Leader in Dental Education Waxing & Investing

INTRODUCTIONINTRODUCTION
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.comwww.indiandentalacademy.com

The american dental association has haveThe american dental association has have
categorized waxes into 2 types:categorized waxes into 2 types:
Type 1- a medium wax (generally used for theType 1- a medium wax (generally used for the
direct technique)direct technique)
Type 2- softer wax (used in indirect fabricationType 2- softer wax (used in indirect fabrication
technique)technique)

ARMAMENTARIUMARMAMENTARIUM
Bunsen burnerBunsen burner
Inlay waxInlay wax
Waxing instrumentsWaxing instruments
Cotton cleaning clothCotton cleaning cloth
Sharp colored pencil (contrasting colour to wax)Sharp colored pencil (contrasting colour to wax)
Separating liquidSeparating liquid
Occlusal indicator powderOcclusal indicator powder
Soft toothbrushSoft toothbrush
Cotton ballsCotton balls
Fine nylon hoseFine nylon hose
Marking tapeMarking tape

WAXING INSTRUMENTSWAXING INSTRUMENTS
Can be categorized by the intent of the design:Can be categorized by the intent of the design:
Wax addition, carving, or burnishingWax addition, carving, or burnishing
The popularThe popular PKT carversPKT carvers designed bydesigned by Dr. PeterDr. Peter
K. ThomasK. Thomas are used:are used:
No. 1 and 2 are wax addition instruments.No. 1 and 2 are wax addition instruments.
No. 3 is a burnisher for refining occlusal anatomy.No. 3 is a burnisher for refining occlusal anatomy.
No. 4 and 5 are wax carvers.No. 4 and 5 are wax carvers.

Wax is added by heating the instrument in theWax is added by heating the instrument in the
bunsen flame, touching it to the wax, andbunsen flame, touching it to the wax, and
quickly reheating it shank in the flame.quickly reheating it shank in the flame.
Wax flows away from the hottest part of theWax flows away from the hottest part of the
instrument, so if the shank is heated, a bead ofinstrument, so if the shank is heated, a bead of
wax will flow off the tip.wax will flow off the tip.
However, if the tip is heated, the wax will flow upHowever, if the tip is heated, the wax will flow up
the shank of the instrument.the shank of the instrument.

The following sequence is recommended for waxThe following sequence is recommended for wax
pattern fabrication:pattern fabrication:
Internal surface.Internal surface.
Wax pattern removal and evaluation.Wax pattern removal and evaluation.
Proximal surfaces.Proximal surfaces.
Axial surfaces.Axial surfaces.
Incisal/occlusal surface.Incisal/occlusal surface.
Margin finishing.Margin finishing.

Internal surface: the wax must reproduce all theInternal surface: the wax must reproduce all the
retentive features of the restoration.retentive features of the restoration.

Wax pattern removal : Wax pattern should beWax pattern removal : Wax pattern should be
allowed to cool thoroughly before the coping isallowed to cool thoroughly before the coping is
removed from the die.removed from the die.

Wax pattern evaluation: The objective of theWax pattern evaluation: The objective of the
first waxing step is a perfectly adaptedfirst waxing step is a perfectly adapted
reproduction of the prepared tooth surfaces.reproduction of the prepared tooth surfaces.

Proximal surfaces: They are flat or slightlyProximal surfaces: They are flat or slightly
concave from the contact area to theconcave from the contact area to the
cementoenamel junction.cementoenamel junction.

Contact areas: The size and location of theContact areas: The size and location of the
contact areas should be established beforecontact areas should be established before
waxing the remainder of the proximal surface.waxing the remainder of the proximal surface.
Reference is made to contacts between theReference is made to contacts between the
contralateral teeth and knowledge of anatomiccontralateral teeth and knowledge of anatomic
form.form.

Axial surfaces: The buccal and lingual surfacesAxial surfaces: The buccal and lingual surfaces
should be shaped similarly to those of theshould be shaped similarly to those of the
adjacent teeth.adjacent teeth.

