undercut present

Answer 28

add material to the tooth

- create a guide plane

Question 29

where should the RPD load be directed

Answer 29

down the long axis of the tooth

Question 30

rest seats of maxillary anteriors

Answer 30

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

Question 31

rest seats on mandibular anteriors

Answer 31

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

Question 32

rest seats in posterior teeth

Answer 32

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

Question 33

how far do you need the minor connector from gingival margin

Answer 33

3mm

in order to be cleansable
- maintain gingival health and food less likely to get stuck

Question 34

guide planes

Answer 34

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

Question 35

4 things guide planes provide

Answer 35

Increased stability
Reciprocation
Prevention of clasp deformation
Improved appearance

Question 36

guide surface should extend….

Answer 36

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)

Question 37

what happens if the clasp is placed to close to occlusal surface

Answer 37

Occlusal interference
- Patient annoyance
Deformation of clasp

due to unfavourable survey lines

Question 38

how to create retentive areas

Answer 38

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

Question 39

clinical requirements for taking master impression

Answer 39

Obtain an accurate impression of the denture-bearing area

Use individual special trays

Use an appropriate impression material

Question 40

laboratory requirements of taking master impressions

Answer 40

Produce casts

Produce casting (if cobalt chrome base, 2 needed, one 100% and one imporved)

Produce record blocks

Produce trial denture

Produce finished denture

Question 41

special/individual trays

Answer 41

Made on primary casts from heat-cured or light cured acrylic

• Try in
• Adjust periphery if required with green stick

Question 42

what type of material if green stick

Answer 42

thermo plastic

Question 43

how to use green stick

Answer 43

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

Question 44

where do you use green stick in individual/special trays

Answer 44

Use in distal aspect of upper tray
- Stop incisally

May have in edge of lower lingual to capture surface form

Question 45

3 types of impression material

Answer 45

alginate

Polyvinylsiloxane e.g. Extrude (medium body)

Polyether e.g. Pentamix

Plus correct adhesive (different for each material)

Question 46

properties of alginate

Answer 46

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

Question 47

what may you do if long time (e.g. summer) between taking master impressions and jaw registration?

Answer 47

delay stages as master may not fit and take when back as patients teeth may drift/move

Question 48

what should you put around mouth/on beard to stop impression material sticking?

Answer 48

vaseline

Question 49

how to take upper impressions

Answer 49

behind patient

- Use handle in centre of mouth to align

Question 50

how to take lower impressions

Answer 50

in front of patient

- Use hand on chin to support

Question 51

3 things to check impression for after taking it

Answer 51

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)