Removable Prosthodontics Fall Final Exam Review

 

This review is brought to you by Wildlife®

 

The final exam will consist of 70 multiple choice questions over the following topics:

 

House Personality Traits

Philosophical	Thoughtful Understands nature of problem	BEST Prognosis
Exacting	Methodical, precise, hyperaccurate Needs all details (explain everything) Much care, effort & patience from DDS	Prognosis depends on expertise of DDS   Any flaws, even minor, will annoy patient
Indifferent	Patient doesn’t care Not interested or motivated Apathetic Not cooperative Blames others for problems (i.e., previous dentist)	Prognosis is generally unfavorable
Hysterical	Emotionally unstable Apprehensive, excitable Usually needs psychiatric intervention	Poor prognosis

 

 

Denture Processing

 

A)   Lid

B)    Intermediary (intermediate
ring)

C)    Base

 

All three components comprise the flask

 

Filling the flask (Investing):

1)      embed the master cast in the base with plaster or stone just to the edge of the base
          purpose is to hold the cast in place and avoid undercuts when opening the flask
          will just cover the base of the master cast

2)    invest teeth/wax-up with next layer of plaster or stone (just to incisal edges)
          records contours of wax-up and position of teeth
          a separator (Vaseline or Cosep) is used between stone layers à NOT applied to teeth or wax
          à if the separator is applied to teeth, it could alter the shape/contour of the denture
          (some professional labs will add a 2^nd mix at incisal margins before the 3^rd mix)

3)    3^rd mix, or CAP is placed as the next layer
          engages only the incisal edges and occlusal surfaces
          purpose is to record and preserve the occlusal position
          easy to remove this layer à makes denture visible

 

What forms the internal surface of the final denture?  à the Master Cast

Note: the wax pattern is boiled away, and the record base is removed and discarded

          This is different from investing an inlay pattern (wax pattern is invested and reproduced)

          For dentures, internal surface is formed by pressure with acrylic forced against master cast

          Thus, it is very important not to damage the master cast!

 

After Investing

4)    Wax Elimination
Flask is placed in boiling water, which softens the wax
The softened wax is flushed out with boiling water, detergent, or steam
Creates a “clean space” for placement of acrylic

5)    Open Flask
Master cast is still in the base
Teeth are in the intermediate ring, and the underside of them is visible
          a DIATORIC (retention hole) is placed in each tooth
          allows better bonding of acrylic to teeth

6)    Place Separator
This separator is placed acrylic-to-gypsum, NOT on teeth (want acrylic to bind to teeth!)
Tin Foil Substitute à water-based agar substance (Vaseline not used b/c not water-soluble)

7)    Add Acrylic
Mix Powder and Liquid (the ratio is 3:1 à necessary to avoid shrinkage of acrylic)
Liquid à MMA (methylmethacrylate), this is the monomer
Powder à PMMA (polymethylmethacrylate), this is already processed monomer
          “pre-shrunk”, allows resin acrylic to be a “workable dough”
Dough is placed into clean space (also called mold space)

8)    Close Flask
Once the acrylic is placed, the flask is reassembled
Assure complete closure by metal-to-metal contact

9)    Curing
This acrylic is known as a Heat Cured Denture Base Resin
An accelerator is in the resin, and is activated by heat
Conventional Cure à 160°F for 9 hours
Fast Cure à 160°F for 1½ hours, followed by boiling (212°F) for 30 min.
Which cure has the lowest amount of residual monomer? The fast cure has the lowest.
          à important for patients with monomer allergy
          with these patients, the boiling time can be increased to hours
Why not just boil completely?  In thicker areas of acrylic, boiling creates porosities
          because the rxn is exothermic.
When completely cured, the denture is 90% PMMA

10) Finishing
The completed denture is polished, with rough edges removed
Must be careful to avoid warping of denture
Warping can be caused by…
          heat of polishing (friction)
          thermal shock from rapid cooling
          drying out of denture over time (denture should always be stored in water)
Some excess monomer can be polymerized by the frictional heat of polishing

11)  Remount
Lab Remount à immediately after processing
          corrects errors of processing (usually w/ incisal table off, occlusion will expand)
          re-align denture with articulator
Clinical Remount à done at delivery with remount cast
          allows for denture to fit patient
          pumice is used to block undercuts of ridge
          recheck centric record with patient
          remount denture with new record on articulator
Central Bearing Device
          used at centric record appointment
          creates a centered force on denture
          occlusal load is centered when patient bites
          allows for optimizing occlusion
Plaster Index
          upper and lower casts are typically destroyed during processing
          a plaster index is taken BEFORE processing
          preserves the face-bow mounting of upper cast
          allows repositioning of upper cast during remount
Summary
          Upper cast à positioned via Plaster Index
          Lower cast à positioned via Centric Record
          Occlusal Adjustment is done (once mounted) for delivery to patient

12) Repairs
A Cold Cure resin is used for repairs (as opposed to heat cure for processing)
Doesn’t need long water bath protocol
Includes a chemical accelerator
Density improved with pressure and warm/hot water