Incisal/occlusal surface: Opposing incisorsIncisal/occlusal surface: Opposing incisors
should make even contact during protrusiveshould make even contact during protrusive
movements but not during lateral excursions.movements but not during lateral excursions.
The cusps and ridges of the occlusal surfacesThe cusps and ridges of the occlusal surfaces
should be shaped as to allow even contact withshould be shaped as to allow even contact with
the opposing teeth while stabilizing the teeththe opposing teeth while stabilizing the teeth
and directing the forces along the long axes ofand directing the forces along the long axes of
the teeth.the teeth.

Margin finishing: For finalizing and adaptation,Margin finishing: For finalizing and adaptation,
the margins should be reflowed and refinishedthe margins should be reflowed and refinished
immediately prior to investing the wax pattern.immediately prior to investing the wax pattern.

““Invest the best to get casting free of pest”Invest the best to get casting free of pest”
Prof D.R.DavisProf D.R.Davis

INVESTMENTS
DEFINITIONS:
Invest (GPT 8) : To surround, envelop, or embed in an
investment material.
Investing (GPT 8) : The process of covering or enveloping,
wholly or in parts; an object such as a denture, tooth, wax
form, crown etc. with a suitable investment material before
processing, soldering or casting.
Investment (K.J. Anusavice) refractory material used to
form a mould casting for cast metals or hot pressed
ceramics.

Classification according to Binders used:
GYPSUM BONDED INVESTMENT:
- alloys that fuse below 1975°F (1080°c)
- Casting of gold alloys inlays, onlays, crowns and fixed
partial dentures.
PHOSPHATE BONDED INVESTMENTS:
- for higher fusing alloys
- Designed primarily for alloys used to produce copings or
frame works for metal ceramic prosthesis and for some base
metal alloys. It can also be used for press able ceramics.
ETHYL SILICATE- BONDED INVESTMENTS:
- for casting of removable partial dentures with base metal
alloys (cobalt based or nickel based alloys)www.indiandentalacademy.comwww.indiandentalacademy.com

Gypsum bounded is further classified by ADA
specification no 2 (casting investment) into two types
depending upon the expansion required to
compensate for the contraction of the molten gold
alloys during solidification.
TYPE I: THERMAL EXPANSION TYPE:
For casting of inlays and crowns
TYPE II: HYGROSCOPIC EXPANSION TYPE:
For casting inlays , onlays and crowns
TYPE III: ARE USED IN CONSTRUCTION OF
PARTIAL DENTURES WITH GOLD ALLOY.

TWO TYPES OF PHOSPHATE BONDEDTWO TYPES OF PHOSPHATE BONDED
INVESTMENTSINVESTMENTS
TYPE I: for inlays crowns and other fixedTYPE I: for inlays crowns and other fixed
restoration.restoration.
TYPE II: for partial dentures and other castTYPE II: for partial dentures and other cast
removable restorationremovable restoration

IDEAL REQUIREMENTS
An ideal investment should incorporate the following
features:
Controllable expansion to compensate precisely for
shrinkage of the cast alloy during cooling
The ability to produce smooth castings with accurate
surface reproduction without nodules
Chemical stability at high casting temperatures
Adequate strength to resist casting forces
Sufficient porosity to allow for gas escape
Easy recovery of the castingwww.indiandentalacademy.comwww.indiandentalacademy.com

INVESTINGINVESTING
Vacuum mixing of investment materials isVacuum mixing of investment materials is
highly recommended for consistent results inhighly recommended for consistent results in
casting with minimal surface defects,casting with minimal surface defects,
especially when phosphate-bondedespecially when phosphate-bonded
investments are used .investments are used .
Good results are possible withGood results are possible with
brush application of vacuum mixedbrush application of vacuum mixed
investment or when the investment is pouredinvestment or when the investment is poured
into the ring under vacuum.into the ring under vacuum.
Vacuum mixing with brushVacuum mixing with brush
application of the investment is theapplication of the investment is the
suggested mode.suggested mode.www.indiandentalacademy.comwww.indiandentalacademy.com

