CLINICAL WORK Flashcards
- What are the advantages and disadvantages of using a custom tray for alginate impressions?
- Advantages
- Uniform thickness and prevent perforated impression by occlusal stop
- No compound needed
- Custom-made → less tray modification required and less impression materials used
- Alginate is relatively uniform in thickness
- Disadvantages
- Extra laboratory procedures
- Custom tray produced cannot be used immediately (setting stability) → extra dental appointment
- Cannot be used on another patient
- Upon framework try in, an occlusal interference was found on a rest seat, but the rest seat is very thin already. What could have caused this?
Insufficient tooth preparation
Impression errors
Technical and processing errors during framework fabrication
Inaccurate jaw registration
- OR and Perio (Formative, 2009)
a. Clinical and lab steps for obtaining a muco-displacing impression. (5)
Acrylic resin tray material added to framework to form a base that covers relevant edentulous area
Inspect for under or over extension and adjust accordingly and remove undercuts in impression surface
Surface dried and apply zinc oxide impression paste
Framework placed in mouth and seated on teeth by pressure on occlusal rests
Impression set, framework removed from mouth and impression checked
Add wax rims to framework
Cut relevant edentulous area out from original master cast
New composite cast produced by pouring artificial stone into saddle impression
Acrylic tray removed from framework.
Add a small portion of cold curing acrylic resin to the mesh if a metal foot can be seen, to support framework on the cast
- Describe briefly the clinical and laboratory procedures of taking mucodisplacing impression for the fee end saddle. (Altered cast technique). (5)
- Clinical
- After denture framework try in and obtain satisfactory fit, acrylic resin tray material is added to framework to form a base covering the edentulous space
- Dry surface and apply zinc oxide eugenol / medium viscosity silicone
- Seat framework in mouth
- Ensure seat on teeth by applying pressure to rest only, and no occlusion
- Pressure on saddle will displace the material
- Lab
- Relevant edentulous area are cut from original master cast
- Seat framework carefully on the cast
- New composite cast is produced by pouring stone into saddle impression
- Remove acrylic tray from framework
- Metal foot attached to spaced mesh has lost contact with underlying ridge
- Add a few cold curing acrylic resin to the mesh to re-establish contact to support framework on cast
Patient requests replacement of existing denture made 1 year ago. Given: I/O photo of upper cobalt chromium RPD.
a. What is a diagnostic wax-up and what are its functions for the patient in this case? (4)
- Definition
- A process applied to a model of patient’s teeth to simulate the procedure and results of planned reconstruction or repair
- Functions
- Evaluation of occlusion and esthetic
- Assist Framework fabrication: indicate the position of retention and strengthening pin
- Help making silicon Index for setting up teeth
- Communicate between technician, dentist and patient
- Allow adjustment of OVD
- Modification before final product
Information given: A faulty RPD Design of upper arch of replacement of 21,22,23
Discrepancy: Major connector: lingual bar
Retention: only recriprocal arm present on 17 and 27. No clasp. Support: absence of rest seat to support saddle.
Indirect retention (cingulum rest on 23 and molars) not properly positioned.
a. What burs will you use to prepare the rest seats for the patient? (2)
Occlusal: round bur first, with cylindrical diamond bur to remove undercut
Cingulum: cylindrical diamond bur
Information given: A faulty RPD Design of upper arch of replacement of 21,22,23
Discrepancy: Major connector: lingual bar
Retention: only recriprocal arm present on 17 and 27. No clasp. Support: absence of rest seat to support saddle.
Indirect retention (cingulum rest on 23 and molars) not properly positioned.
b. What is the purpose of aesthetic try-in? (1)
Check aesthetic with patients
Assist framework fabrication (facilitate position of retention, strengthening pin, metal backing)
Production of silicone index for teeth set up
Information given: A faulty RPD Design of upper arch of replacement of 21,22,23
Discrepancy: Major connector: lingual bar
Retention: only recriprocal arm present on 17 and 27. No clasp. Support: absence of rest seat to support saddle.
Indirect retention (cingulum rest on 23 and molars) not properly positioned.
c. What is the thickness of “shimstock”? (1)
12 micron
Information given: A faulty RPD Design of upper arch of replacement of 21,22,23
Discrepancy: Major connector: lingual bar
Retention: only recriprocal arm present on 17 and 27. No clasp. Support: absence of rest seat to support saddle.
Indirect retention (cingulum rest on 23 and molars) not properly positioned.
d. The aesthetic try-in was fit to the patient’s mouth. However, at the delivery, there is 3
mm occlusal discrepancy found on the master cast. What will be your advice to the laboratory? (4)
Wrong jaw registration
Retake a bite registration in clinic and instruct technician remount the master cast at correct jaw relationship, adjust occlusal errors and check bite
