Info
These are lectures of The Gulfie Dentist Online Coaching
PROSTHO FPD
PROSTHO FPD
Explicit
4. Principles of tooth prep 2
8 JAN 2022 · Structural Durability :-
i. Functional cusp bevel -2 mm* for structural durability
ii. Proper oclusal / incisal clearance
iii. Incisal edge — 2 mm *
iv. labial — 1.5 mm
METAL CROWNS
All surface reduction of 0.5 (max-1.0mm)
Sharp line angles are okay
METAL-CERAMIC CROWN
- 1.5 (max-2MM) PREP (0.5 FOR METAL, 1-1.5 FOR CERAMIC)
- FUNCTIONAL CUSP / INCISAL – 2MM REDUCTION
- WALLS -6 DEGREE TAPER, NOT MORE THAT 10DEGREE
- CHAMFER FINISH LINE
- ALL MARGINS PLACED SUPRAGINGIVALLY
- Can have sharpline angles
ALL CERAMIC CROWN
SAME CONFIGURATIONS 1.5-2mm
At incisal / cuspa – 2mm for any type of preparation
Shoulder finish lines
ALL line angles SHOULD BE ROUNDED, NO SHARP ANGLES
THIS IS TO AVOID PORCELAIN FRACTURE
Q. For onlays preparation reduction of functional cusp 1.5 mm.
Q. The amount of reduction in all ceramic crown 1 – 1.5 mm.
Q. The amount of reduction in PFM crown 1.5 – 2 mm.
Q. The incisal reduction for a metal ceramic restoration should be 2 mm.
Q. The amount of reduction in metallic crown 0.5 mm.
*Minimum thickness of metal — 0.5 mm required, thus gives adequate strength
*Bevel all functional cusp — to give thick material at the region and thus resist
occlusal forces
Maryland / Resin bonded bridge
i. Indication
a. maxillary lateral incisors *
b. poor oral hygiene
ii. Advantage
a. better hygiene maintainability
b. conserve tooth structure.
iii. Disadvantage — weak bond — poor retention of resin and metal
3. Principles of Tooth Preparation
8 JAN 2022 · PRINCIPLES OF TOOTH PREPARATION
Preservation of the tooth structure - 4 models of preparations
1. THREE QUARTER CROWN
i. Occlusal + proximals + lingual
ii. Labial is untouched
iii. They are retained by grooves on mesial, distal & occlusal surfaces.
iv. For all teeth
v. Bur used to add retentive groove is – Tapered (/radial) fissure bur*
vi. Always made of cast metal.
2. REVERSE / MODIFIED ¾ CROWN
Preserves lingual surface
Commonly for mandibular molars
Damaged buccal surface with intact lingual side
Also useful on lingually tilted molar, coz lare amount of tooth
structure may need to be removed, might involve the pulp.
So to avoid that.
3. MESIAL / PROXIMAL HALF CROWN
vii. Mesially tilted mandibular molars
4. SEVEN BY EIGHT CROWN
For posterior esthetics
On maxillary molars
Mesiobuccal area not prepared or crowned
Mesial 1/3rd of buccal surface — unprepared.
Useful in distal surface caries
More coverage than a ¾ th crown
Mesially Tilted crown cases — mandibular molars.
b. Orthodontic uprighting (theoretically 1st choice , for exam point of view)
c. Use of non-rigid connectors (key and key hole, tenon-mortis etc)
d. Mesial half crown
e. Telescopic crown (least preferred type)
