Removable - RPDs/Spring Final
Cingulum rests -Slightly ____ and ___ shape -In the ____ of the cingulum or right ___ - ___-___ mm wide at center - ____ in width toward the mesial and distal
- Slightly ROUNDED and INVERTED "V" shape - In the BULGE of the cingulum or RIGHT ABOVE - 1.0-1.5 mm wide at CENTER - TAPERS in width toward the mesial and distal
When to use lingual plate?
- Used when lingual frenum is "high" and/or not sufficient SPACE for the Lingual Bar - Common choice for MOBILE teeth and/or gingival RECESSION...can add teeth to this later if needed - Common for CLASS I cases where ridges have RESORBED; helps resist rotation horizontally
To help when trimming the mandibular arch, how do you make the lingual tongue space?
- flat wet paper towel - cover with alginate - don't cover borders of the impression - smooth with wet fingers - pour impression
What do you need for taking the impression?
1) Accu-Dent ALGINATE --> and extra alginate for mandibular tongue space! 2) Two Rubber Mixing BOWLS (syringe and tray material) 3) Two Alginate SPATULAS 4) WATER measure for Accu-Dent --> 73° F Water --> can be colder if you more time to work! 5) Accu-Dent SYRINGE 6) METAL PERFORATED Impression TRAYS --> need a rigid tray!! (no plastic trays) 7) Have JADE stone, VACCUMIX equipment, etc. ready in lab! **we also use this for the full denture preliminary impression!**
What burs should be used to SMOOTH REST PREPS?
1) CHAYES (WHITE) Stone or 2) Operative COMPOSITE FINISHING bur 3) brownie points and greenie points ** don't use anything abrasive like a diamond!**
4 parts of a basic clasp assembly?
1) Direct retainer (retention) --> buccal --> terminal 1/3 of retentive arm in the GINGIVAL 1/3 of tooth into the undercut 2) Bracing arm (stabilization and reciprocation) --> lingual --> MIDDLE 1/3 3) minor connector (stabilization) 4) Rest (support) --> OCCLUSAL 1/3
4 components of BRACING and STABILIZATION?
1) Lingual Coverage 2) Minor connectors 3) Bracing arms 4) Guide plates (where the guide planes are!)
Rests do what other 4 things?
1) MAINTAINS components in their PLANNED POSITION 2) MAINTAINS OCCLUSAL RELATIONSHIPS --> by PREVENTING SETTLING of RPD 3) PREVENTS IMPINGEMENT of soft tissue 4) DISTRIBUTES OCCLUSAL LOADS to ABUTMENT teeth
Items to present to Assigned Faculty for Approval / Sent To Lab For RPD Framework Fabrication?
1) STUDY CAST --> With Design Drawn on it in Red-Blue pencil 2) MASTER CAST --> No Drawing on it!!! 3) WORK AUTHORIZATION --> In Ink and drawing in Red-Blue pencil --> This Is A Legal Document 4) PRINT out of $ BALANCE --> printed statement from Axium 5) LAB FORM is SWIPED/approved by faculty in Axium
Some Typical Problems with Master Cast?
1) VOIDS in stone in critical areas (see study cast framework design) 2) Bad SURFACE TEXTURE --> due to mucous or water in impression 3) Cast BREAKS when separating --> Weak cast due to not enough BASE thickness 4) Problems with rest preps/ guide planes 5) Distorted impression - Not poured within 15 minutes - Separation of tray with impression / before pour - Dehydration or incorrect water/powder ratio - Tray not rigid 6) Improper mix of stone 7) Trapping air in cast 8) Soft, chalky surface from retarding action of hydrocolloid --> Not separating cast from impression for extended time period --> Mucous saliva left in impression **This can result in significant delay of treatment!**
Where should you inject the Syringe material? (3)
1) into VESTIBULES, 2) REST SEATS, 3) RUGAE
Why is Smoothing and polishing of the rest preps required? (2)
1) to make prepared areas COMFORTABLE to patient AND 2) to PREVENT SHARP EDGES from BREAKING off the MASTER CAST --> causing the metal framework to not fit the patient! (bc it is made to fit the broken cast)
How much clearance do you want on the rest preps to make sure that there is enough room for the metal framework?
1.5 mm --> can check by using the green sheet wax the is .5mm thick (fold it three times = 1.5mm)
There should be ____ mm of clearance with the opposing teeth at the marginal ridge for occlusal rests
1.5 mm --> so there is room for the metal!!
Incisal rest dimensions?
1.5 mm DEEP (at deepest portion) ~ 2mm WIDE
In Texas, a work authorization is maintained for___ years
2 yrs --> it is a legal document!
lingual bar needs to be how wide?
3-4mm wide and 4mm away from Gingival margins! --> so need 7-8mm space!
total set time about ___ min
3:45 minutes
Examination Of Impression: need ____ mm of material THICKNESS and ACCURATE ___ areas
4-5 mm thickness accurate anatomical areas
minimal gingival clearance on MX?