13) Delivery of Denture
Important to monitor pressure of denture on tissues
Paint PIP (Pressure Indicating Paste) on denture then seat
PIP is pushed away at high pressure spots
PIP will also disclose undercuts
How much undercut do we remove? The patient is the guideline à relieve until no pain
Disclosing Wax is used at the periphery of the denture (build up wax over flange)
Indicates an overextension of denture border (PIP won’t work b/c too thin)

14) Occlusal Adjustment
Excursive movements are guided by multiple posterior stops
          For Working Side Lateral Excursive Interferences (aka laterotrusive) à use BULL rule
          For Non-Working Side Lateral Excursive Interferences (aka mediotrusive) à use LUBL rule
Final Protrusive movement should end in edge-to-edge contact of incisors
          Necessary because humans use incisors to grasp things
          For Protrusive Interferences à use DUML rule

 

Immediate Dentures

à delivered at time of extraction (“pre-made”)

Advantages	·        Wound protection device (controls bleeding, protects sockets) ·        Preserves tooth form/shape ·        Preserves vertical dimension ·        Gives instant restoration of function and appearance ·        Patient can adapt to changes right away (this can encourage pts to complete the extractions)
Disadvantages	·        No anterior try-in appointment (pt doesn’t know what he/she will look like with the new denture) ·        No preservation of bone ·        Increased patient adaptation (more office visits for re-lines) ·        Increased expense

 

What happens to bone upon extraction of teeth?

          The bone resorbs

Will the bone resorb with a different pattern with the use of a denture?

          No, the denture does not preserve bone

Will people with dentures have less bone loss than those without dentures?

          No, the denture does not preserve bone

 

Bone Resorption

          Immediate denture does not preserve the ridge that was present before extractions

          Bone loss is variable to the individual and to site of extraction

It makes no difference, with regard to bone loss, if the patient wears a denture or not

à EXCEPT for heavy bruxers, who have increased bone loss with dentures

Bone loss can also be increased in patients with active periodontal disease

Bone loss can also be increased in diabetic patients, or those who are severely immunocompromised

HIV+ patients, or those with arthritis or hypertension will have NO difference in bone loss

Increased bone loss can cause problems for immediate dentures (proper fit, etc.)

         

Strategies for the Edentulous Patient

Ideal à Maxillary complete denture opposing mandibular partial

Worst à Maxillary partial and mandibular complete

          If a patient needs a mandibular complete denture, discuss implants instead

 

Immediate Denture Adjustments

As bone loss occurs in the first couple of months à reline as needed

From 3 to 6 months, there are two options:

1. Permanent Reline à re-coat inside with acrylic
2. Rebase the Denture à completely remove old base and redo
             provides a new, uniform base

Within 1 to 2 years à plan on making the patient a new definitive denture

          The old one can then become an emergency use denture

 

Why is it important to retain some mobile teeth while preparing an immediate denture?

          Retaining vertical dimension

          Retaining esthetic reference

 

Border Molding for Final Impression

Mold to optimal extension, with a thin labial flange (1-2 mm max., don’t make a hockey puck)

          à thin flange won’t over bulk the lips

If a mistake is going to be made, it is better to under-extend the mold

          Can be corrected with a re-line

An over-extended mold is a huge problem

          Causes pain, and must be adjusted à will never be optimal

 

Centric Record

Patient bites into wax

Determine VDO w/ natural teeth (before extractions)

Under what condition is a patient allowed to bite until the teeth touch?

          If the patient has their natural anterior teeth WITHOUT a Centric Slide

Teeth should not be mobile

Desirable Traits:

• firm, low mobility teeth
• no centric (CR/CO) deflection or slide
• patient close on wax until teeth touch IF AND ONLY IF vertical dimension on natural teeth is physiologically appropriate for the patient

**If these three traits are met, then the centric record can be taken with the natural teeth

 

Immediate denture should match VDO of centric record (there is no compensation made during processing, nor are there any changes made to VDO)

 

Maxillofacial Prosthodontics

• Area of prosthodontics related to restoring and replacing stomatognathic and craniofacial structures
• Most closely related to removable prosthodontics
• Treatment for squamous cell carcinoma in 85% of head and neck cases; remainder is other types of tumor damage
• Maxillectomy – removal of part of the maxilla
            Caused by sinus tumors
            Creates a hole in the hard or soft palate
            Requires an obturator (a prosthesis that fills the empty space; not used on mandible)
• Velopharyngeal Insufficiency
            Caused by tumor, cleft palate, stroke
            Identified by speech patterns (hyper- or hyponasal), and by swallowing
            No change in breathing of mastication
• Mid-Facial Prosthesis
            Useful with mid-facial resection
            Involves à Nose, Upper Lip, Hard Palate (which may involve the use of an obturator)
            PMMA à useful for prosthetic nose, obturator, and cranial implants
                      used for biocompatibility (it is a clear acrylic, like plexi-glass)
            Silicone Materials à useful for facial prostheses (need for flexibility)
                      smaller prostheses can be held in place with spray-on skin adhesive
                      larger prostheses can be held in place with implants
• Multi-discipline Approach
            Medical, social rehabilitation, internal medicine, surgeons
            Communication is very important!
                      à Written, Verbal, Study Casts, Surgical Stent
            Everything should be well communicated prior to any surgical procedures

 

“If you know all of this stuff, you are going to do great on this test.”  - Dr. LaBarre