Retention and Resistence
a) Degree of taper - 6° tapering
b) Best bur — tapered fissure
---------i. Diamond coated
---------ii. Or tungsten coated carbide bur, known as 159L bur
TWO PLANE PREPARATION *
COMPLICATIONS OF 1 PLANE
A. Incisal only — food lodgement
i. Poor oral hygiene
ii. Gingival health compromised
B. Gingival only — opaqueness on incisal edge
Q. The ideal post drill for most posterior teeth is: peso drill size 2-3.
Q. Instrument used for wax grooving for a die in FPD: * Instrument we use to make a groove in the wax is: PKT no3.
4.2 Marginal Integrity - Finish Lines
8 JAN 2022 · Marginal Integrity – FINISH LINES
a) Finish line — the junction between prepared and unprepared position — should be at contra bevel — core
b) Position of the finish line;
Supra — best, hygienic maintenance
Equi — for gold crowns only, gingival 1/3rd
Subgingival — gingival 1/5th
Shoulder – 1.0-1.5mm thick
o All-ceramic crowns, coz edge strength of porcelain is low- so need but joint, 90 degree
o For the labial side of Anterior PFM also, as it maximizes the aesthetics by eliminating the display of metal.
o Bur used is – diamond end cutting bur
Light Chamfer – 0.3-0.5mm thick
o Mostly for gold crowns & Metal crowns
o rarely in PFM
o Preferred finish line For cast Gold restorations
o Leaves adequate bulk for marginal strength with acute angle & produces minimal stress at the margin.
Heavy chamfer - 1.0-1.5mm thick
o Best for PFM, esp in posteriors
o And some all-ceramic crowns
o If not given enough thickness at the finish line, the lab will be forced to over contour the crown – means to increase the thickness at the margin – it will stick- bacteria will accumulate and eventually affect the gingiva
o metal-ceramic labial only
Knife edge
o — SS crowns (subgingival)
Most important aspect of FPD abutment complex is its finish line.
margin of crown if brokn — causes caries
if caries at margin
----o marginal leakage
----o unsupported crown
----o redo crown
Failure of marginal caries — crown margin damage
Failure of margin of crown —caries
4.1 Veneers
8 JAN 2022 · VENEERS
Etching porcelain veneer by 9.6 % hydrofluoric acid *
The amount of reduction in laminate veneer
o 0.3 (gingival 3rd)
o 0.5 mm (mid-facial reduction)
o 1-2mm (incisal)
Grooves are made using tapered fissure
1. Assessment for FPD
29 AUG 2020 · FIXED PARTIAL DENTURE
THE PROCESS
1. Treatment planning
a. See if abridge is possible
b. Check the health of the abutment
c. Check if we can follow Ante’s law
d. Choose the pontic
2. Primary Impression-for temporary bridge
3. Crown preparation
4. Take the Impression
5. Pour cast
6. Provisional restoration
7. Crown from lab
8. Cementation
ABUTMENT TEETH
It is not a part of FPD unit / Bridge itself !
Selection
o Should have Well sounded periodontium
o Must fullfill ante’s law
o Caries if any must have been restored
o Should be able to withstand force
o Must be in alignment with the common path of insertion (not tilted cases)
Best abutment — ankylosed teeth
- Diverging multirooted, curved roots preferred to fused, single conical roots
Least preferred — endo treated tooth
- 3rd molar if it is tilted, short-fused root.
ANTE’S LAW:-
States thaaaat : Root surface area of the 2 orrrr three abutment teeth supported by bone should be greater than or at least equal to, to the root surface area of the tooth or teeth that is being replaced.
Root/Crown Ratio:-
𝑅𝑜𝑜𝑡/𝐶𝑟𝑜𝑤𝑛 =2/1 --- ] 𝐼𝑑𝑒𝑎𝑙
𝑅𝑜𝑜𝑡/𝐶𝑟𝑜𝑤𝑛=3/2 ----- ] 𝑟𝑒𝑐𝑜𝑚𝑚𝑒𝑛𝑑𝑒𝑑
2 abutments 1 pontic 3 abutment teeth 2 pontics
Remember, Crown is always the lesser no.