6mm from gingival margin to border of major connector
How much room for an AP Strap?
7-8 mm + 15mm space +7-8mm = at least 29mm of total space
•7-8 mm width each strap •Posterior strap as far back but anterior to junction of hard and soft palate CLASS II and IV
AP strap --> 15 mm Minimum space between straps!!
Where should the INDIRECT RETAINERS be placed in RELATION TO the FULCRUM LINE?
AS FAR AS POSSIBLE!
The "GREEN SHEET" and DRAWING ON CAST ... --> Should be DONE and APPROVED BY FACULTY when?
BEFORE APPOINTMENT!! --> do the green sheet first and get that approved --> then draw on cast and get that approved **bring both already approved to the appointment to show and discuss with pt!** --> NOW can start rest preps and guide planes for impression for framework
those components that prevent the RPD from moving in the HORIZONTAL plane under masticatory forces
Bracing and Stabilizing Components
When to use a U shaped connector?
Can FLEX under occlusal forces, so lacks rigidity compared to other major connectors!! --> only use if there is a TORUS --> often used when anterior teeth are missing
BILATERAL edentulous areas located posterior to the remaining natural teeth (Bilateral distal extension)
Class I
When to use FULL palatal connector?
Class I or II arch without bumpy torus
A UNILATERAL edentulous area located posterior to the remaining natural teeth (unilateral distal extension)
Class II
A UNILATERAL edentulous area with natural TEETH REMAINING BOTH anterior and posterior to it
Class III
A SINGLE, but BILATERAL (CROSSING the MIDLINE) edentulous area located ANTERIOR to the remaining natural teeth
Class IV
There can be NO MODIFICATION AREAS in Class ___ arches:
Class IV arches!! --> another edentulous area lying posterior to the "single bilateral area crossing the midline" would instead determine the classification!!
the Accu-dent alginate (tray and syringe) is classified as...
Classified as ELASTOMERIC Impression Material --> IRREVERSIBLE HYDROCOLLOID
Incisal Rests: Deeper toward the ____ of the tooth (M-D'ly); Angles slightly downward on the ____ of the tooth (B-L'ly). Lingual should be ____
Deeper toward the CENTER of the tooth (M-D'ly); Angles slightly downward on the FACIAL of the tooth (B-L'ly). Lingual should be ROUNDED
the part of the RPD that RESTS on the supporting SOFT TISSUES and ATTACHES THE TEETH to the FRAMEWORK of the RPD
Denture BASE
a CLASP or attachment applied to an ABUTMENT tooth to retain a removable partial denture in position
Direct retainer
Edentulous areas other than those determining the classification are referred to as _____ and are designated by their _____
Edentulous areas other than those determining the classification are referred to as MODIFICATIONS and are designated by their NUMBER
Applegate's Rules for Classification: Classification should follow or precede any extractions of teeth that might alter the original classification?
FOLLOW ex: if there are wisdom teeth in the back it is a class III, but if you are going to extract both of them it is a Class I (bilateral distal extension)!
a part of a rpd that ASSISTS the DIRECT RETAINERS in preventing displacement of --> DISTAL EXTENSION DENTURE BASES by functioning through --> LEVER ACTION on the OPPOSITE SIDE of the FULCRUM LINE.
INDIRECT Retainers
A way of helping RESIST the LIFTING of a DISTAL EXTENSION by providing a "STOP" in the ANTERIOR part of the RPD
INDIRECT retainers --> RESTS that work by LEVER ACTION --> needed only when there is a distal extension!! (to make a fulcrum)
If a third molar is missing and not to be replaced, is it considered in the classification? (i.e. if missing both third molars would it be considered a class 1 distal extension on both sides?)
If a third molar is missing and not to be replaced, it is NOT considered in the classification! --> BUT if a third molar is present and IS to be used as an abutment, it is considered in the classification!!
The angle formed by the occlusal rest and the vertical minor connector from which it originates should be ____ than 90 deg
LESS than 90 deg
the unit of the partial denture that connects the parts of the prosthesis located on one side of the arch with those on the opposite side
Major Connector
arise from the major connector and connect other parts of the RPD to the major connector
Minor Connectors
Adequate base thickness is important (where should "thickness" be measured from?)
Mx: middle of the palate Md: lingual tongue space ** should be at least 1/2 in thick! **
Can you place Incisal rests on MX incisors?
NO --> Not esthetic; avoid highly visible areas when possible. NOT on max incisors!!
the Cingulum rest is NOT ADEQUATE if...
Not an adequate rest if just on an INCLINED PLANE --> can end up orthodontically pushing the tooth outwards away from the partial if not an adequate rest!
____ can also be used to check rest prep clearance with opposing teeth
Occlusal indicating wax --> In our clinic these are green thin sheets/strips that are folded up for the patient to bite on.
