Prosthodontics Flashcards
What does RPI stand for?
R- Mesial Rest
P- Proximal guide plate
I- Gingival approaching I Bar clasp
What is the mechanism of action for an RPI?
On loading- clasp and proximal plate disengage
-> Clasp moved down and forward
-> Place moves into undercut
Relieves pressure/traumatic torque
What radiographic views can be used to asses position of an unerupted tooth?
OPT and occlusal- vertical parallax
2 PA- horizontal parallax
What complications can arise when extracting unerupted premolar tooth in very resorbed denture bearing area in a patient with OP?
MRONJ- if patient on bisphosphonates
Nerve damage
Jaw fracture
Pain, bleeding, bruising, swelling, infection, dry socket
When are the aspects to consider when designing a replacement complete lower denture, with partially erupted tooth to be kept in situ?
Extension
Support and stability
Retention
Occlusion- FWS, OVD, RVD, occlusal and incisal planes
Comfort- relief around partially erupted tooth, soft lining
Appearance- tooth shape, shade, mould
Speech- ensure patient can speak
What measurements are required for a lingual bar?
8mm in total
-> 3mm below gingival margin, 4mm height of bar, 1mm clearance to functional floor of mouth
What is the method of producing a new denture of the same spec?
Replica method
How can a loose denture be adjusted?
Reline- soft and hard
Rebase
Remake
What should you check at the try-in stage?
LIMBO
ESROCAS
What is retention?
Resistance to vertical displacement
What is stability?
Resistance to lateral displacement
How are upper complete dentures retained?
Muscular
Extension into sulcus
Adhesion and cohesion
Post dam
What is biometric guidance when setting upper and lower teeth?
Aim to place teeth in pre extraction sites
Maxillary teeth placed buccally to the ridge promotes lower denture stability
Mandibular teeth placed over the ridge
-> palatal cusps of uppers occlude with fossa of lowers
-> forces are appropriately directed
-> reduces tongue restriction
What are the aetiological factors involved in Denture stomatitis?
Poor denture hygiene
Dentures worn at night
Immunocompromised patient- diabetes
Deficiency
Old dentures
How is Denture stomatitis managed?
Take denture out at night
Clean denture with a soft brush
Steep denture- Milton (3 x 30 mins per week- not chrome)
Chlorhexidine mouthwash
Use of nystatin or fluconazole
Consider making new denture
Consider deficiency/disease that may be underlying- diabetes or haematinic deficiency
How do you restore FWS in very worn dentures?
What issue is caused by complete upper denture occluding against partial lower?
Combination syndrome- results in flabby ridge
What occurs in combination syndrome?
Bone loss from the anterior part of the maxillary ridge
Hypertrophy of the tuberosities
Papillary hyperplasia in the hard palate
Extrusion of the mandibular anterior teeth
-> Bone loss under the opposing denture base
How is flabby ridge managed?
Mucostatic impression technique
Removing fibrous tissue- less denture bearing area
Implant retained denture
What is Kennedy classification 2 modification 1?
Unilateral free end saddle with additional bounded saddle
What are the steps in the system of design used in designing partial dentures?
- Saddles
- Support
- Retention
- Bracing/reciprocation
- Connectors
- Indirect retention
- Simplification
What are the advantages and disadvantages of upper horseshoe connector?
ADV
* Wider so can be thinner
* Comfort- less edges
* Doesn’t cover any more gingival margins than full coverage
DIS
* Not as rigid
What are the ADV/DIS of upper ring connectors?
ADV
* Palate free for sensation
* Strong
* Posterior bar can act as main connector allowing anterior to be thinner
DIS
* More edges
* Difficult impression
* Less support for FES
What are the ADV/DIS of lingual plates?
ADV
* Thinner
* Provides indirect retention
DIS
* Covers gingival margin and cingulum
What are the ADV/DIS of lingual bar connectors?