It will be easy to remember if they alter the ratio position,
𝑅𝑜𝑜𝑡/ 𝐶𝑟𝑜𝑤𝑛 = 1/1 --- ] 𝑚𝑖𝑛𝑖𝑚𝑢𝑚
Cantilever for lateral
Q. crown to root ratio: a. ideal 1-2 b. Optimum 2-3 c. normal 1-1.5 d. acceptable 1-1.
2. Parts of Fpd- Pontic designs
29 AUG 2020 · PARTS OF FPD/BRIDGE
1. Pontic – that we replace for the missing tooth
2. Crown /Retainer – that is placed on the abutment
3. Connectors – that connects the pontic with the crown & thereby the abutment teeth
CONNECTORS: -
>RIGID
--- casted connectors
--- fixed
>NON – RIGID
---- key and keyway connectors— Tenon and mortise – male female design
---- Included when we are not able to get a coomon path of insertion
---- For example a tilted crown – wich will have an oblique path of insertion, compared to the path of insertion that is parallel to the long axis in the normal tooth on the other end of the bridge.
---- So we put the single crown 1st and then the bridge unit on it.
Any connector in a PFM should have a min vertical height of 3mm
PONTIC DESIGNS
Replaces the missing natural tooth / teeth
1. SANITARY / HYGIENIC
Can clean with brush
Best pontic in posterior*
Best overall pontic*
2. SADDLE/ RIDGE LAP SHAPE
1st type of pontic design
It grips firmly on the ridge both buccally and lingually, not giving any space to clean
Concavity on the center area ∴ food lodgement possible
Bad hygiene
Least preferred- Actually never use.
3. EGG-SHAPED / CONICAL
Conical shape
One point contact at the ridge
More hygienic than ridge lap
Less hygienic than sanitary pontic
4. MODIFIED – RIDGE LAP / SADDLE LAP
Touches ridge at labial / buccal aspect only
Mimics natural tooth – as it appears emerging from the gingiva labially
Good aesthetics
Best for anteriors
5. OVATE
Most superior aesthetics
In cases where there's a ditch – like in Recently extracted areas
Accident cases- replacing immediately after extraction..
It Touches the ridge at the center
Egg-shaped
Has great emergence profile
5. Aesthetic crowns
29 AUG 2020 · ANTERIOR CROWNS
IPS impress — most esthetic
Inceram — high esthetic + high strength — anterior deepbite
Zirconia — high strength
6. Biological width
29 AUG 2020 · Preservation of Periodontium: -
The disaster of crown / FPD — Overhanging /Overcontoured crown
o food lodgement
o could affect perio eventually
Biological width — junctional epithelium + connective tissue = 2 mm
If at aaalll we are going subgingivally – it is only for aesthetic reasons, otherwise never preferred.
Preserve about 3 mm for assurance of preservation of periodontium.
7. Ferrule effect+ temporary crowns
29 AUG 2020 · FERRULE EFFECT: -
Value = 1.5 to 2 mm — minimum height / length of crown after prep
Most important factor for placement of crown*
If not enough height
o Surgical crown lengthening + clinical post and core
o Orthodontic extrusion (#ed at gingival part)
Q. The degree of the inclination of an abutment, which can be used 15 – 25 º.
TEMPORARY CROWN
Anterior — polycarbonate-Prefabricated crown-like cover
*most esthetic than acrylic and composite
Transparent cellulose acetate covers-trim the template-fill it with material-stick it on the tooth and after setting remove the plastic cover.
Putty impression template
Materials used
----o PMMA- INDIRECT METHOD, EXOTHERMIC
----o Bis acryl composite is used for direct method, little
brittle so good for single or short span bridge
Try-in — if correct fit
And final — poor fit is due to
over contouring
8. Layers of PFM
29 AUG 2020 · LAYERS OF PFM
CORE METAL : cast metallic framework. Also known as coping
OPAQUE PORCELAIN :
o first layer consisting of porcelain modified with opacifying oxides.
o Mask the darkness of the oxidized metal framework
o metal-ceramic bond
o Initiate the colour
Final buildup of DENTIN AND ENAMEL PORCELAIN
o Best tissue tolerated material
o Highly glazed layer *
These are lectures of The Gulfie Dentist Online Coaching
Information
| Author | Dr. Mayakha Mariam |
| Organization | Dr. Mayakha Mariam |
| Categories | Courses |
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