Plating more teeth adds tooth support which helps when edentulous ridges are severely resorbed. Having acrylic in posterior allows placement of a posterior palatal seal (like a complete denture)
Palatal Linguoplate --> only one where distal extension does not have connector that extends to pterygomaxillary notch
Broader strap covering ½ or more of palate; can help keep symmetry and metal can be made uniformly thin; Used more with Kennedy CLASS I
Palatal Plate
Needs min. 8 mm width ; used mostly for Kennedy CLASS III Not used to connect to anterior tooth replacements
Palatal Strap
Why are CINGULUM rests PREFERRED over INCISAL rests?
Preferred over incisal rests because... --> NEARER the HORIZONTAL AXIS of ROTATION (tipping axis of the tooth) --> however not always thick enough enamel (e.g. many mand. canines).
the unit of a partial denture that rests on a tooth surface to provide VERTICAL support.
RESTS --> These rests are placed on natural teeth or cast restorations in areas called REST SEATS
Indirect retainers are ALWAYS what?
RESTS placed in prepared rest seats (anterior to the fulcrum line!)
The metal part is called...
RPD FRAMEWORK (The metal part)
a REST SEAT is a ___ shape and has no ____
SPOON shape --> so it has NO LINE ANGLES they are rounded off
What is the ONLY FUNCTION of the TISSUE STOP?
SUPPORTS the retentive CRIBWORK during PACKING of the ACRYLIC resin! --> This is its only function!!
Need to FLUSH Impression Of...
Saliva Mucous --> to prevent distortion ** rinse, don't immerse!!**
The ____ of the modification is NOT considered, only the...
The EXTENT (or SIZE) of the modification is NOT considered, only the... --> NUMBER of additional edentulous areas!
When you have MULTIPLE EDENTULOUS AREAS (mods) which one DETERMINES the CLASSIFICATION?
The MOST POSTERIOR edentulous area determines the classification
What is the WIDTH of an OCCLUSAL REST?
Width is 1/2 the INTERCUSPAL DISTANCE (1/2 distance from buccal cusp to lingual cusp)
Does the cast need a base and land areas?
YES --> Build up enough stone for a 1/2 INCH thick BASE!! --> Have "WIDE" STONE SUPPORT around the PERIPHERY for land area (extra on sides for land area ) **CANNOT ADD A BASE LATER bc won't be one strong solid piece**
Do you need to hold the tray the whole time it is setting up in the mouth?
YES --> during setting (some manipulation of soft tissues and tongue helps get proper extension of vestibules);
When should you separate the cast / impression ?
about an hour or two --> don't wait overnight for alginate to get all dried out!!
The "floor" of the rest seat should be ____ to the marginal ridge
apical
The RPD TEETH get ATTACHED to the FRAME where? with what material?
at the RETENTIVE MESH, or CRIBBING --> with ACRYLIC RESIN
DIRECT retainer is always on what side of the tooth?
buccal --> the clasps!
Deepest portion of the rest is toward the ____ of the tooth
center
What shape is a lingual bar cross-section?
half pear --> thicker towed floor of mouth for rigidity and thinner towards tongue to hide it --> for strength and to blend in where tongue rests
If a second molar is missing and is NOT to be REPLACED, is it considered in the classification? (e.g. if the opposing second molar is likewise missing and is not to be replaced)
it is NOT considered in the classification:
Double Kennedy Bar?
large interprox. spaces and severe overlapping
Why can't you do a cingulum rests on many mandibular canines?
not always thick enough enamel
Outline form of an OCCLUSAL REST is a ____ shape
rounded triangular shape --> apex toward center; "spoon- shaped"
How should the tray be removed? What to avoid?
should be removed in a quick snap trying to keep one path of insertion! --> Remove tray WITHOUT ROCKING from side to side (can distort it!)
WAX IMPRESSIONS can be done with a piece of ROPE WAX to check rest preps for....
smooth, rounded internal surface --> Also can be used on cingulum rests to see the sloped floor of the prep!
RPDs are supported by...
supported by the TEETH AND/OR MUCOSA (tooth borne vs tooth-tissue borne)
do NOT let tray touch ___ or ___
teeth or ridges
Cingulum rests Should be DEEPER TOWARD...
the CENTER of the tooth B-L'ly i.e. the floor of the rest slants downward toward the facial
Why do you need to use a metal tray instead of plastic?
the plastic trays are too flexible! --> need a metal rigid tray for a more accurate impression --> also use jade stone and vacuum mix for more accurate cast
What is important to remember about RPDs with Tooth-TISSUE borne or distal extensions?
these areas will FLEX and MOVE during function unlike tooth borne RPDs --> have to DESIGN the RPD CORRECTLY or there could be DAMAGE to the TEETH from the flexure/movements!
Rests PRIMARY purpose?
to provide VERTICAL SUPPORT for the partial
When can you place an incisal rest in the middle of the tooth?
when there is INCISAL WEAR
how fast do you need to pour up the impression?
within 15 minutes!! --> Using Vacu-mixed Jade® Stone (Type IV stone for abrasive resistance)