ADV
* Less noticeable
* Doesn’t cover margin
DIS
* week if long span
* not great for FES
* Difficult to obtain functional impression
* Requires 8mm clearance
What is support?
Resistance to occlusal directed load
What is indirect retention?
Resistance to rotational displacement
-> place components on both sides of axis of rotation
-> good for FES/long bounded saddles
What are the Cawood and Howell’s ridge classifications?
- Dentate
- Post extraction
- Broad alveolar process
- Knife edge
- Flat ridge (no alveolar process)
- Submerged/ inverted ridge (loss of basal bone)
What is a knife edge ridge?
Ridge with adequate height but not width
What are the causes of a Knife edge ridge?
Faster resorption at buccal and lingual aspects of ridge
How is a knife edge ridge managed?
Take flap and smooth edge
What is the difference between a soft-lining and tissue conditioner?
Soft linings are used for:
* Parafunctional habits
* If ridges very atrophic
* On obturators in cancer and cleft patients
-> good for sensitive naso-pharngeal tissues
Tissue conditioners are used:
* if grossly ill-fitting dentures
* for reducing inflammation in denture bearing area to aid healing
What is a functional impression?
Mucompressive impression
-> denture bearing area is loaded produce uniform reduction in volume which will be compressed during denture wearing
-> uses high viscosity material like compound
How can retention of dentures be improved?
Reline
Rebase
Implant retained
Precision attachments in tooth supported dentures
How is retention checked clinically?
Pull on anterior teeth, canines and premolars
What are the steps in making a Replica Denture?
Stage 1
1. Disinfect denture
2. Modify denture with greenstick if required (minor)
3. Replicate dentures using lab made putty and 2 large stock trays with adhesive on them (out of the mouth)
4. Remove denture from mould, clean and return to patient
5. Disinfect moulds
6. Get lab to make replica wax blocks with shellac base
Stage 2:
1. Disinfect blocks
2. Upper/lower master imps on record block (doubles as special tray)- border mould etc
3. Jaw reg with both blocks in- use jet bite
4. Choose shade and mould (technician will see previous mould)
5. Disinfect
6. Ask lab to cast impressions, mount on articulator and set upper and lower teeth in wax
Carry on as normal
Landmarks on Upper cast:
Labial Frenum
Incisive papilla
Buccal sulcus
Labial sulcus
Rugea area
Hauler notch
Tuberosity
Palatine Raphe
Palatine fovea
Landmarks on lower cast:
Retromolar pad
Mylohyoid ridge
Lingual sulcus
Buccal shelf
Buccal sulcus
Labial sulcus
Lingual frenum
What are the issues with incorrect OVD?
Instability
Clicking
Whistling
Pain
Occlusal trauma in RPD
TMD aggravation
Angular cheilitis
What medicines are used for Denture stomatitis?
Topical
* Miconazole
* Nystatin
* CHX
Systemic
* Fluconazole
* Itraconazole
Where should the post dam be?
At vibrating line (between hauler notches)- junction of hard and soft palate
What is the distal extension of lower complete denture?
2/3 along the retromolar pad
Why is the buccal shelf used for support?
Non-resorbable
What anatomical features helps set incisors?
1cm anterior to incisive papilla
Parallel to inter-pupillary line
Using philtre as midline
Have 1-2mm incisal edge showing at rest
What 4 things make up shade?
Value
Chroma
Hue
Translucency
What are the advantages of immediate dentures?
Maintains aesthetics
Haemorrhage control
Maintains soft tissue
Helps with transition
Protects socket
Maintains jaw relationship
Maintains face height
What are the disadvantages of immediate dentures?
Patient needs to pay for 2 sets or reline/rebase
Resorption makes fit poor
No trial stage
Difficult after surgical extractions
What should a prescription for special tray for upper and Lower dentures contain?
Please construct upper and lower special trays in light cure acrylic with IO/EO handles and spacing
Spacing:
Alginate- 3mm
Silicone or polyether:
Upper- 2mm
Lower- 0.5-1mm