ArmamentariumArmamentarium
Vacuum mixer andVacuum mixer and
bowlbowl
VibratorVibrator
Investment powderInvestment powder
(gypsum or phosphate(gypsum or phosphate
bonded)bonded)
Water or colloidalWater or colloidal
silicasilica
SpatulaSpatula
BrushBrush
SurfactantSurfactant
Casting ring and linerCasting ring and linerwww.indiandentalacademy.comwww.indiandentalacademy.com

Brush technique: In this technique, pattern
is first painted with surface tension reducer; the
surface must be wet completely. The
procedures is as follows:
Add investment powder to the liquid in the
mixing bowl and quickly incorporate it by hand.
Attach the vacuum hose to the bowl, evacuate
the bowl, and mechanically spatulate.
The mixing should be carefully timed in
accordance with the manufacturer’s
instructions.

Coat the entire pattern
with investment,
pushing the material
ahead of the brush
from a single point.
Gently vibrate through
out the application of
investment, being
especially careful to
coat the internal
surface and the margin
of the pattern.

A finger positioned underA finger positioned under
the crucible former on thethe crucible former on the
table of the vibratortable of the vibrator
minimizes the risk ofminimizes the risk of
excessive vibration andexcessive vibration and
possible breaking of thepossible breaking of the
pattern from the sprue.pattern from the sprue.
After the pattern hasAfter the pattern has
been completely coated,been completely coated,
the ring is immediatelythe ring is immediately
filled by vibrating thefilled by vibrating the
remaining investment outremaining investment out
of the bowl.of the bowl.

When the investment reaches the level of theWhen the investment reaches the level of the
pattern, tilt the ring several times to cover andpattern, tilt the ring several times to cover and
uncover the pattern, thereby minimizing theuncover the pattern, thereby minimizing the
possible entrapment of air. Investing must bepossible entrapment of air. Investing must be
performed quickly within the working time of theperformed quickly within the working time of the
investment. If the investment begins to set tooinvestment. If the investment begins to set too
soon, rinse it off quickly with cold water.soon, rinse it off quickly with cold water.
After the ring is filled to the rim, allow theAfter the ring is filled to the rim, allow the
investment to set.investment to set.
If the hygroscopic technique is used, the ring isIf the hygroscopic technique is used, the ring is
placed in a 37placed in a 37°°C (100C (100°°F) water bath for 1 hourF) water bath for 1 hour

VACUUM TECHNIQUE
1. First, hand spatulate the mix
2. With the crucible former and pattern in place
attach the ring to the mixing bowl
3. Attach the vacuum hose and mix according to the
manufacturer’s recommendations
4. Invert the bowl and fill the ring under vibration
5. Remove the vacuum hose before shutting of the
mixer
6. Remove the filled ring and crucible former from
the bowl
7. Immediately clean the bowl and mixing blade
under running water.

Investing ProceduresInvesting Procedures
• Small ring: 1Small ring: 1
packagepackage
• Large ring: 2Large ring: 2
packagespackages
• Hand mix for 15Hand mix for 15
secondsseconds
• Vacuum mix for 60Vacuum mix for 60
secondsseconds
• Working time: 2-3Working time: 2-3
minutesminutes

Mixing RatiosMixing Ratios
• GeneralGeneral::
• More investment liquid,More investment liquid,
less water =less water =
more expansionmore expansion
• Less investment liquid,Less investment liquid,
more water =more water =
less expansionless expansion
• Begin with a dry bowlBegin with a dry bowl
• Use a maximum of 27mlUse a maximum of 27ml
of liquidof liquid
Using more liquid resultsUsing more liquid results
in ain a
weak moldweak mold

Mixing RatiosMixing Ratios
• For 100gms ofFor 100gms of
investmentinvestment::
• Crowns/veneers: 22mlCrowns/veneers: 22ml
liquid, 5ml distilled waterliquid, 5ml distilled water
• Inlays/Onlays: 16mlInlays/Onlays: 16ml
liquid, 11ml distilled waterliquid, 11ml distilled water
• Two year shelf life on theTwo year shelf life on the
investment from theinvestment from the
manufacturing datemanufacturing date
• Follow instructions onFollow instructions on
investment packetinvestment packet

CLINICAL CASECLINICAL CASE

Leader in Dental Education Waxing & Investing

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